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  Subjects -> BIOLOGY (Total: 3206 journals)
    - BIOCHEMISTRY (242 journals)
    - BIOENGINEERING (119 journals)
    - BIOLOGY (1533 journals)
    - BIOPHYSICS (49 journals)
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    - BOTANY (236 journals)
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    - MICROSCOPY (10 journals)
    - ORNITHOLOGY (27 journals)
    - PHYSIOLOGY (73 journals)
    - ZOOLOGY (142 journals)

BIOLOGY (1533 journals)                  1 2 3 4 5 6 7 8 | Last

Showing 1 - 200 of 1720 Journals sorted alphabetically
AAPS Journal     Hybrid Journal   (Followers: 23)
Achievements in the Life Sciences     Open Access   (Followers: 5)
ACS Synthetic Biology     Hybrid Journal   (Followers: 25)
Acta Biologica Colombiana     Open Access   (Followers: 7)
Acta Biologica Hungarica     Full-text available via subscription   (Followers: 4)
Acta Biologica Sibirica     Open Access   (Followers: 2)
Acta Biologica Turcica     Open Access  
Acta Biomaterialia     Hybrid Journal   (Followers: 27)
Acta Biotheoretica     Hybrid Journal   (Followers: 4)
Acta Chiropterologica     Full-text available via subscription   (Followers: 6)
acta ethologica     Hybrid Journal   (Followers: 4)
Acta Fytotechnica et Zootechnica     Open Access   (Followers: 1)
Acta Limnologica Brasiliensia     Open Access   (Followers: 3)
Acta Médica Costarricense     Open Access   (Followers: 2)
Acta Musei Silesiae, Scientiae Naturales     Open Access  
Acta Neurobiologiae Experimentalis     Open Access  
Acta Parasitologica     Hybrid Journal   (Followers: 11)
Acta Scientiarum. Biological Sciences     Open Access   (Followers: 2)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis     Open Access   (Followers: 1)
Actualidades Biológicas     Open Access   (Followers: 1)
Advanced Health Care Technologies     Open Access   (Followers: 4)
Advanced Journal of Graduate Research     Open Access  
Advanced Nonlinear Studies     Hybrid Journal  
Advanced Studies in Biology     Open Access  
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Bioinformatics     Open Access   (Followers: 17)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4)
Advances in Biology     Open Access   (Followers: 9)
Advances in Biosensors and Bioelectronics     Open Access   (Followers: 7)
Advances in Cell Biology/ Medical Journal of Cell Biology     Open Access   (Followers: 26)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 13)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Ecological Research     Full-text available via subscription   (Followers: 44)
Advances in Environmental Sciences - International Journal of the Bioflux Society     Open Access   (Followers: 16)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10)
Advances in High Energy Physics     Open Access   (Followers: 19)
Advances in Human Biology     Open Access   (Followers: 4)
Advances in Life Science and Technology     Open Access   (Followers: 17)
Advances in Life Sciences     Open Access   (Followers: 6)
Advances in Marine Biology     Full-text available via subscription   (Followers: 18)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3)
Advances in Regenerative Biology     Open Access   (Followers: 1)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Tropical Biodiversity and Environmental Sciences     Open Access  
Advances in Virus Research     Full-text available via subscription   (Followers: 5)
African Journal of Range & Forage Science     Hybrid Journal   (Followers: 8)
AFRREV STECH : An International Journal of Science and Technology     Open Access   (Followers: 1)
Ageing Research Reviews     Hybrid Journal   (Followers: 11)
Aging Cell     Open Access   (Followers: 20)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Agrokreatif Jurnal Ilmiah Pengabdian kepada Masyarakat     Open Access  
AJP Cell Physiology     Hybrid Journal   (Followers: 18)
AJP Endocrinology and Metabolism     Hybrid Journal   (Followers: 24)
AJP Lung Cellular and Molecular Physiology     Hybrid Journal   (Followers: 3)
Al-Kauniyah : Jurnal Biologi     Open Access  
Alasbimn Journal     Open Access   (Followers: 1)
Alces : A Journal Devoted to the Biology and Management of Moose     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Biology Teacher     Full-text available via subscription   (Followers: 14)
American Fern Journal     Full-text available via subscription   (Followers: 1)
American Journal of Agricultural and Biological Sciences     Open Access   (Followers: 8)
American Journal of Bioethics     Hybrid Journal   (Followers: 13)
American Journal of Human Biology     Hybrid Journal   (Followers: 14)
American Journal of Medical and Biological Research     Open Access   (Followers: 8)
American Journal of Plant Sciences     Open Access   (Followers: 19)
American Journal of Primatology     Hybrid Journal   (Followers: 16)
American Malacological Bulletin     Full-text available via subscription   (Followers: 3)
American Naturalist     Full-text available via subscription   (Followers: 76)
Amphibia-Reptilia     Hybrid Journal   (Followers: 6)
Anadol University Journal of Science and Technology B : Theoritical Sciences     Open Access  
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access  
Anaerobe     Hybrid Journal   (Followers: 4)
Analytical Methods     Full-text available via subscription   (Followers: 11)
Anatomical Science International     Hybrid Journal   (Followers: 3)
Animal Cells and Systems     Hybrid Journal   (Followers: 4)
Animal Models and Experimental Medicine     Open Access  
Annales de Limnologie - International Journal of Limnology     Hybrid Journal   (Followers: 1)
Annales françaises d'Oto-rhino-laryngologie et de Pathologie Cervico-faciale     Full-text available via subscription   (Followers: 3)
Annales Henri Poincaré     Hybrid Journal   (Followers: 3)
Annals of Applied Biology     Hybrid Journal   (Followers: 7)
Annals of Biomedical Engineering     Hybrid Journal   (Followers: 17)
Annals of Human Biology     Hybrid Journal   (Followers: 5)
Annals of Science and Technology     Open Access  
Annual Review of Biomedical Engineering     Full-text available via subscription   (Followers: 13)
Annual Review of Biophysics     Full-text available via subscription   (Followers: 23)
Annual Review of Cancer Biology     Full-text available via subscription   (Followers: 2)
Annual Review of Cell and Developmental Biology     Full-text available via subscription   (Followers: 37)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Annual Review of Genomics and Human Genetics     Full-text available via subscription   (Followers: 25)
Annual Review of Phytopathology     Full-text available via subscription   (Followers: 12)
Anthropological Review     Open Access   (Followers: 23)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antibiotics     Open Access   (Followers: 9)
Antioxidants     Open Access   (Followers: 4)
Antioxidants & Redox Signaling     Hybrid Journal   (Followers: 8)
Antonie van Leeuwenhoek     Hybrid Journal   (Followers: 5)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apidologie     Hybrid Journal   (Followers: 4)
Apmis     Hybrid Journal   (Followers: 1)
APOPTOSIS     Hybrid Journal   (Followers: 9)
Applied Biology     Open Access  
Applied Bionics and Biomechanics     Open Access   (Followers: 7)
Applied Vegetation Science     Full-text available via subscription   (Followers: 10)
Aquaculture Environment Interactions     Open Access   (Followers: 4)
Aquaculture International     Hybrid Journal   (Followers: 26)
Aquaculture Reports     Open Access   (Followers: 3)
Aquaculture, Aquarium, Conservation & Legislation - International Journal of the Bioflux Society     Open Access   (Followers: 7)
Aquatic Biology     Open Access   (Followers: 6)
Aquatic Ecology     Hybrid Journal   (Followers: 36)
Aquatic Ecosystem Health & Management     Hybrid Journal   (Followers: 15)
Aquatic Science and Technology     Open Access   (Followers: 3)
Aquatic Toxicology     Hybrid Journal   (Followers: 23)
Archaea     Open Access   (Followers: 3)
Archiv für Molluskenkunde: International Journal of Malacology     Full-text available via subscription   (Followers: 3)
Archives of Biological Sciences     Open Access  
Archives of Microbiology     Hybrid Journal   (Followers: 9)
Archives of Natural History     Hybrid Journal   (Followers: 7)
Archives of Oral Biology     Hybrid Journal   (Followers: 3)
Archives of Virology     Hybrid Journal   (Followers: 5)
Archivum Immunologiae et Therapiae Experimentalis     Hybrid Journal   (Followers: 2)
Arid Ecosystems     Hybrid Journal   (Followers: 2)
Arquivos do Instituto Biológico     Open Access   (Followers: 1)
Arquivos do Museu Dinâmico Interdisciplinar     Open Access  
Arthropod Structure & Development     Hybrid Journal   (Followers: 2)
Arthropods     Open Access   (Followers: 1)
Artificial DNA: PNA & XNA     Hybrid Journal   (Followers: 3)
Asian Bioethics Review     Full-text available via subscription   (Followers: 3)
Asian Journal of Biodiversity     Open Access   (Followers: 4)
Asian Journal of Biological Sciences     Open Access   (Followers: 3)
Asian Journal of Cell Biology     Open Access   (Followers: 5)
Asian Journal of Developmental Biology     Open Access   (Followers: 2)
Asian Journal of Medical and Biological Research     Open Access   (Followers: 4)
Asian Journal of Nematology     Open Access   (Followers: 4)
Asian Journal of Poultry Science     Open Access   (Followers: 4)
Atti della Accademia Peloritana dei Pericolanti - Classe di Scienze Medico-Biologiche     Open Access  
Australian Life Scientist     Full-text available via subscription   (Followers: 2)
Australian Mammalogy     Hybrid Journal   (Followers: 6)
Autophagy     Hybrid Journal   (Followers: 3)
Avian Biology Research     Full-text available via subscription   (Followers: 4)
Avian Conservation and Ecology     Open Access   (Followers: 11)
Bacteriology Journal     Open Access   (Followers: 1)
Bacteriophage     Full-text available via subscription   (Followers: 3)
Bangladesh Journal of Bioethics     Open Access  
Bangladesh Journal of Plant Taxonomy     Open Access  
Bangladesh Journal of Scientific Research     Open Access   (Followers: 1)
Batman Üniversitesi Yaşam Bilimleri Dergisi     Open Access  
Berita Biologi     Open Access   (Followers: 1)
Between the Species     Open Access   (Followers: 1)
Bio Tribune Magazine     Hybrid Journal  
BIO Web of Conferences     Open Access  
BIO-Complexity     Open Access  
Bio-Grafía. Escritos sobre la Biología y su enseñanza     Open Access  
Bioanalytical Reviews     Hybrid Journal   (Followers: 2)
Biocatalysis and Biotransformation     Hybrid Journal   (Followers: 6)
BioCentury Innovations     Full-text available via subscription   (Followers: 1)
Biochemistry and Cell Biology     Hybrid Journal   (Followers: 16)
Biochimie     Hybrid Journal   (Followers: 7)
BioControl     Hybrid Journal   (Followers: 5)
Biocontrol Science and Technology     Hybrid Journal   (Followers: 5)
Biodemography and Social Biology     Hybrid Journal  
BioDiscovery     Open Access   (Followers: 2)
Biodiversidade e Conservação Marinha : Revista CEPSUL     Open Access  
Biodiversitas : Journal of Biological Diversity     Open Access  
Biodiversity Data Journal     Open Access   (Followers: 4)
Biodiversity Informatics     Open Access   (Followers: 1)
Biodiversity Information Science and Standards     Open Access  
Biodiversity: Research and Conservation     Open Access   (Followers: 27)
Bioedukasi : Jurnal Pendidikan Biologi FKIP UM Metro     Open Access  
Bioeksperimen : Jurnal Penelitian Biologi     Open Access  
Bioelectrochemistry     Hybrid Journal   (Followers: 2)
Bioelectromagnetics     Hybrid Journal   (Followers: 1)
Bioenergy Research     Hybrid Journal   (Followers: 3)
Bioengineering and Bioscience     Open Access   (Followers: 1)
BioEssays     Hybrid Journal   (Followers: 10)
Bioethics     Hybrid Journal   (Followers: 15)
BioéthiqueOnline     Open Access  
Biofabrication     Hybrid Journal   (Followers: 4)
Biofilms     Full-text available via subscription   (Followers: 1)
Biogeosciences (BG)     Open Access   (Followers: 9)
Biogeosciences Discussions (BGD)     Open Access   (Followers: 2)
Bioinformatics     Hybrid Journal   (Followers: 324)
Bioinformatics and Biology Insights     Open Access   (Followers: 11)
Bioinspiration & Biomimetics     Hybrid Journal   (Followers: 7)
Biointerphases     Open Access   (Followers: 1)
Biojournal of Science and Technology     Open Access  
BioLink : Jurnal Biologi Lingkungan, Industri, Kesehatan     Open Access   (Followers: 1)
Biologia     Hybrid Journal  
Biologia on-line : Revista de divulgació de la Facultat de Biologia     Open Access  
Biological Bulletin     Partially Free   (Followers: 6)
Biological Control     Hybrid Journal   (Followers: 4)
Biological Invasions     Hybrid Journal   (Followers: 22)
Biological Journal of the Linnean Society     Hybrid Journal   (Followers: 18)

        1 2 3 4 5 6 7 8 | Last

Journal Cover
Annals of Biomedical Engineering
Journal Prestige (SJR): 1.042
Citation Impact (citeScore): 3
Number of Followers: 17  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-9686 - ISSN (Online) 0090-6964
Published by Springer-Verlag Homepage  [2352 journals]
  • Pulse Arrival Time and Pulse Interval as Accurate Markers to Detect
           Mechanical Alternans
    • Authors: Stefan van Duijvenboden; Ben Hanson; Nick Child; Pier D. Lambiase; Christopher A. Rinaldi; Gill Jaswinder; Peter Taggart; Michele Orini
      Abstract: Mechanical alternans (MA) is a powerful predictor of adverse prognosis in patients with heart failure and cardiomyopathy, but its use remains limited due to the need of invasive continuous arterial pressure recordings. This study aims to assess novel cardiovascular correlates of MA in the intact human heart to facilitate affordable and non-invasive detection of MA and advance our understanding of the underlying pathophysiology. Arterial pressure, respiration, and ECG were recorded in 12 subjects with healthy ventricles during voluntarily controlled breathing at different respiratory rate, before and after administration of beta-blockers. MA was induced by ventricular pacing. A total of 67 recordings lasting approximately 90 s each were analyzed. Mechanical alternans (MA) was measured in the systolic blood pressure. We studied cardiovascular correlates of MA, including maximum pressure rise during systole (dPdtmax), pulse arrival time (PAT), pulse wave interval (PI), RR interval (RRI), ECG QRS complexes and T-waves. MA was detected in 30% of the analyzed recordings. Beta-blockade significantly reduced MA prevalence (from 50 to 11%, p < 0.05). Binary classification showed that MA was detected by alternans in dPdtmax (100% sens, 96% spec), PAT (100% sens, 81% spec) and PI (80% sens, 81% spec). Alternans in PAT and in PI also showed high degree of temporal synchronization with MA (80 ± 33 and 73 ± 40%, respectively). These data suggest that cardiac contractility is a primary factor in the establishment of MA. Our findings show that MA was highly correlated with invasive measurements of PAT and PI. Since PAT and PI can be estimated using non-invasive technologies, these markers could potentially enable affordable MA detection for risk-prediction.
      PubDate: 2019-02-12
      DOI: 10.1007/s10439-019-02221-4
       
  • A How-To Guide for Promoting Diversity and Inclusion in Biomedical
           Engineering
    • Authors: Naomi C. Chesler
      Abstract: To accelerate the development of an inclusive culture in biomedical engineering (BME), we must accept complexity, seek to understand our own privilege, speak out about diversity, learn the difference between intent and impact, accept our mistakes, and learn how to engage in difficult conversations. In turn, we will be rewarded by the ideas, designs, devices and discoveries of a new generation of problem solvers and thought leaders who bring diverse experiences and perspectives.
      PubDate: 2019-02-11
      DOI: 10.1007/s10439-019-02223-2
       
  • Probing the Depth of the Myocardium: Vasculature, Transit Time, and
           Perfusion Within the Left Ventricular Wall
    • Authors: Erik L. Ritman; A. J. Vercnocke; M. Zamir
      Abstract: The branching architecture of arterial trees traversing the thickness of the left ventricular wall is studied to determine the way in which adequate blood supply is provided to myocardial tissue at different depths within the wall thickness from arterial trees originating at the epicardial surface. The study is based on micro-CT images of tissue biopsies, coupled with a dedicated vascular tree analysis program. The results show that this combination of methodologies allows a more detailed and much more accurate exploration of the vasculature within the sampled tissue than is possible by histological means. The spatial density of the smallest resolvable “end” arterioles is found to be higher in the sub-endocardial region than in the sub-epicardial region, with vascular branching architecture consistent with a fractal structure. The concept of “transit time” is introduced as an approximate measure of the time it takes bulk flow to reach different regions of the myocardium. Our data suggest that a transit time differential is a major contributor to the equalization of transmural perfusion gradient against unequal distribution of “end’ arteriolar density.
      PubDate: 2019-02-07
      DOI: 10.1007/s10439-019-02208-1
       
  • IGBT-Based Pulsed Electric Fields Generator for Disinfection: Design and
           In Vitro Studies on Pseudomonas aeruginosa
    • Authors: Andrey Ethan Rubin; Klimenty Levkov; Osman Berk Usta; Martin Yarmush; Alexander Golberg
      Abstract: Irreversible electroporation of cell membrane with pulsed electric fields is an emerging physical method for disinfection that aims to reduce the doses and volumes of used antibiotics for wound healing. Here we report on the design of the IGBT-based pulsed electric field generator that enabled eradication of multidrug resistant Pseudomonas aeruginosa PAO1 on the gel. Using a concentric electric configuration we determined that the lower threshold of the electric field required to kill P. aeruginosa PAO1 was 89.28 ± 12.89 V mm−1, when 200 square pulses of 300 µs duration are delivered at 3 Hz. These parameters disinfected 38.14 ± 0.79 mm2 area around the single needle electrode. This study provides a step towards the design of equipment required for multidrug-resistant bacteria disinfection in patients with pulsed electric fields.
      PubDate: 2019-02-06
      DOI: 10.1007/s10439-019-02225-0
       
  • Mitral Valve Prosthesis Design Affects Hemodynamic Stasis and Shear In The
           Dilated Left Ventricle
    • Authors: Vi Vu; Lorenzo Rossini; Ricardo Montes; Josue Campos; Juyeun Moon; Pablo Martinez-Legazpi; Javier Bermejo; Juan C. del Álamo; Karen May-Newman
      Abstract: Dilated cardiomyopathy produces abnormal left ventricular (LV) blood flow patterns that are linked with thromboembolism (TE). We hypothesized that implantation of mechanical heart valves non-trivially influences TE risk in these patients, exacerbating abnormal LV flow dynamics. The goal of this study was to assess how mitral valve design impacts flow and hemodynamic factors associated with TE. The mid-plane velocity field of a silicone dilated LV model was measured in a mock cardiovascular loop for three different mitral prostheses, two with multiple orientations, and used to characterize LV vortex properties through the cardiac cycle. Blood residence time and a platelet shear activation potential index (SAP) based on the cumulative exposure to shear were also computed. The porcine bioprosthesis (BP) and the bileaflet valve in the anti-anatomical (BL-AA) position produced the most natural flow patterns. The bileaflet valves experienced large shear in the valve hinges and recirculating shear-activated flow, especially in the anatomical (BL-A) and 45-degree (BL-45) positions, thus exhibited high SAP. The tilting disk valve in the septal orientation (TD-S) produced a complete reversal of flow and vortex properties, impairing LV washout and retaining shear-activated fluid, leading to the highest residence time and SAP. In contrast, the tilting disk valve in the free-wall position (TD-F) exhibited mid-range values for residence time and SAP. Hence, the thrombogenic potential of different MHV models and configurations can be collectively ranked from lowest to highest as: BP, BL-AA, TD-F, BL-A, BL-45, and TD-S. These findings provide new insight about the effect of fluid dynamics on LV TE risk, and suggest that the bioprosthesis valve in the mitral position minimizes this risk by producing more physiological flow patterns in patients with dilated cardiomyopathy.
      PubDate: 2019-02-06
      DOI: 10.1007/s10439-019-02218-z
       
  • Spatiotemporal Complexity of the Aortic Sinus Vortex as a Function of
           Leaflet Calcification
    • Authors: Hoda Hatoum; Lakshmi Prasad Dasi
      Abstract: Several studies have shown the variation of aortic sinus structures’ hemodynamics with different flow and geometric characteristics. They have also correlated aortic sinus hemodynamics with the progression and evolution of calcific aortic valve disease (CAVD). This study aims at visualizing aortic sinus fluid structure variations as functions of different leaflet calcification degrees and assessing their potential relationship with CAVD. A degenerated 23 mm Carpentier-Edwards Perimount Magna valve extracted from a redo-surgery patient was implanted in an aortic root model and tested in a pulse duplicator left heart simulator. The valve has 3 leaflets with 3 different levels of calcium distribution: mild, moderate and severe. High-speed imaging and particle image velocimetry were performed to assess sinus vortices, leaflet tip position and velocity along with shear stress. Results have shown that (a) aortic sinus vortices initiation, entrapment and evolution varied with different calcified leaflet exposure; (b) higher velocities in the sinus were calculated with the mildly calcified leaflet compared to the moderately and severely calcified ones; (c) during systole, the mildly calcified leaflet sinus case shows the most spread-out and higher ranges of shear stress probabilities and highest magnitudes going from (− 1.5 to + 1.8 Pa) compared with (− 1.0 to + 1.0 Pa) for moderately and severely calcified leaflets. The higher the calcification degree the lower the shear stress range and likelihoods of having higher shear stress. This holds in diastole as well. This study shows the impact of calcification on the aortic sinus flow structures.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-019-02224-1
       
  • Quantifying Movement in Preterm Infants Using Photoplethysmography
    • Authors: Ian Zuzarte; Premananda Indic; Dagmar Sternad; David Paydarfar
      Abstract: Long-term recordings of movement in preterm infants might reveal important clinical information. However, measurement of movement is limited because of time-consuming and subjective analysis of video or reluctance to attach additional sensors to the infant. We evaluated whether photoplethysmogram (PPG), routinely used for oximetry in preterm infants in the neonatal intensive care unit (NICU), can provide reliable long-term measurements of movement. In 18 infants [mean post-conceptional age (PCA) 31.10 weeks, range 29–34.29 weeks], we designed and tested a wavelet-based algorithm that detects movement signals from the PPG. The algorithm’s performance was optimized relative to subjective assessments of movement using video and accelerometers attached to two limbs and force sensors embedded within the mattress (five infants, three raters). We then applied the optimized algorithm to infants receiving routine care in the NICU without additional sensors. The algorithm revealed a decline in brief movements (< 5 s) with increasing PCA (13 infants, r = − 0.87, p < 0.001, PCA range 27.3–33.9 weeks). Our findings suggest that quantitative relationships between motor activity and clinical outcomes in preterm infants can be studied using routine photoplethysmography.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02135-7
       
  • Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve
           Design, Part I: Paravalvular Leakage
    • Authors: Eric L. Pierce; Vahid Sadri; Beatrice Ncho; Keshav Kohli; Siddhi Shah; Ajit P. Yoganathan
      Abstract: While transcatheter mitral valve (TMV) replacement technology has great clinical potential for surgically inoperable patients suffering from mitral regurgitation, no TMV has yet achieved regulatory approval. The diversity of devices currently under development reflects a lack of consensus regarding optimal design approaches. In Part I of this two-part study, a test system was developed for the quantification of paravalvular leakage (PVL) following deployment of a TMV or TMV-like device in pressurized, explanted porcine hearts (N = 7). Using this system, PVL rate was investigated as a function of steady trans-mitral pressure (ΔP), TMV shape, and TMV-annular oversizing, using a series of “mock TMV plug” devices. Across all devices, PVL was found to approximately trend with the square of ΔP. PVL rates were approximately 0–15 mL/s under hypotensive pressure, 10–40 mL/s under normotension, and 30–85 mL/s under severe hypertension. D-shaped devices significantly reduced PVL vs. circular devices; however, this effect was diminished upon oversizing to the annulus by 6 mm inter-trigonal distance. In conclusion, this steady pressure, in vitro test system was effective to compare PVL performance across TMV-like designs. PVL exhibited complex dynamics in terms of its response to transvalvular pressure and TMV profile.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02154-4
       
  • Coupled Modeling of Lipid Deposition, Inflammatory Response and
           Intraplaque Angiogenesis in Atherosclerotic Plaque
    • Authors: Muyi Guo; Yan Cai; Chunliu He; Zhiyong Li
      Abstract: We propose a multiphysical mathematical model by fully coupling lipid deposition, monocytes/macrophages recruitment and angiogenesis to investigate the pathophysiological responses of an atherosclerotic plaque to the dynamic changes in the microenvironment. The time evolutions of cellular (endothelial cells, macrophages, smooth muscle cells, etc.) and acellular components (low density lipoprotein, proinflammatory cytokines, extravascular plasma concentration, etc.) within the plaque microenvironment are assessed quantitatively. The thickening of the intima, the distributions of the lipid and inflammatory factors, and the intraplaque hemorrhage show a qualitative consistency with the MRI and histology data. Models with and without angiogenesis are compared to demonstrate the important role of neovasculature in the accumulation of blood-borne components in the atherosclerotic lesion by extravasation from the leaky vessel wall, leading to the formation of a lipid core and an inflammatory microenvironment, which eventually promotes plaque destabilization. This model can serve as a theoretical platform for the investigation of the pathological mechanisms of plaque progression and may contribute to the optimal design of atherosclerosis treatment strategies, such as lipid-lowering or anti-angiogenetic therapies.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02173-1
       
  • Mesh Convergence Behavior and the Effect of Element Integration of a
           Human Head Injury Model
    • Authors: Wei Zhao; Songbai Ji
      Abstract: Numerous head injury models exist that vary in mesh density by orders of magnitude. A careful study of the mesh convergence behavior is necessary, especially in terms of strain most relevant to brain injury. To this end, as well as to investigate the effect of element integration scheme on simulated strains, we re-meshed the Worcester Head Injury Model at five mesh densities (~ 7.2–1000 k high-quality hexahedral elements of the brain). Results from explicit dynamic simulations of three cadaveric impacts and an in vivo head rotation were compared. First, scalar metrics of the whole brain only considering magnitude were used, including peak maximum principal strain and population-based median strain. They were further extended to deep white matter regions and the entire brain elements, respectively, to form two “response vectors” to account for both magnitude and distribution. Using benchmark enhanced full-integration elements (C3D8I), a minimum of 202.8 k brain elements were necessary to converge for response vectors of the deep white matter regions. This model was further used to simulate with reduced integration (C3D8R). We found that hourglass energy higher than the common rule of thumb (e.g., up to 44.38% vs. < 10% of internal energy) was necessary to maintain comparable strain relative to C3D8I. Based on these results, it is recommended that a human head injury model should have a minimum number of 202.8 k elements, or an average element size of no larger than 1.8 mm, for the brain. C3D8R formulation with relax stiffness hourglass control using a high scaling factor is also recommended to achieve sufficient accuracy without substantial computational cost.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02159-z
       
  • Objective Evaluation of Whole Body Kinematics in a Simulated, Restrained
           Frontal Impact
    • Authors: Jeremy M. Schap; Bharath Koya; F. Scott Gayzik
      Abstract: The use of human body models as an additional data point in the evaluation of human-machine interaction requires quantitative validation. In this study a validation of the Global Human Body Models Consortium (GHBMC) average male occupant model (M50-O v. 4.5) in a restrained frontal sled test environment is presented. For vehicle passengers, frontal crash remains the most common mode, and the most common source of fatalities. A total of 55-time history traces of reaction loads and kinematics from the model were evaluated against corresponding PMHS data (n = 5). Further, the model’s sensitivity to the belt path was studied by replicating two documented PMHS cases with prominent lateral and medial belt paths respectively. Results were quantitatively evaluated using open source CORA software. A tradeoff was observed; better correlation scores were achieved on gross measures (e.g. reaction loads), whereas better corridor scores were achieved on localized measures (rib deflections), indicating that subject specificity may dominate the comparison at localized anatomical regions. On an overall basis, the CORA scores were 0.68, 0.66 and 0.60 for force, body kinematics and chest wall kinematics. Belt force responses received the highest grouped CORA score of 0.85. Head and sternum kinematics earning a 0.8 and 0.7 score respectively. The model demonstrated high sensitivity to belt path, resulting in a 20-point increase in CORA score when the belt was routed closer to analogous location of data collection. The human model demonstrated overall reasonable biofidelity and sensitivity to countermeasures in frontal crash kinematics.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02180-2
       
  • Spatiotemporal Analyses of Cellular Tractions Describe Subcellular Effect
           of Substrate Stiffness and Coating
    • Authors: Alicia Izquierdo-Álvarez; Diego A. Vargas; Álvaro Jorge-Peñas; Ramesh Subramani; Marie-Mo Vaeyens; Hans Van Oosterwyck
      Abstract: Cells interplay with their environment through mechanical and chemical interactions. To characterize this interplay, endothelial cells were cultured on polyacrylamide hydrogels of varying stiffness, coated with either fibronectin or collagen. We developed a novel analysis technique, complementary to traction force microscopy, to characterize the spatiotemporal evolution of cellular tractions: We identified subpopulations of tractions, termed traction foci, and tracked their magnitude and lifetime. Each focus consists of tractions associated with a local single peak of maximal traction. Individual foci were spread over a larger area in cells cultured on collagen relative to those on fibronectin and exerted higher tractions on stiffer hydrogels. We found that the trends with which forces increased with increasing hydrogel stiffness were different for foci and whole-cell measurements. These differences were explained by the number of foci and their average strength. While on fibronectin multiple short-lived weak foci contributed up to 30% to the total traction on hydrogels with intermediate stiffness, short-lived foci in such a number were not observed on collagen despite the higher tractions. Our approach allows for the use of existing traction force microscopy data to gain insight at the subcellular scale without molecular probes or spatial constraining of cellular tractions.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02164-2
       
  • The Atheroprotective Nature of Helical Flow in Coronary Arteries
    • Authors: Giuseppe De Nisco; Annette M. Kok; Claudio Chiastra; Diego Gallo; Ayla Hoogendoorn; Francesco Migliavacca; Jolanda J. Wentzel; Umberto Morbiducci
      Abstract: Arterial hemodynamics is markedly characterized by the presence of helical flow patterns. Previous observations suggest that arterial helical blood flow is of physiological significance, and that its quantitative analysis holds promise for clinical applications. In particular, it has been reported that distinguishable helical flow patterns are potentially atheroprotective in the carotid bifurcation as they suppress flow disturbances. In this context, there is a knowledge gap about the physiological significance of helical flow in coronary arteries, a prominent site of atherosclerotic plaque formation. This study aimed at the quantitative assessment of helical blood flow in coronary arteries, and to investigate its possible associations with vascular geometry and with atherogenic wall shear stress (WSS) phenotypes in a representative sample of 30 swine coronary arteries. This study demonstrates that in coronary arteries: (1) the hemodynamics is characterized by counter-rotating bi-helical flow structures; (2) unfavorable conditions of WSS are strongly and inversely associated with helicity intensity (r = − 0.91; p < 0.001), suggesting an atheroprotective role for helical flow in the coronary tree; (3) vascular torsion dictates helical flow features (r = 0.64; p < 0.001). The findings of this work support future studies on the role of helical flow in atherogenesis in coronary arteries.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02169-x
       
  • The Effect of Material Heterogeneity, Element Type, and Down-Sampling on
           Trabecular Stiffness in Micro Finite Element Models
    • Authors: Nikolas K. Knowles; Kenneth Ip; Louis M. Ferreira
      Abstract: Preclinical and clinical bone strength predictions can be elucidated by understanding bone mechanics at a variety of hierarchical levels. As such, down-sampled micro-CT images are often used to make comparisons across image resolutions or used to reduce computational resources in micro finite element models (µFEMs). Therefore, the objectives of this study were to compare trabecular apparent modulus among (i) hexahedral and tetrahedral µFEMs, (ii) µFEMs generated from 32, 64, and 64 µm down-sampled from 32 µm µCT scans, and (iii) µFEMs with homogeneous and heterogeneous tissue moduli. Trabecular µFEMs were generated from scans at the three spatial resolutions taken from the glenoid vault of 14 cadaveric specimens. Simulated unconstrained compression was performed and used to calculate and compare the apparent modulus of each µFEM. It was found that models derived from high-resolution images that account for material heterogeneity are nearly equivalent whether hexahedral or tetrahedral elements are used. However, translation of stiffness from down-sampled scans are not equivalent to scans performed at the down-sampled resolution, or that account for trabecular material heterogeneity. Material heterogeneity is most representative of in vivo trabecular bone and to accurately model trabecular mechanical properties, material heterogeneity should be considered in future µFEM development.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02152-6
       
  • A Review of Integrin-Mediated Endothelial Cell Phenotype in the Design of
           Cardiovascular Devices
    • Authors: Allison Post; Ellen Wang; Elizabeth Cosgriff-Hernandez
      Abstract: Sustained biomaterial thromboresistance has long been a goal and challenge in blood-contacting device design. Endothelialization is one of the most successful strategies to achieve long-term thromboresistance of blood-contacting devices, with the endothelial cell layer providing dynamic hemostatic regulation. It is well established that endothelial cell behavior is influenced by interactions with the underlying extracellular matrix (ECM). Numerous researchers have sought to exploit these interactions to generate improved blood-contacting devices by investigating the expression of hemostatic regulators in endothelial cells on various ECM coatings. The ability to select substrates that promote endothelial cell-mediated thromboresistance is crucial to advancing material design strategies to improve cardiovascular device outcomes. This review provides an overview of endothelial cell regulation of hemostasis, the major components found within the cardiovascular basal lamina, and the interactions of endothelial cells with prominent ECM components of the basement membrane. A summary of ECM-mimetic strategies used in cardiovascular devices is provided with a focus on the effects of key adhesion modalities on endothelial cell regulators of hemostasis.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02171-3
       
  • Development of Open-Source Dummy and Impactor Models for the Assessment of
           American Football Helmet Finite Element Models
    • Authors: J. Sebastian Giudice; Gwansik Park; Kevin Kong; Ann Bailey; Richard Kent; Matthew B. Panzer
      Abstract: The objective of this study was to develop and validate a set of Hybrid-III head and neck (HIII-HN) and impactor models that can be used to assess American football design modifications with established dummy-based injury metrics. The model was validated in two bare-head impact test configurations used by the National Football League and research groups to rank and assess helmet performance. The first configuration was a rigid pendulum impact to three locations on the HIII head (front, rear, side) at 3 m/s. The second configuration was a set of eight 5.5 m/s impacts to the HIII head at different locations using a linear impactor with a compliant end cap. The ISO/TS 18571 objective rating metric was used to quantify the correlation between the experimental and model head kinematics (linear and rotational velocity and acceleration) and neck kinetics (neck force and moment). The HIII-HN model demonstrated good correlation with overall mean ISO scores of 0.69–0.78 in the pendulum impacts and 0.65–0.81 in the linear impacts. These publically available models will serve as an in silico design platform that will be useful for investigating novel football helmet designs and studying human head impact biomechanics, in general.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02155-3
       
  • Ankle Rotation and Muscle Loading Effects on the Calcaneal Tendon Moment
           Arm: An In Vivo Imaging and Modeling Study
    • Authors: Jason R. Franz; Ashish Khanchandani; Hannah McKenny; William H. Clark
      Abstract: In this combined in vivo and computational modeling study, we tested the central hypothesis that ankle joint rotation and triceps surae muscle loading have independent and combinatory effects on the calcaneal (i.e., Achilles) tendon moment arm (CTma) that are not fully captured in contemporary musculoskeletal models of human movement. We used motion capture guided ultrasound imaging to estimate instantaneous variations in the CTma during a series of isometric and isotonic contractions compared to predictions from scaled, lower extremity computational models. As hypothesized, we found that muscle loading: (i) independently increased the CTma by up to 8% and (ii) attenuated the effects of ankle joint rotation, the latter likely through changes in tendon slack and tendon curvature. Neglecting the effects of triceps surae muscle loading in lower extremity models led to an underestimation of the CTma, on average, particularly in plantarflexion when those effects were most prominent. We also found little agreement between in vivo estimates and model predictions on an individual subject by subject basis, alluding to unaccounted for variation in anatomical morphology and thus fundamental limitations in model scaling. Together, these findings contribute to improving our understanding of the physiology of ankle moment and power generation and novel opportunities for model development.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02162-4
       
  • Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve
           Design, Part II: Radial Expansion Forces
    • Authors: Eric L. Pierce; Keshav Kohli; Beatrice Ncho; Vahid Sadri; Charles H. Bloodworth; Fiona E. Mangan; Ajit P. Yoganathan
      Abstract: Transcatheter mitral valve (TMV) replacement technology has great clinical potential for surgically inoperable patients suffering from mitral regurgitation. An important goal for robust TMV design is maximizing the likelihood of achieving a geometry post-implant that facilitates optimal performance. To support this goal, improved understanding of the annular forces that oppose TMV radial expansion is necessary. In Part II of this study, novel circular and D-shaped Radial Expansion Force Transducers (C-REFT and D-REFT) were developed and employed in porcine hearts (N = 12), to detect the forces required to radially expand the mitral annulus to discrete oversizing levels. Forces on both the septal-lateral and inter-commissural axes (FSL and FIC) scaled with device size. The D-REFT experienced lower FSL than the C-REFT (19.8 ± 7.4 vs. 17.4 ± 10.8 N, p = 0.002) and greater FIC (31.5 ± 14.0 vs. 36.9 ± 16.2 N; p = 0.002), and was more sensitive to degree of oversizing. Across all tests, FIC/FSL was 2.21 ± 1.33, likely reflecting low resistance to radial expansion at the aorto-mitral curtain. In conclusion, the annular forces opposing TMV radial expansion are non-uniform, and depend on final TMV shape and size. Based on this two-part study, we propose that radial force applied at the commissural aspect of the annulus has the most potent effect on paravalvular sealing.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02139-3
       
  • Template for MR Visualization and Needle Targeting
    • Authors: Rui Li; Sheng Xu; Ivane Bakhutashvili; Ismail B. Turkbey; Peter Choyke; Peter Pinto; Bradford Wood; Zion T. H. Tse
      Abstract: To improve the targeting accuracy and reduce procedure time in magnetic resonance imaging (MRI)-guided procedures, a 3D-printed flexible template was developed. The template was printed using flexible photopolymer resin FLFLGR02 in Form 2 printer® (Formlabs, Inc., Somerville, MA). The flexible material gives the template a unique advantage by allowing it to make close contact with human skin and provide accurate insertion with the help of the newly developed OncoNav software. At the back of the template, there is a grid comprised of circular containers filled with contrast agent. At the front of the template, the guide holes between the containers provide space and angular flexibility for needle insertion. MRI scans are initially used to identify tumor position as well as the template location. The OncoNav software then pre-selects a best guide hole for targeting a specific lesion and suggests insertion depth for the physician A phantom study of 13 insertions in a CT scanner was carried out for assessing needle placement accuracy. The mean total distance error between planned and actual insertion is 2.7 mm, the maximum error was 4.78 mm and standard deviation was 1.1 mm. The accuracy of the OncoNav-assisted and template-guided needle targeting is comparable to the robot-assisted procedure. The proposed template is a low-cost, quickly-deployable and disposable medical device. The presented technology will be further evaluated in prostate cancer patients to quantify its accuracy in needle biopsy.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02167-z
       
  • Stereotactic Systems for MRI-Guided Neurosurgeries: A State-of-the-Art
           Review
    • Authors: Yue Chen; Isuru Godage; Hao Su; Aiguo Song; Hong Yu
      Abstract: Recent technological developments in magnetic resonance imaging (MRI) and stereotactic techniques have significantly improved surgical outcomes. Despite the advantages offered by the conventional MRI-guided stereotactic neurosurgery, the robotic-assisted stereotactic approach has potential to further improve the safety and accuracy of neurosurgeries. This review aims to provide an update on the potential and continued growth of the MRI-guided stereotactic neurosurgical techniques by describing the state of the art in MR conditional stereotactic devices including manual and robotic-assisted. The paper also presents a detailed overview of MRI-guided stereotactic devices, MR conditional actuators and encoders used in MR conditional robotic-assisted stereotactic devices. The review concludes with several research challenges and future perspectives, including actuator and sensor technique, MR image guidance, and robot design issues.
      PubDate: 2019-02-01
      DOI: 10.1007/s10439-018-02158-0
       
 
 
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