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Yield stress, τy, is a key rheological property of complex materials such as gels, dense suspensions, and dense emulsions. While there is a range of established techniques to measure τy in the order of tens to thousands of pascals, the measurement of low τy, specifically below 1 Pa, remains underexplored. In this article, we present the measurement of low apparent τy using a Hele-Shaw microfluidic extensional flow device (MEFD). Using the MEFD, we observe a gradient in shear stress, τ, such that τ is lower near the center or stagnation point, and higher away from the stagnation point. For a yield stress fluid, we observe that, below a certain flow rate, τ exceeds τy only in the outer region, leading to stagnation or unyielding of the fluid in the inner region. We use scaling analysis based on a Hele-Shaw linear extensional flow to deduce τy by measuring the size of the unyielded region, S. We validate this scaling relationship using Carbopol solutions with concentrations ranging between 0.015 to 0.3%, measuring τy as low as ∼10 mPa to ∼1 Pa, and comparing it with τy measured using a standard rheometer. While the experimental lower limit of our technique is 5 mPa, modifying the geometry or improving the image analysis can reduce this limit to the order of 10-4 Pa. The MEFD facilitates rapid measurement of τy, allowing for its real-time assessment. We further report τy of human blood samples between 30 to 80 mPa with their hematocrit ranging between 14 to 63%. Additionally, we determine τy for a mucus simulant (∼0.7 Pa), and lactic drink (∼7 mPa) to demonstrate the versatility of the MEFD technique. [ABSTRACT FROM AUTHOR]

Myelin basic protein (MBP) is an intrinsically disordered (unstructured) protein known to play an important role in the stability of myelin's multilamellar membrane structure in the central nervous system. The adsorption of MBP and its capacity to interact with and bridge solid substrates has been studied using a surface forces apparatus (SFA) and a quartz crystal microbalance with dissipation (QCM-D). Adsorption experiments show that MBP molecules adsorb to the surfaces in a swollen state before undergoing a conformational change into a more compact structure with a thickness of ∼3 nm. Moreover, this compact structure is able to interact with nearby mica surfaces to form adhesive bridges. The measured adhesion force (energy) between two bridged surfaces is 1.0 ± 0.1 mN/m, (Ead = 0.21 ± 0.02 mJ/m(2)), which is slightly smaller than our previously reported adhesion force of 1.7 mN/m (Ead = 0.36 mJ/m(2)) for MBP adsorbed on two supported lipid bilayers (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775). The saturated surface concentration of compact MBP on a single SiO2 surface reaches a stable value of 310 ± 10 ng/cm(2) regardless of the bulk MBP concentration. A kinetic three-step adsorption model was developed that accurately fits the adsorption data. The developed model is a general model, not limited to intrinsically disordered proteins, that can be extended to the adsorption of various chemical compounds that undergo chemical reactions and/or conformational changes upon adsorbing to surfaces. Taken together with our previously published data (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775), the present results confirm that conformational changes of MBP upon adsorption are a key for strong adhesion, and that such conformational changes are strongly dependent on the nature of the surfaces.

We examined the species richness of birds along the elevation gradient of the Sutlej River basin in Himachal Pradesh in the western Himalaya of India. Birds were sampled at 318 sites categorized into 16 elevation bands ranging from 498 to 3700 m between June 2012 and April 2013. A total of 203 bird species were recorded. Species richness showed a monotonic decline with increasing elevation, with 27% of species recorded within a narrow elevation range. We tested the roles of explanatory variables such as environment (temperature, precipitation, area, & Mid-domain Effect (MDE) richness) and habitat (Normalized Differential Vegetation Index (NDVI): July, November & March) on the observed distribution pattern. The observed species richness pattern was strongly correlated with temperature, while three other variables—precipitation, area, and MDE richness—contributed negligibly to the observed pattern. The present study indicates that climatic conditions and vegetation are the major contributors for determining species richness along the Sutlej River basin. Thus, a customized approach is crucial for conservation of species in the elevation range.

Summary: Autism spectrum disorder (ASD), a neuro developmental disorder is a bottleneck to several clinical researchers owing to the data modularization, subjective analysis and shifts in the accurate prediction of the disorder among the sample population. Subjective clinical analysis suffers from lengthy procedure which is a time‐consuming process. The present research focuses on the prediction of ASD disorder using improved binary whale optimization that provides accuracy in the feature selection for the contribution towards the disorder and improves the accuracy in decision making of predicting the presence of disorder. The proposed technique is carried out in two steps: the acute features contributing to the disorder is selected using the binary whale optimization method and the optimal feature is subjected to that render decision of predicting the presence of ASD. The state‐of‐the‐art disorder dataset is tested with conventional techniques like particle swarm optimization (PSO), genetic algorithm (GA), particle swarm optimization with genetic algorithm (PSO‐GA), whale optimization method and binary whale optimization method. Based on the results, the improved binary whale optimization method is proposed and validates the effectiveness of the deciding the autism spectrum disorder. [ABSTRACT FROM AUTHOR]

Purpose: Retinal displacement is common following rhegmatogenous retinal detachment (RRD) repair. A computer simulation was developed to assess forces applied by a gas tamponade of various sizes in the setting of pneumatic retinopexy (PnR) versus pars plana vitrectomy (PPV). Design: Computer simulation model. Methods: The contact angle and pressure between the tamponade and the retina were calculated using interfacial tension and the densities of gas and vitreous. A simulation determined the dynamics of fluid motion in the subretinal space and calculated deformations of the retina. Results: Bulk flow of fluid away from the tamponade in a direction along gravity stretched the retina and caused displacement in the simulations. Extent of displacement is attributable to the subretinal fluid layer thickness, and area of contact and contact pressure applied by the tamponade. Larger gas tamponades have greater contact pressure applied to the retina. Reducing gas bubble size from 93% to 6.25% with PPV versus PnR, there was a 79% reduction in the mean contact pressure (1.4 mmHg–0.29 mmHg), and a 93% reduction in the surface area of contact (11 cm2–0.8 cm2). Therefore, the contact force applied to the entire retina decreases by 97% from 83 mN (PPV) to 2.9 mN (PnR). The model resembling PnR had more than three times less displacement compared to PPV. Conclusions: This model provides a framework to study retinal displacement. Our findings suggest that proportional to their size, gas tamponades stretched the retina by displacing subretinal fluid following RRD repair. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide ([H.sub.2]S) is an endogenously produced gaseous signaling molecule with diverse physiological activity. The potential protective effects of [H.sub.2]S have not been evaluated in the liver. The purpose of the current study was to investigate if [H.sub.2]S could afford hepatoprotection in a murine model of hepatic ischemia-reperfusion (I/R) injury. Hepatic injury was achieved by subjecting mice to 60 min of ischemia followed by 5 h of reperfusion. [H.sub.2]S donor (IK1001) or vehicle were administered 5 min before reperfusion. [H.sub.2]S attenuated the elevation in serum alanine aminotransferase (ALT) by 68.6% and aspartate aminotransferase (AST) by 70.8% compared with vehicle group. [H.sub.2]S-mediated cytoprotection was associated with an improved balance between reduced glutathione (GSH) vs. oxidized glutathione (GSSG), an attenuated formation of lipid hydroperoxides, and an increased expression of thioredoxin-1 (Trx-1). Furthermore, [H.sub.2]S inhibited the progression of apoptosis after I/R injury by increasing the protein expression of heat shock protein (HSP-90) and Bcl-2. These results indicate that [H.sub.2]S protects the murine liver against I/R injury through an upregulation of intracellular antioxidant and antiapoptotic signaling pathways. apoptosis; liver; glutathione; thioredoxin; heat shock protein 90