Novel active noise-reducing headset using earshell vibration control

Active noise-reducing (ANR) headsets are available commercially in applications varying from aviation communication to consumer audio. Current ANR systems use passive attenuation at high frequencies and loudspeaker-based active noise control at low frequencies to achieve broadband noise reduction. This paper presents a novel ANR headset in which the external noise transmitted to the user's ear via earshell vibration is reduced by controlling the vibration of the earshell using force actuators acting against an inertial mass or the earshell headband. Model-based theoretical analysis using velocity feedback control showed that current piezoelectric actuators provide sufficient force but require lower stiffness for improved low-frequency performance. Control simulations based on experimental data from a laboratory headset showed that good performance can potentially be achieved in practice by a robust feedback controller, while a single-frequency real-time control experiment verified that noise reduction can be achieved using earshell vibration control.     

Phosphinoferrocenylaminophosphines as novel and practical ligands for asymmetric catalysis

[structure: see text] A new series of ligands with a novel phosphine-aminophosphine ligation design as depicted in structure 1 has been prepared on a ferrocenylethyl backbone. These BoPhoz ligands of structure 2 have afforded exceedingly high activity and enantioselectivity in the rhodium-catalyzed asymmetric hydrogenation of dehydro-alpha-amino acid derivatives, itaconic acids, and alpha-ketoesters. These air-stable ligands are readily prepared from cost-effective and non-pyrophoric intermediates.     

Control of multiple filamentation in air

In this Letter we provide what is believed to be the first experimental evidence of suppression of the number of filaments for high-intensity laser pulses propagating in air by beam astigmatism. We also show that the number, pattern, and spatial stability of the filaments can be controlled by varying the angle that a focusing lens makes with the axial direction of propagation. This new methodology can be useful for applications involving atmospheric propagation, such as remote sensing.     

Carrier-envelope phase slip of ultrashort dispersion-managed solitons

The carrier-envelope phase slip of an ultrashort pulse circulating in a mode-locked Ti:sapphire laser is analyzed. The laser cavity is modeled by a dispersion- and nonlinearity-managed nonlinear Schr?dinger equation. The combined contributions to the phase slip induced by nonlinear phase and nonlinear dispersion are found to approach zero for strong dispersion maps. The dependence of the slip on third-order dispersion is found as well. The analytical results are verified using numerical simulations.     

Spaces ofp-vectors of bounded rank

LetV be ann-dimensional space over an infinite field of characteristic different from 2. Therank ofw ∈ Λ ^p V is the minimal dimension of a subspaceU ⊂V such thatw ∈ Λ ^p U. Extending a well-known result on linear spaces in the Grassmannian, it is shown that ifp≤k<n then the maximal dimension of a subspaceW ⊂ Λ ^p V such that rankw≤k for allω ∈W is where∈=1 ifk=p orp=2|k,∈=0 otherwise, andm satisfies . Supported by The Israel Science Foundation founded by the Academy of Sciences and Humanities.     

High-precision measurements of 17O/16O and 18O/16O of O2 and O2/Ar ratio in air

A method for high-precision and high-accuracy mass spectrometric measurements of the ratios among the three oxygen isotopes, and of the O(2)/Ar ratio, is presented. It involves separation of the O(2)-Ar mixture from air and includes a fully automated system that ensures highly reliable sample processing. Repeated measurements of atmospheric oxygen yield the repeatability (+/-SE x t, standard error of the mean (n = 12) multiplied by Student's t-factor for a 95% confidence limit) of 0.004, 0.003 and 0.2 per thousand for delta(18)O, delta(17)O and delta O(2)/Ar, respectively.     

Frequency shifts and interaction strength of model hydrogen-bonded systems: new NBO and QTAIM characteristics

An innovative theoretical study of intermolecular properties of standard hydrogen-bonded complexes of H₂O···HCF₃, NH₃···HCF₃, H₂O···HF, and NH₃···HF is presented in this work. Several computational strategies were used, so initially the MP2/6-311++G(d,p) level of theory was applied to determine the optimized geometries by which the structural parameters, electronic properties, and the stretch vibration modes of these systems were examined. By taking into account the infrared spectrum analysis, the frequency shifted either to the red- or blue-region is the principal interpretation upon formation of intermolecular complexes. Due to this, the analysis of the interaction strengths corroborates with these vibration behaviors, and besides, the Natural Bond Orbital calculations revealed systematic changes in the percentage of the s and p orbitals, by which the stretch deformations on the proton donors (HF and HCF₃) could be understood. In advance, it was quoted the appearing of intermolecular covalence in these complexes, and this event could be theoretically discovered through the topological computations based on the Bader's Quantum Theory of Atoms in Molecules.     

Single‐Scan 2D Hadamard NMR Spectroscopy

Scan and deliver : By combining imaging‐based spectral/spatial 2D radiofrequency manipulations (see scheme, left) with Hadamard‐weighting principles, 2D NMR spectra can be retrieved within a single scan (right). This approach can give homo‐ or heteronuclear correlations with an enhanced sensitivity over conventional ultrafast 2D NMR spectroscopy.

     

Null sets and games in Banach spaces

The notion of Aronszajn-null sets generalizes the notion of Lebesgue measure zero in the Euclidean space to infinite dimensional Banach spaces. We present a game-theoretic approach to Aronszajn-null sets, establish its basic properties, and discuss some ensuing open problems.     

The combinatorics of the Baer-Specker group

We study subgroups of ℤ^ℕ which possess group theoretic properties analogous to properties introduced by Menger (1924), Hurewicz (1925), Rothberger (1938), and Scheepers (1996). The studied properties were introduced independently by Kočinac and Okunev. We obtain purely combinatorial characterizations of these properties, and combine them with other techniques to solve several questions of Babinkostova, Kočinac, and Scheepers. The first author was supported by the EU Research and Training Network HPRN-CT-2002-00287. The second author was partially supported by the Koshland Center for Basic Research.