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Notes: At low temperature, the dominant current transport process of a p-type PtSi Schottky diode on a moderately doped Si substrate is thermionic emission over the barrier. In this paper, current has been measured as a function of temperature at a fixed reverse bias for several Schottky diodes. It is found that diffusion effects due to the limitation upon the diffusion rate through the space-charge region can become significant under some conditions. At moderate field, these conditions are calculated to be at a temperature of 150 K or greater, depending on the doping density of the devices. I-V-T measurements were carried out on several Schottky devices fabricated in slightly different ways, and the diffusion effect was observable in some of these devices. A numerical routine is utilized to fit the experimental data to a combined thermionic emission-diffusion theory in these regions. It is found that the experimental results fit this theory well. In addition, the acceptor density at which diffusion becomes the dominant current at 80 K under moderate field is calculated to be around 5×1011 cm−3.

Notes: The stability of CO-chemisorbed small clusters of copper have been studied both by first principles calculations and by experiment. Evidence is found that the shell model (which predicts that clusters of 8, 18, and 20 electrons are particularly stable) is useful both for the bare metal clusters, and for these clusters with a chemisorbed CO−provided the CO is considered to have contributed two electrons. Experiments supporting this view are reported for gold clusters as well.

Notes: We report on 13C magnetic relaxation in liquid benzene (C6H6 and C6D6) at 293 K at resonance frequencies of 22.63 and 100.6 MHz. The total spin–lattice relaxation rates are separated into contributions from 13C–1H and 13C–2D dipolar, spin–rotation (SR), and chemical shift anisotropy (CSA) interactions. As the principal axis of the 13C chemical shift tensor is collinear with the sixfold axis of benzene, CSA relaxation provides information on the tumbling motion of benzene, hitherto not available from other NMR experiments. The resulting correlation time τ⊥ = 1.63 ps at 20 °C indicates a faster tumbling motion, and hence, a smaller anisotropy of benzene reorientation than usually quoted in the literature. This result is qualitatively confirmed by an analysis of 13C relaxation by SR interaction, and is in fair agreement with recent results obtained in Raman line shape measurements. It is, however, at variance with the figures deduced from Rayleigh scattering experiments. The activation energy for the tumbling motion is found to be 9.8 kJ mol−1, which is markedly larger than the activation energy of 7.7 kJ mol−1 obtained from 2D relaxation data for the motion of in-plane axes.

Notes: We report analytical representations of the six-dimensional potential energy hypersurface for (HF)2, the parameters of which are closely adjusted to low energy experimental properties such as hydrogen bond dissociation energy (D0=1062 cm−1 ) and vibrational–rotational spectra in the far and mid infrared. We present a detailed analysis of properties of the hypersurface in terms of its stationary points, harmonic normal mode amplitudes, and frequencies for the Cs minimum and C2h saddle point and effective Morse parameters and anharmonic overtone vibrational structure for the hydrogen bond and the HF stretching vibrations. The comparison between experimental data and the potential energy surface is carried out by means of accurate solutions of the rotational–vibrational Schrödinger equation with quantum Monte Carlo techniques, which include anharmonic interactions between all modes for the highly flexible dimer. Two extensions of the quantum Monte Carlo technique are presented, which are based on the clamped coordinate quasiadiabatic channel method and allow for the approximate calculation of excited rotational and vibrational levels.Predictions include dissociation energies D0 for isotopomers (XF)2 with X=μ, D, T (D0=477; 1169; 1217 cm−1 ). Unusual anharmonic isotope effects predicted for the out-of-plane bending fundamental ν6 [378; 276; 295; and 358 cm−1 for (HF)2, (DF)2, (HFDF), (DFHF)] can be understood in simple terms. Centrifugal effects both for the high frequency a-axis rotation and low frequency c-axis rotation are accurately calculated for the vibrational ground state and some excited states, with a best equilibrium center of mass distance Req.ab=5.14a0 between the HF monomers. A very large anharmonic interaction constant x46≈−16 cm−1 is predicted for the hydrogen bond vibration ν4 and for out-of-plane bending ν6. This leads to assignment of our earlier experimental observation of a band at 383 cm−1 as ν6+ν4−ν4(K=1←0) at almost exactly the predicted position. The fundamental ν4 is predicted at 130±10 cm−1. A new, indirect assignment of our experimental data gives ν4≈125 cm−1. Monte Carlo calculations are presented for quasiadiabatic channels and transition states for hydrogen bond dissociation. We present a discussion of symmetry correlations for these channels and symmetry effects in predissociation by rotation, nuclear spin symmetry, and parity violation. Large effects from zero point energy on the three-dimensional quantum centrifugal barriers for rotational predissociation are found. On the basis of the new data, a much improved statistical mechanical estimate for the equilibrium 2HF=(HF)2 is obtained.

Notes: We performed programmed ventricular stimulation on 69 patients with left ventricular ejection dysfunction (ejection fraction 〈 50%) and clinically recognized ventricular tachycardia including 28 patients with sustained ventricular tachycardia and 41 patients with nonsustained ventricular tachycardia. An inducible arrhythmia (〉 6 beats ventricular tachycardia) was found in 74% of patients. Patients with clinically sustained arrhythmias were frequently inducible (89%) with a high incidence of inducible monomorphic ventricular tachycardia (82%). Patients with clinically nonsustained ventricular tachycardia had a lower rate of inducibility (63%) including a high incidence of inducible polymorphic ventricular tachycardia (27%). Inducible patients with left ventricular dysfunction and ventricular tachycardia had a low incidence of electrophysiologically demonstrated effective drug therapy (16%). However, if an effective drug was found, the prognosis was good. Empirical drug therapy was associated with a poor prognosis in inducible and noninducible patients. Finally, an unfavorable prognosis was associated with a clinically sustained arrhythmia, a lower ejection fraction, and the presence of a left ventricular aneurysm. An inducible arrhythmia did not predict an unfavorable course. Indeed, patients with noninducible ventricular tachycardia in this group of patients were still at risk for sudden cardiac death.

Notes: Abstract Differences in dental behavior and dental altitudes between people with (almost) all natural teeth, people with a full denture in both jaws and people with a full denture in only the maxilla are visualized by means of correspondence analysis in one overall picture. In this picture the three distinguished subgroups of dental patients and their characteristics are indicated as points in a two-dimensional space. The distances between the points in this picture show to what extent these points are connected. The findings obtained in this study can lead to the conclusion that: a. differences in dental status are related to differences in dental behavior and dental attitudes; b. people with all natural teeth and people with a full demure in both jaws obviously are opposite of each other in many respects, whereas people with a full denture in only one jaw can be characterized as a dental in-between group.

Notes: SUMMARY. 1. The pH range over which the effects of acidification on freshwater organisms become apparent may be quite narrow, in some cases less than half a pH unit. Therefore, accurate measurement is important, particularly in dilute surface waters near the biologically critical threshold of hydrogen ion activity.2. A hypothetical example based on data from two species of fish illustrates the potential errors in predicting mean mortality when pH is measured by probes of varying accuracies, placing our results into an ecosystem management perspective. For a given error, there will be greater uncertainty in predicting mean mortality for species sensitive to increased hydrogen ion activity than for more tolerant species.3. We review field pH measurement errors, and present unique laboratory (measurements at 1°C and under argon) and field comparisons of current instruments used for continuous, in situ pH monitoring, including the only instrument comparison in low conductivity waters during snow melt. Four operator or sampler-caused measurement errors and three electrode-caused pH measurement errors are illustrated with data from four common types of pH probes and meters.4. Studies providing no confidence intervals for a set of pH measurements due to the lack of rigorous quality control and assurance procedures are of limited quantitative value to future investigators attempting to analyse temporal trends of surface water acidification. Management and policy decision attempts will remain seriously hampered until more interpretable results are routinely generated.