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Subseasonal Dispersal of Freshwater in the Northern Bay of Bengal in the 2013 Summer Monsoon Season
No full textNear-surface salinity in the north Bay of Bengal (BoB) is very low for nearly three seasons (July-January), due to freshwater input from summer monsoon rainfall and seasonal discharge from several major rivers, including the Ganga-Brahmaputra-Meghna and the Irrawady. The low-salinity surface layer leads to a very shallow density mixed layer, profoundly influencing air-sea interaction on diurnal to seasonal time scales. We use mooring and satellite observations to study the mechanisms responsible for lateral dispersal of river water in the north BoB on subseasonal time scales (days to weeks) during the summer monsoon season of 2013. A new ocean current data set, the BoB near-surface current and advection estimation (BoBcat), is developed to account for the influence of near-surface stratification on directly wind-forced currents. A salt balance based on Aquarius sea surface salinity, BoBcat currents and moored observations shows that subseasonal sea surface salinity variability is mainly due to lateral advection. A shallow Ekman current, forced by enhanced wind stress during an active spell of the monsoon in mid-August, plays a dominant role in moving freshwater from the western boundary to the interior. During subseasonal spells of weak monsoon winds, stirring by mesoscale eddies is the main mechanism of dispersal of low-salinity water. The dispersal of river water in the BoB is very sensitive to surface wind stress
Rab4A organizes endosomal domains for sorting cargo to lysosome-related organelles
No full textSorting endosomes (SEs) are the regulatory hubs for sorting cargo to multiple organelles, including lysosome-related organelles, such as melanosomes in melanocytes. In parallel, melanosome biogenesis is initiated from SEs with the processing and sequential transport of melanocyte-specific proteins toward maturing melanosomes. However, the mechanism of cargo segregation on SEs is largely unknown. Here, RNAi screening in melanocytes revealed that knockdown of Rab4A results in defective melanosome maturation. Rab4A-depletion increases the number of vacuolar endosomes and disturbs the cargo sorting, which in turn lead to the mislocalization of melanosomal proteins to lysosomes, cell surface and exosomes. Rab4A localizes to the SEs and forms an endosomal complex with the adaptor AP-3, the effector rabenosyn-5 and the motor KIF3, which possibly coordinates cargo segregation on SEs. Consistent with this, inactivation of rabenosyn-5, KIF3A or KIF3B phenocopied the defects observed in Rab4A-knockdown melanocytes. Further, rabenosyn-5 was found to associate with rabaptin-5 orRabip4/4' (isoforms encoded by Rufy1) and differentially regulate cargo sorting from SEs. Thus, Rab4A acts a key regulator of cargo segregation on SEs. This article has an associated First Person interview with the first author of the paper
Mesoporous Silica Nanoparticles: A Comprehensive Review on Synthesis and Recent Advances
No full textRecent advancements in drug delivery technologies utilizing a variety of carriers have resulted in a path-breaking revolution in the approach towards diagnosis and therapy alike in the current times. Need for materials with high thermal, chemical and mechanical properties have led to the development of mesoporous silica nanoparticles (MSNs). These ordered porous materials have garnered immense attention as drug carriers owing to their distinctive features over the others. They can be synthesized using a relatively simple process, thus making it cost effective. Moreover, by controlling the parameters during the synthesis; the morphology, pore size and volume and particle size can be transformed accordingly. Over the last few years, a rapid increase in research on MSNs as drug carriers for the treatment of various diseases has been observed indicating its potential benefits in drug delivery. Their widespread application for the loading of small molecules as well as macromolecules such as proteins, siRNA and so forth, has made it a versatile carrier. In the recent times, researchers have sorted to several modifications in the framework of MSNs to explore its potential in drug resistant chemotherapy, antimicrobial therapy. In this review, we have discussed the synthesis of these multitalented nanoparticles and the factors influencing the size and morphology of this wonder carrier. The second part of this review emphasizes on the applications and the advances made in the MSNs to broaden the spectrum of its use especially in the field of biomedicine. We have also touched upon the lacunae in the thorough understanding of its interaction with a biological system which poses a major hurdle in the passage of this carrier to the clinical level. In the final part of this review, we have discussed some of the major patents filed in the field of MSNs for therapeutic purpose
A Two-Phase Five-Level Converter With Least Number of Power Switches Requiring Only a Single DC Source
No full textA novel single dc source fed five-level converter topology for medium-voltage high-power isolated grid-tied systems requiring only 12 power switches is proposed. The present configuration has two stages namely, five-level converter and the Scott-T transformer. The five-level converter stage generates only two phase voltages. Latter, these voltages are converted into three phases by using the Scott-T transformer connection. This topology requires less number of power devices and its associated gate drivers in comparison to any existing topology. In addition, the dc-link capacitors used in the topology have an ability to self-balance by themselves which eliminates the requirement of capacitor balance circuitry and complex control algorithms. The overall component count in the present configuration is very less in comparison to other topologies. Further, each device in the converter is stressed to only half of the dc-link voltage. A level-shifted carrier pulsewidth modulation scheme is adopted to control the converter, and proportional integral controllers are used to inject current into the grid at unity power factor. Theoretical analysis and simulation of the proposed converter are performed and a prototype with 1 kVA rating is validated by connecting it to a three-phase grid
Assessing bone mineral changes in response to vitamin D supplementation using natural variability in stable isotopes of Calcium in Urine
No full textOsteoporosis is a chronic disease of public health importance, particularly in low and middle income countries. Measuring the bone mineral balance (BMB) in a non-invasive manner, and its response to different interventions, is critical to the definition of optimal strategies for its prevention and management. In this study, we demonstrate the usefulness of natural variability in calcium isotopes (delta(44)/Ca-40) of urine and the derived BMB estimates as a biomarker of bone health and its responsiveness to interventions. Vitamin D-3 is commonly used as a supplement for the prevention and treatment of osteoporosis, along with calcium supplements. We studied the effect of a short term vitamin D3 supplementation on changes in urine delta(44)/Ca-40 and the derived BMB. delta(44)/Ca-40 before and after the vitamin D3 supplementation yielded a statistically significant change (p = 0.050) with a positive delta(44)/Ca-40 enrichment. The mean derived BMB was net positive (0.04 +/- 0.05) in comparison to a net negative value for the control group (-0.03 +/- 0.01). These results indicate the potential usefulness of urinary natural delta(44)/Ca-40 and the derived BMB, which, along with bone mineral density could be used as a sensitive marker for precision in the prevention and treatment of osteoporosis
Curcumin nanoconjugate inhibits aggregation of N-terminal region (A beta-16) of an amyloid beta peptide
No full textThe present study describes a curcumin nanoformulation that inhibits amyloid beta (A beta) aggregation. Curcumin is well known for its anti-carcinogenic, antioxidant and anti-inflammatory properties. Recent studies have shown that curcumin also possesses neuroprotective and cognitive-enhancing properties that may help to delay or prevent amyloid beta aggregation in Alzheimer's disease. However, due to the poor aqueous solubility and bioavailability of curcumin, its clinical applications are limited. To increase the bioavailability of curcumin, a highly stable and completely water soluble system consisting of a polymeric nanoparticle-encapsulated curcumin conjugate with gold nanoparticles decorated on the surface (PVP-C-AuNP) was formulated. The curcumin nano-conjugates were characterized by various physical, chemical and spectroscopic techniques including UV-visible spectroscopy, FT-IR spectroscopy, DLS and zeta potential analysis. The surface morphology of the conjugates was studied using TEM. Though the aggregation properties of full-length A beta 42 have been explored in detail, a shorter A beta fragment from the N-terminal region of the peptide, A beta 1-16, was chosen for the current study as it demonstrates seeding properties for aggregate formation in the healthy brain. The aggregation kinetics of A beta 1-16 was studied using NMR spectroscopy and TEM. The fabricated curcumin nanoformulations were not only found to inhibit A beta 1-16 aggregation but they also disintegrated already formed aggregates
GenLR-Net: Deep framework for very low resolution face and object recognition with generalization to unseen categories
No full textMatching very low resolution images of faces and objects with high resolution images in the database has important applications in surveillance scenarios, street-to-shop matching for general objects, etc. Matching across huge resolution difference along with variations in illumination, view-point, etc. makes the problem quite challenging. The problem becomes even more difficult if the testing objects have not been seen during training. In this work, we propose a novel deep convolutional neural network architecture to address these problems. We systematically introduce different kinds of constraints at different stages of the architecture so that the approach can recognize low resolution images as well as generalize well to images of unseen categories. The reason behind each additional step along with its effect on the overall performance is thoroughly analyzed. Extensive experiments are conducted on two face and object datasets which justifies the effectiveness of the proposed approach for handling these real-life challenging scenarios
Virtual Energy Routers (VERs) for Energy Internet
No full textAdvances in distributed power generation and distribution is rapidly changing the power system landscape. This provides the primary motivation for the concept of Energy Internet. In this nascent and evolving concept of the next generation power distribution system, energy routers have a major role to play. The ongoing research in the field of energy internet aims at building energy routers that control and route the flow of energy quanta or packets. The energy routers are multi-staged power electronic converters. The loads and the distributed energy resources need to be connected to this power electronic converters in a localized manner. This paper proposes the concept of a virtual energy router (VER) in which the router has a virtual presence that can coordinate and control distributed loads and energy resources. A set of such loads and distributed energy resources spread over a hierarchical microgrid system encompasses the virtual energy router. The proposed virtual energy router offers the possibility of replicating a conventional data internet with the additional power flow element and where multiple virtual energy routers can interact amongst themselves to set-up the energy network. The various aspects and functions of a VER are presented in this paper. A set of results indicating the functions of a VER is also put forward and discussed
Enhancement structures for the bat algorithm
No full textBat algorithm is a recently developed !in arm optimization technique which has been found to be a powerful method for multimodal optimization problems. Some of the drawbacks in standard BA are reduced convergence speed due to lack of inertia weight factor and premature convergence due to low diversification capability of the algorithm as the problem's dimension increases. This paper presents an enhanced bat algorithm (EBA) for optimization which employs five different enhancement structures to improve the standard bat algorithm for better global exploration. EBA is tested on several standard test functions and correlated with recently published studies in the literature using non-parametric statistical tests. It shown from statistical test results that EBA is often superior to the standard BA and is also computationally efficient compared to other published algorithms such as GA and PSO
Self assembly of cyclic polygon shaped fluid colloidal membranes through pinning
No full text2D fluid monolayer membranes of rod-like viruses spontaneously form in a mixture of rods and polymers through depletion attraction. The rods are uniformly oriented within the bulk and twist in a zone around the membrane edge. Surprisingly, we find that cyclic polygonal shaped colloidal membranes form when polymers are added to a mixture of long and short-thick rods with the long and short-thick rods forming the faceted core and lobes of the polygon, respectively. We demonstrate that the origin of this anisotropic shape lies in the phenomenon of spreading of one liquid over another in the presence of disorder. As a membrane of short-thick rods spreads over another of longer rods, the edge bound rods untwist to become part of the newly formed two-rod interface. However, a small fraction of rods fail to untwist as the two rod interface forms and act as mobile pinning centers. Capillary flow of short-thick rods drives all the pinning centers to a single location in the composite membrane which now acts like a junction. This pinning junction inhibits complete engulfing of one membrane by the other. Repeated sequential events like this then lead to formation of multiple junctions and the overall cyclic polygon topology. We find that pinning junctions are weakly cross-linked in nature instead of being topological defects. We outline the necessary and sufficient constraints on the nature of rods to obtain stable out of equilibrium cyclic polygon membranes. Our results show a unique counter-intuitive scenario where defects lead to self-assembly of ordered structures