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61.
Scanning tunneling microscopy combined with molecular dynamics simulations reveals a dislocation-mediated island diffusion mechanism for Cu on Ag(111), a highly mismatched system. Cluster motion is tracked with atomic precision at multiple temperatures and diffusion barriers and prefactors are determined from direct measurements of hop rates. The barrier to nucleate a dislocation is sensitive to island size and shape, resulting in a non-monotonic size dependence of the diffusion barrier. 相似文献
62.
The entrainment of oxide films into the bulk material has been shown to have a detrimental effect on casting integrity. A number of mechanisms have been shown to initiate the entrainment of oxide films, including: returning waves, plunging jets, bubble trails and fountains. Therefore, the assessment of the casting system for these features by the foundry engineer is critical in improving casting quality. 相似文献
63.
Norman R. Reilly 《代数通讯》2013,41(11):3624-3659
We study the lattice ?(RSn) of subvarieties of the variety of semigroups generated by completely 0-simple semigroups over groups with exponent dividing n, with a particular focus on the lattice ??(RSn) consisting of those varieties that are generated by completely 0-simple semigroups. The sublattice of ??(RSn) consisting of the aperiodic varieties is described and several endomorphisms of ?(RSn) considered. The complete congruence on ??(RSn) that relates varieties containing the same aperiodic completely 0-simple semigroups is considered in some detail. 相似文献
64.
In a previous paper the authors introduced seven complete congruences on the lattice ev(I of e-varieties of regular semigroups of the form
P
:U
P
VPU=PV, whereP is drawn from a small set of e-varieties: left zero, right zero, rectangular bands, groups, left groups, right groups and completely simple semigroups. Four new complete congruences are introduced here of the form
P
:U
P
VPU=PV, whereP is one of the following classes of regular semigroups: left monoids, right monoids, monoids, idempotent generated semigroups. For each complete congruence on ev(I) and eachUev(I), the -class ofU is an interval [U
,U
] so that there is associated with each such congruence an idempotent operatorUU
on ev(I). This paper establishes numerous results concerning the commutativity of operators of this form.This work was supported in part by NSERC Grant 4044. 相似文献
65.
Devakumar A O'Dell DK Walker JM Reilly JP 《Journal of the American Society for Mass Spectrometry》2008,19(1):14-26
The fragmentation of 5-hydroxy-6-glutathionyl-7,9,11,14-eicosatetraenoic acid [leukotriene C4 or LTC4 (5, 6)] and its isomeric counterpart LTC4 (14, 15) were studied by low and high-energy collisional induced dissociation (CID) and 157 nm photofragmentation. For singly charged protonated LTC4 precursors, photodissociation significantly enhances the signal intensities of informative fragment ions that are very important to distinguish the two LTC4 isomers and generates a few additional fragment ions that are not usually observed in CID experiments. The ion trap enables MSn experiments on the fragment ions generated by photodissociation. Photofragmentation is found to be suitable for the structural identification and isomeric differentiation of cysteinyl leukotrienes and is more informative than low or high-energy CID. We describe for the first time the structural characterization of the LTC4 (14, 15) isomer by mass spectrometry using CID and 157 nm light activation methods. 相似文献
66.
Sharma PK Reilly MJ Jones DN Robinson PM Bhatia SR 《Colloids and surfaces. B, Biointerfaces》2008,61(1):53-60
We present results on the effects of various hydrophobic drugs and additives on the micellar structure of Pluronic F127 solutions. Small-angle neutron scattering experiments on 5wt% F127 solutions were used to measure micelle core size (R(1)), micelle corona size (R(2)), intermicellar interaction distance (R(int)), polydispersity (sigma), and aggregation number (N(agg)); dynamic light scattering was used to measure critical micelle concentration (CMC); and ultraviolet spectroscopy was used to measure drug solubility and apparent micelle-water partition coefficient (K(mw)). The core and corona size were found to generally increase in the presence of the drugs, as did R(int). Both sigma and N(agg) were found to decrease in the presence of most of the drugs, and the CMC was found to vary considerably with no clear correlation. A design of experiments (DOE) approach was used to analyze the results and build empirical correlations. All of the parameters from the SANS experiments were found to depend strongly on drug solubility, with a weak dependence on K(mw) in most cases. The aggregation number, however, was found to depend strongly on both K(mw) and solubility. The correlations can be used to roughly predict the structural parameters of F127 micelles for other hydrophobic drugs. 相似文献
67.
When N-[2-(alkylsulfinyl)phenyl]-1H-indole-2-carboxamides with varying degrees of indolic and amidic N-alkylation are heated in an inert solvent or treated with trifluoroacetic anhydride; only compounds in which the amidic nitrogen is methylated cyclize to indolo[3,2-b]-1,5-benzothiazepinones (9, 10). Successful cyclization is attributed to the ability of N-Me amides to readily adopt a conformation conducive to cyclization, which other derivatives are unable to achieve. The analogous 3-indoleanilide, N,N-dimethyl N-[2-(ethylsulfinyl)phenyl]-1H-indole-3-carboxamide (17a), undergoes SES/rearrangement to produce 10 upon heating in p-xylene. An intermediate 3H-indolinium spirocyclic species is proposed to account for this result. 相似文献
68.
Devakumar A Mechref Y Kang P Novotny MV Reilly JP 《Rapid communications in mass spectrometry : RCM》2007,21(8):1452-1460
Permethylated acidic and neutral N-glycans representing different types of glycan structures, such as linear and branched sialylated structures, high-mannose type and fucosylated complex type, were photodissociated with 157 nm vacuum ultraviolet light in a linear ion trap. Cross-ring fragments corresponding to high-energy fragmentation pathways were observed in abundance for all studied structures. Some product ions appear diagnostic for a linkage of sialic acid residues and the glycan antenna to which these residues are attached. A conclusive assignment of the fucosylation site of the studied glycan structure has been facilitated through measurement of cross-ring fragmentation resulting from photodissociation. 相似文献
69.
Lee J. Silverberg Tapas K. Mal Carlos N. Pacheco Megan L. Povelones Madeline F. Malfara Anthony F. Lagalante Mark A. Olsen Hemant P. Yennawar Hany F. Sobhi Kayla R. Baney Robin L. Bozeman Craig S. Eroh Michael J. Fleming Tracy L. Garcia Casey L. Gregory Julia E. Hahn Alyssa M. Hatter Lexi L. Johns Tianna L. Klinger Jennie J. Li Andrew J. Menig Grace C. Muench Melissa E. Ramirez Jordyn Reilly Nicole Sacco Alexandra M. Sheidy Marla M. Stoner Eric N. Thompson Soroush F. Yazdani 《Molecules (Basel, Switzerland)》2021,26(20)
A series of fourteen 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-phenyl-C-aryl imines with thionicotinic acid, two difficult substrates. The reactions were operationally simple, did not require specialized equipment or anhydrous solvents, could be performed as either two or three component reactions, and gave moderate–good yields as high as 63%. This provides ready access to N-phenyl compounds in this family, which have been generally difficult to prepare. As part of the study, the first crystal structure of neutral thionicotinic acid is also reported, and showed the molecule to be in the form of the thione tautomer. Additionally, the synthesized compounds were tested against T. brucei, the causative agent of Human African Sleeping Sickness. Screening at 50 µM concentration showed that five of the compounds strongly inhibited growth and killed parasites. 相似文献
70.