Preparation and characterization of Ag-added Bi1.84Pb0.4Sr2Ca2.2Cu3O10+x bulk tube conductors for cryogen free superconducting magnet

Bulk tube conductors of Bi _1.84 Pb _0.4 Sr ₂ Ca _2.2 Cu ₃ O _10+x with addition of silver varying from 0 to 25 wt% (not reported earlier) were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical transport and a.c. susceptibility techniques. The tube conductors formed by cold isostatic pressing (CIP) of the powders obtained from spray drying method have been made successfully. It was found that Ag addition has not only affected the formation of the desired Bi-2223 phase and the microstructure of these large bulk tube samples thereby influencing on the critical current ( I _c ),it also reduces the contact resistance to minimize the cryogen losses. These variations have been found to be Ag content dependent. An optimized value of 10 wt% Ag has been found to produce the best quality tubes showing reproducible I _c value > 120 Amp at 77 K which is in general a requirement to energies of the cryogen free conventional/HTSC superconducting magnets below 20 K.     

Basic Concepts of Probability and Statistics

In multiple regression it is shown that parameter estimates based on minimum residual sum of squares have a high probability of being unsatisfactory, if not incorrect, if the prediction vectors are not orthogonal. Proposed is an estimation procedure based on adding small positive quantities to the diagonal of X′X. Introduced is the ridge trace, a method for showing in two dimensions the effects of nonorthogonality. It is then shown how to augment X′X to obtain biased estimates with smaller mean square error.     

Effects of valerian on subjective sedation,field sobriety testing and driving simulator performance

IntroductionThe availability of herbal medicines over-the-counter (OTC) has increased the use of natural products for self-treatment. Valerian has been used to effectively treat generalized anxiety disorder and insomnia. Studies suggest that valerenic acid may increase gamma-aminobutyric acid (GABA) modulation in the brain. Benzodiazepines have a similar mechanism of action and have been linked to an increased risk of hospitalizations due to traffic accidents. Despite the risk of somnolence, the safety of driving while under the influence of valerian remains unknown.PurposeThe purpose of the study was to determine the effects of a one-time valerian 1600 mg dose on subjective sedation effects, standardized field sobriety testing (SFST) and driving simulator performance parameters.MethodsThe study design was a randomized, placebo-controlled, double-blind, cross-over trial. For each session, participants received either a dose of valerian or placebo. The outcome measures included a simple visual reaction test (SVRT), subjective sleepiness scales, SFST performance scores, and driving simulator performance parameters.ResultsThere were no significant differences in the SVRT or sleepiness scales between placebo and valerian exposures, but the study may have been underpowered. SFST total and individual test failure rates were not significantly different between the two exposures. The driving simulator performance parameters were equivalent between the two exposure conditions.ConclusionsA one-time valerian 1600 mg dose, often used to treat insomnia, does not appear to impair driving simulator performance after acute ingestion.     

Possible reasons for the unexpected bad biocompatibility of metal-on-metal hip implants

BackgroundUncemented titanium hip prostheses with a metal-on-metal bearing combination have recently shown an unexpected bad biocompatibility. The cause for the problems has not be found so far. In this work, a connection between scratches on the stem created during insertion and medical complications is assumed. In particular, enduring electrochemical processes at the scratched parts of the surface (involving aluminium and chromium) may give rise to troubles.MethodsElectrochemical impedance spectroscopy (EIS) has been used in order to investigate the chemical processes at the surface in electrolytic environment. Bode and Nyquist diagrams have been measured.ResultsChemical processes take place at the scratches even after repassivation seems to be finished. Aluminium is continuously released, chromium is built into the metal matrix.ConclusionsThe observed processes may be the cause for bad biocompatibility and the observed medical complications with the implants.     

He+ Ion Bombardment of C70 Fullerene: An FT‐IR and Raman Study

Abstract

C₇₀ fullerene films deposited on a silicon substrate have been bombarded with He⁺ ions at 30 keV at room temperature in vacuum. The structural changes undergone by C₇₀ have been followed by both FT‐IR and Raman spectroscopy. The results have been compared to the behavior of C₆₀ fullerene and discussed in an astrochemical context. The main conclusion is that C₇₀, contrary to C₆₀, does not form oligomers at low radiation dose but it is directly and gradually degraded to amorphous carbon (carbon black).     

Short Communication: Some Photophysical Properties of Nanotubes

Abstract

The absorption spectra of (10,10) nanotubes are reported at varying concentrations. In addition, we have found that nanotubes are unable to photosensitize formation of singlet oxygen (¹O₂) and do not significantly quench it. These results imply that nanotubes are not able to form long-lived or localized excited states.     

Solid state bonding of superplastic AA 7475

Abstract

Solid state (diffusion) bonds have been developed in AA 7475E sheet material using different regimes of bonding temperature, pressure, and time. The bonds produced have exhibited shear strengths in the range 30–150 MN m^?2 and have been found to be capable of withstanding peel during a slow high-temperature superplastic forming operation. However, the bonds formed under any one set of bonding conditions showed an extremely wide variation in both shear strength and shear fracture mode. The source of this wide variation has not yet been identified.

MST/601     

A modified collocation method and a penalty formulation for enforcing the essential boundary conditions in the element free Galerkin method

The Element free Galerkin method, which is based on the Moving Least Squares approximation, requires only nodal data and no element connectivity, and therefore is more flexible than the conventional finite element method. Direct imposition of essential boundary conditions for the element free Galerkin (EFG) method is always difficult because the shape functions from the Moving Least Squares approximation do not have the delta function property. In the prior literature, a direct collocation of the fictitious nodal values & u circ; used as undetermined coefficients in the MLS approximation, u ^h (x) [u ^h (x)=Φ·& u circ;], was used to enforce the essential boundary conditions. A modified collocation method using the actual nodal values of the trial function u ^h (x) is presented here, to enforce the essential boundary conditions. This modified collocation method is more consistent with the variational basis of the EFG method. Alternatively, a penalty formulation for easily imposing the essential boundary conditions in the EFG method with the MLS approximation is also presented. The present penalty formulation yields a symmetric positive definite system stiffness matrix. Numerical examples show that the present penalty method does not exhibit any volumetric locking and retains high rates of convergence for both displacements and strain energy. The penalty method is easy to implement as compared to the Lagrange multiplier method, which increases the number of degrees of freedom and yields a non-positive definite system matrix.     

Intermolecular Interaction of [60]Fullerene with Tröger's Base Analogues

Tröger's base (TB, 1) and its analogues were synthesized and were subject to the titration experiments to evaluate their ability of supramolecular complexation with C₆₀. Results demonstrate clearly that the fluorene-based TB analogue (2) and the bioctylfluorene-based TB analogue (3) show 1:1 binding with C₆₀ to form the corresponding complexes while TB 1 does not. Titration experiments exhibited that the association constant (K_ass) of 3/C₆₀ (48.1 ± 7.9 M ^?1) was larger than that of 2/C₆₀ (13.7 ± 1.4 M ^?1)_. The formation of the 1:1 binding complexes 2/C₆₀ and 3/C₆₀ was also confirmed by MALDI-TOF mass spectrometry. Theoretical calculations suggest that 2 and 3 have appropriate cavities to embrace C₆₀. These findings indicate that not only the π/π interaction between the fluorene moieties and the C₆₀ surface but also the CH/π interaction between the octyl groups and the C₆₀ surface serve efficiently in the supramolecular complexation with C₆₀.     

Environmentally benign novel green pigments: Pr1-xCaxPO4 (x = 0-0.4)

Rare earth based materials have recently attracted considerable attention as potential ecofriendly colourants for low temperature as well as high temperature applications. In the present study, we have synthesized a series of Ca-doped PrPO₄ compounds with the general formula, Pr_1-xCa_xPO₄ (x = 0-0.4 in steps of 0.1) and characterized the compounds by powder X-ray diffraction. All the compositions show a monoclinic monazite structure. The optical properties of the brilliantly coloured pigments [ L (brightness),a* (+ red- green),b* (+ yellow - blue) have been examined. These materials can find application as potential green colourants.     

Carbonization and oxidation of metal–organic frameworks based on 1,4-naphthalene dicarboxylates

Abstract

Three new isostructural metal–organic frameworks (MOFs), [V(OH)(NDC)] (1), [Cr(OH)(NDC)] (2), and [Ga(OH)(NDC)] (3) have been synthesized hydrothermally using 1,4-naphthalene dicarboxylate (NDC) as the linker. These MOFs (1, 2 and 3) have been used as a template for the synthesis of metal-oxide-inserted nanoporous carbon materials. The newly synthesized MOFs and the resulting porous carbon hybrid functional materials have been characterized using powder x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopic analysis. Results show that compounds 2 and 3 form their respective metal oxide nanoparticles on the surface of the carbon materials during carbonization at 800 °C. The gas sorption properties of the new MOFs and their corresponding carbon frameworks have been reported.     

Multiple strengthening mechanisms in nanoparticle-reinforced copper matrix composites

The multiple hardening mechanisms of a copper matrix have been presented and discussed. The pre-alloyed ball milled Cu–3 wt.%Al and the atomized Cu–0·6 wt.%Ti–2·5 wt.%TiB ₂ powders have been used as starting materials. Dispersoid particles Al ₂ O ₃ and TiB _2\thinspace _{{\bf 2}\thinspace }were formed in situ. The powders have been hot consolidated. Optical microscopy, SEM, TEM, and X-ray diffraction analysis were performed for microstructural characterization. Increase in microhardness of Cu–3 wt.%Al compacts is a consequence of the crystallite size refinement and the presence of Al ₂ O ₃ particles. High hardening of Cu–0·6 wt.%Ti–2·5 wt.%TiB ₂ is a consequence of the presence of modular structure, Cu ₄ Ti_(m), and TiB ₂ particles.     

Further evidence of tetragonality in bainitic ferrite

Abstract

There is growing evidence that bainitic ferrite which retains a substantial amount of carbon in solid solution does not have cubic symmetry. We provide additional data on a different nanostructured bainitic steel to support this evidence, based on synchrotron X-ray diffraction experiments. The data are consistent only with a displacive transformation mechanism for bainite.     

IR and Raman spectroscopic studies of sol–gel derived alkaline-earth silicate glasses

IR and Raman spectroscopies have been utilized to study the structure and vibrational modes of sol–gel-derived binary silicate glasses. The present study is motivated by the immense geological significance and focuses on the MO–SiO ₂ (M = Ca, Mg) binary systems in an effort to unveil the role of the CaO and MgO modifiers when incorporated to the 3D silica structure. Glasses in the composition range x =0, 0·1, 0·2, 0·3 and 0·4 prepared by the sol–gel method were compared with the corresponding glasses formed by appropriate mixing of SiO ₂ and MO powders through melting and fast cooling. The vibrational spectra of the sol–gel-derived glasses have revealed considerable changes in relative intensities as a function of the MO mole fraction. These changes signify structural modifications on the silica network. The population of the Q ³ species was found to increase for both modified silicate systems. The rate of increase is more pronounced in the CaO–SiO ₂ glasses. The extent of network depolymerization in the porous glass is higher at the same content of alkaline earth oxide compared to the bulk glass. The results are indicative of a more ‘defective’ nature of the sol–gel glasses compared to the corresponding melt-quenched ones.     

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.     

Coherence filters and their uses. I. Basic theory and examples

Abstract

The phenomenon of correlation-induced spectral changes, discovered several years ago and extensively studied since then, is shown to offer the possibility of contructing novel types of spectral filter which have several properties that are not achievable with conventional filters. For example such filters can have different prescribed filtering properties in different directions of observation. In this paper the underlying theory is discussed and is illustrated by a few examples.     

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.     

Synthesis and properties of polycyclic quinones condensed with 1,6-methano[10]annulene

Two types of polycyclic quinones condensed with 1,6-methano[10]annulenes as type A: 1,6-methanonaphtho[2,3-c][10]annulene-7,12-dione 5a, and type B: 1,6-methanonaphtho[2,3-c][10]annulene-5,14-dione 18, bis(1,6-methano[10]annuleno[3,4-b; 3,4-g])anthracene-10,21-dione 20, 1,6-methanoanthraceno[2,3-c][10]annulene-5,16-dione 22, 1,6-methanotetraceno[2,3-c][10]annulene-6,17-dione 23, and 1,6-methano phenanthreno[2,3-c][10]annulene-5,6-dione 24 have been synthesized. The acene derivative 6 corresponding to that of 5a was synthesized by the reduction of quinone 5a. The physical, spectral, and chemical properties of these new compounds have been investigated.     

First-principles calculations of elastic constants for epsilon-carbide and the consequences

ABSTRACT

The elastic constants of ?-carbide at 0?K and zero pressure have been calculated using first-principle methods. The iron to carbon ratio for the carbide is not established and may, in fact, vary between 3 and 2. As a consequence, the calculations have been conducted as a function of the chemical composition using the special quasi-random structures method. In all cases, the elastic constants obtained are consistent with ?-carbide being mechanically stable. The analysis indicates that in comparison with cementite, ?-carbide should be more brittle; that when present as a precipitate in steel, it would be less effective in participating in the overall plastic deformation, and that its coherency strain field in the surrounding matrix should be less extensive than cementite.     

Lysozyme-loaded lipid-polymer hybrid nanoparticles: preparation,characterization and colloidal stability evaluation

Context: Lipid-polymer hybrid nanoparticles (LPNPs) are polymeric nanoparticles enveloped by lipid layers, which have emerged as a potent therapeutic nanocarrier alternative to liposomes and polymeric nanoparticles.

Objective: The aim of this work was to develop, characterize and evaluate LPNPs to deliver a model protein, lysozyme.

Materials and methods: Lysozyme-loaded LPNPs were prepared by using the modified w/o/w double-emulsion-solvent-evaporation method. Poly-?-caprolactone (PCL) was used as polymeric core material and tripalmitin:lechitin mixture was used to form a lipid shell around the LPNPs. LPNPs were evaluated for particle size distribution, zeta potential, morphology, encapsulation efficiency, in vitro drug release, stability and cytotoxicity.

Results: The DLS measurement results showed that the particle size of LPNPs ranged from 58.04?±?1.95?nm to 2009.00?±?0.52?nm. The AFM and TEM images of LPNPs demonstrate that LPNPs are spherical in shape. The protein-loading capacity of LPNPs ranged from 5.81% to 60.32%, depending on the formulation parameters. LPNPs displayed a biphasic drug release pattern with a burst release within 1?h, followed by sustained release afterward. Colloidal stability results of LPNPs in different media showed that particle size and zeta potential values of particles did not change significantly in all media except of FBS 100% for 120?h. Finally, the results of a cellular uptake study showed that LPNPs were significantly taken up by 83.3% in L929 cells.

Conclusion: We concluded that the LPNPs prepared with PCL as polymeric core material and tripalmitin:lechitin mixture as lipid shell should be a promising choice for protein delivery.