Determination of the debris produced from poly(ethylene terephthalate) during KrF excimer laser ablation

Pulsed UV laser beams, which are widely used in the processing of polymers, have many advantages because their photon energy is higher than the binding energy of polymers. Fabricating polymers with a UV laser process is faster, cleaner, and more convenient than with other processes. Nevertheless, some problems occur in the precision microprocessing of polymers. For example, the formation and deposition of surface debris, which is produced from the breakdown of either polymer chains or radical bonds.To determine the formation and origin of surface debris, a KrF excimer laser beam (248 nm) was used in the processing of poly(ethylene terephthalate) (PET). The investigation of the debris formation was facilitated by UV-vis spectroscopy, ATR FT-IR spectroscopy, and NMR spectroscopy. The UV-vis absorption peak indicates that the primary chromophore in the PET is benzoate. Furthermore, because benzoate causes the primary absorption, the absorbed energy is transferred by heat generation to an unsaturated ester. The ATR FT-IR spectrometer measurements show that the phenyl systems in the benzoate are demolished by ablation. This phenomenon indicates that the photochemical reaction causes the benzoate bonds to break down, and this breakdown in turn causes the carbonization to leave debris on the PET.     

Non-conservation of quasiparticles

An adequate canonical transformation of the hamiltonian permitted the full observance of the specific Pauli commutation relations and the elimination of the main quasiparticle non-conservative term. This will allow a correct treatment of the kinematic part of the interaction in many problems.     

Optical electron transitions in a two-dimensional disordered semiconductor

The frequency dependence of the light absorption coefficient associated with electron transitions between states of strong and weak localization is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 22–24, November, 1982.One of us (V. L. Bonch-Bruevich) is grateful to Dr. M. Pepper for sending a preprint.     

On some problems of analysis of isotropic antiferromagnets

An equivalent Hamiltonian method for the analysis of isotropic antiferromagnets is proposed. The Hamiltonian does not contain the terms corresponding to the processes of non-conservation of spin waves and gives the possibility to perform the calculations with a limited and controlled error. The high as well as the low temperature analysis of the system was carried out with the help of the equivalent Hamiltonian. Some results are compared with those of the u?v transformation method.     

Champs affines

The purpose of this work is to introduce a notion of affine stacks, which is a homotopy version of the notion of affine schemes, and to give several applications in the context of algebraic topology and algebraic geometry. As a first application we show how affine stacks can be used in order to give a new point of view (and new proofs) on rational and p-adic homotopy theory. This gives a first solution to A. Grothendieck’s schematization problem described in [18]. We also use affine stacks in order to introduce a notion of schematic homotopy types. We show that schematic homotopy types give a second solution to the schematization problem, which also allows us to go beyond rational and p-adic homotopy theory for spaces with arbitrary fundamental groups. The notion of schematic homotopy types is also used in order to construct various homotopy types of algebraic varieties corresponding to various co-homology theories (Betti, de Rham, l-adic, ...), extending the well known constructions of the various fundamental groups. Finally, just as algebraic stacks are obtained by gluing affine schemes we define $$ \infty $$-geometric stacks as a certain gluing of affine stacks. Examples of $$ \infty $$-geometric stacks in the context of algebraic topology (moduli spaces of dga structures up to quasi-isomorphisms) and Hodge theory (non-abelian periods) are given.     

Synthesis, structure and dioxygen reactivity of a bis(micro-iodo)dicopper(I) complex supported by the [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine ligand

The air-sensitive bis(micro-iodo)dicopper(I) complex 1 supported by [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine (L) has been prepared by treating copper(I) iodide with L in anhydrous THF. Compound 1 crystallizes as a dimer in space group C2/c. Each copper(I) center has distorted tetrahedral N2I2 coordination geometry with Cu-N(pyridyl) distances 2.061(3) and 2.063(3) A, Cu-I distances 2.6162(5) and 2.7817(5) and a Cu...Cu distance of 2.9086(8) A. Complex 1 is rapidly oxidized by dioxygen in CH2Cl2 with a 1 : 1 stoichiometry giving the bis(micro-iodo)peroxodicopper(II) complex [Cu(L)(micro-I)]2O2 (2). The reaction of 1 with dioxygen has been characterized by UV-vis, mass spectrometry, EPR and Cu K-edge X-ray absorption spectroscopy at low temperature (193 K) and above. The mass spectrometry and low temperature EPR measurements suggested an equilibrium between the bis(micro-iodo)peroxodicopper(II) complex 2 and its dimer, namely, the tetranuclear (peroxodicopper(II))2 complex [Cu(L)(micro-I)]4O4 (2'). Complex 2 undergoes an effective oxo-transfer reaction converting PPh3 into O=PPh3 under anaerobic conditions. At sufficiently high concentration of PPh3, the oxygen atom transfer from 2 to PPh3 was followed by the formation of [Cu(PPh3)3I]. The dioxygen reactivity of 1 was compared with that known for other halo(amine)copper(I) dimers.     

Synthesis of new amphiphilic dendrons bearing aliphatic hydrocarbon surface sectors and a monocarboxylic or dicarboxylic acid focal point

[structure: see text]. A new series of amphiphilic G1-G3 dendrons containing purely aliphatic hydrocarbon dendritic surface sectors and one or two carboxylic acid group(s) at the focal point was synthesized in good yields. The key branching steps involve diallylation reactions of diethyl malonate or Meldrum's acid. These dendrons are highly soluble in hexane despite having highly polar carboxylic acid groups at the focal point.     

Water and oil signal assignment in low-moisture mozzarella as determined by time-domain NMR T2 relaxometry

A time-domain ¹H nuclear magnetic resonance relaxometry method was elaborated for the rapid microstructural characterization of mozzarella cheese. For this purpose, there is a strong need to know how the experimentally determined T₂ relaxation time distribution can be related to specific constituents in mozzarella. In this study, a detailed investigation is offered for fresh and aged low-moisture mozzarella cheese, often applied as a pizza cheese, by application of both a conventional Carr–Purcell–Meiboom–Gill (CPMG) sequence and a free-induction decay CPMG (FID-CPMG) sequence. The relaxation behavior was further elucidated by addition of deuterium oxide and by mild heat treatment of samples. The relaxation times of water protons in mozzarella were found to range from a few microseconds to some tens of milliseconds (in aged mozzarella) or to about hundred milliseconds (in fresh mozzarella). The upper limit of the T₂ distribution can even be extended to the seconds range upon releasing water protons from the mozzarella matrix using a mild heat treatment or upon addition of deuterated water. Both stimuli also provided evidence for the absorption of water into the cheese matrix. The potential release and uptake of water demonstrated that mozzarella acts as a very dynamic system during production and storage. The detected differences in the behavior of the water fraction between fresh and aged low-moisture mozzarella might be utilized to study the influence of either production and/or storage conditions on the cheese ripening process.     

Random close packing of spheres in a round cell

The paper describes the method of construction of cells containing large numbers (10⁵-10⁶) of close packed spheres, ranging in packing fractions from 0.2 to 0.60. The cells are constructed in a round form, utilizing varying surface curvature to prevent ordered packing. The properties of the cells are described by a series of distributions: (i) polar angle of contact points, (ii) maximum displacement of loose spheres, (iii) and Voronoi volumes for individual spheres. The cells of varying density appear to show the liquid-to-solid transition. All cells described here contain loose spheres. It is proposed that cells with zero loose spheres are ideal amorphous solids. Ideal amorphous solids are characterized by a number of elements, described herein.