Interstrip Distance Research Articles

Design and Analysis of Photon Imaging Detector Based on Printed Circult Board Technology Cross Strip Anode

Detectors with cross strip (XS) anodes have high application value in deep space exploration, quantum communications, space astronomical telescopes, etc. In this article, a single-layer XS anode based on Printed Circult Board (PCB) technology is proposed, which can conveniently realize large-area array detection with a simple process and low cost. We theoretically studied the electron motion principle and equivalent model of the XS anode and established a model of the XS anode through the finite element method. The model allows us to determine the anode geometry, such as anode strip width, inter-strip distance, and substrate thickness, to optimize the output signal on the XS anode, thereby indirectly affecting the resolution of the detector. The optimal parameters of the detector were processed with the help of our model, such as a strip width of 110 μm, strip spacing of 550 μm, and substrate thickness of 150 μm. The model shows that the strip charge collection ratio is 1:1. Comparing model predictions with experimental measurements reveals key parameters, such as the manufacturing is convenient and simple and can provide some ideas for subsequent large-area array detector imaging.

Presowing Treatment of Winter Wheat Seeds Using Surface Discharge

Effect of products of surface discharge on seeds of soft winter wheat in electrode configurations consisting of parallel strips with interstrip distances of 5 and 10 mm is experimentally studied. In each system, the seeds are exposed for 10, 60, 120, or 180 s at voltages of 1.8, 2.1, 2.4, or 2.7 kV using sine-shaped supply voltage of electrodes with a frequency of 4.4 kHz. The seeds are placed as a single layer on a grounded surface at a distance of 10 mm from the plane of dielectric barrier. The results of treatment are assessed using morphological characteristics of three-day germs. Air flows in the gap are monitored using particle image velocimetry. It is shown that the regimes of treatment are divided into two groups. For the first group, the air flow reaches the plane in which the seeds are placed. For the second group, the air flow does not reach the plane. In the first case, germination can be stimulated at an interstrip distance of 10 mm, a voltage of 2.4–2.7 kV, and any exposure time. Germination percentage remains stable and high in all regimes.

Colloidal liquid crystal type assemblies of spheroidal polystyrene core/polyglycidol‐rich shell particles (P[S/PGL]) formed at the liquid‐silicon‐air interface by a directed dewetting process

A method for the preparation of stripe‐like monolayers of microspheroids is described. The particles were obtained from polystyrene core/polyglycidol‐rich shell microspheres by stretching poly (vinyl alcohol) films that contain embedded particles. The stretching was performed under controlled conditions at temperatures above the Tg of the films and particles. The elongated films were dissolved in water, and the microspheroids were subsequently removed and purified from the poly (vinyl alcohol). The aspect ratio (AR) of the particles, which denotes the ratio of the lengths of the longer to shorter particle axes, was determined by the film elongation. The AR values were in the range of 2.9‐7.7. Spheroidal particles with various ARs were deposited onto silicon wafers from an ethanol (EtOH) suspension. The particle concentration and volume of the suspension were the same in each experiment. Evaporation of the EtOH yielded stripes of spherical particles packed into nematic‐type colloidal crystals and assembled into monolayers. The orientation of the stripes after ethanol evaporation was perpendicular to the triphasic (silicon‐ethanol‐air) interface along the silicon substrate. The adsorbed stripes on the wafers were characterized in terms of their interstripe distance (ID), stripe width, and crystal domain size. Nematic‐type spheroid arrangements in the stripes were the dominant structure, which enabled denser packing of the particles into colloidal crystals than that allowed by the smectic‐type arrangements. Furthermore, the number of spheroids adsorbed per surface unit of the silicon wafers was similar for all ARs, but the width and frequency of the spheroid stripes adsorbed on the wafers were different.

Enhancement of Mass Transfer Through a Homogeneous Anion-Exchange Membrane in Limiting and Overlimiting Current Regimes by Screening Part of Its Surface with Nonconductive Strips

A series of anion-exchange membranes based on a Neosepta AMX-Sb homogeneous membrane (Japan) have been studied by applying parallel nonconducting strips of a 100 to 600 μm width with the interstrip distance ranging from 400 to 1900 μm. The current–voltage characteristics of the membranes and the pH of a NaCl solution (of 0.02 mol/L concentration) have been measured in the course of passing the solution through the desalination compartment of a flow-through electrodialysis cell. Two sets of membranes with a nonconducting surface fraction snc of 5 to 60%, in which the pattern steps on the surface are 1000 and 2000 μm, have been considered. It has been shown that the limiting current density, ilim, depends on the nonconducting surface fraction: ilim exceeds the corresponding value for the initial membrane in the case when snc is in the range from 5 to 20%, reaching a maximum approximately at snc = 10% followed by a decrease with the further increase in snc. At snc = 10%, the value of ilim is greater when the inhomogeneity step is 2000 μm. It has been assumed that the growth in both the limiting current density and the rate of mass transfer through the modified membranes is due to electroconvection. The obtained experimental results correlate well with known mathematical models describing ion transport in membrane systems with allowance for electroconvection in the case of homogeneous and heterogeneous membranes.

Natural variation of the expression pattern of the segmentation gene even-skipped in melanogaster

The evolution of canalized traits is a central question in evolutionary biology. Natural variation in highly conserved traits can provide clues about their evolutionary potential. Here we investigate natural variation in a conserved trait—even-skipped (eve) expression at the cellular blastoderm stage of embryonic development in Drosophila melanogaster. Expression of the pair-rule gene eve was quantitatively measured in three inbred lines derived from a natural population of D. melanogaster. One line showed marked differences in the spacing, amplitude and timing of formation of the characteristic seven-striped pattern over a 50-min period prior to the onset of gastrulation. Stripe 5 amplitude and the width of the interstripe between stripes 4 and 5 were both reduced in this line, while the interstripe distance between stripes 3 and 4 was increased. Engrailed expression in stage 10 embryos revealed a statistically significant increase in the length of parasegment 6 and a decrease in the length of parasegments 8 and 9. These changes are larger than those previously reported between D. melanogaster and D. pseudoobscura, two species that are thought to have diverged from a common ancestor over 25 million years ago. This line harbors a rare 448 bp deletion in the first intron of knirps (kni). This finding suggested that reduced Kni levels caused the deviant eve expression, and indeed we observed lower levels of Kni protein at early cycle 14A in L2 compared to the other two lines. A second of the three lines displayed an approximately 20% greater level of expression for all seven eve stripes. The three lines are each viable and fertile, and none display a segmentation defect as adults, suggesting that early-acting variation in eve expression is ameliorated by developmental buffering mechanisms acting later in development. Canalization of the segmentation pathway may reduce the fitness consequences of genetic variation, thus allowing the persistence of mutations with unexpectedly strong gene expression phenotypes.

Dissipative Structure Formation in Lipid/Lipopolymer Monolayers

We study the formation of dissipative microstructures in monomolecular films of surfactant mixtures, which occur near the three-phase contact line during Langmuir-Blodgett transfer onto a solid substrate. Continuous stripes parallel to the transfer direction are generated over several centimeters, indicating the phase separation of phospholipids and lipids with polymer head groups (lipopolymers). The systematic variation of transfer conditions revealed that transfer speed and subphase viscosity determine the stripe-to-stripe distance from several micrometers to submicrometers. To account for the physical mechanism of such pattern formation, we characterize the local film thickness and the membrane composition in the vicinity of the three-phase contact line using imaging ellipsometry and fluorescence microscopy. At relatively slow rates of substrate lifting, the power law exponent that we found between the interstripe distance and the transfer speed suggests that the stripe formation is due to spinodal decomposition, which can be accounted under the framework of the Cahn-Hilliard equation, whereas at relatively high rates, the distance is found to be proportional to the substrate speed, suggesting a dominant effect of the shear force on the stripe formation.

Coulometric Detection of Components in Liquid Plugs by Microfabricated Flow Channel and Electrode Structures

Coulometry has been demonstrated to be effective for determining the analyte in a liquid plug on the nanoliter-scale confined in a flow channel. A plug prepared in a rhombus structure of an auxiliary flow channel was placed on a thin-film three-electrode system, and hydrogen peroxide was detected as a model analyte. Under a fixed potential, the current decayed rapidly, particularly in shallow flow channels, thus making reproducible amperometric detection difficult. On the other hand, the increasing charge during coulometry facilitated the measurements. A constricted flow channel structure with an array of platinum strips for the working electrode was effective at efficiently consuming the analyte to improve the sensitivity and lower the detection limit. Compared to the case of a single short working electrode with the same area, a 4-fold increase in sensitivity was observed for the best combination of flow channel height and interstrip distance. With an increase in the generated current while maintaining the background at a low level, the detection limit was lowered from 1.3 μM to 410 nM using working electrodes with the same area. Furthermore, the processing of solutions containing L-glutamate or L-glutamate oxidase and the detection of L-glutamate were demonstrated.

Microwave Magnetic Properties of NiFe Nanostrips

The dynamic excitations in the nano-sized Permalloy arrays exhibit a strong resonance mode in ferromagnetic resonance experiments (conventional as well as network analyzer based) for the magnetic field applied in the plane of the array and along the short axis and long axis of the arrays. In network-analyzer experiments, when the dc field was applied along the short axis of the arrays, the resonance frequency goes down with an increasing interstrip distance up to 1 mum and then saturates for higher values. This behavior clearly demonstrates the presence of dipolar interactions between the individual elements, resulting in the increased resonance frequency for the smaller spacing whereas when the field is applied along the long axis, the resonance frequencies go up with increasing interstrip distance.

Cell orientation on a stripe-micropatterned surface

Stripe-micropatterned surfaces have recently been a unique tool to study cell orientation. In this paper, we prepared, by the photolithography transfer technique, stable gold (Au) micropatterns on PEG hydrogel surfaces with defined cell-resistant (PEG hydrogel) and cell-adhesive (gold microstripes) properties. 3T3 fibroblasts were cultured on Au-microstripe surfaces to observe cell adhesion and orientation. Five statistical parameters were defined and used to describe cell orientation on micropatterns. With the increase of inter-stripe distance, the orientational order parameter, the ratio of long and short axes of a cell, and the occupation fraction of cells on stripes increased gradually, whereas the spreading area of a single cell decreased. The abrupt changes of these four parameters did not happen at the same inter-distance. The adhesion ratio of a cell on Au stripes over cell spreading area did not change monotonically as a function of inter-stripe distance. The combination of the 5 statistical parameters represented well the cell orientation behaviors semi-quantitatively.

Luttinger stripes in antiferromagnets

We propose a model for the physics of stripes in antiferromagnets in which the stripes are described by Luttinger liquids hybridized with antiferromagnetic domains. Using bosonization techniques we study the model in the limit where the magnetic correlation length is larger than the inter-stripe distance and propose an explanation for the commensurate-incommensurate phase transition seen in neutron scattering in the underdoped regime of La_{2-x} Sr_x Cu O_4. The explanation is based on a phase to anti-phase domain transition in the spin configuration which is associated with the transverse motion of the stripes. Using a non-linear sigma model to describe the antiferromagnetic regions we conjecture the crystalization of the stripes in the magnetically ordered phase.

Spatio-temporal dynamics of gain-guided semiconductor laser arrays

A continuous model based on the coupled field-matter Maxwell-Bloch equations for a two-level homogeneously broadened single mode laser is developed. The model includes a Langevin formulation to model thermal and spontaneous emission noises and accounts for carrier diffusion, optical field diffraction and current spreading. Our model is flexible enough to simulate any gain-guided longitudinally uniform laser geometry and is applied to both a single-stripe and a four-stripe gain-guided semiconductor lasers where the influence of the injection current, the interstripe distance and carrier diffusion is discussed within the context of the laser dynamics. We show that an array operating with quasi-independent stripes may be achieved at low pumps and larger interstripe distances. However, as injection current is increased or the interstripe distance is decreased, the device passes through a variety of dynamical instabilities which can be analyzed in the context of lateral cavity modes. Moreover, we also show that the array dynamics is strongly influenced by carrier diffusion which may also lead to different thresholds for each element of the array.

Strip detector for short-range particles

A silicon strip detector for the coordinate determination of short range charged particles, particularly heavy ions, has been developed and investigated. The detector has 28 p +n strips made by ion implantation, the pitch is 250 μm and the interstrip distance 50 μm. The coordinates of particles incident between adjacent strips were determined by a two-dimensional amplitude analysis of the charges collected on neighboring strips. Irradiation with α-particles of 226Ra and a scanning laser beam was used. A coordinate determination accuracy better than 1 μm was obtained. In contrast to minimum ionizing particles the plasma tracks of short range particles have higher carrier densities and are located in an inhomogeneous region of the detector. The study of the charge collection times have indicated the essential role of the drift of charges in the inhomogeneous electrical field dependent on the detector geometry, the inhomogeneity of silicon and the built-in charge in the passivating oxide layer between p +n strips.

A HgI2 Microstrip Detector Based on Resistive Charge Division Readout

ABSTRACTA HgI2 linear array detector with a surface resistive layer between the readout strips has been constructed with the aim of achieving the maximum possible active detection area and a spatial resolution of ≈ 50 µm, by using an analog readout of the strip outputs and a centroid finding algorithm.This device has been developed as a high efficiency position-sensitive detector for use in a Bragg X-ray spectrometer, designed for detecting X-ray photons with energies up to ≈ 30 keV.Calculations performed by taking into account the various sources of electronic noise have allowed the optimization of the interstrip distance and resistance.Fabrication techniques and preliminary results on energy and spatial resolution are reported and discussed.

Preliminary tests on a HgI2 microstrip detector with analog readout proposed as PSD in a Bragg X-ray spectrometer

Abstract Energy and spatial resolution of a HgI2 microstrip detector with six differently spaced (0.05 mm through 1.0 mm interstrip distances) microstrips, have been tested by using a 241Am source by an analog readout and a centroid finding method, with the aim of setting up a high-efficiency position-sensitive detector with spatial resolution of ≈ 50 μm for X-ray energies of ≈ 30 keV, to inserted in a Bragg X-ray spectrometer. Analog readout was preferred with respect to improving the spatial resolution by reducing the strip size, in order to not increase the number of readout channels. The energy resolution observed at a single strip, although worse than the one reported in the literature for HgI2 spectrometers, would allow using the centroid finding technique, but only the regions below the strips appear to be active for detection, i.e. the device is equivalent to one with digital readout for position identification. Thus a microstrip detector with a surface resistive layer between the strips is proposed, in order to enhance the active region of detection and to reach the required spatial resolution. Calculations performed by taking into account the various sources of noise allow getting optimized values for the interstrip distance and resistance.

Strip detector for short-range particles

A silicon strip detector for the coordinate determination of short-range charged particles, particularly heavy ions, has been developed. The detector has 28 p/sup +/n strips made by ion implantation. The pitch is 250 mu m, and the interstrip distance is 50 mu m. The coordinates of particles incident between adjacent strips are determined by two-dimensional amplitude analysis of the charges collected on neighboring strips. Irradiation with alpha -particles of /sup 226/Ra and a scanning laser beam was used. A coordinate determination accuracy of better than 1 mu m was obtained. In contrast to the minimum ionized particle, the plasma tracks of short-range particles have higher carrier densities and were located in the inhomogeneity region of the detector. The study of the charge collection times has clarified the essential role of the drift of charges in an inhomogeneous electrical field, dependent on the detector geometry, and the inhomogeneity of silicon and built-in charge in passivating the oxide layer between the p/sup +/n strips.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evolution of alpha particle tracks in silicon strip detectors

The evolution of the plasma tracks is studied for charged particles incident between strips of a silicon strip detector. The registration of the charges collected by adjacent strips at different times allows to obtain information about behavior of the plasma track. Possibility of the alpha particle coordinate determination with accuracy better then 1 μm for the strip detector with the interstrip distance of 50 μm and the strip width of 200 μm fabricated from silicon with resistivity of 1kOhm·cm is shown. Experimental data show that drift in the nonuniform electric field is essential for the track evolution of excess carriers.

Anatomical demonstration of orientation columns in macaque monkey

AbstractIn the macaque monkey striate (primary visual) cortex, the grouping of cells into ocular dominance and orientation columns leads to the prediction of highly specific spatial patterns of cellular activity in response to stimulation by lines through one or both eyes. In the pesent paper these paterns have been examined by the 2‐deoxyuglucose autoradiographic method developed by Sokoloff and his group (Kennedy et al, '76). An anesthetized monkey was given an injection of 14C 2‐deoxyglucose and then visually stimulated for 45 minues with a large array of moving vertical stripes, with both eyes open. The 14C autoradiographs of striate cortex showed vertical bands of label extending through the full cortical thickness. Layer I was at most only lightly labelled, and layers IV b and VI wee the most dense. Layer IV c (the site of terminations of most geniculate afferents) was labelled uniformly along its length, as expected from the lack of orientation specificity of units recorded in that leyer. In the other layers the pattern seen in tangential sections was complex, consisting of swirling stripes with many bifurcations and blind endings, but with occasional more regular regions whee the stripes wee roughly parallel. Interstripe distance was rather constant, at 570 μm. Ocular dominance columns were examined in this same monkey, in the same region, by injecting one eye with 3H‐proline two weeks before the deoxyglucose experiment, and preparing a second set of autoradiographs of the sections after prolonged washing to remove the 14C‐deoxyglucose. As seen in tangential sections through layer IV c, these columns had the usual stripe‐like form, with a period of 770 μm, but were simpler in their pattern than the orientation stripes, with fewer bifurcations and less swirling. A comparison of the two sets of columns in the same area showed many intersections, but no strict or consistent relationships: angles of intersection showed a distribution that was not obviously different from that expected for any two randomly superimposed sets of lines.Another monkey was stimulated with vertical stripes, but with only one eye open. Deoxyglucose autoradiographs of tangential sections showed regular uniform rows of label in layer IV c, with all the characteristic features of eye dominance columns. In the layers above and below IV c the rows in tangential view were broken up into regularly spaced patches of label, presumably representing aggregations of cells responsive to vertically oriented stimuli. The patches showed no consistent alignment across the ocular dominance rows, and indeed no such tendency would be expected, considering the complexity of the orientation columns. This pattern of labelling is again predicted from and confirms the previous physiological studies.