Signatures of quantum phases in a dissipative system.

Lindbladian formalism, as tuned to dissipative and open systems, has been all-pervasive to interpret non-equilibrium steady states of quantum many-body systems. We study the fate of free fermionic and superconducting phases in a dissipative one-dimensional Kitaev model-where the bath acts both as a source and a sink of fermionic particles with different coupling rates. As a function of these two couplings, we investigate the steady state, its entanglement content, and its approach from varying initial states. Interestingly, we find that the steady state phase diagram retains decipherable signatures of ground state critical physics. We also show that early-time fidelity is a useful marker to find a subclass of phase transitions in such situations. Moreover, we show that the survival of critical signatures at late-times, strongly depend on the thermal nature of the steady state. This connection hints at a correspondence between quantum observables and classical magnetism in the steady state of such systems. Our work uncovers interesting connections between dissipative quantum many-body systems, thermalization of a classical spin and many-body quantum critical phenomena.

Crystal property engineering using molecular-supramolecular equivalence: mechanical property alteration in hydrogen bonded systems.

Most crystal engineering strategies exercised until now mainly rely on the alteration of weak non-covalent interactions to design structures and thus properties. Examples of mechanical property alteration for a given structure type are rare with only a few halogen bonded cases. The modular nature of halogen bonds with interaction strength tunability makes the task straightforward to obtain property differentiated crystals. However, the design of such crystals using hydrogen bond interactions has proven to be non-trivial, because of its relatively higher difference in bonding energies, and more importantly, disparate geometries of the functional groups. In the present crystal property engineering exercise, with the support of CSD analysis, we replaced a supramolecular precursor that leads to plastically bendable crystals, with a molecular equivalent, and obtained an equivalent crystal structure. As a result, the new structure, with comparable hydrogen bonding chains, produces elastically bendable single crystals (as opposed to plastically bendable crystals). In addition, the crystals show multidirectional (here two) elastic bending as well as rare elastic twisting. The occurrence of multiple isostructural examples, including a solid solution, with identical properties further demonstrates the general applicability of the proposed model. Crystals cannot display the concerned mechanical property in the absence of the desired structure type and fracture in a brittle manner on application of an external stress. Nanomechanical experiments and energy framework calculations also complement our results. To the best of our knowledge, this is the first example of a rational crystal engineering exercise using solely hydrogen bond interactions to obtain property differentiated crystals. This strategy namely molecular-supramolecular equivalence has been unexplored till now to tune mechanical properties, and hence is useful for crystal property engineering.

Breakthrough infection among healthcare personnel following exposure to COVID-19: Experience after one year of the world's largest vaccination drive.

Context: The COVID-19 vaccination drive globally was supposedly a game-changing event. However, the emerging variants of the virus and waning immunity over time posed new challenges for breakthrough infections. Standing at the frontline of defense against COVID-19, healthcare personnel (HCP) were vulnerable to such infections. Aims: This study estimates i) the vaccine breakthrough infections (VBI) among HCP following exposure to COVID-19 cases, and ii) the mean interval between the second dose of vaccine and laboratory-confirmed SARS-CoV-2 infection. Materials and Methods: A cross-sectional study was conducted including 385 HCP with a history of exposure to COVID-19 cases during January and February 2022. Demographic details and clinical and vaccination history were collected from the test forms and the Web-based hospital management system. Laboratory testing of COVID-19 was carried out by real-time RT-PCR test. Results: The majority of the HCP were males (262; 68.05%) and nurses (180; 46.75%) by occupation. Two doses of vaccines were received by 278 (87.7%) HCP. VBI was confirmed in 185 (66.55%) HCP. No significant difference in VBI between the COVAXIN and COVISHIELD recipients (P = 0.69) was observed. The interval between the second dose and confirmed SARS-CoV-2 infection was significantly higher (P < 0.00001) in COVAXIN recipients (median 228 days) than in COVISHIELD recipients (median 95 days). Conclusions: The incidence of VBI was very high among the HCP, but not statistically different among the COVAXIN and COVISHIELD-recipients. Waning immunity over time suggests boosting immunity with a third dose because of emerging variants.

Thermally activated delayed fluorescence in a mechanically soft charge-transfer complex: role of the locally excited state.

Molecular design for thermally activated delayed fluorescence (TADF) necessitates precise molecular geometric requirements along with definite electronic states to ensure high intersystem crossing (ISC) rate and photoluminescence quantum yield (PLQY). Achieving all these requirements synchronously while maintaining ease of synthesis and scalability is still challenging. To circumvent this, our strategy of combining a crystal engineering approach with basic molecular quantum mechanical principles appears promising. A holistic, non-covalent approach for achieving efficient TADF in crystalline materials with distinct mechanical properties is highlighted here. Charge transfer (CT) co-crystals of two carbazole-derived donors (ETC and DTBC) with an acceptor (TFDCNB) molecule are elaborated as a proof-of-concept. Using temperature-dependent steady-state and time-resolved photoluminescence techniques, we prove the need for a donor-centric triplet state (3LE) to ensure efficient TADF. Such intermediate states guarantee a naturally forbidden, energetically uphill reverse intersystem crossing (RISC) process, which is paramount for effective TADF. A unique single-crystal packing feature with isolated D-A-D trimeric units ensured minimal non-radiative exciton loss, leading to a high PLQY and displaying interesting mechanical plastic bending behaviour. Thus, a comprehensive approach involving a non-covalent strategy to circumvent the conflicting requirements of a small effective singlet-triplet energy offset and a high oscillator strength for efficient TADF emitters is achieved here.

Autonomous self-healing organic crystals for nonlinear optics.

Non-centrosymmetric molecular crystals have a plethora of applications, such as piezoelectric transducers, energy storage and nonlinear optical materials owing to their unique structural order which is absent in other synthetic materials. As most crystals are brittle, their efficiency declines upon prolonged usage due to fatigue or catastrophic failure, limiting their utilities. Some natural substances, like bone, enamel, leaf and skin, function efficiently, last a life-time, thanks to their inherent self-healing nature. Therefore, incorporating self-healing ability in crystalline materials will greatly broaden their scope. Here, we report single crystals of a dibenzoate derivative, capable of self-healing within milliseconds via autonomous actuation. Systematic quantitative experiments reveal the limit of mechanical forces that the self-healing crystals can withstand. As a proof-of-concept, we also demonstrate that our self-healed crystals can retain their second harmonic generation (SHG) with high efficiency. Kinematic analysis of the actuation in our system also revealed its impressive performance parameters, and shows actuation response times in the millisecond range.

The Outbreak of SARS-CoV-2 in a Medical Ward and Its Containment: An Experience From a Tertiary Care Centre in North India.

Background Periodic outbreaks of SARS-CoV-2 in hospital settings amidst the recent pandemic are well known. However, the timely control of such outbreaks was key to preventing morbidity among vulnerable patients as well as reducing sickness absenteeism among healthcare workers. This is the first study of its kind in India. Methods An outbreak investigation was conducted between June 12 and July 18, 2020, at the All India Institute of Medical Sciences, New Delhi, India, during the first wave of COVID-19. Results A total of 27 individuals were infected during this time, including people visiting the hospital and healthcare workers. A thorough investigation led us to the epidemiological link between cases and allowed us to bring reforms to the existing hospital policy of screening and admission of COVID-19 patients and those suspected to have the infection. This experience helped us avoid future outbreaks during the second wave of COVID-19 in our hospital. Conclusion The SARS-CoV-2 virus is highly transmissible, especially in hospital settings due to the high burden of patients and close proximity between patients. Timely intervention is the key to effective control of hospital outbreaks, as it can avoid morbidity in patients and reduce sickness absenteeism among healthcare workers.

Asymmetric rotations and dimerization driven by normal to modulated phase transition in 4-biphenylcarboxy coupled L-phenylalaninate.

Amongst the derivatives of 4-biphenylcarboxylic acid and amino acid esters, the crystal structure of 4-biphenylcarboxy-(L)-phenylalaninate is unusual owing to its monoclinic symmetry within a pseudo-orthorhombic crystal system. The distortion is described by a disparate rotational property around the chiral centers (ϕchiral ≃ -129° and 58°) of the two molecules in the asymmetric unit. Each of these molecules comprises planar biphenyl moieties (ϕbiphenyl = 0°). Using temperature-dependent single-crystal X-ray diffraction experiments we show that the compound undergoes a phase transition below T ∼ 124 K that is characterized by a commensurate modulation wavevector, q = δ(101), δ = ½. The (3+1)-dimensional modulated structure at T = 100 K suggests that the phase transition drives the biphenyl moieties towards noncoplanar conformations with significant variation of internal torsion angle (ϕmaxbiphenyl ≤ 20°). These intramolecular rotations lead to dimerization of the molecular stacks that are described predominantly by distortions in intermolecular tilts (θmax ≤ 20°) and small variations in intermolecular distances (Δdmax ≃ 0.05 Å) between biphenyl molecules. Atypical of modulated structures and superstructures of biphenyl and other polyphenyls, the rotations of individual molecules are asymmetric (Δϕbiphenyl ≈ 5°) while ϕbiphenyl of one independent molecule is two to four times larger than the other. Crystal-chemical analysis and phase relations in superspace suggest multiple competing factors involving intramolecular steric factors, intermolecular H-C...C-H contacts and weak C-H...O hydrogen bonds that govern the distinctively unequal torsional properties of the molecules.

Elastic organic semiconducting single crystals for durable all-flexible field-effect transistors: insights into the bending mechanism.

Although many examples of mechanically flexible crystals are currently known, their utility in all-flexible devices is not yet adequately demonstrated, despite their immense potential for fabricating high performance flexible devices. Here, we report two alkylated diketopyrrolopyrrole (DPP) semiconducting single crystals, one of which displays impressive elastic mechanical flexibility whilst the other is brittle. Using the single crystal structures and density functional theory (DFT) calculations, we show that the methylated diketopyrrolopyrrole (DPP-diMe) crystals, with dominant π-stacking interactions and large contributions from dispersive interactions, are superior in terms of their stress tolerance and field-effect mobility (µ FET) when compared to the brittle crystals of the ethylated diketopyrrolopyrrole derivative (DPP-diEt). Periodic dispersion-corrected DFT calculations revealed that upon the application of 3% uniaxial strain along the crystal growth (a)-axis, the elastically flexible DPP-diMe crystal displays a soft energy barrier of only 0.23 kJ mol-1 while the brittle DPP-diEt crystal displays a significantly larger energy barrier of 3.42 kJ mol-1, in both cases relative to the energy of the strain-free crystal. Such energy-structure-function correlations are currently lacking in the growing literature on mechanically compliant molecular crystals and have the potential to support a deeper understanding of the mechanism of mechanical bending. The field effect transistors (FETs) made of flexible substrates using elastic microcrystals of DPP-diMe retained µ FET (from 0.019 cm2 V-1 s-1 to 0.014 cm2 V-1 s-1) more efficiently even after 40 bending cycles when compared to the brittle microcrystals of DPP-diEt which showed a significant drop in µ FET just after 10 bending cycles. Our results not only provide valuable insights into the bending mechanism, but also demonstrate the untapped potential of mechanically flexible semiconducting crystals for designing all flexible durable field-effect transistor devices.

Automatic prediction of rejected edits in Stack Overflow.

The content quality of shared knowledge in Stack Overflow (SO) is crucial in supporting software developers with their programming problems. Thus, SO allows its users to suggest edits to improve the quality of a post (i.e., question and answer). However, existing research shows that many suggested edits in SO are rejected due to undesired contents/formats or violating edit guidelines. Such a scenario frustrates or demotivates users who would like to conduct good-quality edits. Therefore, our research focuses on assisting SO users by offering them suggestions on how to improve their editing of posts. First, we manually investigate 764 (382 questions + 382 answers) rejected edits by rollbacks and produce a catalog of 19 rejection reasons. Second, we extract 15 texts and user-based features to capture those rejection reasons. Third, we develop four machine learning models using those features. Our best-performing model can predict rejected edits with 69.1% precision, 71.2% recall, 70.1% F1-score, and 69.8% overall accuracy. Fourth, we introduce an online tool named EditEx that works with the SO edit system. EditEx can assist users while editing posts by suggesting the potential causes of rejections. We recruit 20 participants to assess the effectiveness of EditEx. Half of the participants (i.e., treatment group) use EditEx and another half (i.e., control group) use the SO standard edit system to edit posts. According to our experiment, EditEx can support SO standard edit system to prevent 49% of rejected edits, including the commonly rejected ones. However, it can prevent 12% rejections even in free-form regular edits. The treatment group finds the potential rejection reasons identified by EditEx influential. Furthermore, the median workload suggesting edits using EditEx is half compared to the SO edit system.

Disconnected entanglement entropy as a marker of edge modes in a periodically driven Kitaev chain.

We study the disconnected entanglement entropy (DEE) of a Kitaev chain in which the chemical potential is periodically modulated withδ-function pulses within the framework of Floquet theory. For this driving protocol, the DEE of a sufficiently large system with open boundary conditions turns out to be integer-quantized, with the integer being equal to the number of Majorana edge modes localized at each edge of the chain generated by the periodic driving, thereby establishing the DEE as a marker for detecting Floquet Majorana edge modes. Analyzing the DEE, we further show that these Majorana edge modes are robust against weak spatial disorder and temporal noise. Interestingly, we find that the DEE may, in some cases, also detect the anomalous edge modes which can be generated by periodic driving of the nearest-neighbor hopping, even though such modes have no topological significance and not robust against spatial disorder. We also probe the behavior of the DEE for a kicked Ising chain in the presence of an integrability breaking interaction which has been experimentally realized.

Periodically driven many-body quantum battery.

We explore the charging of a quantum battery based on spin systems through periodic modulation of a transverse-field-like Ising Hamiltonian. In the integrable limit, we find that resonance tunneling can lead to a higher transfer of energy to the battery and better stability of the stored energy at specific drive frequencies. When the integrability is broken in the presence of an additional longitudinal field, we find that the effective Floquet Hamiltonian contains terms which may lead to a global charging of the battery. However, we do not find any quantum advantage in the charging power, thus demonstrating that global charging is only a necessary and not sufficient condition for achieving quantum advantage.

Autonomous self-repair in piezoelectric molecular crystals.

Living tissue uses stress-accumulated electrical charge to close wounds. Self-repairing synthetic materials, which are typically soft and amorphous, usually require external stimuli, prolonged physical contact, and long healing times. We overcome many of these limitations in piezoelectric bipyrazole organic crystals, which recombine following mechanical fracture without any external direction, autonomously self-healing in milliseconds with crystallographic precision. Kelvin probe force microscopy, birefringence experiments, and atomic-resolution structural studies reveal that these noncentrosymmetric crystals, with a combination of hydrogen bonds and dispersive interactions, develop large stress-induced opposite electrical charges on fracture surfaces, prompting an electrostatically driven precise recombination of the pieces via diffusionless self-healing.

Recent Advances and Applications of Passive Harmonic RFID Systems: A Review.

Harmonic Radio Frequency Identification (RFID) systems have attracted significant interest over the last decade as it provides many benefits over the conventional RFID systems. Harmonic RFID is desired over conventional RFID systems due to reduced self-jamming, location accuracy from dual frequency, and higher phase noise immunity. In a harmonic RFID system, the tag receives instructions from the reader at an RF carrier frequency and replies back at the harmonic of the RF frequency. A nonlinear element consuming very low power at the tag is required to generate the harmonic carrier for the battery-less system. In this review article, a detailed contrast between conventional and harmonic RFID systems is presented. This is followed by different circuit design techniques to generate harmonics and integration techniques to form a fully operable passive harmonic RFID tag. Also, a wide range of applications, especially sensor integration with harmonic RFID's, along with the future trends are presented.

On the non-innocence and reactive versus non-reactive nature of α-diketones in a set of diruthenium frameworks.

α-Diketones are an important class of building blocks employed in many organic synthetic reactions. However, their coordination chemistry has rarely been explored. In light of this, our earlier report on [(acac)2RuII(µ-2,2'-pyridil)RuII(acac)2] (acac = acetylacetonate) showcased the sensitivity of a diketone fragment towards oxidative C-C cleavage. Following the lead, the synthesis of similar but stable diketo fragments containing diruthenium compounds was attempted. Three diruthenium compounds with the bridge 1,2-bis(2-hydroxyphenyl)ethane-1,2-dione (L) were prepared: diastereomeric [(acac)2RuIII(µ-L2-)RuIII(acac)2], 1a(rac)/1b(meso), [(bpy)2RuII(µ-L2-)RuII(bpy)2](ClO4)2, [2](ClO4)2 and [(pap)2RuII(µ-L2-)RuII(pap)2](ClO4)2, [3](ClO4)2 with ancillary ligands of different donating/accepting characteristics. The metal is stabilised in different oxidation states in these complexes: Ru(iii) is preferred in 1a/1b when σ-donating acac is used as the co-ligand whereas electron rich Ru(ii) is preferred in [2](ClO4)2 and [3](ClO4)2 when co-ligands of moderate to strong π-accepting properties are employed. The oxidative chemistry of these systems is of particular interest with respect to the participation of varying bridging-ligands which contain phenoxide groups. On the other hand, the reduction processes primarily resulting from the metal or the ancillary ligands are noteworthy as the normally reducible 1,2-diketo- group remains unreduced. These results have been rationalised and outlined from thorough experimental and theoretical investigations. The results presented here shed light on the stability of metal coordinated α-diketones as a function of their substituents.

Wireless Battery-Free Harmonic Communication System for Pressure Sensing.

In this paper, an efficient passive wireless harmonic communication system is proposed for the real-time monitoring of the pressurized pipelines. A pressure sensor is fabricated using the additive manufacturing technique and a harmonic radio frequency (RF) tag is designed to operate at the fundamental frequency (fo) of 2 GHz that shifts the phase of the back reflected RF signal according to the applied pressure ranging from 0 to 20 psi. A power efficient phase modulation with virtually no losses is achieved using a hybrid coupler-based phase shifter that efficiently reflect back the incoming signal using an end coupled reactive impedance element/sensor. The phase delay introduced by the reactive element gets doubled with the second harmonic communication, which increases the sensitivity by a factor of two. The concept of harmonic backscattering is exploited to reduce the effects of multi-path interference and self jamming, as well as improving the signal-to-noise ratio (SNR).

Exploring the role of asymmetric-pulse modulation in quantum thermal machines and quantum thermometry.

We explore the consequences of periodically modulating a quantum two-level system (TLS) with an asymmetric pulse when the system is in contact with thermal baths. By adopting the Floquet-Lindblad formalism for our analysis, we find that the unequal "up" and "down" time duration of the pulse has two main ramifications. First, the energy gap of the multiple sidebands or photon sectors created as a result of the periodic modulation are renormalized by a term which is dependent on both the modulation strength as well as the fraction of up (or down) time duration. Second, the weights of the different sidebands are no longer symmetrically distributed about the central band or zero photon sector. We illustrate the advantages of these findings in the context of applications in quantum thermal machines and thermometry. For a thermal machine constructed by coupling the TLS to two thermal baths, we demonstrate that the asymmetric pulse provides an extra degree of control over the mode of operation of the thermal machine. Further, by appropriately tuning the weight of the subbands, we also show that an asymmetric pulse may provide superior optimality in a recently proposed protocol for quantum thermometry, where dynamical control has been shown to enhance the precision of measurement.

Mechanical-Bending-Induced Fluorescence Enhancement in Plastically Flexible Crystals of a GFP Chromophore Analogue.

Single crystals of optoelectronic materials that respond to external stimuli, such as mechanical, light, or heat, are immensely attractive for next generation smart materials. Here we report single crystals of a green fluorescent protein (GFP) chromophore analogue with irreversible mechanical bending and associated unusual enhancement of the fluorescence, which is attributed to the strained molecular packing in the perturbed region. Soft crystalline materials with such fluorescence intensity modulations occurring in response to mechanical stimuli under ambient pressure conditions will have potential implications for the design of technologically relevant tunable fluorescent materials.

Evaluation of rapid diagnostic tests and assessment of risk factors in drug-resistant pulmonary tuberculosis.

BACKGROUND: Early diagnosis and treatment of drug-resistant tuberculosis (TB) is crucial to halt the spread of drug resistance in the community. AIM: The aim of the study was to compare rapid diagnostic tests (GeneXpert and line probe assay, LPA) with conventional liquid culture for the diagnosis of drug-resistant TB and to assess the risk factors for it. METHOD: This cross-sectional study recruited 229 multidrug-resistant TB suspects who were sputum smear positive. They were evaluated by the rapid diagnostic tests and sensitivity, specificity, positive predictive value and negative predictive value were calculated for drug resistance detection as compared to liquid culture drug susceptibility testing. The risk factors for the development of drug resistance were also assessed and the P value of < 0.05 was considered significant. RESULTS: In the final comparison, 193 samples were included. The sensitivity and specificity of GeneXpert for detection of drug resistance (rifampicin) was 100% (95% confidence interval, CI: 88.8-100%) and 99.4% (95% CI: 96.6-99.9%), respectively. Whereas sensitivity and specificity of LPA was 94.3% (95% CI: 80.8-99.3%) and 100% (95% CI: 97.7-100%), respectively. Only three discordant samples were observed. Defaulting to antitubercular therapy, contact with resistant TB, and disseminated disease were found to be significant risk factors for the development of drug-resistant TB with high statistical significance (P value < 0.05). CONCLUSION: Both rapid diagnostic tests have very high sensitivity and specificity for detection of drug resistance in sputum smear positive with the advantage of short turn-around time. Defaulting to antitubercular therapy, contact with resistant TB, and disseminated disease are significant risk factors for drug resistance.

Mechanical Actuation and Patterning of Rewritable Crystalline Monomer-Polymer Heterostructures via Topochemical Polymerization in a Dual-Responsive Photochromic Organic Material.

The dark-orange monomer single crystals of 1,1'-dioxo-1H-2,2'-biindene-3,3'-diyldidodecanoate (BIT-dodeca2) convert to a transparent single-crystalline polymer (PBIT-dodeca2) material via a single-crystal-to-single-crystal (SCSC) polymerization reaction under sunlight, which then undergoes reverse thermal transformation into BIT-dodeca2 single crystals, leading to reversible photo-/thermochromism, coupled with mechanical actuation. We exploit the properties of this unique material to demonstrate the formation of monomer-polymer heterostructures in selected regions of single crystals with micrometer-scale precision using a laser. This is the first example of heterostructure patterning involving monomer-polymer domains in single crystals. We reveal that the speed of photomechanical bending induced by the polymerization reaction in this example is comparable to those of the well-known diarylethene derivatives, in which electrocyclic ring-closing-ring-opening reactions operate. Furthermore, we characterize the distinct mechanical properties of the monomer and polymer using a quantitative nanoindentation technique as well as demonstrate photopatterning on a monomer-coated paper for potential use in security devices. These crystals with several advantages, such as photomechanical bending (weight lifting) even when the crystal size is large, responsiveness to both UV and visible light, distinct solubilities (the polymer is insoluble, whereas the monomer is soluble in most organic solvents) and colors, provide unique opportunities for their use at different length scales of the sample (µm to mm) for various purposes.