Improving the efficiency of induction motor drive by flux and torque control: A hybrid LSE-RERNN approach

A hybrid technique is proposed in this manuscript for the optimal design of an induction motor (IM) drive for the dynamic load profiles during torque and flux control. The proposed hybrid method combines a Ladder-Spherical-Evolution-Search-Algorithm (LSE) and a recalling-enhanced recurrent-neural network (RERNN), which is called an LSE-RERNN technique. The major objective of the proposed method is to minimize IM losses while maintaining control over speed and torque. The proposed method effectively tunes the gain parameter of the PI controller for flux and torque regulation. The LSE methodgenerates a set of gain parameters optimally predicted by RERNN. The method reduces losses without prior knowledge of load profiles, achieving energy savings for steady-state optimum flux. The performance of the proposed technique is done in the MATLAB and is compared with different existing techniques. The value of the proposed method for the mean is 0.328, the standard deviation (SD) is 0.00334, and the median is 0.4173. The loss of the proposed method is much less than 0.3 W while compared to different existing approaches. Moreover, the computation time of the proposed approach is lesser than the existing techniques.

Benthic foraminifera as an environmental proxy for pollutants along the coast of Chennai, India

Benthic foraminifera are increasingly used as an indicator of environmental disturbance. Their sensitivities to pollutants can be reflected by changes in assemblage, which can provide useful information about ecosystem health. This study aimed to investigate the impact of organic and inorganic pollutants on the benthic ecology of the Chennai coast, with a focus on the 2017 oil spill caused by the collision of two ships. Sediment samples collected from five distinct zones along the coast were analysed for pollutants such as polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH), heavy metals (Cr, Cd, Pb) and total organic carbon (TOC). The maximum concentrations of Cr (137 μg/g), Cd (6.93 μg/g) and Pb (34.2 μg/g), as well as TPH (84.3 μg/g) and PAHs (227 ng/g), were observed. A total of 47 species of foraminifera were identified in this study, of which 12 were morphologically abnormal. In the low-impact zone, the species diversity index (H') was higher. TPH and PAH concentrations were positively associated with abnormal species. Pollution-resistant foraminifera species include Ammonia tepida, Elphidium discoidale, and Quinqueloculina lamarckiana, while opportunistic foraminifera include Pararotalia curryi, Nonionella stella, Rosalina globularis, and Spirillina vivipara. PAHs and heavy metals were adversely correlated with foraminiferal abundance, while TPH was positively correlated. To assess the response of the benthic ecosystem to hydrocarbon pollution, indices such as the Foraminiferal Index of Environmental Impact (FIEI), Exponential (H'_bc) index and the Foraminiferal Abnormality Index (FAI) were used as environmental health proxies. FIEI, exp(H'_bc) and FAI values show the impact of hydrocarbon pollution to an extent along the northern Chennai coast.

Large magnetoresistance and quantum oscillations in Sn0.05Pb0.95Te

We have synthesized high-quality single crystals of Sn_xPb_1-xTe and carried out detailed studies of the magnetotransport properties of one of the samples, Sn_0.05Pb_0.95Te. Longitudinal magnetoresistance increases almost linearly with increasing applied field (H) and reaches ∼310% atH= 13 T. At higher fields, both longitudinal and Hall resistance show clear Shubnikov de Haas oscillations. The oscillations are smooth and periodic, and there exists only one frequency,f_α∼ 57 T. However, an additional frequency,f_β∼ 69 T, appears as the angle between the field direction and the normal to the sample surface (θ) is increased. Bothf_αandf_βexhibitθ-dependence;f_αdecreases whereasf_βincreases gradually with increasingθ. The presence of two frequencies in Sn_0.05Pb_0.95Te indicates that there exist two Fermi surface pockets (αandβpockets). We have constructed the Landau-level fan plot and determined the Berry phase (δ) for theαpocket to beδ∼ 0.1. Thisδvalue is very close to the expected value of 0 for a topologically trivial system.

Tocilizumab Use in COVID-19 Cytokine-release Syndrome: Retrospective Study of Two Centers

Introduction

Cytokine-release syndrome (CRS) in COVID-19 patients can cause multiorgan failure and higher mortality. We used a structured protocol based on clinical, biochemical, and interleukin 6 (IL-6) criteria for the identification of the subset of patients with CRS and analyzed the use of tocilizumab for their treatment.

Materials and methods

We did a retrospective case-control analysis of all COVID-19 patients between 15 March and 15 May 2020 with severe to critical disease in ICU. They were evaluated for CRS, and 22 patients who met the criterion were given tocilizumab. The primary objective was to evaluate the effect of tocilizumab on escalation of respiratory support and ICU mortality. The secondary objectives were ICU length of stay, trends of inflammatory markers, and any adverse effects.

Results

The need for escalation of respiratory support was significantly lower in the tocilizumab group as compared to standard treatment (p = 0.001). The mortality at day 7 and 28 was also significantly lower in the tocilizumab group (p = 0.007 and p = 0.001 respectively). There was a significant reduction in C-reactive protein (CRP) who received tocilizumab (p = 0.033).

Conclusion

In our limited number of patients, timely intervention with tocilizumab in COVID-19 patients with CRS significantly improved overall ICU outcome by reducing the need for invasive ventilation and mortality.

How to cite this article

Nasa P, Singh A, Upadhyay S, Bagadia S, Polumuru S, Shrivastava PK, et al. Tocilizumab Use in COVID-19 Cytokine-release Syndrome: Retrospective Study of Two Centers. Indian J Crit Care Med 2020;24(9):771-776.

Tocilizumab Use in COVID-19 Cytokine-release Syndrome: Retrospective Study of Two Centers

INTRODUCTION

Cytokine-release syndrome (CRS) in COVID-19 patients can cause multiorgan failure and higher mortality. We used a structured protocol based on clinical, biochemical, and interleukin 6 (IL-6) criteria for the identification of the subset of patients with CRS and analyzed the use of tocilizumab for their treatment.

MATERIALS AND METHODS

We did a retrospective case-control analysis of all COVID-19 patients between 15 March and 15 May 2020 with severe to critical disease in ICU. They were evaluated for CRS, and 22 patients who met the criterion were given tocilizumab. The primary objective was to evaluate the effect of tocilizumab on escalation of respiratory support and ICU mortality. The secondary objectives were ICU length of stay, trends of inflammatory markers, and any adverse effects.

RESULTS

The need for escalation of respiratory support was significantly lower in the tocilizumab group as compared to standard treatment (p = 0.001). The mortality at day 7 and 28 was also significantly lower in the tocilizumab group (p = 0.007 and p = 0.001 respectively). There was a significant reduction in C-reactive protein (CRP) who received tocilizumab (p = 0.033).

CONCLUSION

In our limited number of patients, timely intervention with tocilizumab in COVID-19 patients with CRS significantly improved overall ICU outcome by reducing the need for invasive ventilation and mortality.

HOW TO CITE THIS ARTICLE

Nasa P, Singh A, Upadhyay S, Bagadia S, Polumuru S, Shrivastava PK, et al. Tocilizumab Use in COVID-19 Cytokine-release Syndrome: Retrospective Study of Two Centers. Indian J Crit Care Med 2020;24(9):771-776.

Gd2Te3: an antiferromagnetic semimetal

We report high-precision magnetization ([Formula: see text]), magnetic susceptibility ([Formula: see text]), specific heat (C _p(T, H)) and 'zero-field' electrical resistivity, [Formula: see text], data taken on Gd₂Te₃ single crystal over wide ranges of temperature and magnetic field (H), with either [Formula: see text]-axis or [Formula: see text]-plane. [Formula: see text] and [Formula: see text] unambiguously establish that the b-axis is the easy direction of magnetization whereas any direction in the ac-plane is a hard direction. The [Formula: see text]-type anomaly in 'zero-field' specific heat, C _p(T, H  =  0), and an abrupt drop in [Formula: see text] (characteristic of the paramagnetic (PM) - antiferromagnetic (AFM) phase transition) are observed at the Néel temperature, [Formula: see text] K. [Formula: see text] and C _p(T,H) clearly demonstrate that [Formula: see text] shifts to lower temperatures with increasing H irrespective of whether H points in the easy or hard direction. When [Formula: see text], the [Formula: see text] isotherms at temperatures in the range 2.5 K [Formula: see text] [Formula: see text] K reveal the existence of a field-induced spin-flop (SF) transition at fields 4.0 T [Formula: see text] [Formula: see text] [Formula: see text] 4.5 T. The first principles electronic band structure and density of states calculations, based on the density functional theory, correctly predict an AFM ground state (stabilized primarily by the 4f  Gd³⁺ - 5p  Te^2-- 4f  Gd³⁺ superexchange interactions) and the observed semi-metallic behavior for the Gd₂Te₃ compound. Moreover, these calculations yield the values [Formula: see text] [Formula: see text] for the ordered magnetic moment per Gd atom at T  =  0, [Formula: see text] mJ mol^-1 K^-2 for the Sommerfeld coefficient for the electronic specific heat contribution and [Formula: see text] K for the Curie-Weiss temperature, respectively. These theoretical estimates conform well with the corresponding experimental values [Formula: see text] [Formula: see text], [Formula: see text] mJ mol^-1 K^-2 and [Formula: see text] K.

Contrasting the Surface Phonon Dispersion of Pb_{0.7}Sn_{0.3}Se in Its Topologically Trivial and Nontrivial Phases

We report inelastic He atom scattering measurements of the (001) surface phonon dispersion of the topological crystalline insulator Pb_{0.7}Sn_{0.3}Se. This material exhibits a temperature-dependent topological transition, so we measure the surface dispersion curves in both the trivial and nontrivial phases. We identify that, peculiarly, most surface modes are resonances, rather than pure surface states. We find that a shear vertical surface resonance branch around 9.0 meV dramatically changes on going from the trivial to the topological phase. We associate this remarkable change with the emergence of surface Dirac fermions. We use the measured dispersion of this resonance branch to determine the corresponding mode-dependent electron-phonon coupling λ_{ν}(q).

Interplay of orbital effects and nanoscale strain in topological crystalline insulators

Orbital degrees of freedom can have pronounced effects on the fundamental properties of electrons in solids. In addition to influencing bandwidths, gaps, correlation strength and dispersion, orbital effects have been implicated in generating novel electronic and structural phases. Here we show how the orbital nature of bands can result in non-trivial effects of strain on band structure. We use scanning–tunneling microscopy to study the effects of strain on the electronic structure of a heteroepitaxial thin film of a topological crystalline insulator, SnTe. By studying the effects of uniaxial strain on the band structure we find a surprising effect where strain applied in one direction has the most pronounced influence on the band structure along the perpendicular direction. Our theoretical calculations indicate that this effect arises from the orbital nature of the conduction and valence bands. Our results imply that a microscopic model capturing strain effects must include a consideration of the orbital nature of bands.

The role of orbital degrees of freedom in determining the electronic structure remains obscured. Here, Walkup et al. report strain-induced band structure changes in a topological crystalline insulator SnTe, whose surprising behavior reflects the  orbital nature of bands.

Evidence of s-wave superconductivity in the noncentrosymmetric La7Ir3

Superconductivity in noncentrosymmetric compounds has attracted sustained interest in the last decades. Here we present a detailed study on the transport, thermodynamic properties and the band structure of the noncentrosymmetric superconductor La 7 Ir 3 (T c  ~ 2.3 K) that was recently proposed to break the time-reversal symmetry. It is found that La7Ir3 displays a moderately large electronic heat capacity (Sommerfeld coefficient γ n  ~ 53.1 mJ/mol K2) and a significantly enhanced Kadowaki-Woods ratio (KWR ~32 μΩ cm mol2 K2 J-2) that is greater than the typical value (~10 μΩ cm mol2 K2 J-2) for strongly correlated electron systems. The upper critical field Hc2 was seen to be nicely described by the single-band Werthamer-Helfand-Hohenberg model down to very low temperatures. The hydrostatic pressure effects on the superconductivity were also investigated. The heat capacity below T c reveals a dominant s-wave gap with the magnitude close to the BCS value. The first-principles calculations yield the electron-phonon coupling constant λ = 0.81 and the logarithmically averaged frequency ω ln  = 78.5 K, resulting in a theoretical T c  = 2.5 K, close to the experimental value. Our calculations suggest that the enhanced electronic heat capacity is more likely due to electron-phonon coupling, rather than the electron-electron correlation effects. Collectively, these results place severe constraints on any theory of exotic superconductivity in this system.

Observation of ultrahigh mobility surface states in a topological crystalline insulator by infrared spectroscopy

Topological crystalline insulators possess metallic surface states protected by crystalline symmetry, which are a versatile platform for exploring topological phenomena and potential applications. However, progress in this field has been hindered by the challenge to probe optical and transport properties of the surface states owing to the presence of bulk carriers. Here, we report infrared reflectance measurements of a topological crystalline insulator, (001)-oriented Pb_1−xSn_xSe in zero and high magnetic fields. We demonstrate that the far-infrared conductivity is unexpectedly dominated by the surface states as a result of their unique band structure and the consequent small infrared penetration depth. Moreover, our experiments yield a surface mobility of 40,000 cm² V⁻¹ s⁻¹, which is one of the highest reported values in topological materials, suggesting the viability of surface-dominated conduction in thin topological crystalline insulator crystals. These findings pave the way for exploring many exotic transport and optical phenomena and applications predicted for topological crystalline insulators.

Probing optical and transport properties of the surface states in topological crystalline insulators remains a challenge. Here, Wang et al. demonstrate that the far-infrared conductivity of Pb_1−xSn_xSe (x = 0.23−0.25) single crystals is dominated by the surface states where carriers show a high surface mobility of 40,000 cm² V⁻¹ s⁻¹.

Emerging Strategies and Challenges for Controlled Delivery of Taxanes: A Comprehensive Review

Taxanes introduction in the mid 90 s leads to significant advancement as well as superlative improvement in the treatment of cancer. Since then, several strategies have been designed to enhance therapeutic potential of these agents by overcoming the limitations in drug delivery and pharmacokinetic constraints associated with conventional delivery. In this regard, controlled drug delivery systems for taxanes have contributed enormously by altering the pharmacokinetic profile, thus ultimately enhancing their therapeutic response. With their conferred stellar merits, controlled drug delivery systems have been able to surmount many of the challenges associated with conventional drug delivery systems. The altered absorption, resistance, low toxicity and cellular uptake profiles that lead to better safety from variegated carrier systems like nanocarriers, liposomes, solid lipid nanoparticles, nanoemulsions, nanocapsules, hydrogels and micelles for controlled delivery of taxanes call for an exhaustive review for future progressive work. Therefore, this review focuses on the altered pharmacokinetic, pharmacodynamic and toxicity patterns achieved from various controlled drug delivery approaches, with the latter half highlighting the clinical profile set ups and commercial aspects of controlled release drug delivery systems.

Large transverse Hall-like signal in topological Dirac semimetal Cd3As2

Cadmium arsenide (Cd₃As₂) is known for its inverted band structure and ultra-high electron mobility. It has been theoretically predicted and also confirmed by ARPES experiments to exhibit a 3D Dirac semimetal phase containing degenerate Weyl nodes. From magneto-transport measurements in high quality single crystals of Cd₃As₂, a small effective mass m^* ≈ 0.05 m_e is determined from the Shubnikov-de Haas (SdH) oscillations. In certain field orientations, we find a splitting of the SdH oscillation frequency in the FFT spectrum suggesting a possible lifting of the double degeneracy in accord with the helical spin texture at outer and inner Fermi surfaces with opposite chirality predicted by our ab initio calculations. Strikingly, a large antisymmetric magnetoresistance with respect to the applied magnetic fields is uncovered over a wide temperature range in needle crystal of Cd₃As₂ with its long axis along [112] crystal direction. It reveals a possible contribution of intrinsic anomalous velocity term in the transport equation resulting from a unique 3D Rashba-like spin splitted bands that can be obtained from band calculations with the inclusion of Cd antisite defects.

Successive spin orderings of tungstate-bridged Li2Ni(WO4)2 of spin 1

Magnetic, thermodynamic, and dielectric properties of Li2Ni(WO4)2 of S  =  1 system have been studied using magnetic susceptibility, specific heat, and dielectric constant measurements. The magnetic orderings can be identified in three stages, including a short range magnetic ordering indicated by the rounded χ(T) peak with maximum at  ∼20 K, and signatures of two successful antiferromagnetic long range orderings near T(N1) ~ 18 K and T(N2) ~ 13 K revealed by the d(χ(T)) /d(T) peaks. The successive long range magnetic orderings are related to the quasi triangular symmetry breaking in the ac- and bc-planes and to the change of the dielectric constant, suggesting the presence of spin-phonon coupling. The specific heat and magnetic entropy analysis for Li2Ni(WO4)2 shows the existence of a significant low dimensional magnetic correlations at high temperature and confirms the long range three-dimensional (3D) behavior of magnetic orderings below T(N1) and T(N2).

Strain engineering Dirac surface states in heteroepitaxial topological crystalline insulator thin films

The unique crystalline protection of the surface states in topological crystalline insulators has led to a series of predictions of strain-generated phenomena, from the appearance of pseudo-magnetic fields and helical flat bands to the tunability of Dirac surface states by strain that may be used to construct 'straintronic' nanoswitches. However, the practical realization of this exotic phenomenology via strain engineering is experimentally challenging and is yet to be achieved. Here, we have designed an experiment to not only generate and measure strain locally, but also to directly measure the resulting effects on Dirac surface states. We grew heteroepitaxial thin films of topological crystalline insulator SnTe in situ and measured them using high-resolution scanning tunnelling microscopy to determine picoscale changes in the atomic positions, which reveal regions of both tensile and compressive strain. Simultaneous Fourier-transform scanning tunnelling spectroscopy was then used to determine the effects of strain on the Dirac electrons. We find that strain continuously tunes the momentum space position of the Dirac points, consistent with theoretical predictions. Our work demonstrates the fundamental mechanism necessary for using topological crystalline insulators in strain-based applications.