liu.seSearch for publications in DiVA
Change search
Link to record
Permanent link

Direct link
BETA
Renner, Johan
Alternative names
Publications (10 of 44) Show all publications
Lantz, J., Renner, J., Länne, T. & Karlsson, M. (2015). Is aortic wall shear stress affected by aging? An image-based numerical study with two age groups. Medical Engineering and Physics, 37(3), 265-271
Open this publication in new window or tab >>Is aortic wall shear stress affected by aging? An image-based numerical study with two age groups
2015 (English)In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 3, p. 265-271Article in journal (Refereed) Published
Abstract [en]

The size of the larger arteries increases during the entire life, but not much is known about how the change in size affects the blood flow. This study compares the flow field in a group of young males (N = 10, age = 23.5 +/- 1.4), with a group of older males (N = 8, age = 58.0 +/- 2.8). Aortic geometries were obtained by magnetic resonance imaging, and the aortic blood flow field was computed using computational fluid dynamics. The aortic wall shear stress was obtained from the computations, and it was concluded that time-averaged wall shear stress decreased with increased age, probably as a consequence of increased aortic diameter and decreased stroke volume, which in turn reduces the shear rates in the aorta. However, the oscillatory shear index, which is a measure of the oscillatory nature of the wall shear stress vector, seemed to be unaffected by aging.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Aorta; Wall shear stress; Oscillatory shear index; Computational fluid dynamics; Aging; Magnetic resonance imaging
National Category
Mechanical Engineering Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-117663 (URN)10.1016/j.medengphy.2014.12.011 (DOI)000352249800002 ()25630809 (PubMedID)
Note

Funding Agencies|Swedish e-Science Research Centre; Centre for Industrial Information Technology [99.11]; Swedish Research Council [2010-4282]; Swedish Heart and Lung Foundation

Available from: 2015-05-12 Created: 2015-05-06 Last updated: 2017-12-04
Simonsson, K., Renner, J., Hallberg, P. & Simonsson, M. (2014). Kamratutvärdering i kurser med stort datorlaborativt inslag. Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Kamratutvärdering i kurser med stort datorlaborativt inslag
2014 (Swedish)Report (Other academic)
Abstract [sv]

De mångfacetterade krav som idag ställs på yrkesverksamma högskole- och civilingenjörer handlar inte enbart om rena ämnesmässiga kunskaper och förmågor, utan även om t.ex. erfarenhet och förmåga att delta i och leda projekt samt (kopplat till detta) kommunikativ skicklighet (såväl muntlig som skriftlig). En annan uppgift som yrkesverksamma ingenjörer måste kunna bemästra i sin profession är att (individuellt, eller som medlemmar i olika typer av styrgrupper) bedöma och utvärdera andras ingenjörsmässiga arbete, en oerhört central uppgift i ett projekt- och kvalitetssäkringsperspektiv.

Det övergripande syftet med arbetet har varit att studera hur kamratbedömning kan implementeras i redan existerande kurser, för att på så sätt ge de studerande möjlighet att träna på att ge och ta emot kritisk bedömning, att förbättra de studerandes lärande via ett större aktivt engagemang under kursen samt att se om potential finns att effektivisera undervisningen m.a.p. lärarinsatsen, genom att lyfta över en del av enklare rutinkontroller till de studerande själva.

Kamratbedömning har implementerats i två sinsemellan likartade kurser inom beräkningsmekanik vid högskole- resp. civilingenjörsprogrammen i Maskinteknik, LiTH (600 studenter ingick i studien). Mer specifikt har till två enklare inledande laborationsuppgifter inkluderats ett moment av kamratbedömning. Utvärderingen av det genomförda arbetet har skett via en kvalitativ studie, där de studerandes perspektiv/synpunkter inhämtats i samband med skriftlig redovisning av inlämningsuppgifter. Utöver detta har den kursansvarige gjort observationer av hur kamratutvärderingsarbetet fortskridit under laborationstid.

Resultatet visar att de studerande har uppskattat granskningen av såväl det egna som kamraternas arbeten, och att de sett det som ett led i lärandeprocessen. Även professionsperspektivet har lyfts fram där de studerande betonar vikten av moment och uppgifter i utbildningen som har en direkt relevans i det kommande yrkeslivet. Den kursansvariges bedömning är vidare att andelen ”viktiga” och ”relevanta” frågor ökat, vilket ger indikationer på att kamratbedömning kan vara en såväl pedagogiskt som effektivitetsmässigt gynnsam metodik. De studerande har dock upplevt logistiken/administrationen kring kamratvärderingen som i vissa avseenden besvärlig.

Sammanfattningsvis är det vår slutsats att kamratbedömning har en stor potential att berika utbildningar m.a.p. förmåga till kritisk granskning, djupinlärning och effektivisering, men att verksamheten inte bara skall implementeras kursvis (med risk för suboptimering och ineffektivitet), utan att den bör inlemmas i ett större perspektiv, med progression genom utbildningen som riktmärke.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. p. 11
National Category
Pedagogy
Identifiers
urn:nbn:se:liu:diva-110630 (URN)
Projects
Kamratutvärdering i kurser med stort datorlaborativt inslag
Available from: 2014-09-16 Created: 2014-09-16 Last updated: 2015-06-02Bibliographically approved
Maleki, S., Björck, H. M., Folkersen, L., Nilsson, R., Renner, J., Caidahl, K., . . . Eriksson, P. (2013). Identification of a novel flow-mediated gene expression signature in patients with bicuspid aortic valve. Journal of Molecular Medicine, 91(1), 129-139
Open this publication in new window or tab >>Identification of a novel flow-mediated gene expression signature in patients with bicuspid aortic valve
Show others...
2013 (English)In: Journal of Molecular Medicine, ISSN 0946-2716, E-ISSN 1432-1440, Vol. 91, no 1, p. 129-139Article in journal (Refereed) Published
Abstract [en]

Rationale: Individuals with bicuspid aortic valve (BAV) are at significantly higher risk of developing serious aortic complications including aortic aneurysm and dissection than individuals with a tricuspid aortic valve (TAV). Studies have indicated an altered aortic blood flow in patients with BAV, however the extent to which altered flow may influence the pathological state of BAV aorta is still unclear.

Objective: To dissect flow-mediated gene expression potentially leading to increased aneurysm susceptibility in patients with BAV.

Methods and Results: A large collection of publically available microarray data sets were screened for consistent co-expression with KLF2, KLF4, TIE1, THBD, and PKD2, five previously well-characterized flow-regulated genes. This identified 122 genes with coexpression probability of >0.5. Of these, 44 genes satisfied two additional filtering criteria in ascending aorta (127 arrays). The criteria were significant correlation with one or more of the 5 query genes (R>0.40) and differential expression between patients with BAV and TAV. No gene fulfilled the criteria in mammary artery (88 arrays). A large proportion of the identified genes were angiogenesis related genes. Further, 55% of the genes differentially expressed between BAV and TAV showed differential expression in disturbed vs. uniform flow pattern regions in rat aorta. Protein expression of ZFP36, PKD2 and GPR116 were analyzed by immunohistochemistry and their association with BAV were further discussed.

Conclusions: With a new strategy to dissect flow-mediated gene expression, we identified novel genes associated with valve morphology. The complex pattern of blood flow, as a consequence of BAV

Place, publisher, year, edition, pages
Springer-Verlag New York, 2013
Keywords
Aneurysm, gene expression, aorta, impaired flow, angiogenesis
National Category
Physiology
Identifiers
urn:nbn:se:liu:diva-73956 (URN)10.1007/s00109-012-0942-8 (DOI)000313077000013 ()
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2018-01-12
Wren, J., Renner, J. & Karlsson, M. (2013). THERMODYNAMICS OF MAN – A CDIO-APPROACH TO UNDERSTANDHUMAN PHYSIOLOGY FROM THE FIRST PRINCIPLE. In: Proceedings of the 9th International CDIO Conference, Massachusetts Institute of Technology and Harvard UniversitySchool of Engineering and Applied Sciences, Cambridge, Massachusetts, June 9 – 13, 2013: . Paper presented at 9th International CDIO Conference, June 9 – 13, 2013.
Open this publication in new window or tab >>THERMODYNAMICS OF MAN – A CDIO-APPROACH TO UNDERSTANDHUMAN PHYSIOLOGY FROM THE FIRST PRINCIPLE
2013 (English)In: Proceedings of the 9th International CDIO Conference, Massachusetts Institute of Technology and Harvard UniversitySchool of Engineering and Applied Sciences, Cambridge, Massachusetts, June 9 – 13, 2013, 2013Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

A multi-disciplinary CDIO project ranging from physiology to thermodynamics are used tointroduce first year engineering students to an engineering task, and to introduce generalengineering skills like project management, group dynamics, human interaction as well aswritten and oral presentations.

Keywords
CDIO, Thermodynamics, Physiology
National Category
Pedagogy
Identifiers
urn:nbn:se:liu:diva-97379 (URN)
Conference
9th International CDIO Conference, June 9 – 13, 2013
Available from: 2013-09-11 Created: 2013-09-11 Last updated: 2016-03-14
Renner, J., Lantz, J., Ebbers, T., Länne, T. & Karlsson, M. (2012). Altered WSS in the human aorta with age – implications for wall remodeling and lesions?. Paper presented at ARTERY '12, Wien, Austria, 18-20 October 2012.
Open this publication in new window or tab >>Altered WSS in the human aorta with age – implications for wall remodeling and lesions?
Show others...
2012 (English)Conference paper, Published paper (Other academic)
Keywords
Human Aorta, Wall Shear Stress, Ageing, Wall Remodelling
National Category
Physiology Medical Image Processing Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:liu:diva-87041 (URN)
Conference
ARTERY '12, Wien, Austria, 18-20 October 2012
Available from: 2013-01-09 Created: 2013-01-09 Last updated: 2018-01-11
Björck, H. M., Renner, J., Maleki, S., Nilsson, S. F. .., Kihlberg, J., Folkersen, L., . . . Länne, T. (2012). Characterization of Shear-Sensitive Genes in the NormalRat Aorta Identifies Hand2 as a Major Flow-ResponsiveTranscription Factor. PLoS ONE, 7(12)
Open this publication in new window or tab >>Characterization of Shear-Sensitive Genes in the NormalRat Aorta Identifies Hand2 as a Major Flow-ResponsiveTranscription Factor
Show others...
2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 12Article in journal (Refereed) Published
Abstract [en]

Objective: Shear forces play a key role in the maintenance of vessel wall integrity. Current understanding regarding shear-dependent gene expression is mainly based on in vitro or in vivo observations with experimentally deranged shear, hence reflecting acute molecular events in relation to flow. Our objective was to determine wall shear stress (WSS) in the rat aorta and study flow-dependent vessel wall biology under physiological conditions.

Methods and Results: Animal-specific aortic WSS magnitude and vector direction were estimated using computational fluid dynamic simulation based on aortic geometry and flow information acquired by MRI. Two distinct flow pattern regions were identified in the normal rat aorta; the distal part of the inner curvature being exposed to low WSS and a non-uniform vector direction, and a region along the outer curvature being subjected to markedly higher levels of WSS and a uniform vector direction. Microarray analysis revealed a strong differential expression between the flow regions, particularly associated with transcriptional regulation. In particular, several genes related to Ca2+-signalling, inflammation, proliferation and oxidative stress were among the most highly differentially expressed.

Conclusions: Microarray analysis validated the CFD-defined WSS regions in the rat aorta, and several novel flow-dependent genes were identified. The importance of these genes in relation to atherosusceptibility needs further investigation.

Keywords
Aorta, wall shear stress, magnetic resonance imaging, computational fluid dynamics, gene expression
National Category
Physiology Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:liu:diva-73954 (URN)10.1371/journal.pone.0052227 (DOI)000312794500119 ()
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2018-01-12
Renner, J., Nadali Najafabadi, H., Modin, D., Länne, T. & Karlsson, M. (2012). Subject-specific aortic wall shear stress estimations using semi-automatic segmentation. Clinical Physiology and Functional Imaging, 32(6), 481-491
Open this publication in new window or tab >>Subject-specific aortic wall shear stress estimations using semi-automatic segmentation
Show others...
2012 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 6, p. 481-491Article in journal (Refereed) Published
Abstract [en]

Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such an entity in-vivo in humans, image-based computational fluid dynamics (CFD) is a useful tool. In this study, we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method, a number of steps are included. One important step is the interpretation of images into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparing WSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of eight healthy male volunteers. The different segmentation methods give slightly different geometrical depictions of the human aorta (difference in the mean thoracic Aorta lumen diameter were 0.7% Pandlt;0.86). However, there is a very good agreement between the resulting WSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time point indicating that the WSS is more sensitive to local geometric differences in these parts of the cardiac cycle (correlation coefficient is 0.96 at peak systole and 0.68 at early diastole). We can conclude that the results show that the semi-automatic segmentation method can be used in future to estimate relevant aortic WSS.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2012
Keywords
aortic arch, human, image-based computational fluid dynamics, magnetic resonance imaging, segmentation, wall shear stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-85079 (URN)10.1111/j.1475-097X.2012.01146.x (DOI)000309393700010 ()
Available from: 2012-11-02 Created: 2012-11-02 Last updated: 2017-12-07Bibliographically approved
Karlsson, M., Lantz, J., Gårdhagen, R. & Renner, J. (2011). Biofluid Mechanics -LES and FSI. In: B. Skallerud and H.I. Andersson (Ed.), : . Paper presented at Sixth national conference on Computational Mechanics (MekIT'11), Trondheim, Norway, 23-24 May 2011 (pp. 23-28). tapir academic press
Open this publication in new window or tab >>Biofluid Mechanics -LES and FSI
2011 (English)In: / [ed] B. Skallerud and H.I. Andersson, tapir academic press , 2011, p. 23-28Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
tapir academic press, 2011
Keywords
Biofluid, CFD, Human Aorta
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-104485 (URN)978-82-519-2798-7 (ISBN)
Conference
Sixth national conference on Computational Mechanics (MekIT'11), Trondheim, Norway, 23-24 May 2011
Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2016-03-14
Renner, J., Ghavami Nejad, M., Nadali Najafabadi, H., Loyd, D., Skoog, P., Abrahamsson, D. & Karlsson, M. (2011). Conduction and convection heat transfer for aluminum ingot in preheating furnace. In: Reijo Karvinen & Matti Lindstedt (Ed.), Proceedings of 6th Baltic Heat Transfer Conference 2011. Paper presented at Proceedings of 6th Baltic Heat Transfer Conference 2011 – BHTC2011 August 24-26, 2011 in Tampere, Finland ISBN 978-.
Open this publication in new window or tab >>Conduction and convection heat transfer for aluminum ingot in preheating furnace
Show others...
2011 (English)In: Proceedings of 6th Baltic Heat Transfer Conference 2011 / [ed] Reijo Karvinen & Matti Lindstedt, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Aluminium is a widely used material, which is found in a number of products e.g. thin aluminium bands that is the base material in many heat exchangers. Rolling processes are used to produce these thin aluminium bands, in order to get the right properties and to get the aluminium easier to roll, heat treatment is needed. This heat treatment of aluminium ingots prior to the rolling is in focus in this work, where computational fluid dynamics and computational heat transfer techniques is used to predict the heating process in a hot air pre-heating furnace. The used approach includes steady state computational fluid dynamics simulations combined with transient computational heat transfer simulations. The simulation results in form of spatial and temporal distributed aluminium ingot temperature was compared with temperature measurement in a thermocouple prepared ingot in the actual pre-heating furnace. Simulation results correspond well with the measurements and there are small differences. Results of the described simulation approach open the possibility to predict spatial and temporal temperature distribution in these kinds of pre-heating processes.

Keywords
CFD, CHT, Heat transfer
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-73617 (URN)978-952-15-2639-8 (ISBN)978-952-15-2638-1 (ISBN)978-952-15-2640-4 (ISBN)
Conference
Proceedings of 6th Baltic Heat Transfer Conference 2011 – BHTC2011 August 24-26, 2011 in Tampere, Finland ISBN 978-
Available from: 2012-01-10 Created: 2012-01-10 Last updated: 2016-03-14
Wren, J. & Renner, J. (2011). Enhancing Student Engagement – A CDIO Approach in anEngineering Physics Master Program. In: Natascha van Hattum-Janssen Rui M. Lima Dinis Carvalho (Ed.), Third International Symposium on Project Approaches in Engineering Education (PAEE’2011):Aligning Engineering Education with Engineering Challenges. Paper presented at Third International Symposium on Project Approaches in Engineering Education (PAEE’2011) (pp. 283-289).
Open this publication in new window or tab >>Enhancing Student Engagement – A CDIO Approach in anEngineering Physics Master Program
2011 (English)In: Third International Symposium on Project Approaches in Engineering Education (PAEE’2011):Aligning Engineering Education with Engineering Challenges / [ed] Natascha van Hattum-Janssen Rui M. Lima Dinis Carvalho, 2011, p. 283-289Conference paper, Published paper (Refereed)
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-73560 (URN)978-989-8525-05-5 (ISBN)
Conference
Third International Symposium on Project Approaches in Engineering Education (PAEE’2011)
Available from: 2012-01-13 Created: 2012-01-09 Last updated: 2012-01-13Bibliographically approved
Organisations

Search in DiVA

Show all publications