Pnictides as symmetrically bridging ligands in novel neutral complexes

The reaction of [LWCl] (3) [L = N(CH2CH2NiPr)3] with LiE(SiMe3)2 (E = P, As, Sb) yields the novel, neutral pnictido-bridged complexes [LW = E = WL] (5-7). By following the reaction, which starts from the LiP-(SiMe3)2 derivative, by 31P NMR spectroscopy, the formation of an intermediate with a terminal pnictido ligand can be ruled out. The paramagnetic complexes 5-7 are comprehensively spectroscopically characterised. The X-ray structure analysis of the heterocumulenes 5-7 reveals a linear structure in which the two W-"tren" units bind to the central pnictido atom in a staggered conformation ["tren" = tren-based ligand; tren = tris(2-aminoethyl)-amine. When N2 is used as the inert gas in the synthesis of the starting material [N(CH2CH2NNp)3WCl] [Np = CH2C-(CH3)3], the complex [[N(CH2CH2NNp)3]W2(mu, eta 1: eta 1-N2)] (4) is formed as a side product. Complex 4 possesses a hydrazido(4-) (N2(4-)) ligand connected by two tungsten-"tren" moieties.     

The index of the pseudo-Riemannian Dirac operator as a transversally elliptic operator

Let (M,r) be a closed, space- and time-orientable, pseudo-Riemannian spin manifold and-let G be a compact group of orientation-preserving isometries on (M,r). If there are no isotropic directions transversal to the orbits of G, then the Dirac operator on (M,r) is transversally elliptic. In this paper we calculate its index.     

Atmospheric interaction radiation from high altitude rocket exhausts

A model for calculating the infrared radiation from rocket exhaust gases at high altitudes (typically above 200 km), caused by collisions between exhaust molecular species and atmospheric species is presented. At altitudes where the atmospheric mean free path is larger than a typical rocket exhaust plume lenght scale, the evolution in space and time of the exhaust gases is described by the kinetic theory of gases. In addition, the collision frequency between exhaust and atmospheric species is sufficiently low that excited molecules have time, on the average, to loose thsis excitation energy via radiative emission before experiencing another collision. Thus, the distribution of excited molecular states is nonthermal in this model. Two examples of such radiation are presented: one for the radiation from the CO₂ (υ₃) mode and the other for the H₂O(υ₃) mode. The atmospheric collision partner for excitation of both of these exhaust species is taken to be atomic oxygen, the dominant atmospheric constituent at high altitudes.     

A study of the 1,2-addition of group IV metallacycles derived from 1-alkynylphosphonates to conjugated enones

Addition of group IV cyclopropenemetallocycles to conjugated enones indicates that the reaction course is mostly dependent on the metallocyle and the enone moiety. The zirconacycle affords the unrearranged products 3. On the other hand, some rearranged products, 1,3-butadienylphosphonates, are obtained when titanacycles are used.     

Effective and safe laser action in the surface fusion of a ternary medium while preserving the functionality of the easily fusible component

The manufacturing of biochips by heating a multicomponent layer of polymeric microparticles that contain sensitive elements is simulated. Heating is performed up to the stage of polymer shell melting without damage to the sensitive elements. The corresponding thresholds of laser parameters (radiation power density) are detected. The preservation of biological complex functionality under these parameters is experimentally shown.     

K-homology and index theory on contact manifolds

This paper applies K-homology to solve the index problem for a class of hypoelliptic (but not elliptic) operators on contact manifolds. K-homology is the dual theory to K-theory. We explicitly calculate the K-cycle (i.e., the element in geometric K-homology) determined by any hypoelliptic Fredholm operator in the Heisenberg calculus. The index theorem of this paper precisely indicates how the analytic versus geometric K-homology setting provides an effective framework for extending formulas of Atiyah–Singer type to non-elliptic Fredholm operators.     

Articulatory and acoustic adaptation to palatal perturbation

Previous work has established that speakers have difficulty making rapid compensatory adjustments in consonant production (especially in fricatives) for structural perturbations of the vocal tract induced by artificial palates with thicker-than-normal alveolar regions. The present study used electromagnetic articulography and simultaneous acoustic recordings to estimate tongue configurations during production of [s s? t k] in the presence of a thin and a thick palate, before and after a practice period. Ten native speakers of English participated in the study. In keeping with previous acoustic studies, fricatives were more affected by the palate than were the stops. The thick palate lowered the center of gravity and the jaw was lower and the tongue moved further backwards and downwards. Center of gravity measures revealed complete adaptation after training, and with practice, subjects' decreased interlabial distance. The fact that adaptation effects were found for [k], which are produced with an articulatory gesture not directly impeded by the palatal perturbation, suggests a more global sensorimotor recalibration that extends beyond the specific articulatory target.