Technicolor contribution to lepton plus photon+E-T events at the Fermilab Tevatron

Events with one lepton, one photon, and missing energy are the subject of recent searches at the Fermilab Tevatron. We compute possible contributions to these types of events from the process pp ->gamma l nu(l)nu(tau)nu(tau), where l=e, mu in the context of a low scale technicolor model. We find that with somewhat tighter cuts than the ones used in the CDF search, it could be possible to either confirm or exclude this model in a small region of its parameter space.

NN -> NN pi(+) reaction near threshold in a chiral power counting approach

Power-counting arguments are used to organize the interactions contributing to the NN-->d pi,pn pi reactions near threshold. We estimate the contributions from the three formally leading mechanisms: the Weinberg-Tomozawa (WT) term, the impulse term, and the Delta-excitation mechanism. Subleading but potentially large mechanisms, including S-wave pion rescattering, the Galilean correction to the WT term, and short-ranged contributions are also examined. The WT term is shown to be numerically the largest, and the other contributions are found to approximately cancel. Similarly to the reaction pp-->pp pi(0), the computed cross sections are considerably smaller than the data. We discuss possible origins of this discrepancy.

Desenvolvimento de detector eletroquímico para cromatografia líquida de alta eficiência baseado em um eletrodo modificado com nanopartículas metálicas para determinação de ácidos carboxílicos em vinhaça de cana-de-açúcar

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Temperature Effect on the Two-Photon Absorption Spectrum of All-trans-beta-carotene

In this report, we investigate the influence of temperature on the two-photon absorption (2PA) spectrum of all-trans-beta-carotene using the femtosecond white-light-continuum Z-scan technique. We observed that the 2PA cross-section decreases quadratically with the temperature. Such effect was modeled using a three-energy-level diagram within the sum-over-essential states approach, assuming temperature dependencies to the transition dipole moment and refractive index of the solvent. The results show that the transition dipole moments from ground to excited state and between the excited states, which governed the two-photon matrix element, have distinct behaviors with the temperature. The first one presents a quadratic dependence, while the second exhibits a linear dependence. Such effects were attributed mainly to the trans -> cis thermal interconversion process, which decreases the effective conjugation length, contributing to diminishing the transition dipole moments and, consequently, the 2PA cross-section.

Two-photon excitation and optical limiting in polyfluorene derivatives

Fluorene-based polymers are widely known materials due to a combination of features such as photoluminescence and electroluminescence, oxidative stability, and film-forming ability. However, studies reporting nonlinear optical properties in this class of conjugated polymer are scarce. Here, we report a new class of polyfluorene derivatives poly(9,9'-n-dihexyl-2,7-fluorenedilvinylene-alt-1,4-phenylenevinylene), poly(9,9'-n-dihexyl-2,7-fluorenedilvinylene-alt-2,5-thiophene), and poly[(9,9-di-hexylfluorenediylvinylene-alt-1,4-phenylenevinylene)-co-((9,9'-(3-t-butylpropanoate) fluorene-1,4-phenylene)] displaying high two-photon absorption (2PA) in the spectral range from a 490 to 1100 nm. The 2PA cross-section peak values for these materials are as high as 3000 Goppert Mayer (1 GM = 1 x 10-50 cm4 s/photon), which is related to the high degree of conjugation along the polymer backbone. The polymers that were used in this study presented a strong two-photon luminescence and also displayed optical limiting behavior, which, in combination with their well-established properties, make them highly suitable for nonlinear optical devices. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 148153, 2012

Further investigating the determination of phosphorus in plants by INAA using bremsstrahlung measurement

Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy. Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because (32)P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from (32)P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg(-1) were irradiated at a thermal neutron flux of 9.5 x 10(12) cm(-2) s(-1) and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated, the production of (32)P from sulfur, and the contribution of Compton scattering should be considered for producing good results.

Polarization effect on the two-photon absorption of a chiral compound

In this report, we investigate the polarization effect (linear, elliptical and circular) on the two-photon absorption (2PA) properties of a chiral compound based in azoaromatic moieties using the femtosecond Z-scan technique with low repetition rate and low pulse energy. We observed a strong 2PA modulation between 800 nm and 960 nm as a function the polarization changes from linear through elliptical to circular. Such results were interpreted employing the sum-over-essential states approach, which allowed us to model the 2PA circular-linear dichroism effect and to identifier the overlapping of the excited electronic states responsible by the 2PA allowed band. (C) 2012 Optical Society of America

Potential of a neutrino detector in the ANDES underground laboratory for geophysics and astrophysics of neutrinos

The construction of the Agua Negra tunnels that will link Argentina and Chile under the Andes, the world's longest mountain range, opens the possibility of building the first deep underground laboratory in the Southern Hemisphere. This laboratory has the acronym ANDES (Agua Negra Deep Experiment Site) and its overburden could be as large as similar to 1.7 km of rock, or 4500 mwe, providing an excellent low background environment to study physics of rare events like the ones induced by neutrinos and/or dark matter. In this paper we investigate the physics potential of a few kiloton size liquid scintillator detector, which could be constructed in the ANDES laboratory as one of its possible scientific programs. In particular, we evaluate the impact of such a detector for the studies of geoneutrinos and Galactic supernova neutrinos, assuming a fiducial volume of 3 kilotons as a reference size. We emphasize the complementary roles of such a detector to the ones of the Northern Hemisphere neutrino facilities, given the advantages of its geographical location.

Flow injection analysis of free glycerol in biodiesel using a copper electrode as an amperometric detector

The main goal of this work was to develop a simple analytical method for quantification of glycerol based on the electrocatalytic oxidation of glycerol on the copper surface adapted in a flow injection system. Under optimal experimental conditions, the peak current response increases linearly with glycerol concentration over the range 60-3200 mg kg(-1) (equivalent to 3-160 mg L(-1) in solution). The repeatability of the electrode response in the flow injection analysis (FIA) configuration was evaluated as 5% (n = 10), and the detection limit of the method was estimated to be 5 mg kg(-1) in biodiesel (equivalent to 250 mu g L(-1) in solution) (S/N = 3). The sample throughput under optimised conditions was estimated to be 90 h(-1). Different types of biodiesel samples (B100), as in the types of vegetable oils or animal fats used to produce the fuels, were analysed (seven samples). The only sample pre-treatment used was an extraction of glycerol from the biodiesel sample containing a ratio of 5 mL of water to 250 mg of biodiesel. The proposed method improves the analytical parameters obtained by other electroanalytical methods for quantification of glycerol in biodiesel samples, and its accuracy was evaluated using a spike-and-recovery assay, where all the biodiesel samples used obtained admissible values according to the Association of Official Analytical Chemists. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

Relationships of Photosynthetic Photon Flux Density, air Temperature and Humidity with Tomato Leaf Diffusive Conductance and Temperature

The objective was to study the leaf temperature (LT) and leaf diffusive vapor conductance (gs) responses to temperature, humidity and incident flux density of photosynthetically active photons (PPFD) of tomato plants grown without water restriction in a plastic greenhouse in Santa Maria, RS, Brazil. The plants were grown in substrate and irrigated daily. The gs was measured using a steady-state null-balance porometer on the abaxial face of the leaves during the daytime. Both leaf surfaces were measured in one day. The PPFD and LT were measured using the porometer. Leaf temperature was determined using an infrared thermometer, and air temperature and humidity were measured using a thermohygrograph. The leaves on the upper layer of the plants had higher gs than the lower layer. The relationship between the gs and PPFD was different for the two layers in the plants. A consistent relationship between the gs and atmospheric water demand was observed only in the lower layer. The LT tended to be lower than the air temperature. The mean value for the gs was 2.88 times higher on the abaxial than adaxial leaf surface.

EVAPORATIVE LIGHT-SCATTERING DETECTOR FOR ANALYSIS OF NATURAL PRODUCTS

EVAPORATIVE LIGHT-SCATTERING DETECTOR FOR ANALYSIS OF NATURAL PRODUCTS. The interest in the use of evaporative light scattering detector (ELSD) for the analysis of different classes of natural products has grown over the years. This is because this detector has become an excellent alternative compared to other types of detectors, such as the refractive index detector and the ultraviolet (UV) detector. This review describes the basic principles of ELSD functioning and discusses the advantages and disadvantages in using an ELSD for the analysis of organic compounds. Additionally, an overview, covering the last 23 years, of ELSD applications in natural products analysis (saponins, terpenes, carbohydrates, glycosides, alkaloids, steroids, flavonoids, peptides, polyketides, coumarins and iridoids) is presented and discussed.

Experimental and Theoretical Study on the One- and Two-Photon Absorption Properties of Novel Organic Molecules Based on Phenylacetylene and Azoaromatic Moieties

This Article reports a combined experimental and theoretical analysis on the one and two-photon absorption properties of a novel class of organic molecules with a pi-conjugated backbone based on phenylacetylene (JCM874, FD43, and FD48) and azoaromatic (YB3p2S) moieties. Linear optical properties show that the phenylacetylene-based compounds exhibit strong molar absorptivity in the UV and high fluorescence quantum yield with lifetimes of approximately 2.0 ns, while the azoaromatic-compound has a strong absorption in the visible region with very low fluorescence quantum yield. The two-photon absorption was investigated employing nonlinear optical techniques and quantum chemical calculations based on the response functions formalism within the density functional theory framework. The experimental data revealed well-defined 2PA spectra with reasonable cross-section values in the visible and IR. Along the nonlinear spectra we observed two 2PA allowed bands, as well as the resonance enhancement effect due to the presence of one intermediate one-photon allowed state. Quantum chemical calculations revealed that the 2PA allowed bands correspond to transitions to states that are also one-photon allowed, indicating the relaxation of the electric-dipole selection rules. Moreover, using the theoretical results, we were able to interpret the experimental trends of the 2PA spectra. Finally, using a few-energy-level diagram, within the sum-over-essential states approach, we observed strong qualitative and quantitative correlation between experimental and theoretical results.

Effect of Solvent-Induced Coil to Helix Conformational Change on the Two-Photon Absorption Spectrum of Poly(3,6-phenanthrene)

This paper investigates the effect of solvent-induced conformational changes of poly(3,6-phenanthrene) on their two-photon absorption (2PA). Such effect was studied employing the wavelength-tunable femtosecond Z-scan technique and modeled using the sum-over-essential states approach. We observed a strong reduction of the 2PA cross-section when the sample was prepared in hexane (poor solvent) in comparison to chloroform (good solvent), which is related to the conformation adopted by the polymer in each case. In chloroform it adopts a random coil conformation, as opposed to the one-handed helix conformation in hexane. Our results pointed out that the coil to helix conformation change decreases the degree of molecular planarity of the polymer pi-conjugated backbone, which is primarily responsible for their optical nonlinearity, contributing to diminishing the effective transition dipole moments and, consequently, the 2PA cross-section. Moreover, by studying the nonlinear response with different light polarization, we showed that, although the solvent-induced conformational change does not alter the molecular symmetry of the polymer, it modifies considerably the direction of the transition dipole moments between the excited states.

Indirect doping of microstructures fabricated by two-photon polymerization with gold nanoparticles

Nanoplasmonics and metamaterials sciences are rapidly growing due to their contributions to photonic devices fabrication with applications ranging from biomedicine to photovoltaic cells. Noble metal nanoparticles incorporated into polymer matrix have great potential for such applications due to their distinctive optical properties. However, methods to indirectly incorporate metal nanoparticles into polymeric microstructures are still on demand. Here we report on the fabrication of two-photon polymerized microstructures doped with gold nanoparticles through an indirect doping process, so they do not interfere in the two-photon polymerization (2PP) process. Such microstructures present a strong emission, arising from gold nanoparticles fluorescence. The microstructures produced are potential candidates for nanoplasmonics and metamaterials devices applications and the nanoparticles production method can be applied in many samples, heated simultaneously, opening the possibility for large scale processes. (C) 2012 Optical Society of America

Emission features of microstructures fabricated by two-photon polymerization containing three organic dyes

Fabrication of microstructures containing active compounds, such as fluorescent dyes and nanoparticles have been exploited in the last few years, aiming at applications from photonics to biology. Here we fabricate, using two-photon polymerization, microstructures containing the fluorescent dyes Stilbene 420, Disodium Fluorescein and Rhodamine B. The produced microstructures, containing dyes at specific sites, present good structural integrity and a broad fluorescence spectrum, from about 350 nm until 700 nm. Such spectrum can be tuned by using different excitation wavelengths and selecting the excitation position in the microstructure. These results are interesting for designing multi-doped structures, presenting tunable and broad fluorescence spectrum. (C)2012 Optical Society of America