Primitive symmetric designs with prime power number of points

In this paper we either prove the non‐existence or give explicit construction of primitive symmetric (v, k, λ) designs with v=p^m<2500, p prime and m>1. The method of design construction is based on an automorphism group action; non‐existence results additionally include the theory of difference sets, multiplier theorems in particular. The research involves programming and wide‐range computations. We make use of software package GAP and the library of primitive groups which it contains. © 2009 Wiley Periodicals, Inc. J Combin Designs 18: 141–154, 2010     

Antibacterial 3-(arylamino)-1-ferrocenylpropan-1-ones: Synthesis, spectral, electrochemical and structural characterization

Syntheses of fourteen new 3-(arylamino)-1-ferrocenylpropan-1-ones have been achieved in good to excellent yields by an aza-Michael addition of different arylamines to acryloylferrocene. The reaction was performed by microwave (MW) irradiation (500 W/5 min) of a mixture of reactants and montmorillonite K-10, without a solvent. The obtained compounds were spectrally and electrochemically (cyclic voltammetry) fully characterized, whereas single-crystal X-ray analysis has been performed for three of them. In a microdilution assay, all of the compounds were shown to have a broad-spectrum effect on Gram-negative and -positive bacteria, although the degree of inhibition varied. A notable activity was observed for all compounds in inhibiting the growth of an important human pathogen Staphylococcus aureus.     

Effect of Induced Transition on the Quantum Entanglement and Coherence in Two-Coupled Double Quantum Dot System

Studying quantum properties in solid-state systems is a significant avenue for research. In this scenario, double quantum dots appear as a versatile platform for technological breakthroughs in quantum computation and nanotechnology. This work inspects the thermal entanglement and quantum coherence in two-coupled DODs, where the system is exposed to an external stimulus that induces an electronic transition within each subsystem. The results show that the introduction of external stimulus induces a quantum level crossing that relies upon the Coulomb potential changing the degree of quantum entanglement and coherence of the system. Thus, the quantum properties of the system can be tuned by changing the transition frequency, leading to the enhancement of its quantum properties.     

Enhanced Fibril Fragmentation of N‐Terminally Truncated and Pyroglutamyl‐Modified Aβ Peptides

N‐terminal truncation and pyroglutamyl (pE) formation are naturally occurring chemical modifications of the Aβ peptide in Alzheimer's disease. We show herein that these two modifications significantly reduce the fibril length and the transition midpoint of thermal unfolding of the fibrils, but they do not substantially perturb the fibrillary peptide conformation. This observation implies that the N terminus of the unmodified peptide protects Aβ fibrils against mechanical stress and fragmentation and explains the high propensity of pE‐modified peptides to form small and particularly toxic aggregates.     

Reaction of 3-nitro- and 3-diethylphosphonocoumarin with phenacyl bromide. X-ray molecular structure of 3-nitro-3,4-phenacylidenecoumarin

3-Nitro- and 3-diethylphosphonocoumarins 4a,b react with phenacyl bromide stereoselectively under phase-transfer conditions, in the presence of a base and of a transfer agent, to give the cyclopropyl derivatives 6 and 7 in good yields. A mechanistic explanation is given for the stereoselectivity of the reaction. The X-ray molecular structure of compound 6a is also presented.     

One (96,20,4)-symmetric Design and related Nonabelian Difference Sets

New (96,20,4)-symmetric design has been constructed, unique under the assumption of an automorphism group of order 576 action. The correspondence between a (96,20,4)-symmetric design having regular automorphism group and a difference set with the same parameters has been used to obtain difference sets in five nonabelian groups of order 96. None of them belongs to the class of groups that allow the application of so far known construction (McFarland, Dillon) for McFarland difference sets.AMS lassification: 05B05     

Absolute configuration of (−)‐4‐(3,4‐di­chloro­phenyl)‐4‐(2‐pyridyl)­butanoic acid: essential information to determine crucial steric features of ­arpromidine‐type hist­amine H2 receptor agonists

The structural information gained from the study of the chiral building block (R)‐(?)‐4‐(3,4‐di­chloro­phenyl)‐4‐(2‐pyridyl)­butanoic acid–l ‐(?)‐ephedrine [methyl(1‐hydroxy‐1‐phenyl­prop‐2‐yl)ammon­ium 4‐(3,4‐di­chloro­phenyl)‐4‐(2‐pyrid­yl)but­an­oate], C₁₀H₁₆NO⁺·C₁₅H₁₂Cl₂NO₂^?, can be used to deduce the absolute configuration of highly potent arpromidine‐type hist­amine H₂ receptor agonists, as the chiral butanoic acid can be converted to (R)‐(?)‐3‐(3,4‐di­chloro­phenyl)‐3‐(2‐pyridyl)­propyl­amine and to the corresponding R‐configured arpromidine analogue.     

Aero-Acoustic Optimisation of Airflow Components in Gas Turbines

There is always a great interest in the improvement of the efficiency of gas turbines. This requires the reduction of energetic losses like pressure losses induced by vortices, turbulence and secondary flow. In the current investigation, effects caused by aero-acoustic oscillation are of interest. The possibility to control these effects or to make them usable has several advantages, for example reducing pressure losses, reducing noise, and influencing the heat transfer and charging effects. This concerns potentially oscillatory flow systems in gas turbines like pipes, cavities and annuli. In particular annuli can not be considered theoretically using one-dimensional pipe acoustic. The start of oscillation occurs due to turbulent shear stress, solid oscillating surfaces and time fluctuating pressure fields as well as thermal stimulation. This study focuses on the impact of aero-acoustic oscillation caused by shear stress and rotating pressure fields on the through flow. A numerical study of axial, radial and circumferential acoustic eigen-modes and a time harmonic analysis have been done with several boundary conditions. The achieved results have to be proved in a further experiment. An improvement in the aero-acoustical design of gas turbine flow components will be possible thanks to the results gained from both the numerical study and planned experiment. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rheological behaviour of VPVC/RPVC Blends

Different blends of virgin pipe‐grade PVC and PVC recyclate according to their rheological behaviour, processability and mechanical properties have been investigated. Our results showed that an easy and simple way to improve processability of PVC compounds for pipes was to blend them with recycled PVC obtained from postconsumed oil bottles, which indicated very good processing behaviour. Energy and time savings up to 80% depending on the amount of the added recyclate without depressing the mechanical properties have been noticed. In addition, lower processing temperature has been achieved.     

Determination of elongational viscosity of polymer melts by RME and Rheotens experiments

Several linear (LLDPE, HDPE, PS) and long-chain-branched (LDPE, PP) polymer melts were investigated by an elongational rheometer (RME Rheometrics) and by Rheotens (Göttfert). The Molecular Stress Function (MSF) theory is briefly reviewed and used to extrapolate the steady-state elongational viscosity. To evaluate Rheotens experiments, a new process model is introduced which assumes that the elongational viscosity in the Rheotens test is a function of the draw ratio only. The apparent elongational viscosities extracted from Rheotens curves are found to lie in between the steady-state elongational viscosity and three times the shear viscosity.