PubMed Health⌕ Search

Biomedical subjects

S Sridhar

Publications and source records attributed to S Sridhar.

At least 19 recordsLinked to original sources
PubMed2004

Negative refraction and left-handed electromagnetism in microwave photonic crystals.

We demonstrate the negative refraction of microwaves in a metallic photonic crystal prism. The spectral response of the photonic crystal prism, which manifests both positive and negative refraction, is in complete agreement with band-structure calculations and numerical simulations. The validity of Snell's law with a negative refractive index is confirmed experimentally and theoretically. The negative refraction observed corresponds to left-handed electromagnetism that arises due to the dispersion characteristics of waves in a periodic medium. This mechanism for negative refraction is different from that in metamaterials.

Journal Article↗
PubMed2004

Short rib polydactyly syndrome-Type I.

Short rib polydactyly syndrome (SRPS) consists of a group of lethal skeletal dysplasias presenting with short limbs and ribs, hypoplastic thorax and polydactyly with or without visceral abnormalities. The authors report a case of SRPS in a fresh stillborn baby who had these features along with dysplastic kidneys. Clinical and radiological findings in this baby were consistent with SRPS - Type I (Saldino-Noonan Type). The diagnosis of SRPS, as in this case, can be made by antenatal ultrasonography.

Consanguinity↗
PubMed2003

Fractal Weyl laws for chaotic open systems.

We present a conjecture relating the density of quantum resonances for an open chaotic system to the fractal dimension of the associated classical repeller. Mathematical arguments justifying this conjecture are discussed. Numerical evidence based on computation of resonances of systems of n disks on a plane are presented supporting this conjecture. The result generalizes the Weyl law for the density of states of a closed system to chaotic open systems.

Journal Article↗
PubMed2003

Isospectrality in chaotic billiards.

We consider a modification of isospectral cavities whereby the classical dynamics changes from pseudointegrable to chaotic. We construct an example where we can prove that isospectrality is retained. We then demonstrate this explicitly in microwave resonators.

Journal Article↗
PubMed2003

Saccular cyst.

Explore the source record for details and available documents.

Airway Obstruction↗
PubMed2003

Internet based expert system for the management of gallstones, renal, ureteric and bladder calculi.

An Internet based expert system for the management of gallstones, Renal, Ureteric and bladder calculi based on ultrasound images is presented in this paper. Calculi are due to abnormal collection of certain chemicals like oxalate, phosphate and Uric acid. These calculi can be present in kidney, Ureter or in Urinary bladder and also in gall bladder. The expert system is designed to assist the physician to detect, extract, classify and diagnose calculi with greater accuracy. It also helps physicians in the management of calculi based on the etiological analysis of calculi. The Expert system takes an ultrasound image as input along with the symptoms of the patients. The expert system extracts the renal calculi and analyzes it using different image processing techniques to extract the image features like size, location and texture. These image features along with the clinical data of the patient enable the expert system to provide the decisions to decide the future course of treatment with more accuracy.

Artificial Intelligence↗
PubMed2002

Neonatal spinal cord injury.

Neonatal spinal cord injury (SCI) is well described in the literature, though its diagnosis is often delayed or missed in the neonatal period. We present a neonate who was referred with upper gastrointestinal bleed and a diagnosis of spinal cord injury was subsequently made clinically and confirmed radiologically.

Birth Injuries↗
PubMed2002

Acid suppression in healthy subjects following lansoprazole or pantoprazole.

AIM: To compare the effect of lansoprazole, 30 mg once daily, with that of pantoprazole, 40 mg once daily, for the inhibition of gastric acid secretion. METHODS: Two randomized, single-blind, two-way, crossover studies were conducted in 74 healthy male volunteers. Lansoprazole, 30 mg, or pantoprazole, 40 mg, was administered once daily for five consecutive days with at least a 2-week washout period between regimens. Ambulatory 24-h intragastric pH was recorded at baseline and on days 1 and 5 of each crossover treatment period. RESULTS: On day 1 in both studies, lansoprazole, 30 mg, produced significantly higher mean 24-h intragastric pH values when compared to pantoprazole, 40 mg (3.78 vs. 3.08, P < 0.001, and 3.97 vs. 3.20, P < 0.001, in the first and second studies, respectively). In both studies, lansoprazole, 30 mg, produced significantly greater proportions of time that the intragastric pH was above 3, 4 and 5 when compared with pantoprazole, 40 mg (P < 0.005 in all comparisons). By treatment day 5 in the first study, lansoprazole, 30 mg, continued to produce a higher mean 24-h intragastric pH (4.15 vs. 3.91, P=0.014) and a significantly greater percentage of time that the intragastric pH was above 4 (63% vs. 56%, P=0.017) and 5 (41% vs. 30%, P < 0.001) when compared with pantoprazole, 40 mg. In the second study, the effects on intragastric pH were comparable between the two treatment groups. Headache was the most commonly reported adverse experience (nine lansoprazole-treated subjects, seven in the first study and two in the second study; six pantoprazole-treated subjects, five in the first study and one in the second study). CONCLUSIONS: Lansoprazole, 30 mg once daily, produces a faster onset and greater degree of acid inhibition than pantoprazole, 40 mg once daily. The implications for these differences on symptom relief and healing of erosive oesophagitis should be explored.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2002

Segmentation of renal calculi in ultrasound images.

An algorithm proposed by Sridhar and Kumaravel is extended to include a framework for the detection of renal calculi. Calculi occur due to abnormal collection of certain chemicals like oxalate, phosphate and uric acid. These calculi can be present in the kidney, ureter or urinary bladder. Performance analysis is done to a set of five known algorithms using parameters such as success rate in calculi detection, border error metric and time. The framework is constructed by combining the best algorithm based on the performance analysis and a procedure to validate the detected calculi using the shadow it casts in ultrasound images. Ultrasound images of 37 patients are used for testing the algorithm. The detected calculi based on the framework match those determined by expert clinicians in more than 95% of the cases.

Algorithms↗
PubMed2001

Differential expression of members of the tumor necrosis factor alpha-related apoptosis-inducing ligand pathway in prostate cancer cells.

Androgen ablation therapy induces apoptosis only in androgen-sensitive prostate cancer cells; therefore, other cytotoxic drugs are being used to induce apoptosis in androgen-refractory cells. Mifepristone, an antiprogestin used individually or together with the antiestrogen Tamoxifen, has been recommended for induction of cell death and treatment of several hormonal cancers. However, little is known about the mechanism of action of these drugs in prostate cancer. Therefore, we investigated the effect of Mifepristone on the tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL) pathway, a newly identified and very effective member of tumor necrosis factor-alpha family. Mifepristone and Tamoxifen induced significant expression of death receptors in prostate cancer cells in vitro and in xenografts. However, Mifepristone in combination with Tamoxifen did not increase prostate cancer cell death compared with their individual values. The involvement of the TRAIL pathway was further confirmed by the activation of caspase-8 in Mifepristone-treated cells. This was followed by truncation of Bid, confirming that Mifepristone activates the TRAIL pathway. This knowledge is being used to design a combination treatment of TRAIL and Mifepristone to induce significant apoptosis in prostate cancer cells.

Animals↗
PubMed2001

Isolation and characterisation of an anticryptococcal protein in human cerebrospinal fluid.

An earlier study reported that human cerebrospinal fluid (CSF) has fungistatic activity for Cryptococcus neoformans. The present study reports that molecular sieve fractionation of concentrated CSF yielded three protein peaks, one of which (p2) had anticryptococcal activity. On a DEAE-Sephacel anion-exchange column the active molecular sieve peak (p2) gave two peaks that contained anticryptococcal activity. The first (DEAE-1) eluted with 0.1 M NaCl and the second (DEAE-2) eluted with 0.2 M NaCl in buffer. Fungistatic activity of DEAE-1 was reversed by FeCl3. Moreover, FeCl3 reversed inhibition of C. neoformans growth by CSF. In contrast, activity of DEAE-2 was not reversed by FeCl3, indicating that inhibition was produced by an iron-independent mechanism. Immunoblot assays showed that transferrin was present in DEAE-1 but not in DEAE-2, whereas albumin was present in DEAE-2 but not in DEAE-1. On NuPAGE, DEAE-1 protein migrated as a single band corresponding to transferrin and DEAE-2 protein gave a single band corresponding to albumin. In control experiments, human serum albumin subjected to the same isolation protocol acquired anticryptococcal activity similar to that of DEAE-2. Therefore, CSF albumin (DEAE-2) activity was associated with the isolation protocol. These data indicate that transferrin, present in or isolated from CSF, sequesters trace amounts of ferric iron, inhibits growth of C. neoformans and acts as an innate defence mechanism.

Cerebrospinal Fluid↗
PubMed2001

Automatic segmentation of medical images for renal calculi and analysis.

Development of an automated system to identify renal calculi based on its physical characteristics is proposed. Calculi are due to abnormal collection of certain chemicals like oxalate, phosphate and uric arid. Renal calculi may be present in kidney, ureter or in urinary bladder. An algorithm is proposed to detect calculus using its shadow. The system also extracts the properties of calculi such as size, shape and location, which are vital for reliable diagnosis. This method has been implemented in the MATLAB/IDL platform and a considerable success rate is obtained.

Algorithms↗
PubMed2001

Use of heparin in the investigation of obscure gastrointestinal bleeding.

OBJECTIVE: To determine if the administration of heparin improves the predictive value of angiography in the investigation of obscure gastrointestinal (GI) bleeding. METHODS: 18 patients with a history of chronic GI bleeding were investigated with angiography. For 6 patients, the cause of GI bleeding was established with angiography; the 12 patients who had negative results were given heparin for 24 h and were reassessed with angiography. RESULTS: After heparin administration, the source of GI bleeding was determined with angiography for 6 of the remaining 12 patients. Thus, heparinization increased diagnostic yield from 33% (6 of 18) to 67% (12 of 18). No significant complications, such as uncontrolled GI bleeding, occurred. CONCLUSION: Heparinization improves the diagnostic yield of angiography when obscure GI bleeding is being investigated.

Angiography↗
PubMed2000

Quantum fingerprints of classical ruelle-pollicott resonances

Quantum and classical correlations are studied experimentally in model n-disk microwave billiards. The wave vector kappa autocorrelation C(kappa) of the quantum spectrum displays nonuniversal oscillations for large kappa, comparable to the universal random matrix theory behavior observed for small kappa. The nonuniversal behavior is shown to be completely determined by the classical Ruelle-Pollicott resonances, arising from the complex eigenvalues of the Perron-Frobenius operator, and calculated using periodic orbit theory. This work establishes a fundamental connection between the quantum and classical correlations of an open system.

Journal Article↗