137 research outputs found
Energy Calculations of The Realistic Quantum Slab
We calculated the total energy of a semiconductor quantum dot which is
defined by the trench gate method. In our calculation we used a recently
developed energy functional called ``orbital-free energy functional". We
compared the total energies obtained by Thomas-Fermi approximation,
orbital-free energy functional and standard local-density approximation for the
square quantum slab geometry. We have seen that this newly developed energy
functional is numerically very efficient, superior to the Thomas-Fermi
approximation and is in good agreement with the local-density approximation for
two different sizes of quantum dot systems.Comment: 8 pages, 4 figure
Mapping the stellar age of the Milky Way bulge with the VVV : II. Deep JK s catalog release based on PSF photometry
Context. The bulge represents the best compromise between old and massive Galactic components, and as such its study is a valuable opportunity to understand how the bulk of the Milky Way formed and evolved. In addition, being the only bulge in which we can individually resolve stars in all evolutionary sequences, the properties of its stellar content provide crucial insights into the formation of bulges. Aims. We are providing a detailed and comprehensive census of the Milky Way bulge stellar populations by producing deep and accurate photometric catalogs of the inner ∼300 deg 2 of the Galaxy. Methods. We performed DAOPHOT/ALLFRAME point spread function (PSF) fitting photometry of multi-epochs J and K s images provided by the VISTA Variables in the Vía Láctea (VVV) survey to obtain deep photometric catalogs. Artificial star experiments have been conducted on all images to properly assess the completeness and the accuracy of the photometric measurements. Results. We present a photometric database containing nearly 600 million stars across the bulge area surveyed by the VVV. Through the comparison of derived color-magnitude diagrams of selected fields representative of different levels of extinction and crowding, we show the quality, completeness and depth of the new catalogs. With the exception of the fields located along the plane, this new photometry samples stars down to ∼1-2 mag below the old main sequence turnoff with unprecedented accuracy. To demonstrate the tremendous potential inherent to this new dataset, we give a few examples of possible applications, including (i) star count studies through the dataset completeness map; (ii) surface brightness map; and (iii) cross-correlation with Gaia DR2. Conclusions. The database presented here represents an invaluable collection for the whole community, and we encourage its exploitation. The photometric catalogs including completeness information are publicly available through the ESO Science Archive as part of the MW-BULGE-PSPHOT release.Peer reviewedFinal Accepted Versio
Organik Hayvan Yemi Üretiminde Monogastrik (Tek Mideli) Hayvanlar için Protein, Ruminantlar Gevişgetirenler) için Kaba Yem Kaynağı olarak Yüksek Lif Kalitesine Sahip Rafine Edilmiş Yerel Kaynaklı Baklagil Yem Bitkilerinin Üretimi (PROREFINE Project)
Organik hayvan yemi üretiminde tüm dünyada yeterli bir üretim söz konusu değildir. Özellikle protein kaynağı açısından yem açığı çok fazladır. Organik yem temini açısından yaşanan zorluklardan dolayı alternatif çözümler aranmıştır. Bu proje ile baklagil yem bitkilerinden olan yonca üretiminden sonra, bazı rafine yöntemler kullanılarak proteince zengin yemlerin elde edilerek, lif kalitesi yüksek yemlerin üretimi planlanmıştır. Değişik parçalama ve ekstraksiyon yöntemleri kullanılarak organik yem pazarında yeni ürünler oluşturulması amaçlanmıştır
Theoretical Investigation of Local Electron Temperature in Quantum Hall Systems
In this work we solve thermo-hydrodynamical equations considering a two
dimensional electron system in the integer quantum Hall regime, to calculate
the spatial distribution of the local electron temperature. We start from the
self-consistently calculated electrostatic and electrochemical potentials in
equilibrium. Next, by imposing an external current, we investigate the
variations of the electron temperature in the linear-response regime. Here a
local relation between the electron density and conductivity tensor elements is
assumed. Following the Ohm's law we obtain local current densities and by
implementing the results of the thermo-hydrodynamical theory, calculate the
local electron temperature. We observe that the local electron temperature
strongly depends on the formation of compressible and incompressible strips.Comment: 10 pages, 4 figure
Characterization of platinum nitride from first-principles calculations
We have performed a systematic study of the ground state properties of the zinc-blende, rock-salt, tetragonal, cuprite, fluorite and pyrite phases of platinum nitride by using the plane wave pseudopotential calculations within the density functional theory. The equilibrium structural parameters and bulk moduli are computed within both the local density approximation (LDA) and generalized gradient approximation (GGA). The comparison of the equation of state (EOS) calculated within the LDA for the pyrite structure with the experimental results demonstrates an excellent agreement, hence the use of the LDA rather than the GGA is essential. Complete sets of elastic moduli are presented for cubic forms. The analysis of the results reveal that the pyrite phase with PtN2 stoichiometry leads to the formation of a hard material with the shear modulus G = 206GPa. The electronic structure of pyrite PtN2 is given, which shows a narrow indirect gap. The vibrational properties of platinum nitride are investigated in detail from lattice dynamical calculations. The calculations show that fluorite and pyrite structures are dynamically stable as well. However, the calculated vibrational modes of pyrite PtN2 do not show complete agreement with experimental Raman frequencies. © 2009 IOP Publishing Ltd
Mapping the stellar age of the Milky Way bulge with the VVV. I. The method
Recent observational programmes are providing a global view of the Milky Way
bulge that serves as template for detailed comparison with models and
extragalactic bulges. A number of surveys (i.e. VVV, GIBS, GES, ARGOS, BRAVA,
APOGEE) are producing comprehensive and detailed extinction, metallicity,
kinematics and stellar density maps of the Galactic bulge with unprecedented
accuracy. However, the still missing key ingredient is the distribution of
stellar ages across the bulge. To overcome this limitation, we aim to age-date
the stellar population in several bulge fields with the ultimate goal of
deriving an age map of the Bulge. This paper presents the methodology and the
first results obtained for a field along the Bulge minor axis, at .
We use a new PSF-fitting photometry of the VISTA Variables in the V\'{i}a
L\'{a}ctea (VVV) survey data to construct deep color-magnitude diagrams of the
bulge stellar population down to 2 mag below the Main Sequence turnoff.
We find the bulk of the bulge stellar population in the observed field along
the minor axis to be at least older than 7.5 Gyr. In particular, when
the metallicity distribution function spectroscopically derived by GIBS is
used, the best fit to the data is obtained with a combination of synthetic
populations with ages in between 7.5 Gyr and 11 Gyr. However, the
fraction of stars younger than 10 Gyr strongly depends upon the number
of Blue Straggler Stars present in the bulge. Simulations show that the
observed color-magnitude diagram of the bulge in the field along the minor axis
is incompatible with the presence of a conspicuous population of
intermediate-age/young (i.e. Gyr) stars.Comment: 14 pages, 7 figues, Accepted for publication on A&
Polynomial Solution of Non-Central Potentials
We show that the exact energy eigenvalues and eigenfunctions of the
Schrodinger equation for charged particles moving in certain class of
non-central potentials can be easily calculated analytically in a simple and
elegant manner by using Nikiforov and Uvarov (NU) method. We discuss the
generalized Coulomb and harmonic oscillator systems. We study the Hartmann
Coulomb and the ring-shaped and compound Coulomb plus Aharanov-Bohm potentials
as special cases. The results are in exact agreement with other methods.Comment: 18 page
The antioxidant activity of some curcuminoids and chalcones
The antioxidant properties of the synthetic compound (C1)–(C8), which comprised 7 curcuminoids and a chalcone, were evaluated by two complementary assays, DPPH and β-carotene/linoleic acid. It was found that, in general, the free radical scavenging ability of (C1)–(C8) was concentration-dependent. Compounds (C1) and (C4), which contained (4-OH) phenolic groups, were found to be highly potent antioxidants with higher antioxidant values than BHT suggesting that synthetic curcuminoids are more potent antioxidants than standard antioxidants like BHT. Using β-carotene-linoleic acid assay, only the water-soluble 2, 4,6-trihydroxyphenolic chalcone (C5) showed 85.2 % inhibition of the formation of conjugated dienes reflecting on its potent antioxidant activity
COVID-19. Pandemic surgery guidance
Abstract – Based on high quality surgery and scientific data, scientists and surgeons are committed to protecting patients as well as healthcare staff and hereby provide this Guidance to address the special issues circumstances related to the exponential spread of the Coronavirus disease 2019 (COVID-19) during this
pandemic. As a basis, the authors used the British Intercollegiate General Surgery Guidance as well as recommendations from the USA, Asia, and Italy. The aim is to take responsibility and to provide guidance for surgery
during the COVID-19 crisis in a simplified way addressing the practice of surgery, healthcare staff and patient
safety and care. It is the responsibility of scientists and the surgical team to specify what is needed for the protection of patients and the affiliated healthcare team. During crises, such as the COVID-19 pandemic, the
responsibility and duty to provide the necessary resources such as filters, Personal Protective Equipment
(PPE) consisting of gloves, fluid resistant (Type IIR) surgical face masks (FRSM), filtering face pieces, class
3 (FFP3 masks), face shields and gowns (plastic ponchos), is typically left up to the hospital administration
and government. Various scientists and clinicians from disparate specialties provided a Pandemic Surgery
Guidance for surgical procedures by distinct surgical disciplines such as numerous cancer surgery disciplines,
cardiothoracic surgery, ENT, eye, dermatology, emergency, endocrine surgery, general surgery, gynecology,
neurosurgery, orthopedics, pediatric surgery, reconstructive and plastic surgery, surgical critical care, transplantation surgery, trauma surgery and urology, performing different surgeries, as well as laparoscopy, thoracoscopy and endoscopy. Any suggestions and corrections from colleagues will be very welcome as we are all
involved and locked in a rapidly evolving process on increasing COVID-19 knowledg
- …