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41.
The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) ( 1 ) reacts with YCl3 in tetrahydrofuran to give the tris-allyl complex Y(CH2CHCHSiMe3)3 ( 2 ), while K(CH2CHCHSiMe2tBu) ( 3 ) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{η2-NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) ( 5 ), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis-allyl complex {1,3-C3H3(SiMe3)2}2Sc(μ-Cl)2Li(THF)2 ( 6 ), while the analogous reaction of K{1,3-C3H3(SiMe3)2} ( 7 ) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d6 show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. 相似文献
42.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
43.
Hugo E. Delgado Ph.D. Ramanath I. Ramakrishnan M.S. Timothy E. Howson D.E.S. 《JOM Journal of the Minerals, Metals and Materials Society》1994,46(9):21-23
Computer-aided engineering tools are routinely used to simulate forging and heat-treatment operations and to perform thermal and stress analyses. This review gives a few examples of the current uses of process modeling tools and outlines some developing capabilities and near-term applications. 相似文献
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Inflammation in nasal and airway tissue caused by allergens, microbial infection, and air pollution are likely to be regulated by inflammatory mediators produced by airway epithelial cells. We have therefore investigated the baseline expression of a number of cytokine genes known to be important inducers and modulators of inflammation, in freshly isolated human nasal epithelium. Cells were obtained by superficial scraping of turbinate tissue, and cDNA for polymerase chain reaction (PCR) amplification was reverse-transcribed directly from lysates of 3 x 10(3) to 5 x 10(3) epithelial cells using random hexamers. Constitutive expression of relatively high levels of interleukin-8 (IL-8) mRNA but undetectable levels (< 1 mRNA copy/cell) of granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-6, IL-1, or tumor necrosis factor (TNF) mRNA were found after PCR amplification of the cDNA. IL-8 protein, but not IL-6, was identified in the nasal epithelial cells by immunocytochemistry. Infection with respiratory syncytial virus (RSV) or stimulation of nasal epithelium for 4 h with TNF or IL-1 in vitro resulted in a 4- to 10-fold increase in IL-8 mRNA expression but not in the expression of detectable levels of mRNA for the other cytokines. IL-8 was secreted by RSV-, IL-1-, and TNF-stimulated as well as unstimulated nasal epithelial cells after 6 to 20 h of culture. Neither IL-6, GM-CSF, nor TNF activity/immunoreactivity was detectable in the culture supernatants. Thus, it appears that IL-8 is a major cytokine of human nasal epithelium, constitutively expressed and readily secreted upon virus infection or stimulation with IL-1 and TNF. 相似文献
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47.
AH Enk J Saloga D Becker M Mohamadzadeh J Knop 《Canadian Metallurgical Quarterly》1994,179(4):1397-1402
Interleukin 10 (IL-10) is released during the induction phase of contact sensitivity and was shown in prior functional studies to convert epidermal Langerhans cells (LC) from potent inducers of primary immune responses to specifically tolerizing cells in vitro. To investigate whether IL-10 also subserves the function of a tolerizing agent in vivo ears of BALB/c or C3H mice were injected intradermally with 1-2 micrograms of recombinant mouse (rm)IL-10 8 h before epicutaneous application of 3% trinitrochlorobenzene (TNCB; a contact allergen). As a control, mice were injected with phosphate-buffered saline or IL-10 plus neutralizing amounts of anti-IL-10 mAb. 5 d later, mice were challenged with 1% TNCB on contralateral ears and ear swelling response was measured 24 h later. Whereas control-treated mice showed a normal ear swelling response to epicutaneous challenge (delta mm-2 = 25 +/- 5), ear swelling response of IL-10-treated animals was significantly inhibited (delta mm-2 = 3 +/- 2). Coinjection of IL-10-specific mAb together with rmIL-10 completely abrogated this effect. To differentiate between a state of nonresponsiveness and induction of tolerance by IL-10, mice initially treated with IL-10 and TNCB were resensitized with 3% TNCB in the absence of any treatment after 14 d of rest (group 1). Again mice were challenged 5 d later and ear swelling responses were tested. Whereas control mice treated with allergen alone (group 2) showed a good swelling response (delta mm-2 = 28 +/- 6), IL-10-treated mice (group 1) showed a minimal response towards application of allergen (delta mm-2 = 4 +/- 2). To show that anergy induction by IL-10 was antigen-specific, mice initially treated with IL-10 plus TNCB were exposed to 0.5% dinitrofluorobenzene (DNFB) 14 d later (group 1). After challenge with 0.1% DNFB, IL-10-treated mice showed an ear swelling response (delta mm-2 = 13 +/- 3; group 1) similar to that of control mice only sensitized with DNFB (delta mm-2 = 14 +/- 3; group 3). In an attempt to show the induction of antigen-specific tolerance in these mice in vitro, regional lymph nodes of mice initially treated with TNCB plus IL-10 (group 1) and control-treated mice (groups 2 and 3) were prepared and cultured in the presence of TNBS, dinitrobenzene sulfonate (DNBS), or medium to measure antigen-specific proliferation.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
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49.
The effects of not breastfeeding on mortality due to diarrhea and acute lower respiratory infection (ALRI) in children under 2 years of age were examined using data from a 1988-1991 longitudinal study of 9,942 children in Metro Cebu, The Philippines. Cox regression methods were used to study the magnitude of the risks, possible interactions with birth weight and nutritional status, and the effect of additional confounding factors. Not breastfeeding had a greater effect on diarrheal mortality than on ALRI mortality. In the first 6 months of life, failing to initiate breastfeeding or ceasing to breastfeed resulted in an 8- to 10-fold increase in the rate of diarrheal mortality. The rate of mortality associated with both ALRI and diarrhea was increased nearly six times by not breastfeeding, but the rate of ALRI mortality alone was not increased. The data also suggested that the risk of mortality associated with not breastfeeding was greater for low birth weight infants and infants whose mothers had little formal education. After age 6 months, the protective effects of breastfeeding dropped dramatically. These findings underscore the importance of promoting breastfeeding, especially during the first 6 months of life, and of targeting high risk groups such as low birth weight babies and those of low socioeconomic status. 相似文献
50.
F. Goschenhofer J. Gerschütz A. Pfeuffer-Jeschke R. Hellmig C. R. Becker G. Landwehr 《Journal of Electronic Materials》1998,27(6):532-535
N-type Hg1−xCdxTe layers with x values of 0.3 and 0.7 have been grown by molecular beam epitaxy using iodine in the form of CdI2 as a dopant. Carrier concentrations up to 1.1 × 1018 cm−3 have been achieved for x = 0.7 and up to 7.6 × 1017 cm−3 for x=0.3. The best low temperature mobilities are 460 cm2/(Vs) and 1.2 × 105 cm2/(Vs) for x=0.7 and x=0.3, respectively. Using CdI2 as the dopant modulation doped HgTe quantum well structures have been grown. These structures display very pronounced Shubnikov-de
Haas oscillations and quantum Hall plateaus. Electron densities in the 2D electron gas in the HgTe quantum well could be varied
from 1.9 × 1011 cm−2 up to 1.4 × 1012 cm−2 by adjusting the thicknesses of the spacer and doped layer. Typical mobilities of the 2D electron gas are of the order of
5.0 × 104 cm2/(Vs) with the highest value being 7.8 × 104 cm2/(Vs). 相似文献