1,338 research outputs found
Synthesis, vacuum ultraviolet and near ultraviolet-excited luminescent properties of GdCaAl3O7: RE3+ (RE=Eu, Tb)
Vacuum ultraviolet (VUV) excitation and photoluminescent (PL) properties of Eu3+ and Tb3+ ion-doped aluminate phosphors, GdCaAl 3O7:Eu3+ and GdCaAl3O 7:Tb3+ have been investigated. X-ray diffraction (XRD) patterns indicate that the phosphor GdCaAl3O7 forms without impurity phase at 900 °C. Field emission scanning electron microscopy (FE-SEM) images show that the particle size of the phosphor is less than 3 μm. Upon excitation with VUV irradiation, the phosphors show a strong emission at around 619 nm corresponding to the forced electric dipole 5D0→7F2 transition of Eu 3+, and at around 545 nm corresponding to the 5D 4→7F5 transition of Tb3+. The results reveal that both GdCaAl3O7:RE3+ (RE=Eu, Tb) are potential candidates as red and green phosphors, respectively, for use in plasma display panel (PDP). © 2005 Elsevier Inc. All rights reserved.postprin
The Dichotomy between Nodal and Antinodal Quasiparticles in Underdoped (LaSr)CuO Superconductors
High resolution angle-resolved photoemission measurements on underdoped
(LaSr)CuO system show that, at energies below 70 meV, the
quasiparticle peak is well defined around the (/2,/2) nodal region
and disappears rather abruptly when the momentum is changed from the nodal
point to the (,0) antinodal point along the underlying ``Fermi surface''.
It indicates that there is an extra low energy scattering mechanism acting upon
the antinodal quasiparticles. We propose that this mechanism is the scattering
of quasiparticles across the nearly parallel segments of the Fermi surface near
the antinodes.Comment: to appear in Phys. Rev. Let
Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors
Through the measurements of magnetic field dependence of specific heat in
in zero temperature limit, we determined the nodal slope
of the quasiparticle gap. It is found that has a very
similar doping dependence of the pseudogap temperature or value
. Meanwhile the virtual maximum gap at () derived from
is found to follow the simple relation upon
changing the doping concentration. This strongly suggests a close relationship
between the pseudogap and superconductivity. It is further found that the
superconducting transition temperature is determined by both the residual
density of states of the pseudogap phase and the nodal gap slope in the zero
temperature limit, namely, , where
is the extracted zero temperature value of the normal state
specific heat coefficient which is proportional to the size of the residual
Fermi arc . This manifests that the superconductivity may be formed by
forming a new gap on the Fermi arcs near nodes below . These observations
mimic the key predictions of the SU(2) slave boson theory based on the general
resonating-valence-bond (RVB) picture.Comment: 6 pages, 6 figures, to be published in Phys. Rev.
Efficient Anonymous Authenticated Key Agreement Scheme for Wireless Body Area Networks
Wireless body area networks (WBANs) are widely used in telemedicine, which can be utilized for real-time patients monitoring and home health-care. The sensor nodes in WBANs collect the client’s physiological data and transmit it to the medical center. However, the clients’ personal information is sensitive and there are many security threats in the extra-body communication. Therefore, the security and privacy of client’s physiological data need to be ensured. Many authentication protocols for WBANs have been proposed in recent years. However, the existing protocols fail to consider the key update phase. In this paper, we propose an efficient authenticated key agreement scheme for WBANs and add the key update phase to enhance the security of the proposed scheme. In addition, session keys are generated during the registration phase and kept secretly, thus reducing computation cost in the authentication phase. The performance analysis demonstrates that our scheme is more efficient than the currently popular related schemes
Effects of DNMT1 silencing on malignant phenotype and methylated gene expression in cervical cancer cells
<p>Abstract</p> <p>Background</p> <p>DNA methylation has been widely used in classification, early diagnosis, therapy and prediction of metastasis as well as recurrence of cervical cancer. DNMT methyltransferase 1 (DNMT1), which plays a significant role in maintaining DNA methylation status and regulating the expression of tumor suppressor genes. The aim of this research was to investigate the relationship between DNMT1 and abnormal methylation of tumor suppressor genes and malignant phenotype in cervical cancer.</p> <p>Methods</p> <p>Levels of DNMT1 mRNA and protein were detected using qPCR and Western blot, respectively. Cell proliferation was analyzed by MTT and apoptosis was performed by Annexin V-FITC/PI double staining flow cytometry, respectively. MeDIP-qPCR and qPCR were performed to measure demethylation status and mRNA re-expression level of 7 tumor-suppressor genes (CCNA1, CHFR, FHIT, PAX1, PTEN, SFRP4, TSLC1) in Hela and Siha cells after silencing DNMT1.</p> <p>Results</p> <p>The average expression levels of DNMT1 mRNA and protein in Hela and Siha cells were decreased significantly compared with control group. The flow cytometry and MTT results showed that Hela and Siha cells apoptosis rates and cell viabilities were 19.4 ± 2.90%, 25.7 ± 3.92% as well as 86.7 ± 3.12%, 84.16 ± 2.67% respectively 48 h after transfection (<it>P </it>< 0.01). Furthermore, the promoter methylation of five tumor suppressor genes was decreased with the increased mRNA expression after silencing DNMT1, whereas there were no significant changes in PTEN and FHIT genes in Hela cells, and CHFR and FHIT genes in Siha cells.</p> <p>Conclusions</p> <p>Our experimental results demonstrate that methylation status of DNMT1 can influence several important tumor suppressor genes activity in cervical tumorigenesis and may have the potential to become an effective target for treatment of cervical cancer.</p
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