Watson's theorem and electromagnetism in K -> pi pi decay

We consider what constraints unitarity and CPT invariance yield on the strong and electromagnetic phases entering K -> pi pi decay. In particular, we show that the relative size of the electromagnetically-induced changes in the I=0 and I=2 phase shifts in the two--pion final state do not depend on the explicit coupling to the pi^+ pi^- gamma channel. This demonstrates that Watson's theorem can be extended to include the presence of electromagnetism. We point out the consequences for the general structure of the K -> pi pi decay amplitudes in the presence of isospin violation.Comment: 7 pages, LaTeX, axodraw.st

Metformin-mediated increase in DICER1 regulates microRNA expression and cellular senescence

Metformin, an oral hypoglycemic agent, has been used for decades to treat type 2 diabetes mellitus. Recent studies indicate that mice treated with metformin live longer and have fewer manifestations of age-related chronic disease. However, the molecular mechanisms underlying this phenotype are unknown. Here, we show that metformin treatment increases the levels of the microRNA-processing protein DICER1 in mice and in humans with diabetes mellitus. Our results indicate that metformin upregulates DICER1 through a post-transcriptional mechanism involving the RNA-binding protein AUF1. Treatment with metformin altered the subcellular localization of AUF1, disrupting its interaction with DICER1 mRNA and rendering DICER1 mRNA stable, allowing DICER1 to accumulate. Consistent with the role of DICER1 in the biogenesis of microRNAs, we found differential patterns of microRNA expression in mice treated with metformin or caloric restriction, two proven life-extending interventions. Interestingly, several microRNAs previously associated with senescence and aging, including miR-20a, miR-34a, miR-130a, miR-106b, miR-125, and let-7c, were found elevated. In agreement with these findings, treatment with metformin decreased cellular senescence in several senescence models in a DICER1- dependent manner. Metformin lowered p16 and p21 protein levels and the abundance of inflammatory cytokines and oncogenes that are hallmarks of the senescence-associated secretory phenotype (SASP). These data lead us to hypothesize that changes in DICER1 levels may be important for organismal aging and to propose that interventions that upregulate DICER1 expression (e.g., metformin) may offer new pharmacotherapeutic approaches for age-related disease

Specific targeting of human caspases using designed ankyrin repeat proteins

Caspases play important roles in cell death, differentiation, and proliferation. Due to their high homology, especially of the active site, specific targeting of a particular caspase using substrate analogues is very difficult. Although commercially available small molecules based on peptides are lacking high specificity due to overlapping cleavage motives between different caspases, they are often used as specific tools. We have selected designed ankyrin repeat proteins (DARPins) against human caspases 1-9 and identified high-affinity binders for the targeted caspases, except for caspase 4. Besides previously reported caspase-specific DARPins, we generated novel DARPins (D1.73, D5.15, D6.11, D8.1, D8.4, and D9.2) and confirmed specificity for caspases 1, 5, 6, and 8 using a subset of caspase family members. In addition, we solved the crystal structure of caspase 8 in complex with DARPin D8.4. This binder interacts with non-conserved residues on the large subunit, thereby explaining its specificity. Structural analysis of this and other previously published crystal structures of caspase/DARPin complexes depicts two general binding areas either involving active site forming loops or a surface area laterally at the large subunit of the enzyme. Both surface areas involve non-conserved surface residues of caspase

Cirugía de la fibrilación auricular

Atrial fibrillation surgery is based on creating scars in the atrium, in order to avoid re-entry phenomena that may initiate and perpetuate arrhythmia, and driving the normal stimuli from the sinus node to the atrio-ventricular node. The complexity and increased risk of the initial surgical technique, based on a "cut-and-sew" procedure, have enhanced other current procedures, in which different energies are used making it possible to perform scars in a safer and less invasive way. At present, atrial fibrillation surgery is not performed routinely in all cardiothoracic surgical centers, and there is no consensus in which is the best type of technique. Even if the results are good, they depend on multiples factors such as duration of arrhythmia, atrial size and type of technique employed. In addition, there is some variability in the description within the scientific community of the results and procedures used, which makes its analysis confusing. In this paper we review the different techniques described, the results and their application in minimally invasive surgery

Neural encoding of behaviourally relevant visual-motion information in the fly

Egelhaaf M, Kern R, Krapp HG, Kretzberg J, Kurtz R, Warzecha A-K. Neural encoding of behaviourally relevant visual-motion information in the fly. Trends in Neurosciences. 2002;25(2):96-102.Information processing in visual systems is constrained by the spatial and temporal characteristics of the sensory input and by the biophysical properties of the neuronal circuits. Hence, to understand how visual systems encode behaviourally relevant information, we need to know about both the computational capabilities of the nervous system and the natural conditions under which animals normally operate. By combining behavioural, neurophysiological and computational approaches, it is now possible in the fly to assess adaptations that process visual-motion information under the constraints of its natural input. It is concluded that neuronal operating ranges and coding strategies appear to be closely matched to the inputs the animal encounters under behaviourally relevant conditions

Theoretical analysis of thin-wire elliptic antennas

In this communication we extend the state-of-the art by providing closed-form equations for thin-wire elliptical antennas with arbitrary current distributions, valid from low frequencies to the infrared regime. To this end, we derive an electric-field integral equation (EFIE) for imperfectly conducting wires and elliptical geometries. Using this formulation, we obtain unknown arbitrary current distributions through a modal expansion, enabling thus the calculation of far-fields and other radiation parameters. Results shown not only achieve remarkable but also to show the superior design possibilities of elliptical geometries in comparison to the classical circular loops, which may be considered just a particular case of the methodology here presented. Special attention is paid to mathematical details of electric farfield equations, thus providing guidelines to produce efficient codes

Low Energy Constants from High Energy Theorems

New constraints on resonance saturation in chiral perturbation theory are investigated. These constraints arise because each consistent saturation scheme must map to a representation of the full QCD chiral symmetry group. The low-energy constants of chiral perturbation theory are then related by a set of mixing angles. It is shown that vector meson dominance is a consequence of the fact that nature has chosen the lowest-dimensional nontrivial chiral representation. It is further shown that chiral symmetry places an upper bound on the mass of the lightest scalar in the hadron spectrum.Comment: 11 pages TeX and mtexsis.te

Walls talk: Microbial biogeography of homes spanning urbanization.

Westernization has propelled changes in urbanization and architecture, altering our exposure to the outdoor environment from that experienced during most of human evolution. These changes might affect the developmental exposure of infants to bacteria, immune development, and human microbiome diversity. Contemporary urban humans spend most of their time indoors, and little is known about the microbes associated with different designs of the built environment and their interaction with the human immune system. This study addresses the associations between architectural design and the microbial biogeography of households across a gradient of urbanization in South America. Urbanization was associated with households' increased isolation from outdoor environments, with additional indoor space isolation by walls. Microbes from house walls and floors segregate by location, and urban indoor walls contain human bacterial markers of space use. Urbanized spaces uniquely increase the content of human-associated microbes-which could increase transmission of potential pathogens-and decrease exposure to the environmental microbes with which humans have coevolved