Biomedical subjects
Publications and source records attributed to S Chopra.
We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.
Aneurysmal bone cyst in temporal region is rare. It is a benign condition and may extend intracranially. Total surgical removal is recommended, whenever possible in one stage or in multiple stages. Prognosis is excellent and total removal will effect a cure. An unusual case of aneurysmal bone cyst of temporal region is reported.
We present an interesting case of sacral perineural cyst which caused chronic perineal pain. Perineural cyst is relatively rare, especially the sacral region. Chronic perineural pain is an often encountered problem that is difficult to evaluate and sacral perineural cyst may be the etiology of chronic perineal pain in many instances.
The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.
We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.
We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.
We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.
The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.
We report on a study of the ratio of inclusive three-jet to inclusive two-jet production cross sections as a function of total transverse energy in p&pmacr; collisions at a center-of-mass energy sqrt[s] = 1.8 TeV, using data collected with the D0 detector during the 1992-1993 run of the Fermilab Tevatron Collider. The measurements are used to deduce preferred renormalization scales in perturbative O(alpha(3)(s)) QCD calculations in modeling soft-jet emission.
We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.
We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.
Spinal dysraphism is a general term which encompasses a wide variety of anomalies of the spine, all of which result from imperfect midline fusion of the embryonic neural tube. This term refers to large defects that involve the spine and not to small vertical clefts commonly seen within the spinal process of L5 or S1. We present a spectrum of MR imaging findings selected from a retrospective review of 100 patients of spinal dysraphism evaluated at our institution.
Pectinases are one of the upcoming enzymes of fruit and textile industries. These enzymes break down complex polysaccharides of plant tissues into simpler molecules like galacturonic acids. The role of acidic pectinases in bringing down the cloudiness and bitterness of fruit juices is well established. Recently, there has been a good number of reports on the application of alkaline pectinases in the textile industry for the retting and degumming of fiber crops, production of good quality paper, fermentation of coffee and tea, oil extractions and treatment of pectic waste water. This review discusses various types of pectinases and their applications in the commercial sector.
Both erythema gyratum repens (EGR) and acquired ichthyosis are distinctive dermatoses which have strong associations with internal malignancy. EGR usually precedes the diagnosis of malignancy whereas acquired ichthyosis commonly manifests after the detection of malignancy. We report a patient who initially presented with a figurate eruption of EGR which later developed into a widespread ichthyosis with disappearance of the serpiginous rash. Further investigations revealed an underlying transitional cell carcinoma of the kidney, an association which has not previously been reported with either EGR or acquired ichthyosis. The occurrence of two paraneoplastic skin disorders in the same patient may be explained by tumour cell secretion of transforming growth factor alpha, which has been shown to be mitogenic for keratinocytes.
The maize p1 gene encodes a Myb-homologous regulator of red pigment biosynthesis. To investigate the tissue-specific regulation of the p1 gene, maize plants were transformed with constructs combining promoter and cDNA sequences of two alleles which differ in pigmentation patterns: P1-wr (white pericarp/red cob) and P1-rr (red pericarp/red cob). Surprisingly, all promoter/cDNA combinations produced transgenic plants with red pericarp and red cob (RR pattern), indicating that the P1-wr promoter and encoded protein can function in pericarp. Some of the RR patterned transgenic plants produced progeny plants with white pericarp and red cob (WR pattern), and this switch in tissue-specificity correlated with increased transgene methylation. A similar inverse correlation between pericarp pigmentation and DNA methylation was observed for certain natural p1 alleles, which have a gene structure characteristic of standard P1-wr alleles, but which confer red pericarp pigmentation and are consistently less methylated than standard P1-wr alleles. Although we cannot rule out the possible existence of tissue-specific regulatory elements within the p1 non-coding sequences or flanking regions, the data from transgenic and natural alleles suggest that the tissue-specific pigmentation pattern characteristic of the P1-wr phenotype is epigenetically controlled.
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OBJECTIVE: This study was performed to compare the clinical outcome after gallbladder aspiration with that after percutaneous cholecystostomy in non-critically ill patients with acute cholecystitis who were at high risk from surgery. MATERIALS AND METHODS: Medical records of 53 consecutive non-critically ill, high-surgical-risk patients admitted with acute cholecystitis between July 1995 and July 1999 were reviewed. Thirty-one had gallbladder aspiration and 22 had percutaneous cholecystostomy. The primary outcome measure of clinical response within 72 hr and the secondary outcome measures of overall positive response rate, complication rate, time to resolution, and rate of recurrence of acute cholecystitis were compared between the two groups. RESULTS: Gallbladder aspiration and percutaneous cholecystostomy were technically successful in 30 (97%) and 21 (97%) patients, respectively; of these, 23 (77%) and 19 (90%) patients responded clinically within 72 hr (p > 0.2). Complications occurred in three patients (12%) after percutaneous cholecystostomy and in none after gallbladder aspiration (p < 0.05). No significant difference was noted in the other secondary outcome measures of the two groups. CONCLUSION: We found no significant difference in the clinical outcomes of gallbladder aspiration and percutaneous cholecystostomy in the treatment of acute cholecystitis in high-surgical-risk patients who are not critically ill. However, we found gallbladder aspiration to be significantly safer. Therefore, gallbladder aspiration should be the procedure of choice in high-risk patients with acute cholecystitis who are not critically ill, and percutaneous cholecystectomy should be reserved as a salvage procedure if gallbladder aspiration is technically or clinically unsuccessful.