Using the POD sampler for quantitative diffusive (passive) monitoring of volatile and very volatile organics in ambient air: Sampling rates and analytical performance.

POD diffusive samplers loaded with Carbopack X and Carbograph 5TD were exposed to certified calibration mixtures containing a total of 110 different ozone precursor and air toxic compounds. Constant sampling rates were identified for 39 ozone precursors and 33 air toxics. As 9 of these compounds were included in both mixtures, this meant a total of 63 different volatile and very volatile compounds were sampled using the POD with overall expanded uncertainties below 30 % for the sampling rate associated with the whole range of sampling times from 2 to 24 h. Carbograph 5TD exhibited superior performance for diffusive sampling of oxygenated and halogenated compounds in the air toxics mixture, while Carbopack X showed higher sampling efficiencies for aliphatic and aromatic hydrocarbons, as well as halogenated compounds derived from benzene and C2 carbon number hydrocarbons. A model has been developed and applied to estimate sampling rates, primarily for the more volatile and weakly adsorbed compounds, as a function of the collected amount of analyte and the exposure time. For an additional 9 ozone precursors on Carbopack X, and 11 air toxics on Carbograph 5TD, the expanded uncertainties of modelled sampling rates were reduced to below 30 % and have a significantly reduced uncertainty compared to those associated with an averaged sampling rate. The paper provides Freundlich's isotherm parameters for the estimated (modelled) sampling rates and defines a pragmatic approach to their application. It does so by identifying the best sampling time to use for the expected exposure concentrations and associated analyte masses. This allows for expansion of the sampling concentration range from hundreds ng m-3 to mg m-3, while avoiding saturation of the adsorbent. Finally, field measurement comparisons of POD samplers, pumped tube samplers and online gas chromatography (GC), for sampling periods of 3 and 7 days in a semi-rural background area, showed no significant differences between reported concentrations.

A universal tool for stability predictions of biotherapeutics, vaccines and in vitro diagnostic products.

It is of particular interest for biopharmaceutical companies developing and distributing fragile biomolecules to warrant the stability and activity of their products during long-term storage and shipment. In accordance with quality by design principles, advanced kinetic modeling (AKM) has been successfully used to predict long-term product shelf-life and relies on data from short-term accelerated stability studies that are used to generate Arrhenius-based kinetic models that can, in turn, be exploited for stability forecasts. The AKM methodology was evaluated through a cross-company perspective on stability modeling for key stability indicating attributes of different types of biotherapeutics, vaccines and biomolecules combined in in vitro diagnostic kits. It is demonstrated that stability predictions up to 3 years for products maintained under recommended storage conditions (2-8 °C) or for products that have experienced temperature excursions outside the cold-chain show excellent agreement with experimental real-time data, thus confirming AKM as a universal and reliable tool for stability predictions for a wide range of product types.

Creep and aging of hard-sphere glasses under constant stress.

We investigate the aging behavior of glassy suspensions of nearly hard-sphere colloids submitted to a constant shear stress. For low stresses, below the yield stress, the system is subject to creep motion. As the sample ages, the shear rate exhibits a power-law decrease with time with exponents that depend on the sample age. We use a combination of rheological experiments with time-resolved photon correlation spectroscopy to investigate the time evolution of the sample dynamics under shear on various time and length scales. Long-time light-scattering experiments reveal the occurrence of microscopic rearrangement events that are linked with the macroscopic strain deformation of the sample. Dynamic time sweep experiments indicate that while the internal microscopic dynamics slow down continuously with waiting time, the storage and loss moduli are almost constant after a fast, weak decrease, resembling the behavior of quenched systems with partially frozen-in stresses.

Funcionalidad y recomendaciones nutricionales de ácidos grasos esenciales y sus derivados en la alimentación del lactante a partir de los 6 meses de edad / Functonality and nutritional recommendations of essential fatty acids and their derivatives in breastfeeders of six months onwards

Los requerimientos de ácidos grasos esenciales (AGEs) y ácidos grasos poliinsaturados de cadena larga (AGPI-CL) durante los últimos meses de gestación y los primeros años de vida son importantes de acuerdo al crecimiento y desarrollo neuronal que está teniendo lugar durante este periodo de vida. El objetivo de este trabajo ha sido destacar la importancia de garantizar un correcta ingesta de AGEs para cubrir los requerimientos nutricionales de estos, a través de la ingesta de alimentos que contienen en su composición nutricional a estos ácidos de forma natural o han sido enriquecidos con ellos. La metodología empleada para este fin ha sido la utilización de bases de datos electrónicas como MedLine, ScienceDirect, Scirus, Trip database y de la hemeroteca científica de la Universidad de Murcia; También han sido consultadas las páginas web de organismos nacionales e internacionales tales como la Asociación Española de Pediatría (AEP), Agencia Europea de Seguridad Alimentaria (EFSA) y European Society of Pediatric, Gastroenterology, Health and Nutrition (ESPGHAN). Los resultados obtenidos muestran como los AGEs e incluso los AGPI-CL (DHA y ARA) son esenciales para el correcto desarrollo del lactante y niño de corta edad; pues aún estando el lactante desde el primer día de vida dotado de todo el sistema enzimático necesario para la conversión de AGEs en sus correspondientes AGPI-CL y sus derivados, esta conversión podría ser insuficiente, siendo necesario y/o esencial el aporte de estos AGPI-CL a través de la dieta. Las conclusiones derivadas de este trabajo fueron que durante los seis primeros meses de vida el aporte de AGEs y AGPI-CL está asegurado a través de la leche materna o en su defecto a través de las fórmulas de inicio; a partir de los 6 meses con la introducción de la alimentación complementaria y la introducción de la leche de vaca a partir de los 12 meses de vida (introducción en contra de las recomendaciones de ESPGHAN), podría verse comprometida la aportación de estos ácidos. Existe un vacío legal en cuanto a la aportación de AGEs a través de la alimentación complementaria distinta a los cereales; sin embargo, comités como el de la AEP recomienda que en los tarritos infantiles de carnes y pescados con verdura, el aporte de AL sea entre 3-4.5% de la energía de la dieta y al menos 0.5% desde ALN para satisfacer los requerimientos de AGEs en lactantes y niños de corta edad (AU)

Essential fatty acids and long-chain unsaturated fatty acids are important for growth and neuronal development during the final months of gestation and the early years of life. The aim of this study is to highlight the importance of ensuring a correct intake of EFAs for nutritional requirements through the intake of foods which naturally contain these acids or which have been enriched with them. The methodology used was basee on the review of electronic databases MedLine, ScienceDirect, Scirus, Trip database and that of the scientific journal library of the University of Murcia. National and international websites such as the Asociación Española de Pediatría (AEP), European Agency for Food Safety (EAFS) and the European Society of Pediatric, Gastroenterology, Health and Nutrition (ESPGHAN) were also consulted. The results show how EFAs and also AGPI-CL (DHA and ARA) are essential for the correct development of breastfeeders and infants. Even though the breastfeeder is enzymatically fully equipped from the first day of life to convert EFAs into AGPI-CL and derivatives, the conversion may be insufficient and it may be necessary to include AGPI-CL in the diet. The conclusions are that during the first 6 months of life the provision of EFAs and AGPI-CL is assured thanks to the mother’s milk or through starter formulas; at six months the introduction of complementary foods and the adaptation to cow’s milk at twelve months (against the recommendations of the ESPGHAN) may affect the provision of these acids. There is a legal vacuum in the issue of the provision of EFAs through complementary foods other than cereals although committees like the AEP recommend that AL in meat and fish baby foods with vegetables should suppose 3-4.5% of the energy provision, and ALN at least 0.5% in order to satisfy EFA requirements in breastfee ans infants (AU)

Nonlinear behavior of nematic platelet dispersions in shear flow.

Dispersions of platelets in the nematic phase are submitted to large amplitude oscillatory shear flow and probed by high temporal resolution small angle x-ray scattering. The response displays rich dynamic and structural behavior. Under small amplitude deformations we observe an elastic response, while structurally symmetry is broken: a preferential direction of deformation is selected which induces off-plane orientation of the platelets. We associate the elastic responses with the tilting director of the platelets towards the flow direction at all strain amplitudes. At large strain amplitudes there is a yielding transition between elastic and plastic deformation, accompanied by a flipping of the director. At intermediate strain amplitudes the director has a rich dynamic behavior, illustrating the complex motion of platelets in shear flow. These observations are confirmed by steady-shear flow reversal experiments, which underline the unique character of sheared nematic platelet dispersions.

Shear banding and flow-concentration coupling in colloidal glasses.

We report experiments on hard-sphere colloidal glasses that show a type of shear banding hitherto unobserved in soft glasses. We present a scenario that relates this to an instability due to shear-concentration coupling, a mechanism previously thought unimportant in these materials. Below a characteristic shear rate γ(c) we observe increasingly nonlinear and localized velocity profiles. We attribute this to very slight concentration gradients in the unstable flow regime. A simple model accounts for both the observed increase of γ(c) with concentration, and the fluctuations in the flow.

Slip and flow of hard-sphere colloidal glasses.

We study the flow of concentrated hard-sphere colloidal suspensions along smooth, nonstick walls using cone-plate rheometry and simultaneous confocal microscopy. In the glass regime, the global flow shows a transition from Herschel-Bulkley behavior at large shear rate to a characteristic Bingham slip response at small rates, absent for ergodic colloidal fluids. Imaging reveals both the "solid" microstructure during full slip and the local nature of the "slip to shear" transition. Both the local and global flow are described by a phenomenological model, and the associated Bingham slip parameters exhibit characteristic scaling with size and concentration of the hard spheres.

Use of heme iron concentrate in the fortification of weaning foods.

The purpose of this study was to evaluate the technological feasibility of fortifying homogenized weaning food with a porcine heme concentrate. The stability of iron and the organoleptic qualities of two infant weaning foods (a commercial homogenized nonfortified weaning food, NFWF, and the same food fortified with 0.5% of porcine heme concentrate, FWF) were tested throughout 8 months of storage at room temperature and at 37 degrees C. Heme iron decreased with storage time; however, the proportion of this highly available iron was considerably higher in FWF than in NFWF. The addition of heme iron changed significantly the color of the weaning food measured instrumentally, although high temperatures and length of storage time, did not modify Lab, chroma, and hue angle values in both samples. Organoleptic attributes presented a marked stability even in NFWF stored at room temperature and 37 degrees C.

Atmosphere generation system for the preparation of ambient air volatile organic compound standard mixtures.

A dynamic generation system based on permeation for the preparation of volatile organic compounds at ambient air concentration levels is described herein. The performance of the equipment, sources of uncertainties, and overall uncertainty value are also evaluated. The system is capable of generating multicomponent mixtures at ppb levels and simulating different atmospheric conditions by changing the humidity, concentration level, temperature, and wind velocity. A minimized value for the overall uncertainty in the concentration generated by the system was determined to be ±1.9% for higher weighing time intervals of 4 weeks.