Scopus İndeksli Yayınlar
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Item Value of the ξ parameter in Kl3 decay from the pion-gauge condition(1972) Aydın, Zeki Zekeriya; Fen FakültesiIt is shown with the help of the pion-gauge condition that the divergence of the most general boson current in K l 3 decay vanishes in the limit of zero four-momentum of the pion. This in turn implies ξ = − 1 at the (unphysical) point t = m 2 K . Inasmuch as ξ does not seem, experimentally, to vary much with t , the result is significant in the physical region and agrees with experiment.Item Kl3 and πe3 decays in terms of the Kemmer β current(1973) Aydın, Zeki Zekeriya; Fen FakültesiIt is shown with the help of the pion-gauge condition that the divergence of the most general boson current in K l 3 decay vanishes in the limit of zero four-momentum of the pion. This in turn implies ξ = − 1 at the (unphysical) point t = m 2 K . Inasmuch as ξ does not seem, experimentally, to vary much with t , the result is significant in the physical region and agrees with experimentItem Relativistic composite systems and minimal coupling(1974) Duru, İsamil Hakkı; Fen FakültesiThe problem of minimal coupling of relativistic composite systems having internal degrees of freedom is investigated. The ambiguity in the introduction of various internal coordinates with the same mass spectrum can be solved by probing the system with external electromagnetic interactions. For the generalized Majorana equation this procedure shows that the charged constituent of the system performs a two-dimensional Kepler motion in the Klein-Gordon approximation and not an oscillator motion.Item Internal structure of composite systems described by infinite-component wave equations(1977) Duru, İsmail Hakkı; Fen FakültesiIt is shown that the boson representation of infinite-component SO(4,2) wave equations represents a system of four oscillators as well as three-dimensional Kepler dynamics. These two pictures are complementary to each other; that is, the Kepler dynamics is adequate for small distances, while the oscillator dynamics is more relevant for infinitely large distances, and both pictures are equivalently possible for finite distances. This is interpreted as a sort of constituent confinement.Item Upper limit on the magnetic moment of the neutrino(1982) Aydın, Zeki Zekeriya; Duru, İsmail Hakkı; Fen FakültesiWe have recalculated the processes e ν → e ν and e + e − → ν ¯ ν due to an assumed magnetic moment κ of the neutrino (correcting some errors in the previous calculations). Comparing the results with the Fermi and electroweak models we set a suggestive limit κ ≲ ( gm e M Z ) 2 μ 0 , where m is the electron mass and μ 0 = e 2 m . A very sensitive method to set a good upper limit would be to measure the angular distribution of e ν → e ν near the forward direction.Item Neutrino and antineutrino elastic scattering and photoneutrino reactions(1983) Aydın, Zeki Zekeriya; Fen FakültesiThe processes ν ν → ν ν , ν ¯ ν → ν ¯ ν , ν ¯ ν → 2 γ , and ν γ → ν γ , which are of astrophysical interest, are calculated both in the electroweak model and in the magnetic model when the neutrino has a small magnetic moment κ . Received 31 January 1983Item Euler-form actions and the vanishing of the cosmological constant(1989) Dereli, T; Fen FakültesiWe investigate the conditions of the vanishing cosmological constant and the presence of gravity and vector gauge fields in a D -dimensional non-Abelian Kaluza-Klein theory based on a dimensionally continued 2 N -dimensional Euler-form action. It is shown that these conditions can be satisfied only for D = 2 N + 3 .Item A physical realisation of the super-sine algebra(1992) Verçin, Abdullah; http://orcid.org/0000-0002-0608-6648; Fen FakültesiAn explicit physical realisation of the supersymmetric extension of the sine algebra generated by the symmetries of a spinless Bloch electron in a constant uniform magnetic field is given in terms of the symmetry operators of a spin- 1 2 Bloch electron.Item Two anyons with Coulomb interaction in a magnetic field(1992) Verçin, Abdullah; http://orcid.org/0000-0002-0608-6648; Fen FakültesiWe have computed numerically the energy spectrum of two anyons with Coulomb (1/r) interaction in a uniform magnetic field. Both non-singular and singular energy eigenfunctions are considered. We solve a second order difference equation with boundary conditions by a new, simple and efficient numerical method.Item Scalar leptoquark production at TeV energy γp colliders(1994) Çelikel, Ayşegül; Atağ, Satılmış; Fen FakültesiSingle scalar leptoquark production in the collisions of high energy γ and proton beams has been investigated. It is shown that future γp colliders will be sensitive to scalar leptoquark masses up to fewItem Light-curve and period changes of AB Andromedae(1994) Derman, Ethem; Akalın, A; Selam, Salim O; Müyesseroğlu, Zekeriya; Demirçan, Osman; Fen FakültesiNew photoelectric observations of AB And obtained between 1989 and 1992 have been used, together with all available light curves from the literature, to study the light-curve variation of the system and its probable connection with the orbital period variation. A long-term brightness variation in the light levels is detected. The maximum brightness occurred in 1970 (±3 yr). A period study based on all available times of minimum light (of which 22 are newly determined) reveals that the photometric period of the system oscillates around a mean value (P0≈0.331890d) with an oscillation period of ≈88.0\textpm0.2 yr and a half-amplitude of 0.000 003 76 d. Such a variation can be caused by either (i) a period modulation due to the magnetic activity cycle of the active primary component, or (ii) a light-traveltime effect due to a third body in the system. It is shown that the third body, if it exists, can only be a white dwarf; this can be checked by ultraviolet spectroscopy. The rms light variation of the system predicted by Applegate's theory of the magnetic activity modulation of the orbital period is found to be comparable with the observed amplitude of long-term brightness variations of the system. However, the brightness variation is found to be 90° out of phase with the O–C curve. Such a phase shift can be explained in terms of the damping effect of the convective zone. The theory predicts a subsurface magnetic field of 7.4 kG for the primary component of AB And.Item Pair production of scalar leptoquarks at TeV energy γp colliders(1994) Çakır, Orhan; Ata, S; Fen FakültesiScalar leptoquark pair production in high energy γ -proton collisions is investigated. We show that future TeV energy γ p colliders are convenient places for searching for scalar leptoquarks up to the masses of a few TeV.Item A search for the fourth SM family(1995) Çelikel, A; Çiftçi, Abbas K; Sultansoy, Saleh F; Fen FakültesiArguments favouring the existence of a fourth fermion family in the framework of the Standard Model are given. The masses of the fourth family neutrino, charged lepton and down quark are close to each other within an accuracy of the order of a few GeV and lie between 300–700 GeV. Experiments on the search for these particles are discussed.Item Compensation of lepton charge of matter with relic anti-sneutrinos(1995) Çiftçi, Abbas K; Sultansoy, Saleh F; Tütköz, Shemsettin; Fen FakültesiWe reconsider the idea of the leptonic photon by taking into account the possible compensation of the lepton charge of matter with relic anti-sneutrinos. As a consequence of this compensation we have shown that the available experimental data admit the range of the leptonic interaction constant to be 10−38 < αl < 10−14.Item Pair production of squarks in TeV scale polarized γp collisions(1996) Kandemir, Ayfer; Yılmazer, Ali Ulvi; Fen FakültesiThe production of squarks in the high energy collisions of the real photons off the protons is discussed. The polarizations of both photon and proton beams are considered. Although the cross sections for different initial beam polarizations do not differ much, the polarization asymmetry is sensitive to the squark mass. We conclude that the capacity of the future TeV scale ~JJ colliders is quite promising in the search for SUSY particles.Item Crystal Structure of [1-{(2-Oxyphenyl)iminomethyl}benzen- 2-oxy-N,O,O′]cyclopropylamine-Nnickel(II) Complex(1997) Atakol, Orhan; Eriş, Figen Z; Fen FakültesiThe structures of monomeric Ni complexes in the presence of a tridentate ONO or ONS Schiff-base ligand and different monodentate ligands (piperidinel, pyrrolidine2 and cyclohexylamine3) were reported previously. In those complexes the Ni ion has either a square or distorted square-planar coordination. Here, we report on the structure of a new Ni complex, which has as a monodentate ligand the cyclopropylamine molecule (Fig. 1). As can be seen from Fig. 2, the coordination around the Ni ion in the title complex is also distorted square planar. The Ni-0 and Ni-N bond lengths are [1.814(5) -1.866(5)A] and [1.846(6) -1.929(5)A],Item Crystal Structure of Bis[4-(5-methyl-2-oxyphenyl-κO,2κO)-4-imino-2-penten-2-olato-O, O′,N′]copper(II)(1997) Atakol, Orhan; Yılmaz, Nazife; Fen FakültesiThe title compound, Cu2(C12H13N02)2, is a doubly oxygen-bridged dimeric copper(II) complex. Doubly oxygen bridged complexes with subnormal magnetic moments are known to exhibit super exchange interaction.l-3 The Cu atoms have a distorted square-planar environment, with bond angles in the range 76.9(1) - 100.3(1)° . The average Cu-0 distance is 1.916(2) A and the average Cu-N distance is 1.941(3) A. The Cu l and Cu2 atoms are located 0.0339(5) and 0.0336(5) A off the coordination best plane, respectively. The bridging angles Cu 1-O 1-Cu2, O 1-Cu2-03, Cu 1-03-Cu2 and 01-Cut-03 are 102.8(1), 76.9(1), 102.5(1) and 77.5(1)°Item Crystal structure of [1-{(2-oxyphenyl)iminomethyl}benzen-2-oxy-N,O,O'](cyclopropylamine-N)nickel(II) complex(1997) Atakol, Orhan; Fen FakültesiItem Crystal structure of (N,N'-disalicylidene-2,3-diaminopyridine)copper(II) complex(1997) Atakol, Orhan; Nazır, Hasan; Fen FakültesiItem Evaluation of anti-HIV activity of 5- ( 2-phenyl-3 ‘-indolal) -2- thiohydantoin(1998) Süzen, Sibel; Eczacılık Fakültesi; Buyukbingol, ErdemThe anti-HIV activity of the previously synthesized S-( 2-phenyl-3’-indolal)-Zthiohydantoin I was evaluated. The compound, containing two structural moieties found in highly active anti-HIV agents, exhibited poor activity and rather high cytotoxicity. 8 1998 Elsevier Science S . A. All rights reserved.