The external demagnetizing factor and the static characteristic loop

In this paper a proposal is put forward for the calculation of the shearing factor N_S linked to the well known, demagnetization coefficient N_D, from the data of a sheared saturation loop, obtained by a non-toroidal, open circuit hysteresis measurement. Following that, the paper illustrates the way to recover the real static loop data from an open circuit, measured data. The proposal is based on the hyperbolic model. The proposed method was illustrated on the tests carried out on two closed and open toroidal samples, mimicking the demagnetization effect of the open circuit VSM measurement, made of NO Fe–Si electrical steel sheets. These test results, presented here, agree very well with the calculated results, based on the hyperbolic modeling.     

Ring Enlargement of Phospholenes to Phosphorin Derivatives Through Dichlorocarbene Adducts

Abstract

The ring enlargement of ready available phospholenes by dichlorocarbene addition to the double bond and subsequent opening of the cyclopropane ring is discussed. Adductcs of phospholene wih dichlorocarbene (2)can be synthetised under liquid-liquid phase transfer circumstances. The simplest bray to open the cyclopropane ring in the adducts is thermal transformation giving the two regioisomers of the appropriate dihydrophosphorin (3). Electrophilic reagents can also be used for -the opening of the cyclopropane ring. On heating with silver nitrate in water or in alcohols the adducts are transformed to the -two rcgioisomers of the hydroxy- or the alkoxy -tetrahydrophosphorins, respectively (4, Y=H, CH₃ C₂H₅) In the reaction of adducts with mercury acetate-acetic acid the corresponding acetoxy-derivatives (4, Y=CH₃CO) are formed. The Friedl Crofts reaction of the adducts with benzene iii the presence of aluminium trichloride yields diarylated product.     

DIHALOCARBENE ADDITION TO ARYLSUBSTTTUTED VINYL PHOSPHATES UNDER PHASE TRANSFER CATALYTIC CONDITIONS

Abstract

Dihalocarbene addition to aryl-substituted vinyl phosphates was carried out both in solid-liquid and in liquid-liquid two phase systems. The dihalocyclopropane adducts of vinyl phosphates could be obtained in better yield using dihalocarbenes generated by the latter method and no hydrolysis of the vinyl phosphate and of the adduct occurred under these circumstances. Eighteen new vinyl phosphate-dihalocarbene adducts were synthetized and characterized.     

Reaction of Trialkyl Phosphites with α,β-Unsaturated Carbonyl Compounds

Abstract

Reaction of trialkyl phosphites 1 with α,β-unsaturated oxo-compounds 2 gives oxaphospholenes 3 or/and two types of Arbuzov products, γ-keto-phosphonates 4 and alkyl-enol-ethers 5.     

Quasiliving Carbocationic Polymerization. XV. Forced Ideal Copolymerization of Isobutylene-lsoprene

Forced ideal carbocationic copolymerization of isobutylene and isoprene has been achieved by continuous addition of monomer mixtures of different compositions to cumyl chloride/TiCl₄ charges at -50°C. The overall rate of copolymerization could be kept equal to that of addition rate with up to 10 mol% isoprene in the mixed monomer feed. In this monomer concentration range the composition of the copolymer was identical to that of the feeds. At higher diene concentrations in the feed, chain transfer to monomer and other side reactions (intramolecular cyclization, gel formation) could not be completely avoided. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at 10 mol% isoprene concentrations in the feed (i.e., in the quasiliving range). According to ¹H-NMR and ¹³C-NMR spectroscopy, the products are random copolymers.     

Simple,Safe, Large Scale Synthesis of 5-Arylmethyl-2,2-dimethyl-1,3-dioxane-4,6-diones and 3-Arylpropanoic Acids

Reaction of aryl aldehydes with Meldrum's acid 2 in the presence of formic acid and triethylamine gives 5-arylmethyl Meldrum's acid derivatives 4 at room temperature, whereas at 80–100°C 3-arylpropanoic acids 5 are formed.     

Synthesis of PAF,an Antifungal Protein from P. chrysogenum,by Native Chemical Ligation: Native Disulfide Pattern and Fold Obtained upon Oxidative Refolding

The folding of disulfide proteins is of considerable interest because knowledge of this may influence our present understanding of protein folding. However, sometimes even the disulfide pattern cannot be unequivocally determined by the available experimental techniques. For example, the structures of a few small antifungal proteins (PAF, AFP) have been disclosed recently using NMR spectroscopy but with some ambiguity in the actual disulfide pattern. For this reason, we carried out the chemical synthesis of PAF. Probing different approaches, the oxidative folding of the synthetic linear PAF yielded a folded protein that has identical structure and antifungal activity as the native PAF. In contrast, unfolded linear PAF was inactive, a result that may have implications concerning its redox state in the mode of action.     

Effect of fullerene C60 branching center on the conformational properties of arms and the structure of star-shaped polystyrenes in solutions

The effect of the fullerene C₆₀ branching center on the structure and conformation of star-shaped polystyrenes with different arm lengths at equal concentrations in deuterotoluene (c = 1 g/dL) is studied by the method of small-angle neutron scattering. The analysis of neutron scattering for linear PS precursors and stars (the molecular masses of arms are ～7 × 10³ and ～4 × 10⁴) shows that the stars have ～6 arms that form a dense excluded-volume zone around a core inaccessible to other macromolecules. In low-molecular-mass stars (the molecular mass of the arm is ～7 × 10³), strengthening of the static rigidity of arms is observed; as a result, the size of arms increases relative to the size of free PS chains in a good solvent. At a greater length of arms (M ～ 4 × 10⁴), their individual properties are weakly pronounced in the correlation spectrum of the arm because of the interpenetration of arms, thereby demonstrating similarity in the structures of stars and their linear analogs. The mechanism controlling the effect of fullerene C₆₀ on the conformations of stars via solvent structuring by fullerene is discussed.     

Low volatile monofunctional reactive diluents for radiation curable formulations

In the last decades the importance of UV curable formulations has increased continuously. Their fast curing speed, solvent-free polymerization conditions, and the formation of hard and highly crosslinked photopolymer networks represent major benefits. Commercial UV resins generally consist of multi-functional vinyl oligomers, photoinitiators, additives, and reactive diluents. Mono- and multi-functional reactive diluents serve as thinners to lower the overall resin viscosity and to improve processability. However, many monofunctional reactive diluents like isobornyl (meth)acrylate or benzyl (meth)acrylate exhibit high volatility, often already at room temperature. This causes adverse effects such as unpleasant odor, potential health risks, and changing resin composition during processing. A new group of monomers that show high potential for replacing traditional highly volatile reactive diluents are salicylate (meth)acrylates. In this work, salicylate-based thinners are synthesized, polymerized, and characterized with respect to their viscosity, volatility, thermal stability, photoreactivity, and thermomechanical properties of their homopolymers. Additionally, a first example of their diluting effect in a highly viscous difunctional polyester urethane methacrylate is demonstrated with 30 wt% of a cycloaliphatically and an aromatically substituted salicylate methacrylate. The polymers of the diluted resin exhibit similarly high glass transition temperatures of 110 and 126 °C, which are in the range of the polymers of the undiluted resin.     

Large Cross‐Free Sets in Steiner Triple Systems

A cross‐free set of size m in a Steiner triple system is three pairwise disjoint m‐element subsets such that no intersects all the three ‐s. We conjecture that for every admissible n there is an STS(n) with a cross‐free set of size which if true, is best possible. We prove this conjecture for the case , constructing an STS containing a cross‐free set of size 6k. We note that some of the 3‐bichromatic STSs, constructed by Colbourn, Dinitz, and Rosa, have cross‐free sets of size close to 6k (but cannot have size exactly 6k). The constructed STS shows that equality is possible for in the following result: in every 3‐coloring of the blocks of any Steiner triple system STS(n) there is a monochromatic connected component of size at least (we conjecture that equality holds for every admissible n). The analog problem can be asked for r‐colorings as well, if and is a prime power, we show that the answer is the same as in case of complete graphs: in every r‐coloring of the blocks of any STS(n), there is a monochromatic connected component with at least points, and this is sharp for infinitely many n.