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991.
DM Colton GO Till KJ Johnson SB Dean RH Bartlett RB Hirschl 《Canadian Metallurgical Quarterly》1998,26(10):1716-1724
OBJECTIVE: This study evaluates the ability of perflubron to inhibit pulmonary neutrophil accumulation during partial liquid ventilation (PLV) in the setting of acute lung injury. DESIGN: Randomized, controlled, nonblinded study. SETTING: Research laboratory at a university. SUBJECTS: Male, Sprague-Dawley rats (n = 120, 506 +/- 42 g). INTERVENTIONS: Animals were divided into eight groups (n = 15 in each group, of which n = 12 for myeloperoxidase content and n = 3 for histologic neutrophil counting): a) GV-CVF group, animals received gas ventilation (GV) with the induction of lung injury using cobra venom factor (CVF); b) PLV-CVF group, animals received partial liquid ventilation before the induction of lung injury; c) PEEP-CVF group, animals received positive end-expiratory pressure (PEEP) before the administration of cobra venom factor; d) CVF-PLV group, animals received partial liquid ventilation after cobra venom factor; e) CVF-PEEP group, animals received PEEP after cobra venom factor; f) PLV only group, animals received partial liquid ventilation only; g) GV only group, animals received gas ventilation only; and h) NVSBA group, nonventilated spontaneous breathing animals. MEASUREMENTS AND MAIN RESULTS: After the experimental period, total lung myeloperoxidase content was significantly decreased in the PLV-CVF (0.29 +/- 0.08, p = .02) and PEEP-CVF (0.34 +/- 0.04, p = .01) groups when compared with the GV-CVF group (0.62 +/- 0.07). When compared with the GV-CVF group, a trend toward a reduction in myeloperoxidase was observed in the CVF-PLV (0.42 +/- 0.05, p = .07) and the CVF-PEEP (0.39 +/- 0.06, p = .07) groups. When compared with the cobra venom factor only group (GV-CVF 47 +/- 2 neutrophils/high-power field), reductions in neutrophil count were observed in all groups (neutrophils/high-power field): PLV-CVF (20 +/- 2, p = .009); PEEP-CVF (24 +/- 1, p = .01); CVF-PLV (30 +/- 2, p = .03); and CVF-PEEP (37 +/- 1, p = .04). CONCLUSION: These data suggest that both partial liquid ventilation and PEEP result in a reduction in neutrophil accumulation in the setting of acute lung injury. 相似文献
992.
The traditional understanding of knee kinematics holds that no single fixed axis of rotation exists in the knee. In contrast, a recent hypothesis suggests that knee kinematics are better described simply as two simultaneous rotations occurring about fixed axes. Knee flexion and extension occurs about an optimal flexion axis fixed in the femur, whereas tibial internal and external rotations occur about a longitudinal rotation axis fixed in the tibia. No other translations or rotations exist. This hypothesis has been tested. Tibiofemoral kinematics were measured for 15 cadaveric knees undergoing a realistic loadbearing activity (simulated squatting). An optimization technique was used to identify the locations of the optimal flexion and longitudinal rotation axes such that simultaneous rotations about them could best represent the measured kinematics. The optimal flexion axis was compared with the transepicondylar axis defined by bony landmarks. The longitudinal rotation axis was found to pass through the medial joint compartment. The optimal flexion axis passed through the centers of the posterior femoral condyles. No significant difference was found between the optimal flexion and transepicondylar axes. To an average accuracy of better than 3.4 mm in translation, and 2.9 degrees in orientation, knee kinematics were represented successfully by simple rotations about the optimal flexion and longitudinal rotation axes. The optimal flexion axis is fixed in the femur and can be considered the true flexion axis of the knee. The transepicondylar axis axis, which is identified easily by palpation, closely approximates the optimal flexion axis. 相似文献
993.
K O'Donoghue A Clapham RP Evershed TA Brown 《Canadian Metallurgical Quarterly》1996,263(1370):541-547
Desiccated seeds from a 6th century AD storage vessel recovered from Qasr Ibr?m, Egypt, were examined for the presence of lipids and nucleic acids. A remarkable degree of lipid preservation was discovered, the fatty acid and sterol profiles being very similar to those of modern radish seeds. The only significant differences were hydrolysis of triacylglycerols and depletion of the polyunsaturated fatty acids (C18:2 and C18:3). The delta 13 C values of the principal fatty acids were in the range -25.4 to -29.2/1000, which is congruent with modern radish (C3 seeds) taking account of isotopic shifts caused by recent changes in atmospheric CO2. Deoxyribonucleosides and nucleic acid bases were detected by direct chemical analysis, and polymerase chain reactions gave products with sequences comparable to those from modern radish. The degree of lipid preservation, which was much greater than that reported for other archaeological remains, suggests that the microenvironment within desiccated seeds retards biomolecular decay. The results illustrate the utility of combined lipid-nucleic acid analysis in chemotaxonomic and genotypic studies of archaeobotanical remains. 相似文献
994.
995.
TA Gudasheva SS Boyko VKh Akparov RU Ostrovskaya SP Skoldinov GG Rozantsev TA Voronina VP Zherdev SB Seredenin 《Canadian Metallurgical Quarterly》1996,391(1-2):149-152
Using high-performance liquid chromatography, gas-chromatography and chromato-mass spectrometry methods a novel endogenous cyclic dipeptide cyclo-prolylglycine was identified in rat brain. Its content according to gas chromatography is 2.8 +/- 0.3 nmol/g wet brain. Synthetic cyclo-prolylglycine has demonstrated antiamnesic activity in the passive avoidance test in rats at a dose of 0.1 mg/kg i.p. Cyclic dipeptide cyclo-prolylglycine seems to be a memory facilitating substance and its presence in rat brain suggests the existence of a new mechanism of memory regulation. 相似文献
996.
J. -O. Ndap C. I. Rablau K. Morrow O. O. Adetunji V. A. Johnson K. Chattopadhyay R. H. Page A. Burger 《Journal of Electronic Materials》2002,31(7):802-805
The maximum optical-absorption cross section of Cr2+ ions was evaluated from near-infrared (NIR) absorption spectroscopy and direct measurements of the chromium concentration
in Cr2+:CdSe crystals. The emission lifetime of the excited state, 5E, of Cr2+ was measured as a function of Cr2+ concentration in the 2×1017 −2×1018 ions/cm3 range and as a function of temperature from 77–300 K. Lifetime values were as high as ∼6 μs in the 77–250 K range and decreased
to ∼4 μs at 300 K because of nonradiative decays. Assuming that most of the Cr dopant is in the Cr2+ state, an optical-absorption cross section σa of (1.94±0.56) × 10−18 cm2 was calculated. Implications for laser performance are discussed. 相似文献
997.
David E. Johnson Lawrence S. Moss 《Annals of Mathematics and Artificial Intelligence》1993,8(1-2):133-173
In this paper, we investigate the formal expressive properties of Stratified Feature Grammar (SFG), a new logic-based linguistic
framework motivated by relational grammar and metagraph grammar, as well as by Kasper-Rounds logic. The driving force behind
SFG is the generalization of the conceptfeature from an unanalyzable atomic one to a sequence of so-called R-signs. The linguistic interpretation of thesestratified features is that each R-sign in such a sequence denotes a primitive grammatical relation such as subject or direct object in different
syntactic “strata”. This generalization permits the specification of a rigorous feature-structure-based formalism for natural-language
grammars based on the view that syntax is “multistratal” and “relational”. The introduction of stratified features leads to
several other innovations, two of which might have utility in other frameworks. One is the idea of imposing a partial order
on features. The other is the concept of(data) justification: essentially, this is a stipulation that for an S-graph to be well-formed with respect to some grammarG it must, in addition to satisfying the rules ofG, have each of its “core” data (each feature occurrence, each node-label occurrence and each instance of so-called structure-sharing)
justified in a formally precise manner by some rule of Justification ensures that. Justification ensures that satisfying S-graphs
do not have more structure than absolutely necessary and so makes it appealing to a notion of “minimal model” otiose. Justification
plays a key role in a number of our proofs. The formal results presented here include the following. First, it is proved that
in the unrestricted SFG framework, every type 0 (r.e.) language is generated by some SFG. Then, we restrict the framework
to so-calledbounded SFG with two linguistically motivated principles: Lexical Anchoring and Boundedness. Anchoring requires, in essence, that
each core datum of an S-graph be justified by aword in its yield. Boundedness insures that S-graph features are short. Although these restrictions together put the class of
bounded SFG languages well within the class of recursive languages, we go on to demonstrate that the recognition problem for
bounded SFG is NP-hard. Further, we establish that a bounded SFG language need not be semi-linear. On the matter of upper
bounds, we show that every bounded SFL can be recognized by a nondeterministic Turing machine inn logn space and polynomial time and that the recognition problem for bounded SFL's is NP-complete. 相似文献
998.
999.
JI Risinger A Umar JC Boyer AC Evans A Berchuck TA Kunkel JC Barrett 《Canadian Metallurgical Quarterly》1995,55(23):5664-5669
We have examined a panel of gynecological sarcomas for microsatellite instability. The genomic DNA from 11 of 44 sarcomas contained somatic alterations in the lengths of one or more di-, tri-, tetra-, or pentanucleotide microsatellite sequence markers, and 6 of these cases had alterations in two or more markers. In addition, di-, tri-, and tetranucleotide microsatellites were found to be highly unstable in single cell clones of two cell lines derived from a uterine mixed mesodermal tumor. Since such instability is characteristic of cells defective in postreplication mismatch repair, we examined mismatch repair activity in extracts made from these lines. Both extracts were repair deficient, while an extract of another gynecological sarcoma cell line not exhibiting microsatellite instability was repair proficient. The repair deficiency was complemented by a colon tumor cell extract that was defective in the hMLH1 protein but not by an extract defective in hMSH2 protein. This suggested that the defect in the uterine sarcoma line could be in hMSH2. Subsequent analysis of the gene revealed a 2-bp deletion in exon 14, leading to premature truncation of the hMSH2 protein at codon 796 and no detectable wild-type gene present. These data suggest that the microsatellite instability observed in these cell lines, and possibly in a significant number of gynecological sarcomas, is due to defective postreplication mismatch repair. There was no apparent correlation with microsatellite instability and clinical outcome. 相似文献
1000.
PA Winchester HM Lee NM Khilnani Y Wang DW Trost HL Bush TA Sos 《Canadian Metallurgical Quarterly》1998,9(6):891-9; discussion 900
PURPOSE: To perform a preliminary evaluation of the diagnostic accuracy of contrast-enhanced, two-dimensional (2D) magnetic resonance (MR) digital subtraction angiography (DSA) of the lower extremity by comparison with x-ray angiography (XRA). MATERIALS AND METHODS: Forty lower extremities in 22 patients were imaged at multiple levels with both XRA and 2D MR DSA. Images were retrospectively analyzed by three radiologists in a randomized blinded manner. Seventeen vascular segments were graded as an insignificant lesion, a significant lesion, or as an occlusion. With the use of segments well depicted with XRA as the gold standard, the sensitivity, specificity, and accuracy of 2D MR DSA, as compared with XRA, were evaluated. The McNemar-Stuart-Maxwell test was performed to determine the significance of any differences found. RESULTS: Three hundred eighty-three arterial segments were evaluated with both techniques. Three hundred one segments were well depicted with XRA. There was no significant difference between 2D MR DSA and XRA for assessing the degree of occlusive disease in these 301 segments (.25 < P < .5). The sensitivity, specificity, and diagnostic accuracy of 2D MR DSA were found to be 90%, 98%, and 93%, respectively. CONCLUSION: Two-dimensional MR DSA is an accurate method for assessing arterial lesions in the lower extremity. 相似文献