Characterisation of porous solids using small-angle scattering and NMR cryoporometry

The characteristics of several porous systems have been studied by the use of small-angle neutron scattering [SANS] and nuclear magnetic resonance [NMR] techniques. The measurements reveal different characteristics for sol-gel silicas, activated carbons and ordered mesoporous silicas of the MCM and SBA type. Good agreement is obtained between gas adsorption measurements and the NMR and SANS results for pore sizes above 10 nm. Recent measurements of the water/ice phase transformation in SBA silicas by neutron diffraction are also presented and indicate a complex relationship that will require more detailed treatment in terms of the possible effects of microporosity in the silica substrate. The complementarity of the different methods is emphasised and there is brief discussion of issues related to possible future developments

Molecular ions in L1544. I. Kinematics

We have mapped the dense dark core L1544 in H13CO+(1-0), DCO+(2-1), DCO+(3-2), N2H+(1-0), NTH+(3-2), N2D+(2-1), N2D+(3-2), C18O(1-0), and C17O(1-0) using the IRAM 30-m telescope. We have obtained supplementary observations of HC18O+(1-0), HC17O+(1-0), and D13CO+(2-1). Many of the observed maps show a general correlation with the distribution of dust continuum emission in contrast to C18O(1-0) and C17O(1-0) which give clear evidence for depletion of CO at positions close to the continuum peak. In particular N2D+(2-1) and (3-2) and to a lesser extent N2H+(1-0) appear to be excellent tracers of the dust continuum. We find that the tracers of high density gas (in particular N2D+) show a velocity gradient along the minor axis of the L1544 core and that there is evidence for larger linewidths close to the dust emission peak. We interpret this using the model of the L1544 proposed by Ciolek & Basu (2000) and by comparing the observed velocities with those expected on the basis of their model. The results show reasonable agreement between observations and model in that the velocity gradient along the minor axis and the line broadening toward the center of L1544 are predicted by the model. This is evidence in favour of the idea that amipolar diffusion across field lines is one of the basic processes leading to gravitational collapse. However, line widths are significantly narrower than observed and are better reproduced by the Myers & Zweibel (2001) model which considers the quasistatic vertical contraction of a layer due to dissipation of its Alfvenic turbulence, indicating the importance of this process for cores in the verge of forming a star.Comment: 24 pages, 9 figures, to be published in Ap

Etude de la dégradation de quelques composés organochlorés volatils par photolyse du peroxyde d'hydrogène en milieux aqueux

Le travail a eu pour but d'étudier l'efficacité de la photolyse du peroxyde d'hydrogène sur la dégradation de quelques composés organochlorés aliphatiques saturés (chiorométhanes et chloroéthanes) en milieu aqueux (pH 7,5). Les expériences ont été réalisées en réacteur statique, avec une Lampe basse pression à vapeur de mercure et avec des concentrations initiales en produit chloré de l'ordre de 10-6 mol l-1 et en H202 comprises entre 10-5 et 10-3 mol L-.Les résultats montrent que le système H202/UV peut oxyder les composés organochlorés étudiés à l'exception des composés ne possédant pas d'atome d'hydrogène (CCL4 et C2 CL6). Les rendements d'oxydation obtenus avec Le réacteur utilisé dépendent du temps de réaction, de la concentration initiale en H202, du flux photonique et peuvent être nettement diminués par la présence de pièges à radicaux (ions bicarbonates) dans le milieu réactionnel.Par ailleurs, une étude cinétique de la photolyse du peroxyde d'hydrogène en absence de matière organique est également présentée.The aim of this work was to study oxidation of certain volatile polychlorinated hydrocarbons, using hydrogen peroxide photoactivated by UV. This research was carried out with different mixtures of diluted aqueous solutions of chloromethanes (CHCl3, CCl4) and chloroethanes (C2H3Cl3, C2H2Cl4, C2HCl5, CCl6), which are typical halogenated compounds most frequently found in contaminated groundwater. The effect of the hydrogen peroxide concentration, the light intensity and the bicarbonate concentration on the rate of 1,1,2-trichloroethane (TCE) oxidation was determined. A kinetic study on hydrogen peroxide photolysis in a solution free of organic compounds was also carried out.EXPERIMENTATIONExperiments were conducted in a batch reactor (V = 4 l), equipped with an immersed mercury low-pressure lamp. The intensity emitted at 253.7 nm was roughly 2 1019 photons s-1. The temperature of the reaction mixture was maintained with a regulation system at 16 ± 0.5 °C (figure 1).The solutions were prepared in a phosphate buffer µ = 2 10-2 M, pH = 7.5). The outer surface of the lamp was masked with strips of aluminium, so as to obtain various percentages of initial energy (20 to 100 %).The concentration of the hydrogen peroxide of the samples was determined by spectrophotometry and the chlorinated compounds were analysed by electron capture gas chromatography.RESULTKinetics of hydrogen peroxide photolysis : H202 was decomposed by UV tb produce two hydroxyl radicals. In diluted solutions ([H202] < 10-3 M), the concentration decreases in accordante with a first order law. The rate constant depends on the initial light intensity (Io), on the characteristics of the reactor (volume and distance between the lamp and the watt. of the reactor) and on the motar extinction coefficient of the irradiated solution (equation C). The decomposition rate appears to be dependent on pH, the rate of constant rire has been found to be proportional to the dissociation of hydrogen peroxide into its basic form (EH2O2 = 20 mol-1 cm-1,EH2O2_ = 240 mol-1 cm-1) (figure 2 and 3).Oxidation of the chlorinated compounds : H202/UV is very efficient for the removal of organic compounds. Preliminary experiments showed that both UV and H2O2 treatments do not decompose halogenated compounds. Hydroxyl radicals are extremly reactive and attack organic compounds preferentialty by abs-tracting a hydrogen atom from an organic molecule. This is confirmed by the results which show that chloromethanes and chloroethanes with an H atom are eliminated, but net compounds such as tetrachloride and hexachloroethane (figure 4 to 7).The effectiveness of an H202/UV system depends on various parameters. Studies on the TCE elimination show that the oxidation yields an increase when the reaction time, the UV irradiation dose (figure 9b) and the hydrogen peroxide concentration (figure 8) increase. However, the efficiency decreases in the presence of radical traps such as bicarbonate and carbonate ions (figure 10)

Genetic Modification of Stem Cells in Diabetes and Obesity

Genetic modification, or gene transfer, represents a method of treatment for several diseases. It has been used extensively in the context of cardiovascular diseases; however, its role in the context of metabolic diseases, such as diabetes and obesity, has remained largely unexplored. In this chapter, we will review the use of adult stem cells, focusing on endothelial progenitor cells (EPCs) and mesenchymal stromal cells (MSCs), in the context of diabetes. We have highlighted the use of viral vectors, particularly DNA viruses, as a tool for genetic modification to help stem cells survive and resist apoptosis in a hyperglycemic environment. We then discuss genetic modification of EPCs and MSCs to treat complications of diabetes and obesity. Although there are several unanswered questions in the field of metabolic diseases, the future application of gene transfer technology along with genetic modification of stem cells prior to the therapy holds significant therapeutic promise

Understanding Emissions of Ammonia from Buildings and Application of Fertilizers: An Example from Poland

A Europe-wide dynamic ammonia (NH3) emissions model has been applied for one of the large agricultural countries in Europe, and its sensitivity on the distribution of emissions among different agricultural functions was analyzed by comparing with observed ammonia concentrations and by implementing all scenarios in a CTM model. The results suggest that the dynamic emission model is most sensitive to emission from animal manure, in particular how this is connected to national regulations. In contrast, the model is most robust with respect to emission from buildings and storage. To do this, we obtained activity information on agricultural operations at the sub-national level for Poland, information about infrastructure on storages and current regulations on manure practice from Polish authorities. The information was implemented in the existing emission model and was connected directly with the NWP calculations from the Weather Research and Forecasting model (WRF-ARW). The model was used to calculate four emission scenarios with high spatial (5 km x 5 km) and temporal resolution (3h) for the entire year 2010. In the four scenarios, we have compared the European-wide default model settings against: 1) a scenario that focuses on emission from agricultural buildings, 2) the existing emission method used in WRF-Chem in Poland, and 3) a scenario that takes into account Polish infrastructure and agricultural regulations. The ammonia emission was implemented into the chemical transport model FRAME and modelled ammonia concentrations was compared with measurements. The results suggest that the default setting in the dynamic model is an improvement compared to a non-dynamical emission profile. The results also show that further improvements can be obtained on the national scale by replacing the default information on manure practice with information that is connected with local practice and national regulations. Implementing a dynamical approach for simulation of ammonia emission is a viable objective for all CTM models that continue to use fixed emission profiles. Such models should handle ammonia emissions in a similar way to other climate dependent emissions (e.g. Biogenic Volatile Organic Compounds). Our results, compared with previous results from the DEHM and the GEOS-CHEM models, suggest that implementing dynamical approaches improves simulations in general even in areas with limited information about location of the agricultural fields, livestock and agricultural production methods such as Poland

Electrodynamics of superconducting pnictide superlattices

It has been recently reported (S. Lee et al., Nature Materials 12, 392, 2013) that superlattices where layers of the 8% Co-doped BaFe2As2 superconducting pnictide are intercalated with non superconducting ultrathin layers of either SrTiO3 or of oxygen-rich BaFe2As2, can be used to control flux pinning, thereby increasing critical fields and currents, without significantly affecting the critical temperature of the pristine superconducting material. However, little is known about the electron properties of these systems. Here we investigate the electrodynamics of these superconducting pnictide superlattices in the normal and superconducting state by using infrared reflectivity, from THz to visible range. We find that multi-gap structure of these superlattices is preserved, whereas some significant changes are observed in their electronic structure with respect to those of the original pnictide. Our results suggest that possible attempts to further increase the flux pinning may lead to a breakdown of the pnictide superconducting properties.Comment: 4 pages, two figure

Source apportionment of atmospheric ammonia before, during, and after the 2014 APEC summit in Beijing using stable nitrogen isotope signatures

Stable nitrogen isotope composition (δ15N) offers new opportunities to address the long-standing and ongoing controversy regarding the origins of ambient ammonia (NH3), a vital precursor of PM2.5 (particulate matters with aerodynamic diameter equal or less than 2.5 µm) inorganic components, in the urban atmosphere. In this study, the δ15N values of NH3 samples collected from various sources were constrained using a novel and robust chemical method coupled with standard elemental analysis procedures. Independent of the wide variation in mass concentrations (ranging from 33 (vehicle) to over 6000 (human excreta) µg m−3), different NH3 sources have generally different δ15N values (ranging from −52.0 to −9.6 ‰). Significantly high δ15N values are seen as a characteristic feature of all vehicle-derived NH3 samples (−14.2 ± 2.8 ‰), which can be distinguished from other sources emitted at environmental temperature (−29.1 ± 1.7, −37.8 ± 3.6, and −50.0 ± 1.8 ‰ for livestock, waste, and fertilizer, respectively). The isotope δ15N signatures for a range of NH3 emission sources were used to evaluate the contributions of the different sources within measured ambient NH3 in Beijing, using an isotope mixing model (IsoSource). The method was used to quantify the sources of ambient NH3 before, during and after the 2014 Asia-Pacific Economic Cooperation (APEC) summit, when a set of stringent air quality control measures were implemented. Results show that the average NH3 concentrations (the overall contributions of traffic, waste, livestock, and fertilizer) during the three periods were 9.1 (20.3, 28.3, 23.6, and 27.7 %), 7.3 (8.8, 24.9, 14.3, and 52.0 %), and 12.7 (29.4, 23.6, 31.7, and 15.4 %) µg m−3, respectively, representing a 20.0 % decrease first and then a 74.5 % increase in overall NH3 mass concentrations. During (after) the summit, the contributions of traffic, waste, livestock, and fertilizer decreased (increased) by 56.7 (234.2), 12.0 (−5.0), 39.4 (120.8), and −87.7 % (−70.5 %) when compared with periods before (during) the summit, respectively, signifying that future NH3 control efforts in megacities like Beijing should prioritize traffic sector as well as livestock breeding. The results show that isotope ratio measurements of NH3 to be a valuable tool to quantify the atmospheric sources of NH3 in urban atmospheres

Is the Weigl Colour-Form Sorting Test Specific to Frontal Lobe Damage?

OBJECTIVE: The Weigl Colour-Form Sorting Test is a brief, widely used test of executive function. So far, it is unknown whether this test is specific to frontal lobe damage. Our aim was to investigate Weigl performance in patients with focal, unilateral, left or right, frontal, or non-frontal lesions. METHOD: We retrospectively analysed data from patients with focal, unilateral, left or right, frontal (n = 37), or non-frontal (n = 46) lesions who had completed the Weigl. Pass/failure (two correct solutions/less than two correct solutions) and errors were analysed. RESULTS: A greater proportion of frontal patients failed the Weigl than non-frontal patients, which was highly significant (p < 0.001). In patients who failed the test, a significantly greater proportion of frontal patients provided the same solution twice. No significant differences in Weigl performance were found between patients with left versus right hemisphere lesions or left versus right frontal lesions. There was no significant correlation between performance on the Weigl and tests tapping fluid intelligence. CONCLUSIONS: The Weigl is specific to frontal lobe lesions and not underpinned by fluid intelligence. Both pass/failure on this test and error types are informative. Hence, the Weigl is suitable for assessing frontal lobe dysfunction