Trees, forests and jungles: a botanical garden for cluster expansions

Combinatoric formulas for cluster expansions have been improved many times over the years. Here we develop some new combinatoric proofs and extensions of the tree formulas of Brydges and Kennedy, and test them on a series of pedagogical examples.Comment: 37 pages, Ecole Polytechnique A-325.099

Modulation of 5-Aminolevulinic acid mediated photodynamic therapy induced cell death in a human lung adenocarcinoma cell line

Photodynamic therapy (PDT) is a cancer treatment involving the administration of a photosensitising drug which selectively accumulates in tumor tissue, followed by irradiation with appropriate wavelength light. It triggers photochemical reactions inducing reactive oxygen species (ROS) production with the consequent cellular damage, which ultimately leads to cell death. Porphyrins are the only photosensitizers (PSs) endogenously synthesized by means of administration of the biological precursor, 5- aminolevulinic acid (ALA). Several antioxidants and ROS scavenger agents: reduced glutathione (GSH), mannitol (Man), l-tryptophan (Trp), ascorbate (Asc) and trolox (Trx), were assayed to determine their ability to modulate ALA-based PDT (ALA-PDT); it was performed on A549 human lung adenocarcinoma cells, by incubating with 1mM ALA for 3 hr and followed by irradiation with or without 1 hr pre-incubation with the modulators. They were previously tested for possible cytotoxicity/ photoactivity in concentrations ranging from 0.01 to 20 mM. The ratio between cell survival after ALA-PDT in the presence and in the absence of the scavenger agent (protection grade: PG) was determined, and the concentration showing no cytotoxicity/ photoactivity and providing the highest PG was used in the subsequent experiments. ALA-PDT alone induced a high percentage of apoptotic cell death (98.4 ± 3.5%) as revealed by acridine orange/ethidium bromide staining and AnnexinV-FITC/propidium iodide labelling. Pre-incubation with the modulators at their highest PG concentration significantly reduced apoptotic cells to 48.3 ± 2.7% (Asc), 58.8 ± 4.2 (Trx), 78.5 ± 3.1% (GSH), 64.3 ± 1.6% (Man), 74.6 ± 2.3% (Trp). ROS involvement in early cell death induction after ALA-PDT was tested by flow cytometry using the fluorescent probes dihydro-dichlorofluorescein diacetate (H2-DCFDA) and methoxyvinylpyrene (MVP) for detection of peroxides and singlet oxygen, respectively. ROS production increased after ALA-PDT (H2-DCFDA positive cells, control: 1.1 ± 0.1 %; 10 min-PDT: 69.3 ± 5.6%; MVP positive cells, control: 0.65 ± 0.35%; 10 min-PDT: 83.5 ± 1.9%). Asc prevented peroxide formation (H2-DCFDA positive cells: 50.7 ± 2.8%) and mostly prevented singlet oxygen increase (MVP positive cells: 25.4 ± 5.2%) whereas Trx limited peroxides formation (H2-DCFDA positive cells: 20.8 ± 0.5%), but did not significantly affected singlet oxygen production (MVP positive cells: 73.6 ± 3.4%). Selective scavenger mediated protection against PDT-induced cell death, and direct detection of specific pro-oxidative agents, entail the strong involvement of ROS in ALA-PDT-mediated tumor eradication, suggesting that undesired photodamage to normal tissue might be attenuated by administration of antioxidant agents.Fil: Teijo, Maria Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Investigaciones sobre Porfirinas y Porfirias. Universidad de Buenos Aires. Centro de Investigaciones sobre Porfirinas y Porfirias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Diez, Berenice Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Investigaciones sobre Porfirinas y Porfirias. Universidad de Buenos Aires. Centro de Investigaciones sobre Porfirinas y Porfirias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Battle, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Investigaciones sobre Porfirinas y Porfirias. Universidad de Buenos Aires. Centro de Investigaciones sobre Porfirinas y Porfirias; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín; ArgentinaFil: Fukuda, Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Investigaciones sobre Porfirinas y Porfirias. Universidad de Buenos Aires. Centro de Investigaciones sobre Porfirinas y Porfirias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentin

Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry

For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6 (Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in the same temperature regime. Based on measurements performed on both bulk and powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities. The effect is related to the superconductivity of Ru-1212, but it is not an intrinsic property of this compound. We provide evidence that the observation of magnetization peaks in the superconducting state of Ru-1212 is due to flux motion generated by the movement of the sample in an inhomogeneous field, during the measurement in the SQUID magnetometer. We propose several tests, that help to decide, whether the features observed in a SQUID magnetization measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure

Irreducible Hamiltonian approach to the Freedman-Townsend model

The irreducible BRST symmetry for the Freedman-Townsend model is derived. The comparison with the standard reducible approach is also addressed.Comment: 18 pages, LaTeX 2.0

Shades of green: untying the knots of green photoperception

The development of economical LED technology has enabled the application of different light qualities and quantities to control plant growth. Although we have a comprehensive understanding of plants’ perception of red and blue light, the lack of a dedicated green light sensor has frustrated our utilisation of intermediate wavelengths, with many contradictory reports in the literature. We discuss the contribution of red and blue photoreceptors to green light perception and highlight how green light can be used to improve crop quality. Importantly, our meta-analysis demonstrates that green light perception should instead be considered as a combination of distinct ‘green-’ and ‘yellow-’light induced responses. This distinction will enable clearer interpretation of plants’ behaviour in response to green light as we seek to optimise plant growth and nutritional quality in horticultural contexts

The role of religiousness on substance-use disorder treatment outcomes: a comparison of black and white adolescents

This study compares 41 Black and 124 White adolescents at intake and discharge from a residential treatment program for substance-use disorders. Study data were obtained as part of a larger study (N = 195) that sought to assess the relationship of helping behavior and addiction recovery. This post-hoc analysis aims to identify cultural strengths that may be associated with recovery from substance-use disorders among Black adolescents. Using regression analyses and controlling for the severity of substance use and background variables that distinguish racial groups, religious practices and behaviors at intake were examined. Specifically, Black youth and White youth were compared on treatment outcomes, including alcohol or drug use during treatment, drug craving, 12-Step work, and 12-Step helping. The burden of health and socioeconomic disparities at intake did not disproportionately disfavor Black adolescents. Outcomes related to 12-Step measures were similar between Black and White youth. White adolescents reported higher craving scores at discharge, and Black adolescents were more likely to use drugs during treatment. High levels of religiousness at treatment intake were linked to greater 12-Step work and greater 12-Step helping at discharge. High levels of religiousness at intake were not related to drug use during treatment or to craving scores at discharge. The relationship between intake levels of religiousness and treatment-related outcomes did not differ by race.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3437261/Accepted manuscrip

A note on cluster expansions, tree graph identities, extra 1/ N ! factors!!!

We draw attention to a new tree graph identity which substantially improves on the usual tree graph method of proving convergence of cluster expansions in statistical mechanics and quantum field theory. We can control expansions that could not be controlled before.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43217/1/11005_2004_Article_BF00420041.pd

An improved comparison of atmospheric Ar/N2 time series and paired ocean-atmosphere model predictions

Ar/N2 variations in the atmosphere reflect ocean heat fluxes, air-sea gas exchange, and atmospheric dynamics. Here atmospheric Ar/N2 time series are compared to paired ocean-atmosphere model predictions. Agreement between Ar/N2 observations and simulations has improved in comparison to a previous study because of longer time series and the introduction of automated samplers at several of the atmospheric stations, as well as the refinement of the paired ocean-atmosphere models by inclusion of Ar and N2 as active tracers in the ocean component. Although analytical uncertainties and collection artifacts are likely to be mainly responsible for observed Ar/N2 outliers, air parcel back-trajectory analysis suggests that some of the variability in Ar/N2 measurements could be due to the low-altitude history of the air mass collected and, by extension, the local oceanic Ar/N2 signal. Although the simulated climatological seasonal cycle can currently be evaluated with Ar/N2 observations, longer time series and additional improvements in the signal-to-noise ratio will be required to test other model predictions such as interannual variability, latitudinal gradients, and the secular increase in atmospheric Ar/N2 expected to result from ocean warming. Copyright 2008 by the American Geophysical Union