The Buoyant Behavior of Viral and Bacterial DNA in Alkaline CsCl

In equilibrium density gradient centrifugation, the banding polymer species is electrically neutral. The banding species for a negative polyelectrolyte with a polyanion P_(n)^(-z)n (where n is the degree of polymerization, and z the titration charge per monomer unit) in a CsCl salt gradient is CS_(zn)P_n. If the ion P_(n)^(-z)n is itself a weak acid, it may be titrated to the state P_(n)^(-(Zn+y)) by CsOH; the banding species is then Cs_(zn+y)P_n. Because of the large mass and high effective "density" of a Cs^+ ion, it is to be expected that the buoyant density in a CsCl gradient of a polymer acid will be increased by such a partial alkaline titration with CsOH. This expectation has been confirmed for polyglutamic acid (where z = 0 at low pH). The guanine and thymine monomer units of DNA are weak acids. The present communication is concerned with the increase in buoyant density of DNA in alkaline CsCl solutions. It is well known that the guanine and thymine protons are more readily titrated in denatured DNA than in native DNA. We find that the buoyant density of denatured DNA and of single strand ϕX-174 DNA gradually increases as the pH of the solution is increased beyond pH 9.8. The density of native DNA is not affected until a critical pH > 11 is reached, where the DNA abruptly denatures and increases in density. Similar increases in buoyant density have been observed independently by Baldwin and Shooter in their studies of 5BU[overbar]-substituted DNA's in alkaline solutions

Path integral Monte Carlo simulations of silicates

We investigate the thermal expansion of crystalline SiO$_2$ in the $\beta$-- cristobalite and the $\beta$-quartz structure with path integral Monte Carlo (PIMC) techniques. This simulation method allows to treat low-temperature quantum effects properly. At temperatures below the Debye temperature, thermal properties obtained with PIMC agree better with experimental results than those obtained with classical Monte Carlo methods.Comment: 27 pages, 10 figures, Phys. Rev. B (in press

AEGIS methodology demonstration: case example in basalt

The AEGIS technology has been successfully demonstrated. For the same data, similar unpublished results have been obtained by RHO and INTERA Environmental Consultants, Inc. for contaminant transport. In addition to establishing the utility of computer codes and assessment methodology, the AEGIS technology demonstration in basalt has also produced some practical guidance for future field data gathering programs. The results of this basalt demonstration indicate that the geohydrologic systems separating the nuclear waste from the natural biosphere discharge site mitigate the consequences of the postulated fault intersection event. This analysis suggests that the basalt system satisfies the 1000- and 10,000-yr proposed standards for release to the accessible environment (limited release of /sup 129/I and /sup 14/C). The reader should be cautioned, however, that the results are valid only for one particular set of parameters and one postulated release scenario. A complete sensitivity analysis must be performed to evaluate the range of effects that might be observed under different release conditions and for the different range in parameters

Evidence for Sodium-Coupled Acid-Base Transport Across the Basolateral Membrane of the Reabsorptive Duct of the Human Eccrine Sweat Gland

Intracellular pH was measured in isolated nonperfused ducts of human eccrine sweat glands in vitro to investigate basolateral acid-base transport mechanisms. Bath sodium removal led to a bicarbonate-independent, 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid insensitive acidification. The recovery of this acidification was ethylisopropyl amiloride sensitive, suggestive of basolateral sodium:hydrogen exchange. Whereas bath chloride removal led to a small acidification this was not 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid sensitive and its causes remain unclear. Elevation of bath potassium to depolarize the basolateral membrane led to a small alkalinization but this was not mimicked by addition of barium or chloride removal. As chloride removal and barium addition would be expected to cause larger depolarizations than potassium elevation these observations do not support a major role for electrogenic acid-base transport. In conclusion, although this study does not support a major role for electrogenic acid-base transport, it has demonstrated the basolateral presence of sodium-coupled acid-base transport in the reabsorptive duct of the human eccrine sweat gland, which most likely represents a sodium:hydrogen exchanger involved in regulation of intracellular pH

Salmonella typhi central nervous system infection

This report aims to document Salmonella typhi as a cause of central nervous system infection

Emerging ethical issues regarding digital health data on the world medical association draft declaration on ethical considerations regarding health databases and biobanks

This is the final version of the article. Available from the publisher via the DOI in this record.All authors are affiliated with the Data and IT in Health and Medicine Lab which is coordinated at the Department of Social Science, Health & Medicine, King’s College London (datahealthmedicine.wordpress.com). This article builds upon a response submitted by the Lab to the World Medical Association consultation on the draft Declaration on Ethical Considerations regarding Health Databases and Biobanks in June 2015. DOI: 10.13140/RG.2.1.3334.4163. Barbara Prainsack is a member of the Navigating Knowledge Landscapes (NKL) network led by Anna Lydia Svalastog (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4576744/)

Using plant wax markers to estimate the diet composition of grazing Holstein dairy cows

The objective of this study was to test whether diet selection of dairy cows under grazing conditions could be estimated using plant wax markers. Furthermore, differences between 2 cow strains and the effect of concentrate supplementation on plant species selection were investigated. The experiment was a study with a crossover design performed on an organic farm with 12 Swiss Holstein cows and 12 New Zealand Holstein cows. Both experimental periods consisted of a 21-d adaptation and a 7-d measurement period. All cows grazed full time in a rotational stocking system and received either no concentrate or 6 kg/d of a commercial cereal-grain mix. Representative herbage samples of each grazed paddock were taken and botanical composition of subsamples was manually determined. The average proportions of the plant species were 27.8% Lolium perenne, 6.1% Dactylis glomerata, 10.4% Trifolium repens, and 9.0% Taraxacum officinale. Other grass species were merged as "other grass" (38.2%) and other forb species as "other forbs" (8.5%). n-Alkanes, long-chain fatty acids, and long-chain alcohols (LCOH) were analyzed in the samples of plant species, concentrate, and feces from each cow. A linear discriminant analysis indicated that diet components were differentiated best with LCOH (96%) and worst with the combination of all marker groups together (12%). For each marker, the fecal marker recovery (FR) relative to dosed ytterbium was determined in 2 ways. Estimation of diet composition was performed with the software "EatWhat," and results were compared with botanical composition with the Aitchison distance. The results indicate that the diet composition of grazing dairy cows can be estimated using plant wax markers. Additionally, the calculation of FR led to mostly reliable results, yet this approach needs further validation. The most accurate estimation was achieved with the marker combination of n-alkanes and LCOH with a correction for FR. Less accurate estimations were achieved with long-chain fatty acids alone or in combination with n-alkanes. No difference relating to diet selection between the 2 cow strains was recorded, but supplemented cows apparently ingested higher proportions of T. repens than nonsupplemented cows. Awareness that supplementation influences selection behavior of grazing dairy cows may lead to adaptations in botanical composition of the pasture according to the demand of the animals

Semisyngeneic hybrid resistance to murine teratocarcinoma cells

Resistance to two cultured lines of murine embryonal carcinoma was studied in F 1 hybrids constructed between the tumor-syngeneic mouse strain 129/J and several allogeneic strains. Three of four such hybrid strains were significantly more resistant to the multipotent embryonal carcinoma line PCC3 than the tumor-syngeneic 129/J parent strain. All hybrid strains tested showed significantly higher resistance to the nullipotent embryonal carcinoma line F9 than the syngeneic strain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46734/1/251_2005_Article_BF01561588.pd

On the Absorption of X-rays in the Interstellar Medium

We present an improved model for the absorption of X-rays in the ISM intended for use with data from future X-ray missions with larger effective areas and increased energy resolution such as Chandra and XMM, in the energy range above 100eV. Compared to previous work, our formalism includes recent updates to the photoionization cross section and revised abundances of the interstellar medium, as well as a treatment of interstellar grains and the H2molecule. We review the theoretical and observational motivations behind these updates and provide a subroutine for the X-ray spectral analysis program XSPEC that incorporates our model.Comment: ApJ, in press, for associated software see http://astro.uni-tuebingen.de/nh