Physical Sciences and Mathematics Commons^™

Network Characterization Of Energetic Poly(Glycidyl-Azide), Mehmet S. Eroğlu, Olgun Güven

Turkish Journal of Chemistry

Energetic poly(glycidyl azide) (PGA) elastomers with different crosslink densities were prepared by varying the NCO/OH reactive-groups ratio from 0.8 to 1.0. In the preparation of the elastomers, PGA chains were end-liked with a mixture of hexamethylene diisocyanate (HMDI) and trimethylol propane (TMP) at a fixed TMP/PGA mole ratio. The number average molar mass between junction points of the network chains \overline{{\rm M}}_c was calculated using data obtained from swelling and uniaxial tensile tests and the results were compared. For the mechanical characterization of the networks, Mooney-Rivlin plots were prepared and the values of the constants 2C_1 and 2C_2 of PGA …

Features Of Graft Copolymer Formation Through Reaction Of Functionalized Polyolefins With Poly-\Epsilon-Caprolactam, Elisa Passaglia, Francesco Picchioni, Mauro Aglietto, Giocomo Ruggeri, Francesco Ciardelli

Turkish Journal of Chemistry

The reaction in the melt of polyolefins containing 2-diethylsuccinate groups (DES) with poly-\epsilon-caprolactam (PA6) to give a graft copolymer was investigated under different conditions. Even using a large excess of DES groups over the PA6 terminal amino groups the graft copolymer yield resulted only partial thus suggesting a kinetic control of the reaction. The effect of various catalysts was then examined taking into account results obtained in a model reaction between a low molecular weight amine and diethylsuccinate. The results are discussed in terms of side reactions and miscibility of the pristine polymers.

Synthesis Of The New Cation Exchange Resins Having Poly (Styrene-Caprolactone) Units, S. Savaşkan Yilmaz, Hulisi Özbayrak, Baki Hazer

Turkish Journal of Chemistry

The crosslinked polystyrene-polycaprolactone , PS-PCL-, block copolymers were prepared by the copolymerization of styrene and poly(caprolacton dimethylmethacrylate) (PCL-DM). The molecular weights of polycaprolactone, PCL, PCL-DM were 1250 and 2000. The swelling in H_2O or CHCl_3 of the sulfonated and unsulfonated block copolymers were determined under comparable conditions and investigated. The capacities of the obtained ion exchange resins were 1.31 and 1.10 meq/g.

Thermal Stabilities Of Hydroxyalkyl Terminated Polydimethylsiloxane Oligomers, İskender Yi̇lgor, Emel Yi̇lgor

Turkish Journal of Chemistry

The thermal stabilities of \alpha,\omega-hydroxypropyl, \alpha,\omega-hydroxybutyl \alpha,\omega-2-hydroxypentyl and \alpha,\omega-hydroxyhexyl terminated polydimethylsiloxane oligomers were investigated. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating through the loss of functional end groups, as determined by FTIR spectroscopy and gel permeation chromatography. \alpha,\omega-Hydroxyhexyl and \alpha,\omega-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. The instability of the end groups is due to the backbiting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5-and 6-membered stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the …

New Synthetic Approach For The Synthesis Of Liquid Crystalline Block And Graft Copolymers, Yeşim Hepuzer, İ. Ersin Serhatli, Yusuf Yağci

Turkish Journal of Chemistry

Liquid crystalline block and graft copolymers were synthesized according to the macroinitiator and macroinimer concept. For this purpose, side chain block copolymers (polytetrahydrofuran-b-polymethylmethacrylate) having liquid crystalline 4,4'- cyanobiphenyl blocks were prepared and characterized. Unlike the liquid-crystalline homopolymer with mesogenic units in the side chain, all block and graft copolymers showed a smectic A mesophase. The transition temperatures are hardly affected by the composition and molecular weight of the blolck copolymers.

Electrical Conductivity Of Sodium Doped Poly(4-Vinylpyridine), Murat Özyalçin, Zuhal Küçükyavuz, Aref Jarvaherian, Savaş Küçükyavuz

Turkish Journal of Chemistry

Poly(4-Vinylpyridine) was synthesized by free radicalic polymerization. Solution doping process with metallic sodium was carried out. A conductivity value around 10^{-6} S/cm was obtained. Relative change in the coductivity with dopant concentration, temperature dependence of conductivity, conductivity behavior in atmospheric conditions for the samples were analyzed. SEM and EDX techniques were also used for the characterization of the polymer.

Conducting Polymer Grafts Of Polypyrrole, Levent Toppare

Turkish Journal of Chemistry

Conducting polymer grafts of pyrrole with poly[(methyl methacrylate)-co-(2-(N-pyrollyl) ethyl methacrylate)] wwere synthesized via elctrochemical polymerization of pyrrole in different media. Samples were characterized by SEM, thermal analysis and conductivity measurements.

Crystal Structure Effect In Radiation-Induced Solid-State Polymerization Of Acrylamide, Ali Usanmaz

Turkish Journal of Chemistry

Crystal structure of arcylamide at -150^{\circ}C was studied to understand the role of the crystal structure on the reaction mechanism of radiation-induced polymerization in the solid-state. Acrylamide crystallizes in the monoclinic unit cell with the unit cell parameters as ; a=828.0(2) pm, b=578.0(4) pm, c=974.9(2) pm, \beta=119.62(4)^0, space group =P 2_1/c, Z=4 molecules/unit cell, d_x = 1.165 g/cm^3. From the results of the structural data a polymerization mechanism in the solid-state is suggested. The radiation damage in single crystal of acrylamide was also investigated in detail. The result showed the formation of the amorphous polymer, that phase separated from the …

Electrical Conductivities Of Poly (Alkyl Vinyl Ketones) Reacted With Dopant Solutions, Jun Hui Ma, J. David Tauber, Ülkü S. Ramelow

Turkish Journal of Chemistry

Poly ethyl vinyl ketone (PEVK) and poly methyl vinyl ketone (PMVK) were prepared using photochemical processes. The irradiation of monomers with UV light provides a new method, different from the methods previously used for the polymerization of these monomers. FTIR and UV spectroscopies were used for the structure and reaction mechanism of the polymers. NMR was used to calculate the conversion percentage of MVK and EVK polymers. The conductivity change at various temperatures was traced during reactions of PMVK and PEVK with various dopant concentrations and the activation energy of these reactions were calculated by adding dopants and by adjusting …

A Two-Dimensional Monte Carlo Polymerization Of 5-Membered Rings, Okan Esentürk, H. Önder Pamuk, E. Yurtsever

Turkish Journal of Chemistry

A modification of the kinetic growth model in two dimensions for the polymerization of 5-membered rings is presented. The preliminary results reveal the validity of the modified model.

Phase Transition Of Hydrolyzed Polyacrylamide Gels In Aqueous Solutions Of Poly(Ethylene Glycol), Nilhan Kayaman, Oğuz Okay, B. M. Baysal

Turkish Journal of Chemistry

Hydrolyzed polyacrylamide gels immersed in aqueous solutions of poly(ethylene glycol) (PEG) of molecular weight 300 exhibit a discontinuous volume change upon continuous increase of the PEG concentration in the external solution. As the duration of hydrolysis increases, that is, as the proportion of the ionic groups on the network chains increases, the critical concentration of PEG required for a discontinuous volume change rises and, also, the magnitude of the volume collapse becomes larger. Experimental results indicate that the gel collapse in PEG solution is due to the osmotic deswelling of the ionic gel rather than due to a complex formation …

High Rates Of Fluorescence Quenching Between Perylene Dodecyldiimide And Certain \Pi-Electron Donors, S. İçli̇, H. İci̇l, İ. Gürol

Turkish Journal of Chemistry

Perylene bis-n-dodecyl diimide is found to quench fluorescenc emissions of naphthalene, phenanthrene and dihydrocarbazolocarbazole molecules at rates of 4.4\times10^{11}, 2.8\times10^{12} and 2.5\times10^4 M^{-1} sec^{-1}, in respective order of aromaticity. These unusulally high rates of fluorecence quenchings are attributed to Perrin model static quenching and presence of electron transfer through singlet excited state of perylene diimide. Calculated free energy of electron transfer, \Delta G_{ET}=-120.5 kJ/mol, between perylene diimide and dihydrocarbazolocarbazole is taken as evidence for observation of high fluorescence quenching rate for carbazolocarbazole molecule. Keywords: Fluorescence quenching, Photoenergy transfer, Perylene diimide and Carbazolocarbazole

Possible Roles Of Transition Metals In Cloudwater Relative To The Solar Short-Wave Radiation Absorption Anomaly, Xudong Huang, S. Sinan Keski̇n, Francis Pink, İlhan Ölmez

Turkish Journal of Chemistry

Measurements of the absorption of solar short-wave radiation by clouds exceed those predicted by theoretical calculations. In order to understand the roles of minor and trace species in this absorption anomaly, cloudwater samples were collected from individual precipitating clouds and analyzed for trace metals and anionic species. Two generalized approaches were used to assess the direct impact of the absorption of solar short-wave radiation by transition metals and/or their anionic complexes. Additionally, it was suggested that iron and manganese may act as catalyts in the formation of sulfate aerosols which efficiently scatter solar radiation.

Constituents Of Salvia Verticillata, Ufuk Sönmez, Gülaçtı Topçu, Ayhan Ulubelen

Turkish Journal of Chemistry

Three new and fourteen known compounds were isolated from the roots of {\it Salvia verticillata L.} Spectral methods were used for the structure determination besides TLC comparisons with authentic samples for the known compounds.

Immobilization Of Glucose Oxidase And Urease In Hydrogel Matrices, İhsan Gürel, M.Yakup Arica, Vasıf Hasirci

Turkish Journal of Chemistry

Immobilization of glucose oxidase and urease in hydrogels of 2-hydroxyethyl methacrylae, and N-vinyl pyrrolidone (NVP) was achieved by irradiation (using UV kand \gamma- rays). The effect of radiation on entrapment efficiencies, retention of activities and swelling rates was obtained. To optimize the system, duration of exposure, reaction temperature, co-monomer concentrations, initiator and cross linker compositions were varied. The repeated reusability of the generated products was also tested. It was found that\gamma-irradiation at very low temperatures did not have a detrimental effect on the enzyme activity. Incorporation of more hydrophilic monomer (NVP), influenced matrix morphology and entrapment efficiencies and retained enzyme …

A Study Of The Thermodynamical Interactions Of Bisphenol-A Polycarbonate With Some Solvents By Gas Chromatography, Özlem Cankurtaran, Ferdane Yilmaz

Turkish Journal of Chemistry

Retentin diagrams of polycarbonate for n-nonane, ethyl acetate and n-butyl acetate were obtained using inverse gas chromatography in the temperature range 80-240^{\circ}C. The specific retention volumes, V^{\circ}_{g} the Flory-Huggins interaction parmeters, \chi^{\infty}_{12}, interaction parameters, \chi^{\ast}_{12}, and effective exchange-energy parameters \bar{X}_{12} of the equation-of-state theory of polycarbonate for n-octane, n-nonane, n-decane, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate and isoamyl acetate were obtained in the temperature range 200-240^{\circ}C. The parameter \delta_2 was estimated to be 10.7 (cal/cm^3)^{1/2} at room temperature using the \chi^{\infty}_{12} extrapolated to room temperature. Keywords: Bisphenol-A polycarbonate, polymer-solvent interactions, inverse gas chromatography, solubility parameter.

Photoelectron Spectroscopy: A Tool In Sorption Studies, Şefik Süzer, Hasan N. Erten

Turkish Journal of Chemistry

Photoelectron spectroscopy using AlK\alpha (h\nu=1486.3 eV) has been applied to study the sorption of Cs^+, Sr^{2+}, Ba^{2+}, Zn^{2+} and Co^{2+} on magnesite kaolinite, smectite and chlorite. From the observed intensities of photoelectron peaks it was determined that in magnesite the sorption affinity of the above ions follow the order: Ba^{2+}>Co^{2+}\congSr^{2+}\congZn^{2+}>Cs^+. The order for the sorption of Ba^{2+} and Cs^+ are also determined as chlorite>magnesite>smectite>kaolinite and smectite>chlorite\congkaolinite>magnesite, respectively.

A Topological Approach To The Stabilities Of Isomeric Hückel And Mobius Type Cyclacenes, Lemi Türker

Turkish Journal of Chemistry

Within the constraints of Hückel molecular orbital theory, Hückel and Mobius type cyclacenes were investigated in terms of their angle of total \pi-electron energy, O_{\pi}, and cos O_{\pi} to find out how structural changes affect the stabilities. It has been theoretically deduced that as the number of benzenoid rings (R) increases the isomeric Hückel and Mšbius type cyclacenes should have comparable stabilities, although for low values of R odd-Hückel type and even-Mobius type are predicted to be more stable.

Potentiometric And Spectroscopic Determinaton Of Acid Dissociation Constants Of Some Phenols And Salicylic Acids, Rahmiye Aydin, Ulviye Özer, Naciye Türkel

Turkish Journal of Chemistry

The dissociation constant of the catechol derivatives 4-nitrocatechol (NCAT), 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxybenzoic acid (3,4-DBHA), 3,4-dihydroxyhenylacetic acid (3,4-DPHA) and 3,4-dihydroxycinnamic acid (3,4-DHCA) were identified in 0.1M NaClO_4 ionic medium, at t=25^{\circ}C, by potentiometry. In addition, the first and second dissociation constants of the salicylic acid derivatives 5-nitrosalicylic acid (5-NSA), 4-hydroxysalicylic acid (4-HSA) 5-nitrosalicylic acid (5-HSA) were also determined by potentiometry. Furthermore, the second acid dissociation constants of these ligands were evaluated in I=0.1M NaClO_4 ionic medium, at a temperature of 25^{\circ}C by computer analysis of spectroscopic data.

Estimating Transition Probabilities From Aggregate Samples Augmented By Haphazard Recaptures Ii. The Case Of Covariates., Chien-Pai Han, D. L. Hawkins

Mathematics Technical Papers

The paper extends the authors' earlier methods for estimating transition probabilities, by combining aggregate and haphazard recapture data, to the case of categorical covariates. Both fixed and time-dependent covariates are considered. A two-stage estimation procedure is proposed. The first stage uses a Markov model to estimate multivariate transition probabilities for the response and all covariates. The second stage uses the Stage 1 estimates to model covariate effects. The required number of sampling waves depends only on the number of response levels and time-dependent covariate levels — and not on the number of fixed covariate levels. Recommendations are given for the …

A Quadratic Volterra Integral Equation And Its Solution For Various Kernels, Merlynd K. Nestell, Mostafa Ghandehari

Mathematics Technical Papers

Consider the Volterra integral equation [see pdf for notation], ^ is a parameter Solutions of this equation are discussed for separable and difference kernels using Laplace transform and differential equation techniques. Existence and uniqueness questions are explored for various assumptions on the kernel.

Long Term Stability Of A Terrestrial Cave Community, Claudio Di Russo, Gianmaria Carchini, Mauro Rampini, Marco Lucarelli, Valerio Sbordoni

International Journal of Speleology

We report data on the spatial structure and seasonal variation of the community of Valmarino cave, a medium sized sandstone cave, located a few kilometres from the coast line, in Central Italy. Due to both its habitat features and its relatively recent geological history, Valmarino cave is only inhabited by terrestrial, troglophilic elements, i.e facultative cave dwellers. By means of monthly censuses and density plot estimates we have investigated species abundance, diversity and their spatial organization, by considering separately samples from different cave sectors. Homogeneous sampling design allowed to compare series of samplings performed in 1974 and 1994. On the …

A Strategy For Monitoring Glaciers, Andrew G. Fountain, Robert M. Krimmel, Dennis C. Trabant

Geography Faculty Publications and Presentations

Glaciers are important features in the hydrologic cycle and affect the volume, variability, and water quality of runoff. Assessing and predicting the effect of glaciers on water resources require a monitoring program to provide basic data for this understanding. The monitoring program of the U.S. Geological Survey employs a nested approach whereby an intensively studied glacier is surrounded by less intensively studied glaciers and those monitored solely by remote sensing. Ideally, each glacierized region of the United States would have such a network of glaciers. The intensively studied glacier provides a detailed understanding of the physical processes and their temporal …

Harmonic Oscillation In The Presence Of Multiple Damping Forces, Chris Pelto '97

Honors Projects

The relatively mundane damped harmonic oscillator is found to exhibit interesting motion once under the influence of both a velocity dependent and a Coulombic frictional damping force. Data for the decay of the amplitude as a function of time were collected on a specially prepared torsional oscillator. with a variable electromagnetic damping mechanism. An analytical solution of the appropriate equation of motion was obtained by the method of Laplace transforms. In both the limits of zero Coulombic friction and zero velocity damping, the solution reduces to the well-known answers to the problem. the solution, when plotted with the correct parameters, …

Investigation Of The Optical Properties Of Ordered Semiconductor Materials, Jack E. Mccrae Jr.

Theses and Dissertations

Optical studies have been conducted upon CdGeAs₂ and ZnGeP₂, two of the most promising semiconductors being developed for mid-infrared non-linear optics applications. These experiments included photoluminescence (PL) studies of both compounds as well as photoreflectance (PR) measurements upon CdGeAs₂. In addition, Hall effect measurements were carried out upon CdGeAs₂, to aid in interpretation of the optical data. PL was measured as a function of laser power, sample temperature, and crystal orientation for CdGeAs₂. One broad weak peak near 0.38 eV, and another somewhat narrower and often far brighter peak near 0.57 …

Steiner Trees Over Generalized Checkerboards, Meta M. Voelker '97

Honors Projects

To minimize the length of a planar network, we can build a Steiner minimal tree that is, a tree consisting of the original network points, as well as additional, strategically-placed (Steiner) points. Chung, Gardner and Graham [2] investigated building Steiner trees over grids of unit squares. We generalize their ideas to grids of rhombuses, and show that two near-optimal Steiner trees exist for each grid, one built from Steiner trees over rhombuses and one built from Steiner trees over isosceles triangles. Further, we conjecture that for grids with an odd number of layers, only the small angle of the rhombus …

Development And Evaluation Of Interactive Courseware For Visualization Of Graph Data Structure And Algorithms, Thomas E. Beutel

CCE Theses and Dissertations

The primary goal of this dissertation was to develop and pilot test interactive, multimedia courseware which would facilitate learning the abstract structures, operations, and concepts associated with graph and network data structures in Computer Science. Learning objectives and prerequisites are presented in an introduction section of the courseware and a variety of learning activities are provided including tutorials, animated demonstrations, interactive laboratory sessions, and self-tests. Courseware development incorporated principles and practices from software engineering, instructional design, and cognitive learning theories. Implementation utilized an easy-to-use authoring tool, NeoBook Professional (1994), to create the overall framework and the user interfaces, and Microsoft …

Issues And Conflicts In The Management Of The Public Domain Of The Saddle Mountains In Eastern Washington: A Case Study, James Jack Sharpe

All Master's Theses

This thesis examines the prehistoric, historic, and contemporary patterns of land use and their effects in the Saddle Mountains of eastern Washington. Federal laws and Indian treaties require that federal lands be managed to preserve natural and cultural resources while meeting the demands of private interests for economic development and of the general public for recreational access. Land management conflicts created by these diverse interests are reviewed in the context of the history of the study area, the legal framework that directs its management, and the management process as it actually works. It concludes with recommendations to resolve land use …

Irreducible K-To-1 Maps Onto Grids, Susan M. Parker

Honors Theses

In this paper we explore the existence of exactly k-to-1 continuous functions between graphs, and more specifically 2-to-1 continuous function between graphs that are irreducibly 2-to-1, meaning that no restriction of the function to a subgraph is 2-to-l. We show how to construct such functions in some general cases, and then more specifically onto rectangular grids. We have in mind an application to distributed networks and signal verification.

Induced Acceleration Of Phosphine Exchange In Metal Carbonyls By Pendant Groups Of Coordinated Polyphosphines, Ping Ye

Masters Theses

The kinetics and thermodynamics of isomerization of (OC)₅CrPPh₂CH₂CH(PPh₂)₂ to its linkage isomer, (OC)₅CrPPh₂CH(PPh₂)CH₂PPh₂, in chloroform-d have been studied with ³¹P{¹H} NMR.

(OC)₅Cr[η¹-PPh₂CH₂CH(PPh₂)₂] ⇄ (OC)5Cr[η¹-PPh₂CH(PPh₂)CH₂PPh₂]

The equilibrium constants for the reaction are 3.60, 2.61, 2.04, and 1.67 at 10 °C, 25 °C, 40 °C, and 53 °C, respectively. The forward reaction becomes more favorable as the temperature …