Dissolution Rate of Griseofulvin from Solid Dispersions with Poly(Vinylmethylether/Maleic Anhydride)

Abstract

A solid dispersion technique with poly(vinylmethylether/ maleic anhydride) (PVM/MA) and its half esters has been used to enhance griseofulvin dissolution.

A marked increase of the dissolution rate and solubility of griseofulvin contained in these solid dispersions was observed compared with that of drug alone and that of physical mixture with the carrier.

Differences in dissolution rates resulted from the molecular weight and the chemical structure of the carrier.

X-Ray powder diffractometry, differential scanning calorimetry (DSC) and wettability tests were employed to investigate the nature of the studied forms.     

STABILITY OF FLOWS IN FLUIDIZED BEDS

ABSTRACT

We study the linearlized stability of the state of uniform fiuidization, within the context of the theory of mixtures. The mixture is assumed to be made up of a classical linearly viscous fluid infused with particles. In marked departure from most of the previous studies, we model the solid as a granular material and assume a constitutive relation that stems from classical motions in continuum mechanics. The linearized stability analysis of the state of uniform fiuidization, in general, for a three-dimensional disturbance leads to an eighth order equation for the characteristic whose root implies instability, when positive.     

Frances Benjamin Johnston 1864˜1952

Abstract

A short obituary in Time magazine, published in June 1952, marked the passing of one of America's foremost women photographers, whose death had occurred almost three months earlier, on 16th March 1952.     

Effect of calcium treatment on hot workability of Cr–Ni–0·7N stainless steel

Abstract

The high nitrogen 20Cr–10Ni–0·7N austenitic stainless steels were produced in a high pressure induction furnace and their hot workability was investigated. The results of torsion and drop hammer tests showed that the optimum temperature range for hot working was from 1350 to 1523 K, suggesting the difficulty in hot rolling. The precipitation of nitrides, which reduced the ductility; occurred below 1350 K. However, calcium treatment or reducing the oxygen and sulphur contents resulted in a marked improvement in hot workability and made hot rolling possible in these high nitrogen stainless steels.

MST/1102     

Dissolution Behaviour of Indomethacin Capsule Formulations: Comparison of Two Types of Usp Apparatus

Abstract

The dissolution behaviour of indomethacin from six commercial brands of indomethacin capsules, using the USP rotating basket apparatus and the USP paddle apparatus have been studied. The products showed marked differences in their dissolution profiles. The dissolution rates have been different in different brands, and variation has also been observed depending on the method of testing used. The rotating basket apparatus showed superior discriminating capacity than the paddle method.     

Effect of microstructure on fatigue behaviour of cast Al–7Si–Mg alloy

Abstract

The fatigue behaviour of a cast Al–7Si–Mg alloy, conforming to A356, has been studied. Specimens of this material were tested in both the as cast condition and a solution treated and aged condition. It was observed that the size, number, and position of casting defects influenced the fatigue life very strongly. This marked effect nearly hides that of the heat treatment. Nevertheless, if the analysis is carried out considering only results obtained from sound specimens it is revealed that the heat treatment causes an improvement in the fatigue resistance of the alloy.     

An All-optical Mechanism of Sub-poissonian Light Generation

Abstract

We investigate the interaction of two counterpropagating linearly polarized waves in a dielectric waveguide grating in the presence of an intensity-dependent contribution to the refractive index (optical Kerr effect). The resulting nonlinear distributed-feedback (DFB) mechanism responsible, from a classical point of view, for a marked limiting effect which stabilizes the intensity of one of the two waves, is shown to generate, once the problem is treated in a quantum-mechanical way, a field exhibiting sub-Poissonian photon statistics.     

Preparation and Characterization of Solid Dispersions of Piroxicam with Hydrophilic Carriers

ABSTRACT

The objective of this study was to improve the dissolution rate of a poor water soluble drug, piroxicam, by solid dispersion technique. Solid dispersions were prepared by three different methods depending on the type of carrier. The dissolution rate of piroxicam was markedly increased in solid dispersion of myrj 52, Eudragit® E100 and mannitol. Solubility studies revealed a marked increase in the solubility of piroxicam with an increase in myrj 52 and Eudragit® E100 concentrations. Data from the X-ray diffraction and FT-IR spectroscopy showed that piroxicam was amorphous in the solid dispersions prepared with dextrin and Eudragit® E100.     

Preparation of polymer-blended quinine nanocomposite particles by spray drying and assessment of their instrumental bitterness-masking effect using a taste sensor

Abstract

Context: The development of taste-masking technologies for foods and drugs is essential because it would enable people to consume and receive healthy and therapeutic effect without distress.

Objective: In the current study, in order to develop a novel method to prepare nanocomposite particles (microparticles containing bitter nanoparticles) in only one step, by using spray drying, a two-solution mixing nozzle-equipped spray dryer that we previously reported was used. The nanocomposite particles with or without poorly water-soluble polymers prepared using our spray-drying technique were characterized.

Methods: (1) The organic solution containing quinine, a model of bitter compound and poorly water-soluble polymers and (2) sugar alcohol (mannitol) aqueous solution were separately flown in tubes and two solutions were spray dried through two-solution type spray nozzle to prepare polymer-blended quinine nanocomposite particles. Mean diameters of nanoparticles, taste-masking effect and dissolution rate of quinine were evaluated.

Results: The results of taste masking by taste sensor suggested that the polymer (Eudragit EPO, Eudragit S100 or Ethyl cellulose)-blended quinine nanocomposite particles exhibited marked masking of instrumental quinine bitterness compared with the quinine nanocomposite particles alone. Quinine nanocomposite formulations altered the quinine dissolution rate, indicating that they can control intestinal absorption of quinine.

Conclusion: These results suggest that polymer-blended quinine composite particles prepared using our spray-drying technique are useful for masking bitter tastes in the field of food and pharmaceutical industry.     

Minimal strict siphons extraction for S3PMR

Abstract

A siphon is an important structure object for deadlock control. Insufficiently marked siphons lead to deadlocks. Deadlock occurs due to inappropriate resource sharing. Hence most of the research focuses on the minimal siphon extraction problem covering a set of places representing resources, which, for general Petri Nets is known to be an NP‐Complete problem. Control places and arcs are often added to the original net to prevent a siphon from becoming insufficiently marked. The number of siphons grows rapidly with the size of the net leading to very complicated control nets. Efficient enumeration of problematic siphons is an urgent research topic. Earlier, we proposed fast algorithms to find all such siphons for both S³PR and S²CPR (System of Synchronized Choice Processes with Resources). However, it was assumed that siphons occur between adjacent processes. This paper removes this assumption and develops an algorithm for S³PMR which is more powerful than S³PR by allowing a state to use more than one resource and than S²CPR by allowing more than one state to use the same resources. Comparisons with previously published work have been made.     

Cyclic deformation behaviour of ferritic Fe-19Cr-4Ni-2Al alloy at elevated temperatures

Abstract

Cyclic stress response of ferritic Fe-19Cr-4Ni-2Al alloy was investigated under low cycle fatigue at elevated temperatures. The deformation microstructure developed was examined by transmission electron microscopy. The results showed that the alloy exhibited marked cyclic hardening at 773 K but continuous cyclic softening at 923 K. The cyclic hardening was considered to be associated with dynamic strain aging while the cyclic softening was interpreted in terms of the precipitate-dislocation interaction.     

Enhanced dissolution and absorption of trimethoprim from coprecipitates with polyethylene glycols and polyvinylpyrrolidone

Abstract

Coprecipitates of trimethoprim have been prepared by solvent method using polyethylene glycols 4000, 6000 and 9000, and polyvinylpyrrolidone (M.W. 40,000) as water soluble carriers. A marked increase in the dissolution rate of trimethoprim in the coprecipitates was observed compared with that of the drug alone. Coprecipitates with polyethylene glycol 6000 (1:2) showed faster release as well as bioavailability of the drug in human volunteers.     

Effects of vanadium on upper-nose temper embrittlement and other Mechanical properties of Cr–Ni–Mo low-alloy steels

Abstract

Large components manufactured from Cr–Mo–Ni low-alloy steels are usually heavily tempered for the purpose of stress relieving, with resultant undesirable loss of strength and the inception of upper-nose temper embrittlement (UNTE). This paper describes an investigation on the effects of vanadium additions and of variation in the molybdenum content on the properties of these heavily tempered steels. It is shown that the addition of vanadium to these steels leads to a substantial improvement in their strength without impairment of their ductility and toughness, and also to a marked improvement in their resistance to UNTE. An increase in the molybdenum content of the steel from 0·5 to 1·0% leads to a moderate improvement in its strength, but has an aggravating effect on its susceptibility to UNTE, as a result of an increase in the coarsening rate of the grain boundary carbides and the formation of unfavourable M₂₃C₆ and M_aC_b molybdenum-rich large carbides.

MST/390     

Effect of Tablet Lubricants on Axial and Radial Work of Failure

Abstract

During diametral compression and axial tensile strength testing force-displacement curves were obtained for tablets of microcrystalline cellulose. The area under the curve, termed work of failure, was determined by planimetry. For each of the five lubricants studied as the concentration of the lubricant was increased in the tablet, the work of failure was considerably less. The effect was especially marked in the axial plane.     

Recrystallisation following non-proportional straining in aluminium

Abstract

Recrystallisation in commercial purity aluminium following different strain paths has been investigated. The deformation was carried out using torsion, compression, fully reversed torsion, and torsion followed by compression along the torsion axis, the latter combination giving an orthogonal change in straining state. Recrystallisation behaviour following deformation was determined by optical metallography. Complete reversal of deformation had a very marked effect, significantly retarding subsequent recrystallisation compared with unidirectional deformation to the same levels of accumulated effective strain. In contrast, orthogonal straining had little significant effect. A larger grain size also resulted from fully reversed deformation. The results can be notionally explained by considering the effect of strain path changes on the cell structure developed in deformation.

MST/3125     

Theoretical study of the zero-gap organic conductor α-(BEDT-TTF)2I3

Abstract

The quasi-two-dimensional molecular conductor α-(BEDT-TTF)₂I₃ exhibits anomalous transport phenomena where the temperature dependence of resistivity is weak but the ratio of the Hall coefficient at 10 K to that at room temperature is of the order of 10⁴. These puzzling phenomena were solved by predicting massless Dirac fermions, whose motions are described using the tilted Weyl equation with anisotropic velocity. α-(BEDT-TTF)₂I₃ is a unique material among several materials with Dirac fermions, i.e. graphene, bismuth, and quantum wells such as HgTe, from the view-points of both the structure and electronic states described as follows. α-(BEDT-TTF)₂I₃ has the layered structure with highly two-dimensional massless Dirac fermions. The anisotropic velocity and incommensurate momenta of the contact points, ±k₀, originate from the inequivalency of the BEDT-TTF sites in the unit cell, where ±k₀ moves in the first Brillouin zone with increasing pressure. The massless Dirac fermions exist in the presence of the charge disproportionation and are robust against the increase in pressure. The electron densities on those inequivalent BEDT-TTF sites exhibit anomalous momentum distributions, reflecting the angular dependences of the wave functions around the contact points. Those unique electronic properties affect the spatial oscillations of the electron densities in the vicinity of an impurity. A marked behavior of the Hall coefficient, where the sign of the Hall coefficient reverses sharply but continuously at low temperatures around 5 K, is investigated by treating the interband effects of the magnetic field exactly. It is shown that such behavior is possible by assuming the existence of the extremely small amount of electron doping. The enhancement of the orbital diamagnetism is also expected. The results of the present research shed light on a new aspect of Dirac fermion physics, i.e. the emergence of unique electronic properties owing to the structure of the material.     

Effect of Active Raw Material Variability on Tablet Production: Physicochemical,Physiocomechanical and Pilot Plant Studies

Abstract

Batch-to-batch variation in an active raw material was evaluated following a production process change by the raw material supplier. Physicochemical and physicomechanical tests were applied and indicated that polymorphism or solvate formation was not occurring but changes in crystal properties in terms of size and degree of aggregation were involved. Other more subtle differences in crystal properties were also possible

The deleterious effect of the raw material process change on tablet production was noted and a method of overcoming the problem identified

The necessity for comprehensive? reformulation studies including physicomechanical screening is underlined. Such studies are also necessary if changes in raw material production methods occur to avoid process problems related to the marked hatch-to-batch variation that can occur in these instances     

Metal Gratings with Dielectric Coating of Variable Thickness within a Period

Abstract

The rigorous theory of diffraction is applied to metallic gratings with dielectric coating. The modulation depth of the profile between coating and air is assumed to be lower than the modulation depth of the profile between metal and coating. We call this levelling. For monochromator mounting together with a special coating thickness levelled single-coated gratings with blaze show a marked increase of the efficiencies for wavelengths greater than the blaze maximum wavelength. Optimal improvements run over two octaves of the wavelength.     

Going local: placing entrepreneurial microgeographies in a larger regional context

ABSTRACT

As cities seek to promote innovation, they are increasingly investing in localised institutional entrepreneurial supports. Some institutions are hyperlocal, operating within distinct geographic sub-spaces and funnelling entrepreneurial ventures within spatially bounded microgeographies. In this paper, we focus on the University of North Carolina, where actors from the business school helped build a unique web of hyperlocal entrepreneurial supports that reinforced core educational and research missions but also culminated in proximate university business incubators. We examine how this programmatic changes correspond to a marked increase in entrepreneurial intensity as well as ageographic tightening of firms in and around the campus. Yet we also find evidence for an additional effect, namely an earlier launch of entrepreneurial firms based on less-tested technologies. The results speak to the power of institutional actors in shaping entrepreneurial activities while raising broader questions about the impact of university programming on regional industry and innovation.     

Editorial

Abstract

Silicon thin films, phosphorus doped in situ, have been deposited on to glass substrates using low pressure chemical vapour deposition at 550°C. The doping level is determined by adjusting the phosphine/silane molar ratio. Using this method a wide range of concentration is controllable. For a gas molar ratio varying between 4×10^?8 and 4 × 10^?4, phosphorus atomic incorporation is in the range 3 × 10¹⁶?3 × 10²⁰ cm^?3. The resistivity of the layers varies from 8·3 × 10⁵ to 1·5 × 10^?3 Ω cm. Lightly doped samples were passivated by hydrogenation, and Hall measurements were carried out, showing a marked improvement of the electrical properties. A lightly in situ doped drain thin film transistor suitable for active matrix applications was fabricated which exhibited good electrical properties.

MST/3335