Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
90
result(s) for
"Hinks, David"
Sort by:
Universal features in the photoemission spectroscopy of high-temperature superconductors
The energy gap for electronic excitations is one of the most important characteristics of the superconducting state, as it directly reflects the pairing of electrons. In the copper–oxide high-temperature superconductors (HTSCs), a strongly anisotropic energy gap, which vanishes along high-symmetry directions, is a clear manifestation of the d -wave symmetry of the pairing. There is, however, a dramatic change in the form of the gap anisotropy with reduced carrier concentration (underdoping). Although the vanishing of the gap along the diagonal to the square Cu–O bond directions is robust, the doping dependence of the large gap along the Cu–O directions suggests that its origin might be different from pairing. It is thus tempting to associate the large gap with a second-order parameter distinct from superconductivity. We use angle-resolved photoemission spectroscopy to show that the two-gap behavior and the destruction of well-defined electronic excitations are not universal features of HTSCs, and depend sensitively on how the underdoped materials are prepared. Depending on cation substitution, underdoped samples either show two-gap behavior or not. In contrast, many other characteristics of HTSCs, such as the dome-like dependence of [Formula] on doping, long-lived excitations along the diagonals to the Cu–O bonds, and an energy gap at the Brillouin zone boundary that decreases monotonically with doping while persisting above [Formula] (the pseudogap), are present in all samples, irrespective of whether they exhibit two-gap behavior or not. Our results imply that universal aspects of high-[Formula] superconductivity are relatively insensitive to differences in the electronic states along the Cu–O bond directions.
Journal Article
High efficiency ultra-deep dyeing of cotton via mercerization and cationization
A potentially environmentally responsible dyeing procedure for ultra-deep shades on cotton was developed using a cationization method in combination with mercerization. The effects of both treatments on dyeing performance and colorfastness properties of cotton fabrics dyed with reactive dyes were analyzed individually and in combination. Both mercerization and cationization have been proved to be effective in increasing the depth of shade on cotton. The colorfastness properties, except colorfastness to wet crocking, of mercerized–cationized cotton fabrics dyed without salt were much better than untreated cotton dyed using a conventional dyeing procedure. Unlike untreated cotton fabrics, the concentration of Na₂CO₃ in the dyeing process of mercerized–cationized cotton fabrics was lowered from 20 to 5 g/L without compromising dye fixation and colorfastness properties. With low concentrations of dyes and Na₂CO₃ and no electrolyte in the dye bath effluent, the dyeing procedure of mercerized–cationized cotton fabrics for ultra-deep shades is potentially a more environmentally benign method than conventional dyeing with reactive dyes.
Journal Article
Design, Synthesis, and Pharmacological Screening of Novel Porphyrin Derivatives
A series of porphyrin derivatives 2a–f was synthesized, namely, 5,10,15,20-mesotetrakis[p-methoxyphenyl]-21H,23H-porphyrin (2a), 5,10,15,20-mesotetrakis[2,6-dichloro-phenyl]-21H,23H-porphyrin (2b), 5,10,15,20-mesotetrakis[4-hydroxy-3,5-dimethoxyphenyl]-21H,23H-porphyrin (2c), 5,10,15,20-mesotetrakis[3,4-dimethoxyphenyl]-21H,23H-porphyrin (2d), 5,10,15,20-mesotetrakis[2,4-dichlorophenyl]-21H,23H-porphyrin (2e), and 5,10,15,20-mesotetrakis[3,4,5-trimethoxyphenyl]-21H,23H-porphyrin (2f), in high yields using a new method via a capping mechanism. These dyes were used as a model to study the free radical-induced damage of biological membranes and the protective effects of these porphyrins. It was demonstrated that these dyes were effective in the inhibition of the free radical-induced oxidative haemolysis of rat blood cells. Dyes 2d and 2f which bear methoxy functionality exhibited markedly higher antihaemolysis activity than the other analogs. Molecular modeling methods using ZINDO/INDO-1, with a configuration interaction of 26, and TD-DFT using the energy functional B3LYP and the basis set DGTZVP were used to study the vertical electronic excitations of porphyrins 2a–f and it was shown that the λmax calculated using TD-DFT method was in excellent agreement with the experimental results, while the ZINDO method was inferior. Moreover, excellent correlation between the LUMO energy and cytotoxicity of dyes 2a–f was found.
Journal Article
Pilot-plant investigation on low-temperature bleaching of cotton fabric with TBCC-activated peroxide system
Cotton fabric was bleached at a pilot-plant scale with the activated peroxide system based on
N
-[4-(triethylammoniomethyl) benzoyl] caprolactam chloride (TBCC). The performance of the TBCC-activated peroxide system on low-temperature bleaching of cotton fabric was evaluated by measuring the degree of whiteness, degree of polymerization, water absorbency, extractable contents, and dyeing properties of bleached cotton fabrics. For comparison purpose, cotton fabric was also bleached at the same pilot-plant scale with a traditional hydrogen peroxide system using a standard recipe. It was found that the pilot-plant bleaching with the TBCC-activated peroxide system resulted in a comparable degree of whiteness and a slightly lower water absorbency of cotton fabric but no apparent fiber damage. The bleached cotton fabric could meet requirements for trichromatic reactive dyeing. The investigation on resource utilization revealed that the pilot-plant bleaching of cotton fabric with the TBCC-activated peroxide system could save 60% water, 38% steam and 27% electric power in comparison with the traditional hydrogen peroxide system. These pilot-plant results are of great importance for further scaling up the TBCC-activated peroxide system to full-scale commercial production.
Journal Article
Activated peroxide bleaching of regenerated bamboo fiber using a butyrolactam-based cationic bleach activator
Regenerated bamboo fibers are potentially a valuable source of renewable fibers for use in a wide variety of applications. As with almost all natural fibers, inherent yellowness must be reduced or eliminated in order for the fibers to be used effectively in processes such as dyeing. Oxidative bleaching in the form of hot alkaline hydrogen peroxide is the most common method for bleaching cellulosic fibers. However, significant fiber damage results, especially in the case of regenerated bamboo. Recently, more benign oxidative bleaching methods have been developed using so-called bleach activators. Reported is an effective bleaching method using a novel bleach activator, N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC). The ratio of TBBC to hydrogen peroxide and pH were found to be critical to achieving effective bleaching at low temperature. Using equimolar amounts of TBBC and hydrogen peroxide at pH 7 and 50 °C, comparable whiteness and less fiber damage compared with conventional peroxide bleaching was obtained. However, at pH 11.5, TBBC had no effect on whiteness.
Journal Article
Bleaching cellulosic fibers via pre-sorption of N-4-(triethylammoniomethyl)-benzoyl-butyrolactam chloride
The sorption of a novel cationic bleach activator, N-[4-(Triethylammoniomethyl)benzoyl]-butyrolactam Chloride (TBBC), was measured on regenerated bamboo fiber. At 25 °C near neutral pH, the sorption rate of TBBC onto the fiber was initially rapid and equilibrium was reached within 20 min. Adsorption equilibria experiments followed a Freundlich isotherm. At the sorption equilibrium, bleaching was initiated by addition of sodium perborate to liberate hydrogen peroxide, which reacted with TBBC to generate a peracid that is a more kinetically active oxidant than peroxide. A sorption-activation model was developed that supports the enhanced bleaching of cellulosic fibers using cationic bleach activators under neutral to alkaline conditions.
Journal Article
Real-time dyebath monitoring of reactive dyeing on cationized cotton for levelness control: part 1—influence of dye structure, temperature, and addition of soda ash
Chemical cationization of cotton has been a subject of increased interest due to the ability of cationized cotton to attract negatively charged dyes, thus eliminating the use of electrolytes during dyeing and increasing color yield. However, electrostatic attractions between cationized cotton and anionic dyes also result in significantly increased dye strike rates, which may cause levelness problems, especially when light to medium shades are required. In this study, cotton fabric cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride was used to investigate the method for obtaining appropriate dye strike rate to produce a level reactive dyeing on cationized cotton. To effectively control the dyeing kinetics of reactive dyes on cationized cotton, real-time exhaustion of six commercially significant reactive dyes were monitored. The influence of temperature, dye structure, and addition of soda ash on dyeing kinetics and levelness of cationized cotton were evaluated.
Journal Article
Real-time dyebath monitoring of reactive dyeing on cationized cotton for levelness control: part 2—effects of leveling agents and dye dosing
Cationization of cotton brings advantages in the reactive dyeing process, such as eliminating the use of electrolytes and increasing color yield. However, high dye strike rates caused by the electronic attractions between anionic dyes and cationized cotton may result in poor levelness of dyeing, especially for light shades. For some monochloritriazine–monochloritriazine homobifunctional reactive dyes, lowering dyeing temperature and controlling the addition of electrolytes can effectively control the dye strike rate and improve the levelness of dyed cationized cotton. However, for other reactive dyes, the use of effective leveling agents is necessary. In this study, a variety of anionic, cationic, and amphoteric leveling agents were applied to control the dye exhaustion process of three monochloritriazine–vinylsulphone heterobifunctional reactive dyes on the cotton fabric cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride. The leveling effect of adding dyes in portions was also evaluated and it was used in combination with leveling agents to further improve the levelness of dyeing.
Journal Article
Spectral Accuracy and Sulfur Counting Capabilities of the LTQ-FT-ICR and the LTQ-Orbitrap XL for Small Molecule Analysis
Color Index Disperse Yellow 42 (DY42), a high-volume disperse dye for polyester, was used to compare the capabilities of the LTQ-Orbitrap XL and the LTQ-FT-ICR with respect to mass measurement accuracy (MMA), spectral accuracy, and sulfur counting. The results of this research will be used in the construction of a dye database for forensic purposes; the additional spectral information will increase the confidence in the identification of unknown dyes found in fibers at crime scenes. Initial LTQ-Orbitrap XL data showed MMAs greater than 3 ppm and poor spectral accuracy. Modification of several Orbitrap installation parameters (e.g., deflector voltage) resulted in a significant improvement of the data. The LTQ-FT-ICR and LTQ-Orbitrap XL (after installation parameters were modified) exhibited MMA ≤ 3 ppm, good spectral accuracy (χ
2
values for the isotopic distribution ≤ 2), and were correctly able to ascertain the number of sulfur atoms in the compound at all resolving powers investigated for AGC targets of 5.00 × 10
5
and 1.00 × 10
6
.
Journal Article