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1
Shushruth, S., Jennifer M. Ichida, Jonathan B. Levitt, and Alessandra Angelucci. "Comparison of Spatial Summation Properties of Neurons in Macaque V1 and V2." Journal of Neurophysiology 102, no. 4 (October 2009): 2069–83. http://dx.doi.org/10.1152/jn.00512.2009.
Повний текст джерелаАнотація:
In visual cortex, responses to stimulation of the receptive field (RF) are modulated by simultaneous stimulation of the RF surround. The mechanisms for surround modulation remain unidentified. We previously proposed that in the primary visual cortex (V1), near surround modulation is mediated by geniculocortical and horizontal connections and far surround modulation by interareal feedback connections. To understand spatial integration in the secondary visual cortex (V2) and its underlying circuitry, we have characterized spatial summation in different V2 layers and stripe compartments and compared it to that in V1. We used grating stimuli in circular and annular apertures of different sizes to estimate the extent and sensitivity of RF and surround components in V1 and V2. V2 RFs and surrounds were twice as large as those in V1. As in V1, V2 RFs doubled in size when measured at low contrast. In both V1 and V2, surrounds were about fivefold the size of the RF and the far surround could exceed 12.5° in radius, averaging 5.5° in V1 and 9.2° in V2. The strength of surround suppression was similar in both areas. Thus although differing in spatial scale, the interactions among RF components are similar in V1 and V2, suggesting similar underlying mechanisms. As in V1, the extent of V2 horizontal connections matches that of the RF center, but is much smaller than the largest far surrounds, which likely derive from interareal feedback. In V2, we found no laminar or stripe differences in size and magnitude of surround suppression, suggesting conservation across stripes of the basic circuit for surround modulation.
2
Kingdom, Frederick A. A., Barbara Blakeslee, and Mark E. McCourt. "Brightness with and without Perceived Transparency: When Does it Make a Difference?" Perception 26, no. 4 (April 1997): 493–506. http://dx.doi.org/10.1068/p260493.
Повний текст джерелаАнотація:
Subjects matched the brightness of test patches whose inner (adjacent) surrounds appeared either as transparent overlays on a wider background that included the test patch or as regions differing in reflectance from the test patch and the outer surround. In the above configurations the luminance and spatial extent of the inner surround was identical, thus controlling for the effects of surround luminance. Configuration condition had a significant effect on test-patch brightness. In general, test-patch brightness was significantly elevated under conditions favouring the interpretation of the stimulus as including a transparent overlay. The largest effect occurred for the configuration in which the perception of transparency was supported by stereo depth cues. The brightness effect was mediated by the virtual transmittance of the transparent overlay, increasing in magnitude with decreasing transmittance. Further, the effect of transparency on brightness was greatest for test-patch luminances near to those of their immediate surrounds.
3
Eifuku, Satoshi, and Robert H. Wurtz. "Response to Motion in Extrastriate Area MSTl: Disparity Sensitivity." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2462–75. http://dx.doi.org/10.1152/jn.1999.82.5.2462.
Повний текст джерелаАнотація:
Many neurons in the lateral-ventral region of the medial superior temporal area (MSTl) have a clear center surround separation in their receptive fields. Either moving or stationary stimuli in the surround modulates the response to moving stimuli in the center, and this modulation could facilitate the perceptual segmentation of a moving object from its background. Another mechanism that could facilitate such segmentation would be sensitivity to binocular disparity in the center and surround regions of the receptive fields of these neurons. We therefore investigated the sensitivity of these MSTl neurons to disparity ranging from three degrees crossed disparity (near) to three degrees uncrossed disparity (far) applied to both the center and the surround regions. Many neurons showed clear disparity sensitivity to stimulus motion in the center of the receptive field. About [Formula: see text] of 104 neurons had a clear peak in their response, whereas another [Formula: see text] had broader tuning. Monocular stimulation abolished the tuning. The prevalence of cells broadly tuned to near and far disparity and the reversal of preferred directions at different disparities observed in MSTd were not found in MSTl. A stationary surround at zero disparity simply modulated up or down the response to moving stimuli at different disparities in the receptive field (RF) center but did not alter the disparity tuning curve. When the RF center motion was held at zero disparity and the disparity of the stationary surround was varied, some surround disparities produced greater modulation of MSTl neuron response than did others. Some neurons with different disparity preferences in center and surround responded best to the relative disparity differences between center and surround, whereas others were related to the absolute difference between center and surround. The combination of modulatory surrounds and the sensitivity to relative difference between center and surround disparity make these MSTl neurons particularly well suited for the segmentation of a moving object from the background.
4
LEVITT, JONATHAN B., and JENNIFER S. LUND. "The spatial extent over which neurons in macaque striate cortex pool visual signals." Visual Neuroscience 19, no. 4 (July 2002): 439–52. http://dx.doi.org/10.1017/s0952523802194065.
Повний текст джерелаАнотація:
We recorded activity of single units in macaque monkey primary visual cortex (V1) to define the retinotopic extent of the visual inputs that drive or modulate V1 neuron responses in parafoveal and peripheral (calcarine) cortex. We used high-contrast drifting grating stimuli to define the extent of the area over which responses summate and the extent of the receptive-field surround. We found responses of most V1 cells to summate over 1 deg, with a suppressive surround typically twice that in diameter, though for some cells (even in parafoveal V1) surrounds exceeded 13 deg in diameter. Surprisingly, we found no significant laminar differences in these dimensions or in the strength of surround suppression. We found that surround suppression in most cells arises from both the ends and sides of the receptive field. Our measures indicate that the strongest modulatory input arises from regions immediately adjacent to the excitatory summation area. These physiological measures suggest that the high-contrast summation field of V1 neurons can be accounted for by the sum of lateral geniculate nucleus (LGN) inputs offered to the local cortical column, with monosynaptic lateral connections within area V1 adding the larger dimensions of the low-contrast summation field and the near surround. Neither of these inputs suffice to explain the largest surrounds, which most likely derive from feedback from extrastriate visual areas.
5
Previc, Fred H., and Michael Donnelly. "The Effects of Visual Depth and Eccentricity on Manual Bias, Induced Motion, and Vection." Perception 22, no. 8 (August 1993): 929–45. http://dx.doi.org/10.1068/p220929.
Повний текст джерелаАнотація:
The relationship between the effects of visual-surround roll motion on compensatory manual tracking of a central display and the perceptual phenomena of induced motion and vection were investigated. To determine if manual-control biases generated in the direction of surround rotation compensate primarily for the perceived counterrotation of the central display (‘induced motion’) or the perceived counterrotation of the entire body (‘vection’), the depth and eccentricity of the visual surround were varied. In the first experiment, twelve subjects attempted to keep an unstable central display level while viewing rotating visual surrounds in three depth planes: near (∼20 cm in front of the central display), coplanar, and far (∼21 cm behind the central display). In the second experiment, twelve additional subjects viewed a rotating surround that was presented either in the full visual field (0–110 deg) or in central and peripheral regions of similar width. Manual-control biases and induced motion were shown to be closely related to one another and strongly influenced both by central and by peripheral surround motion at or beyond the plane of fixation. Vection, on the other hand, was shown to be much more dependent on peripheral visual inputs.
6
Royden, Constance S., James F. Baker, and John Allman. "Perceptions of Depth Elicited by Occluded and Shearing Motions of Random Dots." Perception 17, no. 3 (June 1988): 289–96. http://dx.doi.org/10.1068/p170289.
Повний текст джерелаАнотація:
A computer-controlled display of random dots was used to study perceptions of depth. In this display, a field of stationary random dots surrounded a rectangular area in which random dots moved with uniform velocity in a single direction. The boundaries of this rectangle did not move. When dot motion was perpendicular to the longer boundary of the rectangle (occluded motion), the rectangle seemed to be behind the stationary background surround. Motion parallel to the longer boundary of the rectangle (shearing motion) made it appear in front of the surround. The relative lengths of the sides of the rectangle determined which effect predominated. Thus, for motion perpendicular to the long axis of the rectangle the occlusion predominated and naive subjects reported that the central area seemed farther away than the surround. For shearing motion parallel to the long axis, the subjects reported that the rectangle was closer than the surround and the strength of both effects also depended on the length-to-width ratio of the rectangle. If there was occluded motion along the long axis, as the length-to-width ratio increased so did the likelihood that subjects would report seeing the rectangle behind the surround. Conversely, with shearing motion along the long axis, increasing the length-to-width ratio increased the likelihood that the rectangle would appear unambiguously in front of the surround. Some subjects integrated the two cues with the resulting perception being a rotating cylinder. The occlusion effect was stronger than the shearing effect. In fact, this ‘far’ depth effect was so powerful that it tended to override conflicting depth cues such as height in the visual field or stereopsis. The ‘near’ depth effect produced by shearing motion was definite but these other depth cues could often override it.
7
Seymour, Kiley, and Susan Wardle. "Differential orientation tuning of near and far surround suppression in human V1." Journal of Vision 17, no. 10 (August 31, 2017): 797. http://dx.doi.org/10.1167/17.10.797.
Повний текст джерела
8
Khang, Byung-Geun, and Edward A. Essock. "Apparent Relative Motion from a Checkerboard Surround." Perception 26, no. 7 (July 1997): 831–46. http://dx.doi.org/10.1068/p260831.
Повний текст джерелаАнотація:
To better understand the Ouchi illusion in which a stationary picture generates illusory relative motion, the spatial properties of the constituent elements of the rectangular checkerboard background were examined. Results of experiment 1 revealed that the largest illusion was obtained with elements of approximately 20–30 min in width and 4–6 min in height, an orientation of the constituents that was orthogonal to that of the test grating, and a phase shift of the alternate stripes that was close to 180°. In experiment 2 it was found that the illusion increased in magnitude with increasing achromatic contrast but was minimal with a pattern of high chromatic contrast near isoluminance. In experiment 3, two test patches were presented simultaneously in the checkerboard background and were varied independently in their orientation to explore whether or not their motions were perceived as coherent (common fate). Patches having identical orientations, and nearly orthogonal to the surround, were synchronized more strongly than those having reflected orientations. Hysteresis related to the gain control of spatially overlapping visual units differing in their polarity (ON/OFF) was discussed as a possible cause of this phenomenon.
9
Li, Guoteng, Chengshi Zheng, Yuxuan Ke, and Xiaodong Li. "Deep Learning-Based Acoustic Echo Cancellation for Surround Sound Systems." Applied Sciences 13, no. 3 (January 17, 2023): 1266. http://dx.doi.org/10.3390/app13031266.
Повний текст джерелаАнотація:
Surround sound systems that play back multi-channel audio signals through multiple loudspeakers can improve augmented reality, which has been widely used in many multimedia communication systems. It is common that a hand-free speech communication system suffers from the acoustic echo problem, and the echo needs to be canceled or suppressed completely. This paper proposes a deep learning-based acoustic echo cancellation (AEC) method to recover the desired near-end speech from the microphone signals in surround sound systems. The ambisonics technique was adopted to record the surround sound for reproduction. To achieve a better generalization capability against different loudspeaker layouts, the compressed complex spectra of the first-order ambisonic signals (B-format) were sent to the neural network as the input features directly instead of using the ambisonic decoded signals (D-format). Experimental results on both simulated and real acoustic environments showed the effectiveness of the proposed algorithm in surround AEC, and outperformed other competing methods in terms of the speech quality and the amount of echo reduction.
10
Raiguel, S. E., D. K. Xiao, V. L. Marcar, and G. A. Orban. "Response Latency of Macaque Area MT/V5 Neurons and Its Relationship to Stimulus Parameters." Journal of Neurophysiology 82, no. 4 (October 1, 1999): 1944–56. http://dx.doi.org/10.1152/jn.1999.82.4.1944.
Повний текст джерелаАнотація:
A total of 310 MT/V5 single cells were tested in anesthetized, paralyzed macaque monkeys with moving random-dot stimuli. At optimum stimulus parameters, latencies ranged from 35 to 325 ms with a mean of 87 ± 45 (SD) ms. By examining the relationship between latency and response levels, stimulus parameters, and stimulus selectivities, we attempted to isolate the contributions of these factors to latency and to identify delays representing intervening synapses (circuitry) and signal processing (flow of information through that circuitry). First, the relationship between stimulus parameters and latency was investigated by varying stimulus speed and direction for individual cells. Resulting changes in latencies were explainable in terms of response levels corresponding to how closely the actual stimulus matched the preferred stimulus of the cell. Second, the relationship between stimulus selectivity and latency across the population of cells was examined using the optimum speed and direction of each neuron. A weak tendency for cells tuned for slow speeds to have longer latencies was explainable by lower response rates among slower-tuned neurons. In contrast, sharper direction tuning was significantly associated with short latencies even after taking response rate into account, ( P = 0.002, ANCOVA). Accordingly, even the first 10 ms of the population response fully demonstrates direction tuning. A third study, which examined the relationship between antagonistic surrounds and latency, revealed a significant association between the strength of the surround and the latency that was independent of response levels ( P < 0.002, ANCOVA). Neurons having strong surrounds exhibited latencies averaging 20 ms longer than those with little or no surround influence, suggesting that neurons with surrounds represent a later stage in processing with one or more intervening synapses. The laminar distribution of latencies closely followed the average surround antagonism in each layer, increasing with distance from input layer IV but precisely mirroring response levels, which were highest near the input layer and gradually decreased with distance from input layer IV. Layer II proved the exception with unexpectedly shorter latencies ( P < 0.02, ANOVA) yet showing only modest response levels. The short latency and lack of strong direction tuning in layer II is consistent with input from the superior colliculus. Finally, experiments with static stimuli showed that latency does not vary with response rate for such stimuli, suggesting a fundamentally different mode of processing than that for a moving stimulus.
11
Wacker, R. T., M. A. Bullimore, H. Dornbusch, K. Pruett, I. L. Bailey, and A. Hall. "Illumination Characteristics of Mobility Lights." Journal of Visual Impairment & Blindness 84, no. 9 (November 1990): 461–64. http://dx.doi.org/10.1177/0145482x9008400904.
Повний текст джерелаАнотація:
The authors measured the light-distribution patterns and the decay in light output of three mobility lights that visually impaired persons can use for night travel: the Wide-Angle Mobility Light (WAML), the Streamlight, and the Mag-Lite. The WAML had a wide beam with a medium-bright central region. The beam of the Streamlight had the brightest central region and a moderately wide surround of lower illumination. The Mag-Lite had the narrowest light distribution about a bright central spot. Both the Streamlight and the Mag-Lite maintained near-maximum brightness before undergoing rapid decay, while the WAML showed a gradual decay changing from near-maximum brightness to near extinction in almost a linear fashion 40 to 80 minutes after being turned on.
12
Porzucek, Sławomir, Monika Łój, Karolina Matwij, and Wojciech Matwij. "Modern Geodetic Measurement Techniques in Gravimetric Studies on the Example of Gypsum Karst in the Siesławice Region." E3S Web of Conferences 35 (2018): 03002. http://dx.doi.org/10.1051/e3sconf/20183503002.
Повний текст джерелаАнотація:
In the region of Siesławice (near Busko-Zdrój, Poland) there are unique phenomena of gypsum karst. Atmospheric factors caused numerous gypsum outcrops, canals and underground voids. The article presents the possibility of using non-invasive gravimetric surveys supplemented with geodetic measurements to illustrate karst changes occurring around the void. The use of modern geodetic measurement techniques including terrestrial and airborne laser scanning enables to generate a digital terrain model and a three-dimensional model of voids. Gravimetric field studies allowed to map the anomalies of the gravitational field of the near-surface zone. Geodetic measurement results have made it possible to accurately determine the terrain correction that supplemented the gravimetric anomaly information. Geophysical interpretation indicate the presence of weathered rocks in the near surface zone and fractures and loosened zones located surround the karst cave.
13
Hupé, Jean-Michel, Andrew C. James, Pascal Girard, and Jean Bullier. "Response Modulations by Static Texture Surround in Area V1 of the Macaque Monkey Do Not Depend on Feedback Connections From V2." Journal of Neurophysiology 85, no. 1 (January 1, 2001): 146–63. http://dx.doi.org/10.1152/jn.2001.85.1.146.
Повний текст джерелаАнотація:
We analyzed the extracellular responses of 70 V1 neurons (recorded in 3 anesthetized macaque monkeys) to a single oriented line segment (or bar) placed within the cell classical receptive field (RF), or center of the RF. These responses could be modulated when rings of bars were placed entirely outside, but around the RF (the “near” surround region), as described in previous studies. Suppression was the main effect. The response was enhanced for 12 neurons when orthogonal bars in the surround were presented instead of bars having the same orientation as the center bar. This orientation contrast property is possibly involved in the mediation of perceptual pop-out. The enhancement was delayed compared with the onset of the response by about 40 ms. We also observed a suppression originating specifically from the flanks of the surround. This “side-inhibition,” significant for nine neurons, was delayed by about 20 ms. We tested whether these center/surround interactions in V1 depend on feedback connections from area V2. V2 was inactivated by GABA injections. We used devices made of six micropipettes to inactivate the convergent zone from V2 to V1. We could reliably inactivate a 2- to 4-mm-wide region of V2. Inactivation of V2 had no effect on the center/surround interactions of V1 neurons, even those that were delayed. Therefore the center/surround interactions of V1 neurons that might be involved in pop-out do not appear to depend on feedback connections from V2, at least in the anesthetized monkey. We conclude that these properties are probably shaped by long-range connections within V1 or depend on other feedback connections. The main effect of V2 inactivation was a decrease of the response to the single bar for about 10% of V1 neurons. The decrease was delayed by <20 ms after the response onset. Even the earliest neurons to respond could be affected by the feedback from V2. Together with the results on feedback connections from MT (previous paper), these findings show that feedback connections potentiate the responses to stimulation of the RF center and are recruited very early for the treatment of visual information.
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Reda, Ruqaa Badr, and Mukhtar Khamis Haba. "The Development of the Pronephros in Sailfin Fish Poecelia Latipinna." NeuroQuantology 20, no. 3 (March 31, 2022): 288–94. http://dx.doi.org/10.14704/nq.2022.20.3.nq22278.
Повний текст джерелаАнотація:
This study included the development of the pronephros kidney in one invasive species in Iraq, the sailfin fish Poecelia latipinna which spread in the aquatic surfaces particularly the marshes which situated in the south portion of Iraq. This study depends on the length of the embryos. The bilateral progenitor pronephric cells appear in the mesodermal plate in embryo 1.5 mm in long. In embryo 2mm in long, the histological sections showed the occurrence of the progenitor cells with the precursors of the blood cells near the notochord and dorsal aorta. The undifferentiated pronephric tubules formed in the embryo 4mm in long and the pronephric kidney started to surround with connective tissue cells. In embryo 5mm in long, the histological sections appeared that the pronephric tissue completely surrounded by connective tissue to form capsule, the tubules differentiated to proximal and distal tubules and the glomeruli appeared as well, also the pronephric ducts were completed in this stage to fuse with the cloaca.
15
Reda, Ruqaa Badr, and Mukhtar Khamis Haba. "The Development of the Pronephros in Sailfin Fish Poecelia Latipinna." NeuroQuantology 20, no. 5 (April 30, 2022): 25–31. http://dx.doi.org/10.14704/nq.2022.20.5.nq22145.
Повний текст джерелаАнотація:
This study included the development of the pronephros kidney in one invasive species in Iraq, the sailfin fish Poecelia latipinna which spread in the aquatic surfaces particularly the marshes which situated in the south portion of Iraq. This study depends on the length of the embryos. The bilateral progenitor pronephric cells appear in the mesodermal plate in embryo 1.5 mm in long. In embryo 2mm in long, the histological sections showed the occurrence of the progenitor cells with the precursors of the blood cells near the notochord and dorsal aorta. The undifferentiated pronephric tubules formed in the embryo 4mm in long and the pronephric kidney started to surround with connective tissue cells. In embryo 5mm in long, the histological sections appeared that the pronephric tissue completely surrounded by connective tissue to form capsule, the tubules differentiated to proximal and distal tubules and the glomeruli appeared as well, also the pronephric ducts were completed in this stage to fuse with the cloaca.
16
Howard, Ian P., and Thomas Heckmann. "Circular Vection as a Function of the Relative Sizes, Distances, and Positions of Two Competing Visual Displays." Perception 18, no. 5 (October 1989): 657–65. http://dx.doi.org/10.1068/p180657.
Повний текст джерелаАнотація:
In studies where it is reported that illusory self-rotation (circular vection) is induced more by peripheral displays than by central displays, eccentricity may have been confounded with perceived relative distance and area. Experiments are reported in which the direction and magnitude of vection induced by a central display in the presence of a surround display were measured. The displays varied in relative distance and area and were presented in isolation, with one moving and one stationary display, or with both moving in opposite directions. A more distant display had more influence over vection than a near display. A central display induced vection if seen in isolation or through a ‘window’ in a stationary surrounding display. Motion of a more distant central display weakened vection induced by a nearer surrounding display moving the other way. When the two displays had the same area their effects almost cancelled. A moving central display nearer than a textured stationary surround produced vection in the same direction as the moving stimulus. This phenomenon is termed ‘contrast-motion vection’ because it is probably due to illusory motion of the surround induced by motion of the centre. Unequivocal statements about the dominance of an eccentric display over a central display cannot be made without considering the relative distances and sizes of the displays and the motion contrast between them.
17
Makus, Donald J. "(181) Effect of Mulch, Mycorrhizal Inoculation, and Surround on Late Fall Pepper Production." HortScience 40, no. 4 (July 2005): 999D—999. http://dx.doi.org/10.21273/hortsci.40.4.999d.
Повний текст джерелаАнотація:
Four week-old pepper (Capsicum annuum) cultivars Sonora Anaheim and Capistrano were transplanted on 7 Oct. 2004 into a sandy loam soil near Weslaco, Texas (lat. 26°08'N). Plants were subject to eight treatments consisting of sweet sorghum mulch, mycorrhizal (Bio Organics) inoculation, kaolin (Surround) application and their factorial combinations. Mulch was applied at 2.4 kg·m-2 and kaolin weekly at 25 kg·ha-1. Mulch applications reduced soil temperatures at 5 cm typically 8 °C during the 1200–1800 HR period of the day during the first 14 days after planting, but decreased soil temperatures to less than 2 °C by 22 Dec. Volumetric soil moisture content at 0–20 cm was initially 4% (absolute) higher in the mulch treatments during the first week after planting but deceased with time as the mulch deteriorated. Mulching increased root dry weight 70 days after transplanting. Mycorrhizal association was evaluated in four treatments, where incidence of mycorrhizal infection was “mulch + mycorrhizae” > “mycorrhizae only” = `“mulch only” » “control.” Kaolin reduced plant height, plant top fresh weight, and improved yield in both cultivars by increasing earlier flowering and, in the case of `Sonora Anaheim', reducing fruit drop caused by pepper weevil (Anthonomus eugenii). In both cultivars, mulch reduced yields and mycorrhizal inoculation gave no agronomic benefit.
18
Niu, Xiaoke, Shuman Huang, Minjie Zhu, Zhizhong Wang, and Li Shi. "Surround Modulation Properties of Tectal Neurons in Pigeons Characterized by Moving and Flashed Stimuli." Animals 12, no. 4 (February 15, 2022): 475. http://dx.doi.org/10.3390/ani12040475.
Повний текст джерелаАнотація:
Surround modulation has been abundantly studied in several mammalian brain areas, including the primary visual cortex, lateral geniculate nucleus, and superior colliculus (SC), but systematic analysis is lacking in the avian optic tectum (OT, homologous to mammal SC). Here, multi-units were recorded from pigeon (Columba livia) OT, and responses to different sizes of moving, flashed squares, and bars were compared. The statistical results showed that most tectal neurons presented suppressed responses to larger stimuli in both moving and flashed paradigms, and suppression induced by flashed squares was comparable with moving ones when the stimuli center crossed the near classical receptive field (CRF) center, which corresponded to the full surrounding condition. Correspondingly, the suppression grew weaker when the stimuli center moved across the CRF border, equivalent to partially surrounding conditions. Similarly, suppression induced by full surrounding flashed squares was more intense than by partially surrounding flashed bars. These results suggest that inhibitions performed on tectal neurons appear to be full surrounding rather than locally lateral. This study enriches the understanding of surround modulation properties of avian tectum neurons and provides possible hypotheses about the arrangement of inhibitions from other nuclei, both of which are important for clarifying the mechanism of target detection against clutter background performed by avians.
19
TROY, J. B., D. L. BOHNSACK, and L. C. DILLER. "Spatial properties of the cat X-cell receptive field as a function of mean light level." Visual Neuroscience 16, no. 6 (November 1999): 1089–104. http://dx.doi.org/10.1017/s0952523899166094.
Повний текст джерелаАнотація:
Our objective with this study was to provide a near complete characterization of how mean light level changes the spatial receptive-field properties of X-cells. Single X-cells were recorded extracellularly either from cell bodies in the retina or from their axons in the optic tract. Frequency responses of the cells at 2 Hz were measured for a set of gratings of different spatial frequencies and for a stimulus designed to probe the spatial properties of the receptive-field surround. Predicted frequency responses of a Gaussian center-surround model for the receptive field were fit simultaneously to both sets of measurements and the parameters of the model that best fit the data used to characterize the spatial properties of the receptive field. Measurements were made at a number of mean light levels for each cell and changes in receptive-field properties were characterized by changes in the parameters of the Gaussian center-surround model. The range of illuminances studied covered the bulk of the range encountered by a cat naturally and three distinct functional ranges appeared to express themselves in the data. One range corresponded to the cat's photopic range of vision. The other two ranges were where signals originating in rods dominate X-cell responses. We argue that one corresponds to the range that rod signals pass predominantly through rod bipolars en route to the X-cell, while the other is where rod signals flow predominantly through cones via gap junctions and then follow the path of cone signals to the X-cell. Among the major findings are that Weber's Law is followed throughout the photopic but not the scotopic range, that center radius expands under scotopic conditions, and that the surround is present even at the lowest scotopic levels we studied.
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Liu, Xiaotao, Bernard Vancil, Matthew Beck, and Thomas Balk. "Near-Surface Material Phases and Microstructure of Scandate Cathodes." Materials 12, no. 4 (February 20, 2019): 636. http://dx.doi.org/10.3390/ma12040636.
Повний текст джерелаАнотація:
Scandate cathodes that were fabricated using the liquid-solid process and that exhibited excellent emission performance were characterized using complementary state-of-the-art electron microscopy techniques. Sub-micron BaAl2O4 particles were observed on the surfaces and edges of tungsten particles, as seen in cross-section samples extracted from the scandate cathode surface regions. Although several BaAl2O4 particles were observed to surround smaller Sc2O3 nanoparticles, no chemical mixing of the two oxides was detected, and in fact the distinct oxide phases were separately verified by chemical analysis and also by 3D elemental tomography. Nanobeam electron diffraction confirmed that the crystal structure throughout W grains is body-centered cubic, indicating that they are metallic W and did not experience noticeable changes, even near the grain surfaces, as a result of the numerous complex chemical reactions that occur during cathode impregnation and activation. 3D reconstruction further revealed that internal Sc/Sc2O3 particles tend to exhibit a degree of correlated arrangement within a given W particle, rather than being distributed uniformly throughout. Moreover, the formation of Sc/Sc2O3 particles within W grains may arise from W surface roughening that occurs during the liquid-solid synthesis process.
21
Okubo, Kyohei, Masakazu Umezawa, and Kohei Soga. "Near Infrared Fluorescent Nanostructure Design for Organic/Inorganic Hybrid System." Biomedicines 9, no. 11 (October 30, 2021): 1583. http://dx.doi.org/10.3390/biomedicines9111583.
Повний текст джерелаАнотація:
Near infrared (NIR) light offers high transparency in biological tissue. Recent advances in NIR fluorophores including organic dyes and lanthanide-doped inorganic nanoparticles have realized the effective use of the NIR optical window for in vivo bioimaging and photodynamic therapy. The narrow energy level intervals used for electronic transition that involves NIR light, however, give rise to a need for guidelines for reducing heat emission in luminescence systems, especially in the development of organic/inorganic hybrid structures. This review presents an approach for employing the polarity and vibrational energy of ions and molecules that surround the luminescence centers for the development of such hybrid nanostructures. Multiphonon relaxation theory, formulated for dealing with heat release in ionic solids, is applied to describe the vibrational energy in organic or molecular systems, referred to as phonon in this review, and we conclude that surrounding the luminescence centers either with ions with low vibrational energy or molecules with small chemical polarity is the key to bright luminescence. NIR photoexcited phosphors and nanostructures in organic/inorganic mixed systems, designed based on the guidelines, for photodynamic therapy are reviewed.
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Rattanaphanee, Panarat, Watcharapong Laha, and Chontira Boonfung. "Desiccant from Cassava for Dehydration of Alcohol Vapor at Near Azeotropic Concentration." Advanced Materials Research 651 (January 2013): 126–30. http://dx.doi.org/10.4028/www.scientific.net/amr.651.126.
Повний текст джерелаАнотація:
Wet cassava pulp is generated in large quantity during a production of cassava starch. Major utilization of the pulp is in animal feed manufacturing. During a period of low demand, this material could accumulate and decompose causing air pollution in areas surround the starch factories. This research used biomass desiccant prepared from cassava pulp in a bench-scale packed-bed adsorption system to study the dehydration of ethanol and n-propanol vapor at concentration near their azeotropic points. The sorption capacity was found to be 0.053 and 0.119 gwater/gdesiccant for ethanol and iso-propanol at concentration of 80 %(w/w) and 0.109 gwater/gdesiccant for n-propanol at concentration of 65 %(w/w). Alcoholic solutions with concentration higher than their aqueous azeotropic points, which could not be achieved by normal fractional distillation, were obtained in all the experiments. This study elucidates that cassava pulp could be value-added, and water adsorption using cassava-derived desiccant could be an alternative technique for production of high purity alcohols.
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DACEY, DENNIS M., JOANNA D. CROOK, and ORIN S. PACKER. "Distinct synaptic mechanisms create parallel S-ON and S-OFF color opponent pathways in the primate retina." Visual Neuroscience 31, no. 2 (July 29, 2013): 139–51. http://dx.doi.org/10.1017/s0952523813000230.
Повний текст джерелаАнотація:
AbstractAnatomical and physiological approaches are beginning to reveal the synaptic origins of parallel ON- and OFF-pathway retinal circuits for the transmission of short (S-) wavelength sensitive cone signals in the primate retina. Anatomical data suggest that synaptic output from S-cones is largely segregated; central elements of synaptic triads arise almost exclusively from the “blue-cone” bipolar cell, a presumed ON bipolar, whereas triad-associated contacts derive primarily from the “flat” midget bipolar cell, a hyperpolarizing, OFF bipolar. Similarly, horizontal cell connectivity is also segregated, with only the H2 cell-type receiving numerous contacts from S-cones. Negative feedback from long (L-) and middle (M-) wavelength sensitive cones via the H2 horizontal cells elicits an antagonistic surround in S-cones demonstrating that S versus L + M or “blue-yellow” opponency is first established in the S-cone. However, the S-cone output utilizes distinct synaptic mechanisms to create color opponency at the ganglion cell level. The blue-cone bipolar cell is presynaptic to the small bistratified, “blue-ON” ganglion cell. S versus L + M cone opponency arises postsynaptically by converging S-ON and LM-OFF excitatory bipolar inputs to the ganglion cell’s bistratified dendritic tree. The common L + M cone surrounds of the parallel S-ON and LM-OFF cone bipolar inputs appear to cancel resulting in “blue-yellow” antagonism without center-surround spatial opponency. By contrast, in midget ganglion cells, opponency arises by the differential weighting of cone inputs to the receptive field center versus surround. In the macula, the “private-line” connection from a midget ganglion cell to a single cone predicts that S versus L + M opponency is transmitted from the S-cone to the S-OFF midget bipolar and ganglion cell. Beyond the macula, OFF-midget ganglion cell dendritic trees enlarge and collect additional input from multiple L and M cones. Thus S-OFF opponency via the midget pathway would be expected to become more complex in the near retinal periphery as L and/or M and S cone inputs sum to the receptive field center. An important goal for further investigation will be to explore the hypothesis that distinct bistratified S-ON versus midget S-OFF retinal circuits are the substrates for human psychophysical detection mechanisms attributed to S-ON versus S-OFF perceptual channels.
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BALTENKOV, A. S., V. K. DOLMATOV, and S. T. MANSON. "MULTICENTERED THEORY OF MOLECULAR PHOTOIONIZATION." Surface Review and Letters 09, no. 02 (April 2002): 1143–48. http://dx.doi.org/10.1142/s0218625x02003421.
Повний текст джерелаАнотація:
A new theory for near-threshold photoionization of inner electrons of atoms confined in multicentered atomic formations, e.g. molecules or clusters, is developed. The formulas for fixed-in-space molecules have been derived. The interaction of the photoelectron in the continuum with atoms that surround the atom being ionized, is replaced by the suitable boundary conditions imposed on the photoelectron wave function at the location of nuclei of these atoms in the molecule. The general formulas derived are used to calculate photoelectron angular distributions of diatomic molecules. The calculated data are in qualitative agreement with experimental data and results of other calculations.
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YU, HSIN-HAO, and MARCELLO G. P. ROSA. "Uniformity and diversity of response properties of neurons in the primary visual cortex: Selectivity for orientation, direction of motion, and stimulus size from center to far periphery." Visual Neuroscience 31, no. 1 (October 25, 2013): 85–98. http://dx.doi.org/10.1017/s0952523813000448.
Повний текст джерелаАнотація:
AbstractAlthough the primary visual cortex (V1) is one of the most extensively studied areas of the primate brain, very little is known about how the far periphery of visual space is represented in this area. We characterized the physiological response properties of V1 neurons in anaesthetized marmoset monkeys, using high-contrast drifting gratings. Comparisons were made between cells with receptive fields located in three regions of V1, defined by eccentricity: central (3–5°), near peripheral (5–15°), and far peripheral (>50°). We found that orientation selectivity of individual cells was similar from the center to the far periphery. Nonetheless, the proportion of orientation-selective neurons was higher in central visual field representation than in the peripheral representations. In addition, there were similar proportions of cells representing all orientations, with the exception of the representation of the far periphery, where we detected a bias favoring near-horizontal orientations. The proportions of direction-selective cells were similar throughout V1. When the center/surround organization of the receptive fields was tested with gratings with varying diameters, we found that the population of neurons that was suppressed by large gratings was smaller in the far periphery, although the strength of suppression in these cells tended to be stronger. In addition, the ratio between the diameters of the excitatory centers and suppressive surrounds was similar across the entire visual field. These results suggest that, superimposed on the broad uniformity of V1, there are subtle physiological differences, which indicate that spatial information is processed differently in the central versus far peripheral visual fields.
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Pan, Ye, Oyewole Oyekoya, and Anthony Steed. "A Surround Video Capture and Presentation System for Preservation of Eye-Gaze in Teleconferencing Applications." Presence: Teleoperators and Virtual Environments 24, no. 1 (February 1, 2015): 24–43. http://dx.doi.org/10.1162/pres_a_00213.
Повний текст джерелаАнотація:
We propose a new video conferencing system that uses an array of cameras to capture a remote user and then show the video of that person on a spherical display. This telepresence system has two key advantages: (i) it can capture a near-correct image for any potential observer viewing direction because the cameras surround the user horizontally; and (ii) with view-dependent graphical representation on the spherical display, it is possible to tell where the remote user is looking from any viewpoint, whereas flat displays are visible only from the front. As a result, the display can more faithfully represent the gaze of the remote user. We evaluate this system by measuring the ability of observers to accurately judge which targets the actor is gazing at in two experiments. Results from the first experiment demonstrate the effectiveness of the camera array and spherical display system, in that it allows observers at multiple observing positions to accurately tell at which targets the remote user is looking. The second experiment further compared a spherical display with a planar display and provided detailed reasons for the improvement of our system in conveying gaze. We found two linear models for predicting the distortion introduced by misalignment of capturing cameras and the observer's viewing angles in video conferencing systems. Those models might be able to enable a correction for this distortion in future display configurations.
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Shushruth, S., L. Nurminen, M. Bijanzadeh, J. M. Ichida, S. Vanni, and A. Angelucci. "Different Orientation Tuning of Near- and Far-Surround Suppression in Macaque Primary Visual Cortex Mirrors Their Tuning in Human Perception." Journal of Neuroscience 33, no. 1 (January 2, 2013): 106–19. http://dx.doi.org/10.1523/jneurosci.2518-12.2013.
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Van Aelst, A. C., E. S. Pierson, J. L. Van Went, and M. Cresti. "Ultrastructural changes of Arabidopsis thaliana pollen during final maturation and rehydration." Zygote 1, no. 2 (May 1993): 173–79. http://dx.doi.org/10.1017/s096719940000143x.
Повний текст джерелаАнотація:
SummarySeveral ultrastructural changes occur during dehydration and subsequent rehydration of Arabidopsis thaliana pollen. The cytoplasmic channels, present in the outer part of the intine of the mature, dehydrating pollen grain, degenerate and develop into electron-dense inclusions. At the same time a large quantity of electron-dense material is deposited in the cavities of the exine. A large number of vesicles is produced in the vegetative cell, and they become predominantly located in the peripheral region near the intine. Starch of amyloplasts is consumed and the lipid bodies which originally surround the sperm cells become randomly distributed. In addition, the individual lipid bodies become enveloped by single rough endoplasmic reticulum cisterns.
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Mittal, Hemant, Ashutosh Sharma, and Ajay Gairola. "Investigation of pedestrian-level wind environment near two high-rise buildings in different arrangements." Advances in Structural Engineering 22, no. 12 (May 20, 2019): 2620–34. http://dx.doi.org/10.1177/1369433219849832.
Повний текст джерелаАнотація:
The presence of buildings that surround the wind environment adversely affects at the pedestrian level. The present study investigates the effect of different arrangement of two buildings on wind flow structure and modification of wind speed conditions at the pedestrian level. The investigation was carried out for parallel, tandem, and staggered arrangement of two buildings using computational fluid dynamics simulations. The wind tunnel experiments were conducted to validate the computational fluid dynamics results. The computational fluid dynamics simulations were performed using the standard [Formula: see text] model with LK modification and revised closure coefficients. Different flow features such as skew-symmetric vortex structure for parallel arrangement, reattachment of shear layer on the surfaces of the downstream building for tandem arrangement, and deviation of wake region behind the upstream building to leftward of the flow direction for staggered arrangement were observed. It was observed that the strong wind conditions were mostly affected by tandem and parallel location of the twin buildings. The results of numerical simulation obtained using the modified SKE model were found to be in good agreement with the experimental results.
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Anantharamaiah, K. R., and Farhad Yusef-Zadeh. "A Survey of Radio Recombination Line Emission From the Galactic Center Region." Symposium - International Astronomical Union 136 (1989): 159–66. http://dx.doi.org/10.1017/s0074180900186474.
Повний текст джерелаАнотація:
Preliminary results of a systematic survey of H78α, H91α and H98β emission from the inner 40′ of the Galactic center region are presented. This region consists of two prominent continuum features, the Sgr A complex and the radio continuum Arc. In spite of much nonthermal emission arising from these two features, we detected strong line emission with large line widths in more than half of the observed 130 positions. Many of the detections are new, in particular −50 km s−1 ionized gas linking the Sgr A complex and the Arc, β line emission from GO.1+0.08 (the arched filaments), and α line emission from the loop-like structures which surround the non-thermal filaments near G0.2−0.05. We find that much of the detected lines are probably associated with the −50 km s−1 and the 20 km s−1 molecular clouds, known to lie near the Galactic center. We present line profiles of a number of Galactic center sources including Sgr B1, Sgr C and Sgr D.
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NOTHDURFT, HANS-CHRISTOPH, JACK L. GALLANT, and DAVID C. VAN ESSEN. "Response profiles to texture border patterns in area V1." Visual Neuroscience 17, no. 3 (May 2000): 421–36. http://dx.doi.org/10.1017/s0952523800173092.
Повний текст джерелаАнотація:
Cells in area V1 of the anesthetized macaque monkey were stimulated with large texture patterns composed of homogeneous regions of line elements (texels) with different orientations. To human observers, such patterns appear to segregate, with the percept of sharp boundaries between texture regions. Our objective was to investigate whether the boundaries are reflected in the responses of single cells in V1. We measured responses to individual texels at different distances from the texture border. For each cell, patterns of optimally or orthogonally orientated texels were adjusted so that only one texel fell into the receptive field and all other texels fell in the visually unresponsive regions outside. In 37 out of 156 neurons tested (24%), texels immediately adjacent to a texture border evoked reliably larger responses than identical texels farther away from the border. In 17 neurons (11%), responses to texels near the border were relatively reduced. Border enhancement effects were generally stronger than border attenuation effects. When tested with four different border configurations (two global orientations and two edge polarities), many cells showed reliable effects for only one or two configurations, consistent with cells encoding information about the orientation of the texture border or its location with respect to the segmented region. Across the sample, enhancement effects were similar for all texture borders. Modulation by the texture surround was predominantly suppressive; even the responses near texture borders were smaller than those to a single line. We compared these results with the results of a popout test in which the line in the receptive field was surrounded by homogeneous texture fields either orthogonal or parallel to the center line. The patterns of response modulation and the temporal onset of differential responses were similar in the two tests, suggesting that the two perceptual phenomena are mediated by similar neural mechanisms.
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Muggeridge, K. J., and I. J. Jordaan. "Microstructural change in ice: III Observations from an iceberg impact zone." Journal of Glaciology 45, no. 151 (1999): 449–55. http://dx.doi.org/10.3189/s0022143000001301.
Повний текст джерелаАнотація:
AbstractDuring a full-scale iceberg-impact study conducted in July 1995 on the Labrador coast, Canada, a sample of ice was retrieved from the impacted surface of an iceberg. The sample was thin-sectioned and the observations of the contact-zone microstructure are presented in this paper.Thin sections were prepared from two slabs cut parallel to the impacted surface. In each of the thin sections taken from the impacted-surface slab, fine-grained material was found to surround parent-size grains (as observed in the second slab). A boundary between the parent grains and the grains of modified microstructure was found running approximately parallel to the impacted surface in each of the thin sections taken from the impacted-surface slab. This boundary was pronounced towards the edges of the contact zone. Lateral movement of grains outward along this boundary was observed in thin sections near the edges but not near the centre of the contact zone.The thin sections were compared to the results of medium-scale indentation tests in 1989 and 1990 from the Arctic Ocean. The same type of fine-grained material and layer formation of modified microstructure was found in the contact zones.
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Muggeridge, K. J., and I. J. Jordaan. "Microstructural change in ice: III Observations from an iceberg impact zone." Journal of Glaciology 45, no. 151 (1999): 449–55. http://dx.doi.org/10.1017/s0022143000001301.
Повний текст джерелаАнотація:
AbstractDuring a full-scale iceberg-impact study conducted in July 1995 on the Labrador coast, Canada, a sample of ice was retrieved from the impacted surface of an iceberg. The sample was thin-sectioned and the observations of the contact-zone microstructure are presented in this paper.Thin sections were prepared from two slabs cut parallel to the impacted surface. In each of the thin sections taken from the impacted-surface slab, fine-grained material was found to surround parent-size grains (as observed in the second slab). A boundary between the parent grains and the grains of modified microstructure was found running approximately parallel to the impacted surface in each of the thin sections taken from the impacted-surface slab. This boundary was pronounced towards the edges of the contact zone. Lateral movement of grains outward along this boundary was observed in thin sections near the edges but not near the centre of the contact zone.The thin sections were compared to the results of medium-scale indentation tests in 1989 and 1990 from the Arctic Ocean. The same type of fine-grained material and layer formation of modified microstructure was found in the contact zones.
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Jurečić, Denis, Jana Žiljak Gršić, Diana Bratić, and Silvio Plehati. "Separating Information on Transparent Polypropylene Labels on Packaging with Dual Properties for the Visible Spectrum and Instrumental Infrared Observation." Polymers 14, no. 24 (December 7, 2022): 5341. http://dx.doi.org/10.3390/polym14245341.
Повний текст джерелаАнотація:
Transparent linear NIR digital graphics with the intention of security information were printed on a polypropylene material. A label for expensive juices in transparent glass or plastic packaging is demonstrated. Obligatory information about the contents of the liquid was made to be read with the naked eye. The “Z” (near-infrared) information is expanded with data integrated for joint digital printing. This data does not disrupt the original, planned visual appearance of the label, “V” (visible). Although the two graphics are in the same place, the IR graphics on the label cannot be discerned with the naked eye. This brings elements of secrecy and protection against attempts to counterfeit the contents of the transparent packaging. The separation and recognition of the two pieces of information, V and Z, are achieved with a security camera in the near-infrared mode or with one of the many NIR detectors that surround us. In the article, the “VZ” algorithm for the integration of two independent graphics and the limitations set by digital printing are published. Toner properties and the method for developing the recipes for the composition of twin colorants for two spectral ranges are presented using spectroscopy.
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XIA, YINGQIU, та SCOTT NAWY. "The gap junction blockers carbenoxolone and 18β-glycyrrhetinic acid antagonize cone-driven light responses in the mouse retina". Visual Neuroscience 20, № 4 (липень 2003): 429–35. http://dx.doi.org/10.1017/s0952523803204089.
Повний текст джерелаАнотація:
Gap junctions are widely expressed throughout the retina, and play an important role in the processing of visual information. It has been proposed that horizontal cells express unpaired gap junctions, or hemichannels, in their dendrites, and that current flowing through hemichannels reduces transmembrane voltage at cone terminals, promoting the opening of Ca2+ channels near sites of transmitter release. This model predicts that pharmacological block of gap junctions should reduce the Ca2+ current at the equivalent cone voltage, thereby decreasing the postsynaptic light response. To test this prediction, and estimate the relative magnitude of this effect on third-order cells, we recorded light responses in mouse ganglion cells under photopic conditions and applied two gap junction antagonists, carbenoxolone and the structurally related 18β-glycyrrhetinic acid (GA). Both carbenoxolone and GA decreased the size of the light response to about 30% of control. Cells that were physiologically identified as ON, OFF, or ON/OFF were equally affected by carbenoxolone/GA. These gap junction blockers did not interfere with gamma-aminobutyric acid (GABA) or glutamate receptors, as they did not affect responses to direct activation of these receptors. Under control conditions, spots larger than 200 μm in diameter activated ganglion cell receptive-field surrounds. Comparing responses to small and large spots before and during carbenoxolone treatment, we found that carbenoxolone did not preferentially inhibit surround antagonism at the ganglion cell level, but instead scaled the responses to all spot sizes. Our results extend the findings of studies in lower vertebrates which showed that light responses in horizontal cells are decreased by carbenoxolone treatment, and support the idea that hemichannels in the outer retina, most likely on horizontal cells, constitute important gates that are critical for allowing light responses to move forward into the retinal circuit. Furthermore, it suggests that ganglion cell surrounds are generated in the inner retina.
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Priambodo, Galih, Mariyanto Mariyanto, and Wien Lestari. "Magnetotelluric data analysis using 2D resistivity modelling in Gondang region, Bojonegoro." Journal of Physics: Conference Series 2309, no. 1 (July 1, 2022): 012020. http://dx.doi.org/10.1088/1742-6596/2309/1/012020.
Повний текст джерелаАнотація:
Abstract Previous studies in Gondang Subdistricthave identified underground mud reservoirnear a rock intrusion, while another study near Gondang Subdistrict has identified deep fault structures. This study will identify the distribution and characteristics of possible geological features in the area using magnetotelluric (MT) method to further describe the relationship between the geological features related to local geology. MT data measurements were conducted on 7 stations alonga north-south line, then modelled in 2D using nonlinear conjugate gradient algorithm. The model was used to describe the subsurface resistivity distribution and to identify the geological features. The results show 5 resistive zones (20–1250 Ω⋅m) and 4 conductive zones (≤10 Ω⋅m). The former consist of 4 vertical zones, 1 vertical zone deeper than 5 km, and 1 horizontal zone near the surface. 2 conductive zones surround a resistive zone, while 2 others stretch below the horizontal resistive zone. The vertical resistive zones are interpreted as andesite intrusions, and the horizontal one as volcanic breccia. The conductive zones are interpreted consisting of tuff and marl with possible saline water content. 3 vertical intrusions are thought to have the same source, and all vertical intrusions are suspected to co-occurr with the Pandan Volcano intrusion.
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Bonal, Claire, Isabelle Avril та Pedro L. Herrera. "Experimental models of β-cell regeneration". Biochemical Society Transactions 36, № 3 (21 травня 2008): 286–89. http://dx.doi.org/10.1042/bst0360286.
Повний текст джерелаАнотація:
The control of glucose metabolism by pancreatic endocrine cells throughout life relies on a tight regulation of the mass of insulin-producing β-cells. How this homoeostasis is achieved is not well understood. Over the last few years, experimental rodent models with altered β-cell mass, and, more recently, new transgenic approaches designed to tackle this problem, have provided abundant information. Processes such as β-cell proliferation and apoptosis, or even β-cell differentiation from poorly characterized progenitor cells, whether immature or differentiated, appear to be implicated. A complex picture is thus emerging in which the nature of the pancreatic lesion appears to determine the kind of regenerative response. The environment formed by acinar and ductal cells, and also by vascular and neuronal structures, which surround islets and penetrate into their β-cell core, might play crucial roles so far unsuspected, which should be explored in the near future.
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Calarco, Patricia G. "Gamma Tubulin is Localized to a New Organelle, The Multivesicular Aggregate, In Mammalian Oocytes." Microscopy and Microanalysis 4, S2 (July 1998): 1124–25. http://dx.doi.org/10.1017/s1431927600025745.
Повний текст джерелаАнотація:
Oocyte meiotic maturation occurs without the aid of centrioles in the mouse; instead the division spindles are organized by a number of microtubule organizing centers (MTOC). Immunofluorescence microscopy using anti-γ tubulin shows that multiple MTOCs migrate to surround the central nucleus (germinal vesicle, GV) during early maturation.. However, at the EM level, recognizable MTOCs have never been seen prior to the nucleation of microtubules (MT) which occurs near the time of nuclear envelope breakdown. Recently, I described multivesicular aggregates (MVAs) as the organelles most likely to represent immature MTOCs prior to MT nucleation4. These are first seen at time zero by EM as two large aggregates in the cortex, with sizes averaging 10um. MVA subsequently fragment into smaller units as they migrate centrally.Materials and Methods: Female ICR mice were injected IP with 100 iu of chorionic gonadotropin (Sigma) to stimulate follicle growth, and ovaries were removed 48 hours later.
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Khaitin, Andrey. "Calcium in Neuronal and Glial Response to Axotomy." International Journal of Molecular Sciences 22, no. 24 (December 12, 2021): 13344. http://dx.doi.org/10.3390/ijms222413344.
Повний текст джерелаАнотація:
Neurotrauma assumes an instant or delayed disconnection of axons (axotomy), which affects not only neurons, but surrounding glia as well. Not only mechanically injured glia near the site of disconnection, especially transection, is subjected to the damage, but also glia that is remote from the lesion site. Glial cells, which surround the neuronal body, in turn, support neuron survival, so there is a mutual protection between neuron and glia. Calcium signaling is a central mediator of all post-axotomy events, both in neuron and glia, playing a critical role in their survival/regeneration or death/degeneration. The involvement of calcium in post-axotomy survival of the remote, mechanically intact glia is poorly studied. The purpose of this review is to sum up the calcium-involving mechanisms in responses of neurons and glial cells to axotomy to show their importance and to give some suggestions for future research of remote glia in this context.
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Levä, Tapio, Mahya Ilaghi, Vilen Looga, Miika Komu, Nicklas Beijar, and Oleksiy Mazhelis. "Adoption of Constrained Application Protocol." International Journal of Innovation in the Digital Economy 7, no. 1 (January 2016): 38–53. http://dx.doi.org/10.4018/ijide.2016010104.
Повний текст джерелаАнотація:
Among billions of Internet enabled devices that are expected to surround us in the near future, many will be resource constrained, i.e., will have limited power supply, processing power and memory. To cope with these limitations, the Constrained Application Protocol (CoAP) has been recently introduced as a lightweight alternative to HTTP for connecting the resource limited devices to the Web. Although the new protocol offers solid technical advantages, it remains uncertain whether a successful uptake will follow, as it depends also on its economic feasibility for the involved stakeholders. Therefore, this paper studies the techno-economic feasibility of CoAP using a systematic methodological framework. Based on eleven expert interviews complemented with a literature survey, the paper identifies potential deployment challenges for CoAP, both technical and business-related, and suggests approaches to overcome them. The findings should facilitate the uptake of CoAP by supporting the potential adopters of the protocol in their decision-making.
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Cuny, Thomas, Wouter de Herder, Anne Barlier, and Leo J. Hofland. "Role of the tumor microenvironment in digestive neuroendocrine tumors." Endocrine-Related Cancer 25, no. 11 (November 2018): R519—R544. http://dx.doi.org/10.1530/erc-18-0025.
Повний текст джерелаАнотація:
Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.
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Baek, Kelly, Semran Mann, Qais Alemi, Akinchita Kumar, Penny Newman, Rhonda Spencer-Hwang, and Susanne Montgomery. "Impact of Heart Disease Risk Factors, Respiratory Illness, Mastery, and Quality of Life on the Health Status of Individuals Living Near a Major Railyard in Southern California." International Journal of Environmental Research and Public Health 15, no. 12 (December 6, 2018): 2765. http://dx.doi.org/10.3390/ijerph15122765.
Повний текст джерелаАнотація:
The potential health risks for communities that surround railyards have largely been understudied. Mastery and quality of life (QoL) have been associated with self-reported health status in the general population, but few studies have explored this variable among highly vulnerable low-income groups exposed to harmful air pollutants. This study investigates the relationship between self-reported health status and correlates of Heart Disease Risk Factors (HDRF) and Respiratory Illness (RI) with mastery and QoL acting as potential protective buffers. This cross-sectional study of 684 residents residing near a Southern California railyard attempts to address this limitation. Results from three separate hierarchal linear regressions showed that those who reported being diagnosed with at least one type of HDRF and/or RI reported lower perceived health status. For those that lived further from the railyard, mastery and QoL predicted modest increases in perceived health status. Results suggest that mastery and QoL may be helpful as tools in developing interventions but should not solely be used to assess risk and health outcomes as perceived health status may not measure actual health status.
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Brunn, Stanley D., Marcin Semczuk, Rafał Koszek, Karolina Gołuszka, and Gabriela Bołoz. "Poland’s Voivodeships and Poviats and the Geographies of Knowledge: Addressing Uneven Human Resources." Studies of the Industrial Geography Commission of the Polish Geographical Society 30, no. 2 (November 12, 2016): 198–208. http://dx.doi.org/10.24917/20801653.302.13.
Повний текст джерелаАнотація:
In a postindustrial economic world, information economies are key components in local, regional and national development. These are service economies, built on the production, consumption and dissemination of information, including education, health care, outsourcing, tourism, sustainability and related human welfare services. We explore the geography/knowledge intersections in Poland’s voivodeships and poviats by using the volumes of information or hyperlinks about selected information economies. Google hyperlinks are electronic knowledge data that can be mapped to highlight the areas of most and least information about certain subject categories. While some mapping results are expected, such as Warsaw and Krakow, being prominent, in other regions there are unexpected gaps within eastern, northern and southern Poland, including some places near major metropolitan centers. There is a significant difference between the cities with poviat rights, which stand out in the number of information on items comparing to the poviats that surround them. The majority of poviats in Mazowieckie voivodeship are surprisingly recognized as core areas on the map of knowledge, nevertheless they are considered undeveloped from the economic point of view.
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Estelita, Maria Emília Maranhão, and Ana Claudia Rodrigues. "Silicon location through backscattered electron imaging and X-ray microanalysis in leaves of Cyperus ligularis L. and Rhynchospora aberrans C. B. Clarke (Cyperaceae)." Acta Botanica Brasilica 26, no. 2 (June 2012): 275–80. http://dx.doi.org/10.1590/s0102-33062012000200004.
Повний текст джерелаАнотація:
The Cyperaceae show the ability to incorporate silicon by depositing colloidal silica, which is recorded by the occurrence of projections in the form of cones, in inner tangential walls of some epidermal cells or "silica cells". Leaves of C. ligularis and R. aberrans were analyzed through the technique of electron backscatter. Cyperus ligularis accumulates silica, in addition to "silica cells", in some stomata, trichomes and the cell walls that surround the cavities of the aerenchyma. The silica in the latter occurs in various forms; however, the cells located near the vascular bundles have conical projections, similar to those of the epidermis. Rhynchospora aberrans presents "silica cells" whose projections have tapered "satellites". In this species, silica also occurs in stomata and certain epidermal cells adjacent to them. It appears that the silicon deposition occurs in combination with the wall (with no apparent structural changes), and structures of secretion, or projections of the wall. These structural changes in the species, and location, are probably related to functional and environmental factors, especially the soil, in addition to relation with taxonomic groups.
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CONTOPOULOS, G., M. HARSOULA, R. DVORAK, and F. FREISTETTER. "RECURRENCE OF ORDER IN CHAOS." International Journal of Bifurcation and Chaos 15, no. 09 (September 2005): 2865–82. http://dx.doi.org/10.1142/s021812740501371x.
Повний текст джерелаАнотація:
The standard map x′ = x + y′, y′ = y + (K/2π) sin (2πx), where both x and y are given modulo 1, becomes mostly chaotic for K ≥ 8, but important islands of stability appear in a recurrent way for values of K near K = 2nπ (groups of islands I and II), and K = (2n + 1)π (group III), where n ≥ 1. The maximum areas of the islands and the intervals ΔK, where the islands appear, follow power laws. The changes of the areas of the islands around a maximum follow universal patterns. All islands surround stable periodic orbits. Most of the orbits are irregular, i.e. unrelated to the orbits of the unperturbed problem K = 0. The main periodic orbits of periods 1, 2 and 4 and their stability are derived analytically. As K increases these orbits become unstable and they are followed by infinite period-doubling bifurcations with a bifurcation ratio δ = 8.72. We find theoretically the connections between the various families and the extent of their stability. Numerical calculations verify the theoretical results.
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Mueller, Adrienne L., Adam Davis, Samantha Sovich, Steven S. Carlson, and Farrel R. Robinson. "Distribution of N-Acetylgalactosamine-Positive Perineuronal Nets in the Macaque Brain: Anatomy and Implications." Neural Plasticity 2016 (2016): 1–19. http://dx.doi.org/10.1155/2016/6021428.
Повний текст джерелаАнотація:
Perineuronal nets (PNNs) are extracellular molecules that form around neurons near the end of critical periods during development. They surround neuronal cell bodies and proximal dendrites. PNNs inhibit the formation of new connections and may concentrate around rapidly firing inhibitory interneurons. Previous work characterized the important role of perineuronal nets in plasticity in the visual system, amygdala, and spinal cord of rats. In this study, we use immunohistochemistry to survey the distribution of perineuronal nets in representative areas of the primate brain. We also document changes in PNN prevalence in these areas in animals of different ages. We found that PNNs are most prevalent in the cerebellar nuclei, surrounding >90% of the neurons there. They are much less prevalent in cerebral cortex, surrounding less than 10% of neurons in every area that we examined. The incidence of perineuronal nets around parvalbumin-positive neurons (putative fast-spiking interneurons) varies considerably between different areas in the brain. Our survey indicates that the presence of PNNs may not have a simple relationship with neural plasticity and may serve multiple functions in the central nervous system.
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Kluska, J., H. Van Winckel, Q. Coppée, G. M. Oomen, K. Dsilva, D. Kamath, V. Bujarrabal, and M. Min. "A population of transition disks around evolved stars: Fingerprints of planets." Astronomy & Astrophysics 658 (February 2022): A36. http://dx.doi.org/10.1051/0004-6361/202141690.
Повний текст джерелаАнотація:
Context. Post-asymptotic giant branch (post-AGB) binaries are surrounded by massive disks of gas and dust that are similar to the protoplanetary disks that are known to surround young stars. Aims. We assembled a catalog of all known Galactic post-AGB binaries featuring disks. We explore the correlations between the different observables with the aim of learning more about potential disk-binary interactions. Methods. We compiled spectral energy distributions of 85 Galactic post-AGB binary systems. We built a color-color diagram to differentiate between the different disk morphologies traced by the characteristics of the infrared excess. We categorized the different disk types and searched for correlations with other observational characteristics of these systems. Results. Between 8 and 12% of our targets are surrounded by transition disks, that is, disks having no or low near-infrared excess. We find a strong link between these transition disks and the depletion of refractory elements seen on the surface of the post-AGB star. We interpret this correlation as evidence of the presence of a mechanism that stimulates the dust and gas separation within the disk and that also produces the transition disk structure. We propose that such a mechanism is likely to be due to a giant planet carving a hole in the disk, effectively trapping the dust in the outer disk parts. We propose two disk evolutionary scenarios, depending on the actual presence of such a giant planet in the disk. Conclusions. We advocate that giant planets can successfully explain the correlation between the transition disks and the depletion of refractory materials observed in post-AGB binaries. If the planetary scenario is confirmed, disks around post-AGB binaries could be a unique laboratory for testing planet-disk interactions and their influence on the late evolution of binary stars. The question of whether such planets are first- or second-generation bodies also remains to be considered. We argue that these disks are ideal for studying planet formation scenarios in an unprecedented parameter space.
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Pannabecker, Thomas L., and William H. Dantzler. "Three-dimensional architecture of collecting ducts, loops of Henle, and blood vessels in the renal papilla." American Journal of Physiology-Renal Physiology 293, no. 3 (September 2007): F696—F704. http://dx.doi.org/10.1152/ajprenal.00231.2007.
Повний текст джерелаАнотація:
Three-dimensional architecture of vasculature and nephrons in rat renal papilla was assessed by digital reconstruction. Descending vasa recta (DVR), ascending vasa recta (AVR), descending thin limbs (DTLs), ascending thin limbs (ATLs), and collecting ducts (CDs) were identified with antibodies against segment-specific proteins. DTLs are distributed nonuniformly in transverse sections of papilla, but lateral compartmentation between DTLs and CD clusters that occurs in outer IM makes no contribution to concentrating mechanism in papilla. ATLs are distributed nearly uniformly throughout IM. Vasa recta within ∼2 mm of the papilla tip are primarily fenestrated vessels; therefore, AVR and DVR can only be determined by blood flow direction. CDs within ∼500 μm of the papilla tip have nearly 100% greater circumference than CDs within first 1–2 mm below the IM base. Return of water to general circulation from deep papillary CDs appears to be facilitated by a 150% increase in the number of AVR closely abutting these CDs. Consequently, average fractional CD surface area abutting AVR is 0.61, about the same as that (0.54) for smaller CDs that lie near the IM base. Interstitial nodal compartments, bounded by CDs, ATLs, and AVR, surround CDs along the axis of the IM. Fewer ATLs exist in the final 1 mm, as there are fewer loops and the number of these nodal arrangements is therefore reduced. However, tips of many of those loops reaching this area have bends with 50–100% greater transverse lengths than bends of loops near the IM base. This may be significant for solute movement out of loop bends.
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Christ, Jheniffer Abeldt, Valderes Bento Sarnaglia-Junior, Lucas Mesquita Barreto, Elsie Franklin Guimarães, Mário Luís Garbin, and Tatiana Tavares Carrijo. "The genus Piper (Piperaceae) in the Mata das Flores State Park, Espírito Santo, Brazil." Rodriguésia 67, no. 4 (December 2016): 1031–46. http://dx.doi.org/10.1590/2175-7860201667413.
Повний текст джерелаАнотація:
Abstract The conservation and management of the Atlantic Forest depends upon reliable knowledge about how many and which species this biome shelters. Floristic inventories have an important role in this process, especially when conducted in poorly known remnants, with a high conservation priority. This paper presents the study of the genus Piper (Piperaceae) in the Mata das Flores State Park, Castelo municipality, Espírito Santo state (ES). The study was based on the analysis of dried specimens, as well as those observed in the field, from February 2012 to August 2015. Twenty species of piper were identified. Amongst these species, Piper dilatatum, P. macedoi and P. piliovarium were recorded for the first time for the Espírito Santo state. Piper bicorne, an endemic species from ES and known only for the Santa Leopoldina municipality, had its geographical distribution expanded to the Castelo municipality. Most of the Piper species in the MFSP occur in valleys, and they are commonly found near watercourses. This is worrying given that these areas are just the most affected by the expansion of the rural and urban areas that surround the Park.
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Fernandes, Matheus C., Mehdi Saadat, Patrick Cauchy-Dubois, Chikara Inamura, Ted Sirota, Garrett Milliron, Hossein Haj-Hariri, Katia Bertoldi, and James C. Weaver. "Mechanical and hydrodynamic analyses of helical strake-like ridges in a glass sponge." Journal of The Royal Society Interface 18, no. 182 (September 2021): 20210559. http://dx.doi.org/10.1098/rsif.2021.0559.
Повний текст джерелаАнотація:
From the discovery of functionally graded laminated composites, to near-structurally optimized diagonally reinforced square lattice structures, the skeletal system of the predominantly deep-sea sponge Euplectella aspergillum has continued to inspire biologists, materials scientists and mechanical engineers. Building on these previous efforts, in the present study, we develop an integrated finite element and fluid dynamics approach for investigating structure–function relationships in the complex maze-like organization of helical ridges that surround the main skeletal tube of this species. From these investigations, we discover that not only do these ridges provide additional mechanical reinforcement, but perhaps more significantly, provide a critical hydrodynamic benefit by effectively suppressing von Kármán vortex shedding and reducing lift forcing fluctuations over a wide range of biologically relevant flow regimes. By comparing the disordered sponge ridge geometry to other more symmetrical strake-based vortex suppression systems commonly employed in infrastructure applications ranging from antennas to underwater gas and oil pipelines, we find that the unique maze-like ridge organization of E. aspergillum can completely suppress vortex shedding rather than delaying their shedding to a more downstream location, thus highlighting their potential benefit in these engineering contexts.