Biofunctional nanomaterials based on ultra fine silica, protein and aminocarbohydrates

Aim. Investigation of adsorptive interactions of N-acetyl-D-glucosamine (GlcNAc) and N-acetylneuraminic acid (NANA) with ultra fine silica (UFS) modified by protein bovine serum albumin (BSA). Methods. Adsorption, IR-, 1H NMR- and laser Doppler spectroscopy. Results. Conditions for obtaining bionanocomposites (BNC) UFS/GlcNAc, UFS/BSA/GlcNAc and UFS/BSA/NANA are developed. Conclusions. Impellent ability of deconservated bovine gametes decreased in the presence of BNC after adsorptive fastening of protein on UFS surface. The 1H NMR spectroscopy data proved that interaction of GlcNAc with protein was accompanied by essential dehydratation of protein molecules.Цель. Исследование адсорбционных взаимодействий N-ацетил-D-глюкозамина (GlcNAc) и N-ацетилнейраминовой кислоты (N-АНК) с высокодисперсным кремнеземом (ВДК), модифицированным белком бычьим сывороточным альбумином (БСА). Методы. Адсорбция, ИК-, 1Н ЯМР- и лазерно-допплеровская спектроскопия. Результаты. Разработаны условия получения бионанокомпозитов (БНК) ВДК/GlcNAc; ВДК/БСА/GlcNAc и ВДК/БСА/N-АНК. Выводы. Двигательная способность деконсервированных гамет быка снижается в присутствии БНК после адсорбционного закрепления на его поверхности белка. На основе данных 1Н ЯМР-спектроскопии установлено, что взаимодействие GlcNAc с белком сопровождается сильной дегидратацией его молекул.Мета. Дослідження адсорбційних взаємодій N-ацетил-D-глюкозаміну (GlcNAc) та N-ацетилнейрамінової кислоти (N-АНК) з високодисперсним кремнеземом (ВДК), модифікованим білком бичачим сироватковим альбуміном (БСА). Методи. Адсорбція, ІЧ-, 1Н ЯМР- та лазерно-допплерівська спектроскопія. Результати. Розроблено умови отримання біонанокомпозитів (БНК): ВДК/GlcNAc; ВДК/БСА/GlcNAc та ВДК/БСА/N- АНК. Висновки. Здатність до руху деконсервованих гамет бика знижується за присутності БНК після адсорбційного закріплення на його поверхні білка. На основі даних 1Н ЯМР- спектроскопії встановлено, що взаємодія GlcNAc з білком супроводжується сильною дегідратацією його молекул

Critical Dynamics of Magnets

We review our current understanding of the critical dynamics of magnets above and below the transition temperature with focus on the effects due to the dipole--dipole interaction present in all real magnets. Significant progress in our understanding of real ferromagnets in the vicinity of the critical point has been made in the last decade through improved experimental techniques and theoretical advances in taking into account realistic spin-spin interactions. We start our review with a discussion of the theoretical results for the critical dynamics based on recent renormalization group, mode coupling and spin wave theories. A detailed comparison is made of the theory with experimental results obtained by different measuring techniques, such as neutron scattering, hyperfine interaction, muon--spin--resonance, electron--spin--resonance, and magnetic relaxation, in various materials. Furthermore we discuss the effects of dipolar interaction on the critical dynamics of three--dimensional isotropic antiferromagnets and uniaxial ferromagnets. Special attention is also paid to a discussion of the consequences of dipolar anisotropies on the existence of magnetic order and the spin--wave spectrum in two--dimensional ferromagnets and antiferromagnets. We close our review with a formulation of critical dynamics in terms of nonlinear Langevin equations.Comment: Review article (154 pages, figures included

Weak antiferromagnetism due to Dzyaloshinskii-Moriya interaction in Ba3_3Cu2_2O4_4Cl2_2

The antiferromagnetic insulating cuprate Ba$_3$Cu$_2$O$_4$Cl$_2$ contains folded CuO$_2$ chains with four magnetic copper ions ($S=1/2$) per unit cell. An underlying multiorbital Hubbard model is formulated and the superexchange theory is developed to derive an effective spin Hamiltonian for this cuprate. The resulting spin Hamiltonian involves a Dzyaloshinskii-Moriya term and a more weak symmetric anisotropic exchange term besides the isotropic exchange interaction. The corresponding Dzyaloshinskii-Moriya vectors of each magnetic Cu-Cu bond in the chain reveal a well defined spatial order. Both, the superexchange theory and the complementary group theoretical consideration, lead to the same conclusion on the character of this order. The analysis of the ground-state magnetic properties of the derived model leads to the prediction of an additional noncollinear modulation of the antiferromagnetic structure. This weak antiferromagnetism is restricted to one of the Cu sublattices.Comment: 13 pages, 1 table, 4 figure

Magnetic Field Effects on Neutron Diffraction in the Antiferromagnetic Phase of UPt3UPt_3

We discuss possible magnetic structures in UPt$_3$ based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures $T<T_N$. The existing experimental data can be explained by a single-{\bf q} antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-{\bf q} magnetic structure is also consistent with neutron experiments, but in general leads to a non-uniform magnetization in the crystal. New experiments could decide between these structures.Comment: 5 figures included in the tex