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On evolution of relatively large combinational logic circuits
Evolvable hardware (EHW) (Yao and Higuchi, 1999) is a technique introduced to automatically design circuits where the circuit configuration is carried out by evolutionary algorithms. One of the main difficulties in using EHW to solve real-world problems is the scalability. Until now, several strategies have been proposed to avoid this problem, but none of them completely tackle the issue. In this paper three different methods for evolving the most complex circuits have been tested for their scalability. These methods are bi-directional incremental evolution (SO-BIE); generalised disjunction decomposition (GD-BIE) and evolutionary strategies (ES) with dynamic mutation rate. In order to achieve the generalised conclusions the chosen approaches were tested using multipliers, traditionally used in EHW, but also logic circuits taken from MCNC (Yang, 1991) benchmark library and randomly generated circuits. The analysis of the approaches demonstrated that PLA-based ES is capable of evolving logic circuits of up to 12 inputs. The use of SO-BIE allows the generation of fully functional circuits of 14 inputs and GD-BIE is estimated to be able to evolve circuits of 21 inputs
Ydj1 governs fungal morphogenesis and stress response, and facilitates mitochondrial protein import via Mas1 and Mas2
We thank Zhen-Yuan Lin for help in the preparation of the AP-MS samples, and Cathy Collins for technical assistance. MDL is supported by a Sir Henry Wellcome Postdoctoral Fellowship (Wellcome Trust 096072), LEC is supported by a Canada Research Chair in Microbial Genomics and Infectious Disease and by Cana-dian Institutes of Health Research (CIHR) Grants MOP-119520 and MOP-86452. OK is supported by National Insti-tutes of Health grant 5R01GM108975. A-CG is supported by a CIHR Foundation Grant (FDN143301), Genome Cana-da Genomics Innovation Network (GIN) Node and Tech-nical Development Grants, and a Canada Research Chair in Functional Proteomics. J-PL was supported by a TD Bank Health Research Fellowship at the Lunenfeld-Tanenbaum Research Institute and by a Scholarship for the Next Gen-eration of Scientists from the Cancer Research Society. JLX is supported by a CIHR â Frederick Banting and Charles Best Canada Graduate Scholarship. The funding agencies had no role in the study design, data collection and inter-pretation, or the decision to submit the work for publication.Peer reviewedPublisher PD
Deforming the Maxwell-Sim Algebra
The Maxwell alegbra is a non-central extension of the Poincar\'e algebra, in
which the momentum generators no longer commute, but satisfy
. The charges commute with the momenta,
and transform tensorially under the action of the angular momentum generators.
If one constructs an action for a massive particle, invariant under these
symmetries, one finds that it satisfies the equations of motion of a charged
particle interacting with a constant electromagnetic field via the Lorentz
force. In this paper, we explore the analogous constructions where one starts
instead with the ISim subalgebra of Poincar\'e, this being the symmetry algebra
of Very Special Relativity. It admits an analogous non-central extension, and
we find that a particle action invariant under this Maxwell-Sim algebra again
describes a particle subject to the ordinary Lorentz force. One can also deform
the ISim algebra to DISim, where is a non-trivial dimensionless
parameter. We find that the motion described by an action invariant under the
corresponding Maxwell-DISim algebra is that of a particle interacting via a
Finslerian modification of the Lorentz force.Comment: Appendix on Lifshitz and Schrodinger algebras adde
Self consistent theory of unipolar charge-carrier injection in metal/insulator/metal systems
A consistent device model to describe current-voltage characteristics of
metal/insulator/metal systems is developed. In this model the insulator and the
metal electrodes are described within the same theoretical framework by using
density of states distributions. This approach leads to differential equations
for the electric field which have to be solved in a self consistent manner by
considering the continuity of the electric displacement and the electrochemical
potential in the complete system. The model is capable of describing the
current-voltage characteristics of the metal/insulator/metal system in forward
and reverse bias for arbitrary values of the metal/ insulator injection
barriers. In the case of high injection barriers, approximations are provided
offering a tool for comparison with experiments. Numerical calculations are
performed exemplary using a simplified model of an organic semiconductor.Comment: 21 pages, 8 figure
All-optical control of ferromagnetic thin films and nanostructures
The interplay of light and magnetism has been a topic of interest since the
original observations of Faraday and Kerr where magnetic materials affect the
light polarization. While these effects have historically been exploited to use
light as a probe of magnetic materials there is increasing research on using
polarized light to alter or manipulate magnetism. For instance deterministic
magnetic switching without any applied magnetic fields using laser pulses of
the circular polarized light has been observed for specific ferrimagnetic
materials. Here we demonstrate, for the first time, optical control of
ferromagnetic materials ranging from magnetic thin films to multilayers and
even granular films being explored for ultra-high-density magnetic recording.
Our finding shows that optical control of magnetic materials is a much more
general phenomenon than previously assumed. These results challenge the current
theoretical understanding and will have a major impact on data memory and
storage industries via the integration of optical control of ferromagnetic
bits.Comment: 21 pages, 11 figure
Dp-branes, NS5-branes and U-duality from nonabelian (2,0) theory with Lie 3-algebra
We derive the super Yang-Mills action of Dp-branes on a torus T^{p-4} from
the nonabelian (2,0) theory with Lie 3-algebra. Our realization is based on Lie
3-algebra with pairs of Lorentzian metric generators. The resultant theory then
has negative norm modes, but it results in a unitary theory by setting VEV's of
these modes. This procedure corresponds to the torus compactification,
therefore by taking a transformation which is equivalent to T-duality, the
Dp-brane action is obtained. We also study type IIA/IIB NS5-brane and
Kaluza-Klein monopole systems by taking other VEV assignments. Such various
compactifications can be realized in the nonabelian (2,0) theory, since both
longitudinal and transverse directions can be compactified, which is different
from the BLG theory. We finally discuss U-duality among these branes, and show
that most of the moduli parameters in U-duality group are recovered. Especially
in D5-brane case, the whole U-duality relation is properly reproduced.Comment: 1+26 page
Oxygen Abundances in Two Metal-Poor Subgiants from the Analysis of the 6300 A Forbidden O I Line
Recent LTE analyses (Israelian et al. 1998 and Bosegaard et al. 1999) of the
OH bands in the optical-ultraviolet spectra of nearby metal-poor subdwarfs
indicate that oxygen abundances are generally higher than those previously
determined. The difference increases with decreasing metallicity and reaches
delta([O/Fe]) ~ +0.6 dex as [Fe/H] approaches -3.0.
Employing high resolution (R = 50000), high S/N (~ 250) echelle spectra of
the two stars found by Israelian et al. (1998) to have the highest
[O/Fe]-ratios, viz, BD +23 3130 and BD +37 1458, we conducted abundance
analyses based on about 60 Fe I and 7-9 Fe II lines. We determined from Kurucz
LTE models the values of the stellar parameters, as well as abundances of Na,
Ni, and the traditional alpha-elements, independent of the calibration of color
vs scales. We determined oxygen abundances from spectral synthesis of
the stronger line (6300 A) of the [O I] doublet.
The syntheses of the [O I] line lead to smaller values of [O/Fe], consistent
with those found earlier among halo field and globular cluster giants. We
obtain [O/Fe] = +0.35 +/- 0.2 for BD +23 3130 and +0.50 +/- 0.2 for BD +37
1458. In the former, the [O I] line is very weak (~ 1 mA), so that the quoted
[O/Fe] value may in reality be an upper limit.
Therefore in these two stars a discrepancy exists between the [O/Fe]- ratios
derived from [O I] and the OH feature, and the origin of this difference
remains unclear. Until the matter is clarified, we suggest it is premature to
conclude that the ab initio oxygen abundances of old, metal-poor stars need to
be revised drastically upward.Comment: 38 pages, 5 tables, 14 figures To appear in July 1999 AJ Updated
April 16, 1999. Fixed typo
The 'Forbidden' Abundance of Oxygen in the Sun
We reexamine closely the solar photospheric line at 6300 A, which is
attributed to a forbidden line of neutral oxygen, and is widely used in
analyses of other late-type stars.
We use a three-dimensional time-dependent hydrodynamical model solar
atmosphere which has been tested successfully against observed granulation
patterns and an array of absorption lines. We show that the solar line is a
blend with a Ni I line, as previously suggested but oftentimes neglected.
Thanks to accurate atomic data on the [O I] and Ni I lines we are able to
derive an accurate oxygen abundance for the Sun: log epsilon (O) = 8.69 +/-
0.05 dex, a value at the lower end of the distribution of previously published
abundances, but in good agreement with estimates for the local interstellar
medium and hot stars in the solar neighborhood. We conclude by discussing the
implication of the Ni I blend on oxygen abundances derived from the [O I] 6300
A line in disk and halo stars.Comment: 16 pages, 3 eps figures included; a more compact PostScript version
created using emulateapj.sty is available from
http://hebe.as.utexas.edu/recent_publi.html; to appear in ApJ
Open String Amplitudes in Various Gauges
Recently, Schnabl constructed the analytic solution of the open string
tachyon. Subsequently, the absence of the physical states at the vacuum was
proved. The development relies heavily on the use of the gauge condition
different from the ordinary one. It was shown that the choice of gauge
simplifies the analysis drastically. When we perform the calculation of the
amplitudes in Schnabl gauge, we find that the off-shell amplitudes of the
Schnabl gauge is still very complicated. In this paper, we propose the use of
the propagator in the modified Schnabl gauge and show that this modified use of
the Schnabl gauge simplifies the computation of the off-shell amplitudes
drastically. We also compute the amplitudes of open superstring in this gauge.Comment: 23 pages, minor correction
Sub-gap conductance in ferromagnetic-superconducting mesoscopic structures
We study the sub-gap conductance of a ferromagnetic mesoscopic region
attached to a ferromagnetic and a superconducting electrode by means of tunnel
junctions. In the absence of the exchange field, the ratio of the two tunnel junction resistances determines the behaviour of
the sub-gap conductance which possesses a zero-bias peak for and for
a peak at finite voltage. We show that the inclusion of the exchange
field leads to a peak splitting for , while it shifts the zero-bias
anomaly to finite voltages for .Comment: 5 pages revte
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