Transport optimization on complex networks

We present a comparative study of the application of a recently introduced heuristic algorithm to the optimization of transport on three major types of complex networks. The algorithm balances network traffic iteratively by minimizing the maximum node betweenness with as little path lengthening as possible. We show that by using this optimal routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing. A formula is proved and tested with numerical simulation that allows quick computation of the average number of hops along the path and of the average travel times once the betweennesses of the nodes are computed. Using this formula, we show that routing optimization preserves the small-world character exhibited by networks under shortest path routing, and that it significantly reduces the average travel time on congested networks with only a negligible increase in the average travel time at low loads. Finally, we study the correlation between the weights of the links in the case of optimal routing and the betweennesses of the nodes connected by them.     

Temperature Dependence of the Emission Spectrum of Silicon Nanoparticles in Acetone and Isopropanol Solvents

This study investigated the emission spectra of select silicon nanoparticles when subjected to various temperature changes. Two sizes of silicon nanoparticles, dispersed in both isopropanol and acetone solvents, were studied. Photoluminescence responses of the samples were measured in an environmental chamber that allowed exposure to temperatures in the range of ?73 to 65 °C (?100 to 150 °F). These silicon nanoparticles exhibited emission dependence on the temperature of their environment. The emission become brighter as the temperature decreased and less intense as the temperature increased. Thus, the response of these silicon nanoparticles in a harsh environment has been qualified.     

Measurement of lattice damage caused by ion-implantation doping of semiconductors†

Two new techniques have been used to measure the lattice damage produced in gallium arsenide by the implantation of 60 keV cadmium ions. In one of these methods, optical reflection spectra of the ion-implanted samples were measured in the wavelength range from 2000 to 4600Å. The decrease in reflectivity resulting from ion- implantation was used to determine the relative amount of lattice damage as a function of ion dose. The second technique employed the scanning electron microscope. Patterns very similar in appearance to Kikuchi electron diffraction patterns are obtained when the secondary and/or backscattered electron intensity is displayed in the scanning electron microscope as a function of the angle of incidence of the electron beam on a single crystal surface. The degradation of these ‘Coates-Kikuchi’ patterns resulting from ion implantation was used to obtain a quantitative measure of the lattice damage caused by the implantation process. The results of measurements made by both of the methods described have been compared with each other, and with data obtained by the more established method of measuring lattice damage by Rutherford scattering of 1 MeV helium ions.     

The Intersection of Opposed Big Cells in The Real Flag Variety of Type G2

We compute the Euler characteristics of the individual connectedcomponents of the intersection of two opposed big cells in thereal flag variety of type G₂, verifying a conjecture of Rietsch[6]. 2000 Mathematical Subject Classification: primary 14M15; secondary20G20.     

Towards the nonstick egg: designing fluorous proteins

Anyone who has made scrambled eggs will have had cause to praise the properties of Teflon. Teflon's highly chemically inert and nonstick nature derives from the perfluorinated polymer polytetrafluoroethylene. Perfluorocarbons have unique and valuable physical properties not found in nature. By incorporating fluorine into proteins, it might be possible to produce biological molecules with novel and useful properties.     

Experimental investigation of the two-photon widths of the chi(c0) and the chi(c2) mesons

Using 12.7 fb(-1) of data collected with the CLEO detector at CESR, we observed two-photon production of the cc states chi(c0) and chi(c2) in their decay to pi(+)pi(-)pi(+)pi(-). We measured gamma(gammagamma)(chi(c))xB(chi(c)-->pi(+)pi(-)pi(+)pi(-)) to be 75+/-13(stat)+/-8(syst) eV for the chi(c0) and 6.4+/-1.8(stat)+/-0.8(syst) eV for the chi(c2), implying gamma(gammagamma)(chi(c0)) = 3.76+/-0.65(stat)+/-0.41(syst)+/-1.69(br) keV and gamma(gammagamma)(chi(c2)) = 0.53+/-0.15(stat)+/-0.06(syst)+/-0.22(br) keV. Also, cancellation of dominant experimental and theoretical uncertainties permits a precise comparison of gamma(gammagamma)(chi(c0))/gamma(gammagamma)(chi(c2)), evaluated to be 7.4+/-2.4(stat)+/-0.5(syst)+/-0.9(br), with QCD-based predictions.     

Measurements of F2 and xF(nu)(3) - xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe Data in a Physics Model-Independent Way

We report on the extraction of the structure functions F2 and DeltaxF(3) = xF(nu)(3)-xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe differential cross sections. The extraction is performed in a physics model-independent (PMI) way. This first measurement of DeltaxF(3), which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The ratio of the F2 (PMI) values measured in nu(mu) and mu scattering is in agreement (within 5%) with the predictions of next-to-leading-order parton distribution functions using massive charm production schemes, thus resolving the long-standing discrepancy between the two sets of data.     

Broadband time-domain reflectometry measurement of attenuation and phase velocity in highly attenuating suspensions with application to the ultrasound contrast medium Albunex

We describe a technique for broadband measurements of the attenuation coefficient and phase velocity of highly attenuating liquid suspensions. To validate the technique we apply it to the ultrasound contrast agent Albunex at concentrations ranging from 0.69 x 10(6) particles/mL to 364 x 10(6) particles/mL. These longitudinal wave measurements were performed on Albunex suspensions maintained at 37 degrees C in a special time-domain reflectometer designed and constructed in our laboratory. The frequency-dependent attenuation coefficients and phase velocities obtained in the reflectometer are compared to broadband through-transmission measurements of these same quantities, which were also performed in our laboratory. Although comparison data between the two techniques are only available at lower concentrations, the agreement is quite good and serves to validate the methods described in this paper.     

Quasi phase matching in GaAs--AlAs superlattice waveguides through bandgap tuning by use of quantum-well intermixing

We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs-AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient chi((2))(zxy), which we realized by periodically tuning the superlattice bandgap. Second-harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4microm . The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of ~110 nW was obtained for the second harmonic by use of an average launched pump power of ?2.3mW .