Different mechanisms of nucleation and self-organization of droplets in ferroelectric smectic membranes

New mechanisms of droplet nucleation and self-organization in ferroelectric membranes are described. The droplets may be accompanied by different number of topological defects (zero, one, two) whose location may be on the droplet boundary or in the membrane. Nucleation and self-organization of droplets with total topological charge S = 0 , S = + 1 and S = - 1 were investigated. We found that an S = - 1 topological defect may be the center of both droplet nucleation and chain formation. This mechanism of chaining drastically differs from the droplet self-organization described earlier which is realized by attraction of droplet-defect pairs. Our observations demonstrate new possibilities for manipulating the inclusions and their self-organization in smectic membranes.

Polarization studies of resonant forbidden reflections in liquid crystals

We report the results of resonant x-ray diffraction experiments performed on thick films of a biaxial liquid crystal made of achiral bent-core molecules. Polarization properties of forbidden reflections are observed as a function of the sample rotation angle phi about the scattering vector Q for the first time on a fluid material. The experimental data are successfully analyzed within a tensor structure factor model by taking the nonperfect alignment of the liquid crystal into account. The local structure of the B2 mesophase is hence determined to be SmC_{S}P_{A}.

Classification of EEG signals using a genetic-based machine learning classifier

This paper investigates the efficacy of the genetic-based learning classifier system XCS, for the classification of noisy, artefact-inclusive human electroencephalogram (EEG) signals represented using large condition strings (108bits). EEG signals from three participants were recorded while they performed four mental tasks designed to elicit hemispheric responses. Autoregressive (AR) models and Fast Fourier Transform (FFT) methods were used to form feature vectors with which mental tasks can be discriminated. XCS achieved a maximum classification accuracy of 99.3% and a best average of 88.9%. The relative classification performance of XCS was then compared against four non-evolutionary classifier systems originating from different learning techniques. The experimental results will be used as part of our larger research effort investigating the feasibility of using EEG signals as an interface to allow paralysed persons to control a powered wheelchair or other devices.

Unique pitch evolution in the smectic-C+alpha phase

Employing resonant x-ray diffraction, we observed unique pitch evolutions in the smectic-C*(alpha) phase in mixtures of two antiferroelectric liquid crystals. Our results show that the pitch in this phase continuously evolves across 4 layers, contradicting a theoretical model that predicts that the smectic-C*(FI2) phase intervenes in the smectic-C*(alpha) phase. The phase sequences we found can be explained by another model that includes one type of long-range interaction among smectic layers.

Electro-optical and dielectric characterizations of the Goldstone mode relaxation in ferroelectric chiral smectic C liquid crystals

We report structural (helical pitch), electro-optical (tilt angle and spontaneous polarization) and dielectric (Goldstone mode) investigations of ferroelectric liquid crystals (FLCs) exhibiting the chiral smectic C phase (SmC(*)). All these characterizations were performed on two pure FLCs showing the SmC(*)-SmA-N(*) phase sequence and having small pitch, high spontaneous polarization and a large relaxation frequency. We have determined the Goldstone rotational viscosity and the twist elastic constant in the SmC(*) phase from the helical pitch, tilt angle, polarization, dielectric strength experimental data and from the relaxation frequency of the Goldstone-mode relaxation. An Arrhenius-type behaviour of the Goldstone rotational viscosity was obtained and the corresponding activation energies were evaluated.

Field-temperature phase diagrams in chiral tilted smectics, evidencing ferroelectric and ferrielectric phases

Usual ferroelectric compounds undergo a paraelectric-to-ferroelectric phase transition when the susceptibility of the electric polarization density changes its sign. The temperature is the only thermodynamic field that governs the phase transition. Chiral tilted smectics may also present an improper ferroelectricity when there is a tilt angle between the average long axis direction and the layer normal. The tilt angle is the order parameter of the phase transition which is governed by the temperature. Although the electric susceptibility remains positive, a polarization proportional to the tilt appears due to their linear coupling allowed by the chiral symmetry. Further complications come in when the chirality increases, as new phases are encountered with the same tilt inside the layers but a distribution of the azimuthal direction which is periodic with a unit cell of two (SmC(A)*, three (SmC(Fi1)*, four (SmC(Fi2)* or more (SmC(alpha)* layers. In most of these phases, the layer normal is a symmetry axis so there is no macroscopic polarization except for the SmC(Fi1)* in which the average long axis is tilted so the phase is ferrielectric. By studying a particular compound with only a SmC(Fi2)* and a SmC(alpha)* phase, we show that we recover the uniformly tilted ferroelectric SmC* when applying an electric field. We are thus led to build field-temperature phase diagrams for this class of compounds by combining different experimental techniques described here.

Guided self-assembly of integrated hollow Bragg waveguides

We describe the fabrication of integrated hollow waveguides through guided self-assembly of straight-sided, thin film delamination buckles within a multilayer system of chalcogenide glass and polymer. The process is based on silver photodoping, which was used to control both the stress and adhesion of the chalcogenide glass films. Straight, curved, crossing, and tapered microchannels were realized in parallel. The channels are cladded by omnidirectional dielectric reflectors designed for low-loss, air-core guiding of light in the 1550-1700 nm wavelength range. Loss as low as ~15 dB/cm was measured for channels of height ~2.5 mum, in good agreement with both an analytical ray optics model and finite difference numerical simulations. The loss is determined mainly by the reflectivity of the cladding mirrors, which is ~0.995 for the as-fabricated devices.

Rearrangement of topological defects and anchoring on the inclusion boundary in ferroelectric smectic membranes

We report experiments on a ferroelectric membrane and droplets with tunable surface properties. In smectic membranes the configuration of the c -director field near inclusions may be rearranged drastically with temperature. The transformation of the c -director field results from the competition between the elastic and polar properties of the membranes. We demonstrate that anchoring conditions on the inclusion boundary are not fixed but depend on the temperature. A dipolar c -director configuration near droplets can evolve to a mixed configuration and to a quadrupolar one. These modifications of the c -director field near the inclusions lead to a change of the interaction between the inclusions, their self-organization, and even to the destruction of structures already formed by the inclusions. Our observations open new possibilities for manipulating inclusions and controlling their self-organization.

Wireless real-time head movement system using a personal digital assistant (PDA) for control of a power wheelchair

Loss of mobility can occur for a variety of reasons, such as spinal cord injury or motor neurone disease. The onset of these conditions often brings with it an associated loss of personal independence, which is primarily due to the fact that the sufferer is no longer able to control their mobility. This project aims to address this problem through the creation of a head movement based wheelchair control system. Using a personal digital assistant (PDA) artificial intelligence techniques on an embedded LINUX operating system, a wireless head movement wheelchair control system has been designed and implemented. This system provides relief for sufferers of conditions which inhibit mobility through a method of wheelchair control which offers enhanced ease of use, attractiveness and independence.

Real-time head movement system and embedded Linux implementation for the control of power wheelchairs

Mobility has become very important for our quality of life. A loss of mobility due to an injury is usually accompanied by a loss of self-confidence. For many individuals, independent mobility is an important aspect of self-esteem. Head movement is a natural form of pointing and can be used to directly replace the joystick whilst still allowing for similar control. Through the use of embedded LINUX and artificial intelligence, a hands-free head movement wheelchair controller has been designed and implemented successfully. This system provides for severely disabled users an effective power wheelchair control method with improved posture, ease of use and attractiveness.

Mammogram object detection using dendronic image analysis

Breast cancer can be treated with better patient outcomes and significantly lower costs if detected early. Using the spatial dendronic structure, image masks can be obtained, showing regions in the mammogram image corresponding to the breast and lead marker. The technique is robust to noise and placement of the breast within the image. The technique not only reduces the size of the region to be analysed, but also provides the dendronic structure of the breast in which stealth-like masses can be found more easily.

Comparing regional transcript profiles from maize primary roots under well-watered and low water potential conditions

Regionally distinct elongation responses to water stress in the maize primary root tip have been observed in the past. A genetic basis for such differential responses has been demonstrated. Normalized bar-coded cDNA libraries were generated for four regions of the root tip, 0-3 mm (R1), 3-7 mm (R2), 7-12 mm (R3), and 12-20 mm (R4) from the root apex, and transcript profiles for these regions were sampled. This permitted a correlation between transcript nature and regional location for 15 726 expressed sequence tags (ESTs) that, in approximately equal numbers, derived from three conditions of the root: water stress (water potential: -1.6 MPa) for 5 h and for 48 h, respectively, and well watered (5 h and 48 h combined). These normalized cDNA libraries provided 6553 unigenes. An analysis of the regional representation of transcripts showed that populations were largely unaffected by water stress in R1, correlating with the maintenance of elongation rates under water stress known for R1. In contrast, transcript profiles in regions 2 and 3 diverged in well-watered and water-stressed roots. In R1, transcripts for translation and cell cycle control were prevalent. R2 was characterized by transcripts for cell wall biogenesis and cytoskeleton formation. R3 and R4 shared prevalent groups of transcripts responsible for defence mechanisms, ion transport, and biogenesis of secondary metabolites. Transcripts which were followed for 1, 6, and 48 h of water stress showed distinct region-specific changes in absolute expression and changes in regulated functions.

Use of a large-scale Triticeae expressed sequence tag resource to reveal gene expression profiles in hexaploid wheat (Triticum aestivum L.)

The US Wheat Genome Project, funded by the National Science Foundation, developed the first large public Triticeae expressed sequence tag (EST) resource. Altogether, 116,272 ESTs were produced, comprising 100,674 5' ESTs and 15 598 3' ESTs. These ESTs were derived from 42 cDNA libraries, which were created from hexaploid bread wheat (Triticum aestivum L.) and its close relatives, including diploid wheat (T. monococcum L. and Aegilops speltoides L.), tetraploid wheat (T. turgidum L.), and rye (Secale cereale L.), using tissues collected from various stages of plant growth and development and under diverse regimes of abiotic and biotic stress treatments. ESTs were assembled into 18,876 contigs and 23,034 singletons, or 41,910 wheat unigenes. Over 90% of the contigs contained fewer than 10 EST members, implying that the ESTs represented a diverse selection of genes and that genes expressed at low and moderate to high levels were well sampled. Statistical methods were used to study the correlation of gene expression patterns, based on the ESTs clustered in the 1536 contigs that contained at least 10 5' EST members and thus representing the most abundant genes expressed in wheat. Analysis further identified genes in wheat that were significantly upregulated (p < 0.05) in tissues under various abiotic stresses when compared with control tissues. Though the function annotation cannot be assigned for many of these genes, it is likely that they play a role associated with the stress response. This study predicted the possible functionality for 4% of total wheat unigenes, which leaves the remaining 96% with their functional roles and expression patterns largely unknown. Nonetheless, the EST data generated in this project provide a diverse and rich source for gene discovery in wheat.

Structural and functional analyses of the wheat genomes based on expressed sequence tags (ESTs) related to abiotic stresses

To gain insights into the structure and function of the wheat (Triticum aestivum L.) genomes, we identified 278 ESTs related to abiotic stress (cold, heat, drought, salinity, and aluminum) from 7671 ESTs previously mapped to wheat chromosomes. Of the 278 abiotic stress related ESTs, 259 (811 loci) were assigned to chromosome deletion bins and analyzed for their distribution pattern among the 7 homoeologous chromosome groups. Distribution of abiotic stress related EST loci were not uniform throughout the different regions of the chromosomes of the 3 wheat genomes. Both the short and long arms of group 4 chromosomes showed a higher number of loci in their distal regions compared with proximal regions. Of the 811 loci, the number of mapped loci on the A, B, and D genomes were 258, 281, and 272, respectively. The highest number of abiotic stress related loci were found in homoeologous chromosome group 2 (142 loci) and the lowest number were found in group 6 (94 loci). When considering the genome-specific ESTs, the B genome showed the highest number of unique ESTs (7 loci), while none were found in the D genome. Similarly, considering homoeologous group-specific ESTs, group 2 showed the highest number with 16 unique ESTs (58 loci), followed by group 4 with 9 unique ESTs (33 loci). Many of the classified proteins fell into the biological process categories associated with metabolism, cell growth, and cell maintenance. Most of the mapped ESTs fell into the category of enzyme activity (28%), followed by binding activity (27%). Enzymes related to abiotic stress such as β-galactosidase, peroxidase, glutathione reductase, and trehalose-6-phosphate synthase were identified. The comparison of stress-responsive ESTs with genomic sequences of rice (Oryza sativa L.) chromosomes revealed the complexities of colinearity. This bin map provides insight into the structural and functional details of wheat genomic regions in relation to abiotic stress.

Smectic-Calpha*-smectic-C* phase transition and critical point in binary mixtures

We have investigated the smectic-Calpha*-smectic-C* (SmCalpha*-SmC*) transition in a series of binary mixtures with resonant x-ray diffraction, differential optical reflectivity, and heat capacity measurements. Results show that the phases are separated by a first-order transition that ends at a critical point. We report the observation of such a critical point. We have proposed the appropriate order parameter and obtained values of two critical exponents associated with this transition. The values of the critical exponents suggest that long-range interactions are present in the SmCalpha*-SmC* critical region.

Role of molecular weight and phase sequence in the temperature variation of film tension above the bulk isotropic transition in freestanding liquid-crystal films

Building upon our previous report [Veum, Phys. Rev. E 17, 020701(R) (2005)] involving two compounds, we have performed a systematic study of the temperature variation of film tension above the bulk isotropic transition in freestanding films to include a total of six smectic liquid-crystal compounds. Consistent with the previous results, the tension increases sharply with temperature above the transition, the tension-temperature slope is proportional to the film's thickness, and the data can be interpreted in the context of theoretical models for layer thinning. Our data suggest that both molecular weight and bulk phase appearing below its isotropic phase play important roles in the slope values.

Pooled analysis of data from multiple quantitative trait locus mapping populations

Quantitative trait locus (QTL) analysis on pooled data from multiple populations (pooled analysis) provides a means for evaluating, as a whole, evidence for existence of a QTL from different studies and examining differences in gene effect of a QTL among different populations. Objectives of this study were to: (1) develop a method for pooled analysis and (2) conduct pooled analysis on data from two soybean mapping populations. Least square interval mapping was extended for pooled analysis by inclusion of populations and cofactor markers as indicator variables and covariate variables separately in the multiple linear models. The general linear test approach was applied for detecting a QTL. Single population-based and pooled analyses were conducted on data from two F(2:3) mapping populations, Hamilton (susceptible) x PI 90763 (resistant) and Magellan (susceptible) x PI 404198A (resistant), for resistance to soybean cyst nematode (SCN) in soybean. It was demonstrated that where a QTL was shared among populations, pooled analysis showed increased LOD values on the QTL candidate region over single population analyses. Where a QTL was not shared among populations, however, the pooled analysis showed decreased LOD values on the QTL candidate region over single population analyses. Pooled analysis on data from genetically similar populations may have higher power of QTL detection than single population-based analyses. QTLs were identified by pooled analysis on linkage groups (LGs) G, B1 and J for resistance to SCN race 2 whereas QTLs on LGs G, B1 and E for resistance to SCN race 5 in soybean PI 90763 and PI 404198A. QTLs on LG G and B1 were identified in both PI 90763 and PI 404198A whereas QTLs on LG E and J were identified in PI 90763 only. QTLs on LGs G and B1 for resistance to race 2 may be the same or closely linked with QTLs on LG G and B1 for resistance to race 5, respectively. It was further demonstrated that QTLs on G and B1 carried by PI 90763 were not significantly different in gene effect from QTLs on LGs G and B1 in PI 404198A, respectively.

Management of spasticity in adults: practical application of botulinum toxin

Spasticity, characterized by increased muscle tone, exaggerated stretch reflexes, and abnormal limb posture, is a common sequel of central nervous system pathology. Historically, medicinal treatments have been of limited efficacy. This review discusses the clinical features of spasticity, the functional and pathological consequences, and treatment. It reviews the most common patterns of spasticity encountered in the upper and lower limbs and focuses on focal treatment of spastic muscles with the three commercially available botulinum toxins Botox, Dysport, and Myobloc/NeuroBloc. It addresses practical details such as muscle selection and identification, drug dilution, and doses.

Management of spasticity in adults: practical application of botulinum toxin

Spasticity, characterized by increased muscle tone, exaggerated stretch reflexes, and abnormal limb posture, is a common sequel of central nervous system pathology. Historically, medicinal treatments have been of limited efficacy. This review discusses the clinical features of spasticity, the functional and pathological consequences, and treatment. It reviews the most common patterns of spasticity encountered in the upper and lower limbs and focuses on focal treatment of spastic muscles with the three commercially available botulinum toxins Botox, Dysport, and Myobloc/NeuroBloc. It addresses practical details such as muscle selection and identification, drug dilution, and doses.

Frustrated structure of an anticlinic-like smectic-C phase

We present a polarising optical microscopy study of the low-temperature anticlinic-like tilted mesophase of the liquid-crystal compound octylphenyl-2-chloro-4-(p-cyano-benzoyloxy) (DB8Cl). This mesophase has been described as a bilayer smectic structure in which the molecules within each layer are organised in an anticlinic way. The optical textures observed in samples with planar orientation show a double stripe pattern, with the lines aligned parallel to the rubbing direction, characteristic of a double periodic modulation of the refractive index of the material. The long-period modulation is temperature dependent and disappears for thin sample cells (< 5 microm). The short-period modulation is nearly independent of the thickness of the cells. The experimental results are analysed in terms of a model which considers that there is a special distribution of the principal optical axis which may be in or out of the polariser-analyser plane. The observed periodic variation of the principal optical axis could not be interpreted in terms of the original structure proposed for this phase. DB8Cl presents a structure formed by dimers that can be viewed as flexible bent-core-like molecules, showing similarities with phases found in banana-like systems, but exhibiting a much more complex structure.

Optical and resonant X-ray diffraction studies confirm a SmC*FI2-SmC* liquid crystal phase sequence reversal

Employing both null transmission ellipsometry and resonant x-ray diffraction, we confirmed the SmC*FI2-SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by two recent theoretical advances. Moreover, the temperature range for the SmC*FI2 phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds.

Improved omnidirectional reflectors in chalcogenide glass and polymer by using the silver doping technique

We describe the fabrication and characterization of omnidirectional reflectors based on silver-doped chalcogenide glass and polymer. We deposited periodically alternating layers of thermally evaporated Ge33As12Se55 chalcogenide glass, sputtered silver, and spun-cast polyamide-imide polymer. The silver was subsequently dissolved into each adjacent chalcogenide glass layer, either by exposing the multilayer to visible light (photodoping) or by heating the sample. The resultant silver concentration within the chalcogenide glass layers is estimated to be ~20 at. %. Silver doping red-shifts the band edge of the glass, and produces an increase of ~0.3-0.4 in the refractive index. The glass retains good transparency in the near infrared after doping, and the technique enables the omnidirectional bandwidth to be increased from ~100 nm to ~200 nm in the 1550 nm wavelength region.

Application of an automation system and a supervisory control and data acquisition (SCADA) system for the optimal operation of a membrane adsorption hybrid system

The application of automation and supervisory control and data acquisition (SCADA) systems to municipal water and wastewater treatment plants is rapidly increasing. However, the application of these systems is less frequent in the research and development phases of emerging treatment technologies used in these industries. This study involved the implementation of automation and a SCADA system to the submerged membrane adsorption hybrid system for use in a semi-pilot scale research project. An incremental approach was used in the development of the automation and SCADA systems, leading to the development of two new control systems. The first system developed involved closed loop control of the backwash initiation, based upon a pressure increase, leading to productivity improvements as the backwash is only activated when required, not at a fixed time. This system resulted in a 40% reduction in the number of backwashes required and also enabled optimised operations under unsteady concentrations of wastewater. The second system developed involved closed loop control of the backwash duration, whereby the backwash was terminated when the pressure reached a steady state. This system resulted in a reduction of the duration of the backwash of up to 25% and enabled optimised operations as the foulant build-up within the reactor increased.

Identification of QTLs associated with resistance to soybean cyst nematode races 2, 3 and 5 in soybean PI 90763

Soybean cyst nematode (SCN) is a major soybean pest throughout the soybean growing regions in the world, including the USA. Soybean PI 90763 is an important SCN resistance source. It is resistant to several SCN populations including races 2, 3 and 5. But its genetics of resistance is not well known. The objectives of this study were to: (1) confirm quantitative trait loci (QTLs) for resistance to SCN race 3 in PI 90763 and (2) identify QTLs for resistance to SCN races 2 and 5. QTLs were searched in Hamilton x PI 90763 F(2:3)populations using 193 polymorphic simple sequence repeats (SSRs) covering 20 linkage groups (LGs). QTLs for resistance to SCN were identified on LGs A2, B1, E, G, J and L. The same QTL was suggested for resistance to different SCN races where their 1-LOD support intervals of QTL positions highly overlapped. The QTL on LG G was associated with resistance to races 2, 3 and 5. The QTL on LG B1 was associated with resistance to races 2 and 5. The QTL on LG J was associated with resistance to races 2 and 3. The QTLs on LGs A2 and L were associated with resistance to race 3. The QTL on LG E was associated with resistance to race 5. We conclude that LGs A2 and B1 may represent an important distinction between resistance to SCN race 3 and resistance to SCN races 2 and 5 in soybean.

Identification of QTLs associated with resistance to soybean cyst nematode races 2, 3 and 5 in soybean PI 90763

Soybean cyst nematode (SCN) is a major soybean pest throughout the soybean growing regions in the world, including the USA. Soybean PI 90763 is an important SCN resistance source. It is resistant to several SCN populations including races 2, 3 and 5. But its genetics of resistance is not well known. The objectives of this study were to: (1) confirm quantitative trait loci (QTLs) for resistance to SCN race 3 in PI 90763 and (2) identify QTLs for resistance to SCN races 2 and 5. QTLs were searched in Hamilton x PI 90763 F(2:3)populations using 193 polymorphic simple sequence repeats (SSRs) covering 20 linkage groups (LGs). QTLs for resistance to SCN were identified on LGs A2, B1, E, G, J and L. The same QTL was suggested for resistance to different SCN races where their 1-LOD support intervals of QTL positions highly overlapped. The QTL on LG G was associated with resistance to races 2, 3 and 5. The QTL on LG B1 was associated with resistance to races 2 and 5. The QTL on LG J was associated with resistance to races 2 and 3. The QTLs on LGs A2 and L were associated with resistance to race 3. The QTL on LG E was associated with resistance to race 5. We conclude that LGs A2 and B1 may represent an important distinction between resistance to SCN race 3 and resistance to SCN races 2 and 5 in soybean.