7,671 research outputs found
Low-temperature specific heat of real crystals: Possibility of leading contribution of optical and short-wavelength acoustical vibrations
We point out that the repeatedly reported glass-like properties of
crystalline materials are not necessarily associated with localized (or
quasilocalized) excitations. In real crystals, optical and short-wavelength
acoustical vibrations remain damped due to defects down to zero temperature. If
such a damping is frequency-independent, e.g. due to planar defects or charged
defects, these optical and short-wavelength acoustical vibrations yield a
linear-in- contribution to the low-temperature specific heat of the crystal
lattices. At low enough temperatures such a contribution will prevail over that
of the long-wavelength acoustical vibrations (Debye contribution). The
crossover between the linear and the Debye regime takes place at , where is the concentration of the defects responsible for the
damping. Estimates show that this crossover could be observable.Comment: 5 pages. v4: Error in Appendix corrected, which does not change the
main results of the pape
Comment on "Regge Trajectories for All Flavors"
We show that Regge trajectories for all flavors suggested recently by
Filipponi et al. cannot combine both meson spectroscopy and additivity of
intercepts. Other defects of these trajectories are also discussed.Comment: 2 pages, LaTe
Electromagnetic wave refraction at an interface of a double wire medium
Plane-wave reflection and refraction at an interface with a double wire
medium is considered. The problem of additional boundary conditions (ABC) in
application to wire media is discussed and an ABC-free approach, known in the
solid state physics, is used. Expressions for the fields and Poynting vectors
of the refracted waves are derived. Directions and values of the power density
flow of the refracted waves are found and the conservation of the power flow
through the interface is checked. The difference between the results, given by
the conventional model of wire media and the model, properly taking into
account spatial dispersion, is discussed.Comment: 17 pages, 11 figure
The Influence of Mineral Nutrition on the Productivity of Spring Rape
This article presents data on the influence of mineral nutrition on the productivity of spring bird rape varieties in the conditions of the non-chernozem zone of Russia. The experiments were carried out on agro-gray loamy soils of the experimental agrotechnological station of the Federal State Budgetary Educational Institution of Higher Education “Ryazan State Agrotechnological University” (FSBEI HE RSATU) in the Ryazan Region in 2016-2018. A level of mineral nutrition for spring bird rape was calculated asN180P100K100. Based on this, the options for mineral nutrition in research were established. According to the results of the experiments, the duration of the growing season of spring bird rape varieties was established: 73-91 days.An increase in nitrogen to 150 kg of the active substance turned out to be less effective, as the yield increased slightly or remained at the level of N90P50K50. The use of phosphoruspotassium fertilizers did not contribute to the creation of such a nutritional regime that would increase seed productivity. An increase in the nitrogen nutrition of the plants led to increased protein content anddecreased oil content in seeds. This trend was observed in all varieties of spring bird rape. The average oil content was 38.5-45.5% and the average protein contentwas 18.0-24.7%, depending on the variety and the level of mineral nutrition. On average, the highest oil content was shown by varieties Lipchanka (44.1%) and Kulta (42.6%).
Keywords: agro-gray soil, level of mineral nutrition, oil content, productivity, spring bird rape, variet
Sub-wavelength imaging: Resolution enhancement using metal wire gratings
An experimental evidence of subwavelength imaging with a "lens", which is a
uniaxial negative permittivity wire medium slab, is reported. The slab is
formed by gratings of long thin parallel conducting cylinders. Taking into
account the anisotropy and spatial dispersion in the wire medium we
theoretically show that there are no usual plasmons that could be exited on
surfaces of such a slab, and there is no resonant enhancement of evanescent
fields in the slab. The experimentally observed clear improvement of the
resolution in the presence of the slab is explained as filtering out the
harmonics with small wavenumbers. In other words, the wire gratings (the wire
medium) suppress strong traveling-mode components increasing the role of
evanescent waves in the image formation. This effect can be used in near-field
imaging and detection applications.Comment: 12 pages, 6 figure
- …