Interpreting signals from astrophysical transient experiments

Time domain astronomy has come of age with astronomers now able to monitor the sky at high cadence both across the electromagnetic spectrum and using neutrinos and gravitational waves. The advent of new observing facilities permits new science, but the ever increasing throughput of facilities demands efficient communication of coincident detections and better subsequent coordination among the scientific community so as to turn detections into scientific discoveries. To discuss the revolution occurring in our ability to monitor the Universe and the challenges it brings, on 2012 April 25-26 a group of scientists from observational and theoretical teams studying transients met with representatives of the major international transient observing facilities at the Kavli Royal Society International Centre, UK. This immediately followed the Royal Society Discussion meeting "New windows on transients across the Universe" held in London. Here we present a summary of the Kavli meeting at which the participants discussed the science goals common to the transient astronomy community and analysed how to better meet the challenges ahead as ever more powerful observational facilities come on stream.

An efficient and robust case sorting for algorithm for transient stability assessment

An efficient and robust case sorting algorithm based on Extended Equal Area Criterion (EEAC) is proposed in this paper for power system transient stability assessment (TSA). The time-varying degree of an equivalent image system can be deduced by comparing the analysis results of Static EEAC (SEEAC) and Dynamic EEAC (DEEAC), the former of which neglects all time-varying factors while the latter partially considers the time-varying factors. Case sorting rules according to their transient stability severity are set combining the time-varying degree and fault messages. Then a case sorting algorithm is designed with the “OR” logic among multiple rules, based on which each case can be identified into one of the following five categories, namely stable, suspected stable, marginal, suspected unstable and unstable. The performance of this algorithm is verified by studying 1652 contingency cases from 9 real Chinese provincial power systems under various operating conditions. It is shown that desirable classification accuracy can be achieved for all the contingency cases at the cost of very little extra computational burden and only 9.81% of the whole cases need to carry out further detailed calculation in rigorous on-line TSA conditions.

SN 2009ip at late times - an interacting transient at+2 years

We present photometric and spectroscopic observations of the interacting transient SN 2009ip taken during the 2013 and 2014 observing seasons. We characterize the photometric evolution as a steady and smooth decline in all bands, with a decline rate that is slower than expected for a solely Co-56-powered supernova at late phases. No further outbursts or eruptions were seen over a two year period from 2012 December until 2014 December. SN 2009ip remains brighter than its historic minimum from pre-discovery images. Spectroscopically, SN 2009ip continues to be dominated by strong, narrow (less than or similar to 2000 km s(-1)) emission lines of H, He, Ca, and Fe. While we make tenuous detections of [Fe II] lambda 7155 and [O I] lambda lambda 6300, 6364 lines at the end of 2013 June and the start of 2013 October, respectively, we see no strong broad nebular emission lines that could point to a core-collapse origin. In general, the lines appear relatively symmetric, with the exception of our final spectrum in 2014 May, when we observe the appearance of a redshifted shoulder of emission at +550 km s(-1). The lines are not blueshifted, and we see no significant near-or mid-infrared excess. From the spectroscopic and photometric evolution of SN 2009ip until 820 d after the start of the 2012a event, we still see no conclusive evidence for core-collapse, although whether any such signs could be masked by ongoing interaction is unclear.

Alzheimer's disease-like pathology has transient effects on the brain and blood metabolome

The pathogenesis of Alzheimer's disease (AD) is complex involving multiple contributing factors. The extent to which AD pathology impacts upon the metabolome is still not understood, nor is it known how disturbances change as the disease progresses. For the first time we have profiled longitudinally (6, 8, 10, 12 and 18 months) both the brain and plasma metabolome of APP/PS1 double transgenic and wild type (WT) mice. A total of 187 metabolites were quantified using a targeted metabolomics methodology. Multivariate statistical analysis produced models that distinguished APP/PS1 from WT mice at 8, 10 and 12 months.Metabolic pathway analysis found perturbed polyamine metabolism in both brain and blood plasma. There were other disturbances in essential amino acids,branched chain amino acids and also in the neurotransmitter serotonin.Pronounced imbalances in phospholipid and acylcarnitine homeostasis was evident in two age groups. AD-like pathology therefore impacts greatly on both the brain and blood metabolomes, although there appears to be a clear temporal sequence whereby changes to brain metabolites precede those in blood.

Transient receptor potential (TRP) channel expression in pulpal fibroblasts

Introduction: Transient receptor potential (TRP) channels are widely, but not uniformly, distributed in tissues. To date the dominant focus of attention has been on TRP expression and functionality in neurons. However, their expression and activation in selected non-neuronal cells suggest TRPs have a potential role in coordinating cross-talk during the inflammatory process. Fibroblasts comprise the major cell type in the dental pulp and play an important role in pulpal inflammation. Objectives: The aim of this study was to investigate the expression and functionality of the TRP channels TRPA1, TRPM8, TRPV4 and TRPV1 in human dental pulp fibroblasts. Methods: Dental pulp fibroblasts were derived by explant culture of pulps removed from extracted healthy teeth. Fibroblasts were cultured in DMEM supplemented with 10% FCS, 100U/ml penicillin and 100µg/ml streptomycin. Protein expression of TRP channels was investigated by SDS- polyacrylamide gel electrophoresis and Western blotting of cell lysates from fibroblast cells in culture. TRPA1, TRPM8, TRPV4 and TRPV1 expression was determined by specific antibodies, detected using appropriate anti-species antibodies and chemiluminescence. Functionality of TRP channels was determined by Ca2+ microfluorimetry. Cells were grown on cover slips and incubated with Fura 2AM prior to stimulation with icilin (TRPA1 agonist), menthol (TRPM8 agonist), 4 alpha-phorbol 12,13-didecanoate (4alphaPDD) (TRPV4 agonist) or capsaicin (TRPV1 agonist). Emitted fluorescence (F340/F380) was used to determine intracellular [Ca2+] levels. Results: Fibroblast expression of TRPA1, TRPM8, TRPV4 and TRPV1 was confirmed at the protein level by Western blotting. Increased intracellular [Ca2+] levels in response to icillin, methanol, 4alphaPDD and capsacin, indicated functional expression of TRPA1, TRPM8, TRPV4 and TRPV respectively. Conclusions: The presence and functionality of TRP channels on dental pulp fibroblasts suggests a potential role for these cells in the pulpal neurogenic inflammatory response. (Supported by a research grant from the Royal College of Surgeons of Edinburgh).