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排序方式: 共有1426条查询结果,搜索用时 31 毫秒
111.
RN Shain JM Piper ER Newton ST Perdue R Ramos JD Champion FA Guerra 《Canadian Metallurgical Quarterly》1999,340(2):93-100
Using annual bite-wing radiographs, the incidence and progression of approximal caries (4d-7m) were assessed longitudinally in teenagers and adolescents whose treatment had been based on remineralizing rather than restorative strategies. A closed cohort of 536 children initially was followed from 11 to 22 years of age. The scoring system was: 0 = no visible radiolucency; 1-2 = radiolucency in the enamel up to the enamel-dentin border; 3 = radiolucency with a broken enamel-dentin border but with no obvious progression in the dentin; 4 = radiolucency with obvious spread in the outer half of the dentin, and 5 = radiolucency in the inner half of the dentin. Caries rates were estimated as the number of new lesions/100 tooth surface-years, and the Kaplan-Meier estimate was used to calculate the cumulative survival time of each approximal surface. Three events were used: the transitions from states 0 to 2, 2 to 4 and 3 to 4. The results showed a considerable variation between the surfaces in both caries rates and survival time. For all surfaces combined, the median caries rate from state 0 to 2 was 3.9 new lesions/100 tooth surface-years; from state 2 to 4, the rate was 5.4, and from state 3 to 4 it was 20.3. Of the sound surfaces (state 0), 75% survived 6.3 years without reaching state 2. Given state 2, 75% survived 4.8 years without reaching the outer half of the dentin (state 4), while given a lesion at the enamel-dentin border (state 3), 75% survived 1.3 years without doing the same. The median survival time of lesions from state 3 to 4 was 3.1 years. The group with DMFSappr>1 at the age of 11-12 years had a risk of new approximal enamel lesions (state 0-2) that was 2.5 times greater than that of the group with DMFSappr = 0-1. 相似文献
112.
The analytical flow simulation of fresh concrete is a recent challenge to researchers. Due to its heterogeneity, the concrete mix shows neither a perfectly viscous nor perfectly particulate behavior. However, the particulate behavior of fresh concrete flow like arching and blocking in pipes and in complex boundary conditions, is very common. This is further magnified due to high pressure in the case of shotcreting. For the first time in shotcrete research, authors propose the application of the Distinct Element Method [1] (DEM) to predict particle behavior and amount of rebound loss, and to assess the quality of the shotcrete analytically. Also, the effect of an accelerating agent, the way its effect is modeled, effects of gradual change in shooting pressure, the resulting rebound is shown. The void of the attached concrete is also compared with that of normal cast concrete in an analytical way. 相似文献
113.
Vapor phase adsorption equilibrium of carbon tetrachloride, a priority pollutant, on dry soils was studied at 288, 293, and 298 K. Using a gravimetric adsorption apparatus, adsorption /desorption isotherms of carbon tetrachloride were generated on two different soil samples. The effects of temperature and soil characteristics were examined. Isosteric heals of adsorption were calculated and heat curves were constructed.
Adsorption isotherms of carbon tetrachloride on dry soil samples were Type II, indicating formation of multilayers of adsorbate on the soil particle surface. Considerable hysteresis effects, associated with capillary condensation, were observed upon desorption. Thermal data confirmed that the adsorption of carbon tetrachloride vapor on soil was primarily physical adsorption. Heat curves showed that the soil samples had energetically heterogeneous surfaces. A positive correlation between The soil's specific surface area and its sorption capacity was observed. Clay content and pore size were also dominating factors.
The experimental data were correlated by the Polanyi Potential, the BET, and the GAB models in order to provide input lo fate and transport models predicting the degradation or movement of volatile organic pollutants in soil. The BET equation gave accurate data fit, within a deviation range of 2·63-5·40%, for up to 40% of the saturation pressure. The GAB equation provided superior fit of the data for the entire relative pressure range. Absolute error percentages from the GAB model ranged from 1·77 to 5·38%. Results followed the Potential Theory satisfactorily and led to a single temperature-independent characteristic curve. 相似文献
Adsorption isotherms of carbon tetrachloride on dry soil samples were Type II, indicating formation of multilayers of adsorbate on the soil particle surface. Considerable hysteresis effects, associated with capillary condensation, were observed upon desorption. Thermal data confirmed that the adsorption of carbon tetrachloride vapor on soil was primarily physical adsorption. Heat curves showed that the soil samples had energetically heterogeneous surfaces. A positive correlation between The soil's specific surface area and its sorption capacity was observed. Clay content and pore size were also dominating factors.
The experimental data were correlated by the Polanyi Potential, the BET, and the GAB models in order to provide input lo fate and transport models predicting the degradation or movement of volatile organic pollutants in soil. The BET equation gave accurate data fit, within a deviation range of 2·63-5·40%, for up to 40% of the saturation pressure. The GAB equation provided superior fit of the data for the entire relative pressure range. Absolute error percentages from the GAB model ranged from 1·77 to 5·38%. Results followed the Potential Theory satisfactorily and led to a single temperature-independent characteristic curve. 相似文献
114.
Ashok K. Sood James E. Egerton Yash R. Puri Enrico Bellotti Donald D’Orsogna Latika Becker Raymond Balcerak Ken Freyvogel Robert Richwine 《Journal of Electronic Materials》2005,34(6):909-912
Multicolor infrared (IR) focal planes are required for high-performance sensor applications. These sensors will require multicolor
focal plane arrays (FPAs) that will cover various wavelengths of interest in mid wavelength infrared/long wavelength infrared
(MWIR/LWIR) and long wavelength infrared/very long wavelength infrared (LWIR/VLWIR) bands. There has been significant progress
in HgCdTe detector technology for multicolor MWIR/LWIR and LWIR/VLWIR FPAs.1–3 Two-color IR FPAs eliminate the complexity of multiple single-color IR FPAs and provide a significant reduction of weight
and power in simpler, reliable, and affordable systems. The complexity of a multicolor IR detector MWIR/LWIR makes the device
optimization by trial and error not only impractical but also merely impossible. Too many different geometrical and physical
variables need to be considered at the same time. Additionally, material characteristics are only relatively controllable
and depend on the process repeatability. In this context, the ability of performing “simulation experiments” where only one
or a few parameters are carefully controlled is paramount for a quantum improvement of a new generation of multicolor detectors
for various applications. 相似文献
115.
116.
The firefly luciferase (Luc) protein and the jellyfish green fluorescent protein (GFP) are two commonly used molecular reporters that can be detected noninvasively in living cells. The properties that make GFP or Luc useful for a particular experimental application are quite distinct. A recombinant protein with both fluorescent and bioluminescent characteristics might take advantage of the strengths of both reporters. An expression vector encoding a chimeric protein in which GFP was tethered to Luc through a 19-amino acid linker was prepared and characterized. Western blotting with antibodies specific for either GFP or Luc showed that a protein of appropriate size was expressed in transfected cells. Fluorescence microscopy revealed bright green fluorescence from transfected cells, indicating proper formation of the GFP chromophore. Luc enzymatic activity in protein extracts from transfected cells showed that Luc was fully functional. The treatment of living cell cultures stably expressing the GFP-Luc fusion protein with the protein translation-inhibitor cycloheximide (Chx) was used to show that the half-life for Luc protein activity was approximately 2 h at 37 degrees C. The utility of this dual-function reporter protein was shown by the identification of single living cells expressing the chimeric protein within a population by fluorescence microscopy, followed by quantification of Luc activity from the same living cells. 相似文献
117.
MA Pfaller RN Jones GV Doern HS Sader RJ Hollis SA Messer 《Canadian Metallurgical Quarterly》1998,36(7):1886-1889
An international program of surveillance of bloodstream infections (BSIs) in the United States, Canada, and South America between January and December 1997 detected 306 episodes of candidemia in 34 medical centers (22 in the United States, 6 in Canada, and 6 in South America). Eighty percent of the BSIs were nosocomial and 50% occurred in patients hospitalized in an intensive care unit. Overall, 53.3% of the BSIs were due to Candida albicans, 15.7% were due to C. parapsilosis, 15.0% were due to C. glabrata, 7.8% were due to C. tropicalis, 2.0% were due to C. krusei, 0.7% were due to C. guilliermondii, and 5.8% were due to Candida spp. However, the distribution of species varied markedly by country. In the United States, 43.8% of BSIs were due to non-C. albicans species. C. glabrata was the most common non-C. albicans species in the United States. The proportion of non-C. albicans BSIs was slightly higher in Canada (47.5%), where C. parapsilosis, not C. glabrata, was the most common non-C. albicans species. C. albicans accounted for 40.5% of all BSIs in South America, followed by C. parapsilosis (38.1%) and C. tropicalis (11.9%). Only one BSI due to C. glabrata was observed in South American hospitals. Among the different species of Candida, resistance to fluconazole (MIC, > or = 64 microg/ml) and itraconazole (MIC, > or = 1.0 microg/ml) was observed with C. glabrata and C. krusei and was observed more rarely among other species. Isolates of C. albicans, C. parapsilosis, C. tropicalis, and C. guilliermondii were all highly susceptible to both fluconazole (99.4 to 100% susceptibility) and itraconazole (95.8 to 100% susceptibility). In contrast, 8.7% of C. glabrata isolates (MIC at which 90% of isolates are inhibited [MIC90], 32 microg/ml) and 100% of C. krusei isolates were resistant to fluconazole, and 36.9% of C. glabrata isolates (MIC90, 2.0 microg/ml) and 66.6% of C. krusei isolates were resistant to itraconazole. Within each species there were no geographic differences in susceptibility to fluconazole or itraconazole. 相似文献
118.
Radiolabeling permits the detection of trace amounts of zwitterionic detergent remaining in extracted hydrophobic or membrane proteins. To develop a sensitive and specific assay for its presence, the commonly used zwitterionic membrane protein detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps) was synthesized in a tritiated form. Synthesis via 7-ketodeoxycholic acid gave [7-3H]Chaps in 53% yield with a specific activity of 0.85 mCi/mmol. A novel solvent extraction system for cholic acid obviated the need for chromatographic isolation of this intermediate. The protocol can be readily modified to yield [7-3H]Chaps of higher specific activity. [7-3H]Chaps was used to monitor the efficiency of various strategies for detergent removal from concentrated bacterial culture supernatants containing 0.2% (w/v) Chaps. Dialysis removed 95% of Chaps and the addition of detergent-affinity beads to the dialysis buffer resulted in 97% removal of Chaps. Gel-filtration chromatography removed 99.9% of Chaps, while a detergent-affinity bead chromatography column removed 99.99%. Overall, gel-filtration chromatography was the most convenient and economical method for the one-step removal of the zwittergent from complex biological mixtures. 相似文献
119.
Electrolysis has been performed since 1875. Electrolysis satisfactorily removes hair from women with static hair growth, but women with hirsutism often require concomitant management of their hormonal problems. We have found the blend method to be the most effective modality for permanent hair removal. Attention must be given to proper electrolysis technique, including accurate needle insertion and appropriate intensities and duration. Scarring does not occur with properly performed electrolysis. Hair is not an electrical conductor and electronic tweezers do not result in permanent hair removal. Shaving 1 to 5 days before electrolysis greatly increases efficacy because it ensures that only growing anagen hairs are epilated. The recent availability of EMLA (eutectic mixture of local anesthetics) has been beneficial in reducing the sensations of electrolysis. The availability of prepackaged, presterilized, individual electrolysis needles has greatly reduced the need for more complicated sterilization procedures. 相似文献
120.