Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase.

Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS

Gas Requirements in Pressurized Transfer of Liquid Hydrogen

Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper

The Kinetic Interpretation of the DGLAP Equation, its Kramers-Moyal Expansion and Positivity of Helicity Distributions

According to a rederivation - due to Collins and Qiu - the DGLAP equation can be reinterpreted (in leading order) in a probabilistic way. This form of the equation has been used indirectly to prove the bound $|\Delta f(x,Q)| < f(x,Q)$ between polarized and unpolarized distributions, or positivity of the helicity distributions, for any $Q$. We reanalize this issue by performing a detailed numerical study of the positivity bounds of the helicity distributions. To obtain the numerical solution we implement an x-space based algorithm for polarized and unpolarized distributions to next-to-leading order in $\alpha_s$, which we illustrate. We also elaborate on some of the formal properties of the Collins-Qiu form and comment on the underlying regularization, introduce a Kramers-Moyal expansion of the equation and briefly analize its Fokker-Planck approximation. These follow quite naturally once the master version is given. We illustrate this expansion both for the valence quark distribution $q_V$ and for the transverse spin distribution $h_1$.Comment: 38 pages, 27 figures, Dedicated to Prof. Pierre Ramond for his 60th birthda

Solving for Micro- and Macro- Scale Electrostatic Configurations Using the Robin Hood Algorithm

We present a novel technique by which highly-segmented electrostatic configurations can be solved. The Robin Hood method is a matrix-inversion algorithm optimized for solving high density boundary element method (BEM) problems. We illustrate the capabilities of this solver by studying two distinct geometry scales: (a) the electrostatic potential of a large volume beta-detector and (b) the field enhancement present at surface of electrode nano-structures. Geometries with elements numbering in the O(10^5) are easily modeled and solved without loss of accuracy. The technique has recently been expanded so as to include dielectrics and magnetic materials.Comment: 40 pages, 20 figure

QCD at Photon Colliders

The novel possibilities of probing the photon structure and high energy limit of QCD at photon colliders are summarised. We discuss the photon structure function $F_2^{\gamma}(x,Q^2)$, the gluon distribution in the photon and the spin dependent structure function $g_1^{\gamma}(x,Q^2)$ of the photon and emphasise advantages of the photon colliders for measuring these quantities. The possibility of probing the QCD pomeron and odderon in $\gamma\gamma$ and $e \gamma$ collisions is also described.Comment: 14 pages with 3 postscript figures included, introductory talk given at the International Workshop on High Energy Photon Colliders, 14th - 17th June 2000, DESY, Hamburg, German

Resummed QCD Power Corrections to Nuclear Shadowing

We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken $x$-, $Q^2$- and $A$-dependence of nuclear shadowing in $F_2^A(x,Q^2)$ and the nuclear modifications to $F_L^A(x,Q^2)$, obtained in terms of the QCD factorization approach, are consistent with the existing data. We demonstrate that the low-$Q^2$ behavior of these data and the measured large longitudinal structure function point to a critical role for the power corrections when compared to other theoretical approaches.Comment: 4 pages, 3 figures, uses RevTeX 4. As published in Phys.Rev.Let

Uncertainties of the CJK 5 Flavour LO Parton Distributions in the Real Photon

Radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real, unpolarized photon, calculated in the CJK model being an improved realization of the CJKL approach, have been recently presented. The results were obtained through a global fit to the experimental F2^gamma data. In this paper we present, obtained for the very first time in the photon case, an estimate of the uncertainties of the CJK parton distributions due to the experimental errors. The analysis is based on the Hessian method which was recently applied in the proton parton structure analysis. Sets of test parametrizations are given for the CJK model. They allow for calculation of its best fit parton distributions along with F2^gamma and for computation of uncertainties of any physical value depending on the real photon parton densities. We test the applicability of the approach by comparing uncertainties of example cross-sections calculated in the Hessian and Lagrange methods. Moreover, we present a detailed analysis of the chi^2 of the CJK fit and its relation to the data. We show that large chi^2/DOF of the fit is due to only a few of the experimental measurements. By excluding them chi^2/DOF approx 1 can be obtained.Comment: 28 pages, 8 eps figures, 2 Latex figures; FORTRAN programs available at http://www.fuw.edu.pl/~pjank/param.html; table 10, figure 10 and section 6 correcte

Gender Differences in Attitudes Toward Animal Research

Although gender differences in attitudes toward animal research have been reported in the literature for some time, exploration into the nature of these differences has received less attention. This article examines gender differences in responses to a survey of attitudes toward the use of animals in research. The survey was completed by college students and consisted of items intended to tap different issues related to the animal research debate. Results indicated that women were more likely than men to support tenets of the animal protection movement. Likewise, women were more likely than men to favor increased restrictions on animal use and were more concerned than men about the suffering of research animals. Analysis of item contents suggested that women endorsed items reflecting a general caring for animals, were more willing than men to make personal sacrifices such as giving up meat and medical benefits in an effort to protect animals, and were more likely than men to question the use of animals in research on scientific grounds. Men, on the other hand, tended to emphasize the potential benefits arising from the use of animals in research

Gender Differences in Attitudes Toward Animal Research

Although gender differences in attitudes toward animal research have been reported in the literature for some time, exploration into the nature of these differences has received less attention. This article examines gender differences in responses to a survey of attitudes toward the use of animals in research. The survey was completed by college students and consisted of items intended to tap different issues related to the animal research debate. Results indicated that women were more likely than men to support tenets of the animal protection movement. Likewise, women were more likely than men to favor increased restrictions on animal use and were more concerned than men about the suffering of research animals. Analysis of item contents suggested that women endorsed items reflecting a general caring for animals, were more willing than men to make personal sacrifices such as giving up meat and medical benefits in an effort to protect animals, and were more likely than men to question the use of animals in research on scientific grounds. Men, on the other hand, tended to emphasize the potential benefits arising from the use of animals in research

A preliminary assessment of the geologic setting, hydrology, and geochemistry of the Hueco Tanks geothermal area, Texas and New Mexico

Tx Doc no. : Z, UA220.7, G292, 81-1UT Librarie