On thermodynamic and quantum fluctuations of cosmological constant

We discuss from the condensed-matter point of view the recent idea that the Poisson fluctuations of cosmological constant about zero could be a source of the observed dark energy. We argue that the thermodynamic fluctuations of Lambda are much bigger. Since the amplitude of fluctuations is proportional to V^{-1/2}, where V is the volume of the Universe, the present constraint on the cosmological constant provides the lower limit for V, which is much bigger than the volume within the cosmological horizon.Comment: 4 pages, version submitted to JETP Letter

SDSS J142625.71+575218.3: A Prototype for A New Class of Variable White Dwarf

We present the results of a search for pulsations in six of the recently discovered carbon-atmosphere white dwarf ("hot DQ") stars. On the basis of our theoretical calculations, the star SDSS J142625.71 + 575218.3 is the only object expected to pulsate. We observe this star to be variable, with significant power at 417.7 s and 208.8 s ( first harmonic), making it a strong candidate as the first member of a new class of pulsating white dwarf stars, the DQVs. Its folded pulse shape, however, is quite different from that of other white dwarf variables and shows similarities with that of the cataclysmic variable AM CVn, raising the possibility that this star may be a carbon-transferring analog of AM CVn stars. In either case, these observations represent the discovery of a new and exciting class of object.NSF AST-0507639, AST-0602288, AST-0607480, AST-0307321Astronom

Challenging empowerment: AIDS-affected southern African children and the need for a multi-level relational approach

Critics of empowerment have highlighted the concept's mutability, focus on individual transformation, one-dimensionality and challenges of operationalisation. Relating these critiques to children's empowerment raises new challenges. Drawing on scholarship on children's subjecthood and exercise of power, alongside empirical research with children affected by AIDS, I argue that empowerment envisaged as individual self-transformation and increased capacity to act independently offers little basis for progressive change. Rather it is essential to adopt a relational approach that recognises the need to transform power relationships at multiple levels. This analysis has implications for our wider understanding of empowerment in the 21st century. © The Author(s) 2013.This research was funded by DFID

Factors Affecting Retention of Undergraduate Students in Fisheries and Wildlife Programs

Undergraduate enrollment in agriculture and natural resources‐related programs has steadily declined for the past decade or more. College administrators and faculty struggle to separate the real causes of this decline from the superficial and often mythical factors. How programs should address this decline is of similar concern. Rather than speculate on why students do not pursue a degree in a natural resources field, specifically fisheries and wildlife (FW), we decided to investigate the question of FW student retention from the perspective of the students themselves. Specifically, we wanted to know: (a) Why do students say they chose to leave the FW program at MSU? (b) Why did students who persisted in program say they chose to stay? and (c) What reasons did transfer students give for choosing FW as a major? We conducted a series of face‐to‐face interviews with these three groups of students, and asked them a series of 10‐14 questions related to their experiences in the Department of Fisheries and Wildlife at Michigan State University in an effort to better understand student reasons for leaving, persisting, and immigrating into the program. Although our project is just beginning, preliminary results offer some interesting insights into the departure puzzle. Specific, but limited, findings from interviewees include: (a) the importance of job prospects and earnings potential, (b) a general reluctance to pursue postgraduate education, (c) a degree of disillusionment at the relative lack of outdoor experiences offered by the program in classroom and extracurricular activities, and (d) a desire for more active participation and field experiences in the undergraduate program. Several students in this study told us that they selected FW out of a desire to spend more time in the field, and were disappointed this was frequently not the case. Some students expressed a general feeling of deception at the realities of the departmental curriculum, although these were poorly defined and may be the product of other issues such as unrealistic program expectations. This ongoing study has the potential to inform natural resource programs on techniques to attract, retain, and educate undergraduate students

Hazard Detection Software for Lunar Landing

The Autonomous Landing and Hazard Avoidance Technology (ALHAT) Project is developing a system for safe and precise manned lunar landing that involves novel sensors, but also specific algorithms. ALHAT has selected imaging LIDAR (light detection and ranging) as the sensing modality for onboard hazard detection because imaging LIDARs can rapidly generate direct measurements of the lunar surface elevation from high altitude. Then, starting with the LIDAR-based Hazard Detection and Avoidance (HDA) algorithm developed for Mars Landing, JPL has developed a mature set of HDA software for the manned lunar landing problem. Landing hazards exist everywhere on the Moon, and many of the more desirable landing sites are near the most hazardous terrain, so HDA is needed to autonomously and safely land payloads over much of the lunar surface. The HDA requirements used in the ALHAT project are to detect hazards that are 0.3 m tall or higher and slopes that are 5 or greater. Steep slopes, rocks, cliffs, and gullies are all hazards for landing and, by computing the local slope and roughness in an elevation map, all of these hazards can be detected. The algorithm in this innovation is used to measure slope and roughness hazards. In addition to detecting these hazards, the HDA capability also is able to find a safe landing site free of these hazards for a lunar lander with diameter .15 m over most of the lunar surface. This software includes an implementation of the HDA algorithm, software for generating simulated lunar terrain maps for testing, hazard detection performance analysis tools, and associated documentation. The HDA software has been deployed to Langley Research Center and integrated into the POST II Monte Carlo simulation environment. The high-fidelity Monte Carlo simulations determine the required ground spacing between LIDAR samples (ground sample distances) and the noise on the LIDAR range measurement. This simulation has also been used to determine the effect of viewing on hazard detection performance. The software has also been deployed to Johnson Space Center and integrated into the ALHAT real-time Hardware-in-the-Loop testbed