Ion exchange determines iodine-131 concentration in aqueous samples

Inorganic radioiodide in aqueous media is analyzed by separating the radioactive iodine-131 as the iodide ion on a silver chloride column. The activity in the final precipitate may be determined by beta or gamma counting

Direct determination of lead-210 by liquid-scintillation counting

Soft betas, the internal conversion electrons, and unconverted gamma rays from lead-210 are efficiently detected in a liquid scintillation counting system with efficiency of 97 percent. The counter is interfaced with a multichannel pulse height analyzer. The spectra obtained is stored on paper tape and plotted on an x-y plotter

Bounded Model Checking of State-Space Digital Systems: The Impact of Finite Word-Length Effects on the Implementation of Fixed-Point Digital Controllers Based on State-Space Modeling

The extensive use of digital controllers demands a growing effort to prevent design errors that appear due to finite-word length (FWL) effects. However, there is still a gap, regarding verification tools and methodologies to check implementation aspects of control systems. Thus, the present paper describes an approach, which employs bounded model checking (BMC) techniques, to verify fixed-point digital controllers represented by state-space equations. The experimental results demonstrate the sensitivity of such systems to FWL effects and the effectiveness of the proposed approach to detect them. To the best of my knowledge, this is the first contribution tackling formal verification through BMC of fixed-point state-space digital controllers.Comment: International Symposium on the Foundations of Software Engineering 201

Evaluating RNA Structural Flexibility: Viruses Lead the Way.

Our understanding of RNA structure has lagged behind that of proteins and most other biological polymers, largely because of its ability to adopt multiple, and often very different, functional conformations within a single molecule. Flexibility and multifunctionality appear to be its hallmarks. Conventional biochemical and biophysical techniques all have limitations in solving RNA structure and to address this in recent years we have seen the emergence of a wide diversity of techniques applied to RNA structural analysis and an accompanying appreciation of its ubiquity and versatility. Viral RNA is a particularly productive area to study in that this economy of function within a single molecule admirably suits the minimalist lifestyle of viruses. Here, we review the major techniques that are being used to elucidate RNA conformational flexibility and exemplify how the structure and function are, as in all biology, tightly linked

Rhodobacter capsulatus porphobilinogen synthase, a high activity metal ion independent hexamer

BACKGROUND: The enzyme porphobilinogen synthase (PBGS), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. This paper reports new information on the metal ion independence and quaternary structure of PBGS from the photosynthetic bacterium Rhodobacter capsulatus. RESULTS: The gene for R. capsulatus PBGS was amplified from genomic DNA and sequencing revealed errors in the sequence database. R. capsulatus PBGS was heterologously expressed in E. coli and purified to homogeneity. Analysis of an unusual phylogenetic variation in metal ion usage by PBGS enzymes predicts that R. capsulatus PBGS does not utilize metal ions such as Zn(2+), or Mg(2+), which have been shown to act in other PBGS at either catalytic or allosteric sites. Studies with these ions and chelators confirm the predictions. A broad pH optimum was determined to be independent of monovalent cations, approximately 8.5, and the K(m )value shows an acidic pK(a )of ~6. Because the metal ions of other PBGS affect the quaternary structure, gel permeation chromatography and analytical ultracentrifugation experiments were performed to examine the quaternary structure of metal ion independent R. capsulatus PBGS. The enzyme was found to be predominantly hexameric, in contrast with most other PBGS, which are octameric. A protein concentration dependence to the specific activity suggests that the hexameric R. capsulatus PBGS is very active and can dissociate to smaller, less active, species. A homology model of hexameric R. capsulatus PBGS is presented and discussed. CONCLUSION: The evidence presented in this paper supports the unusual position of the R. capsulatus PBGS as not requiring any metal ions for function. Unlike other wild-type PBGS, the R. capsulatus protein is a hexamer with an unusually high specific activity when compared to other octameric PBGS proteins

BLM and RMI1 alleviate RPA inhibition of topoIIIα decatenase activity

RPA is a single-stranded DNA binding protein that physically associates with the BLM complex. RPA stimulates BLM helicase activity as well as the double Holliday junction dissolution activity of the BLM-topoisomerase IIIα complex. We investigated the effect of RPA on the ssDNA decatenase activity of topoisomerase IIIα. We found that RPA and other ssDNA binding proteins inhibit decatenation by topoisomerase IIIα. Complex formation between BLM, TopoIIIα, and RMI1 ablates inhibition of decatenation by ssDNA binding proteins. Together, these data indicate that inhibition by RPA does not involve species-specific interactions between RPA and BLM-TopoIIIα-RMI1, which contrasts with RPA modulation of double Holliday junction dissolution. We propose that topoisomerase IIIα and RPA compete to bind to single-stranded regions of catenanes. Interactions with BLM and RMI1 enhance toposiomerase IIIα activity, promoting decatenation in the presence of RPA

Results with the Talent thoracic stent graft in the VALOR trial

OBJECTIVE: We report the 5-year outcomes of thoracic endovascular aneurysm repair (TEVAR) using the Medtronic Vascular Talent Thoracic Stent Graft System (Medtronic Vascular, Santa Rosa, Calif) in patients considered low or moderate risk for open surgical repair. METHODS: The Evaluation of the Medtronic Vascular Talent Thoracic Stent Graft System for the Treatment of Thoracic Aortic Aneurysms (VALOR) trial was a prospective, nonrandomized, multicenter, pivotal study conducted at 38 U.S. sites. Between December 2003 and June 2005, VALOR enrolled 195 patients who were low or moderate risk (0, 1, and 2) per the modified Society for Vascular Surgery and American Association for Vascular Surgery criteria. The patients had fusiform thoracic aortic aneurysms (TAAs) and/or focal saccular TAAs/penetrating atherosclerotic ulcers. Standard follow-up interval examinations were conducted at 1 month, 6 months, 1 year, and annually thereafter. RESULTS: Over the 5-year follow-up, 76 deaths occurred (43.9%). Freedom from all-cause mortality was 83.9% at 1 year and 58.5% at 5 years. Most deaths were due to cardiac, pulmonary or cancer-related causes. Freedom from aneurysm-related mortality (ARM) was 96.9% at 1 year and 96.1% at 5 years. There was only 1 case of ARM after the first year of follow-up. Over the 5-year follow-up period, four patients were converted to open surgery and four patients experienced aneurysm rupture. The 5-year freedom from aneurysm rupture was 97.1% and the 5-year freedom from conversion to surgery was 97.1%. The incidence of stent graft migration (>10 mm) was ≤ 1.8% in each year of follow-up. The rate of type I endoleak was 4.6% at 1 month, 6.3% from 1 month to 1 year, and 3.8% during year 5. The rate of type III endoleak was 1.3% at 1 month, 1.9% from 1 month to 1 year, and 1.9% during year 5. Through 5 years, 28 patients (14.4%) underwent 31 additional endovascular procedures on the original target lesion. The 5-year freedom from secondary endovascular procedures was 81.5%. CONCLUSIONS: Through 5-year follow-up in patients who were candidates for open surgical repair, TEVAR using the Talent Thoracic Stent Graft System has demonstrated sustained protection from ARM, aneurysm rupture, and conversion to surgery, and durable stent graft performance. Close patient follow-up remains essential after TEVAR

Patent Politics: Intellectual Property, the Railroad Industry, and the Problem of Monopoly

As winter descended on Washington in December 1878, the Forty-fifth Congress gathered for what promised to be a hectic third and final session. At this critical juncture in American politics, the Senate found itself embroiled in a long and complex discussion of the virtues and deficiencies of the patent system. Patent policy resonated with powerfully felt ideologies and tapped into strongly felt beliefs. Patents were exclusive privileges that the federal government granted to certain individuals for a limited period of time, and, like all monopoly grants, their regulation raised some of the most fundamental questions of the age. The monopoly issue confronted every branch of nineteenth-century American government as well as every jurisdiction: federal, state, and local. In essence, the issue boiled down to two interrelated questions: Did the government have the authority to regulate the monopolies it had created? And, if so, how? The ramifications of the patent issue were practical as well as ideological. At its core, it posed a special challenge for two groups of economic actors, namely, farmers and railroads, who were often at odds not only with Congress but also with each other

The conserved C-terminus of the PcrA/UvrD helicase interacts directly with RNA polymerase

Copyright: © 2013 Gwynn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a Wellcome Trust project grant to MD (Reference: 077368), an ERC starting grant to MD (Acronym: SM-DNA-REPAIR) and a BBSRC project grant to PM, NS and MD (Reference: BB/I003142/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD