A formulation approach for development of HPMC-based sustained release tablets for tolterodine tartrate with a low release variation

Objective: The purpose of this study was to develop hydroxypropylmethylcellulose (HPMC)-based sustained release (SR) tablets for tolterodine tartrate with a low drug release variation.

Methods: The SR tablets were prepared by formulating a combination of different grades of HPMC as the gelling agents. The comparative dissolution study for the HPMC-based SR tablet as a test and Detrusitol^® SR capsule as a reference was carried out, and the bioequivalence study of the two products was also conducted in human volunteers.

Results: The amount of HPMC, the grade of HPMC and the combination ratio of different grades of HPMC had remarkable effects on drug release from the SR tablets. Both the test and reference products had no significant difference in terms of comparative dissolution patterns in four different media (f₂ > 50). Furthermore, the dissolution method and rotation speed showed no effects on the drug release from the two products. The 90% confidence intervals of the AUC_0–36 and C_max ratios for the test and reference products were within the acceptable bioequivalence intervals of log0.8–log1.25.

Conclusions: A HPMC-based SR tablet for tolterodine tartrate with a low release variation was successfully developed, which was bioequivalent to Detrusitol^® SR capsule.     

The Underdoped Region of the Phase Diagram of YBa2Cu3O6+x

Here we present a reviewed phase diagram of the high-T _c superconducting YBa₂Cu₃O_{6+ x} compound, finely mapped in the strongly underdoped region (0 < x < 0.5), from the pure antiferromagnetic state to the superconducting regime. The Neèl and spin freezing temperatures have been measured by μSR experiments while the hole density per Cu atom in the CuO₂ planes has been determined from the resistive T _c and from Seebeck coefficients at 290 K. The phase diagram is discussed in comparison to those of La_{2− x} Sr _x CuO₄ and Y_{1− x} Ca _x Ba₂Cu₃O₆ cuprate systems.     

Calculated ternary diagram of Ti–Al–Si system

Abstract

The phase equilibria between β (body centred cubic, bcc), α (hexagonal closed packed, hcp), Ti₃ Al–α ₂ (hcp), and Ti₅ Si₃ (hcp) in the Ti–Al–Si system have been investigated in the temperature range 700–1200°C. Isothermal sections of the ternary phase diagram have been assessed employing thermodynamic software, which uses the compound energy model to describe the phases mathematically. Available experimental phase equilibria results on the Ti–Al–Si system were used to calculate missing binary and ternary interaction parameters and assess isothermal phase diagrams. Extrapolations in the resulting tie triangles indicate the existence of three eutectoid reactions in the Ti rich corner of the ternary diagram: β → α + Ti₅ Si₃ , α → α ₂ + Ti₅ Si₃ , and β → α ₂ + Ti₅ Si₃ . Additionally, extrapolations in the β + α₂ + α tie triangle observed at 1100°C indicate that two possibilities arise to represent a peritectoid reaction involving α, β, and α ₂phases: β + α₂ → α and β + α → α₂ , depending on the alloy composition and the effect of temperature on the solubitlity of Si in the α phase.     

Wurtzite-derived ternary I–III–O2 semiconductors

Abstract

Ternary zincblende-derived I–III–VI₂ chalcogenide and II–IV–V₂ pnictide semiconductors have been widely studied and some have been put to practical use. In contrast to the extensive research on these semiconductors, previous studies into ternary I–III–O₂ oxide semiconductors with a wurtzite-derived β-NaFeO₂ structure are limited. Wurtzite-derived β-LiGaO₂ and β-AgGaO₂ form alloys with ZnO and the band gap of ZnO can be controlled to include the visible and ultraviolet regions. β-CuGaO₂, which has a direct band gap of 1.47 eV, has been proposed for use as a light absorber in thin film solar cells. These ternary oxides may thus allow new applications for oxide semiconductors. However, information about wurtzite-derived ternary I–III–O₂ semiconductors is still limited. In this paper we review previous studies on β-LiGaO₂, β-AgGaO₂ and β-CuGaO₂ to determine guiding principles for the development of wurtzite-derived I–III–O₂ semiconductors.     

Interface chemistry in aluminium alloy castings reinforced with iron base inserts

Bimetallic automotive components consisting of an Al–Si light alloy reinforced with a cast iron insert have been manufactured by gravity die moulding. Special precautions have been taken to ensure a uniform wetting of the insert by the liquid light alloy. Under these conditions, three intermetallic compounds are formed at the insert/alloy interface: η (Al₅Fe₂), τ5 (Al_7.4Fe₂Si) and τ6 (Al_4.5FeSi). Upon subsequent heat-treatment, τ2 (Al₅Fe₂Si₂) and τ10 (Al₁₂Fe₅Si₃) also appear. Growth of these compounds is discussed in terms of thermodynamics, kinetics and reaction mechanism in the Al–Fe and Al–Fe–Si systems. The effect of these chemical changes on the mechanical properties of the insert/alloy joint will be examined.     

Formulation Design of an HPMC-Based Sustained Release Tablet for Pyridostigmine Bromide as a Highly Hygroscopic Model Drug and its In Vivo/In Vitro Dissolution Properties

Pyridostigmine bromide (PB), a highly hygroscopic drug was selected as the model drug. A sustained-release (SR) tablet prepared by direct compression of wet-extruded and spheronized core pellets with HPMC excipients and exhibited a zero-order sustained release (SR) profile. The 2³ full factorial design was utilized to search an optimal SR tablet formulation. This optimal formulation was followed zero-order mechanism and had specific release rate at different time intervals (released % of 1, 6, and 12 hr were 15.84, 58.56, and 93.10%). The results of moisture absorption by Karl Fischer meter showed the optimum SR tablet could improve the hygroscopic defect of the pure drug (PB). In the in vivo study, the results of the bioavailability data showed the T_max was prolonged (from 0.65 ± 0.082 hr to 4.83 ± 1.60 hr) and AUC_0–t (from 734.88 ± 230.68 ng/ml.hr to 1153.34 ± 488.08 ng/ml.hr) and was increased respectively for optimum PB-SR tablets when compared with commercial immediate release (IR) tablets. Furthermore, the percentages of in vitro dissolution and in vivo absorption in the rabbits have good correlation. We believe that PB-SR tablets designed in our study would improve defects of PB, decrease the frequency of administration and enhance the retention period of drug efficacy in vivo for personnel exposed to contamination situations in war or terrorist attacks in the future.     

Low cycle fatigue resistance of Al–Li alloys

Abstract

Low cycle fatigue (LCF) resistance data from binary Al–Li, ternary Al–Li–Cu, and quaternary Al–Li–Cu–Mg alloys have been compiled and discussed. The LCF resistance is measured in terms of the variation of the number of reversals to failure 2N _fwith the plastic strain amplitude Δ? _p /2 as well as a modified average plastic strain energy per cycle (ΔW _p )_modified , obtained at different applied total strain amplitudes (Δ? _t /2). The data show the effects of microstructural features, namely dominant strengthening precipitates and the degree of recrystallisation as well as crystallographic texture. Lithium content, when in excess of 2·5 wt-%in aluminium decreases the low cycle fatigue resistance the most. The degree of aging, the degree of recrystallisation, and the degree of texture also influence the LCF resistance; among which the effect of the degree of aging is the most pronounced. The effects of lithium content in aluminium solid solution and strengthening precipitates obtainable by the change in the Li/Cu ratio are found to be marginal. Based on a modified total cyclic plastic strain energy till fracture, it is shown that most of the Al–Li alloys exhibit degradation in their LCF resistance in both hypotransition (higher fatigue lives) and hypertransition (lower fatigue lives) regions. Such degradation is attributed to the combined effects of mechanical fatigue, strain localisation through dislocation–precipitate interaction, environmental effects, and finally strain localisation through the high angle grain boundaries. In comparison with the currently used 2XXX and 7XXX series aluminium alloys, Al–Li alloys require substantial improvement before they can be considered for fatigue critical applications.     

Microstructure and mechanical properties of Mg–6Li–xAl–0.8Sn alloys

As-cast and as-extruded Mg–6Li–xAl–0.8Sn (x?=?0, 1, 3 and 5?wt-%) alloys were prepared. The microstructure and mechanical properties were investigated and discussed. The experimental results show that the Mg–6Li–0.8Sn alloy is composed of three phases: α-Mg, Mg₂Sn and Li₂MgSn. With the addition of Al, the test alloys display typical α-Mg?+?β-Li duplex structures. The new Mg₁₇Al₁₂ and LiMgAl₂ phases were found in the Mg–6Li–1Al–0.8Sn alloy. The lamellar-type AlLi phase was formed whereas the Mg₁₇Al₁₂ phase disappeared in Mg–6Li–3Al–0.8Sn alloy. The LiMgAl₂ phase vanished in the Mg–6Li–5Al–0.8Sn alloy. The mechanical properties of as-extruded alloys were remarkably improved. The as-extruded Mg–6Li–3Al–0.8Sn alloy exhibited the best mechanical properties, with a yield strength, tensile strength and elongation of 209.8?MPa, 242.6?MPa and 15.5%, respectively.     

Effects of Non-Magnetic Impurities on Cu-Spin Dynamics and Superconductivity in La2−x Sr x Cu1−y Zn y O4 Around x = 0.115

Muon-spin-relaxation (SR) and magnetic susceptibility measurements have been carried out in La_2–x Sr _x Cu_1–y Zn _y O₄ with x=0.13 changing y finely up to 0.10, with the aim at clarifying effects of the non-magnetic impurity Zn on the Cu-spin dynamics and superconductivity. It has been found that the y dependence of the volume fraction of the superconducting region estimated from susceptibility measurements highly correlates with that of the magnetically ordered region estimated from the SR results. The rapid decrease in the superconducting region and the rapid increase in the magnetically ordered region by the doping of a small amount of Zn can be interpreted as follows; Zn pins the dynamical spin correlation or the dynamical stripe correlations and hence the superconductivity is destroyed around itself.     

Metal–Organic Frameworks and Their Derived Materials: Emerging Catalysts for a Sulfate Radicals‐Based Advanced Oxidation Process in Water Purification

With the ever‐growing environmental issues, sulfate radical (SO₄^??)‐based advanced oxidation processes (SR‐AOPs) have been attracting widespread attention due to their high selectivity and oxidative potential in water purification. Among various methods generating SO₄^??, employing heterogeneous catalysts for activation of peroxymonosulfate or persulfate has been demonstrated as an effective strategy. Therefore, the future advances of SR‐AOPs depend on the development of adequate catalysts with high activity and stability. Metal–organic frameworks (MOFs) with large surface area, ultrahigh porosity, and diversity of material design have been extensively used in heterogeneous catalysts, and more recently, enormous effort has been made to utilize MOFs‐based materials for SR‐AOPs applications. In this work, the state‐of‐the‐art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials for SR‐AOPs, is summarized. The mechanisms, including radical and nonradical pathways, are also detailed in the discussion. This work will hopefully promote the future development of MOFs‐based materials toward SR‐AOPs applications.     

Development of ternary Mg based alloy for soldering of AZ31B magnesium alloy

Abstract

Two kinds of ternary Mg based alloys were designed to join the AZ31B magnesium alloy plates by high frequency induction soldering with argon shielding gas. The microstructures and properties of the filler metals and joints were investigated by SEM, X-ray diffraction, differential scanning calorimetry, spreading test and tensile test. The results have shown that the microstructures of Mg–31·5Al–10Sn filler metal mainly consist of Mg₁₇Al₁₂, Mg₂Sn and a trace amount of α-Mg phases, while the microstructures of Mg–29·5Zn–1Sn filler metal include α-Mg phase and Mg₇Zn₃ with a trace of α-Mg and Mg₂Sn phases. Both of the filler metals have narrow melting zones; however, the spreading area of the Mg–31·5Al–10Sn filler metal is much larger than that of the Mg–29·5Zn–1Sn filler metal on the AZ31B base metal. The average tensile strength of solder joints with Mg–31·5Al–10Sn filler metal is a little higher than that of the latter solder joints with Mg–29·5Zn–1Sn filler metal.     

A crystallographic study of a new compound of lanthanum silicon nitride,LaSi3N5

A new compound of lanthanum silicon nitride, LaSi₃N₅ has been prepared by the reaction between Si₃N₄ and La₂O₃ under a 50 atm nitrogen pressure at 2000° C for 2 h. The space group is P2₁2₁2₁, Z=4, a=7.838 Å, b=11.236 Å and c=4.807 Å, D _c=4.6 g cm^–3. The crystal structure data and X-ray powder diffraction data are given. The characteristics of the structure have been noted and the similarities between LaSi₃N₅ and Si₃N₄ have been discussed in terms of the fundamental structural unit of SiN₄ tetrahedra.     

Experimental investigation and optimization during the fabrication of arrayed structures using reverse EDM

In recent years, reverse electric discharge machining (R-EDM) has been evolved as a method for the fabrication of arrayed structures for surface texturing which find applications in fabrication of fins and component assembly. In this study, the feasibility of R-EDM process in the fabrication of arrayed features of ?3?mm and height 2?mm on mild steel has been investigated utilizing response surface methodology (RSM)-based experimentation. Influence of control variables such as peak current (I_p), pulse-on time (T_on), and flushing pressure (F_p) on some of the vital geometric characteristics like taper and cylindricity error along with material removal rate (MRR), surface roughness (SR), microhardness, and surface morphology of pillared structure has been investigated. Analysis of variance (ANOVA) results show that I_p has a significant influence followed by T_on on MRR. I_p has a significant contribution toward SR, taper, and cylindricity error. High microhardness was found in heat-affected zone (HAZ). The optimal combination of parameter obtained using principal component analysis (PCA)-based grey relational analysis (GRA) is determined to be I_p?=?10 A, T_on?=?100 μs, and F_p?=?0.3?kg/cm², which was further ascertained using confirmatory test.     

Heterojunction photodetector based on graphene oxide sandwiched between ITO and p-Si

The drop casting method is utilized on indium tin oxide (ITO)-coated glass in order to prepare a sandwiched ITO/graphene oxide (ITO/GO) with silicon dioxide/p-type silicon (SiO₂/p-Si) heterojunction photodetector. The partially sandwiched GO layer with SiO₂/p-Si substrate exhibits dual characteristics as it showed good sensitivity towards the illumination of infrared (IR) laser at wavelength of 974 nm. Excellent photoconduction is also observed for current–voltage (I–V) characteristics at various laser powers. An external quantum efficiency greater than 1 for a direct current bias voltage of 0 and 3 V reveals significant photoresponsivity of the photodetector at various laser frequency modulation at 1, 5 and 9 Hz. The rise times are found to be 75, 72 and 70 μs for 1, 5 and 9 Hz while high fall times 455, 448 and 426 are measured for the respective frequency modulation. The fabricated ITO/GO-SiO₂/p-Si sandwiched heterojunction photodetector can be considered as a good candidate for applications in the IR regions that do not require a high-speed response.     

Controlling the material removal and roughness of Inconel 718 in laser machining

Nickel alloys including Inconel 718 are considered as challenging materials for machining. Laser beam machining could be a promising choice to deal with such materials for simple to complex machining features. The machining accuracy is mainly dependent on the rate of material removal per laser scan. Because of the involvement of many laser parameters and complexity of the machining mechanism it is not always simple to achieve machining with desired accuracy. Actual machining depth extremely varies from very low to aggressively high values with reference to the designed depth. Thus, a research is needed to be carried out to control the process parameters to get actual material removal rate (MRR_act) equals to the theoretical material removal rate (MRR_th) with minimum surface roughness (SR) of the machined surfaces. In this study, five important laser parameters have been used to investigate their effects on MRR and SR. Statistical analysis are performed to identify the significant parameters with their strength of effects. Mathematical models have been developed and validated to predict the machining responses. Optimal set of laser parameters have also been proposed and confirmed to achieve the actual MRR close to the designed MRR (MRR_% = 100.1%) with minimum surface roughness (R_a = 2.67 µm).     

Effect of thermal cycling on martensitic transformation temperatures in Ti–Ni–Cu shape memory alloys

Abstract

Changes in martensitic transformation temperatures during thermal cycling in Ti–Ni–Cu shape memory alloys have been investigated by means of electrical resistivity measurements, thermal cycling tests under constant load and transmission electron microscopy. During thermal cycling without applied stress, the B2→B19′ transformation temperature M _s decreased, while the B2→B19 transformation start temperature M _s′ kept almost constant. During thermal cycling with applied stress, in solution treated Ti–45Ni–5Cu alloy, changes in M _s depended on the amount of applied stress. That is, M _s decreased when the applied stress was 39.2 MPa, while its value kept almost constant when a stress of 117.2 MPa was applied. It was also found that M _s′ increased during thermal cycling in the solution treated Ti–35Ni–15Cu and Ti–30Ni–20Cu alloys, irrespective of the amount of applied stress. All changes in M _s and M _s′ during thermal cycling with applied stress in Ti–Ni–Cu alloys were explained well by a combination of the thermal cycling effect and the structural refinement effect.     

Effects of SnO on growth and physical properties of BSCCO whiskers

Abstract

Superconductor whiskers doped with SnO have been fabricated by annealing a melt quenched (Bi₂Sn₁)-223 precursor using suitable heat treatment cycles. Approximately 5 μm thick, 90 μm wide and 5 mm long whiskers were fabricated, and their physical, electrical and magnetic properties were investigated. Crystallisation activation energies of glass phase fabricated were calculated to be 390 kJ mol^–1 using Kissinger method based on the differential thermal analysis data. The T _c value of the whiskers was found to be 94 K from M–T measurement. The magnetisation of whiskers before superconducting transition increased with decreasing temperature, and after superconducting transition, the magnetisation of whiskers decreased, from positive to negative, due to the diamagnetic nature of superconductivity. The change on magnetisation dependence of applied magnetic fields (M–H) showed that whiskers have paramagnetic–diamagnetic multiphase structure.     

Influence of a Weak Magnetic Field on Photoconductivity Spectrum of C60 Single Crystal

Abstract

Comparative research of the excitation photoconductivity spectra (quantum light energy 2–5 eV) of C₆₀ single crystal in and out of magnetic field at the temperature T = 250–350 K has been carried. The spectral evolution at this temperature range is described. It is shown that the spectra changes abrupt at temperature T ₁ ～ 260 K and T ₂ ～ 315 K. An increase in the photoconductivity up to 15% was observed in the magnetic field (B = 0.4 T) within the photon energy range 2.5–4.5 eV. Local photoconductivity peak's appearances in the magnetic field have been proven that the charge transfer excitons take part in a photoconductivity.     

Single crystals of Hg-12(n?1)n and infinite layer-CaCuO2 obtained at gas pressure P=10kbar

Single crystals of Hg_l-xPb_xBa₂Ca_n-lCu_nO_2n+2+(x=0,0.2,0.5; n=2,3,4,5) and infinite layer CaCuO₂ compounds have been grown using a high gas pressure. Resistivity measurements have been performed in fields up to 10 T. The Hg_0.8Pb_0.2-1234 single crystals of a size up to 0.5×0.5 mm² have a T _c onset of 130 K. Single crystals of CaCuO₂ of a size up to 2×1 mm² have a T _c onset between 70 and 100 K. X-ray structural refinements have been performed on the CaCuO₂ and HgPb-12(n–1)n single crystals.     

2.19 Conduction phenomena in NbNb2O5Au thin film structures fabricated by various techniques

Conduction mechanisms have been studied in niobium-niobium oxide-gold thin film sandwich structures with the oxide prepared by anodic oxidation and reactive sputtering, respectively. Different I–V characteristics have been obtained with diodes having gold electrodes made by both evaporation and sputtering. Significant rectification was found only, when evaporation techniques were used. For this type of diode the NbNb₂O₅ interface is generally assumed to act as ohmic contact, whereas the Nb₂O₅Au interface behaves like a Schottky contact. Conduction mechanisms relevant to the various portions of the I–V characteristics are discussed. Current drifts are also treated, which are attributed to the migration of ionized traps. A theoretical model explaining the drift phenomena is presented.