Spectroscopy of Four Cataclysmic Variables with Periods above 7 Hours

We present spectroscopy of four cataclysmic variables. Using radial velocity measurements, we find orbital periods for the first time. The stars and their periods are GY Hya, 0.347230(9) d; SDSS J204448-045929, 1.68(1) d; V392 Hya, 0.324952(5) d; and RX J1951.7+3716, 0.492(1) d. We also detect the spectra of the secondary stars, estimate their spectral types, and derive distances based on surface brightness and Roche lobe constraints.Comment: 22 pages, 3 figures, 5 tables, to be published in December 2006 PAS

Optical Studies of Twenty Longer-Period Cataclysmic Binaries

We obtained time-series radial velocity spectroscopy of twenty cataclysmic variable stars, with the aim of determining orbital periods P_orb. All of the stars reported here prove to have P_orb > 3.5 h. For sixteen of the stars, these are the first available period determinations, and for the remaining four (V709 Cas, AF Cam, V1062 Tau, and RX J2133+51) we use new observations to improve the accuracy of previously-published periods. Most of the targets are dwarf novae, without notable idiosyncracies. Of the remainder, three (V709 Cas, V1062 Tau, and RX J2133+51) are intermediate polars (DQ Her stars); one (IPHAS 0345) is a secondary-dominated system without known outbursts, similar to LY UMa; one (V1059 Sgr) is an old nova; and two others (V478 Her and V1082 Sgr) are long-period novalike variables. The stars with new periods are IPHAS 0345 (0.314 d); V344 Ori (0.234 d); VZ Sex (0.149 d); NSVS 1057+09 (0.376 d); V478 Her (0.629 d); V1059 Sgr (0.286 d); V1082 Sgr (0.868 d); FO Aql (0.217 d); V587 Lyr (0.275 d); V792 Cyg (0.297 d); V795 Cyg (0.181 d); V811 Cyg (0.157 d); V542 Cyg (0.182 d); PQ Aql (0.247 d); V516 Cyg (0.171 d); and VZ Aqr(0.161 d). Noteworthy results on individual stars are as follows. We see no indication of the underlying white dwarf star in V709 Cas, as has been previously claimed; based on the non-detection of the secondary star, we argue that the system is farther away that had been thought and the white dwarf contribution is probably negligible. V478 Her had been classified as an SU UMa-type dwarf nova, but this is incompatible with the long orbital period we find. We report the first secondary-star velocity curve for V1062 Tau. In V542 Cyg, we find a late-type contribution that remains stationary in radial velocity, yet the system is unresolved in a direct image, suggesting that it is a hierarchical triple system.Comment: P.A.S.P., in press. 34 pages and 8 figure

A Complexity View of Rainfall

We show that rain events are analogous to a variety of nonequilibrium relaxation processes in Nature such as earthquakes and avalanches. Analysis of high-resolution rain data reveals that power laws describe the number of rain events versus size and number of droughts versus duration. In addition, the accumulated water column displays scale-less fluctuations. These statistical properties are the fingerprints of a self-organized critical process and may serve as a benchmark for models of precipitation and atmospheric processes.Comment: 4 pages, 5 figure

Levels of interaction: a user-guided experience in large-scale virtual environments

This paper investigates a range of challenges faced in the design of a serious game, teaching history to a player immersed in an 'open' virtual environment. In the context of this paper, such an environment is described as an exploratory, expansive virtual world within which a user may interact in a non-linear, situated fashion with both the environment and virtual characters. The main contribution of this paper consists in the introduction of the levels of interaction (LoI), a novel framework designed to assist in the creation of interactions between the player and characters. The LoI approach also addresses the necessity for balancing computational efficiency with the need to provide believable and interactive virtual characters, by allowing varying degrees of animation, display and, ultimately, interaction detail. This paper demonstrates the challenges faced when implementing such a technique, as well as the potential benefits it brings

The lesson of causal discovery algorithms for quantum correlations: Causal explanations of Bell-inequality violations require fine-tuning

An active area of research in the fields of machine learning and statistics is the development of causal discovery algorithms, the purpose of which is to infer the causal relations that hold among a set of variables from the correlations that these exhibit. We apply some of these algorithms to the correlations that arise for entangled quantum systems. We show that they cannot distinguish correlations that satisfy Bell inequalities from correlations that violate Bell inequalities, and consequently that they cannot do justice to the challenges of explaining certain quantum correlations causally. Nonetheless, by adapting the conceptual tools of causal inference, we can show that any attempt to provide a causal explanation of nonsignalling correlations that violate a Bell inequality must contradict a core principle of these algorithms, namely, that an observed statistical independence between variables should not be explained by fine-tuning of the causal parameters. In particular, we demonstrate the need for such fine-tuning for most of the causal mechanisms that have been proposed to underlie Bell correlations, including superluminal causal influences, superdeterminism (that is, a denial of freedom of choice of settings), and retrocausal influences which do not introduce causal cycles.Comment: 29 pages, 28 figs. New in v2: a section presenting in detail our characterization of Bell's theorem as a contradiction arising from (i) the framework of causal models, (ii) the principle of no fine-tuning, and (iii) certain operational features of quantum theory; a section explaining why a denial of hidden variables affords even fewer opportunities for causal explanations of quantum correlation

Left Ventricular Hypertrophy is a predictor of cardiovascular events in elderly hypertensives: hypertension in the the very elderly trial (HYVET)

Objective: We assessed the prognostic value of electrocardiographic left ventricular hypertrophy (LVH) using Sokolow-Lyon (SL-LVH), Cornell Voltage (CV-LVH) or Cornell Product (CP-LVH) Criteria in 3043 hypertensive people aged 80 years and over enrolled in the Hypertension in the Very Elderly Trial. Methods: Multivariate Cox proportional hazard models were used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for all-cause mortality, cardiovascular diseases, stroke and heart failure in participants with and without LVH at baseline. The mean follow-up was 2.1 years. Results: LVH identified by CV- or CP-LVH Criteria was associated with a 1.6 to 1.9-fold risk of cardiovascular disease and stroke. The presence of CP-LVH was associated with an increased risk of heart failure (HR 2.38, 95% CL 1.16-4.86). In gender specific analyses, CV-LVH (HR 1.94, 95%Cl 1.06-3.55) and CP-LVH (HR 2.36, 95% CI 1.25-4.45) were associated with an increased risk of stroke in women and of heart failure in men, CV-LVH (HR 6.47, 95 % Cl 1.41-29.79) and CP-LVH (10.63, 95Cl % 3.58-31.57), respectively. There was no significant increase in the risk of any outcomes associated with SL LVH. LVH identified by these three methods was not a significant predictor of all-cause mortality. Conclusions: Use of Cornell Voltage and Cornell Product criteria for LVH predicted the risk of cardiovascular disease and stroke. Only Cornell Product was associated with an increased the risk of heart failure. This was particularly the case in men. The identification of electrocardiographic LVH proved to be important in very elderly hypertensive people

Seawater redox variations during the deposition of the Kimmeridge Clay Formation, United Kingdom (Upper Jurassic): evidence from molybdenum isotopes and trace metal ratios

The Kimmeridge Clay Formation (KCF) and its equivalents worldwide represent one of the most prolonged periods of organic carbon accumulation of the Mesozoic. In this study, we use the molybdenum (Mo) stable isotope system in conjunction with a range of trace metal paleoredox proxies to assess how seawater redox varied both locally and globally during the deposition of the KCF. Facies with lower organic carbon contents (TOC 1–7 wt %) were deposited under mildly reducing (suboxic) conditions, while organic-rich facies (TOC >7 wt %) accumulated under more strongly reducing (anoxic or euxinic) local conditions. Trace metal abundances are closely linked to TOC content, suggesting that the intensity of reducing conditions varied repeatedly during the deposition of the KCF and may have been related to orbitally controlled climate changes. Long-term variations in ?98/95Mo are associated with the formation of organic-rich intervals and are related to third-order fluctuations in relative sea level. Differences in the mean ?98/95Mo composition of the organic-rich intervals suggest that the global distribution of reducing conditions was more extensive during the deposition of the Pectinatites wheatleyensis and lower Pectinatites hudlestoni zones than during the deposition of the upper Pectinatites hudlestoni and Pectinatites pectinatus zones. The global extent of reducing conditions during the Kimmerigidan was greater than today but was less widespread than during the Toarcian (Early Jurassic) oceanic anoxic event. This study also demonstrates that the Mo isotope system in Jurassic seawater responded to changes in redox conditions in a manner consistent with its behavior in present-day sedimentary environment