Extensions of string theories

With the motivation that critical dimensionsD≠4 might be suggesting that string theories have not been completely formulated, we study more general alternatives. We first consider a direct extension in the world-sheet formulation withN _B bosons andN _F fermions and analyze the conditions for canceling the anomaly in all possible combinations ofN _B ,N _F andD. Later on we incorporate degrees of freedom of antisymmetric tensors to the previous model. The only possibility to cancel the anomaly in this case is withN _B =N _F =1 and the our everyday spacetime dimensionD=4.     

Strings with zero tension

We describe bosonic strings by using a kind of Lagrangian compatible with the zero tension limit. The work is developed on an extended configuration space and the quantization is carried out with details.     

Exploiting sequential injection analysis with lab-on-valve and miniaturized potentiometric detection: Epinephrine determination in pharmaceutical products

Miniaturized potentiometric units were constructed, evaluated and incorporated in a SIA-LOV manifold in order to the control of pharmaceutical analysis. The method validation was done with ephinefrine determinations in commercial pharmaceutical products. The optimization procedures were directed at potential versus epinephrine concentration. This approach was achieved by selecting 60 cm of reactor and a flow rate of 11 μL s⁻¹ and injecting 78 μL of epinephrine standard solutions in a 1.0 × 10⁻³ mol L⁻¹ IO₄⁻ solution. A linear range was found for epinephrine concentrations between 2.0 × 10⁻⁴ and 2.5 × 10⁻³ mol L^−l with a slope of 35528 mV L mol^−l and r² = 0.997. Under these conditions the analytical results for the commercial pharmaceutical formulations of 0.908 and 0.454 mg mL⁻¹, respectively, with a R.S.D. of 0.34 for both, was obtained. Through down scaling periodate-selective electrode it was possible to benefit from the recognized advantages of the lab-on-valve sequential-injection based systems, namely regarding equipment portability, reduced consumption of the sample and the reagents and the reduction of effluent waste. Furthermore, the new periodate electrode configuration is easy to achieve in common laboratories and enables the implementation of low volume detection cell where the electrical noise, that is frequently presented in potentiometric based procedures, is significantly reduced.     

Separation of human alloalbumin variants by isoelectric focusing

A technique for the separation of human alloalbumin variants by means of isoelectric focusing in the presence of 8M urea and 60 mM L-serine is described. The potential usefulness of this technique in the detection and classification of genetic heterogeneity at the albumin locus is demonstrated by the differentiation of three human alloalbumin variants of European origin.     

Use of Cucurbit[6]uril as Ionophore in Ion Selective Electrodes for Etilefrine Determination in Pharmaceuticals

Cucurbiturils are macrocyclic molecules and have been used with promising results in the development of electrochemical sensors and biosensors due to their main properties such as shape, selectivity, binding interactions and solubility. However, its application for the development of ion selective electrodes has been scarce. In this work, cucurbit[6]uril was used as molecular‐recognition compound for etilefrine sensing membrane with potentiometric transduction. The etilefrine selective electrode was evaluated and proposed as an alternative methodology for pharmaceutical quality control. Different membranes composition were evaluated, considering the use of different solvent mediators and the presence of anionic additives. The best membrane comprises 9.24 mmol.Kg^?1 of cucurbit[6]uril, 68.90 % (w/w) of dibutylsebacate and 30.18 % (w/w) of carboxylated polyvinyl chloride. The electrode exhibited selective cationic response toward the etilefrine in a concentration interval of more than four decades, with an slope of 57.4±0.5 mV dec^?1, a practical detection limit of (8±1)×10^?7 mol L^?1 and a low limit of linear range of (1.25±0.28)×10^?6 mol L^?1. The selectivity of the electrode towards different interfering was high. A comparative evaluation of the accuracy and precision of both procedures was done using the t‐student test (t4,12=1.135) and the Fischer test (F12,4=2.42) and compared with the tabulated ones (t4,12=1.135, F11,3=5.91) for the level of confidence of 95 %.     

Courtship and agonistic sounds by the cichlid fish Pseudotropheus zebra

Courtship and agonistic interactions in an African cichlid species present a richer diversity of acoustic stimuli than previously reported. Male cichlids, including those from the genus Pseudotropheus (P.), produce low frequency short pulsed sounds during courtship. Sounds emitted by P. zebra males in the early stages of courtship (during quiver) were found to be significantly longer and with a higher number of pulses than sounds produced in later stages. During agonistic intrasexual quiver displays, males produced significantly longer sounds with more pulses than females. Also, male sounds had a shorter duration and pulse period in courtship than in male-male interactions. Taken together, these results show that the acoustic repertoire of this species is larger than what was previously known and emphasize the importance of further research exploiting the role of acoustic stimuli in intra- and interspecific communication in African cichlids.     

Determination of gas-phase acidities of dimethylphenols: Combined experimental and theoretical study

The gas-phase acidities of the six dimethylphenol isomers were determined experimentally, by using the kinetic method, and theoretically, through quantum chemistry calculations. The experimental values, relative to the gas-phase acidity of phenol, are (in kJ mol⁻¹): −1.76 ± 0.76 (2,3-Me₂C₆H₃OH), 1.78 ± 0.29 (2,4-Me₂C₆H₃OH), 0.83 ± 0.58 (2,5-Me₂C₆H₃OH), −4.39 ± 0.89 (2,6-Me₂C₆H₃OH), 5.38 ± 1.08 (3,4-Me₂C₆H₃OH), and 1.88 ± 0.08 (3,5-Me₂C₆H₃OH). This trend was discussed by considering the substituent effects on the thermodynamic stabilities both of the parent phenols and the corresponding phenoxide ions. The above acidity data, the literature values for 2-, 3-, and 4-methylphenol, and the substituent effects analysis allowed to develop a simple empirical method to estimate the acidity of any methyl-substituted phenol.     

Perturbative symplectic field theory and Wigner function

We study relativistic quantum field theories in phase space, based on representations of the Poincaré group, using the Moyal product. We develop a perturbative theory for quantizing fields, with functional methods in phase space. The two-point function is related to relativistic Wigner functions for bosons and fermions. As an example we analyze the complex scalar field with quartic self-interaction.     

CONTROLLING THE 3D NANOSCALE ORGANIZATION OF BULK HETEROJUNCTION POLYMER SOLAR CELLS

In this study,the three dimensional nanoscale organization in the photoactive layers of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM) is revealed by transmission electron tomography.After annealing treatment,either at elevated temperature or during slow solvent evaporation,nanoscale interpenetrating networks are formed with high crystalline order and favorable concentration gradients of both components through the thickness of the photoactive layer.Such a tailored morphology acco...     

Cellulosic Films Obtained from the Treatment of Sugarcane Bagasse Fibers with N-methylmorpholine-N-oxide (NMMO)

Ethanol/water organosolv pulping was used to obtain sugarcane bagasse pulp that was bleached with sodium chlorite. This bleached pulp was used to obtain cellulosic films that were further evaluated by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). A good film formation was observed when temperature of 74 °C and baths of distilled water were used, which after FTIR, TGA, and SEM analysis indicated no significant difference between the reaction times. The results showed this to be an interesting and promising process, combining the prerequisites for a more efficient utilization of agro-industrial residues.