261 research outputs found
Point sources identification problems with pointwise overdetermination
This article is devoted to inverse problems of recovering point sources in
mathematical models of heat and mass transfer. The main attention is paid to
well-posedness questions of these inverse problems with pointwise
overdetermination conditions. We present conditions for existence and
uniqueness of solutions to the problem, display non-uniqueness examples, and,
in model situations, we give estimates on the number of measurements that allow
completely identify sources and their locations. The results rely on asymptotic
representations of Green functions of the corresponding elliptic problems with
a parameter. They can be used in constructing new numerical algorithms for
determining a solution.Comment: This article is actually a survey of the results obtained in the
previous articles of the authors. In some model cases, we discuss the
uniqueness and existence results for some classes of inverse problems. The
results uses a new approach based on asymptotic representations of the Green
function of the corresponding elliptic proble
Molecular dissection of Penelope transposable element regulatory machinery
© 2008 The Authors. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The definitive version was published in Nucleic Acids Research 36 (2008): 2522-2529, doi:10.1093/nar/gkm1166Penelope-like elements (PLEs) represent a new class of retroelements identified in more than 80 species belonging to at least 10 animal phyla. Penelope isolated from Drosophila virilis is the only known transpositionally active representative of this class. Although the size and structure of the Penelope major transcript has been previously described in both D. virilis and D. melanogaster transgenic strains, the architecture of the Penelope regulatory region remains unknown. In order to determine the localization of presumptive Penelope promoter and enhancer-like elements, segments of the putative Penelope regulatory region were linked to a CAT reporter gene and introduced into D. melanogaster by P-element-mediated transformation. The results obtained using ELISA to measure CAT expression levels and RNA studies, including RT–PCR, suggest that the active Penelope transposon contains an internal promoter similar to the TATA-less promoters of LINEs. The results also suggest that some of the Penelope regulatory sequences control the preferential expression in the ovaries of the adult flies by enhancing expression in the ovary and reducing expression in the carcass. The possible significance of the intron within Penelope for the function and evolution of PLEs, and the effect of Penelope insertions on adjacent genes, are discussed.This
work was supported by grants from Russian Academy of
Sciences (Cell and Molecular Biology to M.E.), and
Welcome Trust Grant (075698) to M.E and D.J.F
Waveguide-Integrated Electrically Driven Light-Emitting Carbon Nanotubes
In this work proof-of-concept devices with light-emitting electrically driven carbon nanotubes (CNTs) integrated in nanophotonic environments are presented.
Electroluminescent and incandescent CNTs can be envisioned as waveguide-integrated light sources for future on-chip data communication due to their unique structural, electrical and optical properties. The challenge thereby is to integrate and electrically contact solution processed CNTs across CMOS compatible waveguide structures and to enforce efficient coupling of light from the CNT into the waveguide.
Various nanophotonic devices with versatile functionalities were fabricated and equipped with CNTs by means of site-selective dielectrophoresis. The realized electrically driven CNT-based light emitters integrated with nanophotonic circuits allow for efficient coupling and propagation of light in waveguides over centimeter distances. Furthermore, in scope of the thesis it was demonstrated how spectral properties of a CNT emitter can be controlled directly on a chip with passive devices using grating structures, Mach-Zehnder interferometers and directional couplers.
Moreover, it was observed that in combination with a one-dimensional photonic crystal cavity CNT becomes an emitter with exceptionally narrow linewidths at desired adjustable wavelength. Finally, the usage of electrically driven CNTs as fast waveguide-integrated light emitters with Gbit/s response speed was shown.
Therefore direct, near-field coupling of electrically generated CNT-emitted light into a waveguide, opposed to far-field fiber coupling of external light sources, opens new avenues for scalable nanoscale optoelectronic systems in a CMOS compatible framework
On the nature of ill-posedness of the forward-backward heat equation
We study the Cauchy problem with periodic initial data for the
forward-backward heat equation defined by the J-self-adjoint linear operator L
depending on a small parameter. The problem has been originated from the
lubrication approximation of a viscous fluid film on the inner surface of the
rotating cylinder. For a certain range of the parameter we rigorously prove the
conjecture, based on the numerical evidence, that the set of eigenvectors of
the operator does not form a Riesz basis in \L^2 (-\pi,\pi). Our method
can be applied to a wide range of the evolutional problems given by
symmetric operators.Comment: 21 pages; Remark 5.2 added, acknowledgements added, several typos
fixe
The similarity problem for indefinite Sturm-Liouville operators and the HELP inequality
We study two problems. The first one is the similarity problem for the
indefinite Sturm-Liouville operator A=-(\sgn\, x)\frac{d}{wdx}\frac{d}{rdx}
acting in . It is assumed that w,r\in L^1_{\loc}(-b,b) are
even and positive a.e. on .
The second object is the so-called HELP inequality
where the coefficients \tilde{w},\tilde{r}\in L^1_{\loc}[0,b) are
positive a.e. on .
Both problems are well understood when the corresponding Sturm-Liouville
differential expression is regular. The main objective of the present paper is
to give criteria for both the validity of the HELP inequality and the
similarity to a self-adjoint operator in the singular case. Namely, we
establish new criteria formulated in terms of the behavior of the corresponding
Weyl-Titchmarsh -functions at 0 and at . As a biproduct of this
result we show that both problems are closely connected. Namely, the operator
is similar to a self-adjoint one precisely if the HELP inequality with
and is valid.
Next we characterize the behavior of -functions in terms of coefficients
and then these results enable us to reformulate the obtained criteria in terms
of coefficients. Finally, we apply these results for the study of the two-way
diffusion equation, also known as the time-independent Fokker-Plank equation.Comment: 42 page
Comportamiento ruidoso de los residentes de un edificio de apartamentos como una cuestión de ley de vecindad (el caso de la relación entre dueños de perros y vecinos)
The aim of this study is to examine in detail such a segment of neighborhood law as the silence related relations of neighbors in an apartment building. Neighborhood law, despite its long existence in the legal systems of foreign countries, remains unspecific in the regulation of relations between apartment owners, while in Russia neighborhood law has not received due attention from the federal legislator. We believe that competition between public and private law on this issue should be resolved in favor of private law. Civil law in the current state contains a great potential for the regulation of neighborhood relations and protection of neighborhood rights. The possibilities of civil law in this area should be expanded in the course of the forthcoming reform of property legislation. It is necessary to continue the development of neighborhood law in Russia.El objetivo de este estudio es examinar en detalle un segmento de la ley del vecindario como las relaciones de vecinos relacionadas con el silencio en un edificio de apartamentos. La ley de vecindad, a pesar de su larga existencia en los sistemas legales de paÃses extranjeros, sigue siendo inespecÃfica en la regulación de las relaciones entre los propietarios de apartamentos, mientras que en Rusia la ley de vecindad no ha recibido la debida atención del legislador federal. Creemos que la competencia entre el derecho público y privado en este tema debe resolverse a favor del derecho privado. La ley civil en el estado actual tiene un gran potencial para la regulación de las relaciones vecinales y la protección de los derechos vecinales. Las posibilidades del derecho civil en esta área deberÃan ampliarse en el curso de la próxima reforma de la legislación de propiedad. Es necesario continuar el desarrollo de la ley de vecindad en Rusia
Collinear cluster tripartition as sequential binary fission in the U(n,f) reaction
The mechanism leading to the formation of the observed products of the
collinear cluster tripartition is carried out within the framework of the model
based on the dinuclear system concept. The yield of fission products is
calculated using the statistical model based on the driving potentials for the
fissionable system. The minima of potential energy of the decaying system
correspond to the charge numbers of the products which are produced with large
probabilities in the sequential fission (partial case of the collinear cluster
tripartition) of the compound nucleus. The realization of this mechanism
supposes the asymmetric fission channel as the first stage of sequential
mechanism. It is shown that only the use of the driving potential calculated by
the binding energies with the shell correction allows us to explain the yield
of the true ternary fission products. The theoretical model is applied to
research collinear cluster tripartition in the reaction U(n,f). Calculations showed that in the first stage of this fission reaction,
the isotopes Ge and Nd are formed with relatively large
probabilities and in the second stage of sequential fission of the isotope Nd
mainly Ni and Ge are formed. This is in agreement with the yield of the isotope
Ni which is observed as the product of the collinear cluster
tripartition in the experiment.Comment: 20 pages, 9 figure
On a necessary aspect for the Riesz basis property for indefinite Sturm-Liouville problems
In 1996, H. Volkmer observed that the inequality
is
satisfied with some positive constant for a certain class of functions
on if the eigenfunctions of the problem form a Riesz basis of the Hilbert space
. Here the weight is assumed to satisfy
a.e. on .
We present two criteria in terms of Weyl-Titchmarsh -functions for the
Volkmer inequality to be valid. Using these results we show that this
inequality is valid if the operator associated with the spectral problem
satisfies the linear resolvent growth condition. In particular, we show that
the Riesz basis property of eigenfunctions is equivalent to the linear
resolvent growth if is odd.Comment: 26 page
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