Cutting and Welding of Nanomaterials with an Electron Beam

1 Results Scanning tunneling microscope and atomic force microscope have been applied to manipulate individual atoms or clusters on a clean surface.Focused ion beam technique is routinely used to cut materials down to sub-100 nm dimension.However,in between the atomic and the sub-100 nm scales,i.e.,at the nanometer scale,to date there is no well-established physical modification technique.Here we demonstrate that localized,impurity-free nano-welding and nano-cutting techniques with a high-intensity elec...     

Leishmania donovani in hamsters: Stimulation of non-specific resistance by some novel glycopeptides and impact on therapeutic efficacy

Summary Several glycopeptides structurally related to muramyl dipeptide (MDP) have been synthesized and evaluated for their ability to stimulate the non-specific resistance of hamsters againstL. donovani infection. These compounds have been named CDRI compounds. The synthetic procedure used for compounds 86/448 and 84/212 is described.MDP and its synthetic congeners were administered as immunostimulants at a prophylactic dose of 3 mg/kg at two weeks interval. The challenge infection (1×10⁷ amastigotes i.c./hamster) was given in between two doses of the compounds. One of the glycopeptides, CDRI comp. 86/448, has been found to be significantly more potent than MDP, effecting 92% inhibition of the challenge dose, whereas MDP produced only 26.5% inhibition. The effect of comp. 86/448 lasted until day 7 of challenge. The efficacy of sodium stibogluconate was appreciably improved in hamsters treated with comp. 86/448.     

D-Aspartate oxidase activity and D-aspartate content in a mutant mouse strain lacking D-amino acid oxidase

Summary A mutant mouse strain ddY/DAO^– lacks D-amino acid oxidase activity and accumulates free neutral D-amino acids in its tissues. In this study, D-aspartate oxidase activity and D-aspartate content in the tissues of these mutant mice were compared with those of normal mice. No significant difference was observed, indicating that the metabolism of acidic D-amino acids was unaffected in the mutant.     

D-amino acids in mouse tissues are not of microbial origin

Neutral free D-amino acid contents in the serum, kidney, liver, brain, small intestine and urine in germ-free mice and those in specific pathogen-free mice were compared. No significant difference was found. This strongly suggests that the free D-amino acids which were shown to be present in mice in our previous work did not originate from the enteric microbial flora.     

Gene conversion in the chicken immunoglobulin locus: A paradigm of homologous recombination in higher eukaryotes

Gene conversion was first defined in yeast as a type of homologous recombination in which the donor sequence does not change. In chicken B cells, gene conversion builds the antigen receptor repertoire by introducing sequence diversity into the immunoglobulin genes. Immunoglobulin gene conversion continues at high frequency in an avian leukosis virus induced chicken B cell line. This cell line can be modified by homologous integration of transfected DNA constructs offering a model system for studying gene conversion in higher eukaryotes. In search for genes which might participate in chicken immunoglobulin gene conversion, we have identified chicken counterparts of the yeastRAD51, RAD52, andRAD54 genes. Disruption and overexpression of these genes in the chicken B cell line may clarify their role in gene conversion and gene targeting.     

Preparation and Characterization of Carbon Coated Silicon Nanoparticle as Anode Material for Li-ion Batteries

Silicon has been regarded as one of the most promising anode materials for Li-ion batteries. Its theoretical capacity （4 000 mAh/g） is much higher than that of the commercialized graphite （372 mAh/g）. However, the cycle performance of silicon is poor due to the severe volume expansion and shrinkage during Li^＋ insertion/extraction which results in pulverization of Si particles, eventually losing its Li^＋ storage ability. To solve this problem, nanosized Si particles were utilized and achieved a partial improvement by reducing the absolute volume change. Nevertheless, a new problem was encountered with nanosized material that small Si particles were aggregated to be larger one during Li^＋ insertion/extraction, and then pulverized again. In this work, we have succeeded to improve the cycle performance of nanosized Si particles by synthesis of carbon coated silicon nanopartiele.     

Ecdysteroid conjugates in the ovaries of the silkworm,Bombyx mori: 3-phosphates of 2,22-dideoxy-20-hydroxyecdysone and of bombycosterol

Summary Two novel ecdysteroid conjugates, 2,22-dideoxy-20-hydroxyecdysone 3-phosphate (1) and bombycosterol 3-phosphate (2), as well as four known ecdysteroid 22-phosphate esters, have been isolated and characterized from the ovaries of the silkworm,Bombyx mori.     

Acyl fluorides as reactive mimics of aldehyde pheromones: hyperactivation and aphrodisiac inHeliothis virescens

Summary Substitution of fluorine for the aldehydic hydrogen provides behaviorally active, chemically reactive pheromone mimics. In male moths of the tobacco budwormHeliothis virescens, Z9–14:Acf and Z11–16:Acf cause hyperactivity and irreversible extension of the genitalia in over 80% of treated moths. In addition, a combination of the two components leads to 10–50% of the pairs involving one treated partner becoming locked in copula.Supported by NSF grant PCM-8112755 and DMB-8316931, by a Fellowship from the Alfred P. Sloan Foundation (1981–85), and by Teacher-Scholar Grant from the Camille and Henry Dreyfus Foundation (1981–86) to G.D.P. Address correspondence to G.D.P.     

Subtypes of protein kinase C in rat cerebral microvessels

Summary Protein kinase C in rat cerebral microvessels was characterized. By hydroxyapatite column chromatography, protein kinase C in the soluble fraction was resolved into two major peaks corresponding to type II and III enzymes, in the proportions of 57% and 38%, respectively. Since each subtype is considered to have a distinct role, the high proportion of type II enzyme found in this study suggests that this type may be involved in specific functions of the cerebral microvessels.