2,684 research outputs found
Effect of Gr Contents on Wear Properties of Al2024/MgO/Al2O3/Gr Hybrid Composites
In the present study, hybrid metal matrix composites, Al2024/10Al2O3, Al2024/10Al2O3/3MgO, Al2024/10Al2O3/6MgO, Al2024/10Al2O3/3MgO/1.5 Gr, Al2024/10Al2O3/3MgO/3Gr, and reinforcement samples (AA 2024) produced with powder metallurgy process. AA 2024 and reinforcement powders were determined mixture rations and separately mixed during 30 minutes in a three-dimensional Turbula mixer. The mixed compositions were pressed at 300 MPa and sintered at 550°C during 1 h. After that, three materials were extruded at the same temperature. Experimental results show that hybrid metal matrix composites (HMMCs) a better wear resistance than the reinforcement samples because of higher hardness. Gr behave as a lubricant during wear process. The wear resistance of HMMCs can be optimized with controlling of the reinforcement content and type. © 2018 The Authors
Assessment of ecological quality status of Küçükçekmece Bay (Marmara Sea) by applying BENTIX, AMBI, BOPA and BO2A biotic indexes
This study was carried out to explore the effectiveness of different biotic indexes in the Marmara Sea. The assessment of ecological quality status (EQS) was performed by applying the biotic indexes BENTIX, AMBI, BOPA, BO2A and Shannon-Wienerdiversity, in combination with the estimation of total organic carbon (TOC) content of sediments. BOPA and BO2A indexes tended to overestimate the EQS of the stations. BENTIX was the most efficient index as it demonstrated conceivable EQS results with respect to TOC load and successfuly determined “acceptable” or “not acceptable” status of the stations. TOC content of sediment, which significantly correlated with several benthic measures (S, N, AMBI, BENTIX), proved to be a valuable proxy measure in evaluating the likelihood of benthic impairment. When overall EQS of northern Marmara Sea was discussed, the region was designated as ecologically disturbed with only 25.7% of the stations in acceptable status
Spectroscopic and Photometric Study of the Contact Binary BO CVn
We present the results of the study of the contact binary system BO CVn. We
have obtained physical parameters of the components based on combined analysis
of new, multi-color light curves and spectroscopic mass ratio. This is the
first time the latter has been determined for this object. We derived the
contact configuration for the system with a very high filling factor of about
88 percent. We were able to reproduce the observed light curve, namely the flat
bottom of the secondary minimum, only if a third light has been added into the
list of free parameters. The resulting third light contribution is significant,
about 20-24 percent, while the absolute parameters of components are: M1=1.16,
M2=0.39, R1=1.62 and R2=1.00 (in solar units). The O-C diagram shows an upward
parabola which, under the conservative mass transfer assumption, would
correspond to a mass transfer rate of dM/dt = 6.3 \times 10-8M\odot/yr, matter
being transferred from the less massive component to the more massive one. No
cyclic, short-period variations have been found in the O-C diagram (but
longer-term variations remain a possibility)Comment: 16 pages, 5 figures, 5 tables, accepted for publication by New
Astronom
Self-avoiding walks on a bilayer Bethe lattice
We propose and study a model of polymer chains in a bilayer. Each chain is
confined in one of the layers and polymer bonds on first neighbor edges in
different layers interact. We also define and comment results for a model with
interactions between monomers on first neighbor sites of different layers. The
thermodynamic properties of the model are studied in the grand-canonical
formalism and both layers are considered to be Cayley trees. In the core region
of the trees, which we may call a bilayer Bethe lattice, we find a very rich
phase diagram in the parameter space defined by the two activities of monomers
and the Boltzmann factor associated to the interlayer interaction between bonds
or monomers. Beside critical and coexistence surfaces, there are tricritical,
bicritical and critical endpoint lines, as well as higher order multicritical
points.Comment: 21 pages, 10 figures. Journal of Statistical Mechanics: Theory and
Experiment (in press
Chemical abundances of the metal-poor horizontal-branch stars CS 22186-005 and CS 30344-033
We report on a chemical-abundance analysis of two very metal-poor
horizontal-branch stars in the Milky Way halo: CS 22186-005 ([Fe/H]=-2.70) and
CS 30344-033 ([Fe/H]=-2.90). The analysis is based on high-resolution spectra
obtained at ESO, with the spectrographs HARPS at the 3.6 m telescope, and UVES
at the VLT. We adopted one-dimensional, plane-parallel model atmospheres
assuming local thermodynamic equilibrium. We derived elemental abundances for
13 elements for CS 22186-005 and 14 elements for CS 30344-033. This study is
the first abundance analysis of CS 30344-033. CS 22186-005 has been analyzed
previously, but we report here the first measurement of nickel (Ni; Z = 28) for
this star, based on twenty-two NiI lines ([Ni/Fe]=-0.210.02); the
measurement is significantly below the mean found for most metal-poor stars.
Differences of up to 0.5 dex in [Ni/Fe] ratios were determined by different
authors for the same type of stars in the literature, which means that it is
not yet possible to conclude that there is a real intrinsic scatter in the
[Ni/Fe] ratios. For the other elements for which we obtained estimates, the
abundance patterns in these two stars match the Galactic trends defined by
giant and turnoff stars well. This confirms the value of horizontal-branch
stars as tracers of the chemical properties of stellar populations in the
Galaxy. Our radial velocities measurements for CS 22186-005 differ from
previously published measurements by more than the expected statistical errors.
More measurements of the radial velocity of this star are encouraged to confirm
or refute its radial velocity variability
The effect of cationic surfactant and some organic/inorganic additives on the morphology of mesostructured silica templated by pluronics
Cataloged from PDF version of article.Tri-block copolymers (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), represented as EOxPOyEOx), pluronics (F127=EO106PO70EO106, P65=EO20PO30EO20, P85=EO27PO39EO27, P103= EO17PO55EO17, and P123 = EO20PO70EO20) and cationic surfactants (cethyltrimethylammonium bromide (CTAB)), two surfactant systems, form complex micelles that self-assemble into mesostructured particles with distinct morphology depending on the pluronic type, the concentration of the cationic surfactant and the organic-inorganic ingredients in a siliceous reaction media under acidic conditions. The CTAB-P65 and CTAB-P85 systems form spheres, CTAB-P103 and CTAB-P123 systems form wormlike particles, and CTAB-F127 system form single crystals of mesostructured silica particles under very similar conditions. However addition of various salts (such as KCI and NaNO3) into a CTAB-P103 or CTAB-P123 solution system and cyclohexane and KCI into a CTAB-P85 solution system produces the mesostructured silica spheres and wormlike particles, respectively. By controlling the hydrophilic-hydrophobic character of the pluronics, core-corona interface, by means of additives, such as small organic molecules or salts, one could obtain the desired morphology that is dictated by the shape of the micelles of the pluronic-cationic surfactant complex. The effects of the additives and the formation mechanism of those morphologies have been discussed using spectroscopy (FT-IR and Raman), diffraction (XRD) and microscopy (POM and SEM) data. (c) 2008 Elsevier Inc. All rights reserved
Agricultural Academy
abstract ALBAYRAK, Sebahattin and Mevlut TURK, 2011. Effects of fertilization on forage yield and quality of crested wheatgrass (Agropyron cristatum L. Gaertn.). Bulg. J. Agric. Sci., This study aimed to determine the effects of six nitrogen rates (0, 40, 80, 120, 160 and 200 kg ha -1 ) on forage yield and quality of crested wheatgrass (Agropyron cristatum L. Gaertn.). Dry matter (DM) yield, N, P, K, Ca, Mg, (K/Ca+Mg), NDF, ADF, TDN, DDM, DMI, RFV and NE 1 were determined. Nitrogen rates significantly affected most of the components determined in crested wheatgrass. Nitrogen applications increased DM yield, N, P and K contents but decreased Ca, Mg, tetany ratio, NDF and ADF. TDN, DDM, DMI, RFV and NE 1 increased by increasing N fertilization. The results showed that crested wheatgrass at the 160 kg ha -1 nitrogen treatment achieved a higher forage yield and quality than other nitrogen doses
X-ray Doppler Imaging of 44i Boo with Chandra
Chandra High-Energy Transmission Grating observations of the bright eclipsing
contact binary 44i Boo show X-ray line profiles which are Doppler-shifted by
orbital motions. The X-ray emission spectrum contains a multitude of lines
superimposed on a weak continuum, with strong lines of O VIII, Ne X, Fe XVII,
and Mg XII. The profiles of these lines from the total observed spectrum show
Doppler-broadened widths of ~ 550 km s^{-1}. Line centroids vary with orbital
phase, indicating velocity changes of > 180 km s^{-1}. The first-order light
curve shows significant variability, but no clear evidence for either primary
or secondary eclipses. Flares are observed for all spectral ranges;
additionally, the light curve constructed near the peak of the emission measure
distribution (T_e = 5 to 8 X 10^6 K) shows quiescent variability as well as
flares. The phase-dependences of line profiles and light curves together imply
that at least half of the emission is localized at high latitude. A simple
model with two regions on the primary star at relatively high latitude
reproduces the observed line profile shifts and quiescent light curve. These
first clear X-ray Doppler shifts of stellar coronal material illustrate the
power of Chandra.Comment: 15 pages, 6 figures to be published in Astrophysical Journal Letter
Molekularna dijagnostika i serološka istraživanja pestivirusa u ovaca.
In this research, the virological and serological presence of pestiviruses, such as border disease virus (BDV) was investigated in a sheep in the Central and Eastern Black Sea Regions of Turkey. The study material consisted of 40 organ materials collected from 13 aborted lambs, which were suspected to have pestiviruses, BDV and Bovine Viral Diarrhoea Virus (BVDV). Viral nucleic acids were investigated by using the reverse transcription polymerase chain reaction (RT-PCR). Nine of 13 aborted lambs (69.2%) and 24 of 40 organ samples (60%) obtained from those sheep were BDV RNA positive, whilst all the animals and organ samples were BVDV-RNA negative. Serum samples collected from 401 randomly selected sheep were investigated for pestivirus antibodies using competitive ELISA (cELISA) and the serum microneutralisation test (SNT) using BVDV-NADL strain. Seropositivity was found in between 7.22 and 74.38% with cELISA and 4.81 and 67.76% with SNT. Seropositivity rates in Amasya and Tokat provinces were higher than in Samsun and Giresun. The obtained data indicated that pestivirus infection in sheep is widespread in the Central and Eastern Black Sea Region.U radu su prikazana virološka i serološka istraživanja pestivirusa odnosno borderske bolesti u ovaca na središnjem i istočnom području Crnoga mora u Turskoj. Ukupno je bilo pretraženo 40 uzoraka tkiva različitih organa uzetih od 13 pobačenih plodova pod sumnjom da je uzročnik bio virus borderske bolesti ili virus virusnog proljeva goveda. Uzorci su bili pretraženi na prisutnost virusne nukleinske kiseline lančanom reakcijom polimerazom uz prethodnu reverznu transkripciju (RT-PCR). Devet od 13 pobačenih plodova (69,2%) i 24 od 40 uzoraka tkiva organa (60%) sadržavalo je RNA virusa borderske bolesti. Svi pretraženi uzorci bili su negativni na virus virusnoga proljeva. Uzorci seruma nasumce prikupljeni od 401 ovce bili su pretraženi na prisutnost specifičnih protutijela uporabom kompetitivnoga imunoenzimnoga testa (cELISA) i serum neutralizacijskoga testa (SNT) sa sojem NADL virusa virusnoga proljeva goveda. Ustanovljeno je da sepostotak serološki pozitivnih cELISA-om kretao od 7,22 do 74,38%, a SNT-om od 4,81 do 67,76%. Postotak serološki pozitivnih životinja u provincijama Amasya i Tokat bio je veći nego u provincijama Samsun i Giresun. Rezultati upućuju na zaključak da su pestivirusne zaraze rasprostranjene u ovaca na središnjem i istočnom području Crnoga mora
Podwójne znakowanie immunologiczne CD133 i Ki-67 wskazuje na ich istotną współlokalizację w podtypie włóknistym oponiaków
Background and purpose
A unique molecular and/or cellular marker for meningiomas, the most common intracranial tumours, has not been identified yet.
Material and methods
We investigated the co-localization fraction of CD133/Ki-67 in meningioma tissue array slide composed of 80 meningioma tissue samples of various histological variants. CD133 – a cell membrane stem cell marker – was previously proved to be associated with the initiation and progression of intracerebral gliomas and medulloblastomas.
Results
Immunohistochemical co-localization of CD133/Ki-67 was significantly higher in fibroblastic variant than in meningothelial and transitional subtypes. However, since there were only 3 atypical and 1 malignant meningioma spots in the tumour tissue array slide, it is difficult to draw a firm conclusion regarding the actual co-localization percentage and persistence of CD133/Ki-67 in atypical and malignant meningiomas.
Conclusions
Far higher co-staining percentage of CD133/Ki-67 in fibroblastic meningioma samples compared to meningothelial subtype, a histological meningioma variant, architectonically resembling the non-neoplastic meningeal cells, gave us the impression that CD133 may play a role in the formation and progression of fibroblastic meningioma variants. The persistency and the validity of this finding need to be verified by further histopathological and molecular research in order to clarify the possible role of CD133 in meningiogenesis.Wstęp i cel pracy
Nie określono dotąd unikalnego znacznika molekularnego lub komórkowego dla oponiaków, najczęstszych guzów wewnątrzczaszkowych. Wcześniej wykazano, że CD133 – znacznik błony komórkowej komórek macierzystych – jest związany z zapoczątkowaniem, a także wzrostem wewnątrzczaszkowych glejaków i rdzeniaków płodowych.
Materiał i metody
Zbadano odsetek współlokalizacji CD133/Ki-67 w zestawach macierzy tkankowych oponiaków, złożonych z próbek 80 rozmaitych odmian histologicznych oponiaków.
Wyniki
Immunohistochemiczna współlokalizacja CD133 i Ki-67 była stwierdzana istotnie częściej w podtypie włóknistym oponiaka niż w podtypach meningotelialnym lub przejściowym. Ze względu na małą liczbę preparatów opo-niaków atypowych (3) oraz złośliwych (1) w badanej macierzy tkankowej trudno wyciągnąć jednoznaczne wnioski dotyczące rzeczywistego odsetka współlokalizacji i utrzymywania się CD133/Ki-67 w oponiakach atypowych i złośliwych.
Wnioski
Znacząco większy odsetek wspólnie występującej reaktywności CD133/Ki-67 w preparatach oponiaka włóknistego w porównaniu z podtypem meningotelialnym, którego architektonika przypomina nienowotworowe komórki opon, sprawia wrażenie, że CD133 może odgrywać rolę w powstawaniu i rozwoju oponiaków włóknistych. Trafność tego spostrzeżenia wymaga weryfikacji w dalszych badaniach histopatologicznych i molekularnych w celu wyjaśnienia możliwej roli CD133 w powstawaniu oponiaków
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