136 research outputs found
Melting and Pressure-Induced Amorphization of Quartz
It has recently been shown that amorphization and melting of ice were
intimately linked. In this letter, we infer from molecular dynamics simulations
on the SiO2 system that the extension of the quartz melting line in the
metastable pressure-temperature domain is the pressure-induced amorphization
line. It seems therefore likely that melting is the physical phenomenon
responsible for pressure induced amorphization. Moreover, we show that the
structure of a "pressure glass" is similar to that of a very rapidly (1e+13 to
1e+14 kelvins per second) quenched thermal glass.Comment: 9 pages, 4 figures, LaTeX2
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The Diderot meteorite: The second chassignite
The Diderot meteorite is a dunite discovered in Sahara. The martian origin is unambiguous and Diderot shares strong petrographical similarities with Chassigny
Real-Time Interaction over the Internet: Model for QOS Adaptation
Real-time Interaction over the Internet (RTI2) is an Internet service that is required typically by remote experimentation applications. From a quality of service (QoS) point of view, RTI2 has constraints that differ from usual real-time multimedia services such as video streaming or video conferencing. The RTI2 QoS can be expressed by three values that represent the level of interaction, the dynamics rendering and the semantic content. The RTI2 metrics, derived from these values, are essential to successfully implement an end-to-end (E2E) control scheme that adapts the transmission parameters to the equivalent E2E infrastructure that encompass not only to the network state, but also to the server and client applications processing capabilities. A model of the end-to-end system is exploited to ensure a minimal transmission time for a given E2E system
A combined XAS and XRD Study of the High-Pressure Behaviour of GaAsO4 Berlinite
Combined X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD)
experiments have been carried out on GaAsO4 (berlinite structure) at high
pressure and room temperature. XAS measurements indicate four-fold to six-fold
coordination changes for both cations. The two local coordination
transformations occur at different rates but appear to be coupled. A reversible
transition to a high pressure crystalline form occurs around 8 GPa. At a
pressure of about 12 GPa, the system mainly consists of octahedral gallium
atoms and a mixture of arsenic in four-fold and six-fold coordinations. A
second transition to a highly disordered material with both cations in six-fold
coordination occurs at higher pressures and is irreversible.Comment: 8 pages, 5 figures, LaTeX2
Dedicated controller design for a dual-stage opto-mechatronic system
To improve the resolution of the Very Large Telescope Interferometer (VLTI) a two-stage mechanical system, a so called Differential Delay Line (DDL), is developed jointly by the EPFL and the Observatory of Geneva. The system is designed to reach nanometer accuracy at high bandwidth over large displacements. The coarse stage features a permanent magnet (PM) stepper motor driving a lead screw connected to a double parallelogram flexure with notch-hinges (blade) guiding system, and the fine stage features a stacked piezoelectric device, combine to one single measurable output. This paper compares different control approaches for the DDL with their respective advantages and disadvantages. The developed control methods are based on modern linear and nonlinear control theory. The performance of the control schemes is illustrated via simulation and measurement on the available prototype. The new developed methods are compared to the currently implemented decoupled SISO design which features a direct-coil controller for the coarse stage and a simple PID-controller for the fine one
High resolution spectroscopy for Cepheids distance determination. II. A period- projection factor relation
The projection factor is a key quantity for the interferometric
Baade-Wesselink (hereafter IBW) and surface-brightness (hereafter SB) methods
of determining the distance of Cepheids. Indeed, it allows a consistent
combination of angular and linear diameters of the star. We aim to determine
consistent projection factors that include the dynamical structure of the
Cepheids' atmosphere. Methods. Hydrodynamical models of delta Cep and l Car
have been used to validate a spectroscopic method of determining the projection
factor. This method, based on the amplitude of the radial velocity curve, is
applied to eight stars observed with the HARPS spectrometer. The projection
factor is divided into three sub-concepts : (1) a geometrical effect, (2) the
velocity gradient within the atmosphere, and (3) the relative motion of the
"optical" pulsating photosphere compared to the corresponding mass elements
(hereafter fo-g). Both, (1) and (3) are deduced from geometrical and
hydrodynamical models, respectively, while (2) is derived directly from
observations. The Fe I 4896.439 A line is found to be the best one to use in
the context of IBW and SB methods. A coherent and consistent period-projection
factor relation (hereafter Pp relation) is derived for this specific spectral
line: p = [0.064 +- 0.020] log P + [1.376 +- 0.023]. This procedure is then
extended to derive dynamic projection factors for any spectral line of any
Cepheid. This Pp relation is an important tool for removing bias in the
calibration of the period-luminosity relation of Cepheids. Moreover, it reveals
a new physical quantity fo-g to investigate in the near future
Immunogenicity and safety of concomitant administration of a measles, mumps and rubella vaccine (M-M-RvaxPro®) and a varicella vaccine (VARIVAX®) by intramuscular or subcutaneous routes at separate injection sites: a randomised clinical trial
<p>Abstract</p> <p>Background</p> <p>When this trial was initiated, the combined measles, mumps and rubella (MMR) vaccine was licensed for subcutaneous administration in all European countries and for intramuscular administration in some countries, whereas varicella vaccine was licensed only for subcutaneous administration. This study evaluated the intramuscular administration of an MMR vaccine (M-M-RvaxPro<sup>®</sup>) and a varicella vaccine (VARIVAX<sup>®</sup>) compared with the subcutaneous route.</p> <p>Methods</p> <p>An open-label randomised trial was performed in France and Germany. Healthy children, aged 12 to18 months, received single injections of M-M-RvaxPro and VARIVAX concomitantly at separate injection sites. Both vaccines were administered either intramuscularly (IM group, <it>n </it>= 374) or subcutaneously (SC group, <it>n </it>= 378). Immunogenicity was assessed before vaccination and 42 days after vaccination. Injection-site erythema, swelling and pain were recorded from days 0 to 4 after vaccination. Body temperature was monitored daily between 0 and 42 days after vaccination. Other adverse events were recorded up to 42 days after vaccination and serious adverse events until the second study visit.</p> <p>Results</p> <p>Antibody response rates at day 42 in the per-protocol set of children initially seronegative to measles, mumps, rubella or varicella were similar between the IM and SC groups for all four antigens. Response rates were 94 to 96% for measles, 98% for both mumps and rubella and 86 to 88% for varicella. For children initially seronegative to varicella, 99% achieved the seroconversion threshold (antibody concentrations of ≥ 1.25 gpELISA units/ml). Erythema and swelling were the most frequently reported injection-site reactions for both vaccines. Most injection-site reactions were of mild intensity or small size (≤ 2.5 cm). There was a trend for lower rates of injection-site erythema and swelling in the IM group. The incidence and nature of systemic adverse events were comparable for the two routes of administration, except varicella-like rashes, which were less frequent in the IM group.</p> <p>Conclusion</p> <p>The immunogenicities of M-M-RvaxPro and VARIVAX administered by the intramuscular route were comparable with those following subcutaneous administration, and the tolerability of the two vaccines was comparable regardless of administration route. Integration of both administration routes in the current European indications for the two vaccines will now allow physicians in Europe to choose their preferred administration route in routine clinical practice.</p> <p>Trial registration</p> <p>ClinicalTrials.gov NCT00432523</p
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