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Silk-based nerve guidance conduits with macroscopic holes modulate the vascularization of regenerating rat sciatic nerve

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Neural Regeneration Research 2025年第6期20卷 1789-1800页

作者： Carina Hromada Patrick Heimel Markus Kerbl Lászlógál Sylvia Nürnberger Barbara Schaedl James Ferguson Nicole Swiadek Xavier Monforte Johannes C.Heinzel Antal Nógrádi Andreas H.Teuschl-Woller David Hercher Department Life Science Engineering University of Applied Sciences Technikum WienViennaAustria Austrian Cluster for Tissue Regeneration ViennaAustria Ludwig Boltzmann Institute for Traumatology The Research Center in Cooperation with AUVAViennaAustria University Clinic of Dentistry Medical University of ViennaViennaAustria Department of Plastic Reconstructive and Aesthetic SurgeryLandesklinikum Wiener Neustadt2700 Wiener NeustadtAustria Department of Anatomy Histology and EmbryologyAlbert Szent-Györgyi Medical SchoolUniversity of SzegedSzegedHungary Medical University of Vienna Department of Orthopedics and Trauma SurgeryDevision of Trauma SurgeryViennaAustria Department of Hand- PlasticReconstructive and Burn SurgeryBG Unfallklinik TuebingenUniversity of TuebingenTuebingenGermany

Peripheral nerve injuries induce a severe motor and sensory deficit. Since the availability of autologous nerve transplants for nerve repair is very limited, alternative treatment strategies are sought, including the use of tubular nerve guidance conduits(tNgCs). However, the use of tNgCs results in poor functional recovery and central necrosis of the regenerating tissue, which limits their application to short nerve lesion defects(typically shorter than 3 cm). given the importance of vascularization in nerve regeneration, we hypothesized that enabling the growth of blood vessels from the surrounding tissue into the regenerating nerve within the tNgC would help eliminate necrotic processes and lead to improved regeneration. In this study, we reported the application of macroscopic holes into the tubular walls of silk-based tNgCs and compared the various features of these improved silk^(+) tNgCs with the tubes without holes(silk^(–) tNgCs) and autologous nerve transplants in an 8-mm sciatic nerve defect in rats. Using a combination of micro-computed tomography and histological analyses, we were able to prove that the use of silk^(+) tNgCs induced the growth of blood vessels from the adjacent tissue to the intraluminal neovascular formation. A significantly higher number of blood vessels in the silk^(+) group was found compared with autologous nerve transplants and silk^(–), accompanied by improved axon regeneration at the distal coaptation point compared with the silk^(–) tNgCs at 7 weeks postoperatively. In the 15-mm(critical size) sciatic nerve defect model, we again observed a distinct ingrowth of blood vessels through the tubular walls of silk^(+) tNgCs, but without improved functional recovery at 12 weeks postoperatively. Our data proves that macroporous tNgCs increase the vascular supply of regenerating nerves and facilitate improved axonal regeneration in a short-defect model but not in a critical-size defect model. This study suggests that further optimizatio

关键词： axon regeneration blood vessel functional recovery macroporous nerve lesion peripheral nerve repair sciatic nerve silk-based nerve guidance conduit vascularization

Flow-Field Analysis of Anti-Kidney Vortex Film Cooling

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Journal of Thermal Science 2012年第1期21卷 66-76页

作者： Lars grf Leonhard Kleiser Institute of Fluid Dynamics

Film cooling is an important measure to enable an increase of the inlet temperature of a gas turbine and, thereby, to improve its overall efficiency. The coolant is ejected through spanwise rows of holes in the blades or endwalls to build up a film shielding the material. The holes often are inclined in the downstream direction and give rise to a kidney vortex. This is a counter-rotating vortex pair, with an upward flow direction between the two vortices, which tends to lift off the surface and to locally feed hot air towards the blade outside the pair. Reversing the rotational sense of the vortices reverses these two drawbacks into advantages. In the considered case, an anti-kidney vortex is generated using two subsequent rows of holes both inclined downstream and yawed spanwise with alternating angles. In a previous study, we performed large-eddy simulations (which focused on the fully turbulent boundary layer) of this anti-kidney vortex film-cooling and compared them to a corresponding physical experiment. The present work analyzes the simulated flow field in detail, beginning in the plenum (inside the blade or endwall) through the holes up to the mixture with the hot boundary layer. To identify the vortical structures found in the mean flow and in the instantaneous flow, we mostly use the λ 2 criterion and the line integral convolution (LIC) technique indicating sectional streamlines. The flow regions (coolant plenum, holes, and boundary layer) are studied subsequently and linked to each other. To track the anti-kidney vortex throughout the boundary layer, we propose two criteria which are based on vorticity and on LIC results. This enables us to associate the jet vortices with the cooling effectiveness at the wall, which is the key feature of film cooling.

关键词： Film cooling anti-kidney vortex vortex identification trajectory tracking large-eddy simulation LES compound angle double row kidney vortex jet in cross-flow.

Two-flux method for radiation heat transfer in anisotropic gas-particles media

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Science China(Technological Sciences) 2004年第6期47卷 625-640页

作者： WANg Fei CEN Kefa T.girasole A.garo g.gréhan YAN Jianhua Institute for Thermal Power Engineering Zhejiang UniversityHangzhou 310027China LESP UMR 6614/CORIACNRSUniversitéet INSA de RouenBP1276801Saint Etienne du RouvrayFrance

Two-flux method can be used, as a simplification for the radiative heat transfer, to predict heat flux in a slab consisting of gas and particles. In the original two-flux method (Schuster, 1905 and Schwarzschild, 1906), the radiation field was assumed to be isotropic. But for gas-particles mixture in combustion environments, the scatterings of particles are usually anisotropic, and the original two-flux method gives critical errors when ignoring this anisotropy. In the present paper, a multilayer four-flux model developed by Rozé et al. (2001) is extended to calculate the radiation heat flux in a slab containing participating particles and gas mixture. The analytic resolution of the radiative transfer equation in the framework of a two-flux approach is presented. The average crossing parameter ε and the forward scattering ratio ζ are defined to describe the anisotropy of the radiative field. To validate the model, the radiation transfer in a slab has been computed. Comparisons with the exact analytical result of Modest (1993) and the original two-flux model show the exactness and the improvement. The emissivity of a slab containing flyash/CO2/H2O mixture is obtained using the new model. The result is identical with that of goodwin (1989).

关键词： radiative transfer two-flux anisotropic

Fast laser surface texturing of spherical samples to improve the frictional performance of elasto-hydrodynamic lubricated contacts

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Friction 2021年第5期9卷 1227-1241页

作者： g.BOIDI P.g.grÜTZMACHER A.KADIRIC F.J.PROFITO I.F.MACHADO C.gACHOT D.DINI Department of Mechanical Engineering Imperial College LondonSouth Kensington CampusLondon SW72AZUK AC2T research gmbH Wiener Neustadt 2700Austria Polytechnic School University of São Paulo–USPSão Paulo 05508-030Brazil Department of Engineering Design and Product Development TU WienWien 1060Austria Department of Material Science and Engineering Saarland UniversitySaarbrücken 66123Germany

Textured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure,fluid uptake,or acting as oil or debris ***,texturing techniques often require additional manufacturing steps and costs,thus frequently being not economically feasible for real engineering *** experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances.A femtosecond pulsed laser(Ti:Sapphire)and direct laser interference patterning(with a solid‐state Nd:YAg laser)were used for manufacturing dimple and groove patterns on curved steel surfaces(ball samples).Tribological tests were carried out under elasto‐hydrodynamic lubricated contact conditions varying slide‐roll ratio using a ball‐on‐disk ***,a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured *** steel samples were used to obtain data for the reference *** results showed that dimples promoted friction reduction(up to 20%)compared to the reference smooth specimens,whereas grooves generally caused less beneficial or detrimental *** addition,dimples promoted the formation of full film lubrication conditions at lower *** study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

关键词： surface laser texturing elasto‐hydrodynamic lubrication bearings friction film thickness

Pulsed export of carbon in the north-western Mediterranean Sea

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Journal of Oceanology and Limnology 2023年第1期41卷 189-202页

作者： Michel DENIS Dominique LEFEVRE Melilotus THYSSEN Ian RJENKINSON gérald gr.gORI Aix Marseille Université Universitéde ToulonCNRS/INSUIRDInstitut Méditerranéen d'Océanologie(MIO)Marseille cedex09 13288France Key Laboratory of Marine Ecology and Environmental Sciences Institute of OceanologyChinese Academy of SciencesQingdao 266071China Agency for Consultation and Research in Oceanography Lavergne19320 La Roche CanillacFrance

The short term(hourly scale)variability of heterotrophic prokaryote(HP)vertical distribution and respiratory activity,was investigated in the north-western(NW)Mediterranean *** vertical distribution was determined on board by flow cytometry analysis of seawater samples collected by series of CTD *** counts and viability were determined for all *** respiratory rates were determined later in the laboratory from filtered seawater samples(23 dm^(3))from 300-1150-m *** average cell viability was 94.8%±2.2%(n=240).There was no accumulation of dead cells,due to quick decay of damaged *** the epipelagic layer,three HP groups were distinguished,two(HNA1,HNA2)who se cells exhibited a high nucleic acid content and one(LNA)with low nucleic acid content ***2 was most populated at 50 m but not detected at 90 m and below,presumably aerobic anoxygenic photoheterotrophic bacteria(AAPs).The variability in HP abundance was mainly confined in the upper 80 m.A few secondary peaks of HP abundance were observed(80-150 m)in connection with abundance troughs in the surface *** cells were continuously present in a wide layer around 500 m(mean 191×10^(3)cells/cm^(3)).Below this layer,HP abundance randomly exhibited peaks,coupled to respiratory rate *** HP abundance and variability in the water column was suppressed during a strong wind *** observed sporadic variability was tentatively interpreted through a pulsed carbon-export mechanism induced by the microorganism production of dissolved poly saccharide s,followed by flocculation and rapid *** mechanism would thus contribute to(ⅰ)preventing organic matter accumulation in the epipelagic layer,(ⅱ)seeding the water column with live HP cells,and(ⅲ)supplying the aphotic water column with fre sh and labile organic *** important vertical flux mechanism needs further observations and modelling.

关键词： north-western Mediterranean Sea heterotrophic prokaryote(HP) cell viability cell respiration transparent exopolymeric particle(TEP) aggr.gation flow cytometry

gut hormones, and short bowel syndrome: The enigmatic role of glucagon-like peptide-2 in the regulation of intestinal adaptation

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World Journal of gastroenterology 2006年第26期12卷 4117-4129页

作者： gr Martin PL Beck DL Sigalet University of Calgary gastrointestinal Research group CalgaryAlberta T2N 4N1Canada

Short bowel syndrome （SBS） refers to the malabsorption of nutrients, water, and essential vitamins as a result of disease or surgical removal of parts of the small intestine. The most common reasons for removing part of the small intestine are due to surgical intervention for the treatment of either Crohn＇s disease or necrotizing enterocolitis. Intestinal adaptation following resection may take weeks to months to be achieved, thus nutritional support requires a variety of therapeutic measures, which include parenteral nutrition. Improper nutrition management can leave the SBS patient malnourished and/or dehydrated, which can be life threatening. The development of therapeutic strategies that reduce both the complications and medical costs associated with SBS/long-term parenteral nutrition while enhancing the intestinal adaptive response would be valuable. Currently, therapeutic options available for the treatment of SBS are limited. There are many potential stimulators of intestinal adaptation including peptide hormones, growth factors, and neuronally-derived components. glucagon-like peptide-2 （gLP-2） is one potential treatment for gastrointestinal disorders associated with insufficient mucosal function. A significant body of evidence demonstrates that gLP-2 is atrophic hormone that plays an important role in controlling intestinal adaptation. Recent data from clinical trials demonstrate that gLP-2 is safe, well-tolerated, and promotes intestinal growth in SBS patients. However, the mechanism of action and the localization of the glucagon-like peptide-2 receptor （gLP-2R） remains an enigma. This review summarizes the role of a number of mucosal-derived factors that might be involved with intestinal adaptation processes; however, this discussion primarily examines the physiology, mechanism of action, and utility of gLP-2 in the regulation of intestinal mucosal growth.

关键词： Short bowel syndrome glucagon-likepeptide-2 Epidermal growth factor Insulin-like growthfactor-I Parenteral nutrition Total parenteral nutrition Intestinal adaptation Intestinal mucosa gut hormones Enteric nervous system

Does size matter for resection of giant versus non-giant hepatocellular carcinoma?A meta-analysis

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World Journal of gastrointestinal Surgery 2023年第2期15卷 273-286页

作者： Aaron JL Lee Andrew gr Wu Kuo Chao Yew Vishal g Shelat Lee Kong Chian School of Medicine Nanyang Technological UniversitySingapore 308232Singapore Yong Loo Lin School of Medicine National University of SingaporeSingapore 117597Singapore Department of gastroenterology and Hepatology Tan Tock Seng HospitalSingapore 308433Singapore Department of Hepato-Pancreatico-Biliary Surgery Tan Tok Seng HospitalSingapore 308433Singapore

BACKgrOUND Research on long-term survival after resection of giant(≥10 cm)and non-giant hepatocellular carcinoma(HCC)(<10 cm)has produced conflicting *** This study aimed to investigate whether oncological outcomes a... 详细信息

BACKgrOUND Research on long-term survival after resection of giant(≥10 cm)and non-giant hepatocellular carcinoma(HCC)(g *** This study aimed to investigate whether oncological outcomes and safety profiles of resection differ between giant and non-giant *** PubMed,MEDLINE,EMBASE,and Cochrane databases were *** designed to investigate the outcomes of giant vs non-giant HCC were *** primary endpoints were overall survival(OS)and disease-free survival(DFS).The secondary endpoints were postoperative complications and mortality *** studies were assessed for bias using the Newcastle–Ottawa *** 24 retrospective cohort studies involving 23747 patients(giant=3326;non-giant=20421)who underwent HCC resection were *** was reported in 24 studies,DFS in 17 studies,30-d mortality rate in 18 studies,postoperative complications in 15 studies,and post-hepatectomy liver failure(PHLF)in six *** HR was significantly lower for non-giant HCC in both OS(HR 0.53,95%CI:0.50-0.55,Pgnificant difference was found for 30-d mortality rate(OR 0.73,95%CI:0.50-1.08,P=0.116),postoperative complications(OR 0.81,95%CI:0.62-1.06,P=0.140),and PHLF(OR 0.81,95%CI:0.62-1.06,P=0.140).CONCLUSION Resection of giant HCC is associated with poorer long-term *** safety profile of resection was similar in both groups;however,this may have been confounded by reporting *** staging systems should account for the size differences.

关键词： Hepatectomy giant hepatocellular carcinoma Resection Meta-analysis

Simultaneous 3D temperature and velocity field measurements of micro-flow with laser-induced fluorescence and micro-digital holographic particle tracking velocimetry: Numerical study

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Chinese Optics Letters 2015年第7期13卷 105-109页

作者：姚龙超吴学成阳静吴迎春高翔陈玲红 gérard gréhan 岑可法 State Key Laboratory of Clean Energy Utilization Zhejiang University UMR 6614/CORIA CNRS Normandie Université

We propose a method for simultaneous 3D temperature and velocity measurement of a micro-flow field. The 3D temperature field is characterized with two-color laser-induced fluorescence particles which are tracked with micro-digital holographic particle tracking velocimetry. A diffraction-based model is applied to analyze defo- cused particles to determine the intensity ratio of two fluorescent dyes on the particle. The model is validated with experimental images. As the result shows that the intensity ratio nearly remains unchanged with respect to depth positions, defocused particles can be used as 3D temperature sensors. Numerical work is carried out to check the method, and 3D temperature and velocity field in a 120 μm × 120 μm× 80 μm test volume are retrieved.

关键词： Fluorescence Holography Laser optics Laser produced plasmas Numerical methods Velocimeters Velocity

Context-aware reinforcement learning for cooling operation of data centers with an Aquifer Thermal Energy Storage

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Energy and AI

Energy and AI 2024年第3期17卷 233-246页

作者： Lukas Leindals Peter grønning Dominik Franjo Dominković Rune grønborg Junker Department of Applied Mathematics and Computer Science Technical University of DenmarkDenmark

Data centers are often equipped with multiple cooling units. Here, an aquifer thermal energy storage (ATES) system has shown to be efficient. However, the usage of hot and cold-water wells in the ATES must be balanced for legal and environmental reasons. Reinforcement Learning has been proven to be a useful tool for optimizing the cooling operation at data centers. Nonetheless, since cooling demand changes continuously, balancing the ATES usage on a yearly basis imposes an additional challenge in the form of a delayed reward. To overcome this, we formulate a return decomposition, Cool-RUDDER, which relies on simple domain knowledge and needs no training. We trained a proximal policy optimization agent to keep server temperatures steady while minimizing operational costs. Comparing the Cool-RUDDER reward signal to other ATES-associated rewards, all models kept the server temperatures steady at around 30 °C. An optimal ATES balance was defined to be 0% and a yearly imbalance of −4.9% with a confidence interval of [−6.2, −3.8]% was achieved for the Cool 2.0 reward. This outperformed a baseline ATES-associated reward of 0 at −16.3% with a confidence interval of [−17.1, −15.4]% and all other ATES-associated rewards. However, the improved ATES balance comes with a higher energy consumption cost of 12.5% when comparing the relative cost of the Cool 2.0 reward to the zero reward, resulting in a trade-off. Moreover, the method comes with limited requirements and is applicable to any long-term problem satisfying a linear state-transition system.

关键词： Data centers ATES Smart energy systems Reinforcement learning Delayed rewards