Determination of Electrical and Photoelectrical Properties of Schottky Diodes Made Using New Chitin Derivatives Synthesized as Interface Layer

Silicon - 5-(2,4-dichlorophenyl)-2-furoic acid and anthraquinone-2-carboxylic acid were reacted separately with chitin. The synthesized products were characterized by various spectroscopic methods...     

Thermal decomposition behavior of γ‐irradiated poly(vinyl acetate)/poly(methyl methacrylate) miscible blends

Miscible polymer blends based on various ratios of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) were prepared in film form by the solution casting technique using benzene as a common solvent. The thermal decomposition behavior of these blends and their individual homopolymers before and after γ‐irradiation at various doses (50–250 kGy) was investigated. The thermogravimetric analysis technique was utilized to determine the temperatures at which the maximum value of the rate of reaction (T_max) occurs and the kinetic parameters of the thermal decomposition. The rate of reaction curves of the individual homopolymers or their blends before or after γ‐ irradiation displayed similar trends in which the T_max corresponding to all polymers was found to exist in the same position but with different values. These findings and the visual observations of the blend solutions and the transparency of the films gave support to the complete miscibility of these blends. Three transitions were observed along the reaction rate versus temperature curves; the first was around 100–200°C with no defined T_max, which may arise from the evaporation of the solvent. The second T_max was in the 340–380°C range, which depended on the polymer blend and the γ‐irradiation condition. A third transition was seen in the rate of reaction curves only for pure PVAc and its blends with PMMA with ratios up to 50%, regardless of γ‐ irradiation. We concluded that γ‐irradiation improved the thermal stability of PVAc/PMMA blends, even though the PMMA polymer was degradable by γ irradiation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1773–1780, 2006     

Synthesis of copolymers of tert‐butyl vinyl ether with maleic and citraconic anhydrides

In the present study, the effects of charge‐transfer complex formation and intramolecular fragmentation (side‐chain lactonization) in radical copolymerization of tert‐butyl vinyl ether (t‐BVE) with anhydrides of maleic (MA) and citraconic (CA) acids and the structure–thermal behavior relationships of the resulting copolymers were examined using the ¹H‐NMR, FTIR, DSC, and TGA analysis methods. It was shown that copolymerization under the chosen conditions proceeded through intramolecular fragmentation with the formation of γ‐lactone units. Side‐chain fragmentation of t‐BVE–MA and t‐BVE–CA copolymers also was confirmed by TGA and DSC analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2455–2463, 2006 2006     

Synthesis,characterization, and antitumor activity of poly(maleic anhydride‐co‐vinyl acetate‐co‐acrylic acid)

The ternary copolymerization of maleic anhydride (MA), vinyl acetate (VA), and acrylic acid (AA) [P(MA‐co‐VA‐co‐AA)], which is considered to be an acceptor–donor–acceptor system, was carried out in 1,4‐dioxane with benzoyl peroxide as an initiator at 70°C under a nitrogen atmosphere. Constants of complex formation for the monomer systems in the study were determined by UV–visible (hydrogen‐bonding complex) and ¹H‐NMR (charge transfer complex) methods, respectively. The results show that polymerization of the P(MA‐co‐VA‐co‐AA) system proceeds by an alternating terpolymerization mechanism. It is shown that the synthesized copolymers have typical polyelectrolyte behavior, ability for reversible hydrolysis–anhydrization reactions, and semicrystalline structures. In these cases, including radical polymerization, and formation of semicrystalline structures, the hydrogen‐bonding effect plays a significant role. The in vitro cytotoxicities of the synthesized terpolymer and alternating copolymer were evaluated using Raji cells (human Burkitt lymphoma cell line). The antitumor activities of prepared anion‐active copolymers were studied using methyl–thiazol–tetrazolium colorimetric assay and 50% of the cytotoxic dose of each copolymer and terpolymer were calculated. Hydrolyzed P(MA‐co‐VA‐co‐AA) and P(MA‐alt‐AA) copolymers have sufficiently high antitumor activity, which depends on the amount of hydrogen‐bonding carboxylic groups and their regular distribution in the side chain of functional macromolecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3425–3432, 2006     

Clustering MIT–BIH arrhythmias with Ant Colony Optimization using time domain and PCA compressed wavelet coefficients

In this paper, Ant Colony Optimization (ACO) based clustering analysis of ECG arrhythmias taken from the MIT–BIH Arrhythmia Database is proposed. Both time domain and discrete wavelet transform (DWT) based frequency domain features are used in the analysis. Since the number of wavelet coefficients are huge amount as compared to the time domain parameters, Principal Component Analysis (PCA) based compression is applied on them in order to decrease their number to the number of time domain features. Then, the reduced numbers of frequency parameters are combined with the time domain features, in order to get the total feature sets. Different types of feature sets are tried and the classification results are compared. These are: time domain feature set, frequency domain feature set and the mixture of them. A neural network algorithm is developed in parallel to verify and measure the ACO classifier's success. Moreover, linear discriminant analysis (LDA) is used to show the effect of clustering on the system's results. The method is tested with MIT–BIH database to classify normal beats and five different critical and having vital importance arrhythmia types. Chosen six classes are normal sinus rhythm, premature ventricular contraction (PVC), atrial premature contraction (APC), right bundle branch block (RBBB), ventricular fusion (F) and fusion (f). Comparison results indicate that the mixture feature set gave a better success for the classification.     

A tabu-search based heuristic for the hub covering problem over incomplete hub networks

Hub location problems deal with finding the location of hub facilities and with the allocation of demand nodes to these located hub facilities. In this paper, we study the single allocation hub covering problem over incomplete hub networks and propose an integer programming formulation to this end. The aim of our model is to find the location of hubs, the hub links to be established between the located hubs, and the allocation of non-hub nodes to the located hub nodes such that the travel time between any origin–destination pair is within a given time bound. We present an efficient heuristic based on tabu search and test the performance of our heuristic on the CAB data set and on the Turkish network.     

Soft Matter Technology at KIT: Chemical Perspective from Nanoarchitectures to Microstructures

Bioinspiration has emerged as an important design principle in the rapidly growing field of materials science and especially its subarea, soft matter science. For example, biological cells form hierarchically organized tissues that not only are optimized and designed for durability, but also have to adapt to their external environment, undergo self‐repair, and perform many highly complex functions. Being able to create artificial soft materials that mimic those highly complex functions will enable future materials applications. Herein, soft matter technologies that are used to realize bioinspired material structures are described, and potential pathways to integrate these into a comprehensive soft matter research environment are addressed. Solutions become available because soft matter technologies are benefitting from the synergies between organic synthesis, polymer chemistry, and materials science.     

Template Synthesis of Iminodiacetic Acid Polysiloxane Immobilized Ligand Systems and their Metal Uptake Capacity

Porous solid polysiloxane ligand systems bearing an iminodiacetic acid chelating ligand of the general formula P-IDA (where P- represents [Si-O] _n polysiloxane network and IDA represent an organofunctional group) were achieved in two-step reaction. The first step includes a template synthesis of 3-iodopropylpolysiloxane (P-I) or 3-aminopropylpolysiloxane (P-MA) by hydrolytic polycondensation of TEOS and the corresponding silane agent in the presence of CTAB as a surfactant. The second step includes a modification of 3-iodopropylpolysiloxane with diethyliminodiacetate or 3-aminopropylpolysiloxane with ethylchloroacetate to produce IDA-functionalized polysiloxane ligand systems P-IDA-I & P-IDA-II respectively. It was found that the modified IDA-functionalized polysiloxane ligand systems exhibited higher capacities for uptake of the metal ions (Ni ²⁺, Cu ²⁺ and Pb ²⁺) than those prepared without surfactants.     

Polystyrene Containing Carbinolamine/Azomethine Potentially Useful as Antimicrobial Agent: Synthesis and Biological Evaluation

An investigation of antimicrobial properties of 12 novel modified polymer derived from the condensation reaction of (aminomethyl)polystyrene and four substitute salicylaldehyde (2-hydroxy benzaldehyde, 5-fluoro-2 hydroxy benzaldehyde, 5-fluoro-3-chloro-salicylaldehyde and 5-fluoro-3-methyl-salicylaldehyde) has been carried out and Cr(III) and Ni(II) complexes have been prepared. Modified polymers were characterized by magnetic susceptibility, elemental analyses, and spectral studies. The ¹H NMR and ¹³C NMR spectra analysis of the polymeric carbinolamine/azomethine were determined. In addition, surface morphology and composition were determined by SEM/EDX. Thermo gravimetric analyses of polymers were carried out in nitrogen atmosphere. Antibacterial activities of the polymers attached carbinolamine/azomethine and their complexes were studied by the well-diffusion method against Listeria monocytogenes 4b, Staphylococcus aureus, Escherichia coli, Salmonella typhi H, Brucella abortus, Staphylococcus epidermis sp., Micrococcus luteus, Shigella dysenteria type 10, Bacillus cereus, Pseudomonas putida and antifungal activity against Candida albicans.     

Output-associative RVM regression for dimensional and continuous emotion prediction

Many problems in machine learning and computer vision consist of predicting multi-dimensional output vectors given a specific set of input features. In many of these problems, there exist inherent temporal and spatial dependencies between the output vectors, as well as repeating output patterns and input–output associations, that can provide more robust and accurate predictors when modeled properly. With this intrinsic motivation, we propose a novel Output-Associative Relevance Vector Machine (OA-RVM) regression framework that augments the traditional RVM regression by being able to learn non-linear input and output dependencies. Instead of depending solely on the input patterns, OA-RVM models output covariances within a predefined temporal window, thus capturing past, current and future context. As a result, output patterns manifested in the training data are captured within a formal probabilistic framework, and subsequently used during inference. As a proof of concept, we target the highly challenging problem of dimensional and continuous prediction of emotions, and evaluate the proposed framework by focusing on the case of multiple nonverbal cues, namely facial expressions, shoulder movements and audio cues. We demonstrate the advantages of the proposed OA-RVM regression by performing subject-independent evaluation using the SAL database that constitutes naturalistic conversational interactions. The experimental results show that OA-RVM regression outperforms the traditional RVM and SVM regression approaches in terms of accuracy of the prediction (evaluated using the Root Mean Squared Error) and structure of the prediction (evaluated using the correlation coefficient), generating more accurate and robust prediction models.