Showing papers on "Proton published in 1978"

Higgs Bosons from Two-Gluon Annihilation in Proton-Proton Collisions

Abstract: We estimate the cross section for Higgs-boson production in proton-proton collisions. We find that most of the cross section comes from a two-gluon annihilation process, in which the gluons couple to Higgs bosons via heavy-quark loops.

Molecular mechanisms for proton transport in membranes

Abstract: Likely mechanisms for proton transport through biomembranes are explored. The fundamental structural element is assumed to be continuous chains of hydrogen bonds formed from the protein side groups, and a molecular example is presented. From studies in ice, such chains are predicted to have low impedance and can function as proton wires. In addition, conformational changes in the protein may be linked to the proton conduction. If this possibility is allowed, a simple proton pump can be described that can be reversed into a molecular motor driven by an electrochemical potential across the membrane.

Magnetic cross-relaxation among protons in protein solutions.

Abstract: The magnetic spin-lattice relaxation rates of solvent water nuclei are known to increase upon addition of diamagnetic solute protein. This enhancement of the relaxation rate is a function of magnetic field, and the orientational relaxation time of the protein molecules can be deduced from analysis of the field-dependent relaxation rates. Although the nature of the interactions that convey information about the dynamics of protein motion to the solvent molecules is not established, it is known that there is a contribution to the relaxation rates of solvent protons that plays no role in the relaxation of solvent deuterons and 17O nuclei. We show here that the additional interaction arises from a cross-relaxation process between solvent and solute protons. We introduce a heuristic three-parameter model in which protein protons and solvent protons are considered as two separate thermodynamic systems that interact across the protein-solvent interface. The three parameters are the intrinsic relaxation rates of each system and a cross-relaxation term. The sign of the latter term must always be positive, for all values of magnetic field, in order for magnetization energy to flow from the hotter to the cooler system. We find that the magnetic field-dependence of the cross-relaxation contribution is much like that of the remaining solvent proton relaxation, i.e., about the same as the deuteron relaxation field dependence. This finding is not compatible with the predictions of expressions for the cross-relaxation that have been used by other authors, but not applied to data over a wide range of magnetic field strength. The model predicts that the relaxation behavior of both the protein protons and the solvent protons is the sum of two exponentials, the relative contributions of which would vary with protein concentration and solvent isotopic composition in a fashion suggestive of the presence of two classes of protein protons, when there is in reality only one. This finding has immediate implications for the interpretation of published proton relaxation rates in complex systems such as tissues; these data should be reexamined with cross-relaxation taken into account.

Deep Inelastic e p Asymmetry Measurements and Comparison with the Bjorken Sum Rule and Models of Proton Spin Structure

Abstract: We report new measurements of the asymmetry in the deep-inelastic scattering of longitudinally polarized electrons by longitudinally polarized protons in the kinematic range 2 < or = ..omega.. < or = 10, 1 < or = Q/sup 2/ < or = 4 (GeV/c)/sup 2/, and 2 < or = W < or = 4 GeV. We compare our results with the Bjorken sum rule and with several theoretical models of the internal spin structure of the proton.

Analysis of the 1H‐NMR spectra of ferrichrome peptides. I. The non‐amide protons

Abstract: The thus far unexplored aliphatic region of the proton magnetic resonance spectra of ferrichrome peptides was investigated at 360 MHz. Six isomorphic diamagnetic analogues of the ferric cyclohexapeptide differing in the coordinated cation (AL3+ or Ga3+) and the amino acid composition were studied in d6-DMSO solution. By use of a novel resolution enhancement technique which applies a sinusoidal half-wave window to the free induction decay combined with multiplication by an increasing exponential, the proton chemical shifts and spin-spin couplings were accurately measured. Homonuclear decoupling combined with Fourier difference spectroscopy was used to selectively extract resonances out of crowded spectral regions. The spectra revealed unique features of fine structure in the proton resonance lines. Thus, the conformation-dependent geminal coupling constants of glycyl α-protons were found to be constant throughout the suite of analogue peptides. A similar invariance was observed for the vicinal coupling constants between α-, β-, γ-, and δ-protons in the ornithyl side chains. Comparison of the proton spin–spin coupling constants with the crstallographic dihedral angles led to a unique stereochemical assignment of the side-chain resonances. The combined data sets of x-ray atomic coordinates and 1H-nmr spin-spin coupling parameters have been used to calibrate the coefficients for a Karplus curve related to the torsional x angles in amino acid side chains: Structurial information was also obtained for the seryl residues, where the multiplet structures of the OH resonances indicate preferred spatial arrangements of the side chains.

ISEE-C Solar Wind Plasma Experiment

Abstract: Two 135° spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are successively selected from individual emitters to provide three-dimensional measurements. Speed of the ion measurements is increased by a factor of two by using an active proton peak tracking system to reduce the total range of energy per charge which has to be covered.

Study of the high-mass dimuon continuum in 400-GeV proton-nucleus collisions

Abstract: The mass spectrum of muon pairs in the range 5 to 15 GeV is studied in the inclusive reaction p + nucleus ..-->.. ..mu../sup +/ + ..mu../sup -/ + anything. The UPSILON and continuum distribution are presented as is the A dependence of the continuum. Comparison with a parton-annihilation model yields a sea-quark distribution.

Neutron star matter at high temperatures and densities. I. Bulk properties of nuclear matter

Abstract: We perform calculations of the thermodynamic properties of uniform dense matter at finite temperature using the Skyrme nuclear interaction. The calculations are valid for arbitrary proton concentrations and temperatures. The equation of state is compared with earlier investigations done for a few restricted cases. In order to understand the conditions under which one might expect to find nuclei immersed in a sea of nucleons, we explore the coexistence of two fluid phases with different proton concentrations. At zero temperature, nuclei with proton fractions in the range 0.044-0.335 may coexist with a pure neutron fluid, but at lower proton fractions protons ''drip'' as well. At finite temperatures, nuclear droplets with proton fractions up to 0.5 may coexist with fluid also containing up to 50% protons. A phase diagram for nuclear matter is presented. The critical temperature, as a function of proton concentration, above which no coexistence is possible and nuclei evaporate, is established. Its maximum value is k/sub B/T=20MeV, which occurs in the cse of symmetric nuclear matter.

Quadrispherical LEPEDEAS for ISEE's-1 and -2 Plasma Measurements

Abstract: A new generation of spaceflight instrumentation for comprehensive measurements of plasmas within the earth's magnetosphere and its environs is described. These quadrispherical low energy proton and electron differential energy analyzers (LEPEDEAS) for the ISEE's-l and -2 spacecraft are capable of determining the directional intensities of positive ions and electrons over all but 2 percent of the 4? sr solid angle for charged-particle velocity vectors at the spacecraft positions. The energy range of this instrumentation is 1 eV < E/Q < 45 keV with good energy and angular resolutions. An example of inflight observations within the earth's magnetosheath is presented.

Energy spectra of nuclear fragments produced by high energy protons

Abstract: Fragment energy spectra from the 2.1- and 4.9-GeV proton irradiation of C, Al, Ag, and U targets were measured at several angles to the beam for products ranging from He up to Ar for the heavier targets. The fragments were detected in a telescope consisting of a gas $\ensuremath{\Delta}E$ counter and a silicon $E$ counter. The carbon target measurements are compared with previous data from projectile fragmentation studies. A Maxwellian type functional form which fits the energy spectra from all the targets is presented. The spectra were integrated to obtain values of the cross section as a function of atomic number.

Bidirectional anisotropies in solar cosmic ray events: Evidence for magnetic bottles

Abstract: During the period 1967-1973 data were obtained from five satellites in order to investigate bidirectional anisotropies in low-energy solar protons and to study electron events. Detailed consideration is given to the characteristics of two observed solar electron events. It is particularly noted that (1) the mean duration of bidirectional anisotropy is about 9 hours, (2) for most events the bidirectional anisotropy occurs at the minimum of the associated Forbush decrease, (3) the existence of bidirectional anisotropy in subrelativistic electrons associated with an interplanetary shock is not expected as anisotropies in impulsive solar electron events usually decay quickly within a time of not more than an hour at 1 AU, and (4) simultaneous observations show a significant difference in the nature of the angular distributions first between electrons and protons and second between different proton energies. The formation of bidirectional anisotropy by propagation and by energy change is also discussed.

The hydration of monosaccharides—an NMR study

Abstract: At temperatures close to 0°C proton exchange between sugar hydroxyl groups and water is slow, and separate proton resonance peaks can be detected for the hydroxyl protons. All are shifted downfield of the water resonance, the anomeric hydroxyl proton shift being the greatest. Axial anomeric hydroxyl protons are shifted less than corresponding equatorial protons. Proton exchange with water is strongly acid and base catalyzed, but, at least in some cases, there seems to be an additional pH-independent mechanism involved. From the temperature effect on the shifts, and the effect of added dimethyl sulfoxide, we conclude that each hydroxyl group is bonded on average to two water molecules. This estimate of the hydration number for monosaccharides is far greater than those previously deduced from relaxation studies. It is suggested that the source of this difference lies in the residence times of the bound water molecules. Shifts of the hydroxyl proton resonances for sugars in methanol are compared with those for aqueous solutions and are found to be very similar. Hence it is concluded that these shifts do not reveal any special effects due to water structure. There are quite marked differences in the shifts for different sugars, and, in particular, the anomeric hydroxyl proton shifts for ketoses are smaller than those for aldoses.

Control of proton conduction by the H+ -ATPase in the inner mitochondrial membrane.

Abstract: Proton conduction in submitochondrial particles with various degrees of resolution of the H+-ATPase has been studied. Proton conduction was analyzed by following the kinetics of the anaerobic decay of protons taken up by submitochondrial particles during respiratory pulses. 1 In EDTA submitochondrial particles proton release exhibited biphasic kinetics; both phases were depressed by collapsing aerobic Δφ. 2 The slow phase of proton diffusion was inhibited by oligomycin and N,N′-dicyclohexylcarbodiimide as well as by F1 ligands like adenylyl 5′-imidophosphate and alkyl cations. Inhibition of proton conduction by F1 ligands exhibited a sigmoidal titration curve and was synergistic with inhibition by oligomycin. Removal of the ATPase inhibitor markedly enhanced the kinetic constant of the slow proton diffusion process. 3 The initial rapid phase of proton diffusion was inhibited by N,N′-dicyclohexylcarbodiimide and oligomycin but was unaffected by F1 ligands. 4 When the F1 moiety was removed from the particles, proton conduction became monophasic and was not any more inhibited by F1 ligands. 5 It is concluded that the H+-ATPase contributes to both phases of proton conduction and that energy-linked cooperative interaction of the F1 with the F0 moiety controls proton conductivity. Evidence is also provided for involvement of negatively charged groups in hydrophobic environments of the F1 moiety in proton translocation by the H+-ATPase.

Hadronic deformation energy. II. Two-nucleon interaction

Abstract: The MIT bag model for hadrons is treated in the static cavity approximation. The adiabatic deformation of a six-quark hadron with quantum numbers of the deuteron is studied in a configuration which permits the separation of two triplets with quantum numbers of the neutron and proton. The energy of the system is computed to second order in the gluon coupling and presented as a function of two choices of a single collective variable: a separation parameter for the nucleons and the baryonic quadrupole moment. The present study considers only interactions at short and intermediate range in a state with nuclear spins aligned in parallel along the deformation axis. It does not treat effects depending on nucleon momenta. The energy, when expressed in terms of a nuclear separation parameter, exhibits a soft repulsive core at short range due to a color-magnetic gluon interaction, and strong attraction in intermediate range due to a color-electric interaction.

Nuclear ''time-delay'' and x-ray-proton coincidences near a nuclear scattering resonance

Abstract: The probability for production of K-shell x rays by protons elastically scattered from /sup 58/Ni is observed to change as one varies the proton energy over the s/sub 1/2/ nuclear resonance at E/sub p/ = 3.151 MeV. The results are interpreted theoretically in terms of interfering products of atomic ionization and energy-dependent nuclear scattering amplitudes.

Constant radius magnetic acceleration of a strong non-neutral proton ring

Abstract: The constrained or constant radius magnetic acceleration of a strong non‐neutral proton ring by a modified betatron field is considered. The modified betatron field consists of an azimuthal magnetic field Bϑ superimposed on a betatron field Bz in which the 1 : 2 flux rule is satisfied. An important advantage of the constrained acceleration is that the energy of the nonrelativistic ions increases with the square of the magnetic field. It has been found that the orbits of the gyrating particles are stable when the self‐field index ns{=ω2p[2γ0ϑ(t) Ω20(t)]−1} is much greater than unity, provided that ns< (Bϑ/2Bz)2 at the orbit. For Bϑ=0, the orbits are stable only if ns<1/2.

The K-shell ionisation of atoms by relativistic protons

Abstract: The K-shell ionisation is investigated using an extension of the first-order time-dependent perturbation-theory treatment of Moller (1932) taking Dirac plane waves for the description of the incident and scattered protons and the Darwin approximation for the relativistic wavefunctions of the K-shell atomic electrons and the ejected electron. The differential cross sections delta 2 sigma / delta k delta q and d sigma /dk, where k is the wavenumber of the ejected electron and hq is the momentum change of the proton, are calculated. The double differential cross section for collisions in which a change of spin of the atomic electron occurs is less sharply peaked for small q, and has a broader overall distribution with respect to q, than the double differential cross section for collisions without spin change, although being much less in magnitude than the latter for small q. This leads to total K-shell ionisation cross sections sigma with significant contributions coming from collisions with spin change of the atomic electron for large atomic numbers at high energies of impact.

On the hydrolysis of AgII, TlII, SnIII and CuIII

Abstract: Using pulse radiolysis with optical, conductometric and polarographic detection it is shown that the oxidation of Tl+, Ag+, Cu2+ and Sn2+ by hydroxyl radicals proceeds via on OH adduct: Men++·OH → Me(OH)n+. Depending on pH, the OH adduct may react with a proton followed by water elimination, may add OH– or react with water followed by elimination of a proton. The pK values for the equilibria Me(n+1)+⇌ Me(OH)n+⇌ Me(OH)(n–1)+⇌… decrease with increasing state of oxidation of Me. The oxidative properties decrease with increasing state of hydrolysis.

Asymmetries in Inclusive Proton-Nucleon Scattering at 11.75-GeV/c

Abstract: We have measured the left-right asymmetry for the inclusive production of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, and protons in proton-proton and proton-deuteron collisions at 11.75 GeV/c. The measurements, utilizing the polarized proton beam at the Argonne zero-gradient synchrotron, cover a wide range of kinematic variables [$u$ between 0.6 and -1.5 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $x$ between 0.1 and 0.9 for meson production, $t$ between -0.2 and -2.0 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ and $x$ between -0.25 and 0.75 for proton production]. There is considerable angular structure in the pion-production data but not in the kaon or proton processes. Proton production alone is clearly sensitive to the isotopic spin of the target particle. A simple phenomenological model of baryon-exchange dominance successfully relates the inclusive pion asymmetries to the asymmetries in backward pion-nucleon elastic scattering. A triple-Regge model for the inclusive proton asymmetries is also discussed.