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1998

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Articles 2311 - 2340 of 2574

Full-Text Articles in Physical Sciences and Mathematics

A Study Of Events From Si 28 With Emulsion At 4.5 A Gev/C Without Target Fragmentation, A.A. El-Daiem Jan 1998

A Study Of Events From Si 28 With Emulsion At 4.5 A Gev/C Without Target Fragmentation, A.A. El-Daiem

Turkish Journal of Physics

Atotal sample of 1000 inelastic interactions of Si$^{28}$ in emulsion at 4.5 A GeV/c has been used characteristics of projectile fragments. This paper is therefore to devoted to the study of projectile fragments, with special attention to the class of events $n_h$=0, in which the traget nucleus is unwounded. This paper include the multiplicity distributinon and angular distributions of projectile fragments.

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Transfer Of Photometric Quantities At Arbitrary Distribution Temperatures, İzmir Mamedbeyli̇, Zafer Ürey, A. Kamuran Türkoğlu Jan 1998

Transfer Of Photometric Quantities At Arbitrary Distribution Temperatures, İzmir Mamedbeyli̇, Zafer Ürey, A. Kamuran Türkoğlu

Turkish Journal of Physics

Characteristics of a photometric setup used for the measurement of photometric quantities at the National Institute of Metrology (UME) in Turkey are reported. A high accuracy method is developed to adjust the filaments of incandescent lamps with respect to the optical axis. The method also provides the basis for low uncertainty distance measurements between lamp filaments and photometers. Transfer of photometric quantities at arbitrary distribution temperatures is examined both theoretically and experimentally, and the results are compared to the calibration values of the Bureau International Des Poids Et Measures (BIPM), Paris, France.

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A Study Of Heavy-Ion Elastic Scattering Reactions Using A Semimicroscopic Model, A. A. Farra Jan 1998

A Study Of Heavy-Ion Elastic Scattering Reactions Using A Semimicroscopic Model, A. A. Farra

Turkish Journal of Physics

The differential cross sections for elastic scattering of ^{16}O from ^{20}Ne have been calculated using an optical potential and distorted wave Born approximation (DWBA) calculations. In the present calculations several prescriptions were tried in the ion-ion potential. The DWBA calculations were performed employing folded real and Woods-Saxon optical potentials for the distorted waves. Inclusion of the exchange process explains the large back-angle cross sections. The elastic scattering differential cross sections are successfully described by calculations in which elastic alpha-transfer amplitudes are coherently added to direct elastic scattering amplitudes.

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Optical Anisotropy Of Iron Garnets With Growing Anisotropy, Odil Ochilov Jan 1998

Optical Anisotropy Of Iron Garnets With Growing Anisotropy, Odil Ochilov

Turkish Journal of Physics

The theoretical analysis of the position of principal diachronic directions at magnetization rotation in (100) and (110) planes for the case of growing dichroism axes in random directions was made. The calculations of angular dependencies of dichroic axes (DA) position for different values of the magneto-optical anisotropy parameter, a, have been done. The relations between the growing and magneto-optical dichroism, K/M, and the angle \delta characterizing the direction of principal growing dichroism axes were given. The angular dependences of DA position in epitaxial iron garnet films have been investigated experimentally. The measurements at the different light wavelengths permitted one to …

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Alloying Of Aisi 1008 Steel Surfaces By 10ms Nd: Yag Laser Pulses, Raid A. İsmai̇l Jan 1998

Alloying Of Aisi 1008 Steel Surfaces By 10ms Nd: Yag Laser Pulses, Raid A. İsmai̇l

Turkish Journal of Physics

Hardened surfaces were produced on AISI 1008 steel through a laser surface alloying (LSA) technique. Mixture of pure Boron, Silicon, and Carbon powders of the same grain size were deposited on the substrate. The surface was then melted using pulsed Nd:YAG laser (\tau = 10 ms) at an energy of 12 J. The influence of alloying elements on the microstructure and hardness of treated layer was investigated. Dependending on the alloying elements species, different maximum surface hardness, different maximum depth, and different hardness profile could be obtained. The B+Si alloyed zone exhibited maximum hardness to a nominal alloying depth of …

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Domain Structures Of Epitaxial Perovskite Ferroelectric Films: Part Ii. Applications, S. Pamir Alpay, Alexander L. Roytburd Jan 1998

Domain Structures Of Epitaxial Perovskite Ferroelectric Films: Part Ii. Applications, S. Pamir Alpay, Alexander L. Roytburd

Turkish Journal of Physics

The use of domain stability maps for epitaxial perovskite ferroelectric films is illustrated with some examples. The equilibrium domain structure and domain fractions as a function of temperature are predicted for PbTiO_3(001) films grown epitaxially on three different substrates: MgO(001), KTaO_3(001), and SrTiO_3(001). Misfit dislocation formation at the growth temperature is found to have a profound effect on both the domain selection and relative domain populations. Theoretical predictions are compared with available experimental data.

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Study Of Emission Parameters Of Ir(Iii)-Ba Film System, F. K. Yusifov, A. K. Orujov Jan 1998

Study Of Emission Parameters Of Ir(Iii)-Ba Film System, F. K. Yusifov, A. K. Orujov

Turkish Journal of Physics

Electrophysical properties of Ir(III)-Ba metal-film system have been studied by thermoionic emission (TE), surface ionization (SI) and thermal desorption spectroscopy (TDS) methods. It has been found that the optimum coverage of barium atoms on iridium (III) face is \theta_{opt} = 0.70 \pm 0.05. The dependence of fractional charge of Richardson constant of Ir(III)-Ba metal-film system on coverage \theta of the Ba atoms in the interval 0 \leq \theta \leq 1 has been experimentally obtained. The dependence of work function of Ir(III)-Ba metal-film system on coverage \theta of Ba atoms has been obtained.

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Statistics And Size-Quantized Anisotropy Of Electron States In N-Ge And N-Si Films, Bahshali Kuliev, Vugar Gadjiev Jan 1998

Statistics And Size-Quantized Anisotropy Of Electron States In N-Ge And N-Si Films, Bahshali Kuliev, Vugar Gadjiev

Turkish Journal of Physics

The wave functions and energy spectrum of electrons in size-quantized n-Ge and n-Si films are obtained and the anisotropy of the electron state density is investigated. Also, the analytical expressions for the electronic part of heat capacity at the various approximations of electron gas degeneration are obtained.

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Compositional Dependence Of Properties Of Rf-Sputtered Bi-Sr-Ca-Cu-O Thin Films, Ayhan Güldeste Jan 1998

Compositional Dependence Of Properties Of Rf-Sputtered Bi-Sr-Ca-Cu-O Thin Films, Ayhan Güldeste

Turkish Journal of Physics

Compositional dependence of superconducting transition temperature (T_c) of Bi_2Sr_{3-x}Ca_xCu_2O_{8+x} thin films grown by rf sputtering on single crystal MgO substrates has been investigated. Films have been assessed by considering their initial composition in terms of (Ca+Sr)/Bi ratio with their atomic concentration normalized to Cu:2. It was found that T_{c-zero} of around 80K is achievable for (Ca+Sr)/Bi ratio between 1.4 and 1.65, while T_{c-onset} remains above 90K. Quenching from high temperature increased T_{c-zero,} but it may result in a deterioration in resistivity due to micro cracks induced by the thermal stress.

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Electronic Structure Of Optimized Si_{M}H_{N} Clusters: Mindo3 And Am1 Calculations, Şakir Erkoç, Lemi Türker Jan 1998

Electronic Structure Of Optimized Si_{M}H_{N} Clusters: Mindo3 And Am1 Calculations, Şakir Erkoç, Lemi Türker

Turkish Journal of Physics

We have investigated the electronic structure of optimized hydrogenated silicon microclusters. Si_{m}H_{n} (m=2,3,5,6; n = 4,6) have been investigated. The calculations were performed using both MINDO3 and AM1 semiempirical molecular orbital methods.

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A Mean Field Model With Two Order Parameters For Three-Phase Coexistence Near The Tricritical Point, S. Sali̇hoğlu Jan 1998

A Mean Field Model With Two Order Parameters For Three-Phase Coexistence Near The Tricritical Point, S. Sali̇hoğlu

Turkish Journal of Physics

This study gives a mean field model with two order parameters for three-phase coexistence near the multicritical point. The critical exponents calculated from our model are the tricritical exponents for the order parameters, susceptibility and the specific heat. Hence, our mean field model describes adequately the tricritical behaviour of a system in the region of three-phase coexistence.

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A Mean Field Model For The Coexistence Of Nematic, Smectic A And Smectic C Phases In Liquid Crystals, H. Yurtseven, S. Sali̇hoğlu Jan 1998

A Mean Field Model For The Coexistence Of Nematic, Smectic A And Smectic C Phases In Liquid Crystals, H. Yurtseven, S. Sali̇hoğlu

Turkish Journal of Physics

We present here a mean field model for the nematic-smectic A-smectic C coexistence of a liquid crystal near the NAC point which is a multicritical point. The critical exponents calculated from our model are tricritical expoenents for the order parameters, susceptibility and the specific heat. Our results show that if the NAC point is the tricritical point, then our mean field model describes adequately the liquid crystalline system in the coexistence region of the nematic-smectic A-smectic C phases.

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Numerical Calculation Of Energy Loss Rate For E^+ + E^- \Rightarrow \Nu + \Bar{\Nu} Process, A. Aydemir Jan 1998

Numerical Calculation Of Energy Loss Rate For E^+ + E^- \Rightarrow \Nu + \Bar{\Nu} Process, A. Aydemir

Turkish Journal of Physics

The energy loss rate for pair annihilation is calculated numerically in V-A (Fermi theory) and Weinberg-Salam (Standard theory) theories, taking into account also the variation of density at various temperatures using the results obtained in closed form by Chiu, and Schinder, et al. The calculations made by Chiu, and Salpeter, et al., are seen to be parallel to each other. Dicus has calculated energy loss rate for this process only for a few limiting cases since the integrals can not be taken analytically for all \lambda and \nu. The graph drawn for the values we obtained is compared with the …

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The Effect Of Spatially Dependent Screening On The Donor Ionization Energy In A Quantum Wire, B.N. Onwuagba Jan 1998

The Effect Of Spatially Dependent Screening On The Donor Ionization Energy In A Quantum Wire, B.N. Onwuagba

Turkish Journal of Physics

The effect of the spatially dependent screening on the ionization energy of a shallow donor in a 1D quantum well wire made of Ga_{1-x}Al_x/GaAs superlattice is presented. A variational approach is used to obtain ionization energy of the on-centre impurity at the origin of the well and the results obtained are compared with the existing values.

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Theorems On Three-Term Relations For Hardy Sum, Y. Şi̇mşek Jan 1998

Theorems On Three-Term Relations For Hardy Sum, Y. Şi̇mşek

Turkish Journal of Mathematics

Some three-term and mixed three-term relations for Hardy sums were given by Goldberg [7]. His proofs are based on Bernd's transformation formulae for the logarithms of the classical Theat-functions. Pettet and Sitaramachandararo [9] proved elementary proofs for all of Goldberg's results and also proved some three-term relations of Dedekind sums. In this paper, some new theorems on three-term relations for hardy sums were found by applying derivative operator to three-term polynomial relation. Furthermore, proofs of the reciprocity relations for Hardy sums are presented in a more concise way from the original proofs of Berndt [2, 3, 4] and Goldberg [7].

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Characterization Of An All-Optical Device Based On Organic Materials, Hans-Martin Keller, Mark Andreas Bader, Gerd Marowsky Jan 1998

Characterization Of An All-Optical Device Based On Organic Materials, Hans-Martin Keller, Mark Andreas Bader, Gerd Marowsky

Turkish Journal of Chemistry

We present numerical and first experimental results for an all-optical switching device. The device consists of a periodically modulated nonlinear waveguide, where so-called gap solitons stabilize the switching process. The fabrication of Bragg gratings in different polymeric films, e.g. poly(phenylene vinylene), polydiacetylene or polystyrene by excimer laser photoablation was tested. In preparation of further experiments numerical calculations were performed to characterize the device under realistic conditions, including position dependent index modulations and absorption losses. In further time-dependent simulations the transition from the reflecting to the transparent state was investigated in detail. As a main result, the threshold intensity turns out …

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Poly(3-Alkylthiophene) Modifications, A. Bolognesi Jan 1998

Poly(3-Alkylthiophene) Modifications, A. Bolognesi

Turkish Journal of Chemistry

No abstract provided.

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Some Recursive Relationships Between Acenes And Cyclacenes, Lemi Türker Jan 1998

Some Recursive Relationships Between Acenes And Cyclacenes, Lemi Türker

Turkish Journal of Chemistry

Some structural relationships between acenes and cyclacenes both H\\"{u}ckel- and Mobius-type and within the same class of compounds were demonstrated by the recursive analysis of their $E_{\pi}$ and $I_{\pi}$ values or the first differences thereof. It was found that the first differences of $E_{\pi}$ and $I_{\pi}$ tend to have certain limit values as the number of benzenoid rings increases in each class of compounds studied.

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The Removal Of Organic Sulfur From Two Turkish Lignites By Chlorinolysis, Yücel Y. Kadioğlu, Semra Karaca, Samih Bayrakçeken, M. Şahin Gülaboğlu Jan 1998

The Removal Of Organic Sulfur From Two Turkish Lignites By Chlorinolysis, Yücel Y. Kadioğlu, Semra Karaca, Samih Bayrakçeken, M. Şahin Gülaboğlu

Turkish Journal of Chemistry

The removal of organic sulfur from two Turkish lignites by chlorinolysis with chlorine gas in water and water-carbon tetrachloride media at ambient pressure was examined. The effects of stirring speed (5-20 s^{-1}), particle size (250-425, 150-180 and 74-88 \mu m), temperature (13-70°C) and time (0-10800 s) were investigated. Significant portions of the organic sulfur in the coal samples were removed.

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Reaction Of 3,4-Diformyl-2,5-Dimethylpyrrole With 1,2(Substituted)Diphenyl-1,2-Diaminoethanes, Cemil Öğreti̇r, Fatma Severcan Jan 1998

Reaction Of 3,4-Diformyl-2,5-Dimethylpyrrole With 1,2(Substituted)Diphenyl-1,2-Diaminoethanes, Cemil Öğreti̇r, Fatma Severcan

Turkish Journal of Chemistry

3,4-Diformyl-2,5-dimethylpyrrole (1) reacts with 1,2-diphenyl-1,2-diamine derivatives to form the potentially tautomeric 2:2 macrocyclic adduct (1)=(1). ^1H and ^{13}C n.m.r. spectral data along with acidity measurements indicate that the 2-azafulvene structure (7) is predominant for all adducts.

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Potentiometric Titrations Of Semicarbazone Derivatives 6-Keto 9-17 Mono Methyl Substituted Octadecanoic Acids In Non-Aqueous Media, Mustafa Yalçin, Süleyman Tanyolaç, İrfan Kizilcikli, Aydın Tavman Jan 1998

Potentiometric Titrations Of Semicarbazone Derivatives 6-Keto 9-17 Mono Methyl Substituted Octadecanoic Acids In Non-Aqueous Media, Mustafa Yalçin, Süleyman Tanyolaç, İrfan Kizilcikli, Aydın Tavman

Turkish Journal of Chemistry

The pK$_a$ values of 6-semicarbazone 9-17 monomethyl substituted octadecanoic acids were determined using the potentiometric titration method. 2-Propanol was used as the non-aqueous medium and tetrabutylammonium hydroxide (TBAH) as the titrant in the experiments. The contribution of semicarbazone and methyl groups to the pK$_a$ values of octadecanoic acids was investigated and evaluated. In addition, observations were made on the IR spectra of the compounds.

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Voltammetric Determination Of Salbutamol Based On Electrochemical Oxidation At Platinum And Glassy Carbon Electrodes, Niyazi Yilmaz, Sibel A. Özkan, Bengi Uslu, Zühre Şentürk, İnci Bi̇ryol Jan 1998

Voltammetric Determination Of Salbutamol Based On Electrochemical Oxidation At Platinum And Glassy Carbon Electrodes, Niyazi Yilmaz, Sibel A. Özkan, Bengi Uslu, Zühre Şentürk, İnci Bi̇ryol

Turkish Journal of Chemistry

The oxidative behavior of salbutamol was studied as a function of pH at platinum and activated glassy carbon electrodes. Between pH 1.9 and 12.0, the drug was characterized by a single oxidation step at both electrodes. The process was found to be dependent on the nature and the pH of the supporting elctrolyte. The procedure yielded a linear concentration range of $1 \times 10^{-4}$ to $1 \times 10^{-3}$ M and $2 \times 10^{-5}$ to $1 \times 10^{-3}$ M in 0.2 M sulphuric acid and a phosphate buffer of pH 6, at platinum and glassy carbon electrodes, respectively. The method was …

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Synthesis And Characterization Of Amorphous-Liquid Crystalline Poly(Vinyl Ether) Block Copolymers, İ. Ersin Serhatli, Müge Serhatli Jan 1998

Synthesis And Characterization Of Amorphous-Liquid Crystalline Poly(Vinyl Ether) Block Copolymers, İ. Ersin Serhatli, Müge Serhatli

Turkish Journal of Chemistry

A new series of amorphous-liquid crystalline poly(vinyl ether) block copolymers was synthesized using living cationic polymerization and free-radical polymerization techniques. Vinyl ether monomer was polymerized using a trifluoromethane sulfonic acid and methyl triflouoromethanesulfonate/tetrahydrothiophene initiator system in dichloromethane at -18^oC, and quantitatively terminated with labile azo compounds in order to obtain poly(vinyl ether) with well-defined molecular weight and end groups. This polymer was used in a subsequent blocking step in which azo groups were decomposed at 80^oC in the presence of methyl methacrylate and styrene monomer. In both copolymers, blocks of different chemical composition were segregated in the solid and melt-phase …

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Electrochemical Polymerization And Analysis Of Some Aniline Derivatives, Bekir Sari, Muzaffer Talu Jan 1998

Electrochemical Polymerization And Analysis Of Some Aniline Derivatives, Bekir Sari, Muzaffer Talu

Turkish Journal of Chemistry

In this study, conductive homopolymers of o-chloroaniline, p-bromoaniline and N-methylaniline were synthesized electrochemically in perchloric acidic solution and their properties were analyzed. Initially, the maximum oxidation potential values of these monomer solutions were determined by Cyclic Voltammetry (CV). Their conductive polymers were then synthesized under a nitrogen atmosphere using a potentiostat. FTIR spectra were taken in order to analyze the structural properties of the resulting polymers. Thermogravimetric analysis (TGA) was conducted and surface micrographs were taken by a Scanning Electron Microscope (SEM). The conductivity levels of the polymers were determined by the Four Probe technique. Magnetic properties of the samples …

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Electron Spectroscopy For Material Characterization, Ş. Süzer Jan 1998

Electron Spectroscopy For Material Characterization, Ş. Süzer

Turkish Journal of Chemistry

Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.

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Separation Of Molybdenum, Vanadium And Nickel By Liquid-Liquid Extraction, T. Coşar, R. Zi̇yadanoğullari Jan 1998

Separation Of Molybdenum, Vanadium And Nickel By Liquid-Liquid Extraction, T. Coşar, R. Zi̇yadanoğullari

Turkish Journal of Chemistry

Elements in the ash of asphaltites that is used in thermal central for power generation units are Mo, V, U, Ti and Ni. The main goal of this study was to separate molybdenum, vanadium and nickel from the aqueous solution. The quantities of the above elements in solution were in the range of 50-80 ppm. The separate these elements from solution, the liquid-liquid extraction method was applied to samples. Alamine 336 was used as extractant. During the reduction-oxidation processes, single and multiple extraction methods were applied to the solution in combination. The quantities of molybdenum, vanadium and nickel in the …

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Potentiometric Investigation Of The Effects Of Several Substituents On The Basicity Of Benzilidene-O-Hydroxyaniline, Esma Kiliç, Orhan Atakol, E. Canel, Zehra Ali̇beşeoğlu, Turgut Gündüz, Fitnat Köseoğlu Jan 1998

Potentiometric Investigation Of The Effects Of Several Substituents On The Basicity Of Benzilidene-O-Hydroxyaniline, Esma Kiliç, Orhan Atakol, E. Canel, Zehra Ali̇beşeoğlu, Turgut Gündüz, Fitnat Köseoğlu

Turkish Journal of Chemistry

Chloro-, bromo-, iodo-, nitro-, methoxy- and hydroxy-substituted benzilidene-o-hydroxyaniline were prepared in order to investigate the effects of substituents on the basicity of benzilidene-o-hydroxyaniline. For each substituent, three isomers -- ortho, meta and para -- were synthesised. Schiff bases were titrated potentiometrically with perchloric acid in nitrobenzene solvent at $25^{\circ}$C. All compounds gave well-shaped titration curves, from which half-neutralisation potentials were calculated. The trend in the values of half-neutralisation potentials of Schiff bases were explained in terms of the nature of the substituents. The applicability of the Hammett equation to the effect of substituents in Schiff bases in nitrobenzene solvent was …

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On The Türker Angles In The Theory Of Total \Pi-Electron Energy, Ivan Gutman Jan 1998

On The Türker Angles In The Theory Of Total \Pi-Electron Energy, Ivan Gutman

Turkish Journal of Chemistry

The Türker angles $\theta, \alpha$ and $\beta$ are quantities invented by Lemi Türker, and are used in the theory of total $\pi$-electron energy $(E)$ of unsaturated conjugated hydrocarbons. We report here expressions for $\theta, \alpha$ and $\beta$ in terms of $E$ and the parameters $n$ (= half the number of carbon atoms) and $e$ (= the number of carbon-carbon bonds). The forms of these expressions are remarkably similar. Numerical calculation performed on a representative set of benzenoid hydrocarbons reveals that the dependence of the angles $\alpha$ and $\beta$ on molecular structure is very similar, and that their ratio is almost …

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Strain Analysis Of The Kapidagi Peninsula Shear Zone In The Ocaklargranitoid, Nw Turkey, Rahmi̇ Aksoy Jan 1998

Strain Analysis Of The Kapidagi Peninsula Shear Zone In The Ocaklargranitoid, Nw Turkey, Rahmi̇ Aksoy

Turkish Journal of Earth Sciences

The Kapidagi Peninsula shear zone is a W-to NW-trending, moderately to steeply dipping, sinistral strike-slip shear zone that runs almost parallel to the northern coast of the peninsula. It is a minimum of 28 km in length and extends from Rikoz Cape in the west to the north of Çakil village in the east. A quantitative strain analysis is presented for the shear zone evolved in the Ocaklar Granitoid by a syn-shear granitod intrusion. Deformed autoliths in the granitoids were used as strain markers. Long, intermediate and short axes of autoliths were measured in 66 subareas across the shear zone. …

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Crystallization Processes And Role Of Compositional Convection In Themacrolayer Formation In A Small Layered Complex, Bernard Plateovet Jan 1998

Crystallization Processes And Role Of Compositional Convection In Themacrolayer Formation In A Small Layered Complex, Bernard Plateovet

Turkish Journal of Earth Sciences

The Peloso complex is a 1000m thick gabbroic body composed of two main layered zones (ZA and ZB) that are made up of cyclic macrolayers of olivine gabbro, leucogabbronorite and anorthosite cumulates, and a third zone of unlayered quartz-gabbro (ZC) which may represent a residual liquid. Within a representative macrolayer, cryptic evolution of minerals can not be neglegted, showing that the crystallizing magma batch had a limited volume and was renewed between the formation of two successive macrolayers. The comparison between calculated parental magma density and densities of successive cumulates shows that the residual liquid was probably extracted by compositional …

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