Comparison of Diffusion Studies of Hydrocortisone Between the Franz Cell and the Enhancer Cell

The Franz diffusion cell remains a popular method to study diffusion of transdermal drug delivery systems through membranes. Recently, VanKel Industries, Inc., (Edison, NJ) developed the “Enhancer Cell,” a new device for in vitro transdermal drug diffusion testing. The purpose of this study was to evaluate the enhancer cell for in vitro transdermal diffusion of hydrocortisone from an ointment using a synthetic membrane and a biological membrane and compare it to the traditionally employed Franz cell. The Enhancer cell utilizes existing USP dissolution equipment (USP Apparatus II). Results show a higher cumulative release from the Enhancer cell as compared to the Franz cell. The Enhancer cell demonstrated more durability and was easier to use during experimentation and after completion of the experiment no apparent change was observed in the condition of the ointment or the skin when compared to the Franz cell.     

Validation of an Automated Sampling system with Franz Diffusion Cells

Transdermal penetration studies “in vitro” are tedious and time consuming, and sometimes require complex sampling schedules. If automatic equipment is used, full validation is mandatory. The aim of this study was to validate an automated “in vitro” sampling system using modified Franz diffusion cells. The reproductibility of sample and replace volumes was assessed. The dilution effect induced by the replaced volume was also studied and some equations in order to correct this factor were propossed. Ketorolac trometamol has been used as a model drug in this study.     

Validation of an Automated Sampling system with Franz Diffusion Cells

Abstract

Transdermal penetration studies “in vitro” are tedious and time consuming, and sometimes require complex sampling schedules. If automatic equipment is used, full validation is mandatory. The aim of this study was to validate an automated “in vitro” sampling system using modified Franz diffusion cells. The reproductibility of sample and replace volumes was assessed. The dilution effect induced by the replaced volume was also studied and some equations in order to correct this factor were propossed. Ketorolac trometamol has been used as a model drug in this study.     

新型水三相点瓶与国家基准水三相点瓶的比对

2002年11月由国际计量局组织的水三相点瓶的国际关键比对（简称CCT－K7），中国计量科学研究院研制出新型结构的水三相点瓶，本文详细介绍了新型水三相点瓶，并将其与国家基准水三相点瓶进行了比对，同时，给出了比对结果。     

The Influence of 2-Hydroxypropyl-β-Cyclodextrin on Diffusion Rates and Transdermal Delivery of Hydrocortisone

The influence of 2-hydroxypropyl-β-cyclodextrin (HPβCD) on the permeability of hydrocortisone through semi-permeable cellophane membrane and hairless mouse skin was investigated. When the hydrocortisone concentration was kept constant and the HPβCD concentration in an aqueous vehicle was gradually increased the flux through the semi-permeable membrane was increased until all hydrocortisone had dissolved, after that the flux decreased with increasing HPβCD concentration. A maximum flux was obtained when just enough HPβCD was used to dissolve all the drug in the aqueous vehicle.     

Relationship Between the pH of the Diffusion L'Ayer and the Dissolution Rate of Furosemide

Sodium bicarbonate and ascorbic acid, both highly water-soluble materials, were used to modify the initial dissolution rate of furosemide from tablet formulations in various dissolution media. The observed differences in the initial dissolution rates of the drug have been correlated with changes in the pH of the diffusion layer brought about by the diluents. The initial dissolution rate of furosemide was shown to be dependent on and controlled by the pH of the diffusion layer while the bulk exerted only a secondary effect by controlling the magnitude of the pH-change through its buffer capacity.     

Relationship Between the pH of the Diffusion L'Ayer and the Dissolution Rate of Furosemide

Abstract

Sodium bicarbonate and ascorbic acid, both highly water-soluble materials, were used to modify the initial dissolution rate of furosemide from tablet formulations in various dissolution media. The observed differences in the initial dissolution rates of the drug have been correlated with changes in the pH of the diffusion layer brought about by the diluents. The initial dissolution rate of furosemide was shown to be dependent on and controlled by the pH of the diffusion layer while the bulk exerted only a secondary effect by controlling the magnitude of the pH-change through its buffer capacity.     

Carbon Diffusion Between the Layers in Modern Pattern-Welded Damascus Blades

Pattern-welded Damascus steel blades are made by forge welding together pairs of steels having low- and high-carbon compositions. It is often assumed that these blades consist of hard and soft layers owing to the carbon variations of the original steels and that it is this difference in hardness that produces the etching characteristics that give the surface patterns. Theoretical arguments are presented that show that, with the modern forging techniques used to make these blades, carbon diffusion should be adequate to homogenize the C level between the layers of the blades, which predicts no hardness difference between layers. Experiments are presented on several modern blades, showing that there are no hardness differences found between layers. Arguments are presented for a theory that it is the difference in alloying elements between the layers that produces the differential etching characteristics that give rise to the visual surface patterns of most contemporary pattern-welded Damascus steels.     

Experimental and Theoretical Studies on the Diffusion of Drugs in Polymer Films

An interferonstrie technique was developed and used to determine the diffusion coefficient and the physico-chemical state of different drugs in a polyacrylate-copolymer as a carrier system. By applying Ficks' second law the release rate of the drug was calculated and compared to in vitro/ in vivo data. From the relativly good agreement of the prediction with the experimental results it can he concluded that the pure mohility of the drug in the polymer is the rate determining factor for the mass flux. The physical concept used in the Higuchi equation seems to be not applicable for the examined system with monodispersed drugs.     

Experimental and Theoretical Studies on the Diffusion of Drugs in Polymer Films

Abstract

An interferonstrie technique was developed and used to determine the diffusion coefficient and the physico-chemical state of different drugs in a polyacrylate-copolymer as a carrier system. By applying Ficks' second law the release rate of the drug was calculated and compared to in vitro/ in vivo data. From the relativly good agreement of the prediction with the experimental results it can he concluded that the pure mohility of the drug in the polymer is the rate determining factor for the mass flux. The physical concept used in the Higuchi equation seems to be not applicable for the examined system with monodispersed drugs.     

Contact-Melting Studies of the Phase Composition of the Pb–Bi Diffusion Zone

Pb/Bi contact melting in the nonstationary diffusion regime is shown to be a quasi-equilibrium process. According to our results, the composition range of the resulting liquid layer corresponds to the equilibrium phase diagram. However, the intermetallic compound appearing in the equilibrium phase diagram may only exist as an unstable interphase in the diffusion zone.     

In Vitro Diffusion Studies of Ketoprofen Transdermal Therapeutic Systems

The release of Ketoprofen from the matrix model of TTS were studied. It may be concluded that the pharmaceutical availability of the drug can be regulated by the type and thickness of the matrix. Quantitation of the active agent in the dissolution medium was done by UV-spectroscopy.

The results obtained by the rotating cylinder method were compared to another method utilizing a modified Stricker cell.     

In Vitro Diffusion Studies of Ketoprofen Transdermal Therapeutic Systems

Abstract

The release of Ketoprofen from the matrix model of TTS were studied. It may be concluded that the pharmaceutical availability of the drug can be regulated by the type and thickness of the matrix. Quantitation of the active agent in the dissolution medium was done by UV-spectroscopy.

The results obtained by the rotating cylinder method were compared to another method utilizing a modified Stricker cell.     

Production of a Coacervate Film for Microcapsule Diffusion Studies

Until the last five years, study of microcapsules formed by complex coacervation has been approached almost entirely on an empirical basis. The gelatin-acacia coating formed through complex coacervation is responsible for the sustained release characteristics of the dosage form. Because dissolution of the drug from microcapsules is often limited by the structure and nature of the shell wall, of prime interest would be the construction of an acacia-gelatin film for diffusion studies. Apparent optimal conditions for production of the coacervate film were developed. The conditions were similar to those used to produce microcapsules by various researchers. These conditions produced a coacervate film which could be cut into two square centimeter sections apparently suitable for diffusion studies. Films produced by complex coacervation appeared free from structural defects when observed with a stereo-microscope.     

Studies of Thermal Diffusion in Planar Absorber Designs for the Micro-X Rocket

We have studied a potential design for a transition-edge sensor (TES) microcalorimeter array for the Micro-X High Resolution Microcalorimeter X-ray Imaging Rocket. Diffusion simulations of a design that places a small TES in the center of the pixel with a large in-plane absorber around the TES demonstrate that with high-quality gold films (RRR >6) 2 eV resolution is attainable in a 700 μm pixel, meeting the Micro-X requirement. X-ray hits directly on the TES, however, create a non-gaussian high energy tail to the device response. This high energy tail contains 5% of incident photons and cannot be removed by lowering the optimal filter bandwidth.      

DeviceNet标准与CANopen标准的比较

我国于2002年10月份正式发布了《低压开关设备和控制设备控制器－设备接口（CDI）第三部分DeviceNet》（GB／T 18858．3）作为国家标准,并于2003年4月正式实施。此DeviceNet协议为我国CAN总线领域唯一的国家标准,在工业生产和科技创新方面发挥了重要作用。但是近年来另一种流行的CAN总线协议－CANopen（EN 50325—4）也在国内的实践应用中被广泛采用。     

Four-Terminal-Pair Inductance Comparison Between INRIM and CTU

For 40 years, it has been known that a four-terminal-pair (4TP) definition achieves the highest accuracy in impedance measurement. While, for ac resistors and capacitors, a 4TP standard definition is commonplace, and 4TP commercial measurement systems are available on the market, for inductors, a two- or three-terminal definition is still the most common. This paper describes the first international intercomparison of inductance performed with 4TP measurement systems and a 4TP travelling standard. At the Istituto Nazionale di Ricerca Metrologica (INRIM), the measurement system is based on a 4TP implementation of the three-voltage method , and traceability is to calibrated ac resistors. At Czech Technical University (CTU), Prague, a 4TP double-balance transformer bridge is employed, and traceability is via calibrated capacitors, ac resistance, and ac resistance ratio. The comparison has been performed in the context of EUROMET Project 607, with a 4TP 100-mH temperature-controlled travelling standard constructed for the purpose. Despite the big differences in the measurement methods and traceability chains, the measurements reported by INRIM and CTU are fully compatible, within their relative expanded uncertainties of $7 times 10^{-6}$ and $6.2 times 10^{-5}$, respectively.      

Correlation Between Mesh Geometry and Stiffness Matrix Conditioning for Nonlocal Diffusion Models

Nonlocal diffusion models involve integral equations that account for nonlocal interactions and do not explicitly employ differential operators in the space variables. Due to the nonlocality, they might look different from classical partial differential equation (PDE) models, but their local limit reduces to partial differential equations. The effect of mesh element anisotropy, mesh refinement and kernel functions on the conditioning of the stiffness matrix for a nonlocal diffusion model on 2D geometric domains is considered, and the results compared with those obtained from typical local PDE models. Numerical experiments show that the condition number is bounded by $c\delta^{−2}$ (where $c$ is a constant) for an integrable kernel function, and is not affected by the choice of the basis function. In contrast to local PDE models, mesh anisotropy and refinement affect the condition number very little.