镜像核13N-13C 和15N-15O中的激发态晕或皮(英文)

用非线性相对论平均场对两对镜像核13N-13C 和15N-15O进行了研究. 发现无论在基态还是激发态， 用两套参数所得的结合能都跟实验值很接近. 计算结果显示13N的第一激发态（2s1/2）和第三激发态（1d5/2）各存在一个非束缚的质子晕， 而13C的第三激发态（1d5/2）存在一个弱束缚的中子皮. 另外研究表明, 在另一对镜像核15N-15O的第二激发态（2s1/2）和第一激发态（2s1/2）分别存在一个中子晕和质子皮. Properties of two pairs of mirror nuclei 13N-13C and15N-15O are investigated by using the nonlinear relativistic mean field theory. It is found that all the calculated binding energies with two different parameter sets are very close to the experimental ones for both the ground states and the excited states. The calculations show that the first excited state (2s1/2) and the third excited state (1d5/2) in 13N are both unbound resonances with proton halo structure, whereas the third excited state (1d5/2) in 13C is weakly bound with a neutron skin. It is also predicted that there has a proton halo in the second excited state (2s1/2) of 15N as well as a neutron skin in the first excited state (2s1/2) of 15O.     

理论研究B3Sin0\- (n=15-20)团簇的几何结构、稳定性和电子特性

基于B3LYP/6-311+G(d)下的密度泛函理论和卡里普索结构预测方法,系统研究了B3Sin0\- (n=15-20)团簇的几何结构、稳定性和电子特性。结构搜索发现,三个硼原子易构成三角结构并包裹在硅团簇笼子中。并通过对比实验和理论的光电子谱,进一步确定基态结构的合理性。此外,利用平均结合能、二阶差分能、最高占据轨道和最低未占据轨道能隙研究了体系的稳定性。最后,讨论了体系电荷的分布和转移、红外和拉曼谱等电子特性。     

溴化5-[4-(3-吡啶丙氧基苯基)]-10，15，20-三苯基卟啉对铜离子显色反应的研究

本文研究了溴化 5- [4 - (3-吡啶丙氧基苯基 ) ]- 10 ,15,2 0 -三苯基卟啉 ,在 p H=4 .0时与 Cu2 + 的显色反应条件 ,其络合物最大吸收波长为 4 13nm。在相同条件下 ,试剂最大吸收波长为 4 4 4nm,对比度大约30 nm。试剂与铜络合比为 1∶ 1,表观摩尔吸光系数为 2 .9× 10 5L· mol-1·cm-1,铜含量在 0— 6 0 μg/ L范围内符合比耳定律 ,可用于痕量铜的测定。     

浅谈当前物理教学板书中存在的问题及解决方法

心理学研究表明,外界进入人脑的信息,有80%以上来自眼睛,所以在课堂教学中,教师除了用口头语言提供听觉信息,还要通过文字、符号、图表、图解甚至实物模型等形式,把教学重点、难点、过程分析或关键性的知识写、画或贴在黑板上,给学生提供视觉信息,这些留在黑板上的文字、符号、图表、图解和实物模型等视觉信号叫做板书,好的板书,集教材的"编"、教师的"教"和学生的"学"于一体,既反映了教材内容,又服务于教法和学法的指导,从某种意义上说,板书设计和运用的优劣反映了教师的教学设计水平,但在当前的物理课堂教学中却有很多教师把板书看作是鸡肋--食之无味,弃之可惜,板书技能退化、板书意识淡化的现象在年轻教师中显得更为严重,笔者针对这一现象想就目前板书存在的典型问题及解决方法做一简单的探讨.     

The Influence of Feeding Frequency on Nitrogen Turnover and Whole Body Protein Synthesis in Adult Rats (Estimation using [14C]- and [15N]- Labelled Leucine)

Abstract

Male Wistar rats (17 wks. old, body weight ～400 g), fitted with an intra gastric cannula and with a catheter in the vena jugularis were divided into 3 groups and given a marginal ration of the feeding solution Nutrison Standard (1g protein and 350 kJ ME per day). Group 1 had ad lib. access to the drinking bottle, the groups 2 and 3 were pair fed by gastric infusion, splitted up into 2 greater meals for group 2 respectively into 6 smaller meals for group 3. After adaptation all animals get an i.p. injection of doubly labelled tracer solution (200μl) containing 2.5mg L-[¹⁵N]leucine (72 atom% ¹⁵N) combined with either [1-¹⁴C]- or [U-¹⁴C] leucine (37 kBq).

The course of ¹⁴CO₂ expiration was estimated by breath test over 4h in intervals of 15 min and the course of urinary ¹⁵N excretion over 24h in intervals of 45 resp. 90 min. An infusion of saline (0.9% 5ml/h) into the vena jugularis was used to provoke sustained urine production of the animals during the experiment.

From the parameters of the excretion curves of breath ¹⁴CO₂ resp. urine ¹⁵N (cumulative end value) and from the N balance the portions of leucine-C and leucine-N used for protein synthesis, transamination decarboxylation and total oxidation as well as the kinetic parameters for whole body protein metabolism were computed.

The following conclusions were drawn:

6 x feeding regime produces a small but measurable amino acid economy effect in comparison to 2 x feeding regime.

Protein gain for 2 x feeding group was significant smaller than for 6 x feeding group, though protein synthesis rate was higher, but was overcompensated by a greater increase of protein breakdown rate for the 2 x feeding group. Energy storage in form of fat and glycogen built from decarboxylation was unaffected by feeding frequency. The amount of leucine oxidized for heat production was 4% higher for the 6 x feeding group. Transamination rate for leucine was estimated to 8–15%. Absolute values for protein flux, protein synthesis and protein breakdown may be overestimated or underestimated because the metabolism of [¹⁵N] leucine does not exactly agree with that of total N; but the proportions of them and therefore also the conclusions will be true. Better results for absolute values will be obtained using a mixture of ¹⁵N labelled AA, ¹⁵N labelled protein or hydrolysate of ¹⁵N labelled protein (yeast) as the tracer source.     

The Influence of Ammonium on Nitrate Uptake and Assimilation in 2-Year-Old Ash and Oak Trees - A Tracer-Study with 15N

Abstract

Interactions between ammonium and nitrate as competitive N sources depend on various biotic and abiotic factors. The preference for one of these N sources and the influence of ammonium on nitrate uptake and nitrate reductase activity was investigated in a ¹⁵N labelling experiment using 2-year-old potted plants of ash (Fraxinus excelsior L.) and oak (Quercus robur L.) under greenhouse conditions.

Seedlings of both tree species use ammonium and nitrate in equal amounts when both N forms are supplied in a 1:1 ratio (1.5 mM NH₄ ⁺ + 1.5 mM NO₃ ^?), although there is a slight tendency that ammonium is preferred. In both species total N uptake is higher if ammonium and nitrate are supplied simultaneously when compared with uptake of nitrate alone (3 mM nitrate). If nitrate is the sole N source N uptake is only half as high as if ammonium and nitrate are supplied in a ratio of 1:1.

The distribution of nitrate reductase between shoot and roots is not influenced by the N-form: nitrate reductase activity is always highest in the roots of both species under the conditions of this experiment.

Xylem sap analyses showed that both species transport higher concentrations of amino acids than of nitrate from the roots to the shoot. The amino acid composition is independent of the type of N source. Furthermore, ash trees contain more nitrate in the xylem sap than oak trees, reflecting the higher N uptake and the higher nitrate reductase activity in the leaves of this species.     

The influence of temperature (20-1000 °C) on binary mixtures of solid solutions of CH3COOLi·2H2O-MgHPO4·3H2O

Thermally induced phase transitions (20-1000 °C) in the substrates and binary mixtures of CH₃COOLi·2H₂O(1)-MgHPO₄·3H₂O(11) have been analysed. Changes taking place on dehydration and thermal dissociation of binary mixtures prepared with percent molar ratios of 90-10% were studied by differential thermal analysis (TG, DTG, DTA), IR-spectroscopy and WAXS.The above-mentioned substrates changed their structure when heated for 1 h at 500 or 1000 °C. CH₃COOLi·2H₂O(1) (ID: 23-1171) changed the structure at 500 °C to that of Li₂CO₃ (ID: 22-1141), while at 1000 °C the structure was impossible to analyse as the compound reacted both with porcelain and with platinum (crucible materials). MgHPO₄·3H₂O(11) (Newberyite, ID: 35-780, 19-762) changed its structure at 500 °C to amorphous phase and at 1000 °C to Mg₂P₂O₇ (ID: 32-626).The following compounds were assayed in the respective binary mixtures heated at 500 °C for 1 h: 70% (1)-30%(11): LiMgPO₄ (ID: 18-735), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 18-735), Li₃PO₄ (ID: 25-1030); 30%(1)-70%(11): LiMgPO₄ (ID: 32-574); binary mixtures heated at 1000 °C contained the following compounds: 70%(1)-30%(11): LiMgPO₄ (ID: 32-574,18-735), Li₃PO₄ (ID: 15-760,25-1030), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 32-574, 18-735), MgO (ID: 4-829); 30%(1)-70%(11): LiMgPO₄ (ID: 18-735, 32-574), Mg₂P₂O₇ (ID: 22-1152, 8-38), Li₄SiO₄ (37-1472).