bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delivery of Lipoplexes for Genotherapy of Solid Tumours: Role of Vascular Endothelial Cells
Authors: Dass Crispin R , Su Tao 
Published: October 2002

AbstractThe cells constituting a solid tumour may vary considerably due to biological disparities, but for a solid tumour to pose as a threat to its host, an adequate blood supply has to be established. Although neovascularisation may have dire consequences for the host, it provides a common route by which tumours in general may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue means that selective delivery of drugs may be achieved. A closer examination of the role played by the cells making up the tumour vascular bed, vascular endothelial cells (VECs), is required to facilitate design of ways for enhancing drug delivery to solid tumours via the vascular route.VECs have two major roles in the body, barrier and transport, both of which are highly pertinent to drug delivery. This review discusses the factors regulating VEC function, and how these cells may be manipulated in-vivo to improve the selective delivery of lipoplexes, carriers for gene therapy constructs, to solid tumours. It also discusses how genotherapeutic drugs may be targeted against tumour VECs on the premise that by killing these cells, the tumour itself will perish.
Skin Delivery of Oestradiol from Deformable and Traditiona Liposomes: Mechanistic Studies
Authors: El Maghraby Gamal M M , Williams Adrian C , Barry Brian W 
Published: October 2002

AbstractDeformable vesicles and traditional liposomes were compared as delivery systems for oestradiol to elucidate possible mechanisms of drug delivery through human skin. Accordingly, epidermal permeation of oestradiol from optimized deformable vesicles and traditional liposome formulations was studied under low dose non-occluded conditions. Five mechanisms were investigated. A free drug mechanism compared low-dose permeation through skin with drug release determined after separation of the free drug. Penetration enhancement was researched by studying skin pretreatment with empty vesicles. Improved drug uptake by skin was monitored by dipping stratum corneum into different formulations for 10 min and determining drug uptake. The possibility that intact vesicles permeate through the epidermis was tested by comparing permeation from 136-nm vesicles with that from &gt; 500-nm vesicles, assuming that penetration depends on vesicle size. The possibility that different entrapment efficiencies in alternative formulations could be responsible for the difference in delivery was also evaluated.Lipid vesicles improved the skin delivery of oestradiol compared with delivery from an aqueous control. Maximum flux (Jmax) was increased 14- to 17-fold by use of deformable vesicles and 8.2- to 9.8-fold by use of traditional liposomes. Deformable vesicles were thus superior to traditional liposomes. Drug release was negligible over the period during which skin flux was maximum. Pretreatment with empty vesicles resulted in an enhancement ratio of 4.3 for pure phosphatidylcholine (PC) vesicles but the enhancement ratio ranged from only 0.8 to 2.4 for other formulations. Vesicles increased drug uptake into the stratum corneum 23- to 29-fold. Relative flux values obtained from small and large vesicles were similar. No correlation was found between entrapment efficiency and skin delivery.The results showed no evidence of a free drug mechanism, but revealed a possible penetration-enhancing effect for pure PC vesicles, although this was not the only mechanism operating. The positive uptake suggested that lipid vesicles increased drug partitioning into the skin. The data provided no evidence for in-vitro liposome penetration through skin as distinct from vesicle penetration into the stratum corneum.
The influence of punch blunting on the elastic indentation response
Authors: Korsunsky A. M 
Published: October 2002

Elastic solutions of a family of axisymmetric problems concerning frictionless contact between a rigid punch and a semi-infinite substrate are considered using the method of Green and Zerna and of Collins. The analysis is relevant to the interpretation of experimental results in materials indentation testing, e.g. when substrate properties need to be determined from load—displacement traces, and precise information about the indenter tip shape is crucial. Commonly used solutions for ideal punch shapes, e.g. those having spherical or conical tips, may only be viewed as approximations since, in practice, indenter tips are neither perfectly round nor infinitely sharp. In order to illustrate the influence that small variations in punch shape may have on the contact behaviour, analytical solutions for a blunted Hertzian indenter and a rounded cone are obtained in parametric form, and their asymptotic behavioural the extremes of low and high loads is investigated. A smooth punch is then considered of a general shape, given by a power series, and the resulting general solution is used as a basis for developing an inverse problem formulation of the tip shape calibration procedure. The method allows the best match between the measured and predicted load-displacement dependencies to be established. An example of the application of this procedure to the analysis of some nanoindentation data is presented.
Upper and lower bound limit and shakedown loads for hollow tubes with axisymmetric internal projections under axial loading
Authors: Hardy S. J , Gowhari-Anaraki A. R , Pipelzadeh M. K 
Published: October 2002

In this paper, the elastic compensation method proposed by Mackenzie and Boyle is used to estimate the upper and lower bound limit (collapse) loads and the upper and lower bound shakedown loads for hollow tubes with axisymmetric internal projections subjected to axial loading. The method is based on an iterative elastic analysis procedure and the application of lower and upper bound limit load theorems. Four different geometries with a range of stress concentration factors (from low to high) are considered. Elastic-plastic finite element predictions for collapse and shakedown pressure are found to be within these upper and lower bound estimates. The method is particularly useful because it is founded on an iterative elastic approach and does not require extensive and complex elastic-plastic finite element computations.
A two-term stress function approach to evaluate stress distributions in bonded joints of different geometries
Authors: Lazzarin P , Quaresimin M , Ferro P 
Published: October 2002

The paper presents a method for the evaluation of the singular stress fields in bonded joints of different geometries. The stress distributions are represented by a two-term stress expansion, under the hypothesis that both the first and the second terms are in the variable separable form. The method is based on the stress function approach, where the formulation is completed analytically and the resulting set of ordinary differential equations is solved numerically. The capability of the formulation to account for the actual elastic properties of the substrates allows an accurate description of the singular stress field to be obtained even in the case of joints made of materials with comparable elastic properties. The influence of adhesive joint design parameters such as the type of joint, geometry and material properties on the generalized stress intensity factors will also be presented and discussed.
Compensation algorithms for the real-time correction of time and spatial errors in a vertical machining centre
Authors: Ford D G , Postlethwaite S R , Allen J P , Blake M D 
Published: October 2002

This paper describes research into a machine tool error compensation system for universal application. Based on an indirect identification precalibrated technique, it utilizes a unique algorithm, which allows the compensation system to compensate for the geometric error components of any normal orthogonal machine tool configuration. The movement and position of the machine tool axes can affect individual machine tool axis error components (such as yaw, pitch, roll and straightness). The level of this axis coupling is dependent on the machine tool configuration and the rigidity of the machine tool structure. Also, thermal effects can affect the machine tool axis error components. The kinematic (rigid body) model will be modified to allow for the non-rigid effects, and a novel technique for reducing workpiece errors caused by the thermal distortion of a computer numerical control (CNC) machine tool is introduced. This new approach to thermal error reduction is based on an indirect measurement technique where temperature/distortion relationships are developed by splitting the problem into two parts, a thermal model and a distortion model. Thermal imaging has been used extensively, and research into its usefulness for developing models has been under investigation. The use of separate thermal and distortion models allows analytical techniques, such as finite element analysis, to be used to verify performance. Novel techniques for the fast, accurate and detailed geometric calibration of CNC machine tools were also investigated. Although the wide availability of modern metrology equipment has provided the means for accurate measurement of machine errors, geometric calibration of machine tools is a time consuming, labour intensive and therefore costly process. The methodology and validation of the universal rigid body compensation model with its machine-specific non-rigid body and thermal effects suitably integrated have been demonstrated. Other elements such as calibration methodology, dynamic measurement, non-rigid effects/compensation and thermal distortion models will be the subject of further papers leading to the overall objective.
Development of a structured approach to assessing technology management practice
Authors: Probert D R , Phaal R , Farrukh C J P 
Published: October 2002

The effective application of technology is a key source of competitive advantage for modern industry. However, the integration of technology management systems into established business processes represents a continuing challenge to many firms. This paper describes the development of a practical technique for the assessment of technology management practices. Based on a process model of technology management, it provides a means whereby manufacturing companies can assess the effectiveness of the technology management activities critical to their business, and identify areas for improvement or transfer of good practice. The development of the assessment methodology is discussed in the context of the wider research project of which it is part. Its basis in theory and literature is reviewed, together with the results of its application in a range of manufacturing companies. The main output from the project is a practical management guide [technology management assessment procedure (TMAP)]. The procedure comprises three levels, which span the full range of technology management activities in the firm, linking broad strategic concerns to detailed operational activities in the format of a series of facilitated workshops.
Design for manufacturability: A feature-based agent-driven approach
Authors: Jacquel D , Salmon J 
Published: October 2002

Extensions to mechanical feature-based design and design for manufacturability are presented that adopt the increasingly recognized multiagent paradigm. This approach uses autonomous agents to implement each form feature inside the model being created, thus leading to the creation of a new type of active product model. Designers add new features to their designs by populating a living community of agents that construct the model, therefore creating an active product program as opposed to the traditional passive product data. Feature agents are self-scheduled autonomous entities, able to exchange data with one another and with a degree of self-control over their own geometric data. Using simple manufacturability criteria, each feature agent endlessly applies its embedded knowledge to ensure its own local manufacturability. A global behaviour emerges from the agents' activity inside the model that optimizes the global manufacturability of the component being designed.
Combination of strategy investigation and utilization of sensor signals in robotic assembly
Authors: Qiao H , Zhang B 
Published: October 2002

Recently, various kinds of sensor have been widely used in engineering and technological applications. As feedback devices, sensors are anticipated to provide all the information of a dynamic system or at least the information that is necessary in the real-time control process. Therefore much effort has been devoted to the analysis of the influences of noises on the sensor system and the improvement of the control performance. The oversimplification of the utilization process of sensors has led to the lack of motivation in strategy investigation. However, it should be noted that a dynamic system can be described by different states and the state measured by sensors may be different from that being controlled. Also the measured state may not be able to provide all the information required in the control system. This required information can be defined as information states. Furthermore, in many cases, there is no one to one relationship between the measured state and the information state. Therefore, it is necessary to analyse the whole system from a higher level. In this paper, a new process has been designed to control the dynamic system with sensor feedback. Based on this process, the strategies that can be used to achieve high-precision robotic assembly operations with force sensors have been analysed systematically. It is anticipated that this process can be widely used in other applications.
Surface alignment based on the moment of inertia and improved least-squares methods
Authors: Esat I I , Bahai H 
Published: October 2002

As part of dimensional inspection and error analysis of components it is usually required to place the component in a fixture where its position can be related to its computer aided design (CAD) nominal coordinate axis and the coordinate frame of the measuring system. The fixturing can be expensive and does not completely eliminate the mathematical matching needed between measured and nominal surfaces. Least-squares minimization is one of the most common methods employed in achieving the required alignment. This method, however, works only if the misalignment between two data sets is very small. Furthermore, there is no measure to establish whether this method is likely to converge or not before performing the actual iteration. The requirement for a small angle implies that this method is only suitable if fixturing is also used. The other technique used in obtaining alignment is by consideration of the mass properties of surfaces. This method is more effective and works irrespective of the degree of alignment. The problem with the mass property approach is that its accuracy diminishes when the error is small. This paper compares the two methods and demonstrates that both the r. m.s. minimization and the mass property methods can be expressed as eigenvalue problems, and both approaches produce identical eigenvectors despite having different eigenvalues (error measurements). A method is proposed to determine whether convergence is expected in the least-squares minimization at the first step of iteration. The proposed method may be used for accelerating the convergence operation.
Estimation of the synthetic dynamic accuracy of the die and the press by considering the eccentric load in blanking
Authors: Sekine F 
Published: October 2002

Manufacturing accuracy is ultimately decided by the synthetic dynamic accuracy of the die and the press in press working. In particular, blanking accuracy is determined by the relative mismatch of the upper die to the lower die in blanking. In this research, deformation of a die set and a press subjected to an eccentric load is analysed. Here, the moment of rotations M and the lateral force Q acting on the boundary between the upper die and the press slide are thought to be expressed by the inclination, Q, and the lateral displacement, Dx, of the upper die. In the blanking experiment, a die set is installed on a 600kN high-precision straight-sided press, and Q and Dx are measured under a dynamic eccentric loading of 50–600stroke/min. Then, estimation of the synthetic dynamic accuracy of the press and the die is examined. The effect of the stiffness of the press is discussed. The analytical method proposed in this paper can be used in the selection of a press suitable for a given die set and an eccentric load. In precise press working, the selection of the optimum combination of die and press to make the lateral displacement of the punch as small as possible is facilitated by considering the above-mentioned conditions.
Flexible disassembly systems-layouts and modules for processing obsolete products
Authors: Wiendahl H-P , Scholz-Reiter B , Bürkner S , Scharke H 
Published: October 2002

Currently, a significant amount of worldwide research is dedicated to manual or automated disassembly. This field of application has progressed remarkably over the past few years because industry has been forced to consider new technologies for processing electronic waste. This is due to changing environmental legislation, increasing amounts of obsolete appliances, decreasing landfill space and a growing public awareness of environmental problems. These considerations lead to growing research, development and implementation of manual and automated disassembly systems which are able to process a wide range of obsolete electronic appliances. The present paper investigates different prototypes of manual and automated disassembly cells at disassembly companies and research institutes. The approach, technology and architecture of these systems are described. Typical hardware components of flexible disassembly systems are then identified and explained. Furthermore, suggestions are made for modularization and standardization of these components, even if only at a very cursory level.
Instability phenomena in the gas—metal arc welding self-regulation process
Authors: Bingül Z 
Published: October 2002

Arc instability is a very important determinant of weld quality. The instability behaviour of the gas-metal arc welding (GMAW) process is characterized by strong oscillations in arc length and current. This phenomenon was reported by Halmoy [1] for the short electrode extension and by Lebedev [2] for the long electrode extension, particularly as related to the arc voltage-current characteristics and the thermal inertia of the electrode wire respectively. However, with these studies, a complete theoretical explanation of the instability phenomena is lacking since the process is not modelled dynamically. In the present work, a model of the GMAW process is developed using an exact arc voltage characteristic. This model is used to study stability of the self-regulation process and to develop a simulation program that helps to understand the transient or dynamic nature of the GMAW process and relationships among current, electrode extension and contact tube-work distance (CTWD). The process is shown to exhibit instabilities at both long electrode extension and normal extension. The experimental results agree closely with both Lebedev's and Halmoy's results. Results obtained from simulation runs of the model were also experimentally confirmed by the present author, as reported in this study. In order to explain the concept of the instability phenomena, the metal transfer mode and the arc voltage-current characteristic were examined. Based on this examination, the conclusion of this study is that their combined effects lead to the oscillations in arc current and length.
Temperature changes in hot flat rolling of steels at low strain rates and low reduction
Authors: Aiyedun P O , Sparling L G M , Sellars C M 
Published: October 2002

A finite difference (two-dimensional) model developed to describe the heat flow at low strain rates (0.08–1.5 s−1) and low reduction (∼10 per cent) for a hot flat rolled slab both during air cooling and during roll contact has been used in conjunction with experimentally measured temperatures through specimen thickness during roll contact after reheating to temperatures in the range 1000–1200°C for mild steel, low carbon SS316 and high carbon SS316 (with Nb, V and Ti). At high strain rates (∼1.5 s−1) a steep temperature gradient was produced in the specimen near the surface whereas for low strain rates (∼0.08 s−1) this temperature gradient penetrated deep into the thickness, leading to a large drop in the mean rolling temperature. Roll chilling, leading to higher values of the Zener-Holloman parameter, Z, resulted from a decrease in the mean rolling temperature and the large temperature gradient during roll contact. Temperature changes due to material composition, reheating temperature, contact time and rolling conditions led to precipitation strengthening and roll chilling effects which have accounted for the excess load and torque observed experimentally and industrially.
Investigation into hydromechanical reverse redrawing assisted by separate radial pressure—process development and theoretical verification
Authors: Kim J B , Lee D W , Yang D Y , Park C S 
Published: October 2002

High-quality cups with a deep drawing ratio of more than four cannot be simply drawn by conventional drawing and redrawing. A special technology is required to form cups of a high deep drawing ratio. In the present study, after the conventional mechanical deep drawing process, subsequent hydromechanical reverse redrawing with controlled radial pressure has been developed. In order to increase the deep drawing ratio by more than four, the radial pressure is controlled independently of the chamber pressure and thus an optimum forming condition can be determined by varying the radial pressure. The process has been verified by a rigid-plastic finite element (FE) analysis considering all the external force boundary conditions induced by the hydrostatic pressure. The pressure distribution on the sheet is calculated numerically from the simplified Navier-Stokes equation. Through the experiment and the FE analysis, it has been shown that hydromechanical reverse redrawing assisted by separate radial pressure, developed in the present study, helps to increase the drawability of cylindrical cups, and thus it is useful when forming long cups.