Deconvolving blood-alcohol concentration and alcohol beverage consumption from sensor measurements of transdermal alcohol

We utilize mathematical, statistical and deconvolution techniques to estimate blood alcohol concentration and alcohol ingestion rate from vapor alcohol measurements coming from a new electro-chemical transdermal alcohol bio-sensor. A protocol suggesting how this can be done and a theoretical framework for the convergence of the method are also shown. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

An application of a damage constitutive model to concrete at high temperature and prediction of spalling

A characteristic feature of concrete under uniaxial compression is the development of cracks parallel to the loading direction. A damage constitutive model proposed by Ortiz [Ortiz, M., 1985. A constitutive theory for the inelastic behaviour of concrete. Mech. Mater. 4, 67–93] can predict the transverse tensile stress responsible for these cracks by considering the interaction between the aggregate and the mortar and the development of damage in the latter. When concrete is exposed to high temperature, as is the case during fire, the failure mode is thermal spalling. In order to improve the prediction of the stresses involved in this failure Ortiz’s model is extended to account for the effects of high temperature. Published experimental results for uniaxial and biaxial compression at high temperatures are used to calibrate the temperature dependence of some of the material properties. The transient creep strain is accounted for by modifying the constrained thermal strain. The stress analysis is coupled with hygro-thermal analysis of heat, mass transfer and pore pressure build-up. The effect of pore pressure on the damage evolution is modeled by applying a body force in the stress analysis module proportional to the pressure gradient. A numerical example of concrete under fire is solved and the computed results are discussed. Spalling is predicted when the damage variable reaches its maximum value of unity. The predicted depth and time of spalling for a range of variation of permeability and initial liquid water content are presented. They are in good agreement with published experimental results.     

THE RELATIONSHIP BETWEEN THE MOLAR PARTITION COEFFICIENT AND THE ULTRALOW INTERFACIAL TENSION MINIMUM IN A PETROLEUM SULFONATE/ HYDROCARBON/BRINE SYSTEM

The partitioning of a sodium petroleum sulfonate between heptane and brine yields surfactants with different molar absorptivity and λ_max values in the two phases, except near the point of minimum interfacial tension, e of the surfactant in the heptane phase increases sharply above the point of minimum interfacial tension between the two phases. The molar partition coefficient, M_H/M_W, for the surfactant between the heptane and brine phases is unity at surfactant concentrations in the brine phase below the point of minimum interfacial tension and drops sharply at concentrations above it. The critical micelle concentration of the surfactant in the aqueous phase equilibrated with the heptane phase is considerably below the concentration for minimum interfacial tension     

Relaxation times and line widths of isotopically-substituted nitroxides in aqueous solution at X-band

Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties. Spin lattice relaxation times, spin packet line widths, nuclear hyperfine splitting, and overall lineshapes were characterized for six low molecular weight nitroxides in dilute deoxygenated aqueous solution at X-band. The nitroxides included 6-member, unsaturated 5-member, or saturated 5-member rings, most of which were isotopically labeled. The spectra are near the fast tumbling limit with T₁∼T₂ in the range of 0.50–1.1 μs at ambient temperature. Both spin–lattice relaxation T₁ and spin–spin relaxation T₂ are longer for ¹⁵N- than for ¹⁴N-nitroxides. The dominant contributions to T₁ are modulation of nitrogen hyperfine anisotropy and spin rotation. Dependence of T₁ on nitrogen nuclear spin state m_I was observed for both ¹⁴N and ¹⁵N. Unresolved hydrogen/deuterium hyperfine couplings dominate overall line widths. Lineshapes were simulated by including all nuclear hyperfine couplings and spin packet line widths that agreed with values obtained by electron spin echo. Line widths and relaxation times are predicted to be about the same at 250 MHz as at X-band.     

Rashba spin-splitting control at the surface of the topological insulator Bi2Se3

The electronic structure of Bi(2)Se(3) is studied by angle-resolved photoemission and density functional theory. We show that the instability of the surface electronic properties, observed even in ultrahigh-vacuum conditions, can be overcome via in situ potassium deposition. In addition to accurately setting the carrier concentration, new Rashba-like spin-polarized states are induced, with a tunable, reversible, and highly stable spin splitting. Ab initio slab calculations reveal that these Rashba states are derived from 5-quintuple-layer quantum-well states. While the K-induced potential gradient enhances the spin splitting, this may be present on pristine surfaces due to the symmetry breaking of the vacuum-solid interface.     

Design of Monodisperse and Well‐Defined Polypeptide‐Based Polyvalent Inhibitors of Anthrax Toxin

The design of polyvalent molecules, presenting multiple copies of a specific ligand, represents a promising strategy to inhibit pathogens and toxins. The ability to control independently the valency and the spacing between ligands would be valuable for elucidating structure–activity relationships and for designing potent polyvalent molecules. To that end, we designed monodisperse polypeptide‐based polyvalent inhibitors of anthrax toxin in which multiple copies of an inhibitory toxin‐binding peptide were separated by flexible peptide linkers. By tuning the valency and linker length, we designed polyvalent inhibitors that were over four orders of magnitude more potent than the corresponding monovalent ligands. This strategy for the rational design of monodisperse polyvalent molecules may not only be broadly applicable for the inhibition of toxins and pathogens, but also for controlling the nanoscale organization of cellular receptors to regulate signaling and the fate of stem cells.