Bright Bars Research Articles

1D spatially chirped periodic structures: managing their spatial spectrum and investigating their near-field diffraction.

This work introduces a class of 1D spatial-frequency-modulated structures with transmittance T(x), in which the period changes along the x axis so that the corresponding spatial frequency f(x) sinusoidally alternates between two values. It is shown that T(x) generally is an almost-periodic function and has an impulsive spatial spectrum. However, we find the condition under which T(x) is a periodic function and its spatial spectrum form a lattice of impulses. When the periodicity condition is fulfilled, we call these structures as 1D spatially chirped periodic structures. These structures are characterized by two natural numbers, named as n c and n a v , and a real parameter named as frequency modulation strength (FMS). As an important special case, we define a 1D spatially chirped amplitude sinusoidal grating (SCASG) based on the transmission function of a conventional amplitude sinusoidal grating, in which the phase of conventional amplitude sinusoidal grating is replaced by desired chirped phase. Then the spatial spectrum of a 1D SCASG is investigated in detail, and it is shown that the spatial spectrum can be managed by changing the value of FMS. In other words, the grating's spectrum can be manipulated by adjusting the value of FMS. This feature might find applications in optical sharing of the incident power among different diffraction orders. Moreover, near-field diffraction from 1D SCASGs is studied by using the so-called angular (spatial) spectrum method, and Talbot distances for these gratings are determined and verified experimentally. It is shown that the intensity profiles at quartet- and octant-Talbot distances strongly depend on the values of the parameters n c and n a v . In comparison with the conventional gratings, we see some new and interesting aspects in the diffraction from 1D SCASGs. For instance, unlike the conventional gratings, in some propagation distances, the diffraction patterns possess sharp and smooth intensity bars at which the intensity is several times of the incident light beam's intensity. It is shown that the maximum intensity of these bright bars over the diffraction patterns depends on the characteristic parameters of the grating, including n c , n a v , and FMS of the grating. These intensity bars might find applications for trapping and aggregation of particles along straight lines.

Juvenile-juvenile social signalling: a case for precocial sexual selection in the collared lizard,Crotaphytus collaris(Squamata: Crotaphytidae)?

AbstractSexual selection is widespread in animals, but quite naturally studied in adults. Juvenile males in most animals are not differentiated from females and coloration is usually drab. However, there is no reason to suspect that sexual differences cannot develop before puberty, influence social interactions, and then have fitness pay-offs later in life. Juvenile collared lizards (Crotaphytus collaris (Say, 1822)) show marked dichromatism: males develop bright dorsolateral orange bars whereas females do not. These juvenile orange bars (JOB) disappear at sexual maturity, when males develop different colour traits maintained by sexual selection. We conducted field experiments with juvenile males on their developing territories in which we utilized staged intruders of juvenile males (with JOB) and juvenile females (lacking JOB) and also juvenile male intruders whose JOB were manipulated. Residents reacted significantly more aggressively toward males vs. females, and also toward males whose JOB were emphasized with paint than those whose JOB were masked by paint. These JOB are used in signalling among juveniles and we suggest the social relations established then are retained until sexual maturation the next spring (after the JOB are lost) to benefit males that previously displayed strong JOB by increased matings in the spring as sexually mature yearlings as per a phenomenon we call precocial sexual selection.

Formation mechanism and application of a three-dimensional pattern in dielectric barrier discharge system

We report a continuous three-dimensional pattern with the symmetry of D2h in dielectric barrier discharge by introducing surface discharges (SDs) with a specially designed device for the first time. From the front view, it consists of dark spots and bright bars, which correspond to the conventional volume discharge (VD) and novel VD. Different from the conventional VD, the novel VD bends through three gas gaps and discharges multiple times per half-voltage-cycle, which results from the complex interaction between the VD and SD. By using this device, three surfaces of the sample inserted between electrodes are processed simultaneously, which greatly improves the plasma processing efficiency.

The entry of a second generation at SK Enterprises: challenges and future prospects

Theoretical basis The case discussion begins with an understanding of Davis’s three-circle model. It then leads toward the key resources and challenges, by system and development stage as given by Gersick et al. (1997). After understanding the family business system, the case delves into making the students understand the circumplex model of the marital and family system. This matrix talks about the flexibility in the business structure along with cohesion in the family unit. The case then gets into the discussion about succession and the new generation joining the family business and the conflicts that may arise due to the same. It might be imperative to bring out the different forms of conflict that may arise in the family and business system. Researchers have identified three forms of conflict – task, process and relationship (Mckee, Madden, Kellermans and Eddleston, 2014). As passing the baton would take place next for this business in the case, the current generation needs to look at the future growth strategy for the business. Here, the discussion refers to the exploitation and exploration matrix given by Bergfeld and Weber (2011). Research methodology This is a primary data case. The data has been collected from SK Enterprises. Interviews were conducted to arrive at the issues and challenges discussed in the case. Case overview/synopsis This case talks about the dilemma of a first-generation entrepreneur. Jatinder Agarwal was the owner of SK Enterprises, a light-engineering firm manufacturing bright bars, engine parts and ceiling fan shafts. He had set up the business in 1984. His brother, Ramesh was helping him in the business. The business had prospered and grown from a single product manufacturing workshop in 1984 to two factories manufacturing multiple light engineering products. In 2015, the business was doing well and both Jatinder and Ramesh were excited to involve their respective sons, Pranav and Sanidh in the business after completion of their education. The case is about the challenges faced by Jatinder and Ramesh with the entry of a new generation. Jatinder and Ramesh were working in the family business with an implied structure where the business was a sole proprietorship in the name of Jatinder but the decisions were taken by both the brothers collectively. With the entry of the new generation, Jatinder had to decide how to re-organize the business and avoid conflicts in the family. He also had to take a decision regarding the future course of strategy, which would help the business grow further. Complexity academic level This case is about the dilemmas faced by a first-generation entrepreneur. The case can be taught in an “entrepreneurship” course, in a post-graduate MBA program. This case can also be taught in a family business program as part of the course on “Understanding Family Business – Managing Paradoxes” or “Building Lasting Family Business – Synergy in Vision, Values and Strategy.” This case can also be taught as part of a “business strategy” or “human resource management” in MBA or executive MBA program in the first year.

Psilotris vantasselli, a new species of goby from the tropical western Atlantic (Teleostei: Gobiidae: Gobiosomatini: Nes subgroup).

A new species of goby is described from submersible and scuba collections off Bonaire and New Providence Island, Bahamas. A molecular phylogenetic analysis of mitochondrial and nuclear genes confirms the placement of the new species within the genus Psilotris of the Nes subgroup of the Gobiosomatini. The new species is easily distinguished from congeners and morphologically similar species of Varicus by its unique coloration, which includes eight narrow, bright yellow bars on the trunk, each with a small orange spot centered on the lateral midline. In addition, the combination of the absence of scales on the head and body and the presence of modified ctenoid scales on the base of the caudal fin, branched pelvic-fin rays, and 15-16 pectoral-fin rays further differentiates the new species from other species of Psilotris and Varicus.

A new annual fish of the genus Austrolebias (Cyprinodontiformes: Rivulidae) from Rio Camaquã basin, Laguna dos Patos system, Brazilian Pampa.

A new species of Austrolebias is described from the middle course of the Rio Camaquã, Laguna dos Patos system, Rio Grande do Sul, Brazil. The new species belongs to the Austrolebias alexandri species group, which is distinguished from the remaining congeners by the presence of a dark gray pectoral fin with bright blue iridescence in males. The new species is distinguished from all remaining species of the A. alexandri species group by the following combination of characters: presence of well-defined bright blue bars on the flank in males, shorter caudal fin length in males and females, contact organs in the first three rays of the pectoral fin in males, one to two post-optic neuromasts (rarely three), basihyal width of 50% of the length, and basihyal cartilage about 50-60% of the basihyal length. The recognition of this new species belonging to the A. alexandri group endemic of the middle course of Rio Camaquã and the recent discovery of Austrolebias bagual in the same general region reinforces the claim of the middle Rio Camaquã basin as an area of endemism for annual fishes and as such, a priority area for conservation in southern Brazil.

Mach bands explained by response normalization.

Mach bands are the illusory dark and bright bars seen at the foot and knee of a luminance trapezoid. First demonstrated by Ernst Mach in the latter part of the 19th century, Mach bands are a test bed not only for models of brightness illusions but of spatial vision in general. Up until 50 years ago the dominant explanation of Mach Bands was that they were caused by lateral inhibition among retinal neurons. More recently, the dominant idea has been that Mach bands are a consequence of a visual process that generates a sparse, binary description of the image in terms of “edges” and “bars”. Another recent explanation is that Mach bands result from learned expectations about the pattern of light typically found on sharply curved surfaces. In keeping with recent multi-scale filtering accounts of brightness illusions as well as current physiology, I show however that Mach bands are most simply explained by response normalization, whereby the gains of early visual channels are adjusted on a local basis to make their responses more equal. I show that a simple one-dimensional model of response normalization explains the range of conditions under which Mach bands occur, and as importantly, the conditions under which they do not occur.

Primate area V1: largest response gain for receptive fields in the straight-ahead direction.

Although neuronal responses in behaving monkeys are typically studied while the monkey fixates straight ahead, it is known that eye position modulates responses of visual neurons. The modulation has been found to enhance neuronal responses when the receptive field is placed in the straight-ahead position for neurons receiving input from the peripheral but not the central retina. We studied the effect of eye position on the responses of V1 complex cells receiving input from the central retina (1.1-5.7° eccentricity) while minimizing the effect of fixational eye movements. Contrast response functions were obtained separately with drifting light and dark bars. Data were fit with the Naka-Rushton equation: r(c)=Rmax×c/(c+c50)+s, where r(c) is mean spike rate at contrast c, Rmax is the maximum response, c50 is the contrast that elicits half of Rmax, and s is the spontaneous activity. Contrast sensitivity as measured by c50 was not affected by eye position. For dark bars, there was a statistically significant decline in the normalized Rmax with increasing deviation from straight ahead. Data for bright bars showed a similar trend with a less rapid decline. Our results indicate that neurons representing the central retina show a bias for the straight-ahead position resulting from modulation of the response gain without an accompanying modulation of contrast sensitivity. The modulation is especially obvious for dark stimuli, which might be useful for directing attention to hazardous situations such as dark holes or shadows concealing important objects (Supplement 1: Video Abstract, Supplemental digital content 1, http://links.lww.com/WNR/A295).

FicTrac: A visual method for tracking spherical motion and generating fictive animal paths

Studying how animals interface with a virtual reality can further our understanding of how attention, learning and memory, sensory processing, and navigation are handled by the brain, at both the neurophysiological and behavioural levels. To this end, we have developed a novel vision-based tracking system, FicTrac (Fictive path Tracking software), for estimating the path an animal makes whilst rotating an air-supported sphere using only input from a standard camera and computer vision techniques. We have found that the accuracy and robustness of FicTrac outperforms a low-cost implementation of a standard optical mouse-based approach for generating fictive paths. FicTrac is simple to implement for a wide variety of experimental configurations and, importantly, is fast to execute, enabling real-time sensory feedback for behaving animals. We have used FicTrac to record the behaviour of tethered honeybees, Apis mellifera, whilst presenting visual stimuli in both open-loop and closed-loop experimental paradigms. We found that FicTrac could accurately register the fictive paths of bees as they walked towards bright green vertical bars presented on an LED arena. Using FicTrac, we have demonstrated closed-loop visual fixation in both the honeybee and the fruit fly, Drosophila melanogaster, establishing the flexibility of this system. FicTrac provides the experimenter with a simple yet adaptable system that can be combined with electrophysiological recording techniques to study the neural mechanisms of behaviour in a variety of organisms, including walking vertebrates.

Prediction of cyclic softening in a medium carbon steel during cross roll straightening

Abstract Cross roll straightening is the final operation in the production of bright steel bars. Reports of simulation of the process are sparse, the knowledge of the process being still mainly empirical. The present procedure allows to simulate the process with a reasonable CPU cost. Using a suitable set of constitutive equations, the yield stress values, obtained from tensile tests conducted on SAE 1144 bars that have been straightened under different conditions, are predicted. The predicted softening is in good agreement with the measured one. Predictions of the residual stress state agree qualitatively with experimental values from the literature.

A diffractive barcode using diffusion-dot lines to form intersected bright bars with differentorientations

Conventional barcodes can perform well for the data management of commercial products,but they cannot be used for anti-counterfeiting. Therefore, this paper will propose a newbarcode with macro- and micro-anti-counterfeiting features. A barcode image for aconventional barcode is composed of parallel bars with different widths, whereas abarcode image for the new barcode is composed of intersected bars with differentorientations. Codes for the proposed barcode are composed of bright bars alongfour possible orientations only. The proposed barcode pattern possesses manyparallel diffusion-dot lines. Because diffusion-dot lines can diffract a laser beamto form different bright bar arrangements corresponding to different codes, theproposed barcode is called a ‘diffractive barcode’ here. There are brightness andlength differences between the bars in a bright bar image and the differences aredifficult to counterfeit, so the macrofeatures can be used for anti-counterfeiting. Onthe other hand, because the appearances of the diffusion dots are special andthey cannot be reproduced, the microfeatures can be used for anti-counterfeiting.Moreover, both the encoding and decoding work of the diffractive barcode are easy.

Psychophysical measurements of referenced and unreferenced motion processing using high-resolution retinal imaging

Motion detection thresholds with a stationary frame of reference are significantly lower than unreferenced motion thresholds. To account for this, previous studies have postulated the existence of compensatory mechanisms, driven by the presence of a surround, that cancel the effects of eye movements. In the present study we used an adaptive optics scanning laser ophthalmoscope (AOSLO) to investigate the effects of retinal jitter due to fixation eye movements on referenced and unreferenced motion thresholds. The stimuli were produced by modulation of the AOSLO imaging beam, so that the absolute retinal position of targets was recorded. In Experiment 1 subjects made up/down motion judgments of a dark horizontal bar presented against a stationary 1-degree bright background. In Experiment 2 unreferenced motion thresholds were measured with isolated bright horizontal bars in otherwise complete darkness. In both experiments, AOSLO images for each trial were analyzed offline to extract retinal jitter and the retinal position of targets. For referenced motion, the results were consistent with complete compensation for eye movements by the visual system. In the unreferenced motion case eye movements adversely affected motion judgments, although there was evidence of partial compensation for such eye movements. Compensatory processes completely cancel the effect of fixation jitter for referenced motion but such compensation is partial for unreferenced motion.

Nano features of Al/Au ultrasonic bond interface observed by high resolution transmission electron microscopy

Nano-scale interfacial details of ultrasonic AlSi1 wire wedge bonding to a Au/Ni/Cu pad were investigated using high resolution transmission electron microscopy (HRTEM). The intermetallic phase Au 8Al 3 formed locally due to diffusion and reaction activated by ultrasound at the Al/Au bond interface. Multilayer sub-interfaces roughly parallel to the wire/pad interface were observed among this phase, and interdiffusional features near the Au pad resembled interference patterns, alternately dark and bright bars. Solid-state diffusion theory cannot be used to explain why such a thick compound formed within milliseconds at room temperature. The major formation of metallurgical bonds was attributed to ultrasonic cyclic vibration.

Role of synaptic and intrinsic membrane properties in short-term receptive field dynamics in cat area 17.

We examined the mechanisms through which the prolonged presentation of either a high-contrast stimulus or an artificial scotoma [equivalent to the stimulation of the receptive field (RF) surround] induces changes in the RF properties of neurons intracellularly recorded in cat primary visual cortex. Discharge and synaptic RFs were quantitatively characterized using bright and dark bars randomly flashed in various positions. Compared with the lack of stimulation (0% contrast for 15-30 s), stimulation with high-contrast sine-wave gratings (15-30 s) was followed by a strong reduction in gain and a weak but significant reduction in width of spike discharge RFs. These reductions were accompanied by a membrane potential hyperpolarization, a decrease of synaptic RF width, and varying changes of synaptic RF gain. Passive hyperpolarization by DC injection also produced significant reduction in the width and gain of discharge RF. Mimicking, in single neurons, high-contrast stimulation with high-intensity current injection also induced a membrane potential hyperpolarization, whose amplitude was correlated with discharge RF gain and width changes. Recovery from adaptation to high-contrast stimulation during the period of gray screen or scotoma presentation was associated with an increase in gain and discharge RF size. Stimulation of the RF surround with an artificial scotoma did not have any additional aftereffects over those of adaptation to a gray screen, indicating that the contraction and expansion of RF gain and size are attributable to intrinsic and synaptic mechanisms underlying adaptation and de-adaptation to strong visual stimuli.

Masking effect produced by Mach bands on the detection of narrow bars of random polarity.

Difficulties arise in measuring masking by Mach bands because very-low-contrast signals distort the bands. [J. Opt. Soc. Am. A 17, 1147 (2000).] Adding narrow luminance increments (bright bars) in the dark Mach band widens the dark band; adding decrements (dark bars) narrows the dark band, and conversely in the bright bands. Randomizing signal polarity prevents observers from using the distortion of the Mach bands as a cue to the presence of the signal. We measured (two-alternative-forced-choice) Mach bands' masking of randomly selected bright (incremental) or dark (decremental) bars. Detection was worse in both dark and bright Mach bands than on the neighboring plateaus. Separate analysis of trials containing only one polarity signal revealed 9-cycle/deg oscillations in performance as a function of location. Oscillations in the two polarities were approximately 180 degrees out of phase.

Effects of grating spatial orientation on visual evoked potentials and contrast sensitivity in multiple sclerosis.

Previous studies suggest a delay of pattern visual evoked potentials (PVEPs) in multiple sclerosis (MS) depending on grating orientation. We examined a group of 14 patients with definite MS recording PVEPs to vertical and horizontal grating and analysing latency and amplitude of P60, N70 and P100 waves. We evaluated contrast sensitivity (CS) to dark and bright bars of several spatial frequencies (SF). The aim was to evaluate the diagnostic value of evoked responses and CS in revealing involvement of cortical structures. PVEPs to 1 degrees cycle/degree (c/d) vertical bars were abnormal in 25% for P60, in 32% for N70 and in 36%, for P100; in 25%, 36% and 42% respectively at 4 c/d; as regards horizontal bars at 1 c/d we found alterations of P60, N70 and P100 in 11%, 19% and 27% respectively; at 4 c/d in 19%, 27%) and 35%. CS resulted more abnormal for vertical grating, with a maximum impairment for 3.7 c/d SF. We may conclude that the use of vertical grating in clinical routine is more reliable both for PVEPs and CS testing; in addition CS can be abnormal even with normal PVEPs: this could mean an early impairment of CS and provide useful indications about a subclinical involvement of visual cortex.

Colour vision in billfish.

Members of the billfish family are highly visual predatory teleosts inhabiting the open ocean. Little is known about their visual abilities in detail, but past studies have indicated that these fishes were likely to be monochromats. This study, however, presents evidence of two anatomically distinct cone types in billfish. The cells are arranged in a regular mosaic pattern of single and twin cones as in many fishes, and this arrangement suggests that the different cone types also show different spectral sensitivity, which is the basis for colour vision. First measurements using microspectrophotometry (MSP) revealed a peak absorption of the rod pigment at 484 nm, indicating that MSP, despite technical difficulties, will be a decisive tool in proving colour vision in these offshore fishes. When hunting, billfish such as the sailfish flash bright blue bars on their sides. This colour reflects largely in ultraviolet (UV) light at 350 nm as revealed by spectrophotometric measurements. Billfish lenses block light of wavelengths below 400 nm, presumably rendering the animal blind to the UV component of its own body colour. Interestingly, at least two prey species of billfish have lenses transmitting light in the UV waveband and are therefore likely to perceive a large fraction of the UV peak found in the blue bar of the sailfish. The possible biological significance of this finding is discussed.

Detection of incremental and decremental bars at different locations across Mach bands and related stimuli.

Two-alternative forced-choice procedures were used to measure the detectability of bright and dark bars at various locations across luminance patterns that produced Mach bands. Detection performance was significantly affected by both dark and bright Mach bands: poor detection performance was observed at locations near, but not in, the Mach bands; relatively good detection performance at locations within the Mach bands was caused by reliable changes in the width, depth, or symmetry of the bands produced by the signal bars. The changes were apparent with signals of lower luminance than that needed for detection in the plateau regions far from the bands, but, because the cues were not sufficiently reliable to allow errorless performance, unusually shaped psychometric functions were obtained.

Structure and dynamics of receptive fields in the visual cortex of the cat (area 18) and the influence of GABAergic inhibition.

Receptive fields (RFs) in the visual cortex are characterized by spatiotemporal profiles that have been described in detail for area 17 simple cells. In this study, we analyse spatial and temporal RF properties of simple and complex cells in layer II/III of area 18 of the anaesthetized adult cat, using the reverse correlation method with brief 50 ms presentations of flashing bright and dark bars. Stimuli were presented with preferred orientation as previously determined by moving bars. Simple cell RFs were characterized by spatially and temporally separable ON and OFF subfields, while in complex cells ON and OFF subfields were superimposed. To discriminate possible contributions of GABAergic inhibition to RF structure and response dynamics in area 18, we have used three-barrelled micropipettes for single cell recordings and microiontophoresis, and have documented ON and OFF responses before, during and after application of bicuculline methiodide for blockade of GABAA receptors. During blockade of GABAergic inhibition, the stimulus-induced and resting discharge frequency increased, and in about 50% of the cells both ON and OFF subfields changed significantly in space and/or time in a reversible manner. In space, blockade of inhibition widened RF subfields, whereas in time, it shortened the duration of the excitatory cell response in simple and complex cells. ON and OFF subfields separated in space and time (simple cells), or time (complex cells) became less isolated or even superimposed. The results indicate substantial local inhibitory processing contributing to spatiotemporal RF properties in layers II/III of area 18 of the cat.

The mechanisms for detecting compressively sampled gratings.

Contrast thresholds for sine-wave gratings are raised when the gratings are compressively sampled into a set of narrow bright bars on a dark background, even though this method of sampling preserves the mean luminance and contrast of the grating. Burr et al. [(1985). Vision Research, 25, 717-727] suggested threshold elevation was due to localized luminance adaptation to the sample bars, whose average peak luminance necessarily increased when fewer bars per cycle were present. Previously, we reported results using decrement-bar compressively sampled gratings (CSGs), which consist of dark sample bars on a bright background, which favoured the local luminance adaptation hypothesis (Kingdom & Rainville, 1995). Here we report experiments that suggest that this hypothesis is untenable. Using increment-bar CSGs (bright sample bars on a dark background) we found that raising background luminance while holding sample bar luminance constant reduced thresholds by as much as a factor of ten. This suggests that it is the contrast of the bars, rather than their luminance, which determines thresholds. Further experiments showed that CSG detection was facilitated by unsampled grating pedestals, and thresholds were elevated when the fundamental was physically cancelled. This implied that CSGs were detected by the same mechanisms as the unsampled gratings from which they are derived. Finally, we provide evidence for the involvement of a dynamic gain control component for increment-bar CSG detection.