Thin Black Line Research Articles

Cognitive Set Reconfiguration Signaled by Macaque Posterior Parietal Neurons

When faced with problems, we can flexibly change our ways of thinking or our point of view. Our cognitive flexibility arises from this ability of shifting cognitive sets. To elucidate how this dynamic process is implemented in the primate brain, single-unit activity was recorded from the posterior parietal cortex (PPC) of two monkeys performing analogs of the Wisconsin Card Sorting Test, which is most commonly used to test cognitive flexibility in humans. We successfully trained the monkeys to promptly perform set shifting, mostly within a single trial, and found shift-related activity: PPC neurons were transiently activated when the monkeys shifted from one cognitive set to another, but not when they shifted in the opposite direction. This shift-related activity emerged about 4 s before the actual behavioral responses, and it well predicted whether the cognitive set would be successfully shifted. These results provide insights into single-unit level mechanisms of cognitive flexibility.

NOLA Flow: A Callaloo Retreat in New Orleans

NOLA FlowA Callaloo Retreat in New Orleans Nelly Rosario (bio) March 6, 2008: Thursday En route, 5 PM–2AM We can’t help being thirsty, moving toward the voice of water. —Rumi Stuff is in the H2O from the moment we leave San Marcos, Texas, for the straight eight-hour drive to New Orleans. Two Piscean writers take turns driving through sheets of relentless rain, with an eight-year-old bull playing on her DS in the backseat. My white students here at Texas State University were kind enough to see me off with: “Um, don’t stop after Houston.” Shit. To our delight, the Camry we’ve rented has a Magellan RoadMate GPS Navigating System. Ferdinand, the first to supposedly have sailed an expedition westward from Europe to Asia and to cross the Pacific Ocean, would be proud of our efforts. His namesake isn’t. Though she speaks proper British Travel Agentese, I swear she’s nettled by our detours to Jack in the Box and Wal-Mart. After driving for four hours and insulting myself with four carcinogenic tacos, I move over to the passenger seat, where I promptly fall into a swampy sleep. When I resurface, we’re crossing a bridge and the world’s going backwards and forwards at 60 mph: in the darkness and rain, trees rise like prehistoric monsters, and behind them, the Baton Rouge steel refineries promise post historic oblivion. Our blue arrow on the Magellan screen is tracing a dangerously thin black line through an expanse of blue. “Oh. My. God.” That’s Sheila Maldonado, horror-stricken driver-poet. We’re driving over swamp, being showered by zooming tractor trailers, in a violent rainstorm. All this for spice, Ferdinand? We arrive in the Crescent City at 3 AM. Naturally, the French Quarter reminds me of Havana and of Puerto Plata, my mother’s Dominican hometown. It reminds my daughter of San Juan, Puerto Rico, “except it smells different.” After brushing our teeth in the Prince Conti Hotel sink, we both agree that the bathroom water smells fishtanky. [End Page 616] March 7, 2008: Friday Closed Session 2, 10:30 AM–12 PM Man—despite his artistic pretensions, his sophistication, and his many accomplishments—owes his existence to a six-inch layer of topsoil and the fact that it rains. —Author Unknown We head to the Hotel St. Marie for the Closed Session. On our way, a mini-carnival crosses our path in “celebration of Friday” and getting on their St. Patrick’s a week ahead. Fine by us. Like proper pirates, mother and daughter gather all the beads and loot we can. We arrive late to the session. The St. Marie’s Audubon Room can’t be more appropriate a place for the session moderated by Fred D’Aguiar (Virginia Tech), whose surname’s derived from the Portuguese for “eagle.” The roundtable, composed of literary critics and writers, is already in the throes of discussion when I shuffle in. I buckle down to catch up, taking notes, which I always wonder how I will ever put to use, let alone remember I’ve even written them down in the first place. Of course, I later lose them and am now doomed to reconstruct memory in stylized present tense. Therefore, the following are merely notes on my notes of the session: • Koritha Mitchell (Ohio State University) earnestly expresses feeling intimidated when confronting works of poetry. I admire her admission, which she doles out apologetically. Later, writer Emily Raboteau will marvel at how many critics spoke, compared to the artists. Just as well, I think, imagining that perhaps there aren’t as many forums for academic critics of color to discuss issues specific to them amongst each other. Artists are spoiled. And sometimes we talk too much. • At one point, Christian Campbell (Franklin & Marshall College) fesses up to being a “miscegenated” poet, referring to his dual role as critic and artist. Everyone chuckles. Having shown up to the Audubon Room a, um, late bird, it takes me a minute to get the, uh, worm. My laughter’s delayed: the term sounds weirdly fascist. • I look down at the Callaloo Retreat brochure...

Siemens Multileaf Collimator Characterization and Quality Assurance Approaches for Intensity-Modulated Radiotherapy

Application of the multileaf collimator (MLC) has evolved from replacing blocks to create treatment fields to creating photon fluence modulation for intensity-modulated radiotherapy (IMRT). Multileaf collimator system performance requirements are far more stringent for such applications and will require increased performance for future applications, such as motion tracking. This article reviews Siemens MLC systems, including a technical description and dosimetric characteristics of 56-, 82-, and 160-leaf designs. Routine quality assurance of MLC for IMRT necessitates frequent and critical assessment of MLC leaf position calibration errors that can present in many different ways (e.g., accuracy, reproducibility, longevity, hysteresis, and collimator/gantry angle dependencies). Several techniques for measuring these errors are presented, along with qualitative and quantitative techniques for analyzing results. In particular, increased accuracy of leaf position measurement at variable gantry angles is enabled by spatial transformations to electronic portal imaging device position quantified by calibration protocols introduced with megavoltage cone beam. Measured values of X-ray transmission (intra-leaf, inter-leaf, and through abutting leaf pairs) and penumbra (leaf end, leaf tongue, leaf groove) are presented with an evaluation of their characterization by a treatment-planning system. The dosimetric impact of planning system model inadequacies is demonstrated for collimator scatter, dose profile values within 30 mm of the field edge, and the resultant effect demonstrated on clinical cases. Finally, a description of automated quality assurance delivery, analysis, and calibration protocols applicable for the specific vendor's system is provided.

Atomic Level Insight into the Oxidative Half-reaction of Aromatic Amine Dehydrogenase

The quinoprotein aromatic amine dehydrogenase (AADH) uses a covalently bound tryptophan tryptophylquinone (TTQ) cofactor to oxidatively deaminate primary aromatic amines. Recent crystal structures have provided insight into the reductive half-reaction. In contrast, no atomic details are available for the oxidative half-reaction. The TTQ O7 hydroxyl group is protonated during reduction, but it is unclear how this proton can be removed during the oxidative half-reaction. Furthermore, compared with the electron transfer from the N-quinol form, electron transfer from the non-physiological O-quinol form to azurin is significantly slower. Here we report crystal structures of the O-quinol, N-quinol, and N-semiquinone forms of AADH. A comparison of oxidized and substrate reduced AADH species reveals changes in the TTQ-containing subunit, extending from residues in the immediate vicinity of the N-quinol to the putative azurin docking site, suggesting a mechanism whereby TTQ redox state influences interprotein electron transfer. In contrast, chemical reduction of the TTQ center has no significant effect on protein conformation. Furthermore, structural reorganization upon substrate reduction places a water molecule near TTQ O7 where it can act as proton acceptor. The structure of the N-semiquinone, however, is essentially similar to oxidized AADH. Surprisingly, in the presence of substrate a covalent N-semiquinone substrate adduct is observed. To our knowledge this is the first detailed insight into a complex, branching mechanism of quinone oxidation where significant structural reorganization upon reduction of the quinone center directly influences formation of the electron transfer complex and nature of the electron transfer process.

Malacosoma parallela

<i>Malacosoma parallela</i>

Thin edges and the induced contrast asynchrony

The Induced Contrast Asynchrony is a visual effect that demonstrates a perceptual separation between luminance and contrast (Shapiro et al, in press). The basic version of the effect consists of two physically identical rectangular patches whose luminance levels are modulated at 2 Hz (.75×1.5 deg, 40 + 15*sin(tw) cd/m2); one patch is surrounded by a dark field (6×6 deg, 20 cd/m2) and the other by a light field (6×6 deg, 60 cd/m2). This produces a configuration in which the luminance of the two patches modulates in phase and the contrast modulates in antiphase. Observers perceive primarily the contrast signal (i.e., the patches modulate in antiphase), but at low frequencies, observers can also attend to the luminance signal. This year we present the effects of the edge widths on the appearance of the asynchronous contrast signal. We measure psychometric functions for the perceived contrast signal versus the width of the introduced lines over a range of patch sizes (width .15 to 1.2 deg). We show that 1) the contrast asynchrony can be produced when the surrounding field is of minimal width, indicating that the contrast signal arises primarily at the patch/surround edge; 2) placing a thin (.05 deg) white or black line adjacent to one side of the modulating rectangular patch suppresses perception of the asynchronous contrast signal; 3) a variety of stimulus configurations (e.g., circular patch with a two-tone surround or gradient bar adjacent to a modulating patch) can produce new versions of the contrast asynchrony; and 4) the combination of thin edges and single-patch modulation can produce a novel form of contrast-defined apparent position shifts. Most of the results can be explained by a model with separate contrast (i.e., rectified difference) and luminance pathways. A sophisticated spatiotemporal analysis is required to account for apparent changes in spatial position. The results offer new insights into static lightness illusions such as White's effect. R15-EY12946

Calcite twin morphology: a low-temperature deformation geothermometer

Twinning of the e-plane is the dominant crystal–plastic deformation mechanism in calcite deformed below about 400 °C. Calcite in a twin domain has a different crystallographic orientation from the host calcite grain. So-called thin twins appear as thin black lines when viewed parallel to the twin plane at 200–320× magnification under a petrographic microscope. Thick twins viewed in the same way have a microscopically visible width of twinned material between black lines. Calcite e-twin width and morphology has been correlated with temperature of deformation in naturally deformed coarse-grained calcite. In this paper, we present a compilation and analysis of data from limestones of the frontal Alps (France and Switzerland) and the Appalachian Valley and Ridge and Plateau provinces (eastern United States) to document this temperature dependence. Mean calcite twin width correlates directly with temperature of deformation such that thin twins dominate below 170 °C and thick twins dominate above 200 °C. Above 250 °C dynamic recrystallization is an important deformation mechanism in calcite. Mean twin intensity (twin planes/mm) correlates negatively with temperature, and a cross plot of twin intensity with twin width can yield information about both strain and temperature of deformation. These relationships provide a deformation geothermometer for rocks that might otherwise yield little or no paleotemperature data.

Phytophthora ramorum as the Cause of Extensive Mortality of Quercus spp. and Lithocarpus densiflorus in California.

A new canker disease, commonly known as sudden oak death, of Lithocarpus densiflorus, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei in California is shown to be caused by Phytophthora ramorum. The pathogen is a recently described species that previously was known only from Germany and the Netherlands on Rhododendron spp. and a Viburnum sp. This disease has reached epidemic proportions in forests along approximately 300 km of the central coast of California. The most consistent and diagnostic symptoms on trees are cankers that develop before foliage symptoms become evident. Cankers have brown or black discolored outer bark and seep dark red sap. Cankers occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length. In L. densiflorus saplings, P. ramorum was isolated from branches as small as 5 mm in diameter. L. densiflorus and Q. agrifolia were inoculated with P. ramorum in the field and greenhouse, and symptoms similar to those of naturally infected trees developed. The pathogen was reisolated from the inoculated plants, which confirmed pathogenicity.

The Thin Black Line of Heroes

The Thin Black Line of Heroes

Wrapping of DNA around the E.coli RNA polymerase open promoter complex.

High-resolution atomic force microscopy (AFM) and biochemical methods were used to analyze the structure of Escherichia coli RNA polymerase.sigma(70) (RNAP) open promoter complex (RP(o)). A detailed analysis of a large number of molecules shows that the DNA contour length of RP(o) is reduced by approximately 30 nm (approximately 90 bp) relative to the free DNA. The DNA bend angle measured with different methods varied from 55 to 88 degrees. The contour length reduction and the DNA bend angle were much less in inactive RNAP-DNA complexes. These results, together with previously published observations, strongly support the notion that during transcription initiation, the promoter DNA wraps nearly 300 degrees around the polymerase. This amount of DNA bending requires an energy of 60 kJ/mol. The structural analysis of the open promoter complexes revealed that two-thirds of the DNA wrapped around the RNAP is part of a region upstream of the transcription start site, whereas the remaining one-third is part of the downstream region. Based on these data, a model of the sigma(70).RP(o) conformation is proposed.

Development and anatomy of the attachment structure of woodrose-producing mistletoes

The formation of woodroses in Sclerocarya birrea (A. Rich.) Hochst, and Combretum collinum Fresen. in reaction to the parasitic mistletoes Erianthemum dregei (Eckl. & Zeyh.) Tiegh, and Pedistylis galpinii (Schinz ex Sprague) was investigated. Eight woodroses of varying sizes, and by implication age, were sectioned with the freeze microtome and the sledge microtome. As the mistletoe entered the host tissues it assumed a flask-shape due to mechanical constriction by layers of host cork. There was a clear differentiation between host cells containing tannin and mistletoe cells without tannin throughout the sections. In addition these were separated by a thin wavy black line of gum. The mistletoe occupied a central position as well as producing finger-like projections into the host tissue. Older sections indicated an increase in tannin and sclereids, while the arrangement of axial xylem elements became increasingly disrupted. There appear to be two strategies to prevent a functional connection with the mistletoe: 1) the production of wound periderm at the host surface and 2) internal necrosis and disruption of internal host tissues. The study species showed signs of both but the mistletoes managed to by-pass these strategies and instead lead to the formation of elaborate and intricate woodroses.

Shape constancy in pictorial relief.

Pictorial relief was measured for a series of pictures of a smooth solid object. The scene was geometrically identical (ie the perspective of the three-dimensional scene remained the same) for all pictures, the rendering different. Some of the pictures were monochrome full-scale photographs taken under different illumination of the scene. Also included were a silhouette (uniform black on uniform white) and a 'cartoon'-style rendering (visual contour and key linear features rendered in thin black line on a uniform white ground). Two subjects were naive and started with the silhouette, saw the cartoon next, and finally the full-scale photographs. Another subject had seen the object and did the experiment in the opposite sequence. The silhouette rendering is impoverished, but has considerable relief with much of the basic shape. The cartoon rendering yields well-developed pictorial relief, even for the naive subjects. Shading adds only small local details, but different illumination produces significant alterations of relief. It is concluded that shape constancy under changes in illumination is dominant throughout, but that the (small) deviations from true constancy reveal the effect of cues such as shading in a natural setting. Such a ¿perturbation analysis' appears more promising than either stimulus-reduction or cue-conflict paradigms.

Depression of Phagocytic Activity of The Immune System Following Traditional Cautery in Experimental Animals

Traditional cautery, which is practiced widely in Saudi Arabia and some other countries, has not been exposed to detailed scientific investigation. In an attempt to elucidate some of its physiological aspects, we assessed the effect of cautery on a normal animal's nonspecific immune system. Male Wistar rats and guinea pigs were cauterized to simulate traditional cautery in size and percentage of cauterized area. Using radioactive sulfur colloid uptake and clearance, the effect of cautery on the mononuclear phagocyte system was evaluated in rats. The respiratory burst in peripheral polymorphonuclear leukocytes (PMNs) after cautery was measured in the guinea pigs using the chemiluminescence technique. The results showed marked reduction in the intravascular clearance of the colloid with prolonged clearance time following cautery. In addition, the liver uptake of the colloid was reduced in cauterized animals compared with control animals and the white cell count was also significantly reduced. The study showed marked inhibition of phagocytic function in guinea pigs in both whole blood and isolated PMNs. These results indicate that traditional cautery reduces the physiological function of the phagocyctic system in normal experimental animals. The influence of traditional cautery on infected animals deserved further investigation.

Line connectivity algorithms for an asynchronous pyramid computer

Line tracing, which has been conjectured to play an important role in the visual perception of connectivity relations, is examined in this paper from the computational point of view. The problem is formulated in terms of pixel connectivity, with thin black lines on a white background serving as input. The complexity of line tracing is discussed relative to several computation models. Two algorithms for a MIMD pyramid with running time better than linear in the line length are presented and analyzed. Their performance is discussed in view of the available psychophysical results, and compared to that of several previously published algorithms.

Suprathreshold stereo-depth matches as a function of contrast and spatial frequency.

Thresholds for stereoscopic-depth perception increase with decreasing spatial frequency below 2.5 cycles deg-1. Despite this variation of stereo threshold, suprathreshold stereoscopic-depth perception is independent of spatial frequency down to 0.5 cycle deg-1. Below this frequency the perceived depth of crossed disparities is less than that stimulated by higher spatial frequencies which subtend the same disparities. We have investigated the effects of contrast fading upon this breakdown of stereo-depth invariance at low spatial frequencies. Suprathreshold stereopsis was investigated with spatially filtered vertical bars (difference of Gaussian luminance distribution, or DOG functions) tuned narrowly over a broad range of spatial frequencies (0.15-9.6 cycles deg-1). Disparity subtended by variable width DOGs whose physical contrast ranged from 10-100% was adjusted to match the perceived depth of a standard suprathreshold disparity (5 min visual angle) subtended by a thin black line. Greater amounts of crossed disparity were required to match broad than narrow DOGs to the apparent depth of the standard black line. The matched disparity was greater at low than at high contrast levels. When perceived contrast of all the DOGs was matched to standard contrasts ranging from 5-72%, disparity for depth matches became similar for narrow and broad DOGs. 200 ms pulsed presentations of DOGs with equal perceived contrast further reduced the disparity of low-contrast broad DOGs needed to match the standard depth. A perceived-depth bias in the uncrossed direction at low spatial frequencies was noted in these experiments. This was most pronounced for low-contrast low-spatial-frequency targets, which actually needed crossed disparities to make a depth match to an uncrossed standard. This bias was investigated further by making depth matches to a zero-disparity standard (ie the apparent fronto-parallel plane). Broad DOGs, which are composed of low spatial frequencies, were perceived behind the fixation plane when they actually subtended zero disparity. The magnitude of this low-frequency depth bias increased as contrast was reduced. The distal depth bias was also perceived monocularly, however, it was always greater when viewed binocularly. This investigation indicates that contrast fading of low-spatial-frequency stimuli changes their perceived depth and enhances a depth bias in the uncrossed direction. The depth bias has both a monocular and a binocular component.

Loosening of the femoral component after total hip replacement. The thin black line and the sinking hip.

Review of the radiographs of 882 consecutive metal-to-polyethylene hip replacements after a mean follow-up of 6.8 years showed 72 cases (8%) of aseptic femoral loosening, all of which showed a lucent zone or black line between metal and cement. In 97% of the series this appeared within two years of the arthroplasty. Progress of loosening was unpredictable and only 24% had significant symptoms. Improved technique with methylmethacrylate cement in Stanmore prostheses had reduced loosening after two years from 7.9% to 0.4%. Methods of detection of early loosening are discussed.

Free-Standing Columns; A Review of Some Architectural School Magazines

world. All this argues, however, is that schools are in a potentially better position, but does not speculate as to why at this moment there should be such a profusion of mags. It is possible to blame the resurgence of interest in history for too much, but with the amount of boring architecture by our late Nineteenth Century forbears that can be found in many publications, this historical renaissance can come in for a little castigation here. Add to this the delight in drawing now also on the upswing, and the rendering of the antique in the fashionable thin black line becomes remarkably attractive. How much better to have proper drawings of Lutyens that enable his plans to be compared to those of Le Corbusier's.

Complexity of context and orientation of figure in the corridor illusion.

12 subjects judged the magnitude of the corridor illusion as two independent variables were manipulated, complexity of context and orientation of the target figures. The contexts included a complete corridor, one with vertical elements deleted, and one having but two converging lines. Figures embedded within these contexts were thin black lines oriented either vertically or horizontally. Although the context had a significant effect upon the magnitude of the illusion, orientation of the judged lines did not. These results suggest that it is legitimate to use the corridor illusion to illustrate size-distance relationships.

Atoms—a three-d opaque molecule system—for color pictures of space-filling or ball-and-stick models

Abstract ATOMS is a set of FORTRAN subroutines for depicting, in color, configurations of space-filling atoms and/or ball-and-stick models. Pictures are rendered as in traditional cartoon animation: solid monochrome areas separated by thin black lines. The user supplies x, y, z, radius, and color information for atoms; atom pairs, thickness and color for bonds, also parameters defining rules for viewing and picture drawing—including position and orientation of a hypothetical camera in user-defined space. The system is ideally suited for use with a filming unit that contains or is driven by a minicomputer. The host computer can then perform visibility calculations, yielding parameterized descriptions of visible patches of various colors; a routine resident in the mini generates the appropriate set of parallel vectors to fill solidly each patch area.