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P Chandra

Publications and source records attributed to P Chandra.

At least 19 recordsLinked to original sources
PubMed2005

Detection of a radio counterpart to the 27 December 2004 giant flare from SGR 1806-20.

It was established over a decade ago that the remarkable high-energy transients known as soft gamma-ray repeaters (SGRs) are located in our Galaxy and originate from neutron stars with intense (< or = 10(15)G) magnetic fields-so-called 'magnetars'. On 27 December 2004, a giant flare with a fluence exceeding 0.3 erg cm(-2) was detected from SGR 1806-20. Here we report the detection of a fading radio counterpart to this event. We began a monitoring programme from 0.2 to 250 GHz and obtained a high-resolution 21-cm radio spectrum that traces the intervening interstellar neutral hydrogen clouds. Analysis of the spectrum yields the first direct distance measurement of SGR 1806-20: the source is located at a distance greater than 6.4 kpc and we argue that it is nearer than 9.8 kpc. If correct, our distance estimate lowers the total energy of the explosion and relaxes the demands on theoretical models. The energetics and the rapid decay of the radio source are not compatible with the afterglow model that is usually invoked for gamma-ray bursts. Instead, we suggest that the rapidly decaying radio emission arises from the debris ejected during the explosion.

Journal Article↗
PubMed2004

Genotoxic effects of cadmium chloride and azadirachtin treated singly and in combination in fish.

The genotoxic effects of cadmium chloride (CdCl(2)) and azadirachtin (Aza) were assessed singly and conjointly in a fish, Oreochromis mossambicus, with endpoints such as chromosome aberrations, abnormal red cell nuclei, abnormal sperm morphology, and protein content (both qualitative and quantitative) of selected tissues, namely, muscle, heart, eye, brain, gill, liver, spleen, and kidney. The primary objectives were, first, to examine if CdCl(2), a common pollutant, and Aza, a natural product of the neem plant used extensively as an 'ecofriendly' agent for many purposes, had any genotoxic effect of their own on nontarget aquatic organisms of economic importance; and second, if Aza could have any ameliorating effect on CdCl(2)-induced genotoxicity in O. mossambicus tissues. As compared with distilled water-treated controls, both CdCl(2) and Aza induced genotoxicity in O. mossambicus, the former in greater quantity than that produced by Aza. However, Cd-induced toxicity in O. mossambicus appeared to be ameliorated to some extent by Aza.

Animals↗
PubMed2003

Treatment of SARS with human interferons.

Effective antiviral agents are needed to treat severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection. We assessed the antiviral potential of recombinant interferons against two clinical isolates of SARS-CoV--FFM-1, from Frankfurt patients, and Hong Kong--replicated in Vero and Caco2 cells. Interferon beta was five to ten times more effective in Caco2 cells. Interferon alpha effectively inhibited SARS-CoV replication, but with a selectivity index 50-90 times lower than that for interferon beta. Interferon gamma was slightly better than interferon alpha in Vero cell cultures, but was completely ineffective in Caco2 cell cultures. Interferon beta could be useful alone or in combination with other antiviral drugs for the treatment of SARS.

Antiviral Agents↗
PubMed2003

Glycyrrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus.

The outbreak of SARS warrants the search for antiviral compounds to treat the disease. At present, no specific treatment has been identified for SARS-associated coronavirus infection. We assessed the antiviral potential of ribavirin, 6-azauridine, pyrazofurin, mycophenolic acid, and glycyrrhizin against two clinical isolates of coronavirus (FFM-1 and FFM-2) from patients with SARS admitted to the clinical centre of Frankfurt University, Germany. Of all the compounds, glycyrrhizin was the most active in inhibiting replication of the SARS-associated virus. Our findings suggest that glycyrrhizin should be assessed for treatment of SARS.

Animals↗
PubMed2002

Hidden orbital order in the heavy fermion metal URu(2)Si(2).

When matter is cooled from high temperatures, collective instabilities develop among its constituent particles that lead to new kinds of order. An anomaly in the specific heat is a classic signature of this phenomenon. Usually the associated order is easily identified, but sometimes its nature remains elusive. The heavy fermion metal URu(2)Si(2) is one such example, where the order responsible for the sharp specific heat anomaly at T(0) = 17 K has remained unidentified despite more than seventeen years of effort. In URu(2)Si(2), the coexistence of large electron electron repulsion and antiferromagnetic fluctuations leads to an almost incompressible heavy electron fluid, where anisotropically paired quasiparticle states are energetically favoured. Here we develop a proposal for the nature of the hidden order in URu(2)Si(2). We show that incommensurate orbital antiferromagnetism, associated with circulating currents between the uranium ions, can account for the local fields and entropy loss observed at the 17 K transition. We make detailed predictions for the outcome of neutron scattering measurements based on this proposal, so that it can be tested experimentally.

Journal Article↗
PubMed2001

Cardiac memory in canine atrium : identification and implications.

BACKGROUND: Memory is a diverse biological phenomenon whose importance in the ventricle has been demonstrated. We hypothesized its occurrence in the atrium, contributing to the modulation of cardiac rhythm. METHODS AND RESULTS: We analyzed P and Ta waves in conscious chronically instrumented dogs with complete heart block. Animals were atrioventricularly sequentially paced at 5% greater than the sinus rate from the lateral right atrium (RA) during control, followed by 2 periods of 1-hour test pacing at 50% greater than the sinus rate, or by equivalent test pacing from the left atrial appendage (LAA) at 5% or 50% greater than the sinus rate. Recovery RA pacing periods of 20- and 30-minute duration, respectively, succeeded each test pacing period. RA test pacing at either rate did not affect the variables measured, but changing the pacing site from RA to LAA altered the P and Ta waves. Displacement of the spatial atrial gradient vector occurred during recovery from LAA pacing, was more marked at rapid pacing rates, and manifested accumulation and resolution consistent with cardiac memory. Concurrently, the right effective refractory period decreased. CONCLUSIONS: Memory is demonstrable in canine atrium, showing rapid onset, accumulation during successive pacing periods, and resolution on cessation of pacing. Given its association with a reduced effective refractory period, it may contribute to the substrate for atrial arrhythmias.

Animals↗
PubMed2001

Optimization of culture conditions for determining hepatobiliary disposition of taurocholate in sandwich-cultured rat hepatocytes.

This study was undertaken to examine the influence of time and volume of collagen overlay, type of media, and media additives on taurocholate (TC) accumulation and biliary excretion in hepatocytes cultured in a collagen-sandwich configuration. Hepatocytes were isolated from male Wistar rats by in situ perfusion with collagenase, seeded onto collagen-coated 60-mm dishes, overlaid with gelled collagen, and cultured for 4 d. Experiments to examine the influence of time and volume of collagen overlay were conducted in Dulbecco's modified Eagle's medium (DMEM) + 1.0 microM dexamethasone (DEX) + 5% fetal bovine serum (FBS). Hepatocytes were overlaid at 0 h with 0.1 or 0.2 ml collagen, or at 24 h with 0.1 or 0.2 ml collagen. The influence of media type and additives was examined in hepatocytes overlaid at 0 h with 0.2 ml collagen and incubated in DMEM + 0.1 microM DEX, DMEM +/- 0.1 microM DEX + 5% FBS, Williams' medium E + 0.1 microM DEX + 1% ITS+, DMEM + 1.0 microM DEX, DMEM + 1.0 microM DEX + 5% FBS, or modified Chee's medium (MCM) + 0.1 microM DEX + 1% ITS+. [3H] TC accumulation by hepatocytes in Hank's balanced salt solution (HBSS) and Ca2+-free HBSS was measured, and the biliary-exeretion index (BEI: percentage of accumulated TC localized in the canalicular compartment) was calculated. Light microscopy and carboxydichlorofluorescein fluorescence were employed to examine the cellular and canalicular morphologies. The volume of collagen used for both the substratum and the overlay did not affect TC accumulation or biliary excretion. The BEI tended to be higher in cells overlaid at 24 h (BEI = 0.649 [0.1 ml collagen]; BEI = 0.659 [0.2 ml collagen]) compared with those overlaid at 0 h after seeding (BEI = 0.538 [0.1 ml collagen]; BEI = 0.517 [0.2 ml collagen]), although the differences were not statistically significant. Hepatocytes cultured in MCM produced consistently the lowest BEI of TC (BEI = 0.396). Differing DEX concentrations (0.1 microM versus 1.0 microM) with or without 5% FBS did not appear to have a significant effect on the BEI of TC.

Animals↗
PubMed2001

Do social programmes contribute to mental well-being? The long-term impact of unemployment on depression in the United States.

BACKGROUND: Important evidence about the mental health effects of unemployment exist; however, little is known about the possible protective effects of various social interventions or about their long-term impact. This study examines the long-term consequences that different types of social programmes, i.e. entitlement and means-tested benefits, might have as regards ameliorating a negative mental health impact of unemployment among women and men. METHODS: Multiple regression models were used to analyse panel data collected in the National Survey of Families and Households in 1987 and 1992. In all 8029 individuals interviewed in both 1987 and 1992 were included in the analysis. A depression index was created from the responses to 15 items from the Center for Epidemiological Studies' Depression Scale-D (CES-D) which were included in the survey. RESULTS: The receipt of government entitlement benefits by unemployed women is associated with a reduction of depression symptoms in the long term. Men and women not working and receiving means-tested or welfare benefits are more likely to report depression in both the short and long term. CONCLUSIONS: The study underscores the need for monitoring the impact of welfare reform on mental health.

Depressive Disorder↗
PubMed2001

The relation of family violence, employment status, welfare benefits, and alcohol drinking in the United States.

OBJECTIVE: To examine the contribution of employment status, welfare benefits, alcohol use, and other individual and contextual factors to physical aggression during marital conflict. METHODS: Logistic regression models were used to analyze panel data collected in the National Survey of Families and Households in 1987 and 1992. A total of 4,780 married or cohabiting persons reinterviewed in 1992 were included in the analysis. Domestic violence was defined as reporting that both partners were physically violent during arguments. RESULTS: Unemployed respondents are not at greater risk of family violence than employed respondents, after alcohol misuse, income, education, age, and other factors are controlled for; however, employed persons receiving welfare benefits are at significantly higher risk. Alcohol misuse, which remains a predictor of violence even after other factors are controlled for, increases the risk of family violence, and satisfaction with social support from family and friends is associated with its decrease. CONCLUSIONS: Alcohol misuse has an important effect on domestic violence, and the potential impact of welfare reform on domestic violence needs to be monitored.

Adolescent↗
PubMed2001

Family violence, employment status, welfare benefits, and alcohol drinking in the United States: what is the relation?

OBJECTIVES: This study examined the contribution of employment status, welfare benefits, alcohol use, and other individual, and contextual factors to physical aggression during marital conflict. METHODS: Logistic regression models were used to analyse panel data collected in the National Survey of Families and Households in 1987 and 1992. A total of 4780 married or cohabiting persons re-interviewed in 1992 were included in the analysis. Domestic violence was defined as reporting that both partners were physically violent during arguments. RESULTS: It was found that non-employed respondents are not at greater risk of family violence in comparison with employed respondents, after controlling for alcohol misuse, income, education, age, and other factors; however, employed persons receiving welfare benefits are at significantly higher risk. Alcohol misuse, which remains a predictor of violence even after controlling for other factors, increases the risk of family violence while satisfaction with social support from family and friends decreases it. CONCLUSION: These results underscore the important effect of alcohol misuse on domestic violence, and the need to monitor the potential impact of welfare reform on domestic violence.

Adult↗
PubMed2001

Safety and efficacy of hysteroscopic endomyometrial resection-ablation for menorrhagia.

OBJECTIVE: To assess the safety and efficacy of endomyometrial resection-ablation as a surgical means of treating patients with chronic, debilitating menorrhagia. STUDY DESIGN: A retrospective review was carried out of the records of 70 consecutive women of reproductive age who had severe uterine bleeding, who did not wish to retain their reproductive potential and who were managed uniformly at Wyckoff Heights Medical Center from July 1993 to March 1999 by operative hysteroscopy and endomyometrial resection-ablation under laparoscopic control. Demographic data were collected, and details of the clinical course were assessed for complications of the procedure. The patients were followed for an average of 24 months to evaluate how effective this technique was for correcting the bleeding problem. RESULTS: Immediate postoperative amenorrhea occurred in nearly all cases (97.1%). It lasted for only three months in most cases, but persisted for as long as eight months in a small number (5.7%). Some degree of hypomenorrhea was reported for as long as eight months in 88.6%. Overall, almost every women reported feeling better (94.3%). Uterine perforation occurred in 8.6%, one case of which was compounded by bladder and ureteral injury. One patient experienced fluid overload. Histopathologic examination of the endometrium obtained intraoperatively showed the range of benign conditions that were associated with the bleeding problems for which these women had sought care. CONCLUSION: Operative hysteroscopy and endomyometrial resection-ablation was safe and effective for surgical management of persistent, severe menorrhagia. Patients were largely satisfied with the results. Transient amenorrhea and hypomenorrhea occurred frequently. There was a satisfactory correlation between preoperative and postoperative histopathologic findings. No endometrial malignancy was missed. Fluid overload was almost entirely averted as a significant complication.

Adult↗
PubMed2000

Two-dimensional periodic frustrated ising models in a transverse field

We investigate the interplay of classical degeneracy and quantum dynamics in a range of periodic frustrated transverse field Ising systems at zero temperature. We find that such dynamics can lead to unusual ordered phases and phase transitions or to a quantum spin liquid (cooperative paramagnetic) phase as in the triangular and kagome lattice antiferromagnets, respectively. For the latter, we further predict passage to a bond-ordered phase followed by a critical phase as the field is tilted. These systems also provide exact realizations of quantum dimer models introduced in studies of high temperature superconductivity.

Journal Article↗