Some results concerning invertible Morishima and anti-Morishima matrices whose associated digraphs are trees

This paper addresses the following questions: Given that A is an invertible Morishima or anti-Morishima matrix, under what conditions will A^-1 be a Morishima or anti-Morishima matrix? Also, given the associated digraph of A and the fact that A, A^-1 are Morishima or anti-Morishima matrices, what can be said about the digraph of A^-1? A class of matrices is introduced where there questions are investigated.     

Model-Year Architectures for Rapid Prototyping

The Rapid Prototyping of Application-Specific Signal Processors (RASSP) program is changing the way engineers design embedded signal processors by providing a process that will reduce by at least a factor of four both the time-to-market and cost, and improve design quality. To achieve these improvements, Lockheed Martin's Advanced Technology Laboratories (ATL) is using a methodology that stresses hardware and software reuse, and model-year architectures that enable interoperability and upgrades through open interface standards. This paper describes ATL's model-year architecture, which defines a framework for reuse to enable low-cost technology upgrades for embedded processors. This approach can be applied to a wide range of military and commercial applications.     

Group VA effects on surfactant aggregation number and dye solubilization efficiency

The effects of changing the charge-bearing atom in the polar head of a surfactant ion on micelle size and dye solubilization efficiency were investigated. Replacement of nitrogen in decyltrimethylammonium bromide by phosphorus or arsenic increases the micellar aggregation number by at least 20% in 0.5 m NaBr solutions. The ability of the surfactants to solubilize the dye Orange-OT is only slightly affected by the substitution of phosphorus for nitrogen, but it is lowered appreciably by the substitution of arsenic.     

The microwave spectrum and structure of chloryl fluoride

The microwave spectra of three isotopic species of chloryl fluoride, FClO₂, in its ground vibrational state, have been measured in the frequency region 8–37 GHz. The spectra have yielded values for the rotational constants, centrifugal distortion constants, and chlorine nuclear quadrupole coupling constants, as well as the molecular dipole moment, 1.722 ± 0.03 D. The molecule has been shown to have C_s symmetry, and a pyramidal configuration, with the chlorine atom at the apex of the pyramid. The following internuclear parameters were obtained:r(Cl?F)1.697±0.003 A r(Cl?F)=1.418±0.002AThe structural parameters, quadrupole coupling constants, dipole moment and force field are explained in terms of a bonding scheme in which a fluorine 2p atomic orbital overlaps with the highest occupied orbital of ClO₂; there is considerable evidence for withdrawal of electron density from this singly occupied antibonding orbital of ClO₂ toward the fluorine atom.     

A virtually nondestructive EPR technique accounting for diagnostic X-rays

We have implemented the method proposed by Aldrich and Pass (Aldrich, J.E., Pass, B., 1988. Determining radiation exposure from nuclear accidents and atomic tests using dental enamel. Health Phys. 54, 469–471.) to measure both the interior and exterior portions of a tooth in order to determine the diagnostic X-ray component of the total dose in the teeth. This was done using a modified nondestructive approach of Haskell et al. (Haskell, E.H., Hayes, R.B., Romanyukha, A.A., Kenner, G.H., 2000. Preliminary report on the development of a virtually non-destructive additive dose technique for EPR dosimetry Appl. Radiat Isot. 52, 1065–1070.) given in Hayes et al. ( Hayes, R.B., Haskell, E.H., Barrus, J.K., Kenner, G.H., Romanyukha, A.A., 2000. Accurate EPR radiosensitivity calibration using small sample masses. Nucl. Instr. Meth. A. 441, 535–550). Here only 5% of the total tooth enamel sample from an enamel crown was used for individual sample sensitivity calibration. A cavity response correction for the low mass samples was also used ( Hayes et al., 2000). The teeth were American wisdom teeth having unknown doses applied by the IAEA in the range of 0 to 1 Gy as part of the second international intercomparison ( Wieser, A., Mehta, K., Amira, S., Aragno, S., Bercea, S., Brik, A., Bugai, A., Callens, F., Chumak, V., Ciesielski, B., Debuyst, R., Dubovsky, S., Duliu, O., Fattibene, P., Haskell, E., Hayes, R., Ignatiev, E., Ivannikov, A., Kirillov, V., Kleschenko, E., Nakamura, N., Nathe, M., Nowak, J., Onori, S., Pass, B., Pivovarov, S., Romanyukha, A., Scherbina, O., Shames, A., Sholom, S., Skvortsov, V., Stepanenko, V., Tikounov, D., Toyoda, S., 2000. The 2nd international intercomparison on EPR tooth dosimetry. Radiat. Meas. in press). Final dose reconstruction estimates of the IAEA applied values showed a very high correlation (R=0.996). The approximate excess dose measured on the outside of the teeth relative to the inside was 49±35 mGy which is attributed to the diagnostic X-ray exposure given to the America wisdom teeth prior to extraction. The method used showed only a small dependence on the accelerating voltage of the X-ray source.     

Predictive Current Control for Multilevel Active Rectifiers With Reduced Switching Frequency

In this paper, a new low-frequency predictive current control is proposed for a single-phase cascaded H-bridge multilevel rectifier. The control method has been fully investigated with theoretical analysis, simulation, and experiments on a laboratory prototype with five series-connected H-bridges. However, the analysis and technique are valid for any general level structure. The simulations and experimental results presented demonstrate the excellent performance of the predictive control in terms of AC current waveform quality, power factor, and reduced switching frequency of each bridge, in comparison to traditional control schemes.     

Polymyxin-coated Au and carbon nanotube electrodes for stable [NiFe]-hydrogenase film voltammetry

We report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier for studying protein film voltammetry (PFV) on Au and single-walled carbon nanotube (SWNT) electrodes. Pretreating the electrodes with PM allows for the subsequent immobilization of an active submonolayer of [NiFe]-hydrogenase from Allochromatium vinosum ( Av H2ase). Probed by cyclic voltammetry (CV), the adsorbed enzyme exhibits characteristic electrocatalytic behavior that is stable for several hours under continuous potential cycling. An unexpected feature of the immobilization procedure is that the presence of chloride ions is a prerequisite for obtaining electrocatalytic activity. Atomic force microscopy (AFM) relates the observed catalytic activity to enzymatic adsorption at the PM/Au(111) surface, and a combination of concentration-dependent CV and AFM is used to investigate the interaction between the enzyme and the PM layer.     

Single-isomer tetrasubstituted olefins from regioselective and stereospecific palladium-catalyzed coupling of beta-chloro-alpha-iodo-alpha,beta-unsaturated esters

The efficient regioselective and stereospecific synthesis of tetrasubstituted olefins using a mild and convenient method is disclosed. 2-Alkynyl esters are selectively converted to E-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. These products are produced cleanly, regio- and stereoselectively, and in high yields. Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions. Selectivity results from reactivity differences in the intermediate substrates.     

Cobinamide chemistries for photometric cyanide determination. A merging zone liquid core waveguide cyanide analyzer using cyanoaquacobinamide

Diaquacobinamide (H₂O)₂Cbi²⁺ or its conjugate base hydroxyaquacobinamide (OH(H₂O)Cbi⁺)) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H₂O)Cbi⁺ is used in excess; when trace amounts of cyanide are added, CN(H₂O)Cbi⁺ should be formed. But the spectral absorption of CN(H₂O)Cbi⁺ is virtually the same as that of OH(H₂O)Cbi⁺. It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. It is shown here that even with excess OH(H₂O)Cbi⁺, (CN)₂Cbi is formed first due to kinetic reasons; this only slowly forms CN(H₂O)Cbi⁺. This understanding implies that CN(H₂O)Cbi⁺ will itself be a better reagent.