A dynamical and kinematical model of the Galactic stellar halo and possible implications for galaxy formation scenarios

We re-analyse the kinematics of the system of blue horizontal branch field (BHBF) stars in the Galactic halo (in particular the outer halo), fitting the kinematics with the model of radial and tangential velocity dispersions in the halo as a function of galactocentric distance r proposed by Sommer-Larsen, Flynn & Christensen (1994), using a much larger sample (almost 700) of BHBF stars. The basic result is that the character of the stellar halo velocity ellipsoid changes markedly from radial anisotropy at the sun to tangential anisotropy in the outer parts of the Galactic halo (r greater than approx 20 kpc). Specifically, the radial component of the stellar halo's velocity ellipsoid decreases fairly rapidly beyond the solar circle, from approx 140 +/- 10 km/s at the sun, to an asymptotic value of 89 +/- 19 km/s at large r. The rapid decrease in the radial velocity dispersion is matched by an increase in the tangential velocity dispersion, with increasing r. Our results may indicate that the Galaxy formed hierarchically (partly or fully) through merging of smaller subsystems - the 'bottom-up' galaxy formation scenario, which for quite a while has been favoured by most theorists and recently also has been given some observational credibility by HST observations of a potential group of small galaxies, at high redshift, possibly in the process of merging to a larger galaxy (Pascarelle et al 1996).Comment: Latex, 16 pages. 2 postscript figures. Submitted to the Astrophysical Journal. also available at http://astro.utu.fi/~cflynn/outerhalo.htm

Investigation on the influence of nematophagous fungi as feed additive on nematode infection risk of sheep and goats on pasture

Gastrointestinal nematodes in small ruminants cause high economic losses. Thus on most farms anthelmintic treatment is required. In response to increasing problems with anthelmintic resistance, biological control, for example the use of nematophagous fungi, has received significant attention. The aim of this study was to investigate the effect of Duddingtonia flagrans orally applied to small ruminants on natural infection with gastrointestinal nematodes in a field study in Northern Germany. 20 goats and 20 sheep were fed daily for 3 months with 5x105 spores of D. flagrans per kg bodyweight. Differences in body weight, faecal egg count and larval development in faeces and on pasture in comparison with same-sized control groups were analysed. After 3 months the control goats showed significantly higher mean faecal egg count than the fungus-fed group. No significant difference was found between the two sheep groups. The maximum in larval reduction in faeces was 81.3 % in the sheep groups and 67.9 % in the goat groups (not significant). At the end of the study the body weight gain in the fungus-treated groups was 1.7 kg higher in goats and 0.7 kg higher in sheep than in the control groups (not significant). Regarding the first-year-grazing goats only, the bodyweights revealed significant differences (p<0.05). No statistically significant differences were observed in pasture larval counts. In the study presented here, no clear effect of fungus could be observed. A modified feeding regimen, perhaps with permanent release boluses or feed blocks, may improve the efficacy. Furthermore, it seems that climatic conditions during the study period could have influenced the results and displayed how sensitive the fungus application may be on such parameters

Dihydropteroate synthase gene mutations in Pneumocystis and sulfa resistance

Pneumocystis pneumonia (PCP) remains a major cause of illness and death in HIV-infected persons. Sulfa drugs, trimethoprim-sulfamethoxazole (TMP-SMX) and dapsone are mainstays of PCP treatment and prophylaxis. While prophylaxis has reduced the incidence of PCP, its use has raised concerns about development of resistant organisms. The inability to culture human Pneumocystis, Pneumocystis jirovecii, in a standardized culture system prevents routine susceptibility testing and detection of drug resistance. In other microorganisms, sulfa drug resistance has resulted from specific point mutations in the dihydropteroate synthase (DHPS) gene. Similar mutations have been observed in P. jirovecii. Studies have consistently demonstrated a significant association between the use of sulfa drugs for PCP prophylaxis and DHPS gene mutations. Whether these mutations confer resistance to TMP-SMX or dapsone plus trimethoprim for PCP treatment remains unclear. We review studies of DHPS mutations in P. jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone

Verification and Optimization of a PLC Control Schedule

We report on the use of the SPIN model checker for both the verification of a process control program and the derivation of optimal control schedules. This work was carried out as part of a case study for the EC VHS project (Verification of Hybrid Systems), in which the program for a Programmable Logic Controller (PLC) of an experimental chemical plant had to be designed and verified. The intention of our approach was to see how much could be achieved here using the standard model checking environment of SPIN/Promela. As the symbolic calculations of real-time model checkers can be quite expensive it is interesting to try and exploit the efficiency of established non-real-time model checkers like SPIN in those cases where promising work-arounds seem to exist. In our case we handled the relevant real-time properties of the PLC controller using a time-abstraction technique; for the scheduling we implemented in Promela a so-called variable time advance procedure. For this case study these techniques proved sufficient to verify the design of the controller and derive (time-)optimal schedules with reasonable time and space requirements

Surveying the Inner Halo of the Galaxy with 2MASS-Selected Horizontal Branch Candidates

We use 2MASS photometry to select blue horizontal branch (BHB) candidates covering the sky |b|>15 deg. A 12.5<J<15.5 sample of BHB stars traces the thick disk and inner halo to d<9 kpc, with a density comparable to that of M giant stars. We base our sample selection strategy on the Century Survey Galactic Halo Project, a survey that provides a complete, spectroscopically-identified sample of blue stars to a similar depth as the 2MASS catalog. We show that a -0.20<(J-H)_0<0.10, -0.10<(H-K)_0<0.10 color-selected sample of stars is 65% complete for BHB stars, and is composed of 47% BHB stars. We apply this photometric selection to the full 2MASS catalog, and see no spatial overdensities of BHB candidates at high Galactic latitude |b|>50 deg. We insert simulated star streams into the data and conclude that the high Galactic latitude BHB candidates are consistent with having no ~5 deg wide star stream with density greater than 0.33 objects deg^-2 at the 95% confidence level. The absence of structure suggests there have been no major accretion events in the inner halo in the last few Gyr. However, at low Galactic latitudes a two-point angular correlation analysis reveals structure on angular scales <1 deg. This structure is apparently associated with stars in the thick disk, and has a physical scale of 10-100 pc. Interestingly, such structures are expected by cosmological simulations that predict the majority of the thick disk may arise from accretion and disruption of satellite mergers.Comment: 11 pages, including figures. Accepted by AJ with minor revision

Runoff Quality Responses to Cattle-Gazing Strategy and Grassed Buffer Zone Length

Grazed pastures represent a source of potential nonpoint pollution. In comparison to other nonpoint sources (e.g., row-cropped lands), relatively little information exists regarding possible magnitudes of pollution from grazed pasture; how that pollution is affected by weather, soil, management and other variables; and how the pollution can be minimized. The objective of this study was to assess how the quality of runoff from simulated grazed pasture is influenced by grazing duration (4-12 weeks), grazing strategy (no grazing, conventional grazing and rotational grazing), and by the use of grassed buffer strips (ranging in length from O to 18.3 m) installed down-slope of simulated pasture. The study was conducted at the University of Kentucky Maine Chance Agricultural Experiment Station north of Lexington. Plots (2.4 m wide by 6.1 to 30.5 m long) were constructed and established in Kentucky 31 tall fescue (Festuca arundinacea Schreb.) to represent pasture. Grazing was simulated by application of beef cattle manure to the plots. Runoff was generated by applying simulated rainfall. Runoff samples were collected and analyzed according to standard methods for nitrogen (N), phosphorus (P), total suspended solids (TSS), and fecal coliform (FC). Runoff concentrations and transport of N and P from the plots used to simulate conventional and rotational grazing were low and, in many cases, not different from those measured for ungrazed plots. Runoff FC concentrations were greater for the simulated grazed plots than for the control plots, but there was no difference in concentrations between the simulated conventional and rotational grazing treatments. The buffer strips were very effective in removing TKN, P04-P, TSS and FC in incoming runoff from manured plots. Concentrations of all these parameters were indistinguishable from background levels after crossing a buffer length of 6.1 m. This finding is attributed largely to very high infiltration in the plots used to assess the buffer strips

Conditional Lower Bounds for Space/Time Tradeoffs

In recent years much effort has been concentrated towards achieving polynomial time lower bounds on algorithms for solving various well-known problems. A useful technique for showing such lower bounds is to prove them conditionally based on well-studied hardness assumptions such as 3SUM, APSP, SETH, etc. This line of research helps to obtain a better understanding of the complexity inside P. A related question asks to prove conditional space lower bounds on data structures that are constructed to solve certain algorithmic tasks after an initial preprocessing stage. This question received little attention in previous research even though it has potential strong impact. In this paper we address this question and show that surprisingly many of the well-studied hard problems that are known to have conditional polynomial time lower bounds are also hard when concerning space. This hardness is shown as a tradeoff between the space consumed by the data structure and the time needed to answer queries. The tradeoff may be either smooth or admit one or more singularity points. We reveal interesting connections between different space hardness conjectures and present matching upper bounds. We also apply these hardness conjectures to both static and dynamic problems and prove their conditional space hardness. We believe that this novel framework of polynomial space conjectures can play an important role in expressing polynomial space lower bounds of many important algorithmic problems. Moreover, it seems that it can also help in achieving a better understanding of the hardness of their corresponding problems in terms of time