Direct Measurement of the

One of the main neutron sources for the astrophysical s process is the reaction ^{13}C(α,n)^{16}O, taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230 keV energy window (Gamow peak). At these sub-Coulomb energies, cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s-process calculations. We present the results from a new deep-underground measurement of ^{13}C(α,n)^{16}O, covering the energy range 230-300 keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s-process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular, the two radioactive nuclei ^{60}Fe and ^{205}Pb, as well as ^{152}Gd.

The baryon density of the Universe from an improved rate of deuterium burning.

Light elements were produced in the first few minutes of the Universe through a sequence of nuclear reactions known as Big Bang nucleosynthesis (BBN)1,2. Among the light elements produced during BBN1,2, deuterium is an excellent indicator of cosmological parameters because its abundance is highly sensitive to the primordial baryon density and also depends on the number of neutrino species permeating the early Universe. Although astronomical observations of primordial deuterium abundance have reached percent accuracy3, theoretical predictions4-6 based on BBN are hampered by large uncertainties on the cross-section of the deuterium burning D(p,γ)3He reaction. Here we show that our improved cross-sections of this reaction lead to BBN estimates of the baryon density at the 1.6 percent level, in excellent agreement with a recent analysis of the cosmic microwave background7. Improved cross-section data were obtained by exploiting the negligible cosmic-ray background deep underground at the Laboratory for Underground Nuclear Astrophysics (LUNA) of the Laboratori Nazionali del Gran Sasso (Italy)8,9. We bombarded a high-purity deuterium gas target10 with an intense proton beam from the LUNA 400-kilovolt accelerator11 and detected the γ-rays from the nuclear reaction under study with a high-purity germanium detector. Our experimental results settle the most uncertain nuclear physics input to BBN calculations and substantially improve the reliability of using primordial abundances to probe the physics of the early Universe.

Comparison of digital coincidence modules used at POLATOM and PTB for TDCR and 4πß(LS)-γ coincidence counters.

Activity measurements of 3H, 241Am and 60Co solutions were performed to compare digital coincidence modules used at PTB and POLATOM for TDCR and 4πß(LS)-γ coincidence counting. The activities determined with various coincidence modules connected in parallel to the same counter at PTB were found to be consistent. Observed discrepancies caused by differences in the coincidence resolving time did not exceed 0.14%. Accidental coincidences simulated by a frequency generator were registered, and the coincidence resolving time was determined.

Direct Capture Cross Section and the E_{p}=71 and 105 keV Resonances in the

The ^{22}Ne(p,γ)^{23}Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E_{p}=156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E_{p}=71 and 105 keV. Here, new ^{22}Ne(p,γ)^{23}Na data with high statistics and low background are reported. Stringent upper limits of 6×10^{-11} and 7×10^{-11} eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the ^{22}Ne(p,γ)^{23}Na rate is now reduced by 3 orders of magnitude.

Erratum: Three New Low-Energy Resonances in the

This corrects the article DOI: 10.1103/PhysRevLett.115.252501.

Tunable thermodynamic activity of La x Sr1-x Mn y Al1-y O3-δ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) perovskites for solar thermochemical fuel synthesis.

Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO2 and/or H2O to produce CO and/or H2 (syngas), we investigate the equilibrium thermodynamics of the La x Sr1-x Mn y Al1-y O3-δ perovskite family (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and La0.6Ca0.4Mn0.8Al0.2O3-δ , and compare them to those of CeO2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La0.2Sr0.8Mn0.8Al0.2O3-δ at 1773 K and 2.37 mbar O2. As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La0.6Sr0.4Mn0.4Al0.6O3-δ , rendering it attractive for CO2 and H2O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence.

Splitting CO2 with a ceria-based redox cycle in a solar-driven thermogravimetric analyzer.

Thermochemical splitting of CO2 via a ceria-based redox cycle was performed in a solar-driven thermogravimetric analyzer. Overall reaction rates, including heat and mass transport, were determined under concentrated irradiation mimicking realistic operation of solar reactors. Reticulated porous ceramic (RPC) structures and fibers made of undoped and Zr4+-doped CeO2, were endothermally reduced under radiative fluxes of 1280 suns in the temperature range 1200-1950 K and subsequently re-oxidized with CO2 at 950-1400 K. Rapid and uniform heating was observed for 8 ppi ceria RPC with mm-sized porosity due to its low optical thickness and volumetric radiative absorption, while ceria fibers with µm-sized porosity performed poorly due to its opacity to incident irradiation. The 10 ppi RPC exhibited higher fuel yield because of its higher sample density. Zr4+-doped ceria showed increasing reduction extents with dopant concentration but decreasing specific CO yield due to unfavorable oxidation thermodynamics and slower kinetics.

Improved Direct Measurement of the 64.5 keV Resonance Strength in the

The ^{17}O(p,α)^{14}N reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as ^{17}O and ^{18}F, which can provide constraints on astrophysical models. A new direct determination of the E_{R}=64.5 keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date ωγ=10.0±1.4_{stat}±0.7_{syst} neV, thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at E_{x}=5672 keV in ^{18}F is Γ_{p}=35±5_{stat}±3_{syst} neV. This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the ^{17}O(p, α)^{14}N reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower ^{17}O/^{16}O ratios, with important implications on the interpretation of astrophysical observables from these stars.

Oxygen nonstoichiometry and thermodynamic characterization of Zr doped ceria in the 1573-1773 K temperature range.

This work encompasses the thermodynamic characterization and critical evaluation of Zr(4+) doped ceria, a promising redox material for the two-step solar thermochemical splitting of H2O and CO2 to H2 and CO. As a case study, we experimentally examine 5 mol% Zr(4+) doped ceria and present oxygen nonstoichiometry measurements at elevated temperatures ranging from 1573 K to 1773 K and oxygen partial pressures ranging from 4.50 × 10(-3) atm to 2.3 × 10(-4) atm, yielding higher reduction extents compared to those of pure ceria under all conditions investigated, especially at the lower temperature range and at higher pO2. In contrast to pure ceria, a simple ideal solution model accounting for the formation of isolated oxygen vacancies and localized electrons accurately describes the defect chemistry. Thermodynamic properties are determined, namely: partial molar enthalpy, entropy, and Gibbs free energy. In general, partial molar enthalpy and entropy values of Zr(4+) doped ceria are lower. The equilibrium hydrogen yields are subsequently extracted as a function of the redox conditions for dopant concentrations as high as 20%. Although reduction extents increase greatly with dopant concentration, the oxidation of Zr(4+) doped ceria is thermodynamically less favorable compared to pure ceria. This leads to substantially larger temperature swings between reduction and oxidation steps, ultimately resulting in lower theoretical solar energy conversion efficiencies compared to ceria under most conditions. In effect, these results point to the importance of considering oxidation thermodynamics in addition to reduction when screening potential redox materials.

Three New Low-Energy Resonances in the

The ^{22}Ne(p,γ)^{23}Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between ^{20}Ne and ^{27}Al in asymptotic giant branch stars and novae. The ^{22}Ne(p,γ)^{23}Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the ^{22}Ne(p,γ)^{23}Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless ^{22}Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars.

Molecular epidemiology of hepatitis C virus genotypes and subtypes among injecting drug users in Hungary.

The aim of this study was to determine the geographical distribution of hepatitis C virus genotypes/subtypes among people who inject drugs (PWID) recruited at 22 needle exchange sites and drug outpatient services in all seven Planning and Statistical Regions of Hungary. Of 198 such PWID, 147 (74.2%), 45 (22.7%) and six (3.0%) carried genotype 1, 3 or 4, respectively, and 31 (72.1%) of the 43 genotype 1 sequences were of subtype 1a. Genotype 3 was significantly more prevalent in provincial towns than in the capital, Budapest. Injecting for a longer period and an older age both correlated with a higher prevalence of genotype 3, suggesting possible future changes in genotype distribution. The distributions of hepatitis C virus genotypes/ subtypes differed significantly between the tested PWID and the general population. The identification of genotype 3 reflected its worldwide occurrence among PWID. Our results underline the importance of genotyping before treatment, especially among people who have ever injected drugs in Hungary.

Prevalence and genotyping of group 3 torque teno viruses detected in health care workers in Hungary.

Torque teno viruses (TTVs) are classified into the Anellovirus genus of the Circoviridae family. In addition to TTV isolates, TTV genogroup 3 also includes the 8 virus strains known as SENV-A to H. In this study, the prevalence of TTV group 3 viruses and that of SENV-D and H in particular were determined among the staff of a hospital in Budapest. Viruses were genotyped using type-specific PCR primers and by cloning and sequencing of PCR products. Frequency of infection with TTV group 3 was high among both the hospital staff and the control group. Prevalence of SENV-H was similar in the two groups, but SENV-D infection was significantly more common in the study group than in controls. Sequencing of PCR products showed that viruses closely related to isolate TUS01 are common in Hungary. Several sequences could not be genotyped and may represent a previously undescribed genotype within the genogroup. TTV group 3 sequences detected in the serum samples of a symptomless health care worker were followed-up for 15 years. Some strains persisted for up to 10 years, while others caused transient infections and could be detected in only one of the samples. Results showed that TTV infection, superinfection, and viral clearance often occur over the years without apparent symptoms.

Variability of the PreS1/PreS2/S regions of hepatitis B virus in Hungary.

Infection with the hepatitis B virus can occur perinatally, parenterally, or sexually, and it can cause acute or chronic liver diseases. Phylogenetic analysis of the virus has led to its classification into eight genotypes (A-H), which show a characteristic worldwide distribution. The aim of this study was to reveal the HBV genotypes present in Hungary and to investigate a nosocomial and an intrafamilial outbreak. The collected samples were tested by nested PCR, and a 650-nucleotide-long segment of the preS1/preS2/S region was sequenced. As no previous genotype data were available from Hungary, sera of 24 HBsAg-positive patients were collected from different regions of the country. They also served as control samples for the molecular epidemiologic study. Nineteen of them carried genotype D of hepatitis B virus, and five of them carried genotype A. Twenty-nine patients from a haemato-oncology unit were affected in a nosocomial outbreak. The patients had haematological and/or oncological diseases, most of them were immunosuppressed. In twenty-eight cases, based on phylogenetic analysis of the viruses, there was presumably a common source of infection, and an epidemiological investigation showed that the infections seemed to be hospital-acquired. In the intrafamilial outbreak, two asymptomatic carrier children infected their foster mother. The three sequences were totally identical.

Nanocrystalline silver dressings as an efficient anti-MRSA barrier: a new solution to an increasing problem.

The emergence of multi-drug-resistant strains of bacteria represents a particular challenge in the field of wound management. The aim of the current study was to investigate whether nanocrystalline silver dressings possess the physical properties to act as a barrier to the transmission of methicillin-resistant Staphylococcus aureus (MRSA) in the laboratory setting and in a clinical setting. Initially, MRSA suspension and colony culture experiments were performed showing that nanocrystalline silver dressings act as potent and sustained antimicrobial agents, efficiently inhibiting MRSA penetration. Subsequently, a double-centre clinical trial was initiated using nanocrystalline silver dressings as a cover for 10 MRSA colonized wounds in a total of seven patients. By delineating the MRSA load on the upper side of the dressing and the wound bed each time the dressing was changed (i.e. after 1, 24, 48 and 72 h), nanocrystalline silver dressings were found to provide a complete, or almost complete, barrier to the penetration/spread of MRSA in 95% of readings. In addition, 67% of all wound observations showed a decrease in the MRSA load with an eradication rate of 11%. We believe that nanocrystalline silver dressings may become an important part of local MRSA management, with cost benefits to both patients and the healthcare system.

Genotypic distribution of human herpesvirus-8 strains circulating in HIV-positive patients with and without Kaposi's sarcoma in Hungary.

Open reading frame (ORF) 26 of human herpesvirus-8 (HHV-8) from peripheral blood samples of 15 Hungarian HIV-positive patients with or without Kaposi's sarcoma (KS) were amplified and sequenced. Four variants of HHV-8 were identified according to ORF 26 genotyping. Most of the samples were shown to be subtype A3, however, subtypes A, B3/C2/C2', and C3 (ORF 26 region) were also identified. The ORF 26 subtypes A and C3 of HHV-8 were only recovered from patients with KS while A3 was dominant in KS negative cases. The amplification of the hypervariable ORF K1 gene was successful only from 2 of the same 15 patients. Sequence analysis of the amplified ORF K1/VR1 regions identified subtype A3 from 2 patients with AIDS-associated KS. A novel ORF K1/VR1 variant belonging to subgroup A' was detected in a different sample in one of them. Amplification of the ORF K15, another representative locus for HHV-8 genotyping, was not successful from any of the peripheral blood samples. Unsuccessful amplification of the terminal K1 and K15 ORFs from peripheral blood samples suggests that KS biopsy specimens are needed for complete genotyping of HHV-8 strains from Hungary.

Protein-DNA interaction and CpG methylation at rep*/vIL-10p of latent Epstein-Barr virus genomes in lymphoid cell lines.

The viral interleukin-10 promoter (vIL-10p), overlapping the rep* element in the Epstein-Barr virus (EBV) genome, is a promoter element active mostly in the late phase of the lytic cycle and immediately upon infection of B cells. rep* was, through transfection experiments with small plasmids, characterised as a cis element supporting oriP replicative function. In this study, in vivo protein binding and CpG methylation at rep*/vIL-10p were analysed in five cell lines that harbour strictly latent EBV genomes. Contrary to the invariably unmethylated dyad symmetry element (DS) of oriP, rep*/vIL-10p was highly methylated and showed only traces of protein binding in all examined cell lines. This result is in agreement with vIL-10p being an inactive promoter of EBV genomes, and makes it less likely that rep* functions as a replicative element of latent EBV genomes.

Molecular characterization and heterologous expression of hypCD, the first two [NiFe] hydrogenase accessory genes of Thermococcus litoralis.

The hypCD genes, encoding the counterparts of mesophilic proteins involved in the maturation of [NiFe] hydrogenases, were isolated from the hyperthermophilic archaeon Thermococcus litoralis. The deduced gene products showed 30-40% identity to the corresponding mesophilic proteins. HypC and HypD were synthesized by the T7 expression system. Heterologous complementation experiments were done in Escherichia coli and Ralstonia eutropha strains lacking functionally active hypC and hypD genes. Only the cytoplasmic hydrogenase of R. eutropha could be processed by HypD from T. litoralis. This was the first demonstration of mesophilic hydrogenase processing using a hyperthermophilic archaeal accessory protein to produce an active enzyme.

Epigenetics of latent Epstein-Barr virus genomes: high resolution methylation analysis of the bidirectional promoter region of latent membrane protein 1 and 2B genes.

We analysed the methylation patterns of CpG dinucleotides in a bidirectional promoter region (LRS, LMP 1 regulatory sequences) of latent Epstein-Barr virus (EBV) genomes using automated fluorescent genomic sequencing after bisulfite-induced modification of DNA. Transcripts for two latent membrane proteins, LMP 1 (a transforming protein) and LMP 2B, are initiated in this region in opposite directions. We found that B cell lines and a clone expressing LMP 1 carried EBV genomes with unmethylated or hypomethylated LRS, while highly methylated CpG dinucleotides were present at each position or at discrete sites and within hypermethylated regions in LMP 1 negative cells. Comparison of high resolution methylation maps suggests that CpG methylation-mediated direct interference with binding of nuclear factors LBF 2, 3, 7, AML1/LBF1, LBF5 and LBF6 or methylation of CpGs within an E-box sequence (where activators as well as repressors can bind) is not the major mechanism in silencing of the LMP 1 promoter. Although a role for CpG methylation within binding sites of Sp1 and 3, ATF/CRE and a sis-inducible factor (SIF) cannot be excluded, hypermethylation of LRS or regions within LRS in LMP 1 negative cells suggests a role for an indirect mechanism, via methylcytosine binding proteins, in silencing of the LMP 1 promoter.

Protein-DNA binding and CpG methylation at nucleotide resolution of latency-associated promoters Qp, Cp, and LMP1p of Epstein-Barr virus.

Epstein-Barr viral (EBV) latency-associated promoters Qp, Cp, and LMP1p are crucial for the regulated expression of the EBNA and LMP transcripts in dependence of the latency type. By transient transfection and in vitro binding analyses, many promoter elements and transcription factors have previously been shown to be involved in the activities of these promoters. However, the latency promoters have only partially been examined at the nucleotide level in vivo. Therefore, we undertook a comprehensive analysis of in vivo protein binding and CpG methylation patterns at these promoters in five representative cell lines and correlated the results with the known in vitro binding data and activities of these promoters from previous transfection experiments. Promoter activity inversely correlated with the methylation state of promoters, although Qp was a remarkable exception. Novel protein binding data were obtained for all promoters. For Cp, binding correlated well with promoter activity; for LMP1p and Qp, binding patterns looked similar regardless of promoter activity.

Relative deficiency in CpG dinucleotides is a widespread but not unique feature of Gammaherpesvirinae genomes.

Since methylcytosine is relatively unstable, a deficiency of CpG dinucleotides and accumulation of mutations that manifest as TpG (and its complement CpA) is a diagnostic feature of higher eukaryotic DNA sequences subjected to methylation by DNA (cytosine-5) methyltransferases. Latent viral genomes may also be affected by DNA methylation in their host cells. We calculated, therefore, frequencies of dinucleotides in 20 completely sequenced herpesvirus genomes. We found a relative deficiency of CpG dinucleotides and a surplus of TpG + CpA dinucleotides in all lymphotropic gammaherpesvirus genomes except for two strains of rhesus rhadinovirus. DNAs of two strains of human herpesvirus 7, a betaherpesvirus targeting helper T cells, and equine herpesvirus 4, an alphaherpesvirus residing in the lymphoreticular system, also had a moderate CpG deficiency and TpG + CpA surplus. In contrast, most members of Alpha-, and Betaherpesvirinae subfamilies contained a relative surplus of CpG dinucleotides in their DNAs. Our data are consistent with the idea that methylated latent genomes are involved, after reactivation and productive replication, in the natural transmission cycle of most members of Gammaherpesvirinae and certain lymphotropic members of Alpha- and Betaherpesvirinae.