Super-resolution in respiratory synchronized positron emission tomography

Respiratory motion is a major source of reduced quality in positron emission tomography (PET). In order to minimize its effects, the use of respiratory synchronized acquisitions, leading to gated frames, has been suggested. Such frames, however, are of low signal-to-noise ratio (SNR) as they contain reduced statistics. Super-resolution (SR) techniques make use of the motion in a sequence of images in order to improve their quality. They aim at enhancing a low-resolution image belonging to a sequence of images representing different views of the same scene. In this work, a maximum a posteriori (MAP) super-resolution algorithm has been implemented and applied to respiratory gated PET images for motion compensation. An edge preserving Huber regularization term was used to ensure convergence. Motion fields were recovered using a B-spline based elastic registration algorithm. The performance of the SR algorithm was evaluated through the use of both simulated and clinical datasets by assessing image SNR, as well as the contrast, position and extent of the different lesions. Results were compared to summing the registered synchronized frames on both simulated and clinical datasets. The super-resolution image had higher SNR (by a factor of over 4 on average) and lesion contrast (by a factor of 2) than the single respiratory synchronized frame using the same reconstruction matrix size. In comparison to the motion corrected or the motion free images a similar SNR was obtained, while improvements of up to 20% in the recovered lesion size and contrast were measured. Finally, the recovered lesion locations on the SR images were systematically closer to the true simulated lesion positions. These observations concerning the SNR, lesion contrast and size were confirmed on two clinical datasets included in the study. In conclusion, the use of SR techniques applied to respiratory motion synchronized images lead to motion compensation combined with improved image SNR and contrast, without any increase in the overall acquisition times.     

On-the-Fly Reseeding: A New Reseeding Technique for Test-Per-Clock BIST

In this paper we present a new reseeding technique for test-per-clock test pattern generation suitable for at-speed testing of circuits with random-pattern resistant faults. Our technique eliminates the need of a ROM for storing the seeds since the reseeding is performed on-the-fly by inverting the logic value of some of the bits of the next state of the Test Pattern Generator (TPG). The proposed reseeding technique is generic and can be applied to TPGs based on both Linear Feedback Shift Registers (LFSRs) and accumulators. An efficient algorithm for selecting reseeding points is also presented, which targets complete fault coverage and allows to well exploiting the trade-off between hardware overhead and test length. Using experimental results we show that the proposed method compares favorably to the other already known techniques with respect to test length and the hardware implementation cost.     

Detecting unauthorized and compromised nodes in mobile ad hoc networks

Security of mobile ad hoc networks (MANET) has become a more sophisticated problem than security in other networks, due to the open nature and the lack of infrastructure of such networks. In this paper, the security challenges in intrusion detection and authentication are identified and the different types of attacks are discussed. We propose a two-phase detection procedure of nodes that are not authorized for specific services and nodes that have been compromised during their operation in MANET. The detection framework is enabled with the main operations of ad hoc networking, which are found at the link and network layers. The proposed framework is based on zero knowledge techniques, which are presented through proofs.     

FPGA-based System for Real-Time Video Texture Analysis

This paper describes a novel system for real-time video texture analysis. The system utilizes hardware to extract second-order statistical features from video frames. These features are based on the Gray Level Co-occurrence Matrix (GLCM) and describe the textural content of the video frames. They can be used in a variety of video analysis and pattern recognition applications, such as remote sensing, industrial and medical. The hardware is implemented on a Virtex-XCV2000E-6 FPGA programmed in VHDL. It is based on an architecture that exploits the symmetry and the sparseness of the GLCM and calculates the features using integer and fixed point arithmetic. Moreover, it integrates an efficient algorithm for fast and accurate logarithm approximation, required in feature calculations. The software handles the video frame transfers from/to the hardware and executes only complementary floating point operations. The performance of the proposed system was experimentally evaluated using standard test video clips. The system was implemented and tested and its performance reached 133 and 532 fps for the analysis of CIF and QCIF video frames respectively. Compared to the state of the art GLCM feature extraction systems, the proposed system provides more efficient use of the memory bandwidth and the FPGA resources, in addition to higher processing throughput, that results in real time operation. Furthermore, its fundamental units can be used in any hardware application that requires sparse matrix representation or accurate and efficient logarithm estimation.

Efficient architectures for modulo 2n − 2 arithmetic units

Moduli of the 2ⁿ and 2ⁿ ± 1 forms are usually employed in designs that adopt the residue number system. However, in several cases such as in finite impulse response filters and communication components, a modulo value equal to 2ⁿ ? 2 can be used. So far, modulo 2ⁿ ? 2 arithmetic units have been based either on look-up tables or on generic modulo arithmetic units. In this work, by taking advantage of the properties of modulo 2ⁿ ? 2 arithmetic, we propose efficient modulo 2ⁿ ? 2 multi-operand adder, multiplier as well as squarer architectures. The proposed circuits are based on the corresponding ones for modulo 2^n?1 ? 1 arithmetic and some simple logic. Experimental results validate that the proposed circuits achieve significant area and delay savings compared to those previously presented.     

三倍体毛白杨KP法蒸煮中木素结构的变化

以三倍体毛白杨为研究对象,进行了常规硫酸盐法蒸煮。采用酶-弱酸解两段法分别从原料和KP纸浆中分离出原料木素和纸浆残余木素。采用酸析法从KP蒸煮黑液中分离出溶出木素样品,经过弱酸水解得到纯木素试样。通过凝胶渗透色谱分析(GPC),对所有试样分别进行了分子质量的检测,得出各种木素样品的分子质量及其分布,分析了木素溶出过程中的分子质量的变化。通过磷谱核磁共振31P-NMR技术得出木素结构谱图,对原料木素、纸浆残余木素和黑液溶出木素结构中各官能团进行了定量分析对比,研究了木素结构在KP蒸煮过程中的变化规律。     

Evaluation of the antiradical and reducing properties of selected Greek white wines: correlation with polyphenolic composition

The total hydroxycinnamate (THC) and total flavanol (TF) contents were determined in 26 selected Greek white wines of ‘Appellation of Origin of High Quality’ using well‐established spectrophotometric methodology. Furthermore, two parameters related to the antioxidant capacity of wines, the antiradical activity (A_AR) and the reducing power (P_R), were also determined using the stable DPPH· radical and a ferric reducing power assay respectively. THC content varied from 64.4 to 197.1 mg l^?1 chlorogenic acid equivalents (CGAE), whereas TF content exhibited larger variation, ranging from 3.3 to 205.3 mg l^?1 catechin equivalents (CTE). A_AR and P_R were found to range from 0.47 to 0.60 mM Trolox equivalents (TRE) and from 0.32 to 2.05 mM quercetin equivalents (QE) respectively. Regression analysis at 95% significance level indicated that reducing effects are likely to be exerted by the flavanol fraction (SF < 0.05), as opposed to antiradical efficiency which is primarily affected by the sum of THC and TF contents (SF < 0.05), suggesting that synergistic phenomena account for the overall antioxidant status of white wines. © 2002 Society of Chemical Industry