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排序方式: 共有102条查询结果,搜索用时 46 毫秒
51.
Hayden T. Robinson Christian T. Haakansson Timothy R. Corkish Peter D. Watson Prof. Allan J. McKinley Dr. Duncan A. Wild 《Chemphyschem》2023,24(7):e202200733
Hydrogen bonding and halogen bonding are important non-covalent interactions that are known to occur in large molecular systems, such as in proteins and crystal structures. Although these interactions are important on a large scale, studying hydrogen and halogen bonding in small, gas-phase chemical species allows for the binding strengths to be determined and compared at a fundamental level. In this study, anion photoelectron spectra are presented for the gas-phase complexes involving bromide and the four chloromethanes, CH3Cl, CH2Cl2, CHCl3, and CCl4. The stabilisation energy and electron binding energy associated with each complex are determined experimentally, and the spectra are rationalised by high-level CCSD(T) calculations to determine the non-covalent interactions binding the complexes. These calculations involve nucleophilic bromide and electrophilic bromine interactions with chloromethanes, where the binding motifs, dissociation energies and vertical detachment energies are compared in terms of hydrogen bonding and halogen bonding. 相似文献
52.
The permeation of benzene and acetone vapors through sulfur-cured natural rubber was studied by the time-lag method. The experimental results were analyzed by a method suggested by Meares. The zero concentration diffusion coefficient D0 was obtained by the early-time method. The Frisch time-lag equation was utilized to estimate both the solubility coefficient s and the additional parameter b required to define the concentration dependence of the diffusion coefficient: D(c) = D0 exp {bc}. This form of concentration dependence was manifested by the corresponding permeability coefficient values. At low entering penetrant pressure, where the transport coefficients are constant, indirect evidence was obtained that D0 is the mechanistically correct diffusion coefficient. The solubility coefficient values calculated for benzene vapor in natural rubber are in reasonable agreement with published equilibrium sorption data for a similar rubber compound. At higher entering penetrant pressures, average diffusion coefficients obtained at steady state tended to be larger than the corresponding average diffusion coefficients derived from the time lags. This same effect has been detected by other experimental approaches. Permeation experiments designed for this rapid method of analysis appear capable of yielding information consistent with that obtained by more time-consuming traditional methods. 相似文献
53.
54.
Cooper PD Kjaergaard HG Langford VS McKinley AJ Quickenden TI Schofield DP 《Journal of the American Chemical Society》2003,125(20):6048-6049
We have measured the infrared spectrum of H2O.HO in argon matrices at 11.5 +/- 0.5 K. We have also calculated the vibrational frequencies and intensities of the H2O.HO complex. As a result of these measurements and calculations, we have assigned a previously unassigned absorption band at 3442.1 cm-1 to the OH stretch in the radical complexed to the water molecule. This absorption originates from a complex that is situated in a different site within the argon matrix to those absorptions already assigned to this vibration at 3452.2 and 3428.0 cm-1. We observe a decrease in intensity of the OH radical stretching vibration of the H2O.HO complex upon isotopic substitution of D for H that agrees well with our calculations. 相似文献
55.
Tom McKinley 《Linear and Multilinear Algebra》2013,61(2):245-256
We study simultaneous block-diagonalization of cyclic d-tuples of commuting matrices. Some application to ideal projectors are also presented. In particular, we extend Hans Stetter's theorem characterizing Lagrange projectors. 相似文献
56.
Lin Zhou L.Pamela Cook Gareth H. McKinley 《ournal of non Newtonian Fluid Mechanics》2010,165(21-22):1462-1472
We explore the use of large amplitude oscillatory shear (LAOS) deformation to probe the dynamics of shear-banding in soft entangled materials, primarily wormlike micellar solutions which are prone to breakage and disentanglement under strong deformations. The state of stress in these complex fluids is described by a class of viscoelastic constitutive models which capture the key linear and nonlinear rheological features of wormlike micellar solutions, including the breakage and reforming of an entangled network. At a frequency-dependent critical strain, the imposed deformation field localizes to form a shear band, with a phase response that depends on the frequency and amplitude of the forcing. The different material responses are compactly represented in the form of Lissajous (phase plane) orbits and a corresponding strain-rate and frequency-dependent Pipkin diagram. Comparisons between the full network model predictions and those of a simpler, limiting case are presented. 相似文献
57.
We explore the utility of strain-controlled large amplitude oscillatory shear (LAOS) deformation for identifying and characterizing
apparent yield stress responses in elastoviscoplastic materials. Our approach emphasizes the visual representation of the
LAOS stress response within the framework of Lissajous curves with strain, strain rate, and stress as the coordinate axes,
in conjunction with quantitative analysis of the corresponding limit cycle behavior. This approach enables us to explore how
the material properties characterizing the yielding response depend on both strain amplitude and frequency of deformation.
Canonical constitutive models (including the purely viscous Carreau model and the elastic Bingham model) are used to illustrate
the characteristic features of pseudoplastic and elastoplastic material responses under large amplitude oscillatory shear.
A new parameter, the perfect plastic dissipation ratio, is introduced for uniquely identifying plastic behavior. Experimental
results are presented for two complex fluids, a pseudoplastic shear-thinning xanthan gum solution and an elastoviscoplastic
invert-emulsion drilling fluid. The LAOS test protocols and the associated material measures provide a rheological fingerprint
of the yielding behavior of a complex fluid that can be compactly represented within the domain of a Pipkin diagram defined
by the amplitude and timescale of deformation. 相似文献
58.
Campos R Guenthner AJ Meuler AJ Tuteja A Cohen RE McKinley GH Haddad TS Mabry JM 《Langmuir : the ACS journal of surfaces and colloids》2012,28(25):9834-9841
The liquid repellency and surface topography characteristics of coatings comprising a sprayed-on mixture of fluoroalkyl-functional precipitated silica and a fluoropolymer binder were examined using contact and sliding angle analysis, electron microscopy, and image analysis for determination of fractal dimensionality. The coatings proved to be an especially useful class of liquid repellent materials due to their combination of simple and scalable deposition process, low surface energy, and the roughness characteristics of the aggregates. These characteristics interact in a unique way to prevent the buildup of binder in interstitial regions, preserving re-entrant curvature across multiple length scales, thereby enabling a wide range of liquid repellency, including superoleophobicity. In addition, rather than accumulating in the interstices, the binder becomes widely distributed across the surface of the aggregates, enabling a mechanism in which a simple shortage or excess of binder controls the extent of coating roughness at very small length scales, thereby controlling the extent of liquid repellence. 相似文献
59.
Rich JP McKinley GH Doyle PS 《Langmuir : the ACS journal of surfaces and colloids》2012,28(8):3683-3689
The process of assembling particles into organized functional structures is influenced by the rheological properties of the matrix fluid in which the assembly takes place. Therefore, tuning these properties represents a viable and as yet unexplored approach for controlling particle assembly. In this Letter, we examine the effect of the matrix fluid yield stress on the directed assembly of polarizable particles into linear chains under a uniform external magnetic field. Using particle-level simulations with a simple yield stress model, we find that chain growth follows the same trajectory as in Newtonian matrix fluids up to a critical time that depends on the balance between the yield stress and the strength of magnetic interactions between particles; subsequently, the system undergoes structural arrest. Appropriate dimensionless groups for characterizing the arresting behavior are determined and relationships between these groups and the resulting structural properties are presented. Since field-induced structures can be indefinitely stabilized by the matrix fluid yield stress and "frozen" into place as desired, this approach may facilitate the assembly of more complex and sophisticated structures. 相似文献
60.
Scaffidi A Waters MT Skelton BW Bond CS Sobolev AN Bythell-Douglas R McKinley AJ Dixon KW Ghisalberti EL Smith SM Flematti GR 《Organic & biomolecular chemistry》2012,10(20):4069-4073
Karrikinolide is a naturally derived potent seed germination stimulant that is responsible for triggering the germination of numerous plant species from various habitats around the world. We now report that solar irradiation of karrikinolide yields two novel head-to-head cage photodimers with the formation, stability and bioactivity of both presented herein. 相似文献