172 research outputs found
Raman and IR spectra of pure and doped forsterite single crystals
Forsterite single crystals were grown by the Czochralski technique in air. The lattice parameters were determined by X-ray power diffraction. The IR and Raman spectra of pure and doped (V3+, V5+, and Ni4+) Mg2SiO4 single crystals were measured at room temperature. We studied the phonon properties and discussed the influence of dopants
Sliding Columnar Phase of DNA-Lipid Complexes
We introduce a simple model for DNA-cationic-lipid complexes in which
galleries between planar bilayer lipid lamellae contain DNA 2D smectic lattices
that couple orientationally and positionally to lattices in neighboring
galleries. We identify a new equilibrium phase in which there are long-range
orientational but not positional correlations between DNA lattices. We discuss
properties of this new phase such as its X-ray structure factor S(r), which
exhibits unusual exp(- const.ln^2 r) behavior as a function of in-plane
separation r.Comment: This file contains 4 pages of double column text and one postscript
figure. This version includes interactions between dislocations in a given
gallery and presents an improved estimate of the decoupling temperature. It
is the published versio
Structural Properties of the Sliding Columnar Phase in Layered Liquid Crystalline Systems
Under appropriate conditions, mixtures of cationic and neutral lipids and DNA
in water condense into complexes in which DNA strands form local 2D smectic
lattices intercalated between lipid bilayer membranes in a lamellar stack.
These lamellar DNA-cationic-lipid complexes can in principle exhibit a variety
of equilibrium phases, including a columnar phase in which parallel DNA strands
from a 2D lattice, a nematic lamellar phase in which DNA strands align along a
common direction but exhibit no long-range positional order, and a possible new
intermediate phase, the sliding columnar (SC) phase, characterized by a
vanishing shear modulus for relative displacement of DNA lattices but a
nonvanishing modulus for compressing these lattices. We develop a model capable
of describing all phases and transitions among them and use it to calculate
structural properties of the sliding columnar phase. We calculate displacement
and density correlation functions and x-ray scattering intensities in this
phase and show, in particular, that density correlations within a layer have an
unusual dependence on separation r. We
investigate the stability of the SC phase with respect to shear couplings
leading to the columnar phase and dislocation unbinding leading to the lamellar
nematic phase. For models with interactions only between nearest neighbor
planes, we conclude that the SC phase is not thermodynamically stable.
Correlation functions in the nematic lamellar phase, however, exhibit SC
behavior over a range of length scalesComment: 28 pages, 4 figure
KARSTIC LANDSCAPE STUDY BASED ON REMOTE SENSING DATA: THE CASE OF KSIROMERO REGION, AITOLOAKARNANIA - WESTERN GREECE
The aim of this study is to investigate and recognize karst landforms in the area of Ksiromero (Aitoloakarnania, Western Greece) based on medium resolution remote sensing data. In order to highlight karstic structures appropriate and innovative methodologies of image analysis have been developed, applied and compared. In particular, the original Landsat 5 TM bands have been, first, ad-hoc stretched and then processed to obtain the so-called Tasseled Cap Features and the Principal Component images. Finally, a comparative study between the two methods has been carried out
Magnetically induced splitting of a giant vortex state in a mesoscopic superconducting disk
The nucleation of superconductivity in a superconducting disk with a Co/Pt
magnetic triangle was studied. We demonstrate that when the applied magnetic
field is parallel to the magnetization of the triangle, the giant vortex state
of vorticity three splits into three individual F0-vortices, due to a
pronounced influence of the C3 symmetry of the magnetic triangle. As a result
of a strong pinning of the three vortices by the triangle, their configuration
remains stable in a broad range of applied magnetic fields. For sufficiently
high fields, F0-vortices merge and the nucleation occurs through the giant
vortex state. The theoretical analysis of this novel reentrant behaviour at the
phase boundary, obtained within the Ginzburg - Landau formalism, is in
excellent agreement with the experimental data.Comment: to be published in Phys. Rev. B - Rapid. Com
Intenzitet habanja kod razliÄito toplinski poboljÅ”anog nodularnog lijeva
In the paper we investigate the relationship between the wear intensity of two nodular cast irons and their heat treatment conditions. Disks tempered by austempering and isothermal procedure were used. The wear test was realized by using Pin and Disk tribometer. Measurement of the disks wear, after the contact for duration of 30 min, was done by the PQ meter. The quantity of the wear products in lubricant is determined by the PQ index. The best wear resistance posses the disk isothermally tempering with 30 minutes holding at 390 Ā°C temperature.U ovom radu je ispitivana zavisnost izmeÄu intenziteta habanja dva nodularna lijeva kao i uvjeta pri njihovoj toplinskoj obradi. Uzorci za ispitivanje nodularnog lijeva su bili poboljÅ”ani klasiÄnim i izotermalnim postupkom. Ispitivanje intenziteta habanja je realizirano uz pomoÄ Pin on Disc tribometra. Mjerenje pohabanosti diska, nakon trenja u trajanju od 30 minuta, je obavljeno na PQ metru. KoliÄina Äestica nastalih kao produkti habanja, u sredstvu za hlaÄenje i podmazivanje je odreÄena PQ indexom. NajveÄu otpornost na habanje posjeduje disk izotermalno temperovan na 390 Ā°C u trajanju od 30 minuta
Risk Management of a Hydro Power Plant - Fracture Mechanics Approach
Risk management of a hydro power plant has been analysed from fracture mechanics point of view. The research is focused on the risk and integrity assessment of pressure equipment in a reversible hydro power plant in order to determine to what extent it poses a risk to Bajina Basta settlement and its inhabitants. The risk matrix has been used to assess risk level according to probability and consequence in a more descriptive way, whereas the failure assessment diagram has been used as an alternative engineering approach, including level II analysis
Nonlinear Elasticity of the Sliding Columnar Phase
The sliding columnar phase is a new liquid-crystalline phase of matter
composed of two-dimensional smectic lattices stacked one on top of the other.
This phase is characterized by strong orientational but weak positional
correlations between lattices in neighboring layers and a vanishing shear
modulus for sliding lattices relative to each other. A simplified elasticity
theory of the phase only allows intralayer fluctuations of the columns and has
three important elastic constants: the compression, rotation, and bending
moduli, , , and . The rotationally invariant theory contains
anharmonic terms that lead to long wavelength renormalizations of the elastic
constants similar to the Grinstein-Pelcovits renormalization of the elastic
constants in smectic liquid crystals. We calculate these renormalizations at
the critical dimension and find that , where is a wavenumber. The behavior of
, , and in a model that includes fluctuations perpendicular to the
layers is identical to that of the simple model with rigid layers. We use
dimensional regularization rather than a hard-cutoff renormalization scheme
because ambiguities arise in the one-loop integrals with a finite cutoff.Comment: This file contains 18 pages of double column text in REVTEX format
and 6 postscript figure
Synthesis of Anatase Nanopowders by Sol-gel Method and Influence of Temperatures of Calcination to Their Photocatalitic Properties
The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique from tetrabutyl titanate as a precursor, varying the temperature of calcination (from 500 to 550 degrees C with the step of 10 degrees C). XRPD results have shown that all synthesized nanopowders are dominantly in anatase phase. The analysis of the shift and linewidth of the most intensive anatase E-g Raman mode confirmed the XRPD results and added the presence of small amount of highly disordered brookite phase in all samples. The analysis of pore structure from nitrogen sorption experimental data described all samples as mesoporous, with mean pore diameters in the range of 1.5 and 4.5 nm. Nanopowder properties have been related to the photocatalytic activity, tested in degradation of the textile dye (C.I. Reactive Orange 16). The sample calcined at temperature of 510 degrees C showed the best photocatalytic performance
Ispitivanje moguÄnosti iznalaženja optimalne koncentracije evaporiranog mlijeka radi proizvodnje mlijeka u prahu na spray postrojenju, s osvrtom na Maillard-ov tip potamnjivanja
Autori su ispitivali utjecaj koncentracije evaporiranog mlijeka na kvalitetu mlijeka u prahu i pojavu Maillardove reakcije. Na osnovu rezultata provedenih fiziÄko-kemijskih i organoleptiÄkih ispitivanja zakljuÄuju da je optimalno suÅ”enje evaporiranog mlijeka sa 50 % s.t. U toku uskladiÅ”tenja obranog i punomasnog (25 %) mlijeka u prahu do 90 dana na sobnoj temperaturi poveÄava se intenzitet Maillard-ove reakcije znatno brže, nego u mlijeku skladiÅ”tenom kod 4 Ā°C
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