Tunable Brownian Vortex at the Interface

A general kind of Brownian vortexes are demonstrated by applying an external nonconservative force field to a colloidal particle bound by a conservative optical trapping force at a liquid-air interface. As the liquid medium is translated at a constant velocity with the bead trapped at the interface, the drag force near the surface provide enough rotational component to bias the particle's thermal fluctuations in a circulatory motion. The interplay between the thermal fluctuations and the advection of the bead in constituting the vortex motions is studied, inferring that the angular velocity of the circulatory motion offers a comparative measure of the interface fluctuations.Comment: Accepted for publication in Phys. Rev.

Optical tweezer for probing erythrocyte membrane deformability

We report that the average rotation speed of optically trapped crenated erythrocytes is direct signature of their membrane deformability. When placed in hypertonic buffer, discocytic erythrocytes are subjected to crenation. The deformation of cells brings in chirality and asymmetry in shape that make them rotate under the scattering force of a linearly polarized optical trap. A change in the deformability of the erythrocytes, due to any internal or environmental factor, affects the rotation speed of the trapped crenated cells. Here we show how the increment in erythrocyte membrane rigidity with adsorption of $Ca^{++}$ ions can be exhibited through this approach.Comment: Published in Appl. Phys. Lett. 95, 233703 (2009); Two supplementary multimedia files are available at the journal page: http://link.aip.org/mm/APPLAB/1.3272269/083949aplv1.mov and http://link.aip.org/mm/APPLAB/1.3272269/083949aplv2.mo

Irreversibility-to-reversibility crossover in transient response of an optically trapped particle

We study the transient response of a colloidal bead which is released from different heights and allowed to relax in the potential well of an optical trap. Depending on the initial potential energy, the system's time evolution shows dramatically different behaviors. Starting from the short-time reversible to long-time irreversible transition, a stationary reversible state with zero net dissipation can be achieved as the release point energy is decreased. If the system starts with even lower energy, it progressively extracts useful work from thermal noise and exhibits an anomalous irreversibility. In addition, we have verified the Transient Fluctuation Theorem and the Integrated Transient Fluctuation Theorem even for the non-ergodic descriptions of our system

Out-of-equilibrium microrheology using optical tweezers to probe directional viscoelastic properties under shear

Many wormlike micellar systems exhibit appreciable shear thinning due to shear-induced alignment. As the micelles get aligned introducing directionality in the system, the viscoelastic properties are no longer expected to be isotropic. An optical-tweezers-based active microrheology technique enables us to probe the out-of-equilibrium rheological properties of a wormlike micellar system simultaneously along two orthogonal directions -parallel to the applied shear, as well as perpendicular to it. While the displacements of a trapped bead in response to active drag force carry signature of conventional shear thinning, its spontaneous position fluctuations along the perpendicular direction manifest an orthogonal shear thickening, an effect hitherto unobserved

Elevated Risk of Compound Extreme Precipitation Preceded by Extreme Heat Events in the Upper Midwestern United States

Compound extreme events can potentially cause deadlier socio-economic consequences. Although several studies focused on individual extreme climate events, the occurrence of compound extreme events is still not well studied in the upper Midwestern United States. In this study, compound extreme precipitation preceded by extreme hot day events was investigated. Results showed a strong linkage between extreme precipitation events and extreme hot days. A significant increasing trend was noticed mainly in Iowa (10.1%), northern parts of Illinois (5.04%), and Michigan (5.04%). Results also showed a higher intensity of extreme precipitation events preceded by an extremely hot day compared to the intensity of extreme precipitation events not preceded by an extremely hot day, mostly in the central and lower parts of Minnesota, western and upper parts of Iowa, lower and upper parts of Illinois, parts of Ohio, Michigan, and Wisconsin for 1950–2010. In other words, extreme heat contributed to more extreme precipitation events. Our findings would provide important insights related to flood management under future climate change scenarios in the region

Optically-driven red blood cell rotor in linearly polarized laser tweezers

We have constructed a dual trap optical tweezers set-up around an inverted microscope where both the traps can be independently controlled and manipulated in all the three dimensions. Here we report our observations on rotation of red blood cells (RBCs) in a linearly polarized optical trap. Red blood cells deform and become twisted in hypertonic phosphate buffer saline and when trapped, experience an unbalanced radiation pressure force. The torque generated from the unbalanced force causes the trapped RBC to rotate. Addition of Ca++ ions in the solution, keeping the osmolarity same, makes the cell membranes stiffer and the cells deform less. Thus the speed of rotation of the red blood cells can be controlled, as less deformation and in turn less asymmetry in shape produces less torque under the radiation pressure resulting in slower rotation at the same laser power

Spatial Heterogeneity of Temporal Shifts in Extreme Precipitation across India

When analyzing trends and patterns of extreme precipitation, one can easily generalize the shifts caused by external climate forcings and map a single temporal shift of annual precipitation. However, the complexity of a changing environment evidences spatially distributed shifts particularly those of extreme precipitation which are essential in planning and designing enterprises and, ultimately, in managing infrastructure across scales. The goal of this study is to characterize the spatial heterogeneity of shifts in the increasing pace of extreme events over India. The study has a two-part hypothesis: (1) the number of grid cells with significant trends in annual precipitation (P), extreme precipitation (R95) and very extreme precipitation (R99) will reflect the extent of geophysically vulnerable areas subject to increasing or decreasing annual precipitation and (2) the dispersion of cells with significant shifting points (which has occurred at different historical periods) will evidence the heterogeneity of the changes in P, R95 and R99 regimes. To test this hypothesis, we used the Mann-Kendall and Pettitt’s tests to estimate the significance of the increasing and decreasing trends and shifting points, respectively, in P, R95 and R99 from 1901-2015 for mainland India. Based on a gridded dataset of 0.25° resolution, results showed significant temporal trends for spatially averaged R95 and R99, whereas non-significant inclining temporal trend was found for P. Trend analyses applied to the precipitation gridded product of the Indian Meteorological Department revealed statistically significant trends for almost 38%, 36% and 31% of India’s territory for P, R95 and R99, respectively. Further, the magnitude of these trends proved higher for R95 (i.e., 0.42 mm year-1) compared with R99 (i.e., 0.31 mm year-1), supporting the idea of an increasing liability for flash floods. Results also showed that most of the temporal shifts in the time series of P, R95 and R99 occurred between 1941-1980, at 34%, 31% and 22% of the grids, respectively. In addition, the opposite trends before and after the inflection point were found for locations showing significant temporal shifts in R95 and R9

Identifying Factors Associated with Maternal Deaths in Jharkhand, India: A Verbal Autopsy Study

Maternal mortality has been identified as a priority issue in health policy and research in India. The country, with an annual decrease of maternal mortality rate by 4.9% since 1990, now records 63,000 maternal deaths a year. India tops the list of countries with high maternal mortality. Based on a verbal autopsy study of 403 maternal deaths, conducted in 2008, this paper explores the missed opportunities to save maternal lives, besides probing into the socioeconomic factors contributing to maternal deaths in Jharkhand, India. This cross-sectional study was carried out in two phases, and a multistage sampling design was used in selecting deaths for verbal autopsy. Informed consent was taken into consideration before verbal autopsy. The analytical approach includes bivariate analysis using SPSS 15, besides triangulation of qualitative and quantitative findings. Most of the deceased were poor (89%), non-literates (85%), and housewives (74%). Again, 80% died in the community/at home, 28% died during pregnancy while another 26% died during delivery. Any antenatal care was received by merely 28% women, and only 20% of the deliveries were conducted by skilled birth attendants (doctors and midwives). Delays in decision-making, travel, and treatment compounded by ignorance of obstetric complications, inadequate use of maternal healthcare services, poor healthcare infrastructure, and harmful rituals are the major contributing factors of maternal deaths in India

Coin Based Solar Mobile Charger

Energy plays a very important role for powering the system to work well either in Humans or in any artificial system. Communication is fundamental need for humans and a mobile system provides the power to communicate with the world so easily. Mobile phone is like a part of our day to day life. Without it, one feels incomplete and unsecure because most of the work is done with the help of it. Smartphone is the most common gadget in cities and also in the small towns now. But a big backlog of this phone is high battery consumption due to several features. Thus, most of the time the smart phones users runs out of battery, suppose on a Railway station a person is waiting for train by enjoying music on phone or surfing internet for any important information and suddenly run out of battery. That time if the charging facility is available somewhere then it is like boon. So, this necessity is being conceptualized in this paper. A Coin Insertion based mobile charger can be useful in today’s scenario. It can be used on bus stations, railway compartments, railway stations, etc