Opacity of hot, highly compressed hydrogen Final report

Ballistic piston compressor used to study opacity of hot highly compressed hydroge

The maximum density droplet to lower density droplet transition in quantum dots

We show that, Landau level mixing in two-dimensional quantum dot wave functions can be taken into account very effectively by multiplying the exact lowest Landau level wave functions by a Jastrow factor which is optimized by variance minimization. The comparison between exact diagonalization and fixed phase diffusion Monte Carlo results suggests that the phase of the many-body wave functions are not affected much by Landau level mixing. We apply these wave functions to study the transition from the maximum density droplet state (incipient integer quantum Hall state with angular momentum L=N(N-1)/2) to lower density droplet states (L>N(N-1)/2).Comment: 8 pages, 5 figures, accepted for publication in Phys. Rev.

L'Expressió al testicle de la proteïna transportadora d'esteroides sexuals humana (SHBG) té lloc a les cèl·lules germinals i no a les cèl·lules de Sertoli

El gen de la proteïna transportadora d'esteroides sexuals humana (hSHBG) conté dues unitats de transcripció diferents. Una d'aquestes unitats de transcripció fa aproximadament 4,3 kb, i codifica un precursor polipeptídic que és processat i secretat pels hepatòcits, i que donarà lloc a la SHBG plasmàtica. La seqüència promotora humana d'aquesta unitat de transcripció és diferent de la seqüència dels promotors dels altres mamífers que expressen el gen de la SHBG a les cèll. ules de Sertoli. Concretament, el promotor humà de la SHBG conté un lloc d'unió per a uns factors de transcripció anomenats USF, que s'uneixen al promotor i inhibeixen la seva expressió a les cèll. ules de Sertoli. Tot i que el gen de la SHBG humana no s'expressa a les cèll. ules de Sertoli, es poden detectar transcrits per a la SHBG al testicle humà. Aquests transcrits contenen un exó 1 alternatiu, es troben a les cèll. ules germinals i són producte d'una altra unitat de transcripció que conté una regió promotora que es troba a unes 2 kb de la primera regió promotora. Els transcrits d'aquesta segona regió promotora codifiquen una isoforma de la SHBG que és uns 5 kDa més petita que la SHBG plasmàtica. Aquesta isoforma de la SHBG s'acumula als espermatozoides entre la membrana exterior de l'acrosoma i la membrana plasmàtica, i s'allibera al medi durant la reacció de capacitació. Aquestes diferències tan importants en l'expressió del gen de la SHBG al testicle entre l'humà i els altres mamífers ens obliguen a reconsiderar la funció de la SHBG en el testicle en relació a la reproducció masculina.The human sex hormone binding globulin (SHBG) gene contains at least two transcription units. A 4.3 kb human SHBG transcription unit encodes the precursor polypeptide, which is processed and secreted by hepatocytes as plasma SHBG. The proximal promoter of this transcription unit differs from the corresponding sequence in other mammals, in which it is also expressed in Sertoli cells. In particular, its proximal promoter sequence contains a binding-site for USF transcription factors that represses its activity in Sertoli cells. Although human SHBG is not expressed in Sertoli cells, human SHBG transcripts containing an alternative exon 1 sequence are present in testicular germ cells. These are the products of an ~8 kb human SHBG transcription unit, and they appear to encode an SHBG isoform that is 4-5 kDa smaller than plasma SHBG. This sperm SHBG isoform accumulates between the outer acrosomal membrane and the sperm plasma membrane, and it is released during the capacitation reaction. These remarkable differences in the expression of human SHBG in the testis, when compared to other mammals, force us to reconsider the functional significance of SHBG expression in the testis in relation to male reproduction

Dilute Bose gases interacting via power-law potentials

Neutral atoms interact through a van der Waals potential which asymptotically falls off as r^{-6}. In ultracold gases, this interaction can be described to a good approximation by the atom-atom scattering length. However, corrections arise that depend on the characteristic length of the van der Waals potential. We parameterize these corrections by analyzing the energies of two- and few-atom systems under external harmonic confinement, obtained by numerically and analytically solving the Schrodinger equation. We generalize our results to particles interacting through a longer-ranged potential which asymptotically falls off as r^{-4}.Comment: 7 pages, 4 figure

Morality, responsibility and risk: Gay men and proximity to HIV

No abstract available

Few-body resonances of unequal-mass systems with infinite interspecies two-body s-wave scattering length

Two-component Fermi and Bose gases with infinitely large interspecies s-wave scattering length $a_s$ exhibit a variety of intriguing properties. Among these are the scale invariance of two-component Fermi gases with equal masses, and the favorable scaling of Efimov features for two-component Bose gases and Bose-Fermi mixtures with unequal masses. This paper builds on our earlier work [D. Blume and K. M. Daily, arXiv:1006.5002] and presents a detailed discussion of our studies of small unequal-mass two-component systems with infinite $a_s$ in the regime where three-body Efimov physics is absent. We report on non-universal few-body resonances. Just like with two-body systems on resonance, few-body systems have a zero-energy bound state in free space and a diverging generalized scattering length. Our calculations are performed within a non-perturbative microscopic framework and investigate the energetics and structural properties of small unequal-mass two-component systems as functions of the mass ratio $\kappa$, and the numbers $N_{1}$ and $N_2$ of heavy and light atoms. For purely attractive Gaussian two-body interactions, we find that the $(N_1,N_2)=(2,1)$ and $(3,1)$ systems exhibit three-body and four-body resonances at mass ratios $\kappa = 12.314(2)$ and 10.4(2), respectively. The three- and four-particle systems on resonance are found to be large. This suggests that the corresponding wave function has relatively small overlap with deeply-bound dimers, trimers or larger clusters and that the three- and four-body systems on resonance have a comparatively long lifetime. Thus, it seems feasible that the features discussed in this paper can be probed experimentally with present-day technology.Comment: 17 pages, 17 figure

Nutrient uptake by soybeans on two Iowa soils

Although the soybean was introduced into the United States in 1804, it is only recently that its production has increased to the point where as a cash-grain crop it ranks fourth in the United States and second in the Midwest. It is perhaps owing to the relatively new status of the soybean as an important crop that the soil fertility requirements are not as yet well understood. Notwithstanding the fact that soybean yields increase with the fertility level of the soil, experiments in the Midwest have shown in general that soybeans do not give the profitable response to direct application of fertilizer that is obtained with corn. The yield increases produced by direct application of fertilizers are comparatively small and unpredictable. This behavior may result from plant characteristics that have been classified as feeding power or it may result from a lack of knowledge of the plant in relation to its environment so that advantage is not taken of the proper means to bring about a profitable increase in yield from fertilizer application. Regarding\u27 the latter point, Norman (20) has suggested that information on the nutritional needs of the plant during its various stages of growth might be of considerable value in the experimental approach to the soil fertility problems of the soybean. To obtain such information for soybeans grown in the field on two Iowa soils differing widely in fertility level was the primary object of the present investigation