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2006

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Articles 5221 - 5250 of 5872

Full-Text Articles in Physical Sciences and Mathematics

Comments On The Mechanism Of Aging Of Antimony Doped Tin Oxide Based Electrochromic Devices, Joo C. Chan, Nicole A. Hannah, Shankar B. Rananavare, Laura Yeager, Liviu Dinescu, Ashok Saraswat, Pradeep Iyer, James P. Coleman Jan 2006

Comments On The Mechanism Of Aging Of Antimony Doped Tin Oxide Based Electrochromic Devices, Joo C. Chan, Nicole A. Hannah, Shankar B. Rananavare, Laura Yeager, Liviu Dinescu, Ashok Saraswat, Pradeep Iyer, James P. Coleman

Chemistry Faculty Publications and Presentations

Electrochromic effects of antimony doped tin oxide (ATO) nanoparticles are investigated to probe device yellowing (degradation). Voltage vs contrast ratio curves exhibit hysteresis, i.e., image-sticking phenomena due to irreversible charge insertion. X-ray, impedance and optical b* studies suggest that the yellowing/charge trapping is nanoparticle size-dependent with 4 nm size particles exhibiting the least yellowing. Yellowing results in increased impedances of electrode–electrolyte interface and electrode corrosion. Plausible sources of discoloration are formation of insulating complex alkali oxide film, carrier inversion (n-to-p type) through electrochemical Li doping, redeposition of the corroded electrode material and perhaps residual concentration of charge-transfer species.

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How Abundant Is Pedogenic Magnetite? Abundance And Grain Size Estimates For Loessic Soils Based On Rock Magnetic Analyses, Christoph Geiss, C. William Zanner Jan 2006

How Abundant Is Pedogenic Magnetite? Abundance And Grain Size Estimates For Loessic Soils Based On Rock Magnetic Analyses, Christoph Geiss, C. William Zanner

Faculty Scholarship

The upper soil horizons of many modern and ancient soils are enriched in fine-grained pedogenic ferrimagnetic minerals. We use three grain-size- and concentration-dependent proxies (anhysteretic remanent magnetization/isothermal remanent magnetization ratios, coercivity spectra derived from alternating field demagnetization of saturation isothermal remanent magnetization and hysteresis properties) to quantify the abundance and grain size of the pedogenic magnetic component. Our analyses of modern loessic soils from the midwestern United States show that relatively small additions (2–10 vol % of the total ferrimagnetic component) of fine-grained (coarse superparamagnetic to fine pseudosingle domain) magnetite or maghemite are sufficient to explain the changes in concentration …

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Electronic Publishing For Engineering Education, Donald G. Dudley Jan 2006

Electronic Publishing For Engineering Education, Donald G. Dudley

Turkish Journal of Electrical Engineering and Computer Sciences

Electronic transmission of text is a revolution in progress with a profound effect on engineering education. As with all revolutions, the result is both a threat and a promise. The promise is the ease and speed of dissemination of text. The threat involves serious difficulties that arise in efforts to protect the intellectual property rights of the authors and publishers of the technical information. In this paper, we discuss both the threat and the promise. We highlight the differences in dealing with books and with journals. We give a wide range of examples from both inside of and outside of …

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Introducing Students To Communications Concepts Using Optical And Low-Power Wireless Devices, James M. Conrad, Ivan Howitt Jan 2006

Introducing Students To Communications Concepts Using Optical And Low-Power Wireless Devices, James M. Conrad, Ivan Howitt

Turkish Journal of Electrical Engineering and Computer Sciences

Wireless communication has become an important feature for commercial products and a popular research topic within the last ten years. There are now more mobile phone subscriptions than wired-line subscriptions. Lately, one area of commercial interest has been low-cost, low-power, and short-distance wireless communication used for "personal wireless networks." Technology advancements are providing smaller and more cost effective devices for integrating computational processing, wireless communication, and a host of other functionalities. These embedded communications devices will be integrated into applications ranging from homeland security to industry automation and monitoring. They will also enable custom tailored engineering solutions, creating a revolutionary …

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An Experience On Problem Based Learning In An Engineering Faculty, Cüneyt Güzeli̇ş Jan 2006

An Experience On Problem Based Learning In An Engineering Faculty, Cüneyt Güzeli̇ş

Turkish Journal of Electrical Engineering and Computer Sciences

In 2001, Engineering Faculty of Dokuz Eylül University has started to change its undergraduate education in a radical way. As being among the first examples in the world, the Departments of Electrical and Electronics, Geological and Geophysics Engineering in 2002 and Mining Engineering Department in 2003 have adopted the so-called "modular-staged problem based active learning system". The system is based on real engineering problems which values teamwork and the integration of information from different disciplines and it places the student at the center of the learning process. The faculty has learned many things and it needs to learn many other …

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Secure Digital Communication Using Chaotic Symbolic Dynamics, Ajeesh P. Kurian, Sadasivan Puthusserypady Jan 2006

Secure Digital Communication Using Chaotic Symbolic Dynamics, Ajeesh P. Kurian, Sadasivan Puthusserypady

Turkish Journal of Electrical Engineering and Computer Sciences

One of the major hurdles in implementing chaotic communication schemes is the synchronization of chaotic systems. For the last two decades, numerous contributions of varying successes have been made by researchers from different disciplines for the synchronization of chaotic systems. Symbolic dynamics based synchronization method is shown to be capable of providing high quality synchronization (HQS), which is essential for reliable communication. In this work, using this method, a secure digital communication system is proposed. The well known piece-wise linear 1-D map such as tent map and Bernoulli shift map are used for this study. Since the information is dynamically …

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Human Identification Using Gait, Murat Eki̇nci̇ Jan 2006

Human Identification Using Gait, Murat Eki̇nci̇

Turkish Journal of Electrical Engineering and Computer Sciences

Gait refers to the style of walking of an individual. This paper presents a view-invariant approach for human identification at a distance, using gait recognition. Recognition of a person from their gait is a biometric of increasing interest. Based on principal component analysis (PCA), this paper describes a simple, but efficient approach to gait recognition. Binarized silhouettes of a motion object are represented by 1-D signals, which are the basic image features called distance vectors. The distance vectors are differences between the bounding box and silhouette, and are extracted using 4 projections of the silhouette. Based on normalized correlation of …

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State-Space Synthesis Of Current-Mode First-Order Log-Domain Filters, Ali̇ Kirçay, Uğur Çam Jan 2006

State-Space Synthesis Of Current-Mode First-Order Log-Domain Filters, Ali̇ Kirçay, Uğur Çam

Turkish Journal of Electrical Engineering and Computer Sciences

This paper proposes current-mode first-order log-domain filters, which are systematically derived using the state-space synthesis procedure. First-order low-pass, high-pass, and all-pass responses are obtained with different circuit types. The filter circuits have very simple structures, since they use only bipolar junction transistors (BJTs) and a grounded capacitor. They can be electronically tuned by changing an external current. The filters have a greater bandwidth due to inherently current-mode and log-domain operation. PSPICE simulations are given to confirm the theoretical analysis.

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Readjusting The Current Trend In Electrical Power Engineering, Johan Smit, Peter Morshuis, Edward Gulski Jan 2006

Readjusting The Current Trend In Electrical Power Engineering, Johan Smit, Peter Morshuis, Edward Gulski

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper the electrical power education curriculum is analyzed from the viewpoint of the electrical power industry and from the viewpoint of young people that contemplate their future academic study. From the perspective of young people in industrialized countries contemplating their future and the possibilities of an academic study, the current curriculum in (power) engineering lacks attraction. The number of freshmen still shows a decreasing trend. This paper is aimed to be a contribution towards readjusting this trend

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A Labview-Based Virtual Instrument For Engineering Education: A Numerical Fourier Transform Tool, Levent Sevgi̇, Çağatay Uluişik Jan 2006

A Labview-Based Virtual Instrument For Engineering Education: A Numerical Fourier Transform Tool, Levent Sevgi̇, Çağatay Uluişik

Turkish Journal of Electrical Engineering and Computer Sciences

Engineering is based on practice. The minima of this practice should be given during the university education. This has become more and more comprehensive and expensive parallel to high-technology devices developed and presented to societies. Computers, microprocessor-based devices, programmable systems on Chip (PSoC), etc., make engineering education not only very complex but interdisciplinary as well. Building undergraduate labs has become more and more expensive if only physical experimentation and hands-on training are targeted. On the other hand, simple, comparatively much cheaper software may turn a regular personal computer (PC) into a virtual lab. The key question therefore is, to establish …

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Sturm-Liouville Equation: The Bridge Between Eigenvalue And Green's Function Problems, Levent Sevgi̇ Jan 2006

Sturm-Liouville Equation: The Bridge Between Eigenvalue And Green's Function Problems, Levent Sevgi̇

Turkish Journal of Electrical Engineering and Computer Sciences

This article is intended as an educational aid and discusses guided wave propagation problems that are modeled via the Sturm-Liouville equation in electromagnetics. The bridge between source-free (eigenvalue) and source-driven (Green's function) problems that are represented by the same Sturm-Liouville equation is emphasized. The presentation focuses on representation of an arbitrary source from the features (eigenfunctions) of the problem geometry and extraction of the eigenvalues of a problem from propagation characteristics (Green's function) on a canonical problem; a homogeneously filled parallel plate waveguide with non-penetrable boundaries

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Agents For Integrating Distributed Data For Complex Computations, Ahmed M. Khedr, Raj Bhatnagar Jan 2006

Agents For Integrating Distributed Data For Complex Computations, Ahmed M. Khedr, Raj Bhatnagar

Turkish Journal of Electrical Engineering and Computer Sciences

Algorithms for many complex computations assume that all the relevant data are available on a single node of a computer network. In the emerging distributed and networked knowledge environments, databases relevant for computations may reside on a number of nodes connected by a communication network. These data resources cannot be moved to other network sites due to privacy, security, and size considerations. The desired global computation must be decomposed into local computations to match the distribution of data across the network. The capability to decompose computations must be general enough to handle different distributions of data and different participating nodes …

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Controlling Rail Potential Of Dc Supplied Rail Traction Systems, Mehmet Turan Söylemez, Süleyman Açikbaş, Adnan Kaypmaz Jan 2006

Controlling Rail Potential Of Dc Supplied Rail Traction Systems, Mehmet Turan Söylemez, Süleyman Açikbaş, Adnan Kaypmaz

Turkish Journal of Electrical Engineering and Computer Sciences

Most modern DC electrified mass transit systems use a totally floating earth as their grounding strategy. A well-known problem related with totally floating systems is that the touch potentials can be dangerously high. In order to reduce the voltages on rails, several devices exist. Most of these devices allow a direct connection to earth when a certain voltage threshold is exceeded. In this paper, the working principles of these devices are given and the effect of certain parameters related with these devices on the minimum achievable touch potentials is investigated.

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Inverse Scattering Transform For The Camassa-Holm Equation, Adrian Constantin, Vladimir Gerdjikov, Rossen Ivanov Jan 2006

Inverse Scattering Transform For The Camassa-Holm Equation, Adrian Constantin, Vladimir Gerdjikov, Rossen Ivanov

Articles

An Inverse Scattering Method is developed for the Camassa-Holm equation. As an illustration of our approach the solutions corresponding to the reflectionless potentials are constructed in terms of the scattering data. The main difference with respect to the standard Inverse Scattering Transform lies in the fact that we have a weighted spectral problem. We therefore have to develop different asymptotic expansions.

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Ocean Warming And Freshening In The Northern Gulf Of Alaska, Thomas C. Royer, Chester E. Grosch Jan 2006

Ocean Warming And Freshening In The Northern Gulf Of Alaska, Thomas C. Royer, Chester E. Grosch

CCPO Publications

Water column temperatures on the shelf in the northern Gulf of Alaska have increased more than 0.8 degrees C and vertical density stratification has increased since 1970 near Seward, Alaska throughout the 250 m depth. This high latitude marine system has low water temperatures, high rates of precipitation, glacial melting, high wind speeds and high rates of biological productivity. A more than 300 km alongshore shift ( locally westward) of isotherms is suggested. The observations are consistent with a conceptual ocean-atmosphere circulation model that employs coastal freshwater discharge, glacial ablation and wind forcing. Positive regional feedback mechanisms accelerate the discharge …

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Field, Petrographic, And Geochemical Characteristics Of Price Creek, Russ Mccormack Jan 2006

Field, Petrographic, And Geochemical Characteristics Of Price Creek, Russ Mccormack

Undergraduate Review

No abstract provided.

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Development Of Dirhodium Sugar-Substituted Carboxylate And Acetamide Complexes And Evaluation Of Their Potential As Lectin Inhibitors, Bethany Masten Jan 2006

Development Of Dirhodium Sugar-Substituted Carboxylate And Acetamide Complexes And Evaluation Of Their Potential As Lectin Inhibitors, Bethany Masten

Undergraduate Review

No abstract provided.

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The Impact Of Financial Market And Resale Market On Firm Strategies, Zhiling Guo, Andrew B. Whinston Jan 2006

The Impact Of Financial Market And Resale Market On Firm Strategies, Zhiling Guo, Andrew B. Whinston

Research Collection School Of Computing and Information Systems

The ever-increasing use of information technology (IT) in business transactions greatly expands firms? exposure to different electronic markets. This paper provides a framework to understand how firms can leverage different strategies across external financial markets and an internal resale market to improve overall profitability. We develop a model in which a group of risk-averse retailers sell a homogeneous product to their respective uncertain consumer markets. We study a scenario where an internal resale market can be constructed among the retailers and outside financial markets can be used to improve their ability to manage uncertainty. We identify strategies for retailers operating …

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Grid-Partition Index: A Hybrid Approach To Nearest-Neighbor Queries In Wireless Location-Based Services, Baihua Zheng, Jianliang Xu, Wang-Chien Lee, Dik Lun Lee Jan 2006

Grid-Partition Index: A Hybrid Approach To Nearest-Neighbor Queries In Wireless Location-Based Services, Baihua Zheng, Jianliang Xu, Wang-Chien Lee, Dik Lun Lee

Research Collection School Of Computing and Information Systems

Traditional nearest-neighbor (NN) search is based on two basic indexing approaches: object-based indexing and solution-based indexing. The former is constructed based on the locations of data objects: using some distance heuristics on object locations. The latter is built on a precomputed solution space. Thus, NN queries can be reduced to and processed as simple point queries in this solution space. Both approaches exhibit some disadvantages, especially when employed for wireless data broadcast in mobile computing environments. In this paper, we introduce a new index method, called the grid-partition index, to support NN search in both ondemand access and periodic broadcast …

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Towards Better Quality Specification Miners, David Lo, Siau-Cheng Khoo Jan 2006

Towards Better Quality Specification Miners, David Lo, Siau-Cheng Khoo

Research Collection School Of Computing and Information Systems

Softwares are often built without specification. Tools to automatically extract specification from software are needed and many techniques have been proposed. One type of these specifications – temporal API specification – is often specified in the form of automaton (i.e., FSA/PFSA). There have been many work on mining software temporal specification using dynamic analysis techniques; i.e., analysis of software program traces. Unfortunately, the issues of scalability, robustness and accuracy of these techniques have not been comprehensively addressed. In this paper, we describe a framework that enables assessments of the performance of a specification miner in generating temporal specification of software …

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Melting And Solidification Study Of As-Deposited And Recrystallized Bi Thin Films, M. K. Zayed, H. E. Elsayed-Ali Jan 2006

Melting And Solidification Study Of As-Deposited And Recrystallized Bi Thin Films, M. K. Zayed, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Melting and solidification of as-deposited and recrystallized Bi crystallites, deposited on highly oriented 002-graphite at 423 K, were studied using reflection high-energy electron diffraction (RHEED). Films with mean thickness between 1.5 and 33 ML (monolayers) were studied. Ex situ atomic force microscopy was used to study the morphology and the size distribution of the formed nanocrystals. The as-deposited films grew in the form of three-dimensional crystallites with different shapes and sizes, while those recrystallized from the melt were formed in nearly similar shapes but different sizes. The change in the RHEED pattern with temperature was used to probe the melting …

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New Einsteins Need Positive Environment, Independent Spirit, Amin Dharamsi Jan 2006

New Einsteins Need Positive Environment, Independent Spirit, Amin Dharamsi

Electrical & Computer Engineering Faculty Publications

After reading the letters about Lee Smolin’s “Why No ‘New Einstein’?” (PHYSICS TODAY, June 2005, page 56; January 2006, page 13), I could not help but relive my undergraduate and graduate experiences at Columbia University from 1968 to 1978. As one of the few black and Hispanic people with a PhD in theoretical physics from that institution, I hope my observations expand the argument about creativity and the perception of it, particularly regarding minorities and how they are perceived by others.

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Phytochemical Studies On The Underground Parts Of Asperula Taurina Subsp. Caucasica, Ufuk Özgen, Cavi̇t Kazaz, Hasan Seçen, Maksut Coşkun Jan 2006

Phytochemical Studies On The Underground Parts Of Asperula Taurina Subsp. Caucasica, Ufuk Özgen, Cavi̇t Kazaz, Hasan Seçen, Maksut Coşkun

Turkish Journal of Chemistry

One naphthohydroquinone (mollugin) (1), 3 anthraquinones (1-hydroxy-2-methyl-9,10-anthraqinone (2), 1,3-dihydroxy-2-methoxymethyl- 9,10-anthraquinone (4) and 1,3-dihydroxy-2-carboxy-9,10-anthraquinone (7, munjistin)), \beta-sitosterol (3), 1 naphthalene glycoside (2-carbomethoxy-3-prenyl-1,4-naphtho-hydroquinone, 1,4-di-O-\beta -glucoside (5)) and 1 anthraquinone glycoside (lucidin-3-O-\beta -primeveroside (6)) were isolated from the underground parts of A. taurina subsp. caucasica. The structures of the isolates were established by MS, ^1H-NMR and ^{13}C-NMR analysis.

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Cyclic Triterpenoid Saponins From Campanula Lactiflora, Nuretti̇n Yayli, Asu Usta, Ahmet Yaşar, Osman Üçüncü, Canan Güleç, Mustafa Küçükislamoğlu Jan 2006

Cyclic Triterpenoid Saponins From Campanula Lactiflora, Nuretti̇n Yayli, Asu Usta, Ahmet Yaşar, Osman Üçüncü, Canan Güleç, Mustafa Küçükislamoğlu

Turkish Journal of Chemistry

Two cyclic natural compounds, 3\beta-O-[\alpha-L-rhamnopyranosyl- (1 \to 2)-\beta-D-glucopyranosyl]-13\alpha,14\alpha-epoxy-8\alpha,12\beta, 15-trihydroxy-(17E,21E)-17,21-campanuldien-6'(30)-olide, called lactifloroside A, 1, and 3\beta-O-[\beta-D-glucopyranosyl-(1 \to 2)-\beta-D-glucopyranosyl]- 13\alpha,14\alpha-epoxy-8\alpha,12\beta-dihydroxy-(17E,21E)-17,21-campanuldien- 6'(30)-olide, called lactifloroside B, 2, were isolated for the first time from Campanula lactiflora and their structures deduced by high field 1D and 2D 400 MHz NMR, FT-IR, HPLC, GC-MS, (+/-) LC-MS/MS and (+) FAB-MS spectra. The aglycones of the 2 saponins were named 13\alpha,14\alpha-epoxy-3\beta,8\alpha,12\beta,15-tetrahydroxy-(17E,21E)- 17,21-campanuldien-30-oic acid and 13\alpha,14\alpha-epoxy-3\beta,8\alpha, 12\beta-trihydroxy-(17E,21E)-17,21-campanuldien-30-oic acid, and designated as campanuloic acid and 15-deoxycampanuloic acid, respectively.

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Synthesis And Characterization Of Metal Complexes Of Cu(Ii), Ni(Ii), Zn(Ii), Co(Ii), Mn(Ii) And Cd(Ii) With Tetradentate Schiff Bases, Jianning Liu, Bo-Wan Wu, Bing Zhang, Yongchun Liu Jan 2006

Synthesis And Characterization Of Metal Complexes Of Cu(Ii), Ni(Ii), Zn(Ii), Co(Ii), Mn(Ii) And Cd(Ii) With Tetradentate Schiff Bases, Jianning Liu, Bo-Wan Wu, Bing Zhang, Yongchun Liu

Turkish Journal of Chemistry

4-(Benzeneazo)salicylaldehyde was synthesized with aniline, sodium nitrite and salicylaldehyde. Two tetradentate ligands, N,N'-bis[4-(benzeneazo) salicylaldehyde]-o-phenylenediamine (H_2L) and N,N'-bis[4-(benzeneazo) salicylaldehyde]ethylenediamine (H_2L') were formed by the 2:1 molar condensation of 4-(benzeneazo) salicylaldehyde with o-phenylenediamine or ethylenediamine. Their Cu(II), Ni(II), Zn(II), Co(II), Mn(II) and Cd(II) complexes were synthesized and characterized by elemental analysis, molar conductivity measurements, and infrared and electronic spectral data. Two ligands and their Ni(II) and Zn(II) complexes were further identified using ^1H NMR spectra. The results suggest that the metal is bonded to the ligand through the phenolic oxygen and the imino nitrogen.

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First- And Second-Derivative Spectrophotometry For Simultaneous Determination Of Copper And Cobalt By 1-(2-Pyridylazo)-2-Naphthol In Tween 80 Micellar Solutions, Habibollah Eskandari, Ali Ghanbari Saghseloo, Mansour Arab Chamjangali Jan 2006

First- And Second-Derivative Spectrophotometry For Simultaneous Determination Of Copper And Cobalt By 1-(2-Pyridylazo)-2-Naphthol In Tween 80 Micellar Solutions, Habibollah Eskandari, Ali Ghanbari Saghseloo, Mansour Arab Chamjangali

Turkish Journal of Chemistry

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous determination of copper and cobalt at trace levels. PAN at pH 1.89 forms red and green complexes with copper and cobalt, respectively, which are soluble in aqueous Tween 80 micellar media and are stable for at least 3 days. Under optimum conditions, calibration graphs were obtained for individual determination of copper and cobalt by zero- and first-derivative spectrophotometry and for simultaneous determination by first- and second-derivative spectrophotometry. Zero-crossing first-derivative spectrophotometry at 555 and 581 nm for cobalt and copper was used for the simultaneous determination, respectively. The second derivative method at 577 …

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Kinetics And Mechanism Of Oxidation Of 1,3--Butylene Glycol By Dihydroxyditellutoargentate(Iii) In Alkaline Medium, Jin-Huan Shan, Shu-Ying Huo, Shi-Gang Shen, Han-Wen Sun Jan 2006

Kinetics And Mechanism Of Oxidation Of 1,3--Butylene Glycol By Dihydroxyditellutoargentate(Iii) In Alkaline Medium, Jin-Huan Shan, Shu-Ying Huo, Shi-Gang Shen, Han-Wen Sun

Turkish Journal of Chemistry

The kinetics of oxidation of 1,3--butlene glycol (\beta - BG) by dihydroxyditelluto- argentate(III) were studied spectrophotometrically between 298.2 and 313.2 K in alkaline medium. The reaction rate showed pseudo-first order dependence in oxidant and fractional order in \ss-BG. The pseudo-first order rate constant k_{obs} increased with an increase in the concentration of OH^- and a decrease in the concentration of TeO_4^{2-} . There was a negative salt effect and no free radicals were detected. Thus, the dihydroxymonotelluratoargentate(III) species is assumed to be the active species. The activation parameters along with the rate constants of the rate-determining step were calculated.

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Composition And Antimicrobial Activities Of Volatile Components Of Minuartia Meyeri, Nuretti̇n Yayli, Canan Güleç, Osman Üçüncü, Ahmet Yaşar, Serdar Ülker, Kami̇l Coşkunçelebi̇, Sali̇h Terzi̇oğlu Jan 2006

Composition And Antimicrobial Activities Of Volatile Components Of Minuartia Meyeri, Nuretti̇n Yayli, Canan Güleç, Osman Üçüncü, Ahmet Yaşar, Serdar Ülker, Kami̇l Coşkunçelebi̇, Sali̇h Terzi̇oğlu

Turkish Journal of Chemistry

The essential oil of air-dried Minuartia meyeri (Boiss.) Bornm. (Caryophyllaceae) was obtained by hydrodistillation in a Clevenger-type apparatus and analyzed by GC-MS. Fifty-two components were identified in the oil. The main components in the essential oil of M. meyeri were nonacosane (6.2%), 6,10,14-trimethyl-2-pentadecanone (5.1%), nonanal (4.6%), and beta-caryophyllene (2.9%). The antimicrobial activity of the isolated essential oil of the plant was also investigated and it showed moderate antibacterial activity against Gram-positive and Gram-negative bacteria, but no antifungal activity was observed against 2 yeast-like fungi.

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Chromium(Iii) Complexes With Different Chromospheres Macrocyclic Ligands: Synthesis And Spectroscopic Studies, Rajiv Kumar, Rajeev Singh Jan 2006

Chromium(Iii) Complexes With Different Chromospheres Macrocyclic Ligands: Synthesis And Spectroscopic Studies, Rajiv Kumar, Rajeev Singh

Turkish Journal of Chemistry

Symmetric tetradentate (L^1) and asymmetric pentadentate (L^2) macrocyclic ligands that possess 2 dissimilar coordination sites were prepared. One has a 4-coordinate (N_4) and the other has a 5-coordinate (N_2O_3S) donor set. Trivalent Cr(III) complexes were synthesized with L^1 and L^2 and their structures were investigated using elemental analyses and magnetic moment, electronic, IR, ^1H NMR, ^{13}C NMR and EPR spectra. All the Cr(III) complexes show magnetic moments corresponding to a high-spin configuration. \Delta values indicate the energy difference between the principle bands, which are formed due to ligand field absorption. The spin-orbit coupling parameter, z, gives no significance because the …

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A Novel Alkaloid From Stapelia Hirsuta, Marwan Shabana, Mariam Gonaid, Maha Mahmoud Salama, Essam Abdel-Sattar Jan 2006

A Novel Alkaloid From Stapelia Hirsuta, Marwan Shabana, Mariam Gonaid, Maha Mahmoud Salama, Essam Abdel-Sattar

Turkish Journal of Chemistry

A novel alkaloid (1,8,8-trimethyl-5,8-dihydro-1H-pyrano[3,4-b]pyridine-4,6-dione) was isolated from the chloroformic traction obtained from the total alcoholic extract of the aerial parts of Stapelia hirsuta L. In addition, apigenin, luteolin and \beta-sitosterol-3-O-\beta-D- glucopyranoside were also isolated.

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