Stability of Biaxial Nematic Phase for Systems with Variable Molecular Shape Anisotropy

We study the influence of fluctuations in molecular shape on the stability of the biaxial nematic phase by generalizing the mean field model of Mulder and Ruijgrok [Physica A {\bf 113}, 145 (1982)]. We limit ourselves to the case when the molecular shape anisotropy, represented by the alignment tensor, is a random variable of an annealed type. A prototype of such behavior can be found in lyotropic systems - a mixture of potassium laurate, 1-decanol, and $D_2O$, where distribution of the micellar shape adjusts to actual equilibrium conditions. Further examples of materials with the biaxial nematic phase, where molecular shape is subject to fluctuations, are thermotropic materials composed of flexible trimeric- or tetrapod-like molecular units. Our calculations show that the Gaussian equilibrium distribution of the variables describing molecular shape (dispersion force) anisotropy gives rise to new classes of the phase diagrams, absent in the original model. Depending on properties of the shape fluctuations, the stability of the biaxial nematic phase can be either enhanced or depressed, relative to the uniaxial nematic phases. In the former case the splitting of the Landau point into two triple points with a direct phase transition line from isotropic to biaxial phase is observed.Comment: 18 pages containing 6 figure

A Discussion on Life Systems Security and the Systems Approach

The relationship between information technology and information security historically has been quite reactive. New innovations in information technology have often been accompanied by new security threats that create challenges to its reliability and overall integrity. In this paper, a historical perspective that outlines the evolution in the development of the security function is used as a starting base. Changes in the way security issues are viewed and how this view affects the design and development of secure systems are then postulated. It is proposed that these changes should be incorporated into the security functions of any waterfall development model, and especially during the initial and terminating stages

Asymptotics of large eigenvalues for a class of band matrices

We investigate the asymptotic behaviour of large eigenvalues for a class of finite difference self-adjoint operators with compact resolvent in $l^2$

Understanding the experiences of positive life changes during postgraduate study on a Masters in Applied Positive Psychology programme: An Interpretative Phenomenological Analysis

There is a global increase in the teaching of positive psychology at postgraduate level. Anecdotally, it has been suggested that university-based positive psychology programmes can be “life changing”. This exploratory qualitative study aimed to enhance our understanding of the positive life experiences of students registered on a Masters in Applied Positive Psychology (MAPP) programme. The researcher interviewed five postgraduate students undertaking a MAPP at the University of East London. Interpretative phenomenological analysis was used to identify emerging themes before these were analysed and clustered into a number of overarching themes. Participants reported experiencing a number of positive life changes as a result of the MAPP programme. Key themes that emerged were the sense that there were “myriad different thoughts and potential opportunities”; that studying positive psychology was “like coming home”; that participants enjoyed having time for reflection; and the sense that “it’s all about the people”.  This study raised the question of whether the MAPP programme could, in itself, be considered a positive psychological intervention.

Artificial Neural Network-Based Gain-Scheduled State Feedback Speed Controller for Synchronous Reluctance Motor

This paper focuses on designing a gain-scheduled (G-S) state feedback controller (SFC) for synchronous reluctance motor (SynRM) speed control with non-linear inductance characteristics. The augmented model of the drive with additional state variables is introduced to assure precise control of selected state variables (i.e. angular speed and d-axis current). Optimal, non-constant coefficients of the controller are calculated using a linear-quadratic optimisation method. Non-constant coefficients are approximated using an artificial neural network (ANN) to assure superior accuracy and relatively low usage of resources during implementation. To the best of our knowledge, this is the first time when ANN-based gain-scheduled state feedback controller (G-S SFC) is applied for speed control of SynRM. Based on numerous simulation tests, including a comparison with a signum-based SFC, it is shown that the proposed solution assures good dynamical behaviour of SynRM drive and robustness against q-axis inductance, the moment of inertia and viscous friction fluctuations

Isolation and characterization of a putative collagen receptor from Staphylococcus aureus strain Cowan 1.

In a previous study we demonstrated that cells of Staphylococcus aureus strain Cowan bind 125I-collagen in a receptor-ligand type of interaction (Speziale, P., Raucci, G., Visai, L., Switalski, L.M., Timpl, R., and Hook, M. (1986) J. Bacteriol. 167, 77-81). In the present communication we report on the isolation and preliminary characterization of a putative collagen receptor from a lysate of S. aureus strain Cowan. Antibodies raised against a collagen receptor positive strain inhibit the binding of 125I-collagen to bacterial cells, whereas antibodies raised against a collagen receptor negative strain were without effect. Solubilized cell surface components did not exhibit any measurable affinity for collagen-Sepharose. However, the inhibitory effect of the antibodies against bacterial cells was neutralized by the lysate from a receptor-positive but not receptor-negative strain. A collagen receptor assay was designed based on this observation and used to develop a receptor purification protocol involving anion exchange chromatography, ammonium sulfate precipitation, and gel chromatography. Using this procedure a protein with an apparent Mr of 135,000 was purified. This protein which was present on a collagen receptor-positive strain but not on a receptor-negative strain could completely neutralize the inhibitory activity of the antibodies raised against S. aureus strain Cowan. Furthermore, antibodies raised against the 135-kDa protein inhibited the binding of collagen to bacteria, and this protein is tentatively identified as a collagen receptor

Short-Term Creep Tests on Phenol-Resorcinol-Formaldehyde (PRF) Resin Undergoing Moisture Content Changes

The objective of the study was to develop an experimental technique that would allow determination of the hygro-mechanical properties of thin uniform resin films undergoing moisture content changes; and to use the technique for assessment of the hygro-mechanical performance of phenol-resorcinol-formaldehyde (PRF) resin.Creep tests on 6 small specimens of PRF film under constant stress (50% of the short-term ultimate stress level), at room temperature (23°C ± 2°C) and controlled relative humidity (RH) conditions (drying or wetting) were carried out. Digital images of the specimens were acquired using a CCD camera at discrete time intervals during the experiments. Displacements were then measured by comparing successive images using digital image correlation principles. Separation of strain components from total strain recorded during the creep tests was carried out by using data from two reference tests performed on the same material: 1) free deformations of unloaded specimens during drying or wetting conditions, and 2) creep under equilibrium conditions.The experimental method developed for the study provided a tool to determine hygro-mechanical properties of thin resin films. Quantitative data on material properties of hygroscopic resins determined by means of the technique may be used for modeling the behavior of adhesive bonds as well as adhesive bonded materials in varying climate conditions. The PRF resin revealed a distinct mechano-sorptive behavior, though it seems to be less significant than that reported for wood in transverse directions

Hygro-Mechanical Behavior of Red Spruce in Tension Parallel to the Grain

The principal objective of the project was to provide a reliable testing protocol for determination of the material-level (e.g. local and decoupled from the artifacts of the test protocol) mechano-sorptive properties of wood in the longitudinal direction that could be used for modeling of the long-term structural response of wood and wood composite elements. The method also involves determination of the hygro-mechanical characteristics of free shrinkage and swelling and short-term viscoelastic characteristics from reference tests performed on matched specimens. Tensile creep tests in the longitudinal direction at varying climate conditions were performed on small (1-mm x 25-mm x 300-mm) clear specimens of red spruce (Picea rubra). All tests were conducted in a temperature-controlled environment. Optical deformation measurement techniques were used. Strains were calculated by comparing successive digital images using Digital Image Correlation (DIC) principles. The mechano-sorptive component of total strains measured on the loaded specimens was separated by: 1) subtracting free shrinkage/swelling measured on matched reference specimens; and 2) subtraction of the magnitude of viscoelastic creep measured separately on matched specimens at constant MC (in 'dry' and 'wet' conditions). The results confirmed earlier findings reported in the literature by other researchers that the effect of cumulative moisture content change on mechano-sorptive compliance is not linear. However, no fundamentally different governing mechanisms during the first and consecutive moisture cycles were observed. The effects of applied stress level and initial moisture content on the mechano-sorptive response of wood in tension were found insignificant at the 95% confidence level. The experimentally determined mechano-sorptive compliances were expressed in terms of generalized rheological model equations with cumulative moisture content change (rather than time) as the independent variable. Based on these findings, a minimal testing protocol was proposed for routine determination of hygro-mechanical characteristics for other structurally important species

A reliability study of the new back strain monitor based on clinical trials

A new Back Strain Monitor (BSM) device has been developed in order to measure, record and analyze movements of the lower back. The purpose of this study was to examine the inter-tester and the intra-tester reliability of the movement measurements given by the BSM accelerometers, and compare it with the reliability of two other conventional measurement methods: the Double Inclinometer method (DI) and the Modified-Modified Schober (MMS) method. The clinical studies included 23 participants (16 males, 7 females) with no recent history of lower back pain, who wore the device during a combination of different anatomical movements (flexion, extension, left lateral flexion and right lateral flexion of the lumber spine). The tests were conducted by three therapists (testers). The reliability results for the BSM accelerometers clearly outperform the results obtained for the DI and the MMS methods. The inter-tester reliability gives the Intra-Class Correlation (ICC) value of 0.95 for the BSM flexion, 0.89 for the DI flexion and 0.74 for the MMS. The intra-tester reliability gives the ICC value of 0.99 for BSM flexion, 0.94 for DI flexion and 0.77 for the MMS. The BSM accelerometers were highly reliable in assessing back movements, measuring these movements with less error than the DI and MMS methods