Asymmetric phospholipid: lipopolysaccharide bilayers; a Gram-negative bacterial outer membrane mimic

The Gram-negative bacterial outer membrane (OM) is a complex and highly asymmetric biological barrier but the small size of bacteria has hindered advances in in vivo examination of membrane dynamics. Thus, model OMs, amenable to physical study, are important sources of data. Here, we present data from asymmetric bilayers which emulate the OM and are formed by a simple two-step approach. The bilayers were deposited on an SiO₂ surface by Langmuir–Blodgett deposition of phosphatidylcholine as the inner leaflet and, via Langmuir–Schaefer deposition, an outer leaflet of either Lipid A or Escherichia coli rough lipopolysaccharides (LPS). The membranes were examined using neutron reflectometry (NR) to examine the coverage and mixing of lipids between the bilayer leaflets. NR data showed that in all cases, the initial deposition asymmetry was mostly maintained for more than 16 h. This stability enabled the sizes of the headgroups and bilayer roughness of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and Lipid A, Rc-LPS and Ra-LPS to be clearly resolved. The results show that rough LPS can be manipulated like phospholipids and used to fabricate advanced asymmetric bacterial membrane models using well-known bilayer deposition techniques. Such models will enable OM dynamics and interactions to be studied under in vivo-like conditions.     

The relationship between social capital and traffic law violations: Israeli Arabs as a case study

Social aspects of a community may be correlated with driver's involvement in road traffic accidents. This study focused on examining this association in the context of the social capital theory. A survey of 600 Arab drivers living in 19 towns and villages was conducted using a face-to-face interview. Structural equation modeling was applied to explore paths of associations between the model components. Most of the proposed relationships in the path model were found to be significant, where the model explained 37% of the variation. The results indicate that only volunteering and reciprocity have direct correlations with traffic law violations. While the other correlations (except political involvement), were mediated by attitudes toward traffic laws violation.     

外滚道剥落的高速轴承转子非线性系统及其振动响应分析

为了建立符合工程实际的外滚道剥落高速轴承转子系统动力学模型,将滚道剥落引起的时变位移和时变冲击激励、油膜时变刚度和时变阻尼、钢球与滚道时变接触刚度和时变接触角、时变接触力等非线性因素综合考虑,结合JONES的高速球轴承动力学模型建立了外滚道剥落的高速轴承转子系统非线性动力学模型.基于该模型研究了剥落尺寸和转速变化时轴承...     

Subwavelength-grating-induced wavefront aberrations: a case study

The on-axis wavefront aberrations of a one-dimensional subwavelength-grating antireflection coating on an f/1.7 lens surface are shown to be small with noticeable contributions of defocus, astigmatism, and piston. The astigmatism is 0.02 wave, and the magnitude of the piston approaches one wave peak-to-valley. The difference in aberrations between orthogonally polarized wavefronts, or the retardance aberration, shows 0.01 wave of astigmatismlike variation and more than 0.01 wave of retardance-induced defocuslike variation. A small coupling between polarization states occurs in the form of the familiar Maltese cross, yielding a maximum of 3% coupling in the four diagonal edges of the pupil.     

Computer monitor recycling: a case study

The total number of computer monitors being scrapped per year worldwide is predicted to rise to 30 million units by the year 2005. Monitors contain significant quantities of lead (in the solder and CRT glass) and polybrominated flame retardants, which are potentially hazardous if released to the environment. A recent study investigated the possibility of cost-effectively recycling monitors     

Economic attribute sampling schemes: a case study

Quality Control is perhaps not normally thought of as an area in which operational research has any contribution to make; yet, when viewed from the point of balancing inspection costs against costs of allowing defective items into the production process, it is in the mould of a typical operational research problem. Quality control is often approached via the repeated hypothesis test of classical statistics, whereby we may discuss the cost of errors of types I and II and the need to balance these costs in any inspection scheme can be discussed.

This paper is a case study on the design of a quality control scheme which minimizes the total expected costs associated with the scheme and takes into account the past quality record of consignments submitted for inspection.     

Economics of sugar production: a case study

The manufacture of sugar from crushed sugar-cane involves processing through a number of stages. The yield of crystalline sugar per unit of processed juice depends on a variety of process parameters. Increased yield is also related to the determination of a suitable mix of in-process ingredients. In this paper a case study is presented where the use of product mix has been made. The product mix in this case is arrived at by considering the profit motive of the entrepreneur and keeping in view the constraints imposed by the processing times at various stages and the capacities of the equipment at each stage. The problems of implementation of the proposed product mix were then explored and a suitable production schedule has been suggested taking into consideration certain important constraints imposed by the Indian environment.     

Balancing two-sided assembly lines: a case study

We describe the design and use of a computer program to balance two-sided assembly lines. The program embodies a balancing algorithm that emphasizes speed over accuracy for the interactive, rapid refinement of solutions. We argue that this is a more useful approach to balancing real assembly lines than the typical optimality-seeking techniques. We also discuss some theoretical properties of two-sided lines; and we include the data for a real assembly line, which to our knowledge is the first to appear in the open literature in over 30 years     

Cirrus cloud iridescence: a rare case study

On the evening of 25 November 1998, a cirrus cloud revealing the pastel colors of the iridescence phenomenon was photographed and studied by a polarization lidar system at the University of Utah Facility for Atmospheric Remote Sensing (FARS). The diffraction of sunlight falling on relatively minute cloud particles, which display spatial gradients in size, is the cause of iridescence. According to the 14-year study of midlatitude cirrus clouds at FARS, cirrus rarely produce even poor iridescent patches, making this particularly long-lived and vivid occurrence unique. In this unusually high (13.2-14.4-km) and cold (-69.7 degrees to -75.5 degrees) tropopause-topped cirrus cloud, iridescence was noted from approximately 6.0 degrees to approximately 13.5 degrees from the Sun. On the basis of simple diffraction theory, this indicates the presence of particles of 2.5-5.5-microm effective diameter. The linear depolarization ratios of delta = 0.5 measured by the lidar verify that the cloud particles were nonspherical ice crystals. The demonstration that ice clouds can generate iridescence has led to the conclusion that iridescence is rarely seen in midlatitude cirrus clouds because populations of such small particles do not exist for long in the presence of the relatively high water-vapor supersaturations needed for ice-particle nucleation.     

Robust design of a spindle motor: a case study

Robust design is the process of minimising variability of products and processes in order to improve their quality and reliability. In recent years, it has seen wide spread application in many fields such as mechanical [J Quality Technol 24 (1992) 22], chemical [Quality Engng 9 (1997) 391] and civil [Quality Engng 9 (1997) 441] engineering. As an additional application, this paper investigates the use of robust design techniques during early design process, in order to predict, analyse and improve quality and reliability of spindle motors found within hard disks. The spindle motor is an integral component of the hard disk that rotates the recording media. Constant speed rotation is an absolute necessity for accurate reading and recording of information. However, it is difficult to achieve this due to the effects of cogging torque. In this paper, the robust design of a spindle motor is attempted. The motor was modelled using multiple regression analysis. A dual response approach [J Quality Technol 22 (1990) 38] was then used. This performed a constrained minimisation of the mean of the cogging response, the constraint being that the variance be within a specified limit. The results showed that the current operating point was near optimal. However, the redesign was still able to achieve a 4% and 25% reduction in the mean and the variance of the cogging torque, respectively, before actual prototypes were made.     

Optical analysis of crack tip stress fields: a comparative study

Four optical techniques for evaluating stress intensity factors in opaque specimens are described in outline, and compared for both an artificial crack and a fatigue crack. The results are compared to a standard solution for the geometry considered. All the techniques gave acceptable results over a range of stress levels and crack lengths. The methods of caustics and strain gauges were less good, whilst photoelasticity gave consistent results over a wide range of stress levels. Comments on the ease of application and the resource implications are also made in order to assist practitioners.     

Kaizen costing for lean manufacturing: a case study

In the past decade due to increasing global competition US firms have radically changed their manufacturing practices to improve their competitiveness. In pursuing this goal they have adopted a number of advanced techniques, such as just-in-time, total quality management, lean manufacturing, flexible manufacturing systems, process improvement, and design for manufacturability, to name a few. The objectives of all these programmes have been to reduce cost, improve quality, reduce cycle time, and increase flexibility on the factory floor. Support systems such as finance and cost management, however, have generally not kept pace with the level of corresponding operational changes being implemented. This paper presents a case study of kaizen costing as practised by Boeing Commercial Airplane Company, IRC Division. The purpose of this study is to describe a method used to set kaizen costs which will provide relevant cost data to support lean production decisions that would be useful to practitioners.     

Problem identification in maintenance modelling: a case study

This paper is concerned with a problem identification and problem focus process in maintenance modelling. It endeavours to describe the process of moving from vague problem understanding towards more specific problem formulation and problem focus in the pursuit of practical decision making. This process was conducted using several analytical tools that complemented each other such as regression analyses, snapshot modelling and delay time modelling. As in many case studies related to maintenance modelling, this study also makes use of the experience of experts. It can be seen from the paper that subjective data estimates can prove to be a useful input for modelling. The analysis shows how simple modelling of maintenance problems can provide useful insights and better understanding of the problem in hand.     

Self-reinforcing mechanisms for cellularisation: a longitudinal case study

Firms that adopt cellular manufacturing (CM) often need to restructure their products, personnel, equipment, factory management and organisation culture. Despite voluminous literature on CM, only a few case studies related to cellularisation exist. Therefore, to enhance understanding in this area, this paper presents a longitudinal case study on cellularisation in an electronic assembly plant. Six years of data were collected from the observations and discussions of an industrialist and an academician. Events instrumental to the persistence of CM were highlighted, with reference to path dependence analysis. Cellularisation is not entirely evolutionary or teleological but is an interplay of the two; it is significantly influenced by the positive feedback of self-reinforcing mechanisms after departing from critical junctures. The observed self-reinforcing mechanisms were expounded and divided into six categories.     

On Green Area implementation problems: a case study

In this paper the implementation approach, adopted by an engineering company, of an innovative team management system known as the ‘green area’ concept is researched and analysed. The system was introduced to improve contract time and cost control and change the business culture to one of high personnel involvement and responsibility. The determinants for successful business implementation of this system are evaluated using a multi-attribute framework. These determinants have been specified as a net of organizational change parameters for the successful implementation of business improvement strategies.     

Uncertainty in optical measurement applications: a case study

The uncertainty related to a measurement is at least as important as the measurement itself. Apart from being able to determine intervals of confidence around the final result within which the true measurement value is expected to lie at a certain level of confidence, the rigorous treatment of uncertainty throughout an algorithm allows increasing its robustness against disturbing influences and judging its applicability to a given task. This paper addresses the propagation of uncertainty within a quality control application using image-based sensors. Simulations and real-world results are provided to show the applicability of the proposed application.     

Flexibility analysis: A methodology and a case study

A methodology for analysing manufacturing flexibility is proposed. A real-life case is discussed to demonstrate the proposed methodology. The case involves the grinding operations of an engine manufacturer. As an integral part of the methodology, statistical analyses using response surface methodology are carried out. Potential applications of the proposed methodology are discussed. Planning models and flexibility measure used are outlined in the appendices.     

Reliability estimation of semi-Markov systems: a case study

In this article, we are concerned with the estimation of the reliability and the availability of a turbo-generator rotor using a set of data observed in a real engineering situation provided by Electricité De France (EDF). The rotor is modeled by a semi-Markov process, which is used to estimate the rotor's reliability and availability. To do this, we present a method for estimating the semi-Markov kernel from a censored data.