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Recent advances in electrochemical nonenzymatic hydrogen peroxide sensors based on nanomaterials: a review
No full textThe development of efficient electrochemical hydrogen peroxide (H2O2) sensors has received great attention due to the significance of H2O2 in biological systems and its practical applications in various fields. With the new class of H2O2 sensors, the nonenzymatic detection of the target can provide many attractive characteristics, such as simple fabrication, ultrahigh sensitivity, and excellent stability. Considering the rapid expansion of nonenzymatic H2O2 detection using advanced nanomaterials, an overview of the current state of methods for electrochemical nonenzymatic H2O2 sensors is presented (with 399 refs.). The first part of the review covers the sensors based on the use of nanoparticles consisting of metals, metal oxides/sulfides, and bimetallic nanoparticles/alloys. The next major section discusses sensors that make use of carbon nanomaterials, such as carbon nanotubes, graphene, graphene oxide, carbon dots, and of other carbonaceous materials. Advantages and the intrinsic drawbacks of employing various nanomaterials to detect H2O2 are emphasized
A novel impedance sensing approach for precise electromechanical characterization of cells
No full textIn this paper, we demonstrate a microfluidic impedance spectroscopy platform that simultaneously probes two important biophysical parameters of cells-one, their electrical properties and two, their mechanical properties. Instead of using a high-speed camera for estimation of mechanical properties (deformability) of cells, we present a new design where deformability is estimated using the time difference (transit time) between the generation of electrical signals. The concept was validated using chemically stiffened erythrocytes. The presented design also involves a novel flow correction technique that was developed to negate the errors arising from flow rate fluctuations in such devices, resulting in rapid and error-free data acquisition. Using this platform, we further investigate changes in deformability and cellular properties of lymphocytes in diabetic patients by comparing them with healthy volunteers. Results from testing >9000 cells in each population suggest significant changes in properties of diabetic lymphocytes
Survey of last ten years of work done in India in some selected areas of functional analysis and operator theory
No full textResearch in functional analysis and operator theory over the last ten years in India has broadly been under the following areas: Hilbert space operator theory and certain special subsets of DOUBLE-STRUCK CAPITAL C2 and DOUBLE-STRUCK CAPITAL C3 where strong interaction between complex analysis and operator theory has been developed resulting in important discoveries in complex analysis through Hilbert space methods. Hermitian holomorphic vector bundles and their curvatures. This has intimate connection with Hilbert modules over function algebras. A Hilbert module over a function algebra is a Hilbert space along with a bounded operator T or a commuting tuple of bounded operators (T1; T2; ... ; Tn): That is how operator theory enters this study. Multivariable operator theory involving dilation of commuting contractions of certain special types. This involves the study of the submodule as well as the quotient module of the kind of Hilbert module mentioned above. This also includes important work on weighted shifts. Operator theory motivated by mathematical physics. This includes trace formulae of Krein and Koplienko and their multivariable generalizations. Perturbation of self-adjoint operators is the main theme of study here. From the seminal work from the 60's by S. Kakutani, J. Lindenstrauss, G. Choquet and T. Ando, the study of geometric aspects of Banach spaces (the so called isometric theory) emerged as an important area. Indian researchers contributed both to the abstract study as well as towards understanding the structure of specific function spaces and spaces of operators. As the descriptions above show, operator theory has a great deal of relationship to several other branches of mathematics - geometry and complex analysis being perhaps the closest. This interaction is one source of pleasure that we shall try to bring out in this article. There has been a significant amount of excellent work done on operator algebras including Hilbert C*-modules and in matrix theory in India in recent times. Since there would be separate articles on those, this article does not include them
Inducing apatite pre-layer on titanium surface through hydrothermal processing for osseointegration
No full textCommercially available titanium (Ti) having high mechanical strength and a low area of cross-section can be adequately exploited for minimally invasive dental implantation. Current directions in clinical dental implant therapy focus on endosseous dental implant surfaces with nanoscale topographies using easy and economical processing approaches. The present study describes the generation of a novel nanolayer nucleating agent on the surface of Ti implant for early endosseous after implantation. The strategy is to modify the surface of Ti implant using Ca(OH)(2) via hydrothermal technique (Ti-FIT). The X-ray photoelectron spectroscopy analysis confirmed the presence of chemically bonded Ca ions on the Ti surface in the form of CaTiO3. In vitro studies are carried out to confirm the bone bonding ability of calcium enriched Ti surface. The apatite deposition on the surface after exposure to SBF for 7 days is confirmed via scanning electron microscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy and energy-dispersive X-ray spectroscopy techniques. The cell viability of Ti-HT was evaluated using direct contact method and MTT assay. The potential of Ca2+ ion on Ti surface via hydrothermal pre-treatment to enhance osseointegration of Ti has been proposed for achieving early stability for dental implants
Average-case linear matrix factorization and reconstruction of low width algebraic branching programs
No full textA matrix X is called a linear matrix if its entries are affine forms, i.e., degree one polynomials in n variables. What is a minimalsized representation of a given matrix F as a product of linearmatrices? Finding such a minimal representation is closely related to finding an optimal way to compute a given polynomial via an algebraic branching program. Herewe devise an efficient algorithm for an average-case version of this problem. Specifically, given w, d, n. N and blackbox access to the w2 entries of a matrix product F = X1 Xd, where each Xi is a w x w linear matrix over a given finite field Fq, we wish to recover a factorization F = Y1 Yd , where every Yi is also a linear matrix over Fq (or a small extension of Fq). We show that when the input F is sampled from a distribution defined by choosing random linear matrices X1,..., Xd over Fq independently and taking their product and n = 4w2 and char(Fq) = (dn)O(1), then an equivalent factorization F = Y1 Yd can be recovered in (randomized) time (dn log q)O(1). In fact, we give a (worst-case) polynomial time randomized algorithm to factor any non-degenerate or pure matrix product (a notion we define in the paper) into linear matrices; a matrix product F = X1 Xd is pure with high probability when the Xi's are chosen independently at random. We also show that in this situation, ifwe are instead given a single entry of F rather than its w2 correlated entries, then the recovery can be done in (randomized) time (d(w3) n log q)(O(1))
Seasonal variations in the time?activity budget of Royle?s pika in the Western Himalaya, India
No full textThe time activity budget of a species has ecological relevance because natural selection often favours individuals that utilise their time most efficiently. Details of time?activity budgets can provide information on how animals allocate time to their various activities through the day and during different seasons to most efficiently cope with varying energy demands and environmental changes that may threaten their survival. Efficient use of time?activity budget is also crucial for alpine small mammals, which live in a highly seasonal environment with restricted periods in which to gain energy and successfully reproduce. Hence, variations in the time?activity budget of the high-elevation lagomorph Royle?s pika (Ochotona roylei) were analysed during different seasons over 2 years across an elevational gradient (2900?3680 m). Seven behavioural conditions were recorded in adult and juvenile pikas through daily focal sampling between 0600 and 1900 hrs. Royle?s pika had bimodal activity: animals were most active during the morning and early evening and relatively inactive during midday hours. Adult pikas allocated the largest proportion of their time?activity budget to foraging and the smallest proportion to vocalisation. Greater food availability during the monsoon season encouraged pikas to spend more of their time foraging than on other activities. In the autumn, pikas spent more time on locomotory and musing activities. Vigilance activities were most frequent during midday hours, possibly due to a high risk of predation. Locomotion and foraging were the predominant behaviours of juveniles during the summer and monsoon seasons. Prominent food hoarding activities were not observed in either adult or juvenile pikas. Information on time allocation to different activities during different seasons should provide a baseline for future behavioural ecology and bioenergetic analyses of pikas and help to understand their potential for adaptation to climate change
van der Waals heteroepitaxy on muscovite
No full textAs current electronics makes a transition from bulky and rigid templates to lightweight and flexible ones, the emerging field of soft technology is set to revolutionize our daily life. Currently, polymer based templates dominate this field due to their excellent mechanical characteristics and low cost, but limited thermal budget and stabilities are the major technological bottlenecks resulting in poor performance and short duration of lifetime. Recently, the technology based on van der Waals heteroepitaxy on muscovite is considered as a promising solution to overcome these barriers at once. In this paper, the characteristics of muscovite and the mechanism of van der Waals heteroepitaxy will be introduced, after that, a variety of materials on muscovite via van der Waals heteroepitaxy and the efforts on practical applications are reported. With the outlook of material science and help of advanced measurements, the evidence of heteroepitaxy of muscovite and overlayers has been deeply analyzed. Moreover, various measurements of properties was carried under bending conditions to demonstrate the mechanical stability and reliability. Through this review, we pave the path to develop more material systems on muscovite to make MICAtronics completely
3D inkjet printing of biomaterials with strength reliability and cytocompatibility: Quantitative process strategy for Ti-6Al-4V
No full textAmong additive manufacturing (AM) techniques, laser or electron beam based processes have been widely investigated for metallic implants. Despite the potential in manufacturing of patient-specific biomedical implants, 3D inkjet powder printing (3DLIPP, a variant of AM) of biomaterials is still in its infancy, as little is known quantitatively about the transient process physics and dynamics. An equally important challenge has been the ink formulation to manufacture biomaterials with reliable mechanical properties and desired biocompatibility. We have developed, for the very first time, the theoretical foundation and experimental formulation of a unique process strategy involving the `on-demand' delivery of a novel in situ polymerisable acrylic ink system to print a model biomaterial, Ti-6Al-4V. The post-ejection in-flight dynamics of ink droplets have been captured in situ by employing high speed stroboscopic shadowgraphy, to quantitatively estimate the dimensionless numbers of fluid physics for `printability' assessment. Washburn model was adapted extensively to quantify the capillary ink infiltration time in porous powder bed of finite thickness. On the other hand, particle tracking mode in diffusing wave spectroscopy (DWS) was exploited to analyse the timescale for effective binding of powder particles during in situ polymerisation. The clinically relevant combination of 3D porous architecture with 98.4% interconnectivity among 10-40 mu m pores together with modest combination of elastic modulus (4 GPa) and strength reliability (Weibull modulus similar to 8.1) establish the potential of inkjet printed Ti-6Al-4V as cortical bone analogue. A better cell attachment, viability, cytoskeletal spreading with pronounced proliferation of murine fibroblasts and pre-osteoblasts on 3DIJPP Ti-6Al-4V, when benchmarked against the metallurgically processed (commercial) or selective laser melted (SLM) Ti-6Al-4V, has been demonstrated, in vitro. The enhanced cellular activities on the 3DIJPP Ti-6Al-4V was explained in terms of an interplay among the elastic stiffness, surface roughness and wettability against the same benchmarking. It is conceived that the quantitative understanding of the integrated process physics and dynamics to print Ti-6Al-4V with reliable mechanical properties together with better cytocompatibility can lead to a paradigm shift in adapting the scalable 3DIJPP for manufacturing of metallic biomaterials
Finite time stable attitude estimation of rigid bodies with unknown dynamics
No full textAn almost global finite time stable attitude estimation scheme for a rigid body that does not require the knowledge of the dynamics or the probability distribution of the sensor noise is presented. The attitude of the rigid body is estimated from measurements of at least two linearly independent known vectors and the angular velocity in the body-fixed frame. The estimation scheme is shown to be almost globally finite time stable using a Lyapunov analysis in the absence of measurement errors. A generalized Wahba's cost function, designed to be a Morse function on SO(3), is used to derive the nonlinear estimation scheme and show its stability. The proposed scheme is discretized as a geometric variational integrator for digital implementation. The stability and convergence of the estimation scheme are shown analytically, and validated through numerical simulations
Paper swab based SERS detection of non-permitted colourants from dals and vegetables using a portable spectrometer
No full textRising concern about the use of non-permitted colourants, in common food items such as dals and green vegetables sold in Indian markets, have led to a demand for low-cost point-of-use chemical analysis tools. Conventional food-analysis techniques involving tedious sample preparation protocols are not suited for in-field applications. Surface Enhanced Raman Spectroscopy (SERS) is an analytical technique that is well-suited for point-of-use chemical analysis with molecular level detection capability, which can also serve as a quality assurance tool for businesses. Effective and rapid signal collection from a large-area sample within a field-setting using disposable, low-cost SERS substrates is a key challenge in implementing such a solution. Herein, we demonstrate the use of inkjet-printed thin films comprising of robust nanostructuredsilver as flexible, paper-based SERS (P-SERS) swabs for the direct detection of Metanil Yellow (MY) from toor dal (yellow split pigeon peas) samples and Malachite Green (MG) from green peas and green chillies. The macroscopic uniformity of these thin-films in combination with a portable Raman spectrometer equipped with orbital raster scanning (ORST) technology for signal collection results in an unprecedented precision (RSD similar to 1.6%) upon characterizing samples saturated with Rhodamine-6G (R6G), a standard Raman probe. As several food-cleansing products have appeared in the marketplace, the adulterant removal efficacy of some commercially available `washes' as well as products such as `ozoniser', which was determined by SERS characterization of swabs before and after use, is also reported