THEORETICAL STUDY OF THE INTENSITY DEPENDENCE OF TOTAL EFFECTIVE TRAP DENSITY IN PHOTOREFRACTIVE CRYSTALS

Intensity dependence of the total effective trap density N_eff is studied theoretically for the two-centre and the three-charge-state photorefractive crystals. The results show that N_eff always increases with increasing intensity in three-charge-state crystals, whereas it has more complicated behaviors in two-centre crystals. When S_Dγ_T/S_Tγ_D is small, N_eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S_Dγ_T/S_Tγ_D is large, N_eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals. The different intensity dependences of N_eff in the two types of crystals come from their different level structures.     

钙稀土氟碳酸盐矿物中三种B_8S_6型新规则混层结构的高分辨电镜研究

用选区电子衍射（ＳＡＥＤ）和高分辨电子显微术（ＨＲＥＭ）研究钙稀土氟碳酸盐矿物及其衍生多晶体结构，发现三种不同的氟碳铈矿（Ｂ）与直氟碳钙铈矿（Ｓ）具８：６新规则混层结构（Ｂ_６Ｓ_６－Ⅰ、Ｂ_８Ｓ_６－Ⅱ和Ｓ_８Ｓ_６－Ⅲ），确定了各自的晶体结构类型、晶胞参数、堆垛模式及晶体化学式等。高分辨像的观察分析，揭示出三种Ｂ_８Ｓ_６规则混层结构中的Ｃｅ－Ｆ离子层以及两个Ｃｅ－Ｆ离子层之间的ＣＯ_３离子组具有不同的排列方式，观察和讨论了上述规则混层结构中的无序夹层及堆垛层错等非均匀结构现象     

CRYSTAL AND MOLECULAR STRUCTURE OF STEMOTININE

<正> C18H25NO5, Mr = 335.40, tetragonal, P41212, a = 15.578(4), c =14.723(3) A, V =3573(2) A3, Z = 8, D = 1.247 g cm-3, MoKα,λ= 0.71069 A, μ = 0.;85 cm-1, T = 293K, final R .= 0.100 and RW (on F2) = 0.080 for 1095 observed data [|FO| > 2σ(|FO|)]. The structure confirms the spectrbscopic assignment of a pentacyclic skeleton containing two α-methyl-γ-lactone rings, one ether and one tertiary amine.     

四氢呋喃聚合向丁二酸酐链转移的研究

四氢呋喃聚合向丁二酸酐链转移的研究栗方星，马克勤，陈琰，文佳，霍玉杰（南开大学化学系，天津，３０００７１）（天津安普公司，天津）关键词ＴＨＦ，ＴＤＩ，ＣＨ_３ＣＯＳｂＣｌ_６，表观聚合速率常数在ＴＨＦ阳离子聚合的过程中，活性中心向丁二酸酐链转移［１］可...     

Pt-W/GC对甲醇的电催化氧化及动力学参数的测定

直接甲醇燃料电池（DMFC）具有结构简单，燃料便于携带与储存，理论能量密度高和环境友好等优点，特别适宜作为便携式电源和电动机车电源，因而具有广阔的应用前景。直接甲醇燃料电池的阳极电催化剂多使用贵金属铂（Pt），但由于甲醇阳极氧化过程中产生的中间产物CO在催化剂Pt表面上的强吸附与积累，导致催化剂中毒失活，是阻碍直接甲醇燃料电池商业化的重要原因之一。因此，研究出高活性催化剂仍是目前的热点．向Pt中添加一种或多种亲氧金属如Ru或W等，制成二元或多元铂合金，     

肉类及水产品中四环素类抗生素残留量的高效液相色谱测定方法

建立了肉类中土霉素(OTC)、四环素(TC)、金霉素(CTC)残留量的高效液相色谱荧光检测方法.样品经5%HClO4除蛋白后,离心过滤.采用Waters XTerra RP18(5 μm,4.6×150 mm)色谱柱,以V(甲醇):V(CaCl2缓冲液)=30:70(pH 6.6)为流动相,等度洗脱,流速0.8 mL/min,柱温25℃.经CaCl2缓冲液衍生化,在激发波长(Zx)350 nm和发射波长(Zm)520nm处检测土霉素、四环素和金霉素的残留量.结果表明,在此条件下,测得上述3种抗生素在0.09～4.64μg/mL范围内线性良好,土霉素的最小检测限为1.48 ng/mL,四环素为1.20ng/mL,金霉素为2.32 ng/mL,方法的精密度为0.69%～1.23%,加样回收率为64.63%～90.89%.实验证明本方法可用于检测肉类中土霉素、四环素和金霉素的残留量.     

QCM 表面自组装胱氨酸1，3－桥连杯[4]芳烃膜用于识别气相丁胺

Two cystine-bearing 1,3-bridged calix[4]arenes were used as the coatings of the quartz crystal microbalance (QCM) with gold electrodes. The two calix[4]arene derivatives were self-assembled onto the gold electrode surface by the covalent attachment between the di-sulfur and gold. The compound of cystine-bearing bi-phenylalanine 1,3-bridged calix[4]arene (CPC) with longer alkyl chain had better self-assembled capacity onto the fresh surfaces of gold electrode than that of cystine-bearing 1,3-bridged calix[4]arene (CC) with comparably shorter alkyl chain.The modified QCM sensors were used to recognize the butylamine isomers in gas. The results showed that the QCM coated with both compounds had preferential affinity to n-butylamine, then i-butylamine, t-butylamine in the range of low concentrations, indicating that in the recognition process, the steric hindrance effect played an important role when forming complex with guest molecules. When the concentrations of the analytes were increased, the polarity and the magnetism of the butylamine became determinative factors. The reversibility was improved greatly and the equilibrium time was much shorter on the self-assembled film than on the film obtained by dropping coating.     

2—羟基—3,8—二甲氧基萘的甲酰化

为合成2-羟基-3、8-二甲氧基萘醛(Ⅰ),选用2-羟基-3、8-二甲氧基萘(Ⅱ))为原料,试以Gattermann-Adams法,及Duff反应进     

關於進行物理實驗時的安全辦法

在工作的進行中,物理教師要使用非常多的各種各樣的仪器、工具和物品;也要使用熱源、電源和光源。在教室中作示教實驗時,以及在学生自己作的實驗課的時間內,應當遵守保證教師和學生進行實驗時的充分安全的條件和消防的安全規則等等。遵守使用儀器的規則和小心謹慎地來作實驗。除了能保障一般的安全之外,又能使物理實驗室的设備,得到更好的保管。正当地使用学校物理實驗室裹所用的儀器和器具時,是沒有任何危險的。但是,使用有毛病的仪器,不正當地使用儀器,不遵守消防安全規則,或保存危險的和有毒的物品,就可能發生創伤性的損害、燒傷和中毒等等。