Non Gaussian information of heterogeneity in Soft Matter

Heterogeneity in dynamics in the form of non-Gaussian molecular displacement distributions appears ubiquitously in soft matter. We address the quantification of such heterogeneity using an information-theoretic measure of the distance between the actual displacement distribution and its nearest Gaussian estimation. We explore the usefulness of this measure in two generic scenarios of random walkers in heterogeneous media. We show that our proposed measure leads to a better quantification of non-Gaussianity than the conventional ones based on moment ratios

A microvillus based approach to model cell rolling

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 45-50).Cell rolling is a physiological phenomenon, which allows leukocytes to attach to activated vascular endothelium and reach sites of inflammation. A novel approach to model cell rolling is presented in this thesis. The model incorporates all the aspects known to be important to rolling in a semi-analytical framework making it computationally efficient. Bond kinetics have been used to define microvillus attachment probability which is in turn used to find out the net force on the cell. Deformability is also taken into account by an empirical relation which allows shear modulation of cell-surface contact area. The model showed excellent agreement with experimental results over a wide range of shear stresses. Using the model, the effects of cell deformability and microvillus structure have been studied and its implications discussed. The model was also used to predict rolling of microspheres, which showed reasonable agreement with experiments. Finally, the contribution of different features towards stabilization of rolling was elucidated by simulating different hypothetical cases with contributions from different cellular features.by Suman Bose.S.M

The role of cell membrane strain in sonoporation characterised by microfluidic-based single-cell analysis

In the present study we have investigated the sonoporation dynamics in a single cell using a novel microfluidic-based approach. Our methodology has successfully addressed the biophysical mechanisms underlying US-induced cell membrane sonoporation by performing in situ measurement of localised cell membrane deformation, and simultaneous quantification of both intracellular calcium concentration ([Ca2+]i) and transmembrane transfer of extracellular membrane-impermeable probes. We have highlighted novel aspects of microbubble-cluster dynamics combined with localised cell membrane strain, which could be responsible for membrane permeabilisation and transmembrane pore formation correlated with the transduction of intracellular biochemical signals (i.e. [Ca2+]i influx) as a result of microbubble-cell interaction

Heating of the auroral ionosphere by traveling ionospheric disturbances initiated by atmospheric gravity waves

In the presence of perturbations of the thermospheric auroral region produced by traveling ionospheric disturbances during the propagation of atmospheric gravity waves, an analytical expression of the velocity of the thermospheric plasma is derived through magnetohydrodynamic formalism. The expressions of the Joule heating and the viscous heating are derived, and their rates of variation are presented. A threshold height for their transition has been determined from their ratio, which is in agreement with the experimental data. The analysis indicates that the time taken by the thermospheric plasma to reach a steady-state corresponds to the nature of the traveling ionospheric disturbances in the medium

Examining the Lateral Displacement of HL60 Cells Rolling on Asymmetric P-Selectin Patterns

Author Manuscript 2011 July 4.The lateral displacement of cells orthogonal to a flow stream by rolling on asymmetrical receptor patterns presents a new opportunity for the label-free separation and analysis of cells. Understanding the nature of cell rolling trajectories on such substrates is necessary to the engineering of substrates and the design of devices for cell separation and analysis. Here, we investigate the statistical nature of cell rolling and the effect of pattern geometry and flow shear stress on cell rolling trajectories using micrometer-scale patterns of biomolecular receptors with well-defined edges. Leukemic myeloid HL60 cells expressing the PSGL-1 ligand were allowed to flow across a field of patterned lines fabricated using microcontact printing and functionalized with the P-selectin receptor, leveraging both the specific adhesion of this ligand−receptor pair and the asymmetry of the receptor pattern inclination angle with respect to the fluid shear flow direction (α = 5, 10, 15, and 20°). The effects of the fluid shear stress magnitude (τ = 0.5, 1, 1.5, and 2.0 dyn/cm[superscript 2]), α, and P-selectin incubation concentration were quantified in terms of the rolling velocity and edge tracking length. Rolling cells tracked along the inclined edges of the patterned lines before detaching and reattaching on another line. The detachment of rolling cells after tracking along the edge was consistent with a Poisson process of history-independent interactions. Increasing the edge inclination angle decreased the edge tracking length in an exponential manner, contrary to the shear stress magnitude and P-selectin incubation concentration, which did not have a significant effect. On the basis of these experimental data, we constructed an empirical model that predicted the occurrence of the maximum lateral displacement at an edge angle of 7.5°. We also used these findings to construct a Monte Carlo simulation for the prediction of rolling trajectories of HL60 cells on P-selectin-patterned substrates with a specified edge inclination angle. The prediction of lateral displacement in the range of 200 μm within a 1 cm separation length supports the feasibility of label-free cell separation via asymmetric receptor patterns in microfluidic devices.Deshpande Center for Technological InnovationNational Science Foundation (U.S.) (CAREER Award 0952493)National Institutes of Health (U.S.) (Grant DE019191)National Institutes of Health (U.S.) (Grant HL095722)National Institutes of Health (U.S.) (Grant HL097172)American Heart Association (Grant 0970178N

Nanofiltration across Defect-Sealed Nanoporous Monolayer Graphene

Monolayer nanoporous graphene represents an ideal membrane for molecular separations, but its practical realization is impeded by leakage through defects in the ultrathin graphene. Here, we report a multiscale leakage–sealing process that exploits the nonpolar nature and impermeability of pristine graphene to selectively block defects, resulting in a centimeter-scale membrane that can separate two fluid reservoirs by an atomically thin layer of graphene. After introducing subnanometer pores in graphene, the membrane exhibited rejection of multivalent ions and small molecules and water flux consistent with prior molecular dynamics simulations. The results indicate the feasibility of constructing defect-tolerant monolayer graphene membranes for nanofiltration, desalination, and other separation processes.Samsung (Firm) (Fellowship)United States. Dept. of Energy. Office of Basic Energy Sciences (Award number DE-SC0008059)King Fahd University of Petroleum and Minerals (Center for Clean Water and Clean Energy at MIT and KFUPM, project number R10-CW-09

Affinity flow fractionation of cells via transient interactions with asymmetric molecular patterns

Flow fractionation of cells using physical fields to achieve lateral displacement finds wide applications, but its extension to surface molecule-specific separation requires labeling. Here we demonstrate affinity flow fractionation (AFF) where weak, short-range interactions with asymmetric molecular patterns laterally displace cells in a continuous, label-free process. We show that AFF can directly draw neutrophils out of a continuously flowing stream of blood with an unprecedented 400,000-fold depletion of red blood cells, with the sorted cells being highly viable, unactivated, and functionally intact. The lack of background erythrocytes enabled the use of AFF for direct enumeration of neutrophils by a downstream detector, which could distinguish the activation state of neutrophils in blood. The compatibility of AFF with capillary microfluidics and its ability to directly separate cells with high purity and minimal sample preparation will facilitate the design of simple and portable devices for point-of-care diagnostics and quick, cost-effective laboratory analysis

Aerodynamic Models for the Low Density Supersonic Declerator (LDSD) Supersonic Flight Dynamics Test (SFDT)

An overview of pre-flight aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a large helium balloon, then accelerating the TV to Mach 4 and and 53 km altitude with a solid rocket motor. The first flight test (SFDT-1) delivered a 6 meter diameter robotic mission class decelerator (SIAD-R) to several seconds of flight on June 28, 2014, and was successful in demonstrating the SFDT flight system concept and SIAD-R. The trajectory was off-nominal, however, lofting to over 8 km higher than predicted in flight simulations. Comparisons between reconstructed flight data and aerodynamic models show that SIAD-R aerodynamic performance was in good agreement with pre-flight predictions. Similar comparisons of powered ascent phase aerodynamics show that the pre-flight model overpredicted TV pitch stability, leading to underprediction of trajectory peak altitude. Comparisons between pre-flight aerodynamic models and reconstructed flight data are shown, and changes to aerodynamic models using improved fidelity and knowledge gained from SFDT-1 are discussed

Assessment of hypertension association with arsenic exposure from food and drinking water in Bihar, India

Epidemiological studies have associated chronic exposure to arsenic (As) from drinking water with increased risk of hypertension. However, evidence of an association between As exposure from food and hypertension risks is sparse. To quantify the association between daily As intake from both food (rice, wheat and potatoes) and drinking water (Aswater) along with total exposure (Astotal) and hypertension risks in a study population in Bihar, India, we conducted an individual level cross-sectional analysis between 2017 and 2019 involving 150 participants. Arsenic intake variables and three indicators of hypertension risks (general hypertension, low-density lipoprotein (LDL) and high-density lipoprotein (HDL)) were derived, and any relationship was quantified using a series of crude and multivariable log-linear or logistic regression models. The prevalence of general hypertension was 40% for the studied population. The median level of HDL was 45 mg/dL while median value of LDL was 114 mg/dL. Apart from a marginally significant positive relationship between As intake from rice and the changes of LDL (p-value = 0.032), no significant positive association between As intake and hypertension risks could be ascertained. In fact, Astotal was found to be associated with lower risks of general hypertension and higher levels of HDL (p-value = 0.020 and 0.010 respectively) whilst general hypertension was marginally associated with lower Aswater (p-value = 0.043). Due to limitations regarding study design and residual confounding, all observed marginal associations should be treated with caution

Wheat is an emerging exposure route for arsenic in Bihar, India

In arsenic (As) endemic areas of south-east Asia, where a subsistence rice-based diet is 19 prevalent, As exposure from food is mainly focused on rice intake. However, consumption of 20 wheat is substantial and increasing. We present a probabilistic assessment of increased cancer 21 risk from wheat-based food intake in a study population of rural Bihar, India where As exposure 22 is endemic. Total As in wheat grains (43.64±48.19 μg/kg, n=72) collected from 77 households 23 across 19 villages was found to be lower than reported As in wheat grains from other south-24 east Asian countries but higher than a previous study from Bihar. As concentration in wheat flour was used for risk estimation, bearing in mind that it was the 26 flour obtained after indigenous household processing of the grains that was used for making 27 the home-made bread (chapati) which contributed 95% of wheat intake for the studied 28 population. Interestingly, while 78% of the surveyed participants (n=154) consumed rice every 29 day, chapati was consumed every day by 99.5% of the participants. In contrast to previous 30 studies, where As concentration in wheat grain was found to be lower than the flour due to the 31 removal of the bran on grinding, we did not find any appreciable lowering of arsenic in the 32 wheat flour (49.80±74.08 μg/kg, n=58), most likely due to external contamination during 33 processing and grinding. Estimated gender adjusted excess lifetime cancer risk of 1.23x10-4 for 34 the studied rural population of Bihar indicated risk higher than the 10-4-10-6 range, typically 35 used by the USEPA as a threshold to guide regulatory values. Hence, our findings suggest As 36 exposure from wheat-based food intake to be of concern not only in As endemic areas of rural 37 Bihar but also in non-endemic areas with similar wheat-based diet due to public distribution of 38 the wheat across India