Radial Bias Research Articles

Measurement of the eddy dispersion term in chromatographic columns: III. Application to new prototypes of 4.6 mm I.D. monolithic columns

We investigated the mass transfer mechanism in four research prototypes of silica monolithic columns of the second generation provided by their manufacturer (Merck KGaA, Darmstadt, Germany). The heights equivalent to a theoretical plate (HETP) of these columns were measured. The different contributions to the total HETP (longitudinal diffusion term B/uS, skeleton/eluent mass transfer resistance term CuS, and eddy diffusion term A) were determined experimentally for a non-retained (uracil) and for a retained (naphthalene) compound. We used the peak parking method to determine the longitudinal diffusion term, a recently developed accurate model of effective diffusion in silica monolithic structures to determine the skeleton/eluent mass transfer resistance term, and an accurate method of measurement of the total column HETP to determine the eddy diffusion term. The results show that the minimum plate heights of these monolithic column prototypes range between 6 and 7μm for retained analytes, three times lower than those observed for monolithic columns of the first generation. A detailed analysis of the eddy diffusion term demonstrates that the improvement observed in the column efficiency is explained in part by the 40% reduction of the domain size (which provides thinner half-height peak width) but mostly by a two-fold decrease of the radial velocity bias across the silica rods (which provides more symmetrical peaks). Yet, the rods in these columns exhibit a residual radial heterogeneity leading to a minimum HETP of only 10μm for non-retained compounds.

Impact of Earth radiation pressure on GPS position estimates

GPS satellite orbits available from the International GNSS Service (IGS) show a consistent radial bias of up to several cm and a particular pattern in the Satellite Laser Ranging (SLR) residuals, which are suggested to be related to radiation pressure mismodeling. In addition, orbit-related frequencies were identified in geodetic time series such as apparent geocenter motion and station displacements derived from GPS tracking data. A potential solution to these discrepancies is the inclusion of Earth radiation pressure (visible and infrared) modeling in the orbit determination process. This is currently not yet considered by all analysis centers contributing to the IGS final orbits. The acceleration, accounting for Earth radiation and satellite models, is introduced in this paper in the computation of a global GPS network (around 200 IGS sites) adopting the analysis strategies from the Center for Orbit Determination in Europe (CODE). Two solutions covering 9 years (2000–2008) with and without Earth radiation pressure were computed and form the basis for this study. In previous studies, it has been shown that Earth radiation pressure has a non-negligible effect on the GPS orbits, mainly in the radial component. In this paper, the effect on the along-track and cross-track components is studied in more detail. Also in this paper, it is shown that Earth radiation pressure leads to a change in the estimates of GPS ground station positions, which is systematic over large regions of the Earth. This observed “deformation” of the Earth is towards North–South and with large scale patterns that repeat six times per GPS draconitic year (350 days), reaching a magnitude of up to 1 mm. The impact of Earth radiation pressure on the geocenter and length of day estimates was also investigated, but the effect is found to be less significant as compared to the orbits and position estimates.

COSMOLOGICAL MAGNETOHYDRODYNAMIC SIMULATIONS OF CLUSTER FORMATION WITH ANISOTROPIC THERMAL CONDUCTION

(abridged) The ICM has been suggested to be buoyantly unstable in the presence of magnetic field and anisotropic thermal conduction. We perform first cosmological simulations of galaxy cluster formation that simultaneously include magnetic fields, radiative cooling and anisotropic thermal conduction. In isolated and idealized cluster models, the magnetothermal instability (MTI) tends to reorient the magnetic fields radially. Using cosmological simulations of the Santa Barbara cluster we detect radial bias in the velocity and magnetic fields. Such radial bias is consistent with either the inhomogeneous radial gas flows due to substructures or residual MTI-driven field rearangements that are expected even in the presence of turbulence. Although disentangling the two scenarios is challenging, we do not detect excess bias in the runs that include anisotropic thermal conduction. The anisotropy effect is potentially detectable via radio polarization measurements with LOFAR and SKA and future X-ray spectroscopic studies with the IXO. We demonstrate that radiative cooling boosts the amplification of the magnetic field by about two orders of magnitude beyond what is expected in the non-radiative cases. At z=0 the field is amplified by a factor of about 10^6 compared to the uniform magnetic field evolved due to the universal expansion alone. Interestingly, the runs that include both radiative cooling and anisotropic thermal conduction exhibit stronger magnetic field amplification than purely radiative runs at the off-center locations. In these runs, shallow temperature gradients away from the cluster center make the ICM neutrally buoyant. The ICM is more easily mixed in these regions and the winding up of the frozen-in magnetic field is more efficient resulting in stronger magnetic field amplification.

Visual Neglect in Horizontal and Radial Space: When Left Goes Right, Proximal Goes Distal

Hemi-spatial neglect can manifest in both the horizontal and radial spatial plane. However, debate exists over how closely the two forms of neglect relate. Here we compared the ability of a neglect patient to bisect stimuli in horizontal versus radial orientation. When oriented horizontally, single lines were mis-bisected to the right, yet when surrounded by visual distracters, the lines were mis-bisected to the left. A leftward bias also emerged when horizontally aligned strings of symbols were bisected. Unexpectedly, an analogous pattern of bias appeared when the stimuli were bisected in radial orientation; stimuli that induced a leftward bias now induced a proximal bias, while stimuli that induced a rightward bias induced a distal bias. Spontaneous reversals in radial bias have not been previously reported, and given that they were coupled with the horizontal reversals, suggest that the spatial boundaries of horizontal and radial neglect are strongly constrained by common stimulus configurations.

Desempenho de um trator agrícola equipado com pneus radiais e diagonais com três níveis de lastros líquidos

A utilização correta de pneus em tratores, tanto em relação ao seu tipo quanto à calibração de sua pressão interna, e a lastragem ideal para cada condição de carga são fatores que influem significativamente no desempenho do trator. Esta pesquisa teve como objetivo comparar o desempenho de um trator equipado com pneus radiais e com pneus diagonais, para três condições de lastragem líquida (0%, 40% e 75% de água), em três condições superficiais de um Nitossolo Vermelho distrófico (superfície firme, preparada e com cobertura vegetal de resto de milho) e em três velocidades teóricas de deslocamento (4 km h-1, 5 km h-1 e 7 km h-1), informadas no painel do trator, correspondendo às marchas B1, B2 e C1. O melhor desempenho do trator, equipado com pneu diagonal, ocorreu na condição de 75% de água nos pneus, apresentando maior velocidade de deslocamento, menor patinhagem do trator, menor consumo horário de combustível e gerando maior potência na barra de tração. Com pneus radiais, o melhor desempenho do trator ocorreu na condição de 40% de água nos pneus, proporcionando maiores velocidades de deslocamento do trator, menores patinhagens, menores consumos, horário e específico de combustível, e maiores potência e rendimento na barra de tração.

Behavioral Modeling of Power Amplifiers With Dynamic Fuzzy Neural Networks

In this letter, dynamic fuzzy neural networks (D-FNN) are applied to model power amplifiers (PAs) with memory effects. The D-FNN model implements Takagi-Sugeno-Kang (TSK) fuzzy systems based on extended radial bias function (RBF) neural networks. The parameters of the model are trained by the online self-organized learning algorithm, in which the neurons can be recruited or deleted dynamically according to their significance to system performance, and the over fitting or over training problems can be avoided. The D-FNN model is validated in our test bench in which a Doherty PA is excited with 10 MHz and 20 MHz worldwide interoperability for microwave access (WiMAX) signals. Experimental results show that the D-FNN model can give an accurate approximation to characterize the wideband PAs with memory effects.

Feeling Down: Idiom or Nature?

Feeling Down: Idiom or Nature?

Differential Diagnosis and Physical Therapy Management of a Patient With Radial Wrist Pain of 6 Months' Duration: A Case Report

Case report. Differential diagnosis for patients with radial wrist pain requires consideration of systemic disease, referred pain to the radial aspect of the wrist, and local dysfunction. The list of possible local dysfunctions should include De Quervain syndrome, as well as entrapment neuropathy of the superficial radial nerve. The patient was a 57-year-old man with right radial wrist pain of 6 months' duration. The referral diagnosis was De Quervain syndrome, but a previous course of electrophysical agents-based physical therapy management had been unsuccessful. The physical examination ruled out the cervical, shoulder, elbow, and wrist joints as possible sources of pain. In this case, the diagnosis of entrapment neuropathy of the superficial radial nerve, rather than De Quervain syndrome, was primarily based on the symptom provocation resulting from a modified radial bias upper limb nerve tension test. Based on this diagnosis, treatment consisted of active and passive exercises using neurodynamic techniques. After 1 treatment session, the patient noted changes with regard to current pain intensity and function that exceeded the minimal clinically important difference and the minimal detectable change, respectively. After only 2 treatment sessions, the patient reported a complete resolution of symptoms and a full return to work. This case report critically evaluates the diagnostic process for patients with radial wrist pain and suggests neuropathy of the superficial sensory branch of the radial nerve as a differential diagnostic option. Therapy, level 4.J Orthop Sports Phys Ther 2010;40(6):361-368, Epub 22 April 2010. doi:10.2519/jospt.2010.3210.

Radial structure of dolphin insula

The brain of the bottlenose dolphin exhibits patterns of isocortical parcellation and cytoarchitecture distinct from those seen in primates, yet cell clusters in anterior insula are comparable in scale to module-like cell arrangements found throughout isocortex in other placental mammalian species with long divergent evolutionary histories. This similarity may be due to common ancestry, or to convergence as a result of selective constraints on organization of connections within such modules. Differences reflect alternate arrangements of minicolumns, an elemental cytoarchitectonic motif of isocortex defined by radially oriented pyramidal cell arrays. In contrast with larger modular structures incorporating them, minicolumns have been highly conserved in mammalian evolution. In this study a previously validated imaging method was employed to assess verticality, D, a parameter indicating radial bias of isocortex. Photomicrographs of coronal Nissl-stained sections of dolphin anterior insular cortex were compared with sections from human brains of putatively homologous areas as well as other isocortical areas differing in modular organization. Dolphin insula exhibited a high degree of verticality consistent with conserved minicolumnar organization. Our findings indicate that a basic structural motif of isocortex is synapomorphic in a species of marine mammal exhibiting unique phylogenetically derived isocortical characteristics.

Recurrence quantification analysis of turbulent fluctuations in the plasma edge of Tokamak Chauffage Alfvén Brésilien tokamak

Recurrences are close returns of a given state in a time series, and can be used to identify different dynamical regimes and other related phenomena, being particularly suited for analyzing experimental data. In this work, we use recurrence quantification analysis to investigate dynamical patterns in scalar data series obtained from measurements of floating potential and ion saturation current at the plasma edge of the Tokamak Chauffage Alfvén Brésilien [R. M. O. Galvão et al., Plasma Phys. Controlled Fusion 43, 1181 (2001)]. We consider plasma discharges with and without the application of radial electric bias, and also with two different regimes of current ramp. Our results indicate that biasing improves confinement through destroying highly recurrent regions within the plasma column that enhance particle and heat transport.

Directional anisotropy of motion responses in retinotopic cortex

Recently, evidence has emerged for a radial orientation bias in early visual cortex. These results predict that in early visual cortex a tangential bias should be present for motion direction. We tested this prediction in a human imaging study, using a translating random dot pattern that slowly rotated its motion direction 360 degrees in cycles of 54 s. In addition, polar angle and eccentricity mapping were performed. This allowed the measurement of the BOLD response across the visual representations of the different retinotopic areas. We found that, in V1, V2, and V3, BOLD responses were consistently enhanced for centrifugal and centripetal motion, relative to tangential motion. The relative magnitude of the centrifugal and centripetal response biases changed with visual eccentricity. We found no motion direction biases in MT+. These results are in line with previously observed anisotropies in motion sensitivity across the visual field. However, the observation of radial motion biases in early visual cortex is surprising considering the evidence for a radial orientation bias. An additional experiment was performed to resolve this apparent conflict in results. The additional experiment revealed that the observed motion direction biases most likely originate from anisotropies in long range horizontal connections within visual cortex.

Radial Biases in the Processing of Motion and Motion-Defined Contours by Human Visual Cortex

Luminance gratings reportedly produce a stronger functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) signal in those parts of the retinotopic cortical maps where they are oriented radially to the point of fixation. We sought to extend this finding by examining anisotropies in the response of cortical areas V1-V3 to motion-defined contour stimuli. fMRI at 3 Tesla was used to measure the BOLD signal in the visual cortex of six human subjects. Stimuli were composed of strips of spatial white noise texture presented in an annular window. The texture in alternate strips moved in opposite directions (left-right or up-down). The strips themselves were static and tilted 45 degrees left or right from vertical. Comparison with maps of the visual field obtained from phase-encoded retinotopic analysis revealed systematic patterns of radial bias. For motion, a stronger response to horizontal was evident within V1 and along the borders between V2 and V3. For orientation, the response to leftward tilted contours was greater in left dorsal and right ventral V1-V3. Radial bias for the orientation of motion-defined contours analogous to that reported previously for luminance gratings could reflect cue-invariant processing or the operation of distinct mechanisms subject to similar anisotropies in orientation tuning. Radial bias for motion might be related to the phenomenon of "motion streaks," whereby temporal integration by the visual system introduces oriented blur along the axis of motion. We speculate that the observed forms of radial bias reflect a common underlying anisotropy in the representation of spatiotemporal image structure across the visual field.

Wind-bias correction method for narrowband sodium Doppler lidars using iodine absorption spectroscopy

We present a technique to measure the frequency chirp introduced by the laser pulse amplification process in the transmitter of the Colorado State University sodium lidar system. This chirp causes a systematic radial wind bias that must be removed from the reported wind measurements. An iodine absorption line located near the lidar operating wavelength of 589.16 nm is used for real-time monitoring and measurement of the chirp for the correction of radial wind bias. This technique has been thoroughly characterized in the laboratory and validated by field testing, facilitating simultaneous measurements of temperature and horizontal wind in the mesopause region of the atmosphere (80-105 km).

Laboratory wind tunnel testing of three commonly used saltation impact sensors

Saltation Impact Sensors (SIS) of acoustic and piezo-electric design are increasingly used to study wind erosion in the laboratory and in the field. In spite of their wide-spread use, little is known about how to compare data collected with the different types of SIS or what physical limitations may exist. We tested four each of the Saltiphone, an acoustic sensor, and four each of the Sensit and Safire, two piezo-electric sensors, for sampling efficiency in a laboratory wind tunnel. We tested each SIS with seven diameter ranges of glass beads from 53 to 420 μm diameter inclusive at wind speeds of 7.5, 10, and 15 m s−1 both with a multiplexer in the circuit and without a multiplexer in the circuit. In another wind tunnel, we tested the sensors at the three wind speeds using Kootwijkerzand drift sand with a median diameter of 299 μm and also with a simulated 100 mm h−1 rainfall. All SIS appeared to be unable to detect impacts from beads of less than 100 μm diameter with the exception of the Sensit at the 15 m s−1 wind speed. The Sensit had the lowest threshold diameter of bead to which it would respond followed closely by the Saltiphone. The Safire was insensitive to beads of less than 200 μm diameter at any wind speed. The threshold diameter tended to decrease and all instruments became more efficient at detecting impacts as the wind speed and resulting particle momentum increased. The response of the SIS efficiencies to the presence of a multiplexer in the circuit varied among the SIS types. The Sensit was least sensitive to raindrop noise and the Saltiphone was most sensitive. Within each SIS type, inter-instrument variability of sampling efficiencies raised concerns about the use of SIS to quantify saltation in the field or laboratory. Further, radial bias in the piezo-electrically based sensors would contribute additive errors as wind direction varied during an event or between events. We believe that the use of SIS in wind erosion studies should be limited to the study of temporal or spatial patterns of saltation and should not be used to quantify saltation unless the sensors have been calibrated for the specific soil and wind conditions of the event.

Discrimination of the local orientation structure of spiral Glass patterns early in human visual cortex

The local orientation structure of a visual image is fundamental to the perception of spatial form. Reports of reliable orientation-selective modulations in the pattern of fMRI activity have demonstrated the potential for investigating the representation of orientation in the human visual cortex. Orientation-selective voxel responses could arise from anisotropies in the preferred orientations of pooled neurons due to the random sampling of the cortical surface. However, it is unclear whether orientation-selective voxel responses reflect biases in the underlying distribution of neuronal orientation preference, such as the demonstrated over-representation of radial orientations (those collinear with fixation). Here, we investigated whether stimuli balanced in their radial components could evoke orientation-selective biases in voxel activity. We attempted to discriminate the sense of spiral Glass patterns (opening anti-clockwise or clockwise), in which the local orientation structure was defined by the placement of paired dots at an orientation offset from the radial. We found that information within the spatial pattern of fMRI responses in each of V1, V2, V3, and V3A/B allowed discrimination of the spiral sense with accuracies significantly above chance. This result demonstrates that orientation-selective voxel responses can arise without the influence of a radial bias. Furthermore, the finding indicates the importance of the early visual areas in representing the local orientation structure for the perception of complex spatial form.

Radial orientation and direction biases in the response of human visual cortex to kinetic contours

Event Abstract Back to Event Radial orientation and direction biases in the response of human visual cortex to kinetic contours It has recently been observed using fMRI that radial orientations produce higher activity in retinotopic regions of visual cortex (Sasaki, Y. et al. (2006) Neuron 51, 661-670). Here, we report analogous biases for: (1) the axis of motion (horizontal or vertical) of unoriented textures; (2) the orientation of ‘kinetic’ contours defined solely by the borders between strips of texture moving in opposite directions. fMRI at 3T was used to measure the BOLD signal (1.5mm cubic voxels; TR = 3s.) in the visual cortex of six human subjects viewing kinetic contour stimuli presented in 15-second blocks. Stimuli were composed of 0.6° strips of spatial white noise texture presented in an annulus 1-6° in radius. The texture in alternate strips moved in opposite directions (left-right or up-down) at 3°. The strips themselves were static and tilted 45°either left or right from vertical. A systematic pattern of bias across the cortical surface was evident in response to the axis of motion of the textures when data were pooled across the orientation of the kinetic contours. Comparison with flat maps of the visual field representation obtained from phase-encoded retinotopic analysis revealed that representations of the vertical (horizontal) meridian tended to respond more strongly to vertical (horizontal) motion. Specifically, a bias for horizontal motion was evident within V1 and along the borders between V2 and V3; a bias for vertical motion was apparent along the borders between V1 and V2 and at the extremes of V3. Pooling data across the axis of motion of the textures revealed a different pattern of bias: the response to a given orientation was stronger in the quadrants of the visual field for which contour orientation was predominantly radial. Specifically, the response to leftward (rightward) tilted gratings tended to be stronger in the dorsal part of the left (right) visual cortex and the ventral part of the right (left) visual cortex. Quantitative analysis of the variation in the proportion of voxels preferring a particular axis of motion as a function of the meridian angle of the visual field representation (in 10° bins) revealed a radial direction bias significant across subjects at p < 0.05 or better in each of areas V1, V2 and V3. Similar analysis showed a radial bias for the orientation of kinetic contours at p < 0.01 in each of these areas. Radial orientation bias likely results from a disproportionate number of neurons being tuned to radial orientations. The existence of radial biases for the orientation of kinetic (‘non-Fourier’) as well as luminance-defined (‘Fourier’) contours could reflect processing by cue-invariant orientation mechanisms or by distinct neuronal populations subject to similar anisotropies in orientation tuning. The radial bias for motion might be related to the phenomenon of ‘motion streaks’ whereby temporal integration by the visual system introduces oriented blur along the axis of motion. We speculate that all the observed forms of radial bias reflect a single underlying anisotropy in the way (Fourier and non-Fourier) stimulus energy is processed across the visual field. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Radial orientation and direction biases in the response of human visual cortex to kinetic contours. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.016 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 29 Jan 2009; Published Online: 29 Jan 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Is it what you see, or how you say it? Spatial bias in young and aged subjects

Healthy subjects demonstrate leftward bias on visual-spatial tasks. However, young controls may also be left-biased when drawing communicatively, depicting the subject of a sentence leftward on a page relative to the sentence object, that is, a spatial-syntactic, implicit task. A leftward visual-spatial bias may decrease with aging, as right-hemisphere, dorsal, visual-spatial activation may be reduced in elderly subjects performing these tasks. We compared horizontal and radial (near-far) visual spatial bias, and spatial-syntactic bias, in healthy young and aged participants. Both horizontal and radial visual-spatial bias were smaller in aged participants when explicitly, but not implicitly assessed. Mean implicit far bias was greater in aged subjects, although this varied by task. We observed less implicit, spatial-syntactic left bias in aged than young participants. These results may be consistent with relatively less dominance of right hemisphere, dorsal spatial systems with aging.

Detectability of exoplanetary transits from radial velocity surveys

Of the known transiting extra-solar planets, a few have been detected through photometric follow-up observations of radial velocity planets. Perhaps the best known of these is the transiting exoplanet HD 209458b. For hot Jupiters (periods less than ~5 days), the a priori information that 10% of these planets will transit their parent star due to the geometric transit probability leads to an estimate of the expected transit yields from radial velocity surveys. The radial velocity information can be used to construct an effective photometric follow-up strategy which will provide optimal detection of possible transits. Since the planet-harbouring stars are already known in this case, one is only limited by the photometric precision achieveable by the chosen telescope/instrument. The radial velocity modelling code presented here automatically produces a transit ephemeris for each planet dataset fitted by the program. Since the transit duration is brief compared with the fitted period, we calculate the maximum window for obtaining photometric transit observations after the radial velocity data have been obtained, generalising for eccentric orbits. We discuss a typically employed survey strategy which may contribute to a possible radial velocity bias against detection of the very hot Jupiters which have dominated the transit discoveries. Finally, we describe how these methods can be applied to current and future radial velocity surveys.

Modeling of Feature Profile Evolution in SiO2 as functions of Radial Position and Bias Voltage under Competition among Charging, Deposition, and Etching in Two-Frequency Capacitively Coupled Plasma

A feature profile evolution model of a trench in SiO2 is developed in a two-frequency capacitively coupled plasma in CF4(5%)/Ar by considering two layers, a mixing layer and an overlaying polymer layer on the basis of a database of etching yield by extending our original physical computer-aided design (CAD) tool, VicAddress (vertically integrated computer-aided design for device processes). That is, the surface exposed to fluorocarbon plasma is considered under competition among the charging of electrons and ions, the deposition of radicals, and reactive etching by ions. The feature profile is also discussed in terms of the bias amplitude and the position on the wafer.

The Radial Bias: A Different Slant on Visual Orientation Sensitivity in Human and Nonhuman Primates

It is generally assumed that sensitivity to different stimulus orientations is mapped in a globally equivalent fashion across primate visual cortex, at a spatial scale larger than that of orientation columns. However, some evidence predicts instead that radial orientations should produce higher activity than other orientations, throughout visual cortex. Here, this radial orientation bias was robustly confirmed using (1) human psychophysics, plus fMRI in (2) humans and (3) behaving monkeys. In visual cortex, fMRI activity was at least 20% higher in the retinotopic representations of polar angle which corresponded to the radial stimulus orientations (relative to tangential). In a global demonstration of this, we activated complementary retinotopic quadrants of visual cortex by simply changing stimulus orientation, without changing stimulus location in the visual field. This evidence reveals a neural link between orientation sensitivity and the cortical retinotopy, which have previously been considered independent.