Modulation Of Orientation Research Articles

A Mini‐OSCE for Formative Assessment of Diagnostic and Radiographic Skills at a Dental College in India

The objective structured clinical examination (OSCE) is being widely used for assessment of skills in dental education around the world. In India, OSCE awareness is rising, and a few exploratory attempts have been made in its implementation. This article describes use of a five-station mini-OSCE for formative assessment of dental diagnostic and radiographic skills in an undergraduate curriculum. Besides gaining experience in OSCEs, the purpose of this project was to study their validity, objectivity, feasibility, acceptability to students and faculty, and impact on student performance. The mini-OSCE was found to be a fairly valid and reliable tool for formative assessment, though it required more planning, preparation, and resources than other means of assessment. A specially developed orientation module improved its feasibility. The nineteen students perceived it to be a meaningful examination and a fair method due to uniformity of tasks and time allocation; they found the scoring to be transparent and objective. The specific and immediate feedback received was appreciated by both students and faculty members.

The Nature of the Dietary Protein Impacts the Tissue-to-Diet 15N Discrimination Factors in Laboratory Rats

Due to the existence of isotope effects on some metabolic pathways of amino acid and protein metabolism, animal tissues are 15N-enriched relative to their dietary nitrogen sources and this 15N enrichment varies among different tissues and metabolic pools. The magnitude of the tissue-to-diet discrimination (Δ15N) has also been shown to depend on dietary factors. Since dietary protein sources affect amino acid and protein metabolism, we hypothesized that they would impact this discrimination factor, with selective effects at the tissue level. To test this hypothesis, we investigated in rats the influence of a milk or soy protein-based diet on Δ15N in various nitrogen fractions (urea, protein and non-protein fractions) of blood and tissues, focusing on visceral tissues. Regardless of the diet, the different protein fractions of blood and tissues were generally 15N-enriched relative to their non-protein fraction and to the diet (Δ15N>0), with large variations in the Δ15N between tissue proteins. Δ15N values were markedly lower in tissue proteins of rats fed milk proteins compared to those fed soy proteins, in all sampled tissues except in the intestine, and the amplitude of Δ15N differences between diets differed between tissues. Both between-tissue and between-diet Δ15N differences are probably related to modulations of the relative orientation of dietary and endogenous amino acids in the different metabolic pathways. More specifically, the smaller Δ15N values observed in tissue proteins with milk than soy dietary protein may be due to a slightly more direct channeling of dietary amino acids for tissue protein renewal and to a lower recycling of amino acids through fractionating pathways. In conclusion, the present data indicate that natural Δ15N of tissue are sensitive markers of the specific subtle regional modifications of the protein and amino acid metabolism induced by the protein dietary source.

Orientation gradient detection exhibits variable coupling between first- and second-stage filtering mechanisms

We investigated sensitivity to orientation modulation using visual stimuli with bandpass filtered noise carriers. We characterized the relationship between the spatial parameters of the modulator and the carrier using a 2-AFC detection task. The relationship between these two parameters is potentially informative of the underlying coupling between first- and second-stage filtering mechanisms, which, in turn, may bear on the interrelationship between striate and extrastriate cortical processing. Our previous experiments on analogous motion stimuli found an optimum sensitivity when the ratio of the carrier and modulator spatial frequency parameters (r) was approximately ten. The current results do not exhibit an optimum sensitivity at a given value of the ratio r. Previous experiments involving second-order modulation sensitivity show an inconsistent range of estimates of optimum sensitivity at values of r between 5 and 50. Our results, using a complementary approach, confirm these discrepancies, demonstrating that the coupling between carrier and modulator frequency parameters depends on a number of stimulus-specific factors, such as contrast sensitivity, stimulus eccentricity, and absolute values of the carrier and modulator spatial frequency parameters. We show that these observations are true for a stimulus limited in eccentricity and that this orientation-modulated stimulus does not exhibit scale invariance. Such processing can not be modeled by a generic filter-rectify-filter model.

Capacity Analysis For Orthogonal Halftone Orientation Modulation Channels

Halftone dot orientation modulation has recently been proposed as a method for data hiding in printed images. Extraction of data embedded with halftone orientation modulation is accomplished by computing, from the scanned hardcopy image, detection statistics that uniquely identify the embedded orientation. From a communications perspective, this data hiding setup forms an interesting class of channels with dot orientation as input and a vector of statistics as the output. This paper derives capacity expressions for these channels that allow for numerical evaluation of the capacity. Results provide significant insight for orientation modulation based print-scan resilient data hiding: the capacity varies significantly as a function of the image graylevel and experimentally observed error free data rates closely mirror the variation in capacity.

Modulation of Heme Orientation and Binding by a Single Residue in Catalase HPII of Escherichia coli

Heme-containing catalases have been extensively studied, revealing the roles of many residues, the existence of two heme orientations, flipped 180° relative to one another along the propionate-vinyl axis, and the presence of both heme b and heme d. The focus of this report is a residue, situated adjacent to the vinyl groups of the heme at the entrance of the lateral channel, with an unusual main chain geometry that is conserved in all catalase structures so far determined. In Escherichia coli catalase HPII, the residue is Ile274, and replacing it with Gly, Ala, and Val, found at the same location in other catalases, results in a reduction in catalytic efficiency, a reduced intensity of the Soret absorbance band, and a mixture of heme orientations and species. The reduced turnover rates and higher H(2)O(2) concentrations required to attain equivalent reaction velocities are explained in terms of less efficient containment of substrate H(2)O(2) in the heme cavity arising from easier escape through the more open entrance to the lateral channel created by the smaller side chains of Gly and Ala. Inserting a Cys at position 274 resulted in the heme being covalently linked to the protein through a Cys-vinyl bond that is hypersensitive to X-ray irradiation being largely degraded within seconds of exposure to the X-ray beam. Two heme orientations, flipped along the propionate-vinyl axis, are found in the Ala, Val, and Cys variants.

Human primary visual cortex (V1) is selective for second-order spatial frequency.

A variety of cues can differentiate objects from their surrounds. These include "first-order" cues such as luminance modulations and "second-order" cues involving modulations of orientation and contrast. Human sensitivity to first-order modulations is well described by a computational model involving spatially localized filters that are selective for orientation and spatial frequency (SF). It is widely held that first-order modulations are represented by the firing rates of simple and complex cells ("first-order" neurons) in primary visual cortex (V1) that, likewise, have spatially localized receptive fields that are selective for orientation- and SF. Human sensitivity to second-order modulations is well described by a filter-rectify-filter (FRF) model, with first- and second-order filters selective for orientation and SF. However, little is known about how neuronal activity in visual cortex represents second-order modulations. We tested the FRF model by using an functional (f)MRI-adaptation protocol to characterize the selectivity of activity in visual cortex to second-order, orientation-defined gratings of two different SFs. fMRI responses throughout early visual cortex exhibited selective adaptation to these stimuli. The low-SF grating was a more effective adapter than the high-SF grating, incompatible with the FRF model. To explain the results, we extended the FRF model by incorporating normalization, yielding a filter-rectify-normalize-filter model, in which normalization enhances selectivity for second-order SF but only for low spatial frequencies. We conclude that neurons in human visual cortex are selective for second-order SF, that normalization (surround suppression) contributes to this selectivity, and that the selectivity in higher visual areas is simply fed forward from V1.

Spectral preference and temporal modulation of photic orientation by Colorado potato beetle on a servosphere

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), is a diurnal insect that strongly relies on visual cues to guide its walk. In the present study, we investigated the orientation behavior of non-diapausing walking CPB in response to emissive colors produced by light emitting diodes (LEDs) in a dual choice arena adapted to a servosphere, where the only illumination available came from the photo-stimuli. Our results demonstrate that CPB show positive phototactic behavior when stimulated with different wavelengths of light; they preferred to orient towards white (420–775 nm), ultraviolet (UV) (351 nm), blue (472 nm), green (570 nm), yellow (585 nm), orange (590 nm), and red (660 nm) over darkness when both alternatives were offered, but no orientation responses were elicited by infrared (940 nm). Both males and females preferred yellow and green over other colors, but did not show any particular preference between them, thus correlating with their preference for wavelengths reflected by vegetation. Sexual differences were noted in that male CPB preferred white over either red or UV, whereas female CPB did not show any preferences when offered these colors. Female CPB preferred UV and blue over red, whereas males showed no preferences when these colors were offered. Colorado potato beetles turned at higher angles and performed more tortuous walks in complete darkness and when infrared vs. darkness were offered compared with the rest of the colored lights. Both sexes preferred continuous over pulsed yellow light. Colorado potato beetles subjected to pulsed yellow light showed a temporal alteration of their walking performance by walking less, slower, and turning at a higher rate. The results are discussed with regard to the role of color in the CPB attraction to host plants and conspecifics as well as the role of intermittent photic stimuli in their orientation behavior. The information provided here provides a basis for the improvement of trapping devices for detection and survey of incipient or invasive CPB, and development of alternate control strategies for this important pest of potatoes and other solanaceous crops.

Design and Development of Screw-Drive In-Pipe Robot

The design and development of a screw-drive in-pipe robot is presented. The robot is composed of power-driving module, walking orientation module, universal joints, and accessories. The application of automatic spring structure on the robot improves its adaptability. The robot is able to move smoothly in the vertical, inclined, or horizontal pipelines, or even when the cross-section of the pipe is not strictly circular. The calculation formulae of robot walking speed and motor driving torque are derived in this paper. According to the geometries at the bend and the motion constraints, the robot turning capacity and turning condition are also analyzed. The vertical, bend, and other tests are performed on the experimental prototype, demonstrating that the screw-drive in-pipe robot provides sufficient tractive forces and good maneuverability and adaptability.

High Capacity Color Barcodes: Per Channel Data Encoding via Orientation Modulation in Elliptical Dot Arrays

We present a new high capacity color barcode. The barcode we propose uses the cyan, magenta, and yellow (C,M,Y) colorant separations available in color printers and enables high capacity by independently encoding data in each of these separations. In each colorant channel, payload data is conveyed by using a periodic array of elliptically shaped dots whose individual orientations are modulated to encode the data. The orientation based data encoding provides beneficial robustness against printer and scanner tone variations. The overall color barcode is obtained when these color separations are printed in overlay as is common in color printing. A reader recovers the barcode data from a conventional color scan of the barcode, using red, green, and blue (R,G,B) channels complementary, respectively, to the print C, M, and Y channels. For each channel, first the periodic arrangement of dots is exploited at the reader to enable synchronization by compensating for both global rotation/scaling in scanning and local distortion in printing. To overcome the color interference resulting from colorant absorptions in noncomplementary scanner channels, we propose a novel interference minimizing data encoding approach and a statistical channel model (at the reader) that captures the characteristics of the interference, enabling more accurate data recovery. We also employ an error correction methodology that effectively utilizes the channel model. The experimental results show that the proposed method works well, offering (error-free) operational rates that are comparable to or better than the highest capacity barcodes known in the literature.

Contributions of orientation and spatial frequency modulations in the perception of slanted surfaces

Contributions of orientation and spatial frequency modulations in the perception of slanted surfaces

A role for L‐α‐lysophosphatidylinositol and GPR55 in the modulation of migration, orientation and polarization of human breast cancer cells

Increased circulating levels of L-alpha-lysophosphatidylinositol (LPI) are associated with cancer and LPI is a potent, ligand for the G-protein-coupled receptor GPR55. Here we have assessed the modulation of breast cancer cell migration, orientation and polarization by LPI and GPR55. Quantitative RT-PCR was used to measure GPR55 expression in breast cancer cell lines. Cell migration and invasion were measured using a Boyden chamber chemotaxis assay and Cultrex invasion assay, respectively. Cell polarization and orientation in response to the microenvironment were measured using slides containing nanometric grooves. GPR55 expression was detected in the highly metastatic MDA-MB-231 breast cancer cell line. In these cells, LPI stimulated binding of [(35)S]GTPgammaS to cell membranes (pEC(50) 6.47 +/- 0.45) and significantly enhanced cell chemotaxis towards serum. MCF-7 cells expressed low levels of GPR55 and did not migrate or invade towards serum factors. When GPR55 was over-expressed in MCF-7 cells, serum induced a robust migratory and invasive response, which was further enhanced by LPI and prevented by siRNA to GPR55. The physical microenvironment has been identified as a key factor in determining breast tumour cell metastatic fate. LPI endowed MDA-MB-231 cells with the capacity to detect shallow (40 nm deep) grooved slides and induced marked cancer cell polarization on both flat and grooved surfaces. LPI and GPR55 play a role in the modulation of migration, orientation and polarization of breast cancer cells in response to the tumour microenvironment.

Modulation of Density and Orientation of Amphiphilic DNA on Phospholipid Membranes. II. Vesicles

In the present series of papers, we describe the results of a systematic study on the anchoring of cholesterol-tagged oligonucleotides to phospholipid bilayers followed by membrane-assisted hybridization of the complementary strand in solution. This paper compares the behavior of two cholesteryl modified oligonucleotides, differing in the architecture and hydrophobicity of the lipophilic moiety, in the self-aggregation, hybridization, and insertion in phospholipid vesicle membranes. We have focused our attention on a singly substituted derivative (SC-ON(1)) and a multicholesterol (MC-ON(1)) derivative, where the cholesteryl units are inserted at the desired positions along a noncoupling T-sequence. The self-aggregation properties in solution are also explicitly taken into account and evaluated as competitive with respect to the adsorption at fluid or solid interfaces and to hybridization with the complementary ON(2) sequence. By exploring a wide range of ON derivative concentrations, different peculiar scenarios emerge for different hydrophobicity of the amphiphilic DNA guest molecules on the vesicles, in terms of distribution and conformation of the single strand and consequent coupling properties with the complementary strand in solution.

Modulation of Density and Orientation of Amphiphilic DNA Anchored to Phospholipid Membranes. I. Supported Lipid Bilayers

In the present series of papers, we describe the results of a systematic study on the anchoring of cholesterol-tagged oligonucleotides to phospholipids bilayers followed by membrane-assisted hybridization of the complementary strand in solution. This paper describes the anchoring of novel cholesterol-modified DNA-18mers in supported lipid bilayers (SLB) of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine: we compared the behavior of two anchoring functionalities differing in the number of cholesterol units and in the length of a spacer group. Quartz Crystal Microbalance with impedance monitoring (QCM-Z) measurements showed that both oligonucleotides insert into the bilayer membrane through cholesterol anchoring; however, dramatic differences, in terms of surface organization and thickness, are found as the number of anchoring units increases. In the case of multiple cholesterol units, a peculiar three-regimes concentration dependence was revealed and correlated to the effective size of the adsorbing units. Interestingly, for high oligonucleotide concentration, the adsorption process was rationalized in terms of a compaction model of amphiphilic DNA molecules. QCM-Z temperature cycles of the SLB-anchored double strands provided clear evidence for reversible hybridization at the bilayer interface.

Orientation Modulation for Data Hiding in Clustered-Dot Halftone Prints

We present a new framework for data hiding in images printed with clustered dot halftones. Our application scenario, like other hardcopy embedding methods, encounters fundamental challenges due to extreme bilevel quantization inherent in halftoning, the stringent requirements of image fidelity, and other unavoidable printing and scanning distortions. To overcome these challenges, while still allowing for automated extraction of the embedded data and a high embedding capacity, we propose a number of innovations. First, we perform the embedding jointly with the halftoning by employing an analytical halftone threshold function that allows steering of the halftone spot orientation within each halftone cell based upon embedded data. In this process, image fidelity is emphasized and, if necessary, the capability to recover individual data values is sacrificed resulting in unavoidable erasures and errors. To overcome these and other sources of errors, we propose a suitable data detection and error control methodology based upon a statistical representation for the print-scan channel that effectively models the channel dependence upon the cover image gray-level. To combat the geometric distortion inherent in the print-scan process, we exploit the periodic halftone structure to recover from global scaling and rotation and propose a novel decision directed synchronization technique that counters locally varying printing distortion. Experimental results demonstrate the power of the proposed framework: we achieve high operational rates while preserving halftone image quality.

Orientation- and frequency-modulated textures at low depths of modulation are processed by off-orientation and off-frequency texture mechanisms

Intuitively it may seem likely that orientation-modulated (OM) and frequency-modulated (FM) textures are processed utilizing the first-order channels that are most responsive to the first-order (luminance) information contained in the textures. This assumption would imply that the detection or segmentation of OM or FM textures is accomplished by second-order mechanisms that receive their first-order input from neurons tuned to either the center, or to the peaks in the orientation and spatial-frequency distribution of the texture. Here we show that at low depths of modulation this is not the case. Using an adaptation paradigm, we show that the first-order filters involved in the perception of OM and FM textures are those which maximize the differential response between the different texture regions. Our explanation of this result is similar to that made by Regan and Beverley [J. Opt. Soc. Am. 73 (1983) 1684; J. Opt. Soc. Am. A 2 (1985) 147] for simple grating stimuli. However, we show that whereas Regan and Beverley's results could be accounted for on the basis of the tuning functions of the putative mechanisms involved, our results can be explained in terms of the characteristics of the textures themselves. Some implications of our finding are discussed.

Entamoeba histolytica Phosphoserine aminotransferase (EhPSAT): insights into the structure-function relationship

BackgroundPresence of phosphorylated Serine biosynthesis pathway upstream to the de novo cysteine biosynthesis pathway makes PSAT a crucial enzyme. Besides this, phoshoserine produced by the enzyme can also be taken up directly by cysteine synthase as a substrate. PSAT is a PLP dependent enzyme where the cofactor serves as an epicenter for functional catalysis with the active site architecture playing crucial role in optimum function of the enzyme.FindingsEhPSAT is a homodimer of molecular mass 86 kDa. To understand the structural modulations associated with pH dependent changes in functional activity of EhPSAT detailed biophysical studies were carried out. pH alterations had no significant effect on the secondary structure, cofactor orientation and oligomeric configuration of the enzyme however, pH dependent compaction in molecular dimensions was observed. Most interestingly, a direct correlation between pH induced modulation of functional activity and orientation of Trp 101 present in the active site of the enzyme was observed. Sodium halides nullified the pH induced global changes in the enzyme, however differential effect of these salts on the active site microenvironment and functional activity of the enzyme was observed.ConclusionsThe study unequivocally demonstrates that pH induced selective modification of active site microenvironment and not global change in structure or oligomeric status of the enzyme is responsible for the pH dependent change in enzymatic activity of PSAT.

Intersubband dynamics of spin polarized carriers

The intersubband (ISB) dynamics of spin orientated carriers generated in undoped quantum wells by circularly polarized interband excitations is analyzed theoretically. It is shown that short THz pulses in resonance with the lowest conduction ISB transition can be used to switch the spin orientation in a given subband without changing the total subband occupation. For longer ISB pulses a periodic modulation of the spin orientation is found. However, when the Coulomb interaction is taken into account the total subband density is typically also modulated which differs from expectations based on calculations in a three band model of non-interacting particles. The dependence on the ratio of the subband masses is discussed as well as the observability of these effects in pump-probe type measurements.

Spin-sensitive intersubband dynamics of optically generated carriers in semiconductor quantum wells

A theoretical analysis of the intersubband dynamics in undoped quantum wells is presented where spin-oriented carriers are initially generated by circularly polarized interband excitations. Subsequent resonant intersubband excitations induce Rabi rotations between the subbands resulting in a fast periodic modulation of the spin orientation in each subband. It is investigated whether pure spin modulations can be performed where the charge density of the subbands is kept constant when initially equal occupations of the two lowest conduction subbands with opposite spin orientations have been prepared. While this is the expected behavior for a three-band model of noninteracting particles it turns out that when the Coulomb interaction is taken into account the spin modulations are typically accompanied by corresponding modulations of the subband occupations. It is demonstrated that under realistic conditions it should nevertheless be feasible to realize a pure spin rotation in a given subband provided the intersubband excitations are sufficiently short or the carrier density is sufficiently low. Successive spin rotations are shown to decrease the degree of spin polarization even when spin-relaxation processes are neglected.

Robot System to Detect Line Based on ARM9

In this paper, a new system of visual detect line robot based on CMOS image sensor was designed. Meanwhile a new technology to detect line was proposed and designed. The system includes nuclear module, image collecting module, robot orientation module, electromotor drive module, man-computer interaction module and power supply module. The principle, function and implementation of every module were introduced in detail. Results of experiments show that the system has not only strong real-time capability and high accuracy, but also outstanding stabilization.

THE APPLICATION OF IMU/DGPS-SUPPORTED PHOTOGRAMMETRY

The direct measurement of exterior orientations using the integrated IMU/DGPS system proves to be an effective means.Experiments show that the accurate performance of direct orientation measurement is sufficient for forming orthophotos and small or medium scale maps.Aimed at solving the problems existent in the IMU/DGPS orientation module,this paper deals with the integrated IMU/DGPS system and the elements of IMU/DGPS-based photogrammetry and,on such a basis,emphatically analyzes the overall system calibration.