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Biomedical subjects

S Desai

Publications and source records attributed to S Desai.

At least 19 recordsLinked to original sources

Measurement of atmospheric neutrino flux consistent with tau neutrino appearance.

A search for the appearance of tau neutrinos from nu(mu) <--> nu(tau) oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138+/-48(stat)-32(+15)(syst) events is obtained with an expectation of 78+/-26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma.

Journal Article↗

CT-guided percutaneous core needle biopsy in deep seated musculoskeletal lesions: a prospective study of 128 cases.

OBJECTIVES: Although large lesions of the limbs can easily be biopsied without image guidance, lesions in the spine, paraspinal area and pelvis are difficult to target, and benefit from CT guidance to improve the accuracy of targeting the lesion for biopsy purposes. A prospective study of CT-guided core needle biopsies for deep-seated musculoskeletal lesions was conducted at a referral cancer institute over a 4-year period with the aim of assessing the safety and efficacy of the procedure. PATIENTS & METHODS: From January 2000 to December 2003, 136 consecutive CT-guided biopsy sessions were undertaken for musculoskeletal lesions in 128 patients comprising 73 males and 55 females. The following data was recorded in all patients: demographic data, suspected clinicoradiological diagnosis, data related to core biopsy session (date, site, approach, total time required in minutes, number of cores, surgeon satisfaction with adequacy of cores), patient discomfort, complications, histopathology report and number of further sessions if material obtained during the first biopsy session was not confirmatory. The sample obtained during the biopsy session was considered inconclusive if, in the opinion of the pathologist, inadequate or non-representative tissue had been obtained. The diagnosis was considered inaccurate if the final histopathological diagnosis did not match with the biopsy diagnosis, or if subsequent clinicoradiological evaluation at follow up did not correlate with the biopsy diagnosis in those patients who were treated with modalities other than surgery. RESULTS: In 121 patients, a single session was sufficient to obtain representative material, whilst for six patients two sessions, and for one patient three sessions were necessary. The time taken for biopsy, including the pre-biopsy CT examination time, varied from 15 min to 60 min (median 30 min). For 110 bony lesions 116 sessions were required, and for 18 soft-tissue lesions 20 sessions were required. 108 biopsy sessions yielded a diagnosis, whilst 28 were inconclusive (diagnostic yield of 79.41%). Of 108 diagnostic biopsies, five were considered inaccurate (accuracy rate of 95.37%). The overall diagnostic yield and accuracy rate for bony lesions were 81.03% and 95.74%; and those for soft-tissue lesions were 70% and 92.85%. There were two complications with no permanent sequelae. CONCLUSION: CT-guided core needle biopsy is a safe, easy, and effective technique for the evaluation of deep-seated musculoskeletal lesions, with a high rate of diagnostic yield and accuracy. It facilitates definitive therapy without the patient having to undergo a major surgical procedure for diagnosis.

Adolescent↗

Upper limits on a stochastic background of gravitational waves.

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.

Journal Article↗

Correlation between symptoms and radiological findings in patients with chronic rhinosinusitis: an evaluation study using the Sinonasal Assessment Questionnaire and Lund-Mackay grading system.

Computerised tomography (CT) scans are routinely performed prior to endoscopic sinus surgery (ESS) in order to confirm the diagnosis, assess the response to medical treatment and provide important landmarks for surgery. However, the correlation between the findings of CT scans and the patient's symptoms remains ambiguous. The objective was to assess the correlation between preoperative symptom scores using the validated Sino-Nasal Assessment Questionnaire and CT scores in patients undergoing ESS. Twenty-two patients who attended otolaryngology clinics with chronic rhinosinusitis (CRS) were prospectively enrolled in the study. All of these patients completed Sinonasal Questionnaires (SNAQ) before they had ESS. Their CT scans were scored blindly by the surgeon and a radiologist following Lund-Mackay grading. Patients with high preoperative SNAQ scores had high or low CT scores. The same applied for patients with low preoperative SNAQ scores. There was no statistically significant correlation between SNAQ and Lund-Mackay scores (P = 0.5). However, there was a very strong correlation (P < 0.001) between the scoring of scans by the surgeon and the radiologist, while there was a moderate degree of discrepancy in the grading of anterior ethmoid sinuses and osteo-meatal complexes. Morbidity of patients with CRS cannot be predicted from the magnitude of changes in their CT scans. Significant inter-rater variability exists in the grading of pathological changes in anterior ethmoid sinus and osteo-meatal complex as recorded in CT scans.

Chronic Disease↗

Evidence for an oscillatory signature in atmospheric neutrino oscillations.

Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu(micro)<-->nu(tau) neutrino oscillation parameters; 1.9x10(-3) 0.90 at 90% confidence level.

Journal Article↗

Limits on the neutrino magnetic moment using 1496 days of Super-Kamiokande-I solar neutrino data.

A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)</=(3.6x10(-10))micro(B) at 90% C.L. by fitting to the Super-Kamiokande day-night spectra. The fitting took into account the effect of neutrino oscillation on the shapes of energy spectra. With additional information from other solar neutrino and KamLAND experiments constraining the oscillation region, a limit of micro(nu)</=(1.1x10(-10))micro(B) at 90% C.L. was obtained.

Journal Article↗

A precision measurement of the mass of the top quark.

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Journal Article↗

Search for narrow tt resonances in pp collisions at square root of (s)=1.8 TeV.

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

Journal Article↗

Search for large extra dimensions in the monojet+E(T) channel with the DØ detector.

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

Journal Article↗

How significant is a cervical smear showing glandular dyskaryosis?

OBJECTIVE: To evaluate the incidence, outcome and predictive value of cytology showing glandular dyskaryosis. PARTICIPANTS: Fifty-seven women with a smear diagnosis of glandular dyskaryosis registered between January 1997 and December 2001. SETTING: Colposcopy and cytopathology units in a large district general hospital. RESULTS: Sixty smears in 57 women showing glandular dyskaryosis were identified from a cohort of 135,120 smears, giving an incidence of 0.05%. Hospital records were available for 50 women. Final diagnosis included 13 cases of cervical glandular intraepithelial neoplasia (CGIN), 4 microinvasive cervical adenocarcinomas, 2 undifferentiated tumours, 1 microinvasive squamous carcinoma, 21 cases of CIN and 13 cases of endometrial pathology (8 endometrial cancers). Twelve women had coexistent squamous and glandular disease. Forty-five out of 50 women had significant pathology (positive predictive value 90%). Colposcopy was seen to be of limited value in assessment of smears showing glandular dyskaryosis. Only 1 out of 13 glandular lesions was diagnosed by colposcopy. CONCLUSION: Smears showing glandular dyskaryosis are associated with significant pathology in 90% of cases and malignancy in 32% of cases. Hence, women with a smear showing glandular dyskaryosis should be referred urgently to a colposcopy clinic and flagged up as suspected cancer. Glandular dyskaryosis should be included in the national referral criteria for suspected gynaecological cancer.

Adenocarcinoma↗

Search for nu(e) from the sun at Super-Kamiokande-I.

We present the results of a search for low energy nu(e) from the Sun using 1496 days of data from Super-Kamiokande-I. We observe no significant excess of events and set an upper limit for the conversion probability to nu(e) of the 8B solar neutrino. This conversion limit is 0.8% (90% C.L.) of the standard solar model's neutrino flux for total energy=8-20 MeV. We also set a flux limit for monochromatic nu(e) for E(nu(e))=10-17 MeV.

Journal Article↗

Visual and electrical evoked response recorded from subdural electrodes implanted above the visual cortex in normal dogs under two methods of anesthesia.

Sensitive methods are required to record electrical evoked potentials over the visual cortex to evaluate the efficacy and safety of a retinal prosthesis before it can be implanted on the retinal surface of patients afflicted by outer retinal diseases. This study was designed to examine subdural electrodes as a mean to evaluate cortical evoked potentials in response to light and electrical stimulation of the retina in three dogs under two methods of anesthesia-halothane and propofol. Results showed that subdural electrodes could be stabilized over the visual cortex for several (3-5) months, and that they were 6.95 times more sensitive than subdermal electrodes in recording cortical visual evoked potentials (VEPs) and 4.31 times more sensitive in recording cortical electrical evoked potentials under both methods of anesthesia. The waveforms' shape changed for each electrode in the subdural array during 6/6 (100%) and 20/38 (52%) multi-channel recording sessions under halothane and propofol, respectively. This change could point to a cortical retinotopic organization versus hierarchical organization of different cortical areas for a given retinal stimulus. In summary, subdural electrodes show promising results for recording visual and electrical evoked responses (EERs) and thus for evaluation of the retinal prosthesis.

Anesthesia↗

Search for supernova relic neutrinos at Super-Kamiokande.

A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV.

Journal Article↗

Reversible posterior leukoencephalopathy syndrome in a child with cerebral X-linked adrenoleukodystrophy treated with cyclosporine after bone marrow transplantation.

Reversible posterior leukoencephalopathy syndrome (RPLS) was described by Hinchey and colleagues in 1996. The disorder occurs predominantly in patients with acute hypertension and/or on pharmacological immunosuppression. We report a 6-year-old male with cerebral X-linked adrenoleukodystrophy who received an HLA-matched unrelated bone marrow transplant (BMT). Cyclosporine was used as graft-versus-host disease prophylaxis. At 55 days post-BMT, his cyclosporine concentrations were high for several days and the concentration was still high on day 70 (353 microg/L). He presented 83 days post-BMT with new onset of headache, lethargy, acute visual loss and focal seizures. He was not hypertensive. MRI of the head revealed signal changes that now extended more peripherally into the subcortical and cortical regions of the occipital and temporal lobes. The patient's cyclosporine was stopped for 5 days. The patient's vision returned to normal and his headaches and lethargy resolved with no further seizures 3 weeks later. Follow-up MRI of the head 2 months later showed almost complete resolution of the cortical signal abnormalities. It is important to consider RPLS in patients with cerebral adrenoleukodystrophy who present with acute neurological deterioration. Attention to the pattern of white matter and the presence of cortical grey matter involvement on neuroimaging is important for the diagnosis. When appropriate management is initiated, that is controlling hypertension when present and discontinuing or reducing the dose of offending immunosuppressive agents, the acute neurological symptoms will usually resolve.

Adrenoleukodystrophy↗

A cost-effectiveness analysis of three antimalarial treatments for acute, uncomplicated Plasmodium falciparum malaria in Mumbai, India.

BACKGROUND: Malaria is a major public health problem representing 2.3% of the overall global disease burden. The cost of treatment of malaria continues to rise as older drugs and insecticides become less effective and are replaced by more effective, but also more expensive products. METHODS: A post-hoc pharmacoeconomic analysis (direct and indirect costs only) of three antimalarials, chloroquine, mefloquine and co-artemether, was carried out to address the problem of switch to a more expensive first-line antimalarial in the face of growing chloroquine resistance. RESULTS: From the perspective of a large public hospital, it was seen that in an area of high grade chloroquine resistance, the total expenditure on patients who fail chloroquine would exceed the excess expenditure on mefloquine when the RII + RIII resistance exceeded 9%. CONCLUSIONS: Switch to a more expensive drug like mefloquine as a first-line option would be cost-effective when the moderate-severe chloroquine resistance exceeded 9%.

Antimalarials↗

Search for the production of single sleptons through R-parity violation in pp; collisions at square root (s) =1.8 TeV.

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94+/-5 pb(-1). Assuming that R parity is violated via the single coupling lambda'211, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m(0),m(1/2)) and (m(x),m(v)) planes for lambda(')(211)=0.09, 0.08, and 0.07.

Journal Article↗

Search for R-parity violating supersymmetry in two-muon and four-jet topologies.

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Journal Article↗