Statistical mechanics of collisionless orbits. I. Origin of central cusps in dark-matter halos

We present an equilibrium statistical mechanical theory of collisionless self-gravitational systems with isotropic velocity distributions. Compared to existing standard theories, we introduce two changes: (1) the number of possible microstates is computed in energy (orbit) space rather than phase space and (2) low occupation numbers are treated more appropriately than using Stirling's approximation. Combined, the two modifications predict that the relaxed parts of collisionless self-gravitating systems, such as dark-matter halos, have a differential energy distribution N(E) ~ [exp(phi_0 - E) - 1], dubbed "DARKexp". Such systems have central power-law density cusps rho(r) ~ r^-1, which suggests a statistical mechanical origin of cusps in simulated dark-matter halos.Comment: 6 pages, 2 figure

Star Formation and AGN in the Core of the Shapley Supercluster: A VLA Survey of A3556, A3558, SC1327-312, SC1329-313, and A3562

The core of the Shapley supercluster (A3556, A3558, SC1327-312, SC1329-313, and A3562) is an ideal region in which to study the effects of cluster mergers on the activity of individual galaxies. This paper presents the most comprehensive radio continuum investigation of the region, relying on a 63-pointing mosaic obtained with the Very Large Array yielding an areal coverage of nearly 7 square degrees. The mosaic provides a typical sensitivity of about 80 uJy at a resolution of 16", enabling detection of galaxies with star formation rates as low as 1 solar mass per year. The radio data are complemented by optical imaging in B and R, producing a catalog of 210 radio-detected galaxies with m_R <= 17.36 (M_R <= -19). At least 104 of these radio-detected galaxies are members of the supercluster on the basis of public velocity measurements. Across the entire core of the supercluster, there appears to be a significant deficit of radio galaxies at intermediate optical magnitudes (M_R between -21 and -22). This deficit is offset somewhat by an increase in the frequency with which brighter galaxies (M_R less than -22) host radio sources. More dramatic is the highly significant increase in the probability for fainter galaxies (M_R between -20 and -21) in the vicinity of A3562 and SC1329-313 to be associated with radio emission. The radio and optical data for these sources strongly suggest that these active galaxies are powered by star formation. In conjunction with recent X-ray analysis, this is interpreted as young starbursts related to the recent merger of SC1329-313 with A3562 and the rest of the supercluster.Comment: Accepted by AJ; 50 pages, including 16 figures (for full resolution PDF, see http://mywebpages.comcast.net/nealamiller2/Shapley_pp.pdf

OAO-3 end of mission tests report

Twelve engineering type tests were performed on several subsystems and experiment(s) of the OAO 3 spacecraft near its end of mission. The systems tested include: Princeton experiment package (PEP), fine error system guidance, inertial reference unit, star trackers, heat pipes, thermal control coatings, command and data handling, solar array; batteries, and onboard processor/power boost regulator. Generally, the systems performed well for the 8 1/2 years life of OAO 3, although some degradation was noted in the sensitivity of PEP and in the absorptivity of the skin coatings. Battery life was prolonged during the life of the mission in large part by carefully monitoring the charge-discharge cycle with careful attention not to overcharge

Chance long-distance or human-mediated dispersal? How Acacia s.l. farnesiana attained its pan-tropical distribution

Acacia s.l. farnesiana, which originates from Mesoamerica, is the most widely distributed Acacia s.l. species across the tropics. It is assumed that the plant was transferred across the Atlantic to southern Europe by Spanish explorers, and then spread across the Old World tropics through a combination of chance long-distance and human-mediated dispersal. Our study uses genetic analysis and information from historical sources to test the relative roles of chance and human-mediated dispersal in its distribution. The results confirm the Mesoamerican origins of the plant and show three patterns of human- mediated dispersal. Samples from Spain showed greater genetic diversity than those from other Old World tropics, suggesting more instances of transatlantic introductions from the Americas to that country than to other parts of Africa and Asia. Individuals from the Philippines matched a population from South Central Mexico and were likely to have been direct, trans-Pacific introductions. Australian samples were genetically unique, indicating that the arrival of the species in the continent was independent of these European colonial activities. This suggests the possibility of pre-European human- mediated dispersal across the Pacific Ocean. These significant findings raise new questions for biogeographic studies that assume chance or transoceanic dispersal 2 for disjunct plant distributions

The Impact of the Introduction of Total Mesorectal Excision on Local Recurrence Rate and Survival in Rectal Cancer: Long-Term Results

Purpose: To investigate the influence of the introduction of total mesorectal excision (TME) on local recurrence rate and survival in patients with rectal cancer. Methods: A total of 171 consecutive patients underwent anterior or abdominoperineal resection for primary rectal cancer. When the TME technique was introduced, the clinical setting, including the surgeons, remained the same. Group 1 (1993-95, n=53) underwent conventional surgery and group 2 (1995-2001, n=118) underwent TME. All patients were followed for 7years or until death. Results: Between the two groups, no statistically significant differences were present with regards to patient-, treatment-, or tumor-related characteristics apart from the time point of radiotherapy. The total local recurrence rates were 11 of 53 (20.8%) in group 1 and 7 of 118 (5.9%) in group 2, and the rates of isolated local recurrences were 6 of 53 (11.3%) in group 1 and 2 of 118 (1.7%) in group 2. Both differences were highly statistically significant. The disease-free survival in groups 1 and 2 was 60.4 and 65.3% at 5years, and 58.5 and 65.3% at 7years, respectively. Excluding patients with synchronous or metachronous distant metastasis from the analysis, both the disease-free survival and the cancer-specific survival were statistically significantly better in group 2 than in group 1. No statistically significant difference between the two groups was detected regarding the overall survival. Conclusions: The introduction of TME led to an impressive reduction of the local recurrence rate. Survival is mainly determined by the occurrence of distant metastasis, but TME seems to improve survival in patients without systemic diseas

Structure of the master regulator Rns reveals an inhibitor of enterotoxigenic Escherichia coli virulence regulons

Enteric infections caused by the gram-negative bacteria enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, Shigella flexneri, and Salmonella enterica are among the most common and affect billions of people each year. These bacteria control expression of virulence factors using a network of transcriptional regulators, some of which are modulated by small molecules as has been shown for ToxT, an AraC family member from V. cholerae. In ETEC the expression of many types of adhesive pili is dependent upon the AraC family member Rns. We present here the 3 Å crystal structure of Rns and show it closely resembles ToxT. Rns crystallized as a dimer via an interface similar to that observed in other dimeric AraC’s. Furthermore, the structure of Rns revealed the presence of a ligand, decanoic acid, that inhibits its activity in a manner similar to the fatty acid mediated inhibition observed for ToxT and the S. enterica homologue HilD. Together, these results support our hypothesis that fatty acids regulate virulence controlling AraC family members in a common manner across a number of enteric pathogens. Furthermore, for the first time this work identifies a small molecule capable of inhibiting the ETEC Rns regulon, providing a basis for development of therapeutics against this deadly human pathogen

Towards a one health food safety strategy for palestine: a mixed-method study

Introduction: Foodborne diseases, together with increasing antimicrobial resistance (AMR), pose a threat to public health in an era of huge challenges with climate change and the risks of zoonotic epidemics. A One Health approach to foster food safety is a key for improvement, particularly in complex socio-ecological systems such as in Palestine, to examine human-animal-environment interfaces and promote intersectoral action. Objectives: This study aimed to assess food safety from farm to public health toward an operational One Health strategy for Palestine. This study evaluates the food production (broiler production) and monitoring system to better understanding the zoonotic foodborne illnesses transmission and their resistance to antimicrobials. Methods: The transdisciplinary approach included multi-stakeholder discussion groups and field visits to broiler farms, slaughterhouses, and meat stores in the Ramallah and Al-Bireh and Jerusalem districts using a semi-structured observational tool. A survey with 337 poultry producers and workers in slaughterhouses and meat stores was conducted to assess hygiene knowledge, attitudes, and practices during broiler meat production. Results: The stakeholders point out various challenges along the food production chain in Palestine, such as a striking scarcity of public slaughterhouses, insufficient coordination between authorities, a gap between public and private sectors, and inconsistent application of the law. From observations, it appears that, unlike traditional broiler production, the public slaughterhouses and meat markets have effective hygiene, while large-scale farms implement biosecurity measures. Overall, surveyed participants reported that they are aware of zoonotic disease transmission routes and value hygiene standards. Semi-structured observations and survey results are contradictory. Observations indicate poor hygiene practices; however, the vast majority of broiler meat production chain workers claim that hygiene standards are met. Discussion and Conclusions: Our study found that the overuse of antimicrobials, system fragmentation, insufficient infrastructure, a lack of regulations and controls, and poor hygiene practices are among the main obstacles to improving food safety in Palestine. Considering the risk of an important human health burden of food-related illnesses, enhancing food safety in Palestine is required using an integrated One Health approach. It is crucial to develop an integrated quality control system for food production along with promoting on-farm biosecurity and antimicrobial stewardship. Infrastructure, especially slaughterhouses and laboratories, must be built, training and education provided, and consumer awareness raised. As an important added value within a One Health strategy for better food safety in Palestine, research should be reinforced and accompany any future development of the food production monitoring system

Non-stationary Rayleigh-Taylor instability in supernovae ejecta

The Rayleigh-Taylor instability plays an important role in the dynamics of several astronomical objects, in particular, in supernovae (SN) evolution. In this paper we develop an analytical approach to study the stability analysis of spherical expansion of the SN ejecta by using a special transformation in the co-moving coordinate frame. We first study a non-stationary spherical expansion of a gas shell under the pressure of a central source. Then we analyze its stability with respect to a no radial, non spherically symmetric perturbation of the of the shell. We consider the case where the polytropic constant of the SN shell is $\gamma=5/3$ and we examine the evolution of a arbitrary shell perturbation. The dispersion relation is derived. The growth rate of the perturbation is found and its temporal and spatial evolution is discussed. The stability domain depends on the ejecta shell thickness, its acceleration, and the perturbation wavelength.Comment: 16 page

Enhanced inverse bremsstrahlung heating rates in a strong laser field

Test particle studies of electron scattering on ions, in an oscillatory electromagnetic field have shown that standard theoretical assumptions of small angle collisions and phase independent orbits are incorrect for electron trajectories with drift velocities smaller than quiver velocity amplitude. This leads to significant enhancement of the electron energy gain and the inverse bremsstrahlung heating rate in strong laser fields. Nonlinear processes such as Coulomb focusing and correlated collisions of electrons being brought back to the same ion by the oscillatory field are responsible for large angle, head-on scattering processes. The statistical importance of these trajectories has been examined for mono-energetic beam-like, Maxwellian and highly anisotropic electron distribution functions. A new scaling of the inverse bremsstrahlung heating rate with drift velocity and laser intensity is discussed.Comment: 12 pages, 12 figure

Divergent perceptions of the ‘neo-Australian' forests of lowland eastern Madagascar: Invasions, transitions, and livelihoods

Grevillea banksii (Proteaceae), a non-native shrubby tree, has in the past five decades expanded to cover hundreds of thousands of hectares in lowland eastern Madagascar, accompanied by other Australian and pan-tropical species, including Melaleuca quinquenervia, Acacia mangium, and Eucalyptus spp. We investigate contrasting perceptions of this new landscape with view to facilitate future management. Field research was based on 290 surveys, key informant interviews, and ecological inventories at six sites from Farafangana in the south to Fenerive Est in the north. After documenting the ecology and usage of grevillea, we analyse differing ways in which it can be perceived. Perceptions promoted by scientists and administrators include the contrasting ideas of beneficial landscape greening, rampant biological invasion, novel ecosystems, and forest transition. Perceptions held by local actors are highly determined by practical livelihood concerns. These local views are largely positive due to the major role of grevillea firewood and charcoal sales in livelihoods; however, context plays a major role and a number of disadvantages are perceived as well, including difficulty of removal, competition with crop and pasture land, and the respiratory health impacts of involvement in charcoal production. We conclude that policymakers and managers – in this case and in similar cases around the world – need to be more reflexive on the ways in which environmental problems are framed and to put those frames more in conversation with local people’s experiences in order to productively resolve invasive species management dilemmas