Fibre-optic delivery of time and frequency to VLBI station

The quality of Very Long Baseline Interferometry (VLBI) radio observations predominantly relies on precise and ultra-stable time and frequency (T&F) standards, usually hydrogen masers (HM), maintained locally at each VLBI station. Here, we present an operational solution in which the VLBI observations are routinely carried out without use of a local HM, but using remote synchronization via a stabilized, long-distance fibre-optic link. The T&F reference signals, traceable to international atomic timescale (TAI), are delivered to the VLBI station from a dedicated timekeeping laboratory. Moreover, we describe a proof-of-concept experiment where the VLBI station is synchronized to a remote strontium optical lattice clock during the observation.Comment: 8 pages, 8 figures, matches the version published in A&A, section Astronomical instrumentatio

RNIE: genome-wide prediction of bacterial intrinsic terminators

Bacterial Rho-independent terminators (RITs) are important genomic landmarks involved in gene regulation and terminating gene expression. In this investigation we present RNIE, a probabilistic approach for predicting RITs. The method is based upon covariance models which have been known for many years to be the most accurate computational tools for predicting homology in structural non-coding RNAs. We show that RNIE has superior performance in model species from a spectrum of bacterial phyla. Further analysis of species where a low number of RITs were predicted revealed a highly conserved structural sequence motif enriched near the genic termini of the pathogenic Actinobacteria, Mycobacterium tuberculosis. This motif, together with classical RITs, account for up to 90% of all the significantly structured regions from the termini of M. tuberculosis genic elements. The software, predictions and alignments described below are available from http://github.com/ppgardne/RNIE

58. Influence of total time of surgery and postoperative radiotherapy on the outcome patients with advanced laryngeal carcinoma

AimTo evaluate influence of total time of combined treatment on locoregional outcome of treatment in group patients with larynx cancer.Material/MethodsWe performed retrospective analysis of 254 patients with with stage III or IV squamous cell carcinoma of larynx who were treated between 1993 and 1996. There were 236 men, 18 women, median age was 56.3 years. Surgery consisted of total laryngectomy and elective/selective neck dissection. Patients postoperativly were irradiated in coventional way with total dose of 60 Gy. We used shrinking field technique with lateral opposed photon fields to tumor bed and upper-mid neck nodes. Supraclavicular regions (lower neck lymph nodes) were treated with an anterior field. Total time of combined treatment (from the surgery to the end of radiotherapy) was an average 92 days (range, 65–131 days). The interval between surgery and the beginning of radiotherapy was an average 45 days (range, 22–78 days) and time of irradiation was an average 45 day (range, 40–74 days).ResultsProlongation overall time of combined treatment beyond 90 days is strongly correlated with decreasing of locoregional outcome of treatment (p=0.00036). Also decreasing in outcome of treatment was noted when interval time between surgery and beginning of radiotherapy was more than 50 days (p=0.022) and when the time of irradiation was longer than 44 days (p=0.0026).ConclusionsDecreasing of total time of combined treatment (surgery and postoperative radiotherapy) is crucial in patients with advanced cancer of larynx

Stability and dynamics of free magnetic polarons

The stability and dynamics of a free magnetic polaron are studied by Monte Carlo simulation of a classical two-dimensional Heisenberg model coupled to a single electron. We compare our results to the earlier mean-field analysis of the stability of the polaron, finding qualitative similarity but quantitative differences. The dynamical simulations give estimates of the temperature dependence of the polaron diffusion, as well as a crossover to a tunnelling regime.Comment: 4 pages including 4 .eps figure

GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

Long duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of a massive star. Over the last forty years, our understanding of the GRB phenomenon has progressed dramatically; nevertheless, fortuitous circumstances occasionally arise that provide access to a regime not yet probed. GRB 080319B presented such an opportunity, with extraordinarily bright prompt optical emission that peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. It was captured in exquisite detail by wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous gamma-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. Here we show that the prompt optical and gamma-ray emissions from this event likely arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. The chromatic behaviour of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs. These circumstances can explain the extreme properties of this GRB.Comment: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 200