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排序方式: 共有953条查询结果,搜索用时 31 毫秒
891.
892.
893.
G. Busatto G. Currò F. Iannuzzo A. Porzio A. Sanseverino F. Velardi 《Microelectronics Reliability》2008,48(8-9):1306-1309
The results presented in this paper are related to an experimental study that has the aim to evidence the formation of “latent gate oxide damages” in medium voltage power MOSFETs during the impact with energetic particles. The understanding of these “latent defectiveness” can be an helpful aid in the comprehension of the mechanisms of breach of the oxide layer of MOS structures induced by single energetic particles impact (single event gate rupture). To properly detect the presence of “latent damages” we have developed a high resolution experimental set-up and identified an appropriate region in which the device have to be biased in order to trigger this kind of damage. 相似文献
894.
Rapid diagnosis of fungal infection of intravascular catheters in newborns by scanning electron microscopy. 总被引:1,自引:0,他引:1
Intravascular catheters carry a significant risk of becoming colonized with bacteria and fungi and are important risk factors of septicemia in premature neonates. The study was undertaken to evaluate whether scanning electron microscopy (SEM) examination of removed catheters can be useful in early diagnosis of plastic infection by Candida, providing information useful for initiation of an eventual therapy. The evolution of biofilms in 28 catheters (umbilical or central) implanted in 24 newborns for prematurity was studied by SEM and transmission electron microscopy (TEM). In 4 of 24 patients, SEM examination revealed the presence of Candida in form of yeast or hyphae. In one of these patients, TEM confirmed the presence of organisms. In each case, hemoculture and culture of the catheter itself confirmed the diagnosis. The study demonstrates that SEM can identify fungi in the biomaterials covering the catheter surface in a few hours, allowing an early diagnosis of plastic infection. 相似文献
895.
Claudia Dragonetti Stefania Righetto Dominique Roberto Adriana Valore Tiziana Benincori Francesco Sannicolò Filippo De Angelis Simona Fantacci 《Journal of Materials Science: Materials in Electronics》2009,20(Z1):460-464
The luminescence and second order non linear optical (NLO) response of [Ir(ttpy)2(5-R-1,10-phen)][PF6] (ttpy = cyclometallated 3′-(2-pyridil)-2,2′:5′,2″-terthiophene, phen = phenanthroline; R = Me, NO2) and [Ir(pq)2(5-R-1,10-phen)][PF6] (pq = cyclometallated 2-phenylquinoline) have been investigated experimentally in CH2Cl2 solution and compared with that of [Ir(ppy)2(5-R-1,10-phen)][PF6] (ppy = cyclometallated 2-phenylpyridine), characterized by one of the highest second order NLO response ever reported for
a metal complex. Substitution of ppy with the more π-delocalized pq does not affect significantly the luminescence and NLO
properties. A slightly lower NLO response and a much poorer luminescence is observed for the related complexes with ttpy.
In these complexes, DFT/TDDFT calculations show that the presence of ttpy induces a significant downshift of the HOMO energy,
compared to ppy and pq. The NLO response is dominated by intense MLCT excited states, which are also assigned as originating
the emission. 相似文献
896.
Jon F. Ihlefeld Mark D. Losego Ramòn Collazo William J. Borland Jon-Paul Maria 《Journal of Materials Science》2008,43(1):38-42
Polycrystalline barium titanate thin films have been prepared with 100 ppm of B-site acceptor dopants Ca, Mg, and Mn via chemical solution deposition on base metal substrates. The films are fired in low
pO2 atmospheres at 900 °C to prevent substrate oxidation. All dopant species produce low loss, space-charge free material without
secondary reoxidation anneals. We note that the dopant concentrations required to compensate for oxygen non-stoichiometry
are substantially greater than expected by equilibrium thermodynamic calculations. This observation is rationalized in the
context of a composite oxygen defect model with differing reduction enthalpies for grain interiors and surfaces. 相似文献
897.
A. Saccone D. Macciò S. Delfino R. Ferro 《Metallurgical and Materials Transactions A》1999,30(5):1169-1176
The Nd-Au phase diagram was studied in the 0 to 100 at. pct Au composition range by differential thermal analysis (DTA), X-ray
diffraction (XRD), optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA).
Six intermetallic phases were identified, the crystallographic structures were determined or confirmed, and the melting behavior
was determined, as follows: Nd2Au, orthorhombic oP12-Co2Si type, peritectic decomposition at 810 °C; NdAu, R.T. form, orthorhombic oP8-FeB type, H.T. forms, orthorhombic oC8-CrB type and, at a higher temperature, cubic cP2-CsCl type, melting point 1470 °C; Nd3Au4, trigonal hR42-Pu3Pd4 type, peritectic decomposition at 1250 °C; Nd17Au36, tetragonal tP106-Nd17Au36 type, melting point 1170 °C; Nd14Au51, hexagonal hP65-Gd14Ag51 type, melting point 1210 °C; and NdAu6, monoclinic mC28-PrAu6 type, peritectic decomposition at 875 °C. Four eutectic reactions were found, respectively, at 19.0 at. pct Au and 655 °C,
at 63.0 at. pct Au and 1080 °C, at 72.0 at. pct Au and 1050 °C, and, finally, at 91.0 at. pct Au and 795 °C. A catatectic
decomposition of the (βNd) phase, at 825 °C and ≈1 at. pct Au, was also found. The results are briefly discussed and compared to those for the other
rare earth-gold (R-Au) systems. A short discussion of the general alloying behavior of the “coinage metals” (Cu, Ag, and Au) with the rare-earth
metals is finally presented. 相似文献
898.
David J Drobes Marcus R Munafò Fiona Leigh Michael E Saladin 《Nicotine & tobacco research》2005,7(1):41-46
Despite a growing appreciation that genetic factors may impart vulnerability toward smoking behavior, only a modest consensus has been created about the specific genetic mechanisms that may underlie various aspects of smoking. A core feature of genetic contribution toward any complex human behavior is familial resemblance. Most previous attempts to index familial smoking have classified individuals into discrete categories, based on the number of smokers in a family. We discuss the development of a continuous measure of familial smoking, the Family Smoking Index (FSI), which is based on the proportion of smokers in first- and second-degree family members and provides a more precise weighting according to genetic proximity. We present the psychometric characteristics of the FSI as well as initial validation data from two studies. We also describe current and future directions for continued FSI validation and application. 相似文献
899.
Urease production by Streptococcus thermophilus 总被引:3,自引:0,他引:3
In order to identify potential alternative sources of urease for the removal of urea from alcoholic beverages, 205 strains of lactic acid bacteria belonging to 27 different species were screened for urease production. Only Streptococcus thermophilus produced urease. Cell permeabilization with toluene allowed to increase activity significantly. Optimal pH for urease activity in whole and permeabilized cells and of cell free extracts differed slightly, but was in the range 6.0-7.0. Significant activity was retained at pH 3.0 and 8.0, and, for cell free extracts, at pH 4.0 in the presence of ethanol. Urease production was evaluated in fermentations with pH control (5.25-6.5) and without pH control. Very little urease was produced in absence of urea, which at 5g/l slowed growth significantly in fermentations without pH control, but prevented a decrease in pH below 5.1 and resulted in higher final biomass. Optimal pH for growth was between 6.0 and 6.5 but specific urease activity was higher for fermentations at low pH at the beginning of the exponential phase. However, a higher total urease activity was obtained at pH 6.0 and 6.5 because of higher biomass. Potential technological applications of urease production by S. thermophilus are discussed. 相似文献
900.
Annamaria Passantino F. Conte M. Russo 《Journal für Verbraucherschutz und Lebensmittelsicherheit》2008,3(4):396-399
There is a growing appreciation of the insistence of consumers that animals used in food production should be well treated.
High welfare standards could have both a direct and indirect impact on food safety and quality; regulatory and support systems
in agriculture must adapt accordingly.
Retailers and producers are increasingly recognising animal welfare as a fundamental aspect of product image and quality which
create a need for reliable systems for on farm monitoring of animal welfare status and providing some warranty on appropriate
production conditions.
The article shows an overview of the European strategies for implementing the animal welfare labelling.
Received: July 2, 2008; accepted: July 8, 2008 相似文献