Discovery of kHz Fluctuations in Centaurus X-3: Evidence for Photon Bubble Oscillations (PBO) and Turbulence in a High Mass X-ray Binary Pulsar

We report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at ~330 Hz and ~760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3. These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to $f^{-2}$ behavior between a few Hz and ~100 Hz. Above a hundred Hz, the spectrum shows the QPO features, plus a flat continuum extending to ~1200 Hz and then falling out to ~1800 Hz. These results, which required the co-adding three days of observations of Cen X-3, are at least as fast as the fastest known variations in X-ray emission from an accreting compact object (kHz QPO in LMXB sources) and probably faster since extension to ~1800 Hz is indicated by the most likely parameterization of the data. Multi-dimensional radiation hydrodynamics simulations of optically thick plasma flow onto the magnetic poles of an accreting neutron star show that the fluctuations at frequencies above 100 Hz are consistent with photon bubble turbulence and oscillations (PBO) previously predicted to be observable in this source. For a polar cap opening angle of 0.25 radians, we show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kHz continuum. This has resulted in the first model-dependent measurement of the polar cap size of an X-ray pulsar.Comment: received ApJ: April 1, 1999 accepted ApJ: September 1, 199

Reproducibility of Ambulatory Blood Pressure Changes from the Initial Values on Two Different Days

OBJECTIVE: We tested the reproducibility of changes in the ambulatory blood pressure (BP) from the initial values, an indicator of BP reactivity and cardiovascular health outcomes, in young, healthy adults. METHOD: The subjects wore an ambulatory BP monitor attached by the same investigator at the same time of day until the next morning on two different days (day 1 and day 2) separated by a week. We compared the ambulatory BP change from the initial values at hourly intervals over 24 waking and sleeping hours on days 1 and 2 using linear regression and repeated measures analysis of covariance. RESULTS: The subjects comprised 88 men and 57 women (mean age ¡SE 22.4 ¡0.3 years) with normal BP (118.3¡ 0.9/69.7 ¡ 0.6 mmHg). For the total sample, the correlation between the ambulatory BP change on day 1 vs. day 2 over 24, waking, and sleeping hours ranged from 0.37–0.61; among women, the correlation was 0.38–0.71, and among men, it was 0.24–0.52. Among women, the ambulatory systolic/diastolic BP change was greater by 3.1 ¡1.0/2.4 ¡0.8 mmHg over 24 hours and by 3.0 ¡1.1/2.4 ¡0.8 mmHg over waking hours on day 1 than on day 2. The diastolic ambulatory BP change during sleeping hours was greater by 2.2¡0.9 mmHg on day 1 than on day 2, but the systolic ambulatory BP change during sleeping hours on days 1 and 2 did not differ. Among men, the ambulatory BP change on days 1 and 2 did not differ. CONCLUSION: Our primary findings were that the ambulatory BP change from the initial values was moderately reproducible; however, it was more reproducible in men than in women. These results suggest that women, but not men, may experience an alerting reaction to initially wearing the ambulatory BP monito

We(ed) Hold These Truths to be Self Evident: All Things Cannabis Are Inequitable

Current approaches to social equity in the cannabis industry continue to fail to promote racial equity while simultaneously exacerbating gender, environmental, and other inequities. To better understand the structural dynamics underlying this phenomenon, I first present a multi-disciplinary recounting of not only the racial inequities, but also the stigma, business, research, energy, sex and gender, hemp, and international inequities of the War on Drugs. This serves as the foundation for a compilation of the structural and theoretical reasons for how current social equity policies, whether targeting the cannabis industry, community reinvestment, social justice, or access equity, will only continue to fail to address the inequities they target. In short, state licensing processes, managed market dynamics, and natural characteristics of the industry conspire to undercut states’ attempts to address social inequity solely by reserving limited numbers of “social equity licenses.” State community investment programs to address inequities are funded by taxes on the populations they are intended to help, and industry-led initiatives are treated as marketing campaigns. Retroactive pardons and expungement are routinely underfunded, hobbled by technical issues, unused by beneficiaries, and insufficiently comprehensive to provide effective resentencing solutions, all while states maintain arbitrary criminalization limits that continue to exacerbate inequity. Finally, direct cannabis regulations remain only tangentially associated with the employment, child custody, housing, insurance, bankruptcy, environmental, and medical research issues presented by the ongoing criminality of cannabis, and the associated inequities remain unaddressed by cannabis regulatory regimes to the ongoing detriment of those most negatively impacted by the War on Drugs

Political allocation of U.S. agriculture disaster payments in the 1990s

Legislation passed during the 1990s attempted to move U.S. agriculture disaster relief to a more market oriented process. The failure of this legislation has been attributed to the political system behind agricultural disaster relief. This paper explores the impact of political influence on the allocation of U.S. direct agriculture disaster payments. The results reveal that disaster payments are not based solely on need, but are higher in those states represented by public officials key to the allocation of relief. The effectiveness of legislation aimed at promoting more efficient disaster payments systems, such as crop insurance, over direct cash payments is also examined.Agriculture ; Disaster relief

Visualizing classification of natural video sequences using sparse, hierarchical models of cortex.

Recent work on hierarchical models of visual cortex has reported state-of-the-art accuracy on whole-scene labeling using natural still imagery. This raises the question of whether the reported accuracy may be due to the sophisticated, non-biological back-end supervised classifiers typically used (support vector machines) and/or the limited number of images used in these experiments. In particular, is the model classifying features from the object or the background? Previous work (Landecker, Brumby, et al., COSYNE 2010) proposed tracing the spatial support of a classifier’s decision back through a hierarchical cortical model to determine which parts of the image contributed to the classification, compared to the positions of objects in the scene. In this way, we can go beyond standard measures of accuracy to provide tools for visualizing and analyzing high-level object classification. We now describe new work exploring the extension of these ideas to detection of objects in video sequences of natural scenes

Is an obscured AGN at the centre of the disk galaxy IC 2497 responsible for Hanny's Voorwerp?

We present the results of VLBI and MERLIN observations of the massive disk galaxy IC 2497. Optical observations of IC 2497 revealed the existence of a giant emission nebula "Hanny's Voorwerp" in the proximity of the galaxy. Earlier short-track 18 cm observations with e-VLBI at 18 cm, detected a compact radio component (C1) at the centre of IC 2497. The brightness temperature of C1 was measured to be greater than 4E5 K. Deeper, long-track e-VLBI observations presented here, re-confirm the existence of C1 but also reveal the existence of a second compact component (C2) located about 230 milliarcseconds to the North-East of C1. The brightness temperature of C2 is measured to be greater than 1.4E5 K, suggesting that both components may be related to AGN activity (e.g. a radio core and jet hotspot). Lower resolution 18cm MERLIN observations show both components. C1 is shown to be compact with a slight elongation along the direction of Hanny's Voorwerp, and C2 shows a lot of extended emission in an almost perpendicular direction to the direction of the Voorwerp. Our results continue to support the hypothesis that IC 2497 contains an Active Galactic Nucleus (AGN), and that a jet associated with this AGN clears a path that permits ionising radiation from the AGN to directly illuminate the emission nebula.Comment: Presented at The 8th International e-VLBI Workshop: the Science and Technology of Long Baseline Real-Time Interferometry, EXPReS09, June 22-26 2009 Madrid, Spain. 5 pages, 5 article

Dynamic Bounds on Stochastic Chemical Kinetic Systems Using Semidefinite Programming

Applying the method of moments to the chemical master equation (CME) appearing in stochastic chemical kinetics often leads to the so-called closure problem. Recently, several authors showed that this problem can be partially overcome using moment-based semidefinite programs (SDPs). In particular, they showed that moment-based SDPs can be used to calculate rigorous bounds on various descriptions of the stochastic chemical kinetic system's stationary distribution(s) -- for example, mean molecular counts, variances in these counts, and so on. In this paper, we show that these ideas can be extended to the corresponding dynamic problem, calculating time-varying bounds on the same descriptions

Large structures and tethers working group

The Large Structures and Tethers Working Group sought to clarify the meaning of large structures and tethers as they related to space systems. Large was assumed to mean that the characteristic length of the structure was greater than one of such relevant plasma characteristics as ion gyroradius or debey length. Typically, anything greater than or equal to the Shuttle dimensions was considered large. It was agreed that most large space systems that the tether could be better categorized as extended length, area, or volume structures. The key environmental interactions were then identified in terms of these three categories. In the following Working Group summary, these categories and the related interactions are defined in detail. The emphasis is on how increases in each of the three spatial dimensions uniquely determine the interactions with the near-Earth space environment. Interactions with the environments around the other planets and the solar wind were assumed to be similar or capable of being extrapolated from the near-Earth results. It should be remembered in the following that the effects on large systems do not just affect specific technologies but will quite likely impact whole missions. Finally, the possible effects of large systems on the plasma environment, although only briefly discussed, were felt to be of potentially great concern