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S Natarajan

Publications and source records attributed to S Natarajan.

At least 55 records · Page 3Linked to original sources
PubMed2000

Three-dimensional open-framework cobalt(II) phosphates by novel routes.

Two new three-dimensional open-framework cobalt phosphates, [C2N2H10]2[Co4(PO4)4]H2O, I, and [C4N3H16]3-[Co6(PO4)5(HPO4)3]H2O, II, have been prepared by the reaction of amine phosphates with Co2+ salts. I could also be prepared by the reaction of the cobalt tris amine complex with H3PO4. The crystal data for I and II are as follows: phosphate I, orthorhombic, space group P2(1)2(1)2(1) (no. 19), a = 10.277 (1) A, b = 10.302 (1) A, c = 18.836 (1) A, V = 1994.2 (2) A3, Z = 4; phosphate II, monoclinic, space group P2(1)/c (No. 14), a = 31.950 (1) A, b = 8.360 (1) A, c = 15.920 (1) A, beta = 96.6 (1) degrees V = 4223.4 (2) A3, Z = 4. The structures of both I and II are constructed from alternating CoO4 and PO4 tetrahedra. The connectivity leads to the formation of eight-membered channels in all the crystallographic directions resembling the aluminosilicate zeolite, merlinoite in the case of I and to a rather large, one-dimensional 16-membered channel in II. Strong hydrogen-bond interactions involving the amine and framework oxygen are present in both I and II.

Journal Article↗
PubMed2000

A numerical and experimental study of periodic flow in a model of a corrugated vessel with application to stented arteries.

The investigation presented in this paper has attempted to study, from a fluid dynamics point of view, the consequences of the presence of a stent on the flow of blood. The method adopted is mainly by numerical simulation using a finite element technique, but visualization experiments and an analytical study have also been carried out. The flow of blood is treated as being transient, laminar and Newtonian within a rigid section of the stented vessel. The flow is driven by an imposed pressure gradient in the form of a physiological waveform. A periodic boundary condition has been applied. Particle trajectories, fluid shear rate contours and wall shear stress maps, together with the use of a simplified form of particle image velocimetry in the experimental work, have been used to interpret the results. It was found that the vessel wall experienced oscillating levels of wall shear stress, in particular extensive exposure to low shear stress. Regions of flow recirculation, points of flow separation and reattachment constantly move in regions of low shear stress. Vortices form and then are destroyed rapidly by reversing flow. Their potential physiological significance to stented arteries is discussed.

Arteries↗
PubMed2000

Primary intracerebral rosai-dorfman disease: a case report.

A 45-year-old woman presented with an isolated, contrast-enhancing brain lesion in white matter of the right frontal lobe, preoperatively thought to be either a primary brain neoplasm or metastasis. The lesion was demonstrated by histology and immunohistochemistry to be Rosai-Dorfman disease. Central nervous system (CNS) manifestations of this disease are rare. There have been 27 cases of intracranial involvement reported previously. All of them have been dural-based, where the disease clinically and radiologically resembles meningioma. To our knowledge, this is the first case of an isolated intraparenchymal CNS lesion without dural attachment, where the clinical and radiological features resembled an intraparenchymal glial neoplasm, lymphoma or metastatic tumor.

Biopsy↗
PubMed2000

Nutrition and phylogeny of predacious yeasts.

Yeast predation was studied with respect to the range of its distribution among ascomycetous yeasts, the range of yeast species that can be affected, and nutritional aspects of the phenomenon. The yeasts identified as predators belong to the Saccharomycopsis clade as defined on the basis of rDNA sequence relatedness. The 11 recognized species in the clade, plus three undescribed but related Candida species, were shown to be incapable of utilizing sulfate as sole source of sulfur, and all but two (Saccharomycopsis capsularis and Saccharomycopsis vini) were observed to penetrate and kill other yeasts under some conditions. Other unrelated sulfate transport-deficient yeasts (strains in the genera Pichia and Candida and the two known species of Starmera) are not predacious. The predacious species vary considerably as to the optimal environmental conditions that favour predation. Some are inhibited by the presence of rich nitrogenous nutrients, organic sulfur compounds, or higher concentrations of ammonium nitrogen, whereas other species may be stimulated under the same conditions. An attempt was made to correlate prey susceptibility to the excretion of substances that stimulate the growth of predators, but no correlation was detected between the two phenomena. The range of susceptible prey covers both ascomycetes and basidiomycetes, and includes Schizosaccharomyces pombe, which was previously thought to be immune. The achlorophyllous alga Prototheca zopfii is not killed by predacious yeasts, but the initial steps of penetration have been observed in some cases. Predacious species attack other predacious species, and in some cases, young cultures may penetrate older cultures of the same strain.

Culture Media↗
PubMed1999

Amine Phosphates as Intermediates in the Formation of Open-Framework Structures.

Chain, ladder, layer, and three-dimensional metal phosphates were obtained by the reaction of amine phosphates with metal ions under mild hydrothermal conditions. The role of amine phosphates as intermediates in hydrothermal syntheses was corroborated by in situ NMR spectroscopy and X-ray diffraction studies. The picture shows a simple corner-shared linear chain structure formed in the reaction of piperazine phosphate with Zn(II) ions.

Journal Article↗
PubMed1999

Management of intraocular cysticercosis.

BACKGROUND: A study was carried out to investigate the various posterior segment presentations of intraocular cysticercosis and their management. METHODS: A retrospective study of five consecutive cases of intraocular cysticercosis seen at our institute was done. Pars plana vitreous surgery for removal of intact cysts was done in all cases. RESULTS: Complete removal of the intact cyst through the pars plana route was achieved in all cases. Postoperative periods were uneventful, with visual recovery to 6/9 or better in all cases. CONCLUSIONS: Complete surgical removal of the intact cyst can result in good functional recovery in eyes with intraocular cysticercosis.

Adult↗
PubMed1999

Yield and efficacy of biopty gun testis needle biopsy.

OBJECTIVES: To assess whether a preliminary skin incision enhances diagnostic yield of percutaneous testis biopsy and to further evaluate the clinical efficacy of this procedure. METHODS: A total of 45 men (67 testes) underwent testicular biopsy with two passes of a Biopty gun spring-loaded needle. Twenty-seven biopsies were performed without a preliminary skin incision (group 1), and 40 were performed after a small scrotal incision (group 2). In 56 testes, needle biopsy histopathologic diagnosis was compared with that of open biopsy or orchiectomy specimens from the same patient. Needle and surgical specimens were fixed in Bouin's solution and sent separately for independent, blinded, histologic interpretation. RESULTS: Complications of the procedure were negligible. In all 67 needle biopsies, specimen quality was adequate for histopathologic interpretation. The mean number of seminiferous tubules obtained from needle biopsy was 28% higher among patients having a preliminary skin incision (25.9) compared with those without (18.7, P = 0.023). Correlation between needle and open histopathologic diagnosis was excellent (55 of 56, 98%). CONCLUSIONS: A preliminary skin incision made before needle biopsy increases the diagnostic yield of percutaneous testis biopsy. Percutaneous testis biopsy using the Biopty gun needle provides equal diagnostic information when compared with open testis biopsy or orchiectomy specimens. The concomitant reduction in morbidity and cost make this an attractive diagnostic procedure.

Biopsy, Needle↗
PubMed1999

Virtual microscopy and the Internet as telepathology consultation tools. A study of gastrointestinal biopsy specimens.

Telepathology (TP) is the practice of pathology at a distance using videomicroscopy and telecommunication tools. We explore the use of "virtual microscopy" techniques and the Internet as tools for TP gastrointestinal biopsy consultations. Thirty-five gastrointestinal biopsy specimens were photographed in Los Angeles by using a high-resolution digital camera, a light microscope, and a Pentium 166 microcomputer. Several (2-8) digital photomicrographs were collected at 40x or 100x optical magnification, using 2,700 x 3,400 pixel resolution. The photomicrographs illustrated all the tissue fragments present in 1 of the biopsy levels. They were saved in medium compression JPEG image format. These images can be magnified digitally up to 600% without visible degradation and scrolled at different magnifications on a video monitor, simulating examination under a light microscope. The images files (281 to 3,324 KB) were attached to e-mail messages containing patient information and sent through the Internet to Michigan for interpretation using a Power Macintosh 7100 system. The e-mail process was successful in 100% of instances; 2 files were corrupted owing to user error and had to be resent. Additional photos were requested in 1 case. In 33 of 35 cases, there was diagnostic concordance between the original and the TP diagnoses. The 2 discrepancies were due to diagnostic disagreement. This technology offers pathologists relatively inexpensive and effective tools for gastrointestinal TP consultations.

Biopsy↗
PubMed1998

Angiosarcoma arising in a chronically lymphoedematous leg.

Cutaneous angiosarcoma is a rare aggressive tumour of capillary and lymphatic endothelial cell origin. It presents as multiple purple and red papules and nodules on the head and neck or the extremities. We report an 86-year-old woman with angiosarcoma arising on her chronically lymphoedematous right leg. The lymphoedema, secondary to chronic immobility, had developed gradually over 40 years. No other family members had lymphoedema. The patient presented with a plaque of friable tumour tissue on the lower right leg and dorsum of the foot, and satellite lesions on the knee and groin which initially appeared to be petechial haemorrhages. The satellite lesions in the groin grew into tumour nodules. There was no evidence of a preceding malignancy, nor any operative intervention to the affected limb or abdomen. Histological examination of all tumour specimens revealed moderately to poorly differentiated angiosarcoma. She died within 5 months of the first appearance of the skin nodules.

Aged↗
PubMed1998

Neonatal pemphigus vulgaris associated with mild oral pemphigus vulgaris in the mother during pregnancy.

We report a neonate with immunofluorescence-proven pemphigus vulgaris. The condition presented at birth with widespread skin erosions and ulceration of the oral mucosa. Histopathological and immunofluorescence studies confirmed pemphigus vulgaris. The mother had mild oral pemphigus vulgaris treated during pregnancy with topical corticosteroids. All the neonate's skin erosions had crust formation at day 2 but healed completely within 2 weeks.

Autoimmune Diseases↗