Primary Angle Research Articles

How efficient coding of binocular disparity statistics in the primary visual cortex influences eye rotation strategy

Stereopsis, the ability to perceive depth, is crucial for detecting camouflaged objects and for performing tasks that require estimating distance. Understanding how our brain can so quickly estimate depth from the slightly different images from our left and right eyes, the difference of which is called binocular disparity, is still a major unsolved problem in vision research. Several previous computational studies of binocular disparity have found evidence suggesting that various properties of the primary visual cortex (V1) allow V1 to optimally process natural binocular disparity statistics. In particular, the efficient coding hypothesis suggests that the disparity tuning of V1 binocular neurons should reflect the natural range of disparities [1,2]; the cortical wiring hypothesis suggests that the orientation of ocular dominance stripes should follow the binocular disparity map [3]; and visuomotor optimization theory and the efficient coding hypothesis suggests that eye rotation strategy should be chosen to minimize binocular disparity and motor inefficiency [4,5]. In order to understand how natural binocular disparity statistics might be efficiently coded by the primary visual cortex, we constructed a simulation that links natural scene statistics to eye movements to connections between monocular neurons in V1. We generate a three-dimensional visual environment with two-point statistics and observer-object distance distribution similar to that of a natural environment; a virtual observer rotates her eyes according to the binocular version of Listing's Law to fixate on either edges of objects, centers of objects, or randomly chosen points on objects; and the resulting binocular disparities are mapped to V1 by a Schwartz conformal map fit to physiological data. The effects of two-point statistics, primary Listing's plane exorotation angle, Listing's Law coefficient, and fixation strategy can be revealed using this simulation in ways that would be very difficult (if not impossible) with experiments. For instance, to measure the effect of two-point statistics on binocular disparity statistics using this simulation, we compare the binocular disparity statistics in our more complicated three-dimensional visual environment to a visual environment with the same observer-object distance distribution but no pixel-pixel correlations. Our simulations show that the predicted ocular dominance stripe orientations and stereoscopic search zones are largely insensitive to two-point statistics of the visual environment, but very sensitive to interocular distance and eye rotation strategy. Finally, our more careful treatment of oculomotor strategy and visual environment shows that physiological oculomotor strategy cannot be explained by current visuomotor optimization theory[5]. A modified visuomotor optimization theory will likely require a better understanding of stereopsis-related processing in the visual cortex.

SU‐E‐T‐262: Comparing Linear Accelerator Gantry Angle Measurements Using An EPID and Spirit Level

Purpose: To compare the precision and consistency of measuring Linear Accelerator Gantry Angles between an Electronic Portal Imaging Device (EPID) and a Spirit Level. Methods: A cubical phantom was created by placing radio opaque markers therein at precise positions. The phantom was placed on the treatment table and aligned with the lasers in the treatment room. Using the Linear Accelerators EPID, images of the phantom were taken at the four primary gantry angles 0. 90. 180 and 270 degrees. Over a period of 1 month, 25 images were acquired at each primary gantry angle. The images of the phantoms were analyzed to calculate the gantry angle using a macro created with Image J (NIH). In the same time period, 13 gantry angle measurements were made using a spirit level at the four primary angles. Results: The average and standard deviations of gantry angles for the EPID based method at the four primary gantry angles 0, 90, 180 and 270 were −0.1(0.011), 90.0(0.011), 180.2(0.015) and 270.0(0.006) degrees respectively. In comparison, the spirit level based measurements yielded average gantry angles of 0.2 (0.03), 90.2 (0.04), 180.1(0.01) and 269.9(0.05). Results of each method similar and are within +/− 0.2 degrees of the intended angle. There is however a noteworthy difference in standard deviations between each method. Conclusion: The precision of each method yielded results within the linac specifications. Improvements to the materials and construction of the phantom could improve gantry angle accuracy by reducing positioning errors in the markers. More data needs to be acquired to determine which method is more accurate. However, the EPID gantry angle measurements strongly suggest an advantage over the spirit level results with more reproducible results as demonstrated by smaller deviations from the mean.

Inhibitory effect of biosurfactant purified from probiotic yeast against biofilm producers

Extracellular surface active agents are produced by microorganisms by reutilizing the accumulated waste or by the assimilation of low cost carbon sources or other renewable resources. Isolation, identification, and screening of probiotic yeast Saccharomyces cerevisiae to check for its ability to produce microbial surfactants was the primary angle in the present work. The second angle of the work was to study the inhibitory action of the purified biosurfactant against Candida and Bacillus biofilms or aggregates of microorganism that can adhere to inanimate objects, resulting in the spread of many infections.

Delayed delivery of intravenous gentamicin in neonates: impact of infusion variables

To investigate infusion variables that delay delivery of gentamicin through neonatal infusion lines. Infusions were set up to simulate administration of gentamicin to neonates. The primary infusion was 10% dextrose (Baxter Colleague pump). A syringe driver was used to deliver a coloured marker via the T-connection over 35 min followed by a 1 ml normal saline flush over 35 min. Effects of dextrose concentration, primary infusion rate, dose volume and angle of the primary line were investigated. Gentamicin adsorption to in-line filters (Poisdyne Neo) and administration protocols from different neonatal intensive care units were also investigated. Low dose volumes (<0.4 ml) infused into slow-flowing glucose (dextrose) lines (3.8-4 ml/h) did not mix well at the T-connection. Coloured solutions formed an upper layer that moved in a retrograde direction towards the primary infusion bag. Gentamicin did not adsorb onto Posidyne Neo filters. Comparison of infusion protocols for gentamicin administration showed that slow infusion (30 min) into slow-flowing lines (4 ml/h) containing 10% glucose gave low recovery of drug during the infusion (<30% of intended dose). Poor mixing at the T-connection appears to be the cause of delayed and/or incomplete gentamicin delivery for low dose volumes and slow infusion rates.

Prediction of spinal deformity in scoliosis from geometric torsion.

The shape of a curved line that passes through thoracic and lumbar vertebrae is often used to study spinal deformity with measurements in "auxiliary" planes that are not truly three-dimensional (3D). Here we propose a new index, the geometric torsion, which could uniquely describe the spinal deformity. In this study we assessed whether geometric torsion could be effectively used. to predict spinal deformity with the aid of multiple linear regression. Anatomical landmarks were obtained from multi-view radiographic reconstruction and used to generate 3D model of the spine and rib cage of 28 patients. Fourier series best fitted to the vertebral centroids approximated the spinal shape. For each patient, spinal deformity indices were computed. Torsion was calculated and 20 derived parameters were recorded. Torsion inputs were used in a multiple linear regression model for prediction of key spinal indices. The primary clinical Cobb angle (mainly thoracic) was predicted well, with r=0.89 using all 20 inputs of torsion or r=0.83 using just two. Torsion was also well related to the orientation of plane of maximal deformity (r=0.87). Torsion was less accurate but still significant in predicting maximal vertebral axial rotation (r=0.77). This preliminary study showed promising results for the use of geometric torsion as an alternative 3D index of spinal deformity.

Installation impact on pusher CROR engine low speed performance and noise emission characteristics

The renewed interest in the contra-rotating open rotor (CROR) as a potential highly efficient powerplant for future transport aircraft has prompted a study into the aerodynamic and aeroacoustic performance of this type of engine at DLR. With significant technical challenges related to the noise emissions and installation effects remaining to be addressed prior to realisation of a viable engine of this type, a study of a generic pusher-configuration CROR propulsion system is presented, which focuses on the impact of installation effects on the rotor aerodynamics and noise emissions. The two primary installation effects angle of attack and the pylon wake are studied utilising a high-fidelity coupled analysis based on unsteady Reynolds averaged Navier-Stokes (uRANS) simulations with the CFD solver TAU and the aeroacoustic analysis tool APSIM, both developed at DLR, highlighting the importance of these aspects on CROR in-plane loads and rotor noise emissions.

An accurate ray-based offset-to-angle transform from normal moveout uncorrected multicomponent data in a transversely isotropic medium with vertical symmetry axis

A new ray-based approach for converting multicomponent normal moveout uncorrected offset domain prestack seismic data into angles is presented. From any two-way zero-offset time sample and a given angle of incidence, the exact ray and a few neighboring rays that contribute to the given angle of incidence are traced through the medium to their corresponding source and receiver locations to compute their raypath lengths, traveltimes, and offsets. A polynomial then is fitted locally between these computed offsets and their corresponding traveltimes. Next the traveltimes for the actual offsets on data that lie within these traced rays are computed from this local polynomial fit, and their corresponding time samples are partially stacked and moved to their two-way zero-offset times. Repetition of this procedure for all zero-offset time samples and for all desired angles produces an angle gather. The procedure allows computation of both primary (P-P) and mode-converted (P-SV) angle gathers. Also, by calculating the exact raypath length, an accurate geometric spreading compensation can be computed and applied to these gathers. By using the methodology for a horizontally stratified transversely isotopic medium with a vertical symmetry axis (a VTI medium), it is possible to extract a much more accurate angle-domain response from the ray-based method than is possible from a traditional NMO-based method. Accuracy out to large angles for both primary and mode-converted reflection suggests that this ray-based transform potentially could be used in a multicomponent prestack waveform inversion scheme.

Influence of plane angle on the life of complex mills

Mills are commonly used in the manufacture of complex railroad components. Durability is the most important requirement imposed on mills. The life of any tool depends on many factors. Among these, the tooth geometry of the mill is of particular interest. In the present work, we consider the influence of the primary plane angle ϕ on the life of complex end mills. We conduct a series of experiments, in the light of existing theoretical data. At the same cutting depth t and supply s z per tooth, the thickness a declines with decrease in the primary

Anterior Segment Optical Coherence Tomography in Glaucoma Diagnostics: is Fourier- or Time-domain more useful?

Several new methods based on evolving technologies were introduced in the last decades to enhance and facilitate anterior segment diagnostics in glaucoma. Nowadays, in addition to conventional slit lamp biomicroscopy and gonioscopy, ultrasound biomicroscopy (UBM) and recently anterior segment optical coherence tomography (AS-OCT) are considered to be valuable and indispensable tools especially for patients with primary and secondary angle closure glaucomas. In the early 1990s the AS-OCT was introduced for cornea and glaucoma diagnosis [1]. In contrast to UBM, AS-OCT is a noncontact, high resolution imaging technique which is fast and optimal for noncompliant patients or even children [2] and has been used to image a variety of anatomic ocular structures in glaucoma patients such as filtering bleb, anterior chamber angle, episcleral and intracameral shunts, posterior chamber and iris. An optimal AS-OCT is not yet available, since each module has its own advantages and limitations, making it increasingly difficult to choose among them.

Gonioscopy after phacoemulsification in eyes with primary angle- closure glaucoma

目的 观察单纯超声乳化吸出术治疗伴有白内障的闭角型青光眼手术前后前房角的改变.方法单纯用白内障超声乳化吸出后房人工晶状体植入术治疗闭角型青光眼并发白内障16例(25眼).术前术后常规做视力、裂隙灯显微镜、非接触眼压计检查、前房深度检查及Coldmann前房角镜检查.随访3～18月.结果前房角镜检查:16例(25眼)术前前房角关闭粘连＜1/4圆周者4眼,1/4～1/2圆周者7眼,3/4圆周者5眼,＞3/4圆周者9眼.术后前房角均有增宽,前房角关闭及周边虹膜前粘连范围减小,部分患眼前房角重新开放,其中前房角全部开放12眼,仍存1/4～1/2圆周前房角粘连4眼,小于1/4圆周前房角粘连9眼.随访3～18月未见前房角关闭粘连范围扩大.术后视力均有不同程度提高,前房深度增加,眼压正常.结论超声乳化吸出术治疗闭角型青光眼伴白内障术后前房角增宽或开放,原关闭粘连范围减小,眼压正常,效果良好。

Rosenhain and Sturney revisited: The ‘tear’ chip in cutting interpreted in terms of modern ductile fracture mechanics

Rosenhain and Sturney in 1925 identified the ‘tear’ chip, in addition to the well-known types of chip found in metal cutting, namely continuous with or without a built-up edge and discontinuous. Tear chips occur at deep uncut chip thicknesses and, since their formation results in undesirable surface finish, they have been largely ignored in subsequent analyses of machining. A recent paper by Atkins shows that metal cutting is from the class of ductile fracture problems where there is complete plastic collapse in the formation of the chip. It was demonstrated that incorporation of significant work of surface separation (ductile fracture toughness), in analyses of machining with continuous chip formation, explains many features of metal cutting which traditional ‘plasticity and friction only’ treatments cannot, in particular why the primary shear plane angle is material dependent. It also explained why finite element simulations of machining have to employ a ‘separation criterion’ at the tool tip. The new model is extended in this paper to predict quantitatively the conditions under which the tear chip forms. The production of other well-known types of chip is also considered, and the results are applied to diagrams relating combinations of tool rake angle and uncut chip thickness at which different types of chip are formed. It is demonstrated that the analysis has general applicability to the cutting of other materials such as plastics and wood for which similar diagrams exist.

Primary Malignant Cerebellopontine Angle Melanoma Presenting as a Presumed Meningioma: Case Report and Review of the Literature

Primary Malignant Cerebellopontine Angle Melanoma Presenting as a Presumed Meningioma: Case Report and Review of the Literature

Nondestructive Angle-resolved X-ray Depth Profiling: Interpretation of Angle-resolved Profiles Using a Monte Carlo Approach.

A technique has been developed for the interpretation of composition-depth profiles from angle-resolved X-ray data using a Monte Carlo electron scattering simulation. This is a nondestructive depth profiling procedure. Software has been developed that uses a Monte Carlo scattering simulation to generate the signal intensity from a multilayer sample for any combination of primary beam angle of incidence and take-off angle to the X-ray detector. An interactive C++ application uses this simulation to interpret measured angle-resolved depth profiles. The method has been tested using a custom-made Ag/Al "staircase" sample containing two layers each of Ag and Al. Using the technique, it is possible to quantify the composition-depth profile for the two- and three-layer "steps" of the sample. Qualitative information may be gained about the four-layer area of the sample.

Secondary ion mass spectrometry round-robin study of relative sensitivity factors in gallium arsenide

Round-robin studies on relative sensitivity factors (RSFs) in secondary ion mass spectrometry (SIMS) were conducted using bulk GaAs samples uniformly doped with various impurity elements. A total of 31 laboratories participated in two round-robins. More than 30 sets of relative ion intensities were obtained for B, Si, Cr, Mn, Fe, Cu, Zn, In and Te in GaAs. The RSFs for both positive and negative ions were derived for several types of SIMS instruments. The effect of primary ion incident angle was examined using quadrupole-based instruments and found to be the determining factor of the instrumental dependence of RSF. © 1998 John Wiley & Sons, Ltd.

Profiling Shallow As Implants with Low-energy Cs Bombardment on a Modified Cameca IMS-4f

The inability to decouple primary ion beam energy and incidence angle in Cameca-type magnetic sector SIMS instruments makes profiling shallow As implants (≥20 keV), using typical Cs + bombardment conditions and negative secondary ion detection, problematic. A Cameca IMS-4f has been modified to lower the Cs+ primary beam impact energy by concomitant decreases in primary ion beam energy and sample potential. Evaluation of the instrument's performance after modification shows about a 35% improvement in depth resolution as defined by the decay length, λ, of a 20 keV As implant profile. This is accompanied by a decrease in useful yield, resulting from the lower sample potential, of about a factor of eight. Comparison of Cameca IMSD-4f data from a 5 keV As implant with data obtained on a quadrupol-based instrument suggests that the Cameca's fixed incidence angle at low energy is the limiting factor to further improvements in depth resolution. Nevertheless, the ease and relatively low cost of modification makes this an attractive approach to increasing the range and flexibility of existing Cameca SIMS instruments.

Original papers: Large bimedial rectus recession (6.5 mm or more) in the management of large-angle esotropia

A total of 101 patients (total group) with primary large angle esotropia who had primary bimedial rectus recession (BMR) of 6.5 mm or more were reviewed in a retrospective study. The average pre-operative size of the deviation was 63.5 prism diopters (PD) for near and 58.2 PD for distance. Of these, 26 patients (group I) attended for one post-operative visit only. The remaining 75 patients (group II) were followed for an average period of 17.7 months.Among group II patients there was an average shift in the post-operative deviation towards divergence consisting of-6.4 PD for near and-5.5 PD for distance. The alignment (deviation of 10 PD or below) rate in the first postoperative visit was 31.7%; undercorrection was 60.4% and overcorrection was 7.9%. At the end of the period of follow-up the above rates were 40%, 42.7%, and 17.3% respectively without further surgery. This increase in the overcorrection rate was solely derived from the initially aligned patients. Amblyopia and/or poor fixation were found to be of significance in the production of overcorrection. There was no direct relationship between the age of surgery, duration of follow-up or the degree of the BMR and the rate of correction.Among group II patients, post-operative ocular movements analysis revealed limitation of adduction of-0.5 to-0.75 (out of scale 0 to-4.00) in 22.7% (17/75) and-1.00 to-1.50 in 6.7% (5/75). None had more than-1.5 limitation of adduction.Large BMR is an acceptable surgical modality for the management of large angle esotropia. It has approximately 50% alignment rate. Slight undercorrection is recommended especially in the presence of significant amblyopia and/or poor fixation. No significant limitation of adduction was encountered.

Triple corner reflector antenna and its performance in H-plane

An experimental investigation of a novel corner reflector antenna with improved performance is reported. The corner reflector antenna has been structurally modified by attaching two more reflector elements. The parameters such as the primary corner angle, position, width and angle of the secondary elements have significant effects on the H-plane radiation characteristics of the antenna. Certain symmetric configurations of this triple corner reflector (TCR) antenna provide sharp beams with a gain of the order of 3 dB over that of the conventional corner reflector (CR) antenna.

Argon laser iridoplasty in chronic angle closure glaucoma.

This study evaluated the effect of argon laser iridoplasty (ALI) on 11 eyes with primary chronic angle closure glaucoma (CACG). All eyes had an intraocular pressure greater than 20 mmHg despite maximum medical therapy and were followed up for six months after ALI. Iridoplasty successfully opened at least half of the angle in all eyes, maximally reducing the intraocular pressure (IOP) in all eyes in the first week (paired t test p < 0.002). At three months, the IOP in 7 eyes were medically controlled while 4 eyes required trabeculectomy. The results at six months showed no further changes. Iridoplasty may be useful for lowering IOP in CACG and avoiding the need for surgery for up to six months in 64% of the eyes studied.

Toroidally Shaped Hopg Crystals as Strongly Focusing Bragg Reflectors of Characteristic X-Ray Tube Radiation for Edxrf Analysis

The characteristic 17.441 keV Mo-Kα tube line yields an exceedingly strong reflection at a Bragg angle of 6.0710 on Highly Oriented Pyrolytic Graphite (IIOPG). Using doubly bent toroidally shaped crystals we were able to concentrate the characteristic radiation from a Mo anode fine focus tube onto a small focal spot area of about 1 mm. FWHM diameter, as was observed by an X-Ray sensitive CCD. The radiation of the Mo anode fine focus tube is emitted at a take-off angle of 60 into a total solid angle with an aperture of 120. About 90 percent of this primary radiation solid angle can be used for the desired Bragg reflection on the designed toroidal crystal surface. This feature ensures the high beam intensity needed for special excitation problems.

Reconstruction of LSI Microstructures from Secondary Electron Intensity Profiles

A best-fitting method and a slope-integrating method are proposed for the reconstruction of ISI (large scale integrated circuit) microstructures from secondary electron intensity profiles. In the former method, a rounded edge profile of the photoresist pattern is reconstructed by best-fitting the analytical secondary electron intensity profile for an assumed edge model to the experimental secondary electron intensity profile. The model is a hyperbola with fitting parameters which approximates the cross section of the photoresist pattern. In the latter method, the rounded edge profile is reconstructed by integrating the slope obtained, considering the dependence of the secondary electron yield on the primary electron incidence angle to the specimen