Aggregation and aging in silica gel

Aggregation and aging of silica gels, prepared by controlled addition of water glass to hydrochloric acid, and the transformation of an aged gel to a crystalline phase have been studied in-situ using high-brilliance synchrotron radiation. Small angle X-ray scattering (SAXS) has proved to be very informative in readily detecting transformations in the silica gels which can be described using the concepts of mass and surface fractality. The interpretation of SAXS spectra of aged silica gels has been accompanied by computer simulations of aggregation and aging based on a model for the aging mechanism and the calculation of the corresponding structure-factor patterns. Comparison with experimental spectra of aged silica highlights the important role of particle growth on the fractal dimension. Gel transformations during the transition from an amorphous gel to the crystalline phase of silicalite have been successfully monitored, in-situ, both for heterogeneous and for homogeneous preparations, using the combination of small and wide angle X-ray scattering (SAXS-WAXS

Growth and physiological responses of lettuce grown under pre-dawn or end-of-day sole-source light-quality treatments

The objective of this study was to evaluate growth and physiological responses of ‘Cherokee’ and ‘Waldmann’s Green’ lettuce (Lactuca sativa) exposed to small changes in light quality and intensity within a 24-h period. Three pre-dawn (PD; 0600 to 0700) and three end-of-day (EOD; 2100 to 2200) treatments were evaluated in the study, each providing 50 ± 2 μmol·m−2·s−1 of either blue, red, or broadband white light from light-emitting diodes (LEDs). To account for the main daily light integral (DLI), broadband white LEDs provided 210 ± 2 μmol·m−2·s−1 from 0700 to 2200 or from 0600 to 2100 for the PD or EOD treatments, respectively. A control treatment was included which provided 200 ± 2 μmol·m−2·s−1 of white light from 0600 to 2200. All treatments provided a DLI of 11.5 mol·m−2·day−1 over a 16-h photoperiod. Regardless of cultivar, no treatment difference was measured for hypocotyl length or leaf number. However, plants grown under EOD-blue or PD-white had up to 26% larger leaves than those grown under PD-red and 20% larger leaves than control. In addition, plants grown under EOD-blue produced up to 18% more shoot fresh mass compared to those grown under control, EOD-red, or PD-red. Contrasts for gas-exchange data collected during the main photoperiod showed that light quality was not significant within PD or EOD for any of the parameters evaluated. However, regardless of light quality, stomatal conductance (gs) and transpiration (E) were up to 34% and 42% higher, respectively, for EOD-grown plants compared to control. Our results suggest that 1 h of low intensity EOD-blue light has the potential to promote lettuce growth by increasing leaf area and shoot fresh mass when the main DLI from sole-source lighting is provided by broadband white LEDs

Modeling of Hydrogen Storage Materials: A Reactive Force Field for NaH

Parameterization of a reactive force field for NaH is done using ab initio derived data. The parameterized force field(ReaxFFNaH) is used to study the dynamics governing hydrogen desorption in NaH. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by the parameterized force field. To gain more insight into the mechanism governing structural transformation of NaH during thermal decomposition a heating run in a molecular dynamics simulation is done. The result shows that a clear signature of hydrogen desorption is the fall in potential energy surface during heating

Influence of water on the sulfidation of Co/NaY and Co/CaY prepared by impregnation, A. Mössbauer Emission spectroscopy and EXAFS Study

The influence of physisorbed water on the sulfidation of impregnation type Co/NaY(imp) and Co/CaY(imp) catalysts which contain about 4 wt % Co and are prepared via pore volume impregnation is studied by Mossbauer emission spectroscopy and extended X-ray absorption fine structure. It is found that in the absence as well as in the presence of water, sulfidation of the impregnated samples finally results in the formation of Co9S8-like species at the outer zeolite surface. In the presence of water, this process proceeds via the intermediate formation of a well-ordered ''CoS1+x'' phase (NiAs structure). Water removal prior to sulfidation retards the formation of Co9S8-like species. This retardation in Co9S8 formation is found to be more effective for CaY-zeolite than for NaY- zeolite, which means that a larger part of the formed ''Co- sulfide'' is preserved in highly dispersed ''Co-sulfide'' particles. These findings are clearly different from those obtained earlier with ion exchanged CoNaY(ion ex) samples, for which drying prior to sulfidation resulted in very small ''Co- sulfide'' species with no resemblance to ''Co9S8'

Forage Allowance and Daily Gain Relationships on Rye-Ryegrass Pastures at Different Stocking Rates With Continuous and Rotational Stocking

‘Maton’ cereal rye (Secale cereale L.) and ‘TAM-90’ annual ryegrass (Lolium multiflorum Lam.) are used for winter annual pastures to background stocker cattle in the southeastern US. Rye and ryegrass were sod-seeded into bermudagrass [Cynodon dactylon (L.) Pers.] pastures and fixed-stocked at different rates under continuous and 8-paddock rotation methods during each of 7 years to: 1) compare stocking methods for daily gain per animal (ADG) and gain/ha; and 2) quantify relationships of ADG with forage mass and forage allowance. Each of 3 levels of stocking rate, 4.9, 6.4, and 8.6 hd/ha, significantly affected ADG at 1.24, 1.04, and 0.74 kg/d, and gain/ha at 821, 991, and 794 kg/ha, respectively. There were no effects of stocking method on ADG at 1 kg/ha or gain/ha at 870 kg/ha. There was a 2-stage linear relationship for ADG and forage mass with the join point for maximum gain at 1850 kg/ha forage mass and 16 cm forage height. The 2-stage join point for forage allowance was 1.0 forage dry matter : animal body weight. The primary management strategy for rye + annual ryegrass pastures is that of stocking rate. During this 7-year period, stocker ADG ranged from 0.33 kg/d to 1.38 kg/d with gain/ha ranging from 388 kg/ha to 1291 kg/ha. Stocking strategies must be flexible with climatic changes to obtain optimum economic returns per unit land area. Rotational stocking method becomes a management choice to adjust forage mass options without expectations for increased ADG or gain/ha

Care leavers in early adulthood: How do they fare in Britain, Finland and Germany?

In this paper we examine the longer term outcomes of young people who experienced out of home care (OHC) as children, in Britain, Germany and Finland, countries characterised by different welfare regimes. While there is some evidence on immediate transitions after leaving care (up to age 21), there is less evidence on experiences around age 30, a phase of early adulthood. Drawing on existing longitudinal data for general population samples we focus on outcomes related to education, employment, family, health and receipt of welfare benefits for those who were ever in care and those who were not. We find evidence for continuing disadvantage regarding education and employment for those who were in care as children, but also indications of subjective wellbeing and commitment to family life – possibly a reflection of “normality” and efforts to “fit in” as parents. Surprisingly, despite variations in welfare system and differences in the scope and quality of available data, trends were similar in each of the countries, suggesting that none provide adequately for the needs of care experienced young adults. The findings point towards the need for a revised conceptualisation of the notion of “independence” which has to take into account the manifold and changing relationships between individuals and the state. Instead of a “cliff edge” approach there should be support for a more gradual shift from “dependence” to “independence” enabling those with care experience to develop their full potential. In interpreting the findings, limitations of the available data have to be acknowledged, pointing to the need for generating harmonised and longitudinal data on vulnerable subpopulations to enable effective monitoring of needs and provision

Hydrodesulfurization catalysis by small metal sulfide particles

Monometallic (Mo, Co and Ni) sulfide particles dispersed in the micropores of zeolites can have a very high initial activity for the hydrodesulfurization of thiophene. Catalyst characterization, using Xe-129 NMR, HREM and Mossbauer Emission Spectroscopy (MES), shows that the location (in- or outside the zeolite pores) and size of the sulfide particles depends strongly on catalyst preparation conditions. The kinetics of thiophene HDS has been studied on metal (Mo, Co, Ph and Pt) sulfides dispersed on a carbon support. The order of thiophene in the HDS reaction appears to be a strong function of metal sulfide and temperature. The catalysts show a large compensation effec

Catalytic activity of nickel sulfide catalysts supported on Al-pillared montmorillonite for thiophene hydrodesulfurization.

Al-pillared clays, prepared by exchange with partly hydrolyzed aluminium nitrate solutions, dried in air or freeze-dried, and calcined, were used as supports for nickel sulfide catalysts. The catalysts were tested on their hydrodesulfurization (HDS) activity for thiophene. The catalysts show a high thiophene HDS activity. It appears that details in the preparation and calcination of the pillared clays have a strong influence on the catalytic activity