2091铝-锂合金固态氢含量的测定

运用RH 4 0 2测氢仪测定具有高挥发性物质锂的铝 锂合金的固态氢含量具有相当难度 ,本文就如何鉴别体内氢和表面氢、如何选择加热功率和加热时间及试样大小做了大量探索实验 ,初步形成了可行的铝 锂固态氢含量的分析方法。同时就测量的误差来源及测氢过程中应注意之点进行了讨论。结果重复性好 ,且结果比较准确 (利用俄罗斯铝 锂合金氢标样比较 )。

固态1420铝锂合金中氢的测定方法的研究

介绍利用ＰＨ－４０２测氢仪（载气熔融法）分析固态１４２０铝锂合金中氢含量的方法，重点研究了试样的制备、有效地除尽表面氢以及使体内氢充分释放出来同时又避免高挥发性物质锂的影响，建立一套准确测定固态１４２０铝锂合金中氢的方法。

铝合金固态氢的检测

介绍应用ＲＨ－４０２测氢仪分析固态铝合金中氢含量的检测方法。根据铝合金中不同元素干扰影响测氢分析的不同特点，将铝合金分为铝镁系、铝锌系、铝锂系和其它铝合金４个系列，分别研究其测氢分析方法。本文只对各系列合金的划分、分析条件的确定、分析的特点、准确性与重复性进行介绍，详细分析方法将在以后专题介绍。

Effect of Triptolide on Reproductive Endocrinology and Dihydrotestosterone Receptors in Rats

Triptolide was given orally to adult male Sprague-Dawley rat sat a dosage of 75 μg/kg for 35 days.After 28 days of treatment,the result of mating tests showed that all the drug treated rats were infertile.At the end of drug treatment,the density of caudal spermatozoa and the weight of cpididymis were reduced significantly.All the spermatozoa were immobile.There was no detectable damage of spermatogenesis and epididymal epithelia in triptolide treated rats under microscopical examination.However,modcrate and severe damage of spermatozoa were seen in the corpus and caudal epididymis.The content of cytosolic and nuclear dihydrotestosterone (DHT) receptors in the caput and caudal epididymides was increased but insignificantly as compared with that of the controls.However, the content of DHT receptor in the cytosal of the ventral prostate was elevated very,significantly (P< 0.01).This result suggests that one of the sitcs of action of triptolide might be the epididymis.

Donor‐acceptor carbon nitride with electron‐withdrawing chlorine group to promote exciton dissociation

Carbon nitride(C_(3)N_(4))is promising for photocatalytic hydrogen production,but photogenerated electrons and holes in C_(3)N_(4)usually tend to exist as excitons due to intrinsic Coulomb interactions making its photocatalytic activity unsatisfactory.Herein,a well‐designed intramolecular C_(3)N_(4)‐based donor‐acceptor(D‐A)photocatalytic system was constructed to promote exciton dissociation.Due to its good chemical compatibility with melamine and appropriate sublimation property,2‐amino‐4,6‐dichloropyrimidine unit was chosen as the monomer to react with melamine to construct intramolecular D‐A system(CNCl_(x)).The hydrogen evolution rate of CNCl_(0.15)is 15.3 times higher than that of bulk C_(3)N_(4)under visible light irradiation,with apparent quantum efficiency of 13.6%at 420 nm.The enhanced activity is attributed to introduced electron‐withdrawing−Cl group as terminal group in the resulted CNCl_(x) samples,which can build internal electric field to promote the exciton dissociation into free electron and hole.In addition,lower work function value of CNCl_(x) samples indicates that internal electric field can help free electrons and holes transfer to the surface of CNCl_(x) samples for photocatalytic reaction.

N-H…X(X=F,Cl,Br,and Ⅰ)hydrogen bonding in aromatic amide derivatives in crystal structures

Intramolecular N H···X (X=F, Cl, Br, and Ⅰ) hydrogen bonding patterns of aromatic amides in the solid state are summarized. It is revealed that the key for the formation of this kind of weak intramolecular hydrogen bonding in X-ray crystal structures is to suppress the competition of strong intermolecular N H···O C hydrogen bonding of the amide unit. For amides with identical backbones, the bonding capacity of halogen atoms as hydrogen bonding acceptors is in the order of F>Cl>Br>I, which is in accordance with their electronegativity strength. Generally, the five-membered hydrogen bonding is easier to form than the six-membered one.

POCl_3-mediated H-bonding-directed one-pot synthesis of macrocyclic pentamers,strained hexamers and highly strained heptamers

Previously we have shown that POCl3-mediated H-bonding-directed one-pot macrocyclization allows for the highly selective preparation of five-residue macrocycles as the predominant product with low yields of hexamers and an undetectable occurrence of both tetramers and heptamers.Replacing the interiorly arrayed methyl groups with ethyl groups in these 4-7 residue macrocycles alters the relative stability order among them.Specifically,ethoxy-substituted six-residue macrocycle,rather than pentamer,turns out to be computationally the most stable,suggesting that ethoxy-containing hexamer possibly can be formed as the major product under suitable conditions.We have investigated this possibility by varying reaction temperatures and concentrations,invariably affording pentamer as the major macrocycle with strained circular hexamers and highly strained circular heptamers produced in substantial amounts.This discrepancy can be reasonably explained on the basis of bimolecular reactions between two oligomers higher than monomers via kinetic simulations.In this scenario,the acyclic pentamer is kinetically "trapped" to undergo an intramolecular cyclization to yield circular pentamer,rather than to produce acyclic hexamer.As a result,acyclic hexamer precursor is generated largely from sterically demanding bimolecular reactions between a dimer and a tetramer,or between two trimers that are kinetically slower than the pentamer-producing chain-growth reactions.We additionally found that one-pot macrocyclization proceeds to the largest extent at 40 ℃,an intriguing finding that highlights the low reactivities of acid chloride and amine groups in these H-bond-enforced acyclic oligomeric intermediates.