7,630 research outputs found
Brownian Entanglement
We show that for two classical brownian particles there exists an analog of
continuous-variable quantum entanglement: The common probability distribution
of the two coordinates and the corresponding coarse-grained velocities cannot
be prepared via mixing of any factorized distributions referring to the two
particles in separate. This is possible for particles which interacted in the
past, but do not interact in the present. Three factors are crucial for the
effect: 1) separation of time-scales of coordinate and momentum which motivates
the definition of coarse-grained velocities; 2) the resulting uncertainty
relations between the coordinate of the brownian particle and the change of its
coarse-grained velocity; 3) the fact that the coarse-grained velocity, though
pertaining to a single brownian particle, is defined on a common context of two
particles. The brownian entanglement is a consequence of a coarse-grained
description and disappears for a finer resolution of the brownian motion. We
discuss possibilities of its experimental realizations in examples of
macroscopic brownian motion.Comment: 18 pages, no figure
A Model of the Potential Distribution of Striga hermonthica in the African Continent and its Prospection under Climate Change
The genus Striga (Orobanchaceae) comprises parasitic weeds recognised as a major problem
for crop production in sub-Saharan Africa. Striga hermonthica is an obligate parasite
of pearl millet, sorghum and other important crops in semi-arid and arid regions of the
tropics, producing millions of hectares of yield loses and a great impact on human welfare
in the rural areas where it occurs. Under the present situation and the possible scenarios
within the framework of climate change Striga hermonthica’s current and future distribution
needs to be estimated urgently, in order to efficiently target available prevention
and management strategies. Using the maximum entropy (Maxent) approach for modelling
species’ distributions, our research focuses on better describe the present distribution of
Striga hermonthica and to predict potential future areas where this dangerous parasite
could spread in the African continent
Schroedingers equation with gauge coupling derived from a continuity equation
We consider a statistical ensemble of particles of mass m, which can be
described by a probability density \rho and a probability current \vec{j} of
the form \rho \nabla S/m. The continuity equation for \rho and \vec{j} implies
a first differential equation for the basic variables \rho and S. We further
assume that this system may be described by a linear differential equation for
a complex state variable \chi. Using this assumptions and the simplest possible
Ansatz \chi(\rho,S) Schroedingers equation for a particle of mass m in an
external potential V(q,t) is deduced. All calculations are performed for a
single spatial dimension (variable q) Using a second Ansatz \chi(\rho,S,q,t)
which allows for an explict q,t-dependence of \chi, one obtains a generalized
Schroedinger equation with an unusual external influence described by a
time-dependent Planck constant. All other modifications of Schroeodingers
equation obtained within this Ansatz may be eliminated by means of a gauge
transformation. Thus, this second Ansatz may be considered as a generalized
gauging procedure. Finally, making a third Ansatz, which allows for an
non-unique external q,t-dependence of \chi, one obtains Schroedingers equation
with electromagnetic potentials \vec{A}, \phi in the familiar gauge coupling
form. A possible source of the non-uniqueness is pointed out.Comment: 25 pages, no figure
Blackbody Radiation and the Scaling Symmetry of Relativistic Classical Electron Theory with Classical Electromagnetic Zero-Point Radiation
It is pointed out that relativistic classical electron theory with classical
electromagnetic zero-point radiation has a scaling symmetry which is suitable
for understanding the equilibrium behavior of classical thermal radiation at a
spectrum other than the Rayleigh-Jeans spectrum. In relativistic classical
electron theory, the masses of the particles are the only scale-giving
parameters associated with mechanics while the action-angle variables are scale
invariant. The theory thus separates the interaction of the action variables of
matter and radiation from the scale-giving parameters. Classical zero-point
radiation is invariant under scattering by the charged particles of
relativistic classical electron theory. The basic ideas of the matter
-radiation interaction are illustrated in a simple relativistic classical
electromagnetic example.Comment: 18 page
Quenched lattice fluctuations in optically driven SrTiO3
Many functionally relevant ferroic phenomena in quantum materials can be
manipulated by driving the lattice coherently with optical and terahertz
pulses. New physical phenomena and non-equilibrium phases that have no
equilibrium counterpart have been discovered following these protocols. The
underlying structural dynamics has been mostly studied by recording the average
atomic position along dynamical structural coordinates with elastic scattering
methods. However, crystal lattice fluctuations, which are known to influence
phase transitions in equilibrium, are also expected to determine these dynamics
but have rarely been explored. Here, we study the driven dynamics of the
quantum paraelectric SrTiO3, in which mid-infrared drives have been shown to
induce a metastable ferroelectric state. Crucial in these physics is the
competition between the polar instability and antiferrodistortive rotations,
which in equilibrium frustrate the formation of long-range ferroelectricity. We
make use of high intensity mid-infrared optical pulses to resonantly drive a
Ti-O stretching mode at 17 THz, and we measure the resulting change in lattice
fluctuations using time-resolved x-ray diffuse scattering at a free electron
laser. After a prompt increase, we observe a long-lived quench in R-point
antiferrodistortive lattice fluctuations. The enhancement and reduction in
lattice fluctuations are explained theoretically by considering fourth-order
nonlinear phononic interactions and third-order coupling to the driven optical
phonon and to lattice strain, respectively. These observations provide a number
of new and testable hypotheses for the physics of light-induced
ferroelectricity
Хронобиология и хрономика (Международный симпозиум к 90-летию Франца Халберга)
In July, 2009 90 years from the date of a birth of the great scientist of present Franz Halberg (USA) were executed.В июле 2009 г. исполнилось 90 лет со дня рождения великого ученого современности Франца Халберга (США)
Green Production of Anionic Surfactant Obtained from Pea Protein
A pea protein isolate was hydrolyzed by a double enzyme treatment method in order to obtain short peptide sequences used as raw materials to produce lipopeptides-based surfactants. Pea protein hydrolysates were prepared using the combination of Alcalase and Flavourzyme. The influence of the process variables was studied to optimize the proteolytic degradation to high degrees of hydrolysis. The average peptide chain lengths were obtained at 3–5 amino acid units after a hydrolysis of 30 min with the mixture of enzymes. Then, N-acylation in water, in presence of acid chloride (C12 and C16), carried out with a conversion rate of amine functions of 90%, allowed to obtain anionic surfactant mixtures (lipopeptides and sodium fatty acids). These two steps were performed in water, in continuous and did not generate any waste. This process was therefore in line with green chemistry principles. The surface activities (CMC, foaming and emulsifying properties) of these mixtures were also studied. These formulations obtained from natural renewable resources and the reactions done under environmental respect, could replace petrochemical based surfactants for some applications
Experimental tests of hidden variable theories from dBB to Stochastic Electrodynamics
In this paper we present some of our experimental results on testing hidden
variable theories, which range from Bell inequalities measurements to a
conclusive test of stochastic electrodynamics
Additional roles of a peripheral loop–loop interaction in the Neurospora VS ribozyme
Many RNAs contain tertiary interactions that contribute to folding the RNA into its functional 3D structure. In the VS ribozyme, a tertiary loop–loop kissing interaction involving stem–loops I and V is also required to rearrange the secondary structure of stem–loop I such that nucleotides at the base of stem I, which contains the cleavage–ligation site, can adopt the conformation required for activity. In the current work, we have used mutants that constitutively adopt the catalytically permissive conformation to search for additional roles of the kissing interaction in vitro. Using mutations that disrupt or restore the kissing interaction, we find that the kissing interaction contributes ∼1000-fold enhancement to the rates of cleavage and ligation. Large Mg2+-dependent effects on equilibrium were also observed: in the presence of the kissing interaction cleavage is favored >10-fold at micromolar concentrations of Mg2+; whereas ligation is favored >10-fold at millimolar concentrations of Mg2+. In the absence of the kissing interaction cleavage exceeds ligation at all concentrations of Mg2+. These data provide evidence that the kissing interaction strongly affects the observed cleavage and ligation rate constants and the cleavage–ligation equilibrium of the ribozyme
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