[en] A new method based on absolutely localized molecular orbitals (ALMOs) is proposed to measure the degree of intermolecular electron density delocalization (charge transfer) in molecular complexes. ALMO charge transfer analysis (CTA) enables separation of the forward and backward charge transfer components for each pair of molecules in the system. The key feature of ALMO CTA is that all charge transfer terms have corresponding well defined energetic effects that measure the contribution of the given term to the overall energetic stabilization of the system. To simplify analysis of charge transfer effects, the concept of chemically significant complementary occupied-virtual orbital pairs (COVPs) is introduced. COVPs provide a simple description of intermolecular electron transfer effects in terms of just a few localized orbitals. ALMO CTA is applied to understand fundamental aspects of donor-acceptor interactions in borane adducts, synergic bonding in classical and nonclassical metal carbonyls, and multiple intermolecular hydrogen bonds in a complex of isocyanuric acid and melamine. These examples show that the ALMO CTA results are generally consistent with the existing conceptual description of intermolecular bonding. The results also show that charge transfer and the energy lowering due to charge transfer are not proportional to each other, and some interesting differences emerge which are discussed. Additionally, according to ALMO CTA, the amount of electron density transferred between molecules is significantly smaller than charge transfer estimated from various population analysis methods

[en] In order to improve the properties of melamine foam (MF), a new polyimide–melamine composite foam (PI– MF) was prepared by microwave irradiation foaming with polyimide microspheres (PI) as a modifier and melamine resin as matrix. The micromorphology, temperature resistance, flame retardant and smoke suppression properties and mechanical properties of the foam were characterized and tested. It was observed by SEM that PI microspheres were closely connected to the skeleton of the MF, FT-IR characterization proved the existence of polyimide in the PI–MF. When the amount of PI microspheres is 30%, the overall performance of PI–MF is better. The temperature of 5% weight loss (T5%) is 326.02°C, the limit oxygen index is 35.48%, the maximum smoke density is 9.21%, the smoke density rank is 5.43, the formaldehyde content is 46.65 mg kg^-1 , and the elongation at break of the foam is 35.89%. The introduction of PI microspheres has a good effect on the modification of the thermal stability, flame retardant an^d smoke suppression properties, and mechanical properties of the MF, and has broadened the application range of polyimide. It also provides a new method for the modification of MF. (author)

[en] Experimental results of relative radii of microparticles determination by the analysis of scattered on particles radiation are presented. Due to the monotonous dependence of the indicatrix of particle scattered radiation on particle radius at a specific angle, it becomes possible to determine the relative radii of particles in cloud of particles by one camera picture. Radii of three types of monodisperse powders of melamine formaldehyde particles with known sizes were analyzed by means of Mie theory. The results showed the possibility to determine relative radii of particles to each other in suspended clouds of particles. (paper)

[en] Measurements are reported for the radiation pressure and gas drag forces acting on a single melamine-formaldehyde microsphere. The radiation pressure force coefficient q, which would be unity if all incident photons were absorbed, has the value q=0.94±0.11. For argon, the Epstein gas drag force coefficient δ, which would be unity if impinging molecules underwent specular reflection, has the value δ=1.26±0.13 as measured with our single-particle laser acceleration method, or δ=1.44±0.19 as measured using the vertical resonance method

[en] Engineering and tuning multi-component supramolecular self-assemblies on surfaces is one of the challenges of nanotechnology. We use scanning tunneling microscopy to investigate the influence of molecular ratio on the self-assembly of PTCDA-melamine structures on Au(111)-(22x√3). Our observations reveal that three different chiral supramolecular networks having a PTCDA:melamine ratio of 3:2, 1:2, 1:4 can be selectively created by tuning the ratio of molecules deposited on the surface. The 1:2 ratio network having melamine in excess has been observed previously but the 1:4 network has not yet been reported. In comparison, the multi-component 3:2 network having PTCDA in excess is a completely new structure.

[en] The influence of a plasma environment on melamine formaldehyde particles is studied. High-precision measurements of the vertical confinement frequency with a phase-resolved resonance method indicate that the particle mass is affected in two ways: the deposition of sputtered material at the particle leads to a mass gain, whereas the outgassing of water causes a mass loss.

[en] Radiation sensitive polymers comprising from about 1 to 100 mole % of a polymerized maleimide monomer consisting of a hydrocarbon group having from 2 to 20 carbon atoms, preferably a bridged hydrocarbon group having from 6 to 10 carbon atoms and from 0 to about 99 mole % of at least one additional polymerized ethylenically unsaturated monomer are described. The polymers are soluble in organic solvents, possess desirably high glass transition temperatures and are capable of undergoing a photochemical reaction to yield polymers having isocyanate and oxy-substituted cyclopropane moieties which are capable of crosslinking in the presence of active hydrogen-containing compounds. The polymers are useful in radiation sensitive compositions and elements containing same

[en] Melamine (2,4,6 triamino-s-triazine) is a starting material for the manufacture of polymeric resins, thermosetting plastics, and housewares. The uptake, bioaccumulation and elimination of uniform triazine-labelled [¹⁴C]-melamine was determined in fingerling rainbow trout. Uptake into tissues was monitored in a static exposure system (water conc. = 89-91 ppb) until the steady state of melamine was reached in the fish tissues. The bioconcentration factor (BCF) was determined for muscle and viscera at the steady state. Uptake of [¹⁴C] melamine was low for both muscle and viscera, achieving levels only as high as 10 ppb in either compartment. Steady state was reached in the viscera within 48 hours and in muscle after only 16 hours. The BCF for muscle (0.03 to 0.11) and viscera (0.5-0.11) was less than unity, indicating a propensity of this compound to resist partitioning into the fish or fish tissues. This may be related to high hydrophilicity or a strong solute-solute interaction of malamine. In depuration studies, the half-life of malamine was found to be relatively short +1/2 viscera = 8.06 found to be relatively short (+1/2 muscle = 8.79 hrs), consistent with the rapid achievement of steady state and low BCF

[en] We present the results of experimental researches of the behavior of dust structures formed by particles with different properties (material densities, sizes, forms) under the external influences (applied magnetic field). Only monolayers in structures of a complex geometrical form are used in the experiments. The parameters that can affect the structure and the properties of a glow discharge are selected. The strength of a magnetic field, at which the rotation direction changes the sign, depends linearly on the gas pressure and is independent of the discharge current.

[en] Dusty plasma supports the formation of various dynamical structures including linear and nonlinear waves, wakes, voids, etc. under different discharge conditions. Among these, void is a spectacular dust free empty domain in the dust cloud with a characteristic sharp boundary maintained by the balance between two counteracting force on the dust particles. In the present investigation, we report the formation of highly stable and reproducible void in the cathode sheath region of a specially designed DC dusty plasma experimental setup having circular disk shaped anode and a tray shaped cathode attached with a circular confinement ring. Initially, the glow discharge plasma using Argon gas at a pressure of 0.12 mbar has been produced between anode and grounded cathode by applying 280 V. Then mono-dispersed Melamine Formaldehyde (MF) dust particles having diameter of 10.66 µm are introduced into the plasma using a dust dispenser. While falling down, the dust particles get negatively charged and trapped inside the confinement rings subsequently forms stable strongly coupled coulomb crystal. Increasing the pressure, the homogeneous Coulomb crystal forms void at the center of the dust cloud. The void radius increases from 1.5 mm to 9.0 mm over the pressure range of 0.12 mbar to 0.14 mbar. Further, it is found that the inter-particle distance near the edge of the void decreases with the increase in pressure. The void diameter obtained experimentally over the discharge condition is then compared with the analytical model associated with force balance condition on the dust particles and found a good agreement between them. (author)