In vivo magnetic resonance microscopy of Drosophilae at 9.4 T

In preclinical research, genetic studies have made considerable progress as a result of the development of transgenic animal models of human diseases. Consequently, there is now a need for higher resolution MRI to provide finer details for studies of small animals (rats, mice) or very small animals (insects). One way to address this issue is to work with high-magnetic-field spectrometers (dedicated to small animal imaging) with strong magnetic field gradients. It is also necessary to develop a complete methodology (transmit/receive coil, pulse sequence, fixing system, air supply, anesthesia capabilities, etc.). In this study, we developed noninvasive protocols, both in vitro and in vivo (from coil construction to image generation), for drosophila MRI at 9.4 T. The 10*10*80-μm resolution makes it possible to visualize whole drosophila (head, thorax, abdomen) and internal organs (ovaries, longitudinal and transverse muscles, bowel, proboscis, antennae and optical lobes). We also provide some results obtained with a Drosophila model of muscle degeneration. This opens the way for new applications of structural genetic modification studies using MRI of drosophila.     

Gd complexes of diethylenetriaminepentaacetic acid conjugates of low-molecular-weight chitosan oligosaccharide as a new liver-specific MRI contrast agent

This study was to describe the synthesis of complexes of gadolinium diethylenetriaminepentaacetic acid conjugates of low-molecular-weight chitosan oligosaccharide Gd-DTPA-CSn (n = 6, 8, 11) as a new class of contrast agent as well as its magnetic property in a pilot magnetic resonance imaging. The efficacy of the contrast agent was assessed by measuring the longitudinal relaxivity (r₁), FLASH imaging in phantoms in vitro and signal intensity in vivo of the rat abdominal axial imaging. The r₁ of Gd-DTPA-CS₁₁ was up to 11.65 mM^− 1·s^− 1, which was 3 times higher than that of the analogous MRI contrast agent Gd-DTPA in commercial use. In vivo MR images of rat obtained with Gd-DTPA-CS₁₁ showed strong signal enhancement in liver and the vessels of the liver parenchyma during the extended period of time. The present study suggests that the new synthesized gadolinium complexes can be used as a new class of practical liver-specific MRI contrast agent because of its superior performance compared with Gd-DTPA.     

Automatic segmentation of cerebral white matter hyperintensities using only 3D FLAIR images

Magnetic Resonance (MR) white matter hyperintensities have been shown to predict an increased risk of developing cognitive decline. However, their actual role in the conversion to dementia is still not fully understood. Automatic segmentation methods can help in the screening and monitoring of Mild Cognitive Impairment patients who take part in large population-based studies. Most existing segmentation approaches use multimodal MR images. However, multiple acquisitions represent a limitation in terms of both patient comfort and computational complexity of the algorithms. In this work, we propose an automatic lesion segmentation method that uses only three-dimensional fluid-attenuation inversion recovery (FLAIR) images. We use a modified context-sensitive Gaussian mixture model to determine voxel class probabilities, followed by correction of FLAIR artifacts. We evaluate the method against the manual segmentation performed by an experienced neuroradiologist and compare the results with other unimodal segmentation approaches. Finally, we apply our method to the segmentation of multiple sclerosis lesions by using a publicly available benchmark dataset. Results show a similar performance to other state-of-the-art multimodal methods, as well as to the human rater.     

Transmission and small angle scattering of 15 MeV electrons in silicon single crystals

Abstract

A novel technique for the study of structural damage incurred by single crystal silicon targets during ion implantation is described. The method is based upon copper-decoration of the vacancy rich damaged region, followed by radiochemical measurement of the resulting copper distribution. Utilizing neutron activation, sharply peaked radiocopper profiles are obtained, which are believed to represent the depth distributions of large, relatively immobile defects such as vacancy clusters, voids, or crystalline faults. A more efficient decoration of isolated vacancy-type defects is realized when Wu is employed as a radioisotopic tracer in the decoration step, however, the rapid diffusivity of these smaller species leads to less sharply defined radiocopper profiles. Both the neutron activation and radiotracer modifications of the technique yield damage profiles which are significantly shallower than the corresponding implanted impurity profiles.     

基于扩频码的单载波迭代频域均衡水声通信

单载波时域均衡在长时延扩展水声信道中计算量大,并对接收机参数的选择较为敏感,可靠性低,而正交频分复用信号峰均功率比高、对频率偏移敏感. 针对这些问题,提出基于扩频码的单载波块传输高速率水声通信方法和基于T/4分数间隔迭代频域均衡的接收机算法. 该接收机利用已知扩频码进行信道估计以及对由多普勒偏移引起的旋转相位进行估计,并通过一种低复杂度迭代频域均衡算法改善系统性能. 开展了湖上实验研究,结果表明在浅水1.8 km距离且复杂多径干扰条件下,利用BPSK/QPSK调制可实现10^-2–10^-4的误码率并达到1500–3000 bit/s的有效数据率. 关键词： 水声通信 单载波 频域均衡 迭代处理     

Study on the Interaction Between Oxymatrine and Tungstosilicic Acid by Resonance Rayleigh Scattering and Its Analytical Applications

In the 0.1 mol · L^?1 hydrochloric acid solution, oxymatrine reacted with tungstosilicic acid to form a 2:1 ion-association complexes. This results in a great enhancement of resonance Rayleigh scattering. The maximum resonance Rayleigh scattering wavelength was located at 393 nm. Resonance Rayleigh scattering intensity was proportional to the concentration of oxymatrine in the range of 1.5–26.4 µg · mL^?1, and the detection limit (3σ) was 0.23 µg · mL^?1. The optimum conditions and the effects of coexisting substances on the reaction were investigated. The method shows a wide linear range and high sensitivity, and was applied to the determination of oxymatrine in marine capsules and human urine samples with satisfactory results. Therefore, a highly sensitive, simple, and quick method has been developed for the determination of oxymatrine.     

Fluorescence resonance energy transfer between cerium ion(III) and levofloxacin in micellar solution and its analytical application to the determination of levofloxacin

Fluorescence resonance energy transfer between cerium ion(III) and levofloxacin is studied in a micellar solution of cetyltrimethyl ammonium bromide. A non-fluorescent 1:2 complex was formed between excited cerium ion(III) and ground state levofloxacin. The fluorescence of cerium ion(III) is quenched by levofloxacin with the quenching in accordance with the Stern–Volmer relation. The analytical relationship was established between the ratio of the fluorescence of levofloxacin present and absent cerium ion (III) and the concentration of levofloxacin, which helped to estimate the content of levofloxacin directly.     

On the Populations of Neon Levels in the Low Temperature Plasma of a Hollow Cathode Discharge

Atomic levels population measurements constitute an essential contribution to various aspects of plasma research: balance and cross-section of inelastic processes, admixtures effects on level excitation mechanism, purposeful optimisation of plasma parameters etc. Atomic level populations in the negative glow of a hollow cathode discharge are of utmost interest in view of the peculiarities of the spectral source: a rich spectrum consisting of gas lines, lines of the cathode material and also lines of the substances introduced in the discharge; intensive atomic and ionic lines of high excitation potentials; small spectral linewidth, convenient for analytical purposes.     

Energy Transfer from the Upper Triplet States of Aromatic Molecules

The energy transfer from the upper triplet states of diphenylamine, naphthalene and triphenylene to toluene and hexene-1 is studed. Two mechanisms of dissipation transferred energy in solvents are discussed.