Hedgerow species and environmental conditions effects on soil total C and N and C and N mineralization patterns of soils amended with their prunings

An important criterium in selecting species for alley cropping is themineralization pattern of their prunings. This study determined effects of 5years of hedgerow pruning applications on soil organic C and total N at threelocations in Haiti and mineralization patterns from soil amended with theprunings during an incubation using micro-lysimeters. Soils (0–5cm) under 5 hedgerows were collected at each site and analyzed fororganic C and total N. In the laboratory, ground leaves and stems (<1cm diameter) of the hedgerow species were mixed with soil at ratesof 3 and 1.5 Mg ha^–1, respectively, andaerobically incubated in the dark at 25 °C. A non-amended soilwas used as control. Soils were leached to determine mineral N at 1, 3, 7, 14,28, 42, 84 and 120 days of incubation. Evolved CO₂ was measuredfollowing each leaching procedure. At the calcareous site, application ofprunings from Leucaena leucocephala (Lam.) De Wit andDelonix regia (Boj. ex Hook. Raf.) resulted in 23 and 13%higher soil N than the control, respectively, after 5 years. There were nodifferences in total N at the other sites but soil N was highest underLeucaena hybrid and Acaciaangustissima (Mill.) Kuntze, respectively at the basaltic and highelevation sites. Soils under D. regia (calcareous) andA. angustissima and Leucaena hybrid(high elevation) had higher organic C than the respective controls. Carbon andNmineralization and C turnover were highest when soils were amended with leavesof Leucaena diversifolia (Schlecht.) Benth (calcareous andbasaltic soils) and A. angustissima (high elevation) andlowest in non-amended control soils. Stem-amended soils showed differences in Cmineralization for calcareous and high elevation soils whereas N mineralizationwas similar among treatments within sites. Carbon and N mineralization (highelevation soil) correlated positively with N concentrations of leaf prunings.Amendments with leaf prunings increased soil C and N mineralization andturnoverrates, suggesting greater nutrient availability for the crop during a shortperiod than in non-amended control soils.     

Influence of granular carbons on pitch properties

This paper deals with the study of the variation of properties of four pitches (a commercial impregnating coal tar pitch, an air-blown and two thermally treated pitches) when mixed with four granular carbons (anthracite, graphite, green petroleum coke and foundry coke). As a first step, optical microscopy was used to determine the distribution of the pitch among the granular carbons. The anthracite seems to attract the primary quinoline insolubles present in the commercial and thermally treated pitches. This allows the mesophase spheres to coalesce at unusually low temperatures during the mixing process. In general, the toluene insoluble content of the pitch showed a significant increase after mixing with the granular carbons. This is an indication of the interactions between the different granular carbons and some compounds present in the pitches. Analytical techniques like size exclusion chromatography and differential scanning calorimetric analysis were used in order to obtain information about the characteristics of the components of the pitches that interact with the different granular carbons and their effect on pitch properties. Graphite seems to interact preferentially with the larger molecules whereas the green petroleum coke acts on a wider molecular range.     

Processing of polypropylene–clay nanocomposites: Single‐screw extrusion with in‐line supercritical carbon dioxide feed versus twin‐screw extrusion

This work investigates two different melt‐blending strategies for preparing compatibilized polypropylene‐clay nanocomposites, specifically: (1) conventional twin‐screw extrusion, and (2) single‐screw extrusion capable of direct supercritical carbon dioxide (scCO₂) feed to the extruder barrel. Proportional amounts (3 : 1) of maleic anhydride functionalized polypropylene compatibilizer and organically modified montmorillonite clay at clay loadings of 1, 3, and 5 wt % are melt‐blended with a polypropylene homopolymer using the two approaches. The basal spacing, degree of exfoliation, and dispersion of organoclay is assessed using X‐ray diffraction, transmission electron microscopy, and rheology. In terms of the latter, both steady shear and small‐amplitude oscillatory shear provide information about the apparent yield stress and solid‐like terminal behavior respectively. Finally, nanoindentation is performed to determine the room temperature modulus of each melt‐blended nanocomposite. The results reveal unequivocally that the high shear of the twin‐screw process is vastly superior to the single‐screw with in‐line scCO₂ addition in generating well‐exfoliated, percolated polypropylene‐clay nanocomposites. It is likely that increased contact time between clay and scCO₂ is necessary for scCO₂ to positively affect exfoliation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 884–892, 2007     

Characterization of pedicel,paper, and larval silk from nest ofPolistes annularis (L.)

The pedicel, nest paper, and larval silk ofPolistes annularis nests were analyzed by high-resolution solid-state [¹³C]NMR. The pedicel was found to have a high nitrogen content (11%), and the NMR spectra indicated that it is a mixture of carbohydrate and protein. The pedicel protein has an amino acid composition that is very rich in glycine, alanine, serine, and proline (67% of identified residues), similar to that of some insect silks. Solid-state [¹³C]NMR indicated that the nest paper is composed predominantly of cellulose. Silk, spun by matureP. annularis larvae, was shown by [¹³C] NMR and amino acid analysis to be a protein very high in serine and alanine (53%), but the amino acid composition is distinct from that of the pedicel protein.     

多孔材料在催化CO2与环氧化物环加成反应中的研究进展

以CO2为原料与环氧化物合成环状碳酸酯是实现CO2资源利用最为有效的途径之一，也是缓解温室效应的有效方式之一。在该反应中催化剂的选择至关重要，多孔材料由于具有相对密度低、强度高、比表面积大、稳定性好、合成方法多样等优点而被广泛应用于催化CO2环加成。重点综述了近年来无机多孔材料、多孔有机聚合物材料、金属有机骨架材料在催化CO2与环氧化物合成环状碳酸酯中的研究进展，介绍了各催化剂的优缺点并对未来多孔材料的发展进行了展望。     

OXIDATION OF SULFUR DIOXIDE IN DIFFERENT TYPES OF THREE PHASE REACTORS

Five different types of three-phase reactors are compared with each other by using oxidation of sulfur dioxide on activated carbon. The kinetic measurements were carried out by changing concentrations of sulfur dioxide from 0.04 to 0.17% (volume) and those of oxygen from 2 to 21%. The reaction rate was 0.2 order with respect to sulfur dioxide and 0.5 order with respect to oxygen. The catalytic effectiveness factor and intraparticle diffusivity were evaluated by changing particle sizes of activated carbon from 0.03 to 1.6 mm. Resistances of gas-liquid, liquid-solid mass transfer and intraparticle diffusion were estimated for individual reactors. The optimum reactor was dependent on operating conditions such as gas flow rates, rotating speeds and particle sizes.     

对苯二酚-甲醛有机气凝胶的结构测试及性能研究

首次用溶胶-凝胶法和CO2超临界干燥技术制备了对苯二酚-甲醛有机气凝胶,并经高温碳化处理得到其碳气凝胶,测得气凝胶的比表面积由碳化前的375.28 M2/G增大到碳化后的468.66 M2/G,碳气凝胶的孔径集中分布在15NM以内。观察到其表观形貌,以及碳气凝胶中存在微晶结构。研究了不同反应物配比对凝胶性能的影响,并发现碳气凝胶具有良好导电性。     

活性炭负载Ti(SO_4)_2催化合成丙二酸二丁酯的研究

首次以活性炭负载硫酸钛 (Ti(SO4) 2 /C)作催化剂 ,合成丙二酸二丁酯 ,此催化剂活性高 ,选择性好 ,易分离 ,不腐蚀设备 ,反应时间短 ,是一种环境友好催化剂。考察了影响酯化反应的条件 ,获得优化工艺条件如下 :Ti(SO4) 2 负载量 2 0 % ,丙二酸 0 2mol,正丁醇 0 6mol,催化剂 0 8g ,反应温度 15 0℃ ,反应时间 90min ,丙二酸的转化率 94 %以上     

浸渍法改性活性炭脱硫(H2S)研究

针对普通脱硫剂的硫容较小的问题，我们利用浸渍液对活性炭进行改性试验。结果表明，用7％的碳酸钠(Na2CO3)溶液作为浸渍液对活性炭改性制得的脱硫剂比普通纯活性炭脱硫剂的硫容提高近30％。试验还考查了浸渍液种类、浸渍液浓度、温度对脱硫效率的影响。     

石莼基微/中孔复合结构活性炭的制备及性能

以海洋海藻废弃物石莼为原料,通过热解预炭化,KOH活化制备活性炭。以碘吸附值和亚甲基蓝吸附值为吸附性能评价指标,探究了活化工艺对活性炭吸附性能的影响。结果表明,当KOH与石莼半焦质量比(碱炭比)为3.0∶1.0、活化时间为45 min、活化温度为800℃时,活性炭吸附性能最优,其碘吸附值和亚甲基蓝吸附值最大,分别为1824.19 mg/g、914.98 mg/g。FTIR测试表明,活性炭含有大量羟基等官能团。SEM测试表明,活性炭表面粗糙、存在大量孔结构。活性炭的BET比表面积为2616.3 m2/g,Langmuir比表面积高达4883.5 m2/g,平均孔径为2.73 nm。石莼基活性炭的孔结构为微/中孔复合结构,有作为储能、环保材料的潜质。