Silicon spin diffusion transistor: materials, physics and device characteristics

The realisation that eaveryday electronics has ignored the spin of the carrier in favour of its charge is the foundation of the field of spintronics. Starting with simple two-terminal devices based on GMR and tunnel magnetoresistance, the technology has advanced to consider three-terminal devices that aim to combine spin sensitivity with a high current gain and a large current output. These devices require both efficient spin injection and semiconductor fabrication. In this paper, a discussion is presented of the design, operation and characteristics of the only spin transistor that has yielded a current gain greater than one in combination with reasonable output current

Stellar Abundances in the Early Galaxy and Two r-Process Components

We present quantitative predictions for the abundances of r-process elements in stars formed very early in the Galactic history using a phenomenological two-component r-process model based on the I129 and Hf182 inventory in the early solar system. This model assumes that a standard mass of the ISM dilutes the debris from an individual supernova. High frequency supernova H events and low frequency supernova L events are proposed in the model with characteristics determined by the meteoritic data on I129 and Hf182. The yields in an H or L event are obtained from these characteristics and the solar r-process abundances under the assumption that the yield template for the high mass (A > 130) nuclei associated with W182 or the low mass (A < or = 130) nuclei associated with I127 is the same for both the H and L events and follows the corresponding solar r-pattern in each mass region. The abundance of Eu, not Fe, is proposed as a key guide to the age of very metal-poor stars. We predict that stars with log epsilon (Eu) = -2.98 to -2.22 were formed from an ISM contaminated most likely by a single H event within the first 10**7 yr of the Galactic history and should have an Ag/Eu abundance ratio less than the corresponding solar r-process value by a factor of at least 10. Many of the very metal-poor stars observed so far are considered here to have been formed from an ISM contaminated by many (about 10) r-process events. Stars formed from an ISM contaminated only by a pure L event would have an Ag/Eu ratio higher than the corresponding solar r-process value but would be difficult to find due to the low frequency of the L events. However, variations in the relative abundances of the low and high mass regions should be detectable in very metal-poor stars.Comment: 46 pages, 19 figures, to appear in the Schramm Memorial Volume of Physics Report

Estimating the inelasticity with the information theory approach

Using the information theory approach, in both its extensive and nonextensive versions, we estimate the inelasticity parameter $K$ of hadronic reactions together with its distribution and energy dependence from $p\bar{p}$ and $pp$ data. We find that the inelasticity remains essentially constant in energy except for a variation around $K\sim 0.5$, as was originally expected.Comment: 14 pages, 8 figures. Misprints correcte

Engineering Pathways in Central Carbon Metabolism Help to Increase Glycan Production and Improve N-Type Glycosylation of Recombinant Proteins in E. coli.

Escherichia coli strains have been modified in a variety of ways to enhance the production of different recombinant proteins, targeting membrane protein expression, proteins with disulphide bonds, and more recently, proteins which require N-linked glycosylation. The addition of glycans to proteins remains a relatively inefficient process and here we aimed to combine genetic modifications within central carbon metabolic pathways in order to increase glycan precursor pools, prior to transfer onto polypeptide backbones. Using a lectin screen that detects cell surface representation of glycans, together with Western blot analyses using an O-antigen ligase mutant strain, the enhanced uptake and phosphorylation of sugars (ptsA) from the media combined with conservation of carbon through the glyoxylate shunt (icl) improved glycosylation efficiency of a bacterial protein AcrA by 69% and over 100% in an engineered human protein IFN-α2b. Unexpectedly, overexpression of a gene involved in the production of DXP from pyruvate (dxs), which was previously seen to have a positive impact on glycosylation, was detrimental to process efficiency and the possible reasons for this are discussed

Systemic perturbations of the kynurenine pathway precede progression to dementia independently of amyloid-β

Increasing evidence suggests that kynurenine pathway (KP) dyshomeostasis may promote disease progression in dementia. Studies in Alzheimer's disease (AD) patients confirm KP dyshomeostasis in plasma and cerebrospinal fluid (CSF) which correlates with amyloid-β and tau pathology. Herein, we performed the first comprehensive study assessing baseline levels of KP metabolites in participants enrolling in the Australian Imaging Biomarkers Flagship Study of Aging. Our purpose was to test the hypothesis that changes in KP metabolites may be biomarkers of dementia processes that are largely silent. We used a cross-sectional analytical approach to assess non-progressors (N = 73); cognitively normal (CN) or mild cognitive impairment (MCI) participants at baseline and throughout the study, and progressors (N = 166); CN or MCI at baseline but progressing to either MCI or AD during the study. Significant KP changes in progressors included increased 3-hydroxyanthranilic acid (3-HAA) and 3-hydroxyanthranilic acid/anthranilic acid (3-HAA/AA) ratio, the latter having the largest effect on the odds of an individual being a progressor (OR 35.3; 95% CI between 14 and 104). 3-HAA levels were hence surprisingly bi-phasic, high in progressors but low in non-progressors or participants who had already transitioned to MCI or dementia. This is a new, unexpected and interesting result, as most studies of the KP in neurodegenerative disease show reduced 3-HAA/AA ratio after diagnosis. The neuroprotective metabolite picolinic acid was also significantly decreased while the neurotoxic metabolite 3-hydroxykynurenine increased in progressors. These results were significant even after adjustment for confounders. Considering the magnitude of the OR to predict change in cognition, it is important that these findings are replicated in other populations. Independent validation of our findings may confirm the utility of 3-HAA/AA ratio to predict change in cognition leading to dementia in clinical settings

New insights into bacterial chemoreceptor array structure and assembly from electron cryotomography

FWN – Publicaties zonder aanstelling Universiteit Leide

Short-lived Nuclei in the Early Solar System: Possible AGB Sources

(Abridged) We review abundances of short-lived nuclides in the early solar system (ESS) and the methods used to determine them. We compare them to the inventory for a uniform galactic production model. Within a factor of two, observed abundances of several isotopes are compatible with this model. I-129 is an exception, with an ESS inventory much lower than expected. The isotopes Pd-107, Fe-60, Ca-41, Cl-36, Al-26, and Be-10 require late addition to the solar nebula. Be-10 is the product of particle irradiation of the solar system as probably is Cl-36. Late injection by a supernova (SN) cannot be responsible for most short-lived nuclei without excessively producing Mn-53; it can be the source of Mn-53 and maybe Fe-60. If a late SN is responsible for these two nuclei, it still cannot make Pd-107 and other isotopes. We emphasize an AGB star as a source of nuclei, including Fe-60 and explore this possibility with new stellar models. A dilution factor of about 4e-3 gives reasonable amounts of many nuclei. We discuss the role of irradiation for Al-26, Cl-36 and Ca-41. Conflict between scenarios is emphasized as well as the absence of a global interpretation for the existing data. Abundances of actinides indicate a quiescent interval of about 1e8 years for actinide group production in order to explain the data on Pu-244 and new bounds on Cm-247. This interval is not compatible with Hf-182 data, so a separate type of r-process is needed for at least the actinides, distinct from the two types previously identified. The apparent coincidence of the I-129 and trans-actinide time scales suggests that the last actinide contribution was from an r-process that produced actinides without fission recycling so that the yields at Ba and below were governed by fission.Comment: 92 pages, 14 figure files, in press at Nuclear Physics

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Paradoxical co-existing base metal sulphides in the mantle: The multi-event record preserved in Loch Roag peridotite xenoliths, North Atlantic Craton

The role of the subcontinental lithospheric mantle as a source of precious metals for mafic magmas is contentious and, given the chalcophile (and siderophile) character of metals such as the platinum-group elements (PGE), Se, Te, Re, Cu and Au, the mobility of these metals is intimately linked with that of sulphur. Hence the nature of the host phase(s), and their age and stability in the subcontinental lithospheric mantle may be of critical importance. We investigate the sulphide mineralogy and sulphide in situ trace element compositions in base metal sulphides (BMS) in a suite of spinel lherzolite mantle xenoliths from northwest Scotland (Loch Roag, Isle of Lewis). This area is situated on the margin of the North Atlantic Craton which has been overprinted by a Palaeoproterozoic orogenic belt, and occurs in a region which has undergone magmatic events from the Palaeoproterozoic to the Eocene. We identify two populations of co-existing BMS within a single spinel lherzolite xenolith (LR80) and which can also be recognised in the peridotite xenolith suite as a whole. Both populations consist of a mixture of Fe-Ni-Cu sulphide minerals, and we distinguished between these according to BMS texture, petrographic setting (i.e., location within the xenolith in terms of ‘interstitial’ or within feldspar-spinel symplectites, as demonstrated by X-ray Computed Microtomography) and in situ trace element composition. Group A BMS are coarse, metasomatic, have low concentrations of total PGE (&lt; 40 ppm) and high (Re/Os)N (ranging 1 to 400). Group B BMS strictly occur within symplectites of spinel and feldspar, are finer-grained rounded droplets, with micron-scale PtS (cooperite), high overall total PGE concentrations (15–800 ppm) and low (Re/Os)N ranging 0.04 to 2. Group B BMS sometimes coexist with apatite, and both the Group B BMS and apatite can preserve rounded micron-scale Ca-carbonate inclusions indicative of sulphide-carbonate-phosphate immiscibility. This carbonate-phosphate metasomatic association appears to be important in forming PGE-rich sulphide liquids, although the precise mechanism for this remains obscure. As a consequence of their position within the symplectites, Group B BMS are particularly vulnerable to being incorporated in ascending mantle-derived magmas (either by melting or physical entrainment). Based on the cross-cutting relationships of the symplectites, it is possible to infer the relative ages of each metasomatic BMS population. We tally these with major tectono-magmatic events for the North Atlantic region by making comparisons to carbonatite events recorded in crustal and mantle rocks, and we suggest that the Pt-enrichment was associated with a pre-Carboniferous carbonatite episode. This method of mantle xenolith base metal sulphide documentation may ultimately permit the temporal and spatial mapping of the chalcophile metallogenic budget of the lithospheric mantle, providing a blueprint for assessing regional metallogenic potential. Abbreviations: NAC, North Atlantic Craton; GGF, Great Glen Fault; NAIP, North Atlantic Igneous Province; BPIP, British Palaeogene Igneous Province; SCLM, subcontinental lithospheric mantle; PGE, platinum-group elements; HSE, highly siderophile elements; BMS, base metal sulphid

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio