32 research outputs found
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 of pristine and brominated arc-produced sample
of multiwall carbon nanotubes was measured from 4.2 to 400 K. An additional
contribution to diamagnetic susceptibility of carbon
nanotubes was found at T 50 K for both samples. It is shown that are dominated by quantum correction to for interaction
electrons (interaction effects-IE). The IE shows a crossover from
two-dimensional to three-dimensional at = 5.5 T. The effective interaction
between electrons for interior layers of nanotubes are repulsion and the
electron-electron interaction was estimated to be 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