f t value of the 0(+)-> 0(+) beta(+) decay of (32)Ar: A measurement of isospin symmetry breaking in a superallowed decay

We determined the absolute branch of the T=2 superallowed decay of (32)Ar by detecting the beta(+)-delayed protons and gamma decays of the daughter state. We obtain b(SA)(beta)=(22.71 +/- 0.16)%, which represents the first determination of a proton branch to better than 1%. Using this branch along with the previously determined (32)Ar half-life and energy release, we determined ft=(1552 +/- 12) s for the superallowed decay. This ft value, together with the corrected Ft value extracted from previously known T=1 superallowed decays, yields a measurement of the isospin symmetry breaking correction in (32)Ar decay delta(exp)(C)=(2.1 +/- 0.8)%. This can be compared to a theoretical calculation delta(C)=(2.0 +/- 0.4)%. As by-products of this work, we determined the gamma and proton branches for the decay of the lowest T=2 state of (32)Cl, made a precise determination of the total proton branch and relative intensities of proton groups that leave (31)S in its first excited state and deduced an improved value for the (32)Cl mass.

Coherent Contributions to Isospin Mixing in the Mirror Pair (67)As and (67)Se

Isospin symmetry breaking has been investigated in mass A = 67 mirror nuclei through the experimental determination of the E1 strengths of analog electromagnetic transitions. Lifetimes of excited states have been measured in (67)Se and (67)As with the centroid shift method. Through the comparison of the B(E1) strengths of the mirror 9/2(+) -> 7/2(-) transitions, the isovector and the isoscalar components of the electromagnetic transition amplitude were extracted. The presence of a large isoscalar component provides evidence for coherent contributions to isospin mixing, probably involving the isovector giant monopole resonance.

Dynamical generation of mass in the D = (2+1) Wess-Zumino model

In this work we study the dynamical generation of mass in the massless N = 1 Wess-Zumino model in a three-dimensional spacetime. Using the tadpole method to compute the effective potential, we observe that supersymmetry is dynamically broken together with the discrete symmetry A(x) -> A(x). We show that this model, different from nonsupersymmetric scalar models, exhibits a consistent perturbative dynamical generation of mass after two-loop corrections to the effective potential.

Determination of post-mortem interval using in situ tissue optical fluorescence

In this study we have used fluorescence spectroscopy to determine the post-mortem interval. Conventional methods in forensic medicine involve tissue or body fluids sampling and laboratory tests, which are often time demanding and may depend on expensive analysis. The presented method consists in using time-dependent variations on the fluorescence spectrum and its correlation with the time elapsed after regular metabolic activity cessation. This new approach addresses unmet needs for post-mortem interval determination in forensic medicine, by providing rapid and in situ measurements that shows improved time resolution relative to existing methods. (C) 2009 Optical Society of America

Energy transfer upconversion determination by thermal-lens and Z-scan techniques in Nd(3+)-doped laser materials

The Z-scan and thermal-lens techniques have been used to obtain the energy transfer upconversion parameter in Nd(3+)-doped materials. A comparison between these methods is done, showing that they are independent and provide similar results. Moreover, the advantages and applicability of each one are also discussed. The results point to these approaches as valuable alternative methods because of their sensitivity, which allows measurements to be performed in a pump-power regime without causing damage to the investigated material. (C) 2009 Optical Society of America

Determination of the molecular weight of proteins in solution from a single small-angle X-ray scattering measurement on a relative scale

This paper describes a new and simple method to determine the molecular weight of proteins in dilute solution, with an error smaller than similar to 10%, by using the experimental data of a single small-angle X-ray scattering (SAXS) curve measured on a relative scale. This procedure does not require the measurement of SAXS intensity on an absolute scale and does not involve a comparison with another SAXS curve determined from a known standard protein. The proposed procedure can be applied to monodisperse systems of proteins in dilute solution, either in monomeric or multimeric state, and it has been successfully tested on SAXS data experimentally determined for proteins with known molecular weights. It is shown here that the molecular weights determined by this procedure deviate from the known values by less than 10% in each case and the average error for the test set of 21 proteins was 5.3%. Importantly, this method allows for an unambiguous determination of the multimeric state of proteins with known molecular weights.

Quantitative determination of optical transmission through subwavelength slit arrays in Ag films: Role of surface wave interference and local coupling between adjacent slits

Measurement of the transmitted intensity from a coherent monomode light source through a series of subwavelength slit arrays in Ag films, with varying array pitch and number of slits, demonstrates enhancement (suppression) by factors of as much as 6 (9) when normalized to the transmission efficiency of an isolated slit. Pronounced minima in the transmitted intensity are observed at array pitches corresponding to lambda(SPP), 2 lambda(SPP), and 3 lambda(SPP), where lambda(SPP) is the wavelength of the surface plasmon polariton (SPP). The position of these minima arises from destructive interference between incident propagating waves and pi-phase-shifted SPP waves. Increasing the number of slits to four or more does not increase appreciably the per-slit transmission intensity. A simple interference model fits well the measured transmitted intensity profile.

Cloud point extraction to avoid interferences by structured background on nickel determination in plant materials by FAAS

An analytical procedure based on microwave-assisted digestion with diluted acid and a double cloud point extraction is proposed for nickel determination in plant materials by flame atomic absorption spectrometry. Extraction in micellar medium was successfully applied for sample clean up, aiming to remove organic species containing phosphorous that caused spectral interferences by structured background attributed to the formation of PO species in the flame. Cloud point extraction of nickel complexes formed with 1,2-thiazolylazo-2-naphthol was explored for pre-concentration, with enrichment factor estimated as 30, detection limit of 5 mu g L(-1) (99.7% confidence level) and linear response up to 80 mu g L(-1). The accuracy of the procedure was evaluated by nickel determinations in reference materials and the results agreed with the certified values at the 95% confidence level.

Quantification of some nonsteroidal anti-inflammatory drugs as reducing agents of Cu(II)/4,4 '-dicarboxy-2,2 '-biquinoline complexes in cationic micellar medium

A simple method was developed for spectrophotometric determination of some nonsteroidal anti-inflammatory drugs (meloxicam, piroxicam and tenoxicam) based on the reduction of copper(II) in buffered solution (pH 7.0) and micellar medium containing 4,4'-dicarboxy-2,2'-buffered solution (pH 7.0) and micellar medium containing 4,4'-dicarboxy-2,2'-biquinoline acid. The-biquinoline acid. The absorbance values at 558 nm, characteristic of the formed Cu(I)/4,4'-dicarboxy-2,2'-biquinoline complexes, are linear with the concentrations (5.7-40 mmol L(-1), n = 5) of these oxicams (meloxicam r = 0.998; piroxicam and tenoxicam r = 0.999). The limit of detection values, in mmol L(-1), calculated for meloxicam (2.7), piroxicam (1.2) and tenoxicam (1.3) was obtained with 99% confidence level and the relative standard deviations for meloxicam (3.1%), piroxicam (5.1%) and tenoxicam (1.2%) were calculated using a 25 mmol L(-1) solution (n = 7). Mean recovery values for meloxicam, piroxicam and tenoxicam forms were 100 +/- 6.9, 98.6 +/- 3.6 and 99.4 +/- 2.5%, respectively. The conditional potential of Cu(II)/Cu(I) in complex medium of 7.5 mmol L(-1) BCA was determined to be 629 +/- 11 mV vs. NHE.

Simultaneous determination of Cr, Fe, Ni and V in crude oil by emulsion sampling graphite furnace atomic absorption spectrometry

In this work a simple and reliable method for the simultaneous determination of Cr, Fe, Ni and V in crude oil, using emulsion sampling graphite furnace atomic absorption spectrometry is proposed. Under the best conditions, sample masses around 50 mg were weighed in polypropylene tubes and emulsified in a mixture of 0.5% (v v(-1)) hexane + 6% (m v(-1)) Triton X-100 (R). Considering the compromised conditions, the pyrolysis an atomization temperatures for the simultaneous determination of Cr, Fe, Ni and V were 1400 degrees C and 2500 degrees C, respectively. Aliquots of 20 mu L of reference solution and sample emulsion were co-injected into the graphite tube with 10 mu L of 1.0 g L(-1) Mg(NO(3))(2) as chemical modifier. The detection limits (n = 10, 3 sigma) and characteristic masses were, respectively: 0.07 mu g g(-1) and 19 pg for Cr; 2.15 mu g g(-1) and 31 pg for Fe; 1.25 mu g g(-1) and 44 pg for Ni; and 1.15 mu g g(-1) and 149 pg for V. The reliability of the proposed method was checked by fuel oil Standard Reference Material (SRMTriton X-100 (R) 1634c - NIST) analysis. The concentrations found presented no statistical differences compared to the certified values at 95% confidence level.

Instantaneous characterization of vegetable oils via TAG and FFA profiles by easy ambient sonic-spray ionization mass spectrometry

A fast and reliable method is presented for the analysis of vegetable oils. Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is shown to efficiently desorb and ionize the main oil constituents from an inert surface under ambient conditions and to provide comprehensive triacylglyceride (TAG) and free fatty acid (FFA) profiles detected mainly as either [ TAG + Na](+) or [FFA - H](-) ions. EASI(+/-)-MS analysis is simple, easily implemented, requires just a tiny droplet of the oil and is performed without any pre-separation or chemical manipulation. It also causes no fragmentation of TAG ions hence diacylglyceride (DAG) and monoacylglyceride (MAG) profiles and contents can also be measured. The EASI(+/-)-MS profiles of TAG and FFA permit authentication and quality control and can be used, for instance, to access levels of adulteration, acidity, oxidation or hydrolysis of vegetable oils in general.

Gold is not a Faradaic-Efficient Borohydride Oxidation Electrocatalyst: An Online Electrochemical Mass Spectrometry Study

Direct borohydride fuel cells are promising high energy density portable generators. However, their development remains limited by the complexity of the anodic reaction: The borohydride oxidation reaction (BOR) kinetics is slow and occurs at high overvoltages, while it may compete with the heterogeneous hydrolysis of BH(4)(-). Nevertheless, one usually admits that gold is rather inactive toward the heterogeneous hydrolysis of BH(4)(-) and presents some activity regarding the BOR, therefore yielding to the complete eight-electron BOR. In the present paper, by coupling online mass spectrometry to electrochemistry, we in situ monitored the H(2) yield during BOR experiments on sputtered gold electrodes. Our results show non-negligible H(2) generation on Au on the whole BOR potential range (0-0.8 V vs reversible hydrogen electrode), thus revealing that gold cannot be considered as a faradaic-efficient BOR electrocatalyst. We further propose a relevant reaction pathway for the BOR on gold that accounts for these findings.

Determination of parathion and carbaryl pesticides in water and food samples using a self assembled monolayer/acetylcholinesterase electrochemical biosensor

An acetylcholinesterase (AchE) based amperometric biosensor was developed by immobilisation of the enzyme onto a self assembled modified gold electrode. Cyclic voltammetric experiments performed with the SAM-AchE biosensor in phosphate buffer solutions ( pH = 7.2) containing acetylthiocholine confirmed the formation of thiocholine and its electrochemical oxidation at E-p = 0.28 V vs Ag/AgCl. An indirect methodology involving the inhibition effect of parathion and carbaryl on the enzymatic reaction was developed and employed to measure both pesticides in spiked natural water and food samples without pre-treatment or pre-concentration steps. Values higher than 91-98.0% in recovery experiments indicated the feasibility of the proposed electroanalytical methodology to quantify both pesticides in water or food samples. HPLC measurements were also performed for comparison and confirmed the values measured amperometrically.

ACCUMULATION AND TRANSLOCATION OF SILICON IN RICE AND BEAN PLANTS USING THE 30SI STABLE ISOTOPE

The 30Si silicon isotope stable was used for assessing the accumulation and translocation of Si in rice and bean plants grown in labeled nutritive solution. The isotopic silicon composition in plant materials was determined by mass spectrometry (IRMS) using the method based on SiF4 formation. Considering the total-Si added into nutritive solutions, the quantity absorbed by plants was near to 51% for rice and 15% for bean plants. The accumulated amounts of Si per plant were about 150g in rice and 8.6g in bean. Approximately 70% of the total-Si accumulated was found in leaves. At presented experimental conditions, the results confirmed that once Si is accumulated in the old parts of rice and bean plant tissues it is not redistributed to new parts, even when Si is not supplied to plants from nutritive solution.

A flow injection procedure based on solenoid micro-pumps for spectrophotometric determination of free glycerol in biodiesel

A flow system designed with solenoid micro-pumps is proposed for fast and greener spectrophotometric determination of free glycerol in biodiesel. Glycerol was extracted from samples without using organic solvents. The determination involves glycerol oxidation by periodate, yielding formaldehyde followed by formation of the colored (3,5-diacetil-1,4-dihidrolutidine) product upon reaction with acetylacetone. The coefficient of variation, sampling rate and detection limit were estimated as 1.5% (20.0 mg L(-1) glycerol, n =10), 34 h(-1), and 1.0 mg L(-1) (99.7% confidence level), respectively. A linear response was observed from 5 to 50 mg L(-1), with reagent consumption estimated as 345 mu g of KIO(4) and 15 mg of acetylacetone per determination. The procedure was successfully applied to the analysis of biodiesel samples and the results agreed with the batch reference method at the 95% confidence level. (C) 2010 Elsevier B.V. All rights reserved.