Microdeformation in Vredefort rocks; evidence for shock metamorphism

Planar microdeformations in quartz from basement or collar rocks of the Vredefort Dome have been cited for years as the main microtextural evidence for shock metamorphism in this structure. In addition, Schreyer describes feldspar recrystallization in rocks from the center of the Dome as the result of transformation of diaplectic glass, and Lilly reported the sighting of mosaicism in quartz. These textural observations are widely believed to indicate either an impact or an internally produced shock origin for the Vredefort Dome. Two types of (mostly sub) planar microdeformations are displayed in quartz grains from Vredefort rocks: (1) fluid inclusion trails, and (2) straight optical discontinuities that sometimes resemble lamellae. Both types occur as single features or as single or multiple sets in quartz grains. Besides qualitative descriptions of cleavage and recrystallization in feldspar and kinkbands in mica, no further microtextural evidence for shock metamorphism at Vredefort has been reported to date. Some 150 thin sections of Vredefort basement rocks were re-examined for potential shock and other deformation effects in all rock-forming minerals. This included petrographic study of two drill cores from the immediate vicinity of the center of the Dome. Observations recorded throughout the granitic core are given along with conclusions

Ecumenical modal logic

The discussion about how to put together Gentzen's systems for classical and intuitionistic logic in a single unified system is back in fashion. Indeed, recently Prawitz and others have been discussing the so called Ecumenical Systems, where connectives from these logics can co-exist in peace. In Prawitz' system, the classical logician and the intuitionistic logician would share the universal quantifier, conjunction, negation, and the constant for the absurd, but they would each have their own existential quantifier, disjunction, and implication, with different meanings. Prawitz' main idea is that these different meanings are given by a semantical framework that can be accepted by both parties. In a recent work, Ecumenical sequent calculi and a nested system were presented, and some very interesting proof theoretical properties of the systems were established. In this work we extend Prawitz' Ecumenical idea to alethic K-modalities

Planejamento da atividade leiteira: sugestões para os produtores iniciantes.

bitstream/item/65443/1/COT-56-Planejamento-da-atividade.pd

Linear Logic Programming for Narrative Generation

Abstract. In this paper, we explore the use of Linear Logic programming for story generation. We use the language Celf to represent narrative knowledge, and its own querying mechanism to generate story instances, through a number of proof terms. Each proof term obtained is used, through a resource-flow analysis, to build a directed graph where nodes are narrative actions and edges represent inferred causality relationships. Such graphs represent narrative plots structured by narrative causality. Building on previous work evidencing the suitability of Linear Logic as a conceptual model of action and change for narratives, we explore the conditions under which these representations can be operationalized through Linear Logic Programming techniques. This approach is a candidate technique for narrative generation which unifies declarative representations and generation via query and deduction mechanisms

Investigations on the 1.7 micron residual absorption feature in the vegetation reflection spectrum

The detection and interpretation of the weak absorption features associated with the biochemical components of vegetation is of great potential interest to a variety of applications ranging from classification to global change studies. This recent subject is also challenging because the spectral signature of the biochemicals is only detectable as a small distortion of the infrared spectrum which is mainly governed by water. Furthermore, the interpretation is complicated by complexity of the molecules (lignin, cellulose, starch, proteins) which contain a large number of different and common chemical bonds. In this paper, we present investigations on the absorption feature centered at 1.7 micron; these were conducted both on AVIRIS data and laboratory reflectance spectra of leaves

Focusing in Asynchronous Games

Game semantics provides an interactive point of view on proofs, which enables one to describe precisely their dynamical behavior during cut elimination, by considering formulas as games on which proofs induce strategies. We are specifically interested here in relating two such semantics of linear logic, of very different flavor, which both take in account concurrent features of the proofs: asynchronous games and concurrent games. Interestingly, we show that associating a concurrent strategy to an asynchronous strategy can be seen as a semantical counterpart of the focusing property of linear logic

Epoxy-cross-linked Polyamine CO2 Sorbents Enhanced via Hydrophobic Functionalization

Optimizing sorption capacity and amine efficiency are among the major challenges in developing solid carbon dioxide sorbents. Such materials frequently feature polyamines impregnated onto supports adding weight to the sorbents. This work presents the cross-linking of polyethyleneimine (PEI) by the industrially available epoxy resin, bisphenol-A diglycidyl ether (DER) to form support-free sorbent materials. Prior to cross-linking, the polyamine chain is functionalized with hydrophobic additives; one material modified with the branched chain hydrocarbon 2-ethylhexyl glycidyl ether displays CO2 uptake of 0.195 g/g, 4.43 mmol CO2/g (1 atm single component CO2, 90 °C). The additive loading affects the cross-linking, with the lesser cross-linked materials showing more favorable sorption capacities and higher amine efficiencies. The type of additive also influences sorption, with the larger, longer and bulkier additives better able to free the amine from their hydrogen bonding network, generally promoting better sorption. As well as increasing CO2 uptake, the additives also reduce the optimum sorption temperature, offering a handle to tune sorbents for specific working conditions. The best performing material shows high selectivity for CO2 sorption, and under sorption cycles in a 10% CO2/90% N2 mixture, utilizing temperature swing desorption, demonstrates a good working capacity of 9.5% CO2 uptake over the course of 29 cycles. Furthermore, humidity has been found to promote CO2 sorption at lower temperatures with a CO2 uptake of 0.235 g/g, 5.34 mmol/g (1 atm single component CO2, 25 °C) using a pre-hydrated sample. Overall, these findings confirm the value of our approach where cross-linking emerges as a valid and practical alternative to loading polyamines onto solid supports. This work demonstrates the versatility of these types of materials and their potential for use in large scale carbon capture systems

Temperature measurements of fusion plasmas produced by petawatt laser-irradiated D2-3He or CD4-3He clustering gases

Two different methods have been employed to determine the plasma temperature in a laser-cluster fusion experiment on the Texas Petawatt laser. In the first, the temperature was derived from time-of-flight data of deuterium ions ejected from exploding D2 or CD4 clusters. In the second, the temperature was measured from the ratio of the rates of two different nuclear fusion reactions occurring in the plasma at the same time: D(d, 3He)n and 3He(d, p)4He. The temperatures determined by these two methods agree well, which indicates that: i) The ion energy distribution is not significantly distorted when ions travel in the disassembling plasma; ii) The kinetic energy of deuterium ions, especially the hottest part responsible for nuclear fusion, is well described by a near-Maxwellian distribution.Comment: 13 pages, 4 figure