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941.
942.
Luis E. Aguirre Alexandre de Oliveira David Se? Simon ?opar Pedro L. Almeida Miha Ravnik Maria Helena Godinho Slobodan ?umer 《Proceedings of the National Academy of Sciences of the United States of America》2016,113(5):1174-1179
Probing the surface morphology of microthin fibers such as naturally occurring biofibers is essential for understanding their structural properties, biological function, and mechanical performance. The state-of-the-art methods for studying the surfaces of biofibers are atomic force microscopy imaging and scanning electron microscopy, which well characterize surface geometry of the fibers but provide little information on the local interaction potential of the fibers with the surrounding material. In contrast, complex nematic fluids respond very well to external fields and change their optical properties upon such stimuli. Here we demonstrate that liquid crystal droplets deposited on microthin biofibers—including spider silk and cellulosic fibers—reveal characteristics of the fibers’ surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. Spider silks align nematic molecules parallel to fibers or perpendicular to them, whereas cellulose aligns the molecules unidirectionally or helicoidally along the fibers, indicating notably different surface interactions. The nematic droplets as sensors thus directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization.Natural microfilaments produced by plants, insects, or spiders are fascinating materials not just because of their specific properties such as wear resistance, elasticity, tensile strength, and toughness (1–5) but also because of their microorganization (6–9). Their macroscopic properties can match properties of materials like kevlar but are at the same time biocompatible and biodegradable (10). These fascinating macroscopic properties actually originate from bulk and surface properties of the fibers (1). The chemical composition of the threads combined with their morphology determines the final properties of the material (11–13). The mechanical properties of the spider fibers are determined by the existence of a lyotropic liquid crystalline phase, from which the threads are drawn (14). Such silks are known to include nanoscale networks of defects and cavities that yield surface structures notably dependent on the spider species (3). These differences do not affect much the mechanical performance of the fibers (1, 3, 5). From a technological perspective, many attempts have been made to reproduce these natural bionetworks (15–17). In fact cellulose-based fibers with few micrometers of diameter, produced by electrospinning, can also acquire different morphologies depending upon the processing conditions, giving diverse features of the final threads and mats (18). Therefore, probing the surface structure of the microfibers is crucial for a complete understanding of their individual and interthreaded properties.From another perspective, nematic complex fluids are materials which are inherently responsive to diverse external stimuli, notably including diverse surface interactions which in the literature are known as the surface anchoring (19). Being effectively elastic materials, the orientational order of nematics responds on long, typically micrometer scales (20–22), which results in a spatially varying birefringence that can be optically detected (23). Recently, it was demonstrated that glass fibers induce numerous defects in a well-aligned nematic liquid crystal cell and thus provide a simple illustration of topological phenomena (24). It is also known that liquid crystal droplets can considerably change their structure by the action of otherwise imperceptibly small external stimuli (21). Pierced nematic and chiral nematic droplets develop defects that can be controlled by the liquid crystal elasticity, chirality, and surface boundary conditions (25, 26) indicating exceptional sensitivity. Therefore, to generalize, putting nematics into contact with diverse surfaces (18, 27) can be used as a simple but very powerful technique to detect the surface properties of microobjects such as biological fibers.In this paper we demonstrate the surface morphology sensing of biorelevant fibers, including spider silk and cellulosic microfibers, by nematic droplets that are sprayed onto the fibers. Specifically, we explore the chiral and achiral nature of the fiber’s surface and the in-plane or perpendicular alignment fields the fibers impose on the nematic. Droplets with degenerate in-plane and perpendicular alignment of the nematic at their free surfaces are explored, combining experiments and numerical modeling, to allow for tuning of the sensing precision. Further, the entanglement sites of the fiber webs are explored, with the droplets deposited at the sites clearly revealing contact, noncontact, and entangled morphologies. 相似文献
943.
Davis MA Landesman R Tadmor B Hopmeier M Shenhar G Barker T Pozner CN Binstadt ES Nelson S Look R Shubina M Walls RM 《Annals of emergency medicine》2008,51(4):420-5, 425.e1-5
944.
Horstkotte D Lengyel M Mistiaen WP Piper C Völler H;Working Group on Infection Thrombosis Embolism Bleeding of the Society of;Heart Valve Disease 《The Journal of heart valve disease》2005,14(1):1-7
Major reasons for the considerable heterogeneity among published results of heart valve surgery are inconsistency in follow up techniques, reporting systems and classification of adverse events. The present recommendations are intended to harmonize the presentation of clinical material in order to improve comparison of data from different sources for the analysis of pooled data. The quality of an observational study is largely, if not entirely, due to the follow up technique, which may be graded according to six categories: Self-reporting of adverse events/well-being by the patients may be classified 'excellent'; if the information is gathered and re-checked at short-term intervals. Data obtained from in-hospital or outpatient examinations by qualified examiners at least twice a year or other personal contact through qualified examiners may be regarded as 'sufficient', if the results are re-checked by contacting the treating home physician. All other follow up techniques may be regarded as inappropriate. Consequences of complications are entirely dependent on severity and possible sequelae. It is therefore recommended to grade any reported complication according to its severity by utilizing a score system. Embolisms are best categorized by utilizing the performance status scale. Bleeding events may be categorized according to severity as fatal, major (requiring hospital transmission with transfusion, surgery or with permanently increased disability) or minor (not requiring hospital admission, surgery or transfusion). In some cases it will remain unclear whether an event was primarily embolic or hemorrhagic. These complications should be summarized as 'not categorized'. The reporting of morbid events due to thrombosis, embolism and bleeding should go along with information regarding the quality of antithrombotic management. 相似文献
945.
Brito EM Camacho-Lobato L Paoletti V Gideon M Katz PO Castell DO 《The American journal of gastroenterology》2003,98(1):40-45
OBJECTIVE: Nutcracker esophagus (NE) is defined as the presence of peristaltic contractions in which the average distal esophageal amplitude is greater than 180 mm Hg. The underlying mechanism responsible for these abnormalities is not known. The aim of this study was to test the hypothesis that NE might be caused by a defect in the inhibitory pathway controlling esophageal peristalsis. METHODS: Eight patients with NE (seven women, 1 man, mean age 50 yr) and eight age- and sex-matched normal volunteers (seven women, 1 man, mean age 48 yr) underwent a special protocol using three-channel (3, 8, and 16 cm above the lower esophageal sphincter) solid state esophageal manometry to evaluate deglutitive inhibition. Ten pairs of 5 ml of wet swallows were given at each of five different time intervals (30, 20, 15, 10, and 5 s). Pairs of swallows were spaced by 30 s, and different time intervals were spaced by 1 min. Tracings were recorded using a computer program and blindly automatically analyzed for both amplitude and duration of the contraction separately for the first and second swallow of each pair. Presence of deglutitive inhibition or muscle refractoriness was assessed according to interactions between the first and second swallow of the pair. Results were found abnormal when larger than the mean percent variation of the second and first swallow calculated for the 30-s interval, considered as baseline for each participant. Statistics included paired and nonpaired nonparametrical comparisons as appropriate. RESULTS: The median amplitude for the NE was 202 mm Hg (range 186-376) and for the controls was 118 mm Hg (range 64-167) (p = 0.0002). The median duration in the NE group was 5.1 s (range 4-9.3) versus 4.1 (range 3.3-5.0) for the controls (p = 0.02). The percent variation in duration (p = 0.31), amplitude (p = 0.42), and propagation velocity of the peristaltic waves (p = 0.69) did not differ between the control and NE groups. Peristalsis frequency dropped at the 5-s interval for both studied groups (p = 0.84). CONCLUSION: Central and local inhibitory mechanisms induced by closely timed swallows are preserved in the NE and do not explain the mechanism of the high amplitude and long duration contractions. 相似文献
946.
947.
Ghyslaine Bruna Djeunang Dongho Karthigayan Gunalan Mariangela LEpiscopia Giacomo Maria Paganotti Michela Menegon Rose Efeutmecheh Sangong Georges Bouting Mayaka Joseph Fondop Carlo Severini Martin Sanou Sobze Louis H. Miller Gianluca Russo 《The American journal of tropical medicine and hygiene》2021,104(3):987
948.
949.
José Alexandre da Rocha Curvelo Anna Lea Silva Barreto Camila A. dos Anjos Rafaela S. Santana Ariadne Nunes Alonso Maria Teresa Vilela Romanos Kelly C. G. de Moura Paula Fernandes Carneiro Maristela Barbosa Portela Maria do Carmo F. R. Pinto Rosangela Maria de Araújo Soares 《Medicinal chemistry research》2015,24(3):1155-1161
950.