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排序方式: 共有152条查询结果,搜索用时 15 毫秒
11.
Mehmet Yaman 《光谱学与光谱分析》2013,32(5):1331-1337
The aim of this study is to examine seasonal changes in Cu and Co concentrations of three plant species for monitoring the effects of pollution in Elazig,Turkey.For this purpose,the leaves of the Pinus nigra L.,Cedrus libani and Cupressus arizonica together with soil samples were collected from different points depending on traffic intensity,nearness the city center and cement factory as well as control location during different months of the year.Flame atomic absorption spectrophotometer(FAAS) was used for measurement of the metals in clear digests after the dry ashing method.Copper and Co concentrations were in the ranges from 1.3to 2.6mg.kg-1 and相似文献
12.
Oil-based polyurethanes were synthesized from triglyceride oil-based hydroxyl containing material and toluene diisocyanate or hexamethylene diisocyanate for wound dressing applications. The reactions were carried out with or without catalyst at 90 °C. The amount of free isocyanate during the reaction was determined by a FTIR-ATR method, and the results were compared with those from a back-titration method. The data obtained were used for determination of kinetic parameters. 相似文献
13.
Erhan Temur İsmail Hakkı Boyacı Uğur Tamer Hande Unsal Nihal Aydogan 《Analytical and bioanalytical chemistry》2010,397(4):1595-1604
A very sensitive and highly specific heterogeneous immunoassay system, based on surface-enhanced Raman scattering (SERS) and
gold nanoparticles, was developed for the detection of bacteria and other pathogens. Two different types of gold nanoparticles
(citrate-stabilized gold nanosphere and hexadecyltrimethylammonium bromide (CTAB)-stabilized gold nanorod particles) were
examined and this immunoassay was applied for the detection of Escherichia coli. Raman labels were constructed by using these spherical and rod-shaped gold nanoparticles which were first coated with 5,5′-dithiobis(2-nitrobenzoic
acid) (DTNB) and subsequently with a molecular recognizer. The working curve was obtained by plotting the intensity of the
SERS signal of the symmetric NO2 stretching of DTNB at 1,333 cm−1 versus the concentration of the E. coli. The analytical performance of gold particles was evaluated via a sandwich immunoassay, and linear calibration graphs were
obtained in the E. coli concentration range of 101–105 cfu/mL with a 60-s accumulation time. The sensitivity of the Raman label fabricated with gold nanorods was more than three
times higher than spherical gold nanoparticles. The selectivity of the developed sensor was examined with Enterobacter aerogenes and Enterobacter dissolvens, which did not produce any significant response. The usefulness of the developed immunoassay to detect E. coli in real water samples was also demonstrated. 相似文献
14.
In this paper, we present a primal-dual interior-point method for solving nonlinear programming problems. It employs a Levenberg-Marquardt (LM) perturbation to the Karush-Kuhn-Tucker (KKT) matrix to handle indefinite Hessians and a line search to obtain sufficient descent at each iteration. We show that the LM perturbation is equivalent to replacing the Newton step by a cubic regularization step with an appropriately chosen regularization parameter. This equivalence allows us to use the favorable theoretical results of Griewank (The modification of Newton’s method for unconstrained optimization by bounding cubic terms, 1981), Nesterov and Polyak (Math. Program., Ser. A 108:177–205, 2006), Cartis et al. (Math. Program., Ser. A 127:245–295, 2011; Math. Program., Ser. A 130:295–319, 2011), but its application at every iteration of the algorithm, as proposed by these papers, is computationally expensive. We propose a hybrid method: use a Newton direction with a line search on iterations with positive definite Hessians and a cubic step, found using a sufficiently large LM perturbation to guarantee a steplength of 1, otherwise. Numerical results are provided on a large library of problems to illustrate the robustness and efficiency of the proposed approach on both unconstrained and constrained problems. 相似文献
15.
Hasan Karabıyık Hande Petek Nazan Ocak İskeleli Çiğdem Albayrak Erbil Ağar 《Journal of chemical crystallography》2011,41(11):1642-1648
Abstract
Some molecules having a molecular skeleton similar to that of stilbenes and azobenzenes show orientational disorder in the crystals due to pedal motion. Heretofore, the orientational disorder through pedal motion has been observed for the compounds containing only two aromatic rings in the absence of bulky substituent groups. Here we report that the pedal motion can be detected even in the presence of a bulky substituent group to which orientational disorder becomes invisible as a result of anchor effect arising from phenoxyphtalonitrile group. X-ray crystallographic analysis of the compound, C23H18N4O, reveals the existence of partially overlapped two pedal conformers. The compound crystallizes in the monoclinic space group P21/c with a = 12.9429(11) Å, b = 8.5075(5) Å, c = 21.063(2) Å and β = 123.155(6)°. Major pedal conformer is stabilized by weak C–H···O type hydrogen bond and C–H···π type edge-to-face interactions in solid state. Quantum chemical calculations at B3LYP/6-311G+(d,p) level suggest that the stabilization of the compound decreases with increasing deviation from the planar geometry of trans-azobenzene fragment. 相似文献16.
One perceived deficiency of interior-point methods in comparison to active set methods is their inability to efficiently re-optimize
by solving closely related problems after a warmstart. In this paper, we investigate the use of a primal–dual penalty approach
to overcome this problem. We prove exactness and convergence and show encouraging numerical results on a set of linear and
mixed integer programming problems.
Research of the first author is sponsored by ONR grant N00014-04-1-0145. Research of the second author is supported by NSF
grant DMS-0107450. 相似文献
17.
Hande Yaman 《Mathematical Programming》2006,106(2):365-390
We consider the vehicle routing problem where one can choose among vehicles with different costs and capacities to serve the
trips. We develop six different formulations: the first four based on Miller-Tucker-Zemlin constraints and the last two based
on flows. We compare the linear programming bounds of these formulations. We derive valid inequalities and lift some of the
constraints to improve the lower bounds. We generalize and strengthen subtour elimination and generalized large multistar
inequalities. 相似文献
18.
Mustafa İlhan Ayhan Mergen Cevat Sarıoğlu Cemalettin Yaman 《Journal of Thermal Analysis and Calorimetry》2017,128(2):707-711
Heat capacity measurements of barium tantalate (BaTa2O6) were carried out by using a differential scanning calorimeter at temperatures between 323 and 1323 K. From the heat capacity values of BaTa2O6, other thermodynamic functions (enthalpy and entropy increments) were derived between 298.15 and 1323 K. The C p,m (298.15) value of BaTa2O6 was computed as 184.857 J mol?1 K?1. Moreover, fitted heat capacities exhibited good agreement with Neumann–Kopp rule at the temperatures between 298.15 and 1300 K. 相似文献
19.
Teow Y Asharani PV Hande MP Valiyaveettil S 《Chemical communications (Cambridge, England)》2011,47(25):7025-7038
Many engineered nanomaterials (NMs) are being synthesized and explored for potential use in consumer and medical products. Already, nanoparticles (NPs) of titanium dioxide (TiO(2)), zinc oxide (ZnO), silver (Ag) and other metals or their oxides are present in commercial products such as sunscreens, cosmetics, wound dressings, surgical tools, detergents, automotive paints and tires. More recent and advanced FDA-approved use of NMs includes quantum dots (QDs) in live cell imaging, zirconium oxides in bone replacement and prosthetic devices and nanocarriers in drug delivery. The benefits from nanotechnology are aplenty, comprising antimicrobial activities, scratch- and water-resistance, long-lasting shine, improved processor speeds and better display resolution, to name a few. While developers of these products often focus on the exciting beneficial aspects of their products, safety and toxicity issues are often not discussed in detail. Long-term effects such as chronic exposure and environmental pollution are even less documented. Along with widespread manufacture and use of NMs, concerns for occupational hazards, proper handling, disposal, storage, shipping and clean up are expected to rise. This review focus on the possible biological impact of engineered NPs, serving as a reminder that nanomaterials can become a double-edged sword if not properly handled. 相似文献
20.
报道了0.53μm高功率激光辐照金盘靶产生的受激拉曼散射光光谱和散射光谱能量角分布,由散射光角分布计算的散射光能量与实验通过打靶透镜测得的受激拉曼散射能量不符,而且角的分布的实验结果与受激布里渊散射理论也不符。 相似文献