181 research outputs found
Optimal control of electromagnetic field using metallic nanoclusters
The dielectric properties of metallic nanoclusters in the presence of an
applied electromagnetic field are investigated using non-local linear response
theory. In the quantum limit we find a non-trivial dependence of the induced
field and charge distribution on the spatial separation between the clusters
and on the frequency of the driving field. Using a genetic algorithm, these
quantum functionalities are exploited to custom-design sub-wavelength lenses
with a frequency controlled switching capability.Comment: accepted for publication in New Journal of Physic
Mechanics and Mathematical Modeling of Class III Treatment with Orthodontic Appliances with a Movable Ramp
Treatment of class III is a current problem in orthodontics that requires constant improvement of its methods, development of new or modifications of known methods and techniques. We have developed and studied the modification of removable functionally-directing orthodontic appliances for treatment of Class III, which consists of a plastic base, vestibular arc, retaining clasps, ramp, which is connected with the base by means of two torsion springs. Its usage ensures a prolonged contact of ramp with the teeth. We studied two types of club-shaped springs (torsion springs): one spring, which create an amortization effect during the action of the ramp, but do not change its inclination angle and second one – spring that seek to increase the angle of the ramp inclination due to the disclosure of its curl
Investigation of static and dynamic behavior of anisotropic inhomogeneous shallow shells by Spline approximation method
The present report proposes an efficient approach to solving within the framework of the classic and refined models the stress‐strain problems of shallow shells as well as the problems on free vibrations. In accordance with the approach the initial system of partial differential equations is reduced to one‐dimensional problems by using approximation of the solution in terms of basic splines in one coordinate. The boundary‐value problems obtained and eigenvalue boundary‐value problems for systems of ordinary differential high‐order equations are solved by the stable numerical method of discrete ortogonalization.
Santrauka
Nagrinėjamas efektyvus lėkštųjų kevalų įtempių, deformacijų ir laisvųjų svyravimų nustatymo algoritmas, pagrįstas klasikiniais ir tobulesniais skaičiavimo modeliais. Algoritme dalinių diferencialinių lygčių sistema yra transformuojama į vienmatį uždavinį, sprendžiamą naudojant pagrindinių splainų aproksimaciją į vieną koordinatę. Gaunamas kraštinis uždavinys, kuris sprendžiamas kaip kraštinis savųjų reikšmių nustatymo uždavinys. Uždavinio sąlygas atitinka įprastų aukštesnės eilės diferencialinių lygčių sistema, kuriai spręsti taikomi patikimi diskrečiosios ortogonalizacijos skaitiniai metodai.
First Published Online: 14 Oct 2010
Reikšminiai žodžiai: lėkštieji kevalai, kintamasis storis, modifikuotoji ir klasikinė formuluotės, įtempių ir deformacijų būvis, laisvieji svyravimai
MECHANICS AND MATHEMATICAL MODELING OF CLASS III TREATMENT WITH ORTHODONTIC APPLIANCES WITH A MOVABLE RAMP
Treatment of class III is a current problem in orthodontics that requires constant improvement of its methods, development of new or modifications of known methods and techniques. We have developed and studied the modification of removable functionally-directing orthodontic appliances for treatment of Class III, which consists of a plastic base, vestibular arc, retaining clasps, ramp, which is connected with the base by means of two torsion springs. Its usage ensures a prolonged contact of ramp with the teeth.We studied two types of club-shaped springs (torsion springs): one spring, which create an amortization effect during the action of the ramp, but do not change its inclination angle and second one – spring that seek to increase the angle of the ramp inclination due to the disclosure of its curl
Comment on "Negative Refractive Index in Artificial Metamaterials" [A. N. Grigorenko, Opt. Lett., 31, 2483 (2006)]
A key optical parameter characterizing the existence of negative refraction
in a thin layer of a composite material is the effective refractive index of an
equivalent, homogenized layer with the same physical thickness as the initial
inhomogeneous composite. Measuring the complex transmission and reflection
coefficients is one of the most rigorous ways to obtain this parameter. We
dispute Grigorenko's statement (Optics Letters 31, 2483 (2006)) that measuring
only the reflection intensity spectrum is sufficient for determining the
effective refractive index. We discuss fundamental drawbacks of Grigorenko's
technique of using a best-fit approximation with an a priori prescribed
dispersive behavior for a given metamaterial and an 'effective optical
thickness' that is smaller than the actual thickness of the sample. Our
simulations do not confirm the Grigorenko paper conclusions regarding the
negative refractive index and the negative permeability of the nanopillar
sample in the visible spectral range.Comment: 18 pages, 7 figure
Bogoliubov angle and visualization of particle-hole mixture in superconductors
Superconducting excitations --Bogoliubov quasiparticles -- are the quantum
mechanical mixture of negatively charged electron (-e) and positively charged
hole (+e). Depending on the applied voltage bias in STM one can sample the
particle and hole content of such a superconducting excitation. Recent Scanning
Tunneling Microscope (STM) experiments offer a unique insight into the inner
workings of the superconducting state of superconductors. We propose a new
observable quantity for STM studies that is the manifestation of the
particle-hole dualism of the quasiparticles. We call it a {\em Bogoliubov
angle}. This angle measures the relative weight of particle and hole amplitude
in the superconducting (Bogoliubov) quasiparticle. We argue that this quantity
can be measured locally by comparing the ratio of tunneling currents at
positive and negative biases. This Bogoliubov angle allows one to measure
directly the energy and position dependent particle-hole admixture and
therefore visualize robustness of superconducting state locally. It may also
allow one to measure the particle-hole admixture of excitations in normal state
above critical temperature and thus may be used to measure superconducting
correlations in pseudogap state.Comment: 16 pages, latex file, 9 eps figure
Non-polaritonic effects in cavity-modified photochemistry
Strong coupling of molecules to vacuum fields has been widely reported to
lead to modified chemical properties such as reaction rates. However, some
recent attempts to reproduce infrared strong coupling results have not been
successful, suggesting that factors other than strong coupling may sometimes be
involved. Here we re-examine the first of these vacuum-modified chemistry
experiments, in which changes to a molecular photoisomerisation process were
attributed to strong coupling of the molecules to visible light. We observed
significant variations in photoisomerisation rates for molecules placed in a
variety of optical cavity structures, but found no evidence that these changes
need to be attributed to strong coupling. Instead, we suggest that the
photoisomerisation rates involved are most strongly influenced by the
absorption of ultraviolet radiation in the cavity. Our results indicate that
care must be taken to rule out non-polaritonic effects before invoking strong
coupling to explain any changes of chemical properties arising in cavity-based
experiments.Comment: 31 pages, 16 figure
Cloning and sequence analysis of cDNA for a human homolog of eubacterial ATP-dependent Lon proteases
AbstractOverlapping cDNA clones containing mRNA for a putative Lon protease (LonHS) were isolated from cDNA libraries prepared from human brain poly(A)+ RNA. The determined nucleotide sequence contains a 2814-bp open reading frame with two potential initiation codons (positions 62–64 and 338–340). The 5'-terminal 337-nucleotide fragment of LonHS mRNA is highly enriched with G and C nucleotides and could direct synthesis of the LonHS N-terminal domain. More likely this region promotes initiation of protein synthesis from the second AUG codon in a cap-independent manner. The amino acid sequence initiated at the second AUG codon includes 845 residues, over 30% of which are identical to those of eubacterial Lon proteases. Residues of the ‘A’ and ‘B’ motifs of NTP-binding pattern and a plausible catalytic serine residue are conserved in LonHS. Northern blot analysis revealed LonHS mRNA in lung, duodenum, liver and heart, but not in thymus cells
STUDY OF ANTI-OSTEOPOROTIC ACTION OF DRUGS FROM THE GROUP OF STATINS
In an experiment on female Wistar white rats, the osteoprotective effect of atorvastatin, simvastatin and rosuvastatin was studied in a model of experimental osteoporosis caused by bilateral ovariectomy. It was found that after ovariectomy in female rats develops endothelial dysfunction, including the vessels of the microcirculatory of the bone, leading to a deterioration of blood supply to bone tissue and the occurrence of osteoporosis. It was found that atorvastatin, simvastatin and rosuvastatin, possessing endothelioprotective activity, prevent deterioration of blood supply to bone tissue and thinning of bone trabeculae, thus having anti-osteoporotic activity. Key words: osteoporosis, endothelial dysfunction, statins, atorvastatin, simvastatin, rosuvastatin, strontium ranelate
Optimization of the design of superconducting inhomogeneous nanowires
We study optimization of superconducting properties of inhomogeneous
nanowires. The main goal of this research is to find an optimized geometry that
allows one to maximize the desired property of superconductors, such as the
maximum value of local superconducting gap or total condensation energy. We
consider axially symmetric design of multi-layered nanowires with possibility
to adjust and change the layers thickness. We use numerical solution of the
Bogoliubov-de Gennes equations to obtain the local superconducting gap for
different arrangements of the inhomogeneous structures. The value of the
optimized properties can be up to 300% greater compared to a non-optimized
geometry. The optimized configuration of multilayers strongly depends on the
desired property one wants to optimize and on the number of layers in the
nanowire.Comment: Published in J. Phys.: Condens. Matter 20, 195204 (2008
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