Using temporal distributions of transient events to characterize cosmological source populations

The brightest events in a time series of cosmological transients obey an observation time dependence which is often overlooked. This dependence can be exploited to probe the global properties of electromagnetic and gravitational wave transients (Howell et al. 2007a, Coward & Burman 2005). We describe a new relation based on a peak flux--observation time distribution and show that it is invariant to the luminosity distribution of the sources (Howell et al. 2007b). Applying this relation, in combination with a new data analysis filter, to \emph{Swift} gamma-ray burst data, we demonstrate that it can constrain their rate density.Comment: published in proceedings of FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS: 10th International Symposium, AIP,1246,203, (2010

An improved method for estimating source densities using the temporal distribution of Cosmological Transients

It has been shown that the observed temporal distribution of transient events in the cosmos can be used to constrain their rate density. Here we show that the peak flux--observation time relation takes the form of a power law that is invariant to the luminosity distribution of the sources, and that the method can be greatly improved by invoking time reversal invariance and the temporal cosmological principle. We demonstrate how the method can be used to constrain distributions of transient events, by applying it to Swift gamma-ray burst data and show that the peak flux--observation time relation is in good agreement with recent estimates of source parameters. We additionally show that the intrinsic time dependence allows the method to be used as a predictive tool. Within the next year of Swift observation, we find a 50% chance of obtaining a peak flux greater than that of GRB 060017 -- the highest Swift peak flux to date -- and the same probability of detecting a burst with peak flux > 100 photons s^{-1} cm^{-2} within 6 years.Comment: Submitted to ApJ Letter

A cosmological "probability event horizon" and its observational implications

Suppose an astronomer is equipped with a device capable of detecting emissions -- whether they be electromagnetic, gravitational, or neutrino -- from transient sources distributed throughout the cosmos. Because of source rate density evolution and variation of cosmological volume elements, the sources first detected when the machine is switched on are likely to be ones in the high-redshift universe; as observation time increases, rarer, more local, events will be found. We characterize the observer's evolving record of events in terms of a "probability event horizon", converging on the observer from great distances at enormous speed, and illustrate it by simulating neutron star birth events distributed throughout the cosmos. As an initial application of the concept, we determine the approach of this horizon for gamma-ray bursts (GRBs) by fitting to redshift data. The event rates required to fit the model are consistent with the proposed link between core-collapse supernovae and a largely undetected population of faint GRBs.Comment: 8 pages, 8 figures, accepted by MNRA

Where are the missing gamma ray burst redshifts?

In the redshift range z = 0-1, the gamma ray burst (GRB) redshift distribution should increase rapidly because of increasing differential volume sizes and strong evolution in the star formation rate. This feature is not observed in the Swift redshift distribution and to account for this discrepancy, a dominant bias, independent of the Swift sensitivity, is required. Furthermore, despite rapid localization, about 40-50% of Swift and pre-Swift GRBs do not have a measured redshift. We employ a heuristic technique to extract this redshift bias using 66 GRBs localized by Swift with redshifts determined from absorption or emission spectroscopy. For the Swift and HETE+BeppoSAX redshift distributions, the best model fit to the bias in z < 1 implies that if GRB rate evolution follows the SFR, the bias cancels this rate increase. We find that the same bias is affecting both Swift and HETE+BeppoSAX measurements similarly in z < 1. Using a bias model constrained at a 98% KS probability, we find that 72% of GRBs in z < 2 will not have measurable redshifts and about 55% in z > 2. To achieve this high KS probability requires increasing the GRB rate density in small z compared to the high-z rate. This provides further evidence for a low-luminosity population of GRBs that are observed in only a small volume because of their faintness.Comment: 5 pages, submitted to MNRA

Probing the low-luminosity GRB population with new generation satellite detectors

We compare the detection rates and redshift distributions of low-luminosity (LL) GRBs localized by Swift with those expected to be observed by the new generation satellite detectors on GLAST (now Fermi) and, in future, EXIST. Although the GLAST burst telescope will be less sensitive than Swift's in the 15--150 keV band, its large field-of-view implies that it will double Swift's detection rate of LL bursts. We show that Swift, GLAST and EXIST should detect about 1, 2 & 30 LL GRBs, respectively, over a 5-year operational period. The burst telescope on EXIST should detect LL GRBs at a rate of more than an order of magnitude greater than that of Swift's BAT. We show that the detection horizon for LL GRBs will be extended from $z \simeq 0.4$ for Swift to $z \simeq 1.1$ in the EXIST era. Also, the contribution of LL bursts to the observed GRB redshift distribution will contribute to an identifiable feature in the distribution at $z \simeq 1$.Comment: 6 pages, 4 figures, accepted by MNRA

The Varicocele: Clinical Presentation, Evaluation, and Surgical Management

A varicocele is an abnormal dilatation and tortuosity of the veins of the spermatic cord. Although varicoceles are common in the general population and are frequently found on routine physical examinations, they represent the most common correctable cause of male factor infertility. Varicoceles are also often incidental findings on imaging studies, particularly scrotal ultrasound. Importantly, not all varicoceles should be treated equally (or at all), and basic guidelines on the evaluation and indications for treatment of adult varicoceles should be reviewed before counseling and treatment. A semen analysis should be obtained for any male patient of reproductive age considering intervention. The adolescent varicocele is managed much differently than the adult varicocele and remains a source of controversy. This review describes the clinical presentation and the evaluation of adult and pediatric varicoceles, and provides guidance on their diagnosis and workup. It also describes options for surgical repair and the success and complication rates associated with each surgical approach, ultimately supporting microsurgical subinguinal varicocele repair as the current surgical standard

Measurement of thermal cycles in the weld heat affected zone of mild steel

The thermal cycles in the mild steel parent plate adjacent to a bead on plate weld have been measured for heat inputs of 108, 54 and 42 kJ/inch, by means of embedded thermocouples connected to high response automatic recorders. The results show that decreasing the heat input increases the cooling rate and decreases the width of the heat affected zone. For thermal cycles in which the peak temperatures reached 900°C or above, two points of inflection have been noted in the temperature ranges 400° - 600°C and 950° - 1200°C. The inflection in the lower temperature range, which has been observed by other workers, has been attributed to latent heat from the exothermic transformation of austenite to ferrite. The higher inflection point, not previously reported, has been tentatively related to the solidification in the weld pool and the release of the latent heat of fusion

The Potential of Plasma Screen Technology in Small Group Teaching for Dental Undergraduates

AIM: This study was devised to ascertain the opinion of dental undergraduate students as to whether they preferred observing a live demonstration as a group directly at the workbench or indirectly on a remote Plasma Screen. In addition, to identify whether the students observing remotely believed that they had been disadvantaged by the inability to question the demonstrator during the demonstration. METHOD: 17 students divided into two groups observed a live demonstration of a laboratory technical procedure either at the workbench, or remotely on a Plasma Screen with the aid of video cameras. They subsequently observed a second demonstration with the roles reversed. Questionnaires were used to obtain the students’ views of their ability to see and interact with the demonstrator. RESULTS: The responses of the students observing the demonstration on the Plasma Screen indicated that they felt that they were able to see the demonstration more clearly than those observing at the workbench (p=0.04). Those observing on the Plasma Screen first, indicated this in particular (p=0.03). The majority of students acknowledged their inability to ask questions when observing on the Plasma Screen and supported the idea that the Plasma Screen should be used to complement the demonstration at the workbench. CONCLUSION: Plasma Screen technology has considerable potential as a teaching tool for small groups of student, where it can afford significantly superior views of practicalprocedures. The students considered that the Plasma Screen would be best employed to provide close up views to supplement a live demonstration. The apparatus may be used remotely more successfully if videoconferencing technology were also employed to facilitate interaction with the demonstrator

Diabetic Nephropathy: Novel Molecular Mechanisms and Therapeutic Avenues

This is the final version of the article. Available from Hindawi Publishing Corporation via the DOI in this record