Showing papers by "Paul Scherrer Institute published in 1992"
TL;DR: In this article, a thermodynamic description of the main constituents of hydrated Portland cement, calcium silicate hydrates (CSH-gels), is presented and the incongruent solubility behavior of CSH-gel is described by introducing several independent model solids.
348 citations
TL;DR: The results indicate that patients with Parkinson's disease can show significant and sustained improvement of motor function after intrastriatal implantation of fetal dopamine‐rich mesencephalic tissue.
Abstract: Ventral mesencephalic tissue from aborted human fetuses (age, 6-7 weeks' postconception) was implanted unilaterally into the putamen using stereotaxic surgery in 2 immunosuppressed patients (Patients 3 and 4 in our series) with advanced idiopathic Parkinson's disease. Tissue from 4 fetuses was grafted to each patient. Compared with our previous 2 patients, the following changes in the grafting procedure were introduced: the implantation instrument was thinner, more tissue was placed in the operated structure, and the time between abortion and grafting was shorter. There were no postoperative complications. Both patients showed a gradual and significant amelioration of parkinsonian symptoms (most marked in Patient 3) starting at 6 and 12 weeks after grafting, respectively, reaching maximum stability at approximately 4 to 5 months; patients remained relatively stable thereafter during the 1-year follow-up period. Clinical improvement was observed as a reduction of the time spent in the "off" phase and the number of daily "off" periods; a lessening of bradykinesia and rigidity during the "off" phase, mainly but not solely on the side contralateral to the graft; and a prolongation and change in the pattern of the effect of a single dose of L-dopa. Neurophysiological measurements revealed a more rapid performance of simple and complex arm and hand movements bilaterally, but primarily contralateral to the graft. The results indicate that patients with Parkinson's disease can show significant and sustained improvement of motor function after intrastriatal implantation of fetal dopamine-rich mesencephalic tissue. The accompanying paper by Sawle and colleagues describes the results of repeated positron emission tomography scans in these patients.
341 citations
TL;DR: In this article, the paramagnetic effect found experimentally in some granular high temperature superconductors is explained by a model of a Josephson network of d-wave superconductions.
Abstract: The paramagnetic effect found experimentally in some granular high temperature superconductors is explained by a model of a Josephson network of d -wave superconductors. The unusual microwave absorption characteristics of these systems is also explained in a consistent way. Finally, a new experiment is proposed to give a decisive test for d -wave superconductivity in high T c superconductors.
321 citations
TL;DR: A computer simulation of the dose deposition in the presence of respiratory motion was performed, finding that broad, Gaussian beams result in better dose uniformity than narrow, sharply delineated ones, but produce slower dose fall-off at the edges of the scanned volume.
Abstract: A three-dimensional spot-scanning technique for radiotherapy with protons is being developed at the Paul Scherrer Institute. As part of the effort to optimize the design and ensure clinically useful dose distributions, a computer simulation of the dose deposition in the presence of respiratory motion was performed. Preliminary experiments have characterized the proton beam and the scanning procedure. Using these parameters, the computer program calculated the dose within a uniform volume of water in the presence of respiratory motion. Respiration amplitude, respiration period, respiration direction, number of fractions, size and position of the beamspots and rescanning multiplicity were systematically varied and the effect on the dose distribution determined. The dose uniformity is very dependent on the direction of the respiration relative to the three independent beam scanning directions. The dose uniformity decreases with increasing respiration amplitude, but has little response to changes in respiration frequency. Rescanning the volume, such as with fractionation, improves the dose uniformity roughly as the square root of the number of fractions. Broad, Gaussian beams result in better dose uniformity than narrow, sharply delineated ones, but produce slower dose fall-off at the edges of the scanned volume. Results of this work are being incorporated into the design of the system.
267 citations
TL;DR: In this paper, the number of light neutrino species is found to be Nv=3.30% CL with the constraints of the standard electroweak model, which rules out the possibility of a fourth type of LN at 98% CL.
234 citations
TL;DR: The kinetic data provide evidence of disease progression in the unoperated striatum, which balanced against increasing graft function, may explain why clinical improvement reached a plateau within months after surgery.
Abstract: Two patients with Parkinson's disease who underwent implantation of fetal mesencephalic tissue into the putamen were serially studied using positron emission tomography and [18F]6-L-fluorodopa ([18F]dopa). The uptake of [18F]dopa is related to the functional integrity of the presynaptic dopaminergic system. Preoperative studies revealed a marked decrease in putamen [18F]dopa uptake, with lesser involvement of the caudate. Two and 4 months, respectively, after operation, both patients demonstrated functional improvement, as described elsewhere. One patient was scanned 5, 8, and 13 months after the operation and the other was scanned 7 and 12 months after the operation. In both patients, [18F]dopa uptake increased within the operated putamen despite a progressive decrease in tracer uptake in the unoperated striatal structures. We believe that this increased uptake of [18F]dopa at the implantation site represents functional integrity within a surviving neural graft. While there has been little further clinical improvement beyond the fifth postoperative month, the uptake of [18F]dopa at the operation site in both patients has progressively increased. The kinetic data provide evidence of disease progression in the unoperated striatum, which, balanced against increasing graft function, may explain why clinical improvement reached a plateau within months after surgery.
201 citations
TL;DR: In this paper, a third type of two Higgs model, where neutral scalar bosons possess flavor changing uiuih0 couplings proportional to m i m j, low energy constraints are evaded.
161 citations
TL;DR: Only a small number of parameters in the object plane are necessary for determining the kinoform, which simplifies the calculation of M x N arrays also for large M and N.
Abstract: We discuss the realization of highly efficient fan-out elements. Laser-beam writing lithography is available now for fabricating smooth surface relief microstructures. We develop several methods for optimizing microstructure profiles. Only a small number of parameters in the object plane are necessary for determining the kinoform. This simplifies the calculation of M × N arrays also for large M and N. Experimental results for a 9-beam fan-out element are presented.
118 citations
TL;DR: In this paper, the evolution of the hot central region produced in central heavy ion collisions is analyzed and the main properties of the final state can be understood as a result of an adiabatic expansion process.
115 citations
TL;DR: In this paper, neutral heavy leptons that are isosinglets under the standard SU (2)L gauge group were searched for and no evidence for a signal has been found and the limit Br(NSu0 → vlNl) < 3 x 10−5 at the 95% CL for mass range from 3 GeV up to Mz.
99 citations
TL;DR: In this article, the existence of a finite spin gap for both antiferromagnetic and ferromagnetic coupling in the half-filled Kondo lattice model is confirmed by finite-size analysis of exact diagonalization.
Abstract: By finite-size analysis of exact diagonalization the existence of a finite spin gap is confirmed for both antiferromagnetic and ferromagnetic coupling in the half-filled Kondo lattice model. For all finite values of antiferromagnetic coupling the system belongs to a class of coherent Kondo spin singlet, whereas for any finite ferromagnetic coupling it scales to a spin S=1 antiferromagnetic chain with a Haldane gap.
TL;DR: Standardized clinical testing showed a small but long-term improvement in the first of the two patients following stereotaxic grafts of fetal mesencephalic tissue from aborted human fetuses, and follow-up data from the subsequent year with an emphasis on longitudinal evaluation methodology is provided.
TL;DR: In this article, the structure of hadronic events from Z ≥ 0 decay is studied by measuring event shape variables, factorial moments, and the energy flow distribution, after correction for detector effects and initial and final state radiation, compared with the predictions of different QCD Monte Carlo programs with optimized parameter values.
Abstract: The structure of hadronic events fromZ
0 decay is studied by measuring event shape variables, factorial moments, and the energy flow distribution. The distributions, after correction for detector effects and initial and final state radiation, are compared with the predictions of different QCD Monte Carlo programs with optimized parameter values. These Monte Carlo programs use either the second order matrix element or the parton shower evolution for the perturbative QCD calculations and use the string, the cluster, or the independent fragmentation model for hadronization. Both parton shower andO(α
2
s
matrix element based models with string fragmentation describe the data well. The predictions of the model based on parton shower and cluster fragmentation are also in good agreement with the data. The model with independent fragmentation gives a poor description of the energy flow distribution. The predicted energy evolutions for the mean values of thrust, sphericity, aplanarity, and charge multiplicity are compared with the data measured at different center-of-mass energies. The parton shower based models with string or cluster fragmentation are found to describe the energy dependences well while the model based on theO(α
2
s
calculation fails to reproduce the energy dependences of these mean values.
TL;DR: In this article, the QCD correction to the one-loop electroweak radiative correction of the partial Z-decay width into b-quarks is calculated analytically in the limit of large top mass.
TL;DR: In this paper, a solar receiver-reactor has been designed to conduct solid-gas chemical reactions, using concentrated solar radiation as the energy source of high-temperature process heat, and a small-scale prototype reactor to conduct the thermal decomposition of calcium carbonate at 1300 K was experimentally investigated in a solar furnace.
Abstract: This paper reports that a solar receiver-reactor has been designed to conduct solid-gas chemical reactions, using concentrated solar radiation as the energy source of high-temperature process heat. It consists of a conical cyclone gas-particle separator that has been modified to let concentrated solar energy enter the cavity through a windowless (atmospheric-open) aperture. It combines the advantages of cavity receivers and volumetric reactors, and permits continuous mode of operation. A small-scale prototype reactor to conduct the thermal decomposition of calcium carbonate at 1300 K was experimentally investigated in a solar furnace. Its thermal performance was evaluated. The mean energy absorption efficiency, based on the optically measured power incident on the receiver aperture, was 43 percent. Reaction products showed high degree of calcination.
TL;DR: In this article, a study of the global event shape variables thrust and heavy jet mass, of energy-energy correlations and of jet multiplicities based on 250 000 hadronic Z 0 decays is presented.
TL;DR: In this paper, a probe beam deflection (PBD) transients can be simulated using simple models for the concentration profiles developed for mass transport controlled reactions and for reactions limited by a depletion of the reactant or reacting sites.
TL;DR: In this article, an instrument on the polar ERS-1 satellite failed following a transient high current consumption, which was found to have occurred close to the center of the South Atlantic Anomaly.
Abstract: An instrument on the polar ERS-1 satellite failed following a transient high current consumption. The failure was found to have occurred close to the center of the South Atlantic Anomaly. Ground test showed certain memories to be sensitive to proton-induced latchup. The failure was concluded to be due to latchup during exposure to South Atlantic Anomaly protons. The authors believe that this to be the first time a verified proton-induced latchup in space has been reported. >
TL;DR: In this paper, a photo-ASIC consisting of light-sensitive structures, light-emitting devices and analog and digital circuits is integrated on a single chip, achieving an external quantum efficiency of 50-80% in the visible spectrum.
Abstract: With ‘photo-ASICs’ comprising light-sensitive structures, light-emitting devices and analog and digital circuits, complete optical metrology systems can be integrated on a single chip. We report the realization of key components of such photo-ASICs using an industrual IC CMOS process. We achieve photodiodes with an external quantum efficiency of 50–80% in the visible spectrum and position-sensitive devices (PSDs) with a spatial non-linearity of around 0.3%. We demonstrate surface-channel CCDs with a charge-transfer efficiency of 99.8% at room temperature, as well as bucket-brigade devices (BBDs) with a lower charge-transfer efficiency of 96%. Light-emitting diodes (LEDs) are realized, emitting infrared light at 1160 nm (forward biased) and broadband visible yellow light with a spectral maximum at 640 nm (reverse biased). We discuss simple applications of passive photo-ASICs, such as a centroid detector, a 3-D camera, a motion detector and a focus sensor, used to obtain a relative measure for the local focus of an optically imaged scene, for example, in a photographic camera.
TL;DR: The ground state of the one-dimensional Kondo lattice model is examined in the strong-coupling regime and an effective Hamiltonian is developed to describe low-energy processes, which leads to a ferromagnetic ground state for all conduction electron densities.
Abstract: The ground state of the one-dimensional Kondo lattice model is examined in the strong-coupling regime. An effective Hamiltonian is developed to describe low-energy processes. This leads to a ferromagnetic ground state in this regime for all conduction electron densities. The spin excitations are those of a squeezed spin chain with ferromagnetic Heisenberg exchange coupling. In addition there are quasiparticle excitations, which are discussed in detail only for the case of half filling.
TL;DR: Quartz crystal microbalance (QCM) and probe beam deflection (PBD) were used to evaluate the exchange of mobile species (ions and solvent) during the redox reaction in poly(1-hydroxyphenazine) in aqueous acidic media as discussed by the authors.
TL;DR: In this paper, a cross-flow ultrafiltration with membranes of different pore sizes (450 nm to 1.5 nm) was used to prepare colloid concentrates and ultrafiltrates for analyses of major and trace elements and U- and Th-isotopic compositions.
TL;DR: In this paper, the diffusion and sorption properties of hardened cement paste (HCP) were investigated using the through-diffusion technique for the radionuclides Cl-36, I-125 and Cs-134.
TL;DR: In this article, six different techniques (i.e., stylus profilometry, phase shift interferometry (PSI), phase contrast mode (SOM-DPC), light scattering topography (LST), Scanning Tunneling Microscopy (STM), and atomic force microscopy (AFM) have been used for measurements of silicon surface microroughness.
Abstract: Six different techniques i.e. Stylus profilometry, Phase Shift Interferometry (PSI), Scanning Optical Microscopey in Differential Phase Contrast mode (SOM-DPC), Light Scattering Topography (LST), Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) have been used for measurements of silicon surface microroughness. Specimens with 4 different surface roughness levels have been prepared by variation of the mechanical or chemical components of a traditional polishing process. At low microroughness, a contradiction is observed between 2 groups: on one hand stylus and PSI, which sample the longer length scales from about 1 micron upwards, and STM and AFM on the other hand, which in this work sampled in the submicron range. The results of SOM-DPC and LST, which sample intermediate roughness scales, coincide with the latter group.
TL;DR: In this article, the results on J/ψ production in muon interactions with tin and carbon targets at incident muon energies of 200 and 280 GeV were presented. But the dependence of the cross section ratio on z and pT2 can explain the discrepancy between the results obtained in previous experiments, and the inelastic cross section ratios can be interpreted within the Colour Singlet model as an enhancement of the gluon distribution in tin with respect to that in carbon.
TL;DR: In this article, the first model predictions of the solubility and speciation of U, Th, Ra, Pb, Se, Sn and Ni were made in advance of the sampling exercise presented in a companion paper (Khoury et al., this issue).
TL;DR: It is proved that the ground state of the symmetric periodic Anderson model forms a total spin singlet at half filling, and can be applied to the Kondo lattice model, at least for the weak and the very strong antiferromagnetic-coupling limit.
Abstract: It is proved that the ground state of the symmetric periodic Anderson model forms a total spin singlet at half filling. This result can also be applied to the Kondo lattice model, at least for the weak and the very strong antiferromagnetic-coupling limit. For the strong coupling limit of the Kondo lattice it is additionally proved that the singlet ground state exists even when two holes are doped to the half-filled band.
TL;DR: In particular, the self-consistent renormalization theory of spin fluctuations as discussed by the authors describes a crossover from fermi-liquid regime at low temperatures to the unusual normal state at higher temperatures.
TL;DR: In this paper, the influence of the thermal treatment and reaction atmosphere on the chemical composition and the structural parameter of the spheres were systematically investigated and the correlation of the crushing strength to structural parameters was found.
TL;DR: Data indicate a high frequency of human lymphocyte cultures that do not display an adaptive response, and chromosome and chromatid aberration yields were estimated after challenge doses in the G1, S or G2 phase of lymphocytes which had been adapted in the early G1 phase.
Abstract: Various investigators reported a reduced yield of chromosome and chromatid aberrations in short-term cultures of human lymphocytes if a 'challenge' exposure to ionizing radiation was preceded by an 'adaptive' exposure. In order to examine the cell cycle dependence of the 'adaptive response', chromosome and chromatid aberration yields were estimated after challenge doses in the G1, S or G2 phase of lymphocytes which had been adapted in the early G1 phase. On testing two donors no protective adaptive response was found. Blood samples of four donors were tested for their capability to evoke the adaptive response in a standard experiment with the adaptive dose in the S phase and the challenge dose in the G2 phase. A synergistic response occurred in one out of two similar experiments performed with the same blood sample. The three other blood samples tested did not respond. Apparently these data indicate a high frequency of human lymphocyte cultures that do not display an adaptive response.