1,749 research outputs found
Strain-Dependent Effects on Confinement of Folded Acoustic and Optical Phonons in Short-Period (XC)m/(YC)n with X,Y (≡Si, Ge, Sn) Superlattices
No full textCarbon-based novel low-dimensional XC/YC (with X, Y ≡ Si, Ge, and Sn) heterostructures have recently gained considerable scientific and technological interest in the design of electronic devices for energy transport use in extreme environments. Despite many efforts made to understand the structural, electronic, and vibrational properties of XC and XxY1−xC alloys, no measurements exist for identifying the phonon characteristics of superlattices (SLs) by employing either an infrared and/or Raman scattering spectroscopy. In this work, we report the results of a systematic study to investigate the lattice dynamics of the ideal (XC)m/(YC)n as well as graded (XC)10−∆/(X0.5Y0.5C)∆/(YC)10−∆/(X0.5Y0.5C)∆ SLs by meticulously including the interfacial layer thickness ∆ (≡1–3 monolayers). While the folded acoustic phonons (FAPs) are calculated using a Rytov model, the confined optical modes (COMs) and FAPs are described by adopting a modified linear-chain model. Although the simulations of low-energy dispersions for the FAPs indicated no significant changes by increasing ∆, the results revealed, however, considerable “downward” shifts of high frequency COMs and “upward” shifts for the low energy optical modes. In the framework of a bond polarizability model, the calculated results of Raman scattering spectra for graded SLs are presented as a function of ∆. Special attention is paid to those modes in the middle of the frequency region, which offer strong contributions for enhancing the Raman intensity profiles. These simulated changes are linked to the localization of atomic displacements constrained either by the XC/YC or YC/XC unabrupt interfaces. We strongly feel that this study will encourage spectroscopists to perform Raman scattering measurements to check our theoretical conjectures
Inhibition of HIV-1 Ribonuclease H activity by novel frangula-emodine derivatives
No full textThe HIV-1 reverse transcriptase (RT) associated ribonuclease H (RNase H) activity hydrolyzes the RNA component of the viral heteroduplex RNA:DNA replication intermediate. Even though this function is essential for viral replication, until now only very few compounds have been reported to inhibit it. Anthraquinones are common secondary metabolites which have diverse biological activities. In particular, some of them have been reported to inhibit the HIV-1 RT polymerase and integrase activities in biochemical assays. Given the structural similarities between integrase and RNase H proteins, we synthesized a series of frangula-emodine derivatives and showed that the introduction of a bromine atom in position 7 of the anthraquinone structure leads to derivatives which are able to inhibit both HIV-1 polymerase and RNase H functions at micromolar concentrations. Mechanism of action studies performed on the 7-brom-6-O-phenacyl-1,8-dihydroxy-3-methyl anthraquinone (K67) showed that this compound is a non-competitive inhibitor of the RNase H function and that it binds to a site which is not overlapping to the non-nucleoside RT inhibitors binding site. This study demonstrates that anthraquinone derivatives may be a scaffold to be further developed to obtain selective HIV-1 RNase H inhibitors and represent a new step toward the identification of new anti-RT agents
A Study of Spectral Energetic Properties of Extreme Ultraviolet-Boosted Photo-Ionization for Precise In-Situ Measurement of an Intense Laser Pulse
No full textUltrashort intense laser has a promising future in nano science and nano technology because of its extreme features in time domain and super high energy density for pump/probe research and machining. Study shows that an intense few-cycle laser pulse leaves a clear fingerprint of its field envelope on the photoelectron energy spectrum as it passes through a gas involving a continuous extreme ultraviolet (xuv) radiation. The spectrum resulting from the xuv photoionization processes includes significant quantum enhancement and strong interference between photoelectron wave packets and exhibits interesting and useful energetic properties. The spectral cut-off energies sensitively reflect the strength of the laser field modulation on the photoelectron's energy, pulse duration, and interference. The linear relationships between the spectral energetic properties and the laser parameters (intensity, carrier-envelope phase, pulse-duration, and spatial profile) suggest new methods for precise intense laser pulse measurement in-situ. These methods have the advantages of predicted accuracy (at 0.1% level in the intensity), simplicity, speed, and large dynamic ranges (up to many orders of intensity).National Natural Science Foundation of China [11175010]SCI(E)ARTICLE9,SI6497-65071
YC-1 enhances the anti-tumor activity of sorafenib through inhibition of signal transducer and activator of transcription 3 (STAT3) in hepatocellular carcinoma
No full textBackground: Traditional systemic chemotherapy does not provide survival benefits in patients with hepatocellular carcinoma (HCC). Molecular targeted therapy shows promise for HCC treatment, however, the duration of effectiveness for targeted therapies is finite and combination therapies offer the potential for improved effectiveness. Methods: Sorafenib, a multikinase inhibitor, and YC-1, a soluble guanylyl cyclase (sGC) activator, were tested in HCC by proliferation assay, cell cycle analysis and western blot in vitro and orthotopic and ectopic HCC models in vivo. Results: In vitro, combination of sorafenib and YC-1 synergistically inhibited proliferation and colony formation of HepG2, BEL-7402 and HCCLM3 cells. The combination also induced S cell cycle arrest and apoptosis, as observed by activated PARP and caspase 8. Sorafenib and YC-1 respectively suppressed the expression of phosphorylated STAT3 (p-STAT3) (Y705) in a dose-and time-dependent manner. Combination of sorafenib and YC-1 significantly inhibited the expression of p-STAT3 (Y705) (S727), p-ERK1/2, cyclin D1 and survivin and SHP-1 activity compared with sorafenib or YC-1 used alone in all tested HCC cell lines. In vivo, sorafenib-YC-1 combination significantly suppressed the growth of HepG2 tumor xenografts with decreased cell proliferation and increased apoptosis observed by PCNA and PARP. Similar results were also confirmed in a HCCLM3 orthotopic model. There was a reduction in CD31-positive blood vessels and reduced VEGF expression, which suggested a combinational effect of sorafenib and YC-1 on angiogenesis. The reduced expression of p-STAT3, cyclin D1 and survivin was also observed with the combination of sorafenib and YC-1. Conclusions: Our data show that sorafenib-YC-1 combination is a novel potent therapeutic agent that can target the STAT3 signaling pathway to inhibit HCC tumor growth.Biochemistry & Molecular BiologyOncologySCI(E)[email protected]; [email protected]
Cultural adaptation of the young children's participation and environment measure (YC-PEM) for use by Hispanic families of young children with special health care needs (CSHCN)
No full textIncludes bibliographical references.2016 Summer.Culture informs the occupations in which children engage as well as how they are enacted. Hence, occupational therapists need assessments that are culturally relevant in order to deliver culturally competent practice. Current approaches to cultural adaptation of assessments present with three major limitations: (a) use of inconsistent translation process; (b) current processes assess for some, but not all, elements of cultural equivalence; and (c) limited evidence to guide decision making about whether to undertake cultural adaptation with and without language translation. To our knowledge, this is the first study to systematically develop and compare multiple versions of a culturally adapted questionnaire for potential use by a Hispanic population of young children with special health care needs (CSHCN). The purpose of this study is two-fold: (a) to examine similarities and differences of culturally adapting an occupation-centered pediatric assessment with and without translation; and (b) to examine the feasibility of developing a culturally adapted assessment with and without translation. The Young Children’s Participation and Environment Measure (YC-PEM) underwent cultural adaptation processes (i.e., language translation and cognitive testing) to establish Spanish and English pilot versions for potential use by caregivers of young CSHCN of Mexican descent. Following language translation to develop a Spanish YC-PEM pilot version, 7 caregivers (4 with Spanish as their primary language; 3 with English as their primary language) completed cognitive testing to inform decisions regarding content revisions to the YC-PEM Spanish and English pilot versions. Participant responses were content coded to established cultural equivalencies (i.e., semantic/idiomatic, item, conceptual). Coded data were then summed to draw comparisons on the number of revisions needed to achieve cultural equivalence between the two pilot versions. Feasibility was assessed according to resources required, data collection procedures, and data quality. Results suggest that a greater number of revisions are required to achieve cultural equivalence for the translated (Spanish) version of the YC-PEM. However, issues concerning conceptual equivalence were identified in both the Spanish and English versions. Feasibility results indicate that language translation processes require high resource investment, but may increase translation quality. However, use of questionnaire (i.e., paper, PDF) cognitive testing versus interview methods (e.g., phone, face-to-face) may have limited data saturation. Study results lend preliminary support to the need for and feasibility of pursuing cultural adaptation of the YC-PEM with and without language translation. Larger and more diverse samples are needed to examine the effects of acculturation status on revisions needed to achieve cultural equivalence. Also, interview methods may help improve data quality and confirm study findings
LURR and the San Simeon m 6.5 Earthquake in 2003 and the Seismic Tendency in CA
No full textThe spatial and temporal variation of LURR (Load/Unload Respond Ratio) in California during April 2002 to June 2004 was studied in this paper. The result shows that before the San Simeon earthquake (35.7 N, 121.1 W) on Dec. 22, 2003, Y/Yc anomalous region occurred successively near the epicenter from April 2002 to June 2002, and the maximum anomaly of Y/Yc occurred in May, 2002. The published research work pointed out that the Y/Yc anomaly near the San Simeon earthquake appeared from March, 2002. Compared with the five earthquake cases out of the six with M ≥ 6.5 in California during the period from 1980 to 2001, the maximum Y/Yc and duration of Y/Yc anomaly before this earthquake are among the normal ranges, but the time delay from the maximum anomaly time to the occurrence time of this earthquake is the longest one. The result also shows that two areas with Y/Yc anomalies occurred from Oct. 2002 and Dec. 2002, respectively. According to statistical characteristics of the relationship between Y/Yc anomalies and the coming earthquakes, the seismic tendency in California was discussed in this paper
FOURIER TRANSFORM MICROWAVE SPECTRUM OF THE YC (XA) RADICAL
No full textAuthor Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721The pure rotational spectrum of YC (XA) in the range 4 - 40 GHz has been measured using Fourier transform microwave (FTMW) techniques. The species was produced using Discharge Assisted Laser Ablation Spectroscopy (DALAS) in a supersonic jet expansion of yttrium vapor and HCCH or CH, diluted in argon carrier gas. Three rotational transitions (N = 1 0, 2 1, and 3 2) have been recorded each exhibiting fine structure and hyperfine splittings due to the yttrium nuclear spin of I(Y) = 1/2. The data have been analyzed wtih a case (b) asymmetric top Hamiltonian, and rotational, fine, and hyperfine constants have been determined. The spectrum of this species was previously measured by PPMODR methods, and our data have refined the spectroscopic constants. Measurements of the C isotopologues are currently underway to establish a precise structure for YC
Quantum interference in laser-assisted photoionization and analytical methods for the measurement of an attosecond xuv pulse
No full textInvestigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000293552300016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701OpticsPhysics, Atomic, Molecular & ChemicalSCI(E)EI2ARTICLE2null8
Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations
No full textThis paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural proper-ties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.Physics, MultidisciplinarySCI(E)EI中国科学引文数据库(CSCD)462072-20771
A Study of Spectral Statistical Properties of Extreme Ultraviolet-Boosted Photo-Ionization for Precise In-Situ Measurement of an Intense Laser Pulse
No full textCharacterizing an intense laser pulse for use is challenging. Study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a spatially correlated continuous extreme ultraviolet (XUV) has interesting and useful statistical properties. The total photoionization production is linearly proportional to the time duration of the laser pulse and the square of the beam size. The spectral double energy-integration is an intrinsic value of the laser-assisted XUV photoionization, which linearly depends on the laser intensity and quantitatively reflects the strengths of the laser-field modulation and quantum interference between photoelectrons. The spectral energy width is also linearly dependent on the laser intensity. These linear relationships suggest new methods for in-situ measurement of laser intensity and pulse duration with high precisions.National Natural Science Foundation of China [11175010]SCI(E)ARTICLE9,SI6377-63851
- …
