101 research outputs found
Formalism for obtaining nuclear momentum distributions by the Deep Inelastic Neutron Scattering technique
We present a new formalism to obtain momentum distributions in condensed
matter from Neutron Compton Profiles measured by the Deep Inelastic Neutron
Scattering technique. The formalism describes exactly the Neutron Compton
Profiles as an integral in the momentum variable . As a result we obtain a
Volterra equation of the first kind that relates the experimentally measured
magnitude with the momentum distributions of the nuclei in the sample. The
integration kernel is related with the incident neutron spectrum, the total
cross section of the filter analyzer and the detectors efficiency function. A
comparison of the present formalism with the customarily employed approximation
based on a convolution of the momentum distribution with a resolution function
is presented. We describe the inaccuracies that the use of this approximation
produces, and propose a new data treatment procedure based on the present
formalism.Comment: 11 pages, 8 figure
Trophic Activity of Human P2X7 Receptor Isoforms A and B in Osteosarcoma
The P2X7 receptor (P2X7R) is attracting increasing attention for its involvement in cancer. Several recent studies have shown a crucial role of P2X7R in tumour cell growth, angiogenesis and invasiveness. In this study, we investigated the role of the two known human P2X7R functional splice variants, the full length P2X7RA and the truncated P2X7RB, in osteosarcoma cell growth. Immunohistochemical analysis of a tissue array of human osteosarcomas showed that forty-four, of a total fifty-four tumours (81.4%), stained positive for both P2X7RA and B, thirty-one (57.4%) were positive using an anti-P2X7RA antibody, whereas fifteen of the total number (27.7%) expressed only P2X7RB. P2X7RB positive tumours showed increased cell density, at the expense of extracellular matrix. The human osteosarcoma cell line Te85, which lacks endogenous P2X7R expression, was stably transfected with either P2X7RA, P2X7RB, or both. Receptor expression was a powerful stimulus for cell growth, the most efficient growth-promoting isoform being P2X7RB alone. Growth stimulation was matched by increased Ca2+ mobilization and enhanced NFATc1 activity. Te85 P2X7RA+B cells presented pore formation as well as spontaneous extracellular ATP release. The ATP release was sustained in all clones by P2X7R agonist (BzATP) and reduced following P2X7R antagonist (A740003) application. BzATP also increased cell growth and activated NFATc1 levels. On the other hand cyclosporin A (CSA) affected both NFATc1 activation and cell growth, definitively linking P2X7R stimulation to NFATc1 and cell proliferation. All transfected clones also showed reduced RANK-L expression, and an overall decreased RANK-L/OPG ratio. Mineralization was increased in Te85 P2X7RA+B cells while it was significantly diminished in Te85 P2X7RB clones, in agreement with immunohistochemical results. In summary, our data show that the majority of human osteosarcomas express P2X7RA and B and suggest that expression of either isoform is differently coupled to cell growth or activity
The instrument suite of the European Spallation Source
An overview is provided of the 15 neutron beam instruments making up the initial instrument suite of the
European Spallation Source (ESS), and being made available to the neutron user community. The ESS neutron
source consists of a high-power accelerator and target station, providing a unique long-pulse time structure
of slow neutrons. The design considerations behind the time structure, moderator geometry and instrument
layout are presented.
The 15-instrument suite consists of two small-angle instruments, two reflectometers, an imaging beamline,
two single-crystal diffractometers; one for macromolecular crystallography and one for magnetism, two powder
diffractometers, and an engineering diffractometer, as well as an array of five inelastic instruments comprising
two chopper spectrometers, an inverse-geometry single-crystal excitations spectrometer, an instrument for vibrational
spectroscopy and a high-resolution backscattering spectrometer. The conceptual design, performance
and scientific drivers of each of these instruments are described.
All of the instruments are designed to provide breakthrough new scientific capability, not currently
available at existing facilities, building on the inherent strengths of the ESS long-pulse neutron source of high
flux, flexible resolution and large bandwidth. Each of them is predicted to provide world-leading performance
at an accelerator power of 2 MW. This technical capability translates into a very broad range of scientific
capabilities. The composition of the instrument suite has been chosen to maximise the breadth and depth
of the scientific impact o
Single-particle mean kinetic energy in low-density supercritical
We report novel results from inelastic neutron scattering measurements
at very high momentum transfer, 122 Å performed in
supercritical 4He, along two very low-density isochores ( nm-3 and nm-3) in the temperature
range 5–30 K. The experimental data have been analysed
within the framework of the plane-wave Impulse Approximation and the
temperature dependence of the single-particle mean kinetic energy has
been derived. It is found that this quantity deviates from the
classical behaviour in the whole temperature range explored, showing
the quantum nature of this system even for these very low-density
isochores, the lowest ever experimentally explored. For the higher
density, the temperature evolution of the single-particle mean kinetic
energy has also been derived using a path-integral Monte Carlo
code. These quantum simulation results, as well as those already
available for the low-density isochore, are in good agreement with the
experimental data. It is pointed out that, at these densities, the
temperature dependence of the mean kinetic energy is consistent with
an anharmonic behaviour of 4He induced by the hard-core component
of the interatomic potential
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