949 research outputs found

    Associated production of the ZZ boson with a pair of top quarks in the left-right twin Higgs model

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    In the context of the left-right twin Higgs (LRTH) model, we first examine the effects on the ZttˉZt\bar t production at the ILC and LHC. Our results show that the cross-sections can be significantly deviated from the standard model predictions and thus provide a good probe for the LRTH model. We also estimate the new production channel, ZtTˉZt\bar T or ZtˉTZ\bar t T production, at the LHC. Compared with ZttˉZt \bar t production, we find that the ZtTˉZ t \bar T production can have a sizable production rate when the scale ff is not too high. Considering the dominant decay mode Tϕ+btbbˉT\rightarrow \phi^{+}b\rightarrow tb\bar b, we find that ZtTˉZ t\bar T final state has less background than ZttˉZt\bar t production and may likely be observable at the LHC.Comment: Final version to appear in EP

    Study on Population Distribution, Morphological Structure and Physiological-Biochemical Characteristics of \u3cem\u3eDactylis glomerata\u3c/em\u3e in Different Geographical Areas of Tianshan Mountains of Xinjiang in China

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    As one important cool-season grass with high resource value, Dactylis glomerata has many characteristics such as good adaptability, high nutritional value and so on. It is one of the major cultivated species planted in high quality artificial grassland in the world. Xinjiang is one of the major areas have rich germplasm resource of wild Dactylis glomerata, and it is a natural gene pool. In order to protect and make good use of wild plant resources, this study focused on the distribution patterns, distribution regulation, morphological structure and physiological-biochemical characteristics of wild Dactylis glomerata grown in different geographical areas of Tianshan mountain of Xinjiang. It is aims to reveal the effects of geographical space and habitat on the population distribution in, morphological structure and physiological-biochemical characteristics of Dactylis glomerata

    Nullerical Studies of Body Wave Amplitudes in Full Waveform Acoustic Logs

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    The amplitudes of P and S head waves in a full waveform acoustic log microseismogram are studied numerically as a function of borehole and formation parameters. The technique used is contour integration around the respective branch cuts in the complex wavenumber plane (Tsang and Rader, 1979). The results showed that the P wave amplitude depends on the Poisson's ratio, but the S wave amplitude does not. The well accepted geometric spreading factor for P and S waves in the "far field" is only valid for a limited range of source-receiver spacings, and the onset of "far field" depends on the Poisson's ratio as well as the wavelength. The wave shape factor I[subscript e] for the P wave as defined by Lebreton et al. (1978) has a direct relationship to in situ attenuation.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu

    Topoisomerase II trapping agent teniposide induces apoptosis and G2/M or S phase arrest of oral squamous cell carcinoma

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    BACKGROUND: Teniposide (VM-26) has been widely used in the treatment of small cell lung cancer, malignant lymphoma, breast cancer, etc. However, there are few reports on VM-26 against oral cancers. The present study was designed to identify the effect of VM-26 against oral squamous cell carcinoma in vitro, and to provide evidence for the feasibility and effectiveness of VM-26 for application to the patients with oral cancer. METHODS: Human tongue squamous cell carcinoma cell line, Tca8113, was used. Cells were incubated with different concentrations of VM-26 for a variety of time span. Cisplatin (CDDP) was employed as a control reagent. MTT assay was used to assess the inhibitory rate of Tca8113 growth. Flow cytometer (FCM), transmission electronic microscope (TEM) and fluorescence staining were employed for determining the cell apoptotic rate. Cell cycle distribution of Tca8113 incubated with VM-26 was examined by flow cytometer assay. Statistic software (SAS 6.12, USA) was used for one-way ANOVA. RESULTS: The IC50 of VM-26 against Tca8113 cells was 0.35 mg/l and that of CDDP was 1.1 mg/l. The morphological changes of Tca8113 cells were observed with fluorescence microscope and TEM. Apoptotic morphological feature could be found in the nucleus. Apoptotic rate of Tca8113 cells incubated with 5.0 mg/l of VM-26 for 72 hours was 81.67% and cells waere arrested at S phase. However, when exposed to 0.15 mg/l of VM-26 for 72 hours, G2/M phase increased from 12.75% to 98.71%, while the apoptotic rate was 17.38%, which was lower than that exposed to 5.0 mg/l of VM-26. CONCLUSION: VM-26 could significantly induce apoptosis of oral squamous cell carcinoma and inhibit cell growth. There may be another pathway to induce apoptosis of oral squamous cell carcinoma cells except for G2/M phase arrest

    Structural Transformations in Ferroelectrics Discovered by Raman Spectroscopy

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    Ferroelectrics systems are of great interest from the fundamental as well as applications points, such as ferroelectric random access memories, electro-optic switches and a number of electro-optic devices. Curie temperature (TC) is one of the important parameters of ferroelectrics for high-temperature applications. Particularly, the optical modes, which are associated with the ferroelectric to paraelectric phase transition, are of great interest. Structural transformations that alter the crystal symmetry often have a significant effect on the Raman spectroscopy. This chapter systematically studies the type ferroelectric oxides and rare earth element doped ferroelectric materials such as PbTiO3-Bi(Mg0.5Ti0.5)O3 (PT-BMT), Sr x Ba1−x Nb2O6 (SBN), Pb1−1.5x La x Zr0.42Sn0.4Ti0.18O3 (PLZST), Bi1−xLaxFe1−yTiyO3 (BLFT) and (K0.5Na0.5)NbO3-0.05LiNbO3 (KNN-LN) and so on synthesis of single crystal/ceramic and optical phonon vibration modes and the improvement of the Curie temperature characteristic using spectrometry measurements. The TC, distortion degree, and phase structure of the ferroelectric materials have been investigated by temperature-dependent Raman spectroscopy. Meanwhile, the important physical parameters exhibited a strong dependence on dopants resulting in structural modifications and performance promotion