594 research outputs found
Quenched Charge Disorder and Coulomb Interactions
We develop a general formalism to investigate the effect of quenched fixed
charge disorder on effective electrostatic interactions between charged
surfaces in a one-component (counterion-only) Coulomb fluid. Analytical results
are explicitly derived for two asymptotic and complementary cases: i)
mean-field or Poisson-Boltzmann limit (including Gaussian-fluctuations
correction), which is valid for small electrostatic coupling, and ii)
strong-coupling limit, where electrostatic correlations mediated by counterions
become significantly large as, for instance, realized in systems with
high-valency counterions. In the particular case of two apposed and ideally
polarizable planar surfaces with equal mean surface charge, we find that the
effect of the disorder is nil on the mean-field level and thus the plates
repel. In the strong-coupling limit, however, the effect of charge disorder
turns out to be additive in the free energy and leads to an enhanced long-range
attraction between the two surfaces. We show that the equilibrium inter-plate
distance between the surfaces decreases for elevated disorder strength (i.e.
for increasing mean-square deviation around the mean surface charge), and
eventually tends to zero, suggesting a disorder-driven collapse transition.Comment: 13 pages, 2 figure
Dates of birth and seasonal changes in well-being among 4904 subjects completing the seasonal pattern assessment questionnaire
Background: Abnormal distributions of birthdates, suggesting intrauterine aetiological factors, have been found in several psychiatric disorders, including one study of out-patients with Seasonal Affective Disorder (S.A.D.). We investigated birthdate distribution in relation to seasonal changes in well-being among a cohort who had completed the Seasonal Pattern Assessment Questionnaire (SPAQ). Method: A sample of 4904 subjects, aged 16 to 64, completed the SPAQ. 476 were cases of S.A.D. on the SPAQ and 580 were cases of sub-syndromal S.A.D. (S-S.A.D.). 92 were interview confirmed cases of S.A.D. Months and dates of birth were compared between S.A.D. cases and all others, between S.A.D. and S-S.A.D. cases combined and all others, and between interview confirmed cases and all others. Seasonality, as measured through seasonal fluctuations in well-being on the Global Seasonality Scores (GSS) of the SPAQ, was compared for all subjects by month and season of birth. Results: There was no evidence of an atypical pattern of birthdates for subjects fulfilling criteria for S.A.D., for the combined S.A.D. / S-S.A.D. group or for interview confirmed cases. There was also no relationship between seasonality on the GSS and month or season of birth. Limitations: Diagnoses of S.A.D. made by SPAQ criteria are likely to be overinclusive. Conclusion: Our findings differ from studies of patients with more severe mood disorders, including psychiatric out-patients with S.A.D. The lack of association between seasonality and birthdates in our study adds credence to the view that the aetiology of S.A.D. relates to separable factors predisposing to affective disorders and to seasonality
Statics and Dynamics of Strongly Charged Soft Matter
Soft matter materials, such as polymers, membranes, proteins, are often
electrically charged. This makes them water soluble, which is of great
importance in technological application and a prerequisite for biological
function. We discuss a few static and dynamic systems that are dominated by
charge effects. One class comprises complexation between oppositely charged
objects, for example the adsorption of charged ions or charged polymers (such
as DNA) on oppositely charged substrates of different geometry. The second
class comprises effective interactions between similarly charged objects. Here
the main theme is to understand the experimental finding that similarly and
highly charged bodies attract each other in the presence of multi-valent
counterions. This is demonstrated using field-theoretic arguments as well as
Monte-Carlo simulations for the case of two homogeneously charged bodies.
Realistic surfaces, on the other hand, are corrugated and also exhibit
modulated charge distributions, which is important for static properties such
as the counterion-density distribution, but has even more pronounced
consequences for dynamic properties such as the counterion mobility. More
pronounced dynamic effects are obtained with highly condensed charged systems
in strong electric fields. Likewise, an electrostatically collapsed highly
charged polymer is unfolded and oriented in strong electric fields. At the end
of this review, we give a very brief account of the behavior of water at planar
surfaces and demonstrate using ab-initio methods that specific interactions
between oppositely charged groups cause ion-specific effects that have recently
moved into the focus of interest.Comment: 61 pages, 31 figures, Physics Reports (2005)-in press (high quality
figures available from authors
Counterion-Mediated Weak and Strong Coupling Electrostatic Interaction between Like-Charged Cylindrical Dielectrics
We examine the effective counterion-mediated electrostatic interaction
between two like-charged dielectric cylinders immersed in a continuous
dielectric medium containing neutralizing mobile counterions. We focus on the
effects of image charges induced as a result of the dielectric mismatch between
the cylindrical cores and the surrounding dielectric medium and investigate the
counterion-mediated electrostatic interaction between the cylinders in both
limits of weak and strong electrostatic couplings (corresponding, e.g., to
systems with monovalent and multivalent counterions, respectively). The results
are compared with extensive Monte-Carlo simulations exhibiting good agreement
with the limiting weak and strong coupling results in their respective regime
of validity.Comment: 19 pages, 10 figure
Development of an Arabic text-to-speech system
Research on Text-to-speech technology has received
the interest of professional researchers in many languages which is a consequence of wide range of applications where Text-To-Speech is implemented. However, Arabic language, spoken by millions of people as an official language in 24 different countries, gained less attention compared with other languages despite the fact that it has a religious value for more than 1.6 billion Muslim worldwide. These facts exhibit the need for a high quality, smallsize, and completely free Arabic TTS with the ability of future
improvements. The vowelized written text of Arabic language
carries the pronunciation rules with limited exceptions, so rulebased system with an exception dictionary for words that fail with those letter-to-phoneme rules may be a much more reasonable approach. This paper is a development of a rulebased text-to-speech Hybrid synthesis system which is a
combination formant and concatenation techniques with
acceptable naturalness. The simulation results of the system
shows good quality in handling word, phrase, and sentence level compared to other available Arabic TTS systems. The accuracy of the overall system is 96%. Further improvements need to be done for stressed syllable position and intonation
Electromagnetic fluctuation-induced interactions in randomly charged slabs
Randomly charged net-neutral dielectric slabs are shown to interact across a
featureless dielectric continuum with long-range electrostatic forces that
scale with the statistical variance of their quenched random charge
distribution and inversely with the distance between their bounding surfaces.
By accounting for the whole spectrum of electromagnetic field fluctuations, we
show that this long-range disorder-generated interaction extends well into the
retarded regime where higher-order Matsubara frequencies contribute
significantly. This occurs even for highly clean samples with only a trace
amount of charge disorder and shows that disorder effects can be important down
to the nano scale. As a result, the previously predicted non-monotonic behavior
for the total force between dissimilar slabs as a function of their separation
distance is substantially modified by higher-order contributions, and in almost
all cases of interest, we find that the equilibrium inter-surface separation is
shifted to substantially larger values compared to predictions based solely on
the zero-frequency component. This suggests that the ensuing non-monotonic
interaction is more easily amenable to experimental detection. The presence of
charge disorder in the intervening dielectric medium between the two slabs is
shown to lead to an additional force that can be repulsive or attractive
depending on the system parameters and can, for instance, wash out the
non-monotonic behavior of the total force when the intervening slab contains a
sufficiently large amount of disorder charges.Comment: 9 pages, 5 figure
RAD Module Infrastructure of the Field-programmable Port eXtender (FPX) Version 2.0
The Field-programmable Port eXtender (FPX) provides dynamic, fast, and flexible mechanisms to process data streams at the ports of the Washington University Gigabit Switch (WUGS-20). In order to facilitate the design and implementation of portable hardware modules for the Reprogrammable Application Device (RAD) on the FPX board, infrastructure components have been developed. These components abstract application module designers from device-specific timing specifications of off-chip memory devices, as well as processing system-level control cells. This document describes the design and internal functionality of the infrastructure components and is intended as a reference for future component revisions and additions. Application module designers should refer to the Generalized RAD Module Interface Specification of the Field Programmable Port Extender (FPX), EUCS-TM-01-15
Drag forces on inclusions in classical fields with dissipative dynamics
We study the drag force on uniformly moving inclusions which interact
linearly with dynamical free field theories commonly used to study soft
condensed matter systems. Drag forces are shown to be nonlinear functions of
the inclusion velocity and depend strongly on the field dynamics. The general
results obtained can be used to explain drag forces in Ising systems and also
predict the existence of drag forces on proteins in membranes due to couplings
to various physical parameters of the membrane such as composition, phase and
height fluctuations.Comment: 14 pages, 7 figure
Novel Framework for Hidden Data in the Image Page within Executable File Using Computation between Advanced Encryption Standard and Distortion Techniques
The hurried development of multimedia and internet allows for wide
distribution of digital media data. It becomes much easier to edit, modify and
duplicate digital information. In additional, digital document is also easy to
copy and distribute, therefore it may face many threats. It became necessary to
find an appropriate protection due to the significance, accuracy and
sensitivity of the information. Furthermore, there is no formal method to be
followed to discover a hidden data. In this paper, a new information hiding
framework is presented.The proposed framework aim is implementation of
framework computation between advance encryption standard (AES) and distortion
technique (DT) which embeds information in image page within executable file
(EXE file) to find a secure solution to cover file without change the size of
cover file. The framework includes two main functions; first is the hiding of
the information in the image page of EXE file, through the execution of four
process (specify the cover file, specify the information file, encryption of
the information, and hiding the information) and the second function is the
extraction of the hiding information through three process (specify the stego
file, extract the information, and decryption of the information).Comment: 6 Pages IEEE Format, International Journal of Computer Science and
Information Security, IJCSIS 2009, ISSN 1947 5500, Impact Factor 0.42
Non-monotoic fluctuation-induced interactions between dielectric slabs carrying charge disorder
We investigate the effect of monopolar charge disorder on the classical
fluctuation-induced interactions between randomly charged net-neutral
dielectric slabs and discuss various generalizations of recent results (A. Naji
et al., Phys. Rev. Lett. 104, 060601 (2010)) to highly inhomogeneous dielectric
systems with and without statistical disorder correlations. We shall focus on
the specific case of two generally dissimilar plane-parallel slabs, which
interact across vacuum or an arbitrary intervening dielectric medium. Monopolar
charge disorder is considered to be present on the bounding surfaces and/or in
the bulk of the slabs, may be in general quenched or annealed and may possess a
finite lateral correlation length reflecting possible `patchiness' of the
random charge distribution. In the case of quenched disorder, the bulk disorder
is shown to give rise to an additive long-range contribution to the total
force, which decays as the inverse distance between the slabs and may be
attractive or repulsive depending on the dielectric constants of the slabs. We
show that in the case of two dissimilar slabs the net effect due to the
interplay between the disorder-induced and the pure van der Waals interactions
can lead to a variety of unusual non-monotonic interaction profiles between the
dielectric slabs. In particular, when the intervening medium has a larger
dielectric constant than the two slabs, we find that the net interaction can
become repulsive and exhibit a potential barrier, while the underlying van der
Waals force is attractive. On the contrary, when the intervening medium has a
dielectric constant in between that of the two slabs, the net interaction can
become attractive and exhibit a free energy minimum, while the pure van der
Waals force is repulsive. Therefore, the charge disorder, if present, can
drastically alter the effective interaction between net-neutral objects.Comment: 13 pages, 8 figure
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