基于声透镜成像系统的光声层析成像

光声成像是采用“光激发-超声波成像”的新型成像技术，它是检测强散射介质内部光吸收分布的一种有效医学影像技术.用短脉冲激光照射强散射介质(如生物组织)，强散射介质由于光声效应产生超声信号，使用具有成像能力的声透镜把声压分布成像于像面上，然后利用具有空间分辨能力的阵列光声传感器，把同一像面上的光声信号强度记录下来，最后根据光声信号强度的空间分布进行图像重组.根据成像系统物像共轭原理，同一物平面的光声信号到达像面的时延相等，而不同物面的光声信号到达同一个探测器平面的时延各不相同，因此，利用BOXCAR的门控积分 关键词： 光声层析成像 声透镜 光声信号     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Antiepileptic Drug Tiagabine Does Not Directly Target Key Cardiac Ion Channels Kv11.1, Nav1.5 and Cav1.2

Tiagabine is an antiepileptic drug used for the treatment of partial seizures in humans. Recently, this drug has been found useful in several non-epileptic conditions, including anxiety, chronic pain and sleep disorders. Since tachycardia—an impairment of cardiac rhythm due to cardiac ion channel dysfunction—is one of the most commonly reported non-neurological adverse effects of this drug, in the present paper we have undertaken pharmacological and numerical studies to assess a potential cardiovascular risk associated with the use of tiagabine. A chemical interaction of tiagabine with a model of human voltage-gated ion channels (VGICs) is described using the molecular docking method. The obtained in silico results imply that the adverse effects reported so far in the clinical cardiological of tiagabine could not be directly attributed to its interactions with VGICs. This is also confirmed by the results from the isolated organ studies (i.e., calcium entry blocking properties test) and in vivo (electrocardiogram study) assays of the present research. It was found that tachycardia and other tiagabine-induced cardiac complications are not due to a direct effect of this drug on ventricular depolarization and repolarization.     

Identification of winter tires using vibration signals generated on the road surface

During the winter, traffic regulations state that automobile drivers must use winter tires on unsafe roads such as snowy expressways. The present report is concerned with the development of an automatic tire identification system that can discriminate winter tires from summer tires with high accuracy. The system detects the impact vibration signal that is specifically generated by winter tires when tread blocks with wide grooves strike the road surface during rolling. The signal is picked up by a commercially available vibration sensor. If the signal contains specified impact frequency components, the tire is judged to be a winter tire. Compared with the previous identification system, which used airborne tire/road noise, the proposed system has two advantages. First, it is unaffected by meteorological factors such as wind noise. Second, the proposed system performs well even when the target vehicle is traveling at low speed. We evaluate the performance of the system outdoors using a number of vehicles with various tires and demonstrate an overall improvement in identification accuracy for vehicles traveling at low or moderate speeds.     

Nonlinear optical microscopy: Endogenous signals and exogenous probes

Nonlinear optical microscopy (NLOM) relies on nonlinear light–matter interactions to provide images from larger depths within biological structures compared to conventional confocal fluorescence microscopy. These nonlinear light–matter interactions include multiphoton excitation fluorescence (MPEF), second‐harmonic generation (SHG), coherent anti‐Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS). This review discusses the theories of and instrumentation for various NLOM techniques, with a particular focus on endogenous signals and exogenous probes. These signals and probes expand the breadth of information that optical imaging can provide. We also discuss the application of NLOM in biomedical research, including tissue engineering, drug delivery and clinical diagnostics. Current technological limitations are also discussed.

     

Short transient signals, a challenge for inductively coupled plasma mass spectrometry, a review

The ability to acquire and handle short transient signals is key in order to open new applications for inductively coupled plasma mass spectrometry (ICP-MS), for example, in life sciences. Technological and methodological achievements are reviewed to show challenges and capabilities of short transients in ICP-MS technology or hyphenated techniques. The dynamic processes in the plasma need to be controlled or observed to assure quality of quantitative results. Most precise instrumentation is to date multiple collector sector field MS but drifting isotope ratios are observed in transient signals using these instruments, thus limiting precision of such measurements and leaving unknowns in quantitative results. TOFMS in principle provides fast simultaneous multi-element detection, scanning instruments like quadrupole MS or scanning sector field MS are fundamentally restricted. However, new commercial ICP-MS instruments can be expected in the near future, making short transients more and more attractive to shorten acquisition times and to increase signal to noise ratio of element analyses.     

Determination of compound-specific Hg isotope ratios from transient signals using gas chromatography coupled to multicollector inductively coupled plasma mass spectrometry (MC-ICP/MS)

MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization, followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties were 0.16‰ RSD (n = 8) for the ²⁰²Hg^/198Hg ratio of MeHg and 0.18‰ RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic Hg was measured in the same run, obtaining a value of δ ²⁰²Hg = −1.49 ± 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column.     

The structure of instantaneous frequencies of periodic analytic signals

In this paper, the structure of analytic signals is investigated by means of the relation between analytic signals and functions in the Hardy space. It is shown that an analytic signal is made up of two parts, one depending on the amplitude of the signal and another on the boundary value of an inner function. Based on this result, properties of the instantaneous frequencies of these two parts are studied, and it is found that negative instantaneous frequencies are caused by the amplitude of a signal. Finall...     

混合范数条件下平移不变信号的非均匀平均采样

L~p平移不变子空间中的采样研究通常要求生成函数属于一个不依赖于p的Wiener amalgam空间,此条件因不能控制p而显得太强.本文主要讨论生成函数属于混合范数空间时,非衰减平移不变空间中的非均匀平均采样与重构.生成函数属于混合范数空间的条件弱于Wiener amalgam空间且依赖于参数p.基于混合范数空间中的一些引理,针对两种平均采样泛函建立了采样稳定性,并给出了对应的具有指数收敛的迭代重构算法.     

布拉格型声光双稳系统对弱信号的放大作用研究

在分岔点附近，通过对描述布拉格（Ｂｒａｇｇ）型声光双稳系统的差分－微分方程进行线性稳定性分析，得到了系统对小信号放大时的共振频率，给出了放大倍数的表达式。然后通过数值计算模拟出系统对小信号的放大过程，结果与理论分析相符