The study explores carbon quantum dots (C-dots) as potential candidates for enhancing the signal sensitivity of an electrochemical sensor devised for biologically important molecule, such as uric acid (UA). The C-dots were evaluated for their electrochemical characteristics in combination with Fe3O4 nanoparticles (Fe3O4 NPs), which were applied as the primary electro-catalytic promoter. The hybrid nanocomposite (C-dots/Fe3O4 HCs) formation was achieved by facilitating the adsorption of C-dots over Fe3O4 NPs using amine-carbonyl interactions. Unlike, one pot method, the proposed strategy enables aggregation-free coverage of Fe3O4 NPs with highly conductive layer of C-dots that can act as conduction centres to support ultra-fast electron transfer kinetics to satisfy the need of high signal sensitivity. The hybrid composite demonstrated remarkable signal improvement when tested against the electrochemical oxidation of UA. The heighten current response and lower over-potential values enabled development of a DC-amperometric (DC-AMP) sensor for UA with a linear working range of 0.01 to 0.145 mu M and signal sensitivity measurable up to 6.0 x 10(-9) M. The said improvement was manifested as a synergetic outcome of active redox couple (Fe (III/II)), larger surface area of Fe3O4 NPs engulfed with a layer of highly conductive C-dots acting as efficient charge sensitisers.

Procalcitonin (PCT) protein has recently been identified as a clinical marker for bacterial infections based on its better sepsis sensitivity. Thus, an increased level of PCT could be linked with disease diagnosis and therapeutics. In this study, we describe the construction of the photoelectrochemical (PEC) PCT immunosensing platform based on it situ grown photo-active CuWO4 nanospheres over reduced graphene oxide layers (CuWO4@rGO). The in situ growth strategy enabled the formation of small nanospheres (diameter of 200 nm), primarily composed of tiny self-assembled CuWO4 nanoparticles (2-5 nm). The synergic coupling of CuWO4 with rGO layers constructed an excellent photo-active heterojunction for photoelectrochemical (PEC) sensing. The platform was then considered for electrocatalytic (EC) mechanism-based detection of PCT, where inhibition of the photocatalytic oxidation signal of ascorbic acid (AA), subsequent to the antibody-antigen interaction, was recorded as the primary signal response. This inhibition detection approach enabled sensitive detection of PCT in a concentration range of 10 pgmL(-1) to 50 ng.mL(-1) with signal sensitivity achievable up to 0.15 pgmL(-1). The proposed PEC hybrid (CuWO4@rGO) could further be engineered to detect other clinically important species.

In this study, electrically-conducting poly [Toluidine Blue (PTB)] was applied as artificial receptor. It was organized by molecular imprinting approaches and via electrochemical technique for the sensitive monitoring of prostate-specific antigen (PSA). The protein-imprinted PTB was electropolymerized in a pre-formed glutaraldehyde-cysteamine (GA-Cys A) matrix on the surface of gold electrode, which significantly boosted the stability against degradation of the Molecular Imprinted Polymer (MIP) on the surface of pre-modified gold electrode. Moreover, the MIP bio-receptor ability towards protein recognition was explored by some electrochemical techniques. The binding affinity of MIP system was considerably upper than that of non-imprinted polymer (NIP) system, indicating the success of the method in generating imprinted materials that was specifically use to PSA protein. The incubation of the MIP modified electrode in various concentration of PSA (from 1-60 μg/L) resulted in the increase of the Fe (CN)₆^3-/4- redox peak current. The bio-device also showed linear response from 1-60 μg/L and LLOQ of 1 μg/L by using DPV technique, leading to PSA monitoring in clinical samples. The proposed MIP-based biosensor was satisfactorily applied to the determination of PSA in human plasma samples. Therefore, the developed bio-device provides a new approach for sensitive, simple, rapid, and cost-effective monitoring of 1 μg/L of PSA. Notably, this approach could appear as an appropriate candidate for point-of-care (POC) use in clinical and biomedical analyses.

Biodiesel is a sustainable alternative to petroleum diesel produced by transesterification of vegetable oils in the presence of a catalyst. The present study investigates heterogeneous transesterification of algal oil to biodiesel using novel calcium-doped zinc oxide nanocatalysts synthesized using a UV shaker. The developed catalyst was under different light sources, UV and non-UV; different calcium concentrations (0.01, 0.03, 0.05 M); and different calcination temperatures (600, 700, 800 degrees C). The catalyst has been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and energy-dispersive spectroscopy (EDS). The effects of the different parameters used in catalyst preparation were studied for transesterification of algal oil. The catalyst of 0.05 M calcium loading and 700 degrees C calcination temperature synthesized in UV light is considered as the most suitable nanocatalyst, which achieved 99.18% yield of biodiesel. The catalyst was used three times effectively with 76% yield. The chemical properties of biodiesel have been investigated using gas chromatography (GC).

Sunlight responsible mono-and co-doped TiO2 nanoparticles (Con+ and Fen+) were prepared via sol-gel technique. The X-ray diffraction (XRD) results showed no phase change of TiO2 was observed after the addition of Con+ and Fen+ ions. Diffuse reflectance spectra (DRS) results showed a significant red-shift of the absorption edge after doping TiO2 by Co(n )and Fen+ and the band gap energy reduced sharply from 3.10 to 1.72 eV. X-ray photoelectron spectroscopy (XPS) results emphasized the existence of multivalent states of Co2+, Co3+, Fe2+ and Fe3+. The results of ultraviolet photoelectron spectroscopy (UPS), work function, electron spin resonance (ESR) illustrated the Fe3O4/Co3O4-TiO2 formed of ternary hetero-junctions. The photocatalytic performance of the prepared photocatalysts was determined for photodegradation of tetracycline (TC) and phenol (Pl) and production of hydrogen. The results illustrated the existence of multivalent states of Fe and Co ions (Co2+, Co3+, Fe2+ and Fe3+) together improved the solar light absorption, inhibited the recombination of photo -generated charges and consequently enhanced the photocatalytic efficiency of TiO2 compared with mono-doped TiO2 (Co3O4/TiO2 and Fe3O4/TiO2). The sample with 5%Fe3O4/ Co(3)O(4)4-TiO2 showed the highest photoactivity. The mineralization (TOC), photodegradation mechanism and reusability of prepared photocatalysts were also studied. The Fe3O4/Co3O4-TiO2 nanoparticles showed high photoactivity and stability and can be adopted as a promising materials for different environmental and H-2 production applications. (C) 2022 The Author(s). Published by Elsevier B.V.

FeMoO4 and rGO/FeMoO4 nanocomposites were successfully prepared by a facile hydro-thermal method. The XRD results confirmed that the FeMoO4 has a monometallic b-FeMoO4 crystalline phase while the rGO/FeMoO4 showed both monometallic a-and b-FeMoO4 phases where b-FeMoO4 is the predominant phase. The reduction of graphene oxide (GO) to reduced graphene oxide (rGO) was performed without using any chemical reductions. UV-Vis results showed that the visible light absorption and band gap energy were enhanced after the addition of rGO. The prepared samples were successfully applied for degradation of malachite green (MG) and phenol (Ph) and for H2 evolution under natural solar light irradiation. All the nanocomposites showed higher photocatalytic activities compared with pure FeMoO4 photocatalyst, and the 10%rGO/FeMoO4 gave the highest photodegradation performance for MG and Ph and for H2 evolution. The photodegradation results revealed that the rGO content played the crucial factor in the photodegradation of MG and Ph, and H2 evolution. The mineralization (TOC), photodegradation mechanism and degradation kinetics of MG and Ph were discussed.

Nanostructured materials for visible light driven photo-processes such as photodegradation of organic pollutants and photoelectrochemical (PEC) water oxidation for hydrogen production are very attractive because of the positive impact on the environment. Metal oxides-based nanostructures are widely used in these photoprocesses due to their unique properties. But single nanostructured metal oxide material might suffer from low efficiency and instability in aqueous solutions under visible light. These facts make it important to have an efficient and reliable nanocomposite for the photo-processes. The combination of different nanomaterials to form a composite configuration can produce a material with new properties. The new properties which are due to the synergetic effect, are a combination of the properties of all the counterparts of the nanocomposite. Zinc oxides (ZnO) have unique optical and electrical properties which grant it to be used in optoelectronics, sensors, solar cells, nanogenerators, and photocatalysis activities. Although ZnO absorbs visible light from the sun due to the deep level band, it mainly absorbs ultraviolet wavelengths which constitute a small portion of the whole solar spectrum range. Also, ZnO has a problem with the high recombination rate of the photogenerated electrons. These problems might reduce its applicability to the photo-process. Therefore, our aim is to develop and investigate different nanocomposites materials based on the ZnO nanostructures for the enhancement of photocatalysis processes using the visible solar light as a green source of energy. Two photo-processes were applied to examine the developed nanocomposites through photocatalysis: (1) the photodegradation of organic dyes, (2) PEC water splitting. In the first photo-process, we used the ZnO nanoparticles (NPs), Magnesium (Mg)-doped ZnO NPs, and plasmonic ZnO/graphene-based nanocomposite for the decomposition of some organic dyes that have been used in industries. For the second photo-process, ZnO photoelectrode composite with different silver-based semiconductors to enhance the performance of the ZnO photoelectrode was used for PEC reaction analysis to perform water splitting. The characterization and photocatalysis experiment results showed remarkable enhancement in the photocatalysis efficiency of the synthesized nanocomposites. The observed improved properties of the ZnO are due to the synergetic effects are caused by the addition of the other nanomaterials. Hence, the present thesis attends to the synthesis and characterization of some nanostructured materials composite with ZnO that are promising candidates for visible light-driven photo-processes.  

Doped semiconductors nanostructures (NSs) have shown great interest as a potential for green and efficient photocatalysis activities. Magnesium (Mg)-doped zinc oxide (ZnO) nanoparticles (NPs) has been synthesized by a one-step chemical low temperature (60 °C) co-precipitation method without further calcination and their photocatalytic performance for photodegradation of Methylene blue (MB) dye under the illumination of solar light is investigated. The crystal structure of the synthesized NPs is examined by X-ray diffraction (XRD). XRD data indicates a slight shift towards higher 2θ angle in Mg-doped samples as compared to the pure ZnO NPs which suggest the incorporation of Mg2+ into ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS), UV–Vis spectrophotometer and cathodoluminescence (CL) spectroscopy, were used to study electronics, and optical properties, respectively. The XPS analysis confirms the substitution of the Zn2+ by the Mg2+ into the ZnO crystal lattice in agreement with the XRD data. The photocatalytic activities showed a significant enhancement of the Mg-doped ZnO NPs in comparison with pure ZnO NPs. Hole/radical scavengers were used to reveal the mechanism of the photodegradation. It was found that the addition of the Mg to the ZnO lattices increases the absorption of the hydroxyl ions at the surface of the NPs and hence acts as a trap site leading to decrease the electron-hole pair and consequently enhancing the photodegradation.

High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.

For an active hydrogen gas generation through water dissociation, the sluggish oxygen evolution reaction (OER) kinetics due to large overpotential is a main hindrance. Herein, a simple approach is used to produce composite material based on TiO2/Co3O4 for efficient OER and overpotential is linearly reduced with increasing amount of TiO2. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal the wire like morphology of composite materials, formed by the self-assembly of nanoparticles. The titania nanoparticles were homogenously distributed on the larger Co3O4 nanoparticles. The powder x-ray diffraction revealed a tetragonal phase of TiO2 and the cubic phase of Co3O4 in the composite materials. Composite samples with increasing TiO2 content were obtained (18%, 33%, 41% and 65% wt.). Among the composites, cobalt oxide-titanium oxide with the highest TiO2 content (CT-20) possesses the lowest overpotential for OER with a Tafel slope of 60 mV dec(-1) and an exchange current density of 2.98 x 10(-3)A/cm(2). The CT-20 is highly durable for 45 h at different current densities of 10, 20 and 30 mA/cm(2). Electrochemical impedance spectroscopy (EIS) confirmed the fast charge transport for the CT-20 sample, which potentially accelerated the OER kinetics. These results based on a two-step methodology for the synthesis of TiO2/Co3O4 material can be useful and interesting for various energy storage and energy conversion systems. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The fabrication of efficient, alkaline-stable and nonprecious electrocatalysts for the oxygen evolution reaction is highly needed; however, it is a challenging task. Herein, we report a noble metal-free advanced catalyst, i.e. the chemically reduced mixed transition metal oxide CuO-Co3O4 composite, with outstanding oxygen evolution reaction activity in alkaline media. Sodium borohydride (NaBH4) was used as a reducing agent for the mixed transition metal oxide CuO-Co3O4. The chemically reduced composite carried mixed valence states of Cu and Co, which played a dynamic role in driving an excellent oxygen evolution reaction process. The X-ray photo-electron spectroscopy (XPS) study confirmed high density of active sites in the treated sample with a large number of oxygen vacancies. The developed electrocatalyst showed the lowest overpotential of 144.5 mV vs. the reversible hydrogen electrode (RHE) to achieve the current density of 40 mA cm(-2) and remained stable for 40 hours throughout the chronoamperometry test at the constant potential of 1.39 V vs. RHE. Moreover, the chemically reduced composite was highly durable. Electrochemical impedance spectroscopy (EIS) confirmed the low charge transfer resistance of 13.53 ohms for the chemically reduced composite, which was 50 and 26 times smaller than that of Co3O4 and untreated CuO-Co3O4, respectively. The electrochemically active surface area for the chemically reduced composite was found to be greater than that for pristine CuO, Co3O4 and untreated pristine CuO-Co3O4. These findings reveal the possibility of a new gateway for the capitalization of a chemically reduced sample into diverse energy storage and conversion systems such as lithium-ion batteries and supercapacitors.

There are many challenges associated with the fabrication of efficient, inexpensive, durable and very stable nonprecious metal catalysts for the hydrogen evolution reaction (HER). In this study, we have designed a facile strategy by tailoring the concentration of precursors to successfully obtain nickel-cobalt bimetallic sulfide (NiCo2S4) using a simple hydrothermal method. The morphology of the newly prepared NiCo(2)S(4)comprised a mixture of microparticles and nanorods, which were few microns in dimension. The crystallinity of the composite sample was found to be excellent with a cubic phase. The sample that contained a higher amount of cobalt compared to nickel and produced single-phase NiCo(2)S(4)exhibited considerably improved HER performance. The variation in the salt precursor concentration during the synthesis of a material is a simple methodology to produce a scalable platinum-free catalyst for HER. The advantageous features of the multiple active sites of cobalt in the CN-21 sample as compared to that for pristine CoS and NiS laid the foundation for the provision of abundant active edges for HER. The composite sample produced a current density of 10 mA cm(-2)at an overpotential of 345 mV. Also, it exhibited a Tafel value of 60 mV dec(-1), which predominantly ensured rapid charge transfer kinetics during HER. CN-21 was highly durable and stable for 30 hours. Electrochemical impedance spectroscopy showed that the charge transfer resistance was 21.88 ohms, which further validated the HER polarization curves and Tafel results. CN-21 exhibited a double layer capacitance of 4.69 mu F cm(-2)and a significant electrochemically active surface area of 134.0 cm(2), which again supported the robust efficiency for HER. The obtained results reveal that our developed NiCo(2)S(4)catalyst has a high density of active edges, and it is a non-noble metal catalyst for the hydrogen evolution reaction. The present findings provide an alternative strategy and an active nonprecious material for the development of energy-related applications.

Hydrogen evolution reaction (HER) has been identified as a sustainable and environment friendly technology for a wide range of energy conversion and storage applications. The big barrier in realizing this green technology requires a highly efficient, earth-abundant, and low-cost electrocatalyst for HER. Various HER catalysts have been designed and reported, still, their performance is not up to the mark of Pt. Among them, cobalt-based, especially cobalt disulfide (CoS2) has shown significant HER activity and found suitable candidature for HER due to its low cost, simple to prepare, and exhibits good stability. Herein, we synthesized various nanostructured materials including pure CoS2, Co3O4 and their composites by wet chemical methods and found them active for HER. The scanning electron microscopy (SEM) has revealed a morphology of composite as a mixture of nanowires and round shape spherical nanoparticles with several microns in dimension. The X-ray diffraction (XRD) confirmed the cubic phase of CoS2 and cubic phase of Co3O4 in the composite materials. The chemical deposition of CoS2 onto Co3O4 has tailored the HER activity of CoS2@Co3O4 composite material. Two CoS2@Co3O4 composite materials were produced with varying amounts of Co3O4 and labeled as samples 1 and 2. The Co3O4 reduced the adsorption energy for hydrogen, decreased the aggregation of CoS2 and uplifted the stability of CoS2@Co3O4 a composite material in alkaline media. Sample 1 requires an overpotential of 320 mV to reach a current density of 10 mA/cm(2) and it exhibits a Tafel slope of 42 mVdec(-1) which is the key indicator for the fast HER kinetics on sample 1. The sample 1 is highly durable for 50 h and also it has excellent stability. The electrochemical impedance spectroscopy (EIS) revealed a small charge transfer resistance of 28.81 Ohms for the sample 1 with high capacitance double-layer value of 0.81 mF. EIS has supported polarization and Tafel slope results. Based on the partial physical characterization and the electrochemical results, the as-obtained sample 1 (CoS2@Co3O4 composite material) will find potential applications in an extended range of energy conversion and storage devices owing to its low cost, high abundance, and excellent efficiency. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Micro-Doppler effects are phenomena that occur because of micro-motion. A micro-motion is either a vibration, rotation, or acceleration which is small relative to the motion of the target. These effects can be used in order to characterize a target through their signature movement. These effects were captured using a Frequency Modulated Continous Wave (FMCW) radar on several targets with a distinct signature. The targets were a four-armed drone, a cyclist, and a pedestrian. Using conventional- and super-resolution algorithms allows the user to process the captured data. To best be able to determine these signatures, different algorithms were used, Short-Time Fourier Transform (STFT), Smoothed Pseudo-Wigner-Ville Distribution (SPWVD), Pade Fourier approximation (PFA), and MUltiple SIgnal Classification (MUSIC). The comparison of the algorithms on the measured data was done in MATLAB where the best possible scenario was taken. From the comparison, it was noticed that in order to capture the most details, the MUSIC, PFA, STFT, and SPWVD performed the best with a decreasing order.

The monitoring of hypertension drugs is very critical and important to sustain a healthy life. In this study, we have synthesized nickel oxide (NiO) nanostructures using potassium dichromate as surface modifying agent by hydrothermal method. These NiO nanostructures were found highly active for the oxidation of ADB besylate (ADB). The unit cell structure and morphology were investigated by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The SEM study has confirmed the nano sheet like morphology and XRD analysis has described the cubic unit arrays of NiO. After the physical characterization, NiO nanostructures were used to modify the surface of glassy carbon electrode (GCE) by drop casting method. Then cyclic voltammetry (CV) was used to characterize the electrochemical activity of NiO nanostructures in the0.1 M phosphate buffer solution of pH 10.0 and a well resolved oxidation peak was identified at 0.70 V. The linear range for the NiO nanostructures was observed from 20-90 nM with a regression coefficient of 0.99 using CV. The calculated limit of detection (LOD) was 2.125 nM and the limit of quantification (LOQ) was 4.08 nM. Further to validate the CV calibration plot, an amperometry experiment was performed on the NiO nanostructures and sensors exhibited a linear range of 10 nM to 115 nM with LOD of 1.15 nM. The proposed approach was successfully used for the determination of ADB from commercial tablets and it reveals that the sensor could be capitalized to monitor ADB concentrations from pharmaceutical products. The use of potassium dichromate as a surface modifying agent for the metal oxide nanostructures may be of great interest to manipulate their crystal and surface properties for the extended range of biomedical and energy related applications.

Privacy-preserving distributed beamforming designs are conceived for temporally correlated vector parameter estimation in an orthogonal frequency division multiplexing (OFDM)-based wireless sensor network (WSN). The temporal correlation inherent in the parameter vector is exploited by the rate distortion theory-based bit allocation framework used for the optimal quantization of the sensor measurements. The proposed distributed beamforming designs are derived via fusion of the dual consensus alternating direction method of multiplier (DC-ADMM) technique with a pertinent privacy-preserving framework. This makes it possible for each sensor node (SN) to design its transmit precoders in a distributed fashion, which minimizes the susceptibility of vital information to malicious eavesdropper (Ev) nodes, while simultaneously avoiding the significant communication overhead required by a centralized approach for the transmission of the state information to the fusion center (FC). The Bayesian Cramer-Rao bound (BCRB) is derived for benchmarking the estimation performance of the proposed transmit beamformer and receiver combiner designs, while our simulation results illustrate the performance and explicitly demonstrate the trade-off between the privacy and estimation performance.

Wireless sensor networks (WSNs) are vulnerable to eavesdropping as the sensor nodes (SNs) communicate over an open radio channel. Intelligent reflecting surface (IRS) technology can be leveraged for physical layer security in WSNs. In this paper, we propose a joint transmit and reflective beamformer (JTRB) design for secure parameter estimation at the fusion center (FC) in the presence of an eavesdropper (ED) in a WSN. We develop a semidefinite relaxation (SDR)-based iterative algorithm, which alternately yields the transmit beamformer at each SN and the corresponding reflection phases at the IRS, to achieve the minimum mean-squared error (MSE) parameter estimate at the FC, subject to transmit power and ED signal-to-noise ratio constraints. Our simulation results demonstrate robust MSE and security performance of the proposed IRS-based JTRB technique.

In this study, we have used cotton silk as a source of abundant hydroxyl groups for the fast nucleation/growth of cobalt oxide (Co3O4) nanowires via a hydrothermal method. The crystal planes of the Co3O4 nanowires well matched the cubic phase. The as-synthesized Co3O4 nanowires mainly contained cobalt and oxygen elements and were found to be highly sensitive towards uric acid in 0.01 M phosphate buffer solution at pH 7.4. Importantly, the Co3O4 nanowires exhibited a large surface area, which was heavily utilized during the immobilization of the enzyme uricase via a physical adsorption method. The potentiometric response of the uricase-immobilizing Co3O4 nanowires was measured in the presence of uric acid (UA) against a silver/silver chloride (Ag/AgCl) reference electrode. The newly fabricated uric acid biosensor possessed a low limit of detection of 1.0 +/- 0.2 nM with a wide linear range of 5 nM to 10 mM and sensitivity of 30.6 mV dec(-1). Additionally, several related parameters of the developed uric acid biosensor were investigated, such as the repeatability, reproducibility, storage stability, selectivity, and dynamic response time, and these were found to be satisfactory. The good performance of the Co3O4 nanowires was verified based on the fast charge-transfer kinetics, as confirmed via electrochemical impedance spectroscopy. The successful practical use of the uric acid biosensor was demonstrated based on the recovery method. The observed performance of the uricase-immobilizing Co3O4 nanowires revealed that they could be considered as a promising and alternative tool for the detection of uric acid under both in vitro and in vivo conditions. Also, the use of cotton silk as a source of abundant hydroxyl groups may be considered for the remarkably fast nucleation/growth of other metal-oxide nanostructures, thereby facilitating the fabrication of functional electrochemical devices, such as batteries, water-splitting devices, and supercapacitors.

This study aimed to develop a sodium alginate (50%NaAlg)/polyethylene oxide (50%PEO) blend-based film loaded with nickel and zinc oxide nanoparticles (Ni/ZnO NPs) as a rein-forcing and antibacterial agent. The Ni/ZnO NPs as nanohybrid were synthesized via the sol-gel method at different concentrations (0.0, 5.0, 10.0, 15.0, 20.0 wt.%). The solution cast approach was utilized to create polymer nanocomposites samples from NaAlg/PEO/Ni/ZnO NPs for application in bioactive food packaging. The films were characterized using various procedures in detail. With the addition of Ni/ZnO, the XRD confirms the expansion of amorphous nature within NaAlg/PEO. The crystallinity degree of NaAlg/PEO-Ni/ZnO nanocomposite were decreased from 47 to 25%. The interactions between the compo-nents of NaAlg/PEO and Ni/ZnO NPs are revealed by FTIR findings. The bio-degradable nanocomposites dielectric behavior, electrical conductivity as well as mechanical prop-erties, were investigated. With the addition of Ni/ZnO NPs, the dielectric and AC conduc-tivity properties of the nanocomposites improved with the increase in the concentrations of Ni/ZnO NPs. The loading of Ni/ZnO nanoparticles increased the mechanical character-istics of the nanocomposite, such as tensile strength increased from 30.18 to 72.34, stiff-ness increased from 18.78 to 38.42, and Youngs Modulus increased from 8.24 to 29.76. The antibacterial activity of nanocomposites films was examined against Gram-negative (Escherichia coli), Gram-positive (Staphylococcus aureus), Aspergillus niger (fungus) and Candida albicans (yeast). Though the tested NaAlg/PEO blend did not indicate any activity against the microbial strains, when Ni/ZnO NPs were added, activity against E. coli, S. aureus, fungus and yeast was enhanced. The water solubility of nanocomposites films reduced from 65.5% to 9.81% with increasing of Ni/ZnO NPs content. The present study shown that NaAlg/PEO-Ni/ZnO films were more effective in inhibiting bacteria growth than pure NaAlg/PEO film, confirming the nanocomposites films potential application as anti-microbial food packaging.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

As the request for ready-made food grows, its more important than ever to develop effective antimicrobial food packaging materials to assure foods microbiological safety. The solvent casting method was used to create a chitosan (Cs)/polyvinyl alcohol (PVA) blend based active food packaging material enhanced with Fe2O3/TiO2 (FeTiO2) nanoparticles. The prepared films were characterized by TEM, XRD, FTIR, and ac conductivity. The structural alterations occurring in the nanocomposites are indicated by FTIR spectra and XRD investigations. The AC conductivity and dielectric characteristics of nanocomposites were dramatically improved as the nanoparticle loading was raised. The mechanical properties of blend/FeTiO2 nanocomposites films were better than pure blend film. The nanocomposites films had good antibacterial activity and mechanical properties, suggesting that they could be a viable alternative to non-biodegradable packaging material.

The present study used ultra-sonication approach to manufacture ZnO/NiFe2O4 (ZNF) and casting technique to prepare ZnO/NiFe2O4-Cs/PVP nanocomposite films. The successful creation of these nanocomposites with a significant decrease in the % crystallinity of the polymer blend with doping agent was verified by XRD results. ZNF and the Cs/PVP chains interacted in the polymer nanocomposites, as seen by the spectra of the FTIR. To determine the direct and indirect optical band gaps, tauc graphs were studied using data from UV-Vis analysis. The results indicate that while the Urbach energy was found to increase, the optical band gaps decreased as the weight percentage of the nanofiller increased. Using a thermogravimetric approach, the thermal stability of the produced PNCs has been investigated. Conductivity experiments demonstrated that when the nanofiller ZNF content increased to 2.5 wt%, so did AC conductivity, the dielectric loss, and the dielectric constant. The correlation between the mechanism of conduction and the amount of nanoparticles indicates that an increase in the percentage of ZNF in nanocomposites could increase their conductivity, with values ranging from 3.72 x 10-12 for pure blend to 7.72 x 10-8 S/cm for 2.5%ZNF-Cs/PVP at 100 Hz. The dielectric measurements for the nanocomposite films showed an increase in dielectric losses and dielectric constant, which is indicative of the films' enhanced dielectric polarization. The results of characterization point to possible uses of these polymer nanocomposites in flexible optoelectronic and magneto-electronic applications and energy storage devices.

The Polyethylene glycol (PEG) and Chitosan (CS)/silver nitrate (AgNO3) thin films were prepared by utilizing the casting technique to enhance their optical, dielectric, and electrical properties. Their physicochemical characteristics were investigated using a variety of techniques. The FT-IR study demonstrates that the addition of AgNO3 NPs results in a discernible difference in the intensities and locations of vibrational peaks of all bands, supporting the incorporation of AgNO(3)NPs inside the PEG/CS. The XRD analysis indicates that the peak at 2 theta = 23.1(degrees) broadens and strengthens proportionally with the increase of AgNO3 NPs. This observation suggests that the incorporation of AgNO3 NPs into PEG/CS results in a greater degree of amorphous characteristics compared to the PEG/CS blend. Additionally, when the amount of AgNO3 NPs increases in the PEG/CS, the energy band gap decreases, resulting in the creation of localized states between the valence and conduction bands. These polymer nanocomposite films' electrical conductivity, dielectric constant, and dielectric loss all increased with frequency increased and showed variance for various composite concentrations. These AgNO(3)NPs/PEG/CS films can be promising options for frequency-tunable nanodielectrics, flexible dielectric substrates, and bandgap-regulated materials for upcoming microelectronic, capacitive energy storage, and optoelectronic technologies, according to the experimental results.

In this study, a cast synthesis approach was used to create flexible nanocomposite films made of polyacrylamide (PAM), chitosan (Cs), and zinc ferrite nanoparticles (ZnFe2O4 NPs). XRD analysis was used to examine the composite structure. They demonstrated the effective interaction between ZnFe2O4 NPs and PAM/Cs blend. As the concentration of nanomaterial in the host polymer matrix grew, it was observed that the PAM/Cs matrix's direct and indirect energy band gaps decreased while its absorbance of ultraviolet-visible radiations increased. The nanocomposite's AC conductivity was significantly higher than that of the blend, and 2.5 wt percent of the nanocomposite showed the highest electrical conductivity. It was observed that as frequency raised, the epsilon ' and epsilon '' declined though the concentration of nanoparticles enhanced these characteristics. Because of the high dielectric permittivity of ZnFe2O4, the values of epsilon ' and epsilon '' raised as ZnFe2O4 were higher. The outcome of the vibrating sample magnetometer (VSM) demonstrated the ferromagnetic property of the produced nanocomposites. Furthermore, the VSM study shows that as the nanoparticles content increases, the PAM/Cs/ZnFe2O4 nanocomposites' Ms, Hc, and Mr also increase. These PAM/Cs/ZnFe2O4 films were shown by the experimental results to be promising candidates for bandgap-regulated materials, electromagnetic interference shielders, frequency tunable nanodielectric, and flexible dielectric substrates for future microelectronic, optoelectronic technologies, and capacitive energy storage.

Controlling the reaction kinetics during the nucleation/growth of cupric oxide (CuO) nanostructures is very critical in order to achieve a specific and well-defined morphology. For this purpose, we have slowed down the reaction speed using a mixed solvent concept and successfully obtained a chain-like morphology of CuO nanostructures using hydrothermal method. The CuO chain-like morphology was synthesized using a 1:1 (v/v) ratio of ethylene glycol and water. The morphology and crystalline features of CuO were studied by scanning electron microscopy (SEM) and powder X-ray diffraction techniques. The high resolution transmission electron microscopy revealed 5 nm crystallite size for the CuO material prepared in the mixed solvents. The obtained results have shown that the prepared CuO chains had a monocline phase, containing only Cu and O as main elements as confirmed by energy dispersive spectroscopy. This unique morphology obtained from mixed solvent process has provided a better surface for the loading of urease enzyme, thus it enabled the development of sensitive and selective urea biosensor in phosphate buffer solution of pH 7.4. The physical adsorption method was used to immobilize urease enzyme onto the nano surface of CuO. The fabricated biosensor based on urease/CuO chains has shown a dynamic linear range from 0.0005 to15 mM with a low limit of detection 0.0001 mM. Additionally, a fast response time aroudn1s, h high selectivity, stability, repeatability, storage time, and reproducibility were observed. The effect of pH and temperature on the potentiometric signal of the developed biosensor was also examined. Importantly, the practical aspects of the fabricated urea biosensor were probed and the obtained percent recovery results revealed an outstanding performance. The strategy of using mixed solvent with equal volume ratio would be useful for the preparation of other metal oxides with improved catalytic properties for a wide range of clinical, biomedical and other related applications.

We present an elementary proof of a well-known theorem of Cheeger which states that if a metric-measure space X supports a p-Poincaré inequality, then the N^1,p(X) Sobolev space is reflexive and separable whenever p ∈ (1, ∞). We also prove separability of the space when p=1. Our proof is based on a straightforward construction of an equivalent norm on N^1,p(X), p ∈ [1, ∞), that is uniformly convex when p ∈ (1, ∞). Finally, we explicitly construct a functional that is pointwise comparable to the minimal p-weak upper gradient, when p ∈ (1, ∞).

To split water and produce hydrogen by white light is an excellent solution for the storage and supply of clean and sustainable energy. Efficiency and stability are the key challenges for a successful exploitation. InGaN, evaluated against other semiconductors, metal oxides, carbon based - and organic materials has most suited intrinsic materials properties. Based on this optimum materials choice we report photoelectrochemical (PEC) hydrogen generation under white light illumination by an InGaN-based quantum nanostructure photoelectrode. No degradation occurs for operation over 10 h. Our novel concept, combining quantum nanostructure physics with electrochemistry and catalysis leads to almost 10% efficiency at zero external voltage. The efficiency rises above 25% at 0.2 V. This is unmatched for a single photoelectrode, representing the most advanced technology of low complexity. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Designing a nanocomposite with sensitive and selective determination of ascorbic acid is challenging task. It is possible through the exploitation of attractive features of nanoscience and nanotechnology for the synthesis of nanostructured materials. Herein, we report the decoration of nanoparticle of MoSx on the surface of Co3O4 nanowires by hydrothermal method. The MoSx nanoparticles shared the large surface on the Co3O4 nanowires, thus it supported in the development enzyme free ascorbic acid sensor. Non-enzymatic sensor based on MoSx-Co3O4 composite was found very selective for the determination of ascorbic acid (AA) in phosphate buffer solution of pH 7.4. The MoSx-Co3O4 nanocomposite was used to modify the glassy carbon electrode to measure AA from variety of practical samples. The MoSx-Co3O4 nanocomposite was used to modify the glassy carbon electrode and it has shown the attractive analytical features such as a low working potential +0.3 V, linear range of concentration from 100-7000 mu M, low limit of detection 14 mu M, and low limit of quantification (LOQ) of 42 mu M. The developed sensor is highly selective and stable. Importantly, it was applied successfully for the practical applications such as detection of AA from grapefruit, tomato and lemon juice. The excellent electrochemical properties of fabricated MoSx-Co3O4 nanocomposite can be attributed to the increasing electro active surface area of MoSx. The presented nanocomposite is earth abundant, environment friendly and inexpensive and it holds promising features for the selective and sensitive determination of AA from practical applications. The nanocomposite can be capitalized into the wide range of biomedical applications.

Electrochemical sensing performance of two-dimensional hexagonal boron nitride (2D h-BN) has traditionally been suppressed by their intrinsic electrical insulation and deficient electron transportation mechanism. However, the excellent electrocatalytic activity, high specific surface area, N- and B-active edges, structural defects, adjustable band gap through interaction with other nanomaterials, and chemical functionalization, makes 2D h-BN ideal for many sensing applications. Therefore, finding a pathway to modulate the electronic properties of 2D h-BN while the intrinsic characteristics are well preserved, will evolve a new generation of highly sensitive and selective electrochemical (bio)sensors. That is why extensive research has recently focused on the challenge to functionalize 2D h-BN by controlling the surface chemical reactions with external species, particularly metal nanoparticles. This review summarizes the most recent progress in the application of 2D h-BN nanosheets in electrochemical (bio)sensing. We will explore the fabrication techniques of 2D h-BN for electrochemical applications followed by thorough discussion on their advantages, shortcomings, and promising possibilities as (bio)sensing platforms in near future.

This article presents a compact multiband planar antenna designed for mobile phone applications.The antenna performance is achieved by designing a planar monopole antenna into distributed radiating elements. The proposed antenna is comprised of a chopped circular radiator appended with a meander line and an L-strip coupled element, which is an extension of the ground plane. The combination of a chopped circular patch and L-shaped coupling strip residing on the top side generates lower band while upper band resonances are attained separately by chopped circular resonator and meander line elements. The antenna shows a planar structure which occupies an area of 56 x 17.6 mm and can be directly printed onto a circuit board at low cost making it especially suitable for mobile phone applications. The manufactured antenna is experimentally verified and covers several wireless communication bands, such as LTE 750, GSM 850, GSM 900, DCS, UMTS-2110, Bluetooth, WLAN, WiMAX, and UWB. The high frequency structure simulation is used to design and analyze the antenna performance, and a practical structure was fabricated and tested. The measured and simulated return loss show good agreement.

The effect of different concentrations of urea on the morphology of iron oxide (Fe3O4) magnetic nanoparticles was studied. Fe3O4 magnetic nanoparticles were fabricated by the coprecipitation method. The morphology, crystallinity, compositional purity, and emission characteristics were tested by the techniques of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Raman characterization. The drop-casting technique was successfully used to fabricate a potentiometric urea biosensor producing initially isopropanol and chitosan solution, consisting of Fe3O4 nanoparticles, on a glass fiber filter. To measure the developed biosensors voltage signal from the functionalized nanoparticles, a copper wire was utilized. The Fe3O4 nanoparticle surface functionalization was performed through the electrostatic immobilization of urease with the Fe3O4-chitosan (CH) nanobiocomposite. The presented urea biosensor measured a wide logarithmic range of urea concentration of 0.1-80 mM with a sensitivity of 42 mV/decade, and indicated a fast response time of approximately 12 s. The developed urea biosensor showed enhanced sensitivity, stability, reusability, and specificity. All experimental results demonstrate the application potential of the developed urea sensor for the monitoring of urea concentrations in human serum, drugs, and food industry-related samples.

This paper studies the performance of hybrid digital-analog multi-user multiple-input multiple-output (MU-MIMO) downlink communication based on various antenna systems for 5G applications. The analysis is focused on comprehensive numerical simulations comparing hybrid beamforming schemes for collocated vs distributed phased array antennas (PAA) deployments in two indoor office environments. This study uses measured beamforming radiation patterns from two 28 GHz state-of-the-art PAAs. The channel models employed are the standardized statistical 3GPP 38.901 indoor channel models implemented in the QuaDRiGa software. A beam selection algorithm is implemented to maximize the achievable sum rate, assuming either matched-filtering or zero-forcing precoding. The evaluated figures of merit are the gain of the RF power amplifier, the per-user signal-to-interference-plus-noise ratio (SINR), and the resulting achievable sum-rate capacity. Based on the results, the distributed deployment scenario always shows a higher SINR and achievable sum-rate capacity at the user locations while requiring a lesser amplification of the conducted power. Specifically, the largest PAA with slant-polarized 16 x 4 elements producing 16 horizontal analog beams in combination with zero-forcing digital precoding proved to be the best solution in both open and mixed indoor office environments in absolute values. On the other hand, the array based on the same type of elements but in a more compact realization with 4 x 4 elements, but with beams arranged as 8 horizontal times 2 vertical, offered the most significant relative gains.

Acinetobacter baumannii is the main cause of nosocomial infections in blood, urinary tract, wounds and in lungs leading to pneumonia. Apart from its strong predilection to be the cause of serious illnesses in intensive care units. Herein, we present a specific and sensitive approach for the monitoring of Acinetobacter baumannii genome based on citrate capped silver nanoparticles (Cit-AgNPs) using spectroscopic methods. In this study, (5' SH-TTG TGA ACT ATT TAC GTC AGC ATG C3') sequence was used as a probe DNA (pDNA) of Acinetobacter baumannii. Then, complementary DNA (cDNA) was used for hybridization. After the hybridization of pDNA with cDNA, target DNA (5' GCA TGC TGA CGT AAA TAGTTC ACA A 3') was recognized and detected using turn-on fluorescence bioassay. After the hybridization of pDNA with cDNA, the target DNA was successfully measured in optimum time of 2 min by spectrophotometric techniques. Moreover, the selectivity of designed bioassay was evaluated in the presence of two mismatch sequences and excellent differentiation was obtained. 1 Zepto-molar (zM) of low limit of quantification (LLOQ) was achieved by this genosensor. The present study paved the way for quick (2 min) and accurate detection of Acinetobacter baumannii, which can be a good alternative to the traditional methods. Current study proposed a novel and significant diagnostic test towards Acinetobacter baumannii detection based on silver nanoparticles aggregation which has the capability of being a good alternative to the traditional methods. Moreover, the proposed genosensor successfully could be applied for the detection of other pathogens.

We study a novel degenerate and singular elliptic operator Δ˜(τ,χ) defined by Δ˜(τ,χ)u=τ(x,Du)(|Du|Δ1u+χ(x,Du)Δ∞u), where the singular weights τ(x,s)>0 and χ(x,s)≥0 are continuous functions on Ω×Rn∖{0}. The operator Δ˜(τ,χ) is an extension of Δ(p,q)u=|Du|qΔ1u+(p−1)|Du|p−2Δ∞u,p≥1,q≥0, introduced by the authors in Baravdishet al. (2020), which in turn is an extension of the p-Laplace operator Δp. We establish the well-posedness of the Neumann boundary value problem for the parabolic equation ut=Δ˜(τ,χ)u in the framework of viscosity solutions. For the solution u, the weight χ controls the evolution along the tangential and the normal directions, respectively, on the level surface of u. The weight τ controls the total speed of the evolution of u. We also prove the consistency and the convergence of the numerical scheme for the finite differences method of the parabolic equation above. Numerical simulations show that our novel nonlinear operator Δ˜(τ,χ) gives better results than both the Perona–Malik (Perona and Malik, 1990) and total variation (TV) methods (Chan and Shen, 2005) when applied to image enhancement.

We have in a previous study introduced a novel elliptic operator Δ(p,q)u=|∇u|^qΔ₁u+(p−1)|∇u|^p−2Δ_∞u, p≥1, q≥0, as a generalization of the p-Laplace operator. In this paper, we establish the well-posedness of the parabolic equation u_t=|∇u|^1−qΔ(_1+q,q), where q=q(|∇u|) is continuous and has range in [0,1],in the framework of viscosity solutions. We prove the consistency and convergence of the numerical scheme of finite differences of this parabolic equation. Numerical simulations shows the advantage of this operator applied to image enhancement.

The inverse problem of supervised reconstruction of depth-variable (time-dependent) parameters in a neural ordinary differential equation (NODE) is considered, that means finding the weights of a residual network with time continuous layers. The NODE is treated as an isolated entity describing the full network as opposed to earlier research, which embedded it between pre- and post-appended layers trained by conventional methods. The proposed parameter reconstruction is done for a general first order differential equation by minimizing a cost functional covering a variety of loss functions and penalty terms. A nonlinear conjugate gradient method (NCG) is derived for the minimization. Mathematical properties are stated for the differential equation and the cost functional. The adjoint problem needed is derived together with a sensitivity problem. The sensitivity problem can estimate changes in the network output under perturbation of the trained parameters. To preserve smoothness during the iterations the Sobolev gradient is calculated and incorporated. As a proof-of-concept, numerical results are included for a NODE and two synthetic datasets, and compared with standard gradient approaches (not based on NODEs). The results show that the proposed method works well for deep learning with infinite numbers of layers, and has built-in stability and smoothness. 

Evolution of brain tumours backwards in time is studied using well-established brain tumour growth models being semilinear parabolic equations of reaction-diffusion type. To run the models backwards, the tumour cell density data at a fixed (final) time is used, rendering an inverse ill-posed problem. This problem is recast as the minimisation of a cost functional matching the data against the solution at a final time of a forward parabolic model having the initial cell density as a control function. Regularisation is incorporated via penalising terms involving Sobolev norms. Mathematical properties of the semilinear parabolic equations are shown in Sobolev-Bochner spaces including uniqueness of a solution to the inverse problem. Differentiability of the control-to-state map is established rendering a sensitivity problem. The derivative of the cost functional is calculated and the adjoint state is derived via the Lagrange formalism. A non-linear conjugate gradient method (NCG) is presented for the minimisation. Numerical realisation of the minimisation on the BraTS'20 dataset is included using a standard finite difference discretisation of the space and time derivatives, showing that tumour evolution backwards in time can be accomplished and that the initial tumour cell density can be reconstructed. Comparison is done with a non-linear Landweber method.

A nonlinear conjugate gradient method is derived for the inverse problem of identifying a treatment parameter in a nonlinear model of reaction-diffusion type corresponding to the evolution of brain tumours under therapy. The treatment parameter is reconstructed from additional information about the tumour taken at a fixed instance of time. Well-posedness of the direct problems used in the iterative method is outlined as well as uniqueness of a solution to the inverse problem. Moreover, the parameter identification is recasted as the minimization of a Tikhonov type functional and the existence of a minimizer to this functional is shown. Finite-difference discretization of the space and time derivatives are employed for the numerical implementation. Numerical simulations on full 3D brain data are included showing that information about a spacewise-dependent treatment parameter can be recovered in a stable way.

In this paper, we introduce a new image denoising model: the damped flow (DF), which is a second order nonlinear evolution equation associated with a class of energy functionals of an image. The existence, uniqueness and regularization property of DF are proven. For the numerical implementation, based on the Stormer-Verlet method, a discrete DF, SV-DDF, is developed. The convergence of SV-DDF is studied as well. Several numerical experiments, as well as a comparison with other methods, are provided to demonstrate the efficiency of SV-DDF.

This paper considers a multivariate quickest detection problem with false data injection (FDI) attacks in internet of things (IoT) systems. We derive a sequential generalized likelihood ratio test (GLRT) for zero-mean Gaussian FDI attacks. Exploiting the fact that covariance matrices are positive, we propose strategies to detect positive semi-definite matrix additions rather than arbitrary changes in the covariance matrix. The distribution of the GLRT is only known asymptotically whereas quickest detectors deal with short sequences, thereby leading to loss of performance. Therefore, we use a finite-sample correction to reduce the false alarm rate. Further, we provide a numerical approach to estimate the threshold sequences, which are analytically intractable to compute. We also compare the average detection delay of the proposed detector for constant and varying threshold sequences. Simulations showed that the proposed detector outperforms the standard sequential GLRT detector.

This Paper describes how, based on a symbiosis of American and European thinking, "conceptual" labs for engineering courses have been developed in a series of design-based research projects that started in 1995. Researchers working in engineering education have been encouraged to "look for opportunities to translate research questions, theories, methods, and findings... across national and institutional boundaries", and urged to "think globally about the development of engineering education as a research field". Nevertheless, engineering education has been criticized for being insufficiently global in its practices. The aim of this paper is to meet these challenges. At first the design of labs was inspired by "interactive engagement" curricula such as "RealTime Physics" and "Workshop Physics" developed in the US, after they had been adapted to the Swedish setting and traditions. Variation theory, pragmatic and (post)phenomenological theories of the philosophy of technology, and activity theory influenced later development. Labs for advanced mechanics, and for introductory and advanced courses in electric circuit theory, were later developed using similar ideas. The labs utilized probeware and real-time computer-based measurement technologies as a mediating technology, and tasks were designed according to variation theory. Students learning in several designs of these labs has been studied by recording students activities and interactions by video, and using concept inventories such as the Force and Motion Conceptual Evaluation (FMCE). Some designs resulted in high achievement (normalized gains of 50-60%) on the conceptual tests, well in line with the results from the US. Furthermore, in the labs that led to high achievement, the technology was used help students to focus on important relationships and concepts, i.e. the technology functioned as a "cognitive tool". However, the implementation of probeware technology could also result poor achievement. This is explained by differences in how the tasks are designed and structured in the labs - the necessary patterns of variance and invariance in line with variation theory were missing. These results that identify important factors in students learning in labs differ to some extent from earlier proposals put forward to explain the success of interactive engagement curricula. The results also question some of the assumptions behind "active learning". The analysis presented in this paper was brought forth and facilitated by achieving synergies between American and European thinking.

An important aim in engineering education is that students should not only acquire knowledge, but they should be able to use this knowledge in action. I.e. they should develop professional capabilities for knowledgeable action and actionable knowledge. 

According to Markauskaite and Goodyear professional knowledgeable action requires a holistic, fluent and co-ordinated use of semiotic and material tools, body and environment. Knowledgeable action requires the development of epistemic fluency that involves the ability to smoothly move between abstract, contextual and situated ways of knowing and the capacity to employ multiple epistemic tools. However, the epistemic complexity of knowledgeable action is often underestimated in engineering education. This epistemic complexity has been addressed by Carstensen and Bernhard who have developed the notion of “learning of complex concepts” (LCC-model) that models how students learn to master epistemic tools by “making links”. 

In this study we have used the LCC-model as an investigatory tool to analyse video-recordings from electric circuit theory courses. The aim was to gain an increased understanding in how students develop epistemic fluency. We will discuss critical features in the design of labs and in the use of real experiments, computer simulations, modelling and other semiotic and material tools in labs for students’ development of epistemic fluency. The results of this study show that labs can be designed to facilitate students’ development of epistemic fluency by making links.

Contribution: This paper reports engineering students practical epistemic cognition by studying their interactional work in situ. Studying "epistemologies in action" the study breaks away from mainstream approaches that describe this in terms of beliefs or of stage theories. Background: In epistemology, knowledge is traditionally seen as "justified true belief," neglecting knowledge related to action. Interest has increased in studying the epistemologies people use in situated action, and their development of epistemic fluency. How appropriate such approaches are in engineering and design education need further investigation. Research Questions: 1) How do students in the context of a design project use epistemic tools in their interactional work? and 2) What are the implications of the findings in terms of how students cognitive and epistemological development could be conceptualized? Methodology: A collaborative group of six students were video recorded on the 14th day of a fifth-semester design project, as they were preparing for a formal critique session. The entire, almost 6 h, session was recorded by four video cameras mounted in the design studio, with an additional fifth body-mounted camera. The video data collected was analyzed using video ethnographic, conversation analysis, and embodied interaction analysis methods. Findings: The results show that the students use a wealth of bodily material resources as an integral and seamless part of their interactions as epistemic tools, in their joint production of understanding and imagining. The analysis also suggests that students epistemological and cognitive development, individually and as a group, should be understood in terms of developing "epistemic fluency."

The Engineering Education Research (EER) community in Europe and across the globe has grown considerably in the past decades. There have been some examinations to date of the research corpus that has evolved, although these have been predominantly US-based. An emerging literature has started to chart the ways in which European EER-researchers have a distinctive tradition, which might at least in part be due to the influence of the European “Didaktik” tradition, which conceptualizes teaching and learning as fundamentally resting on an interplay between student, teacher, and the content (subject matter). This is represented in the “Didaktik triangle” where student, teacher, and the content are placed on the vertices of the triangle, and the sides of the triangle represent three important interrelations. This study compares the 50 most highly cited papers in each of the European Journal of Engineering Education (EJEE) and the US-based Journal of Engineering Education (JEE). Our analysis of how the topic(s) of the papers related to the “Didaktik triangle” shows that the conceptualization of the object of study in the EJEE papers was more related to the “Didaktik triangle” as a whole compared with papers published in JEE. The results of our study provide further evidence that there are, indeed, some differences in the aims of American and European EER. A global community would do well to try to draw on the strengths of both of these traditions.

In engineering education there has been a growing interest that the curriculum should include collaborative design projects. However, students’ collaborative learning processes in design projects have, with a few exceptions, not been studied in earlier research. Most previous studies have been performed in artificial settings with individual students using verbal protocol analysis or through interviews. 

The context of this study is a design project in the fifth semester of the PBL-based Architecture and Design programme at Aalborg University. The students had the task to design a real office building in collaborative groups of 5–6 students. The preparation for an upcoming status seminar was video recorded in situ. Video ethnography, conversation analysis and embodied interaction analysis were used to explore what interactional work the student teams did and what kind of resources they used to collaborate and complete the design task. Complete six hours sessions of five groups were recorded using multiple video cameras (2 – 5 cameras per group).

The different collaborative groups did not only produce and reach an agreement on a design proposal during the session – in their design practice they used, and produced, a wealth of tools and bodily-material resources for representational and modelling purposes. As an integral and seamless part of students’ interactional and representational work and the group’s collaborative thinking bodily resources such as “gestured drawings” and gestures, concrete materials such as 3D-foam and papers models, “low-tech” representations such as sketches and drawings by hand on paper and “high-tech” representations as CAD-drawings were used.

These findings highlight the cognitive importance of tools and the use of bodily and material resources in students’ collaborative interactional work in a design setting. Furthermore, our study demonstrates that a focus primarily on digital technologies, as is often the case in the recent drive towards “digital learning”, would be highly problematic.

The 4th Doctoral Symposium at SEFI 2020 attracted 21 doctoral students and 17 senior researchers. For the first time, it was organised as a fully online event. In preparation, the doctoral students wrote extended abstracts to introduce themselves and their PhD projects, while the seniors provided reading tips and advice. The intense, full-day program was based on group discussions and interactive plenary sessions. The Doctoral Symposium was concluded by a session in which each participant presented their take-home message. This paper outlines how the Doctoral Symposium was organised and summarizes some of the documentation.

The design of efficient, stable, durable and noble metal free electro catalysts for oxygen evolution reaction (OER) are of immediate need, but very challenging task. In this study, iron induction into cobalt oxide (Co3O4) has resulted composite structure by wet chemical method. The iron impurity has brought an electronic disorder into Fe3O4/cobalt oxide composite thereby efficient oxygen evolution reaction is demonstrated. An addition of iron content into composite resulted the alternation of morphology from Nano rods to clusters of nanoparticles. The successive addition of iron into composite system reduced the onset potential of OER as compared to the pristine cobalt oxide. A Tafel slope of 80 mVdec(-1) indicates the favorable oxygen evolution reaction kinetics on the sample 4. An over-potential of 370 mV is required to reach a 10 mAcm(-2) current density which is acceptable for a nonprecious catalyst. The catalyst is highly durable and stable for 30 hours. Electrochemical impedance spectroscopy further provided a deeper insight on charge transfer resistance and sample 4 has low charge transfer resistance that supported the OER polarization curves. The sample 4 has more electrochemical active surface area of 393.5 cm(2). These obtained results are exciting and highlighting the importance of composite structure and leave a huge space for the future investigations on composite materials for energy related applications.

Designing a facile and low-cost methodology to fabricate earth-abundant catalysts is very much needed for a wide range of applications. Herein, a simple and straightforward approach was developed to tune the electronic properties of cobalt oxide nanostructures by doping them with nickel and then using them to catalyze the oxygen evolution reaction (OER) in an aqueous solution of 1.0 M KOH. The addition of a nickel impurity improved the conductivity of the cobalt oxide, and further increased its activity towards the OER. Analytical techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and powder X-ray diffraction (XRD) were used to investigate, respectively, the morphology, composition and crystalline structure of the materials used. The nickel-doped cobalt oxide material showed randomly oriented nanowires and a high density of nanoparticles, exhibited the cubic phase, and contained cobalt, nickel and oxygen as its main elements. The nickel-doped cobalt oxide also yielded a Tafel slope of 82 mV dec(-1) and required an overpotential of 300 mV to reach a current density of 10 mA cm(-2). As an OER catalyst, it was shown to be durable for 40 h. Electrochemical impedance spectroscopy (EIS) analysis showed a low charge-transfer resistance of 177.5 ohms for the nickel-doped cobalt oxide, which provided a further example of its excellent OER performance. These results taken together indicated that nickel doping of cobalt oxide can be accomplished via a facile approach and that the product of this doping can be used for energy and environmental applications.

In this research work, we have produced tungsten (W) doped ZnO nanostructures via low-temperature aqueous chemical growth method. The morphology, crystal arrays and composition was investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and energy dispersive X-rays (EDX) respectively. The SEM results indicate the nanowire morphology before and after the doping of W into ZnO and XRD study has shown the hexagonal crystallography of W doped ZnO samples. The EDX study has confirmed the successful doping of W into ZnO crystal lattices. The photodegradation performance of methylene blue was evaluated with W doped ZnO samples and pristine ZnO in aqueous solution. The measured degradation efficiencies for the different W doped ZnO samples were 5 wt%, 10 wt%, 15 wt% and 20 wt% at pH 5 are 87.8%, 92.3%, 92.8% and 96.9%), at pH 9 (72.1%, 90.7%, 92.1%, and 96.4%) and at pH 11 (80%, 85%, 87% and 89%) for the time interval of 90 min respectively. The pH of dye solution has significant effect on the degradation efficiency. These findings show that the W doped ZnO samples have superior degradation efficiency of 96.6% in a very short interval of time. The swift degradation kinetics for the W doped ZnO samples is attributed to the reduction in the energy band gap, decrease in particle size, enhanced surface area, decrease in the recombination rate and foster charge separation process. The obtained results are exciting and providing efficient earth-abundant photocatalysts for the energy and environmental purposes.Kindly confirm the Given names and Family names for all the authors.They are correct.

In this research work, we have produced a composite material consisting titanium dioxide (TiO2) and zinc oxide (ZnO) nanostructures via precipitation method. Scanning electron microscopy (SEM) study has shown the mixture of nanostructures consisting nanorods and nano flower. Energy dispersive spectroscopy (EDS) study has confirmed the presence of Ti, Zn and O as main elements in the composite. X-ray diffraction (XID) study has revealed that the successful presence of TiO2 and ZnO in the composite. The composite material exhibits small optical energy band gap which led to reduction of the charge recombination rate of electron-hole pairs. The band gap for the composite TiO2/ZnO samples namely 1, 2, 3 and 4 is 3.18, 3.00, 2.97 and 2.83 eV respectively. Small optical bandgap gives less relaxation time for the recombination of electron and hole pairs, thus favorable photodegradation is found. The degradation efficiency for the TiO2/ZnO samples for methylene blue in order of 55.03%, 75.7%, 85.14% and 90.08% is found for the samples 1, 2, 3 and 4 respectively. The proposed study of titanium dioxide addition into ZnO is facile and inexpensive for the development of efficient photocatalysts. This can be capitalized at large scale for the energy and environmental applications.