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1.
An efficient method for the oxidation of alcohols is presented. The use of catalytic amounts of sodium chloride in combination with oxone allows the conversion primary aliphatic alcohols to symmetric esters. Secondary alcohols can be easily oxidized to ketones, and benzylic alcohols are converted to the corresponding aldehydes. The method is cost effective and enviromentally benign. 相似文献
2.
A New Approach for the Photosynthetic Antenna–Reaction Center Complex with a Model Organized Around an s‐Triazine Linker 下载免费PDF全文
Susanne Kuhri Dr. Georgios Charalambidis Prof. Panagiotis A. Angaridis Prof. Theodore Lazarides Dr. Georgia Pagona Dr. Nikos Tagmatarchis Prof. Dr. Athanassios G. Coutsolelos Prof. Dr. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2049-2057
Two new artificial mimics of the photosynthetic antenna‐reaction center complex have been designed and synthesized (BDP‐H2P‐C60 and BDP‐ZnP‐C60). The resulting electron‐donor/acceptor conjugates contain a porphyrin (either in its free‐base form (H2P) or as Zn‐metalated complex (ZnP)), a boron dipyrrin (BDP), and a fulleropyrrolidine possessing, as substituent of the pyrrolidine nitrogen, an ethylene glycol chain terminating in an amino group C60‐X‐NH2 (X=spacer). In both cases, the three different components were connected by s‐triazine through stepwise substitution reactions of cyanuric chloride. In addition to the facile synthesis, the star‐type arrangement of the three photo‐ and redox‐active components around the central s‐triazine unit permits direct interaction between one another, in contrast to reported examples in which the three components are arranged in a linear fashion. The energy‐ and electron‐transfer properties of the resulting electron‐donor/acceptor conjugates were investigated by using UV/Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. Comparison of the absorption spectra and cyclic voltammograms of BDP‐H2P‐C60 and BDP‐ZnP‐C60 with those of BDP‐H2P, BDP‐ZnP and BDP‐C60, which were used as references, showed that the spectroscopic and electrochemical properties of the individual constituents are basically retained, although some appreciable shifts in terms of absorption indicate some interactions in the ground state. Fluorescence lifetime measurements and transient absorption experiments helped to elucidate the antenna function of BDP, which upon selective excitation undergoes a rapid and efficient energy transfer from BDP to H2P or ZnP. This is then followed by an electron transfer to C60, yielding the formation of the singlet charge‐separated states, namely BDP‐H2P .+‐ C60 .? and BDP‐ZnP .+‐ C60 . ?. As such, the sequence of energy transfer and electron transfer in the present models mimics the events of natural photosynthesis. 相似文献
3.
Athina P. Bougioukou Apostolos P. Leros Vassilios Papakonstantinou 《Applied Mathematical Modelling》2008
This paper presents a new method for modeling amplitude and frequency non-stationary earthquake ground motions using a scalar first order dynamic mean reverting stochastic differential equation driven by Brownian motion with parametric time varying coefficients. It determines the proper relationship between these time varying parametric coefficients and presents the statistical and probability distribution characteristics of the response solution. It demonstrates the applicability of the method by presenting some simulations of amplitude and frequency non-stationary earthquake ground motions. The verification of the amplitude and frequency non-stationary contents of the mean reverting stochastic ground motions is demonstrated using the Hilbert–Huang transform method. Also a corresponding interpretation between the coefficients of the proposed model and the coefficients of the usual oscillatory second order differential equation driven by white Gaussian noise is presented along with some comments how it can be applied to simulate ground motions consistent with acceleration target records such as boxcar, trapezoidal, other exponential functions, or compound and target records at source, near field, and far field distances. 相似文献
4.
I. Usman Z. Buthelezi J. Carter G.R.J. Cooper R.W. Fearick S.V. Förtsch H. Fujita Y. Fujita Y. Kalmykov P. von Neumann-Cosel R. Neveling P. Papakonstantinou A. Richter R. Roth A. Shevchenko E. Sideras-Haddad F.D. Smit 《Physics letters. [Part B]》2011
The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at Ep=200 MeV. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states. 相似文献
5.
P. Papakonstantinou J. Wambach O. Civitarese T. S. Kosmas 《Czechoslovak Journal of Physics》2006,56(5):481-494
By using the Continuum RPA (CRPA) method, the incoherent transition strength of the exotic μ
−−e− conversion in nuclei is investigated. The question whether excited nuclear states lying high in the continuum give an important
contribution to the incoherent rate is addressed. Results for 40Ca are compared with those obtained previously for 208Pb. For both nuclei we then investigate in detail the admixture of spurious components in the rate coming from 1− excitations, within the self-consistent CRPA with Skyrme interactions as well as within a less consistent version. We employ
and compare two methods for removing the spurious strength: the use of effective operators, as done in a previous work for
208Pb, or simply the exclusion of the spurious state appearing close to zero energy. In all cases, the correction achieved is
quite large.
Presented by P. Papakonstantinou at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece,
September 26–29, 2005. 相似文献
6.
Vasilios Papakonstantinou 《Statistics & probability letters》1984,2(2):111-115
Greenwood and Durand (1955) have expressed the distribution function (d.f.) of the length of N random unit vectors for a von Mises population as a double integral. This double integral is simplified herein by calculating analytically one of the integrals. Hence a numerical calculation for large parameter values now becomes possible. 相似文献
7.
A. Shebeko P. Papakonstantinou E. Mavrommatis 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):143-155
The one-body and two-body density matrices in coordinate space and their Fourier transforms in momentum space are studied
for a nucleus (a nonrelativistic, self-bound finite system). Unlike the usual procedure, suitable for infinite or externally
bound systems, they are determined as expectation values of appropriate intrinsic operators, dependent on the relative coordinates
and momenta (Jacobi variables) and acting on intrinsic wave functions of nuclear states. Thus, translational invariance (TI)
is respected. When handling such intrinsic quantities, we use an algebraic technique based upon the Cartesian representation,
in which the coordinate and momentum operators are linear combinations of the creation and annihilation operators
and
for oscillator quanta. Each of the relevant multiplicative operators can then be reduced to the form: one exponential of
the set {
} times another exponential of the set {
}. In the course of such a normal-ordering procedure we offer a fresh look at the appearance of “Tassie-Barker” factors, and
point out other model-independent results. The intrinsic wave function of the nucleus in its ground state is constructed from
a nontranslationally-invariant (nTI) one via existing projection techniques. As an illustration, the one-body and two-body
momentum distributions (MDs) for the 4He nucleus are calculated with the Slater determinant of the harmonic-oscillator model as the trial, nTI wave function. We
find that the TI introduces quite important effects in the MDs. 相似文献
8.
9.
Recent theoretical work has not led to a consensus regarding the nature of the low-energy E1 strength in the 40,44,48Ca isotopes, for which high-resolution (γ,γ′) data exist. Here we revisit this problem using the first-order quasiparticle random-phase approximation (QRPA) and different interactions. First we examine all even Ca isotopes with N=14–40. All isotopes are predicted to undergo dipole transitions at low energy, of large and comparable isoscalar strength but of varying E1 strength. Provided a moderate and uniform energetic shift is introduced to the results, QRPA with the Gogny D1S interaction is able to account for the (γ,γ′) data, because, up to N=28, it yields a rather pure isoscalar oscillation. A neutron-skin oscillation is anticipated for N?30. This contradicts existing predictions that 44,48Ca develop a neutron-skin mode. Which theoretical result is correct cannot be resolved conclusively using the available data. We propose that alpha-scattering, possibly followed by an electroexcitation experiment, could resolve the situation and thereby help to improve the different models aspiring to describe reliably the low-energy dipole strength of nuclei. 相似文献
10.
Arzum Erdem Pagona Papakonstantinou Hayley Murphy Martin McMullan Hakan Karadeniz Surbhi Sharma 《Electroanalysis》2010,22(6):611-617
Disposable graphite pencil electrodes (PGE) modified with multiwalled carbon nanotubes (MWCNTs)‐streptavidin (STR) conjugates were used for electrochemical monitoring of label‐free DNA hybridization. The surface morphology of PGE electrode before and after hybridization was characterized by scanning electron microscopy. Electrochemical impedance spectroscopy was used to monitor each step of the construction of the DNA biosensor. The biosensor was demonstrated to have excellent selectivity, being able to differentiate complementary sequences from a noncomplementary ones and in addition select the target sequence of DNA from a mixture of other DNA without loss in current sensitivity. 相似文献