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排序方式: 共有1211条查询结果,搜索用时 25 毫秒
1.
Frits van der Klis Jérôme Le Nôtre Rolf Blaauw Jacco van Haveren Daan S. van Es 《European Journal of Lipid Science and Technology》2012,114(8):911-918
A two‐step concept for the production of linear alpha olefins from biomass is reported. As a starting material an internally unsaturated C17 alkene was used, which was obtained by the decarboxylation of oleic acid. Here, we report on the ethenolysis of this bio‐based product, using commercially available metathesis catalysts. The desired alpha olefin products, 1‐nonene and 1‐decene, were obtained in excellent yield (96%) and selectivity (96%). Practical applications: The two‐step conversion described in this contribution, starting from unsaturated fatty acids, provides a method for the production of industrially important linear alpha olefins. These valuable products are widely used as starting materials for the production of surfactants and polymers such as linear low density polyethylene (LLDPE). 相似文献
2.
DD Lund FM Faraci H Ooboshi BL Davidson DD Heistad 《Canadian Metallurgical Quarterly》1999,30(1):120-125
OBJECTIVE: Regional presynaptic dopaminergic function and its regulation by dopamine agonists in different stages of PD can be measured by L-[11C]dopa and PET. In the current investigation, we studied the effects of therapeutic apomorphine on L-[11C]dopa uptake in patients with early and advanced PD. BACKGROUND: With disease progression and chronic dopamine agonist treatment, motor response complications supervene in a majority of PD patients. It is assumed that both presynaptic and postsynaptic changes in the dopaminergic system act to modify dopaminergic efficacy. METHODS: Patients with early and advanced stages of PD were included in the study. All patients were investigated twice with PET and L-[11C]dopa drug free and during a subsequent standardized therapeutic apomorphine infusion. RESULTS: Subregional analysis of the striatum showed differences in the effects of apomorphine infusion on the L-[11C]dopa influx rate in the two patient categories. In patients with early and uncomplicated PD, apomorphine infusion decreased the L-[11C]dopa influx rate. This decrease was most pronounced in the dorsal part of the putamen. In advanced PD patients, apomorphine did not affect the striatal L-[11C]dopa influx rate. CONCLUSIONS: We suggest that in mild and stable PD an upregulated presynaptic inhibitory feedback regulation, particularly in the dorsal putamen, acts to maintain congruity within the dopaminergic system in response to antiparkinsonian medication. However, this inhibitory feedback regulation is diminished with the progression of nigrostriatal degeneration and chronic dopamine agonist treatment. 相似文献
3.
JD Amsterdam F Garcia-Espana J Fawcett FM Quitkin FW Reimherr JF Rosenbaum C Beasley 《Canadian Metallurgical Quarterly》1999,19(1):9-14
PURPOSE: To evaluate the potential diagnostic role of mediastinal sonography in patients with cystic fibrosis (CF), we screened the mediastinum of adult CF patients with and without signs of infection and healthy controls. METHODS: Fifty-four consecutive adult patients with CF and 53 healthy volunteers underwent high-resolution mediastinal sonography. The paratracheal region and aorticopulmonary window of each subject were examined for lymph nodes. Each patient was screened for clinical signs of infection. RESULTS: Lymph nodes were detectable in the mediastinum of 39 of 50 CF patients (78%); the mean total lymph node volume was 1.5 +/- 1.7 cm3. Lymph nodes were detectable in the mediastinum of 31 of 50 controls (62%); the mean total lymph node volume in this group was 0.3 +/- 0.3 cm3 (p < 0.001). In the 30 CF patients with signs of infection, the mean total lymph node volume was larger (2.0 +/- 1.8 cm3) than in the 20 CF patients without signs of infection (0.7 +/- 0.9 cm3; p = 0.002). CONCLUSIONS: These results indicate that lymph node volume determination by high-resolution mediastinal sonography may help assess inflammatory activity in patients with CF. 相似文献
4.
AK Metzger G Mohapatra YA Minn AW Bollen K Lamborn FM Waldman CB Wilson BG Feuerstein 《Canadian Metallurgical Quarterly》1999,90(2):306-314
OBJECT: This study was conducted to determine whether comparative genomic hybridization (CGH) is a more sensitive method for detecting genetic aberrations than other tests currently in use. METHODS: The authors used CGH to examine 40 primary and 13 recurrent adenomas obtained from 52 patients for loss and gain of genetic material. Copy number aberrations (CNAs) were detected in 25 (48%) of the 52 patients studied. The chromosomes affected were, in order of decreasing frequency, 11, 7, X, 1, 8, 13, 5, 14, 2, 6, 9, 10, 12, 3, 18, 21, 4, 16, 15, 19, 22, and Y. Endocrinologically active adenomas were more likely to contain (p = 0.009) and had a greater number (p = 0.003) of CNAs. Of 26 adenomas with CNAs, 18 showed multiple aberrations involving entire chromosomes or chromosome arms. The most frequent CNA involving a chromosome subregion, which was present in four (8%) of 53 adenomas, was the loss of all chromosome 11 material except for a preserved common segment containing 11q13. Immunoperoxidase staining did not detect cyclin D1 expression in those four cases, making cyclin D1 an unlikely target of this rearrangement. CONCLUSIONS: These findings indicate that genetic abnormalities are present in pituitary adenomas at a higher rate than previously reported, are associated with endocrinological activity, and often involve several chromosomes. Rearrangement at 11q13 may inactivate a tumor suppressor gene or activate an oncogene that is important in the initiation or progression of sporadic pituitary adenomas. 相似文献
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6.
Maciej Klis Agnieszka Michota Slawomir Sek Renata Bilewicz 《Electrochimica acta》2007,52(18):5591-5598
Cerrena unicolor laccase was immobilized on the gold electrode by covalent bonding to self-assembled monolayers of mercaptoundecanoic or mercaptopropionic acids. STM images of immobilized laccase proved high population of the laccase molecules on the monolayer modified electrode. The SERS experiments in concert with resonance Raman effect confirmed that the structure at the “blue” copper site of the immobilized protein remained intact. The accessibility of individual copper sites for electron exchange with the gold electrode surface was investigated by voltammetry. The electrode behavior of laccase is different in the presence and absence of oxygen, showing that the immobilized enzyme is reactive towards oxygen. Addition of two common mediators improved the electrical connectivity of the enzyme with the electrode, increased the catalytic efficiency of immobilized laccase and switched the onset of catalytic current to the potentials of the mediator. Immobilization of laccase on well-organized mercaptoundecanoic acid separates efficiently the enzyme from the electrode and does not allow easy access of mediators to the surface. Attachment of the enzyme at smaller distance from the electrode by means of significantly shorter spacer molecule—mercaptopropionic acid improved the efficiency of catalytic reduction of oxygen on the monolayer modified electrode. 相似文献
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9.
Jord J. Warmink Hanneke Van der Klis Martijn J. Booij Suzanne J. M. H. Hulscher 《Water Resources Management》2011,25(2):601-622
Hydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modelling
of river processes involves numerous uncertainties, resulting in uncertain model outcomes. Knowledge of the type and magnitude
of uncertainties is crucial for a meaningful interpretation of the model results and the usefulness of results in decision
making processes. The aim of this study is to identify the sources of uncertainty that contribute most to the uncertainties
in the model outcomes and quantify their contribution to the uncertainty in the model outcomes. Experts have been selected
based on an objective Pedigree analysis. The selected experts are asked to quantify the most important uncertainties for two
situations: (1) the computation of design water levels and (2) the computation of the hydraulic effect of a change in the
river bed. For the computation of the design water level, the uncertainties are dominated by the sources that do not change
between the calibration and the prediction. The experts state that the upstream discharge and the empirical roughness equation
for the main channel have the largest influence on the uncertainty in the modeled water levels. For effect studies, the floodplain
bathymetry, weir formulation and discretization of floodplain topography contribute most to the uncertainties in model outcomes.
Finally, the contribution of the uncertainties to the model outcomes show that the uncertainties have a significant effect
on the predicted water levels, especially under design conditions. 相似文献
10.
N Raffaelli FM Pisani T Lorenzi M Emanuelli A Amici S Ruggieri G Magni 《Canadian Metallurgical Quarterly》1997,179(24):7718-7723
The enzyme nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) catalyzes the synthesis of NAD+ and nicotinic acid adenine dinucleotide. It has been purified to homogeneity from cellular extracts of the thermophilic archaeon Sulfolobus solfataricus. Through a database search, a highly significant match was found between its N-terminal sequence and a hypothetical protein coded by the thermophilic archaeon Methanococcus jannaschii MJ0541 open reading frame (GenBank accession no. U67503). The MJ0541 gene was isolated, cloned into a T7-based vector, and expressed in Escherichia coli cells, yielding a high level of thermophilic NMN adenylyltransferase activity. The expressed protein was purified to homogeneity by a single-step chromatographic procedure. Both the subunit molecular mass and the N-terminal sequence of the pure recombinant protein were as expected from the deduced amino acid sequence of the MJ0541 open reading frame-encoded protein. Molecular and kinetic properties of the enzymes from both archaea are reported and compared with those already known for the mesophilic eukaryotic NMN adenylyltransferase. 相似文献