A deterministic construction of irregular LDPC codes

In order to solve high encoding complexities of irregular low-density parity-check (LDPC) codes, a deterministic construction of irregular LDPC codes with low encoding complexities was proposed. And the encoding algorithms were designed, whose complexities are linear equations of code length. The construction and encoding algorithms were derived from the effectively encoding characteristics of repeat-accumulate (RA) codes and masking technique. Firstly, the new construction modified parity-check matrices of RA codes to eliminate error floors of RA codes. Secondly, the new constructed parity-check matrices were based on Vandermonde matrices, this deterministic algebraic structure was easy for hardware implementation. Theoretic analysis and experimental results show that, at a bit-error rate of 10×10⁻⁴, the new codes with lower encoding complexities outperform Mackay’s random LDPC codes by 0.4–0.6 dB over an additive white Gauss noise (AWGN) channel. Foundation item: Supported by the National Natural Science Foundation of China(60496315, 60572050)     

A perceptual space for underwater man-made sounds towards target classification

This work is the second part in a series of studies about the auditory features for underwater target classification, focusing on man-made vehicle targets (i.e. submarines, patrol boats and large surface ships). A psychoacoustic method, which is suitable for a small number of samples, was used. An optimal model with three common dimensions, specificities and latent classes was selected on the basis of the dissimilarity ratings among representative sounds and with the use of an extended version of the multidimensional scaling algorithm CLASCAL. However, such a three-dimensional space could not absolutely separate targets, whereas the first dimension in the four-dimensional space discriminated the submarines, patrol boats and ships; thus, the four-dimensional space was superior in target classification. The stepwise regression method was used to establish the relationships between individual dimensions and typical auditory features. Results showed that the first dimension was represented by the linear combination of zero-crossing rate and spectral variation, whereas the second dimension was described by attack slope. The last two dimensions were not associated with any features, and they were proved to include meaningless data noises. Finally, through a contrastive analysis, the perceptual space obtained in this study was found to be a good ‘local’ representation of the space in the first part of the study series.     

耳鸣耳聋患者的纯音听阈与微量元素

通过对91例耳鸣耳聋患者的纯音听阈与微量元素锌铰镁间的相关性进行了分析，结果表明，微量元素锌铁镁的缺随听阈的升高而下降，可能为了解本病的实质和治疗设想，提供一定的参考依据。     

Fuzzy logic for auditory evoked response monitoring and control of depth of anaesthesia

This paper describes a self-organizing fuzzy model of patients undergoing surgery which was created from 10 clinical trials with off-line analysis during maintenance of anaesthesia using the drug propofol. The effects of patient sensitivity and surgical disturbances are also represented in this patient model. Hence, this model can be considered to be a qualitative pharmacologically related model for propofol during the anaesthetic maintenance stage. Furthermore, a closed-loop simulation has been designed to validate the patient model and compare the performance of a self-organizing fuzzy logic controller algorithm against a clinically derived linguistic controller. The successful results obtained provide proof-of-concept and encouragement to perform on-line clinical trials using fuzzy logic-based monitoring and control in operating theatre in the near future.     

关于耳蜗电图中AP的N_1,N_2波起源的研究

本文通过12只猫的18支耳的实验,用70dB声强刺激被检查耳,同时描记耳蜗电图(EcochG)和听脑干电位(ABR)的方法,观察到ECochG中AP的各N波和ABR各p波一一相对的一致性。通过切断或破坏耳蜗神经核与听神经联系的实验,结果证明N_2波和PⅡ波一样主要来源于耳蜗核,而1930年Weber等人提出并沿用至今的Ap中N_1、N_2、N_3、全是来自听神经并称为听神经复合动作电位的概念是错误的。根据本文实验结果,目前临床应用的EcochG不仅可以反映耳蜗的病理生理状态,而且可以反映脑干听传导系统……耳蜗核等处的机能状态。     

Cerebrospinal fluid amyloid beta peptide patterns in Alzheimer's disease patients and nondemented controls depend on sample pretreatment: indication of carrier-mediated epitope masking of amyloid beta peptides

A quantitative urea-based amyloid beta (Abeta)-sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Western immunoblot (Abeta-SDS-PAGE/immunoblot) reveals highly conserved and disease-specific Abeta peptide patterns (Abeta 1-37, 1-38, 1-39, 1-40, 1-42) in Alzheimer's disease (AD) patients and nondemented controls. For further standardization of this method, we analyzed cerebrospinal fluid (CSF) of eight probable AD patients and seven nondemented controls using different preanalytical procedures for Abeta-SDS-PAGE/immunoblot and Abeta1-42-enzyme linked immunosorbent assay (ELISA). Both diagnostic groups were discriminated significantly by absolute levels of Abeta1-42 and ratios of Abeta1-42/40, 1-42/38, 1-42/39. Preanalytical freezing of CSF led to a highly significant loss of all Abeta peptide species. This effect was most pronounced for Abeta1-42 and completely prevented by SDS-heat denaturation prior to freezing. Prolonged storage of SDS-heat denatured CSF led to a selective loss of Abeta1-42 and impaired the discrimination of diagnostic groups as measured by Abeta-SDS-PAGE/immunoblot. Neither freezing nor storage significantly affected absolute Abeta1-42 levels as determined by Abeta1-42-ELISA, but both impaired the discrimination of diagnostic groups. Hence, we suggest immediate analysis of samples for Abeta1-42-ELISA, analysis after a short freezing interval for Abeta-SDS-PAGE/immunoblot, and avoidance of prolonged storage intervals. Remarkably, Abeta-SDS-PAGE/immunoblot measured threefold higher levels of Abeta1-42 in CSF than Abeta1-42-ELISA. In summary, our results indicate carrier-mediated epitope masking of Abeta1-42.     

Selective complexometric determination of mercury using sodium nitrite as masking agent

A complexo-titrimetric method for the determination of mercury(II) in the presence of other metal ions is described based on the selective masking ability of sodium nitrite. Mercury and other ions are initially complexed with an excess of EDTA and the surplus EDTA is titrated with Pb(NO₃)₂ solution at pH 5.0–6.0 using xylenol orange as indicator. An excess of solid NaNO₂ is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard Pb(NO₃)₂ solution. Accurate results were obtained for 10–65 mg of mercury with relative errors <0.3% and standard deviations < 0.03 mg. Sn(IV) and Pd(II) interfere but can be easily masked. The method is applied for the determination of Hg(II) in its alloy compositions and complexes.     

Selective Complexometric Determination of Titanium(IV) Using Sodium Potassium Tartrate or Ascorbic Acid as Masking Agent

 A simple, rapid and accurate complexometric method is proposed for the determination of titanium(IV) where sodium potassium tartrate or ascorbic acid were used as masking agents. In the presence of diverse metal ions, titanium is first complexed with excess of EDTA and surplus EDTA is then titrated at pH 5–6 with zinc sulfate, xylenol orange being used as indicator. An excess of 5% aqueous sodium potassium tartrate is then added to displace the complexed EDTA from the Ti-EDTA complex quantitatively, which is titrated with zinc sulfate. Also, ascorbic acid may be used as the releasing agent. The methods work well in the range 1–53 mg of Ti(IV) for sodium potassium tartrate with relative errors ± 0.28% and standard deviations ≤ 0.16 mg. For ascorbic acid the range is 1.00–30.00 mg of Ti(IV) with relative errors of ± 0.40% and standard deviations of ≤ 0.05 mg Received October 9, 2001; accepted August 2, 2002     

Stereophonic channel decorrelation using a binaural masking model

Traditional methods often only use monaural masking models to decorrelate input signals for stereo acoustic echo cancellation. Whereas, it seems more reasonable to use binaural masking models for the following two reasons. First, stereo signals are heard by two ears rather than just one. Second, psychoacoustic researchers have already shown that there are obvious masking level differences between binaural masking models and monaural masking models. By studying binaural masking level difference models, we first introduce a simplified binaural masking model for stereo acoustic echo cancellation. Considering that the interaural time difference is dominant at low frequencies (?$?$1.5  kHz) and the interaural level difference is a major cue at higher frequencies, we propose to use different signal decorrelation schemes at these two frequency bands. In the low-frequency band, a pitch-driven sinusoidal injection scheme is proposed to maintain the interaural time difference, where the amount of injection is determined by the proposed binaural masking model. In the high-frequency band, a modified sinusoidal phase modulation scheme is applied to make a trade-off between preserving the interaural level difference and decorrelating the stereophonic input signals. Assessment results show that the proposed method can effectively improve the non-unique problem and retain good speech quality.     

Investigation of electrochemical hydride generation coupled to microwave plasma torch optical emission spectrometry for the determination of arsenic: analytical figures of merit,interference studies and applications to environmentally relevant samples

A continuous flow thin layer electrolysis cell with a Pt cathode in combination with a microwave plasma torch operated with Ar as working gas was used for the optical emission spectrometric determination of As with the hydride technique. Under the optimised conditions the limit of detection (3σ) in the case of the As(I) 228.81 nm emission line was 81 ng mL^?1. Especially the influence of the transition metals Cu(II), Fe(III) and Ni(II), of the hydride forming elements Sb(III), Se(IV) and Sn(II) and of Na on the determination of As was studied. Cu(II) was found to be the strongest interferent, as in the presence of 100 µg mL^?1 of Cu(II) the signal for 3 µg mL^?1 of As was reduced to 4% of the signal without interferent. Sn(II) and Sb(III) were found to yield an increase of the signal for As. L-cysteine and KI/ascorbic acid (1 : 1) at a concentration of 2% were found effective to reduce the interferences of Cu(II), Fe(III) and Ni(II). For a solution containing 3 µg mL^?1 of As and 100 µg mL^?1 of Ni(II) it was shown that in the presence of L-cysteine or KI/ascorbic acid the signal for As was 99% and 94% of the one without interferent, whereas it was only 43% without masking reagents. The procedure could be used for the determination of As in a digested coal fly ash standard reference material (NIST SRM 1633a®) with a certified value of 145 ± 15 µg g^?1 for As. A concentration of 131 ± 15 µg g^?1 was found. Additionally, As could be determined in two process water samples from a copper refinery. It was found that the amount of As determined with ECHG-MPT-OES agrees well with the values determined by FAAS and ICP-OES at the 0.02 and 1.6 g L^?1 level, respectively.