Transducer design for a portable ultrasound enhanced transdermal drug-delivery system

For application in a portable transdermal drug-delivery system, novel transducers have been designed to enhance insulin transmission across skin using ultrasound. Previous research has shown transdermal delivery of insulin across skin using commercial sonicators operating at 20 kHz with intensities ranging from 12.5 to 225 mW/cm/sup 2/. The goal of this research was to design and construct a small, lightweight transducer or array that could operate with a similar frequency and intensity range as a commercial sonicator used in previous transdermal ultrasound insulin experiments, but without the weight and mass of a sonicator probe. To obtain this intensity range, a cymbal transducer design was chosen because of its light, compact structure and low resonance frequency in water. To increase the spatial ultrasound field for drug delivery across skin, two arrays, each comprising of four cymbal transducers, were constructed. The first array, designated the standard array, used four cymbals transducer elements in parallel. A second array (named the stack array) used four cymbal transducers that used stacked piezoelectric discs to drive the titanium flextensional caps. Under similar driving conditions, the standard array produced intensities comparable to those achieved using a commercial sonicator.     

Biomimetism and bioinspiration as tools for the design of innovative materials and systems

Materials found in nature combine many inspiring properties such as sophistication, miniaturization, hierarchical organizations, hybridation, resistance and adaptability. Elucidating the basic components and building principles selected by evolution to propose more reliable, efficient and environment-respecting materials requires a multidisciplinary approach.     

Density functional methods as computational tools in materials design

Summary This article gives a brief overview of density functional theory and discusses two specific implementations: a numerical localized basis approach (DMol) and the pseudopotential plane-wave method. Characteristic examples include Cu, clusters, CO and NO dissociation on copper surfaces, Li-, K-, and O-endohedral fullerenes, tris-quaternary ammonium cations as zeolite template, and oxygen defects in bulk SiO₂. The calculations reveal the energetically favorable structures (estimated to be within ± 0.02 Å of experiment), the energetics of geometric changes, and the electronic structures underlying the bonding mechanisms. A characteristic DMo1 calculation on a 128-node nCUBE 2 parallel computer shows a speedup of about 107 over a single processor. A plane-wave calculation on a unit cell with 64 silicon atoms using 1024 nCUBE 2 processors runs about five times faster than on a single-processor CRAY YMP.     

Computer tools for integrated conceptual design

This paper outlines the conceptual design process with reference to the integrated computer-aided design tool known as Schemebuilder, and the related work of the Lancaster University Engineering Design Centre. The aim of the Lancaster EDC is to provide highly integrated support for the rapid creation and evaluation of a wide range of outline design schemes. Particular attention is paid to the design of mechatronic systems and devices.     

New starch-based thermoplastic hydrogels for use as bone cements or drug-delivery carriers

The development of new biodegradable hydrogels, based on corn starch/cellulose acetate blends, produced by free-radical polymerization with methyl methacrylate monomer (MMA) and/or an acrylic acid monomer (AA), is reported. The polymerization was initiated by a redox system consisting of a benzoyl peroxide and 4-dimethlyaminobenzyl alcohol at low temperature. These hydrogels may constitute an alternative to the materials currently used as bone cements or drug-delivery carriers. Swelling studies were carried out, as a function of pH and temperature, in buffered solutions. The xerogels were further characterized by Fourier transform–infrared spectroscopy. Tensile and compression tests, and dynamic mechanical thermal analysis were used to assess the mechanical performance of the developed materials. The fracture surfaces were observed by scanning electron microscopy. The developed materials are sensitive to the pH, showing a clear reversible transition in a relatively narrow interval of pH, which is just in the range of physiological conditions. These properties make the materials developed in this study very promising for biomedical applications. Fickian-type diffusion is the mechanism predominant in these systems, except for the composition with a higher concentration of AA, that corresponds to the most desirable kinetical behavior for controlled release (case II-transport mechanism). Furthermore, the results obtained in the mechanical tests are in the range of those reported for typical PMMA bone cements, showing that it is possible to develop partially degradable cements with an adequate mechanical behavior. © 1998 Kluwer Academic Publishers     

Ferri-liposomes as an MRI-visible drug-delivery system for targeting tumours and their microenvironment

The tumour microenvironment regulates tumour progression and the spread of cancer in the body. Targeting the stromal cells that surround cancer cells could, therefore, improve the effectiveness of existing cancer treatments. Here, we show that magnetic nanoparticle clusters encapsulated inside a liposome can, under the influence of an external magnet, target both the tumour and its microenvironment. We use the outstanding T2 contrast properties (r2=573-1,286 s(-1) mM(-1)) of these ferri-liposomes, which are ～95 nm in diameter, to non-invasively monitor drug delivery in vivo. We also visualize the targeting of the tumour microenvironment by the drug-loaded ferri-liposomes and the uptake of a model probe by cells. Furthermore, we used the ferri-liposomes to deliver a cathepsin protease inhibitor to a mammary tumour and its microenvironment in a mouse, which substantially reduced the size of the tumour compared with systemic delivery of the same drug.     

雕刻并联机器人刀具导向期望加工位置研究

为了增强雕刻并联机器人对其末端执行器位置监测以及对其工作环境、状态的主动认知的能力,引入了双目主动视觉的思想,建立了一种新型的基于圆形轨道的双目主动视觉监测平台,实现了并联机器人对空间工作环境的监测,并研究了在双目主动视觉监测平台下使并联机器人将刀具导向期望加工点的方法.研究结果表明,利用视觉信息解决了雕刻并联机器人导向矢量的确定问题,为机器人工作路径自规划提供了一种新方法.     

Digital tools for material selection in product design

The increasing number of normalized materials, promoters and users led to a significant amount and diversity of databases and software for material selection, presenting differentiating abilities for the materials selection process.     

Highly efficient Y-junctions with arc-bend branch structures of sunlight guiding systems for indoor illumination

This paper proposes both symmetrical and asymmetric Y-junctions with arc-bend branch structures for auxiliary indoor-illumination applications. These arc-bend branch structures can be used as a concave-mirror-like light guide, to change the direction of beam propagation and also to converge the beam spread angle. Optical simulation results show that the proposed arc-bend Y-junctions can achieve an inner coupling efficiency, not including plastic/air interfaces, above 90% in both usages: beam combiner and splitter. Particularly, when the applied branch opening angle becomes large, this high optical efficiency becomes more significant than those of linear straight Y-junctions. Moreover, it is also confirmed that the coupling efficiency of the symmetric arc-bend junction can be as high as 90.0%, and the asymmetric coupling efficiency is 93.4%, even if the branch opening angle is quite large.     

Modeling of friction stir welding process for tools design

A three-dimensional friction stir welding (FSW) process model has been developed based on fluid mechanics. The material transport in the welding process has been regarded as a laminar, viscous, and non-Newtonian liquid that flows past a rotating pin. A criterion to divide the weld zone has been given on the basis of cooperation of velocity field and viscosity field. That is, the η₀-easy-flow zone that existed near the tool pin corresponded to the weld nugget zone; the area between the η₀-easy-flow zone and η₁-viscosity band is corresponded to the thermal-mechanical affected zone (TMAZ). The model gives some useful information to improve the understanding of material flow in FSW through the simulation result of velocity distribution. In order to appraise the friction stir pin design, three kinds of pin geometry, one is column pin, the second is taper pin, and the last one is screw threaded taper pin, were used in the model. The pin geometry seriously affected the simulation result of velocity distribution in the η₀-easy-flow zone. The velocity distribution in the η₀-easy-flow zone can be considered as the criterion of optimizing friction stir tool design. This study will benefit to direct the friction stir tool design.     

Aquasomes--a nanoparticulate approach for the delivery of antigen

The development of compound that enhances immune responses to recombinant or synthetic epitopes is of considerable importance in vaccine research. Of the many different types of immunopotentiating compounds that have been researched, aquasomes are of considerable promise, because of their potency and adjuvanticity. Aquasomes were prepared by self-assembling of hydroxyapatite by co-precipitation method and thereafter preliminary coated with polyhydroxyl oligomers (cellobiose and trehalose) and subsequently adsorbed with bovine serum albumin (BSA) as a model antigen. The prepared systems were characterized for size, shape, antigen-loading efficiency, in vitro antigen stability, and in vivo performance. BSA-immobilized aquasomes were around 200 nm in diameter and spherical in shape and had approximately 20-30% BSA-loading efficiency. The immunological activity of the formulated aquasomes was compared with plain BSA and better results were observed. Studies also indicated that aquasome formulations could elicit combined T-helper 1 (Th1) and Th2 immune response.     

Drug solubility in fatty acids as a formulation design approach for lipid-based formulations: a technical note

Lipid-based drug delivery systems have been intensively investigated as a means of delivering poorly water-soluble drugs. Upon ingestion, the lipases in the gastrointestinal tract digest lipid ingredients, mainly triglycerides, within the formulation into monoglycerides and fatty acids. While numerous studies have addressed the solubility of drugs in triglycerides, comparatively few publications have addressed the solubility of drugs in fatty acids, which are the end product of digestion and responsible for the solubility of drug within mixed micelles. The objective of this investigation was to explore the solubility of a poorly water-soluble drug in fatty acids and raise the awareness of the importance of drug solubility in fatty acids. The model API (active pharmaceutical ingredient), a weak acid, is considered a BCS II compound with an aqueous solubility of 0.02?μg/mL and predicted partition coefficient >7. The solubility of API ranged from 120?mg/mL to over 1?g/mL in fatty acids with chain lengths across the range C18 to C6. Hydrogen bonding was found to be the main driver of the solubilization of API in fatty acids. The solubility of API was significantly reduced by water uptake in caprylic acid but not in oleic acid. This report demonstrates that solubility data generated in fatty acids can provide an indication of the solubility of the drug after lipid digestion. This report also highlights the importance of measuring the solubility of drugs in fatty acids in the course of lipid formulation development.     

Methods and tools for decision making in engineering design

This paper describes the background to the setting up of the Cambridge Engineering Design Centre. An overview of the design research and applications programme of the Cambridge EDC is given. Four research themes are identified: functional modelling, configuration and manufacturing optimization, materials and process selection, and process interpretation and management. Application areas include aerospace systems, heavy duty vehicles and medical equipment.     

Section modulus of corner joints in furniture frames as engineering design criteria for their efficient construction

Since joints are often the weakest points in furniture construction a detailed analysis of the factors influencing their load bearing capacity and its effectiveness in utilizing the full strength of the wood is reported here.     

拓扑与形状优化用于有效的产品设计

 介绍了基于有限元法(FEM)的计算机辅助结构优化方法． 拓扑优化有助于设计新零件的形状，形状优化则通过表面几何形状的局部调整改善零件的刚度或使用寿命．     

Computationally efficient modelling of short fatigue crack growth using dislocation formulations

In an attempt to develop a computationally efficient model for simulation of fatigue crack growth of microstructurally short cracks two dislocation based models have been compared. In both models, the geometry of the boundary and the crack is described using dislocation dipole elements, whereas the plasticity is described either by discrete dislocations or by distributed dipole elements. The two models were found to agree qualitatively as well as quantitatively. It was concluded that modelling the plasticity by dipole elements becomes comparatively increasingly more time efficient with increasing grain size plastic zone size. However, plasticity modelling by dipole elements showed to provide somewhat higher crack growth rates.     

基于导向插合的毛刷电接触对结构改进设计

针对现有毛刷电接触对插合过程中随机插合现象导致的插拔力和接触电阻范围过大、可控性较差的现状,提出基于导向插合的毛刷电接触结构改进方案.改进结构包括单针簇导向结构、对接端面导向结构及插针螺旋校直结构.对改进前、后的毛刷电接触对进行2mm插拔深度的插拔力试验及接触电阻试验,结果表明:基于导向插合的毛刷电接触结构改进优化了毛刷电接触对插拔力、接触电阻范围,结构改进前、后的单对毛刷接触对多次插拔力方差值分别为0.39,0.003,结构改进前、后的单对毛刷接触对多次接触电阻方差值分别为0.41,0.008.基于导向插合的毛刷电接触对结构改进设计对改善毛刷电接触性能以及其参数设计提供了参考.