An Open Inflationary Model for Dimensional Reduction and its Effects on the Observable Parameters of the Universe

Assuming that higher dimensions existed in the early stages of the universe where the evolution was inflationary, we construct an open, singularity-free, spatially homogeneous and isotropic cosmological model to study the effects of dimensional reduction that may have taken place during the early stages of the universe. We consider dimensional reduction to take place in a stepwise manner and interpret each step as a phase transition. By imposing suitable boundary conditions we trace their effects on the present day parameters of the universe.Comment: 5 pages, accepted for publication in Int. J. of Mod. Phys.

Some Meat Characteristics in Karya Lambs

A research was conducted during 2008 and 2009 to determine meat quality characteristics in 72 male and female Karya lambs in pasture, pasture plus feeding and intensive conditions. Significant differences were obtained between fattening groups in M. Longissimus Dorsi muscle for L* (lightness) and the highest value was calculated in intensive groups and male lambs. Also the meat colour appeared redder (high a* value) in this group and their male lambs. The intermusculer fat (marbling) was evaluated better in intensive group and male lambs. Regarding fatty acid composition, while SFA and MUFA were increased in intensive conditon, C16:0 was the highest, C18:0 and C18:1 n-9 were the lowest value in pasture lambs. İt is concluded that the pasture feeding increased P/S, CLA and n-6 PUFA/n-3 PUFA values.Animal Production 15(2):127-134, May 201

GEOMETRİ ÖĞRETİMİNDE UZAMSAL DÜŞÜNME BECERİSİNİ GELİŞTİRMEYE YÖNELİK BİLGİSAYAR YAZILIMLARINA GENEL BİR BAKIŞ

Teknolojinin değişmesi ve ilerlemesi insan yaşamının her alanını etkilediği gibi eğitim alanını da etkileyerek ciddi katkılar sağlamıştır. Bu katkıların en belirgin olanlarından biri de şüphesiz bilgisayarların öğrenme öğretme sürecinin içine dâhil edilmesi olmuştur. Genelde teknoloji, matematik eğitimi çalışmalarında faklı amaçlara yönelen değişik dinamik yazılımların kullanım imkânını sunmuştur. Özelde ise geometri kazanımları ile ilgili olarak kullanılan yazılımlardan en popüler olanları GeoGebra, Cabri vb gibi yazılımlardır. Bu yazılımlara ek olarak hem ücretsiz hem de kullanım kolaylığına sahip olan Google SketchUp yazılımı da son yıllarda kullanılmaya başlanmıştır. Geometri başarısında gerekli olduğu düşünülen ve zihinsel yeteneğin bir parçası olarak kabul edilen uzamsal becerilerin önemi birçok araştırmacının üzerinde durduğu bir konudur. Bilgisayar çoğunlukla görsel görüntülerle oynanmasına ortam sağlaması dolayısıyla uzamsal düşünmenin gelişmesine katkı sağlayabilir. Dinamik geometri yazılımlarından GeoGebra, Cabri ve Google SketchUp gibi yazılımların özellikle geometri konularında, uzamsal düşünme becerisinin geliştirilmek istendiği durumlarda oldukça kullanışlı olan bir yazılımdır. Bu nedenle bu çalışmada uzamsal düşünceye katkı sağlayan yazılımlarla ilgili çalışmaların ele alınıp değerlendirilmesi yapılmıştır. Araştırmadan elde edilen bulgulara göre, bu yazılımların uzamsal düşünceyi olumlu katkılar sağladığı tespit edilmiştirThe change and progress of technology affects every aspect of human life as well as it makes a serious contribution to the field of education. One of the most important contributions is undoubtedly the inclusion of computers into the teaching-learning process. In general, technology has offered the possibility of using different dynamic software for different purposes in mathematics education studies. Spesifically, the most popular software used in geometry objectives are GeoGebra, Cabri and so on. In addition to these software, Google SketchUp, which is both free and easy to use, has started to be used more and more in recent years. The importance of spatial skills which are considered necessary in the success of geometry and a part of mental ability is an important matter for many researchers. The computer can provide the environment to play with visual images, thus contributing to the development of spatial thinking. Dynamic geometry software such as GeoGebra, Cabri and Google SketchUp are especially found useful in situations where spatial thinking skills are desired to be improved, specifically in geometry. Therefore, in this study, the studies about the software that made contribution and improvement in spatial thought have been determined and analyzed. Findings obtained from the research can be expressed as these software have been found to provide positive contributions to spatial thinkin

Ab initio calculations of surface phonons of the hydrogen-terminated Si(110)-(1 × 1) surface

A first-principles study, using a linear-response approach based on the pseudopotential method and the generalised gradient approximation, has been made to examine the phonon spectrum of the hydrogen-terminated Si(110)-(1 × 1) surface. The calculated results compare very well with the results determined from a recent high-resolution electron-energy-loss spectroscopy measurement. In particular, the energy locations and polarization characteristics of the H-Si bond bending and H-Si stretching surface phonon modes have been determined and discussed in detail. The zone-centre splitting of the two H-Si stretching surface phonon modes is found to be 2.4 meV, which compares very well with the experimental value of 1.9 meV

Theoretical investigation of superconductivity in ternary silicide NaAlSi with layered diamond-like structure

© 2016 Informa UK Limited, trading as Taylor & Francis Group.We have investigated the electronic structure, phonon modes and electron-phonon coupling to understand superconductivity in the ternary silicide NaAlSi with a layered diamond-like structure. Our electronic results, using the density functional theory within a generalized gradient approximation, indicate that the density of states at the Fermi level is mainly governed by Si p states. The largest contributions to the electron-phonon coupling parameter involve Si-related vibrations both in the x-y plane as well as along the z-axis in the x-z plane. Our results indicate that this material is an s-p electron superconductor with a medium level electron-phonon coupling parameter of 0.68. Using the Allen-Dynes modification of the McMillan formula we obtain the superconducting critical temperature of 6.98 K, in excellent agreement with experimentally determined value of 7 K

Electron-phonon superconductivity in the filled skutterudites LaRu4P12, LaRu4As12, and LaPt4Ge12

This is the final version of the article. Available from American Physical Society via the DOI in this record.We have reported on the structural, elastic, electronic, lattice dynamical and electron-phonon interaction properties of LaT4X12 (T=Ru, Pt and X=P, As, Ge) by using the generalized gradient approximation of the density functional theory and the plane-wave pseudopotential method. These lanthanum-filled skutterudites are found to be characterized with a flat band, resulting in a sharp peak in the electronic density of states, near the Fermi level. The lattice dynamical properties of these materials change considerably when the P atom is replaced by larger As or Ge atoms. The Migdal-Eliashberg approach is used to determine the Eliashberg spectral function for all the considered compounds. Using the calculated Eliashberg spectral function, the value of average electron-phonon coupling parameter is found to be 0.74 for LaRu4P12, 1.03 for LaRu4As12, and 1.08 for LaPt4Ge12. The superconducting critical temperature (Tc) values for LaRu4P12, LaRu4As12, and LaPt4Ge12 are estimated to be 6.95, 11.56, and 8.32 K, respectively, which compare well enough with their experimentally measured values of 7.2, 10.45, and 8.23 K.Some of the calculations for this project were carried out using the computing facilities on the Intel Nehalem (i7) cluster (ceres) in the School of Physics, University of Exeter, United Kingdo

Electron–phonon interaction and superconductivity in the borocarbide superconductor

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.We have made an ab initio investigation of electron–phonon interaction and superconductivity in the borocarbide super-conductor ScNi 2 B 2 C adopting the body-centred tetragonal LuNi 2 B 2 C-type of layered crystal structure. The calculated electronic structure and density of states suggest that the bonding is a combination of covalent, ionic and metallic in nature and that the Fermi level falls in one of the peaks in the electronic density of states. Our electron–phonon interaction calculations suggest that the mechanism for superconductivity is heavily governed by interactions of electrons with acoustic phonon modes and low-frequency optical phonon modes, which strongly modulate NiB 4 tetrahedral bond angles. By integrating the Eliashberg spectral function, the value of average electron–phonon coupling parameter is found to be 0.93 and the superconducting critical temperature is calculated to be 16.28 K, in excellent agreement with the experimentally reported value of 16.0 K

Ab initio investigation of superconductivity in orthorhombic MgPtSi

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Available online 3 March 2016We have performed an ab initio study of electronic, vibrational and superconducting properties of the orthorhombic MgPtSi by employing the density functional theory, a linear-response formalism, and the plane-wave pseudopotential method. Our electronic results suggest that the density of states at the Fermi level is primarily contributed by Pt 5d and Si 3p states with much smaller contribution from Mg electronic states. Phonon anomalies have been found for all three acoustic branches. Due to these phonon anomalies, the acoustic branches make large contributions to the average electron-phonon coupling parameter. From the Eliashberg spectral function, the value of average electron-phonon coupling parameter is found to 0.707. Using this value, the superconducting critical temperature is obtained to be 2.4 K, in excellent accordance with its experimental value of 2.5 K

Theoretical investigation of superconductivity in SrAuSi3 and SrAu2Si2

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Available online 8 April 2016The structural and electronic properties of BaNiSn3-type SrAuSi3 and ThCr2Si2-type SrAu2Si2 have been investigated by using the planewave pseudopotential method and the density functional theory. The electronic structures and phonon dispersion relations of these two materials have been analyzed with and without the inclusion of spin-orbit interaction, and similarities and differences highlighted. By integrating the Eliashberg spectral function α2F(ω), the average electron-phonon coupling parameter is determined to be λ=0.47 for SrAuSi3 and 0.42 for SrAu2Si2. The largest contribution to the electron-phonon coupling for SrAuSi3 comes from the Si p electrons near the Fermi energy and Si-related vibrations. Using a reasonable value of μ∗=0.12 for the effective Coulomb repulsion parameter, the superconducting critical temperature Tc for SrAuSi3 is found to be 1.47 K which compares very well with its experimental value of 1.54 K.This work was supported by the Scientific and Technical Research Council of Turkey (TÜBİTAK) (Project no. MFAG-115F135)