Isochoric thermal conductivity of solid nitrogen

The isochoric thermal conductivity of solid nitrogen has been investigated on four samples of different densities in the temperature interval from 20 K to the onset of melting. In alfa-N2 the isochoric thermal conductivity exhibits a dependence weaker than 1/T; in beta-N2 it increases slightly with temperature. The experimental results are discussed within a model in which the heat is transported by low-frequency phonons or by "diffusive" modes above the mobility boundary. The growth of the thermal conductivity in beta-N2 is attributed to the decreasing "rotational" component of the total thermal resistance, which occurs as the rotational correlations between the neighboring molecules become weaker.Comment: Postscript 12 pages, 3 figures, 1 table. To be published in 200

EVALUATION OF DENTAL HEALTH EDUCATION IN A SCHOOL DENTAL CARE PROGRAM

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65546/1/j.1752-7325.1978.tb03715.x.pd

Amélioration de la qualité microbiologique des eaux de surface dans un bassin versant, dans une zone densément peuplée : scénario des coûts et effets

Colloque avec actes et comité de lecture. Internationale.International audienc

Transport Properties of the One Dimensional Ferromagnetic Kondo Lattice Model : A Qualitative Approach to Oxide Manganites

The transport properties of the ferromagnetic Kondo lattice model in one dimension are studied via bosonization methods. The antiferromagnetic fluctuations, which normally appear because of the RKKY interactions, are explicitly taken into account as a direct exchange between the ``core'' spins. It is shown that in the paramagnetic regime with the local antiferromagnetic fluctuations, the resistivity decays exponentially as the temperature increases while in the ferromagnetic regime the system is an almost perfect conductor. %A non-perturbative description of localized spin polarons %in the paramagnetic region is obtained. The effect of a weak applied field is discussed to be reduced to the case of the ferromagnetic state leading to band splitting. The qualitative relevance of the results for the problem of the Oxide Manganites is emphasized.Comment: 4 pages, REVTe

Absence of the proapoptotic Bax protein extends fertility and alleviates age-related health complications in female mice

The menopausal transition in human females, which is driven by a loss of cyclic ovarian function, occurs around age 50 and is thought to underlie the emergence of an array of health problems in aging women. Although mice do not undergo a true menopause, female mice exhibit ovarian failure long before death because of chronological age and subsequently develop many of the same age-associated health complications observed in postmenopausal women. Here we show in mice that inactivation of the proapoptotic Sax gene, which sustains ovarian lifespan into advanced age, extends fertile potential and minimizes many age-related health problems, including bone and muscle loss, excess fat deposition, alopecia, cataracts, deafness, increased anxiety, and selective attention deficit. Further, ovariectomy studies show that the health benefits gained by aged females from Bax deficiency reflect a complex interplay between ovary-dependent and -independent pathways. Importantly, and contrary to popular belief, prolongation of ovarian function into advanced age by Bax deficiency did not lead to an increase in tumor incidence. Thus, the development of methods for postponing ovarian failure at menopause may represent an attractive option for improving the quality of life in aging females. © 2007 by The National Academy of Sciences of the USA

Successful enteral nutrition in the treatment of esophagojejunal fistula after total gastrectomy in gastric cancer patients

<p>Abstract</p> <p>Background</p> <p>Esophagojejunal fistula is a serious complication after total gastrectomy in gastric cancer patients. This study describes the successful conservative management in 3 gastric cancer patients with esophagojejunal fistula after total gastrectomy using total enteral nutrition.</p> <p>Methods</p> <p>Between January 2004 to December 2008, 588 consecutive patients with a proven diagnosis of gastric cancer were taken to the operation room to try a curative treatment. Of these, 173 underwent total gastrectomy, 9 of them had esophagojejunal fistula (5.2%). In three selected patients a trans-anastomotic naso-enteral feeding tube was placed under fluoroscopic vision when the fistula was clinically detected and a complete polymeric enteral formula was used.</p> <p>Results</p> <p>The complete closing of the esophagojejunal fistula was obtained in day 8, 14 and 25 respectively.</p> <p>Conclusion</p> <p>In some selected cases it is possible to make a successful enteral nutrition using a feeding tube distal to the leak area inserted with the help of fluoroscopic vision. The specialized management of a gastric surgery unit and nutritional therapy unit are highlighted.</p

Magnetoresistance in Mn pyrochlore: electrical transport in a low carrier density ferromagnet

We discuss magnetotransport in a low density electron gas coupled to spin fluctuations near and above a ferromagnetic transition. Provided the density is low enough ($n \lesssim 1/\xi^{3}(T)$, with $\xi(T)$ the ferromagnetic correlation length), spin polarons form in an intermediate temperature regime above $T_c$. Both in the spin polaron regime, and in the itinerant regime nearer $T_c$, the magnetoresistance is large. We propose that this provides a good model for ``colossal'' magnetoresistance in the pyrochlore Tl$_{2-x}$Sc$_x$Mn$_2$O$_7$, fundamentally different from the mechanism in the perovskite manganites such as La$_{1-x}$Sr$_x$MnO$_3$.Comment: 4 pages, LaTex, + 3 figure

Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

We report on the optical properties of undoped single crystal LaMnO_3, the parent compound of the colossal magneto-resistive manganites. Near-Normal incidence reflectance measurements are reported in the frequency range of 20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity, s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance data. The far-infrared spectrum of s_1(w) displays the infrared active optical phonons. We observe a shift of several of the phonon to high frequencies as the temperature is lowered through the Neel temperature of the sample (T_N = 137 K). The high-frequency s_1(w) is characterized by the onset of absorption near 1.5 eV. This energy has been identified as the threshold for optical transitions across the Jahn-Teller split e_g levels. The spectral weight of this feature increases in the low-temperature state. This implies a transfer of spectral weight from the UV to the visible associated with the paramagnetic to antiferromagnetic state. We discuss the results in terms of the double exchange processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure

Calculation of Densities of States and Spectral Functions by Chebyshev Recursion and Maximum Entropy

We present an efficient algorithm for calculating spectral properties of large sparse Hamiltonian matrices such as densities of states and spectral functions. The combination of Chebyshev recursion and maximum entropy achieves high energy resolution without significant roundoff error, machine precision or numerical instability limitations. If controlled statistical or systematic errors are acceptable, cpu and memory requirements scale linearly in the number of states. The inference of spectral properties from moments is much better conditioned for Chebyshev moments than for power moments. We adapt concepts from the kernel polynomial approximation, a linear Chebyshev approximation with optimized Gibbs damping, to control the accuracy of Fourier integrals of positive non-analytic functions. We compare the performance of kernel polynomial and maximum entropy algorithms for an electronic structure example.Comment: 8 pages RevTex, 3 postscript figure