Observations of Gamma-ray Bursts with the Rossi X-ray Timing Explorer

The role of the Rossi X-ray Timing Explorer (RXTE) in the study of Gamma-ray Bursts (GRBs) is reviewed. Through April 2001, the All-Sky Monitor (ASM) and the Proportional Counter Array (PCA) instruments have detected 30 GRBs. In 16 cases, an early celestial position was released to the community, sometimes in conjunction with IPN results. The subsequent optical and radio searches led to the detection of 5 x-ray afterglows, to at least 6 optical or radio afterglows, to 3 of the 17 secure redshifts known at this writing, and to 2 other likely redshifts. The decay curves of early x-ray afterglows have been measured. The rapid determination of the location of GRB 970828 and the absence of optical afterglow at that position gave one of the first indications that GRBs occur in star-forming regions (Groot et al. 1998, ApJ 493, L27). The location of GRB 000301C led to the determination of a break in the optical decay rate (Rhoads and Fruchter 2001, ApJ 546, 117) which is evidence for a jet, and to variability in the optical light curve that could represent gravitational lensing (Garnavich, Loeb, and Stanek 2000, ApJ 544, L11). X-ray light curves of GRB from the ASM in conjunction with gamma-ray light curves exhibit striking differences in different bands and may reveal the commencement of the x-ray afterglow (Smith et al. 2001, ApJ submitted, astroph 0103357).Comment: Accepted for Proceeding Proceedings Of The Joint CNR/ESO Meeting, "Gamma-Ray Bursts in the Afterglow Era: 2nd Workshop", Rome, Italy, October 17-20, 2000, eds. F. Frontera, E. Costa, J. Hjorth, in "ESO Astrophysics Symposia" series, Springer Verlag., 8 pages, 4 figure

The Incidence of Norovirus-Associated Gastroenteritis Outbreaks in Victoria, Australia (2002–2007) and Their Relationship with Rainfall

The relationship between the incidence of norovirus-associated gastroenteritis outbreaks (NAGOs) in Victoria, Australia for the period 2002–2007 and rainfall was examined. Statistical analysis involving the correlation between time series indicated that there was a statistically significant (p < 0.05) correlation between monthly NAGO incidence and average monthly rainfall. There was a lag of an average of about three months between peak average rainfall and a NAGO epidemic. The findings thus indicate rainfall can influence NAGO incidence. In an era where there is concern about the potential effects of global warming on weather patterns, it should be borne in mind that future changes in NAGO incidence may reflect altered world weather patterns

RXTE and BeppoSAX Observations of the Transient X-ray Pulsar XTE J 18591+083

We present observations of the 9.8 s X-ray pulsar XTE J159+083 made with the All-Sky Monitor (ASM) and Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer (RXTE), and the Wide Field Cameras (WFC) on board BeppoSAX. The ASM data cover a 12 year time interval and show that an extended outburst occurred between approximately MJD50, 250, and 50, 460 (1996 June 16 to 1997 January 12). The ASM data excluding this outburst interval suggest a possible 61 day modulation. Eighteen sets of PCA observations were obtained over an approx. one month interval in 1999. The flux variability measured with the PCA appears consistent with the possible period found with the ASM. The PCA measurements of the pulse period showed it to decrease non-monotonically and then to increase significantly. Doppler shifts due to orbital motion rather than accretion torques appear to be better able to explain the pulse period changes. Observations with the WFC during the extended outburst give an error box which is consistent with a previously determined PCA error box but is significantly smaller. The transient nature of XTE J1859+083 and the length of its pulse period are consistent with it being a Be/neutral star binary. The possible 61 day orbital period would be of the expected length for a Be star system with a 9.8 s pulse period

A mapping approach to synchronization in the "Zajfman trap": stability conditions and the synchronization mechanism

We present a two particle model to explain the mechanism that stabilizes a bunch of positively charged ions in an "ion trap resonator" [Pedersen etal, Phys. Rev. Lett. 87 (2001) 055001]. The model decomposes the motion of the two ions into two mappings for the free motion in different parts of the trap and one for a compressing momentum kick. The ions' interaction is modelled by a time delay, which then changes the balance between adjacent momentum kicks. Through these mappings we identify the microscopic process that is responsible for synchronization and give the conditions for that regime.Comment: 12 pages, 9 figures; submitted to Phys Rev

The Milky Way's external disc constrained by 2MASS star counts

Context. Thanks to recent large scale surveys in the near infrared such as 2MASS, the galactic plane that most suffers from extinction is revealed and its overall structure can be studied. Aims. This work aims at constraining the structure of the Milky Way external disc as seen in 2MASS data, and in particular the warp. Methods. We use the Two Micron All Sky Survey (hereafter 2MASS) along with the Stellar Population Synthesis Model of the Galaxy, developed in Besancon, to constrain the external disc parameters such as its scale length, its cutoff radius, and the slope of the warp. In order to properly interpret the observations, the simulated stars are reddened using a three dimensional extinction map. The shape of the stellar warp is then compared with previous results and with similar structures in gas and dust. Results. We find new constraints on the stellar disc, which is shown to be asymmetrical, similar to observations of HI. The positive longitude side is found to be easily modelled with a S shape warp but with a slope significantly smaller than the slope seen in the HI warp. At negative longitudes, the disc presents peculiarities which are not well reproduced by any simple model. Finally, comparing with the warp seen in the dust, it seems to follow a slope intermediate between the gas and the stars.Comment: 9 pages. Accepted for publication in Astronomy and Astrophysic

Soluble fms-Like Tyrosine Kinase 1 (sFlt1), Endoglin and Placental Growth Factor (PlGF) in Preeclampsia among High Risk Pregnancies

Background: Differences in circulating concentrations of antiangiogenic factors sFlt1 and soluble endoglin (sEng) and the pro-angiogenic growth factor PlGF are reported to precede the onset of preeclampsia weeks to months in low-risk pregnant women. The objective of this study was to investigate whether similar changes can be detected in pregnant women at high-risk to develop the syndrome. Methods: This study is a secondary analysis of the NICHD MFMU trial of aspirin to prevent preeclampsia in high-risk pregnancies. Serum samples were available from 194 women with pre-existing diabetes, 313 with chronic hypertension, 234 with multifetal gestation, and 252 with a history of preeclampsia in a previous pregnancy. Samples collected across pregnancy were analyzed in a blinded fashion for sFlt1, sEng and PlGF. Results: The odds of developing preeclampsia were significantly increased among women with multiple fetuses for each 2- fold elevation in sFlt1, sEng and the ratio of angiogenic factors (e.g. OR 2.18, 95% CI 1.46-3.32), and significantly decreased for each 2-fold elevation in circulating PlGF (OR 0.50, 95% CI 0.30-0.82) between 7 and 26 weeks' gestation. Cross-sectional analysis of the angiogenic factors across gestation showed significant differences during the third trimester in women who develop preeclampsia compared with appropriate controls in all high-risk groups. However, when data were examined in relation to the gestational week when preeclampsia was diagnosed only sFlt1 was significantly higher 2 to 5 weeks before the clinical onset of preeclampsia and only in women with previous preeclampsia. Conclusions: The pattern of elevated concentrations of sFlt1 and sEng, and low PlGF in high-risk pregnant subjects who develop preeclampsia is similar to that reported in low-risk pregnant women. However, differences in these factors among high-risk women who do and do not develop preeclampsia are modest, and do not appear to be clinically useful predictors in these high-risk pregnant women

Variational Approximations in a Path-Integral Description of Potential Scattering

Using a recent path integral representation for the T-matrix in nonrelativistic potential scattering we investigate new variational approximations in this framework. By means of the Feynman-Jensen variational principle and the most general ansatz quadratic in the velocity variables -- over which one has to integrate functionally -- we obtain variational equations which contain classical elements (trajectories) as well as quantum-mechanical ones (wave spreading).We analyse these equations and solve them numerically by iteration, a procedure best suited at high energy. The first correction to the variational result arising from a cumulant expansion is also evaluated. Comparison is made with exact partial-wave results for scattering from a Gaussian potential and better agreement is found at large scattering angles where the standard eikonal-type approximations fail.Comment: 35 pages, 3 figures, 6 tables, Latex with amsmath, amssymb; v2: 28 pages, EPJ style, misprints corrected, note added about correct treatment of complex Gaussian integrals with the theory of "pencils", matches published versio

Phase III Randomized Trial of Chemotherapy With or Without Bevacizumab in Patients With Recurrent or Metastatic Head and Neck Cancer.

PURPOSE: We evaluated the addition of bevacizumab, a humanized monoclonal antibody that targets vascular endothelial growth factor, to platinum-based chemotherapy in recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN). PATIENTS AND METHODS: Patients with chemotherapy-naïve (or with prior platinum as part of multimodal therapy completed ≥ 4 months earlier) recurrent or metastatic SCCHN were randomly assigned to receive a platinum-based chemotherapy doublet with or without bevacizumab 15 mg/kg given intravenously every 3 weeks until disease progression. Chemotherapy could be discontinued after six cycles if a maximum response was achieved. RESULTS: The study randomly assigned 403 patients. Median overall survival (OS) was 12.6 months with bevacizumab plus chemotherapy (BC) and 11.0 months with chemotherapy alone (hazard ratio, 0.87; 95% CI, 0.70 to 1.09; P = .22). At 2, 3, and 4 years, the OS rates were 25.2% v 18.1%, 16.4% v 10.0%, and 11.8% v 6.4% for BC versus chemotherapy, respectively. In an analysis of 365 eligible patients who started treatment, the hazard ratio was 0.82 (95% CI, 0.65 to 1.04; P = .10), with a median OS of 14.2 months on BC v 11.1 months on chemotherapy. Median progression-free survival with BC was 6.0 months v 4.3 months with chemotherapy (P = .0014). Overall response rates were 35.5% with BC and 24.5% with chemotherapy (P = .016). There was increased toxicity, including a higher rate of treatment-related grade 3 to 5 bleeding events (6.7% v 0.5%; P \u3c .001) and treatment-related deaths (9.3% v 3.5%; P = .022) with BC versus chemotherapy. CONCLUSION: The addition of bevacizumab to chemotherapy did not improve OS but improved the response rate and progression-free survival with increased toxicities. These results encourage biomarker-driven studies of angiogenesis inhibitors with better toxicity profiles in select patients with SCCHN