Open Interstices Research Articles

Study on anisotropies and momentum densities in AlN, GaN and InN by positron annihilation

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalized positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8-N. Initial results show a clear asymmetrical positron charge distribution relative to the bond center. It is observed that the positron density is maximum in the open interstices and is excluded not only, from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001,110) planes. The results are used to analyze the positron effects in AlN, GaN and InN compounds. Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the twodimensional angular correlation of annihilation radiation (2D-ACAR).

Gulf “alter-latinas:” Cross-dressing Women Travel Beyond the Gulfs of Transnationality and Transexuality

Gulf “alter-latinas:” Cross-dressing Women Travel Beyond the Gulfs of Transnationality and Transexuality Raquel González Rivas (bio) . . . y así se construyen los relatos verdaderos, los relatos rizomas, los relatos manglares, donde el que escribe un silencio y una acción siempre está en el medio de las cosas, acá y allá, adentro y afuera, solo y comunicante en la red de relatos, telaraña de telarañas a lo largo del cuerpo de Dios. . . . and this is how you build a true story, a rhizomatic story, a mangrove story, where s/he who writes a silence and an action is always in the middle of things, here and there, inside and outside, alone and in communion in the web of stories, web of webs across the body of God.1 — Antonio Benítez Rojo, Mujer en Traje de Batalla (Woman in Battle Dress) The shifting boundaries that converge in the Gulf and the watery lines between “Caribbean” and “Southern” open interstices where “alter-latinas” can invent and reinvent themselves. For our purposes, these “alter-latinas” are the cross-dressing heroines in Cuban author Antonio Benítez Rojo’s Mujer en Traje de Batalla (2001) and Confederate soldier Loreta Janeta Velazquez’s memoir, The Woman in Battle (1876). These two narratives highlight the transgender and transnational journeys of their protagonist-avatars: the fictional Henriette [End Page 128] Faber and the self-authored subject Loreta Janeta Velazquez. Here, we will examine how border transgressions of gender and nation go hand in hand in both texts, and how one disavowed relationship loosens others and opens new possibilities. Cultural exile seems to have prepared the way for “gender exile” in Henriette’s and Loreta Janeta’s narratives — as their capacity for acting as either men or women is sharpened by their capacity for moving from one culture to the next. Their knack for switching wardrobe, and switching accents, prepared them for performances that push the limits of national, political and sexual identity. As Judith Butler explains, “bodies never quite comply with the norms by which their materialization is impelled,” but rather rematerialize and spawn rearticulations that call into question the hegemonic force of the law (xii). Butler’s observation helps us examine how the heroines of these two cross-dressing texts rearticulate the gap by which “the heterosexual imperative enables certain sexed identifications and forecloses/disavows other identifications” (xiii). Henriette Faber, the fictional protagonist of Benítez Rojo’s Mujer en Traje de Batalla, is an avatar of many scripted (dis)guises, playing the role, for example, of a European woman posing as a Cuban man in order to gain access to medical training in Paris. Henriette rehearses and foreshadows this key performance in several earlier narrative episodes. First, she disguises as a Turkish messenger to infiltrate Napoleon’s army and meet up with her husband. She is later instructed by Maryse — a mother-figure and a performer herself — during a set of adventures in Maryse’s traveling circus. There are other instances in which Henriette practices or repeats performances that test her ability to blur her own gender and national boundaries, as we will see later. Loreta Janeta Velazquez, for her part, also takes on mentors of gender performance — practicing cross-dressing with the help of a tailor and the support of her own husband whom she persuades to accompany her to camp to test her ability to pass for a soldier. Both Benítez Rojo’s and Velazquez’s texts portray the details of their protagonists’ physical transformations and dress changes, including Loreta Janeta’s elaborate wire net shields to bulk up her appearance (58), and Henriette’s “man’s habit” to conceal her female figure (290). As cross-dressing performers in military theaters, both characters dread the physical exam more than any war danger for fear of being exposed as impostors, and considerable narrative space is given to planning their disguises, demeanor, and linguistic patterns. As cosmopolitan gypsies, neither one of them is easy to describe in terms of [End Page 129] nationality or identity politics. Henriette might be Swiss or French, or Cuban, depending on the stage. Loreta Janeta might be West Indian, Cuban, French Creole or Southern...

Comment on Peckham: contagion-epidemiological models and financial crises

A number of contradictory metaphors are interwoven with network culture. Perhaps the most striking is the computer scientist Tim Berners-Lee’s image of a spider’s web, which is used to represent the open interstices of communication, but also raises questions about network vulnerability. For example, is being on the web tantamount to the experience of a spider or a fly? Indeed, the World Wide Web was preceded by a host of Internet creepy crawlies: namely, the viruses and worms, which surfaced as a threat to the culture of sharing in the 1980s. The viral metaphor was keenly implemented by early computer security researchers who made fairly close, but often crude, analogical comparisons between digital viruses and their biological counterparts, as well as drawing on immunology to inspire a business of viral containment. The dangers of too much connectivity As Robert Peckham argues in relation to the global interdependencies revealed by financial crises since the 1990s, 1 over the last three decades a paradigm shift has taken place: a shift away from a culture of free sharing towards a culture in which proliferating connectivity has given rise to new anxieties about infection. As the age of networks mutated into the age of contagion, the metaphor of virulent infection turned out to be a perfect justificatory device for an indiscriminate security paradigm. While diverse and conflicting interests, including those of marketers and anti-capitalist groups, sought to harness the ‘positive’ viral potential of this network, too much connectivity was deemed to be harmful. The purported danger posed by excessive connectivity provided a rational for organizing and exerting control over a network via, for instance, the application of epidemiological models of disease emergence in the social sphere, but also via the widespread imposition of generalized immunological defenses, anomaly detection and the obligation of personal hygiene. My own work in this area began by asking if we can look beyond these ubiquitous biomedical metaphors of viral infectivity to locate a different kind of contagious property inherent in the physics of network culture itself. 2 Might it be possible, in other words, to redirect theoretical discussion away from conventional biomedical analogies that have dominated discussion of the viral media ecology towards a new understanding of the ‘virality’ of communication? Here, my approach overlaps with Peckham’s critique of contagion theory in economics. While pervasive biomedical analogies have shaped (and constrained) popular discourses surrounding the networked nature of the contemporary media—fueling fears and propelling an ‘antivirus’ industry—the problem of too much connectivity readily dissipates into a transcendent comparison that fails to grasp the specific material relations of network culture. In contrast, ‘virality’ might be understood, not in terms of a divisive pseudo-biological threat that comes from without to disrupt, but as a quality intrinsic to contemporary network culture, where different forms of ‘contagia’— biological and cultural, human and non-human—interact: from trivial video virals and so-called ‘memes’ to more sobering ‘outbreaks’ of financial and emotional contagion.

STUDY ON MOMENTUM DENSITY IN SEMICONDUCTOR ALLOYS GeC and SnC BY POSITRON ANNIHILATION

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalized positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8-N . Initial results show a clear asymmetrical positron charge distribution relative to the bond center. It is observed that the positron density is maximum in the open interstices and is excluded not only from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001, 110) planes. The results are used to analyze the positron effects in GeC and SnC . Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the two-dimensional angular correlation of annihilation radiation (2D-ACAR).

« Anon, anon, sir »: Popular Discourse, Syntactical Limitations and Ideological Containment in 1 Henry IV and Coriolanus

This paper discusses the representation of popular discourse in Shakespeare’s 1Henry IV and Coriolanus. Whether in the tapster of the Boar’s Head or the mutinous citizens of Rome, poor eloquence and disrupted syntax emerge as permanent features of popular discourse. They bespeak simple-mindedness, doubt, flimsiness or mutability, and open interstices inviting manipulation, subversion or radical reversals, exploited either as sheer entertainment or in a political perspective. This paper finally addresses the dialectics of linguistic emergence and containment, and poses the question as to whether popular discourse can be more than a foil to the elaborate discourse of dominant ideology.

Study on momentum density in semiconductor compounds ZnS, ZnSe and ZnTe by positron annihilation

The independent particle model (IPM) coupled with empirical pseudopotential method (EPM) was used to compute the thermalised positron charge densities in specific family of binary tetrahedrally coordinated crystals of formula ANB8?N . Initial results show a clear asymmetrical positron charge distribution relative to the bond centre. It is observed that the positron density is maximum in the open interstices and is excluded not only, from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001, 110) planes. The results are used to analyse the positron effects in ZnS, ZnSe and ZnTe. Our computational technique provides the theoretical means of interpreting the k-space densities obtained experimentally using the two-dimensional angular correlation of annihilation radiation (2D-ACAR).

Theoretical studies of positron annihilation in YN and ScN

Valence electron and positron charge densities in YN and ScN are obtained from wave functions derived in a model pseudopotential band structure calculation coupled with the independent particle model (IPM). It is observed that the positron density is maximum in the open interstices and is excluded not only, from the ion cores but also to a considerable degree from the valence bonds. Electron–positron momentum densities are calculated for the (0 0 1) and (1 1 0) planes. The results are used to analyze the positron effect in binary alloy semiconductors.

Positron annihilation in boron nitride

Electron and positron charge densities are calculated as a function of position in the unit cell for boron nitride. Wave functions are derived from pseudopotential band structure calculations and the independent particle approximation (IPM), respectively, for electrons and positrons. It is observed that the positron density is maximum in the open interstices and is excluded not only from ion cores but also to a considerable degree from valence bonds. Electron-positron momentum densities are calculated for (001,110) planes. The results are used in order to analyse the positron effects in BN.

Pressure dependence of positron annihilation in boron phosphide

We have obtained the valence electron and positron charge densities in boron phosphide from wavefunctions derived in a model pseudopotential band structure calculation. The charge densities are calculated at pressures ranging from 0 to 90 GPa. We find that the positron density is maximum in the open interstices and is excluded not only from the ion cores, but also to a considerable degree from the valence bonds. Electron momentum densities are calculated in the (001–110) plane. The observation that the total positron annihilation rate increases with pressure has been explained in terms of increased positron penetration into the ion cores.

POSITRON ANNIHILATION IN SiC

Valence electron and positron charge densities in SiC are obtained from wave functions derived in a model pseudopotential bandstructure calculation. It is observed that the positron density is maximum in the open interstices and is excluded not only from the ion cores but also, to a considerable degree, from the valence bonds. Electron–positron momentum densities are calculated for the (001–110) plane. The results are used to analyze the positron effect in large gap semiconductors.

Two Designs of Marine Egg Masses and their Divergent Consequences for Oxygen Supply and Desiccation in Air

Two common types of egg masses rely on differing routes of supply of oxygen in water. When embryos are embedded in a gelatinous matrix, oxygen is supplied by diffusion through the gel, and thicker masses require more gel per embryo. When an adherent mass of eggs lacks a gel matrix, oxygen can be provided from water flowing through the open interstices between eggs, and larger eggs provide larger channels and thus less resistance to flow. Both types occur intertidally, where they are periodically exposed to air. Exposure to air can have a greater effect on oxygen supply via interstices than on supply via gel. Oxygen diffusing in interstices drained of water provides increased rates of supply to masses of adherent eggs. In contrast, diffusion through gel is similar for masses in air and water. Effects of emersion on desiccation also differ for the two types of egg masses. Additional gel matrix can reduce salinity change from desiccation while enhancing oxygen supply, whereas draining of interstices, though necessary for oxygen supply, may increase risk of desiccation.

Electronic and Positronic Structure of Diamond under Normal and High Pressure

AbstractEmpirical nonlocal pseudopotentials of diamond which can describe the electronic energy structure over a wide energy range of more than 20 eV from the bottom of the valence band are determined. The nonlocality of the potential is described by the Gaussian model. The optimized nonlocal pseudopotential reproduces the energy band structure within 5%. The valence electron and positron charge densities in diamond are obtained from wave functions derived from this model at normal and under hydrostatic pressure. It is found that the positron density is maximum in the open interstices and is excluded not only as usual, from the ion cores but also to a considerable degree from the valence bonds.

Positron annihilation in narrow‐gap semiconductors

AbstractThe valence electron and positron charge densities in InAs and InSb are obtained from wave functions derived in a model pseudopotential band‐structure calculation. It is found that the positron density is maximum in the open interstices and is excluded not only, as usual, from the ion cores but also to a considerable degree from the valence bonds. Electron‐positron momentum densities are calculated for the (001–110) plane. The results are used to analyze the positron effect in narrow‐gap semiconductors.

Pressure dependence of positron distribution in Si

We have obtained the valence electron and positron charge densities in Si from wavefunctions derived in a model pseudopotential band structure calculation at normal and under hydrostatic pressure. We find that the positron density is maximum in the open interstices and is excluded not only, as usual, from the ion cores but also to a considerable degree from the valence bonds.

Pressure dependence of positron annihilation in InP

We have obtained the valence electron and positron charge densities in InP from wavefunctions derived in a model pseudopotential bandstructure calculation at normal and under hydrostatic pressure. We find that the positron density is maximum in the open interstices and is excluded not only, as usual, from the ion cores but also to a considerable degree from the valence bonds. Electron-positron momentum densities are calculated for the (001–110) plane. The results are used to analyze the positron effect in InP.

Ecological impact of urban stormwater runoff studied in experimental flumes: Population loss by drift and availability of refugial space

Urban stormwater runoff discharged through sewer systems into streams causes flush spills of water and pollutants in the receiving water. To make the right decisions in future plannings of the very costly rehabilitation of sewer systems, a solid ecological data base on the critical parameters of sewer overflows is badly needed. Therefore, we designed a laboratory flume which was operated in circular flow mode (to ensure adaptation of the test organisms) and in flow-through mode during the simulation of sewer overflows (to allow a proper evaluation of population loss by drift). Examples on the behaviour during the adaptation phase and the population loss during the exposure to flush spills of water and/or a mixture of sewage and clean water of a benthic invertebrate (Gammarus pulex) demonstrate the potential of the flume to identify critical parameters of sewer overflows at “quasireal-world-conditions”. We found clear evidence for synergetic effects since the exposure to high flow and sewage caused higher population loss ofGammarus than the sum of population loss at exposure to only high flow or only sewage. Population loss considerably depended on the availability of refugial space: if the interstices of the gravel in the flume were silted, this loss was higher than at open interstices. Only ten minutes of movement of the material forming the flume bottom reduced the population ofGammarus to about 60 or 50% of its initial size. Hence, our data strongly suggest that the characteristics of the receiving stream (refugial space, bed stability) play an important role for the potential ecological impact of a sewer overflow. Changes of stream morphology and/or creation of refugial space plus an appropriate technical solution for overflow treatment may be less costly and more effective than a large-scale technical project. Thus, the stream itself should be a major element in future management decisions.

Constraints on egg masses. II. Effect of spacing, size, and number of eggs on ventilation of masses of embryos in jelly, adherent groups, or thin-walled capsules

Simple physical models indicate constraints on the thickness of egg masses. Constraints differ for scaling of masses of adherent eggs with open interstices, eggs embedded in jelly, and eggs in fluid-filled, thin-walled capsules. (1) For adherent eggs with open interstices, the pressure head necessary to ventilate the mass is proportional to the square of the thickness of the mass and inversely proportional to a power of egg diameter greater than two. A 1-cm thick mass of 100-μm eggs, with oxygen consumption typical of planktonic embryos requires a pressure head >2 cm of water, which cannot be generated by most parents. (2) In contrast, oxygen diffuses through a gelatinous mass and increased spacing of embryos by jelly decreases the oxygen consumption per unit volume of the entire mass. For a spherical gelatinous mass with a constant number of embryos, oxygen supply per embryo increases in proportion to the radius of the mass. (3) Capsules with a thin wall and well-mixed internal fluid permit internal oxygen consumption to increase in proportion to capsule surface area, a less severe constraint than that for gelatinous masses. Ventilation becomes independent of embryo size over a wide range of sizes, a less severe constraint on embryo size than for masses of adherent embryos. Free spawning is a mechanism for adequately spacing small eggs that requires the minimum extraembryonic material. Large eggs are preadapted for life in a mass of adherent embryos. Brooding may be correlated with small adult size in many taxa because large adults cannot ventilate all the eggs that they produce.

Electron Microscopic Study of Inhibition of Macrophage Migration in Delayed Hypersensitivity

Abstract The migration of peritoneal cells from guinea pigs with delayed hypersensitivity to bacillus Calmette-Guérin was studied by light and electron microscopy. To permit satisfactory morphologic study and monitoring of cell migration, cells were concentrated in clots whose open interstices were accessible to medium. This clot technique, compared to the commonly used capillary tube, provided: 1) better viability and more uniform morphology, 2) better sampling for electron microscopy, 3) more uniform exposure to antigen, and 4) the opportunity to use fewer cells. Suspension cultures of spleen cells were also examined. among peritoneal exudate cells from sensitized animals, purified protein derivative (PPD) induced clumping of macrophages, an increase in the number of their microvilli, and some cell death. Many of the clumped cells bore numerous microvilli which intertwined with those of contiguous cells. No intracellular differences between sensitized and control macrophages or lymphocytes, exposed or not exposed to antigen, were discernible. Sensitized cells exposed to PPD in suspension cultures were disc-shaped and clumped. Control cells were flattened on the flask floor, angulated and usually separated. We believe that both the rounded form of the macrophages and their clumping may contribute to the lack of migration.