Structure of thin block copolymer films studied by X-ray reflectivity

Summary X-ray reflectivity may be used to determine the internal structure of thin polymer films. An electron density difference of 10% for polystyrene and polyisoprene is sufficient to distinguish between a random distribution of lamellae, complete orientation parallel to the substrate surface and a surface induced formation of lamellae. The disappearance of the lamellar Bragg-peaks, with heating of the film, shows the transition into the disordered state.     

X-ray diffraction study of 'side-on fixed' homopolysiloxanes from nematic to smectic C phases

The X-ray patterns for the nematic phase in a series of side-on fixed polysiloxanes show different kinds of diffuse elements which imply complex short range ordering. A systematic structural study of the evolution of the patterns versus two molecular parameters, namely the spacer length and the length of the terminal aliphatic tails, suggests the possible occurrence of a smectic C phase for certain values of these parameters. Taking into account these tendencies, new synthesis led to a nematic-smectic C polymorphism observed for the first time in side-on fixed polysiloxanes.     

Nonparametric decision-making models for large samples

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 79–83, September, 1995.     

A case for sharing

Unlike in other branches of science and technology, computer programs and algorithms are generally not fully disclosed. This leads to duplication of effort, and prevents building new knowledge rapidly on existing knowledge. To remedy this, effective patents on computer programs and algorithms should be granted. The community of authors and inventors, along with expert advice from patent attorneys, have to arrive at effective and equitable definitions of obviousness and novelty, so that the boundaries of protection on one side, and free progress on the other, can be defined. The same reasons exist for patenting and disclosing computer software knowledge as for chemistry, electrical and mechanical inventions. Patenting has protected inventors and assured progress for many decades successfully in these fields.     

Complexes in polymers IV. FTIR microscopic characterization of thin organic polymer films containing embedded transition-metal carbonyl complexes

Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules.     

Bound states and resonances ofN-particle discrete Schrödinger operator

The existence of bound states and resonances of the Hamiltonian of a system ofN different quantum lattice particles with nonvanishingN-particle short-range interaction is proved. The dependence of the bound states and the resonances on the coupling constant and the quasimomentum is studied.Samarkand State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 91, No. 1, pp. 51–65, April, 1992.     

Magnetic resonance findings in sarcoidosis of the thorax.

Fifteen patients with sarcoidosis underwent thoracic MRI examinations. The T2 signal intensity of lymphadenopathy varied, with no characteristic pattern noted. Three of four patients with bright lymph nodes on T2 images had stage I sarcoidosis, but low intensity nodes were also seen in stage I patients. Coronal images were complementary to axial images and better depicted subcarinal adenopathy. MRI does not distinguish the lymphadenopathy of sarcoidosis from other entities, but is useful for defining the anatomic extent of disease and differentiating pulmonary artery enlargement from adenopathy.