Wave scattering on lattice structures involving an array of cracks.

Scattering of waves as a result of a vertical array of equally spaced cracks on a square lattice is studied. The convenience of Floquet periodicity reduces the study to that of scattering of a specific wave-mode from a single crack in a waveguide. The discrete Green's function, for the waveguide, is used to obtain the semi-analytical solution for the scattering problem in the case of finite cracks whereas the limiting case of semi-infinite cracks is tackled by an application of the Wiener-Hopf technique. Reflectance and transmittance of such an array of cracks, in terms of incident wave parameters, is analysed. Potential applications include construction of tunable atomic-scale interfaces to control energy transmission at different frequencies.

Discrete scattering by a pair of parallel defects.

Scattering of a time-harmonic anti-plane shear wave due to either a pair of crack tips or a pair of rigid constraint tips on square lattice is considered. The two problems correspond to the so-called zero-offset case of scattering due to a pair of identical Sommerfeld screens. The peculiar structural symmetry allows the reduction of coupled equations to two scalar Wiener-Hopf equations and a total of four geometrically reduced problems on lattice half-plane. Exact solution of each problem for incidence from the bulk lattice, as well as from an associated lattice waveguide, is constructed. A suitable superposition of the four expressions is used to construct the solution of the main problem. The discrete paradigm involving the wave mode incident from the waveguide is relevant for modern applications where an investigation of mechanisms of electronic and thermal transport at nanoscale remains an interesting problem. This article is part of the theme issue 'Modelling of dynamic phenomena and localization in structured media (part 2)'.

A study of association between regulatory polymorphism in the IL-10 gene promoter region and acute viral hepatitis, and acute liver failure.

BACKGROUND: The level of inflammatory cytokine Interleukin (IL)-10 is increased in patients infected with hepatitis-related acute liver failure (ALF), and this was thought to be because of the regulatory polymorphism in the IL-10 gene promoter region. The present study was designed to analyze the possible association between IL-10 gene promoter polymorphism and acute viral hepatitis (AVH), and ALF. An attempt was made to quantify IL-10 levels at admission, during the hospital stay, and at the final outcome to study its relationship with liver injury among patients with AVH, ALF, and controls. METHODS: The study included 40 patients each with ALF and AVH. IL-10 gene promoter polymorphism was detected by the PCR-RFLP method. Quantification of IL-10 was done using commercially available ELISA kits. RESULTS: The individuals with -592 AC, -819 TC, -1082 AA genotypes were found to have a significantly higher risk of ALF whereas those with -592 AA and - 819 CC polymorphism were found to be less susceptible. Individuals with - 819 CC were found to be more susceptible to AVH while those with -592 AA and -819 TT were less susceptible as compared to controls. Mean serum IL-10 at admission was significantly elevated in patients with ALF (38.4±11.3 pg/mL) as compared to patients with AVH (16.7±5.4 pg/mL) and control population (8.3±3.6 pg/mL, p < 0.05). CONCLUSION: Regulatory polymorphism in the IL-10 gene promoter has a possible and significant association with severity and outcome in patients with AVH and ALF. Raised levels of IL-10 could be predictive of prognosis in patients with ALF.

Delayed presentation of congenital diaphragmatic hernia presenting with intrathoracic gastric volvulus: a case report and review.

Acute gastric volvulus associated with congenital diaphragmatic hernia is an unusual surgical emergency and its presentation in adulthood is extremely rare. Gastric volvulus is an uncommon condition which is difficult to diagnose and treat. This case describes a middle aged man presenting with post-traumatic acute abdomen and finally being diagnosed as a case of gastric volvulus due to congenital diaphragmatic hernia which was till now asymptomatic and undiagnosed. Clinical examination and chest x-ray was suggestive of hiatus hernia. Contrast-enhanced CT of thorax and abdomen revealed hiatus hernia and gastric volvulus. A provisional diagnosis of post-traumatic hiatus hernia with associated gastric volvulus was made and was operated on an emergency basis. Surprisingly, the intraoperative findings revealed significant adhesions near the diaphragm suggestive of congenital diaphragmatic hernia. Hence, a diagnosis of gastric volvulus due to congenital diaphragmatic hernia was made which remained asymptomatic and undiagnosed till adulthood. He responded well to operative management and remained asymptomatic afterwards.

Hepatic myelopathy in a patient with decompensated alcoholic cirrhosis and portal colopathy.

Cirrhotic or hepatic myelopathy is a rare neurological complication of chronic liver disease usually seen in adults and presents as a progressive pure motor spastic paraparesis which is usually associated with overt liver failure and a surgical or spontaneous systemic portocaval shunt. We describe the development of progressive spastic paraparesis, in a patient with alcoholic cirrhosis with portal hypertension and portal colopathy who presented with the first episode of hepatic encephalopathy. The patient had not undergone any shunt procedure.