Two-Dimensional Failure Modeling with Minimal Repair

In this paper, we discuss two-dimensional failure modeling for a system where degradation is due to age and usage. We extend the concept of minimal repair for the one-dimensional case to the two-dimensional case and characterize the failures over a two-dimensional region under minimal repair. An application of this important result to a rnanufacturer's servicing costs for a two-dimensional warranty policy is given and we compare the minimal repair strategy with the strategy of replacement of failure. (C) 2003 Wiley Periodicals, Inc.

Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes

The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the {311}, {220}, {331}, {111} and {391} related lattice planes of magnetite and the {222} lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained {311}, {220} and {111} lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct from arrowhead-shaped and bullet-shaped magnetosomes. Elongation of magnetite magnetosomes in the [110] direction has not been reported previously. A Martian hexa-octahedral magnetite particle was previously characterized by Thomas-Keptra et al. and compared with truncated hexa-octahedral magnetite magnetosomes. Hexa-octahedral magnetite magnetosomes with the same morphology and similar sizes and axial ratios as those reported by Thomas-Keptra et al. are characterized here. These observations support their claim that ALH84001 contains evidence for a past Martian biota.

Increased adjuvant activity of minimal CD8 T cell peptides incorporated into lipid-core-peptides

A problem facing the use of subunit peptide and protein vaccines is their inability to stimulate protective immune responses. Many different approaches have been utilized to overcome this inefficient immune activation. The approach we have taken is to modify the vaccine antigen so that it now has adjuvant properties. To do this, multiple copies of minimal CD8 T cell epitopes were attached to a poly lysine lipid core. These constructs are known as lipid-core-peptides (LCP). The research presented here examines the adjuvant activity of LCP. Using mouse models, we were able to show that LCP were indeed able to activate antigen-presenting cells in vitro and to activate cytotoxic T-cell responses in vivo. More importantly, LCP were able to stimulate the development of a protective antitumour immune response.

Minimal instrumentation may compromise failure diagnosis with an ecological interface

Interfaces designed according to ecological interface design (EID) display higher-order relations and properties of a work domain so that adaptive operator problem solving can be better supported under unanticipated system conditions. Previous empirical studies of EID have assumed that the raw data required to derive and communicate higher-order information would be available and reliable. The present research examines the relative advantages of an EID interface over a conventional piping-and-instrumentation diagram (PID) when instrumentation is maximally or only minimally adequate. Results show an interaction between interface and the adequacy of the instrumentation. Failure diagnosis performance with the EID interface with maximally adequate instrumentation is best overall. Performance with the EID interface drops more drastically from maximally to minimally adequate instrumentation than does performance with the PID interface, to the point where the EID interface with minimally adequate instrumentation supports nonsignificantly worse performance than does the equivalent PID interface. Actual or potential applications of this research include design of instrumentation and displays for complex industrial processes.

The Mental Health Policy Template: Domains and elements for mental health policy formulation

Mental disorders are a major and rising cause of disease burden in all countries. Even when resources are available, many countries do not have the policy and planning frameworks in place to identify and deliver effective interventions. The World Health Organization (WHO) and the World Bank have emphasized the need for ready access to the basic tools for mental health policy formulation, implementation and sustained development. The Analytical Studies on Mental Health Policy and Service Project, undertaken in 1999-2001 by the International Consortium for Mental Health Services and funded by the Global Forum for Health Research aims to address this need through the development of a template for mental health policy formulation. A mental health policy template has been developed based on an inventory of the key elements of a successful mental health policy. These elements have been validated against a review of international literature, a study of existing mental health policies and the results of extensive consultations with experts in the six WHO regions of the world. The Mental Health Policy Template has been revised and its applicability will be tested in a number of developing countries during 2001-2002. The Mental Health Policy Template and the work of the Consortium for Mental Health Services will be presented and the future role of the template in mental health policy development and reform in developing countries will be discussed.

Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement

Background: In clinical trials, at the group level, results are usually reported as mean and standard deviation of the change in score, which is not meaningful for most readers. Objective: To determine the minimal clinically important improvement (MCII) of pain, patient's global assessment of disease activity, and functional impairment in patients with knee and hip osteoarthritis (OA). Methods: A prospective multicentre 4 week cohort study involving 1362 outpatients with knee or hip OA was carried out. Data on assessment of pain and patient's global assessment, measured on visual analogue scales, and functional impairment, measured on the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) function subscale, were collected at baseline and final visits. Patients assessed their response to treatment on a five point Likert scale at the final visit. An anchoring method based on the patient's opinion was used. The MCII was estimated in a subgroup of 814 patients ( 603 with knee OA, 211 with hip OA). Results: For knee and hip OA, MCII for absolute ( and relative) changes were, respectively, ( a) -19.9 mm (-40.8%) and -15.3 mm (-32.0%) for pain; ( b) -18.3 mm ( - 39.0%) and -15.2 mm ( -32.6%) for patient's global assessment; ( c) -9.1 ( -26.0%) and -7.9 ( -21.1%) for WOMAC function subscale score. The MCII is affected by the initial degree of severity of the symptoms but not by age, disease duration, or sex. Conclusion: Using criteria such as MCII in clinical trials would provide meaningful information which would help in interpreting the results by expressing them as a proportion of improved patients.

On minimal models of process systems

Minimal representations are known to have no redundant elements, and are therefore of great importance. Based on the notions of performance and size indices and measures for process systems, the paper proposes conditions for a process model being minimal in a set of functionally equivalent models with respect to a size norm. Generalized versions of known procedures to obtain minimal process models for a given modelling goal, model reduction based on sensitivity analysis and incremental model building are proposed and discussed. The notions and procedures are illustrated and compared on a simple example, that of a simple nonlinear fermentation process with different modelling goals and on a case study of a heat exchanger modelling. (C) 2004 Elsevier Ltd. All rights reserved.

D-amino acid residue in a defensin-like peptide from platypus venom: effect on structure and chromatographic properties

The recent discovery that the natriuretic peptide OvCNPb (Ornithorhynchus venom C-type natriuretic peptide B) from platypus (Ornithorynchus anatinus) venom contains a D-amino acid residue suggested that other D-amino-acid-containing peptides might be present in the venom. In the present study, we show that DLP-2 (defensin-like peptide-2), a 42-amino-acid residue polypeptide in the platypus venom, also contains a D-amino acid residue, D-methionine, at position 2, while DLP-4, which has an identical amino acid sequence, has all amino acids in the L-form. These findings were supported further by the detection of isomerase activity in the platypus gland venom extract that converts DLP-4 into DLP-2. In the light of this new information, the tertiary structure of DLP-2 was recalculated using a new structural template with D-Met(2). The structure of DLP-4 was also determined in order to evaluate the effect of a D-amino acid at position 2 on the structure and possibly to explain the large retention time difference observed for the two molecules in reverse-phase HPLC. The solution structures of the DLP-2 and DLP-4 are very similar to each other and to the earlier reported structure of DLP-2, which assumed that all amino acids were in the L-form. Our results suggest that the incorporation of the D-amino acid at position 2 has minimal effect on the overall fold in solution.

Minimal disease activity for rheumatoid arthritis: A preliminary definition

Agreement on response criteria in rheumatoid arthritis (RA) has allowed better standardization and interpretation of clinical trial reports. With recent advances in therapy, the proportion of patients achieving a satisfactory state of minimal disease activity (MDA) is becoming a more important measure with which to compare different treatment strategies. The threshold for MDA is between high disease activity and remission and, by definition, anyone in remission will also be in MDA. True remission is still rare in RA; in addition, the American College of Rheumatology definition is difficult to apply in the context of trials. Participants at OMERACT 6 in 2002 agreed on a conceptual definition of minimal disease activity (MDA): "that state of disease activity deemed a useful target of treatment by both the patient and the physician, given current treatment possibilities and limitations." To prepare for a preliminary operational definition of MDA for use in clinical trials, we asked rheumatologists to assess 60 patient profiles describing real RA patients seen in routine clinical practice. Based on their responses, several candidate definitions for MDA were designed and discussed at the OMERACT 7 in 2004. Feedback from participants and additional on-site analyses in a cross-sectional database allowed the formulation of 2 preliminary, equivalent definitions of MDA: one based on the Disease Activity Score 28 (DAS28) index, and one based on meeting cutpoints in 5 out the 7 WHO/ILAR core set measures. Researchers applying these definitions first need to choose whether to use the DAS28 or the core set definition, because although each selects a similar proportion in a population, these are not always the same patients. In both MDA definitions, an initial decision node places all patients in MDA who have a tender joint count of 0 and a swollen joint count of 0, and an erythrocyte sedimentation rate (ESR) no greater than 10 mm. If this condition is not met: center dot The DAS28 definition places patients in MDA when DAS28

Segmented polyurethane nanocomposites: Impact of controlled particle size nanofillers on the morphological response to uniaxial deformation

A series of TPU nanocomposites were prepared by incorporating organically modified layered silicates with controlled particle size. To our knowledge, this is the first study into the effects of layered silicate diameter in polymer nanocomposites utilizing the same mineral for each size fraction. The tensile properties of these materials were found to be highly dependent upon the size of the layered silicates. A decrease in disk diameter was associated with a sharp upturn in the stress-strain curve and a pronounced increase in tensile strength. Results from SAXS/SANS experiments showed that the layered silicates did not affect the bulk TPU microphase structure and the morphological response of the host TPU to deformation or promote/hinder strain-induced soft segment crystallization. The improved tensile properties of the nanocomposites containing the smaller nanofillers resulted from the layered silicates aligning in the direction of strain and interacting with the TPU sequences via secondary bonding. This phenomenon contributes predominantly above 400% strain once the microdomain architecture has largely been disassembled. Large tactoids that are unable to align in the strain direction lead to concentrated tensile stresses between the polymer and filler, instead of desirable shear stresses, resulting in void formation and reduced tensile properties. In severe cases, such as that observed for the composite containing the largest silicate, these voids manifest visually as stress whitening.

Contact angle effects on microdroplet deformation using CFD

In this paper we use computational fluid dynamics (CFD) to study the effect of contact angle on droplet shape as it moves through a contraction. A new non-dimensional number is proposed in order to predict situations where the deformed droplet will form a slug in the contraction and thus have the opportunity to interact with the channel wall. It is proposed that droplet flow into a contraction is a useful method to ensure that a droplet will wet a channel surface without a trapped lubrication film, and thus help ensure that a slug will remain attached to the wall downstream of the contraction. We demonstrate that when a droplet is larger than a contraction, capillary and Reynolds numbers, and fluid properties may not be sufficient to fully describe the droplet dynamics through a contraction. We show that, with everything else constant, droplet shape and breakup can be controlled simply by changing the wetting properties of the channel wall. CFD simulations with contact angles ranging from 30 degrees to 150 degrees show that lower contact angles can induce droplet breakup while higher contact angles can form slugs with contact angle dependent shape. Crown Copyright (c) 2005 Published by Elsevier Inc. All rights reserved.

A parametric study of droplet deformation through a microfluidic contraction: Low viscosity Newtonian droplets

Numerical simulations are conducted to investigate how a droplet of Newtonian liquid. entrained in a higher viscosity Newtonian liquid, behaves when passing through an axisymmetric microfluidic contraction. Simulations are performed using a transient Volume of Fluid finite volume algorithm, and cover ranges of Reynolds and Weber numbers relevant to microfluidic flows. Results are presented for a droplet to surrounding fluid viscosity ratio of 0.001. In contrast to behaviour at higher viscosity ratios obtained previously by the authors, shear and interfacial tension driven instabilities often develop along the droplet Surface. leading to complex shape development, and in some instances, droplet breakup. (c) 2006 Elsevier Ltd. All rights reserved.

Effect of adsorption deformation on thermodynamic characteristics of a fluid in slit pores at sub-critical conditions

Solvation. pressure due to adsorption of fluids in porous materials is the cause of elastic deformation of an adsorbent, which is accessible to direct experimental measurements. Such a deformation contributes to the Helmholtz free energy of the whole adsorbent-adsorbate system due to accumulation of compression or tension energy by the solid. It means that in the general case the solid has to be considered as not solely a source of the external potential field for the fluid confined in the pore volume, but also as thermodynamically nonmert component of the solid-fluid system. We present analysis of nitrogen adsorption isotherms and heat of adsorption in slit graphitic pores accounting for the adsorption deformation by means of nonlocal density functional theory. (c) 2006 Elsevier Ltd. All rights reserved.

Optimal preventive maintenance of leased equipment with corrective minimal repairs

For leased equipment, the lessor carries out the maintenance of the equipment. Usually, the contract of lease specifies the penalty for equipment failures and for repairs not being carried out within specified time limits. This implies that optimal preventive maintenance policies must take these penalty costs into account and properly traded against the cost of preventive maintenance actions. The costs associated with failures are high as unplanned corrective maintenance actions are costly and the resulting penalties due to lease contract terms being violated. The paper develops a model to determine the optimal parameters of a preventive maintenance policy that takes into account all these costs to minimize the total expected cost to the lessor for new item lease. The parameters of the policy are (i) the number of preventive maintenance actions to be carried out over the lease period, (ii) the time instants for such actions, and (iii) the level of action. (c) 2005 Elsevier B.V. All rights reserved.