Discriminating between a Stochastic Gravitational Wave Background and Instrument Noise

The detection of a stochastic background of gravitational waves could significantly impact our understanding of the physical processes that shaped the early Universe. The challenge lies in separating the cosmological signal from other stochastic processes such as instrument noise and astrophysical foregrounds. One approach is to build two or more detectors and cross correlate their output, thereby enhancing the common gravitational wave signal relative to the uncorrelated instrument noise. When only one detector is available, as will likely be the case with the Laser Interferometer Space Antenna (LISA), alternative analysis techniques must be developed. Here we show that models of the noise and signal transfer functions can be used to tease apart the gravitational and instrument noise contributions. We discuss the role of gravitational wave insensitive "null channels" formed from particular combinations of the time delay interferometry, and derive a new combination that maintains this insensitivity for unequal arm length detectors. We show that, in the absence of astrophysical foregrounds, LISA could detect signals with energy densities as low as $\Omega_{\rm gw} = 6 \times 10^{-13}$ with just one month of data. We describe an end-to-end Bayesian analysis pipeline that is able to search for, characterize and assign confidence levels for the detection of a stochastic gravitational wave background, and demonstrate the effectiveness of this approach using simulated data from the third round of Mock LISA Data Challenges.Comment: 10 Pages, 10 Figure

Habitability in Advanced Space Mission Design

Habitability is a fundamental component of any long-duration human habitat. Due to the pressures on the crew and the criticality of their performance, this is particularly true of habitats or vehicles proposed for use in any human space mission of duration over 30 days. This paper, the second of three on this subject, will focus on evaluating all the vehicles currently under consideration for the Mars Design Reference Mission through application of metrics for habitability (proposed in a previous paper, see references Adams/McCurdy 1999)

Boolean Chaos

We observe deterministic chaos in a simple network of electronic logic gates that are not regulated by a clocking signal. The resulting power spectrum is ultra-wide-band, extending from dc to beyond 2 GHz. The observed behavior is reproduced qualitatively using an autonomously updating Boolean model with signal propagation times that depend on the recent history of the gates and filtering of pulses of short duration, whose presence is confirmed experimentally. Electronic Boolean chaos may find application as an ultra-wide-band source of radio wavesComment: 10 pages and 4 figur

Titrations without the Additions: The Efficient Determination of pKa Values Using NMR Imaging Techniques

It can be very informative to acquire NMR spectra of a sample as a function of the solution pH. Examples can be found in the design of host–guest complexes or in the determination of the pKa values of organic molecules. In the conventional procedure, a series of spectra must be recorded and the pH of the sample adjusted manually between successive NMR measurements. As an alternative to this laborious procedure, we demonstrate how controlled pH gradients may be established in 5 mm NMR tubes and analyzed using standard NMR equipment in a “single shot” experiment. Using 1H NMR imaging techniques and a set of NMR pH indicator compounds, we are able to measure the pH of a sample as a function of position along a pH gradient. We are thus able to obtain the necessary set of 1H NMR spectra as a function of pH from a single sample in a single NMR experiment. As proof of concept, we demonstrate how the technique may be employed for the determination of the pKa values of small organic molecules. We are able to measure pKa values from 1 to 11 to within 0.1 units of their literature values. The method is robust to variations in the setting of the pH gradients and can be readily implemented through an automated sample changer

Bilateral redundancy gain and callosal integrity in a man with callosal lipoma: a diffusion-tensor imaging study

We investigated whether abnormalities in the structural organisation of the corpus callosum in the presence of curvilinear lipoma are associated with increased facilitation of response time to bilateral stimuli, an effect known as the redundancy gain. A patient (A.J.) with a curvilinear lipoma of the corpus callosum, his genetically-identical twin, and age-matched control participants made speeded responses to luminant stimuli. Structural organisation of callosal regions was assessed with diffusion-tensor imaging. A.J. was found to have reduced structural integrity in the splenium of the corpus callosum and produced a large redundancy gain suggestive of neural summation

Job-Related Burnout among Juvenile Probation Officers: Implications for Mental Health Stigma and Competency

The high demands and responsibilities of probation work, particularly with juvenile clients, may lead to burnout, which can negatively impact how probation officers work with clients, particularly individuals with behavioral health concerns. Yet, research examining burnout and related outcomes among juvenile probation officers (JPOs) is limited. We surveyed 246 JPOs in a Midwestern state to identify the prevalence, predictors, and potential outcomes of burnout. JPOs reported moderate levels of burnout; about 30% of the sample scored in the high range for emotional exhaustion and cynicism. Contrary to study hypotheses, there were no group-level differences in burnout scores across gender, race/ethnicity, age, or education. In regression models, burnout was predicted by being White (vs. minority), serving in an urban (vs. rural) county, dissatisfaction with department guidelines, job dissatisfaction, viewing job role as more treatment-oriented along the enforcement−treatment continuum, and turnover intention. JPOs with burnout were more likely to endorse mental health stigma and lack of mental health competency to address juvenile clients with behavioral health concerns. Findings suggest burnout prevention and intervention programs should be considered for JPOs to increase job satisfaction, limit job turnover, reduce burnout, and possibly increase effective practices for managing juvenile clients with behavioral health needs