Chemical surface modification of poly(p-xylylene) thin films

Electrophilic aromatic substitution reactions were studied at poly(p-xylylene) (PPX) film surface-reaction medium interfaces. The extent of the reactions (depth of penetration and degree of substitution) was determined by the interaction of the polymer with the reaction solution. Reaction with chlorosulfonic acid to produce sulfonyl chloride and sulfone functionalities occurred readily in the bulk of PPX, and yields were sensitive to time and temperature. Confinement of this reaction to the PPX surface was achieved by controlling the concentration of the acid. Functionalization of PPX with N-methylol-2-chloroacetamide in sulfuric acid to produce the chloroamidomethylated derivative occurred in high yield and was confined to the surface region of PPX. Hydrolysis of the amide to generate aminomethylated PPX was assessed by XPS and a derivatization reaction. Friedel-Crafts type chemistry (acylation and alkylation reactions) also produced functionalized surfaces, but with lower degrees of substitution than the other two reactions and was strictly surface-confined.     

Anomalous tunneling of phonon excitations between two Bose-Einstein condensates

We discuss the tunneling of phonon excitations across a potential barrier separating two condensates. It is shown that a strong barrier proves to be transparent for the excitations at low energy epsilon. Moreover, the transmission is reduced with increasing epsilon in contrast to the standard dependence. This anomalous behavior is due to the existence of a quasiresonance interaction. The origin of this interaction is a result of the formation of a special well determined by the density distribution of the condensate in the vicinity of a high barrier.     

Numerical Representations of Interval Orders

In the framework of the analysis of orderings whose associated indifference relation is not necessarily transitive, we study the structure of an interval order and its representability through a pair of real-valued functions. We obtain a list of characterizations of the existence of a representation, showing that the three main techniques that have been used in the literature to achieve numerical representations of interval orders are indeed equivalent.     

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.     

First observation of the sigma(*+)(c) baryon and a new measurement of the sigma(*+)(c) mass

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the Sigma(*+)(c) charmed baryon, and an updated measurement of the mass of the Sigma(+)(c) baryon. We find M(Sigma(*+)(c))-M(Lambda(+)(c)) = (231.0+/-1.1+/-2.0) MeV, and M(Sigma(+)(c))-M(Lambda(+)(c)) = (166.4+/-0.2+/-0.3) MeV, where the errors are statistical and systematic, respectively.     

Tunable subnanosecond laser pulse generation using an active mirror concept

We report (theory, experimental check) an improved approach for generation of a tunable, subnanosecond pulse (0.1–0.4 ns), based on a single pulsation (“spike”) separation from the transient oscillations in a dye laser with active mirror (AMIR). A pumping by 20–50 ns pulses from Q-switched Nd:YAG laser is considered. The separation is in original, two-spectral selective channels cavity, where the forced by AMIR quenched generation at one of the wavelength stops initially started spiking generation at the other wavelength after the first spike development. The AMIR quickly starts the quenching generation at a precisely controlled moment and with necessary intensity thus assuring the desired separation. An advantage is a high reproducibility of the separation for high (~250%) pump power fluctuations combined with tuning in large range (~20 nm). To obtain such an operation we form ~1 ns leading front pump pulse by electrooptical temporal cutting of the input pump pulse and use an optical delay line. This increases also a few times the power in the separated spike (to be ~100 kW). Our approach widens the combinations of lasers for effective applications of spike separation technique (dye lasers excited by Q-switched solid-state or Cu-vapor lasers).     

A straightforward synthesis and structure of unprecedented iminium salts of dihydropyrido[3,2-e][1,3]thiazines

Unprecedented 2-iminium chloride salts of 5,8-dihydro-2H-pyrido[3,2-e][1,3]thiazines derivatives (8) were easily synthesized in one step from the corresponding o-chloroformyl-1,4-dihydropyridine (2) and thiourea. The structural study has been carried out by X-ray crystallography and theoretical calculations at the B3LYP/6-31G* levels and reveal that the new salts exhibit appropriate structural features to behave as calcium channel modulators.     

Polydiacetylene-supported silica films formed at the air/water interface

Mesostructured silica films have attracted interest as potential platforms for sensing, molecular sieving, catalysis, and others. The fabrication of free-standing silica films on water, however, is challenging due to the need for scaffolding agents that would constitute effective templates. We describe the assembly of thin film at the air/water interface comprising quaternary silicates and polydiacetylene (PDA), a unique chromatic polymer forming two-dimensional conjugated networks, and the use of these films for biological sensing. PDA exhibits a dual role in the system-both as the amphiphilic matrix facilitating immobilization of the silicate colloidal units at the air/water interface and additionally a chromatic reporter that undergoes visible blue-red transitions, accompanied by fluorescence transformations, in the presence of analytes. We demonstrate the application of the silicate/PDA thin films for the detection of bacterial proliferation.