Density Fluctuations in an Electrolyte from Generalized Debye-Hueckel Theory

Near-critical thermodynamics in the hard-sphere (1,1) electrolyte is well described, at a classical level, by Debye-Hueckel (DH) theory with (+,-) ion pairing and dipolar-pair-ionic-fluid coupling. But DH-based theories do not address density fluctuations. Here density correlations are obtained by functional differentiation of DH theory generalized to {\it non}-uniform densities of various species. The correlation length $\xi$ diverges universally at low density $\rho$ as $(T\rho)^{-1/4}$ (correcting GMSA theory). When $\rho=\rho_c$ one has $\xi\approx\xi_0^+/t^{1/2}$ as $t\equiv(T-T_c)/T_c\to 0+$ where the amplitudes $\xi_0^+$ compare informatively with experimental data.Comment: 5 pages, REVTeX, 1 ps figure included with epsf. Minor changes, references added. Accepted for publication in Phys. Rev. Let

The cDNA-deduced primary structure of human sex hormone-binding globulin and location of its steroid-binding domain

AbstractWe have sequenced a cDNA for sex hormone-binding globulin (SHBG) isolated from a phage λgt 11 human liver cDNA library. The library was screened with a radiolabeled rat androgen-binding protein (ABP) cDNA, and the abundance of SHBG cDNAs was 1 in 750 000 plaques examined. The largest human SHBG cDNA (1194 base-pairs) contained a reading frame for 381 amino acids. This comprised 8 amino acids of a signal peptide followed by 373 residues starting with the known NH2-terminal sequence of human SHBG, and ending with a termination codon. The predicted polypeptide Mr of SHBG is 40 509, and sites of attachment of one O-linked (residue 7) and two N-linked oligosaccharide (residues 351 and 367) chains were identified. Purified SHBG was photoaffinity-labeled with Δ6-[3H]testosterone and cleaved with trypsin. The labeled tryptic fragment was isolated by reverse-phase HPLC, and its NH2-terminal sequence was determined. The results suggest that a portion of the steroid-binding domain of SHBG is located between residue 296 and the 35 predominantly hydrophilic residues at the C-terminus of the protein

Exciton Spin Dynamics in Semiconductor Quantum Wells

In this paper we will review Exciton Spin Dynamics in Semiconductor Quantum Wells. The spin properties of excitons in nanostructures are determined by their fine structure. We will mainly focus in this review on GaAs and InGaAs quantum wells which are model systems.Comment: 55 pages, 27 figure

Balancing end-to-end budgets of the Georges Bank ecosystem

Author Posting. © Elsevier, 2007. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Progress In Oceanography 74 (2007): 423-448, doi:10.1016/j.pocean.2007.05.003.Oceanographic regimes on the continental shelf display a great range in the time scales of physical exchange, biochemical processes and trophic transfers. The close surface-to-seabed physical coupling at intermediate scales of weeks to months means that the open ocean simplification to a purely pelagic food web is inadequate. Top-down trophic depictions, starting from the fish populations, are insufficient to constrain a system involving extensive nutrient recycling at lower trophic levels and subject to physical forcing as well as fishing. These pelagic-benthic interactions are found on all continental shelves but are particularly important on the relatively shallow Georges Bank in the northwest Atlantic. We have generated budgets for the lower food web for three physical regimes (well mixed, transitional and stratified) and for three seasons (spring, summer and fall/winter). The calculations show that vertical mixing and lateral exchange between the three regimes are important for zooplankton production as well as for nutrient input. Benthic suspension feeders are an additional critical pathway for transfers to higher trophic levels. Estimates of production by mesozooplankton, benthic suspension feeders and deposit feeders, derived primarily from data collected during the GLOBEC years of 1995-1999, provide input to an upper food web. Diets of commercial fish populations are used to calculate food requirements in three fish categories, planktivores, benthivores and piscivores, for four decades, 1963-2002, between which there were major changes in the fish communities. Comparisons of inputs from the lower web with fish energetic requirements for plankton and benthos indicate that we obtained reasonable agreement for the last three decades, 1973 to 2002. However, for the first decade, the fish food requirements were significantly less than the inputs. This decade, 1963-1972, corresponds to a period characterized by a strong Labrador Current and lower nitrate levels at the shelf edge, demonstrating how strong bottom-up physical forcing may determine overall fish yields.The research was done under the aegis of the U.S.-GLOBEC Northwest Atlantic Georges Bank Study, a program sponsored jointly by the U.S. National Science Foundation and the U.S. National Oceanic and Atmospheric Administration. We acknowledge NOAA-CICOR award NA17RJ1233 (J.H. Steele), NSF awards OCE0217399 (D.J. Gifford), OCE0217122 (J.J. Bisagni) and OCE0217257 (M.E. Sieracki). W.T. Stockhausen was supported by the NOAA Sponsored Coastal Ocean Research Program