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排序方式: 共有989条查询结果,搜索用时 31 毫秒
61.
Mina Khorami Saeed Hesaraki Aliasghar Behnamghader Hamid Nazarian Sara Shahrabi 《Materials science & engineering. C, Materials for biological applications》2011,31(7):1584-1592
In this study, different concentrations of Li2O (0–12 wt.%) were substituted for Na2O in 45S5 bioglass® and the effect of these substitutions on both in vitro apatite formation ability and osteoblastic cell responses was studied. For these purposes, the structural and topographical properties of the glasses were studied using, XRD, FTIR, SEM/EDXA and AFM techniques, before and after storing in simulated body fluid for different time intervals. Additionally, the proliferation rate and activity of newborn rat calvaria-derived osteoblastic cells on different samples were examined by using dimethylthiazol diphenyl tetrazolium bromide (MTT) and alkaline phosphatase (ALP) assessment methods. From XRD and FTIR data, it was found that poor crystalline carbonated nanoapatite phase was formed on the surface of glasses with maximum concentration of Li or without Li, while at low substitutions an inhibition of apatite formation was observed. The apatite layer formed on the surfaces of the glasses had similar morphology, flakes which tightly entangled to others. All samples had the same surface roughness before soaking but different values after that. It was found that both proliferation rate and alkaline phosphatase activity of the cells cultured on Li-substituted glasses were higher than those of Li-free sample in a dose-dependent manner. The results suggest that lithia-modified glasses may be successfully used as bone defect filler even with more effectiveness than 45S5 bioglass®. 相似文献
62.
Gabriel Loget Janine Carvalho PadilhaEmilse Agostini Martini Michèle Oberson de SouzaRoberto Fernando de Souza 《International Journal of Hydrogen Energy》2009
Different electrodes (nickel, molybdenum, and iron alloys containing chromium, manganese, and nickel) were tested as cathodes for the hydrogen evolution reaction (HER) using 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) ionic liquid (IL) as the electrolyte. HERs were conducted at room temperature, at a cathodic potential of −1.7 V (PtQRE) using 10 vol.% aqueous BMI.BF4 solutions. Reactions performed in a thermostated Hoffman cell gave current densities between 14.6 and 77.5 mA cm−2 and efficiencies in the range 97.0–99.2%. Mo electrocatalysts in IL have been shown to be better than Pt, contrary to the classic behavior observed in an aqueous KOH medium. The electrochemical properties of molybdenum, as well as its resistance to corrosion (studied by Tafel plots and observed using SEM) indicate the potential use of this material as a cathode in an IL medium, which can lead to many attractive technological applications. 相似文献
63.
Friction between a nanoscale tip and a reconstructed Au(111) surface is investigated both by atomic force microscopy (AFM)
and molecular statics calculations. Lateral force AFM images exhibit atomic lattice stick–slip behavior with a superstructure
corresponding to the herringbone reconstruction pattern. However, the superstructure contrast is not primarily due to variations
in the local frictional dissipation (which corresponds to the local width of the friction loop). Rather, the contrast occurs
primarily because the local centerline position of the friction loop is periodically shifted from its usual value of zero.
Qualitatively, similar behavior is reproduced in atomistic simulations of an AFM tip sliding on the reconstructed Au(111)
substrate. In both simulations and experiments, this centerline modulation effect is not observed on unreconstructed surfaces.
Similarly, using a topographically flat surface as a hypothetical control system, the simulations show that the centerline
modulation is not caused by variations in the reconstructed surface’s topography. Rather, we attribute it to the long-range
variation of the local average value of the tip-sample interaction potential that arises from the surface reconstruction.
In other words, surface atoms located at unfavorable sites, i.e., in the transition between face-centered-cubic (FCC) and
hexagonal-close-packed (HCP) regions, have a higher surface free energy. This leads to a varying conservative force which
locally shifts the centerline position of the friction force. This demonstrates that stick–slip behavior in AFM can serve
as a rather sensitive probe of the local energetics of surface atoms, with an attainable lateral spatial resolution of a few
nanometers. 相似文献
64.
Decsi T Boehm G Tjoonk HM Molnár S Dijck-Brouwer DA Hadders-Algra M Martini IA Muskiet FA Boersma ER 《Lipids》2002,37(10):959-965
Long-chain PUFA play an important role in early human neurodevelopment. Significant inverse correlations were reported between
values of trans isomeric and long-chain PUFA in plasma lipids of preterm infants and children aged 1–15 yr as well as in venous cord blood
lipids of full-term infants. Here we report FA compositional data of cord blood vessel wall lipids in 308 healthy, full-term
infants (gestational age: 39.7±1.2 wk, birth weight: 3528±429 g, mean±SD). The median (interquartile range) of the sum of
18-carbon trans FA was 0.22 (0.13)% w/w in umbilical artery and 0.16 (0.10)% w/w in umbilical vein lipids. Nonparametric correlation analysis
showed significant inverse correlations between the sum of 18-carbon trans FA and both arachidonic acid and DHA in artery (r=−0.38, P<0.01, and r=−0.20, P<0.01) and vein (r=−0.36, P<0.01, and −0.17, P<0.01) wall lipids. In addition, the sum of 18-carbon trans FA was significantly positively correlated to Mead acid, a general indicator of EFA deficiency, in both artery (r=+0.35, P<0.01) and vein (r=+0.31, P<0.01) wall lipids. The present results obtained in a large group of full-term infants suggest that maternal trans FA intake is inversely associated with long-chain PUFA status of the infant at birth. 相似文献
65.
N Nicoli Aldini P Caliceti S Lora MC Maltarello M Fini M Rocca L Martini G Giavaresi FM Veronese R Giardino 《Canadian Metallurgical Quarterly》1996,67(6):843-848
Biodegradable polymers gives interesting perspectives of use in making artificial conduits for peripheral nerve reconstruction. Poliphosphazenes are materials highly biocompatible and have a controllable reabsorption rate. According to the substitutes that are introduced in the molecule, they can also be used as a framework for drug release. Conduits obtained with poli [bis(etilalanate) phosphazene] were evaluated as guides for nerve regeneration in an experimental animal model. In six Wistar rats, under general anesthesia and with microsurgical technique, the ischiatic nerve was isolated. On the right side a segment of the nerve was removed in order to create a 10 mm gap. The defect was then repaired using the conduit. On the controlateral limb the nerve continuity was restored using as an autograft the segment removed from the right. Control were performed at 30, 90, 180 days and consisted in histological and electron microscopy investigations. They showed the gradual degradation of the conduit without signs of local and general toxicity. The regeneration of the nerve fibers in the lumen of the conduit was not significantly different from the one obtained with the autologous grafts. So poliphosphazene conduits may be considered effective as a guide for nerve regeneration, above all for the possibility of use the polymer as a carrier for neurite-promoting factors. 相似文献
66.
L Scorolli E Martini SZ Scalinci LG Scorolli R Meduri 《Canadian Metallurgical Quarterly》1996,22(9):1245-1246
We report two cases of capsular bag contraction that occurred within 1 month after continuous curvilinear capsulorhexis, phacoemulsification, and intraocular lens implantation. Neither patient had a known risk for this complication. Both patients had a neodymium:YAG laser anterior capsulotomy, which disrupted the capsulorhexis margin and led to prompt capsular bag distension. 相似文献
67.
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70.
Iwaguchi S Suzuki M Sakai N Nakagawa Y Magee PT Suzuki T 《Yeast (Chichester, England)》2004,21(8):619-634
Electrophoretic karyotype studies have shown that clinical isolates of Candida albicans have extensive chromosome length polymorphisms. Chromosome translocation is one of the causes of karyotypic variation. Chromosome translocation events have been shown to occur very frequently at or near the major repeat sequence (MRS) on chromosomes. The MRS consists of the repeated sequences RB2, RPS and HOK, and the repeated sequences are considered to be the template for recombination. To investigate which element of the MRS is important for chromosome translocation, we constructed three cassettes, each containing a URA blaster and sequences homologous to one of the repeats, for insertion into the MRS region on the chromosomes. The ura3 strain STN22u2, which shows a stable, standard karyotype, was transformed with each construct. Insertion events with each cassette occurred at almost all chromosomes. Insertion into the RB2 repeat, but not into the RPS repeat, was accompanied by chromosome translocation in some transformants: chromosome translocations between chromosomes R and 7 and chromosomes 1 and 7 were found, as well as deletions of 7A and 7C from chromosome 7. We conclude that the insertion at the RB2 region may initiate chromosome translocation in C. albicans. 相似文献