Macrohomogeneity condition in dynamics of micropolar media

We determine the macrohomogeneity (Hill-Mandel type) condition in the dynamic response of inhomogeneous micropolar (Cosserat) materials. The setting calls for small deformation gradients and curvatures, but without restrictions on the constitutive behavior and without any requirements of spatial periodicity. The condition gives admissible boundary loadings, along with extra terms representing kinetic energy contributions of both classical type and micropolar type. The said loadings involve various combinations of average stresses and strains, along with couple-stresses and curvature-torsion tensors. If applied to a specific microstructure in a computational mechanics approach, these boundary loadings will allow one to determine scale-dependent homogenization toward a representative volume element (RVE) of an equivalent homogeneous micropolar medium in either elastic or inelastic settings. By restricting the continuum model to an inhomogeneous Cauchy continuum and/or a quasi-static setting, the macrohomogeneity condition simplifies to conventional versions.     

Nanosized aerosols from consumer sprays: experimental analysis and exposure modeling for four commercial products

Consumer spray products are already on the market in the cosmetics and household sector, which suggest by their label that they contain engineered nanoparticles (ENP). Sprays are considered critical for human health, because the lungs represent a major route for the uptake of ENP into the human body. To contribute to the exposure assessment of ENP in consumer spray products, we analyzed ENP in four commercially available sprays: one antiperspirant, two shoe impregnation sprays, and one plant-strengthening agent. The spray dispersions were analyzed by inductively coupled plasma mass spectrometry (ICPMS) and (scanning-) transmission electron microscopy ((S)TEM). Aerosols were generated by using the original vessels, and analyzed by scanning mobility particle sizer (SMPS) and (S)TEM. On the basis of SMPS results, the nanosized aerosol depositing in the respiratory tract was modeled for female and male consumers. The derived exposure levels reflect a single spray application. We identified ENP in the dispersions of two products (shoe impregnation and plant spray). Nanosized aerosols were observed in three products that contained propellant gas. The aerosol number concentration increased linearly with the sprayed amount, with the highest concentration resulting from the antiperspirant. Modeled aerosol exposure levels were in the range of 10¹⁰ nanosized aerosol components per person and application event for the antiperspirant and the impregnation sprays, with the largest fraction of nanosized aerosol depositing in the alveolar region. Negligible exposure from the application of the plant spray (pump spray) was observed.     

HMBC‐1,1‐ADEQUATE via generalized indirect covariance: a high sensitivity alternative to n,1‐ADEQUATE

1,1‐ADEQUATE and the related long‐range 1,n‐ and n,1‐ADEQUATE variants were developed to provide an unequivocal means of establishing ²J_CH and the equivalent of ⁿJ_CH correlations where n = 3,4. Whereas the 1,1‐ and 1,n‐ADEQUATE experiments have two simultaneous evolution periods that refocus the chemical shift and afford net single quantum evolution for the carbon spins, the n,1‐variant has a single evolution period that leaves the carbon spin to be observed at the double quantum frequency. The n,1‐ADEQUATE experiment begins with an HMBC‐type ⁿJ_CH magnetization transfer, which leads to inherently lower sensitivity than the 1,1‐ and 1,n‐ADEQUATE experiments that begin with a ¹J_CH transfer. These attributes, in tandem, serve to render the n,1‐ADEQUATE experiment less generally applicable and more difficult to interpret than the 1,n‐ADEQUATE experiment, which can in principle afford the same structural information. Unsymmetrical and generalized indirect covariance processing methods can complement and enhance the structural information encoded in combinations of experiments e.g. HSQC‐1,1‐ or ?1,n‐ADEQUATE. Another benefit is that covariance processing methods offer the possibility of mathematically combining a higher sensitivity 2D NMR spectrum with for example 1,1‐ or 1,n‐ADEQUATE to improve access to the information content of lower sensitivity congeners. The covariance spectrum also provides a significant enhancement in the F₁ digital resolution. The combination of HMBC and 1,1‐ADEQUATE spectra is shown here using strychnine as a model compound to derive structural information inherent to an n,1‐ADEQUATE spectrum with higher sensitivity and in a more convenient to interpret single quantum presentation. Copyright © 2012 John Wiley & Sons, Ltd.     

Utilizing Lifetimes to Suppress Random Coil Features in 2D IR Spectra of Peptides

We report that the waiting time delay in 2D IR pulse sequences can be used to suppress signals from structurally disordered regions of amyloid fibrils. At a waiting time delay of 1.0 ps, the random coil vibrational modes of amylin fibrils are no longer detectable, leaving only the sharp excitonic vibrational features of the fibril β-sheets. Isotope labeling with (13)C(18)O reveals that structurally disordered residues decay faster than residues protected from solvent. Since structural disorder is usually accompanied by hydration, we conclude that the shorter lifetimes of random-coil residues is due to solvent exposure. These results indicate that 2D IR pulse sequences can utilize the waiting time to better resolve solvent-protected regions of peptides and that local mode lifetimes should be included in simulations of 2D IR spectra.     

Competitive evaluation of threshold functions in the priced information model

In Charikar et al. (J. Comput. Syst. Sci. 64(4):785–819, 2002) the authors proposed a new model for studying the function evaluation problem based on a variant of the classical decision tree problem for Boolean functions. In this variant each variable of the function to evaluate has an associated cost which has to be paid in order to read the value of the variable. Given a function f and an assignment σ to the variables of f, the performance of an algorithm for evaluating f is measured via the competitive ratio, i.e., the ratio of the total cost spent by the algorithm and the cost of the cheapest set of variables constituting a certificate for the value of the function on the given assignment.     

Differently Glycosidated 2‐Amino‐2‐deoxy‐d‐glucopyranosiduronic Acids as Building Blocks in Peptide Synthesis

Seven differently glycosidated sugar amino acids (SSAs) derived from glucosamine have been prepared. Following standard solution‐phase peptide‐coupling procedures, the glycosidated 2‐amino‐2‐deoxy‐D ‐glucopyranosiduronic acids were condensed with natural amino acids to furnish useful heterodi‐ and ‐trimeric building blocks to be used in peptide synthesis. Combinations of these building blocks yielded hetero‐oligomeric peptides with two sugar amino acid units in different distances to each other. These were prepared to evaluate the influence of glycosidic side chains on the peptide backbone. Conformations of selected examples were examined by means of ROESY spectroscopy in combination with molecular dynamics (MD) simulations and circular‐dichroism (CD) studies.