The Equation of State and the Hugoniot of Laser Shock-Compressed Deuterium

The equation of state and the shock Hugoniot of deuterium are calculated using a first-principles approach, for the conditions of the recent shock experiments. We use density functional theory within a classical mapping of the quantum fluids [ Phys. Rev. Letters, {\bf 84}, 959 (2000) ]. The calculated Hugoniot is close to the Path-Integral Monte Carlo (PIMC) result. We also consider the {\it quasi-equilibrium} two-temperature case where the Deuterons are hotter than the electrons; the resulting quasi-equilibrium Hugoniot mimics the laser-shock data. The increased compressibility arises from hot $D^+-e$ pairs occuring close to the zero of the electron chemical potential.Comment: Four pages; One Revtex manuscript, two postscipt figures; submitted to PR

Integration of the Forward Detectors inside the LHC Machine

Several forward detectors have been installed in the LHC long straight sections located on each side of the experimental caverns. Most of these detectors have been designed by the LHC experiments to study the forward physics while some of them are dedicated to the measurement of the LHC luminosity. The integration and the installation of the forward detectors have required an excellent coordination between the experiments and the different CERN groups involved into the design and the installation of the LHC accelerator. In some cases the integration of these detectors has required a modification of the standard beam lines in order to maximise their physics potential. Finally, additional systems have been installed in the LHC tunnel to ensure the operation of the forward detectors in a high radiation environment

Spin-polarized stable phases of the 2-D electron fluid at finite temperatures

The Helmholtz free energy F of the interacting 2-D electron fluid is calculated nonperturbatively using a mapping of the quantum fluid to a classical Coulomb fluid [Phys. Rev. Letters, vol. 87, 206404 (2001)]. For density parameters rs such that rs<~25, the fluid is unpolarized at all temperatures t=T/EF where EF is the Fermi energy. For lower densities, the system becomes fully spin polarized for t<~0.35, and partially polarized for 0.35<t< 2, depending on the density. At rs ~25-30, and t ~0.35, an ''ambispin'' phase where F is almost independent of the spin polarization is found. These results support recent claims, based on quantum Monte Carlo results, for a stable, fully spin-polarized fluid phase at T = 0 for rs larger than about 25-26.Comment: Latex manuscript (4-5 pages) and two postscript figures; see also http://nrcphy1.phy.nrc.ca/ims/qp/chandre/chnc

Validation of GATE 6.1 for targeted radiotherapy of metastic melanoma using 131I-labeled benzamide

International audienceThe GATE 6.1 Monte Carlo simulation platform based on the GEANT4 toolkit is in constant improvement for dosimetric calculations. Here, we explore its use for calculating internal absorbed dose distribution in mice for the treatment of malignant melanoma after injection of a new specific radiopharmaceutical labeled with iodine 131. We estimate the dosimetric accuracy of GATE 6.1, by calculating first S values and by comparing them and absorbed doses to organswith EGSnrc for a digital mouse phantom and a CT scan based mouse phantom

Efficacy of targeting bone-specific GIP receptor in ovariectomy-induced bone loss

Glucose-dependent insulinotropic polypeptide (GIP) has been recognized in the last decade as an important contributor of bone remodeling and is necessary for optimal bone quality. However, GIP receptors are expressed in several tissues in the body and little is known about the direct versus indirect effects of GIP on bone remodeling and quality. The aims of the present study were to validate two new GIP analogues, called [D-Ala2]-GIP-Tag and [D-Ala2]-GIP1-30, that specifically target either bone or whole body GIP receptors, respectively; and to ascertain the beneficial effects of GIP therapy on bone in a mouse model of ovariectomy-induced bone loss. Both GIP analogues exhibited similar binding capacities at the GIP receptor and intracellular responses as full-length GIP1-42. Furthermore, only [D-Ala2]-GIP-Tag, but not [D-Ala2]-GIP1-30, was undoubtedly found exclusively in the bone matrix and released at acidic pH. In ovariectomized animals, [D-Ala2]-GIP1-30 but not [D-Ala2]-GIP-Tag ameliorated bone stiffness at the same magnitude than alendronate treatment. Only [D-Ala2]-GIP1-30 treatment led to significant ameliorations in cortical microarchitecture. Although alendronate treatment increased the hardness of the bone matrix and the type B carbonate substitution in the hydroxyapatite crystals, none of the GIP analogues modified bone matrix composition. Interestingly, in ovariectomy-induced bone loss, [D-Ala²]-GIP-Tag failed to alter bone strength, microarchitecture and bone matrix composition. Overall, this study shows that the use of a GIP analogue that target whole body GIP receptors might be useful to improve bone strength in ovariectomized animals

The 2-D electron gas at arbitrary spin polarizations and arbitrary coupling strengths: Exchange-correlation energies, distribution functions and spin-polarized phases

We use a recent approach [Phys. Rev. Letters, {\bf 84}, 959 (2000)] for including Coulomb interactions in quantum systems via a classical mapping of the pair-distribution functions (PDFs) for a study of the 2-D electron gas. As in the 3-D case, the ``quantum temperature'' T_q of a classical 2-D Coulomb fluid which has the same correlation energy as the quantum fluid is determined as a function of the density parameter r_s. Spin-dependent exchange-correlation energies are reported. Comparisons of the spin-dependent pair-distributions and other calculated properties with any available 2-D quantum Monte Carlo (QMC) results show excellent agreement, strongly favouring more recent QMC data. The interesting novel physics brought to light by this study are: (a) the independently determined quantum-temperatures for 3-D and 2-D are found to be approximately the same, (i.e, universal) function of the classical coupling constant Gamma. (b) the coupling constant Gamma increases rapidly with r_s in 2-D, making it comparatively more coupled than in 3-D; the stronger coupling in 2-D requires bridge corrections to the hyper- netted-chain method which is adequate in 3-D; (c) the Helmholtz free energy of spin-polarized and unpolarized phases have been calculated. The existence of a spin-polarized 2-D liquid near r_s = 30, is found to be a marginal possibility. These results pertain to clean uniform 2-D electron systems.Comment: This paper replaces the cond-mat/0109228 submision; the new version include s more accurate numerical evaluation of the Helmholtz energies of the para- and ferromagentic 2D fluides at finite temperatures. (Paper accepted for publication in Phys. Rev. Lett.

The Path Integral Monte Carlo Calculation of Electronic Forces

We describe a method to evaluate electronic forces by Path Integral Monte Carlo (PIMC). Electronic correlations, as well as thermal effects, are included naturally in this method. For fermions, a restricted approach is used to avoid the ``sign'' problem. The PIMC force estimator is local and has a finite variance. We applied this method to determine the bond length of H$_2$ and the chemical reaction barrier of H+H$_2\longrightarrow$H$_2$+H. At low temperature, good agreement is obtained with ground state calculations. We studied the proton-proton interaction in an electron gas as a simple model for hydrogen impurities in metals. We calculated the force between the two protons at two electronic densities corresponding to Na ($r_s=3.93$) and Al ($r_s=2.07$) using a supercell with 38 electrons. The result is compared to previous calculations. We also studied the effect of temperature on the proton-proton interaction. At very high temperature, our result agrees with the Debye screening of electrons. As temperature decreases, the Debye theory fails both because of the strong degeneracy of electrons and most importantly, the formation of electronic bound states around the protons.Comment: 18 pages, 10 figure