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排序方式: 共有1417条查询结果,搜索用时 46 毫秒
941.
Hidde H. Brongersma Anja Gildenpfennig Arnoud W. Denier van der Gon Robert D. van de Grampel Wim P. A. Jansen Arie Knoester Jozua Laven Minna M. Viitanen 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):11-18
Low energy ion scattering is used to selectively probe the outermost atomic layer of the surface. The development of double toroidal analyzers has improved the detection sensitivity of low energy ion scattering by orders of magnitude. The features of these analyzers are discussed. It is shown that the absence of matrix effects makes it possible to quantify the surface density of fluorine in polymers with a LiF(1 0 0) surface. The extreme surface sensitivity of LEIS also enables one to study intramolecular segregation processes. As an example the aging of a polypropylene surface that has been activated with atomic oxygen is described. As an example of the LEIS analysis of highly dispersed isolating surfaces, the formation of coke on a commercial three-way catalyst is discussed. 相似文献
942.
DM Banic J de Oliveira-Ferreira LR Pratt-Riccio V Conseil D Gon?alves RR Fialho H Gras-Masse CT Daniel-Ribeiro D Camus 《Canadian Metallurgical Quarterly》1998,58(6):768-774
A parasitophorous vacuole protein of Plasmodium falciparum, p126, is a potential candidate for a malaria vaccine. Its N-terminal region, composed of six repeats of eight amino acids, appears to be involved in the induction of protective immunity against P. falciparum challenge in monkeys. This study evaluated the immune response to p126 and to its N-terminal region (Nt47) in patients (n = 45) living in a malaria-endemic area of Brazil (Colina, Porto Velho, Rondonia). Cellular proliferative responses against Nt47 were low and infrequent. The study of the humoral immune response demonstrated that 95% of the patients had detectable anti-p126 antibodies and 77% had anti-Nt47 antibodies. Analysis of the antibody isotypes specific for Nt47 revealed that all four IgG subclasses were present and individuals with higher levels of anti-Nt47 cytophilic IgG antibody (IgG1 + IgG3/IgG2 + IgG4) had significantly lower parasitemia levels, suggesting that antibodies to the N-terminal region of the p126 protein may contribute to acquisition of immunity to P. falciparum malaria. 相似文献
943.
944.
A retrospective study on the different opening techniques in cataract surgery at our Department in 1996 was carried out. In our everyday practice fornix based conjunctival flap and sclerocorneal oblique or vertical-oblique approach with a center at 12 o'clock was performed. In the case of hemorrhagic diathesis and secondary ACL implantation the corneal approach was preferred. After glaucomatous filtration surgery the incision was made temporally in some cases. 相似文献
945.
Using the general switch management protocol on a multi‐protocol label switching network, we present an efficient method for handling handovers. The proposed method directly changes an established path into a new path for supporting a handover. Our investigation reveals the effects of the proposed scheme and demonstrates that this method significantly reduces signaling costs and delays. 相似文献
946.
Repeated administration of amphetamine-like stimulants to rats results in enhanced behavioral responsiveness to subsequent administration of these drugs. Recent evidence suggests corticosterone may play a role in the development of sensitization perhaps through the down-regulation of glucocorticoid receptor (GR). To test this hypothesis further we examined the effects of five daily injections of amphetamine (AMPH) (2.5 mg/kg) on GR mRNA of adult Sprague-Dawley rats. Two other groups received saline for 4 days and then either saline or AMPH on the fifth day. All animals were killed 24 h after the last treatment and in situ hybridization was performed with an antisense mRNA GR probe. Quantification of hippocampal GR was accomplished by computer analysis of digitized images of CA1 and dentate gyrus. Acute AMPH produced a significant up-regulation of GR mRNA in CA1 and a nonsignificant trend towards up-regulation in the dentate gyrus. Repeated exposure to AMPH resulted in a significant down-regulation in CA1, and a nonsignificant trend towards down-regulation in dentate gyrus. These data support a role for hippocampal GR mRNA in the development of behavioral sensitization. 相似文献
947.
VR Arruda LH Siqueira MS Gon?alves PM von Zuben MC Soares R Menezes JM Annichino-Bizzacchi FF Costa 《Canadian Metallurgical Quarterly》1998,78(4):332-335
Vascular disease is a serious public health problem in the industrialized world, and is a frequent cause of death among the adult population of Brazil. Mild hyperhomocysteinemia has been identified as a risk factor for arterial disease, venous thrombosis, and neural tube defects. Individuals homozygous for the thermolabile variant of methylenetetrahydrofolate reductase (MTHFR-T) are found in 5-15% of the general population and have significantly elevated plasma homocysteine levels which represent one of the genetic risk factors for vascular diseases. We have analyzed the prevalence of individuals homozygous for the MTHFR-T in 327 subjects representing the three distinct ethnic groups in Brazil. The prevalence of homozygotes for the mutated allele MTHFR-T was high among persons of Caucasian descent (10%) and considerably lower among Black (1.45%) and Indians persons populations (1.2%). These data suggest that screening for the MTHFR-T allele should help in identifying individuals with a high risk of vascular disease among populations with a heterogeneous background. 相似文献
948.
Jeong Hyeong Han Min Ju Cha Bong Gon Kim Seog K. Kim Kil Sik Min 《Inorganic chemistry communications》2008,11(7):745-748
Novel nickel(II) hexaaza macrocyclic complexes, [Ni(LR,R)](ClO4)2 (1) and [Ni(LS,S)](ClO4)2 (2), containing chiral pendant groups have been synthesized by an efficient one-pot template condensation and characterized (LR,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. Each complex has a square-planar coordination environment for the nickel(II) ion, and is either an R or an S enantiomorph depending on the pendant groups. The circular dichroism spectrum of 1 showed a negative, positive and negative peak at 345, 440, and 492 nm, respectively, and that of 2 exhibited an enantiomeric pattern. 相似文献
949.
Thermal,Structural, and Crystallization Properties of New Tantalum Alkali‐Germanate Glasses 下载免费PDF全文
Gabriele Matinatti de Pietro Camila Pereira Rogeria Rocha Gonçalves Sidney J. L. Ribeiro Carolina Dakuzaku Freschi Fábia Castro Cassanjes Gael Poirier 《Journal of the American Ceramic Society》2015,98(7):2086-2093
In this work, new glass compositions were prepared in the ternary system GeO2–K2O–Ta2O5. Potassium oxide was added to reach the complete melt of the starting mixture and two composition series were investigated: the first one with a constant K2O molar content of 10% in the ternary system (90–x)GeO2–10K2O–xTa2O5 and the second one with the same molar content of K2O and Ta2O5 in the ternary system (100–2x)GeO2–xK2O–xTa2O5. Homogeneous and transparent glasses could be obtained between x = 0 and 20. X‐ray diffraction analyzes of samples with x = 25 identified orthorhombic Ta2O5 in the first series and an isostructure of K3.8Ge3Nb5O20.4 in the second series where it is assumed that Ta5+ ions are inserted in the Nb5+ sites. As one of our goal with these materials is related with the preparation of glass‐ceramics containing Ta2O5 nanocrystals, the first series has been selected for further characterizations. An increase in glass‐transition temperatures with increasing Ta2O5 content as well as an increase of the thermal stability from x = 0 to 10 has been identified by differential scanning calorimetry. For higher contents, crystallization events were identified. Fourier transform infrared and Raman spectroscopic characterizations allowed to point out the intermediary behavior of Ta2O5 in the vitreous network where TaO6 octahedra are inserted inside the germanate network with TaO6 clusters identified at higher Ta2O5 contents. Heat‐treated samples with high tantalum contents (x = 15 and 20) exhibit preferential precipitation of orthorhombic Ta2O5 with nanometric size, suggesting the possibility of obtaining transparent glass‐ceramics for optical applications. 相似文献
950.
Joana Carla Soares Gonçalves 《Architectural Design》2016,86(3):126-135
Looking beyond the tickbox approach of green-rating systems that apply North American climatic criteria to a Brazilian context, Joana Carla Soares Gonçalves , a professor of environmental design at the Faculty of Architecture and Urbanism of the University of Sâo Paulo, advocates a more far-reaching way forward for sustainability in Brazil. 相似文献