排序方式: 共有32条查询结果,搜索用时 31 毫秒
1.
Mitchell RH Ward TR Chen Y Wang Y Weerawarna SA Dibble PW Marsella MJ Almutairi A Wang ZQ 《Journal of the American Chemical Society》2003,125(10):2974-2988
The syntheses of several new simple negative, a simple positive, and multiple negative photochromes containing the dihydropyrene-cyclophanediene photochromic system are described. The photo-openings of the negative photochromes, the [e]-annelated benzo (7), naphtho (9), anthro (11), furano (19), and triphenyleno (15) derivatives of the parent 2,7-di-tert-butyl-trans-10b,10c-dimethyl-dihydropyrene (5), as well as its 4,5-dibromo derivative (13), are described to give the corresponding cyclophanedienes, as well as their photoclosures and thermal closures back to the dihydropyrenes. These are compared to the results obtained for the positive photochrome dibenzo[e,l]dihydropyrene (21) and to the bis(dihydropyreno)chrysene (44) and the (dihydropyrenobenzo)(benzo)metacyclophanediene (47) photochromes, which have more than one photochromic switch present and thus have more than a simple "on-off" state. Thermodynamic data are obtained for the thermal closing reactions. The anthrodihydropyrene (12) has the fastest thermal closing (tau(1/2) = 20 min), while the furanodihydropyrene (19') has the slowest (tau(1/2) = 63 h) at 46 degrees C. An electrochemical readout of the state of the switch is demonstrated for the benzodihydropyrene (7). 相似文献
2.
Salma A. Al-Tamimi Fatma A. Aly Adibah M. Almutairi 《Journal of Analytical Chemistry》2013,68(4):313-320
Simple and sensitive kinetic spectrophotometric methods were established for the determination of alfuzosin hydrochloride in bulk and in its pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The methods involve determination of alfuzosin HCl by kinetic studies of its oxidation at room temperature for a fixed time of 15 min. The absorbance of the colored manganate ions was measured at 610 nm. Alternatively, the decrease in the absorbance of permanganate upon addition of the studied drug was also measured at 525 nm. The absorbance-concentration plots in both procedures were rectilinear over the range of 2.0–30.0 μg/mL. The different experimental parameters affecting the development were carefully studied and optimized. The determination of alfuzosin HCl by the fixed concentration and initial rate methods is also feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. Both procedures were applied to the determination of alfuzosin HCl in formulations. The results obtained were in good agreement with those obtained using reference methods. 相似文献
3.
Andrew N. Cammidge Rebecca J. Turner Rhoda D. Beskeni Tahani Almutairi 《Liquid crystals》2017,44(12-13):2018-2028
ABSTRACTWe report the unexpected observation of columnar mesophase formation in a simple 2,7-dibromotetramethoxytriphenylene – by far the most lightly substituted discotic mesogen in this class. This derivative was prepared alongside the 3,6-dibromotriphenylene isomer to demonstrate an alternative, modified synthetic strategy that permits late-stage interchange of alkyl chain substituents. The new method is employed alongside the original route to deliver several new materials, including a conjugated ferrocene–triphenylene–ferrocene triad, a BODIPY–triphenylene–BODIPY triad and a new nematic twin linked through imine bridges. 相似文献
4.
Near infrared (NIR) irradiation can penetrate up to 10 cm deep into tissues and be remotely applied with high spatial and temporal precision. Despite its potential for various medical and biological applications, there is a dearth of biomaterials that are responsive at this wavelength region. Herein we report a polymeric material that is able to disassemble in response to biologically benign levels of NIR irradiation upon two-photon absorption. The design relies on the photolysis of the multiple pendant 4-bromo7-hydroxycoumarin protecting groups to trigger a cascade of cyclization and rearrangement reactions leading to the degradation of the polymer backbone. The new material undergoes a 50% Mw loss after 25 sec of ultraviolet (UV) irradiation by single photon absorption and 21 min of NIR irradiation via two-photon absorption. Most importantly, even NIR irradiation at biologically benign laser power is sufficient to cause significant polymer disassembly. Furthermore, this material is well tolerated by cells both before and after degradation. These results demonstrate for the first time a NIR sensitive material with potential to be used for in vivo applications. 相似文献
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6.
Nilghaz A Wicaksono DH Gustiono D Abdul Majid FA Supriyanto E Abdul Kadir MR 《Lab on a chip》2012,12(1):209-218
This paper describes the fabrication of microfluidic cloth-based analytical devices (μCADs) using a simple wax patterning method on cotton cloth for performing colorimetric bioassays. Commercial cotton cloth fabric is proposed as a new inexpensive, lightweight, and flexible platform for fabricating two- (2D) and three-dimensional (3D) microfluidic systems. We demonstrated that the wicking property of the cotton microfluidic channel can be improved by scouring in soda ash (Na(2)CO(3)) solution which will remove the natural surface wax and expose the underlying texture of the cellulose fiber. After this treatment, we fabricated narrow hydrophilic channels with hydrophobic barriers made from patterned wax to define the 2D microfluidic devices. The designed pattern is carved on wax-impregnated paper, and subsequently transferred to attached cotton cloth by heat treatment. To further obtain 3D microfluidic devices having multiple layers of pattern, a single layer of wax patterned cloth can be folded along a predefined folding line and subsequently pressed using mechanical force. All the fabrication steps are simple and low cost since no special equipment is required. Diagnostic application of cloth-based devices is shown by the development of simple devices that wick and distribute microvolumes of simulated body fluids along the hydrophilic channels into reaction zones to react with analytical reagents. Colorimetric detection of bovine serum albumin (BSA) in artificial urine is carried out by direct visual observation of bromophenol blue (BPB) colour change in the reaction zones. Finally, we show the flexibility of the novel microfluidic platform by conducting a similar reaction in a bent pinned μCAD. 相似文献
7.
Fomina N McFearin CL Almutairi A 《Chemical communications (Cambridge, England)》2012,48(73):9138-9140
Photoactivation using two photons of NIR allows non-invasive biological manipulation. We applied the principle of dendritic amplification to improve the materials' sensitivity to NIR light. Light induced uncaging or release of L-glutamic acid was 2.8 fold higher when incorporating 4-bromo-7-hydroxycoumarin (Bhc) with self-immolative dendrimers compared with Bhc directly conjugated to L-glutamic acid. 相似文献
8.
Shakya Anshul Chikhale Rupesh V. Bhat Hans Raj Alasmary Fatmah Ali Almutairi Tahani Mazyad Ghosh Surajit Kumar Alhajri Hassna Mohammed Alissa Siham A. Nagar Shuchi Islam Md Ataul 《Molecular diversity》2022,26(1):265-278
Molecular Diversity - Transmembrane protease serine-2 (TMPRSS2) is a cell-surface protein expressed by epithelial cells of specific tissues including those in the aerodigestive tract. It helps the... 相似文献
9.
In this paper, we investigate the problem of designing ℋ∞ filter for a class of continuous-time uncertain singular systems with nonlinear perturbations, which can be realized in practice.
The perturbation is a time-varying function of the system state and satisfies a Lipschitz constraint. The design objective
is to guarantee that a prescribed upper bound on an ℋ∞ performance of the robust filter is attained for all possible energy-bounded input disturbances and all admissible uncertainties
and which can be implemented on-line to get a good replica of the state. We first establish sufficient condition for the existence
and uniqueness of solution to the singular system connected with the normal filter. Using a linear matrix inequality (LMI)
format, we then provide a sufficient condition for the asymptotic stability of the realizable ℋ∞ filter. Then by means of a convex analysis procedure the filter gain matrices are derived and an important special case is
readily deduced. Finally, a numerical example is presented to illustrate the theoretical developments. 相似文献
10.
Zribi Mohamed Almutairi Naif Abdel-Rohman Mohamed Terro Mohamed 《Nonlinear dynamics》2004,35(1):61-80
This paper presents two control schemes to control the dynamicresponse of an offshore steel jacket platform due to wave-inducedforces. The objective of the controllers is to greatly reduce theinternal system oscillations and to obtain a smooth response ofthe steel jacket platform when subjected to nonlinear self-excitedhydrodynamic forces. The first controller is a nonlinearcontroller whose design is based on Lyapunov theory. The secondcontroller is a robust state feedback linear controller whosedesign is based on an optimal control approach. Both controlschemes guarantee the asymptotic stability of the system. Thetheoretical developments are illustrated through simulationresults of the proposed control schemes. Furthermore, theperformance of the offshore steel jacket platform is presentedwhen a direct velocity feedback controller is applied to thesystem. It is found that the performance of the system with theproposed controllers is better than the performance of the systemwith the direct velocity feedback controller. 相似文献