Synthesis and characterization of nanomagnetite particles and their polymer coated forms

Superparamagnetic nanoparticles were prepared by coprecipitation of ferrous (Fe(2+)) and ferric (Fe(3+)) aqueous solution by a base. Nanomagnetite particles were coated with poly(St/PEG-EEM/DMAPM) and poly(St/PEG-MA/DMAPM) layer by emulsifier-free emulsion polymerization. Chemical structure of nanoparticles was characterized by both FTIR and (1)H NMR. Particle morphologies were determined by Zeta Sizer, DLS, XRD and SAXS. Structural analysis showed that after polymer coating nanomagnetite particles kept their superparamagnetic property. Besides the synthesized magnetites, polymer coated forms of these particles are more biocompatible, well dispersable and uniform. These properties make them a very strong candidate for bioengineering applications, such as bioseparation, gene transfer.     

In vitro cytotoxic evaluation of a novel phosphinyl derivative of boldine

2,9-Dimethoxymethylboldine (2), 2,9-dimethoxymethyl-3-bromoboldine (3) and 2,9-dimethoxymethyl-3-diphenylphosphinylboldine (4) have been synthesized in an effort to find compounds with potential pharmacological applications. The cytotoxic activities of the natural precursor 1 and these three derivatives have been measured as IC?? inhibitory growth. The diphenylphosphinyl derivative 4 showed a significant cytotoxic activity on two breast cancer cell lines, namely MCF-7 and MDA-MB-231, with IC?? values of 55.5 and 62.7 [μM], respectively. These results suggest that the kind of structural modifications introduced to synthesize compound 4 represent a promising way to enhance the cytotoxic activity of boldine derivatives.     

Equation of state of CaMnO3: a combined experimental and computational study

Elastic properties of CaMnO₃ are of primary importance in the science and technology of CaMnO₃-based perovskites. From X-ray diffraction experiments performed at pressures up to 100 kbar using a diamond-anvil cell to hydrostatically compress our sample, a bulk modulus, K ₀, of 1734(96) kbar was obtained after fitting parameters to the third-order Birch–Murnaghan equation of state. Mean field, semiclassical simulations predict, for the first time, the third-order equation-of-state parameters and show how the bulk modulus increases with pressure (the zero pressure value being 2062.1 kbar) and decreases with the extent of nonstoichiometry caused by the formation of oxygen vacancies. These trends are amplified for the shear modulus. A more accurate model that allows for the explicit reduction of Mn ions, or localization of excess electrons, yields qualitatively similar results. The experimental and calculated axial ratios show the same trends in their variation with rising pressure.     

Electron paramagnetic resonance studies on manganite Pr0.5Sr0.5Mn1−x Ga x O3 (x=0 and 0.05)

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite Pr_0.5Sr_0.5MnO₃ and Ga-doped Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth ΔH _pp and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T _C. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃ instead of Pr_0.5Sr_0.5MnO₃ system. As for Pr_0.5Sr_0.5MnO₃, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism.     

高温超导热图像信号采集和处理系统

本文介绍一种高温超导热图像信号采集和处理系统，采用在ＰＣ机中插入采集板的硬件结构和Ｃ语言与汇编语言混合编程的软件设计方法，实现了对高温超导热图像信号的采集和图像处理，图像管理，图像显示等多种功能。     

凝视热成像系统MTF斜缝法测试技术研究

凝视热成像系统MTF测试不同于扫描系统，必须有解决其空间采样的混淆特性。在传统的线扩展函数法基础上发展起来的方法主要有：缝扫描法、最值法、斜斜法。实际使用中，前两种方法需要精确的定位技术，而斜缝法的数据处理较复杂。本文主要论述斜缝测试法，分析其工作原理，介绍其数据处理技术。     

新疆石头花属植物分类研究及其生态地理分布

Gypsophila L.中国有25种。1980年出版的“新疆植物检索表”第二册中收载了5种。“新疆植物名录”中收载了4种。中国高等植物图鉴补编(1:336,1982)收载了11种。本文按现行新疆维吾尔自治区的行政范围进行整理研究,共收载了12种,其中发现全国分布新纪录2种—G.capitata M.B.,G.sericea(Ser.)Kryl.新疆分布新纪录1种—G.licentiana Hand—Mazz。本文阐明了新疆境内石头花属植物的生态、地理分布特点。在新疆境内本属植物的区系地理成分主要是亚洲中部的草原和荒漠成分。     

Correlation between melting behavior and ringed spherulites in poly(trimethylene terephthalate)

The lamellar types as revealed by the multiple melting peaks and possible mechanisms of ringed spherulites in poly(trimethylene terephthalate) (PTT) were analyzed with differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy. Several interesting correlations were found. If PTT is melt‐crystallized in a certain temperature range, it shows multiple melting peaks and rings in PTT. Once rings are formed in the original melt‐crystallized PTT, they do not disappear but persist and become even more apparent upon postcrystallization annealing at higher temperatures. Furthermore, for PTT that is capable of exhibiting ringed spherulites, a temperature range exists where rings do not form. This behavior can be interpreted in relation with the demonstrated thermal behavior in PTT. Reorganization took place upon postcrystallization scanning or annealing to or at higher temperatures. A postulation was proposed and rigorously tested with evidence to correlate the ringed spherulites and melting behavior. Rings in PTT may be related to multiple lamellae in the spherulites. Consequently, if a temperature of crystallization is selected so that there is only one type of lamella in the spherulites, then there should be no rings. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 80–93, 2002     

Iterative solving of variational inclusions under Wijsman perturbations

We prove that the metric regularity of set-valued mappings is stable under some Wijsman-type perturbations. Then, we solve a variational inclusion viewed as a limit-problem using assumptions on a sequence of associated problems. Finally, we apply our results to classical methods for solving variational inclusions.      

Nucleon currents between highly excited nuclei: (II). Influence of the relative motion

A finite-temperature Thomas-Fermi method has been used to study the nucleon flux between two hot semi-infinite slabs of nuclear matter in arbitrary relative motion. As an application, we estimate the imaginary part of the optical potential associated with nucléon transfer at the strong absorption radius. Analytical fits to the exact results are given for head-on and tangential collisions at zero temperature.