Electrochemical and photochemical reaction of isatins: a decade update.

This review presents the latest progress in photochemical and electrochemical reactions involving isatins. Isatin and its functionalized scaffolds e.g., oxindoles, spirooxindoles, and quinolines are privileged heterocycles as they are largely present in several agrochemical, natural products, and pharmaceuticals. Thus, the functionalization of isatins using sustainable approaches, i.e., electro- and photochemical methods is of recent research interest worldwide. In this review, we have discussed most of the important reactions of isatins based on types of bond formation involved under electro- and photochemical conditions over the last decade. The reaction mechanism for each reaction has been discussed in detail to offer an inclusive guide to readers. Lastly, a summary of current challenges and the future outlook toward the development of effective electrochemical and photochemical methods for the reaction of isatins is also presented.

Erratum: Anderson Localization in the Fractional Quantum Hall Effect [Phys. Rev. Lett. 128, 116801 (2022)].

This corrects the article DOI: 10.1103/PhysRevLett.128.116801.

Composite Fermion Pairing Induced by Landau Level Mixing.

Pairing of composite fermions provides a possible mechanism for fractional quantum Hall effect at even denominator fractions and is believed to serve as a platform for realizing quasiparticles with non-Abelian braiding statistics. We present results from fixed-phase diffusion Monte Carlo calculations which predict that substantial Landau level mixing can induce a pairing of composite fermions at filling factors ν=1/2 and ν=1/4 in the l=-3 relative angular momentum channel, thereby destabilizing the composite-fermion Fermi seas to produce non-Abelian fractional quantum Hall states.

Fractional Quantum Hall Effect with Unconventional Pairing in Monolayer Graphene.

Motivated by the observation of even denominator fractional quantum Hall effect in the n=3 Landau level of monolayer graphene [Kim et al., Nat. Phys. 15, 154 (2019)NPAHAX1745-247310.1038/s41567-018-0355-x], we consider a Bardeen-Cooper-Schrieffer variational state for composite fermions and find that the composite-fermion Fermi sea in this Landau level is unstable to an f-wave pairing. Analogous calculation suggests the possibility of a p-wave pairing of composite fermions at half filling in the n=2 graphene Landau level, whereas no pairing instability is found at half filling in the n=0 and n=1 graphene Landau levels. The relevance of these results to experiments is discussed.

Phase diagram of superconductivity in the integer quantum Hall regime.

An interplay between pairing and topological orders has been predicted to give rise to superconducting states supporting exotic emergent particles, such as Majorana particles obeying non-Abelian braid statistics. We consider a system of spin polarized electrons on a Hofstadter lattice with nearest-neighbor attractive interaction and solve the mean-field Bogoliubov-de Gennes equations in a self-consistent fashion, leading to gauge-invariant observables and a rich phase diagram as a function of the chemical potential, the magnetic field, and the interaction. As the strength of the attractive interaction is increased, the system first makes a transition from a quantum Hall phase to a skyrmion lattice phase that is fully gapped in the bulk but has topological chiral edge current, characterizing a topologically nontrivial state. This is followed by a vortex phase in which the vortices carrying Majorana modes form a lattice; the spectrum contains a low-energy Majorana band arising from the coupling between neighboring vortex-core Majorana modes but does not have chiral edge currents. For some parameters, a dimer vortex lattice occurs with no Majorana band. The experimental feasibility and the observable consequences of skyrmions as well as Majorana modes are indicated.

Anderson Localization in the Fractional Quantum Hall Effect.

The interplay between interaction and disorder-induced localization is of fundamental interest. This article addresses localization physics in the fractional quantum Hall state, where both interaction and disorder have nonperturbative consequences. We provide compelling theoretical evidence that the localization of a single quasiparticle of the fractional quantum Hall state at filling factor ν=n/(2n+1) has a striking quantitative correspondence to the localization of a single electron in the (n+1)th Landau level. By analogy to the dramatic experimental manifestations of Anderson localization in integer quantum Hall effect, this leads to predictions in the fractional quantum Hall regime regarding the existence of extended states at a critical energy, and the nature of the divergence of the localization length as this energy is approached. Within a mean field approximation, these results can be extended to situations where a finite density of quasiparticles is present.

Clinical outcomes in COVID-19 patients treated with antivirals: a retrospective analysis.

Drug repurposing is considered as a rapid strategy for COVID-19 drug discovery and many drugs have been tried for treatment of COVID-19. Antivirals like favipiravir and remdesivir have become part of the COVID-19 Management Protocol by Ministry of Health and Family Welfare (MOHFW) as well as Maharashtra State guidelines since beginning, after being approved by Drugs Controller General of India (DCGI). Although these drugs have shown promising results, their efficacy is still not proven completely and needs to be studied in large populations. The purpose of our study was to evaluate the clinical outcomes in hospitalised patients with COVID-19 treated with remdesivir and/or favipiravir. MATERIAL: Retrospective analysis of medical records of 914 adult COVID-19 patients hospitalized in a tertiary care center in Mumbai was conducted. We assessed the following outcomes: severity of disease, need for oxygen supplementation, incidence of complications, discharge from hospital or death, oxygen requirement at the time of discharge, duration of hospital stay. These outcomes were compared between patients who received remdesivir only, patients who received favipiravir only, patients who received both remdesivir and favipiravir and patients who did not receive either remdesivir or favipiravir (control group). OBSERVATION: Of total 914 patients in our study, 55.79% patients received only remdesivir, 13.45% received only favipiravir, 7.76% received remdesivir plus favipiravir and 22.97% did not receive any antivirals. Higher number of patients in remdesivir only group (60.19%) and remdesivir plus favipiravir groups (56.33%) required supplemental oxygen [vs 32.38 % patients in control group and 24.39% in favipiravir only group]. Highest number of patients (91.05%) in favipiravir only group got discharged under Indian Council of Medical Research (ICMR) guidelines closely followed by 88.73% in remdesivir plus favipiravir group, 88.43% in remdesivir only group and 82.38 % patients in control group. 8.43% patients in remdesivir only group, 6.5% in favipiravir only group, 7.04% in remdesivir plus favipiravir group and 10.47 % patients in control group needed oxygen support after discharge. CONCLUSION: Majority of patients in our study got discharged under ICMR guidelines with higher proportion of patients in the treatment groups as compared to the control group. Also, lesser number of patients in the treatment groups required oxygen supplementation post discharge as compared to the control group.

Exactly Solvable Model for Strongly Interacting Electrons in a Magnetic Field.

States of strongly interacting particles are of fundamental interest in physics and can produce exotic emergent phenomena and topological structures. We consider here two-dimensional electrons in a magnetic field, and, departing from the standard practice of restricting to the lowest LL, introduce a model short-range interaction that is infinitely strong compared to the cyclotron energy. We demonstrate that this model lends itself to an exact solution for the ground as well as excited states at arbitrary filling factors ν<1/2p and produces a fractional quantum Hall effect at fractions of the form ν=n/(2pn+1), where n and p are integers. The fractional quantum Hall states of our model share many topological properties with the corresponding Coulomb ground states in the lowest Landau level, such as the edge physics and the fractional charge of the excitations.

Defining the Antimalarial Activity of Cipargamin in Healthy Volunteers Experimentally Infected with Blood-Stage Plasmodium falciparum.

The spiroindolone cipargamin, a new antimalarial compound that inhibits Plasmodium ATP4, is currently in clinical development. This study aimed to characterize the antimalarial activity of cipargamin in healthy volunteers experimentally infected with blood-stage Plasmodium falciparum Eight subjects were intravenously inoculated with parasite-infected erythrocytes and received a single oral dose of 10 mg cipargamin 7 days later. Blood samples were collected to monitor the development and clearance of parasitemia and plasma cipargamin concentrations. Parasite regrowth was treated with piperaquine monotherapy to clear asexual parasites, while allowing gametocyte transmissibility to mosquitoes to be investigated. An initial rapid decrease in parasitemia occurred in all participants following cipargamin dosing, with a parasite clearance half-life of 3.99 h. As anticipated from the dose selected, parasite regrowth occurred in all 8 subjects 3 to 8 days after dosing and allowed the pharmacokinetic/pharmacodynamic relationship to be determined. Based on the limited data from the single subtherapeutic dose cohort, a MIC of 11.6 ng/ml and minimum parasiticidal concentration that achieves 90% of maximum effect of 23.5 ng/ml were estimated, and a single 95-mg dose (95% confidence interval [CI], 50 to 270) was predicted to clear 109 parasites/ml. Low gametocyte densities were detected in all subjects following piperaquine treatment, which did not transmit to mosquitoes. Serious adverse liver function changes were observed in three subjects, which led to premature study termination. The antimalarial activity characterized in this study supports the further clinical development of cipargamin as a new treatment for P. falciparum malaria, although the hepatic safety profile of the compound warrants further evaluation. (This study has been registered at ClinicalTrials.gov under identifier NCT02543086.).

Kohn-Sham Theory of the Fractional Quantum Hall Effect.

We formulate the Kohn-Sham (KS) equations for the fractional quantum Hall effect by mapping the original electron problem into an auxiliary problem of composite fermions that experience a density dependent effective magnetic field. Self-consistent solutions of the KS equations demonstrate that our formulation captures not only configurations with nonuniform densities but also topological properties such as fractional charge and fractional braid statistics for the quasiparticles excitations. This method should enable a realistic modeling of the edge structure, the effect of disorder, spin physics, screening, and of fractional quantum Hall effect in mesoscopic devices.

Prediction of a Non-Abelian Fractional Quantum Hall State with f-Wave Pairing of Composite Fermions in Wide Quantum Wells.

We theoretically investigate the nature of the state at the quarter filled lowest Landau level and predict that, as the quantum well width is increased, a transition occurs from the composite fermion Fermi sea into a novel non-Abelian fractional quantum Hall state that is topologically equivalent to f-wave pairing of composite fermions. This state is topologically distinct from the familiar p-wave paired Pfaffian state. We compare our calculated phase diagram with experiments and make predictions for many observable quantities.

Development of a subsurface LIBS sensor for in situ groundwater quality monitoring with applications in CO2 leak sensing in carbon sequestration.

Sub-surface activity such as geologic carbon sequestration (GCS) has the potential to contaminate groundwater sources with dissolved metals originating from sub-surface brines or leaching of formation rock. Therefore, a Laser Induced Breakdown Spectroscopy (LIBS) based sensor is developed for sub-surface water quality monitoring. The sensor head is built using a low cost passively Q-switched (PQSW) laser and is fiber coupled to a pump laser and a gated spectrometer. The prototype sensor head was constructed using off the shelf components and a custom monolithic, PQSW laser and testing has verified that the fiber coupled design performs as desired. The system shows good calibration linearity for tested elements (Ca, Sr, and K), quick data collection times, and Limits of Detection (LODs) that are comparable to or better than those of table top, actively Q-switched systems. The fiber coupled design gives the ability to separate the PQSW LIBS excitation laser from the pump source and spectrometer, allowing these expensive and fragile components to remain at the surface while only the low-cost, all optical sensor head needs to be exposed to the hostile downhole environment.

Fractional Quantum Hall Effect at ν=2+6/13: The Parton Paradigm for the Second Landau Level.

The unexpected appearance of a fractional quantum Hall effect (FQHE) plateau at ν=2+6/13 [A. Kumar et al., Phys. Rev. Lett. 105, 246808 (2010)PRLTAO0031-900710.1103/PhysRevLett.105.246808] offers a clue into the physical mechanism of the FQHE in the second Landau level (SLL). Here we propose a "3[over ¯]2[over ¯]111" parton wave function, which is topologically distinct from the 6/13 state in the lowest Landau level. We demonstrate the 3[over ¯]2[over ¯]111 state to be a good candidate for the ν=2+6/13 FQHE, and make predictions for experimentally measurable properties that can reveal the nature of this state. Furthermore, we propose that the "n[over ¯]2[over ¯]111" family of parton states naturally describes many observed SLL FQHE plateaus.

Crystallization in the Fractional Quantum Hall Regime Induced by Landau-Level Mixing.

The interplay between strongly correlated liquid and crystal phases for two-dimensional electrons exposed to a high transverse magnetic field is of fundamental interest. Through the nonperturbative fixed-phase diffusion Monte Carlo method, we determine the phase diagram of the Wigner crystal in the ν-κ plane, where ν is the filling factor and κ is the strength of Landau-level (LL) mixing. The phase boundary is seen to exhibit a striking ν dependence, with the states away from the magic filling factors ν=n/(2pn+1) being much more susceptible to crystallization due to Landau-level mixing than those at ν=n/(2pn+1). Our results explain the qualitative difference between the experimental behaviors observed in n- and p-doped gallium arsenide quantum wells and, in particular, the existence of an insulating state for ν<1/3 and also for 1/3<ν<2/5 in low-density p-doped systems. We predict that, in the vicinity of ν=1/5 and ν=2/9, increasing LL mixing causes a transition not into an ordinary electron Wigner crystal, but rather into a strongly correlated crystal of composite fermions carrying two vortices.

Inter-Landau-level Andreev Reflection at the Dirac Point in a Graphene Quantum Hall State Coupled to a NbSe_{2} Superconductor.

Superconductivity and the quantum Hall effect are distinct states of matter occurring in apparently incompatible physical conditions. Recent theoretical developments suggest that the coupling of the quantum Hall effect with a superconductor can provide fertile ground for realizing exotic topological excitations such as non-Abelian Majorana fermions or Fibonacci particles. As a step toward that goal, we report observation of Andreev reflection at the junction of a quantum Hall edge state in a single layer graphene and a quasi-two-dimensional niobium diselenide (NbSe_{2}) superconductor. Our principal finding is the observation of an anomalous finite-temperature conductance peak located precisely at the Dirac point, providing a definitive evidence for inter-Landau-level Andreev reflection in a quantum Hall system. Our observations are well supported by detailed numerical simulations, which offer additional insight into the role of the edge states in Andreev physics. This study paves the way for investigating analogous Andreev reflection in a fractional quantum Hall system coupled to a superconductor to realize exotic quasiparticles.

Demonstration of acid and water recovery systems: Applicability and operational challenges in Indian metal finishing SMEs.

Diffusion dialysis, acid retardation and nanofiltration plants were acquired from Europe and demonstrated in several Indian metal finishing companies over a three year period. These companies are primarily small and medium enterprises (SMEs). Free acid recovery rate from spent pickling baths using diffusion dialysis and retardation was in the range of 78-86% and 30-70% respectively. With nanofiltration, 80% recovery rate of rinse water was obtained. The demonstrations created awareness among the metal finishing companies to reuse resources (acid/water) from the effluent streams. However, lack of efficient oil separators, reliable chemical analysis and trained personnel as well as high investment cost limit the application of these technologies. Local manufacturing, plant customization and centralized treatment are likely to encourage the uptake of such technologies in the Indian metal finishing sector.

Chikungunya outbreak in Delhi, India, 2016: report on coinfection status and comorbid conditions in patients.

Chikungunya fever is a major public health issue in India affecting billions. After 2010, the infection was in a decline until in 2016, when a massive outbreak affected the country. In this report, we present serologic and molecular investigations of 600 patient samples for chikungunya and dengue viruses along with clinical and comorbidity features. We recruited 600 patients during this outbreak and evaluated them for chikungunya and dengue virus antibodies and virus RNA through IgM, NS1 antigen and quantitative real-time PCR (qPCR). We further evaluated Zika virus RNA by qPCR. Additionally, we documented all clinical and comorbid features that were observed during the outbreak in the hospital. We report a total incidence rate of 58% of chikungunya during the outbreak in our hospital. Within the recruited patients, 70% of the patients were positive for chikungunya virus IgM whereas 24.17% were positive by qPCR. None of the samples was positive for Zika virus RNA. Additionally, coinfection of dengue and chikungunya was seen in 25.33% of patients. Analysis of clinical features revealed that 97% of patients had restricted movements of the joints with other features like swelling, itching and rashes of varying severity observed. Twelve patients presented with comorbid conditions, and two fatalities occurred among these comorbid patients. The high incidence of coinfection in the current outbreak warrants implementation of routine testing of both chikungunya and dengue virus in suspected patients for better patient management. The post-acute phase complications reported in the hospitals require in-depth studies to understand the actual impact of the current outbreak.

Density-Functional Theory of the Fractional Quantum Hall Effect.

A conceptual difficulty in formulating the density-functional theory of the fractional quantum Hall effect is that while in the standard approach the Kohn-Sham orbitals are either fully occupied or unoccupied, the physics of the fractional quantum Hall effect calls for fractionally occupied Kohn-Sham orbitals. This has necessitated averaging over an ensemble of Slater determinants to obtain meaningful results. We develop an alternative approach in which we express and minimize the grand canonical potential in terms of the composite fermion variables. This provides a natural resolution of the fractional-occupation problem because the fully occupied orbitals of composite fermions automatically correspond to fractionally occupied orbitals of electrons. We demonstrate the quantitative validity of our approach by evaluating the density profile of fractional Hall edge as a function of temperature and the distance from the delta dopant layer and showing that it reproduces edge reconstruction in the expected parameter region.

Observation of the Quantum Anomalous Hall Insulator to Anderson Insulator Quantum Phase Transition and its Scaling Behavior.

Fundamental insight into the nature of the quantum phase transition from a superconductor to an insulator in two dimensions, or from one plateau to the next or to an insulator in the quantum Hall effect, has been revealed through the study of its scaling behavior. Here, we report on the experimental observation of a quantum phase transition from a quantum-anomalous-Hall insulator to an Anderson insulator in a magnetic topological insulator by tuning the chemical potential. Our experiment demonstrates the existence of scaling behavior from which we extract the critical exponent for this quantum phase transition. We expect that our work will motivate much further investigation of many properties of quantum phase transition in this new context.