Enhancement of fusion rates due to quantum effects in the particles momentum distribution in nonideal media

This study concerns a situation when measurements of the nonresonant cross-section of nuclear reactions appear highly dependent on the environment in which the particles interact. An appealing example discussed in the paper is the interaction of a deuteron beam with a target of deuterated metal Ta. In these experiments, the reaction cross section for d(d,p)t was shown to be orders of magnitude greater than what the conventional model predicts for the low-energy particles. In this paper we take into account the influence of quantum effects due to the Heisenberg uncertainty principle for particles in a non-ideal medium elastically interacting with the medium particles. In order to calculate the nuclear reaction rate in the non-ideal environment we apply both the Monte Carlo technique and approximate analytical calculation of the Feynman diagram using nonrelativistic kinetic Green's functions in the medium which correspond to the generalized energy and momentum distribution functions of interacting particles. We show a possibility to reduce the 12-fold integral corresponding to this diagram to a fivefold integral. This can significantly speed up the computation and control accuracy. Our calculations show that quantum effects significantly influence reaction rates such as p +7Be, 3He +4He, p +7Li, and 12C +12C. The new reaction rates may be much higher than the classical ones for the interior of the Sun and supernova stars. The possibility to observe the theoretical predictions under laboratory conditions is discussed

Possibility of quantitative T2-mapping MRI of cartilage near metal in high tibial osteotomy: A human cadaver study

T2-mapping is a widely used quantitative MRI technique in osteoarthritis research. An important challenge for its application in the context of high tibial osteotomy (HTO) is the presence of metallic fixation devices. In this study, we evaluated the possibility of performing T2-mapping after a HTO, by assessing the extent of magnetic susceptibility artifacts and the influence on T2 relaxation times caused by two commonly used fixation devices. T2-mapping with a 3D fast spin-echo sequence at three Tesla was performed on 11 human cadaveric knee joints before and after implantation of a titanium plate and screws (n = 5) or cobalt chrome staples (n = 6). Mean T2 relaxation times were calculated in six cartila

Separating the Early Universe from the Late Universe: cosmological parameter estimation beyond the black box

We present a method for measuring the cosmic matter budget without assumptions about speculative Early Universe physics, and for measuring the primordial power spectrum P*(k) non-parametrically, either by combining CMB and LSS information or by using CMB polarization. Our method complements currently fashionable ``black box'' cosmological parameter analysis, constraining cosmological models in a more physically intuitive fashion by mapping measurements of CMB, weak lensing and cluster abundance into k-space, where they can be directly compared with each other and with galaxy and Lyman alpha forest clustering. Including the new CBI results, we find that CMB measurements of P(k) overlap with those from 2dF galaxy clustering by over an order of magnitude in scale, and even overlap with weak lensing measurements. We describe how our approach can be used to raise the ambition level beyond cosmological parameter fitting as data improves, testing rather than assuming the underlying physics.Comment: Replaced to match accepted PRD version. Refs added. Combined CMB data and window functions at http://www.hep.upenn.edu/~max/pwindows.html or from [email protected]. 18 figs, 19 journal page

Two-component spike nanoparticle vaccine protects macaques from SARS-CoV-2 infection

Brouwer et al. present preclinical evidence in support of a COVID-19 vaccine candidate, designed as a self-assembling two-component protein nanoparticle displaying multiple copies of the SARS-CoV-2 spike protein, which induces strong neutralizing antibody responses and protects from high-dose SARS-CoV-2 challenge.The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is continuing to disrupt personal lives, global healthcare systems, and economies. Hence, there is an urgent need for a vaccine that prevents viral infection, transmission, and disease. Here, we present a two-component protein-based nanoparticle vaccine that displays multiple copies of the SARS-CoV-2 spike protein. Immunization studies show that this vaccine induces potent neutralizing antibody responses in mice, rabbits, and cynomolgus macaques. The vaccine-induced immunity protects macaques against a high-dose challenge, resulting in strongly reduced viral infection and replication i

Ionentemperaturmessungen an ASDEX mit verbesserter Fusions-Protonen- und -Tritonen-Diagnostik

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Ionenenergietransport in elektronengeheizten Entladungen am Tokamak ASDEX

In the present work conducted at the TOKAMAK experiment ASDEX (axial symmetrical divertor experiment) an optimization of the neutral particle diagnostics was carried out in order to derive reliable ion temperatures from the neutral particle flux, and to establish radial profiles for all important discharge scenaria. Separating high-energetic and non-thermal contributions, relative errors in ion temperature determination could be limited to #+-# 10%, excluding at the same time systematic errors. Based on these experimental and theoretical studies, the local ion energy transport has been analyzed. Results are in line with the basic equations of the neoclassic theory. (WEN)SIGLEAvailable from TIB Hannover: RA 71(III/198) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Statistical analysis of the global energy confinement time #tau#_E in Ohmic discharges in the ASDEX tokamak

In ohmic discharges in all tokamaks at low plasma densities the global energy confinement time #tau#_E increases almost linearly with the density (LOC, Linear Ohmic Confinement). In tokamaks with sufficiently large dimensions #tau#_E saturates at a critical density (ASDEX: anti n_e#approx#3x10"1"9 m"-"3) and is nearly constant at higher densities (SOC, Saturated Ohmic Confinement). In the same density region some experiments report a further confinement regime for deuterium discharges in which #tau#_E exceeds the saturated value and is further increased (IOC, Improved Ohmic Confinement). There the global energy confinement time roughly behaves as in the LOC regime. For both the LOC and the SOC regimes an isotope effect, i.e. the dependence of #tau#_E on the ion mass, is reported as an additional aspect of the ohmic energy confinement. A statistical analysis is performed to identify the parameters which are responsible for the properties of the energy confinement in these discharges in ASDEX. Contrary to earlier reports on confinement time scalings in ASDEX OH, only discharges with a full experimental description of kinetic electron and ion parameters, i.e. profiles of densities, temperatures and Z_e_f_f, are used to evaluate the energy contents of both species. By means of statistics it is shown that the characteristics of #tau#_E are mainly caused by the behaviour of the electron energy flux and the ohmic input power. The ion energy flux, however, does not play a significant role. Furthermore, the IOC regime is explained as a continuation of the low-density LOC regime. Both effects, the isotope effect and the density dependence of #tau#_E, are caused by the features of the electron energy transport. (orig.)30 refs.Available from TIB Hannover: RA 71(205) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman