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We present the results of two 2.3 μm near-infrared (NIR) radial velocity (RV) surveys to detect exoplanets around 36 nearby and young M dwarfs. We use the CSHELL spectrograph (R ~ 46,000) at the NASA InfraRed Telescope Facility (IRTF), combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra. With a spectral grasp of only 5 nm, we are able to reach long-term radial velocity dispersions of ~20–30 m s−1 on our survey targets.
The orbital parameters of extra-solar planets have a significant impact on the probability that the planet will transit the host star. This was recently demonstrated by the transit detection of HD 17156b whose favourable eccentricity and argument of periastron dramatically increased its transit likelihood. We present a study which provides a quantitative analysis of how these two orbital parameters affect the geometric transit probability as a function of period. Further, we apply these results to known radial velocity planets and show that there are unexpectedly high transit probabilities for planets at relatively long periods. For a photometric monitoring campaign which aims to determine if the planet indeed transits, we calculate the significance of a null result and the subsequent constraints that may be applied to orbital parameters.
To achieve maximum planet yield for a given radial velocity survey, the observing strategy must be carefully considered. In particular, the adopted cadence can greatly affect the sensitivity to exoplanetary parameters such as period and eccentricity. Here we describe simulations which aim to maximise detections based upon the target parameter space of the survey.
Plain X-rays, computed tomography (CT) and magnetic resonance imaging (MRI) scans performed for non-ENT reasons often reveal incidental sinus mucosal changes. These changes need to be correlated clinically before diagnosing rhinosinusitis. This study examined the prevalence of such changes in MRI scans in children up to age 16. Scans were scored using an adapted Lund-Mackay classification and were positive when one or more sinuses showed abnormalities. Randomly selected scans in the retrospective arm revealed a prevalence of 20 of 62 (32 3 per cent). In the prospective arm 45 of 60 children were defined as truly asymptomatic, of which 14 scans (31 per cent) were positive. Other studies in adults and children using CT and MRI report a prevalence range of roughly 30 to 45 per cent. This variability may be attributed to differences of study design, definitions of population age, definitions of asymptomatic and definition of abnormal sinus. Other plausible factors to explain regional differences are climate and frequency of upper respiratory tract infections.
Working memory is a system consisting of those long-term memory traces active above threshold, the procedures and skills necessary to achieve and maintain that activation, and limited-capacity, controlled attention. The specific features of our model include:
(2) Domain-specific codes and maintenance (phonological loop and visuospatial sketchpad are two examples but the potential number of such codes is large).
(3) Individual differences in both 1 and 2, but individual differences in capacity for controlled processing are general and possibly the mechanism for general fluid intelligence. Although people can, with practice and expertise, circumvent the abiding limitations of controlled attention in quite specific situations, the limitations reemerge in novel situations and even in the domain of expertise if the situation calls for controlled processing.
(4) Limited-capacity, controlled processing is required for maintaining temporary goals in the face of distraction and interference and for blocking, gating, and/or suppressing distracting events.
(5) The dorsolateral prefrontal cortex (PFC) and associated structures mediate the controlled processing functions of working memory. We also argue that individual differences in controlled processing represent differences in functioning of the PFC.
A number of intellectual influences have served to shape our thinking about working memory (WM) and its evolution as a construct separate from that of short-term memory (STM).
Previous investigators have shown that the Sharpe measure of the performance of a managed portfolio may be flawed when the portfolio manager has market timing ability. Herein we develop the exact conditions under which the Sharpe measure will completely and correctly order market timers according to ability. The derived conditions are necessary, sufficient, and observable. We compare these derived conditions to empirical estimates of actual market conditions and find that, under typical market conditions, the practice of using quarterly portfolio return data will frequently result in a failure of the Sharpe measure to order timers according to ability. We show, however, that such failures can be greatly reduced by more frequent sampling of managed portfolio returns.
Intimate cooperation between American investment bankers and the diplomats of the Department of State occurred in the early 1920s because both groups shared similar goals and interests in Mexico. The resulting exercise in dollar diplomacy achieved some immediate ends but proved very short-sighted and self-defeating in the end.