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2002

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Articles 3151 - 3180 of 3435

Full-Text Articles in Physical Sciences and Mathematics

Collapse Of Interstellar Molecular Clouds, E. Rennan Pekünlü, Esra Tiğrak, Di̇cle Zengi̇n Jan 2002

Collapse Of Interstellar Molecular Clouds, E. Rennan Pekünlü, Esra Tiğrak, Di̇cle Zengi̇n

Turkish Journal of Physics

In this paper we systematically investigate the length and time scales of an interstellar molecular cloud for collapse under the influence of self--gravity, magnetic field and Coriolis forces. We used Magnetohydrodynamic (MHD) equations in linearized form in order to explore the dynamical evolution of perturbations. We found that both the Lorentz force and the Coriolis force support the cloud against self contraction, i.e., they introduce stabilizing effect against gravitational instability. Of the two cloud types with the same physical size, only those threaded by an interstellar magnetic field without rotation or those rotating without magnetic field will survive against gravitational …

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The Spectral Properties Of Two Interacting Electrons In A Quantum Dot, Mohammad Elsaid Jan 2002

The Spectral Properties Of Two Interacting Electrons In A Quantum Dot, Mohammad Elsaid

Turkish Journal of Physics

The shifted 1/N expansion method is used to study the spectral properties of two interacting electrons confined in a QD, under influence of a uniform magnetic field of arbitrary strength. We give explanation to the transitions in the spin and angular momenta of the QD ground state as the magnetic field sweeps. The electron addition energy is also calculated. Based on different comparisons , the shifted 1/N expansion method gives very good result against various methods used to study the spectra of a two electron QD.

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Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli Jan 2002

Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli

Turkish Journal of Physics

In this study, the effect of single and double-layer thin film coatings on the reflectance spectrum of silicon surfaces has been investigated. Thin film coatings have been prepared by vacuum evaporation of the materials with suitable refractive index. Reflectance measurements in the visible and near infrared have shown that the coated samples acquire antireflection properties. Thickness and wavelength dependence of the antireflection properties of SiO, CeO_2 and ZnS single-layer coatings with optical thickness of one quarter wavelength has been studied. In double-layer coatings, a thin film of SiO, CeO_2 and ZnS with optical thickness of quarter wavelength were used as …

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Modulation Frequency-Dependence Of Photocurrent In Amorphous Si:H P-I-N And Chalcogenides, Bengü Kaplan, Ruhi̇ Kaplan Jan 2002

Modulation Frequency-Dependence Of Photocurrent In Amorphous Si:H P-I-N And Chalcogenides, Bengü Kaplan, Ruhi̇ Kaplan

Turkish Journal of Physics

The effects of modulation frequencies (up to 35 kHz) on the intensity- and temperature-dependence of photocurrent of amorphous (a-) Si:H p-i-n and chalcogenide glasses (a-Se and a-As_2Se_3) were investigated in detail. The variation of exponent \nu, and in the power-law relationship \sigma_{ph} or I_{ph} \propto G^{\nu} between the photoconductivity (or photocurrent) and the generation flux, with modulation frequency in chalcogenide glasses is found to be much stronger than that of a-Si:H p-i-n. The activation energies, calculated from the temperature-dependent photocurrent, were determined at different modulation frequencies. We conclude that the activation energy increases with incresing modulation frequencies at low excitation …

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Effects Of The Back Reflector On The Optical Enhancement Factor And Quantum Efficiency Of A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan Jan 2002

Effects Of The Back Reflector On The Optical Enhancement Factor And Quantum Efficiency Of A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan

Turkish Journal of Physics

The effect of tin oxide (SnO_2) texture and back reflector (BR) on optical enhancement factor has been extensively investigated in a series of 4 a-Si:H p-i-n solar cells. The internal quantum efficiency QE in the wavelength range 550--750 nm has been analyzed using an optical model. The optical enhancement factor m, which is a wavelength-dependent fitting parameter, represents the increase in optical pathlength relative to the i-layer thickness. Our solar cells, at low or high haze SnO_{2} with an Al BR, have negligible optical enhancement, m < 1.5, representing failure to obtain multiple reflections. This is consistent with large parasitic absorption at the Al/Si interface. Our solar cells at high haze SnO_{2} with ZnO/Al or ZnO/Ag BRs have peak values of m \sim 3-4, with ZnO/Ag having slightly larger values than ZnO/Al. The maximum values of m , and thus the QE increase with reflectivity of the BR, indicates that efficient light trapping needs a very reflective BR to minimize parasitic absorption losses with each pass.

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Study Of The Effectiveness Of Various Solar Wind Parameters In The Development Of Geomagnetic Storms During Interplanetary Events, -- Badruddin Jan 2002

Study Of The Effectiveness Of Various Solar Wind Parameters In The Development Of Geomagnetic Storms During Interplanetary Events, -- Badruddin

Turkish Journal of Physics

We have selected some interplanetary events responsible for geomagnetic disturbances of varying magnitude, fairly different from one another. We then tried to find the heliospheric structure (e.g. shock/sheath and/or CME/magnetic cloud) responsible for individual disturbances. We have discussed and inter-compared these structures in their plasma and field parameters as well as in their geomagnetic effects. As a parameter for geomagnetic disturbance we have chosen index Dst, to compare it with variations in field and plasma to heliospheric response structures. We considered parameters such as total field strength, its north-south component, solar wind density, temperature and velocity. In addition, we have …

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Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla Jan 2002

Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla

Turkish Journal of Physics

In this research, we studied the kinetics of plasmachemical processes in quasiequilibrium and nonequilibrium conditions. The example of methane conversion into acetylene showed that the most efficient plasmachemical process may be achieved under nonequilibrium conditions, especially, when the reaction was stimulated by vibrational excitation of molecules.

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A New Metallicity Calibration For Dwarf Stars With Rgu-Photometry, Sali̇h Karaali̇, Selçuk Bi̇li̇r Jan 2002

A New Metallicity Calibration For Dwarf Stars With Rgu-Photometry, Sali̇h Karaali̇, Selçuk Bi̇li̇r

Turkish Journal of Physics

We have adopted the procedure of Carney to obtain a metallicity calibration for dwarfs utilising RGU-photometry. For this purpose we selected 76 dwarfs of different metallicities from Carney and from Strobel et al., and evaluated their \delta (U-G) ultra-violet excess relative to the Hyades by transforming UBV magnitudes to RGU via the metallicity dependent equations of Ak-Güngör. The \delta_{0.6}/\delta M normalized factors of Sandage transform \delta (U-G) excess at any G-R to \delta \equiv \delta_{1.08}, i.e. the ultra-violet excess at G-R = 1.08 mag, corresponding to B-V = 0.60 mag in the UBV-system. Finally, the (\delta, [Fe/H]) pairs were shown …

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Microstructure And Critical Current Of Hot-Pressed Ybco Ceramics, Şadan Özcan, Tezer Firat, Engi̇n Özdaş Jan 2002

Microstructure And Critical Current Of Hot-Pressed Ybco Ceramics, Şadan Özcan, Tezer Firat, Engi̇n Özdaş

Turkish Journal of Physics

The effect of hot-pressing (HPing) on the densification and the superconducting properties of YBCO were investigated. The phases and microstructure were analysed by XRD and SEM and transport properties were studied by I-V and AC susceptibility measurements. Relative density up to 93% and critical current density of 509 A/cm^{2} at 77 K were achieved through uniaxial HPing at 800°C under 325 kg/cm^{2} pressure for 4 hours. HPing raised the J_{c} from 80 A/cm^{2} to 509 A/cm^{2}. These results and AC susceptibility measurements reveal that the weak links or pinning forces were improved by increasing HPing pressure.

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Effect Of The Oxygen/Halogen Ratio On The Physical Properties Of Some Sodium-Boro-Vanadate Glasses, Ahmed Gamal El-Din Mostafa Jan 2002

Effect Of The Oxygen/Halogen Ratio On The Physical Properties Of Some Sodium-Boro-Vanadate Glasses, Ahmed Gamal El-Din Mostafa

Turkish Journal of Physics

Four different glass systems of the sodium boro-vanadate type containing halogen ions, were prepared by melting at 1000°C for three hours and annealed at 300°C. These glasses were investigated using dc conductivity, density, molar volume and magnetic susceptibility measurements. It was found that the activation energy shows a decrease as the halogen ions were increased, which was attributed to the increase in the mobility of sodium ions and the gradual formation of some terminal non-bridging halogens, in addition to the electron hopping between the different oxidation states of vanadium. The activation energy values for glasses containing iodine ions was less …

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Paramagnetic Defects In \Gamma-Irradiated, Pure And Doped (With As, Cl And Br) Selenium, Ibrahimgizi Salima Mekhtieva, Ibrahimogli Namig Ibragimov, Isaogli Abasat Isaev, Zeinalogli Vasif Zeinalov, Arifogli Eldar Mamedov Jan 2002

Paramagnetic Defects In \Gamma-Irradiated, Pure And Doped (With As, Cl And Br) Selenium, Ibrahimgizi Salima Mekhtieva, Ibrahimogli Namig Ibragimov, Isaogli Abasat Isaev, Zeinalogli Vasif Zeinalov, Arifogli Eldar Mamedov

Turkish Journal of Physics

This paper presents results of an EPR spectrum investigation of \gamma-irradiated (Co^{60} dose 10^{7} Rad) glasses Se, SeCl_{x}, Se_{0.95}As_{0.05}Cl_{x} and Se_{0.95}As_{0.05}Br_{x} (x=0.001--0.1) at 77 K. An analysis of spectra reveals that two types of paramagnetic radiation-induced defects arise (broken bonds localized on Se and As atoms) from the irradiation of such chalcogenide glasses.

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Characterization Of The Sno_{2}/P Contact Resistance And Sno_{2} Properties In Operating A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan Jan 2002

Characterization Of The Sno_{2}/P Contact Resistance And Sno_{2} Properties In Operating A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan

Turkish Journal of Physics

A method is presented to characterize the TCO/p contact and the TCO sheet resistance in a-Si TCO/p-i-n superstrate devices. It is extremely useful for understanding resistance losses in modulus and diagnosing how plasma processing influences the TCO layers. Analysis of 4-terminal dark J-V measurements as a function of temperature on devices with varying TCO geometry yields the TCO/p contact resistance R_{TCO/p}, its activation energy E_{a} or barrier height, and the TCO sheet resistance R_{SH} in an integrated device structure. The method is applied to devices fabricated on different brands of commercial SnO_{2} substrates with different p-layers. Important new results are …

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The Temperature Dependence Of The Electronic Structure Of Si \Delta-Doped Gaas, Emi̇ne Öztürk Jan 2002

The Temperature Dependence Of The Electronic Structure Of Si \Delta-Doped Gaas, Emi̇ne Öztürk

Turkish Journal of Physics

We investigated theoretically the change of electronic properties of Si \delta-doped GaAs layer as a function of temperature. We studied the influence of temperature on the donor concentration for a nonuniform distribution, which is taken as different from the known Gaussian distribution. In order to obtain the electronic structure we have calculated self-consistent Schrödinger - Poisson equations. We have seen that the change of the electronic properties as dependent on temperature is less pronounced at higher doping concentration.

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Determination Of Cadmium By Faas After Solid-Phase Extraction Of Its 1-Benzylpiperazinedithiocarbamate Complex On Microcrystalline Naphthalene, Hasan Cesur, Beki̇r Bati Jan 2002

Determination Of Cadmium By Faas After Solid-Phase Extraction Of Its 1-Benzylpiperazinedithiocarbamate Complex On Microcrystalline Naphthalene, Hasan Cesur, Beki̇r Bati

Turkish Journal of Chemistry

By using 1-benzylpiperazinedithiocarbamate (1-BPzDC) as a new reagent, a method of solid-phase extraction is described for the pre-concentration of cadmium in water samples prior to its determination by flame atomic absorption spectrometry (FAAS). This method is based on the fact that cadmium forming in aqueous phase cadmium 1-benzylpiperazinedithiocarbamate complex (Cd(1-BPzDC)_{2}) can be extracted with microcrystalline naphthalene on solid phase, then back-extracted with potassium cyanide solution into aqueous phase and measured by FAAS. The optimum experimental parameters for the extraction and back-extraction of cadmium were investigated. The obtained recovery was nearly 97% when the enrichment factor was 500 for spiked cadmium …

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Determination Of The Protonation Constants Of Some Substituted Salicylideneanilines By The Spectrophotometric Method In Ethanol-Water Mixtures, M. Abdülkadi̇r Akay, Esi̇n Canel, Esma Kiliç, Fi̇tnat Köseoğlu Jan 2002

Determination Of The Protonation Constants Of Some Substituted Salicylideneanilines By The Spectrophotometric Method In Ethanol-Water Mixtures, M. Abdülkadi̇r Akay, Esi̇n Canel, Esma Kiliç, Fi̇tnat Köseoğlu

Turkish Journal of Chemistry

Protonation constants of salicylideneaniline and methyl-, ethyl-, methoxy- fluoro-, chloro-, bromo- and iodo- substituted salicylideneanilines were determined by spectrophotomeric titrimetry in 10, 30, 50 and 70% ethanol-water mixtures at constant ionic strength and at 25^{o}C. The results obtained from this work were compared with those obtained using the potentimetric method. The difference between the results found with these two methods was approximately \pm $ 0.20 logK units. The spectrophotometric method was judged to be more suitable than the potentiometric method for halogen substituted salicylideneanilines with the low logK values and in the solvent mixture containing 10% ethanol, due to the …

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Synthesis, Characterization And Biological Activity Of Triorganotin Carboxylates Containing Germanium, Muhammad Aziz Choudhary, Muhammad Mazhar, Saqib Ali, Umm-E Salma, Saima Ashraf, Abdul Malik Jan 2002

Synthesis, Characterization And Biological Activity Of Triorganotin Carboxylates Containing Germanium, Muhammad Aziz Choudhary, Muhammad Mazhar, Saqib Ali, Umm-E Salma, Saima Ashraf, Abdul Malik

Turkish Journal of Chemistry

Some new triorganotin carboxylates containing germanium with general formulae (R^{1}GeCHR^{2}CH_{2}COO) Sn(CH_{2}C(CH_{3})_{3})_{3} where R^{1} = N(CH_{2}CH_{2}O)_{3} and C_{6}H_{5}, R^{2} = C_{6}H_{5}, p-C_{6}H_{4}OCH_{3} and o-/p-C_{6}H_{4}F were synthesized and characterized by elemental analysis, infrared, multinuclear (^{1}H, ^{13}C, ^{119}Sn) NMR and mass spectrometry. Antibacterial activity of these compounds was evaluated against the standard drugs ampicilline and amoxicilline, and found to be more active in some cases than the standard drugs.

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An Investigation Of The Interaction Of 4-Membered Rings With Adjacent Carbanion Centers, Özden Özel Güven, N. Beki̇r Peyni̇rci̇oğlu Jan 2002

An Investigation Of The Interaction Of 4-Membered Rings With Adjacent Carbanion Centers, Özden Özel Güven, N. Beki̇r Peyni̇rci̇oğlu

Turkish Journal of Chemistry

A series of cyclobutylcarbinyl phenyl ketones was prepared and the rates of base catalyzed hydrogen-deuterium exchange of \alpha -hydrogen atoms were compared with those of appropriate model compounds, to test the validity of an earlier finding, which suggested that a four-membered ring, like the three-membered ring, has the ability to stabilize an adjacent carbanion center. In this study, unlike the cyclopropyl group, no clearly defined stabilization of the adjacent carbanion center was detected by the 1-phenyl- and 1-p-nitrophenyl- substituted cyclobutyl groups and only a very slight rate enhancement by the 3-phenylcyclobutyl group was detected. Attempts to detect a stabilization of …

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Iridoid And Phenylethanoid Glycosides From Euphrasia Pectinata, Tayfun Ersöz, M. Zi̇ver Berkman, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland Jan 2002

Iridoid And Phenylethanoid Glycosides From Euphrasia Pectinata, Tayfun Ersöz, M. Zi̇ver Berkman, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland

Turkish Journal of Chemistry

Two specimens of Euphrasia pectinata collected from different regions of northern Anatolia were studied to determine their iridoid and phenylethanoid glycosides. Four iridoid glucosides, aucubin (1), euphroside (2), ixorodoside (3), and boschnaloside (4), and two phenylethanoid glycosides, acteoside (5) and leucosceptoside A (6), were isolated, and characterized from the aerial parts of E. pectinata} collected from Zigana pass (Trabzon). From the aerial parts of E. pectinata} collected from Kartalkaya (Bolu), a phenethyl alcohol glycoside, decaffeoylacteoside (7), was isolated in addition to previously isolated compounds. The structures of the isolated compounds were established by spectroscopic evidence.

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Diterpenes From Sideritis Sipylea And S. Dichotoma, Gülaçti Topçu, Ahmet C. Gören, Turgut Kiliç, Y. Kemal Yildiz, Gülendam Tümen Jan 2002

Diterpenes From Sideritis Sipylea And S. Dichotoma, Gülaçti Topçu, Ahmet C. Gören, Turgut Kiliç, Y. Kemal Yildiz, Gülendam Tümen

Turkish Journal of Chemistry

Two Sideritis species afforded eleven kaurene and one beyerene diterpenes. Structures of the compounds from Sideritis sipylea} were elucidated as linearol (1), 7-epicandicandiol (2), sideridiol (3), siderol (4), isolinearol (5), isosidol (6) and epoxyisolinearol (7). Linearol was treated with m -chloroperbenzoic to afford its analogues ent-3\beta ,7\alpha ,17-trihydroxy-18-acetoxykaur-15-ene (1a) and ent}-7\alpha ,17,18-trihydroxy-3\beta -acetoxykaur-15-ene (1b) as new compounds. From the second species, Sideritis dichotoma, the kaurenes sideridiol (3) siderol (4), ent-7\alpha ,18-dihydroxy-15\beta ,16\beta -epoxykaurane (8)}, ent}-7\alpha -acetoxy,18-hydroxy-15\beta ,16\beta -epoxykaurane (9), ent-7\alpha -acetoxy-15,18-dihydroxy-kaur-16-ene (10), ent-7\alpha ,15,18-trihydroxykaur-16-ene (11) and the beyerene ent-7\alpha ,18-dihydroxybeyer-15-ene (12) were isolated. Structural elucidation is based on NMR techniques …

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Derivative Spectrophotometric Determination Of Caffeine In Some Beverages, Güzi̇n Alpdoğan, Kadi̇r Karabi̇na, Sidika Sungur Jan 2002

Derivative Spectrophotometric Determination Of Caffeine In Some Beverages, Güzi̇n Alpdoğan, Kadi̇r Karabi̇na, Sidika Sungur

Turkish Journal of Chemistry

Caffeine content was determined in cola, coffee and tea by second and third order derivative spectrophotometry without using any separation or background correction technique and reagent. The method is based on the measurement of the distances between two extremum values (peak to peak amplitudes) in the second order (cola) and third order (coffee and tea) derivative spectra of the sample solution. Calibration curves were constructed for the 2.0-10.0 \mu g ml^{-1}concentration range. As a reference method, reversed phase high performance liquid chromatographic procedure was developed. Commercially available beverages were analyzed by the two methods and the results were statistically compared …

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Stabilization Of Papain By Modification With Chitosan, Ali̇ Kilinç, Seçi̇l Önal, Azmi̇ Telefoncu Jan 2002

Stabilization Of Papain By Modification With Chitosan, Ali̇ Kilinç, Seçi̇l Önal, Azmi̇ Telefoncu

Turkish Journal of Chemistry

Papain (EC 3.4.22.2) was immobilized on chitosan by adsorption and subsequent cross-linking with glutaraldehyde. The immobilized papain displayed a lower specific activity than did the native enzyme. The thermal stability of the immobilized papain, relative to that of the free enzyme, was markedly increased. The storage stability of the conjugated enzyme was enhanced such that more than 85% of the initial activity remained after a month storage at 45°C. The optimum pH of immobilized papain was shifted to the acidic region and enzyme stability was increased at pH levels below 3.5.

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Steric Effects On The Oxidation Potential Of 1-Aryl Thioglycosides, Mehmet A. Oturan, Maurice Medebielle, Shirish A. Patil, Robert S. Klein Jan 2002

Steric Effects On The Oxidation Potential Of 1-Aryl Thioglycosides, Mehmet A. Oturan, Maurice Medebielle, Shirish A. Patil, Robert S. Klein

Turkish Journal of Chemistry

The electrochemical oxidation of several 1-arylthioglycosides has been studied by cyclic voltammetry in acetonitrile. We found that the oxidation potential of the \alpha anomer always occurs at a less positive oxidation potential than of the \beta anomer. The difference in the oxidation potential depends on the substituent attached on the C-3 of the sugar moiety and is greatly influenced by the stability of the radical cation obtained after the first electron transfer.

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A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan Jan 2002

A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan

Turkish Journal of Chemistry

A commercial active carbon was tested as an adsorbent for the removal of phenol from aqueous solutions. The optimum conditions for maximum adsorption in terms of shaking time, amount of the adsorbent, and concentration of the adsorbate were identified. The adsorption data fitted the Langmuir isotherm equation in the whole range of concentrations studied. The adsorption of picric acid, pyrogallol and salicylic acid at selected conditions for phenol was also studied. Elution studies to recover the adsorbed phenol from active carbon were performed with distilled water, NaOH and HCl solutions.

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Vapour Liquid Equilibrium In Asymmetric Mixtures Of N-Alkanes With Ethane, Anca Duta, Dan Geana Jan 2002

Vapour Liquid Equilibrium In Asymmetric Mixtures Of N-Alkanes With Ethane, Anca Duta, Dan Geana

Turkish Journal of Chemistry

The paper presents a vapour liquid equilibria study in binary mixtures of n-alkanes with high dimensional asymmetry. Each mixture contains ethane and alkanes higher than eicosane. Calculations were done using two equations of state, Peng-Robinson (PR) and Soave (SRK), in combination with van der Waals mixing rules, corrected with two interaction parameters. A limited temperature dependence of the interaction parameters was found. The correlations between the interaction parameters and the number of carbon atoms of the higher n-alkane led to equations valid for systems ethane + C_{3} up to C_{44}. The results of the prediction calculations were good, both with …

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Synthesis And Protection Of Some Amidines, Kadi̇r Dabak Jan 2002

Synthesis And Protection Of Some Amidines, Kadi̇r Dabak

Turkish Journal of Chemistry

A series of benzamidine derivatives were synthesized from substituted benzonitrile compounds and protected with the tert-butoxycarbonyl group.

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Titrimetric And Spectrophotometric Determinations Of Some Phenothiazine Psychotropics Using Chloramine-T, Kanakapura Basavaiah, Javarappa Manjunathaswamy Jan 2002

Titrimetric And Spectrophotometric Determinations Of Some Phenothiazine Psychotropics Using Chloramine-T, Kanakapura Basavaiah, Javarappa Manjunathaswamy

Turkish Journal of Chemistry

A simple, convenient and accurate indirect titrimetric method and a rapid, sensitive and precise indirect spectrophotometric method for the determination of six phenothiazine drugs using chloramine-T as an oxidant are described. The titrimetric method is based on the oxidation of the drugs in sulphuric acid medium by a known excess of chloramine-T and iodometric determination of the unreacted chloramine-T. In the spectrophotometric method, the unreacted oxidant is made to react with metol in the presence of an aromatic amine to produce a purple-red product with the absorption maximum at 520 nm. The absorbance is found to decrease linearly with increasing …

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Synthesis, Spectral And Thermal Degradation Kinetics Of Divalent Cadmium Complexes Of Dothiepine And Diphenhydramine, Halehatty S. Bhojya Naik, Parasuramapuma R. Chetana, Hosakere D. Revanasiddappa Jan 2002

Synthesis, Spectral And Thermal Degradation Kinetics Of Divalent Cadmium Complexes Of Dothiepine And Diphenhydramine, Halehatty S. Bhojya Naik, Parasuramapuma R. Chetana, Hosakere D. Revanasiddappa

Turkish Journal of Chemistry

Cadmium(II) complexes with 3-(6H-dibenzo[b,e] thiepin-11-ylidene) propyl dimethyl amine chloride (dot) and 2-diphenyl methoxy--N,N-dimethylamine hydrochloride (dp) were synthesised and characterised by reflectance, IR, ^{1}H NMR, magnetic moments and conductivity measurements. The new complexes studied for kinetics of thermal degradation by thermogravimetric analyses (TGA) and derivative thermogravimetric studies (DTG) in a static nitrogen atmosphere at a heating rate of 10°C min^{-1}. The kinetic and thermodynamic parameters such as energy of activation (Ea), frequency factor (lnA), enthalpy (\Delta H), free energy (\Delta H), and entropy (\Delta S) evaluated. The energy of activation values for the degradation of (dot) and (dp) complexes were found …

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Determination Of Ascorbic Acid In Vegetables By Derivative Spectrophotometry, Zeynep Aydoğmuş, S. Müge Çeti̇n, Mahmure Üstün Özgür Jan 2002

Determination Of Ascorbic Acid In Vegetables By Derivative Spectrophotometry, Zeynep Aydoğmuş, S. Müge Çeti̇n, Mahmure Üstün Özgür

Turkish Journal of Chemistry

Determination of ascorbic acid (AA) in garlic, green pepper and chestnut was performed by derivative spectrophotometry without using any pre-separation or background correction techniques. The method is based on the measurement of the distances between two extremum values (peak-to-peak amplitudes) in second and third order derivative spectra of the extracts. Ten percent trichloroacetic acid was found to be the most suitable extraction solution. In the second order derivative spectrum the extrema of 253.2 and 259 nm for garlic, and in the third order derivative spectrum, the extrama of 256.4 and 261.6 nm for green pepper and chestrut samples were used …

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Determination Of Fatty Acid Composition And Total Trans Fatty Acids In Cereal-Based Turkish Foods, Orhan Dağlioğlu, Murat Taşan, Bariş Tunçel Jan 2002

Determination Of Fatty Acid Composition And Total Trans Fatty Acids In Cereal-Based Turkish Foods, Orhan Dağlioğlu, Murat Taşan, Bariş Tunçel

Turkish Journal of Chemistry

The fatty acid composition and trans fatty acids of 13 cereal-based foods produced by Turkish companies were analysed by capillary gas-liquid chromatography. The total fat contents of the samples ranged from 1.8 to 37.9%. Traditional Turkish white bread and bulgur had the lowest fat content (1.8% and 2.3% respectively) and wafer the highest (37.9%). The major fatty acids in the samples were C_{16:0}, C_{18:0}, trans C_{18:1}, C_{18:1} and C_{18:2}. Total unsaturated fatty acid contents varied between 49.0 and 80.3% of total fatty acids, and bulgur had the highest percentage among the samples. Except for bulgur, all the samples contained trans …

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The Effect Of Nicotinamide On Iron Corrosion In Chloride Solutions, Tunç Tüken, Bi̇rgül Yazici, Mehmet Erbi̇l Jan 2002

The Effect Of Nicotinamide On Iron Corrosion In Chloride Solutions, Tunç Tüken, Bi̇rgül Yazici, Mehmet Erbi̇l

Turkish Journal of Chemistry

The use of nicotinamide ``3-pyridineamide'' as an iron corrosion inhibitor was tested in aerated aqueous solutions of NaCl and Na_2SO_4 for different pH values. Polarization resistance (R_p) measurements, polarization curves and AC impedance spectroscopy techniques were used to obtain experimental data. Nicotinamide (ND) was found to exhibit a cationic-type inhibitor behaviour in acidic solution of NaCl (pH 3) and also a weak inhibitory effect in acidic sulphate solution (pH 3). The impedance spectra at open circuit potential showed that the corrosion process of the metal was characterized by two distinguishable capacitive loops. The charge transfer resistance (R_t) and the polarization …

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