T. Roy

Helicobacter pylori, gastric juice, and arterial ammonia levels in patients with cirrhosis

Helicobacter pylori urease activity is a potential source of ammonia in the stomach of patients with cirrhosis. However, the possible role of H. pylori in the pathogenesis of hepatic encephalopathy deserves further investigations. The current study evaluates the relationship among H. pylori infection, gastric juice ammonia concentrations, and arterial ammonia levels in patients with cirrhosis. Overall, 14 patients with cirrhosis with overt hepatic encephalopathy, 19 with subclinical hepatic encephalopathy, and 13 without encephalopathy were enrolled. All patients underwent upper endoscopy, and gastric biopsy specimens were taken for H. pylori assessment (rapid urease test, histology, and culture). A gastric juice sample and an arterial blood sample were obtained for ammonia level assessment. Patients with overt encephalopathy had both higher arterial ammonia levels and a more severe hepatic impairment than the remaining patients, whereas gastric juice ammonia concentrations did not differ among the three groups. H. pylori prevalence was similar among groups. Patients with H. pylori infection had significantly higher gastric juice ammonia concentrations than those without infection (2.3 ± 1.3 vs. 0.9 ± 0.6 mmol/L, respectively;p = 0.003); however, no difference in arterial ammonia levels emerged between the two groups (37.7 ± 18.6 vs. 37.6 ± 18.8 &mgr;mol/L, respectively). No significant correlation was found between gastric juice ammonia concentrations and arterial ammonia levels. The data suggest that liver impairment remains crucial in ammonia disposal in patients with cirrhosis, whereas H. pylori infection does not seem to play a major role in the pathogenesis of hyperammonemia in these patients.

Neuroimaging in epilepsy

Epilepsy is a common neurological disorder with diverse etiologies. Neuroimaging plays an important role in workup of patients with epilepsy. It helps to identify brain pathologies that require specific treatment; and also in formulating syndromic and etiological diagnoses so as to give patients and their relatives an accurate prognosis. Magnetic resonance imaging, specially the 3 tesla MRI is the imaging of choice because of its ability to detect small lesions like mesial temporal sclerosis, cortical dysplasias, small tumors, etc that are not detected by conventional MR or CT scan of brain. Identification of these lesions often helps in managing refractory epilepsies more effectively. However, cost and non-availability of MR in large part of the country necessitate the use of CT as an alternative. CT is often the initial investigation and also useful in acute situations. Functional imagings are used for pre-surgical work-up of refractory epilepsy cases with an aim to identify the epileptogenic focus and to delineate functional areas nearing the focus.

Prolongation structure for a nonlinear equation with explicit space dependence

A nonlinear Schroedinger equation with a term depending explicitly on a space variable, e.g., iψt+ψxx+(−2αx+2‖E‖2) ψ=0 with ψ=Eeiφ has been treated in the language of differential forms and prolongation. The inverse scattering equations previously invented by Liu and Chen are obtained. A unique feature of the analysis is explicit space–time dependence of the pfaffian forms.

Prolongation structure for Langmuir solitons

A systematic analysis of nonlinear partial differential equations governing the formation and evolution of Langmuir solitons has been undertaken with the help of differential forms. The technique of Wahlquist and Estabrook has been applied in conjunction with the representation theory of Lie groups to derive the 3×3 inverse scattering formalism previously derived heuristically by Yajima.

Field theoretic approach to 1S-2S excitation in H-e collision at low energy

ABS>The differential cross sections for the 1S-2S excitation of the hydrogen atom by low-energy electrons were calculated in lowestorder approximation from the viewpoint of field theory for bound states in quartum electrodynamics. The result is found to be in fair agreement with experimental curves of Stebbings et al, (Phys. Rev. 119, 1939 (1960)). (LBS)

A1ρπ couplings andt-channel helicity conservation

Recently experimental observations in hadron-hadron collisions have revealed new features in the high-energy production processes known as diffractive dissociation such as the production and the decay of particles like A 1 and Q mesons (1). The characteristic features of these events are an almost constant total cross-section and the conservat ion of the t-channel helicity inferred from the study of the density matrix of the pro. duced particle (A 1 or Q) in the Gottfried-Jackson frame. Another unusual property of these diffractively produced particles is that their spectrum cannot be fitted by a Breit. Wignertype amplitude and as such their interpretations as resonances are still dubious. At the present t ime there exists no quanti tat ive understanding of these processes as we have for resonance production processes, mediated by Regge exchanges, poles and/or cuts. A qualitative explanation in this regard has been put forward in the form of the selection rule proposed by MORRISON (2), CA~LITZ (S) and CHOW and YANG (4). There have been a few theoretical a t tempts to explain the peculiar features such as the helicity conservation and constant cross-section in terms of the pomeron (P), but these attempts are not very much decisive due to the uncertain nature of the pomeron itself. Recently the very existence of the pomeron in these reactions has been put to quest ion through an elegant analysis of the density matr ix elements in the Gottfried-Jaekson frame in a Veneziano model (which does not incorporate a pomeron) by ROBERTS (5). Further, it has been shown by FREUND et al. (e) that in a twisted-loop model for the pomeron, helicity conservation in the t-channel in = p ~ A i p demands that these conservations hold only if the P-f and p exchange contributions each separately conserve t-channel helicity. MUF, LLER (7) and AHMED et al. (s) obtained information about Alp= couplings by applying the idea of t-channel helicity conservation to ==-~=A~ and ~ A ~ = A ~ scattering, respectively. They have observed that the t-channel helici~y conservation

Global Monopole in Kalb–Ramond Background

In recent, S. SenGupta and S. Sur [Phys. Lett. B 502 (2001) 350] have obtained static vacuum solutions of the gravitational field equations in back ground space time with torsion. The torsion is identified with the field strength of a second-rank anti-symmetric tensor field, namely Kalb-Ramond field. In this work, we present the solutions for the metric outside a monopole resulting from the breaking of a global 0(3) symmetry in Kalb-Ramond background. A comparison is made with the corresponding results predicted by general relativity.

A ALow-Energy Direct Channel Regge-pole Approach to α-C12Elastic Scattering .I

Abstract Differential scattering cross-sections for the elastic scattering of α by C12 at laboratory bombarding energies from 11.0 to 16.0 MeV have been evaluated in the direct channel Regge-pole formalism, taking into account the contributions from a few nearby dominant excited levels of the compound nucleus O16 and incorporating the background effect. The relevant pole-parameters have also been predicted.

A Soliton Perturbation Scheme for 3×3 Inverse Scattering Formalism with Application to the Problem of Self-Focussing of Polarised Wave in a Nonlinear Medium

A perturbation methodology has been developed for soliton solutions of nonlinear equations, tractable with the help of 3 × 3 IST formalism. The necessary formulae have been derived for describing the time evolution of the eigenvalue and the scattering data associated with the linear problem. As an illustration the whole formalism has been applied to the problem of solitary wave formation in a dissipative medium due to the self-focussing of a polarized wave. The corresponding changes of the conservation laws are also discussed.

Electron capture by proton from muonium

Abstract The differential cross-section (DCS) for charge transfer in proton-muonium (M) collisions with the subsequent formation of H(1s) and a muon (μ + ) is computed. The angular distribution of μ + at energies 40, 50, 100 and 500 eV of the incident proton, is obtained. The DCS is found to decrease with the increase of the scattering angle of the μ + at all energies of the incident proton.