低能O~(3+)与H_2碰撞电子俘获过程中靶的同位素效应研究

利用全量子的分子轨道强耦合方法,我们研究了基态的O3+(2s22p2P)与氚分子和氢分子碰撞的电荷转移过程,计算了方位角为45°,能量分别为0.1eV/u,1.0eV/u,100eV/u,500eV/u的单电子俘获的振动分辨的态选择截面及总截面.分子轨道强耦合计算中采用了自旋耦合价带理论计算的三原子分子势能面和径向耦合矩阵元.对体系的电子运动同H2(T2)或H2+(T2+)的转动和振动之间的耦合,根据能量的不同,分别采用了无限阶的冲量近似或振动冲量近似.结果发现,低能O3+与H2碰撞电子俘获过程中靶的同位素效应显著:对不同的同位素靶,单电子俘获的总截面以及振动分辨态选择截面的分布明显不同;入射离子能量越低,同位素效应越显著.

Low-temperature heat capacities and standard molar enthalpy of formation of aspirin

Molar heat capacities (C-p,C-m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of Cp, vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 Kless than or equal toTless than or equal to383 K, C-p,C-m/J mol(-1) K-1=19.086X(4)+15.951X(3)-5.2548X(2)+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {DeltaH(T)-DeltaH(298.15)} and {S-T-S-298.15}, were derived.

不同促腐条件下秸秆还田对土壤微生物量碳氮磷动态变化的影响

通过2年田间定位试验,研究了冀东地区小麦玉米轮作制度下,不同促腐条件下玉米秸秆配施化肥直接还田对土壤微生物量C、N、P���态变化的影响,并讨论了其与土壤养分和酶活性的关系.结果表明,秸秆配施化肥并调节其C/N条件下,施用促腐剂处理作物各生育期土壤微生物量C、N、P���表现出高于未施用处理的趋势,并使微生物量N、P���到高峰期的时间提前,对土壤养分调控效果较好.土壤微生物量C、N、P���土壤酶活性在作物各生育期均表现为显著和极显著正相关关系,但与土壤碱解氮、有效磷的相关性受到施肥制度和作物生长的强烈影响.

Thermodynamic study of ibuprofen by adiabatic calorimetry and thermal analysis

Molar heat capacities of ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 400 K. The polynomial functions of C-p,C-m (J K-1 mol(-1)) versus T were established on the heat capacity measurements by means of the least fitting square method. The functions are as follows: for solid ibuprofen, at the temperature range of 79.105 K less than or equal to T less than or equal to 333.297 K, C-p,C-m = 144.27 + 77.046X + 3.5171X(2) + 10.925X(3) + 11.224X(4), where X = (T - 206.201)/127.096; for liquid ibuprofen, at the temperature range of 353.406 K less than or equal to T less than or equal to 378.785 K, C-p,C-m = 325.79 + 8.9696X - 1.6073X(2) - 1.5145 X-3, where X = (T - 366.095)/12.690. A fusion transition at T = 348.02 K was found from the C-p-T curve. The molar enthalpy and entropy of the fusion transition were determined to be 26.65 kJ mol(-1) and 76.58 J mol(-1) K-1, respectively. The thermodynamic functions on the base of the reference temperature of 298.15 K, (H-T - H-298.15) and (S-T - S-298.15), were derived. Thermal characteristic of ibuprofen was studied by thermo-gravimetric analysis (TG-DTG) and differential scanning calorimeter (DSC). The temperature of fusion, the molar enthalpy and entropy of fusion obtained by DSC were well consistent with those obtained by adiabatic calorimeter. The evaporation process of ibuprofen was investigated further by TG and DTG, and the activation energy of the evaporation process was determined to be 80.3 +/- 1.4 kJ mol(-1). (C) 2003 Elsevier B.V. All rights reserved.

长白山次生针阔混交林叶凋落物中有机物分解与碳、氮和磷释放的关系

采用分解袋法,研究了长白山次生针阔混交林内9种树种叶凋落物34个月的分解过程.结果表明:在次生针阔混交林中,不同树种叶凋落物的初始N和P���度存在很大差异,叶凋落物分解速率(k)与初始N浓度和C/N显著相关.有机物剩余百分率与C剩余百分率呈显著的线性正相关关系,与N和P���余百分率之间呈显著的二项式回归关系.N和P���余百分率在初期阶段随有机物分解而增加,达到峰值后逐渐降低.随着有机物剩余百分率的下降,C/N和C/P���呈逐渐降低趋势,各种叶凋落物之间C/N和C/P���差异逐渐减小,分解末期分别趋近于23和350.随有机物剩余百分率的降低,N/P���化不明显,当有机物剩余百分率低于25%时,不同树种叶凋落物之间N/P���异显著下降.有机物剩余百分率可用来预测C、N和P���剩余百分率.

Investigation of thermodynamic properties of Co2O3 powder

The isobaric molar heat capacities of powder of Co2O3 were determined by an adiabatic calorimeter in the temperature range from 78 to 350 K. No phase transition takes place in this temperature range. The relationship of C-p,C-m with thermodynamic temperature T was established as C-p,C-m = -5 x 10(-6)T(3) + 0.0026T(2) + 0.0325T + 4.2592 (J K-1 mol(-1)), fitting coefficient R-2 = 0.9996. According to this relationship and the relationships between thermodynamic functions, the thermodynamic functions of powder of C2O3 were derived with 298.15 K as reference temperature. Thermal decomposition of Co2O3 powder was studied through thermogravimetry (TG). The possible mechanism of the thermal decomposition reaction was suggested according to the TG result. (C) 2003 Elsevier Science B.V. All rights reserved.

科尔沁沙地小叶锦鸡儿人工林防风固沙及改良土壤效应研究

为探讨小叶锦鸡儿防风固沙、改良土壤养分状况和生物活性的能力,选取6年和11年生小叶锦鸡儿人工固沙林为对象,以流动沙丘为对照,研究不同年龄固沙林降低风速和风沙流结构特征、土壤有机质和N,P���量、土壤酶的活性以及微生物生物量C,N,P���量的变化特征。结果表明:在小叶锦鸡儿灌木林内,各个高度风速和输沙量均显著低于流动沙丘,防风固沙效果明显。随着小叶锦鸡儿固沙群落发育时间的增长,其综合防风性能提高,土壤有机质、N,P,K含量和生物活性逐渐得到改善。O～30 cm土层中磷酸单酯酶、蛋白酶、脲酶、蔗糖酶、硝酸还原酶、多酚氧化酶、脱氢酶的活性和土壤微生物生物量C,N和P���量均大幅度提高,其中0~10 cm土层增幅最大。土壤酶中蔗糖酶的活性增加最为迅速,6年和11年生固沙林0～10 cm土层分别是流动沙丘的28.58倍和55.2l倍。小叶锦鸡儿不仅具有较好的防风固沙性能,而且表现出强大的改善土壤养分和生物活性的能力,可作为优良的固沙植物材料在科尔沁沙地大面积推广应用。

不同氮磷施肥量对玉米生育期土壤微生物量的影响

通过田间小区试验研究了不同N、P���肥量对玉米生育期土壤微生物量C、N、P���影响。结果表明,不同N、P���肥量对微生物量C无明显影响;施N肥量高(225km/hm~2)时降低微生物量N;当施P���达225 km/hm~2时则对微生物量P���生明显的抑制作用。

施肥对日本落叶松不同根序细根养分浓度的影响

以辽宁东部山区16年生日本落叶松人工林为对象,探讨施肥对落叶松1～5级不同根序等级细根养分浓度的变化.结果表明:不同根序等级细根全碳浓度差异不显著,施肥对各级根序全碳浓度没有显著影响;在前5级根序中,1级根非结构性碳水化合物(TNC)浓度最低,N和P���度最高;而5级根TNC浓度最高,N和P���度最低.TNC浓度随着根序增加而升高,N和P���度则相应下降.施肥仅对1级根组织中N和P���度有显著影响;不同根序根组织中C/N/P���有明显差异,1级根平均C/N/P���423∶16∶1,5级根为726∶16∶1,随着根序增加,C在3种元素中的比例显著增加,而N的比例变化不大.施N肥并没有改变C的比例;但施P���或施N+P���均降低了前3级根(0～10cm)或前2级根(10～20cm)C和N在3种元素中的比例.

田块尺度下土壤磷素的空间变异性

采用经典统计学与地统计学相结合的方法,对中国科学院沈阳生态实验站30 m×42 m样地进行网格法分层(0~10和10~20 cm)取样,研究了田块尺度下土壤全P���Olsen-P���空间变异特征.结果表明,49对样本土壤Olsen-P���变异系数(46.56%~56.42%)远高于全P(11.68%~13.33%);全P���Olsen-P���有较好的空间结构且具有较相近的空间相关距离.最佳理论模型的参数显示各变量空间变异主要受结构性因素的影响,各变量半方差变异函数的C/(C0+C)均高于66%.全P���Olsen-P���间及在2个土层之间均具有较相似的空间分布格局.变异系数结合空间格局分析可以大大降低试验取样的数量.

土壤水分梯度对阔叶红松林结构的影响(英文)

2002年8月,在吉林省白河林业局红石林场(12755E,4230N),沿着一个山坡设置了一个长宽为112m8m、包含14个样方的样带。调查了群落结构、0-10cm和10-20cm的土壤含水量、枯落物现存量及其C、N、P���量,主要树种的叶片和枝条的C、N、P���量。沿着山坡的不同位置土壤含水量的不同导致阔叶红松林的群落结构发生变化。蒙古栎的比例随着土壤含水量的下降而逐渐升高,而其他主要阔叶树种则逐渐减少乃至消失。枯落物的水分变化趋势与土壤一致。在不同坡位枯落物的分解状况不同,干重差异显著。坡下枯落物含量较坡上的丰富,部分原因在于群落结构的变化。水分和养分含量的变化影响了枯落物的成分、降解及其养分的释放,进一步影响了林木的生长速度和林分结构并最终影响整个生态系统。图7表2参14。

Structure and electrochemical characteristics of RENi3 alloy

The RENi3 (RE = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y) series compounds have been prepared by arc melting constituent elements under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes, depending on different rare earth (RE) element. The electrochemical characteristics, including the electrochemical capacity, P-C isotherms, high rate chargeability (HRC) and high-rate dischargeability (HRD), of these alloys have been studied through the charge-discharge recycle testing at different temperatures, charge currents and discharge currents. The results show that YNi3 has the largest cell volume, smallest density, and moreover, it shows more satisfactory electrochemical characteristics than other alloys, including discharge capacity, HRC, HRD and low temperature dischargeablity.

Crystallographic and electrochemical characteristics of La0.7Mg0.3Ni3.5-x (Al0.5Mo0.5)(x) (x=0-0.8) hydrogen storage alloys

The crystal structure, hydrogen storage property and electrochemical characteristics of the La0.7Mg0.3Ni3.5-x(Al0.5Mo0.5), (x=0-0.8) alloys have been investigated systematically. It can be found that with X-ray powder diffraction and Rietveld analysis the alloys are of multiphase alloy and consisted of impurity LaNi phase and two main crystallographic phases, namely the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase, and the lattice parameter and the cell volume of both the La(La, Mg)(2)Ni-9 phase and the LaNi5 phase increases with increasing A] and Mo content in the alloys. The P-C isotherms curves indicate that the hydrogen storage capacity of the alloy first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. The electrochemical measurements show that the maximum discharge capacity first increases from 354.2 (v = 0) to 397.6 mAh g(-1) (x = 0.6) and then decreases to 370.4 mAh g(-1) (x= 0.8). The high-rate dischargeability of the alloy electrode increases lineally from 55.7% (x=0) to 73.8% (x=0.8) at the discharge current density of 1200 mA g(-1). Moreover, the exchange current density of the alloy electrodes also increases monotonously with increasing x.

Crystal growth and structural analysis of PrMnO3 and TbMnO3

Single crystals of PrMnO3 and TbMnO3 were grown by floating zone method and the crystal structure was determined by single crystal X-ray diffractometry. The structure of these compounds belongs to the orthorhombic system (space group is Pnma, No. 62) with the lattice parameters alpha approximate to root (.) - a(p), b approximate to 2 (.) a(p) , c approximate to root 2.a(p) and Z = 4, where a(p) is ideal cubic perovskite cell parameter.

Scanning electrochemical microscopy study of electron transfer across the water/1,2-dichloroethane interface induced by common ions

In this work, we report the reverse electron transfer reaction between TCNQ in 1, 2-dichloroethane (DCE) and ferrocyanide in water. This process is a thermodynamic unfavorable reaction and the reverse electron transfer reaction can only be obtained by scanning electrochemical microscopy(SECM) in the presence of suitable potential-determining ions, which govern the interfacial potential difference. In our case, the potential determining ions are tetrabutylammonium ion(TBA(+)) and tetraphenylarsonium ion (TPAs+). The effects of the concentrations of TBA(+) and TPAs+ in two phases and other parameters have been studied in detail. The apparent heterogeneous rate constants(k(i)) were obtained under different values of K-p(K-p=c(i)(w)/c(i)(o)) for both cases by fitting the SECM approach curves with theoretical ones and the results showed that they were controlled by the interfacial potential differences. The relationship between apparent heterogeneous rate constants and the interfacial potential differences obeys Butler-Volmer theory.