Serum inhibin B as a marker of spermatogenesis

Inhibin B is produced by Sertoli cells, provides negative feedback on FSH secretion, and may prove to be an important marker for the functioning of seminiferous tubules. The purpose of the present study was to examine the relationship between the spermatogenic function of the testis of subfertile men and the plasma concentrations of inhibin B and FSH. These parameters were estimated in a group of 218 subfertile men. Serum inhibin B levels were closely correlated with the serum FSH levels (r = -0.78, P < 0.001), confirming the role of inhibin B as feedback signal for FSH production. The spermatogenic function of the testis was evaluated by determining testicular volume and total sperm count. Inhibin B levels were significantly correlated with the total sperm count and testicular volume (r = 0.54 and r = 0.63, respectively; P < 0.001). Testicular biopsies were obtained in 22 of these men. Inhibin B was significantly correlated with the biopsy score (r = 0.76, P < 0.001). Receiver operating characteristic analysis revealed a diagnostic accuracy of 95% for differentiating competent from impaired spermatogenesis for inhibin B, whereas for FSH, a value of 80% was found. We conclude that inhibin B is the best available endocrine marker of spermatogenesis in subfertile men

Energy landscape, two-level systems and entropy barriers in Lennard-Jones clusters

We develop an efficient numerical algorithm for the identification of a large number of saddle points of the potential energy function of Lennard- Jones clusters. Knowledge of the saddle points allows us to find many thousand adjacent minima of clusters containing up to 80 argon atoms and to locate many pairs of minima with the right characteristics to form two-level systems (TLS). The true TLS are singled out by calculating the ground-state tunneling splitting. The entropic contribution to all barriers is evaluated and discussed.Comment: 4 pages, RevTex, 2 PostScript figure

Strong normal-incidence infrared absorption in self-organized InAs/InAlAs quantum dots grown on InP(001)

International audienceInAs self-assembled quantum dots in InAlAs matrix grown on InP001 substrates have been fabricated using Stranski-Krastanov growth mode. A strong in-plane polarized intraband absorption in the 10.6-20 m wavelength region has been observed and ascribed to a transition from the ground electron state to an excited state confined in the layer plane along the 110 direction. The absorption at normal-incidence reaches 7.8% for ten layers of n-doped quantum dots. The oscillator strength of the intraband transition is comparable to that achieved in quantum wells for a conduction band intersubband transition. The dependence of the intraband absorption on carrier concentration and temperature suggests a quantum-wire type confinement potential

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Considerable concern has been raised in recent publications that oestrogen-lihe compounds in either food or the environment cause adverse effects on reproductive health. There is clear evidence that reproductive disruption in wildlife may be caused by environmental pollutants and more specifÌcally by endocrine-disrupting compounds. The increase in the incidence of disorders of the male reproductive tract (e.g. testicular cancer, cryptorchidisn, hypospadias) and the possible decline o[ sperm quality led to the hypothesis in 1993 that the reported increases stem from fetal or neonatal exposure of the developing male to oestrogens. Cryptorchidism, hypospadias, testicular cancer and poor semen quality have also been proposed to be symptoms of one underlying cause, the testicular dysgenesis syndrome, which may deveÌop during fetal life under the influence of environmental factors. However, there is only circumstantial evidence in humans that exposure to endocrine disrupters, especially diethylstilbestrol, during pregnancy causes problems of reproductive health. Oestrogenlike effects have been reported for a variety of naturalÌy occurring oestrogens (so-called phytoestrogens) and for numerous synthetic compounds. The critical issue is whether there are suflìciently high levels of endocrine disrupters in the ambient environment to exert adverse health effects on the general populatio

Structural Probe of a Glass Forming Liquid: Generalized Compressibility

We introduce a new quantity to probe the glass transition. This quantity is a linear generalized compressibility which depends solely on the positions of the particles. We have performed a molecular dynamics simulation on a glass forming liquid consisting of a two component mixture of soft spheres in three dimensions. As the temperature is lowered (or as the density is increased), the generalized compressibility drops sharply at the glass transition, with the drop becoming more and more abrupt as the measurement time increases. At our longest measurement times, the drop occurs approximately at the mode coupling temperature $T_C$. The drop in the linear generalized compressibility occurs at the same temperature as the peak in the specific heat. By examining the inherent structure energy as a function of temperature, we find that our results are consistent with the kinetic view of the glass transition in which the system falls out of equilibrium. We find no size dependence and no evidence for a second order phase transition though this does not exclude the possibility of a phase transition below the observed glass transition temperature. We discuss the relation between the linear generalized compressibility and the ordinary isothermal compressibility as well as the static structure factor.Comment: 18 pages, Latex, 26 encapsulated postscript figures, revised paper is shorter, to appear in Phys. Rev.

Baffin Island Expedition, 1953: A Preliminary Field Report

Contains description and brief summaries of results of the second Baffin Island Expedition of the Arctic Institute of North America, May-Sept. 1953. The 13-man party carried out a program in the Penny Highland region of Cumberland Peninsula, centering on Pangnirtung Pass. Glaciological work on the Penny Icecap and Highway Glacier included studies of glacier physics, seismic work, and meteorological observations on bedrock geology and structure are given. Corrie formation and the geomorphology of Pangnirtung Pass were studied. Specimens of local fauna were collected and biological studies of some species were made. Comparisons of the vegetation of Penny Highland and East and North Greenland were made through extensive plant collections. Eight peaks were climbed and their altitudes determined. A list of 17 new names approved by the Canadian Board on Geographical Names is appended

Mean-atom-trajectory model for the velocity autocorrelation function of monatomic liquids

We present a model for the motion of an average atom in a liquid or supercooled liquid state and apply it to calculations of the velocity autocorrelation function $Z(t)$ and diffusion coefficient $D$. The model trajectory consists of oscillations at a distribution of frequencies characteristic of the normal modes of a single potential valley, interspersed with position- and velocity-conserving transits to similar adjacent valleys. The resulting predictions for $Z(t)$ and $D$ agree remarkably well with MD simulations of Na at up to almost three times its melting temperature. Two independent processes in the model relax velocity autocorrelations: (a) dephasing due to the presence of many frequency components, which operates at all temperatures but which produces no diffusion, and (b) the transit process, which increases with increasing temperature and which produces diffusion. Because the model provides a single-atom trajectory in real space and time, including transits, it may be used to calculate all single-atom correlation functions.Comment: LaTeX, 8 figs. This is an updated version of cond-mat/0002057 and cond-mat/0002058 combined Minor changes made to coincide with published versio

Inhibition of metal dusting using thermal spray coatings and laser treatment

Alloy 600 and Alloy 800H are susceptible to metal dusting. Both alloys were thermally sprayed with two different corrosion resistant coatings: Ni50Cr and Ni31Cr11Al0.6Y. Laser remelting was used to enhance further the effectiveness of these coatings to resist metal dusting by eliminating interconnected porosity and improving coating adhesion. Uncoated, coated and laser-treated coated samples of Alloy 600 and Alloy 800H were exposed to a mixed gas atmosphere (20% H2, 80% CO at 650°C). Samples were examined in plan and cross-section using optical and scanning electron microscopy, electron probe microanalysis and X-ray diffraction. The extent of carbon deposition was tracked by mass difference measurements at intervals during exposure. The thermally sprayed coatings enhanced metal dusting resistance by acting as physical barriers to carbon ingress. The NiCrAlY coating performed well on both substrates. The NiCr coating itself underwent metal dusting and spalled from Alloy 800H due partly to CTE mis-match stresses. Laser treatment of both coatings successfully eliminated interconnected porosity and hence enhanced metal dusting resistance