Metastable states of a ferromagnet on random thin graphs

We calculate the mean number of metastable states of an Ising ferromagnet on random thin graphs of fixed connectivity c. We find, as for mean field spin glasses that this mean increases exponentially with the number of sites, and is the same as that calculated for the +/- J spin glass on the same graphs. An annealed calculation of the number of metastable states of energy E is carried out. For small c, an analytic result is obtained. The result is compared with the one obtained for spin glasses in order to discuss the role played by loops on thin graphs and hence the effect of real frustration on the distribution of metastable states.Comment: 15 pages, 3 figure

Status of the ILC Main Linac BPM R&D

An introduction and the status of R&D activities for a high-resolution, "cold" beam position monitor (BPM) and the related read-out electronics are discussed. Two different BPM detector concepts, to be attached to the SC quadrupole and located inside the ILC cryomodule, are currently under investigation: A resonant dipole-mode cavity-style BPM pickup, developed at Fermilab, and a re-entrant resonant coaxial waveguide BPM, designed by CEA-Saclay. While the 1.5 GHz dipole-mode cavity BPM is still in the R&D phase, the re-entrant BPM has already passed first beam tests, including its read-out system. Furthermore, the LAPP group is developing radiation tolerant digital read-out systems, which are tested at the CLIC test facility (CTF).Comment: LCWS / ILC08 conference contribution, 6 pages, 6 figure

Multi-latin squares

A multi-latin square of order $n$ and index $k$ is an $n\times n$ array of multisets, each of cardinality $k$, such that each symbol from a fixed set of size $n$ occurs $k$ times in each row and $k$ times in each column. A multi-latin square of index $k$ is also referred to as a $k$-latin square. A $1$-latin square is equivalent to a latin square, so a multi-latin square can be thought of as a generalization of a latin square. In this note we show that any partially filled-in $k$-latin square of order $m$ embeds in a $k$-latin square of order $n$, for each $n\geq 2m$, thus generalizing Evans' Theorem. Exploiting this result, we show that there exist non-separable $k$-latin squares of order $n$ for each $n\geq k+2$. We also show that for each $n\geq 1$, there exists some finite value $g(n)$ such that for all $k\geq g(n)$, every $k$-latin square of order $n$ is separable. We discuss the connection between $k$-latin squares and related combinatorial objects such as orthogonal arrays, latin parallelepipeds, semi-latin squares and $k$-latin trades. We also enumerate and classify $k$-latin squares of small orders.Comment: Final version as sent to journa

Physical mechanisms involved in grooved flat heat pipes: experimental and numerical analyses

International audienceAn experimental database, obtained with flat plate heat pipes (FPHP) with longitudinal grooves is presented. The capillary pressure measured by confocal microscopy and the temperature field in the wall are presented in various experimental conditions (vapour space thickness, filing ratio, heat transfer rate, tilt angle, fluid). Coupled hydrodynamic and thermal models are developed. Experimental results are compared to results of numerical models. Physical mechanisms involved in grooved heat pipes are discussed, including the boiling limit and the effect of the interfacial shear stress. Finally, recommendations for future experimental and theoretical research to increase the knowledge on FPHP are discussed

The rodent uterotrophic assay: Critical protocol features, studies with nonyl phenols, and comparison with a yeast estrogenicity assay

The major protocol features of the immature rat uterotrophic assay have been evaluated using a range of reference chemicals. The protocol variables considered include the selection of the test species and route of chemical administration, the age of the test animals, the maintenance diet used, and the specificity of the assay for estrogens. It is concluded that three daily oral administrations of test chemicals to 21- to 22-day-old rats, followed by determination of absolute uterus weights on the fourth day, provide a sensitive and toxicologically relevant in vivo estrogenicity assay. Rats are favored over mice for reasons of toxicological practice, but the choice of test species is probably not a critical protocol variable, as evidenced by the similar sensitivity of rats and mice to the uterotrophic activity of methoxychlor. Vaginal opening is shown to be a useful, but nondefinitive, adjunct to the uterotrophic assay. The ability of test chemicals to reduce or abolish the uterotrophic response of estradiol is suggested to provide a useful extension of the uterotrophic assay for the purpose of detecting antiestrogens. The results of a series of studies on the environmental estrogen nonyl phenol (NP), and its linear isomer n -nonyl phenol, confirm that branching of the aliphatic side chain is important for activity. 17beta-Desoxyestradiol is shown to be of similar activity to estradiol in the uterotrophic assay and is suggested to represent the "parent" estrogen of NP. Benzoylation of NP and 17-desoxyestradiol did not affect their uterotrophic activity, in contrast to the enhancing effect of benzoylation on estradiol. Selected chemicals shown to be active in the immature rat uterotrophic assay were also evaluated in an in vitro yeast human estrogen receptor transactivation assay. Most of the chemicals gave similar qualitative responses to those seen in the uterotrophic assay, and the detection of the estrogen methoxychlor by the yeast assay evidenced a degree of intrinsic metabolic competence. However, the assay had a reduced ability (compared to rodents) to hydrolyze the benzoate ester of estradiol, and the estrogenic benzoate derivative of NP was not active in the yeast assay. These last results indicate that current metabolic deficiencies of in vitro estrogenicity assays will limit the value of negative data for the immediate future. The results described illustrate the intrinsic complexity of evaluating chemicals for estrogenic activities and confirm the need for rigorous attention to experimental design and criteria for assessing estrogenic activity

Investigation of evaporation and condensation processes specific to grooved flat heat pipes

International audienceTemperature and liquid-vapor interface measurements obtained with a flat plate heat pipe (FPHP) in various experimental conditions are presented. The grooved FPHP is made of copper. The results are compared to a thermal model, developed in a previous work, in which heat conduction in the FPHP wall as well as evaporation and condensation heat transfer phenomena are taken into account. The model depends on the shape of the liquid-vapor interface in the grooves and on the fins at the condenser. A good agreement is found between the evaporation model and the experimental data. However the results of the condensation model overestimate the heat transfer coefficient, due to a bad estimation of the condensate film on the fins. Experimental measurements obtained with a second FPHP made of silicon are used to analyze the shape of this film. For both evaporation and condensation models, the results show a strong influence of the accommodation coefficient

Combined effects of the filling ratio and the vapour space thickness on the performance of a flat plate heat pipe

International audienceAn experimental study of a flat plate heat pipe (FPHP) is presented. Temperature fields in the FPHP are measured for different filling ratios, heat fluxes and vapour space thicknesses. The system is hermetically sealed with a transparent plate for meniscus curvature radius observations by confocal microscopy. Experimental results show that the liquid distribution in the FPHP - and thus its thermal performance - depends strongly on both the filling ratio and the vapour space thickness. A small vapour space thickness induces liquid retention and thus reduces the thermal resistance of the system. Nevertheless, the vapour space thickness influences the level of the meniscus curvature radii in the grooves and hence reduces the maximum capillary pressure. As a result, it has to be carefully optimised to improve the performance of the FPHP. In all the cases, the optimum filling is in the range one to two times the total volume of the grooves. A theoretical approach, in non working conditions, has been developed to model the distribution of the liquid inside the FPHP in function of the filling ratio and the vapour space thickness

Analysis of longitudinal bunching inan FEL driven two-beam accelerator

Recent experiments [1] have explored the use of a free-electron laser (FEL) as a buncher for a microwave two-beam accelerator, and the subsequent driving of a standing-wave rf output cavity. Here we present a deeper analysis of the longitudinal dynamics of the electron bunches as they are transported from the end of the FEL and through the output cavity. In particular, we examine the effect of the transport region and cavity aperture to filter the bunched portion of the beam. [1] T. Lefevre, et. al., Phys. Rev. Lett. 84 (2000), 1188.Comment: 3 pages, 8 figures. Submitted to XX Int'l LINAC Conferenc