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In material systems with several interacting degrees of freedom, the complex interplay between these factors can give rise to exotic phases; now superlattices consisting of alternating layers of PbTiO 3 and SrTiO 3 are found to exhibit an unusual form of ferroelectric ordering in the PbTiO 3 layers, in which the electric dipoles arrange themselves into regular, ordered arrays of vortex–antivortex structures. Polar vortex explorations In material systems with several interacting degrees of freedom (such as spin, charge and lattice distortions), the complex interplay between these factors can give rise to exotic phases. A vivid example of such behaviour has been identified by Ramamoorthy Ramesh and colleagues in superlattices consisting of alternating layers of PbTiO 3 and SrTiO 3 . They observe the formation of an unusual form of ferroelectric ordering in the PbTiO 3 layers, in which the electric dipoles arrange themselves into regular vortex–antivortex array structures, suggesting potential routes for further tuning and enhancing the properties of these versatile oxide materials. The complex interplay of spin, charge, orbital and lattice degrees of freedom provides a plethora of exotic phases and physical phenomena 1 , 2 , 3 , 4 , 5 . In recent years, complex spin topologies have emerged as a consequence of the electronic band structure and the interplay between spin and spin–orbit coupling in materials 6 , 7 . Here we produce complex topologies of electrical polarization—namely, nanometre-scale vortex–antivortex (that is, clockwise–anticlockwise) arrays that are reminiscent of rotational spin topologies 6 —by making use of the competition between charge, orbital and lattice degrees of freedom in superlattices of alternating lead titanate and strontium titanate layers. Atomic-scale mapping of the polar atomic displacements by scanning transmission electron microscopy reveals the presence of long-range ordered vortex–antivortex arrays that exhibit nearly continuous polarization rotation. Phase-field modelling confirms that the vortex array is the low-energy state for a range of superlattice periods. Within this range, the large gradient energy from the vortex structure is counterbalanced by the corresponding large reduction in overall electrostatic energy (which would otherwise arise from polar discontinuities at the lead titanate/strontium titanate interfaces) and the elastic energy associated with epitaxial constraints and domain formation. These observations have implications for the creation of new states of matter (such as dipolar skyrmions, hedgehog states) and associated phenomena in ferroic materials, such as electrically controllable chirality.

Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO 3 /SrTiO 3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a 1 / a 2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities. Metal-oxide superlattices were found to possess coexisting phases; a ferroelectric phase and a vortex phase with electric toroidal order. Electric fields interconverted from one phase to another, potentially enabling new functionality.

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3 . Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics. Flexoelectric coupling between strain gradients and polarization influences the physics of ferroelectric devices but it is difficult to directly probe its effects. Here, Li et al. use principal component analysis to compare STEM images with phase-field modeling and extract the flexoelectric contributions.

To meet the unprecedented requirement of diagnostic testing for SARS-CoV-2, a large number of diagnostic kits were authorized by concerned authorities for diagnostic use within a short period of time during the initial phases of the ongoing pandemic. We undertook this study to evaluate the inter-test agreement and other key operational features of 5 such commercial kits that have been extensively used in India for routine diagnostic testing for COVID-19. The five commercial kits were evaluated, using a panel of positive and negative respiratory samples, considering the kit provided by National Institute of Virology, Indian Council of Medical Research (2019-nCoV Kit) as the reference. The positive panel comprised of individuals who fulfilled the 3 criteria of being clinically symptomatic, having history of contact with diagnosed cases and testing positive in the reference kit. The negative panel included both healthy and disease controls, the latter being drawn from individuals diagnosed with other respiratory viral infections. The same protocol of sample collection, same RNA extraction kit and same RT-PCR instrument were used for all the kits. Clinical samples were collected from a panel of 92 cases and 60 control patients, who fulfilled our inclusion criteria. The control group included equal number of healthy individuals and patients infected with other respiratory viruses (n = 30, in each group). We observed varying sensitivity and specificity among the evaluated kits, with LabGun COVID-19 RT-PCR kit showing the highest sensitivity and specificity (94% and 100% respectively), followed by TaqPath COVID-19 Combo and Allplex 2019-nCoV assays. The extent of inter-test agreement was not associated with viral loads of the samples. Poor correlation was observed between Ct values of the same genes amplified using different kits. Our findings reveal the presence of wide heterogeneity and sub-optimal inter-test agreement in the diagnostic performance of the evaluated kits and hint at the need of adopting stringent standards for fulfilling the quality assurance requirements of the COVID-19 diagnostic process.

Background Fingerprints are useful evidence for establishing identities. Development and detection of fingerprints are of immense help in criminal investigation. However, forged fingerprints identical to the real ones are emerging as a worldwide problem. Existing methods for development of fingerprints (powder method/iodine fuming method/ninhydrin test/AgNO 3 ) fail to distinguish between real and forged fingerprints when forged fingerprints are fortified with salts and amino acids. The present study was conducted with the objective to test applicability of C stain for real and forged fingerprint differentiation. Methodology C stain was applied on real and forged fingerprints in combination with conventional methods and was evaluated on the basis of development and differentiation of real and forged fingerprints. Results The proposed technique is successful in differentiating between real and forged fingerprints. Colour difference between real and forged fingerprints was observed by taking a combination of C stain with ninhydrin, black powder and iodine fuming, one at a time. Conclusion C stain method is an effective technique for distinguishing forged fingerprints from the real ones. It works as a distinction tool even when used in combination with existing development methods.

We have carried out a study of optical image encryption in the Fresnel transform ( F r T ) domain, using a random phase mask (RPM) in the input plane and a phase mask based on devil’s vortex toroidal lens (DVTL) in the frequency plane. The original images are recovered from their corresponding encrypted images by using the correct parameters of the F r T and the parameters of DVTL. The use of a DVTL-based structured mask enhances security by increasing the key space for encryption and also aids in overcoming the problem of axis alignment associated with an optical setup. The proposed encryption scheme is a lensless optical system and its digital implementation has been performed using MATLAB 7.6.0 (R2008a). The scheme has been validated for a grayscale and a binary image. The efficacy of the proposed scheme is verified by computing mean-squared-error (MSE) between the recovered and the original images. We have also investigated the scheme’s sensitivity to the encryption parameters and examined its robustness against occlusion and noise attacks.

A new encryption scheme using phase masks based on devil’s vortex Fresnel lens ( DVFL ) has been presented in this study. The encryption is performed using fractional Hartley transform ( FRHT ) in both spatial and frequency domains. Prior to subjecting the plaintext to operations of the conventional 4 f system, it is made to undergo Arnold transform ( AT ) for additional security. The scheme is validated for grayscale amplitude images. In its optical realization, the use of DVFL eliminates the problem of axis-alignment. The parameters of DVFL , and the orders of FRHT in addition to AT order serve as encryption keys. The scheme has been tested for its sensitivity to these parameters. Also, the scheme is evaluated for its robustness against the occlusion and noise attacks. The use of multiple encryption parameters adds to security of the scheme.

Emphysematous pyelonephritis (EPN) is a deadly disease due to its associated morbidity and mortality. Attempts have been made to identify predictors of severity, mortality and need for nephrectomy in EPN with little success. We conducted an ambispective study of EPN patients between March 2014 and September 2019. Retrospective data were collected which included age, sex, comorbidities, symptoms, signs, laboratory investigations including imaging, need for dialysis, management and any complications. All patients were then followed prospectively for renal dynamic scan, stone surgery or nephrectomy. Univariate analysis was performed to identify factors affecting mortality and need for elective nephrectomy. In total, 112 patients were included. Mean patient age was 50.01 years, 55% were female and 5% had bilateral involvement. Fever and flank pain were the most common symptoms. Diabetes was seen in 75% of cases and 30% of cases required haemodialysis at initial presentation. About 60% of patients improved with pigtail drainage. Need for nephrectomy was greater in Huang-Tseng stage 3a (14.8%). Huang-Tseng stages 3b and 4 had higher mortality rates (25%) than the other stages (2.2%). Twelve of 99 patients had non functional kidney on follow-up and underwent elective nephrectomy. Low platelet counts, high body mass index, septic shock, dialysis and higher Huang-Tseng stage were found to be predictive of mortality and renal parenchymal thickness on computed tomography scan was predictive of follow-up nephrectomy. Thrombocytopaenia, high body mass index, septic shock, haemodialysis and higher Huang-Tseng stage are predictors of mortality and renal parenchymal thickness <5mm is a predictor of poor salvage of affected kidney on follow-up.

Background: A suspected food-poisoning outbreak occurred in a residential school in Mirzapur, India, in February, 2017. Objective: We investigated the outbreak to find out the epidemiology and to identify the risk factors. Methods: A descriptive study followed by retrospective-cohort study was done to investigate the outbreak. Cases (defined as ≥3 or more loose stools in 24 h, abdominal pain, or vomiting with onset between February 1 and 4, 2017) were searched by reviewing sick/patient registers from school and nearby health facilities. Cases were also searched through active surveillance by visiting school hostels. Stool samples were sent for microbiological testing. Food sources and food handlers were also assessed. Results: Among 468 students, 204 cases were identified (44% attack rate) without any mortality. The median age was found to be 14 years (range: 10-18 years) and 59% were male. Relative risk with consumption of curd, apple, and panjiri (sweetened wheat flour) was found to be 15.4, 2.5, and 3.7, respectively. All these three food items were served as prasad, a religious offering. Only consumption of sweetened curd (adjusted odds ratio = 36.1, 95% confidence interval = 12.1-107.8) was significantly associated with gastroenteritis. No microorganism was isolated from two tested stool samples. Curd from the vendor was prepared from nonpasteurized milk. There were no illnesses among food-handlers. Conclusions: This outbreak of acute gastroenteritis in a residential school was associated with consumption of curd, likely contaminated with preformed toxins. We recommend implementation of the food safety and standards authority of India regulations.

Upper-tract urothelial cancer comprises only 3% of all urothelial cancers. Risk factors include tobacco smoking, recurrent urinary infection, urolithiasis and analgesic abuse. Urolithiasis-induced chronic inflammation leads to urothelial proliferation and eventual malignant transformation. The most common association is reported with squamous cell cancer. A 54-year man under evaluation for right flank pain was diagnosed with a large distal ureteric stone and urothelial cancer of the entire right ureter and renal pelvis. The patient underwent right nephroureterectomy and stone retrieval, with urinary bladder cuff excision and pelvic lymph node dissection. On follow-up, the patient succumbed to disease recurrence with widespread metastasis. Urothelial cancer associated with stone disease is atypical. Long-standing inflammation causing metaplastic and dysplastic changes is a possible hypothesis. Careful assessment of the malignancy should be looked for in patients with long-standing obstruction due to stone disease.