The diffeomorphism type of certain

In this note we show that the unit tangent bundle of is diffeomorphic to the total space of a certain principal -bundle over , solving a problem of James and Whitehead.

     

Method of measuring the spatial resolution of a photoresist

By analysis of the response of a high-contrast photoresist to sinusoidal illumination, generated interferometrically, one can extract a phenomenological modulation transfer function of the resist material, thereby characterizing its spatial resolution. Deep-ultraviolet interferometric lithography allows the resist response to be quantified at length scales below 100 nm. As an example, the resolution (FWHM) of the commercial resist UVII-HS is found to be approximately 50 nm. This simple method can be applied to materials under development for advanced photolithography with short-wavelength illumination.     

Light-sensitive microemulsions

A photodestructible surfactant, sodium 4-hexylphenylazosulfonate (C6-PAS), has been introduced to AOT-stabilized water-in-heptane microemulsions. Proton NMR spectra show that C6-PAS undergoes UV-induced decomposition, to yield a mixture of 4-hexylphenol and hexylbenzene. The photostationary state was determined by 1H NMR, indicating that nearly 90% of the initial photosurfactant had been destroyed, yielding non-surface-active hexylbenzene as the main product. This phototriggered breakdown gives rise to changes in adsorption and aggregation properties of C6-PAS, representing a novel route to induce microemulsion destabilization. When a series of microemulsions containing different amounts of C6-PAS were exposed to UV light, part of the dispersed water phase-separated. Small-angle neutron scattering (SANS) was used to follow the resulting UV-induced shrinkage of the water nanodroplets: a maximum volume decrease was found to be in the order of 60-70%. Kinetic SANS studies were also carried out in order to follow the changes in aggregation as a function of UV irradiation time. Multicontrast SANS experiments gave further insight; for example, it was demonstrated that the shell thickness remained constant. This study represents the first example of light-induced microemulsion destabilization.     

Advanced selective optical sensors based on periodically organized mesoporous hybrid silica thin films

Mesoporous thin films functionalized with silylated [small beta]-diketone compounds with symmetry mesostructure dependent on the probe quantity were used as fast uranyl species sensors with high selectivity and sensitivity.     

Magnetic ground state of pure and doped CeFe2

A combination of neutron elastic and inelastic, resonant x-ray scattering, and 57Fe M?ssbauer experiments are used to determine the unusual magnetic ground state of CeFe2. The complementarities between different time-scale techniques may allow one to understand the dynamic features of the ground state in CeFe2 and its pseudobinary compounds, and how the frustration of Fe tetrahedra leads the appearance of antiferromagnetic fluctuations in the presence of ferrimagnetism. The resulting model can be used to rationalize many of the unusual and conflicting experimental results reported for this material in the literature.     

Photoacoustic Spectroscopy to determine <Emphasis Type="Italic">in vitro</Emphasis> the non radiative relaxation time of protoporphyrin IX solution containing gold metallic nanoparticles

In order to compare the non radiative relaxation time (NRRT) between standard protoporphyrin IX (PpIX) and protoporphyrin PpIX(1) solution containing gold metallic nanoparticles, we measured the photoacoustic spectroscopy (PAS) signal phase to determine, for each solution, the NRRT by using the Rosencwaig-Gesho theory, modified to include the effect of a finite non radiative deexcitation time. A NRRT average value, obtained for each solution, is reported and compared with some NRRT of triplet states reported in the literature for molecules with the same tetrapyrrolic structure. In the study was used PpIX disodium salt (DS) solution of 25% HCL. From each solution it was obtained its optical absorption spectrum, by using a UV-Vis spectrophotometer. After this, in the maximum observed optical absorption peak (404 nm), it was obtained the Photoacoustic (PA) signal phase as a function of the light modulation frequency, from 17 to 80 Hz. Our investigations are devoted to the improvement of the thermal treatments of drugs for medical applications.     

Systematic studies of small scintillators for new sampling calorimeter

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R&D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated ⁹⁰Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT. The wrapped scintillator that gives the best light yield is determined by comparing the measured pulse height of each 10 × 40 × 2 mm strip scintillator covered with 3M reflective mirror film, teflon, white paint, black tape, gold, aluminum and white paint+teflon. The pulse height dependence on position, length and thickness of the 3M reflective mirror film and teflon wrapped scintillators are measured. Results show that the 3M radiant mirror film-wrapped scintillator has the greatest light yield with an average of 9.2 photoelectrons. It is observed that light yield slightly increases with scintillator length, but increases to about 100% when WLS fiber diameter is increased from 1.0 mm to 1.6 mm. The position dependence measurement along the strip scintillator showed the uniformity of light transmission from the sensor to the PMT. A dip across the strip is observed which is 40% of the maximum pulse height. The block type scintillator pulse height, on the other hand, is found to be almost proportional to scintillator thickness.      

A note on solutions of orientor fields for periodic systems

It is shown that the orientor field problem can be solved for control problems governed by ordinary differential equations where periodic controls give periodic trajectories.This research was partially supported by NSF Grant No. GP-27973.     

Analysis of erythromycin: I. A study of erythromycin-acid dye complexes

Erythromycin forms association complexes with four sulfonic acid dyes that can be extracted into chloroform and quantified by spectrophotometry. Of the dyes studied, MO and O IV form 1:1 complexes with the conjugate acid of erythromycin. Solutions containing 20 to 100 μg/ml of erythromycin can be conveniently analyzed by use of MO and the method described.