The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance

The current uncertainty in Newton's constant, G_N, is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the effect from the current uncertainty in the neutron lifetime, which is often treated as the dominant uncertainty in calculations of Y_P. Recent measurements of G_N seem to be converging within a smaller range; a reduction in the estimated error on G_N by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.

Solar Neutrino Constraints on the BBN Production of Li

Using the recent WMAP determination of the baryon-to-photon ratio, 10^{10} \eta = 6.14 to within a few percent, big bang nucleosynthesis (BBN) calculations can make relatively accurate predictions of the abundances of the light element isotopes which can be tested against observational abundance determinations. At this value of \eta, the Li7 abundance is predicted to be significantly higher than that observed in low metallicity halo dwarf stars. Among the possible resolutions to this discrepancy are 1) Li7 depletion in the atmosphere of stars; 2) systematic errors originating from the choice of stellar parameters - most notably the surface temperature; and 3) systematic errors in the nuclear cross sections used in the nucleosynthesis calculations. Here, we explore the last possibility, and focus on possible systematic errors in the He3(\alpha,\gamma)Be7 reaction, which is the only important Li7 production channel in BBN. The absolute value of the cross section for this key reaction is known relatively poorly both experimentally and theoretically. The agreement between the standard solar model and solar neutrino data thus provides additional constraints on variations in the cross section (S_{34}). Using the standard solar model of Bahcall, and recent solar neutrino data, we can exclude systematic S_{34} variations of the magnitude needed to resolve the BBN Li7 problem at > 95% CL. Additional laboratory data on He3(\alpha,\gamma)Be7 will sharpen our understanding of both BBN and solar neutrinos, particularly if care is taken in determining the absolute cross section and its uncertainties. Nevertheless, it already seems that this ``nuclear fix'' to the Li7 BBN problem is unlikely; other possible solutions are briefly discussed.Comment: 21 pages, 3 ps figure

Primordial Nucleosynthesis for the New Cosmology: Determining Uncertainties and Examining Concordance

Big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) have a long history together in the standard cosmology. The general concordance between the predicted and observed light element abundances provides a direct probe of the universal baryon density. Recent CMB anisotropy measurements, particularly the observations performed by the WMAP satellite, examine this concordance by independently measuring the cosmic baryon density. Key to this test of concordance is a quantitative understanding of the uncertainties in the BBN light element abundance predictions. These uncertainties are dominated by systematic errors in nuclear cross sections. We critically analyze the cross section data, producing representations that describe this data and its uncertainties, taking into account the correlations among data, and explicitly treating the systematic errors between data sets. Using these updated nuclear inputs, we compute the new BBN abundance predictions, and quantitatively examine their concordance with observations. Depending on what deuterium observations are adopted, one gets the following constraints on the baryon density: OmegaBh^2=0.0229\pm0.0013 or OmegaBh^2 = 0.0216^{+0.0020}_{-0.0021} at 68% confidence, fixing N_{\nu,eff}=3.0. Concerns over systematics in helium and lithium observations limit the confidence constraints based on this data provide. With new nuclear cross section data, light element abundance observations and the ever increasing resolution of the CMB anisotropy, tighter constraints can be placed on nuclear and particle astrophysics. ABRIDGEDComment: 54 pages, 20 figures, 5 tables v2: reflects PRD version minor changes to text and reference

The nickel hyperaccumulator plant Alyssum bertolonii as a potential agent for phytoremediation and phytomining of nickel

Experiments were carried out in Italy on the potential use of the hyperaccumulator Alyssum bertolonii in phytomining of ultramafic soils for Ni. In situ experimental plots at Murlo, Tuscany were fertilized with various regimes during a 2-year period. The best fertilizer treatment (N 4- K 4- P) gave a threefold increase of the biomass of reproductive matter to 9.0 t/ha without dilution of the unfertilized Ni content. A Ni content of 0.8% in dry matter (11% in ash), would give a Ni yield of 72 kg/ha without need of resowing for a further crop. There was no correlation between the age of a plant and its Ni content. The long-term cropping sustainability of the soils was simulated by sequential extractions with KH phthalate solutions at pH 2, 4 and 6 that showed a limiting available Ni content of 768 μg/g. Thus just over seven croppings at pH 6 in the rhizosphere would reduce the available Ni pool by 30%. A proposed model for phytomining involves harvesting the crop after 12 months and burning the material to produce a sulphur-free bio-ore with about 11% Ni. Utilising the energy of combustion is also discussed. It is considered that Alyssum bertolonii or other Alyssum species might be used for phytomining throughout the Mediterranean area including Anatolia, as well as in Western Australia and the western United States. The economic limits of phytomining are proposed and at current world prices, the technique would only be feasible for Ni and Co with plants of at least the same biomass as Alyssum. Plants of higher biomass and similar uptake potential as for Ni, could extend the limits to other elements

Anabolic exercise in haemodialysis patients: a randomised controlled pilot study

Background The anabolic response to progressive resistance exercise training (PRET) in haemodialysis patients is unclear. This pilot efficacy study aimed to determine whether high-intensity intradialytic PRET could reverse atrophy and consequently improve strength and physical function in haemodialysis patients. A second aim was to compare any anabolic response to that of healthy participants completing the same program. Methods In a single blind controlled study, 23 haemodialysis patients and 9 healthy individuals were randomly allocated to PRET or an attention control (SHAM) group. PRET completed high-intensity exercise leg extensions using novel equipment. SHAM completed low-intensity lower body stretching activities using ultra light resistance bands. Exercises were completed thrice weekly for 12 weeks, during dialysis in the haemodialysis patients. Outcomes included knee extensor muscle volume by magnetic resonance imaging, knee extensor strength by isometric dynamometer and lower body tests of physical function. Data were analysed by a per protocol method using between-group comparisons. Results PRET elicited a statistically and clinically significant anabolic response in haemodialysis patients (PRET�SHAM, mean difference [95 % CI]: 193[63 to 324]�cm3) that was very similar to the response in healthy participants (PRET�SHAM, 169[�41 to 379]�cm3). PRET increased strength in both haemodialysis patients and healthy participants. In contrast, PRET only enhanced lower body functional capacity in the healthy participants. Conclusions Intradialytic PRET elicited a normal anabolic and strength response in haemodialysis patients. The lack of a change in functional capacity was surprising and warrants further investigation