Search

Acute encephalitis syndrome (AES) is a clinical condition that occurs due to infectious and noninfectious agents- however, viruses are considered to be the dominant pathogen. agents- however, viruses are considered to be the dominant pathogen. In this study, suspected AES cases were enrolled and tested for viral etiology through serology and polymerase chain reaction (PCR)/reverse transcriptase PCR from August 2012-July 2013. During this period, 820 cases were investigated and 96 cases were diagnosed to have a viral etiology whereas 20 patients had IgM antibodies for measles in serum and HSV-1 DNA in cerebrospinal fluid. All 20 of the patients were children below 14 years of age. The median hospital stay was 15 days (IQR: 14.2-17 days) and median GCS score was 7(IQR: 6-8) and were significantly different with patients with co-infections when comapred with patients having HSV-1 infection only. It may be suspected that the measles infection may have a role in the pathogenesis and thus an impact on the prognosis of the AES when present with HSV-1.

Ultrasonic NDE of anisotropic materials, due to its inherent complexity, demands a stringent approach to determine wave propagation path in presence of inhomogeneities. In addition to developing inspection procedures, the ray path information needs to be integrated with the tomographic reconstruction algorithm of composite materials. The present study proposes a method to identify inhomogeneity boundaries using edge detection approach and to implement the same in two-dimensional ray tracing model. In general, inhomogeneity boundaries can be detected on the basis of first-order gradient of a field value (such as Young's modulus). The boundaries can be represented in terms of location and orientation. This information is included in the algorithm for more accurate ray tracing. Examples show the usefulness of the method to take into effect poor penetration of ultrasound energy in certain regions of inhomogeneous materials.

A new, tomographic reconstruction method, C-ART, for anisotropic-materials is presented which accounts for directional dependence of sound velocity in the material. The method reconstructs a two dimensional object, with internal defects, in terms of independent parameters, like elastic constants of the material. Single mode, measurement data is used for the reconstruction. The proposed method is a two-stage process, which involves conventional ART like corrections in the first stage and solution of a set of non-linear equations in the second stage. In the present work, three simple anisotropic functions, simulating direction dependent behaviour, are considered to evaluate the performance of the method. The method is found to perform well even for strong anisotropy. The reconstruction in presence of multiple defects is also attempted. It is shown in this paper that a prior knowledge of the object field is not required as an initial guess. The technique has promise for ultrasonic tomography of composite mat...

There are many practical situations where two bodies are directly in contact and are subjected to dynamic or varying loads. The contact area and the contact conditions are functions of load and load history and are not known a priori at any load thus making the problems nonlinear. The conditions of contact are determined by the kinematic constraints and the Coulomb’s law of friction. Direct solutions do not give unique results if the load steps are large and the finite element mesh is coarse. In the present work a method using the principle of minimum dissipation of energy is proposed and is applied to finite element analysis of a two-dimensional elastic contact problem under quasi-static loading. A combined incremental and iterative procedure is adopted to solve this problem. The results obtained are in good agreement with physical reasoning. The proposed method obtains new results apart from greatly reducing computational time and efforts.

Nondestructive characterization of composite materials has been attempted using the concept of ultrasonic tomography. A new method, Composite-ART (C-ART) is proposed for measuring the 2-d distribution of elastic constants. This leads to a nonlinear relation between the time-of-flight and the field variables. The solution approach employs a nonlinear least-square minimization with appropriate constraints to attain a reliable solution. The method turns out be a multiple parameter reconstruction as the elastic constants characterize a pixel. Extensive studies using simulated data are carried out to establish the robustness of the method. These studies provide the guidelines with regards to choice of the relaxation parameter and an initial guess as the controlling parameters for the reconstruction of a cross-section. The sensitivity of the controlling parameters towards the solution behavior is also discussed in detail. The experimental studies were done using laser-based ultrasound as the source radiation allowing one to exploit the point source and point detector approximation. Unidirectional composites with defects were scanned and good quality reconstructions are obtained. It is observed that a low relaxation parameter helps in presence of noise due to measurement error.

In steady rolling motion, the loads and the fields of strain, stress, and deformations do not change with time at the contact region, as the contact region is continuously being formed by a new rolling surface. The principle of minimum dissipation of energy and the concept of traveling finite elements are made use of in solving such problems and the determination of micro-slips. The conditions of contact are discovered by use of the kinematic constraints and the Coulomb’s law of friction. A two-dimensional plane-strain finite element method along with the iterative procedure is used. The results obtained are in good agreement with expected behavior.