Axis Preferred Orientation Research Articles

Complex Cells in the Cat Striate Cortex Have Multiple Disparity Detectors in the Three-Dimensional Binocular Receptive Fields

Along the visual pathway, neurons generally become more specialized for signaling a limited subset of stimulus attributes and become more invariant to changes in the stimulus position within the receptive fields (RFs). One of the likely mechanisms underlying such invariance appears to be pooling of detectors located at different positions. Does such spatial pooling occur for disparity-selective neurons in primary visual cortex? To examine whether the three-dimensional (3D) binocular RFs are constructed by pooling detectors for binocular disparity, we investigated binocular interactions in the 3D space for neurons in the cat striate cortex. Approximately one-third of complex cells showed the spatial pooling of disparity detectors to a significant degree, whereas the majority of simple cells did not. The degree of spatial pooling of disparity detectors along the preferred orientation axis was generally larger than that along the axis orthogonal to the orientation axis. We then reconstructed 3D binocular RFs in their complete form and examined their structures. Disparity tuning curves were compared across positions along the orientation axis in the RFs. A small population of cells appeared to show a gradual shift of the preferred disparity along this axis, indicating that they can potentially signal inclination in the 3D space. However, the majority of cells exhibited a position-invariant disparity tuning. Finally, disparity tuning curves were examined for all oblique angles in addition to horizontal and vertical. Tunings were broadest along the orientation axis as the disparity energy model predicts.

Effect of deposition temperature on the properties of nitrogen-doped AZO thin films grown on glass by rf reactive magnetron sputtering

Abstract Nitrogen-doped aluminum zinc oxide (NAZO) thin films were deposited on glass substrates at various deposition temperatures by rf reactive magnetron sputtering. The NAZO film deposited at 400 °C shows a strongly c -axis preferred orientation and n-type conduction with a resistivity of 2.1 × 10 −2 Ω cm, Hall mobility of 7.7 cm 2 V −1 s −1 , and electron concentration of 3.8 × 10 19 cm −3 . The optimum crystallographic structure occurs at a deposition temperature of 400 °C, where a considerable crystallinity enhancement of the films is observed. The band gap energies of the NAZO films, obtained by using Tauc model and parabolic bands, are found to significantly depend on the deposition temperature, along with the band gap narrowing at higher deposition temperature due to renormalization effects.

The structure，optical and electrical properties of Li-N dual-acceptor doped p-type ZnO thin films prepared by sol-gel method

采用溶胶-凝胶法在n型Si(100)衬底上沉积Li-N双掺杂ZnO薄膜，经X射线衍射和扫描电镜图片分析，所制备薄膜具有多晶纤锌矿结构和高的c轴择优取向.室温下霍尔效应测试结果显示Li-N双掺杂ZnO薄膜具有p型导电特性.在Li掺杂量为15.0at%，Li/N（摩尔比）为1∶1，700℃退火等优化条件下得到的最佳电学性能结果是：电阻率为0.34 Ω·cm，霍尔迁移率为16.43 cm2/V·s，载流子浓度为2.79×1019 cm-3</s

Effect of heat treatment on microstructure and transparent conducting properties of sol-gel ZnO/Al thin films

Transparent and conducting Al doped ZnO (AZO) thin films with c axis preferred orientation were prepared on glass substrates via the sol-gel route. The physical and chemical changes of the precursors during thermal treatment were systematically investigated by differential scanning calorimeter and thermogravimetric analysis and the crystallinity of AZO films was characterised by X-ray diffraction. The surface morphology evolution of the films post-heated at 420, 450, 530 and 550°C respectively was observed by SEM. Results reveal that the crystallising process of ZnO/Al comprises two stages: the primary nucleation and growth occurs at 318°C and the continuous crystallisation at 488°C. The optimised preheating and post-heating temperatures are determined at 420 and 530°C respectively. The annealing treatment in vacuum can contribute considerably to the electrical conductivity. The film post-heated at 530°C shows a homogenous dense microstructure and exhibits the minimum sheet resistance of 140 Ω/sq. The visible optical transmittance of all films is more than 90%.

Optical Properties and X-ray Photoelectron Spectroscopy Study ofReactive-sputtered Ta-N Thin Films

The optical properties and an X-ray photoelectron spectroscopy (XPS) analysis of amorphous TaN thin films were investigated. Ta-N thin films reactively sputtered at N2 partial pressures (P(N2)) < 0.2 mTorr had the [111]-axis preferred orientation with a cubic δ-TaN phase while amorphous TaN thin films were obtained for P(N2) = 0.2 mTorr. The band gap of the amorphous Ta-N thin films increased from 1.4 eV to 3.6 eV with increasing P(N2) from 0.3 mTorr to 5.0 mTorr. For P(N2) < 0.3 mTorr, the chemical binding states of Ta-N are predominant as the TaN compound. Otherwise, in the chemical states of Ta-N, N-rich metastable phases similar to those of Ta2O5 increase up to a 50% fraction of Ta-N bonding states with increasing P(N2) and are closely related to the optical transparency of amorphous Ta-N thin films.

The influence of Mg doped ZnO thin films on the properties of Love wave sensors

Abstract The influence of Mg dopants on the crystalline structures of MZO thin films and the properties of Love wave sensors has been studied in this paper. 0–20 mol% Mg doped ZnO films with c -axis preferred orientation were deposited on the 64° YX-LiNbO 3 substrates by RF magnetron sputtering technique. XRD, SEM, and AFM measurements investigated characteristics of the films. The phase shift and temperature coefficient of frequency of Love wave devices in MZO/LiNbO 3 structures are presented. The appropriate addition of Mg dopant will produce a rough surface to raise the sensitivity. Besides, the effects of reflector gratings on the properties of Love wave sensors are also investigated.

Crystallinity and Orientation of Solution Deposited Anatase TiO2 Films

The crystallinity of anatase material synthesized from an acidic fluoride-based solution at was raised by increasing the growth temperature by an amount that was significantly lower than that required by postdeposition heat-treatment in air. As higher temperatures lead to more complete dehydration reactions and lower proton incorporation, the long-range attractive forces necessary for crystallinity are disrupted to a lesser degree. In addition, films grown on glass slides at 60 and exhibited preferential -axis orientation due to restricted lateral and off-normal growth of crystallites elongated along the -axis. As the island nucleation density was higher at , this resulted in even less lateral and off-normal crystallite growth compared to the film grown at , giving rise to a greater degree of -axis preferred orientation for the film.

Transparent conductive ZnO thin films on glass substrates deposited by pulsed laser deposition

Abstract ZnO thin films were deposited on the glass substrates at different temperatures (room temperature, 100, 200, 300, 400, and 500 °C) in the pulsed laser deposition (PLD) system. The crystal structure of the thin film was found to be c -axis preferred orientation. The crystal quality of the thin film was confirmed by the ω scan (rocking curve) by measuring the (0 0 2) orientation. The full-width at half-maximum (FWHM) value of the thin film deposited at 400 °C was as small as 0.52°. The band gap energies of the thin films were determined by a linear fit of the transmittance spectra. It was found that, with increasing growth temperature, the band gap energy increases and saturates at 3.28 eV. By the fitting of ellipsometry angles ( Ψ and Δ ) the optical constants and the thicknesses of the thin films were calculated. The refractive indices of the thin films show normal dispersion behavior and are in the reasonable range compared with ZnO single crystal (2.008 at 6328 A ). Luminescent measurements were also carried out by spectrometer. There existed two emission peaks in all thin films; one is the near band edge (NBE) emission at about 379 nm; the other is the wide deep level (DL) emission at about 500 nm. With increasing growth temperature, NBE emission enhanced and DL emission quenched. By measuring the photoluminescence (PL) of the samples at different date after deposition, the aging effects were observed. Micro-Raman was used to investigate the vibrational properties of the thin films. E 2 modes at 101 and 438 cm −1 were observed to locate at 92.1 and 437.6 cm −1 , respectively. This shift was believed to be from the stress in the thin films. Hall measurement indicates that the resistivity decreases and the Hall mobility increases with increasing growth temperature.

Crystal grain growth at theα-uranium phase transformation in praseodymium

Structural phase transformations under pressure are examined in praseodymium metal for the range $0--40\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at ambient temperature. Pressure was generated with a diamond-anvil cell, and data were collected using high-resolution synchrotron x-ray diffraction and the image plate technique. The structural sequence double hexagonal close packed (dhcp)\ensuremath{\rightarrow}face centered cubic (fcc)\ensuremath{\rightarrow}distorted-fcc (d-fcc)\ensuremath{\rightarrow}$\ensuremath{\alpha}$-uranium $(\ensuremath{\alpha}\text{\penalty1000-\hskip0pt}\mathrm{U})$ is observed with increasing pressure. Rietveld refinement of all crystallographic phases provided confirmation of the hR24 structure for the d-fcc phase while the previously reported monoclinic phase between the d-fcc and the $\ensuremath{\alpha}\text{\penalty1000-\hskip0pt}\mathrm{U}$ phase was not confirmed. We observe dramatic crystal grain growth during the volume collapse concurrent with the symmetry-lowering transition to the $\ensuremath{\alpha}\text{\penalty1000-\hskip0pt}\mathrm{U}$ structure. No preferred orientation axis is observed, and the formation process for these large grains is expected to be via a nucleation and growth mechanism. An analogous effect in rare earth metal cerium suggests that the grain growth during transformation to the $\ensuremath{\alpha}\text{\penalty1000-\hskip0pt}\mathrm{U}$ structure is a common occurrence in $f$-electron metals at high pressures.

A morphological basis for orientation tuning in primary visual cortex.

Feedforward connections are thought to be important in the generation of orientation-selective responses in visual cortex by establishing a bias in the sampling of information from regions of visual space that lie along a neuron's axis of preferred orientation. It remains unclear, however, which structural elements-dendrites or axons-are ultimately responsible for conveying this sampling bias. To explore this question, we have examined the spatial arrangement of feedforward axonal connections that link non-oriented neurons in layer 4 and orientation-selective neurons in layer 2/3 of visual cortex in the tree shrew. Target sites of labeled boutons in layer 2/3 resulting from focal injections of biocytin in layer 4 show an orientation-specific axial bias that is sufficient to confer orientation tuning to layer 2/3 neurons. We conclude that the anisotropic arrangement of axon terminals is the principal source of the orientation bias contributed by feedforward connections.

Diluted Magnetic Semiconducting Ti1 − xCox O 2 Thin Films Grown onto SiO2 ( 200 nm ) / Si Substrates by Liquid-Delivery MOCVD

Anatase thin films onto substrates at 400°C using liquid-delivery metallorganic chemical vapor deposition (MOCVD) were successfully prepared and the ferromagnetic properties investigated through microstructural analysis by transmission electron microscopy and high-resolution scanning Auger microscopy as a function of Co-doping concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature and the magnetic and structural properties depend critically on the Co distribution, which varies widely with Co-doping concentration. Annealed thin films with showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are attributed only to the phases. In the case of thin films above Co-rich clusters are formed in homogeneous phases. The solid solubility of Co was approximately 5 atom % in polycrystalline thin films. clusters with a c axis preferred orientation decrease the value of (coercive field) and increase the saturation magnetic field. The polycrystalline anatase thin films prepared by liquid-delivery MOCVD have an advantage for high-density device application in ferromagnetic semiconductor fields. © 2004 The Electrochemical Society. All rights reserved.

Effect of crystallographic orientation dispersion on media thermal stability and recording characteristics

We have studied thermal stability and recording characteristics of CoCrPtB alloy media with varying c axis anisotropy dispersion, preferred orientation (PO), and in-plane orientation ratio (OR) on both glass and NiP-plated Al substrates. With increasing in-plane c axis orientation and OR, improved recording performances such as lower pulsewidth, lower media transition noise, and lower dc noise are achieved. Thermal decay rate is primarily determined by Co anisotropy dispersion and in-plane OR for the same coercivity media. Media having a large out-of-plane c axis component exhibit a wide switching field distribution and have a high signal decay rate. The PW/sub 50/ and dc noise of media with out-of-plane Co grains are very sensitive to changes in write field. On the other hand, highly oriented media having high OR are less sensitive to head writability variations and offer good thermal stability with excellent recording performance.

Coesite eclogite facies metamorphic tectonite: Evidence for ultrahigh pressure deformation

An ultrahigh pressure ductile shear melange crops out on the beach of Yangkou Bay near Qingdao City. The melange is composed of weakly deformed blocks in a highly ductilly flow mylonites. Ultrahigh pressure metamorphic (UHPM) tectonite includes strongly deformed eclogite and mylonitized eclogite. Coesite occurs in the tectonite as both interstitial mineral and inclusions in garnet and omphacite, indicating that the deformation took place in the stability field of coesite (800–850°C, >30 GPa) in the upper mantle. Coesite is rounded or short prismatic grains with undulatory extinction, and often fractured, suggesting brittle deformation. Garnet is also characterized by brittle fractures and sometimes necked and slightly elongated. Omphacite is elongated, with long axis preferred orientation. Undulatory extinction, subgrains and dynamically recrystallized grains suggest plastic flow of omphacite. Ultrahigh pressure metamorphic tectonite was probably formed in the ductile shear zone during the early stage of exhumation of the ultrahigh pressure metamorphic rocks. Its kinematic indicators point to the transport direction of the UHPM slab during the early stage of exhumation.

塩化物浴からの亜鉛電析物の配向性，格子定数，炭素含有量と皮膜硬さに及ぼす有機添加剤の影響

Electrodeposits of zinc from a chloride bath without organic additives had (0002) preferred orientation at low current density and (1120) at high current density. In the presence of additives, however, the (0002) plane of preferred orientation diminished and changed to random deposits of (1010), (1011) and (1120) planes. The relative surface energy of the crystal plane and the mechanism of adsorption inhibition could explain the results of the preferred orientation to some extent. Since the crystal growth on the (0002) axis of preferred orientation was inhibited by the dominative adsorption of additives onto the plane that has the highest value for surface energy, other axes of orientation can be developed. Carbon derived from additives was codeposited to a maximum of 1wt.%, and the lattice constant for the c-axis decreased slightly but clearly with the increase in the codeposition percentage, whereas exhibited no change in the a-axis. The hardness of the deposits from the bath without additives was about 40HV 0.01. Deposits from those with additives rose to about 100HV which was ascribed to the deformation from a slight shrinkage in the direction of the c-axis.

Film orientation of RE123 prepared by chemical solution deposition

We investigated processing temperature dependencies of the preferred orientation axis of REBa/sub 2/Cu/sub 3/O/sub 7-y/ (RE123; RE=Yb, Er, Y, Gd, Sm, Nd, Pr and La) films prepared on various substrates by chemical solution deposition (CSD) using metal naphthenates. In the case of RE=Er, Y, Gd and Sm prepared on SrTiO/sub 3/, a/b-axis oriented films were obtained in a region of low temperatures, whereas there is no such temperature region for RE=Yb, Nd, Pr and La films. On the other hand, RE123 films prepared on LaAlO/sub 3/ gives a/b-axis orientation in a region of low temperatures except for Yb123 film. The (102) pole figures of these films give four high density points with four-fold symmetry, indicating that their axes are in-plane aligned. In order to confirm relationship between a/b-axis oriented growth and ionic radius of RE elements (R/sub i,RE/), we prepared rare-earth mixed Yb/sub 1-x/Er/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-y/ and Sm/sub 1-x/Nd/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-y/ films. Orientation of these films changed critically at certain average R/sub i,RE/'s.

Folding and granite emplacement inferred from structural, strain, TEM and gravimetric analyses: the case study of the Tulle antiform, SW French Massif Central

In the South Limousin (French Massif Central), the Tulle anticline is a kilometre-scale, upright, open fold which re-folds an already foliated Variscan stack of nappes. Three main granodioritic plutons associated with numerous folded dykes and boudinaged sills crop out in the core of the Tulle anticline. Microstructural study, including quartz 〈 c〉-axis petrofabrics and transmission electron microscope (TEM) analysis allows us to recognize the timing of deformation during pluton emplacement and cooling. The earliest fabric is a pre-full crystallization deformation. The second stage corresponds to a high-temperature ( ca 650°C) solid-state deformation. The last deformation is responsible for the 〈 c〉-axis preferred orientation at low temperature. Several methods of strain analysis applied in various mineral phases show that pluton emplacement is coeval to a constrictional strain. This strain is characterized by a NW–SE maximum stretching axis ( X) parallel to the Tulle anticline axis and an intermediate, NE–SW-trending, shortening axis ( Y) also responsible for large open folding of the host rocks. Gravimetric modelling allows us to determine a laccolithic shape for the plutons. Hot Stokes diapirism is ruled out and the hypothesis of granitic magma channelling through dykes is preferred. A laccolith emplacement model based on a syn-folding décollement level is proposed.

Calculation of the aligned fraction in polycrystalline samples with preferred orientation

An analytical expression is derived for the fraction of crystallites which are aligned within an angle, θ (0< θ<90°), of the sample's preferred orientation axis. The expression is given in terms of the preferred orientation parameter obtained in Rietveld refinement of the sample's diffractogram. It is useful in the study of anisotropic materials using aligned polycrystalline samples.

Application of Kohonen's self–organizing feature map algorithm to cortical maps of orientation and direction preference

Cortical maps of orientation preference in cats, ferrets and monkeys contain numerous half–rotation point singularities. Experimental data have shown that direction preference also has a smooth representation in these maps, with preferences being for the most part orthogonal to the axis of preferred orientation. As a result, the orientation singularities induce an extensive set of linear fractures in the direction map. These fractures run between and connect nearby point orientation singularities. Their existence appears to pose a puzzle for theories that postulate that cortical maps maximize continuity of representation, because the fractures could be avoided if the orientation map contained full–rotation singularities. Here we show that a dimension–reduction model of cortical map formation, which implements principles of continuity and completeness, produces an arrangement of linear direction fractures connecting point orientation singularities which is similar to that observed experimentally. We analyse the behaviour of this model and suggest reasons why the model maps contain half–rotation rather than full–rotation orientation singularities.

Human Root Dentin: Structural Anisotropy and Vickers Microhardness Isotropy

The demanding mechanical functions and the variable structure of dentin make it an invaluable material for studying the structure-mechanical function relations of a mineralized collagen-containing tissue. The mineralized collagen fibril axes in human root dentin are mainly located on the incremental plane. Within this plane there is a preferred orientation in the general root-crown direction. The apatite crystals are aligned in three dimensions within an individual collagen fibril, but this orientation does not necessarily extend to the neighboring fibrils. Crystals are also present as aggregates without any preferred orientation. The structure is therefore clearly anisotropic with respect to the collagen fibril orientation, but less so with respect to overall crystal orientation. Vickers microhardness measurements of the root dentin are essentially the same on the three orthogonal planes with respect to the incremental plane. Knoop microhardness measurements are also the same on all three orthogonal planes when the major diagonal is aligned perpendicular to the collagen fibril axis preferred orientation direction. In-plane variations of up to 20% are observed in the orthogonal direction. The material is thus isotropic in the three main directions with respect to Vickers microhardness, but anisotropic in structure. This paradoxical situation is attributed mainly to the variable modes of crystal organization.

Microstructure, composition, and optical properties of PbTiO3 thin films prepared by the sol-gel method

Crack-free and transparent PbTiO3 thin films with a perovskite structure were deposited on NaCl (100), Si(111), and fused quartz substrates by the sol-gel method. The crystal structure, morphology, domain structure, composition, and optical properties of the films were characterized by means of x-ray diffraction, transmission electron microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and optical transmission spectrum. The films on Si and fused quartz substrates exhibit slight a axis preferred orientation, while the films on NaCl substrates show slight c axis preferred orientation. From XPS analysis, no residual carbon or other impurity element was detected on the films after 3 keV Ar+ cleaning. The chemical composition of the films was found to be stoichiometric. A great amount of absorbed oxygen exists on the surfaces of the films. In the fine-grained (≈150 nm) films, no 90° domains are present in most of the grains, while some grains show lamellar 90° domains. A large number of pores exist in the films and their sizes are in the range of 5–30 nm. The packing density of the film fired at 600 °C was estimated to be about 89.3% from its optical transmission spectrum. The film has a surface roughness Δd≈37.5 nm. The refractive index of the film is approximately 2.43 at 630 nm, and the absorption edge is at 321 nm.