Elastic electron scattering on Zr and Mo

Elastic electron scattering on ⁹⁰Zr and ⁹²Mo has been measured at 200 and 300 MeV up to 2 fm⁻¹ momentum transfer. Data analysis led us to adopt the parabolic Gaussian shape as a valuable charge distribution for these nuclei. For ⁹⁰Zr, we have compared this model with charge distributions given by recent Hartree-Fock calculations.     

Support vector machine-based expert system for reliable heartbeat recognition

This paper presents a new solution to the expert system for reliable heartbeat recognition. The recognition system uses the support vector machine (SVM) working in the classification mode. Two different preprocessing methods for generation of features are applied. One method involves the higher order statistics (HOS) while the second the Hermite characterization of QRS complex of the registered electrocardiogram (ECG) waveform. Combining the SVM network with these preprocessing methods yields two neural classifiers, which have been combined into one final expert system. The combination of classifiers utilizes the least mean square method to optimize the weights of the weighted voting integrating scheme. The results of the performed numerical experiments for the recognition of 13 heart rhythm types on the basis of ECG waveforms confirmed the reliability and advantage of the proposed approach.     

High-power InP MISFETs

InP MISFETs with SiO2 as the gate insulator and a deep channel recess have been fabricated. At 9 GHz the highest power output with 4 dB gain was 3.5 W/mm gate width with 33% power added efficiency. This power is more than twice that of the best GaAs MESFET.     

Prototype reflectivity analyses of hydrogen storage levels in single-walled carbon nanotubes

A prototype case study is presented that examines the level of hydrogen content in H-SWNTs using the Surface Plasmon Resonance technique. The damping effect and the angular shift in the resonance minimum of an SWNT-gold interface due to the presence of hydrogen is analyzed using a parametric model, which is based on the concept of an effective permittivity. The new approach provides for a non-invasive analysis of the level of hydrogen content in H-SWNTs and is potentially extendable to other carbon-based hydrogen storage materials.     

Rearrangements of transient neutral molecules in the gas phase. Does the conversion of CCCHO to HCCCO involve oxygen or hydrogen migration?

Stable (CC13CHO)- may be formed in the chemical ionisation ion source of a VG ZAB 2HF mass spectrometer by the SN2(Si) reaction between Me3SiC[triple bond]C13CHO and F-. Vertical (Franck-Condon) one-electron oxidation of (CC13CHO)- in the first of the tandem collision cells of a VG ZAB 2HF mass spectrometer gives CC13CHO. Some of these neutrals have sufficient excess energy to effect rearrangement to HCC13CO, some of which are energised and to decompose to HCC. and 13CO. Thus the neutral rearrangement exclusively involves H migration: no products from O migration are detected. The corresponding two-electron oxidation of (CC13CHO)- gives mainly unrearranged (CC13CHO)+. A minority of these cations are energised and rearrange by H and O migration to yield (HCC13CHO)+ and (OCC13CHO)+ respectively. All experimental observations are backed up by molecular modelling at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory.     

Anechoic chamber qualification: traverse method,inverse square law analysis method,and nature of test signal

Qualification of anechoic chambers is intended to demonstrate that the chamber supports the intended free-field environment within some permissible tolerance bounds. Key qualification issues include the method used to obtain traverse data, the analysis method for the data, and the use of pure tone or broadband noise as the chamber excitation signal. This paper evaluates the relative merits of continuous versus discrete traverses, of fixed versus optimal reference analysis of the traverse data, and of the use of pure tone versus broadband signals. The current practice of using widely space discrete sampling along a traverse is shown to inadequately sample the complexity of the sound field extant with pure tone traverses, but is suitable for broadband traverses. Continuous traverses, with spatial resolution on the order of 15% of the wavelength at the frequency of interest, are shown to be necessary to fully resolve the spatial complexity of pure tone qualifications. The use of an optimal reference method for computing the deviations from inverse square law is shown to significantly improve the apparent performance of the chamber for pure tone qualifications. Finally, the use of broadband noise as the test signal, as compared to pure tone traverses over the same span, is demonstrated to be a marginal indicator of chamber performance.     

Nucleophilic additions to fused bicyclic five-membered ring oxocarbenium ions: evidence for preferential attack on the inside face

Evidence is provided that nucleophilic attack on five-membered ring oxocarbenium ions occurs from the inside face of the envelope. An eight-five fused-bicyclic system in which two substituents are constrained to pseudoequatorial positions underwent nucleophilic addition with selectivity that was comparable to an unconstrained monocyclic system. On the other hand, a bicyclic six-five analogue underwent reaction with low selectivity. This observation indicates that minimization of eclipsing interactions by attacking inside the envelope is not enough to control selectivity, but that the changes in the overall three-dimensional structure of the ring must be favorable as well. In the bicyclic six-five series, the six-membered ring is accommodated in the cation, but it destabilizes the transition state structure leading to the first-formed product of inside attack.