Search

Diethyl chlorophosphate (DCP) has a similar reactivity to sarin, which is widely known as a nerve agent that is often used in terrorist attacks.

Transduction of the gas sensor devices through Impedance Spectroscopy (IS) provides non-conventional route to derive quantified model of equivalent circuit and to address resonant frequency tuned selectivity aspect. The quantification of the equivalent circuit elements possibly enhances the scientific understandings of sensing performance in computational scheme. Simultaneously, resonant frequency tuned selectivity approach is another possible outcome of the IS, applied to the gas sensors. These methodologies, prove the potentiality of the IS highlighting the theoretical as well as practical aspects of gas sensor devices. The present scope focuses on the step-by-step approach of flexible adoption in measuring techniques of the IS from its liquid phase measurement to gas phase one. The comparative analysis of quantitative equivalent circuit in different gas ambient is fruitful to presume the experimental details as well as the underlying physical phenomena. The input signal frequency also paved the path for the resonant frequency tuned selectivity improvement for the gas sensor devices. Importance of the IS, as transduction technique, is also discussed with physical, theoretical and computational insights. This review also dealt with corresponding constraints of IS in gas sensors by thorough inspection of different bottlenecks reported in literatures. The present review also has a focus to instigate further research to mitigate such constraints and to further improve the potentiality of the IS in gas sensor field.

The present work deals with a dark energy model that has an oscillating scalar field potential along with a cosmological constant (CC). The oscillating part of the potential represents the contribution of a light axion field in the dark energy that has its origin in the String-Axiverse scenario. The model has been confronted with the latest cosmological observations. The results show that a sub-Planckian value of the axion field decay constant is consistent with observational data. Furthermore, in terms of the observational data considered in this work, the axion model is preferred over the $\Lambda$CDM model in terms of AIC, BIC information criteria as well as in terms of Bayesian evidence. The oscillating feature in the scalar field evolution and in the equation of state for the dark energy can be observed for the allowed parameters space. It is also observed that cluster number counts in this axion model are suppressed compared to the $\Lambda$CDM and this suppression is enhanced for the sub-Planckian values for the axion decay constant., Comment: 16 pages, LateX style. Revised Version with new data analysis. Some previous results have been strengthened

We review models of the accelerating universe from the perspective of high-energy physics. Focusing on supergravity and the String Theory, we discuss the general framework for the construction of these models. We then go on to discuss explicit constructions.

Moduli potential loses its minima due to external energy sources of inflaton energy density or radiation produced at the end of inflation. But, the non-existence of minima does not necessarily mean destabilization of moduli. In fact, the destabilization of moduli is always dependent on the initial field values of the fields. In this work, we study carefully how the effects of reheating ease the problem of moduli destabilization. The associated time scale to produce the thermal bath allows a larger initial field range to stabilize the field. Contrary to the usual notion, the allowed initial field range is larger for higher temperatures when the effective potential is of a run-away nature. This eases the moduli destabilization problem for heavy mass moduli. For low mass moduli ($\lesssim$ 30 TeV), the allowed field range still causes the cosmological moduli problem by violating the BBN constraints unless its initial abundance is suppressed., 19 pages, 9 figures

We discuss a way in which the geometric scalar field in a Brans-Dicke theory can evade local astronomical tests and act as a driver of the late-time cosmic acceleration. This requires a self-interaction of the Brans-Dicke scalar as well as an interaction with ordinary matter. The scalar field in this construct acquires a density-dependent effective mass much like a Chameleon field. We discuss the viability of this setup in the context of the Equivalence Principle, Fifth Force, and Solar System tests. The cosmological consistency is adjudged in comparison with observational data from recalibrated light curves of type Ia supernova (JLA), the Hubble parameter measurements (OHD), and the Baryon Acoustic Oscillation (BAO). We deduct that the astrophysical constraints indeed favor the existence of a mild scalar-matter interaction in the Jordan Frame., 14 pages, 10 figures, Accepted for publication in MNRAS

This letter explores geometrical optics-based raytracing in combination with modal analysis to realize an open cavity structure as an advanced variant of the resonant cavity antenna (RCA). Additional ray confinement has been ensured by determining accurate phase-locking conditions as demonstrated for the first time. Its combination with the analysis of the cavity mode has also been introduced to determine the optimum design parameters, achieving improved radiation properties. With respect to a reference RCA reported earlier, the proposed approach exhibits a remarkable improvement in gain by 4–9 dB, resulting in about 17 dBi peak value consistently over the full 18% matching bandwidth. This is resultant from an increase in aperture efficiency, typically from 27% to 74%. This is achieved without any compromise with the cross-polarization property. The sidelobe level improves over the band except in higher frequency in H-plane. The proposed concept is commercially viable, showing significantly advantageous features.

In this manuscript, a thorough comparative analysis of six GaAs based nanostructures (hollow and solid) is performed on the basis of their optical performance. These nanostructures are known to exhibit excellent anti-reflection properties, owing to their ability to generate a broadband absorption spectrum through efficient photon harvesting. Using the Finite Element Method (FEM) of the commercially available COMSOL Multiphysics package, the absorption characteristics, optical short circuit current density (JSC), electric field and photogeneration rates of six different nanostructures namely concentric nanocylinder (CNCy), hollow concentric nanocylinder (HCNCy), inverted nanopencil (INPe), hollow nanopencil (HNPe), nanorod + nanohemisphere (NR + NHe), and hollow nanorod + hollow nanohemisphere (HNR + HNHe) are computed. The optical performance of these nanostructures is largely dependent on their geometrical parameters such as filling ratio (FR = Diameter/Period), spacing and structural dimensions. The optimized values of these parameters can play a vital role in capturing the optical resonance modes by the nanostructures to produce absorption enhancement. It has been observed that the nanostructures with base diameter of 240 nm, period in the range of 300–350 nm and FR of 0.8 exhibit better optical characteristics. Optical JSC and optical efficiency of 29.45 mA cm−2 and 42.26%, respectively for CNCy nanostructure with FR of 0.8 and diameter of 240 nm is the highest among all the nanostructures. The effect of the angle of incidence of the photons striking the nanostructures on the average absorptance in both Transverse Electric (TE) and Transverse Magnetic (TM) modes are also investigated. In addition to this, we have also computed the effective refractive index for all the nanostructures using Maxwell Garnett formula in order to estimate the surface anti-reflection characteristics of these nanostructures.

This paper proposes a mathematical model for decomposing a range face image into four basic components (named ‘complement components’) in conjunction with a simple approach for data-level fusion to generate thirty-six additional hybrid components. These forty component faces composing a new face image space called the ‘complement component face space.’ The main challenge of this work was to extract relevant features from the vast face space. Features are extracted from the four basic components and four selected hybrid components using singular value decomposition. To introduce diversity, the extracted feature vectors are fused by applying the crossover operation of the genetic algorithm using a Hamming distance-based fitness measure. Particle swarm optimization-based feature selection is employed on the fused features to discard redundant feature values and to maximize the face recognition performance. The recognition performances of the proposed feature set with a support vector machine-based classifier on three accessible and well-known 3D face databases, namely, Frav3D, Bosphorus, and Texas3D, show significant improvements over those achieved by state-of-the-art methods. This work also studies the feasibility of utilizing the component images in the complement component face space for data augmentation in convolutional neural network (CNN)-based frameworks.

A Sparse Principal Component Analysis Network (SpPCANet) based feature extraction is proposed here for 3D face recognition. The network consists of three basic components: (1) Multistage sparse principal component analysis filters, (2) Binary hashing, and (3) Block-wise histogram computation. Here, the sparse principal component analysis is used to learn multistage filter banks at the convolution stage, which is followed by binary hashing for indexing and block-wise histogram for pooling. Finally, a linear support vector machine (SVM) is used for classifying the features extracted by SpPCANet. The proposed network SpPCANet is a lightweight deep learning network. Three well-known 3D face databases, namely, Frav3D, Bosphorus3D, and Casia3D, are used for validating the proposed system. This proposed network has been extensively studied by varying different parameters, such as the number of filters at the convolution layer and the size of filters at the convolution layer and size of non-overlapping blocks at the pooling layer. Handling all types of variation of faces available in Frav3D, Bosphorus3D, and Casia3D databases, the system has acquired 96.93%, 98.54%, and 88.80% recognition rates, respectively.

Fast responding room temperature ethanol sensor device, having high detection range, was developed employing dual surface engineered (using palladium (Pd) and Reduced Graphene oxide (RGO)) WO3 nanospheres as the sensing layer. Three different types of vapor sensor devices, viz. i) Pd/WO3 (Sensor 1), ii) RGO/WO3 (Sensor 2) and iii) Pd/RGO/WO3 (Sensor 3) were fabricated to study the influence of each of the elements and to account for its exact contribution in improving the gas sensor device performance towards alcohol vapors. Dual surface engineered device (Sensor 3) was found to offer remarkably superior sensing performance in terms of response magnitude, response time and recovery time with a very high detection range (1-700 ppm) at room temperature (~ 27 °C), compared to any of its single surface modified device counterpart (Sensor 1 or Sensor 2). A comprehensive discussion elucidating the individual role of RGO and Pd on WO3 has also been presented employing a semi-quantitative energy band model in correlation with the corresponding electrical equivalent circuit elements.

Herein, the potential impact of tamarind seed polysaccharide (TSP) on the gelation nature and in vitro release of a particular drug, pilocarpine hydrochloride, from different poloxamer 407-based ophthalmic formulations were evaluated. The combination of TSP (0.5–1.5 wt%) and 18 wt% poloxamer (PM) solutions resulted in a significant improvement in gel elasticity under physiological conditions. The introduction of TSP to PM not only enhanced the viscosity of the gel, but also stimulated the gelation procedure. Due to the inclusion of TSP, the gel dissolution rate of the PM-based formulation was greatly reduced. The FTIR spectral analysis revealed the interaction between –OH groups of both polymers, resulting in a decline in the gelation temperature of the PM–TSP-based formulations. It was also detected in the cryo-SEM analysis that the pore size of the PM gel decreased and the depth of its pores increased with the inclusion of TSP. Furthermore, the in vitro release analysis indicated that the retention capacity of PM–TSP-based formulations was superior to that of the only PM-based formulation. The SEM study and the cell viability data demonstrated the biocompatibility and non-toxicity of TSP. Therefore, the designed formulation is fairly promising to be utilized as an in situ ophthalmic drug carrier.

It is well known that Ultra-Light Dark Matter (ULDM), usually scalar fields of mass $m \sim 10^{-22}~{\rm eV}$, can solve some of the outstanding problems of the Cold Dark Matter (CDM) paradigm. Such a scalar field could have non-negligible self-coupling $\lambda$. In this work, using the known observational upper limit on the amount of centrally concentrated dark matter in a galaxy, we arrive at the observational constraints in the $\lambda - m$ (self coupling $-$ mass) parameter space. It is found that the observational limit on the mass $m$ of the ULDM depends upon the sign and strength of the self-interactions. We demonstrate that, for $m \sim 10^{-22}~{\rm eV}$, self-coupling values of ${\cal O}(10^{-96})$ (corresponding to a scattering length of $a_s \sim 10^{-82}~{\rm m}$) can be probed using limits on the dark matter mass within 10 pc of the centre of M87 galaxy. Our analysis suggests that if Ultra Light Axions (ULAs) form all of dark matter, its mass has to be less than $\sim 6 \times 10^{-23}$ eV., Comment: Some revisions with an updated figure; Agrees with the published version

In this paper, an efficient room temperature ethanol sensor device based on p-n homojunction of p-TiO2 nanoparticles (NPs) and n-TiO2 nanotubes (NTs) is reported. p-TiO2 NPs were prepared by low-temperature sol–gel method and coated on n-TiO2 NTs (NPs) grown by electrochemical anodization. Field emission scanning electron microscopy and X-ray diffraction authenticated the formation of stable homojunction between p-type anatase TiO2 NPs and n-type anatase TiO2 NTs. Current–voltage characteristics of the device, in the lower voltage range (0–1.26 V) for 30 °C, followed nonlinear characteristics (Schottky). With increase in voltages (>1.26 V) and temperature (40 °C–100 °C) such nonlinear behavior moves toward more linear ones. The gas sensing performance of the homojunction device was studied at room temperature with alcohols as the test species. The device offered the maximum response magnitude of ~57% (toward ethanol) at 100 ppm with appreciably fast response time and recovery time of ~30 and ~16 s, respectively. Dramatic increase in the effective depletion region area distributed throughout the nanotubular voids and the associated localized electric filed originated from the electrostatic charge separation therein (which helps in easy dissociation of target species) is possibly responsible for such efficient room temperature sensing performance.

Nanostructured conducting polymers are known to function as electroactive materials in sensor devices for adsorption and detection of different analytes. For the purpose of dopamine (DA) detection and CO2 gas adsorption we have prepared nanostructured polypyrrole (PPY) with the help of sodium cholate as surfactant. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) analyses and Brunauer–Emmett–Teller (BET) measurement have been done for the characterization of nanostructure and morphology of the prepared PPY. From the sorption measurement, it is observed that the rodlike PPY structures show highest N2 uptake (91.6 mL g−1) along with appreciable surface area (85.81 m2/g) and porosity (2.53 and 4.51 nm) values. It is also observed that the maximum uptake of CO2 is 173.885 mL g−1 at 195K for the PPY synthesized without any surfactant. Electrochemical characterization of PPY modified glassy carbon electrode (GCE) was done with impedance and cyclic voltammetry experiments. DA sensing in presence of ascorbic acid, uric acid and glucose was done by LSV technique. The PPY modified electrode exhibits sensitivity values of 0.301 and 0.19 μA μM−1 cm2 over two ranges of detection limits of 0.09–0.56 and 10–50 μM for dopamine, respectively (signal/noise = 3).

Decay of the inflaton or moduli which dominated the energy density of the universe at early times leads to a matter to radiation transition epoch. We consider nonthermal sterile dark matter (DM) particles produced as decay product during such transitions. The particles have a characteristic energy distribution---that associated with decays taking place in a matter dominated universe evolving to radiation domination. We primarily focus on the case when the particles are hot dark matter, and study their effects on the cosmic microwave background (CMB) and large scale structure (LSS), explicitly taking into account their nonthermal momentum distribution. Our results for CMB angular power and linear matter power spectra reveal interesting features---such as an order of magnitude higher values of hot dark matter mass in comparison to the thermal case being consistent with the present data. We observe that this is related to the fact that $\mathrm{\ensuremath{\Delta}}{N}_{\mathrm{eff}}$ (the effective number of relativistic degrees of freedom at the time of CMB decoupling) and the hot DM energy density can be independent of each other unlike the case of thermal or nonresonantly produced sterile hot DM. We also find features in the CMB at low $\ensuremath{\ell}$ angular power potentially related to supersonic transmission of hot dark matter through the photon-baryon plasma.

We explore the prospect of producing primordial black holes around the solar mass region during an early matter domination epoch. The early matter-dominated epoch can arise when a moduli field comes to dominate the energy density of the Universe prior to big bang nucleosynthesis. The absence of radiation pressure during a matter-dominated epoch enhances primordial black hole formation from the gravitational collapse of primordial density fluctuations. In particular, we find that primordial black holes are produced in the $0.1-10~M_{\odot}$ mass range with a favorable choice of parameters in the theory. However, they cannot explain all of the merger events detected by the LIGO/Virgo gravitational wave search. In such a case, primordial black holes form about $4\%$ of the total dark matter abundance, of which $95\%$ belongs to the LIGO/Virgo consistent mass range. The rest of the dark matter could be in the form of particles that are produced from the decay of the moduli field during reheating., 23 pages, 5 figures; minor modifications; JCAP published version