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991.
992.
Papadakis CM Darko C Di Z Troll K Metwalli E Timmann A Reiter G Förster S 《The European physical journal. E, Soft matter》2011,34(1):7-8
We have found very slow crystallization in thin films of cylinder-forming poly(isoprene-b -ethyleneoxide) (P(I-b -EO)) diblock copolymers with PEO being the minority block. The film was crystallized at room temperature after melting at
62 °C . Imaging methods were combined with X-ray reflectometry and grazing-incidence small-angle X-ray scattering and diffraction.
Initially, hexagonally packed, amorphous PEO cylinders lie in the film plane. After 148 days, crystallized, finger-like terraces
were observed over the entire film surface. The terrace height is 20% higher than the repeat distance in the as-prepared film.
Thus, at the film surface, the cylinders have been destroyed by crystalline lamellae lying in the film plane. The PEO chain
stems are perpendicular to the substrate surface and are once-folded and fully interdigitated. The substrate-near layers still
consist of the hexagonally packed, amorphous PEO cylinders within the PI matrix. 相似文献
993.
Hierarchy structure of granum in chloroplast was replicated onto titania using a simple and tactical sonochemical method and calcination. The structures of TiO(2) replicas were characterized by XRD, FE-SEM and TEM and the pore structures were characterized by N(2) adsorption/desorption. As a comparison, the preparation without sonication by using impregnation then calcination method was conducted, which shows the efficiency of the ultrasound on the exact replication of granum from micrometers down to nanometers. The optical properties of the TiO(2) replica, the chloroplast and the commercial pure TiO(2) powder together with the compared replica were measured by absorbance spectroscopy. It was found that the absorbance intensity of the TiO(2) replica made by ultrasonication is much better than the soaked one, and is twice of that of the pure TiO(2) powder in ultraviolet - visible light range. The excellent light harvesting performance of the TiO(2) is attributed to the combination of the functionality from the inorganic oxide and the fine hierarchical biological structures. 相似文献
994.
S. Di Maria S. Barros J. Bento P. Teles C. Figueira M. Pereira P. Vaz G. Paulo 《Radiation measurements》2011,46(10):1103-1108
The main purpose of this study was to validate and compare Mean Glandular Dose (MGD) values obtained using Monte Carlo simulations with experimental values obtained from Entrance Surface Dose (ESD) and depth dose measurements performed in a Hospital mammography unit. ESD and depth dose were measured using ThermoLuminescent Dosimeters (TLDs), and a tissue equivalent mammography phantom recommended by the American College of Radiology (ACR). Measurements and Monte Carlo simulations were also compared with the MGD calculated using the Automatic Exposure Control (AEC) system of the mammographic unit. In the simulations the Doppler energy broadening effect was also taken into account. The simulated ESD are about 5%–10% higher than the measured ESD values. The deviation between the measured and simulated MGD values in the phantom is of about 15%. The MGD evaluated using the AEC system is smaller both with respect to the Monte Carlo simulation and experimental result by a factor of about 15% and 25% respectively. Moreover the BackScatter Factor (BSF) estimated by Monte Carlo simulations was used for the MGD calculation according to the Wu’s method. Finally the inclusion of the energy broadening effect on MGD calculation produces negligible variations on the simulated results. 相似文献
995.
GUO KeTao LIANG MingChao XU HongYu & ZHU ChengBo School of Applied Science Jiangxi University of Science Technology Ganzhou China 《中国科学:物理学 力学 天文学(英文版)》2011,(3)
By using the concept of negativity, we investigate the thermal entanglement of a two-spin (1/2, 3/2) mixed-spin Heisenberg XX chain with an inhomogeneous external magnetic field. We obtain the analytical results of entanglement of this model. For the case of uniform magnetic field, we find that the critical temperature is higher than the results of the spin-1/2 chain and (1/2,1) mixed-spin chain. And by adjusting the nonuniform parameter b, one is able to obtain more entanglement at a higher temperature. 相似文献
996.
C. Canali C. Carraro D. Krasnicky V. Lagomarsino L. Di Noto G. Testera S. Zavatarelli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):499-504
Antihydrogen experiments are currently based on non neutral electron, positron or
antiproton plasma manipulation techniques in cylindrical Malmberg-Penning traps. An
experimental study of a plasma manipulation technique based on off-axis diocotron
displacement is presented. The use of the autoresonant excitation of (1, 0) diocotron mode
of pure electron plasma allows a precise positioning of the plasma by moving it across the
magnetic field and allows dumping such plasma in a desired angular position. The
experimental procedure described here will pave the way to positron loading into an
off-axial Penning trap terminated with a positronium converter target as it is proposed
for the AEgIS experimental apparatus. The technique was studied over a range of confining
magnetic field values and reproduces experimental conditions similar to most of the
currently running antihydrogen experiments.
The efficiency of the autoresonant excitation – in terms of plasma expansion rate and
particle loss – is analyzed, studying the behaviour of electron plasma subjected to large
off-axial displacements, showing that this method fulfills the requirements imposed by the
AEgIS experiment. 相似文献
997.
Marcella Reale Antonia Patruno Maria A De Lutiis Mirko Pesce Mario Felaco Massimo Di Giannantonio Marta Di Nicola Alfredo Grilli 《BMC neuroscience》2011,12(1):13
Background
The exact cause of schizophrenia is not known, although several aetiological theories have been proposed for the disease, including developmental or neurodegenerative processes, neurotransmitter abnormalities, viral infection and immune dysfunction or autoimmune mechanisms. Growing evidence suggests that specific cytokines and chemokines play a role in signalling the brain to produce neurochemical, neuroendocrine, neuroimmune and behavioural changes. A relationship between inflammation and schizophrenia was supported by abnormal cytokines production, abnormal concentrations of cytokines and cytokine receptors in the blood and cerebrospinal fluid in schizophrenia. Since the neuropathology of schizophrenia has recently been reported to be closely associated with microglial activation we aimed to determined whether spontaneous or LPS-induced peripheral blood mononuclear cell chemokines and cytokines production is dysregulated in schizophrenic patients compared to healthy subjects. We enrolled 51 untreated first-episode schizophrenics (SC) and 40 healthy subjects (HC) and the levels of MCP-1, MIP-1α, IL-8, IL-18, IFN-γ and RANTES were determined by Elisa method in cell-free supernatants of PBMC cultures. 相似文献998.
999.
Undersampling k-space is an effective way to decrease acquisition time for MRI. However, aliasing artifacts introduced by undersampling may blur the edges of magnetic resonance images, which often contain important information for clinical diagnosis. Moreover, k-space data is often contaminated by the noise signals of unknown intensity. To better preserve the edge features while suppressing the aliasing artifacts and noises, we present a new wavelet-based algorithm for undersampled MRI reconstruction. The algorithm solves the image reconstruction as a standard optimization problem including a ?2 data fidelity term and ?1 sparsity regularization term. Rather than manually setting the regularization parameter for the ?1 term, which is directly related to the threshold, an automatic estimated threshold adaptive to noise intensity is introduced in our proposed algorithm. In addition, a prior matrix based on edge correlation in wavelet domain is incorporated into the regularization term. Compared with nonlinear conjugate gradient descent algorithm, iterative shrinkage/thresholding algorithm, fast iterative soft-thresholding algorithm and the iterative thresholding algorithm using exponentially decreasing threshold, the proposed algorithm yields reconstructions with better edge recovery and noise suppression. 相似文献
1000.
Qingyu Xu Zheng WenJinlong Gao Di WuShaolong Tang Mingxiang Xu 《Physica B: Condensed Matter》2011,406(10):2025-2027
Bi(Fe0.95Co0.05)O3 films were prepared on conductive indium tin oxide (ITO)/glass substrates by chemical solution deposition. Well saturated polarization hysteresis loop has been observed with a remnant polarization value of about 22 μC/cm2 at room temperature. Weak ferromagnetism with saturation magnetization of about 3 emu/cm3 was observed at room temperature. The clear observation of both room temperature ferroelectric and ferromagnetic properties suggests the potential multiferroic applications of Bi(Fe0.95Co0.05)O3. 相似文献