第4届国际超声大会(ICU)在新加坡召开

2013年5月2日至5日,第4届国际超声大会（ICU）在新加坡召开。本次会议在国际声学委员会的组织下,由新加坡声学学会主办,由澳大利亚声学学会、印度声学学会、香港声学学会和印度无损检测学会联合承办。会议致力于促进超声不同领域,包括基础研究、工程技术以及生物医学应用等方面的国际交流与合作。     

锡掺杂二氧化钛相变过程和微结构分析

本文采用溶胶凝胶法制备了锡掺杂纳米二氧化钛,通过高分辨透射电镜法(HRTEM),X-射线衍射法(XRD)等分析手段对样品的相变过程进行了表征.XRD和HRTEM测试表明纯二氧化钛在烧结温度高于500℃时出现金红石相,而25mol; Sn2+掺杂二氧化钛凝胶在300℃烧结2h后少量锐钛矿相析出的同时结晶出金红石相.实验结果表明Sn2掺杂抑制了锐钛矿和金红石相的晶粒长大;Sn2+掺杂明显地促进了锐钛矿向金红石的转变.Sn2氧化后形成Sn4+,Sn4+置换Ti4+而引起二氧化钛晶格膨胀的同时晶格畸变应力增加.     

空间频率域超声背散射参量用于骨质状况的评价*

在超声背散射骨质评价中,不同测量感兴趣区域(ROI)的超声背散射信号会有波动,致使诊断准确度降低。该文目的是研究超声背散射信号随测量区域的变化规律。采用空间扫描方法离体测量了35块骨样本,将超声背散射参数从空间域变换到空间频率域。结果表明,超声背散射参数的主要空间频率成分集中于低频部分;空间频率域超声背散射参量最大值(MASF)与骨矿密度等参数具有中高度显著相关性(R2=0.45~0.83,p0.001);空间频率域超声背散射参量衰减系数(AC)也与松质骨密度及结构特征有显著相关性(R2=0.41~0.72,p0.001)。研究表明空间频率域变换方法有助于明确超声背散射信号随测量ROI的变化规律,空间频率域的超声背散射相关新参量评价松质骨状况具有可行性。     

2-羟基-1-萘甲醛缩-2-萘甲酰腙对Zn2+的选择性识别

设计合成了识别Zn²⁺的荧光传感分子--2-羟基-1-萘甲醛缩-2-萘甲酰腙(3)。 通过红外光谱、核磁共振谱和质谱测试技术表征了其结构。 利用其光谱性质研究了该物质对几种过渡金属离子的识别性质,初步探讨了其结合模式。 结果表明,在乙腈介质中,受体分子3表现出对Zn²⁺良好的选择性,Zn²⁺的加入导致受体分子3的吸收光谱在435 nm处出现1新峰,其吸光度逐渐增强,同时于239、302、330、342和387 nm处观察到5个清晰的等吸收点;在516 nm处荧光增强101倍,而其它过渡金属只引起受体分子]3的荧光略微增强。 Job法实验揭示受体分子3与Zn²⁺的结合比为1∶1。     

Ultrafast proton transfer to solvent: molecularity and intermediates from solvation- and diffusion-controlled regimes

Photoinduced proton transfer (PT) from cations 6-hydroxyquinolinium (6HQc) and 6-hydroxy-1-methylquinolinium (6MQc) to water and alcohols, and solvation of the zwitterionic conjugate base 1-methylquinolinium-6-olate (6MQz) were studied with stationary and transient absorption spectroscopy and by quantum chemical calculations. Transient emission spectra from 6MQz in acetonitrile and protic solvents shift dynamically to the red without changing their shape and intensity. The shift matches the solvation correlation function C(t) either measured with known solvatochromic probes coumarin 343 and coumarin 153 or derived from infrared/dielectric-loss data on neat solvents. This indicates that 6MQz monitors the solvation dynamics and that no intramolecular electron transfer occurs on a subpicosecond or longer time scale. The PT dynamics S(t) from 6HQc and 6MQc closely follows C(t), being initially 2-3 times slower. This allows for the conclusion that PT is controlled by solvation, with a barrier of 2 kJ/mol. In water, a pre-condition of this ultrafast reaction seems to be hydrogen-bonding between the negatively charged oxygen and two water molecules, resulting in a complex 6HQc:H2O:H2O. The complex is stable due to a high (47 kJ/mol) bonding energy between 6HQc and a water molecule. In acetonitrile, the reaction equilibrium is strongly shifted to the cation. There an intermediate PT state was detected, which may be ascribed to the cationic form 6HQc:H2O due to residual water impurities. In water-acetonitrile mixtures, the ultrafast solvent-controlled PT is followed by a diffusion-controlled reaction; the measured rate kD approximately 1010 s-1 M-1 is characteristic for simple bimolecular diffusion. The dependence of the short-time PT signal on water concentration can be fitted with a Poisson distribution of water molecules around the cation. Altogether, the short-time and long-time behaviors provide strong evidence that diffusion of only one water molecule is sufficient to detach the proton. Subsequent solvent stabilization of the products completes the PT reaction.     

Phase Transitions in a Highly Anisotropic Antiferromagnetic Heisenberg Toda Chain

The behavior of the antiferromagnetic spin 112 Heisenberg Toda chain is investigated in a space of interactions which include exchange anisotropy, bond alternation and Toda-like spinlattice coupling by means of coherent-state for spin. We analyse magnetically driven lattice instabilities and find that multiphase structure only occurs under the condition, of bond alternation. Three phase diagrams and tricritical points are obtained and some relevant physical properties are discussed.     

邻羟基萘甲醛缩对二甲氨基苯甲酰腙的合成及其对锌离子的识别

设计并合成了用于识别锌离子的荧光传感分子——2-羟基-1-萘甲醛缩-4-二甲氨基苯甲酰腙(1),其结构经1H NMR,IR和MS表征。利用荧光光谱研究了在乙腈中1对过渡金属离子(Zn2+,Cd2+,Cu2+,Hg2+,Pb2+和N i2+)的识别能力。结果表明:1表现出对Zn2+的良好选择性,Zn2+的加入导致1的长波长荧光增强449倍。Job曲线确定1与Zn2+形成1∶1型配合物。     

Reflection and transmission characteristics of ultrasonic guided waves in fractured long bone

Assessment of fractured long bone using ultrasonic guided wave（GW） has gained considerable attention.This paper focuses on using the hybrid boundary element method （HBEM） to analyze the propagation characteristics of ultrasonic GW in fractured long bones. The reflection coefficients（RC） and transmission coefficients（TC） for different depth-to-width ratio（d/w） cracks were numerically calculated and analyzed.It has been shown that the primary output modes,which include the transmission and reflection modes,are the same as the incidence modes.For some cracks,different TC curves always got the local maxima in adjacent frequencies.For different d/w cracks,most of the TC curves had local maxima which are not overlapped.These simulation results are helpful to optimize the modes and frequencies of the incidence GWs for quantitatively evaluating the bone quality and providing the numeral results of the cracks in long cortical bones.     

骨小梁中超声背散射信号的频率分析及其微结构的估计

骨质疏松症是一种骨强度下降的全身性骨骼疾病,骨强度的下降是骨量减少和骨微结构退化的共同结果。相比于传统的超声透射方法,超声背散射法可提供更多的骨微结构信息,而对于松质骨结构的建模能有助于结构信息的获取。本文将骨小梁简化为单圆柱模型(圆柱状的单根骨小梁浸于骨髓中),并基于此模型对超声背散射与频率的关系进行分析。用铝线代替骨小梁做仿体实验,通过实验与理论结果的比较来验证单圆柱模型的可行性。