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排序方式: 共有109条查询结果,搜索用时 78 毫秒
51.
M. Z. Garaev S. V. Konyagin Yu. V. Malykhin 《Proceedings of the Steklov Institute of Mathematics》2012,276(1):77-89
For fixed q ∈ (0, 4), prime p → ∞, and \(d \leqslant \exp \left( {c\sqrt {\ln p} } \right)\), where c > 0 is a constant, we obtain the asymptotics for the sum of qth powers of distances between neighboring residues of degree d modulo p. 相似文献
52.
We establish a new bound for the exponential sum
where λ is an element of the residue ring modulo a large prime number
and
are arbitrary subsets of the residue ring modulo p − 1 and γ (n) are any complex numbers with | γ (n)| ≦ 1.
Received: 15 June 2005 相似文献
53.
I. Kh. Garaev A. V. Kostochko A. I. Petrov E. N. Ibragimov A. E. Golubev 《Russian Journal of General Chemistry》2016,86(6):1469-1475
Methods of structuring thermoreversible urethane block copolymers on the basis 3,3-bis-(azidomethyl)oxetane (BAMO) and 3-(azidomethyl)-3-methyloxetane (AMMO) were developed for the first time. Type (AB)n copolymers of BAMO and AMMO have an amorphous crystalline structure but differ from the type B(AB)n copolymers in that they contain less crystal phase and have a higher glass transition temperature and better physicomechanical properties. 相似文献
54.
Woohyung Jeon Ramil Baiazitov Matteo Chierchia Kyle Niederer Hongyu Ren Young-Choon Moon Bradley B. Gilbert 《Helvetica chimica acta》2023,106(9):e202300091
A variety of di- and trifluoromethyl-s-triazines are prepared following straightforward synthetic protocols from simple, commercially available starting materials. Trichloromethyl-substituted triazine electrophiles are obtained in good yield and react with amine nucleophiles to afford aminotriazine products in good to excellent yield. The nucleophilic aromatic substitution reaction is broad in scope and proceeds smoothly with both aromatic and aliphatic (primary, secondary, and branched) amines in the presence of non-participating functional groups including alcohols, carboxylic acids, indoles, and common amine protecting groups. Furthermore, most reactions require only a catalytic amount of 4-DMAP with no stoichiometric base and are complete within two hours at ambient temperature. 相似文献
55.
Mathematical Notes - 相似文献
56.
57.
Fontana AR Rodríguez I Ramil M Altamirano JC Cela R 《Analytical and bioanalytical chemistry》2011,401(2):767-775
This work evaluates the suitability of sorptive microextraction, using disposable silicone sorbents, and liquid chromatography
time-of-flight mass spectrometry (LC-TOF-MS) for the determination of 15 fungicides in wine. Under optimized conditions, wine
samples (10 mL) were diluted with the same volume of ultrapure water and poured in a glass vessel containing a magnetic stirrer
and 4 g of sodium chloride. Extractions were performed at room temperature for 4 h, using an inexpensive silicone disk (12 μL
volume) exposed directly to the sample. Thereafter, analytes were recovered with 0.2 mL of acetonitrile. The electrospray
ionization (ESI) source was operated in the fast polarity switching mode obtaining, in the same injection, selective LC-MS
records (extracted with a mass window of 10 ppm) of compounds rendering [M + H]+ and [M-H]− ions. The method provided limits of quantification (LOQs) between 0.1 and 2.2 ng mL−1, linear response ranges up to 500 ng mL−1, relative recoveries from 75% to 117% and an inter-day variability below 15% for all analytes in red and white wine samples.
The feasibility of in situ sample enrichment followed by delayed desorption and analysis is also assessed. 相似文献
58.
Gupta V Chaudhary N Srivastava R Sharma GD Bhardwaj R Chand S 《Journal of the American Chemical Society》2011,133(26):9960-9963
Recent research in organic photovoltaic (OPV) is largely focused on developing low cost OPV materials such as graphene. However, graphene sheets (GSs) blended conjugated polymers are known to show inferior OPV characteristics as compared to fullerene adduct blended with conjugated polymer. Here, we demonstrate that graphene quantum dots blended with regioregular poly(3-hexylthiophene-2,5-diyl) or poly(2-methoxy-5-(2-ethylhexyloxy)-1,4phenylenevinylene) polymer results in a significant improvement in the OPV characteristics as compared to GSs blended conjugated polymers. This work has implications for inexpensive and efficient solar cells as well as organic light emitting diodes. 相似文献
59.
Fontana AR Rodríguez I Ramil M Altamirano JC Cela R 《Journal of chromatography. A》2011,1218(16):2165-2175
In this work, a reliable and selective procedure for the determination of thirteen fungicides in red and white wine samples is proposed. Solid-phase extraction (SPE) and liquid chromatography (LC) tandem mass spectrometry (MS/MS), based on a hybrid quadrupole time-of-flight (QTOF) system, were used as sample preparation and determination techniques, respectively. Extraction and purification of target analytes was carried out simultaneously by using a reversed-phase Oasis HLB (200mg) SPE cartridge combined with acetonitrile as elution solvent. Fungicides were determined operating the electrospray source in the positive ionization mode, with MS/MS conditions adjusted to obtain at least two intense product ions per compound, or registering two transitions per species when a single product was noticed. High selective MS/MS chromatograms were extracted using a mass window of 20 ppms for each product ion. Considering external calibration as quantification technique, the overall recoveries (accuracy) of the procedure ranged between 81% and 114% for red and white wine samples (10-20 mL), spiked at different concentrations between 5 and 100 ng mL(-1). Relative standard deviations of the above data stayed below 12% and the limits of quantification (LOQs) of the method, calculated for 10 mL of wine, varied between 0.1 ng mL(-1) for cyprodinil (CYP) and 0.7 ng mL(-1) for myclobutanil (MYC). The optimized method was applied to seventeen commercial wines produced in Spain and obtained from local supermarkets. Nine fungicides were determined, at levels above the LOQs of the method, in the above samples. The maximum concentrations and the highest occurrence frequencies corresponded to metalaxyl (MET) and iprovalicarb (IPR). 相似文献
60.
Let p be a large prime number, K, L, M, λ be integers with 1 ≤ M ≤ p and gcd(λ, p) = 1. The aim of our paper is to obtain sharp upper bound estimates for the number I
2(M; K, L) of solutions of the congruence
xy o l (mod p), K+ 1 £ x £ K +M, L+ 1 £ y £ L +M,xy \equiv \lambda \quad ({\rm mod} p), \quad K+ 1 \leq x \leq K +M,\quad L+ 1 \leq y \leq L +M, 相似文献 |