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Electroluminescence from a series of polymers and copolymers which exhibit photoinduced excited-state intramolecular proton transfer (ESIPT) is reported. Among these polymers containing ESIPT moieties in the main chain or side chain are poly(1,4-(2-hydroxy)phenylene benzobisthiazole-co-decamethylene benzobisthiazole), poly (styrene-co-3-hydroxy-4'-ethenylflavone) and poly(2,5-benzoxazolediyl(2,2,2-trifluoro-1 -(trifluoromethyl) ethylidene)-5,2-benzoxazolediyl-4-hydroxy 1, 3-phenylene). The electroluminescence spectra of these polymers are identical to their photoluminescence spectra, indicating that electroluminescence originates from electrically-generated intramolecular proton transfer (EGIPT). Because electroluminescence from EGIPT implies electrically-induced population inversion, these results demonstrate the possibility of electrically-pumped organic solid-state laser diodes.

We introduce a simple method for characterizing reactive pathways in quantum systems. Flux auto- correlation and cross-correlation functions are employed to develop a quantitative measure of dynamical coupling in quantum transition events, such as reactive tunneling and resonant energy transfer. We utilize the method to study condensed-phase proton-coupled electron transfer (PCET) reactions and to determine the relative importance of competing concerted and sequential reaction pathways. Results presented here include numerically exact quantum dynamics simulations for model condensed-phase PCET reactions. This work demonstrates the applicability of the new method for the analysis of both approximate and exact quantum dynamics simulations.

The longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons has been measured for the first time in proton-proton collisions at $\sqrt{s} = 200 \mathrm{GeV}$ with the STAR detector at RHIC. The measurements cover pseudorapidity, $\eta$, in the range $|\eta| < 1.2$ and transverse momenta, $p_\mathrm{T}$, up to $4 \mathrm{GeV}/c$. The longitudinal spin transfer is found to be $D_{LL}= -0.03\pm 0.13(\mathrm{stat}) \pm 0.04(\mathrm{syst})$ for inclusive $\Lambda$ and $D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst})$ for inclusive $\bar{\Lambda}$ hyperons with $ = 0.5$ and $ = 3.7 \mathrm{GeV}/c$. The dependence on $\eta$ and $p_\mathrm{T}$ is presented.

The longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons has been measured for the first time in proton-proton collisions at $\sqrt{s} = 200 \mathrm{GeV}$ with the STAR detector at RHIC. The measurements cover pseudorapidity, $\eta$, in the range $|\eta| < 1.2$ and transverse momenta, $p_\mathrm{T}$, up to $4 \mathrm{GeV}/c$. The longitudinal spin transfer is found to be $D_{LL}= -0.03\pm 0.13(\mathrm{stat}) \pm 0.04(\mathrm{syst})$ for inclusive $\Lambda$ and $D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst})$ for inclusive $\bar{\Lambda}$ hyperons with $ = 0.5$ and $ = 3.7 \mathrm{GeV}/c$. The dependence on $\eta$ and $p_\mathrm{T}$ is presented.

Possible differences between free and bound protons may be observed in the ratio of polarization-transfer components, $P'_x/P'_z$. We report the measurement of $P'_x/P'_z$, in the $^2\textrm{H}(\vec{e},e^{\prime}\vec{p})n$ reaction at low and high missing momenta. Observed increasing deviation of $P'_x/P'_z$ from that of a free proton as a function of the virtuality, similar to that observed in \hefour, indicates that the effect in nuclei is due to the virtuality of the knock-out proton and not due to the average nuclear density. The measured differences from calculations assuming free-proton form factors ($\sim10\%$), may indicate in-medium modifications.

A novel mechanism for switching a molecular junction based on a proton transfer reaction triggered by an external electrostatic field is proposed. As a specific example to demonstrate the feasibility of the mechanism, the tautomers [2,5-(4-hydroxypyridine)] and {2,5-[4(1H)-pyridone]} are considered. Employing a combination of first-principles electronic structure calculations and Landauer transport theory, we show that both tautomers exhibit very different conductance properties and realize the "on" and "off" states of a molecular switch. Moreover, we provide a proof of principle that both forms can be reversibly converted into each other using an external electrostatic field.

Electron scattering experiments on the proton were carried out in a range of momentum transfers squared of 0.025 (Fermi -2) to be 0.65 (Fermi -2). Polyethylene was used as target material and the proton data were normalized against carbon electron scattering data taken at higher momentum transfer. The relative proton data obtained in this manner do not fit the generally accepted form factor curve. Possible reasons for the deviations in view of recent suggestions about the existence of a proton halo are offered. However, it is not possible at the present stage of accuracy to make any definite statement except that the data are not inconsistent with the existence of a proton halo.

Using theoretical and computational chemistry methods, we have studied the oxygen reduction and proton transfer in molten carbonate salts related to solid oxide fuel cells, and adsorption of nerve agents of sarin on surfaces of CaO, graphene and graphane. The mechanism of oxygen reduction through CO52- and CO42- is confirmed for the first time by DFT. It was found the proton has very good mobility in molten carbonate salts with activation energy of 8.0 kcal/mol, which agrees with the value measured by experiment. For sarin on the selected surfaces, its polarized phosphate region as Lewis-base acts as the binding agent. The binding energy ranges from 2.4-13.2 kcal/mol at the level of CI, showing relative weak interactions with the surfaces.

High precision measurements of the proton elastic form factor ratio have been made at four-momentum transfers, Q^2, between 0.2 and 0.5 GeV^2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q^2 range the deviation from unity is primarily due to GEp being smaller than the dipole parameterization.

Linear energy transfer spectrum of proton exposure on mercury mission ma-9

This article primarily reviews recent work on ultrafast experiments on excited state intramolecular electron and proton transfer, with an emphasis on experiments on chemical systems that have been analyzed theoretically. In particular, those systems that have been quantitatively characterized by static spectroscopy, which provides detailed information about the reaction potential energy surface and about other parameters that are necessary to make a direct comparison to theoretical predictions, are described.

An effective Hamiltonian is considered for hydrogen bonding between two molecules due to the quantum mechanical interaction between the orbitals of the H-atom and the donor and acceptor atoms in the molecules. The Hamiltonian acts on two diabatic states and has a simple chemically motivated form for its matrix elements. The model gives insight into the "H-bond puzzle", describes different classes of bonds, and empirical correlations between the donor-acceptor distance R and binding energies, bond lengths, and the softening of vibrational frequencies. A key prediction is the UV photo-dissociation of H-bonded complexes via an excited electronic state with an exalted vibrational frequency.

An effective Hamiltonian is considered for hydrogen bonding between two molecules due to the quantum mechanical interaction between the orbitals of the H-atom and the donor and acceptor atoms in the molecules. The Hamiltonian acts on two diabatic states and has a simple chemically motivated form for its matrix elements. The model gives insight into the "H-bond puzzle", describes different classes of bonds, and empirical correlations between the donor-acceptor distance R and binding energies, bond lengths, and the softening of vibrational frequencies. A key prediction is the UV photo-dissociation of H-bonded complexes via an excited electronic state with an exalted vibrational frequency.

It is shown that the energy of protons accelerated in laser-matter interaction experiments may be significantly increased through the process of splitting the incoming laser pulse into multiple interaction stages of equal intensity. From a thermodynamic point of view, the splitting procedure can be viewed as an effective way of increasing the efficiency of energy transfer from the laser light to protons, which peaks for processes having the least amount of entropy gain. It is predicted that it should be possible to achieve $\apprge 100%$ increase in the energy efficiency in a six-stage laser proton accelerator compared to a single laser-target interaction scheme.

Four diabatic states are used to construct a simple model for double proton transfer in hydrogen bonded complexes. Key parameters in the model are the proton donor-acceptor separation R and the ratio, D_1/D_2, between the proton affinity of a donor with one and two protons. Depending on the values of these two parameters the model describes four qualitatively different ground state potential energy surfaces, having zero, one, two, or four saddle points. In the limit D_2=D_1 the model reduces to two decoupled hydrogen bonds. As R decreases a transition can occur from a concerted to a sequential mechanism for double proton transfer.

Well known 2-(2-hydroxyphenyl)benzoxazole 1, intramolecular hydrogen-bonded compound bis-2,5- (2-benzoxazolyl)phenol, 3, and the new polymers poly(m-(2-hydroxy)-phenylene benzobisoxazole) (mHPBO, 4) and poly(p-(2-hydroxy)-phenylene benzobisoxazole) (pHPBO, 5), are used to elucidate the effects of molecular size, conjugation length, and competition with excimer formation on excited-state intramolecular proton transfer (ESIPT). It is shown that whereas 1, 3 and 4 exhibit ESIPT, S does not. The results suggest that whereas molecular size does not appear to inhibit ESIPT, the competition with excimer formation and the extent of pi-electron delocalization both do. jg

A non-relativistic potential-model version of the factorization assumption, used in perturbative QCD calculations of hadronic form factors, is used, along with the Born approximation valid at high energies, to derive a remarkably simple relationship between the impulse approximation contribution to the deuteron form factor at high momentum transfer and the high energy neutron-proton scattering amplitude. The relation states that the form factor at a given value of $Q^2$ is proportional to the scattering amplitude at a specific energy and scattering angle. This suggests that an accurate computation of the form factors at large $Q^2$ requires a simultaneous description of the phase-shifts at a related energy, a statement that seems reasonable regardless of any derivation. Our form factor-scattering amplitude relation is shown to be accurate for some examples. However, if the potential consists of a strong short distance repulsive term and a strong longer ranged attractive term, as typically occurs in many realistic potentials, the relation is found to be accurate only for ridiculously large values of $Q$. More general arguments, using only the Schroedinger equation, suggest a strong, but complicated, relationship between the form factor and scattering amplitude. Furthermore, the use of recently obtained soft potentials, along with an appropriate current operator, may allow calculations of form factors that are consistent with the necessary phase shifts.

The differential cross section, $d\sigma/dt$ for $\omega$ meson exclusive photoproduction on the proton above the resonance region ($2.6

The ratio of the proton elastic electromagnetic form factors, $G_{Ep}/G_{Mp}$, was obtained by measuring $P_{t}$ and $P_{\ell}$, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic $\vec e p \to e\vec p$ ~reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV$^2$. In the single-photon exchange approximation, the ratio $G_{Ep}/G_{Mp}$ is directly proportional to the ratio $P_t/P_{\ell}$. The simultaneous measurement of $P_{t}$ and $P_{\ell}$ in a polarimeter reduces systematic uncertainties. The results for the ratio $G_{Ep}/G_{Mp}$ show a systematic decrease with increasing $Q^2$, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. The data have been re-analyzed and systematic uncertainties have become significantly smaller than previously published results.

The ratio of the proton elastic electromagnetic form factors, $G_{Ep}/G_{Mp}$, was obtained by measuring $P_{t}$ and $P_{\ell}$, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic $\vec e p \to e\vec p$ ~reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV$^2$. In the single-photon exchange approximation, the ratio $G_{Ep}/G_{Mp}$ is directly proportional to the ratio $P_t/P_{\ell}$. The simultaneous measurement of $P_{t}$ and $P_{\ell}$ in a polarimeter reduces systematic uncertainties. The results for the ratio $G_{Ep}/G_{Mp}$ show a systematic decrease with increasing $Q^2$, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. The data have been re-analyzed and systematic uncertainties have become significantly smaller than previously published results.

The apparent discrepancy between the Rosenbluth and the polarization transfer method for the ratio of the electric to magnetic proton form factors can be explained by a two-photon exchange correction which does not destroy the linearity of the Rosenbluth plot. Though intrinsically small, of the order of a few percent of the cross section, this correction is kinematically enhanced in the Rosenbluth method while it is small for the polarization transfer method, at least in the range of (Q^2) where it has been used until now.

Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical accuracy of a few percent. The scaling power for the s-dependence of the cross section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.

This article is from The Journal of Biological Chemistry , volume 289 . Abstract Background: The mechanism of cofactor-free dioxygenases has not been clearly elucidated.Results: Mutation of the His/Asp dyad in (1H)-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase strongly affects substrate deprotonation and overall catalysis.Conclusion: Base mechanism is demonstrated where His-251 acts as catalytic base and Asp-126 modulates basicity.Significance: Many dioxygenases activate their substrates via deprotonation, which is an essential step for later reaction with oxygen.

This article is from The Journal of Biological Chemistry , volume 289 . Abstract Background: The mechanism of cofactor-free dioxygenases has not been clearly elucidated.Results: Mutation of the His/Asp dyad in (1H)-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase strongly affects substrate deprotonation and overall catalysis.Conclusion: Base mechanism is demonstrated where His-251 acts as catalytic base and Asp-126 modulates basicity.Significance: Many dioxygenases activate their substrates via deprotonation, which is an essential step for later reaction with oxygen.

This article is from The Journal of Biological Chemistry , volume 287 . Abstract Background: The active site of mannitol 2-dehydrogenase from Pseudomonas fluorescens is connected with bulk solvent through a narrow protein channel. Glu292 adopts flexible positions down and up the channel.Results: Evidence linking motions of Glu292 to proton translocation to and from the active site.Conclusion: Glu292 controls proton transfer through a water chain mechanism.Significance: Dynamic features of the proton transfer mechanism have been elucidated.

The cross section for $\phi$ meson photoproduction on the proton has been measured for the first time up to a four-momentum transfer -t = 4 GeV^2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. At low four-momentum transfer, the differential cross section is well described by Pomeron exchange. At large four-momentum transfer, above -t = 1.8 GeV^2, the data support a model where the Pomeron is resolved into its simplest component, two gluons, which may couple to any quark in the proton and in the $\phi$.

Multiple electron and proton transfers in nanomaterials pose significant demands and challenges across the various fields such as renewable energy, chemical processes, biological applications, and photophysics. In this context, pH-responsive functional groups-enriched Carbon dots (C-Dots) emerge as superior proton-coupled electron transfer (PCET) agents owing to the presence of multiple functional groups (-COOH, -NH2, and -OH) on the surface and redox-active sites in the core. Here, we elucidate the 2e-/2H+ transfer ability of carboxylic-enriched C-Dots (C-Dot-COOH) and amine-enriched C-Dots (C-Dot-NH2) with molecular 2e-/2H+ acceptors (benzoquinone, BQ) as a function of pKa, facilitated by the formation of new O-H bonds. The ground state and excited state pKa values of different functional groups on the surface of C-Dots are determined using steady-state absorbance and photoluminescence (PL) spectroscopy. Optical spectroscopy and electrochemical studies are employed to comprehend the influence of the surface and core of C-Dots on the proton and electron transfer processes as a function of pH. The cyclic voltammetry analysis reveals a standard Nernstian shift in E1/2 per pH unit of 30 mV, indicating that the finalized C-Dots hold promise as candidates for the 2e-/2H+ transfer process. Calculated bond dissociation free energy (BDFE) of the electroactive O-H/N-H bonds provides a more nuanced and detailed understanding of PCET thermodynamic landscapes. These findings underscore the potential of nanoscale functionalized C-Dots for facilitating the multiple PCET reactions in future energy technologies.

Multiple electron and proton transfers in nanomaterials pose significant demands and challenges across the various fields such as renewable energy, chemical processes, biological applications, and photophysics. In this context, pH-responsive functional groups-enriched Carbon dots (C-Dots) emerge as superior proton-coupled electron transfer (PCET) agents owing to the presence of multiple functional groups (-COOH, -NH2, and -OH) on the surface and redox-active sites in the core. Here, we elucidate the 2e-/2H+ transfer ability of carboxylic-enriched C-Dots (C-Dot-COOH) and amine-enriched C-Dots (C-Dot-NH2) with molecular 2e-/2H+ acceptors (benzoquinone, BQ) as a function of pKa, facilitated by the formation of new O-H bonds. The ground state and excited state pKa values of different functional groups on the surface of C-Dots are determined using steady-state absorbance and photoluminescence (PL) spectroscopy. Optical spectroscopy and electrochemical studies are employed to comprehend the influence of the surface and core of C-Dots on the proton and electron transfer processes as a function of pH. The cyclic voltammetry analysis reveals a standard Nernstian shift in E1/2 per pH unit of 30 mV, indicating that the finalized C-Dots hold promise as candidates for the 2e-/2H+ transfer process. Calculated bond dissociation free energy (BDFE) of the electroactive O-H/N-H bonds provides a more nuanced and detailed understanding of PCET thermodynamic landscapes. These findings underscore the potential of nanoscale functionalized C-Dots for facilitating the multiple PCET reactions in future energy technologies.

In two recent papers it is argued that the 'proton radius puzzle' can be explained by truncating the electron scattering data to low momentum transfer and fit the rms radius in the low momentum expansion of the form factor. It is shown that this procedure is inconsistent and violates the Fourier theorem. The puzzle cannot be explained in this way.

Surface sensitive synchrotron-X-ray scattering studies reveal the distributions of monovalent ions next to highly charged interfaces. A lipid phosphate (dihexadecyl hydrogen-phosphate) was spread as a monolayer at the air-water interface, containing CsI at various concentrations. Using anomalous reflectivity off and at the $L_3$ Cs$^+$ resonance, we provide, for the first time, spatial counterion distributions (Cs$^+$) next to the negatively charged interface over a wide range of ionic concentrations. We argue that at low salt concentrations and for pure water the enhanced concentration of hydroniums H$_3$O$^+$ at the interface leads to proton-transfer back to the phosphate group by a high contact-potential, whereas high salt concentrations lower the contact-potential resulting in proton-release and increased surface charge-density. The experimental ionic distributions are in excellent agreement with a renormalized-surface-charge Poisson-Boltzmann theory without fitting parameters or additional assumptions.

Excited state intramolecular and intermolecular proton transfer reactions in cold, isolated 2-allylphenol, 2-propenylphenol and 2-propylphenol and their clusters with water and ammonia are investigated employing a combination of spectroscopic techniques (mass resolved excitation, threshold photo-ionization, dispersed emission), a semi-empirical MNDO calculation (MOPAC 5) and a potential energy calculation of cluster structure. Threshold photo- ionization spectroscopy proves to be useful for the identification of molecular conformers in these systems but has mixed results for the identification of proton transfer in their clusters.

The Spin Asymmetries of the Nucleon Experiment investigated the spin structure of the proton via inclusive electron scattering at the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory in Newport News, VA. A double--polarization measurement of polarized asymmetries was performed using the University of Virginia solid polarized ammonia target with target polarization aligned longitudinal and near transverse to the electron beam, allowing the extraction of the spin asymmetries $A_1$ and $A_2$, and spin structure functions $g_1$ and $g_2$. Polarized electrons of energies of 4.7 and 5.9 GeV were scattered to be viewed by a novel, non-magnetic array of detectors observing a four-momentum transfer range of 2 to 6 GeV$^2$. This document addresses the extraction of the spin asymmetries and spin structure functions, with a focus on spin structure function $g_2$, which we have measured as a function of $x$ and $W$ in four $Q^2$ bins.

The inclusive single and double differential cross-sections for neutral and charged current processes with four-momentum transfer squared Q^2 between 150 and 30,000 GeV2 and with Bjorken x between 0.0032 and 0.65 are measured in e^+ p collisions. The data were taken with the H1 detector at HERA between 1994 and 1997, and they correspond to an integrated luminosity of 35.6 pb^-1. The Q^2 evolution of the parton densities of the proton is tested, yielding no significant deviation from the prediction of perturbative QCD. The proton structure function F_2(x,Q^2) is determined. An extraction of the u and d quark distributions at high x is presented. At high Q^2 electroweak effects of the heavy bosons Z0 and W are observed and found to be consistent with Standard Model expectation.

We analyze a transfer ionization (TI) reaction in the fast proton-helium collision $\rm H^+ + He \to H^0 + He^{2+} + e^-$ by solving a time-dependent Schr\"odinger equation (TDSE) under the classical projectile motion approximation in one-dimensional kinematics. In addition, we construct various time independent analogues of our model using lowest order perturbation theory in the form of the Born series. By comparing various aspects of the TDSE and the Born series calculations, we conclude that the recent discrepancies of experimental and theoretical data may be attributed to deficiency of the Born models used by other authors. We demonstrate that the correct Born series for TI should include the momentum space overlap between the double ionization amplitude and the wave function of the transferred electron.

Compton scattering from the proton was investigated at s=6.9 (GeV/c)**2 and \t=-4.0 (GeV/c)**2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.

Picosecond laser techniques were both used and developed to obtain new information on ultrafast molecular processes in liquids. From these studies, primarily of organic molecules, were have gained insight into: the physical and chemical pathways by which excited state molecules dissipate their energy by proton and electron transfer phenomena, the nature of intermolecular motions (cage effects in chemical reactions) and intramolecular motions about methylene groups, photodissociation of excited molecules and energy relaxation in the fragments generated, e.g. diphenylcarbene, the photoionization and subsequent electron solvation dynamics of pyrene in alcohols. The information we have obtained has important implications in the photostability of dye lasers and polymer systems, the development of new lasers based on the generation of large excited state populations in transient species; and the general effects of intense lasers on materials. (Author)

The mechanism of the oxidation of 2-mercapto-5-methyl-1,3,4-thiadiazole (McMT) to its disulfide dimer (BMT) and its subsequent reduction has been examined with a combined approach employing experimental data and digital simulation. In order to elucidate the influence of proton transfers on these redox processes, special attention has been paid to the influence of various bases, including triethylamine, pyridine, 3-chloro-pyridine, lutidine and 2,6-di-tert-butyl- pyridine, and proton donors, including methanesulfonic acid and trifluoromethanesulfonic acid, on both the oxidation and reduction reactions. Based on detailed comparisons of the experimental data with simulations of several mechanistic models, it is found that proton transfer pathways have a pronounced influence on both the oxidative and reductive pathways. In particular, McMT oxidation is facilitated by a rapid bimolecular proton transfer from McMT to weak bases such as Py that produces McMT, the thiolate form, which is then oxidized. The overall kinetic scheme by which these redox processes proceed both in the presence and absence of proton transfer agents is discussed, especially with regard to the potential use of a related dithiolate compound as a cathode material in Li secondary batteries.

We evaluate the two-photon exchange (TPE) correction to the unpolarized elastic electron-proton scattering at small momentum transfer $ Q^2 $. We account for the inelastic intermediate states approximating the double virtual Compton scattering by the unpolarized forward virtual Compton scattering. The unpolarized proton structure functions are used as input for the numerical evaluation of the inelastic contribution. Our calculation reproduces the leading terms in the $ Q^2 $ expansion of the TPE correction and goes beyond this approximation by keeping the full $ Q^2 $ dependence of the proton structure functions. In the range of small momentum transfer, our result is in good agreement with the empirical TPE fit to existing data.

Memory devices operating due to the fast proton transfer (PT) process are proposed by means of the first-principles calculations. Writing an information is performed using the electrostatic potential of the scanning tunneling microscopy (STM). Reading an information is based on the effect of the local magnetization induced at the zigzag graphene nanoribbon (Z-GNR) edge - saturated with oxygen or the hydroxy group - and can be realized with the use of the giant magnetoresistance (GMR), magnetic tunnel junction (MTJ) or spin-transfer torque (STT) devices. The energetic barriers for the hop-forward and -backward processes can be tuned by the distance and potential of the STM tip. Thus, enabling to tailor the non-volatile logic states. The proposed system enables very dense packing of the logic cells and could be used in the random access and flash memory devices.

We have investigated the radiation damage effects on a CCD to be employed in the Japanese X-ray astronomy mission including the Monitor of All-sky X-ray Image (MAXI) onboard the International Space Station (ISS). Since low energy protons release their energy mainly at the charge transfer channel, resulting a decrease of the charge transfer efficiency, we thus focused on the low energy protons in our experiments. A 171 keV to 3.91 MeV proton beam was irradiated to a given device. We measured the degradation of the charge transfer inefficiency (CTI) as a function of incremental fluence. A 292 keV proton beam degraded the CTI most seriously. Taking into account the proton energy dependence of the CTI, we confirmed that the transfer channel has the lowest radiation tolerance. We have also developed the different device architectures to reduce the radiation damage in orbit. Among them, the ``notch'' CCD, in which the buried channel implant concentration is increased, resulting in a deeper potential well than outside, has three times higher radiation tolerance than that of the normal CCD. We then estimated the charge transfer inefficiency of the CCD in the orbit of ISS, considering the proton energy spectrum. The CTI value is estimated to be 1.1e-5 per each transfer after two years of mission life in the worse case analysis if the highest radiation-tolerant device is employed. This value is well within the acceptable limit and we have confirmed the high radiation-tolerance of CCDs for the MAXI mission.

This contribution reports on a proof-of-principle measurement of the longitudinal spin transfer $D_{LL}$ in inclusive $\Lambda$ and $\bar \Lambda$ production in polarized proton-proton collisions at a center of mass energy $\sqrt{s}$ = 200 GeV. The data sample consists of about 3 $\times$ $10^6$ minimum bias events collected in the year 2005 by the STAR experiment at RHIC with proton beam polarizations of up to 50%. The $\Lambda$($\bar \Lambda$) candidates are reconstructed at mid-rapidity ($|\eta|

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract This paper reports the 1H, 13C and 15N NMR experimental study of five benzimidazoles in solution and in the solid state (13C and 15N CPMAS NMR) as well as the theoretically calculated (GIAO/DFT) chemical shifts. We have assigned unambiguously the "tautomeric positions" (C3a/C7a, C4/C7 and C5/C6) of NH-benzimidazoles that, in some solvents and in the solid state, appear different (blocked tautomerism). In the case of 1H-benzimidazole itself we have measured the prototropic rate in HMPA-d18.

We extend a semiclassical model of transfer reactions to the case in which one of the collision partners is a vibrational nucleus. The model is applied to one- and two-proton stripping reactions in the 37Cl + 98Mo system, for which a rapid transition from normal to anomalous slope in the two proton transfer reaction at energies around the Coulomb barrier is experimentally observed. This behavior is satisfactorily reproduced by the present extension of the model.

This article is from BMC Proceedings , volume 7 . Abstract None

A high-pressure hollow cathode ionizer is combined with an ion-mobility-spectrometer (IMS) for the detection of trace amounts of organic compounds in gas. The ionizer uses H.sub.3 0.sup.+, ions which do not react with air to ionize the organic compounds and the organic compounds are soft ionized. The ionized organic compounds are detected in the IMS at levels of parts per billion and identified using calibrated reference tables. Applications include but are not limited to the fields of: (1) medicine as a breath analyzer for detection of lung cancer, diabetes, liver cirrhosis, (2) law enforcement in drug interdiction and explosives detection, (3) food monitoring and control, (4) environmental monitoring and (5) space applications.

The endothermic proton transfer reaction, H2+(v+) + He yields HeH(+) + H(Delta E=0.806 eV), is investigated over a broad range of reactant vibrational levels using high-resolution vacuum ultraviolet to prepare reactant ions either through excitation of autoionization resonances, or using the pulsed-field ionization-photoelectron-secondary ion coincidence (PFI-PESICO) approach. In the former case, the translational energy dependence of the integral reaction cross sections are measured for v+ =0-3 with high signal-to-noise using the guided-ion beam technique. PFI-PESICO cross sections are reported for v(+) = 1-15 and v(+) = 0-12 at center-of-mass collision energies of 0.6 and 3.1 eV, respectively. All ion reactant states selected by the PFI-PESICO scheme are in the N(+) = 1 rotational level. The experimental cross sections are complemented with quasiclassical trajectory (QCT) calculations performed on the ab initio potential energy surface provided by Palmieri et al. [Mol. Phys. 98, 1839 (2000)]. The QCT cross sections are significantly lower than the experimental results near threshold, consistent with important contributions due to resonances observed in quantum scattering studies. At total energies above 2 eV, the QCT calculations are in excellent agreement with the present results. PFI-PESICO time-of-flight (TOF) measurements are also reported for v(+) = 3 and 4 at a collision energy of 0.6 eV. The velocity inverted TOF spectra are consistent with the prevalence of a spectator-stripping mechanism.

The endothermic proton transfer reaction, H2+(v+) + He yields HeH(+) + H(Delta E=0.806 eV), is investigated over a broad range of reactant vibrational levels using high-resolution vacuum ultraviolet to prepare reactant ions either through excitation of autoionization resonances, or using the pulsed-field ionization-photoelectron-secondary ion coincidence (PFI-PESICO) approach. In the former case, the translational energy dependence of the integral reaction cross sections are measured for v+ =0-3 with high signal-to-noise using the guided-ion beam technique. PFI-PESICO cross sections are reported for v(+) = 1-15 and v(+) = 0-12 at center-of-mass collision energies of 0.6 and 3.1 eV, respectively. All ion reactant states selected by the PFI-PESICO scheme are in the N(+) = 1 rotational level. The experimental cross sections are complemented with quasiclassical trajectory (QCT) calculations performed on the ab initio potential energy surface provided by Palmieri et al. [Mol. Phys. 98, 1839 (2000)]. The QCT cross sections are significantly lower than the experimental results near threshold, consistent with important contributions due to resonances observed in quantum scattering studies. At total energies above 2 eV, the QCT calculations are in excellent agreement with the present results. PFI-PESICO time-of-flight (TOF) measurements are also reported for v(+) = 3 and 4 at a collision energy of 0.6 eV. The velocity inverted TOF spectra are consistent with the prevalence of a spectator-stripping mechanism.

It is demonstrated that an emission of collinear photons by the polarized initial electron in elastic electron-proton polarization transfer scattering leads to an apparent shifting of real events with small momentum transfer into the data sample with large momentum transfer. Effectively this shows a fictive enhancement of the cross section at large momentum transfer. However, the enhancement is different for transverse and longitudinal polarizations of the recoil proton. The former is responsible for a deformation of results when extracting the proton electromagnetic form factors ratio from the data on electron-proton polarization transfer scattering. Nevertheless, this effect does not explain the suppression of the Dirac form factor at large momentum transfer completely.

The influence of an intramolecular proton transfer reaction on the conductance of a molecular junction is investigated employing a generic model, which includes the effects of the electric field of the gate and leads electrodes and the coupling to a dissipative environment. Using a quantum master equation approach it is shown that, depending on the localization of the proton, the junction exhibits a high or low current state, which can be controlled by external electric fields. Considering different regimes, which range from weak to strong hydrogen bonds in the proton transfer complex and comprise situations with high and low barriers, necessary preconditions to achieve control are analyzed. The results show that systems with a weak hydrogen bond and a significant energy barrier for the proton transfer can be used as molecular transistors or diodes.

Spin transfer observables for the strangeness-production reaction Antiproton-Proton -> Antilambda-Lambda have been measured by the PS185 collaboration using a transversely-polarized frozen-spin target with an antiproton beam momentum of 1.637 GeV/c at the Low Energy Antiproton Ring at CERN. This measurement investigates observables for which current models of the reaction near threshold make significantly differing predictions. Those models are in good agreement with existing measurements performed with unpolarized particles in the initial state. Theoretical attention has focused on the fact that these models produce conflicting predictions for the spin-transfer observables D_{nn} and K_{nn}, which are measurable only with polarized target or beam. Results presented here for D_{nn} and K_{nn} are found to be in disagreement with predictions from existing models. These results also underscore the importance of singlet-state production at backward angles, while current models predict complete or near-complete triplet-state dominance.