排序方式: 共有73条查询结果,搜索用时 15 毫秒
51.
Let R be a ring with center Z(R). An additive mapping ${F : R \longrightarrow R}$ is said to be a generalized derivation on R if there exists a derivation ${d : R \longrightarrow R}$ such that F(xy) = F(x)y + xd(y), for all ${x, y \in R}$ (the map d is called the derivation associated with F). Let R be a semiprime ring and U be a nonzero left ideal of R. In the present note we prove that if R admits a generalized derivation F, d is the derivation associated with F such that d(U) ≠ (0) then R contains some nonzero central ideal, if one of the following conditions holds: (1) R is 2-torsion free and ${F(xy) \in Z(R)}$ , for all ${x, y \in U}$ , unless F(U)U = UF(U) = Ud(U) = (0); (2) ${F(xy) \mp yx \in Z(R)}$ , for all ${x,y \in U}$ ; (3) ${F(xy) \mp [x,y] \in Z(R)}$ , for all ${x,y \in U}$ ; (4) F ≠ 0 and F([x,y]) = 0, for all ${x, y \in U}$ , unless Ud(U) = (0); (5) F ≠ 0 and ${F([x, y]) \in Z(R)}$ , for all ${x, y \in U}$ , unless either d(Z(R))U = (0) or Ud(U) = (0)n. 相似文献
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Wireless monitoring systems with passive surface acoustic wave (SAW) sensors offer novel and prodigious perspectives for remote monitoring and control in harsh environments. This paper reviews the working principle of such passive sensors and their state-of-the-art behavior. All major fields of the SAW sensor require operation over a longer reading range, which is the current limitation, hindering the massive implementation of these passive devices. This foremost limitation of the SAW based sensor system occurs when the reply signal strength at the reader becomes too weak for reliable recognition and identification. SAW sensor network read range limitations and advanced techniques for its enhancement are deliberated. Deployment design to maintain the communication reliability and connectivity of the sensor/interrogators network is also discussed. 相似文献
53.
Franzmann E Khalil F Weidmann C Schröder M Rohnke M Janek J Smarsly BM Maison W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(31):8596-8603
By following a biomimetic design principle, tetravalent scaffolds based on an adamantyl and trisalkylmethyl core structure have been synthesized. These scaffolds have been coupled to three catecholamines, thus resembling the characteristic tripodal recognition motif of many natural metal binders, such as mussel adhesion proteins and siderophores, for example, enterobactin. Besides this tripodal recognition element, our scaffolds provide a fourth position for the conjugation of effector molecules. These effectors can be conjugated through biocompatible conjugation techniques to the scaffold and can be used to tailor the properties of different metal surfaces for a range of applications, for example, in implant engineering. Herein, we describe the synthesis of several tripodal metal binders and their immobilization on TiO(2) surfaces by using a simple dip-coating procedure. Furthermore, we demonstrate the conjugation of our surface binders to the dye eosin Y as an effector molecule by peptide coupling. The resulting surfaces have been analyzed by using ellipsometry, time-of-flight secondary ion mass spectrometry, IR spectroscopy, and contact-angle measurements to confirm the specific loading on TiO(2) films and nanoparticles with our trivalent surface binders. As a proof of concept, we have demonstrated the functionalization of TiO(2) nanoparticles with the eosin Y dye. 相似文献
54.
Faiza A.Salama 《Acta Mechanica Sinica》2011,27(4):531-540
A boundary layer analysis is presented to investigate numerically the effects of radiation,thermophoresis and the dimensionless heat generation or absorption on hydromagnetic flow with heat and mass transfer over a flat surface in a porous medium.The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and they are solved numerically by using the fourth order Runge-Kutta method with shooting technique for some values of physical parameters.Comparisons with previously published work are performed and the results are found to be in very good agreement.Many results are obtained and a representative set is displayed graphically to illustrate the influence of the various parameters on the dimensionless velocity,temperature and concentration profiles as well as the local skin-friction coefficient,wall heat transfer,particle deposition rate and wall thermophoretic deposition velocity.The results show that the magnetic field induces acceleration of the flow,rather than deceleration(as in classical magnetohydrodynamics(MHD) boundary layer flow) but to reduce temperature and increase concentration of particles in boundary layer.Also,there is a strong dependency of the concentration in the boundary layer on both the Schmidt number and mass transfer parameter. 相似文献
55.
Synthesis and affliations of oxophosphonates in organic chemistry. This work devoted to oxophosphonates deals with three different series of compounds: the α-ketophosphonates, the β-ketophosphonates and finally the γ- and δ-ketophosphonates which were considered as one series of compounds. For each type of products, the various synthetic methods as well as their reactivity were presented. In the last part, we have developed different methods of reduction, nucleophilic addition and substitution reactions. Particular attention was focused on sulfur and nitrogen containing derivatives as well as fluorinated and chlorinated compounds. 相似文献
56.
Faiza?ShujatEmail author Shahoor?Khan 《Rendiconti del Circolo Matematico di Palermo》2015,64(1):77-81
Let \(R\) be a prime ring, \(L\) a noncentral Lie ideal of \(R\), \(F\) a generalized derivation with associated nonzero derivation \(d\) of \(R\). If \(a\in R\) such that \(a(d(u)^{l_1} F(u)^{l_2} d(u)^{l_3} F(u)^{l_4} \ldots F(u)^{l_k})^{n}=0\) for all \(u\in L\), where \(l_1,l_2,\ldots ,l_k\) are fixed non negative integers not all are zero and \(n\) is a fixed integer, then either \(a=0\) or \(R\) satisfies \(s_4\), the standard identity in four variables. 相似文献
57.
Mejri Faiza Karmali Amin Jaoued Najeh Casabianca Hervé Hosni Karim 《Applied biochemistry and biotechnology》2019,189(2):576-588
Applied Biochemistry and Biotechnology - In this study, peroxidases (PODs) from three waste by-products: broad bean pods (BBP), pea pods (PP), and artichoke stems (ARS) were purified and their... 相似文献
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59.
Faiza?Zarif Sajid?Rauf Muhammad?Zahid?Qureshi Noor?Samad?Shah Akhtar?HayatEmail author Nawshad?MuhammadEmail author Abdur?Rahim Mian?Hasnain?Nawaz Muhammad?Nasir 《Mikrochimica acta》2018,185(6):302
Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30–300 μM H2O2 concentration range, and the detection limit is 0.15 μM. 相似文献
60.
A series of nano-sized single phase W-type SrGaxZn2Fe16?xO27 (x = 0.0, 0.1, 0.2, 0.3, 0.4) hexaferrites prepared by sol gel technique and sintered at 950 °C have been investigated. The thermal decomposition behavior of nitrate–citrate gel of as prepared powder was investigated by means of DTA/TGA analysis. The sintered powders were characterized by FTIR, XRD, SEM, VSM and vector network analyzer (VNA). X-ray diffraction patterns for pure and substituted W-type hexaferrites show the single phase structure with no impurity phase. The lattice parameters (a and c) decrease with the increase of Ga contents (x). The grain size estimated from SEM images is in the range of 139–76 nm which confirms the nanocrystalline nature of the investigated samples. The saturation magnetization (Ms) decreases whereas coercivity (Hc) increases with the increase of Ga contents (x). The values of Hc for all of the investigated samples lie in the range of few hundred oersteds which is one of the necessary conditions for EM materials. The microwave absorption property is enhanced in the frequency (with respect to ?20 dB) from 0.5 to 13 GHz, and the bandwidth reaches 0.899 GHz. The attenuation peak value is ?32 dB at the matching thickness of 3.4 mm. 相似文献