Effect of Trader Composition on Stock Market

In this study, we build a double auction market model, which containstwo types of agent traders, i.e., the noise traders and fundamentalists, to investigate the effect of the trader composition on the stock market. It is found that, the non-trivial Hurst exponent and the fat-tailed distribution of transaction prices can be observed at any ratio of the noise traders. Analyses on the price variation properties, including the Hurst exponent and the price variation region, show that these properties are stable when the ratio is moderate. However, the non-price variation properties, including the trading volume and the profitability of the two kinds of agents, do not keep stable untrivially in any interval of the ratio of noise traders.     

具有可控分散性的不同粒径氨基酸双功能化介孔二氧化硅纳米颗粒

通过表面活性剂,共结构导向剂（CSDAs）和硅源的自组装合成了具有分散性的不同粒径氨基酸双功能化介孔二氧化硅纳米颗粒. 通过表面活性剂头部与带相反电荷的CSDAs之间的静电相互作用使氨基和羧基基团均匀排列在介孔孔道表面. 通过调节助溶剂或分散剂的加入量来控制颗粒粒径,调节合成溶液pH改变纳米颗粒表面羧基和氨基基团的电荷切换性及其量来控制颗粒的分散性.     

分子印迹微凝胶模拟酶的研究

采用油包水反相乳液法, 以马来酸酐酯化葡聚糖-氨基吡啶偶联物(Dex-MA-AP)为功能大单体、过渡态类似物p-硝基苯磷酸酯(NPP)为模板分子、Co2+为中心离子, 制得分子印迹微凝胶模拟酶(MIGs). 用紫外光谱研究了Dex-MA-AP上吡啶功能基团与NPP之间的相互作用. 用SEM观察了MIGs的形貌和大小. 研究发现, MIGs催化活性受模板分子和交联剂用量的影响,MIGs催化p-硝基乙酸苯酯(NPA)水解反应行为可用Michaelis-Menten方程进行描述, 其最大催化水解反应速率(Vm)和Michaelis-Menten常数(Km)分别为25.1 nmol/h和0.030 mmol/L, 且具有较好的催化选择性.     

一个具有双重反馈作用的异类经纪人herding模型

一个具有双重反馈作用的异类经纪人herding模型被提出.该模型认为,金融市场是由不同大小和行为倾向的经纪人集团组成.当两个不同行为倾向的经纪人集团相遇时,他们有可能发生一次交易;当两个同种行为倾向的经纪人集团相遇时,他们可能合并成一个更大的经纪人集团.交易或合并的成功率跟市场上一次波动程度有关.当两个经纪人集团发生一次交易后,处于亏损方的经纪人集团有可能分化和翻转,分化和翻转的概率取决于经纪人集团的亏损程度和市场信念等因素.数值计算表明,该模型能较好地反映市场的经济行为和动力学特性.     

Acoustic characterization of a new trisacryl contrast agent. Part I: In vitro study

The objective of the study was to acoustically characterize trisacryl polymeric microparticles (TMP), which are derived from biocompatible embolic agents.With significant acoustic properties, these polymeric particles could be potentially used as targeted ultrasound contrast agents, directed towards a specific site, with ligands conjugation on the polymeric network surface. In the in vitro study, a pulser/receiver (PRF of 1 kHz), associated to different transducers (5, 10 and 15 MHz), was used to measure the acoustic properties of the TMP inserted in a Couette flow device. Acoustic characterization according to TMP concentration (0.12-15.63 mg/ml), frequency (4.5-17 MHz, defined by each transducer bandwidth), ultrasound pressure (137-378 kPa) and exposure time (0-30 min) was conducted. Particle attenuation was also evaluated according to TMP concentration and emission frequency. Backscattering increased non linearly with concentration and maximum enhancement was of 16.4 dB ± 0.89 dB above 7.8 mg/ml. This parameter was found non-linear with increasing applied pressure and no harmonic oscillation could be noticed. Attenuation reached approximately 1.4 dB/cm at 15 MHz and for the 15.6 mg/ml suspension.The TMP have revealed in vitro ultrasound properties comparable to those observed with known contrast agents, studied in similar in vitro systems. However, such set-ups combined with a rather aqueous suspending medium, have some limitations and further investigations need now to be conducted to approach in vivo conditions in terms of flow and blood environment.     

Effect of hydroxylamine hydrochloride on the floral decoration of zinc oxide synthesized by solution method

Effect of the structure-directing agent on the floral (depicting flower) morphological variation of ZnO is systematically studied and presented here. Flowery decorated (resembling flower) zinc oxide structure composed of hexagonal nanorods (sharp tips and wider bases) was synthesized at 90 °C using zinc acetate dihydrate and sodium hydroxide at various concentrations of hydroxylamine hydrochloride for 12 h by solution method. Single crystalline nature with the wurtzite hexagonal phase remained unaltered with increasing concentration of hydroxylamine hydrochloride while the morphology changes from nanorod to plate like structure. Photoelectron spectroscopic measurement presented spectra close to the standard bulk ZnO, with an O 1s peak composed of surface adsorbed OH group, O²⁻ in the oxygen vacancies on ZnO structure and ZnO. At higher concentration (0.8 M), surface adsorbed OH group increases while other component decreases because of the changes in the nucleation and surface energy. Results clearly indicate that hydroxylamine hydrochloride works as a structure-directing agent without affecting other properties.     

Molecular Design and Fluorescent Whitening Emission from Novel Lanthanide Activated Organic–Inorganic Covalently Hybrid Micro-particles

A series of potential lanthanide activated fluorescent-whitening hybrid micro-particles has been prepared by sol-gel method. The precursor derived from 2,2′-dipyridylamine derivative modified though hydrogen transfer addition exhibited a self-organization under the coordination to RE³⁺ (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, respectively) evaluated by SEM (micrometric scale) and X-ray diffraction studies (nanometric scale). The adapting traditional routes used in this paper affected the shape of the materials and can be taken as a new method to control the hydrolysis-polycondensation process. Fourier transform infrared (FTIR), Diffuse reflectance ultraviolet-visible spectra (DRUVS) and ¹H NMR spectra were used to confirm the modifications. These activated phosphors with lanthanide ions represent a novel way to produce fluorescent whitening agents.     

The effect of experimental parameters on the signal decay in double-PGSE experiments: negative diffractions and enhancement of structural information

Double pulsed gradient spin echo (d-PGSE) experiment has been recently suggested for detecting microscopic anisotropy in macroscopically isotropic samples. This sequence is complex and has many variables, including, intra alia, combinations of directions and amplitudes of the pulsed gradients, diffusion times in each of the encoding periods and the mixing time period. The effect of these experimental parameters of the d-PGSE sequence was studied in an array of water filled microcapillaries of micron diameters. We found that negative diffractions occur, as indeed predicted by recently published simulations. We also found differential effects of prolongation of the mixing time between collinear and orthogonal d-PGSE experiments. The d-PGSE experiment in the collinear direction perpendicular to the long axis of the cylinder exhibited a marked dependence on the mixing time, while the orthogonal d-PGSE experiment exhibited no such dependence at all. Interestingly, one of the most important predictions by the simulations was that the d-PGSE sequence could potentially discriminate between compartments of different sizes better than the single PGSE (s-PGSE) and it seems that our experimental results indeed corroborate these predictions.     

Optimized 3D bright blood MRI of aortic plaque at 3 T

PURPOSE: To evaluate the feasibility of an optimized bright blood MRI protocol at 3 T in combination with contrast agent administration for the detection and characterization of aortic high-risk plaques for the improved workup of acute stroke patients. MATERIALS AND METHODS: ECG synchronized T1-weighted 3D gradient echo MRI was performed in 45 acute stroke patients. Data were acquired with high near isotropic spatial resolution (approximately 1 mm(3)) covering the entire thoracic aorta. To compensate for breathing and vessel motion artifacts, images were collected using respiratory navigator gating in combination with short diastolic data acquisition windows adjusted on a patient-by-patient basis. In patients with aortic plaques > or =3 mm in thickness, gadolinium contrast agent was administered and both pre- and post-contrast T1-weighted 3D measurements with identical vessel coverage were performed. RESULTS: Bright blood 3D MRI detected 33 high-risk plaques with an average maximum plaque thickness of 4.2+/-1.0 mm in 23 of 45 acute stroke patients. The availability of pre- and post-contrast images acquired within the same session enhanced the identification of calcified plaque components in 77% of all analyzed plaques: post-contrast MRI clearly improved the delineation of hypointense plaque cores in 23 of 30 cases and assisted in the classification of core shape and of core fraction. CONCLUSION: 3D bright blood MRI at 3 T was feasible for the detection of aortic high-risk sources and may help to improve the detection of causes of cerebral embolism in acute stroke patients.     

Magnetic properties of novel superparamagnetic MRI contrast agents based on colloidal nanocrystals

Novel systems based on colloidal magnetic nanocrystals (NCs), potentially useful as superparamagnetic (SP) contrast agents for magnetic resonance imaging (MRI) have been investigated. The NCs we have studied comprise organic-capped single-crystalline maghemite (γ-Fe₂O₃) cores possessing controlled sizes and shapes. We have comparatively examined spherical and tetrapod-like NCs, the latter being branched particles possessing four arms which depart out at tetrahedral angles from a central point. The as-synthesized NCs are passivated by hydrophobic surfactant molecules and thus are fully dispersible in nonpolar media only. The NCs have been made soluble in aqueous solution by applying a procedure based on the surface intercalation and coating with an amphiphilic polymer shell. NMR relaxivities R₁ and R₂ were compared with ENDOREM^®, one of the standard commercial SP-MRI contrast agent. We found that the spherical NCs exhibit R₁ and R₂ relaxivities slightly lower than those of ENDOREM^®, over the whole frequency range; on the contrary, tetrapods show relaxivities about one order of magnitude lower. The physical origin of such difference in relaxivities between tetrapod- and spheres-based nanostructures is under investigation and it is possibly related to different sources of the magnetic anisotropy.