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501.
You Y Huh HS Kim KS Lee SW Kim D Park SY 《Chemical communications (Cambridge, England)》2008,(34):3998-4000
An investigation of the photophysics of Ir(iii) complexes with controlled ligand structures and our quantum chemical calculations attest that the most probable explanation for the reported 'aggregation-induced phosphorescent emission', which was originally claimed to be related to an intermolecular excimer, is restricted intramolecular motion. 相似文献
502.
Stretching DNA has emerged as a vital process for studying the physical and biological properties of these molecules. Over
the past decade, there has been increasing research interest in utilizing nanoscale fluidic channels to confine and stretch
single DNA molecules. Nanofabricated systems for linearizing DNA have revealed new and important insights into the conformation
changes of DNA molecules. They also have emerged as innovative techniques for efficiently separating DNA molecules based on
size and for physically mapping genetic information along the genome. This review describes physical theories of DNA linearization,
current DNA stretching techniques based on nanofabricated channels, and breakthroughs resulting from the use of nanofluidic
channels for DNA linearization. 相似文献
503.
Niamh Holland Patrick Duggan Eleanor Owens Wayne Cummins June Frisby Helen Hughes Peter McLoughlin 《Analytical and bioanalytical chemistry》2008,391(4):1245-1253
A powerful method utilising direct probe thermal desorption GC–MS is presented for the study of molecularly imprinted polymers
(MIPs). A series of 2-aminopyridine (2-apy)-imprinted methacrylic acid–ethyleneglycol dimethacrylate (MAA–EGDMA) copolymers
were prepared under identical conditions but with varying amounts of EGDMA (crosslinking monomer). The use of appropriate
temperature programmes permitted template removal, and the subsequent assessment of polymer affinity and specificity, all
of which were found to be dependent on polymer composition and morphology. The system was sufficiently sensitive to identify
a specific response of imprinted polymers over nonimprinted counterparts. Correlations were found to exist between thermal
desorption analysis and solution phase binding, which was assessed by UV spectroscopy, where specificity was found to diminish
with decreasing EGDMA concentration. This was attributed to the increased number of free carboxyl groups in those polymers
containing a lower percentage of EGDMA. Thermal desorption profiles obtained for the analyte were found to be unaffected by
the physical and chemical properties of the solvent used for analyte reloading.
An erratum to this article can be found at 相似文献
504.
Proton beam is useful to target tumor tissue sparing normal cells by allowing precise dose only into tumor cells. However, the cellular and molecular mechanisms by which proton beam induces tumor cell death are still undefined. We irradiated three different tumor cells (LLC, HepG2, and Molt-4) with low energy proton beam (35 MeV) with spread out Bragg peak (SOBP) in vitro, and investigated cell death by MTT or CCK-8 assay at 24 h after irradiation. LLC and HepG2 cells were sensitive to proton beam at over 10 Gy to induce apoptosis whereas Molt-4 showed rather low sensitivity. Relative biological effectiveness (RBE) values for the death rate relative to gamma-ray were ranged from 1.1 to 2.3 in LLC and HepG2 but from 0.3 to 0.7 in Molt-4 at 11 d after irradiation by colony formation assay. The typical apoptotic nuclear DNA morphological pattern was observed by staining with 4'-6-diamidino-2-phenylindole (DAPI). Tiny fragmented DNA was observed in HepG2 but not in Molt-4 by the treatment of proton in apoptotic DNA fragment assay. By FACS analysis after stained with FITC-Annexin-V, early as well as median apoptotic fractions were clearly increased by proton treatment. Proton beam-irradiated tumor cells induced a cleavage of poly (ADP-ribose) polymerase-1 (PARP-1) and procaspases-3 and -9. Activity of caspases was highly enhanced after proton beam irradiation. Reactive oxygen species (ROS) were significantly increased and N-acetyl cysteine pretreatment restored the apoptotic cell death induced by proton beam. Furthermore, p38 and JNK but not ERK were activated by proton and dominant negative mutants of p38 and JNK revived proton-induced apoptosis, suggesting that p38 and JNK pathway may be activated through ROS to activate apoptosis. In conclusion, our data clearly showed that single treatment of low energy proton beam with SOBP increased ROS and induced cell death of solid tumor cells (LLC and HepG2) in an apoptotic cell death program by the induction of caspases activities. 相似文献
505.
Sung‐June Baek Aaron Park Aiguo Shen Jimming Hu 《Journal of Raman spectroscopy : JRS》2011,42(11):1987-1993
In this paper, we consider a new background elimination method for Raman spectra. As a background is usually slowly varying with respect to wavelength, it could be approximated by a slowly varying curve. However, the usual curve‐fitting method cannot be applied because there is a constraint that the estimated background must be beneath a measured spectrum. To meet the requirement, we adopt a polynomial as an approximating function and show that background estimation could be converted to a linear programming problem which is a special case of constrained optimization. In addition, we present an order selection algorithm for automatic baseline elimination. According to the experimental results, it is shown that the proposed method could be successfully applied to experimental Raman spectra as well as synthetic spectra. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
506.
In this paper, we investigated the propagation of shear waves in a transversely isotropic poroelastic layer constrained between two elastic layers. Following Biot’s theory, the dispersion equation for shear waves in this structure was derived. The numerical values on the dimensionless phase velocities are calculated and presented graphically to illustrate the dependences upon geometry, anisotropy and porosity comparatively. It is observed that the phase velocities increase with the increase of the porosity and the decrease of the anisotropy. In addition, the geometry in this structure has a significant effect on the phase velocity of the shear waves. 相似文献
507.
Hui June Zhu 《Proceedings of the American Mathematical Society》2006,134(2):323-331
We prove that for any pair of integers such that or 0$">, there exists a (hyper)elliptic curve over of genus and -rank whose automorphism group consists of only identity and the (hyper)elliptic involution. As an application, we prove the existence of principally polarized abelian varieties over of dimension and -rank such that .
508.
Joe DJ Wu CJ Bok T Lee EJ Lee CH Han WS Kang SO Lee BY 《Dalton transactions (Cambridge, England : 2003)》2006,(33):4056-4062
The Suzuki-coupling reaction of 2-(dihydroxyboryl)-3,4-dimethyl-2-cyclopenten-1-one and 2-(dihydroxyboryl)-3-methyl-2-cyclopenten-1-one with 2-bromoaniline derivatives affords cyclopentenone compounds from which cyclopentadiene compounds, 4,6-R'(2)-2-(2,5-Me2C5H3)C6H2NH2 and 4,6-R'(2)-2-(2,3,5-Me3C5H2)C6H2NH2 are prepared. After sulfonation of the -NH2 group with p-TsCl, metallation is carried out by successive addition of Ti(NMe2)4 and Me2SiCl2 affording o-phenylene-bridged Cp/sulfonamido titanium dichloride complexes, [4,6-R'(2)-2-(2,5-Me2C5H2)C6H2NSO2C6H4CH3)]TiCl2 (R'=H, ; R'=Me, ; R'=F, ) and [4,6-R'(2)-2-(2,3,5-Me3C5H)C6H2NSO2C6H4CH3)]TiCl2 (R'=H, ; R'=Me, ; R'=F, ). The molecular structures of and [2-(2,5-Me2C5H2)C6H4NSO2C6H4CH3)]Ti(NMe2)2 are determined by X-ray crystallography. The Cp(centroid)-Ti-N angle in is smaller (100.90 degrees) than that observed for the CGC (constrained-geometry catalyst), [Me2Si(eta5-Me4Cp)(NtBu)]TiCl2 (107.6 degrees) indicating a more "constrained feature" in than in the CGC. Complex shows the highest activity among the newly prepared complexes in ethylene/1-octene copolymerization but it is slightly inferior to the CGC in terms of activity, comonomer-incorporation ability, and molecular weight of the obtained polymers. 相似文献
509.
Two basic disadvantages of the symmetric rank one (SR1) update are that the SR1 update may not preserve positive definiteness
when starting with a positive definite approximation and the SR1 update can be undefined. A simple remedy to these problems
is to restart the update with the initial approximation, mostly the identity matrix, whenever these difficulties arise. However,
numerical experience shows that restart with the identity matrix is not a good choice. Instead of using the identity matrix
we used a positive multiple of the identity matrix. The used positive scaling factor is the optimal solution of the measure
defined by the problem—maximize the determinant of the update subject to a bound of one on the largest eigenvalue. This measure
is motivated by considering the volume of the symmetric difference of the two ellipsoids, which arise from the current and
updated quadratic models in quasi-Newton methods. A replacement in the form of a positive multiple of the identity matrix
is provided for the SR1 update when it is not positive definite or undefined. Our experiments indicate that with such simple
initial scaling the possibility of an undefined update or the loss of positive definiteness for the SR1 method is avoided
on all iterations. 相似文献
510.
Seon Young Ryu Hae Young Choi Ki Soo Chang Geon Hee Kim Woo June Choi Sang-Gun Ahn Yong Chul Kim Jung-Hoon Yoon Byeong Ha Lee 《Optics Communications》2012,285(9):2478-2482
We propose a fiber optic single-unit but dual-mode optical imaging system that can provide fast cross-sectional imaging capabilities of swept-source optical coherence tomography (SS-OCT) and functional capabilities of fluorescence spectroscopy (FS). By adopting a fiber optic FS system into a fiber-based SS-OCT system, a compact and effective multimodal single-unit SSOCT-FS system is achieved. Here, the key element of the proposed multimodal imaging system is a specially designed fiber coupler based on double-clad fiber (DCF), which has only cladding-mode coupling capability. The DCF couplers are fabricated with home-drawn DCF by several fabrication methods; a twisting method, a side-polishing method and a fused biconical tapered (FBT) method. Experimentally, the FBT method provides rather flat cladding mode coupling efficiency over 40% in a wide wavelength range. With this specially designed DCF coupler, the OCT signal and the fluorescence signal is measured independently but with a single-unit system. The performance of the SSOCT-FS system is confirmed by measuring the cross-sectional image and the fluorescence signal of a photosensitizer chlorin e6 injected in-vivo rat tumor model. 相似文献