Symmetry of coherent vortices in plane couette flow

A numerical continuation method is carried out in a homotopy space connecting two different flows, the Plane Couette Flow (PCF) and the Laterally Heated Flow in a vertical slot (LHF). This numerical continuation method enables us to obtain an exact steady solution in PCF. The new solution has the shape of hairpin vortices (HVS: hairpin vortex solution), which is observed ubiquitously in turbulent shear flows.

Finite-size effects in on-line learning of multilayer neural networks

We complement recent advances in thermodynamic limit analyses of mean on-line gradient descent learning dynamics in multi-layer networks by calculating fluctuations possessed by finite dimensional systems. Fluctuations from the mean dynamics are largest at the onset of specialisation as student hidden unit weight vectors begin to imitate specific teacher vectors, increasing with the degree of symmetry of the initial conditions. In light of this, we include a term to stimulate asymmetry in the learning process, which typically also leads to a significant decrease in training time.

Lobe growth variation and the maintenance of symmetry in foliose lichen thalli

The aim of this study was to determine how thallus symmetry could be maintained in foliose lichens when variation in the growth of individual lobes may be high. Hence, the radial growth of a sample of lobes was studied monthly, over 22 months, in 7 thalli of Parmelia conspersa (Ehrh. Ex Ach.) Ach. And 5 thalli of P. glabratula ssp fuliginosa (fr. ex Duby) Laund. The degree of variation in the total radial growth of different lobes within a thallus over 22 months varied between thalli. Individual lobes showed a fluctuating pattern of radial growth from month to month with alternating periods of fast and slow growth. Monthly variations in radial growth of different lobes were synchronized in some but not in all thalli. Few significant correlations were found between the radial growth of individual lobes and total monthly rainfall or shortwave radiation. The levels of ribitol, arabitol and mannitol were measured in individual lobes. All three polyols varied significantly between lobes within a thallus suggesting that variations in algal phostosynthesis and in the partitioning of fungal polyols may contribute to lobe growth variation. The effect on thallus symmetry of lobes which grew radially either consistently faster or slower than average was studied. Slow growing lobes were overgrown, and gaps in the perimeter were eliminated by the growth of neighbouring lobes, in approximately 7 to 9 months. However, a rapidly growing lobe, with its neighbours removed on either side, continued to grow radially at the same rate as rapidly growing control lobes. The results suggested that lobe growth variation results from a combination of factors which may include the origin of the lobes, lobe morphology and the patterns of algal cell division and hyphal elongation in different lobes. No convincing evidence was found to suggest that exchange of carbohydrate occurred between lobes which would tend to equalize their radial growth. Hence, the fluctuating pattern of lobe growth observed may be sufficient to maintain a degree of symmetry in most thalli. In addition, slow growing lobes would tend to be overgrown by faster growing neighbours thus preventing the formation of indentations in the thallus perimeter.

The impact of Foreign Direct Investment and trade openness on ICT expansion: A comparative analysis of Asia-Pacific and Middle Eastern countries

This study investigates the impact of foreign direct investment (FDI) inflow and trade openness on the expansion of information and communication technologies (ICTs) for the period of 1996 to 2005, in the Asia-Pacific and Middle East regions. The results of regression analyses conducted indicate that while dissimilarities exist among the countries included in this study in terms of their level of socio-economic and political development, factors such as trade openness, education and the growth of GDP had a positive impact on their ICT development. While FDI inflow had positive impact on the expansion of ICTs on Asia-Pacific countries its impact on Middle Eastern countries was not statistically significant. The study results also show that governmental intervention in economic activities has a negative impact on ICT expansion in both regions. In the Middle East, regional conflict imposes additional negative impact on FDI inflow and trade openness and consequently, ICT expansion. The regression results show that those countries that implemented liberalization of their ICT sector were able to not only reduce the digital divide with other developed countries, but also increase their operations in both local and global markets.

Thermodynamics of binding of regulatory ligands to tissue transglutaminase

The transamidating activity of tissue transglutaminase is regulated by the ligands calcium and GTP, via conformational changes which facilitate or interfere with interaction with the peptidyl-glutamine substrate. We have analysed binding of these ligands by calorimetric and computational approaches. In the case of GTP we have detected a single high affinity site (K (D) approximately 1 muM), with moderate thermal effects suggestive that binding GTP involves replacement of GDP, normally bound to the protein. On line with this possibility no significant binding was observed during titration with GDP and computational studies support this view. Titration with calcium at a high cation molar excess yielded a complex binding isotherm with a number of "apparent binding sites" in large excess over those detectable by equilibrium dialysis (6 sites). This binding pattern is ascribed to occurrence of additional thermal contributions, beyond those of binding, due to the occurrence of conformational changes and to catalysis itself (with protein self-crosslinking). In contrast only one site for binding calcium with high affinity (K (D) approximately 0.15 muM) is observed with samples of enzyme inactivated by alkylation at the active site (to prevent enzyme crosslinkage and thermal effects of catalysis). These results indicate an intrinsic ability of tissue transglutaminase to bind calcium with high affinity and the necessity of careful reassessment of the enzyme regulatory pattern in relation to the concentrations of ligands in living cells, taking also in account effects of ligands on protein subcellular compartimentation.

Numerical and statistical analysis of long-haul undersea optical communication systems

Firstly, we numerically model a practical 20 Gb/s undersea configuration employing the Return-to-Zero Differential Phase Shift Keying data format. The modelling is completed using the Split-Step Fourier Method to solve the Generalised Nonlinear Schrdinger Equation. We optimise the dispersion map and per-channel launch power of these channels and investigate how the choice of pre/post compensation can influence the performance. After obtaining these optimal configurations, we investigate the Bit Error Rate estimation of these systems and we see that estimation based on Gaussian electrical current systems is appropriate for systems of this type, indicating quasi-linear behaviour. The introduction of narrower pulses due to the deployment of quasi-linear transmission decreases the tolerance to chromatic dispersion and intra-channel nonlinearity. We used tools from Mathematical Statistics to study the behaviour of these channels in order to develop new methods to estimate Bit Error Rate. In the final section, we consider the estimation of Eye Closure Penalty, a popular measure of signal distortion. Using a numerical example and assuming the symmetry of eye closure, we see that we can simply estimate Eye Closure Penalty using Gaussian statistics. We also see that the statistics of the logical ones dominates the statistics of the logical ones dominates the statistics of signal distortion in the case of Return-to-Zero On-Off Keying configurations.

Femtosecond laser inscribed Bragg sensor in Terfenol-D coated optical fibre with ablated microslot for the detection of static magnetic fields

A novel device for the detection and characterisation of static magnetic fields is presented. It consists of a femtosecond laser inscribed fibre Bragg grating (FBG) that is incorporated into an optical fibre with a femtosecond laser micromachined slot. The symmetry of the fibre is broken by the micro-slot, producing non-uniform strain across the fibre cross section. The sensing region is coated with Terfenol-D making the device sensitive to static magnetic fields, whereas the symmetry breaking results in a vectorial sensor for the detection of magnetic fields as low as 0.046 mT with a resolution of ±0.3mT in transmission and ±0.7mT in reflection. The sensor output is directly wavelength encoded from the FBG filtering, leading to simple demodulation through the monitoring of wavelength shifts that result as the fibre structure changes shape in response to the external magnetic field. The use of a femtosecond laser to both inscribe the FBG and micro-machine the slot in a single stage, prior to coating the device, significantly simplifies the sensor fabrication.

Femtosecond laser inscribed Bragg sensor in Terfenol-D coated optical fibre with ablated microslot for the detection of static magnetic fields

A novel device for the detection and characterisation of static magnetic fields is presented. It consists of a femtosecond laser inscribed fibre Bragg grating (FBG) that is incorporated into an optical fibre with a femtosecond laser micromachined slot. The symmetry of the fibre is broken by the micro-slot, producing non-uniform strain across the fibre cross section. The sensing region is coated with Terfenol-D making the device sensitive to static magnetic fields, whereas the symmetry breaking results in a vectorial sensor for the detection of magnetic fields as low as 0.046 mT with a resolution of ±0.3mT in transmission and ±0.7mT in reflection. The sensor output is directly wavelength encoded from the FBG filtering, leading to simple demodulation through the monitoring of wavelength shifts that result as the fibre structure changes shape in response to the external magnetic field. The use of a femtosecond laser to both inscribe the FBG and micro-machine the slot in a single stage, prior to coating the device, significantly simplifies the sensor fabrication.

Observed and predicted hydrogen bond motifs in crystal structures of hydantoins, dihydrouracils and uracils

A survey of crystal structures containing hydantoin, dihydrouracil and uracil derivatives in the Cambridge Structural Database revealed four main types of hydrogen bond motifs when derivatives with extra substituents able to interfere with the main motif are excluded. All these molecules contain two hydrogen bond donors and two hydrogen bond acceptors in the sequence of NH, C = O, NH, and C=O groups within a 5-membered ring (hydantoin) and two 6-membered rings (dihydrouracil and uracil). In all cases, both ring NH groups act as donors in the main hydrogen bond motif but there is an excess of hydrogen bond acceptors (two C=O able to accept twice each) and so two possibilities are found: (i) each carbonyl O atom may accept one hydrogen bond or (ii) one carbonyl O atom may accept two hydrogen bonds while the other does not participate in the hydrogen bonding. We observed different preferences in the type and symmetry of the motifs adopted by the different derivatives, and a good agreement is found between motifs observed experimentally and those predicted using computational methods. We identified certain molecular factors such as chirality, substituent size and the possibility of C-H⋯O interactions as important factors influencing the motif observation. © 2012 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Lobe growth in foliose lichen thalli

The margins of foliose lichen thalli comprise individual lobes which grow radially and divide. This results in a complex marginal structure in which lobes differing in morphology, state of division, and growth pattern are crowded together. Various aspects of the biology of these lobes are reviewed including their carbohydrate supply, morphology, pattern of division and branching, the effect of lobe overcrowding and interactions between neighbouring lobes. As the thalus grows, lobes become increasingly crowded together and this restricts further lateral growth. Restriction of lobe width may be reponsible for the changes in radial growth rate (RGR) with size observed in foliose species. Various aspects of lobe biology may be responsible for lobe growth variation including the physical independence of lobes from their neighbours, the genetic origin of the lobes, and the pattern of lobe branching. Overall symmetry of a thallus is maintained by a fluctuating pattern of growth of individual lobes in successive months together with competition for space at the margin

Inference by replication in densely connected systems

An efficient Bayesian inference method for problems that can be mapped onto dense graphs is presented. The approach is based on message passing where messages are averaged over a large number of replicated variable systems exposed to the same evidential nodes. An assumption about the symmetry of the solutions is required for carrying out the averages; here we extend the previous derivation based on a replica-symmetric- (RS)-like structure to include a more complex one-step replica-symmetry-breaking-like (1RSB-like) ansatz. To demonstrate the potential of the approach it is employed for studying critical properties of the Ising linear perceptron and for multiuser detection in code division multiple access (CDMA) under different noise models. Results obtained under the RS assumption in the noncritical regime give rise to a highly efficient signal detection algorithm in the context of CDMA; while in the critical regime one observes a first-order transition line that ends in a continuous phase transition point. Finite size effects are also observed. While the 1RSB ansatz is not required for the original problems, it was applied to the CDMA signal detection problem with a more complex noise model that exhibits RSB behavior, resulting in an improvement in performance. © 2007 The American Physical Society.

Do foreign direct investment (FDI) and trade openness explain the disparity in ICT diffusion between Asia-Pacific and the Islamic Middle Eastern countries?

This study investigates the impact of FDI and trade openness on ICT diffusion in the Asia-Pacific and Middle East regions from 1996-2005. The results indicate that while dissimilarities exist between the economies included in this study in terms of their level of socio-economic and political development, education and the growth of GDP have had a positive impact on ICT diffusion in both regions. However, while FDI has generally had a positive and significant impact on ICT diffusion in Asia-Pacific economies, its impact on Middle Eastern economies has been detrimental. The results of this study also show that trade-openness has had, in general, a positive and significant impact on ICT diffusion. Copyright © 2010, IGI Global.

Visual field severity indices demonstrate dose-dependent visual loss from Vigabatrin therapy

Purpose: The aims of this study were to develop an algorithm to accurately quantify Vigabatrin (VGB)-induced central visual field loss and to investigate the relationship between visual field loss and maximum daily dose, cumulative dose and duration of dose. Methods: The sample comprised 31 patients (mean age 37.9 years; SD 14.4 years) diagnosed with epilepsy and exposed to VGB. Each participant underwent standard automated static visual field examination of the central visual field. Central visual field loss was determined using continuous scales quantifying severity in terms of area and depth of defect and additionally by symmetry of defect between the two eyes. A simultaneous multiple regression model was used to explore the relationship between these visual field parameters and the drug predictor variables. Results: The regression model indicated that maximum VGB dose was the only factor to be significantly correlated with individual eye severity (right eye: p = 0.020; left eye: p = 0.012) and symmetry of visual field defect (p = 0.024). Conclusions: Maximum daily dose was the single most reliable indicator of those patients likely to exhibit visual field defects due to VGB. These findings suggest that high maximum dose is more likely to result in visual field defects than high cumulative doses or those of long duration.

Furnace chemical vapor deposition (FCVD) method for special optical fibers fabrication

The features of the Furnace Chemical Vapor Deposition (FCVD) method of manufacturing preforms for special optical fibers are considered. It is shown that misalignment of substrate silica tube and furnace hole axes has a negative effect on the quality of fabricated preforms, leading to angular and radial asymmetry of the refractive index profile. Ways of getting rid of this and other disadvantages of the FCVD method are described. Some advantages of the FCVD method over the MCVD method are shown. It was demonstrated that the FCVD method, despite some drawbacks, allows to manufacture high-quality fiber preforms with good symmetry of the refractive index profile, and thus it is promising for fabrication of dispersion, dispersion varying and active fibers. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Understanding and improving the manufacturing and changeover process in Saudi Arabian business - a multiple case study approach

The importance of the changeover process in the manufacturing industry is becoming widely recognised. Changeover is a complete process of changing between the manufacture of one product to manufacture of an alternative product until specified production and quality rates are reached. The initiatives to improve changeover exist in industry, as better changeover process typically contribute to improved quality performance. A high-quality and reliable changeover process can be achieved through implementation of continuous or radical improvements. This research examines the changeover process of Saudi Arabian manufacturing firms because Saudi Arabia’s government is focused on the expansion of GDP and increasing the number of export manufacturing firms. Furthermore, it is encouraging foreign manufacturing firms to invest within Saudi Arabia. These initiatives, therefore, require that Saudi manufacturing businesses develop the changeover practice in order to compete in the market and achieve the government’s objectives. Therefore, the aim of this research is to discover the current status of changeover process implementation in Saudi Arabian manufacturing businesses. To achieve this aim, the main objective of this research is to develop a conceptual model to understand and examine the effectiveness of the changeover process within Saudi Arabian manufacturing firms, facilitating identification of those activities that affect the reliability and high-quality of the process. In order to provide a comprehensive understanding of this area, this research first explores the concept of quality management and its relationship to firm performance and the performance of manufacturing changeover. An extensive body of literature was reviewed on the subject of lean manufacturing and changeover practice. A research conceptual model was identified based on this review, and focus was on providing high-quality and reliable manufacturing changeover processes during set-up in a dynamic environment. Exploratory research was conducted in sample Saudi manufacturing firms to understand the features of the changeover process within the manufacturing sector, and as a basis for modifying the proposed conceptual model. Qualitative research was employed in the study with semi-structured interviews, direct observations and documentation in order to understand the real situation such as actual daily practice and current status of changeover process in the field. The research instrument, the Changeover Effectiveness Assessment Tool (CEAT) was developed to evaluate changeover practices. A pilot study was conducted by examining the CEAT, proposed for the main research. Consequently, the conceptual model was modified and CEAT was improved in response to the pilot study findings. Case studies have been conducted within eight Saudi manufacturing businesses. These case studies assessed the implementation of manufacturing changeover practice in the lighting and medical products sectors. These two sectors were selected based on their operation strategy which was batch production as well as the fact that they fulfilled the research sampling strategy. The outcomes of the research improved the conceptual model, ultimately to facilitate the firms’ adoption and rapid implementation of a high-quality and reliability changeover during the set-up process. The main finding of this research is that Quality’s factors were considering the lowest levels comparing to the other factors which are People, Process and Infrastructure. This research contributes to enable Saudi businesses to implement the changeover process by adopting the conceptual model. In addition, the guidelines for facilitating implementation were provided in this thesis. Therefore, this research provides insight to enable the Saudi manufacturing industry to be more responsive to rapidly changing customer demands.