Field-asymmetric transverse magnetoresistance in a nonmagnetic quantum-size structure

A new phenomenon is observed experimentally in a heavily doped asymmetric quantum-size structure in a magnetic field parallel to the quantum-well layers - a transverse magnetoresistance which is asymmetric in the field (there can even be a change in sign) and is observed in the case that the structure has a built-in lateral electric field. A model of the effect is proposed. The observed asymmetry of the magnetoresistance is attributed to an additional current contribution that arises under nonequilibrium conditions and that is linear in the gradient of the electrochemical potential and proportional to the parameter characterizing the asymmetry of the spectrum with respect to the quasimomentum.Comment: 10 pages, 5 figures. For correspondence, mail to [email protected]

Electron-electron interaction in multiwall carbon nanotubes

Magnetic susceptibility $\chi$ of pristine and brominated arc-produced sample of multiwall carbon nanotubes was measured from 4.2 to 400 K. An additional contribution $\Delta \chi(T)$ to diamagnetic susceptibility $\chi(T)$ of carbon nanotubes was found at T $<$ 50 K for both samples. It is shown that $\Delta \chi(T)$ are dominated by quantum correction to $\chi$ for interaction electrons (interaction effects-IE). The IE shows a crossover from two-dimensional to three-dimensional at $B$ = 5.5 T. The effective interaction between electrons for interior layers of nanotubes are repulsion and the electron-electron interaction $\lambda$$_c$ was estimated to be $\lambda_c\sim$ 0.26.Comment: 10 pages, 7 figure

Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones

Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport measurements, were prepared by compressing under high pressure (~25 kbar) a nanotube precursor synthesized through thermal decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution transmission electron microscopy. In the low-temperature range (4.2 - 100 K) the electric resistance of the samples changes according to the law ln \rho ~ (T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the density of electron states at the Fermi level of about 5 10^{21} eV^{-1} cm^{-3}.Comment: 8 pages, 4 figures. EM photographic images on figures 1a, 1b, 1c attached as JPG files. For correspondence mail to [email protected]

Three small systems showing probable room-temperature superconductivity

I shall discuss three small systems in which I think room-temperature superconductivity has been observed. These are: 1. Narrow channels through films of oxidised atactic polypropylene (OAPP) and other polymers. 2. Some multiwalled carbon nanotubes or mats of nanotubes. 3. Sandwich structures based on CdF_2. The main emphasis will be on polymer films.Comment: 8 pages. Physica C, to be published. Changes from v2: Journal of publication added. Two sentences added on both page 1 and page 6. Three references adde

Фізико-хімічні та органолептичні показники рослинного молока, яке використовують у готельно-ресторанних комплексах

The article highlights the current state of the production of dairy and vegetable food products. The results of studies of organoleptic and physical, chemical indicators of the quality of various herbal drinks: coconut, almond and oat, are presented, as well as an analysis and comparison with cow's milk, which is used in hotel and restaurant complexes in Bela Tserkva. For assessing the quality according to the organoleptic characteristics of the beverages, the following were examined: appearance, color, smell, taste and consistency. It was found that according to these indicators, herbal drinks comply with the regulatory documentation for these products. When assessing the quality by physical and chemical indicators, the mass fraction of fat, dry matter, titratable and active acidity, and density were established. The titratable acidity of milk-like drinks was within the normal range and did not exceed 10 ⁰T. The mass fraction of fat in coconut milk was 1.2 %, almond-rice milk – 1.3 % and oat milk – 2.4 %. Mass fraction of coconut milk solids was 7.6%, almond-rice 10.5% and oat milk 11.4%. The density of all types of herbal drinks was in the range of 1005–1015 kg/m3. The indicators of the quality of cow's milk, which is used in hotel and restaurant complexes, have been investigated in a comparative form. In terms of organoleptic indicators, the quality of cow's milk corresponds to the normative documentation. The fat mass fraction of cow's milk was 2.5 %, the mass fraction of solids was 12.5%, the titratable acidity was at the level of 18 ⁰T, the active acidity pH was 6.6, and the density was 1028 kg/m3. Analysis of various types of vegetable and cow's milk, which are used in hotel and restaurant complexes in the city of Bela Tserkva, in terms of physicochemical and organoleptic quality indicators, allows us to consider herbal drinks as substitutes for traditional products capable of providing the human body with essential nutritional factors.У статті висвітлено сучасний стан виробництва молочно-рослинних харчових продуктів. Наведено результати досліджень органолептичних та фізико-хімічних показників якості різних рослинних напоїв: кокосового, мигдального та вівсяного, а також проведено аналіз та порівняння з коров’ячим молоком, яке використовують у готельно-ресторанних комплексах м. Біла Церква. За проведення оцінки якості за органолептичними показниками напоїв досліджували: зовнішній вигляд, колір, запах, смак та консистенцію. Встановлено, що за цими показниками рослинні напої відповідають нормативній документації на дані продукти. Під час проведення оцінки якості за фізико-хімічними показниками встановлювали масову частку жиру, сухих речовин, титровану та активну кислотність, густину. Титрована кислотність молокоподібних напоїв була в межах норми і не перевищує 10 ⁰Т. Масова частка жиру кокосового молока становила 1,2 %, мигдально-рисового – 1,3 % та вівсяного – 2,4 %. Масова частка сухих речовин кокосового молока становила – 7,6 %, мигдально-рисового 10,5 % та вівсяного – 11,4 %. Густина всіх видів рослинних напоїв була в межах 1005–1015 кг/м3. У порівняльній формі досліджено показники якості молока коров’ячого, яке використовують у готельно-ресторанних комплексах. За органолептичними показниками якість молока коров’ячого відповідає нормативній документації. Масова частка жиру молока коров’ячого становила 2,5 %, масова частка сухих речовин 12,5 %, титрована кислотність була на рівні 18 ⁰Т, активна кислотність рН – 6,6, густина – 1028 кг/м3. Аналіз різних видів рослинного і коров’ячого молока, які використовують у готельно-ресторанних комплексах м. Біла Церква за фізико-хімічними та органолептичними показниками якості дозволяє розглядати рослинні напої як замінники традиційних продуктів здатних забезпечувати організм людини есенціальними факторами живлення

Graphene as a quantum surface with curvature-strain preserving dynamics

We discuss how the curvature and the strain density of the atomic lattice generate the quantization of graphene sheets as well as the dynamics of geometric quasiparticles propagating along the constant curvature/strain levels. The internal kinetic momentum of Riemannian oriented surface (a vector field preserving the Gaussian curvature and the area) is determined.Comment: 13p, minor correction