Intra-chain correlation functions and shapes of homopolymers with different architectures in dilute solution

We present results of Monte Carlo study of the monomer-monomer correlation functions, static structure factor and asphericity characteristics of a single homopolymer in the coil and globular states for three distinct architectures of the chain: ring, open and star. To rationalise the results we introduce the dimensionless correlation functions rescaled via the corresponding mean-squared distances between monomers. For flexible chains with some architectures these functions exhibit a large degree of universality by falling onto a single or several distinct master curves. In the repulsive regime, where a stretched exponential times a power law form (de Cloizeaux scaling) can be applied, the corresponding exponents $\delta$ and $\theta$ have been obtained. The exponent $\delta=1/\nu$ is found to be universal for flexible strongly repulsive coils and in agreement with the theoretical prediction from improved higher-order Borel-resummed renormalisation group calculations. The short-distance exponents $\theta_{\upsilon}$ of an open flexible chain are in a good agreement with the theoretical predictions in the strongly repulsive regime also. However, increasing the Kuhn length in relation to the monomer size leads to their fast cross-over towards the Gaussian behaviour. Likewise, a strong sensitivity of various exponents $\theta_{ij}$ on the stiffness of the chain, or on the number of arms in star polymers, is observed. The correlation functions in the globular state are found to have a more complicated oscillating behaviour and their degree of universality has been reviewed. Average shapes of the polymers in terms of the asphericity characteristics, as well as the universal behaviour in the static structure factors, have been also investigated.Comment: RevTeX 12 pages, 10 PS figures. Accepted by J. Chem. Phy

Crush injuries and crush syndrome -a review. Part 2: the local injury

Crush injuries can occur in considerable numbers following natural disasters or acts of war and terrorism. They can also occur sporadically after industrial accidents or following periods of unconsciousness from drug intoxication, anaesthesia, trauma or cerebral events. A common pathophysiological pathway has been elucidated over the last century describing traumatic rhabdomyolysis leading to myoglobinuric acute renal failure and a systemic 'crush syndrome' affecting many organ systems. If left unrecognised or untreated then mortality rates are high. If treatment is commenced early and the systemic effects are minimised then patients are often faced with significant morbidity from the crushed limbs themselves. We have performed a thorough review of the English language literature from 1940-2009 investigating crush injuries and crush syndrome and present a comprehensive, two-part summary. Part 1: The systemic injury, we concentrate on the systemic crush syndrome. We determine the pathophysiology, clinical and prognostic indicators and treatment options such as forced alkaline diuresis, mannitol therapy, dialysis and haemofiltration. We discuss more controversial treatment options such as allopurinol, potassium binders, calcium therapy and other diuretics. We also discuss the specific management issues of the secondary 'renal disaster' that can occur following earthquakes and other mass disasters. Part 2: The local injury, we look in more detail at the pathophysiology of skeletal muscle damage following crush injuries and discuss how to minimise morbidity by salvaging limb function. In particular we discuss the controversies surrounding fasciotomy of crushed limbs and compare surgical management with conservative techniques such as mannitol therapy, hyperbaric oxygen therapy, topical negative pressure therapy and a novel topical treatment called gastric pentadecapeptide BPC 157

Dynamic Critical Behavior of an Extended Reptation Dynamics for Self-Avoiding Walks

We consider lattice self-avoiding walks and discuss the dynamic critical behavior of two dynamics that use local and bilocal moves and generalize the usual reptation dynamics. We determine the integrated and exponential autocorrelation times for several observables, perform a dynamic finite-size scaling study of the autocorrelation functions, and compute the associated dynamic critical exponents $z$. For the variables that describe the size of the walks, in the absence of interactions we find $z \approx 2.2$ in two dimensions and $z\approx 2.1$ in three dimensions. At the $\theta$-point in two dimensions we have $z\approx 2.3$.Comment: laTeX2e, 32 pages, 11 eps figure

Polydisperse star polymer solutions

We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations and the phase behavior of star polymers in a good solvent. The effective interaction potential between two star polymers with different arm numbers is derived using scaling theory. The resulting expression is tested against monomer-resolved molecular dynamics simulations. We find that the theoretical pair potential is in agreement with the simulation data in a much wider polydispersity range than other proposed potentials. We then use this pair potential as an input in a many-body theory to investigate polydispersity effects on the structural correlations and the phase diagram of dense star polymer solutions. In particular we find that a polydispersity of 10%, which is typical in experimental samples, does not significantly alter previous findings for the phase diagram of monodisperse solutions.Comment: 14 pages, 7 figure

Wood ash residue causes a mixture of growth promotion and toxicity in Lemna minor

The use of wood as a sustainable biofuel results in the generation of residual wood ash. The ash contains high amounts of plant macronutrients such as phosphorus, potassium, calcium as well as several micronutrients. To explore the potential use of wood ash as a fertiliser, the growth enhancing properties of Sitka spruce (Picea sitchensis Bong.) wood ash were contrasted with the potential toxic action, using common duckweed (Lemna minor L.) as a model test species. The growth of L. minor exposed to wood bottom and fly ash solids and corresponding leachates was assessed in ultra-oligotrophic and eutrophic media. Ash solids and leachates were also tested as neutralized preparations. Suspended ash solids promoted L. minor growth up to concentrations of 2.5–5 g/L. Leachates promoted growth up to 10 g ash equivalents per litre, but for bottom ash only. Beneficial effects of wood ash were most pronounced on ultra-oligotrophic medium. However, on such nutrient-deficient medium severe inhibition of L. minor biomass and frond growth was observed at relatively low concentrations of fly ash (EC50 = 14 g/L). On standard, eutrophic medium, higher concentrations of fly ash (EC50 = 21 g/L), or neutralized fly ash (EC50 = 37 g/L) were required to impede growth. Bottom ash, or neutralized bottom ash retarded growth at concentrations of 51 g/L and 74 g/L (EC50), respectively, in eutrophic medium. It appears that phytotoxicity is due to the elemental composition of the ash, its alkaline character, and possible interactions between these two properties. Growth promotion was due to the substantial content of plant nutrients. This study underlines the importance of the receiving environment (nutrient status and pH) in determining the balance between toxicity and growth promotion, and shows that the margin between growth promoting and toxicity inducing concentrations can be enlarged through ash neutralization

Molecular Epidemiology of Early and Acute HIV Type 1 Infections in the United States Navy and Marine Corps, 2005–2010

The U.S. military represents a unique population within the human immunodeficiency virus 1 (HIV-1) pandemic. The last comprehensive study of HIV-1 in members of the U.S. Navy and Marine Corps (Sea Services) was completed in 2000, before large-scale combat operations were taking place. Here, we present molecular characterization of HIV-1 from 40 Sea Services personnel who were identified during their seroconversion window and initially classified as HIV-1 negative during screening. Protease/reverse transcriptase (pro/rt) and envelope (env) sequences were obtained from each member of the cohort. Phylogenetic analyses were carried out on these regions to determine relatedness within the cohort and calculate the most recent common ancestor for the related sequences. We identified 39 individuals infected with subtype B and one infected with CRF01_AE. Comparison of the pairwise genetic distance of Sea Service sequences and reference sequences in the env and pro/rt regions showed that five samples were part of molecular clusters, a group of two and a group of three, confirmed by single genome amplification. Real-time molecular monitoring of new HIV-1 acquisitions in the Sea Services may have a role in facilitating public health interventions at sites where related HIV-1 infections are identified

Differential energy measurement between He- and Li-like uranium intra-shell transitions

We present the first clear identification and highly accurate measurement of the intra-shell transition 1s2p\, ^3P_2 \to 1s2s\, ^3S_1 of He-like uranium performed via X-ray spectroscopy. The present experiment has been conducted at the gas-jet target of the ESR storage ring in GSI (Darmstadt, Germany) where a Bragg spectrometer, with a bent germanium crystal, and a Ge(i) detector were mounted. Using the ESR deceleration capabilities, we performed a differential measurement between the 1s2p\, ^3P_2 \to 1s2s\, ^3S_1 He-like U transition energy, at 4510 eV, and the 1s^22p\ ^2P_{3/2} \to 1s^22s\, ^2S_{1/2} Li-like U transition energy, at 4460 eV. By a proper choice of the ion velocities, the X-ray energies from the He- and Li-like ions could be measured, in the laboratory frame, at the same photon energy. This allowed for a drastic reduction of the experimental systematic uncertainties, principally due to the Doppler effect, and for a comparison with the theory without the uncertainties arising from one-photon QED predictions and nuclear size corrections

Hepatitis B Seroprevalence in the U.S. Military and its Impact on Potential Screening Strategies

INTRODUCTION: Knowledge of the contemporary epidemiology of hepatitis B virus (HBV) infection among military personnel can inform potential Department of Defense (DoD) screening policy and infection and disease control strategies. MATERIALS AND METHODS: HBV infection status at accession and following deployment was determined by evaluating reposed serum from 10,000 service members recently deployed to combat operations in Iraq and Afghanistan in the period from 2007 to 2010. A cost model was developed from the perspective of the Department of Defense for a program to integrate HBV infection screening of applicants for military service into the existing screening program of screening new accessions for vaccine-preventable infections. RESULTS: The prevalence of chronic HBV infection at accession was 2.3/1,000 (95% CI: 1.4, 3.2); most cases (16/21, 76%) identified after deployment were present at accession. There were 110 military service-related HBV infections identified. Screening accessions who are identified as HBV susceptible with HBV surface antigen followed by HBV surface antigen neutralization for confirmation offered no cost advantage over not screening and resulted in a net annual increase in cost of $5.78 million. However, screening would exclude as many as 514 HBV cases each year from accession. CONCLUSIONS: Screening for HBV infection at service entry would potentially reduce chronic HBV infection in the force, decrease the threat of transfusion-transmitted HBV infection in the battlefield blood supply, and lead to earlier diagnosis and linkage to care; however, applicant screening is not cost saving. Service-related incident infections indicate a durable threat, the need for improved laboratory-based surveillance tools, and mandate review of immunization policy and practice