Butterfly Hysteresis and Slow Relaxation of the Magnetization in (Et4N)3Fe2F9: Manifestations of a Single-Molecule Magnet

(Et4N)3Fe2F9 exhibits a butterfly--shaped hysteresis below 5 K when the magnetic field is parallel to the threefold axis, in accordance with a very slow magnetization relaxation in the timescale of minutes. This is attributed to an energy barrier Delta=2.40 K resulting from the S=5 dimer ground state of [Fe2F9]^{3-} and a negative axial anisotropy. The relaxation partly occurs via thermally assisted quantum tunneling. These features of a single-molecule magnet are observable at temperatures comparable to the barrier height, due to an extremely inefficient energy exchange between the spin system and the phonons. The butterfly shape of the hysteresis arises from a phonon avalanche effect.Comment: 18 pages, 5 eps figures, latex (elsart

Selective effect of thiazides on the human osteoblast-like cell line MG-63

Selective effect of thiazides on the human osteoblast-like cell line MG-63. Thiazide diuretics have been shown to decrease bone-loss rate and to improve bone mineral density in patients using this medication. However, the exact role of thiazides on bone cells is still debated. In the present work, we studied whether thiazides could affect the normal features of osteoblasts using the human model cell line MG-63. Hydrochlorothiazide (HCTZ) did not affect cell growth nor DNA synthesis in these cells, yet slightly increased alkaline phosphatase activity in these cells at pharmacologically relevant concentrations. Under similar conditions, HCTZ dose-dependently inhibited 1,25(OH)2D3-induced osteocalcin secretion by these cells (maximal effect, -40 to 50%, P < 0.005). However, HCTZ did not inhibit the basal production of osteocalcin in MG-63 cells (without 1,25(OH)2D3 induction), which was very low to undectable. Two different thiazide derivatives, chlorothiazide and cyclothiazide, and two structurally related sulfonamides with selective inhibition of carbonic anhydrase (Acetazolamide) or hyperglycemic effects (Diazoxide) were also tested. Chlorothiazide (1000 µm) inhibited osteocalcin secretion (-42 ± 12.7%) at doses 10-fold higher than HCTZ (100 µm) while cyclothiazide was effective at doses of 1 µm(-27 ± 3.6%), and hence 100-fold lower than HCTZ, compatible with the relative natriuretic effect in vivo of these compounds. Acetazolamide (10 µm) poorly affected osteocalcin secretion at doses 100-fold higher than those needed in vivo to inhibit carbonic anhydrase. Likewise, Diazoxide (100 µm) poorly affected osteocalcin secretion at doses known to promote its biological effect. Higher doses of acetazolamide and diazoxide induced cell death. Neither Acetazolamide nor Diazoxide affected alkaline phosphatase, whereas chlorothiazide had a weak positive effect on this enzymatic activity. The production of macrophage colony-stimulating factor (M-CSF) was stimulated in the presence of 1,25(OH)2D3 (50nm), TNF-α (2 ng/ml) both in MG-63 cells. HCTZ (25 µm, 24hr of preincubation) did not modify basal M-CSF production and did not reduce the response to 1,25(OH)2D3 alone. In contrast, HCTZ inhibited the response to TNF-α alone (P < 0,05), and also reduced the response to a combination of 1,25(OH)2D3 and TNF-α (P < 0.01). In conclusion, these results indicate that thiazide diuretics show a selective inhibion of osteocalcin secretion and M-CSF production by MG-63 cells unlike structurally related drugs. Therefore, these features may explain, in part, the positive effect of thiazides on bone mineral density

Population structure and growth acclimation of mountain maple along a successional gradient in the southern boreal forest

A range of stands was sampled in the southern boreal forest of eastern Canada to determine the impact of forest development stages and light availability on the dynamics of an abundant understory shrub: mountain maple (Acer spicatum). Mountain maple was studied at both the population and individual stem levels. At the population level, a total of 190 1-m2 quadrats were sampled in five forest types representing a successional gradient (young aspen, mature aspen, mixedwood, shade-tolerant conifer, and old spruce budworm-affected conifer forests). At the individual stem level, a total of 100 stems of different sizes were harvested in a sub-sample of the quadrats. Mountain maple stem biomass, density, and population structure were found to be affected by forest composition, the coniferous forest being the least favourable. At the individual stem level, light availability and stem size were found to have an important impact on stem morphology and growth, suggesting a high level of plasticity in relation to canopy opening. From these results, four developmental phases of mountain maple population dynamics were identified: 1) following a drastic disturbance, a first phase of rapid growth, and potentially intense competition with aspen suckers, when present, takes place; 2) following the development of a closed aspen canopy, the overall density, biomass, and presence of mountain maple in the understory increase; 3) following recruitment of conifer trees into the overstory canopy, mountain maple enters a suppression phase associated with a decrease in light; and 4) following the occurrence of small scale disturbances, mountain maple quickly responds to rapidly dominate the openings, which further ensures its maintenance in the understory

Germline mutations in retinoma patients: Relevance to low-penetrance and low-expressivity molecular basis

PURPOSE: To study phenotype-genotype correlation in patients who have retinoma, which is a benign tumor resembling the post irradiation regression pattern of retinoblastoma (RB). METHODS: We selected patients who had retinoma and positive family history for RB and patients who had retinoma in one eye and either retinoma or RB in the other eye. The study included 22 patients with available DNA: 18 from 11 families and four sporadic cases. DNA was extracted from peripheral blood leukocytes. The RB1 gene was screened by DHPLC and direct sequencing of the promoter and all the exons. RESULTS: We identified 17 occurrences of 11 distinct germline mutations in two sporadic and in 15 familial cases (nine families). The 11 identified mutations were located in exons 1, 10,11,13,14, and 19 to 23. Four of the identified mutations were not previously reported, including g.64407delT, g.153236A&gt;T, g.156743delTCTG, and g.162078delA. Eight out the 11 mutations were truncating and three were nontruncating (missense). There was no correlation between the type of mutation and the number of tumor foci per eye (RB or retinomas). Highly heterogeneous intrafamilial expressivity was observed. CONCLUSIONS: To our knowledge, this study is the largest series of mutations of consecutive retinoma patients. The present data suggest that the type of inherited mutations underlying retinoma is undistinguishable from RB related ones, i.e., largely dominated by truncating mutants. This finding is in contrast with the RB1 genotypic spectrum of mutations associated with low-penetrance RB, i.e., nontruncating mutants. The molecular mechanism underlying low-penetrance and attenuated expressivity (retinomas) appeared to be distinct

Effects of Humidity and Temperature on Burying Beetle (Coleoptera: Silphidae) Survival and Flight

Terrestrial arthropods must prevent lethal desiccation during activity in dry environments. The small size of arthropods and high surface area to volume ratios increase the tremendous challenges to limit desiccation especially at warmer temperatures and lower humiditys. Among the insects, beetles in the family Silphidae include most species with shortened elytra and exposed abdomens. The silphids occur in communities that contain between 5 and 20 closely-related species that use carrion for food and reproduction. In the subfamily Nicrophorinae, burying beetles must locate appropriately sized, recently deceased vertebrates and bury them in the ground before they are discovered and consumed by predators or competitors. This activity requires the capacity for long sustained flights. The largest and most studied Silphidae is the endangered American burying beetle (ABB), Nicrophorus americanus, which is nocturnal and uses the largest carcasses. This study compared field data of activity patterns of the ABB with closely related species in Nebraska and Oklahoma. Laboratory studies of flight were conducted on Nicrophorus orbicollis, a proxy for ABBs, at temperatures between 10oC and 40oC, at three different relative humidity settings (INSERT THESE). The lowest and highest temperatures affected short flight activity while humidity did not. Desiccation rates were tested for three Silphinae and five Necrophorinae with different ecological and morphological traits at 23oC. Water loss rates varied among species and were not tightly linked to subfamily, size, or activity pattern, suggesting that other ecological factors are important for members of the Silphidae. These data are useful for modeling Silphidae niches and niche overlap based on environmental factors. Based on the results, increasing daily temperatures could affect the activity of day-active species, but are unlikely to limit the activity of ABB and other night—active species. Shifts in weather pattern and droughts are likely to affect carrion beetle communities, increasing some species while eliminating others.Entomology & Plant Pathology (MS

Marcé – Fossés des Romains

Le projet de réalisation d’un aérodrome à l’emplacement de la seule partie bien conservée d’un fossé long de 8 km, décrit au siècle dernier comme un retranchement, a suscité une étude préliminaire du site. Un sondage a montré que ce fossé en V, de 15 m environ de largeur, est profond de 5 m et bordé de deux talus résiduels, sensiblement symétriques de 6 m de large. La fouille du remplissage a livré, vers la base, des fragments d’un pichet (xiiie-xive s.). L’étude toponymique et les prospectio..

The constraint equations for the Einstein-scalar field system on compact manifolds

We study the constraint equations for the Einstein-scalar field system on compact manifolds. Using the conformal method we reformulate these equations as a determined system of nonlinear partial differential equations. By introducing a new conformal invariant, which is sensitive to the presence of the initial data for the scalar field, we are able to divide the set of free conformal data into subclasses depending on the possible signs for the coefficients of terms in the resulting Einstein-scalar field Lichnerowicz equation. For many of these subclasses we determine whether or not a solution exists. In contrast to other well studied field theories, there are certain cases, depending on the mean curvature and the potential of the scalar field, for which we are unable to resolve the question of existence of a solution. We consider this system in such generality so as to include the vacuum constraint equations with an arbitrary cosmological constant, the Yamabe equation and even (all cases of) the prescribed scalar curvature problem as special cases.Comment: Minor changes, final version. To appear: Classical and Quantum Gravit

Gasser-Leutwyler coefficients: A progress report

Last year, we reported our first results on the determination of Gasser-Leutwyler coefficients using partially quenched lattice QCD with three flavors of dynamical staggered quarks. We give an update on our progress in determining two of these coefficients, including an exhaustive effort to estimate all sources of systematic error. At this conference, we have heard about algorithmic techniques to reduce staggered flavor symmetry breaking and a method to incorporate staggered flavor breaking into the partially quenched chiral Lagrangian. We comment on our plans to integrate these developments into our ongoing program.Comment: 3 pages, 2 figures, Lattice2002(spectrum

Effects of process conditions on foaming in stirred tanks

International audienceThe effect of impeller speed and type, as well as gas flow rate on the amount of foam generated in a 5L stirred tank has been studied. Foam height was found to increase with increasing impeller speed after a critical impeller speed was reached. It also increased with increasing gas flow rate. The disc turbine creates significantly more foam than the down-pumping hydrofoil for a given tip speed. Scale-up guidance to correctly replicate the amount of foaming in larger scale tank was also investigated. It was found that impeller tip speed was the best scale-up invariant, compared with power per unit volume and the Weber and Froude numbers. It is less clear, however, which is the best scale-up invariant for the gas flow rate; aeration number appears more adapted than the superficial gas velocity or the ratio of gas flow rate to liquid volume, however it does not always correctly replicate the gas-liquid flow regime

Sarrigné – Le bourg

La construction d’une salle des fêtes a provoqué l’exploration et le relevé d’une partie d’un souterrain aménagé, de plan complexe ; plusieurs salles étaient reliées par des conduits percés dans la roche ; deux puits communiquaient avec la surface. Les sondages montrent une occupation médiévale et une réutilisation à l’Époque moderne. Lors des terrassements, quatre tombes rupestres, orientées grossièrement nord-sud, ont été mises au jour. L’une d’elles a ·livré un individu aux membres inférie..