Dirac-like approach for consistent discretizations of classical constrained theories

We analyze the canonical treatment of classical constrained mechanical systems formulated with a discrete time. We prove that under very general conditions, it is possible to introduce nonsingular canonical transformations that preserve the constraint surface and the Poisson or Dirac bracket structure. The conditions for the preservation of the constraints are more stringent than in the continuous case and as a consequence some of the continuum constraints become second class upon discretization and need to be solved by fixing their associated Lagrange multipliers. The gauge invariance of the discrete theory is encoded in a set of arbitrary functions that appear in the generating function of the evolution equations. The resulting scheme is general enough to accommodate the treatment of field theories on the lattice. This paper attempts to clarify and put on sounder footing a discretization technique that has already been used to treat a variety of systems, including Yang--Mills theories, BF-theory and general relativity on the lattice.Comment: 11 pages, RevTe

The Drosophila Gene abnormal spindle Encodes a Novel Microtubule-associated Protein That Associates with the Polar Regions of the Mitotic Spindle

abnormal spindle, a gene required for normal spindle structure and function in Drosophila melanogaster, lies immediately adjacent the gene tolloid at 96A/B. It encodes a 220-kD polypeptide with a predicted pI of 10.8. The recessive mutant allele asp1 directs the synthesis of a COOH terminally truncated or internally deleted peptide of ∼124 kD. Wild-type Asp protein copurifies with microtubules and is not released by salt concentrations known to dissociate most other microtubule-associated proteins. The bacterially expressed NH2-terminal 512-amino acid peptide, which has a number of potential phosphorylation sites for p34cdc2 and MAP kinases, strongly binds to microtubules. The central 579-amino acid segment of the molecule contains one short motif homologous to sequences in a number of actin bundling proteins and a second motif present at the calmodulin binding sites of several proteins. Immunofluorescence studies show that the wild-type Asp protein is localized to the polar regions of the spindle immediately surrounding the centrosome. These findings are discussed in relation to the known spindle abnormalities in asp mutants

Precipitation Process in Fe-Ni-Al-based Alloys

This chapter covers first the precipitation and coarsening processes in Fe-Ni-Al alloys aged artificially at high temperatures, as well as their effect on the mechanical properties. These results show the precipitation evolution, morphology of precipitates, coarsening kinetics and mechanical properties such as hardness. Additionally, the effect of alloying elements such as copper and chromium is also studied on the precipitation and coarsening processes. The main results of this section are concerning on the coarsening kinetics and its effect on hardness. Besides, the diffusion couple method is employed to study the precipitation and coarsening process in different Fe-Ni-Al alloy compositions, as well as its effect on the hardness. All the above aspects of precipitation and coarsening are also supported with Thermo-Calc calculations

Resultados oncológicos en enfermedad N1 posterior a la prostatectomía radical

ResumenAntecedentesLa prostatectomía radical+linfadenectomía pélvica puede mejorar la supervivencia libre de progresión y supervivencia cáncer-específica en la enfermedad ganglionar.ObjetivoAnalizar las características de los pacientes con enfermedad ganglionar en el análisis histopatológico de la prostatectomía radical.Material y métodosEstudio retrospectivo de pacientes sometidos a prostatectomía radical con enfermedad ganglionar metastásica de 1988 a 2015.ResultadosSe incluyeron 25 pacientes, de 66.5 años (DE±6.5); antígeno prostático específico medio de 20.17ng/dL (RIC: 18); con una mediana de seguimiento en 63 meses (RIC: 86). Clasificación de riesgo por D’Amico, 15 (60%) pacientes de alto, 8 (32%) intermedio y 2 (8%) de riesgo bajo. Se encontraron márgenes positivos en 15 casos (60%); estadio tumoral T2 en 4 (16%), T3A en 3 (12%), T3B en 17 (68%) y T4 en 1 (4%); cantidad de ganglios positivos, uno en 14 (56%), 2 en 3 (12%) y más de 2 en 8 (32%) casos. Recibieron radioterapia 3 pacientes (16%) y bloqueo hormonal 24 (96%). La supervivencia libre de progresión fue de 105 meses y la supervivencia cáncer-específica fue del 86 y 45% a 5 y 10 años respectivamente. El HR para progresión bioquímica fue significativo en márgenes positivos (HR: 9.5, IC95%: 0.99-91.5, p=0.50) y ≥2 ganglios positivos (HR: 8.5, IC95%: 1.1-61.9, p=0.34). La afectación≥2 ganglios predijo progresión con una OR de 7.2 (IC95% 1.06-48.6, p=0.043).ConclusionesLa supervivencia media a 5 años es superior al 80%. El número de ganglios positivos podría ser un factor predictor de progresión bioquímica.AbstractBackgroundRadical prostatectomy+pelvic lymph node dissection can improve progression-free survival and cancer-specific survival in lymph node disease.AimTo analyze the characteristics of patients with lymph node disease in the histopathologic findings of the radical prostatectomy and lymph node dissection.Material and methodsA retrospective study was carried out on patients that underwent radical prostatectomy with metastatic lymph node disease within the time frame of 1988 to 2015.ResultsThe study included 25 patients with a mean 66.5 years of age (SD±6.5), a mean prostate-specific antigen of 20.17ng/dl (IQR: 18), and a median follow-up period of 63 months (IQR: 86). According to the D’Amico classification, 15 (60%) patients were high-risk, 8 (32%) were intermediate-risk, and 2 (8%) were low-risk. Positive margins were found in 15 cases (60%); 4 (16%) patients had T2 tumor stage, 3 (12%) had T3A, 17 (68%) had T3B, and one patient (4%) had T4. Fourteen (56%) patients had one positive lymph node, 3 (12%) patients had 2 positive lymph nodes, and 8 (32%) patients had more than 2 positive lymph nodes. Three (16%) patients received radiotherapy and 24 (96%) underwent hormone blockade. Progression-free survival was 105 months and cancer-specific survival was 86% at 5 years and 45% at ten years. The HR for biochemical progression was significant in positive margins (HR: 9.5, 95% CI: 0.99-91.5, P=.50) and when there were≥2 positive lymph nodes (HR: 8.5, 95% CI: 1.1-61.9, P=0.34). Involvement of≥2 lymph nodes predicted progression with an odds ratio of 7.2 (95% CI: 1.06-48.6, P=.043).ConclusionsThe average 5-year survival was above 80%. The number of positive lymph nodes could be a predictive factor for biochemical progression

Extended Loops: A New Arena for Nonperturbative Quantum Gravity

We propose a new representation for gauge theories and quantum gravity. It can be viewed as a generalization of the loop representation. We make use of a recently introduced extension of the group of loops into a Lie Group. This extension allows the use of functional methods to solve the constraint equations. It puts in a precise framework the regularization problems of the loop representation. It has practical advantages in the search for quantum states. We present new solutions to the Wheeler-DeWitt equation that reinforce the conjecture that the Jones Polynomial is a state of nonperturbative quantum gravity.Comment: 12pp, Revtex, no figures, CGPG-93/12-

Intestinal region-specific Wnt signalling profiles reveal interrelation between cell identity and oncogenic pathway activity in cancer development.

BACKGROUND: Cancer results from the accumulation of mutations leading to the acquisition of cancer promoting characteristics such as increased proliferation and resistance to cell death. In colorectal cancer, an early mutation leading to such features usually occurs in the APC or CTNNB1 genes, thereby activating Wnt signalling. However, substantial phenotypic differences between cancers originating within the same organ, such as molecular subtypes, are not fully reflected by differences in mutations. Indeed, the phenotype seems to result from a complex interplay between the cell-intrinsic features and the acquired mutations, which is difficult to disentangle when established tumours are studied. METHODS: We use a 3D in vitro organoid model to study the early phase of colorectal cancer development. From three different murine intestinal locations we grow organoids. These are transformed to resemble adenomas after Wnt activation through lentiviral transduction with a stable form of β-Catenin. The gene expression before and after Wnt activation is compared within each intestinal origin and across the three locations using RNA sequencing. To validate and generalize our findings, we use gene expression data from patients. RESULTS: In reaction to Wnt activation we observe downregulation of location specific genes and differentiation markers. A similar effect is seen in patient data, where genes with significant differential expression between the normal left and right colon are downregulated in the cancer samples. Furthermore, the signature of Wnt target genes differs between the three intestinal locations in the organoids. The location specific Wnt signatures are dominated by genes which have been lowly expressed in the tissue of origin, and are the targets of transcription factors that are activated following enhanced Wnt signalling. CONCLUSION: We observed that the region-specific cell identity has a substantial effect on the reaction to Wnt activation in a simple intestinal adenoma model. These findings provide a way forward in resolving the distinct biology between left- and right-sided human colon cancers with potential clinical relevance

Comunidades, hábitat y tipos de suelos sobre los que se desarrolla la manzanilla de Sierra Nevada

Se realiza un estudio de la ''Manzanilla de la Sierra" (Artemisia granatensis Boiss.), describiendo el tipo de suelo en que vive este curioso endemismo de Sierra Nevada, así como su ecología, corología y comunidades en que se integra.It 's made an study of "Camomile of the Sierra" (Artemisia granatensis Boiss.), describing the kind of soil in which lives this curious endemism of Sierra Neveda, and its ecology, cOrology and cornmunity where is made up