Ya Liu

Third Military Medical University, Ch’ung-ch’ing-shih, Chongqing Shi, China

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Publications (21)29.96 Total impact

  • PLoS ONE 03/2015; 10(3):e0121007. DOI:10.1371/journal.pone.0121007 · 3.53 Impact Factor
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    ABSTRACT: In order to obtain high-precision navigation satellite system time, the errors of navigation satellite system signal need to be calibrated during its transmission, among which, troposphere delay is one of the major errors of navigation satellite system precision positioning. The calibration of troposphere delay has been compared and studied on the basis of model function theory. The troposphere models described include Marini model, Hopfield model, Saastamoinen model, Black model, and the impact extent of meteorological parameters like temperature, pressure, humidity and geographic information of observation station have been analysed quantitatively, which have been systematically analysed the characteristic of troposphere delay and the accuracy of error calibration model. Moreover, by using the data collected by IGS tracking stations to validate the analysis results of models, which has shown that Black model is better than other models when it comes to the extent of meteorological influence and also superior to the troposphere delay generated by the internal calibration model in GPS receiver.
    08/2014; 602-605:2553-2560. DOI:10.4028/www.scientific.net/AMM.602-605.2553
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    ABSTRACT: Background Prenatal exposure to Lipopolysaccharide (LPS) produces hypertension in adult offspring rats. The present study was to explore the effects of prenatal inflammation on morphological and functional changes in the aorta from offspring rats and to further assess its susceptibility to cardiovascular diseases. Methods and Results Pregnant rats were treated intraperitoneally on gestation Days 8, 10 and 12 with saline, LPS (0.79 mg/kg), or pyrrolidine dithiocarbamate (PDTC, 100 mg/kg)+LPS, respectively. Aortic ring reactivity and histopathological alteration were analyzed in offspring at the age of 12 weeks. The detections of connexin (Cx) 37, Cx40, Cx43, and Cx45, including immunofluorescent patterns, protein levels and mRNA expression in the aorta, were performed as well. Furthermore, the expressions of Nuclear factor (NF)-κB (p65), IκBα, phospho-IκBα and IκBβ were determined. The results showed that prenatal LPS exposure leads to morphological abnormalities and impaired aortic reactivity in offspring. Prenatal LPS exposure also decreased the protein and mRNA expression of Cx37 in the aorta from offspring rats. NF-κB and phospho-IκBα levels were both increased, IκBα level, however, was decreased in the aorta of offspring from the maternal LPS exposure compared to the controls. Simultaneously, PDTC treatment markedly reversed the action of LPS. Conclusions Decreased expression of Cx37 contributed to the aortic dysfunction of prenatal LPS exposure offspring, which should be associated with NF-κB activation.
    PLoS ONE 07/2014; 9(7):e102273. DOI:10.1371/journal.pone.0102273 · 3.53 Impact Factor
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    ABSTRACT: To measure frequency stability of 10.23MHz signal, a 10.2299MHz frequency source based on AD9854 was developed. The performance of frequency source was tested using a phase noise and Allan deviation test set 5125A. According to the experiment results, the following conclusion can be drawn that the Allan deviation of the 10.2299MHz frequency signal is about 2.6E-14 at 1s when the 10MHz reference signal was generated by a frequency and phase offset generator HROG-10. The 10.2299MHz frequency source can be used as a common source in dual mixer time difference and as a reference signal in beat frequency method when measuring the frequency stability of 10.23MHz signal.
    06/2014; 568-570:336-339. DOI:10.4028/www.scientific.net/AMM.568-570.336
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    ABSTRACT: To explore the role of prenatal exposure to lipopolysaccharides (LPS) on aortic morphology in the neonatal offspring rats.
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    ABSTRACT: Background: Endothelial progenitor cells (EPCs) derived from the bone marrow (BM) play a key role in the homeostasis of vascular repair by enhanced reendothelialization. Panax notoginseng saponins (PNS), a highly valued traditional Chinese medicine, has been shown to reduce morbidity and mortality from coronary artery disease. The present research was designed to explore the contribution of progenitor cells to the progression of atherosclerotic plaques and the possible modulatory role of PNS in this process. Methods: PNS (60 or 120 mg/kg via intraperitoneal injection) was administered over 8 weeks in apolipoprotein E knockout mice on an atherogenic diet. The sizes and histochemical alteration of atherosclerotic lesions and numbers of EPCs in BM and peripheral blood were analyzed. The expression of chemokine stromal cell-derived factor 1α (SDF-1α) and its receptor, CXCR4, was monitored as well. Results: PNS significantly reduced the lesion area and intima-to-media ratio compared to vehicle treatment. PNS also augmented endothelialization and reduced the smooth muscle cell (SMCs) content of the lesions. The number of c-kit and sca-1 double-positive progenitor cells and flk-1 and sca-1 double-positive progenitor cells were significantly increased in the BM and the peripheral blood of the PNS-treated groups. PNS treatment increased the plasma levels of SDF-1α and SCF as well as the BM levels of matrix metalloproteinase-9 (MMP-9). Moreover, the mRNA levels of SDF-1α and protein levels of CXCR4 were both increased in the BM of mice treated with PNS, while SDF-1α expression decreased. Conclusion: PNS reduce the size of atherosclerotic plaques, and this effect appears to involve progenitor cell mobilization. SDF-1α-CXCR4 interactions and the possible modulatory role of PNS in this process may contribute to the increased progenitor cell mobilization. © 2013 S. Karger AG, Basel.
    Cellular Physiology and Biochemistry 09/2013; 32(4):814-826. DOI:10.1159/000354484 · 3.55 Impact Factor
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    ABSTRACT: As a key technology of the measurement of precise time-frequency signal, network test is one of the important directions of development of the test system. By means of putting the measurement equipment under remote control via Internet, the network test system provides anytime and anywhere monitoring and controlling of the measurement process. Moreover, the users can also set the measurement parameters and process the measurement results through the network test system so that the measurement interference affected by human activities can be reduced and the measurement accuracy can be improved. By doing so, this system provides widely hardware resources-sharing and system expansion, as well as enhancement of efficiency of instruments testing. This paper introduces the advantages of network test system at the beginning, then, it describes the basic components of system, operating principle and the implementation of this system in a very detail way. The results of the practical use indicate that the network test system has the advantages of flexible, stability and expansibility.
    08/2013; DOI:10.2991/icacsei.2013.19
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    ABSTRACT: The Gαq protein carboxyl terminus imitation polypeptide (GCIP)-27 has been shown to affect cardiac hypertrophy and vascular remodeling in various models both in vitro and in vivo. Transport across the plasma membrane is a critical step in regulating the action of this peptide drug. This study was designed to explore the mechanisms underlying the transmembrane transport of GCIP-27. The peptide drug was labeled with fluorescein isothiocyanate (FITC), and measured in a time- and concentration-dependent manner using laser confocal microscopy. Various transport inhibitors, including energy and endocytosis inhibitors, were used to identify the factors that regulate its transmembrane transport. GCIP-27 transport was examined in cardiomyocytes, cardiac fibroblasts, vascular endothelial cells, vascular smooth muscle cells (VSMCs) and hepatocytes. Atomic force microscopy and scanning electron microscopy were used to determine the ultrastructure of the cardiomyocyte membranes. The results showed that GCIP-27 was transported through the plasmalemma in a time- and concentration-dependent manner. The rate of uptake and the level of GCIP-27 in the cells decreased significantly after treatment with energy inhibitors, methyl-ß-cyclodextrin chlorpromazine or heparin. GCIP-27 levels in VSMCs and cardiomyocytes were significantly greater than the levels observed in hepatocytes, cardiac fibroblasts and vascular endothelial cells. Treatment with GCIP-27 led to a marked increase in the surface roughness of the cellular membrane. In conclusion, the transmembrane transport of GCIP-27 is mediated by endocytosis, which requires energy, and GCIP-27 preferentially enters myocardial cells and VSMCs.
    European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences 06/2013; DOI:10.1016/j.ejps.2013.05.028 · 3.01 Impact Factor
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    ABSTRACT: Numerous clinical epidemiology and laboratory studies have demonstrated a close association between inflammation or immunity and the occurrence of hypertension. Our group has previously shown that upon intraperitoneal injection of lipopolysaccharide (LPS) or zymosan (Zym) into pregnant rats, the offspring of the experimental group exhibited higher blood pressure levels compared with the control group, and these may be associated with the effects of an accumulation of gene expression changes on female rats during pregnancy. The present study used the Affymetrix GeneChip® Rat Genome 230 2.0 Array to examine gene expression profile changes in the embryos of experimental pregnant rats intraperitoneally injected with LPS or Zym vs. the untreated controls. We discovered that genes associated with DNA replication and mRNA processing were significantly upregulated by the stimuli from analysis using GenMAPP. By contrast, genes involved in the calcium regulatory pathway in cardiac myocytes and the signaling pathway in smooth muscle contraction and relaxation were the most downregulated. Results of the microarray analysis showed that immuno-inflammatory stimuli during pregnancy affected the gene expression profiles of the embryos. These changes in gene expression may affect the developmental and metabolic status of the offspring, thereby increasing their susceptibility to hypertension and obesity.
    Molecular Medicine Reports 05/2013; 8(1). DOI:10.3892/mmr.2013.1498 · 1.48 Impact Factor
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    ABSTRACT: Global navigation satellite systems (GNSS) receivers can be used in time and frequency metrology by exploiting stable GNSS time scales. This paper proposes a low-cost method for precise measurement of oscillator frequency instability using a single-frequency software GNSS receiver. The only required hardware is a common radio frequency (RF) data collection device driven by the oscillator under test (OUT). The receiver solves the oscillator frequency error in high time resolution using the carrier Doppler observation and the broadcast ephemeris from one of the available satellites employing the onboard reference atomic frequency standard that is more stable than the OUT. Considering the non-stable and non-Gaussian properties of the frequency error measurement, an unbiased finite impulse response (FIR) filter is employed to obtain robust estimation and filter out measurement noise. The effects of different filter orders and convolution lengths are further discussed. The frequency error of an oven controlled oscillator (OCXO) is measured using live Beidou-2/Compass signals. The results are compared with the synchronous measurement using a specialized phase comparator with the standard coordinated universal time (UTC) signal from the master clock H226 in the national time service center (NTSC) of China as its reference. The Allan deviation (ADEV) estimates using the two methods have a 99.9% correlation coefficient and a 0.6% mean relative difference over 1–1000 s intervals. The experiment demonstrates the effectiveness and high precision of the software receiver method.
    Advances in Space Research 03/2013; 51(6):969–977. DOI:10.1016/j.asr.2012.11.007 · 1.24 Impact Factor
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    ABSTRACT: Danggui Buxue Tang (DBT), a Chinese medicinal decoction that contains Radix Angelicae sinensis (Danggui) and Radix Astragali (Huangqi) at a ratio of 1:5, is used commonly for treating women's ailments. The present study explored the effects of this preparation on chronic fatigue syndrome (CFS). Rats were subjected to a combination of food restriction and forced swimming to induce CFS, and rats were gavaged once daily with either 12 or 24 g/kg DBT for 28 days. Body weights, T-cell subset counts, (3) H-TdR incorporation measurements and mRNA levels of IL-1β, TNF-α, NF-кB, p38MAPK and JNK were determined on days 14 and 28. The swimming endurance capacity was measured on day 28. Rats that received DBT exhibited increased body weight and endurance capacity, corrected T cell subsets counts, increased (3) H-TdR incorporation and decreased mRNA levels of IL-1β, TNF-α, NF-кB, p38MAPK and JNK compared with rats that did not receive DBT. The results indicate that DBT can ameliorate CFS through immune modulation and may act to normalize cytokines and their related signaling pathways.
    Phytotherapy Research 12/2011; 25(12):1825-32. DOI:10.1002/ptr.3499 · 2.40 Impact Factor
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    Applications of Digital Signal Processing, 11/2011; , ISBN: 978-953-307-406-1
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    ABSTRACT: Gq-protein is located at the convergent point in signal transduction pathways leading to vascular remodeling. The carboxyl terminus of Gα-subunit plays a vital role in G-protein-receptor interaction. The present study was designed to explore the effects of a synthetic Gαq carboxyl terminus imitation peptide, namely GCIP-27, on vascular smooth muscle cells (VSMC) in vitro and vascular remodeling in spontaneous hypertensive rats (SHR). Hyperplasia and hypertrophy of VSMC wre determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, [(3)H]-thymidine and [(3)H]-leucine incorporation, and [Ca(2+)](i) was measured with Fluo-3/AM staining. Systolic blood pressure (SBP), the ratio of media thickness to lumen diameter (MT/LD) of aorta, collagen content, and phospholipase C activity in aorta were measured in SHR. GCIP-27 (3-100 µg/l) significantly decreased proliferation activity, protein content, incorporation of [(3)H]-thymidine and [(3)H]-leucine, and [Ca(2+)](i) level in VSMC. SBP, MT/LD, collagen content, and phospholipase C activity in aorta of SHR were decreased significantly in GCIP-27 (7, 20, 60 µg/kg)-treated groups and losartan (6 mg/kg) group compared with vehicle group. In conclusion, GCIP-27 could inhibit vascular remodeling effectively in vitro and in vivo.
    Biological & Pharmaceutical Bulletin 01/2011; 34(10):1527-32. DOI:10.1248/bpb.34.1527 · 1.78 Impact Factor
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    ABSTRACT: Accumulating evidence has indicated that Panax notoginseng saponins (PNS), the major ingredients in Panax notoginseng (Burk.) F.H. Chen which could be found widely in Asia, can attenuate atherogenesis in vivo. This study was designed to examine the relationship of PNS with cholesterol ester in foam cells sourced from macrophages and the effect of PNS on the expression of ATP-binding cassette transporter A1 (ABCA1). Foam cells sourced from macrophages were cultured with PNS. The content of cholesterol ester in foam cells was analyzed and expressions of ABCA1 and liver X receptor α (LXRα) in foam cells were measured by real-time PCR and western blotting methods. The results showed that PNS could significantly decrease the level of cholesterol ester in foam cells at middle and high dosages. The real-time PCR and western blotting assays indicated that the expression of ABCA1 was up-regulated by PNS in a dose-dependent manner. Analysis based on these results showed that the cholesterol ester level was negatively correlated with ABCA1 expression. As a result, we conclude that by up-regulating the expression of ABCA1, PNS could lower the cholesterol ester level, which resulted in the attenuation of the foam cell formation. This bioactivity might be associated with the special chemical structures of PNS that are similar to the natural agonist of LXRα.
    Journal of ethnopharmacology 10/2010; 132(1):297-302. DOI:10.1016/j.jep.2010.08.033 · 2.94 Impact Factor
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    ABSTRACT: Symmetricom's Multi-channel Measurement System (TSC MMS) is a phase measurement device based on the measurement principle of dual mixer time difference method (DMTD). TSC MMS is purchased by Time and Frequency measurement laboratory in National Time Service Center of Chinese Academy of Sciences. In order to evaluate the measurement capability of DMTD and research the improved method of performance, in this paper, the TSC MMS performance test platform is set up. We ensure the test signals have better stability than system, and the invariant environment to reduce the effect of measurement produced by external environment as much as possible. Under the same condition, three-day data are collected to measure the noise floor of a system. Finally, we analyze the reasons attributing to the measurement results and proposed a improving method in detail. The measured results demonstrate that the Allan deviation stability will reach 3E-13 per second when the frequency of the input signals is 10MHz.
    Proceedings of SPIE - The International Society for Optical Engineering 08/2010; DOI:10.1117/12.885393 · 0.20 Impact Factor
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    ABSTRACT: An Offset Generator with low noise floor has been developed by Time & Frequency Measurement & Control Department, NTSC. The Offset Generator is designed with Phase Lock Loop, and the +100Hz offset is generated in the output stage. The Allan deviation noise floor of the Offset Generator is 1x10-12 at 1 second. The Offset Generator has been installed in "Digital Multi-Channel Frequency Stability Analyzer" (DFSA), developed by Time & Frequency Measurement & Control Department, NTSC, too, and the Allan deviation noise floor of DFSA using current Offset Generator is about 4x10-14 at 1 second and <1x10-15 at 1000 second.
    Proceedings of SPIE - The International Society for Optical Engineering 08/2010; DOI:10.1117/12.885873 · 0.20 Impact Factor
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    ABSTRACT: Prenatal exposure to inflammation produces offspring that are hypertensive in adulthood. The present study was to explore the role of intrarenal renin-angiotensin (Ang) system in the development of hypertension programmed by prenatal exposure to zymosan. Pregnant rats were randomly divided into control group and zymosan group (n = 6). Rats in these two groups were administered intraperitoneally with 0.5 ml vehicle and 2.37 mg/kg zymosan, respectively, on the eighth, tenth, and 12th day during gestation. The results showed the glomerular number and creatinine clearance rate decreased significantly in offspring of zymosan-treated rats. The renal cortex renin mRNA expression, Ang II-positive cells in renal cortex, and Ang II expression in renal medulla increased significantly in offspring of zymosan-treated rats at 7, 16, and 25 weeks of age. The plasma renin activity and Ang II concentration were unchanged. In conclusion, prenatal exposure to zymosan resulted in the activation of intrarenal renin-Ang system in adult offspring rats.
    Inflammation 03/2010; 33(6):408-14. DOI:10.1007/s10753-010-9199-y · 1.92 Impact Factor
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    ABSTRACT: Panax notoginseng saponins (PNS) are highly valued traditional Chinese medicine. The effects of PNS (120 mg/kg, once daily administrated intragastrically (i.g.)) on atherosclerosis induced by a high-cholesterol diet and chronic inflammation, which was derived through zymosan (10 mg/kg, once every 2 d) administration intraperitoneally, were evaluated in rabbits for 8 weeks. A normal group, a simple high-fat diet group, and a zymosan plus high-cholesterol diet group (Zym) were used as controls. Typical pathologic changes associated with atherosclerosis in rabbits following induction by zymosan were alleviated by PNS treatment. After 2, 4, 6, and 8 weeks of treatment, PNS decreased the serum levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, interleukin-6 and C-reactive protein as well as increased high-density lipoprotein cholesterol level significantly in comparison with those in the Zym group, except for triglycerides at week 2. In addition, PNS treatment significantly decreased the mRNA expression levels of monocyte chemoattactant protein-1 and nuclear factor-kappaB/p65 in the aorta wall after 8 weeks of treatment compared with the Zym group. In conclusion, PNS attenuates atherogenesis through an antiinflammatory action and regulation of the blood lipid profile.
    Biological & Pharmaceutical Bulletin 01/2010; 33(8):1324-30. DOI:10.1248/bpb.33.1324 · 1.78 Impact Factor
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    ABSTRACT: A multi-channel beat-frequency digital measurement system (BFDMS) using digital signal processing method has been developed and operated in NTSC. The system can high-precision analyze and monitor high-stability frequency sources. It consists of three independent measuring channels what can be operated simultaneously and one calibrating channel to correct the systematic error. This result that the measured noise floor Allan deviation is approximately 3e-14 at one second has been approved in system test. The key technique is the digital correlation algorithm that has been designed to reduce the effecting of beat-frequency device noise floor on measurement accuracy. So the limit factor of improving measurement precision that is brought by circuit noise of beat-frequency technology has been solved. The algorithm can calculate phase difference either. To improve ability of measurement, the system has a calibration channel what is designed to remove the systematic error. In this channel, the known reference frequency can be used to deduce systematic error. And then this result will be used to modify the value of measurement channels. The principles of operation, and error analysis have been verified will be introduced in detail in this article.
    Frequency Control Symposium, 2009 Joint with the 22nd European Frequency and Time forum. IEEE International; 05/2009
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    ABSTRACT: The performance of two high precision frequency-stability measurement systems, analog beat method time-interval analyzer, has been compared with digital beat method systems developed at the National Time Service Center. In this paper, the digital beat method system is a measuring technique that uses a multi-channel beat note digital analyzer in place of the time interval counter. This technique uses the local oscillator and mixer to convert the test signals and reference signals to a low frequency. This article reports on the frequency-stability analysis of the digital beat method in detail based upon the beat method working at 10 MHz with 1 Hz beat note and the cross correlation arithmetic. The principle of the system is reviewed, the design approach and compared system is described, and the experimental results are present. The measurement system shows that the digital beat method system can achieve a stability of 3times10<sup>-14</sup> /tau (Allan deviation, tau =1s ) when the analog beat method can acquire a stability of 4.7times10<sup>-12</sup> /tau (Allan deviation, tau =1s ) by using the SR620. An approach to reduce quantization noise effects and evaluate performance of the algorithm problems has been tested too.
    Frequency Control Symposium, 2008 IEEE International; 06/2008