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81.
Some recent developments in boundary layer instabilities and transition are reviewed. Background disturbance levels determine
the instability mechanism that ultimately leads to turbulence. At low noise levels, the traditional Tollmien-Schlichting route
is followed, while at high levels, a ‘by-pass’ route is more likely. Our recent work shows that spot birth is related to the
pattern of secondary instability in either route. 相似文献
82.
A green and robust reverse-phase liquid chromatographic method has been developed for the determination of fenoverine (FEN), by applying combined principles of green analytical chemistry and quality by design approaches on a Spherisorb C18 column (150?×?4.6?mm, 3?µm) with UV detection at 262?nm. A two level fractional factorial design (2^7-3) Res IV was used for screening of influential chromatographic factors. The critical method parameters actively affecting critical quality attributes (CQAs) were identified and further optimized using Box–Behnken design. The predicted optimum assay conditions comprised of methanol and ammonium acetate buffer 20?mM, in an extent of 81:19% v/v individually having a flow rate of 1.0?mL/min with a column oven temperature of 33°C. The drug was stressed in hydrolytic, oxidative, reductive, thermal, and photolytic conditions. The developed method was validated successfully. The detector response was linear in the concentration of 0.5–160?µg/mL with a limit of detection (LOD) and limit of quantitation (LOQ) as 0.1 and 0.3?µg/mL, respectively. The % recovery was found to be 99.7%. The analytical method volume intensity value for developed method was 45?mL and the environment assessment tool (EAT) score was 41.07. The method is simple, environmentally benign, rapid, and robust for the determination of FEN in bulk and in its dosage form. 相似文献
83.
Highly selective label free colorimetric sensor based on AgNPs stabilized by phenolic chelating ligand, N,N′-bis(2-hydroxybenzyl)-1,2-diaminobenzene (1), for NO2− anions has been developed. Addition of NO2− showed selective decolourisation of brownish yellow colour of 1-AgNPs with the detection limit of 10−7 M. Absorption studies showed the complete disappearance of 1-AgNPs peak at 426 nm due to the conversion of AgNPs to silver ions. The presence silver ions were confirmed by white precipitates of AgCl formation with NaCl. The interference studies confirmed the high selectivity of NO2− sensing in presence of anions as well as cations by 1-AgNPs. A linear relationship was observed between the change of absorption and concentration of NO2−. The present approach could be performed at room temperature and ambient conditions. The practical applications of 1-AgNPs for selective sensing of NO2− in different water samples such as ground, river, pond and tap water have also been demonstrated. 相似文献
84.
85.
A series of novel thiourea based receptors (1-12) with different signaling units and spacers have been synthesized for the detection of cyanide ion. Among these receptors, 4,4'-bis-[3-(4-cyanophenyl)thiourea]diphenyl sulfide 6 and 4,4'-bis-[3-(3-cyanophenyl)thiourea]diphenyl sulfide 9 exhibited selective detection of cyanide by the naked-eye as well as by UV-Vis spectroscopy. Furthermore, the chemosensor is insensitive to the presence of other environmentally relevant anions. The chromogenic transformation permits the detection of cyanide (TBA(+) and K(+) salts) in the natural environment. 相似文献
86.
Organocatalytic conjugate addition of thiols to α-substituted N-acryloyloxazolidin-2-ones followed by asymmetric protonation has been studied in the presence of cinchona alkaloid derived thioureas. Both of the enantiomers are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The addition/protonation products have been converted to useful biologically active molecules. 相似文献
87.
In this paper, a singularly perturbed delay differential equation of first order has been considered. The problem is solved by using a hybrid scheme on a Shishkin mesh. The difference scheme is shown to converge to the continuous solution uniformly with respect to the perturbation parameter. Truncation errors are obtained. Finally, numerical experiments are carried out on a test problem, confirming the effectiveness of the proposed technique. 相似文献
88.
A new chromogenic protocol has been developed for rapid and selective detection of nerve agents like tabun. The chemsensor displayed a drastic color change from its colorless solution to yellow instantaneously with an 89 nm bathochromic shift. No inference of other chemical warfare agents and its mimics was observed either with the naked-eye or by UV-Vis spectroscopy. The development of a portable chemosensor kit for tabun demonstrates its practical application in real-time monitoring. 相似文献
89.
Cyanine dyes are triggered to form fluorescent H-aggregates in IL [C(n)mim][BF(4)], whereas J-aggregates are observed to form in ILs with other anions as 2 wt% 1 M aqueous NaOH is added at room temperature; difference in hydrolytic properties of [BF(4)](-) ILs over other ILs is hypothesized to be the reason. 相似文献
90.