Orientation Distortion Research Articles

Micro-wires self-assembled and 3D-connected with the help of a nematic liquid crystal

We discuss a method for producing automatic 3D connections at right places between substrates in front of one another. The idea is based on the materialization of disclination lines working as templates. The lines are first created in the nematic liquid crystal (5CB) at the very place where microwires have to be synthesized. Due to their anchoring properties, colloids dispersed into the nematic phase produce orientational distortions around them. These distortions, which may be considered as due to topological charges, result in a nematic force, able to attract the colloids towards the disclinations. Ultimately, the particles get trapped onto them, forming micro- or nano-necklaces. Before being introduced in the nematic phase, the colloids are covered with an adhering and conducting polypyrrole film directly synthesized at the surface of the particles (heterogeneous polymerization). In this manner, the particles become conductive so that we may finally perform an electropolymerization of pyrrole monomers solved in 5CB, and definitely stick the whole necklace. The electric connection thus synthesized is analyzed by AFM, and its strength is checked by means of hydrodynamic tests. This wiring method could allow Moore's law to overcome the limitations that arise when down-sizing the electronic circuits to nanometer scale.

MAPPING CROP STATUS FROM AN UNMANNED AERIAL VEHICLE FOR PRECISION AGRICULTURE APPLICATIONS

Abstract. Remote sensing system mounted on unmanned aerial vehicle (UAV) could provide a complementary means to the conventional satellite and aerial remote sensing solutions especially for the applications of precision agriculture. UAV remote sensing offers a great flexibility to quickly acquire field data in sufficient spatial and spectral resolution at low cost. However a major problem of UAV is the high instability due to the low-end equipments and difficult environment situation, and this leads to image sensor being mostly operated under a highly uncertain configuration. Thus UAV images exhibit considerable derivation in spatial orientation, large geometric and spectral distortion, and low signal-to-noise ratio (SNR). To achieve the objectives of agricultural mapping from UAV, we apply a micro-helicopter UAV with a multiple spectral camera mounted and develop a framework to process UAV images. A very important processing is to generate mosaic image which can be aligned with maps for later GIS integration. With appropriate geometric calibration applied, we first decompose a homography of consecutive image pairs into a rotational component and a simple perspective component, and apply a linear interpolation to the angle of the rotational component, followed by a linear matrix interpolation operator to the perspective component, and this results in an equivalent transformation but ensures a smooth evolution between two images. Lastly to demonstrate the potential of UAV images to precision agriculture application, we perform spectral processing to derive vegetation indices (VIs) maps of crop, and also show the comparison with satellite imagery. Through this paper, we demonstrate that it is highly feasible to generate quantitative mapping products such as crop stress maps from UAV images, and suggest that UAV remote sensing is very valuable for the applications of precision agriculture.

The role of problem orientation and cognitive distortions in depression and anxiety interventions for young adults

Interventions that aim to improve social problem-solving skills can significantly reduce the severity of anxiety and depression symptoms in young people. Anxious and depressed individuals often have a negative orientation to problem solution which acts as a barrier to implementing problem-solving skills. Research with older adults suggests that symptoms impair problem-solving abilities through cognitive processes associated with the development of anxiety and depression. In this study we extend previous investigations by assessing the extent to which specific cognitive distortions and symptoms of anxiety and depression are associated with negative problem orientation (NPO) in a sample of 285 young adults aged 18–25 years. Results found that cognitive distortions and depressive symptoms were strong predictors in a regression model that explained approximately half of the variance in NPO. Results also found that the relationship between cognitive distortions and NPO was strengthened as depressive symptoms became more intense. The distortion ‘You think you know what the future will bring; you expect disaster and gloom’ had the strongest individual association with NPO and depressive symptoms. Implications for enriching prevention and early intervention initiatives for young adults are discussed.

Effect of ZnO nanoparticles on the SmC*-SmA* phase transition temperature in electroclinic liquid crystals

ZnO nanoparticles (NPs), synthesized in an alcoholic medium at room temperature, were added to electroclinic liquid crystal (ELC) materials. The addition of ZnO NPs in ELCs, caused a remarkable shift in SmC*-SmA* phase transition which was investigated from the dielectric and electro-optical measurements. The anchoring of ELC molecules around ZnO NPs creates orientational distortions near the surface, which may give additional ordering to the ELC molecular arrangement. After analyzing collective dielectric relaxation processes of ZnO NP doped ELCs, three distinct loss peaks were observed. The different behavior of ZnO NP doped ELC from pure ELC has been explained by determining the dielectric strength, the distribution parameter and the corresponding relaxation frequency, and so on, and then these results have been compared with the data calculated by using the theoretical model. The effect of ZnO NPs addition on physical parameters, such as spontaneous polarization (Ps) and rotational viscosity (η) has also been observed.

Shock compression and spallation of palladium bicrystals with a Σ5 grain boundary

We investigate an elementary process of shock response of grain boundaries (GBs) using molecular dynamics simulations: shock compression and spallation in Pd bicrystals with a symmetric Σ5/(210)/〈100〉 GB. The loading direction is normal to GB. An elastic shock may induce the elastic-plastic or two-wave structure at the GB. The GB serves as a wave scattering center for the transverse motion perpendicular to the GB rotation axis and the shock direction: it induces a phase shift of 180∘, an increase in the amplitude of the particle velocity, GB sliding and grain orientation distortion. The GB is the preferred nucleation site both for dislocations and voids. Our results suggest that both microstructure and the loading geometry contribute to dynamic response of a solid.

Banded spatiotemporal chaos in sheared nematogenic fluids

We present the results of a numerical study of a model of the hydrodynamics of a sheared nematogenic fluid, taking into account the effects of order-parameter stresses on the velocity profile but allowing spatial variations only in the gradient direction. When parameter values are such that the stress from orientational distortions is comparable to the bare viscous stress, the system exhibits steady states with the characteristics of shear banding. In addition, nonlinearity in the coupling of extensional flow to orientation leads to the appearance of a new steady state in which the features of both spatiotemporal chaos and shear banding are present.

Effects of lanthanum doping on the preferred orientation, phase structure and electrical properties of sol–gel derived Pb 1–3 x/2 La x (Zr 0.6Ti 0.4)O 3 thin films

Pb 1–3 x/2 La x (Zr 0.6Ti 0.4)O 3 thin films (0 ≤ x ≤ 0.08) were prepared on the Pt (1 1 1)/Ti/SiO 2/Si (1 0 0) substrates by a sol–gel method. The morphology, preferred orientation, phase structure, dielectric and ferroelectric properties of the films have been investigated. Our results show that lanthanum doping is favorable to enhance crystalline and obtain (1 0 0)-preferred orientation of the films. Meanwhile, it is suggested that the films undergo a structure change from “rhombohedral” phase to monoclinic phase as the lanthanum-doped content is increased to x ≈ 0.05. Results of dielectric properties and ferroelectric properties indicate that lanthanum doping contributes to improve film dielectric constant and dielectric loss while it brings about a striking decrease in remnant polarization value. Possible explanations for the variations of electrical properties have been discussed in terms of preferred orientation, phase structure and large lattice distortion.

Gravitational field-induced orientational transition of aligned nematic liquid crystals

We demonstrate induced orientational transition of liquid crystal (LC) E7 between two optical fibre tips in a gravitational field as a result of minimising the free energy. The LC orientational transition is from a homeotropic state, with respect to fibre tip, to a tilted state as the spacing between two fibre tips is increased. The orientational distortion introduces birefringence in the optical fibre that changes the polarised direction of the output light. At short spacing, the undistorted homeotropic orientation of LC is preferred. However, at longer spacing, a distorted orientation is preferred. Once the LC director profile is known, a Finite Difference Time Domain method is used to calculate the optical properties, which agree well with the experimental results.

Effect of crystalline orientation and lattice distortion of FeCo spin polarization enhancement layer in perpendicular magnetic tunnel junction with RE-TM alloy films

Relationship between FeCo crystalline orientation and magnetic properties of TbFeCo/FeCo/Ta trilayer films was investigated. FeCo crystalline orientation could be controlled by changing FeCo deposition rate. Ferromagnetic Hall effect observation clarified that perpendicular component of magnetization in FeCo layer of TbFeCo/FeCo(001)/Ta were better than that of TbFeCo/FeCo(110)/Ta. Lattice spacing of both FeCo(001) films and FeCo(110) ones in the TbFeCo(50 nm)/FeCo (X nm) was also observed. Expansion ratios of FeCo(001) toward film normal direction were higher than that of FeCo(110) as increasing FeCo film thickness, and this indicated that FeCo(001) films were more favorable for magnetic coupling with rare-earth transition metal (RE-TM) alloy films than FeCo(110) ones when FeCo films become thick. However investigation of relationship between FeCo expansion ratios and magnetic properties of TbFeCo/FeCo(001) or (110) (X nm)/Ta trilayer films showed that squareness ratios of specimens with FeCo(001) were worse than that with FeCo(110).

Dynamic Simulation of Capillary Breakup of Nematic Fibers: Molecular Orientation and Interfacial Rupture

We simulate the breakup of cylindrical fibers of a nematic liquid crystal surrounded by a quiescent Newtonian fluid. The nematic is described by the Leslie-Ericksen theory, and the interfacial motion is captured by a phase-field method from the initial linear instability to final breakup. The focus is on the coupling between liquid crystal molecular orientation and the evolution of the interface. In particular, we examine how molecular anchoring on the interface and orientational distortion in the bulk affect the growth of capillary waves. Results show that the nematic order tends to hinder capillary wave development, in qualitative agreement with prior linear instability analysis. For typical materials, however, the effect becomes prominent only for nano-scale fibers. In addition, anisotropic viscosity plays a significant role in the growth rate of the capillary wave. In the nonlinear stage of the instability, neighboring waveforms grow at different speeds and lead to daughter drops of nonuniform sizes, which typically display the bipolar configuration with two boojum defects. Despite quantitative differences, the breakup of nematic fibers proceeds in mostly the same way as Newtonian ones. The numerical simulations are in general agreement with previous experimental observations.

Intragranular strain field in columnar ice during transient creep regime and relation with the local microstucture

Transient effects in the creep of polycrystalline ice could play a crucial role for several ice flows (e.g. interaction between Antarctic ice shelves and ocean tides) and also have a major impact concerning deformation mechanisms of ice. During creep de- formation of polycrystalline ice, strong stress and strain-rate intragranular heterogeneities are expected. These heterogeneities come from the very large viscoplastic anisotropy of ice crystals (with essentially a single easy plane for the dislocations to glide) which is responsible for the strong mechanical interaction between adjacent grains (1). In order to go one step further in the quantitative understanding of this process, and to character- ize the development of strain heterogeneities at a microscopic (intragranular) scale, we have performed deformation tests on 2-D polycrystalline ice exhibiting columnar grains with controlled grain size. Specimens were submitted to creep test and transient effects, in which both elastic and viscoplastic responses come in play, are investigated. A Digi- tal Image Correlation (DIC) technique, with spatial resolution far smaller than the mean grain size, has been set to get continuous record of the intragranular displacement field during the test (2). Experimental parameters have been optimized to improve the precision of the DIC results. In parallel, specimen microstructures were analyzed with an automatic ice texture analyzer, before and after deformation, and post-mortem measurements of lo- cal misorientations at the intragranular scale were performed. For the first time in ice, this work presents a direct link between grain orientation, strain localization, and lattice distortion at the intragranular scale.

Ground based astrometric searches for extrasolar planets in multiple stellar systems

We present a method to measure the dynamical mass of extrasolar planets in multiple stellar systems with a single aperture from the ground using high-precision relative astrometry. To reach the precision needed, accurate monitoring of the astrometric stability (pixel scale, orientation, and field distortions of the detector) is necessary. Thus, we always observe an astrometric calibration cluster to compare these astrometric criteria with those of our observations. For our first target observed, the binary HD 19994, we achieved a relative precision of 100...150 µas which is sufficient to detect an astrometric companion around the A component down to about 5 MJup.

Calamitic Liquid‐Crystalline Elastomers Swollen in Bent‐Core Liquid‐Crystal Solvents

2009 WILEY-VCH Verlag Gmb Liquid-crystal elastomers (LCEs) combine the properties of liquid crystals (LCs) and rubber elasticity. They are unique materials in their ability to change shape spontaneously by large degrees as a consequence of their global orientational (nematic) or combined orientational/positional (smectic) order. LCE systems are thermotropic, and may also be responsive to light, magnetic fields, or electric fields. They have possible uses as artificial muscles or sensors in addition to being intriguing materials for basic research. Bent-core nematic LCs (BCNs) are a relatively new class of mesogenic materials (compared to their calamitic—or rodshaped—cousins). They exhibit both rich phase behavior and novel properties; they also hold the potential of fundamentally new technological applications. In particular, some BCNs have recently been shown to exhibit a giant flexoelectric effect (electric polarization induced by orientational distortion of the average direction of molecular alignment). Since the reported flexoelectric coefficients are some three orders of magnitude larger than standard calamitics, these BCNs have exciting potential for applications ranging from power generation to sensing. Additionally, the phase behavior of mixtures of calamitic (rod-shaped) nematics and BCNs show that the range of the nematic phase can be extended to temperatures approaching ambient, presumably by frustrating the formation of the crystal phase. The flexoelectric response of such mixed BCN and calamitic LCs is still sufficiently large to be promising for applications, even at fairly low unit concentrations of the BCN. However, to realize practical materials that take advantage of this response, one needs a method of encapsulating the BCN in a mechanically robust but flexible matrix that stabilizes (or ruggedizes) the BCN orientational order against variations in environmental conditions. A well-known property of common isotropic elastomeric systems is their ability to swell in suitable solvents. Applied to LCEs in both isotropic and anisotropic solvents of calamitic LCs, this property has proven an effective means to manipulate viscoelastic properties and phase behavior. In this study, we demonstrate, to our knowledge for the first time, the swelling of a calamitic nematic monodomain LCE with large amounts (greater than 30mol%) of two types of bent-core mesogens, both of which show large flexoelectric response in their pure nematic states. LCEs swollen with the two mesogens are additionally investigated with respect to the degree of saturation of the latter’s hydrocarbon chains. We report on the swelling degree (amount of bent-core material imbibed), characteristic swelling times, the resulting phases and transition temperatures, and the orientational order parameter of the swollen LCEs. This study demonstrates a potential method for creating a robust liquid-crystalline device with enhanced flexoelectricity. The chemical structures of the various bent-core materials utilized in our study are presented in Figure 1a and b. The bent-core compound 4-chloro-1,3-phenylene bis[4-(10-decenyloxy) benzoyloxy]benzoate (BCa) was synthesized and purified following a previously described procedure. Versions with symmetric saturated and unsaturated hydrocarbon chains (designated ‘‘uu’’ and ‘‘ss,’’ respectively) were prepared. In BCa, the arms are relatively flexible, as the outer benzene rings are separated by ester groups. The other bent-core mesogen, 4,6-dichloro-1,3-phenylene-bis 4-[{40-(9-octenyloxy)}biphenyl] carboxylate (denoted BCb), features two chlorine units in its central phenyl ring, and the aromatic rings of the arms are directly linked, making themmuchmore rigid. This material and in variants featuring unsaturated (uu) and saturated (ss) chains as well as an asymmetric combination of the two (designated ‘‘us’’) were prepared by a synthetic route previously published. The purity of the samples was checked by high-performance liquid chromatography using a Merck–Hitachi chromatograph equipped with a Merck RP18 column (Cat. No. 16051). Various properties of the nematic and isotropic phases of the neat BCa and BCb mesogens are described in Refs.[19,20]. Unsaturation of the hydrocarbon chain generally results in lowering of the transition temperatures and increasing the flow viscosity, which is, strikingly, several orders of magnitude higher in both nematic and isotropic phases than for typical rod-shaped mesogens. The transition temperatures and associated enthalpy values of the BCa and BCb compounds are shown in Table 1. All mesogens exhibit nematic phases; BCa-ss also exhibits a smectic phase whose detailed in-layer structure is unknown, but is believed to be of the tilted (smectic-C) type. A conventional poly[oxy(methylsilylene)]-based side-chain monodomain calamitic LCE, whose components are shown in

Buckling-induced zebra stripe patterns in nematic F-actin

Rather than forming a simple and uniform nematic liquid crystal, concentrated solutions of semiflexible polymers, such as F-actin, have been observed to display a spatially periodic switching of the nematic director. When observed with polarization microscopy, these patterns appear as alternating light and dark bands, often referred to as zebra stripe patterns. Zebra stripe patterns, although not fully characterized, are due to periodic orientation distortions in the nematic order. We characterize such patterns by using a combination of two techniques. Using polarization microscopy, we quantify the periodic orientation distortions and show that the magnitude of the order parameter also varies periodically in the striped domains. When using fluorescently labeled filaments as markers, filaments spanning the striped domains are seen to undergo large angle bends. With fluorescence, clear density differences between adjacent stripes are also observed with domains of lesser density corresponding to strongly bent filaments. By directly comparing patterned areas with both polarization and fluorescence techniques, we show that periodic variation in the orientation, order parameter, filament bending, and density are correlated. We propose that these effects originate from the coupling of orientation and density that occurs for highly concentrated solutions of long semiflexible polymers subject to shear flows, as previously proposed [P. de Gennes, Mol. Cryst. Liq. Cryst. (Phila. Pa.) 34, 177 (1977)]. After cessation of shearing, strong interfilament interactions and high compressibility can lead to periodic buckling from the relaxation of filaments stretched during flows. The characterization of zebra stripe patterns presented here provides evidence that buckling in confined F-actin nematics produces strong periodic bending that is responsible for the observed features.

Magnetic distortion in motion labs, implications for validating inertial magnetic sensors

Background Ambulatory 3D orientation estimation with Inertial Magnetic Sensor Units (IMU's) use the earth magnetic field. The magnitude of distortion in orientation in a standard equipped motion lab and its effect on the accuracy of the orientation estimation with IMU's is addressed. Methods Orientations of the earth magnetic field vectors were expressed in the laboratory's reference frame. The effect of a distorted earth magnetic field on orientation estimation with IMU's (using both a quaternion and a Kalman fusing algorithm) was compared to orientations derived from an optical system. Findings The magnetic field varied considerably, with the strongest effects at 5 cm above floor level with a standard deviation in heading of 29°, decreasing to 3° at levels higher than 100 cm. Orientation estimation was poor with the quaternion filter, for the Kalman filter results were acceptable, despite a systematic deterioration over time (after 20–30 s). Interpretation Distortion of the earth magnetic field is depending on construction materials used in the building, and should be taken into account for calibration, alignment to a reference system, and further measurements. Mapping the measurement volume to determine its ferromagnetic characteristics in advance of planned experiments can be the rescue of the data set. Conclusions To obtain valid data, “mapping” of the laboratory is essential, although less critical with the Kalman filter and at larger distances (>100 cm) from suspect materials. Measurements should start in a “safe” area and continue no longer than 20–30 s in a heavily distorted earth magnetic field.

High‐pressure NMR characterization of triacetyl‐β‐cyclodextrin in supercritical carbon dioxide

Cyclodextrins are used in many drug formulations since their cavities provide microenvironments where drug molecules can enter and form inclusion complexes for controlled drug delivery. Supercritical carbon dioxide (scCO(2)) is an alternative to organic solvents and a very attractive medium for the preparation of these inclusion complexes. The potential ability of triacetyl-beta-cyclodextrin (TA-beta-CD) to form inclusion complexes in addition to its high miscibility in liquid and scCO(2) could offer a chance for an economical and environmental friendly chemical processing. In this work, high-pressure NMR studies were performed in order to obtain information on the molecular structure and dynamics of TA-beta-CD in scCO(2) at 313.15 K and 20 MPa and its ability to form inclusion complexes under these conditions was studied. The influence of scCO(2) on a number of NMR spectral parameters, such as chemical shifts, spin-spin coupling constants, nuclear Overhauser effect (NOE) and spin-lattice relaxation (T(1)) has been studied. We unequivocally show for the first time structural changes of TA-beta-CD in scCO(2), like acetyl chain orientation and overall shape distortions that can affect its inclusion capability in this medium. The possibility of cavity self-closure is discussed and the results of two inclusion studies that support cavity self-closure, with the angiotensin-converting enzyme inhibitor, captopril, and the nonsteroid anti-inflammatory drug, flufenamic acid, are presented.

Robust Handwritten Character Recognition with Features Inspired by Visual Ventral Stream

This paper focuses on the applicability of the features inspired by the visual ventral stream for handwritten character recognition. A set of scale and translation invariant C2 features are first extracted from all images in the dataset. Three standard classifiers kNN, ANN and SVM are then trained over a training set and then compared over a separate test set. In order to achieve higher recognition rate, a two stage classifier was designed with different preprocessing in the second stage. Experiments performed to validate the method on the well-known MNIST database, standard Farsi digits and characters, exhibit high recognition rates and compete with some of the best existing approaches. Moreover an analysis is conducted to evaluate the robustness of this approach to orientation, scale and translation distortions.

CLASP Modulates Microtubule-Cortex Interaction during Self-Organization of Acentrosomal Microtubules

CLASP proteins associate with either the plus ends or sidewalls of microtubules depending on the subcellular location and cell type. In plant cells, CLASP's distribution along the full length of microtubules corresponds with the uniform anchorage of microtubules to the cell cortex. Using live cell imaging, we show here that loss of CLASP in Arabidopsis thaliana results in partial detachment of microtubules from the cortex. The detached portions undergo extensive waving, distortion, and changes in orientation, particularly when exposed to the forces of cytoplasmic streaming. These deviations from the normal linear polymerization trajectories increase the likelihood of intermicrotubule encounters that are favorable for subsequent bundle formation. Consistent with this, cortical microtubules in clasp-1 leaf epidermal cells are hyper-parallel. On the basis of these data, we identify a novel mechanism where modulation of CLASP activity governs microtubule-cortex attachment, thereby contributing to self-organization of cortical microtubules.

Controllable Synthesis of One-Dimensional Chinelike Superstructures of Homogeneous Bi100–xSbx Alloys via a Template-Free Electrodeposition

One-dimensional (1D) superstructures are attracting increasing interests because of their unique physical and chemical properties. In our work, 1D chinelike superstructures of homogeneous Bi100–xSbx (x = 0–100) alloys were synthesized in aqueous solutions via a template-free electrochemical route at room temperature. The cyclic voltammetric analysis and the X-ray diffraction (XRD) study proved that BiIII and SbIII can be coreduced as a homogeneous solid solution; the Bi/Sb ratio in the alloy was greatly correlated to that in the aqueous solution, while also being affected by the deposition potential. The structures of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). These 1D chinelike superstructures consisted of orderly aligned subcrystallites with only slight orientational distortion. The formation of these 1D superstructures was affected mainly by the deposition potential, and as the deposition potential became less and less negative, the products changed gradually from fine dendrites to big 1D chinelike superstructures. The orientational distortion in the structure, which is the reason for the chinelike pattern, might enhance the phonon scattering at subcrystallite boundaries and thus reduce the thermoconductivity, resulting in the improvement of the thermoelectric property.

Zoom-Dependent Camera Calibration in Digital Close-Range Photogrammetry

One of the well-known constraints applying to the adoption of consumer-grade digital cameras for photogrammetric measurement is the requirement to record imagery at fixed zoom and focus settings. The camera is then calibrated for the lens setting employed. This requirement arises because calibration parameters vary significantly with zoom/focus setting. In this paper, a zoom-dependent calibration process is proposed whereby the image coordinate correction model for interior orientation and lens distortion is expressed as a function of the focal length written to the EXIF header of the image file. The proposed approach frees the practitioner from the requirement to utilize fixed zoom/focus settings for the images forming the photogrammetric network. Following a review of the behavior of camera calibration parameters with varying zoom settings, an account of the newly developed zoom-dependent calibration model is presented. Experimental results of its application to four digital cameras are analysed. These show that the proposed approach is suited to numerous applications of medium-accuracy, digital, close-range photogrammetry.