Simple and Straightforward Synthesis of Porous Ionosilica for Efficient Chromate Adsorption

We report a very simple synthesis strategy for the formation of moderately porous ionosilica materials containing ammonium groups. We synthesized an ionosilica xerogel and an ionosilica aerogel, either via conventional or supercritical work‐up. The synthesis scheme of both precursor and ionosilica materials could easily be up‐scaled to a 100 g scale. All syntheses and work‐up procedures are sustainable as no additional agent and very low quantities of solvents were used, and no additional purifications steps were necessary. Although both materials show excellent anion exchange properties for chromate adsorption, noticeable differences were found regarding the thermodynamics of the exchange process. We attribute these differences to different surface chemistries of the materials, induced by the different work‐up procedures. Due to the easy availability of high quantities of material, ionosilicas can be implemented as functional ion exchange materials in larger scale processes, thus opening new fields of applications.     

Hydrolysis of biliary phospholipids in the upper small intestine of the chick

Chick endogenous phospholipids were doubly labeled by an intravenous injection of [³²P] phosphate and [1-¹⁴C] oleic acid, and the free fatty acid and phospholipid fraction of gall bladder bile and in contents of upper small intestine were analyzed 4 days later. There was evidence of hydrolysis of biliary phosphatidylcholine to lysophosphatidylcholine in the duodenum and jejunum, but this did not account for the pronounced increase in the¹⁴C radioactivity of the free fatty acids relative to the³²P phospholipid radioactivity between bile and upper intestinal segments. It is suggested that phosphatidylcholine is largely absorbed in the duodenum of the chick while the remainder is progressively hydrolyzed and absorbed.     

Formation and behavior of mechanoradicals in pulp cellulose

The mechanical degradation of pulp cellulose fiber was studied at ambient temperature and at 77°K. ESR findings reveal that mechanical degradation occurs via free-radical routes. Three types of mechanoradicals contributing singlet, doublet, and triplet ESR signals are identified. The singlet signals are derived from the alkoxy radicals at C₄ positions as a consequence of the cleavage of glucosidic bonds, the radical pairs generated at C₁ positions contributing the doublet signals. Triplet signals are derived from the C₂ and C₃ positions due to the cleavage of C₂ and C₃ bonds. Of these radicals, alkoxy radicals are the most stable at ambient temperature. Carbon radicals are capable of interacting rapidly with oxygen molecules to produce peroxy radical intermediates, where alkoxy radicals are inert toward oxygen molecules. ESR study also reveals that cellulose mechanoradicals are capable of initiating vinyl polymerization. MMA propagating radicals are identified when the monomers are in contact with cellulose mechanoradicals. The ability of mechanoradicals to initiate graft copolymerization from cellulose fiber is discussed.     

Contribution to DEMO reactor RH maintenance assessment

The scope of this paper is a preliminary assessment of the maintenance scheme in support of the European study for the next generation of fusion reactor: DEMO. Despite other fusion machine requiring remote handling maintenance operations, DEMO is supposed to work under steady state operational conditions. Therefore, requirement on the maintenance scheme is stronger. To target a good availability of the machine along machine operation plan, it is necessary to draw an adequate maintenance scheme. Indeed, due to the high fluxes generated by the plasma in the vacuum vessel, the first wall lifetime is limited, so the frequent replacement is necessary. On current fusion experimental machine, as first wall load conditions are less severe, DEMO condition implies high level of requirement on maintenance time. During DEMO lifetime, several full first wall replacements are expected. To provide access to the vacuum vessel machine for first wall removal, preparatory work is required to set the machine to adequate maintenance conditions and to open the machine properly, the same situation at the end of the maintenance period. Shutdown duration for first wall replacement should be as short as possible to reach the availability target of the machine. From this statement, the maintenance duration should not exceed 20% of the total lifetime of the reactor operation. First wall segmentation (i.e. total number of component to replace) has a high impact onto the replacement time. Considering the number of feasible designs for the first wall segmentation, we concentrate remote handling concept assessments one type of segmentation, the one minimizing the numbers of modules to replace [4], [5], [6]. Assumption on Divertor segmentation for these DEMO studies have similarities with Divertor ITER design; therefore ITER design output is relevant [1], [2]. We assume divertor removal performed in shadow time, while removing the other first wall modules.     

Neutronic characterization of the MEGAPIE target

The MEGAPIE project aimed to design, build and operate a liquid metal spallation neutron target of about 1 MW beam power in the SINQ facility at the Paul Scherrer Institut (Villigen, Switzerland). This project is an important step in the roadmap towards the demonstration of the accelerator driven system (ADS) concept and high power liquid metal targets in general. Following the design phase, an experimental program was defined to provide a complete characterization of the facility by performing a “mapping” of the neutron flux at different points, from the center of the target to the beam lines. The neutronic performance of the target was studied using different experimental techniques with the goals of validating the Monte Carlo codes used in the design of the target; additionally, the performance was compared with the solid lead targets used before and after the MEGAPIE experiment.     

Flux measurements for a DD neutron generator using neutron activation analysis

The fast and maximum thermal neutron fluxes from the DD-109 neutron generator at the University of Sharjah were experimentally measured by the activation technique using different neutron reactions. The thermal and fast neutron fluxes were found to be 2.960 × 10~6 and6.186 × 10~7 n/cm~2 s, respectively. This was done to verify the modeling results for the optimum moderator thickness needed to maximize the thermal neutron flux. The optimum moderator thickness was found to be between 3.5 and4 cm. The present data were compared with the detailed MCNP model-based calculation performed in earlier work to simulate the generator.     

Improving Wheat Productivity in Pakistan: Econometric Analysis Using Panel Data from Chaj in the Upper Indus Basin

Abstract

Increasing water scarcity, degradation of land and water resources, continuing low agricultural productivity, and increasing populations are posing the largest ever challenges for development of agricultural economies in many developing countries including Pakistan. Using panel data from irrigated settings in Chaj sub-basin of the Indus basin in Pakistani Punjab, we attempt to: (a) analyze the causes of low productivity; (b) disentangle factors (both land, water and other factors) contributing to productivity variations; and (c) identify limits and opportunities for narrowing productivity gaps and increasing overall wheat production, with a view to enhance food security for the poor. The results of the study indicate that locational inequities in distribution of canal water, use of groundwater of varying quality, differences in use of seed varieties, and other inputs lead to significant variations in wheat productivity. Key implications are that large gains in wheat productivity are possible by (a) improving the production environment at the tail-end through integrated water management practices; (b) adjusting the mix of canal and groundwater use; and (c) using technological interventions to improve the adoption of modern wheat varieties and dissemination of knowledge on planting dates and timings and application rates of inputs, especially water and fertilizer. Not only such interventions are economically, financially, and environmentally desirable, they are also pro-poor. What is needed is a strong political will and commitment.     

The Yellow River Basin: Water Accounting,Water Accounts,and Current Issues

Abstract

There is increasing recognition of the problems facing China in meeting the growing water demand in the Yellow River basin, the “cradle of Chinese Civilization” and a critically important agricultural and industrial region. Meaningful debate on the range and relative costs of options available to policy-makers in addressing the problem depend fundamentally on an accurate understanding of basin water resources. Unfortunately, the ability of outsiders to participate in the de bate and for Chinese, with their long history of water management, to contribute to similar discussions elsewhere in the world is hindered to some extent by a lack of understanding of differences in water accounting systems and concepts. This paper attempts to address this problem by describing the water accounting system used in the Yellow River basin and elsewhere in China. The paper shows that the primary difference between water accounting methodologies in the Yellow River and those typically applied elsewhere is related to supply accounting in general and groundwater accounting in particular. Although not currently included in its water accounting system, Chinese concepts of environmental water use, when included, will also differ substantially from those familiar to outside researchers. In terms of actual Yellow River balances, the paper highlights the apparent declining trend in basin rainfall and runoff and the dramatic growth in industrial and domestic water use. Together declining supply and rising demand will increasingly cause policy-makers to face hard choices in assessing their water planning options. These choices will only become more difficult as managers in the Yellow River, as elsewhere in the world, try to incorporate ecological needs in the water accounting equation.