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201.
Blackburn RS Harvey A Kettle LL Manian AP Payne JD Russell SJ 《The journal of physical chemistry. B》2007,111(30):8775-8784
Chlorhexidine (CH) is an effective antimicrobial agent. There has been very little work published concerning the interactions of CH with, and its adsorption mechanism on, cellulose. In this paper, such physical chemistry parameters are examined and related to computational chemistry studies. Adsorption isotherms were constructed following application of CH to cellulose. These were typical of a Langmuir adsorption isotherm, but at higher concentrations displayed good correlation also with a Freundlich isotherm. Sorption was attributed to a combination of electrostatic (major contribution) and hydrogen bonding forces, which endorsed computational chemistry proposals: electrostatic interactions between CH and carboxylic acid groups in the cellulose dominate with a contribution to binding through hydrogen bonding of the biguanide residues and the p-chlorophenol moieties (Yoshida H-bonding) with the cellulose hydroxyl groups. At high CH concentrations, there is evidence of monolayer and bilayer aggregation. Differences in sorption between CH and another antimicrobial agent previously studied, poly(hexamethylenebiguanide) (PHMB), are attributed to higher molecular weight of PHMB and higher charge density of biguanide residues in CH (due to the relative electron withdrawing effect of the p-chlorophenol moiety). 相似文献
202.
Parikshit Goswami Richard S. Blackburn Jim Taylor Patrick White 《Cellulose (London, England)》2011,18(4):1063-1072
Cellulose is a linear 1,4-β-glucan polymer where the units are able to form highly ordered structures, as a result of extensive
interaction through intra- and intermolecular hydrogen bonding of the three hydroxyl groups in each cellulose unit. Alkali
has a substantial influence on morphological, molecular and supramolecular properties of cellulose II polymer fibres causing
changes in crystallinity. Lyocell fibres pre-treated with 0.0, 2.0, and 4.0 mol dm−3 aqueous NaOH solution were dyed with hydrolyzed reactive dyes that had different molecular shapes and sizes. Overall exhaustion
(q
e), value of K, and −ΔG increased for lyocell samples pre-treated with aqueous NaOH solution in the following order: 2.0 > 4.0 > 0.0 mol dm−3 NaOH. The same trends were observed for colour strength (K/S) values of the dyeings. Pre-treatment of lyocell with 2.0 mol dm−3 NaOH creates the substrate that achieves the most thermodynamically favourable system for sorption of hydrolyzed reactive
dyes, as at this concentration crystallinity decreases (with respect to 0.0 mol dm−3 NaOH treated lyocell) to afford higher sorption; however, at higher alkali concentrations the macro-sorbent forms a compacted
unit that limits diffusion within the sorbent interior. Molecular size of the sorbate dye has a significant effect on the
sorption process: for the largest dye structure the sorption isotherm is most closely correlated to a Langmuir isotherm; as
the size of the dye decreases correlation to a Langmuir isotherm is observed, but with good correlation to the Freundlich
isotherm; as the size of the dye is decreased further sorption is more typical of a Freundlich isotherm. 相似文献
203.
Bertin PA Georganopoulou D Liang T Eckermann AL Wunder M Ahrens MJ Blackburn GF Meade TJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):9096-9101
Novel dithiazepane-functionalized ferrocenyl-phenylethynyl oligomers 1 and 2 have been synthesized. Self-assembled monolayers (SAMs) of these ferrocene derivatives have been studied by X-ray photoelectron spectroscopy, ellipsometry, and cyclic voltammetry. It has been shown by XPS that monolayers of the dithiazepane-anchored molecules on gold electrodes contain gold-thiolate species. Cyclic voltammetry of the SAMs were characteristic of stable electroactive monolayers even for single-component SAMs of 1 and 2, with the more ideal responses recorded for the two-component SAMs diluted with undecanethiol. The small variation in peak splittings at progressively higher scan rates in these SAMs makes dithiazepane-bridged redox species promising candidates for further studies on molecular wires with bipodal anchoring. 相似文献
204.
Blackburn E Hiess A Bernhoeft N Rheinstädter MC Häussler W Lander GH 《Physical review letters》2006,97(5):057002
We report on a single crystal neutron spin-echo investigation of the low-energy dynamic response in the heavy-fermion superconductor UPd2Al3 in the vicinity of the antiferromagnetic wave vector Q(0)=(0 0 0.5). Well inside the superconducting phase, antiferromagnetic quasielastic scattering, which is present in the normal state, is absent for relaxation times up to 10 ns, equivalent to an energy resolution of approximately 1 microeV. This places strong constraints on possible models for this magnetic superconductor. 相似文献
205.
Blackburn RS Harvey A Kettle LL Payne JD Russell SJ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(13):5636-5644
Antimicrobial agents such as poly(hexamethylene biguanide) (PHMB) find application in medical, apparel, and household textile sectors; although it is understood that certain concentrations need to be applied to achieve suitable performance, there has been very little work published concerning the interactions of the polymer and its adsorption mechanism on cellulose. In this paper, such physical chemistry parameters are examined and related to computational chemistry studies. Adsorption isotherms were constructed: at low concentrations, these were typical Langmuir isotherms; at higher concentrations, they were more indicative of Freundlich isotherms, attributed to a combination of electrostatic and hydrogen-bonding forces, which endorsed computational chemistry proposals. At lower concentrations, electrostatic interactions between PHMB and carboxylic acid groups in the cellulose dominate with a contribution to binding through hydrogen bonding; as the concentration of PHMB increases, hydrogen bonding with cellulose becomes increasingly dominant. At high PHMB concentrations, observations of increasing PHMB adsorption are attributed to monolayer aggregation and multilayer stacking of PHMB through electrostatic interactions with counterions and hydrogen bonding of biguanide groups. 相似文献
206.
Simon R. Blackburn Douglas R. Stinson Jalaj Upadhyay 《Designs, Codes and Cryptography》2012,64(1-2):171-193
In this article, we analyze the complexity of the construction of the 2 k -diamond structure proposed by Kelsey and Kohno (LNCS, Vol 4004, pp 183–200, 2006). We point out a flaw in their analysis and show that their construction may not produce the desired diamond structure. We then give a more rigorous and detailed complexity analysis of the construction of a diamond structure. For this, we appeal to random graph theory (in particular, to the theory of random intersection graphs), which allows us to determine sharp necessary and sufficient conditions for the message complexity (i.e., the number of hash computations required to build the required structure). We also analyze the computational complexity for constructing a diamond structure, which has not been previously studied in the literature. Finally, we study the impact of our analysis on herding and other attacks that use the diamond structure as a subroutine. Precisely, our results shows the following:
- The message complexity for the construction of a diamond structure is ${\sqrt{k}}$ times more than the amount previously stated in literature.
- The time complexity is n times the message complexity, where n is the size of hash value.
207.
G. Michael Blackburn Peter R. Ashton Mao-Jun Guo Michael Rogers Graham Taylor Andrzej Guranowski Donald Watts 《Heteroatom Chemistry》1991,2(1):163-170
The enzymatic cleavage of a scissile P O bond can be blocked by recourse to phosphonate analogues of biological phosphate esters. α-Fluorophosphonates have an enhanced electronegativity at the bridging carbon, which, in many cases, makes them superior to simple methylene phosphonates for the study of enzyme reactions. Thus, the β,γ-difluoro-methylene analogue of ATP is a good substrate for the interferon-induced (2→5)An synthetase, which converts it into a (2→5)A4 species having a 5′-β,γ-difluoromethylenetriphosphate. This binds strongly to RNase L but does not activate it. The unsymmetrical Ap4Aases from Artemia and Lupin are strongly inhibited by P1,P4-dithiophosphate analogues of diadenosyl-5′,5‴-P1,P4-tetraphosphate although nonregiospecific cleavage of certain P2,P3-methylene analogues can be observed. Some of these analogues are remarkably effective inhibitors of platelet aggregation and are effective inhibitors in vivo of arterial blood-clotting in rabbits. Separation of all diastereoisomers of P1,P4-dithiophosphate analogues of Ap4A is achieved cleanly using reverse-phase hplc chromatography and this provides direct access to β,γ-CHF-bridged analogues of ATP with resolved stereochemistry at the CHF center. Lastly, growing cells of Dictyostelium discoideum not only tolerate a range of substituted methylene bisphosphonates in their growth medium but actually incorporate them into nucleotide analogues of ATP and Ap4A. 相似文献