In an orthogonal frequency division multiplexing (OFDM) system, the cyclic prefix (CP) has traditionally been not useful for data detection at the receiver. This paper presents a low-complexity turboOFDM receiver to exploit all of the extra information offered by the CP to improve the data detection and channel estimation performance. In the receiver, two iterative processes, namely, the outer iteration based on the turbo equalization principle and the inner iteration based on the expectation-maximization algorithm, are proposed. The CP observation, which contains extra information about data and channel, is represented by a Forney-style factor graph and incorporated into the inner iteration for joint channel estimation and data detection, using a Gaussian message passing process. The extrinsic messages of the data enhanced by exploiting the CP are then exchanged in the outer iteration for joint channel estimation, data detection, and decoding to further improve a system performance. To effectively implement the receiver, several approximations are introduced to reduce the computational complexity to be logarithmic in the length of the OFDM symbol N, i.e., O(NlogN) per OFDM symbol. Extensive simulation results show that the bit error rate performance of the proposed low-complexity turbo-OFDM receiver is superior to that of existing turbo-OFDM receivers with exploiting the channel information in the CP only or without exploiting the CP, as well as conventional OFDM receivers, in particular for time-varying channels.

This paper considers the coded OFDM system and instead of discarding the cyclic prefix (CP) at the receiver, we utilize the CP observation for joint detection, decoding and channel estimation. In particular, detection and decoding are performed iteratively between an equalizer and a soft-input soft-output (SISO) decoder based on the turbo principle, and the expectation-maximization (EM) algorithm is employed in the equalizer for joint detection and channel estimation via message passing. Models for the CP observation, non-CP observation and the time correlation of the time-varying channel are presented in Forney-style factor graphs (FFGs), and a scheduling scheme is proposed to pass messages between the graphs. Simulation results show that with unknown channel impulse response (CIR), the performance of the proposed algorithm approaches the case where CIR is perfectly known and through proper exploitation of the CP, the proposed algorithm outperforms the conventional algorithm (i.e. CP is discarded) with known CIR, as well as the alternative algorithm in the literature (where CP is exploited) with unknown CIR.

目的 研究敌敌畏对大鼠的肾脏毒性的影响,探讨其氧化应激机制.方法 将40只Wistar大鼠分成对照组和3个染毒组,分别以0、2.4、7.2和21.6 mg/kg.bw通过饮水给予大鼠,连续给药24周,测定血清胆碱酯酶活性、肌酐和尿素氮含量以及肾脏组织中超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPx)、过氧化氢酶活性(CAT)和丙二醛(MDA)含量,并观察肾脏组织病理学变化.结果 敌敌畏染毒后中、高剂量组大鼠血清中胆碱酯酶活性均显著降低,肌酐和尿素氮均显著增加,差异有统计学意义.肾脏组织中、高剂量组SOD、GPx、CAT活性及MDA含量均显著增加,差异有统计学意义;组织病理学显示中、高剂量组肾脏出现肾小管上皮细胞颗粒,空泡变性.结论 长期低剂量暴露敌敌畏不仅能诱导机体氧化应激水平升高,而且可以通过诱导脂质过氧化引起肾脏组织的损伤.

This study aims to assess the metabolomic profile and related histopathological outcomes of rat plasma after chronic low-dose exposure to dichlorvos (DDVP). A total of 120 male Wistar rats were treated with 0, 2.4, 7.2, and 21.6 mg/kg of body weight/day DDVP continuously for 24 weeks by drinking water. Rat plasma samples were collected at different time-points to measure the metabolomic profiles by ultra-performance liquid chromatography–mass spectrometry (UPLC-MS). Liver tissue analysis was performed to correlate histopathological outcome status to plasma metabolomics. Significant changes in some of the metabolites were found in all the treated groups compared with the control group. LysoPC (15:0/0:0), LysoPC (16:0/0:0), LysoPC (17:0/0:0), LysoPC (0:0/18:0), sphingosine, sphinganine, C16 sphinganine, C17 sphinganine, and arachidonic acid were decreased in the treated groups. LysoPE (16:0/0:0) was increased after dosing with DDVP. Histopathological test outcomes coincided with the plasma metabolomic-profile analysis results obtained by UPLC-MS. The livers were damaged following chronic exposure to DDVP. Abnormal changes in some lipids in the plasma, such as LysoPC (0:0/18:0), were closely related to liver dysfunction. Therefore, metabolomic analysis provides the unique advantages of unveiling the mechanisms of DDVP.

In OFDM systems, cyclic prefix (CP) insertion and removal enables the use of a set of computationally efficient single-tap equalizers at the receiver. Due to the extra transmission time and energy, the CP causes a loss in both spectrum efficiency and power efficiency. On the other hand, as a repetition of part of the data, the CP brings extra information and can be exploited for detection. Therefore, instead of discarding the CP observation as in the conventional OFDM system, we utilize all the received signals in a soft-input soft-output equalizer of a turbo equalization OFDM system. First, the models for both the CP part and the non-CP part of observation are presented in a Forney-style factor graph (FFG). Then based on the computation rules of the FFG and the Gaussian message passing (GMP) technique, we develop an equalization algorithm. With proper approximation, the complexity of the proposed algorithm is reduced to \changedmathcal O(2RNlog 2 N+4RGlog 2 G+2RG) per data block for R iterations, where N is the length of the data block and G is equal to P+L-1 with P the length of the CP and L the maximum delay spread of the channel. To justify the performance improvement, SNR analysis is provided. Simulation results show that the proposed approach achieves a significant gain over the conventional approach and the turbo equalization system converges within two iterations.

This paper investigates the MMSE-based frequency domain equalization (FDE) algorithms in turbo equalization systems. As opposed to the conventional FDE systems where the cyclic prefix (CP) is discarded at the receiver, we take advantage of the redundancy and make use of all the observed signals for equalization purpose. First, we interpret the conventional frequency domain equalizer as a Forney-style factor graph (FFG), and accordingly an equalization algorithm is derived based on the Gaussian message passing (GMP) technique. Second, the normally discarded CP part is presented similarly using an FFG, and an algorithm that integrates both of the FFGs is proposed. As a result, two extrinsic messages about the data symbols are obtained rather than one, and they are merged together based on a symbol-wise combination. Third, with approximations made on two covariance matrices, the complexity of the proposed equalization algorithm is maintained at the same order as that of the conventional FDE algorithm, i.e. O(Nlog(2)N) per block per iteration. Simulations results verify that, a gain of around 0.7dB is achieved compared with the conventional algorithm at 1/4 CP ratio, for both 16QAM and 64QAM system with Gray mapping over AWGN or ISI channels.

In OFDM systems, the cyclic prefix (CP) eliminates the interblock interference and enables the use of the computationally efficient single-tap equalizers at the receiver. While posing a loss in both spectrum efficiency and power efficiency, the CP brings extra information about the data which can be used for detection. Therefore, instead of discarding the CP as in the conventional OFDM systems, this paper takes advantage of the prefix redundancy and utilizes it in the soft-input soft-output equalizer of a turbo equalization system. By using factor graph, an equalization algorithm is developed, and with proper approximation, the complexity of the proposed algorithm is reduced to O(2Rlog2N + 4RG/N log2G + 2RG/N) per data symbol for R iterations, where N is the length of the block and G is equal to P + L - 1 with P the CP length and L the channel length. Simulation results show that the turbo equalization system converges within two iterations and the proposed equalization approach achieves significant gain compared to the conventional approach.

This study assessed the effects of long-term, low-dose dimethoate administration to rats by ultra-performance liquid chromatography–mass spectrometry (UPLC–MS). Dimethoate (0.04, 0.12, and 0.36mg/kg body weight/day) was administered daily to male Wistar rats through their drinking water for 24weeks. Significant changes in serum clinical chemistry were observed in the middle- and high-dose groups. UPLC–MS revealed evident separate clustering among the different dose groups using global metabolic profiling by supervised partial least squares-discriminant analysis. Metabonomic analysis showed alterations in a number of metabolites (12 from urine and 13 from plasma), such as l-tyrosine, dimethylthiophosphate (DMTP), dimethyldithiophosphate (DMDTP), citric acid, uric acid, suberic acid, glycylproline, allantoin, isovalerylglutamic acid and kinds of lipids. The results suggest that long-term, low-dose exposure to dimethoate can cause disturbances in liver function, antioxidant and nervous systems, as well as the metabolisms of lipids, glucose, fatty acids, amino acids, and collagen in rats. DMTP and DMDTP, which had the most significant changes among all other studied biomarkers, were considered as early, sensitive biomarkers of exposure to dimethoate. The other aforementioned proposed toxicity biomarkers in metabonomic analysis may be useful in the risk assessment of the toxic effects of dimethoate. Metabonomics as a systems toxicology approach was able to provide comprehensive information on the dynamic process of dimethoate induced toxicity. In addition, the results indicate that metabonomic approach could detect systemic toxic effects at an earlier stage compared to clinical chemistry. The combination of metabonomics and clinical chemistry made the toxicity of dimethoate on rats more comprehensive.

To study the toxic effect of chronic exposure to acephate at low-dose levels, a metabolomics approach based on ultra-performance liquid chromatography/mass spectrometry (UPLC-MS) was applied. Three different doses of 0.5 mg/kg/day, 1.5 mg/kg/day, and 4.5 mg/kg/day acephate were administered to Wistar rats for 24 weeks. Endogenous metabolite profiles were obtained with UPLC-MS for all rats at six time points after treatment. Some metabolites like dimethylthiophosphate and uric acid in urine were detected at week 4. Dimethylthiophosphate, which had the most significant elevations compared with other biomarkers, was considered as an early, sensitive biomarker of exposure to acephate. Moreover, there were some endogenous metabolite changes, which demonstrated that the doses of 1.5 mg/kg/day and 4.5 mg/kg/day of acephate led to renal injury and perturbed the normal metabolic processes of rats, including glucose, nucleic acid, and protein metabolism. A connection between exposure to acephate and the metabolic disturbance has been found and interpreted. Our study indicates that the metabolomics approach based on UPLC-MS of urine provides more information on toxicity than the conventional toxicological evaluation methods in measuring changes and can be considered as a promising technique for the study of the toxic effect of acephate.

<正>乙酰甲胺磷由于其低毒、安全、广谱等特点,作为高毒农药甲胺磷的替代品而被广泛应用〔1〕,同时也对环境造成了不同程度的污染,使人群不可避免的暴露于乙酰甲胺磷。这种长期低剂量暴露特点对机体健康影响存在不确定性。有文献报道乙酰甲胺磷在高剂量(47.25mg/kg)染毒下,对大鼠生殖

Organophosphorous pesticides, commonly used in agriculture for achieving better quality products, are toxic substances that have harmful effects on human health. Recent research on pesticides, especially pesticide mixtures, has shown that they are one of the key environmental health issues. The aim of the present study was to investigate whether dichlorvos, acephate, dimethoate and phorate, either used separately or in combination, can induce oxidative damage in rat livers. The levels of superoxide dismutase, glutathione peroxidase, catalase and lipid peroxidation products (malondialdehyde) were used as criteria. Low, middle and high doses of pesticides in drinking water were continuously administered orally to rats ad libitum for 24 weeks. Results show that the antioxidative defense mechanisms and lipid peroxidation in the rat livers display different responses, depending on the pesticide treatments and doses. The parameters for acephate, dichlorvos, phorate and dimethoate in the low-dose group, and the corresponding low-dose co-treated group were not altered. The oxidative damage in rat livers showed different responses with increasing pesticide dose according to the different pesticide treatments. The combination group of dichlorvos, acephate, dimethoate and phorate displayed different responses compared with the single pesticide-treated group. However, these responses did not constitute the sum of the response produced by each pesticide in the liver.

The purpose of the current study was to assess the effects of long-term exposure to low levels of DDVP on the biochemical parameters and metabolic profiles of rats. Three different doses (2.4, 7.2, and 21.6mg/kgbody weight/day) of DDVP were administered to rats through their drinking water over 24 weeks. Significant changes in blood cholinesterase, creatinine, urea nitrogen, aspartate aminotransferase, alanine aminotransferase, and albumin concentrations were observed in the middle and high dose groups. Changes in the concentration of some urine metabolites were detected via ultra performance liquid chromatography–mass spectrometry (UPLC–MS). Dimethyl phosphate (DMP), which was exclusively detected in the treated groups, can be an early, sensitive biomarker for DDVP exposure. Moreover, DDVP treatment resulted in an increase in the lactobionic acid, estrone sulfate, and indoxyl sulfic concentrations, and a decrease in citric acid, suberic acid, gulonic acid, urea, creatinine, and uric acid. These results suggest that chronic exposure to low-level DDVP can cause a disturbance in carbohydrate and fatty acid metabolism, the antioxidant system, etc. Therefore, an analysis of the metabolic profiles can contribute to the understanding of the adverse effects of long-term exposure to low doses of DDVP.

Epidemiologic studies have shown that populations that consume more fruits and vegetables have lower incidences of some diseases. These health effects have largely been attributed to flavonoid intake and bioavailability. However, no published data on the estimated flavonol and flavone intake of Chinese adults are currently available. Considering reports that food frequency questionnaires (FFQs) have been shown to provide good measurements of energy, macronutrient, and micronutrient intakes, we hypothesized that FFQ may be used to estimate intake of dietary flavonol and flavone. The two 7-day 24-hour dietary recalls (24-HDRs) and plasma levels were used as reference criteria. A total of 128 subjects each completed two 7-day 24-HDR and 2 FFQs, and 92 subjects donated 2 plasma samples. Pearson correlation coefficients and the agreement of quartile categorization between the FFQ and each reference instrument were conducted. Pearson correlation coefficients between 2 FFQs were 0.62 for flavonol and 0.65 for flavone and ranged from 0.48 (quercetin) to 0.63 (luteolin) (all P < .05). Pearson correlation coefficients between FFQ and 24-HDR were 0.62 for flavonol and 0.68 for flavone and ranged from 0.36 (quercetin) to 0.63 (luteolin) (all P < .05). Between the FFQ and plasma samples, Pearson correlation coefficients were 0.52 for flavonol and 0.41 for flavone and ranged from 0.32 (quercetin) to 0.44 (kaempferol) (all P < .05). The complete and partial agreement by quartiles ranged from 70% to 89%. The findings indicate that administering FFQ is a reliable and accurate method of assessing dietary intake of flavonol and flavone.

This paper considers the cooperative schemes where the source, relay and the destination are all multi-antenna terminals. Zero-forcing equalization and maximum ratio combining technique are employed in this scheme. We extend the classical selection relaying into the multi-antenna setup. Based on a predefined threshold, the source decides to cooperate only when it needs help. The source picks only one relay to cooperate with and the optimal relay is the one which has the maximum instantaneous value of the relay's metric, which is a modified version of the harmonic mean function of its source-relay (S-R) and relay-destination (R-D) channel gains. We also presented some simulation results to verify the proposed relay selection scheme.