Bisquinolines. 2. Antimalarial N,N-bis(7-chloroquinolin-4-yl)heteroalkanediamines

N,N-Bis(7-chloroquinolin-4-yl)heteroalkanediamines 1-11 were synthesized and screened against Plasmodium falciparum in vitro and Plasmodium berghei in vivo. These bisquinolines had IC50 values from 1 to 100 nM against P. falciparum in vitro. Six of the 11 bisquinolines were significantly more potent against the chloroquine-resistant W2 clone compared to the chloroquine-sensitive D6 clone. For bisquinolines 1-11 there was no relationship between the length of the bisquinoline heteroalkane bridge and antimalarial activity and no correlation between in vitro and in vivo antimalarial activities. Bisquinolines with alkyl ether and piperazine bridges were substantially more effective than bisquinolines with alkylamine bridges against P. berghei in vivo. Bisquinolines 1-10 were potent inhibitors of hematin polymerization with IC50 values falling in the narrow range of 5-20 microM, and there was a correlation between potency of inhibition of hematin polymerization and inhibition of parasite growth. Compared to alkane-bridged bisquinolines (Vennerstrom et al., 1992), none of these heteroalkane-bridged bisquinolines had sufficient antimalarial activity to warrant further investigation of the series.     

Prevention of zinc neurotoxicity in vivo by N,N,N',N'-tetrakis (2-pyridylmethyl) ethylene-diamine (TPEN)

Intrahippocampal injections of zinc chloride (10 nmol) produce lesions in the rat hippocampus. A heavy metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylene-diamine (TPEN), co-injected with zinc chloride in vivo, totally prevented zinc-induced neuronal loss. Furthermore, intrahippocampal injections of TPEN (10 nmol) were non-toxic when compared with controls. TPEN injections in vivo quenched the in vitro staining of brain sections for zinc (Timm's stain), particularly the staining of the hippocampal mossy fibres. This demonstrates that TPEN is taken up by zinc-containing neurones in vivo. The use of TPEN to block the actions of zinc could help define the possible role of zinc in the pathology of various neurological disorders.     

Identification of 4(-) states in the 14C(p,n)14N reaction at 135 MeV

The tadpole larva of solitary ascidians has 40 notochord cells in its tail. Of these cells, 32 in the anterior and middle part of the tail are derived from the A-line blastomeres, while 8 in the posterior part of the tail originate from the B-line blastomeres. Previous experiments involving continuous dissociation of daughter blastomeres from the first cleavage to the 110-cell stage suggested that cellular interactions may be involved in the formation of notochord cells. In the present study, the presumptive-notochord blastomeres isolated from the 32-cell embryos did not develop features of notochord. These results suggest that cellular interactions may be required for the fate specification of notochord, that is to say, notochord formation occurs as a result of inductive interaction between blastomeres. In order to confirm the involvement of induction in the determination of notochord and to identify the inducer blastomeres, the presumptive-notochord blastomeres at the 32-cell stage were coisolated or recombined with one of the surrounding blastomeres in a series of experiments. The results suggested that, for the A-line precursors, notochord differentiation occurs as the result of an inductive influence from vegetal blastomeres that include the presumptive-endoderm blastomeres and the presumptive-notochord blastomeres themselves. It was also suggested that induction of notochord is complete by the 64-cell stage and that inductive interactions have to be initiated before the decompaction of blastomeres during the 32-cell stage. Ascidians are Urochordata and are closely related to vertebrates. In vertebrates, it is well known that inductive interactions play a crucial role in the determination of notochord. It appears, therefore, that induction of notochord is common throughout the phylum Chordata.     

长颗粒(柱状晶)Si3N4陶瓷的研究及进展

Si3N4陶瓷材料由于具有很好的高温性能及高的力学性能，而被广泛地用于结构陶瓷，如切削刀具等。然而，因为其对缺陷很敏感，故易受灾难性的失效。人们发展了多种Si3N4增韧陶瓷，其中自增韧由于一些优异的性能越来越受到人们的重视。在此文中，着重介绍了影响Si3N4陶瓷长颗粒(柱状晶)晶粒生成的因素，并介绍了国内外对长颗粒Si3N4晶的控制研究。     

Combustion synthesis of α-Si3N4-(MgO, Y2O3) composites

The possibility of obtaining composite powders of α-Si₃N₄-Y₂O₃ and α-Si₃N₄-MgO by self-propagating high-temperature synthesis (SHS) is studied. It is established that the α → β phase transformation starts at temperatures lower than the melting points of the corresponding eutectics. Metastable composite powders based on α-Si₃N₄ with a high rate of phase transition are obtained. The composite powders (α-Si₃N₄-Y₂O₃, α-Si₃N₄-MgO) are used in hot pressing technology. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 10–14, 2007.     

Nb(C,N) Precipitation and Austenite Recrystallization

The influence of boron addition, amount of deformation, and solution heat-treatment temperature on the precipitation and recrystallization behaviors of a family of high-strength low-alloy (HSLA) steels was studied. A stress relaxation technique was employed to detect the occurrence of austenite recrystallization and to determine the precipitation start(P _s) and finish(P _f) times. After preheating to 1100 °C or 1200 °C for 30 minutes, the specimens were cooled to test temperatures between 800 °C and 1000 °C. They were subsequently deformed to true strains of 5 or 25 pct and subjected to stress relaxation. The advent of recrystallization produced a sharp increase in relaxation rate, while the occurrence of carbonitride precipitation led to the appear- ance of a stress plateau. The results indicate that the presence of boron (1) accelerates carbo- nitride precipitation and (2) retards austenite recrystallization when present in combination with Nb. The precipitation-time-temperature (PTT) diagrams determined in this investigation are C-shaped for both the B-free as well as the B-modified Nb steels. These data were analyzed in terms of the classical theory of nucleation, on the basis of which it is demonstrated that the acceleration of the nucleation kinetics of precipitation can be attributed to the segregation of boron and of boron-vacancy complexes to dislocations and grain boundaries, as well as to the faster diffusion of Nb in the presence of boron.