Boundary Terms for Causal Sets

We propose a family of boundary terms for the action of a causal set with a spacelike boundary. We show that in the continuum limit one recovers the Gibbons-Hawking-York boundary term in the mean. We also calculate the continuum limit of the mean causal set action for an Alexandrov interval in flat spacetime. We find that it is equal to the volume of the codimension-2 intersection of the two light-cone boundaries of the interval

L’anti-théologie janséniste de Sade

Sade : une pensée et une œuvre de part en part déicides – non pas seulement sans Dieu mais contre Dieu. C’est de l’anti-théologie sadienne dont nous parle ici Michel Surya, une anti-théologie qui engage avec elle la sexualité, la littérature et la pensée. L’hypothèse d’un jansénisme paradoxal chez Sade est une idée qu’il fallait savoir défendre – cet entretien en témoigne

L’anti-théologie janséniste de Sade

Sade : une pensée et une œuvre de part en part déicides – non pas seulement sans Dieu mais contre Dieu. C’est de l’anti-théologie sadienne dont nous parle ici Michel Surya, une anti-théologie qui engage avec elle la sexualité, la littérature et la pensée. L’hypothèse d’un jansénisme paradoxal chez Sade est une idée qu’il fallait savoir défendre – cet entretien en témoigne

Kinking nonlinear elastic solids, nanoindentations, and geology

Physical Review Letters, 92(25): pp. 2555081-4.The physical mechanism responsible for nonlinear elastic, hysteretic, and discrete memory response of nonlinear mesoscopic elastic solids has to date not been identified.We show, by nanoindenting mica single crystals, that this response is most likely due to the formation of dissipative and fully reversible, dislocation-based kink bands. We further claim that solids with high c=a ratios, which per force are plastically anisotropic, should deform by kinking, provided they do not twin. These kinking nonlinear elastic solids include layered ternary carbides, nitrides, oxides, and semiconductors, graphite, and the layered phases, such as mica, present in nonlinear mesoscopic elastic solids

Spherical nanoindentations and kink bands in Ti3SiC2

Journal of Materials Research, 19(4): pp. 1139-1148. Retrieved September 19, 2006 from http://www.mse.drexel.edu/max/pdf%20references/drexel_pdfs/papers/MRS_Anand.pdf.We report for the first time on load versus depth-of-indentation response of Ti3SiC2 surfaces loaded with a 13.5 m spherical tipped diamond indenter up to loads of 500 mN. Using orientation imaging microscopy, two groups of crystals were identified; one in which the basal planes were parallel to, and the other normal to, the surface. When the load-penetration depth curves were converted to stress-strain curves the following was apparent: when the surfaces were loaded normal to the c axis, the response at the lowest loads was linear elastic—well described by a modulus of 320 GPa—followed by a clear yield point at approximately 4.5 GPa. And while the first cycle was slightly open, the next 4 on the same location were significantly harder, almost indistinguishable, and fully reversible. At the highest loads (500 mN) pop-ins due to delaminations between basal planes were observed. When pop-ins were not observed the indentations, for the most part, left no trace. When the load was applied parallel to the c axis, the initial response was again linear elastic (modulus of 320 GPa) followed by a yield point of approximately 4 GPa. Here again significant hardening was observed between the first and subsequent cycles. Each cycle resulted in some strain, but no concomitant increase in yield points. This orientation was even more damage tolerant than the orthogonal direction. This response was attributed to the formation of incipient kink bands that lead to the formation of regular kink bands. Remarkably, these dislocation-based mechanisms allow repeated loading of Ti3SiC2 without damage, while dissipating significant amounts of energy per unit volume, Wd, during each cycle. The values of Wd measured herein were in excellent agreement with corresponding measurements in simple compression tests reported earlier, confirming that the same mechanisms continue to operate even at the high (≈9 GPa) stress levels typical of the indentation experiments

Microscale modeling of kinking nonlinear elastic solids

Physical Review B: Condensed Matter and Materials Physics, 71(13): pp. 134101-1—134101-8. Retrieved September 19, 2006 from http://www.mse.drexel.edu/max/pdf%20references/drexel_pdfs/papers/PRBTheory_71_134101.pdf. DOI: http://dx.doi.org/10.1103/PhysRevB.71.134101Recently we identified and classified a class of solids as kinking nonlinear elastic sKNEd because they deform by the formation of kink bands. KNE solids represent a large family that include, among others, layered ternary carbides and nitrides, layered oxides and semiconductors, zinc, cadmium, graphite, ice, and the layered silicates, such as mica, present in nonlinear mesoscopic elastic solids. Herein we present a microscale model that accounts for the mechanical response of KNE solids to compressive stresses and apply it to two very different solids: Ti3SiC2 and graphite. Building on the Frank and Stroh model put forth in the 1950’s for the formation of kink bands, we developed a comprehensive theory that accounts for the contributions of incipient kink bands sIKBsd and dislocations pile-ups produced by normal glide processes to the nonlinear strains and stored strain energies. The theory provides estimates for the densities of IKBs, the dislocation densities, both from the IKBs and dislocation pileups, as well as the energy dissipated by the motion of the dislocations

Dynamic elastic hysteretic solids and dislocations

Physical Review Letters, 94(8): pp. 085501-1—085501-4. Retrieved September 19, 2006 from http://www.mse.drexel.edu/max/pdf%20references/drexel_pdfs/papers/PhysRevLett_94_085501.pdf. DOI: http://dx.doi.org/10.1103/PhysRevLett.94.085501Recently we showed that the quasistatic response of nonlinear mesoscopic elastic solids to stress can be explained by invoking the formation of dislocation-based incipient kink bands. In this Letter, using resonant ultrasound spectroscopy, we confirm that the dynamical behavior of these nonlinear elastic systems is due to the interaction of dislocations with the ultrasound waves, thus resolving a long-standing mystery

Implementation of a Shared Data Repository and Common Data Dictionary for Fetal Alcohol Spectrum Disorders Research

Many previous attempts by fetal alcohol spectrum disorders researchers to compare data across multiple prospective and retrospective human studies have failed due to both structural differences in the collected data as well as difficulty in coming to agreement on the precise meaning of the terminology used to describe the collected data. Although some groups of researchers have an established track record of successfully integrating data, attempts to integrate data more broadly amongst different groups of researchers have generally faltered. Lack of tools to help researchers share and integrate data has also hampered data analysis. This situation has delayed improving diagnosis, intervention, and treatment before and after birth. We worked with various researchers and research programs in the Collaborative Initiative on Fetal Alcohol Spectrum Disorders (CI-FASD) to develop a set of common data dictionaries to describe the data to be collected, including definitions of terms and specification of allowable values. The resulting data dictionaries were the basis for creating a central data repository (CI-FASD Central Repository) and software tools to input and query data. Data entry restrictions ensure that only data which conform to the data dictionaries reach the CI-FASD Central Repository. The result is an effective system for centralized and unified management of the data collected and analyzed by the initiative, including a secure, long-term data repository. CI-FASD researchers are able to integrate and analyze data of different types, collected using multiple methods, and collected from multiple populations, and data are retained for future reuse in a secure, robust repository

The question concerning human rights and human rightlessness: disposability and struggle in the Bhopal gas disaster

In the midst of concerns about diminishing political support for human rights, individuals and groups across the globe continue to invoke them in their diverse struggles against oppression and injustice. Yet both those concerned with the future of human rights and those who champion rights activism as essential to resistance, assume that human rights – as law, discourse and practices of rights claiming – can ameliorate rightlessness. In questioning this assumption, this article seeks also to reconceptualise rightlessness by engaging with contemporary discussions of disposability and social abandonment in an attempt to be attentive to forms of rightlessness co-emergent with the operations of global capital. Developing a heuristic analytics of rightlessness, it evaluates the relatively recent attempts to mobilise human rights as a frame for analysis and action in the campaigns for justice following the 3 December 1984 gas leak from Union Carbide Corporation’s (UCC) pesticide manufacturing plant in Bhopal, India. Informed by the complex effects of human rights in the amelioration of rightlessness, the article calls for reconstituting human rights as an optics of rightlessness