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S Sampath

Publications and source records attributed to S Sampath.

17 recordsLinked to original sources
PubMed2003

Intermediate-range order in permanently densified GeO2 glass.

Information about the partial structure factors of densified GeO2 glass has been obtained from neutron and x-ray diffraction measurements. Densification causes a reduction in the length scale of the intermediate range order (IRO). The difference structure factors obtained by combining the x-ray and neutron data so as to eliminate one partial structure factor at a time shows the greatest effects when the Ge-Ge correlations are eliminated and least when O-O correlations are eliminated. This implies that the reduced length scale results from a decrease in the next-nearest neighbor Ge-O and O-O distance caused by a rotation about the Ge-O-Ge bonds and a distortion of the GeO4 tetrahedra.

Journal Article↗
PubMed2002

Failed endoscopic third ventriculostomy in children: management options.

Endoscopic third ventriculostomy (ETV) for obstructive hydrocephalus has a failure rate of 20-50% in various series. The present study analyzes ETV failures in 72 patients over a 2-year period and attempts to outline a management plan. Of the 72 patients who underwent ETV, it failed in 13. Seven of these failures occurred within 1 month, and in 5 others, ETV failed after 1-2 months. Another patient had a delayed failure 2 years after the initial surgery. Upon clinical failure, MRI scans were performed in all patients using either T2 fast spin echo or two-dimensional phase contrast MRI techniques. Of these, no flow could be demonstrated in 12 patients, whereas in 1 patient, good flow was observed. Endoscopic exploration was undertaken in the 12 patients in whom flow could not be demonstrated. Of the 12 who underwent endoscopic exploration, a patent stoma was observed in 7, necessitating insertion of a ventriculoperitoneal shunt (VPS). In the other 5, the stoma had closed by gliosis and a repeat ETV was performed. In 3 of these patients, in addition to the ETV, a VPS was also inserted in accordance with the family's wishes. VPS insertion was carried out in the patient with suggestion of good flow through the stoma. In failed ETV, MRI with flow studies is essential to identify the possible cause of failure. Endoscopic exploration is indicated for patients with no evidence of flow. A repeat ETV is indicated in patients with a closed stoma. Patients with a patent stoma could require insertion of a cerebrospinal fluid shunt.

Adolescent↗
PubMed2001

Imaging longitudinal cardiac strain on short-axis images using strain-encoded MRI.

This article presents a new method for measuring longitudinal strain in a short-axis section of the heart using harmonic phase magnetic resonance imaging (HARP-MRI). The heart is tagged using 1-1 SPAMM at end-diastole with tag surfaces parallel to a short-axis imaging plane. Two or more images are acquired such that the images have different phase encodings in a direction orthogonal to the image plane. A dense map of the longitudinal strain can be computed from these images using a simple, fast computation. Simulations are conducted to study the effect of noise and the choice of out-of-plane phase encoding values. Longitudinal strains acquired from a normal human male are shown.

Adult↗
PubMed2001

Electrochemical and spectroscopic characterization of quinone functionalized exfoliated graphite.

Natural graphite was exfoliated by thermal decomposition of graphite-bisulfate intercalation compound. Oxidative/reductive pre-treatment of exfoliated graphite was subsequently carried out to introduce various functional groups on the graphite surface. The resulting material was covalently modified with redox active quinones. The covalent modification was effected through oxygen containing functional groups formed on the graphite surface. The modified exfoliated graphite was characterized by infra-red (FTIR) and X-ray photoelectron spectroscopy (XPS). Electrochemical characterization of the pressed pellets of the modified graphite showed that the modification occurred at the edge sites. These electrodes were found to be very stable and the surface renewal was simply accomplished by polishing the surface using SiC emery sheets. Application of the benzoquinone modified electrode for the electrocatalysis of ascorbic acid oxidation was demonstrated.

Journal Article↗
PubMed2001

Endoscopic approach to intraventricular cysticercal lesions.

Various surgical approaches to treat intraventricular cysticercosis have been practiced over the years. We now present our experience with the use of the endoscope in the removal of intraventricular cysticercal cysts in patients with intraventricular cysticercal lesions associated with hydrocephalus. From 1995 to 1998, we have excised intraventricular cysticercal cysts from 9 patients. They were located in lateral ventricle in 4, in the third ventricle in two and in the fourth ventricle in three patients. A Gaab's rigid neuroendoscope system was used to enter and excise cysts in the lateral and third ventricle. The flexible fiberoptic scope was used for excising cysts in the fourth ventricle, through a transaqueductal route. In all cases a precoronal frontal burr hole was used for entry. All have been treated with albendazole in the postoperative period. All the cysts were removed successfully using endoscopic neurosurgery alone. One patient had a superficial injury to the rigid side of the aqueduct with a postoperative deficit, which improved. Three septal perforations, three third ventriculostomies, and one aqueductoplasty were done in the same sitting after cyst removal for CSF diversion. None of the nine cases required further surgery up to date. The follow-up period varied from 12 to 45 months with a median of 18 months. Endoscopic neurosurgery is a minimally invasive technique enabling removal of intraventricular cyticercal cysts from all locations, avoiding major craniotomies/posterior fossa explorations and shunts.

Adolescent↗
PubMed2001

Intracranial infective aneurysms: angiographic evaluation with treatment.

Infective intracranial aneurysms are relatively uncommon. They develop due to septic embolisation of the vasa vasorum or lumen of the artery, with resultant focal arteritis and necrosis, leading to aneurysm formation. They are an important cause for intracranial haemorrhage. Six cases of infective aneurysms are described. A focus of infection could be detected in all the patients. Surgery was done in three cases, out of which two patients made significant recovery, while one patient died in the immediate postoperative period. Out of the three cases, treated conservatively with antibiotic therapy, there was total resolution on follow up angiogram in two, while one patient was lost to follow up.

Adolescent↗
PubMed2000

A binderless, bulk-modified, renewable surface amperometric sensor for NADH and ethanol.

Graphite particles are exfoliated and subsequently functionalized with toluidine blue. The resulting covalently modified graphite particles are restacked without any binder to form a surface-renewable, bulk-modified electrode. Electrocatalytic oxidation of NADH and its application in the amperometric biosensing of ethanol using alcohol dehydrogenase enzyme have been demonstrated with this material.

Alcohol Dehydrogenase↗
PubMed2000

Spatial working memory and hippocampal size across pregnancy in rats.

The present experiments investigated the effects of pregnancy on performance in the Morris water maze and on hippocampal volume. In the first study, pregnant rats (in between the first and second trimester) outperformed nonpregnant rats on the Morris water maze on 1 day of testing. In the second study, rats were tested in a working memory variation of the maze in which the spatial location of the platform varied. Pregnant females traveled shorter distances than nonpregnant females during the first two trimesters, but performed worse than nonpregnant females during the third trimester. Latency measures showed a similar profile. Group differences in performance were not related to changes in swim speed. However, changes in performance in pregnant females may be related to estrogen, progesterone, and/or corticosterone levels during pregnancy, with low levels of estradiol and high levels of progesterone being associated with better performance. There were no significant differences between pregnant and nonpregnant animals on any of the brain measures, although pregnant animals tended to have a smaller hippocampus than nonpregnant animals. These results indicate that pregnancy can affect performance, possibly related to the hormonal changes that accompany pregnancy.

Animals↗
PubMed1999

Parasellar neurenteric cyst: unusual site and histology: case report

OBJECTIVE AND IMPORTANCE: Intracranial neurenteric cyst is an exceedingly rare, congenital, benign, space-occupying lesion, and only a few reports of intracranial neurenteric cysts have been documented. We report a case of parasellar neurenteric cyst, a site not previously reported in the literature. A further rarity was the presence of smooth muscle as part of the cyst wall. This feature provides support for an endodermal origin of the cyst. CLINICAL PRESENTATION: A 27-year-old man presented with recurrent episodes of headache, vomiting, and left ptosis. Magnetic resonance imaging disclosed a cystic lesion in the parasellar region. INTERVENTION: A well-circumscribed cystic lesion was resected through a left frontotemporal craniotomy. At follow-up examination, persistent cranial nerve deficits were present. CONCLUSION: Hitherto unreported, a parasellar location of a well-encapsulated neurenteric cyst is described. The presence of a subepithelial smooth muscle layer, reminiscent of bronchiolar/intestinal muscularis mucosa, provides strong evidence for an endodermal origin of this cystic lesion.

Journal Article↗
PubMed1994

Creating a knowledge base of biological research papers.

Intelligent text-oriented tools for representing and searching the biological research literature are being developed, which combine object-oriented databases with artificial intelligence techniques to create a richly structured knowledge based of Materials and Methods sections of biological research papers. A knowledge model of experimental processes, biological and chemical substances, and analytical techniques is described, based on the representation techniques of taxonomic semantic nets and knowledge frames. Two approaches to populating the knowledge base with the contents of biological research papers are described: natural language processing and an interactive knowledge definition tool.

Algorithms↗
PubMedDate not supplied

The history of MRI.

Explore the source record for details and available documents.

Europe↗
PubMedDate not supplied

Use of the logistic organ dysfunction system to study mortality in an Indian intensive care unit.

BACKGROUND: Mortality in Indian intensive care units has not been well studied. Scoring systems are used to predict mortality of patients admitted to such units. Some scoring systems predict hospital mortality while others predict mortality in intensive care units. We used the logistic organ dysfunction system to study the hospital and intensive care unit mortalities in our intensive care unit. METHODS: We prospectively studied 527 consecutively admitted patients in 1997 to the medical intensive care unit in St John's Medical College Hospital, Bangalore. The outcomes studied were death in hospital and death in the intensive care unit. Using standardized mortality ratios, we compared our observed hospital and intensive care unit mortalities with the hospital mortality predicted by the logistic organ dysfunction system. RESULTS: The standardized mortality ratios for hospital deaths was 1.3 with a confidence interval of 1.17-1.49 and for intensive care unit deaths it was 1.0 with a confidence interval of 0.89-1.18. The hospital mortality rates in our setting are significantly higher (p < 0.05) than the predicted hospital mortality rates of the published western model for intensive care unit patients. The intensive care unit mortality rates are not significantly different from the predicted hospital mortality rates of the published western model for intensive care unit patients. CONCLUSION: Our intensive care unit mortality rate is comparable to the western hospital mortality rate. However, after transfer of patients out of the unit, the hospital mortality is higher.

Adolescent↗