Knudsen effect on plasma-particle mass transfer. I. Formulation and application to self-diffusion

The Knudsen effect on mass transfer between a plasma gas and a small particle is investigated. A predictive model is developed by incorporating the Z-potential approach into the jump theory. The predictions of the model are explored through a case study. The results indicate that the Knudsen effect is significant and depends strongly on the particle size and the surface conditions. The plasma and the particle surface temperatures are also found to be determining factors. Under certain conditions, it is observed that the Knudsen effect can enhance the plasma-particle mass transfer, contrary to the predictions of the previous near-isothermal models.     

Synthesis and liquid crystal properties of 4-alkoxybenzylidene-4'-aminocinnamic acid 1-trifluoromethylalkyl esters The ABACT series

The synthesis of homologues of 4-alkoxybenzylidene-4'-aminocinnamic acid 1-trifluoromethylalkyl esters is reported. Only three of the compounds exhibit smectic phases. Phases were identified using optical and electro-optic techniques together with X-ray diffraction studies. Some of the compounds, while not exhibiting liquid crystal phases, show crystalline polymorphism.     

Reacquisition of contrastive stress in an adventitiously deaf speaker using a single-channel cochlear implant

Acoustic correlates of contrastive stress, i.e., fundamental frequency (F0), duration, and intensity, and listener perceptions of stress, were investigated in a profoundly deaf subject (RS) pre/post single-channel cochlear implant and longitudinally, and compared to the overall patterns of age-peer profoundly deaf (JM) and normally hearing subjects (DL). The stimuli were a group of general American English words in which a change of function from noun to verb is associated with a shift of stress from initial to final syllable, e.g., CON'trast versus conTRAST'. Precochlear implant, RS was unable to produce contrastive stress correctly. Hearing one day post-stimulation resulted in significantly higher F0 for initial and final stressed versus unstressed syllables. Four months post-stimulation, RS maintained significantly higher F0 on stressed syllables, as well as generalization of significantly increased intensity and longer syllable duration differences for all stressed versus unstressed syllables. Perceptually, listeners judged RS's contrastive stress placement as incorrect precochlear implant and as always correct post-cochlear implant. JM's contrastive stress was judged as 96% correct, and DL's contrastive stress placement was 100% correct. It was concluded that RS reacquired all acoustic correlates needed for appropriate differentiation of contrastive stress with longitudinal use of the cochlear implant.     

Low-loss all-fiber acousto-optic tunable filter

We report significant advances in the development of simple all-fiber, tunable acousto-optic spectral filters based on null couplers. The performance agrees well with theoretical predictions and is attributed to improved control of the coupler uniformity. Furthermore, using a double-pass arrangement, we demonstrate filter bandwidth reduction and improved sidelobe suppression of -20 dB . The double-pass configuration is also shown to double the frequency shifts that are obtainable from such devices.     

Dinuclear Copper(II) Complexes Incorporating a New Septadentate Polyimidazole Ligand

The dinuclear copper(II) complexes [Cu(2)(tmihpn)(prz)](ClO(4))(2).2CH(3)CN (6) and [Cu(2)(tmihpn)(O(2)CCH(3))](ClO(4))(2).CH(3)CN (7) were prepared, where tmihpn is the deprotonated form of N,N,N',N'-tetrakis[(1-methylimidazol-2-yl)methyl]-1,3-diaminopropan-2-ol and prz is the pyrazolate anion. The crystal structures of 6 and 7 were determined and revealed that both complexes contain bridging alkoxide ligands as well as bridging pyrazolate and acetate ions, respectively. Crystal data: compound 6, triclinic, P&onemacr;, a = 18.089(2) ?, b = 22.948(3) ?, c = 9.597(2) ?, alpha = 93.37(2) degrees, beta = 94.49(2) degrees, gamma = 81.69(2) degrees, V = 3925.1 ?(3), Z = 4; compound 7, triclinic, P&onemacr;, a = 12.417(2) ?, b = 15.012(3) ?, c = 10.699(2) ?, alpha = 104.76(2) degrees, beta = 102.63(2) degrees, gamma = 99.44(2) degrees, V = 1830.1 ?(3), Z = 2. In compound 6, the coordination geometry around both copper centers resembles a distorted square pyramid, while the stereochemistry around the copper centers in 7 is best described as trigonal bipyramidal. Both complexes display well-resolved isotropically shifted (1)H NMR spectra. Selective substitution studies and integration data have been used to definitively assign several signals to specific ligand protons. Results from the solution (1)H NMR studies suggest that the basal and apical imidazole groups do not exchange rapidly on the NMR time scale and the solid state structures of the complexes are retained in solution. In addition, the magnetochemical characteristics of 6 and 7 were determined and provide evidence for "magnetic orbital switching". Antiferromagnetic coupling in 6 (J = -130 cm(-)(1)) is strong, while the copper centers in compound 7 are ferromagnetically coupled (J = +16.4 cm(-1)). Differences in the magnetic behavior of the two copper centers have been rationalized using the "ligand orbital complementary" concept. The ground state magnetic orbitals involved in spin coupling in 6 (d(x)()()2(-)(y)()()2) are different from those in 7 (d(z)()()2).