Rings, chains and planes: Variation ofT g with composition in chalcogenide glasses

We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship between the glass transition temperature,T _g ,and the molar volume V _m.The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge-Se and As-S) and a pseudo-binary system (As ₄₀ Se _x Te _60-x .     

Synthesis and behavior of novel phthalocyanines possessing intramolecular crown ether bridges between their different aromatic rings for effective extraction multi metal inclusion

Novel Cu- and Co-phthalocyanines (7a–e, 8a, b) possessing intramolecular crown ether bridges between their different aromatic rings were successfully synthesized from the reaction of the corresponding bisphthalonitriles (6a–e) bearing polyethyleneoxy chains in the presence of CuCl and CoCl₂, respectively. As 1,8-diazabicyclo [5.4.0]-7-undecene (DBU) was used as a base in n-pentanol at reflux temperature for 30 h under N₂ atmosphere, these new phthalocyanines were found to be characteristic of satisfactory solubility in some of organic solvents, and showed strong absorption bands in ultraviolet and visible wave length region (λ_maxZ719–739 nm). Extraction experiment of metal chlorides (NaCl, KCl, MgCl₂, CaCl₂, CeCl₃, ZnCl₂, FeCl₃) in chloroform was carried out by using Cu-phthalocyanine (7b) bearing two intramolecular bridges with tri(ethyleneoxy) chains. Among these metal salts, 7b formed a complex (9b) with only FeCl₃, which showed a dark-red amorphous solid. Spectroscopic analysis of the complex (9b) indicated that original strong absorption bands near 738 nm characteristic for phthalocyanines completely disappeared, and new two strong bands appeared near 799–853 nm. FAB-MASS spectrum of the complex (9b) showed that new strong peaks came out in the region centered at m/z Z1879 and 1881 besides original peaks in the region centered at 1488, which corresponded to molecular peak of the starting phthalocyanine (7b). These facts indicated that the complex (9b) included two molecules of FeCl₃ into the protonated crown ether bridges of the phthalocyanine skeleton. Furthermore, it was found that the complex (9b) was transformed to the original phthalocyanine (7b) quantitatively by treatment with triethylamine.     

Development and characterization of a mucoadhesive sublingual formulation for pain control: extemporaneous oxycodone films in personalized therapy

Objective: The aim of this work was the development of mucoadhesive sublingual films, prepared using a casting method, for the administration of oxycodone.

Materials and methods: A solvent casting method was employed to prepare the mucoadhesive films. A calibrated pipette was used to deposit single aliquots of different polymeric solutions on a polystyrene plate lid. Among the various tested polymers, hydroxypropylcellulose at low and medium molecular weight (HPC) and pectin at two different degrees of esterification (PC) were chosen for preparing solutions with good casting properties, capable of producing films suitable for mucosal application.

Results and discussion: The obtained films showed excellent drug content uniformity and stability and rapid drug release, which, at 8?min, ranged from 60% to 80%. All films presented satisfactory mucoadhesive and mechanical properties, also confirmed by a test on healthy volunteers, who did not experience irritation or mucosa damages. Pectin films based on pectin at lower degrees of esterification have been further evaluated to study the influence of two different amounts of drug on the physicochemical properties of the formulation. A slight reduction in elasticity has been observed in films containing a higher drug dose; nevertheless, the formulation maintained satisfactory flexibility and resistance to elongation.

Conclusions: HPC and PC sublingual films, obtained by a simple casting method, could be proposed to realize personalized hospital pharmacy preparations on a small scale.     

Longitudinal and transverse waves in anisotropic elastic materials

Summary It is shown that a necessary and sufficient condition for a longitudinal wave to propagate in the direction n in an anisotropic elastic material is that the elastic stiffness C ₁₁ (n) is a stationary value (maximum, minimum or saddle point) at n. Explicit expressions of all n and the corresponding elastic stiffness C ₁₁ (n) for which a longitudinal wave can propagate are presented for orthotropic, tetragonal, trigonal, hexagonal and cubic materials. As to longitudinal waves in triclinic and monoclinic materials, only few explicit expressions are possible. We also present necessary and sufficient conditions for a transverse wave to propagate in the direction n. As an illustration, explicit expressions of all n, the polarization vector a and the wave speed c for which a transverse wave can propagate in cubic and hexagonal materials are given. The search for n in hexagonal materials confirms the known fact that a transverse wave can propagate in any direction. A longitudinal wave is necessarily accompanied by two transverse waves. However, a transverse wave can propagate without being accompanied by a longitudinal wave.     

Comparison of glide mechanisms in hcp Ti and Ti3Al

Several dislocation glide mechanisms are studied in Ti and Ti₃Al by means of in situ straining experiments in a transmission electron microscope at various temperatures. The prismatic glide of α titanium occurs by the jerky motion of straight screw a-dislocations subjected to a frictional force. An explanation for the discontinuity in the temperature dependence of the corresponding activation area is proposed, on the basis of the experimentally measured variation of the corresponding dislocation jump length. In Ti₃Al, superlattice 2a-dislocations exhibit two different dissociation modes in prismatic planes corresponding to highly different antiphase boundary energies. The properties of these two types of dislocation are compared and discussed. It is shown that the motion of 2c+a superlattice dislocations in pyramidal planes is controlled by a new mechanism: the self-nucleation of small-size obstacles as the result of irreversible atomic displacements. The tension/compression asymmetry observed between type 1 and type 2 pyramidal planes is finally discussed.     

Cryocornea – toward enhancing the capacity and throughput of ex vivo corneal model

Abstract

Objective: The objective of this study was to investigate the effects of the concentration of two intracellular (i.e. propylene glycol and glycerol) and four extracellular (i.e. dextran, hydroxypropyl methylcellulose, polyvinylpyrolidone, trehalose) cryoprotective agents as well as the effects of freeze-thawing procedures on the corneal cryoprotection.

Significance: The corneal cryopreservation may possibly become the long-term storage technique of choice for collection of animal corneas suitable for ex vivo drug testing.

Methods: The integrity of corneal barrier was evaluated by measurements of transepithelial electrical resistance.

Results: Under the investigated experimental conditions the best result was obtained for slow freezing (2?h at ?20?°C followed by 46?h at ?70?°C) and rapid thawing (0.25?h at 34?°C) procedure where 20% (w/V) trehalose in Krebs Ringer buffer solution was used as extracellular cryoprotective agent.

Conclusions: The selection of corneal freeze-thawing protocol as well as the optimal type and concentration of a cryoprotective agent allows the cryostorage of porcine corneal tissues with suitable TEER properties (cryocornea).     

Efficient infrared upconversion via a ladder-type atomic configuration

We have demonstrated experimentally that infrared light at 1529.4?nm can be converted into the visible at 780?nm with 54% efficiency through a ladder-type atomic configuration in ⁸⁵Rb. Specifically we theoretically analyze that high efficiency is due to the large nonlinear dispersion of the index of refraction from the off-resonant enhancement in a four-wave mixing (FWM) process. By using two perpendicular polarized pump fields, the coherence of two FWM processes in this configuration is verified.     

Photon Number Distribution in a Linear Directional Coupler

Abstract

The photon counting distribution of two modes in a directional coupler is studied, looking in particular at the behaviour of photon number states when losses are taken into account.     

Writing an arbitrary non-periodic pattern using interference lithography

Abstract

We propose a technique to write non-periodic patterns using interference lithography. Arbitrary patterns in one and two dimension are constructed by continuous scanning of multiple coherent sources at various incident angles and intensities.     

Statistical Optimization of a Controlled Release Formulation Obtained by a Double Compression Process: Application of an Hadamard Matrix and a Factorial Design

Abstract

A formulation containing an antiinflammatory agent (diclofenac sodium), two inert matrices (ethylcellulose and polyvinyl chloride) and two lubricants (magnesium stearate and talc) was optimized by a double compression process

In a first stage, preliminary trials were performed in order to study the effect of lubricants added before and after precompression

An Hadamard matrix H(8) was applied to estimate the main effects of four parameters: applied force at the upper punch (UPF) during precompression, particle size range after grinding, UPF during the final compression and concentration of ethylcellulose added before the final compression

Following the Hadamard matrix, a factorial design 2² was built. The complete linear models were fitted by regression for each response reflecting the compression behaviour and dissolution kinetics

In an optimal point, the validation was carried out with the area under the dissolution curve, being the major response to be optimized

The dissolution curves were well fitted by the Weibull distribution     

Dislocation structures of low-angle boundaries in Nb-doped SrTiO3 bicrystals

Dislocation core structures in low-angle boundaries of Nb-doped SrTiO₃ bicrystals were investigated by high-resolution electron microscopy. Bicrystals with tilt angles of 2°, 4°, 6° and 8° with respect to the [001] zone axis were prepared by joining two single crystals at 1873 K. All of the boundaries consisted of a regular array of dislocations whose spacing gradually decreased with an increase in tilt angle. Except for the 2° tilt-angle boundary, the dislocation cores exhibited a dissociation from a[010] into two partials of a/2[010] on (100). Furthermore, two kinds of dislocation core structures were observed; Sr–Sr atomic columns and Ti–O atomic columns inside the cores. In addition, it was found that the positioning of adjacent cores along the boundary tended to change from a linear form to a zig-zagg shape as the tilt angle was increased from 4° to 8°. In the case of the linear array, dislocation core structures including Sr–Sr columns or Ti–O columns alternately appear. In contrast, only one core structure was observed in the zig-zagged array. On the other hand, the dislocation cores in the 2°-tilt-angle boundary had another type of dissociation with a/2[110] or a/2[111] partials, which included the twist component at a tilt axis of [001].     

On the algebraic characterization of a Mueller matrix in polarization optics. II. Necessary and sufficient conditions for Jones-derived Mueller matrices

Abstract

We show that every Mueller matrix, that is a real 4 × 4 matrix M which transforms Stokes vectors into Stokes vectors, may be factored as M = L ₂ KL ₁ where L ₁ and L ₂ are orthochronous proper Lorentz matrices and K is a canonical Mueller matrix having only two different forms, namely a diagonal form for type-I Mueller matrices and a non-diagonal form (with only one non-zero off-diagonal element) for type-II Mueller matrices. Using the general forms of Mueller matrices so derived, we then obtain the necessary and sufficient conditions for a Mueller matrix M to be Jones derived. These conditions for Jones derivability, unlike the Cloude conditions which are expressed in terms of the eigenvalues of the Hermitian coherency matrix T associated with M, characterize a Jones-derived matrix M through the G eigenvalues and G eigenvectors of the real symmetric N matrix N = [Mtilde]GM associated with M. Appending the passivity conditions for a Mueller matrix onto these Jones-derivability conditions, we then arrive at an algebraic identification of the physically important class of passive Jones-derived Mueller matrices.     

Short communication Low temperature forgeability of Ti–48Al–2Cr–2Nb alloy

Abstract

A two phase (γ + α) titanium aluminide alloy Ti–48Al–2Cr–2Nb, at.-% was isothermally forged along all the three axes in succession at an initial forging temperature of 1273 K, followed by another two sets of forgings at lower temperatures of 1173 and 1123 K. The combined effects of heavy multiaxial strains (? = 2·07, per set of forgings), progressively lower temperatures, and a moderate strain rate (10^-3 s^-1 ) transformed the microstructure to a fine and equiaxed shape. The microstructure developed is suitable for working at a low temperature.     

Optical properties of samarium doped zinc-tellurite glasses

Glasses with the composition, (Sm₂ O ₃) _x (ZnO)_(40-x)(TeO ₂)₍₆₀₎, were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been explained.     

Absolute Value of the Surface Tension of Liquid 4He

In 1985 Iino et al. [J. Low Temp. Phys. 61, 155 (1985)] measured the surface tension of liquid ⁴ He by the surface-wave resonance method, and reported that the surface tension at 0K is 354 N/m. Recently, Roche et al. [J. Low Temp. Phys. 106, 565 (1997)] obtained the absolute value at 0K to be 375 N/m from the dispersion relation of a capillary wave at a micron wavelength. There is a 6% discrepancy between those two values. To determine the meniscus effects for the surface waves and the absolute value of the surface tension, we measured the resonance frequencies of the surface wave in two parallelepiped cavities with different widths. By comparing the same wave number of the two cavities, it was found that the resonance frequencies are shifted to be slightly smaller by the meniscus effects. The absolute value of the surface tension, which was obtained by eliminating these effects by using the resonance frequencies of the two cavities, was in agreement with that of Iino et al.     

Vortex Mutual Friction in Superfluid 3He

We give a full account of our extensive measurements of vortex mutual friction in rotating superfluid ³He, in both the A- and B-phases. The B-phase results are in qualitative agreement with a theory based on the concept of “spectral flow”; the agreement becomes quantitative if an effective energy gap of 0.63 Δ is used, but the Justification for such a substitution is not clear. The vortex core transition, at first not seen because of metastability and hysteresis, has now been observed. Detailed investigation suggests that the high temperature vortex state is a temperature dependent mixture of at least two vortex types. The A-phase mutual friction is found to be well described by two hydrodynamic coefficients, the orbital viscosity and the orbital inertia. The latter corresponds to an orbital angular momentum per Cooper pair of (0.0015 ± 0.0017 ) ħ, consistent with the prediction of the spectral flow theory. We find that the most uniform l texture is obtained by cooling through T_c while rotating, and then stopping rotation. Detailed investigation of textural memory effects shows that the uniform l-up and l-down textures are associated with opposite directions of rotation. We discuss the various types of texture that may be formed in our experiments. Finally, we compare our mutual friction results with those found in ⁴HeII.     

Symmetric and non-symmetric periodic orbits for the digital filter map

We exhibit instances of non-symmetric periodic orbits for the digital filter map, resolving a question posed in the literature as to whether such orbits can exist. This piecewise irrational rotation, depending on a parameter a = 2cos θ, is an isometry of [?1, 1) × [?1, 1) and reflections in the two diagonals are time-reversing symmetries for the map. Symmetric orbits are plentiful and have been much investigated. Each periodic orbit is paired with a symbolic string, from the alphabet {?, 0, +}, arising under iteration of the map because of the presence of a line of discontinuity. We prove the existence of an infinite family of non-symmetric orbits where the period N starts at 29 and increases in steps of 5; they correspond to the strings (+00)⁵(+?)² 0 ^N?19. We describe several computer algorithms to find non-symmetric periodic orbits and their symbolic strings and list non-symmetric strings both for a = 0.5, and for N ≤ 100 across the parameter range. Our evidence suggests that non-symmetric orbits, though not plentiful, are characteristic of the dynamics of the map for all parameter values.     

Hydrothermal syntheses, structures and magnetic properties of coordination frameworks of divalent transition metals

The hydrothermal syntheses, single-crystal X-ray structures and magnetic properties of [Co(C₄O₄)(H₂O)₂] (1), [Co₃(OH)₂(C₄O₄)₂] · 3H₂O (2) and [Fe(OH)₂(C₄O₄)] (3) are described. Pale yellow cubes of 1 and brown red crystals of 2 were obtained from the reaction of Co(OH)₂ and squaric acid at 200 °C. Brown needle of 3 were obtained similarly from Fe(SO₄) · 7H₂O, squaric acid and NaOH. 1 consists of a cubic sodalite arrangement with empty cavities where the Co atoms are connected by μ₄-squarate and two trans-water molecules each, while 2 and 3 contain metal-hydroxide double-chains of edge-sharing octahedral, brucite-type for 2 and goethite for 3, connected by μ₆-squarate. 2 contains water molecules in the channels which can be removed and re-inserted repeatedly without loss of crystallinity. All three compounds possess 3D frameworks made up of coordination and hydrogen bonds. 1 behaves as a paramagnet while 2 and 3 are antiferromagnets and 2 transforms to a ferromagnet reversibly upon dehydration and rehydration. The structures of two one-dimensional polymers employing 2,5-pyridinedicarboxylate, [Co₂(H₂O)₆(2,5-pydc)₂] · 2H₂O (4) and Cu(2,5-pydc)₂ (5), are also reported.     

Two novel propylenedioxythiophene-based copolymers with donor–acceptor structures for organic solar cell materials

Two novel conjugated copolymers consisting of alternating electron-rich propylenedioxythiophene and electron-deficient 2,3-diphenyltheno[3,4-b]pyrazine or 6,7-diphenyl[1,2,5]thiadiazole units have been synthesized through palladium catalyzed Sonogashira triple-bond coupling reaction. The structures and properties of the two copolymers, P ₁ , P ₂ , were characterized by FT-IR, NMR, UV–Vis absorbance (Abs), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and cyclic voltammetry (CV). UV–Vis absorption spectra of the polymers show two absorption bands both in CHCl₃ solution and films. The absorption peak maxima of P ₁ , P ₂ are 600 nm, 766 nm in solution and 627 nm, 823 nm in films, respectively. Thermal gravimetric analysis demonstrates that the two polymers are stable below 300 °C. Cyclic voltammetry studies reveal that the band gaps of P ₁ , P ₂ are 1.62 eV and 1.50 eV, suggesting their potential for applications as organic solar cell materials.     

Processes of Charge State Change at Collisions of He2+ and ArZ+ Ions with Fullerenes

Abstract

Using coincidence technique the relative cross-sections of charge state change and fragmentation at one and two electron capture processes have been measured for the first time at collisions of He²⁺ and Ar^z+ projectiles with fullerenes in the energy range (3-35)z keV.