Profile driven interfaces in 1 + 1 dimensions : periodic steady states, dynamical melting and detachment

We study the steady state structure and dynamics of a 2-d Ising interface placed in an inhomogeneous external field with a sigmoidal profile which moves with velocity $v_{e}$. In the strong coupling limit the problem maps onto an assymmetric exclusion process involving motion of particles in 1-d with position dependent right and left jump probabilities. For small $v_{e}$, the interface is stuck to the field profile. As $v_{e}$ increases the profile detaches from the interface. At the transition point(and beyond), the interfacial structure and dynamics is characterized by KPZ exponents. For small $v_{e}$, on the other hand, the interface is macroscopically smooth with a vanishing roughness exponent $\alpha$. The interfacial structure is periodic with a periodicity which depends on the orientation of the interface. For a fixed orientation this periodic structure ``melts'' as $v_e$ is increased. We determine the dynamical ``phase - diagram'' of this system in the $v_e$ - orientation plane.Comment: 11 pages, 6 figures, To appear in Physica A as conference proceedings of Statphys - Kolkata I

Stress relaxation in a perfect nanocrystal by coherent ejection of lattice layers

We show that a small crystal trapped within a potential well and in contact with its own fluid, responds to large compressive stresses by a novel mechanism -- the transfer of complete lattice layers across the solid-fluid interface. Further, when the solid is impacted by a momentum impulse set up in the fluid, a coherently ejected lattice layer carries away a definite quantity of energy and momentum, resulting in a sharp peak in the calculated phonon absorption spectrum. Apart from its relevance to studies of stability and failure of small sized solids, such coherent nanospallation may be used to make atomic wires or monolayer films.Comment: 4 pages, 4 figures, published version, changed conten

One-dimensional spin-orbit coupled Dirac system with extended ss-wave superconductivity: Majorana modes and Josephson effects

Motivated by the spin-momentum locking of electrons at the boundaries of topological insulators, we study a one-dimensional system of spin-orbit coupled massless Dirac electrons with $s$-wave superconducting pairing. As a result of the spin-orbit coupling, our model has only two kinds of linearly dispersing modes, which we take to be right-moving spin-up and left-moving spin-down. Both lattice and continuum models are studied. In the lattice model, we find that a single Majorana zero energy mode appears at each end of a finite system provided that the $s$-wave pairing has an extended form, with the nearest-neighbor pairing being larger than the on-site pairing. We confirm this both numerically and analytically by calculating the winding number. Next we study a lattice version of a model with both Schr\"odinger and Dirac-like terms and find that the model hosts a topological transition between topologically trivial and non-trivial phases depending on the relative strength of the Schr\"odinger and Dirac terms. We then study a continuum system consisting of two $s$-wave superconductors with different phases of the pairing. Remarkably, we find that the system has a {\it single} Andreev bound state which is localized at the junction. When the pairing phase difference crosses a multiple of $2 \pi$, an Andreev bound state touches the top of the superconducting gap and disappears, and a different state appears from the bottom of the gap. We also study the AC Josephson effect in such a junction with a voltage bias that has both a constant $V_0$ and a term which oscillates with a frequency $\omega$. We find that, in contrast to standard Josephson junctions, Shapiro plateaus appear when the Josephson frequency $\omega_J= 2eV_0/\hbar$ is a rational fraction of $\omega$. We discuss experiments which can realize such junctions.Comment: 16 pages, 9 figures; made some significant changes, added a figure and several reference

Coexisting pathology of ectopic pregnancy and dermoid cyst: An uncommon occurrence

Mature cystic teratomas (dermoid cysts) are common benign ovarian neoplasms. About 10% of dermoid cysts are detected duringpregnancy. Multiple gynecologic pathologies occurring together are uncommon, and both an ectopic pregnancy and dermoid cystare seen concurrently being unknown and poorly documented. Here, we report a case of ectopic pregnancy and dermoid cystoccurring simultaneously in a 30-year-old woman

DISSEMINATED TUBERCULOSIS PRESENTING AS HEMOPHAGOCYTIC LYMPHOHISTIOCYTOSIS

ABSTRACTHemophagocytic lymphohistiocytosis (HLH) is an immune dysregulation syndrome which is characterized by widespread but ineffective activationof immune system of our body. This activation leads to release of a large pool of cytokines from the activated lymphocytes and macrophages. Thishypercytokinemia leads to the development of characteristic features of HLH such as fever, cytopenias, hepatosplenomegaly, raised serum ferritinlevel, hemophagocytosis in marrow/spleen/lymph nodes, low fibrinogen and or hypertriglyceridemia, low natural killer cell activity, and high-solubleCD25 [1]. Five out of the above eight features are required for the diagnosis. There are 2 variants of HLH, primary HLH; where the defect in theimmune system is hereditary and secondary HLH; where it is caused by other secondary diseases such as infections, hematological malignancies,autoimmune and auto-inflammatory diseases. In this article, we have reported a case of HLH, which was secondary to disseminated tuberculosis.There are only few case reports of HLH secondary to disseminated tuberculosis. Mortality may be as high as 50%. Although tuberculosis has variousmanifestations, our patient presented with fever, skin rash, cytopenias, splenomegaly, and very high ferritin. Marrow examination showed epithelioidgranuloma, hemophagocytosis, and positive Ziehl–Neelsen staining. At present, no definite treatment guidelines have been formulated becauseof multiple drug interactions and toxicities. We treated our patient with non-hepatotoxic anti-tubercular drugs and steroids, followed by additionof isoniazid, rifampicin, and pyrazinamide on improvement of hepatic profile. Thus, high index of clinical suspicion, prompt diagnosis, and earlymanagement may reduce the mortality in this devastating disease. Moreover, this is more common in immunocompromised patients, but here, wehave diagnosed this case in an immunocompetent man.Keywords: Erythematous rash, Fever, Disseminated tuberculosis

Evaluation the results of surgical management of traumatic paraplegia in traumatic thoracolumbar fractures

Background: Thoracolumbar spine fractures are common injuries that can result in significant disability, deformity and neurological deficit. Aim of this study was to evaluate the results of surgical management of traumatic paraplegia, complete or incomplete as classified by Frankel scoring.Methods: A prospective study was conducted in patients attending outdoor and emergency department of Orthopedics of a tertiary care teaching institute in Kolkata, West Bengal with traumatic paraplegia involving the dorsolumbar spine. The important objectives are the time for recovery of various functions like sensory, motor and bowel and bladder function, comparison between early and late decompression, results of posterolateral fusion and time taken for solid bony fusion after operation. Total 46 cases were selected within a minimum of 6-month post-operative follow-up of which 4 cases lost in follow-up. Data collected from patient records included age, sex, time from injury to hospitalization, initial neurological status as per Frankel Score, MRI findings, surgery performed, postoperative course and neurological status at the time of discharge and latest follow up. Patients lost to follow up were not studied for outcome analysis.Results: When decompression done within 1st week in incomplete paraplegia, 80% of the patients showed return of grade 3 power. In complete paraplegia cases, 11% of the patients had return of power up to grade 3 when decompression done within 1 week, where no cases showed return of grade 3 power when decompression done after 2nd or 3rd week.Conclusions: After recovery from spinal shock, the earlier the surgical compression done, the better the neurological and bowel/bladder function recovery both in complete and incomplete paraplegic cases. Reduction is better and easy and less time consuming in early decompression than in late. Motor recovery can continue for over 6 months after decompression