17,686 research outputs found
Back-electron transfer suppresses the periodic length dependence of DNA-mediated charge transport across adenine tracts
DNA-mediated charge transport (CT) is exquisitely sensitive to the integrity of the bridging π-stack and is characterized by a shallow distance dependence. These properties are obscured by poor coupling between the donor/acceptor pair and the DNA bridge, or by convolution with other processes. Previously, we found a surprising periodic length dependence for the rate of DNA-mediated CT across adenine tracts monitored by 2-aminopurine fluorescence. Here we report a similar periodicity by monitoring N2-cyclopropylguanosine decomposition by rhodium and anthraquinone photooxidants. Furthermore, we find that this periodicity is attenuated by consequent back-electron transfer (BET), as observed by direct comparison between sequences that allow and suppress BET. Thus, the periodicity can be controlled by engineering the extent of BET across the bridge. The periodic length dependence is not consistent with a periodicity predicted by molecular wire theory but is consistent with a model where multiples of four to five base pairs form an ideal CT-active length of a bridging adenine domain
VLSI architectures for computing multiplications and inverses in GF(2-m)
Finite field arithmetic logic is central in the implementation of Reed-Solomon coders and in some cryptographic algorithms. There is a need for good multiplication and inversion algorithms that are easily realized on VLSI chips. Massey and Omura recently developed a new multiplication algorithm for Galois fields based on a normal basis representation. A pipeline structure is developed to realize the Massey-Omura multiplier in the finite field GF(2m). With the simple squaring property of the normal-basis representation used together with this multiplier, a pipeline architecture is also developed for computing inverse elements in GF(2m). The designs developed for the Massey-Omura multiplier and the computation of inverse elements are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation
A parallel VLSI architecture for a digital filter of arbitrary length using Fermat number transforms
A parallel architecture for computation of the linear convolution of two sequences of arbitrary lengths using the Fermat number transform (FNT) is described. In particular a pipeline structure is designed to compute a 128-point FNT. In this FNT, only additions and bit rotations are required. A standard barrel shifter circuit is modified so that it performs the required bit rotation operation. The overlap-save method is generalized for the FNT to compute a linear convolution of arbitrary length. A parallel architecture is developed to realize this type of overlap-save method using one FNT and several inverse FNTs of 128 points. The generalized overlap save method alleviates the usual dynamic range limitation in FNTs of long transform lengths. Its architecture is regular, simple, and expandable, and therefore naturally suitable for VLSI implementation
Environment, morphology and stellar populations of bulgeless low surface brightness galaxies
Based on the Sloan Digital Sky Survey DR 7, we investigate the environment,
morphology and stellar population of bulgeless low surface brightness (LSB)
galaxies in a volume-limited sample with redshift ranging from 0.024 to 0.04
and . The local density parameter is used to
trace their environments. We find that, for bulgeless galaxies, the surface
brightness does not depend on the environment. The stellar populations are
compared for bulgeless LSB galaxies in different environments and for bulgeless
LSB galaxies with different morphologies. The stellar populations of LSB
galaxies in low density regions are similar to those of LSB galaxies in high
density regions. Irregular LSB galaxies have more young stars and are more
metal-poor than regular LSB galaxies. These results suggest that the evolution
of LSB galaxies may be driven by their dynamics including mergers rather than
by their large scale environment.Comment: 12 pages, 13 figures, Accepted by A&
Relationship between High-Energy Absorption Cross Section and Strong Gravitational Lensing for Black Hole
In this paper, we obtain a relation between the high-energy absorption cross
section and the strong gravitational lensing for a static and spherically
symmetric black hole. It provides us a possible way to measure the high-energy
absorption cross section for a black hole from strong gravitational lensing
through astronomical observation. More importantly, it allows us to compute the
total energy emission rate for high-energy particles emitted from the black
hole acting as a gravitational lens. It could tell us the range of the
frequency, among which the black hole emits the most of its energy and the
gravitational waves are most likely to be observed. We also apply it to the
Janis-Newman-Winicour solution. The results suggest that we can test the cosmic
censorship hypothesis through the observation of gravitational lensing by the
weakly naked singularities acting as gravitational lenses.Comment: 6 pages, 2 figures, improved version, accepted for publication as a
Rapid Communication in Physical Review
A VLSI pipeline design of a fast prime factor DFT on a finite field
A conventional prime factor discrete Fourier transform (DFT) algorithm is used to realize a discrete Fourier-like transform on the finite field, GF(q sub n). A pipeline structure is used to implement this prime factor DFT over GF(q sub n). This algorithm is developed to compute cyclic convolutions of complex numbers and to decode Reed-Solomon codes. Such a pipeline fast prime factor DFT algorithm over GF(q sub n) is regular, simple, expandable, and naturally suitable for VLSI implementation. An example illustrating the pipeline aspect of a 30-point transform over GF(q sub n) is presented
Probing neutrino mass hierarchies and with supernova neutrinos
We investigate the feasibility of probing the neutrino mass hierarchy and the
mixing angle with the neutrino burst from a future supernova. An
inverse power-law density with varying is adopted in the
analysis as the density profile of a typical core-collapse supernova. The
survival probabilities of and are shown to reduce to
two-dimensional functions of and . It is found that in the
parameter space, the 3D plots of the probability
functions exhibit highly non-trivial structures that are sensitive to the mass
hierarchy, the mixing angle , and the value of . The conditions
that lead to observable differences in the 3D plots are established. With the
uncertainty of considered, a qualitative analysis of the Earth matter
effect is also included.Comment: 16 pages, 3 figures. Ref [11] added, and some typos correcte
Strong field gravitational lensing in scalar tensor theories
Strong field gravitational lensing in the Brans-Dicke theory has been
studied. The deflection angle for photons passing very close to the photon
sphere is estimated for the static spherically symmetric space-time of the
theory and the position and magnification of the relativistic images are
obtained. Modeling the super massive central object of the galaxy by the
Brans-Dicke space-time, numerical values of different strong lensing observable
are estimated. It is found that against the expectation there is no significant
scalar field effect in the strong field observable lensing parameters. This
observation raises question on the potentiality of the strong field lensing to
discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio
Deposition morphology of non-homogeneous debris flow and its energy characteristics
Non-homogeneous two-phase debris flows are widely found in the western mountainous regions of China. To investigate the characteristics of the debris flow deposition process related to the morphology and extent of the debris fan, a series of physical experiments were carried out using an experimental flume. Some useful relationships were obtained to link the flow velocity with the geometric characteristics of deposition morphology and the corresponding area or volume. Based on these, some expressions about energy dissipation process in both the transport-deposition zone and deposition zone are presented, and improved equations describing solid-liquid two-phase energy transformations in the specific deposition zone are also established. These results provide a basis for further investigating the underlying mechanisms of non-homogeneous debris flows, based upon which effective disaster control measures can be undertaken
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