Study of the stability of the fermionic instanton solutions by the scale index method

In the last years, there has been great interest to the formulation and application of wavelet transformation in variety of fields to investigate the characteristics of dynamical systems. Recently, a method based on the scalogram analysis of the continuous wavelet transform, the scale index has been proposed to measure aperiodicity and determine the transitions from aperiodic behaviour to periodic behaviour in nonlinear dynamical systems. In this work we test the scale index method by performing the analysis of the deterministic behaviour of the fermion-like two-dimensional Akdeniz–Smailagic instanton solution in Thirring Model. We show that the scale index method can also be considered to detect the periodic behaviours of the fermion-like instanton solutions.     

Investigation of the effect of dual-size coatings on the hydrophobicity of cotton surface

A series of silica nanoparticles with two different length scales were introduced onto the cotton substrates to study the correlation between the surface structure and observed hydrophobicity. SiO₂ nanoparticles of 7, 12, 20, and 40 nm in size were individually functionalized using 3-aminopropyl triethoxysilane or 3-glycidoxypropyltrimethoxysilane. Amino functionalized silica nanoparticles were durably attached to the cotton surface that was previously treated with epichlorohydrin. By depositing an additional layer of epoxy modified silica nanoparticles, a dual-size hierarchical coating was obtained. It was found that the order of deposition of particles to develop dual-size coatings determines the surface roughness, hydrophobicity and the amount of silica loaded on the cotton substrate. Deposition of the bigger nanoparticles on top of smaller ones resulted in rougher surfaces, higher hydrophobicity and higher amount of silica loading onto the cotton surface. A strong correlation between the size ratio of deposited nanoparticle combinations and the amount of silica loading was observed. It was found that there is also a direct relationship between the surface roughness and the hydrophobicity of the samples generated. Based upon these correlations, it is now possible to tune surface roughness and subsequent wettability by controlling the sizes of the dual-type nanoparticle layers.     

Bis (trimethylsilyl) thioketone

Tris (trimethylsilyl) methylsulphenylbromide undergoes facile Me₃ SiBr elimination to give bis (trimethylsilyl) thioketone.     

Preparation and Optical Characterization of Sol-Gel Deposited Pb(Zr0.45Ti0.55)O3 Films

Homogeneous crack-free lead zirconate titanate (Pb(Zr_0.45Ti_0.55)O₃: PZT 45/55) films were prepared by a chemically modified sol-gel process using lead acetate trihydrate, zirconium n-propoxide, and titanium isopropoxide precursors. The coating solutions were modified by the addition of diethanolamine. Single and multilayer films were deposited with a 2000 rpm spin rate on fused silica and MgO(100) substrates. Multiple spin coating with an intermediate heat treatment in air at 400°C for 3 min between coatings was performed to obtain films up to 2 m in thickness. The formation of the tetragonal perovskite structure was found to depend on the intermediate firing temperature, final annealing temperature, and annealing time. A 650°C rapid thermal annealing treatment in oxygen was required to crystallize the PZT film into the perovskite structure. The films were characterized using optical spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermo-gravimetry and differential scanning calorimetry (TG-DSC). The optical constants of the PZT films were evaluated from spectral transmittance and reflectance measurements. Optical constants are presented over the visible and near infrared region.     

Synthesis, characterization and nonlinear absorption of novel octakis-POSS substituted metallophthalocyanines and strong optical limiting property of CuPc

In this study, the preparation of some novel metallophthalocyanine (MPcs) complexes substituted with octakis(mercaptopropylisobutyl-POSS) functional group was achieved. By the reaction of [1-(3-mercapto)propyl-3,5,7,9,11,13,15-isobutylpentacyclo[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane 1 with 4,5-dichloro-1,2-dicyanobenzene 2 in THF as the solvent in the presence of K2CO3 as the base, the phthalonitrile derivative 3 was synthesized. Compound 3 reacted with CoCl2 x 6H2O in ethylene glycol to furnish a novel cobalt(II) phthalocyanine . The tetramerization of 3 with urea and CuCl in the absence of solvent gave the novel Cu(II) phthalocyanine 4; while with Zn(OAc)2 x 2H2O in dry DMF gave the novel zinc(ii) phthalocyanine 6. The structures of the target compounds were confirmed by elemental analysis, UV/VIS, IR, MALDI-TOF MS and 1H NMR spectra. Nonlinear absorptions of MPcs in chloroform solution were investigated by using Z-scan measurement technique with 4 ns pulses at 532 nm wavelength. While CuPc 5 showed very high nonlinear absorption, MPcs 4 and 6 did not show considerable nonlinear absorption. Investigations of optical limiting properties of 5 revealed that this material is a very good candidate for optical limiting applications.     

Siliciumorganische verbindungen : LIX. 1,5-Bis(trimethylsilyl)-naphthalin

The addition vs. deprotonation ratio in the reaction of nitriles with n-PrMgBr is increased by complexation of the Grignard reagent with LiClO₄. For nitriles having moderately labile α-hydrogen atoms the deprotonation reaction is almost completely suppressed; but for nitriles having very labile α-hydrogen atoms (CH₃ CN, PhCH₂CN) yields in ketones are increased from 2 to 10–20%.     

In memoriam Dr. Werner Heilig (1933-2003)

A dear friend and colleague, Dr. Werner Heilig, died last December (2-12-2003) after a short and painful illness. Dr. Heilig was well known and respected in the world-wide shock wave family due to his contributions to our understanding of shock reflection and interaction phenomena.Dr. Werner Heilig was born in Freiburg in January 1933. He received his matriculation from the Kepler-Gymnasium in Freiburg in 1953 and immediately thereafter started studying Mathematics and Physics at the Albert-Ludwigs University in Freiburg, from which he graduated in early 1958. After graduation he took an extra two years of pedagogy studies in order to qualify as a teacher of mathematics in a high school (Gymnasium), and indeed he served as a mathematics teacher in a Gymnasium from January 1961 until March 1964. A big change in his professional career took place in April 1964 when he joined the Ernst-Mach-Institute in Freiburg. Simultaneously with his new work at the Ernst-Mach-Institute he was teaching every morning from 8 to 9 oclock mathematics at the St. Ursula Gymnasium, walking to his new place of work immediately after teaching. At that time he also started his PhD studies at the University of Karlsruhe. The title of his thesis was: Theoretical and experimental studies of shock wave interaction with a sphere and a cylinder (Theoretische und experimentelle Untersuchungen zur Beugung von Stosswellen an Kugeln und Zylindern). Dr. Heilig continued this investigation, as well as other related topics, throughout his professional career. His PhD research was co-supervised by Professors Zierep and Oertel and the degree was granted in July 1969. In his dissertation he also discussed the transition criteria from regular to Mach reflection for shock wave reflection from wedges or cylinders (as is evident from Fig. 13 in his dissertation). However, since his results were not published in a reviewed journal, he has not received the credit he duly deserved.After receiving his PhD degree, Dr. Heilig started building his reputation as a careful and reliable researcher in gas dynamics, focusing his attention on shock wave reflection from wedges, shock and blast wave propagation in ducts and tunnels, and shock wave interaction with boundaries of various shapes. Until the mid 1980s most of his work was experimental, that being the strong side of the Ernst-Mach-Institute at the time. In early 1984 Dr. Heilig was assigned to introduce CFD to the Ernst-Mach-Institute. This move forced him to go from being an experimentalist to a CFD researcher, which proved to be very demanding. However, Dr. Heilig did it well, relying on his mathematical skills earned as a student in the 1950s. From the mid 1980s on he was the head of the gas dynamics group at the Ernst-Mach-Institute, and in January 1997 he became the vice-director of the Ernst-Mach-Institute, a position he held until his retirement in February 1998. Once free from formal obligations, he avidly continued his research activities, submitting proposals for (and receiving) research contracts, and writing the chapter on shock wave propagation in ducts and tunnels in the Handbook of Shock Waves which was published in 2000 by Academic Press.I first met Dr. Heilig when he attended the 12th Shock Waves Symposium, which was held in Jerusalem in July 1979, and we kept in touch ever since. We jointly proposed and conducted research on various aspects of shock wave interaction with bodies of numerous shapes, and co-authored several papers based on the results of our joint-research. It was a pleasure working with Dr. Heilig; he was a very careful scientist who was never fazed by challenging problems. His untimely death has shocked and saddened us all. May the emptiness left in our hearts by his departure be filled by gentle memories of Dr. Werner Heilig, an outstanding researcher, colleague and friend.Published online: 18 February 2005[/PUBLISHED]     

Calorimetric studies on renaturation by CaCl2 addition of metal-free α-amylase from Bacillus Licheniformis (BLA)

In our previous work we characterized the Ca binding properties of BLA by analysis of Ca-induced renaturation in the presence of urea. In this study we focused on the renaturing capacity of CaCl₂ in the absence of urea and analysed the apparent thermodynamic and kinetic properties of renatured BLA by DSC, CD and dynamic light scattering (DLS) measurements. Ca-free protein did not return fully to the native state even after extensive dialysis against high concentrations of calcium. Thus Ca removal provokes changes in protein structure that can not be reversed completely even by addition of an excess of calcium. However, activity studies performed simultaneously with the DSC experiments showed a significant return of enzymatic activity despite the failure of complete return of native stability. This conclusion is in excellent agreement with findings of Machius et al. who suggested on the basis of their X-ray studies that it is not possible to remove CaI and CaII without introducing significant structural changes. It is important to note that all unfolding reactions of metal-free, partially renatured and native protein were found to be irreversible. Therefore the DSC transition curves were fitted using irreversible transition models. It turned out that the apparent heat capacity profiles of partially renatured BLA could be well represented by superposition of two irreversible processes each following the two-state irreversible model.