1,208 research outputs found
Studies on organic semiconductors. 15: Effects of the substituents on the photoconductivities of substituted anthracenes
The photocurrents of the substituted anthracenes, 1,5-diacetylanthracene (2), 1-acetylanthracene (3), 9-acetylanthracene (4), 1,5-dichloroanthracene (5), 1,5-diethylanthracene (6), 1,5-dimethoxyanthracene (7), 9-cyanoanthracene (8), and anthracene (1) were measured by using their surface type cells in nitrogen. The compounds of (1), (5), (6), (7), and (8) showed the photocurrent spectra which corresponded to the absorption spectra of their evaporated films. In the cases of (2) and (3), however, the anomalous photocurrent appeared in the threshold region of their absorption spectra. The appearance of the anomalous photocurrent was characteristic of anthracenes having the acetyl group at 1- and/or 5-position. The magnitude of the photocurrents of the 1,5-disubstituted anthracenes was similar to that of (1). The photocurrents of the monosubstituted anthracenes were smaller than that of (1). Among the monosubstituted anthracenes, the compound (4) showed no photocurrent under the same conditions. Contrary to the results obtained in the cases of phenazines, the photoconductivities of the anthracene derivatives became better in air
Substituent effects on the electrical conductivities of the phenazine derivatives
The and/or photoconductivities of 16 substituted phenazines having methoxy, hydroxy, chloro, nitro, amino or t-butyl group at 1-, 2-, 1, 6- or 2,7- positions of the phenazine ring measured by using the surface type cells. The energy gaps of the dark conductivities in the range 2.0 to 2.3 were independent of the kinds and the positions of the substituent groups, although the photo-absorption wavelength of the evaporated films changed with them. No correlation between photoconductivity and fluorescence was observed. The photocurrent was affected by the position of the substituents; namely, the photocurrents of the 1,6-di-substituted phenazines. When the substituent at 1,6-positions was hydroxy or amino group, however, the photocurrents decreased. The photocurrents decreased drastically in the presence of oxygen
Preparations of methoxynitrophenazines and their photoconductivities
Eight methoxynitrophenazines with a methoxy group at the 1 or 2 position and a nitro group at the 6-, 7-, 8- or 9-position of the phenazine ring 1,6, 1,7. 1,8, 1,9, 2,6, 2,7, 2,8 and 2,9 were prepared and their photocurrents were measured by illuminating the surface-type cell with white light from a W lamp under a N atmosphere at room temp. The photocurrents of 1-nitrophenazine 6 and 2-nitrophenazine 7 are compared with those of the methoxynitrophenazines. The photocurrent (i sub p) increases with increasing light intensity (I), thus satisfying log i varies as n log I. The n values are 0.5-1.0. When the nitro group is located at the beta-position of the phenazine ring, the photocurrent becomes larger owing to the electron withdrawing property of the nitro group. On the other hand, the photocurrents of phenazines with the nitro group at the Alpha-position are extremely small. The photoconductivities of methoxynitrophenazines are lower in air
Boosting up quantum key distribution by learning statistics of practical single photon sources
We propose a simple quantum-key-distribution (QKD) scheme for practical
single photon sources (SPSs), which works even with a moderate suppression of
the second-order correlation of the source. The scheme utilizes a
passive preparation of a decoy state by monitoring a fraction of the signal via
an additional beam splitter and a detector at the sender's side to monitor
photon number splitting attacks. We show that the achievable distance increases
with the precision with which the sub-Poissonian tendency is confirmed in
higher photon number distribution of the source, rather than with actual
suppression of the multi-photon emission events. We present an example of the
secure key generation rate in the case of a poor SPS with , in
which no secure key is produced with the conventional QKD scheme, and show that
learning the photon-number distribution up to several numbers is sufficient for
achieving almost the same achievable distance as that of an ideal SPS.Comment: 11 pages, 3 figures; published version in New J. Phy
Nonclassical correlations of phase noise and photon number in quantum nondemolition measurements
The continuous transition from a low resolution quantum nondemolition
measurement of light field intensity to a precise measurement of photon number
is described using a generalized measurement postulate. In the intermediate
regime, quantization appears as a weak modulation of measurement probability.
In this regime, the measurement result is strongly correlated with the amount
of phase decoherence introduced by the measurement interaction. In particular,
the accidental observation of half integer photon numbers preserves phase
coherence in the light field, while the accidental observation of quantized
values increases decoherence. The quantum mechanical nature of this correlation
is discussed and the implications for the general interpretation of
quantization are considered.Comment: 16 pages, 5 figures, final version to be published in Phys. Rev. A,
Clarifications of the nature of the measurement result and the noise added in
section I
Compressibility of Mixed-State Signals
We present a formula that determines the optimal number of qubits per message
that allows asymptotically faithful compression of the quantum information
carried by an ensemble of mixed states. The set of mixed states determines a
decomposition of the Hilbert space into the redundant part and the irreducible
part. After removing the redundancy, the optimal compression rate is shown to
be given by the von Neumann entropy of the reduced ensemble.Comment: 7 pages, no figur
Bioinformatics tools in predictive ecology: Applications to fisheries
This article is made available throught the Brunel Open Access Publishing Fund - Copygith @ 2012 Tucker et al.There has been a huge effort in the advancement of analytical techniques for molecular biological data over the past decade. This has led to many novel algorithms that are specialized to deal with data associated with biological phenomena, such as gene expression and protein interactions. In contrast, ecological data analysis has remained focused to some degree on off-the-shelf statistical techniques though this is starting to change with the adoption of state-of-the-art methods, where few assumptions can be made about the data and a more explorative approach is required, for example, through the use of Bayesian networks. In this paper, some novel bioinformatics tools for microarray data are discussed along with their ‘crossover potential’ with an application to fisheries data. In particular, a focus is made on the development of models that identify functionally equivalent species in different fish communities with the aim of predicting functional collapse
Nuclear Spins in a Nanoscale Device for Quantum Information Processing
Coherent oscillations between any two levels from four nuclear spin states of
I=3/2 have been demonstrated in a nanometre-scale NMR semiconductor device,
where nuclear spins are all-electrically controlled. Using this device, we
discuss quantum logic operations on two fictitious qubits of the I=3/2 system,
and propose a quantum state tomography scheme based on the measurement of
longitudinal magnetization, .Comment: 5 pages, 4 figure
Entangled webs: Tight bound for symmetric sharing of entanglement
Quantum entanglement cannot be unlimitedly shared among arbitrary number of
qubits. Larger the number of entangled pairs in an N-qubit system, smaller the
degree of bi-partite entanglement is. We analyze a system of N qubits in which
an arbitrary pair of particles is entangled. We show that the maximum degree of
entanglement (measured in the concurrence) between any pair of qubits is 2/N.
This tight bound can be achieved when the qubits are prepared in a pure
symmetric (with respect to permutations) state with just one qubit in the basis
state |0> and the others in the basis state |1>.Comment: 4 pages, 1 figur
Quantum non-demolition (QND) modulation of quantum interference
We propose an experiment where quantum interference between two different
paths is modulated by means of a QND measurement on one or both the arm of the
interferometer. The QND measurement is achieved in a Kerr cell. We illustrate a
scheme for the realisation of this experiment and some further developments.Comment: accepted for publicatio
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