Some Dynamical Effects of the Cosmological Constant

Newton's law gets modified in the presence of a cosmological constant by a small repulsive term (antigarvity) that is proportional to the distance. Assuming a value of the cosmological constant consistent with the recent SnIa data ($\Lambda \simeq 10^{-52} m^{-2}$) we investigate the significance of this term on various astrophysical scales. We find that on galactic scales or smaller (less than a few tens of kpc) the dynamical effects of the vacuum energy are negligible by several orders of magnitude. On scales of 1Mpc or larger however we find that vacuum energy can significantly affect the dynamics. For example we show that the velocity data in the Local Group of galaxies correspond to galactic masses increased by 35% in the presence of vacuum energy. The effect is even more important on larger low density systems like clusters of galaxies or superclusters.Comment: 5 two column pages, 2 figure

Gravitational lensing statistics with extragalactic surveys. II. Analysis of the Jodrell Bank-VLA Astrometric Survey

We present constraints on the cosmological constant $\lambda_{0}$ from gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS). Although this is the largest gravitational lens survey which has been analysed, cosmological constraints are only comparable to those from optical surveys. This is due to the fact that the median source redshifts of JVAS are lower, which leads to both relatively fewer lenses in the survey and a weaker dependence on the cosmological parameters. Although more approximations have to be made than is the case for optical surveys, the consistency of the results with those from optical gravitational lens surveys and other cosmological tests indicate that this is not a major source of uncertainty in the results. However, joint constraints from a combination of radio and optical data are much tighter. Thus, a similar analysis of the much larger Cosmic Lens All-Sky Survey should provide even tighter constraints on the cosmological constant, especially when combined with data from optical lens surveys. At 95% confidence, our lower and upper limits on $\lambda_{0}-\Omega_{0}$, using the JVAS lensing statistics information alone, are respectively -2.69 and 0.68. For a flat universe, these correspond to lower and upper limits on \lambda_{0} of respectively -0.85 and 0.84. Using the combination of JVAS lensing statistics and lensing statistics from the literature as discussed in Quast & Helbig (Paper I) the corresponding $\lambda_{0}-\Omega_{0}$ values are -1.78 and 0.27. For a flat universe, these correspond to lower and upper limits on $\lambda_{0}$ of respectively -0.39 and 0.64.Comment: LaTeX, 9 pages, 18 PostScript files in 6 figures. Paper version available on request. Data available from http://gladia.astro.rug.nl:8000/ceres/data_from_papers/papers.htm

Abnormally high content of free glucosamine residues identified in a preparation of commercially available porcine intestinal heparan sulfate

Heparan sulfate (HS) polysaccharides are ubiquitous in animal tissues as components of proteoglycans, and they participate in many important biological processes. HS carbohydrate chains are complex and can contain rare structural components such as N-unsubstituted glucosamine (GlcN). Commercially available HS preparations have been invaluable in many types of research activities. In the course of preparing microarrays to include probes derived from HS oligosaccharides, we found an unusually high content of GlcN residue in a recently purchased batch of porcine intestinal mucosal HS. Composition and sequence analysis by mass spectrometry of the oligosaccharides obtained after heparin lyase III digestion of the polysaccharide indicated two and three GlcN in the tetrasaccharide and hexasaccharide fractions, respectively. (1)H NMR of the intact polysaccharide showed that this unusual batch differed strikingly from other HS preparations obtained from bovine kidney and porcine intestine. The very high content of GlcN (30%) and low content of GlcNAc (4.2%) determined by disaccharide composition analysis indicated that N-deacetylation and/or N-desulfation may have taken place. HS is widely used by the scientific community to investigate HS structures and activities. Great care has to be taken in drawing conclusions from investigations of structural features of HS and specificities of HS interaction with proteins when commercial HS is used without further analysis. Pending the availability of a validated commercial HS reference preparation, our data may be useful to members of the scientific community who have used the present preparation in their studies

Environmental Site Characterization and Risk-Based Evaluation of a Site Contaminated with Tetrachloroethene (PCE) and Trichloroethene (TCE)

A healthcare company purchased property in eastern Iowa for a facility expansion. Before the purchase, a Phase I environmental site assessment (ESA) revealed that the property was the site of a former dry cleaning business. Phase II sampling and testing indicated that tetrachloroethene (PCE) and trichloroethene (TCE) had affected site soil and groundwater. Maximum concentrations of PCE and TCE in groundwater were 538 and 209 µg/L, respectively, and 105 and 1.51 mg/kg in soil. Additional sampling delineated the vertical and horizontal extent of contamination in the soil. The concentrations of the chlorinated solvents in both the soil and groundwater were below levels of regulatory concern. However, the company was concerned that the Iowa statewide standard for PCE in soil (780 mg/kg) might not provide adequate protection for several exposure pathways and wanted to assess the risk to the public from the contamination at the site. The results of a receptor survey were used to develop site-specific target levels (SSTLs) for contamination, using accepted human health exposure factors, models, and chemical-specific toxicity values. The recommended remedial options allowed the company to minimize the human health risks posed by contamination at the site