An embedded optical tracking system for motion-corrected magnetic resonance imaging at 7T

Object

Prospective motion correction using data from optical tracking systems has been previously shown to reduce motion artifacts in MR imaging of the head. We evaluate a novel optical embedded tracking system.

Materials and methods

The home-built optical embedded tracking system performs image processing within a 7T scanner bore, enabling high speed tracking. Corrected and uncorrected in vivo MR volumes are acquired interleaved using a modified 3D FLASH sequence, and their image quality is assessed and compared.

Results

The latency between motion and correction of the slice position was measured to be (19?±?5)?ms, and the tracking noise has a standard deviation no greater than 10???m/0.005° during conventional MR scanning. Prospective motion correction improved the edge strength by 16?% on average, even though the volunteers were asked to remain motionless during the acquisitions.

Conclusion

Using a novel method for validating the effectiveness of in vivo prospective motion correction, we have demonstrated that prospective motion correction using motion data from the embedded tracking system considerably improved image quality.     

Amphiphilic fluorinated block-copolymer coating for the preparation of hydrophobic porous materials

A new approach to the preparation of hydrophobic porous polymers has been proposed. Three series of porous polymers which pores equally well-absorbed as water and organic liquids (benzene and iso-octane) were synthesized by visible light polymerization from compositions based on three different dimethacrylic esters with n-butanol. Three block copolymers based on N-vinylpyrrolidone and 2,2,3,3-tetrafluoropropyl methacrylate, differing in the length of the poly-(2,2,3,3-tetrafluoropropyl methacrylate) block, were synthesized for the purpose of hydrophobization of such porous polymers. A distinctive feature of synthesized block copolymers is that they are soluble only in methanol. It has been found that the treatment of porous polymers only with 2 wt.% of block copolymer methanol solution leads to a decrease water uptake by an order of magnitude, and the absorption of organic liquids does not change. In the course of the study it was possible to obtain a hydrophobic porous polymer sample that has water contact angle θ?=?121^° and a low value of the polar component of the surface Gibbs energy (\( {\gamma}_s^p=0.2 \) mJ·m^?2). The fundamental possibility of using such material for purification of organic liquids from water is shown.

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Efficient parameterized string matching

In parameterized string matching the pattern P matches a substring t of the text T if there exist a bijective mapping from the symbols of P to the symbols of t. We give simple and practical algorithms for finding all such pattern occurrences in sublinear time on average. The algorithms work for a single and multiple patterns.     

Transverse magnetoresistance peculiarities of thermoelectric Lu-doped Bi2Te3 compound due to strong electrical disorder

The n-type thermoelectric Bi_1.9Lu_0.1Te₃ was prepared by microwave-solvothermal method and spark plasma sintering. The magnetic field and temperature dependences of transverse magnetoresistance measured within temperature 2–200 K interval allow finding the peculiarities characteristic for strongly disordered and inhomogeneous semiconductors. The first peculiarity is due to appearance of linear-in-magnetic field contribution to the total magnetoresistance reflected in a crossover from quadratic magnetoresistance at low magnetic fields to linear magnetoresistance at high magnetic fields. The linear magnetoresistance can result from the Hall resistance picked up from macroscopically distorted current paths due to local variations in stoichiometry of the compound studied. The second peculiarity is that both linear magnetoresistance magnitude and crossover field are functions of carrier mobility which is in agreement with the Parish and Littlewood model developed for disordered and inhomogeneous semiconductors. An increase in the mobility due to a decrease in temperature is accompanied by an increase in the magnetoresistance magnitude and a decrease in the crossover field. Finally, the third peculiarity is related to the remarkable deviation of the total magnetoresistance measured at various temperatures from the Kohler's rule. Presence of strong inhomogeneity and disorder in the Bi_1.9Lu_0.1Te₃ structure concluded from the magnetoresistance peculiarities can be responsible for the remarkable reduction in the total thermal conductivity of this compound.     

利用高性能同时采样ADC降低高级电力线监测系统的成本

人们对电力需求的增长以及节能意识的增强使得全球在电力传输基础架构领域的投资迅速增长,这也带动了高级电力线监控系统在单相和多相应用中的市场,使其成为新一代智能电网的关键技术。随着对系统性能的要求越来越严格,设计人员开始在电力线监测或多通道SCADA(管理控制和数据采集)系统中关注同时采样、多通道、高性能ADC的使用。     

Unusual super-ductility at room temperature in an ultrafine-grained aluminum alloy

Processing by severe plastic deformation (SPD) typically increases the strength of metals and alloys drastically by decreasing their grain size into the submicrometer or nanometer range but the ductility of such materials remains typically low. This report describes the first demonstration that it is possible to increase the room temperature ductility of aluminum-based alloys processed by SPD and to attain elongations to failure of >150% while retaining the enhanced strength. This unique combination of properties is due to the occurrence of grain boundary sliding at room temperature. The sliding was obviously achieved by introducing a grain boundary wetting of the aluminum/aluminum grain boundaries.     

Organ-specific antigens of the human intestines detectable in tumors

Rabbit antisera to an organospecific intestinal antigen are obtained. This antigen has beta 2-electromobility, is thermolabile, is not extracted by perchloric acid and phenol and immunologically differs from CEA. The antigen is found in bottom zone of colonic crypt and in carcinomas of colon and rectum.     

Distribution of one of the ascitic fluid antigens of ovarian cancer patients in malignant tumors of the stomach and intestines

The indirect immunofluorescent technique was used to study the distribution of the ascitic fluid antigen (AgD) on histological sections from surgical specimens of gastric and colon tumours from proximal to distal lines of resection. AgD was found in gastric tumours exceptionally in the tumour area and in colon cancer--both in the tumour stroma and in surrounding histologically normal mucosa.     

A low-jitter 125-1250-MHz process-independent and ripple-poleless0.18-μm CMOS PLL based on a sample-reset loop filter

This paper describes a low-jitter phase-locked loop (PLL) implemented in a 0.18-μm CMOS process. A sample-reset loop filter architecture is used that averages the oscillator proportional control current which provides the feedforward zero over an entire update period and hence leads to a ripple-free control signal. The ripple-free control current eliminates the need for an additional filtering pole, leading to a nearly 90° phase margin which minimizes input jitter peaking and transient locking overshoot. The PLL damping factor is made insensitive to process variations by making it dependent only upon a bandgap voltage and ratios of circuit elements. This ensures tracking between the natural frequency and the stabilizing zero. The PLL has a frequency range of 125-1250 MHz, frequency resolution better than 500 kHz, and rms jitter less than 0.9% of the oscillator period