Quantum Kramers' equation for energy diffusion and barrier crossing dynamics in the low friction regime

Based on a true phase space probability distribution function and an ensemble averaging procedure we have recently developed [Phys. Rev. E 65, 021109 (2002)] a non-Markovian quantum Kramers' equation to derive the quantum rate coefficient for barrier crossing due to thermal activation and tunneling in the intermediate to strong friction regime. We complement and extend this approach to weak friction regime to derive quantum Kramers' equation in energy space and the rate of decay from a metastable well. The theory is valid for arbitrary temperature and noise correlation. We show that depending on the nature of the potential there may be a net reduction of the total quantum rate below its corresponding classical value which is in conformity with earlier observation. The method is independent of path integral approaches and takes care of quantum effects to all orders.Comment: 26 pages, RevTe

Approach to Quantum Kramers' Equation and Barrier Crossing Dynamics

We have presented a simple approach to quantum theory of Brownian motion and barrier crossing dynamics. Based on an initial coherent state representation of bath oscillators and an equilibrium canonical distribution of quantum mechanical mean values of their co-ordinates and momenta we have derived a $c$-number generalized quantum Langevin equation. The approach allows us to implement the method of classical non-Markovian Brownian motion to realize an exact generalized non-Markovian quantum Kramers' equation. The equation is valid for arbitrary temperature and friction. We have solved this equation in the spatial diffusion-limited regime to derive quantum Kramers' rate of barrier crossing and analyze its variation as a function of temperature and friction. While almost all the earlier theories rest on quasi-probability distribution functions (like Wigner function) and path integral methods, the present work is based on {\it true probability distribution functions} and is independent of path integral techniques. The theory is a natural extension of the classical theory to quantum domain and provides a unified description of thermal activated processes and tunneling.Comment: RevTex, 18 pages, 2 figures; Minor corrections; To appear in Phys. Rev.

Structural and textural development in Singhbhum shear zone, eastern India

The rocks within the Singhbhum shear zone in the North Singhbhum fold belt, eastern India, form a tectonic melange comprising granitic mylonite, quartz-mica phyllonite, quartz-tourmaline rock and deformed volcanic and volcaniclastic rocks. The granitic rocks show a textural gradation from the least-deformed variety having coarse-to medium-grained granitoid texture through augen-bearing protomylonite and mylonite to ultramylonite. Both type I and type II S-C mylonites are present. The most intensely deformed varieties include ultramylonite. The phyllosilicate-bearing supracrustal rocks are converted to phyllonites. The different minerals exhibit a variety of crystal plastic deformation features. Generation of successive sets of mylonitic foliation, folding of the earlier sets and their truncation by the later ones results from the progressive shearing movement. The shear sense indicators suggest a thrust-type deformation. The microstructural and textural evolution of the rocks took place in an environment of relatively low temperature, dislocation creep accompanied by dynamic recovery and dynamic recrystallization being the principal deformation mechanisms. Palaeostress estimation suggests a flow stress within the range of 50-190 MPa during mylonitization

Molecular Detection of Carbapenem Resistance in Clinical Isolates of Klebsiella pneumoniae in Tertiary Care Hospital

Antibiotic resistance has become a serious global threat, mainly due to misuse, overuse of antibiotics and non-compliance with infection control protocol. Superbugs are multidrug-resistant (MDR) and extended drug-resistant (XDR) bacteria, mainly Klebsiella pneumoniae and Escherichia coli from the Enterobacteriaceae family, which cause opportunistic infections and raise death rates and hospital expenditures. The present study was conducted at a tertiary care teaching hospital to study the epidemiology and molecular detection of carbapenem-resistant K. pneumoniae isolated from various clinical specimens. 240 K. pneumoniae isolates were collected from January 2020 to December 2021 at the Bacteriology laboratory, Index Medical College and Hospital, Indore. All isolates were analyzed for carbapenem resistance by the conventional disc diffusion method. All carbapenem-resistant isolates were tested for carbapenemase production using the phenotypic double-disk synergy test (DDST) and modified Hodge test (MHT) as per 2020 CLSI guidelines. All isolates were negative by phenotypic methods, further confirmed by conventional PCR to detect the gene responsible for carbapenemase production. 240 isolates of K. pneumoniae were included during the study periods. Out of 240 isolates, 102 isolates were found resistant to carbapenem drugs. All 102 isolates were confirmed carbapenemase and MBL producers by MHT and DDST tests. Among 102, 60 isolates were found to be MBL producers negative by MHT and DDST tests. Sixty phenotypic negative carbapenem-resistant isolates were tested by conventional PCR. One or more carbapenemase genes were detected in 61.0% of isolates. The blaKPC was detected in 13/60 (21%) isolates, followed by blaNDM 10/60 (16%) isolates, followed by blaVIM in 6/60(10%), blaOXA-48 in 5/60 (8%) and blaIMP in 3/60(5%) isolates. K. pneumoniae produces carbapenemase, which enhances resistance to the carbapenem class of antibiotics. The simultaneous detection of these resistance genes expressed by Klebsiella pneumoniae might be managed by early detection and adhering to antibiotic policies that limit the use of antibiotics

Understanding Protein Structure from a Percolation Perspective

Underlying the unique structures and diverse functions of proteins area vast range of amino-acid sequences and a highly limited number of folds taken up by the polypeptide backbone. By investigating the role of noncovalent connections at the backbone level and at the detailed side-chain level, we show that these unique structures emerge from interplay between random and selected features. Primarily, the protein structure network formed by these connections shows simple (bond) and higher order (clique) percolation behavior distinctly reminiscent of random network models. However, the clique percolation specific to the side-chain interaction network bears signatures unique to proteins characterized by a larger degree of connectivity than in random networks. These studies reflect some salient features of the manner in which amino acid sequences select the unique structure of proteins from the pool of a limited number of available folds

Quantum Smoluchowski equation: escape from a metastable state

We develop a quantum Smoluchowski equation in terms of a true probability distribution function to describe quantum Brownian motion in configuration space in large friction limit at arbitrary temperature and derive the rate of barrier crossing and tunneling within a unified scheme. The present treatment is independent of path integral formalism and is based on canonical quantization procedure