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  • Author: Hua Li x
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Overcoming Environmental Dose Rate Changes in Luminescence Dating of Waterlain Deposits

This study investigates lacustrine and fluvial sediments on the Sala Us River in the Mu Us Desert in central north China. Significant changes in environmental dose rate in part of the section could be shown to have occurred from measurements of the present day radioactivity and by the age reversal for some samples that had been dated by optically stimulated luminescence (OSL) measurements on quartz. These changes in dose rate can be attributed to recent uptake of radioactive elements found in the sediments; this resulted in significant underestimation of the OSL ages. In this study, the new isochron method using K-feldspar grains has been applied to overcome the effects of changes in dose rate. Calculations are used to show that changes in the environmental dose rate factors, i.e. K, U, Th, water content and cosmic ray flux, and disequilibrium in the U and Th decay chains, e.g. radon escape, have a negligible effect on the isochron age. After applying the new isochron method, the effects of changes in dose rate caused by recent uptake of radioactive elements and changes in past water content were effectively overcome and true ages are obtained; this was verified by repeating the luminescence isochron measurements on samples of overlying and underlying sediments.

Abstract

Thermoluminescence (TL) and isothermal thermoluminescence (ITL) signals from K-feldspar were studied. The signals from K-feldspar have provided multiple thermometers for thermochronological study. Protocols of multiple aliquot (MA) additive-dose (A) and regenerative-dose (R) have been applied and tested for equivalent dose (De) determinations using TL and ITL signals (MAA-TL, MAR-TL, MAA-ITL and MAR-ITL). Single aliquot regenerative-dose (SAR) protocol was only applied for De determination using ITL signals (SAR-ITL). A 50–60°C translation of heating temperature was necessary for the ITL De values to agree with TL De values. Based on the experiment results and merits-drawbacks comparison of the five tested protocols, the MAR-TL and SAR-ITL are favorable because of their efficiency and accuracy in De determinations. These two protocols were further applied to the samples from the Nujiang River valley and both explicitly demonstrated the thermal history of the samples. They are suitable for K-feldspar thermochronology study. They, as a parallelism of the previous studies of quartz TL and ITL signals, can provide multiple measures for a rock sample with the same thermal history in geo-thermochronological studies.

Abstract

The residual doses and sensitivity change for potassium-rich feldspar (K-feldspar) have been studied using the post-infrared infrared stimulated luminescence (pIRIR) and multi-elevated-temperature post-IR IRSL (MET-pIRIR) protocols. Laboratory simulated poorly-bleached and well-bleached samples were those K-feldspar grains bleached using a solar simulator for 10 minutes and 8 hours, respectively. The residual doses rise with stimulation temperature and time. The poorly-bleached sample has larger residual doses than the well-bleached sample, especially at high stimulation temperatures. The high-temperature pIRIR signals contain a large amount of hard-to-bleach signals. A decrease of luminescence sensitivity was observed after conducting a high-temperature-treatment in the measurement cycles. The sensitivity decreases significantly between the first and the second cycle. The extent of decrease in sensitivity shows a clear temperature trend. The higher the stimulation temperature of pIRIR signals is, the larger the sensitivity decreases. This decrease is more severe for the poorly-bleached sample than for the well-bleached sample, and could possibly lead to problems in sensitivity correction.

Abstract

Let S = (a 1,. . . , a m; b 1, . . . , b n), where a 1, . . . , a m and b 1, . . . , b n are two sequences of nonnegative integers. We say that S is a bigraphic pair if there exists a simple bipartite graph G with partite sets {x 1, x 2, . . . , x m} and {y 1, y 2, . . . , y n} such that d G(x i) = a i for 1 ≤ im and d G(y j) = b j for 1 ≤ jn. In this case, we say that G is a realization of S. Analogous to Kundu’s k-factor theorem, we show that if (a 1, a 2, . . . , a m; b 1, b 2, . . . , b n) and (a1 − e1, a2 − e2, . . . , am − em; b1 − f1, b2 − f2, . . . , bn − fn) are two bigraphic pairs satisfying kf ik + 1, 1 ≤ in (or ke ik + 1, 1 ≤ im), for some 0 ≤ km − 1 (or 0 ≤ kn − 1), then (a 1, a 2, . . . , a m; b 1, b 2, . . . , b n) has a realization containing an (e 1, e 2, . . . , e m; f 1, f 2, . . . , f n)-factor. For m = n, we also give a necessary and sufficient condition for an (k n; k n)-factorable bigraphic pair to be connected (k n; k n)-factorable when k ≥ 2. This implies a characterization of bigraphic pairs with a realization containing a Hamiltonian cycle.

Abstract

Manas Lake is a closed lake basin in northern Xinjiang Province of China, with its current lake bed at 244 m a.s.l. Sediments from the lake area provide valuable information about the paleoenvironmental changes in the Westerlies-dominated arid region. To obtain a chronological constraint on the past changes, optically stimulated luminescence dating was conducted on sediments from the lake beaches. The results show that lacustrine episodes dated at ~80–73 ka ago were recorded in northwestern side of the lake at 270 m a.s.l., while paleoshoreline to near-shore environments during ~80–90 ka ago were recorded in the opposite side of the lake at 262 m a.s.l. The ~80 ka old sedimentary layers are overlain by paleoshoreline sediments formed within the last ~1 ka, separated by a large age gap. From this study and the results from previous studies, it is concluded that breaks in sedimentary records are common in the lake area at elevation > 260 m a.s.l. When comparing sedimentary environments at different times from different sites in this study and previous studies, it is suggested that a small amount of uplift of the northwestern side of Manas Lake relative to the southeastern side may have occurred in the last 80 ka.

Abstract

Introduction: Tiletamine-xylazine-tramadol (XFM) has few side effects and can provide good sedation and analgesia. Adenosine 5’-monophosphate-activated protein kinase (AMPK) can attenuate trigeminal neuralgia. The study aimed to investigate the effects of XFM and its specific antagonist on AMPK in different regions of the brain. Material and Methods: A model of XFM in the rat was established. A total of 72 Sprague Dawley (SD) rats were randomly divided into three equally sized groups: XFM anaesthesia (M group), antagonist (W group), and XFM with antagonist interactive groups (MW group). Eighteen SD rats were in the control group and were injected intraperitoneally with saline (C group). The rats were sacrificed and the cerebral cortex, cerebellum, hippocampus, thalamus, and brain stem were immediately separated, in order to detect AMPKα mRNA expression by quantitative PCR. Results: XFM was able to increase the mRNA expression of AMPKα1 and AMPKα2 in all brain regions, and the antagonist caused the opposite effect, although the effects of XFM could not be completely reversed in some areas. Conclusion: XFM can influence the expression of AMPK in the central nervous system of the rat, which can provide a reference for the future development of anaesthetics for animals.

Abstract

The Turán number of a graph H, denoted by ex(n, H), is the maximum number of edges of an n-vertex simple graph having no H as a subgraph. Let S denote the star on + 1 vertices, and let k · S denote k disjoint copies of S . Erdős and Gallai determined the value ex(n, k · S 1) for all positive integers k and n. Yuan and Zhang determined the value ex(n, k · S 2) and characterized all extremal graphs for all positive integers k and n. Recently, Lan et al. determined the value ex(n, 2 · S 3) for all positive integers n, and Li and Yin determined the values ex(n, k · S ) for k = 2, 3 and all positive integers and n. In this paper, we further determine the value ex(n, 4 · S ) for all positive integers and almost all n, improving one of the results of Lidický et al.

Abstract

Quartz has been the main mineral used for optically stimulated luminescence (OSL) dating of sediments over the last decade. The quartz OSL signal, however, has been shown to saturate at relatively low doses of ∼200–400 Gy, making it difficult to be used for dating beyond about 200 thou-sand years (ka), unless the environmental dose rate is low. The infrared stimulated luminescence (IRSL) from feldspars has been shown to continue to grow to higher dose levels than quartz OSL. The application of IRSL dating of feldspars, however, has long been hampered by the anomalous fading effect. Recent progress in understanding anomalous fading of the infrared stimulated luminescence (IRSL) signals in potassium-feldspar has led to the development of post-IR IRSL (pIRIR) protocols and also a multiple elevated temperature (MET) stimulation (MET-pIRIR) protocol. These procedures have raised the prospect of isolating a non-fading IRSL component for dating Quaternary deposits containing feldspars. In this study, we review the recent progress made on (1) overcoming anomalous fading of feldspar, and (2) the development of pIRIR dating techniques for feldspar. The potential and problems associated with these methods are discussed.

Abstract

The convergence rate and the continuous tracking precision are two main problems of the existing adaptive notch filter (ANF) for frequency tracking. To solve the problems, the frequency is detected by interpolation FFT at first, which aims to overcome the convergence rate of the ANF. Then, referring to the idea of negative feedback, an evaluation factor is designed to monitor the ANF parameters and realize continuously high frequency tracking accuracy. According to the principle, a novel adaptive frequency estimation algorithm based on interpolation FFT and improved ANF is put forward. Its basic idea, specific measures and implementation steps are described in detail. The proposed algorithm obtains a fast estimation of the signal frequency, higher accuracy and better universality qualities. Simulation results verified the superiority and validity of the proposed algorithm when compared with original algorithms.

Knockdown of stat3 expression by RNAi inhibits in vitro growth of human ovarian cancer

Background. The aim of the study was to investigate the suppressive effects of pSilencer2.1-U6-siRNA-stat3 recombinant plasmids on the growth of ovarian cancer in vitro.

Material and methods. Three pairs of DNA template (stat3-1, stat3-2, stat3-3) specific for different target sites on stat3 mRNA were synthesized to reconstruct pSilencer2.1-U6-siRNA-stat3s, which were transfected into SKOV3 cells. The expressions of STAT3, BcL-2, cyclin D1 and C-myc in these cells were detected by Western blot and Northern blot. The cell cycle and the growth were determined by flow cytometry (FCM) and MTT assay, respectively. Cell apoptosis was determined by TUNEL staining.

Results. Of the three siRNAs, only siRNA targeting stat3-3 markedly suppressed the protein expression of stat3 in SKOV3 cells; MTT assay and FCM showed that transfection of stat3-3 siRNA could significantly suppress the growth of SKOV3 cells and arrest the cell cycle in vitro. TUNEL staining also showed massive apoptosis in SKOV3 cells transfected with stat3-3 siRNA.

Conclusions. pSilencer2.1-U6-siRNA-stat3-3 can significantly inhibit the STAT3 expression in human ovarian cancer cells resulting in the inhibition of the cancer growth and the increase of apoptosis of cancer cells.