Characterization of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized by various methods

Microwave-induced combustion with glycine, CTAB-assisted hydrothermal process with NaOH and NH3, EDTA assisted-hydrothermal methods have been applied to prepare NiFe₂O₄ nanoparticles for the first time. Structural and magnetic properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmison electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and electron spin resonance spectrometry (EPR). TEM measurements showed that morphology of the product depends on the synthesis method employed. The average cystallite size of NiFe₂O₄ nanoparticles was in the range of 14–59 nm as measured by XRD. The uncoated sample (Method A) had an EPR linewidth of 1973 Oe, the coated samples reached lower values. The magnetic dipolar interactions existing among the Ni ferrite nanoparticles are reduced by the coatings, which could cause the decrease in the linewidth of the EPR signals. Additionally, the linewidth increases with an increase in the size and the size distribution of nanoparticles.     

Evolution of the degree of polarization of an electromagnetic Gaussian Schell-model beam in a Gaussian cavity

The interaction of an electromagnetic Gaussian Schell-model (EGSM) beam with a Gaussian cavity is analyzed. In particular, the evolution of the degree of polarization of the EGSM beam is investigated. The results show that the behavior of the degree of polarization depends on both the statistical properties of the source that generates the EGSM beam and the parameters of the cavity.     

Scintillations of laser array beams

The scintillation index of a laser array beam is analytically derived and numerically evaluated for weak turbulence conditions. On-axis as well as off-axis positions of the receiver plane are considered. Our graphical illustrations prove that at longer propagation ranges and at some midrange radial displacement parameters, laser array beams exhibit less scintillations, when compared to a fundamental Gaussian beam. However, when compared among themselves, laser array beams tend to have reduced scintillations with rising numbers of beamlets, longer propagation wavelengths, at midrange radial displacement parameters, at intermediate Gaussian source sizes, at bigger inner scales and smaller outer scales of turbulence. However, in this improvement, the number of beamlets does not seem to have a major role. PACS 42.25.Dd; 42.25.Ja; 42.25.Kb     

阴离子对鼠尾草提取物中Ni盐前体绿色合成的NiO纳米粒子磁性和结构性能的影响

采用绿色合成方法,将鼠尾草提取物用作还原和封端剂合成氧化镍纳米颗粒(NiO NPs)。此外,使用各种前驱体合成了NiO NPs,并使用扫描电子显微镜对其形貌进行了分析。利用傅里叶变换红外光谱和粉末X射线衍射(PXRD)对NiO NPs的结构进行了表征,使用振动样品磁强计测量了它们的磁性。PXRD研究表明,所有合成的NiO NPs都表现出具有高结晶度的面心立方相,并且形成了具有高纯度相的NiO。磁化研究结果表明,3种镍盐(乙酸盐、氯化物和硫酸盐)前驱体合成的NiO NPs分别表现出超顺磁、软铁磁和顺磁行为。     

Optimal control policies for ambulance diversion

Ambulance diversion (AD) is used by emergency departments (EDs) to relieve congestion by requesting ambulances to bypass the ED and transport patients to another facility. We study optimal AD control policies using a Markov Decision Process (MDP) formulation that minimizes the average time that patients wait beyond their recommended safety time threshold. The model assumes that patients can be treated in one of two treatment areas and that the distribution of the time to start treatment at the neighboring facility is known. Assuming Poisson arrivals and exponential times for the length of stay in the ED, we show that the optimal AD policy follows a threshold structure, and explore the behavior of optimal policies under different scenarios. We analyze the value of information on the time to start treatment in the neighboring hospital, and show that optimal policies depend strongly on the congestion experienced by the other facility. Simulation is used to compare the performance of the proposed MDP model to that of simple heuristics under more realistic assumptions. Results indicate that the MDP model performs significantly better than the tested heuristics under most cases. Finally, we discuss practical issues related to the implementation of the policies prescribed by the MDP.     

FTIR studies of vitamin E-cholesterol-DPPC membrane interactions in CH 2 region

Binary and ternary mixtures of -tocopherol (T), cholesterol and dipalmitoyl phosphatidylcholine (DPPC) in the form of multilamellar liposomes have been investigated by Fourier Transform Infrared Spectroscopy (FTIR). Investigation of frequencies, bandwidths and band shapes of CH₂ stretching and scissoring bands indicate that the effect of T is dominant in comparison with cholesterol and T decreases the interaction of cholesterol with phospholipid membranes.     

Correlation properties of random electromagnetic beams in laser resonators

With the help of the generalized Huygens–Fresnel principle and the tensor approach for electromagnetic stochastic beams we investigate the behavior of their two-point spatial correlation properties on interaction with a laser resonator. In particular, the evolution of the degree of coherence, of the degree of cross-polarization and of the intensity correlations (at one and two points in space) is analyzed for typical beams and cavities. The theory is illustrated by numerical curves pertaining to various correlation properties of typical electromagnetic Gaussian Schell-model beams.     

Effects of extremely strong turbulent medium on scintillations of partially coherent annular and flat-topped Gaussian beams

Scintillation index of partially coherent annular and partially coherent flat-topped Gaussian beams propagating in horizontal links is found at the receiver origin when these beams propagate in extremely strong atmospheric turbulence. Scintillation index of coherent versions of such beams attain unity saturation value whereas the decrease in the degree of source coherence results in the decrease of the scintillations. At a fixed degree of partial coherence, thin ring sized annular beams possess smaller scintillations than thick ones. For partially coherent flat-topped Gaussian beams, higher flatness yields smaller intensity fluctuations. In extremely strong turbulence, partially coherent annular and partially coherent flat-topped Gaussian beams have smaller scintillations when compared to partially coherent single Gaussian beam scintillations.     

Twist phase-induced reduction in scintillation of a partially coherent beam in turbulent atmosphere

The scintillation index of a Gaussian Schell-model beam with twist phase (i.e., twisted GSM beam) in weak turbulent atmosphere is formulated with the help of a tensor method. Variations of the scintillation index of a twisted GSM beam on propagation in turbulent atmosphere are studied in detail. It is interesting to find that the scintillation index of a twisted GSM beam can be smaller than that without twist phase in weak turbulent atmosphere. Thus, modulation of the twist phase of a partially coherent beam provides a new way to reduce turbulence-induced scintillation.     

Energy and Momentum of Higher Dimensional Black Holes

In this paper, we devote to investigate the energy-momentum problem of higher dimensional black holes in the general theory of relativity. The energy and momentum complex of M?ller has been used for the calculations. Also, total energy and total momentum of some special cases for higher dimensional black holes such as Schwarzschild-like black holes, Reissner-Nordstr?m-like charged black holes, AdS-like black holes, topological black holes, BTZ-like and charged BTZ-like black holes were obtained. It is invented that the momentum of black holes vanishes everywhere while the energy of black holes are not equal to zero in higher dimension. Also the results agree with Yang and Radinschi or Vagenas results in three and four dimensional black holes, respectively (Jang and Radinschi in AIP Conf. Proc. 895, 325, 2007; Vagenas in Mod. Phys. Lett. A 21, 1947, 2006).