Can Local Stress Enhancement Induce Stability in Fracture Processes? Part I: Apparent Stability

By comparing the evolution of the local and equal load sharing fiber bundle models, we point out the paradoxical result that stresses seem to make the local load sharing model stable when the equal load sharing model is not. We explain this behavior by demonstrating that it is only an apparent stability in the local load sharing model, which originates from a statistical effect due to sample averaging. Even though we use the fiber bundle model to demonstrate the apparent stability, we argue that it is a more general feature of fracture processes.Comment: 7 pages, 8 figure

Non-Commutative Batalin-Vilkovisky Algebras, Homotopy Lie Algebras and the Courant Bracket

We consider two different constructions of higher brackets. First, based on a Grassmann-odd, nilpotent \Delta operator, we define a non-commutative generalization of the higher Koszul brackets, which are used in a generalized Batalin-Vilkovisky algebra, and we show that they form a homotopy Lie algebra. Secondly, we investigate higher, so-called derived brackets built from symmetrized, nested Lie brackets with a fixed nilpotent Lie algebra element Q. We find the most general Jacobi-like identity that such a hierarchy satisfies. The numerical coefficients in front of each term in these generalized Jacobi identities are related to the Bernoulli numbers. We suggest that the definition of a homotopy Lie algebra should be enlarged to accommodate this important case. Finally, we consider the Courant bracket as an example of a derived bracket. We extend it to the "big bracket" of exterior forms and multi-vectors, and give closed formulas for the higher Courant brackets.Comment: 42 pages, LaTeX. v2: Added remarks in Section 5. v3: Added further explanation. v4: Minor adjustments. v5: Section 5 completely rewritten to include covariant construction. v6: Minor adjustments. v7: Added references and explanation to Section

A Worldsheet Description of Planar Yang-Mills Theory

We extend previous work by developing a worldsheet description of non-abelian gauge theory (Yang-Mills). This task requires the introduction of Grassmann variables on the world sheet analogous to those of the Neveu-Schwarz-Ramond formulation of string theory. A highlight of our construction is that once the three gluon vertices of Yang-Mills Feynman diagrams are given a worldsheet description, the worldsheet formalism automatically produces all of the quartic vertices.Comment: 18 pages, 15 figures, reference added, paragraph added to section 3.3, erroneous statement in section 4 corrected, typos correcte

Avaliação da vulnerabilidade ambiental das terras da microbacia do córrego Fonseca, região Serrana do estado do Rio de Janeiro.

O objetivo deste trabalho foi avaliar a vulnerabilidade ambiental das terras na área da microbacia do córrego Fonseca, visando fornecer subsídios para o planejamento de uso das terras em pequenas propriedades rurais. Os procedimentos utilizados envolveram a aquisição, conversão e armazenamento de dados básicos em meio digital, construção de um banco de dados digitais, superposição de mapas temáticos em SIG, com atribuição de valores específicos a cada um deles, segundo a importância dos fatores em relação à vulnerabilidade ambiental. O mapa final, produzido na escala 1:10.000, estratifica a área de estudo em 6 classes de vulnerabilidade ambiental, sendo elas: baixa, moderada, alta, alta a muito alta, muito alta e extremamente alta. Os resultados produzidos contribuem para o planejamento ambiental da área

Suscetibilidade dos solos à erosão na microbacia do córrego Fonseca, região Serrana do estado do Rio de Janeiro.

O objetivo deste trabalho foi avaliar a suscetibilidade dos solos à erosão na área da microbacia do córrego Fonseca, visando fornecer subsídios para o planejamento de uso das terras em pequenas propriedades rurais. Os procedimentos utilizados constaram da interpretação de parâmetros dos tipos de solo, cobertura vegetal, litologia, relevo, precipitação e uso das terras, aliados à superposição temática em SIG, com atribuição de valores específicos a cada um deles, segundo o grau de importância desses fatores em relação à erosão. Foi gerado um mapa na escala 1:10.000, estratificado em 7 classes de suscetibilidade à erosão, discriminando e quantificando as classes de erosão que ocorrem na área. Os resultados contribuem para o plano de manejo conservacionista da área de estudo

Uso atual e cobertura das terras na área da microbacia do córrego Fonseca, região serrana do estado do Rio de Janeiro.

O presente trabalho mapeia o uso e cobertura vegetal das terras na área da microbacia do córrego Fonseca, visando fornecer informações para a gestão sustentável das terras. A metodologia utilizada combinou práticas de geoprocessamento, produtos de sensoriamento remoto, sistema de informação geográfica (SIG) e trabalhos de campo. A distribuição espacial das classes de uso e cobertura das terras mostram que a maior parte da área encontra-se recoberta, sendo 27,89% com floresta e 11,24% com reflorestamento de eucalipto, seguidos de fruticultura com 15,35%, os demais 45,52% corresponde às outras classes de uso e cobertura das terras. Os resultados contribuem para o plano de manejo conservacionista da área de estudo

Migrena a biomarkery chorób układu sercowo-naczyniowego u kobiet

W omawianym badaniu występowanie migreny było skojarzone z niekorzystnym profilem sercowo-naczyniowym. Analizując kohortę 27 626 kobiet w wieku 45 lat lub więcej, dokonano oceny współwystępowania migreny z aurą lub bez aury z podwyższonymi stężeniami cholesterolu całkowitego (TC, total cholesterol), cholesterolu frakcji HDL (high-density lipoprotein cholesterol) oraz cholesterolu frakcji nie-HDL, apolipoprotein (Apo) A-1 i B100, lipoproteiny A, białka C-reaktywnego (CRP, C-reactive protein), fibrynogenu, homocysteiny, kreatyniny, międzykomórkowej molekuły adhezji-1 (ICAM-1, intercellular adhesion molecule-1). Ponad 5000 kobiet (5087) w wywiadzie chorobowym wskazało epizody migrenowe. W porównaniu z kobietami bez wywiadu migrenowego u kobiet z migreną stwierdzono wyższe stężenia: TC (iloraz szans [OR, odds ratio] 1,09; 95% przedział ufności [CI, confidence interval] 1,01-1,18), cholesterolu frakcji nie-HDL (OR 1,14; 95% CI 1,05-1,23), Apo-B100 (OR 1,09; 95% CI 1,01-1,18) i CRP (OR 1,13; 95% CI 1,05-1,22). Wartości powyższych biomarkerów nie różniły się w zależności od występowania aury migrenowej lub częstości napadów migreny. Należy nadmienić, że zależności stwierdzone w badanej dużej kohorcie kobiet miały charakter istotny statystycznie, ale ilorazy szans różniły się tylko nieznacznie w grupach z migreną i bez migreny. Polski Przegląd Neurologiczny 2008; 4 (1): 40-4

A Worldsheet Description of Large N_c Quantum Field Theory

The N_c to infinity limit of a matrix quantum field theory is equivalent to summing only planar Feynman diagrams. The possibility of interpreting this sum as some kind world-sheet theory has been in the air ever since 't Hooft's original paper. We establish here just such a world sheet description for a scalar quantum field with interaction term g\Tr\phi^3, and we indicate how the approach might be extended to more general field theories.Comment: 16 pages, 3 figures, latex, typos corrected, references added, interpretation of ghost determinant clarifie

Absolute instruments and perfect imaging in geometrical optics

We investigate imaging by spherically symmetric absolute instruments that provide perfect imaging in the sense of geometrical optics. We derive a number of properties of such devices, present a general method for designing them and use this method to propose several new absolute instruments, in particular a lens providing a stigmatic image of an optically homogeneous region and having a moderate refractive index range.Comment: 20 pages, 9 image

Minimal short-term effect of dietary 2'-fucosyllactose on bacterial colonisation, intestinal function and necrotising enterocolitis in preterm pigs

AbstractHuman milk decreases the risk of necrotising enterocolitis (NEC), a severe gastrointestinal disease that occurs in 5–10 % of preterm infants. The prebiotic and immune-modulatory effects of milk oligosaccharides may contribute to this protection. Preterm pigs were used to test whether infant formula enriched with α1,2-fucosyllactose (2'-FL, the most abundant oligosaccharide in human milk) would benefit gut microbial colonisation and NEC resistance after preterm birth. Caesarean-delivered preterm pigs were fed formula (Controls, n 17) or formula with 5 g/l 2'-FL (2'-FL, n 16) for 5 d; eight 2'-FL pigs (50 %) and twelve Controls (71 %) developed NEC, with no difference in lesion scores (P=0·35); 2'-FL pigs tended to have less anaerobic bacteria in caecal contents (P=0·22), but no difference in gut microbiota between groups were observed by fluorescence in situ hybridisation and 454 pyrosequencing. Abundant α1,2-fucose was detected in the intestine with no difference between groups, and intestinal structure (villus height, permeability) and digestive function (hexose absorption, brush border enzyme activities) were not affected by 2'-FL. Formula enrichment with 2'-FL does not affect gut microbiology, digestive function or NEC sensitivity in pigs within the first few days after preterm birth. Milk 2'-FL may not be critical in the immediate postnatal period of preterm neonates when gut colonisation and intestinal immunity are still immature.</jats:p