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ABSTRACT: Soluble oligomers of human islet amyloid polypeptide (h-IAPP) are implicated in the initiation of beta-cell apoptosis leading to type 2 diabetes mellitus (T2DM). Cleavage of the h-IAPP included in an oligomer may provide a novel method for reducing the level of h-IAPP oligomers, offering a new therapeutic option for T2DM. From the combinatorial library of triazine derivatives prepared by exploiting the Co(III) complex of cyclen as the cleavage center for peptide bonds, eight compounds were selected as cleavage agents for oligomers of h-IAPP. After reaction with cleavage agents for 36 h at 37 degrees C and pH 7.50, up to 20 mol% of h-IAPP (initial concentration: 4.0 microM) was cleaved, although the target oligomers existed as transient species. Considerable activity was manifested at agent concentrations as low as 100 nM.
JBIC Journal of Biological Inorganic Chemistry 07/2008; 13(5):693-701. · 3.29 Impact Factor
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ABSTRACT: In this paper, a novel preamble structure, including a synchronization field (S-field) and a cell-search field (C-field), is proposed for orthogonal-frequency-division-multiplexing-based cellular systems. An efficient algorithm for downlink synchronization and cell search using the preamble is also proposed. The synchronization and cell-search process includes the initial symbol-timing estimation using continuously or, at least, periodically transmitted downlink signal, the frame detection, the fine symbol-timing estimation, the frequency-offset estimation using the preamble S-field, and the cell identification using the preamble C-field. Performance of each synchronization and cell-search step is analyzed and verified by computer simulation. The overall performance of the synchronization and cell search is then analyzed in terms of the mean acquisition time. It is shown that the proposed preamble with the corresponding synchronization and cell-search algorithm can provide a very robust synchronization and cell-search capability, even in bad cellular environments.
IEEE Transactions on Vehicular Technology 12/2007; · 1.92 Impact Factor
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ABSTRACT: We describe a 51-year-old man with a 3-year history of multiple system atrophy, who developed a reversible posterior leukoencephalopathy syndrome (RPLS) after receiving prescription midodrine for therapeutic treatment of orthostatic hypotension. Typical reversible magnetic resonance imaging findings, following treatment with midodrine, suggested a possible relationship between midodrine treatment, supine hypertension, and RPLS, although a cause-and-effect relationship cannot be confirmed.
Movement Disorders 06/2007; 22(7):1043-6. · 4.51 Impact Factor
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European Neurology 02/2007; 58(1):54-6. · 1.81 Impact Factor
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Junghun Suh,
Sang Ho Yoo,
Min Gyum Kim,
Keunhong Jeong, Jae Young Ahn,
Myoung-soon Kim,
Pil Seok Chae,
Tae Yeon Lee,
Jaehwa Lee,
Jeongkuk Lee,
Yun Ah Jang,
Eun Hwa Ko
Angewandte Chemie International Edition 02/2007; 46(37):7064-7. · 13.45 Impact Factor
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ABSTRACT: In this paper, a new method of inter-cell interference (ICI) cancellation in the downlink is proposed for users at the cell boundary in OFDM-based cellular systems, by using the concept of a subcarrier-based virtual multiple-input multiple-output (SV- MIMO) where multiple antenna techniques are performed on a set of subcarriers, not on the actual antenna array. In the proposed SV-MIMO, "subcarrier signatures," obtained at the mobile station (MS) with a single antenna, are exploited to separate the desired signal from ICIs. The concept of a virtual signature randomizer (VSR) is introduced to improve channel separability in the SV-MIMO approach. Also, the concept of a virtual smart antenna, in which the steering vector is formed by a set of subcarriers with the estimated symbol timing offset (STO) between BSs, is compared with conventional ICI reduction methods. It is shown by simulation that the proposed method is effective in reducing ICI and inter-sector interference for fully- loaded OFDM cellular systems with a frequency reuse factor equal to 1, compared with conventional methods.
Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th; 10/2006
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Proceedings of the 63rd IEEE Vehicular Technology Conference, VTC Spring 2006, 7-10 May 2006, Melbourne, Australia; 01/2006
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ABSTRACT: In this paper, a concept of virtual smart antenna (SA) is introduced for OFDM-based cellular systems with a frequency reuse factor equal to 1. An estimation method of intercell symbol timing offsets (STOs) from received OFDM signals impinging on virtual antenna is proposed for users at a cell boundary. Also, adaptive beamforming methods for virtual SA are proposed to reduce intercell interference (ICI) from adjacent base stations (BSs)
Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
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ABSTRACT: A search algorithm for stopping sets in a Tanner graph is proposed for designing good low-density parity-check (LDPC) codes. By applying the belief-propagation algorithm with messages containing the information of originated variable nodes and their connected edges, the stopping sets can be detected. Furthermore, a code design method using the algorithm is presented and the performances of the designed code over several channels are shown
Information Theory, 2005. ISIT 2005. Proceedings. International Symposium on; 10/2005
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ABSTRACT: In this paper, we propose an LDPC-coded OFDMA system with a resource allocation method suitable for the uplink of mobile cellular environments. At the receiver of the proposed system, an iterative channel estimation and decoding (IED) method with a Wiener filter adapting to the channel variation rate is employed to support high mobility without boosting the pilot power. For practical applications, the channel variation rate is also estimated with pilot symbols to select Wiener filter coefficients for every received packet dynamically allocated. It is shown that the proposed system supports the mobility up to 250 km/h and exhibits more than 1 dB performance gain over the system with conventional non-iterative receiver.
Communications, 2004 IEEE International Conference on; 07/2004
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ABSTRACT: An adaptive MIMO transmission scheme using QAM and LDPC code is proposed for an OFDM cellular system employing FDD. By approximating the LLR distribution to a Gaussian distribution, only two parameters, the mean and the normalized standard deviation, are required to be sent to the transmitter, which requires only a few more bits than those required in currently used single carrier cellular systems, such as cdma2000-1x EV-DO. It is shown by computer simulation that the proposed adaptive transmission scheme can provide up to 2∼3 dB gain over the conventional system using the mean SNR only, at the expense of only 3 more bits in the feedback information.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: An LDPC-coded frequency hopping OFDMA system is proposed for the uplink of cellular systems, where the frequency hopping is based on a resource block (RB) for coherent demodulation. For the system, two different RB types are considered, either for better intercell interference averaging capability or for better channel estimation performance. A turbo receiver with iterative channel estimation and decoding is also proposed to provide better channel estimation performance without boosting the pilot power. The performance is evaluated both in single- and multi-cell environments to investigate the effect of the interference on the overall system performance.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: To achieve high-bit-rate transmission in a mobile communication system, adaptive modulation and coding (AMC) having lots of variation levels in accordance with fading channel variation is a promising technique. In this paper, we compare the performance of AMC methods with cluster in an OFDM system. The AMC schemes applied into each cluster or cluster group are selected by the minimum or the average SNR value. It is important to compare the simulation result by different cluster patterns because AMC performance can be varied according to the number and position of the cluster. It is shown by computer simulation that the AMC method outperforms the fixed modulation one in terms of bandwidth efficiency and its performance can be determined by the position and number of clusters. Also, the AMC scheme with average SNR shows better the outage and bandwidth efficiency performance than the scheme having minimum SNR value.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: Adaptive modulation and coding (AMC), which has a number of variation levels in accordance with the fading channel variation, is a promising technique for communication systems. In this paper, we present the AMC method using the cluster in OFDM system for bandwidth efficiency and performance improvement. The AMC schemes applied into each cluster or some clusters are determined by the minimum or the average SNR value among all the subcarriers within the corresponding cluster. It is important to find the optimal information for cluster because AMC performance can be varied according to the number and position of cluster. It is shown by computer simulation that the AMC method outperforms the fixed modulation in terms of outage probability and bandwidth efficiency and its performance can be determined by the position and number of clusters.
Signals, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on; 12/2003
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ABSTRACT: In this paper, we propose a new residual carrier frequency and timing offset tracking scheme for a SC-FDE (single carrier - frequency domain equalizer) with frequency-domain pilots. The SC-FDE is a field that gathers more and more interest as a modulation scheme for the broadband wireless communications. For simple channel equalization SC-FDE systems perform equalization in frequency-domain instead of time-domain using FFT, IFFT and CP (cyclic prefix). We analyze the effect of frequency and timing offset in a frequency-domain and propose a new method of frequency and timing synchronization. Also, we describe a method to assign frequency-domain pilots and tracking algorithms for residual carrier frequency and timing offset using these pilots. Moreover, we verify the algorithm with a numerical analysis and computer simulation.
Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003. 14th IEEE Proceedings on; 10/2003
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ABSTRACT: In this paper, a network architecture for the integration of
IRIDIUM and CDMA systems is proposed. In particular we design the
architecture of Clearing House. The mechanisms of signaling protocol
translation and parameter matching for numbering between IRIDIUM and
CDMA systems have been designed and realized in Clearing House. New
signaling procedures for location registration and call setup in the
integrated network are also proposed
Communications, 1997. ICC 97 Montreal, 'Towards the Knowledge Millennium'. 1997 IEEE International Conference on; 07/1997
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ABSTRACT: This paper introduces a channel model for land mobile satellite
communication that is a combination of Rice and log-normal statistics,
with independent shadowing affecting each direct and diffuse component,
respectively. This model extends the channel model of a combined Rice
and log-normal, proposed by Corazza (1994), to include the independent
shadowing. The validity of the model is confirmed by comparisons with
the data collected in the literature (the analytical model and the
computer model) in terms of probability distribution of the envelope of
each model. The model turns out to be one of many well-known narrowband
models in limiting cases, e.g. Rayleigh, Rice, log-normal, Suzuki, Loo,
and Corazza
Vehicular Technology Conference, 1997, IEEE 47th; 06/1997
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ABSTRACT: A very simple and efficient scheme for jitter reduction is proposed for a carrier frequency recovery loop using phase differential frequency estimation which estimates current frequency offset from the difference of the average phases of two successive intervals. Analytical and numerical results presented in this paper show that the steady-state jitter performance can be improved by simply overlapping the observation intervals for successive frequency error estimations by half, which does not require any additional hardware circuitry. Numerical results show that the proposed scheme also improves the convergence speed.
Telecommunications, 2003. ICT 2003. 10th International Conference on;
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ABSTRACT: In this paper, we propose the residual carrier frequency offset tracking and sampling clock offset tracking algorithm that can be used in IEEE 802.11a and HIPERLAN Type 2 systems. Above Wireless LAN systems has short and long preambles, the carrier frequency offset is estimated and compensated. In case that the frame length is long, however, residual carrier frequency offset induces the severe performance degradation due to a phase rotation. And the sampling frequency offset also degrades the system performance. To prevent such performance degradations, the carrier frequency offset and sampling frequency tracking algorithms using pilot symbols are necessary. We can extract synchronization parameters by observing the phase variation of pilot symbols, such as an average and a slope. The initially estimated channel updates by using these synchronization parameters. In the frequency domain equalizer, we compensate the synchronization parameters. Computer simulation results demonstrate the performance of the proposed algorithm.
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ABSTRACT: In this letter, a pilot structure and an efficient algorithm for downlink synchronization and cell searching in OFDM-based cellular systems are proposed. The pilots, randomly allocated in the frequency domain, allow us to minimize inter-cell interference (ICI) as well as to increase cell searching capability, estimation range of integer carrier frequency offset (CFO), and estimation accuracy of symbol timing offset (STO). The proposed low-complexity joint algorithm for integer CFO estimation, cell searching, and downlink detection is robust to ICI, multipath channel, STO and fine CFO.
