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991.
Jim Lawrence 《Discrete and Computational Geometry》1988,3(1):307-324
Given a collection of convex polytopes, let() denote the set of all convex transversals of. If and are two such collections, of finite cardinality, then there is a simple, arithmetical condition which holds precisely when ()=(). Another such condition, involving what we call the Sallee-Shephard mapping, characterizes those pairs and for which (())=().As these results are established, several distributive lattices involving convex sets are introduced, and relationships between their valuation modules are determined. In particular, it is proven that the Sallee-Shephard mapping is an isomorphism of the additive, abelian group of simple functions generated by the characteristic functions of the open, convex sets and that generated by those of the closed, convex sets. 相似文献
992.
993.
994.
Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils 总被引:1,自引:0,他引:1
Solid-phase microextraction was used as a technique for headspace sampling of extra virgin olive oil and virgin olive oil samples with different off-flavours. A 100 microm coated polydimethylsiloxane fiber was used to extract volatile aldehydes, the sampling temperature was 45 degrees C and the fiber has been exposed to the headspace for 15 min. Nonanal and 2-decenal were present in all the olive oils with extraction off-flavours but were not in extra virgin olive oil sample. 相似文献
995.
996.
M. Jim Hendry S. Lee Barbour Erin E. Schmeling 《Isotopes in environmental and health studies》2016,52(3):203-213
The dominant transport mechanisms controlling the migration of contaminants in geologic media are advection and molecular diffusion. To date, defining which transport mechanism dominates in saturated, non-lithified sediments has been difficult. Here, we illustrate the value of using detailed profiles of the conservative stable isotope values of water (δ2H and δ18O) to identify the dominant processes of contaminant transport (i.e. diffusion- or advection-dominated transport) in near-surface, non-lithified, saturated sediments of the Interior Plains of North America (IPNA). The approach presented uses detailed δ18O analyses of glacial till, glaciolacustrine clay, and fluvial sand core samples taken to depths of 11–50 m below ground at 22 sites across the IPNA to show whether transport in the fractured and oxidized sediments is dominated by advection or diffusion. Diffusion is by far the dominant transport mechanism in fine-textured lacustrine and glacial till sediments, but lateral advection dominates transport in sand-rich sediments and some oxidized, fine-textured lacustrine and glacial till sediments. The approach presented has a number of applications, including identifying dominant transport mechanisms in geomedia and potential protective barriers for underlying aquifers or surface waters, constraining groundwater transport models, and selecting optimum locations for monitoring wells. These findings should be applicable to most glaciated regions of the world that are composed of similar hydrogeologic units (i.e. low K clay till layers overlain by higher K coarse-textured aquifers or weathered clay till layers) and may also be applicable to non-glaciated regions exhibiting similar hydrogeologic characteristics. 相似文献
997.
Gonzalez V Wilson T Kurihara I Imai A Thomas JA Otsuki J 《Chemical communications (Cambridge, England)》2008,(16):1868-1870
A dinuclear ruthenium(II) complex groove binds to DNA and this interaction results in distinctive color changes that are dependent on both DNA sequence and structure. 相似文献
998.
Beavers MP Myers MC Shah PP Purvis JE Diamond SL Cooperman BS Huryn DM Smith AB 《Journal of chemical information and modeling》2008,48(7):1464-1472
The papain/CLIK-148 coordinate system was employed as a model to study the interactions of a nonpeptide thiocarbazate inhibitor of cathepsin L ( 1). This small molecule inhibitor, a thiol ester containing a diacyl hydrazine functionality and one stereogenic center, was most active as the S-enantiomer, with an IC 50 of 56 nM; the R-enantiomer ( 2) displayed only weak activity (33 microM). Correspondingly, molecular docking studies with Extra Precision Glide revealed a correlation between score and biological activity for the two thiocarbazate enantiomers when a structural water was preserved. The molecular interactions between 1 and papain were very similar to the interactions observed for CLIK-148 ( 3a and 3b) with papain, especially with regard to the hydrogen-bonding and lipophilic interactions of the ligands with conserved residues in the catalytic binding site. Subsequent docking of virtual compounds in the binding site led to the identification of a more potent inhibitor ( 5), with an IC 50 of 7.0 nM. These docking studies revealed that favorable energy scores and correspondingly favorable biological activities could be realized when the virtual compound design included occupation of the S2, S3, and S1' subsites by hydrophobic and aromatic functionalities of the ligand, and at least three hydrogen bonding contacts between the ligand and the conserved binding site residues of the protein. 相似文献
999.
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrated to be a potentially
useful tool for the rapid identification of yeasts, the grouping of Candida albicans strains, and the monitoring of germ tube-specific markers. Co-crystallized with sinapinic acid as the MALDI matrix, intact
yeast cells yielded a sufficient number of medium-sized ions (4–15 kDa) in MALDI mass spectra to provide “mass signatures”
that were diagnostic of strain type. For most isolates, the mass signatures were affected by the growth medium, length of
incubation and the cell preparation method. While the overall past success of this methodology for fungal cells has been relatively
low compared to its application to bacteria, fixing the yeast cells in 50% methanol inactivated the cells, reduced cell aggregation
in aqueous suspension solution, and more importantly, it significantly improved the mass signature quality. This simple but
critical advance in sample treatment improved mass spectrometric signal-to-noise ratios and allowed the identification of
yeasts by a mass signature approach. Under optimized conditions, Candida species (C. albicans, C. glabrata, C. krusei, C. kefyr), Aspergillus species (A. terreus, A. fumigatus, A. syndowii) and other yeast genera (Cryptococcus neoformans, Saccharomyces cerevisiae and a Rhodotorula sp.) could be distinguished. Within the C. albicans species, several common ions in the m/z 5,000–10,000 range were apparent in the mass spectra of all tested strains. In addition to shared ions, the mass spectra
of individual C. albicans strains permitted grouping of the strains. Principal component analysis (PCA) was employed to confirm spectral reproducibility
and C. albicans strain grouping by mass signatures. Finally, C. albicans germ tubes produced MALDI-TOF mass signatures that differed from yeast forms of this species. This is a rapid, sensitive
and simple method for identifying yeasts, grouping strains and following the morphogenesis of C. albicans.
Figure 相似文献
1000.
A LC-MS/MS method using a LC column packed with sub-2 micron particles and elevated column temperatures was validated for the quantitation of SCH 503034 diastereomers (SCH 534128 and SCH 534129) in human plasma. The method was validated over the concentration range of 2.5 to 1250 ng/mL. Inter-assay precision, based on percent relative deviation for n = 18 replicate quality controls, was 4.5% for SCH 534128 and 4.9% for SCH 534129. Inter-assay accuracy based on n = 18 replicate quality controls was +/- 7.8% for both SCH 534128 and SCH 534129. The method involved the novel application of ion pairing reagents to increase the stereoselectivity of the separation. Temperature, types of ion pairing reagent, and concentration of ion pairing reagent were all found to play significant roles in the resolution of the SCH 534128 and SCH 534129 diastereomers on a LC column packed with sub-2 micron particles. Specifically, a sensitivity increase of five-fold was demonstrated by increasing the column temperature. Without sacrificing resolution, the run time was significantly shortened when the column temperature was elevated to 100 degrees C. 相似文献