Self-diffusion of tris-naphthylbenzene near the glass transition temperature

We present a direct measurement of self-diffusion of a single-component glass-forming liquid at the glass transition temperature. Forward recoil spectrometry is used to measure the concentration profiles of deuterio and protio 1,3-bis-(1-naphthyl)-5-(2-naphthyl)benzene (TNB) following annealing-induced diffusion in a vapor-deposited bilayer. These experiments extend the range of measured diffusion coefficients in TNB by 6 orders of magnitude. The results indicate a decoupling of translational diffusion coefficients from viscosity or rotation. At T(g), D(T) is 400 times larger than expected from the Stokes-Einstein equation.     

Sectionally Semicomplemented Distributive Nearlattices

A nearlattice S is a meet semilattice together with the property that any two elements possessing a common upper bound have a supremum. Here the authors have introduced the notion of sectionally semicomplemented distributive nearlattices and given several characterizations of them. The skeleton SCon(S) of Con(S), the congruence lattice, consists of all those nearlattice congruences which are the pseudocomplements of members of Con(S). The relationship between skeletal congruences and kernel of skeletal congruences leads to numerous characterizations of sectionally semicomplemented distributive nearlattices and semiboolean algebras. For example we prove, for a distributive nearlattice S with 0, the following conditions are equivalent:

Infrared optical fibers for surgical applications

The basic characteristics of fibers that are appropriate for surgical use in the infrared are reviewed. New fiber materials, such as sapphire, fluorozirconate and chalcogenide glasses, and polycrystalline fibers are discussed as well as their applicability for surgical procedures.     

Precision measurement of neutrino oscillation parameters at INO-ICAL detector

A magnetized Iron CALorimeter (ICAL) detector at the India-based neutrino observatory (INO) is used to study neutrino oscillation sensitivity using atmospheric muon neutrino source. The ICAL detector will be able to detect muon tracks and hadron showers produced by neutrino interactions with the iron target. We have performed precision measurement analysis for the atmospheric neutrino oscillation parameters with the muon neutrino events, generated by Monte Carlo NUANCE event generator. A marginalized χ² analysis based on reconstructed neutrino energy and muon zenith angle binning scheme has been performed to determine the sensitivity for the atmospheric neutrino mixing parameters, \(\sin ^{2}\theta _{23}\) and \(| {\Delta } m^{2}_{23}|\).     

Polystyrene local dynamics in dilute solution: Temperature and solvent dependence of C-D vector correlation function shape

Variable temperature ²H-NMR T₁ experiments were performed on backbone deuterated atactic polystyrene in four solvents at two Larmor frequencies. Temperature-frequency superposition, which is consistent with experimental results for many other polymers, cannot describe our data. This indicates that the shape of the correlation function for C-D vector reorientation is temperature dependent. A modified log χ² distribution, of relaxation times, i.e., a delta function plus a log χ² distribution, was used to fit the experimental data. These fits are consistent with literature ¹³C T₁ and NOE data. As polystyrene local dynamics slow down by a factor of 5, the FWHM of the log χ² distribution increases from 0.8 to 1.1 decades. Solvent identity does not play a major role in determining the shape of the correlation function. The fraction of the correlation function decay caused by librational motion was determined to be 0.28. The quantity was compared for series of polymers and found to correlate with the size of the side group. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1241–1250, 1997     

Probe rotation near and below the glass transition temperature: Relationship to viscoelasticity and physical aging

Reorientation times ť_c for two probes in several amorphous polymers near the glass transition temperature T_g are reported. T_g for these polymers ranges from 205 to 459 K. Probe reorientation was measured in the time window from 10⁻² to 10⁴ s with a recently developed photobleaching method. ť_c for a given probe at the T_gs of the different polymers varies more than three decades. Viscoelastic relaxation times characteristic of the Rouse modes of the matrix polymers are closely related to probe rotation times and thus also not constant at T_g. The characteristic length scale of motions responsible for the glass transition varies significantly for the three polymers studied. Preliminary physical aging results indicate that probe reorientation in polystyrene ages slightly faster than the volume.     

Dynamic operation of liquid crystal cell with inherently nanogroove-featured aligned carbon nanotube sheets

The use of a highly aligned carbon nanotube (CNT) sheet as a multifunctional constituent for liquid crystal (LC) displays and electro-optic LC applications is assessed. The CNT sheet can perform a dual function: one is an alignment layer for LCs, replacing the commonly used rubbed polyimide film, and the other is a transparent conductive layer, taking the place of indium tin oxide. The hydrophobic treatment improved the adhesion quality between aligned CNT bundles and the glass substrate, which helps to preserve the inherently aligned nanogroove morphology of transparent CNT sheets. The test LC display cells, comprising 4-cyano-4′-pentylbiphenyl molecules sandwiched between CNT-sheet-on-glass substrates, demonstrate the operation characteristics comparable to that of the conventional cell under temperature variation and ac electric field of 1?kHz. The results offer a possibility of deploying multifunctional CNT-sheet alignment layers in LC-based devices, especially in the future flexible display applications.