The frequency of sudden, strong warming events is projected to increase in the future. The effects of such events on spring phenology of trees might depend on their timing because spring warming has ...generally been shown to advance spring budburst while fall and winter warming have been shown to delay spring phenology. To understand the mechanism behind timing-specific warming effects on spring phenology, I simulated warming events during fall, mid-winter and at the end of winter and quantified their effects on bud dormancy depth and subsequently on spring leaf out. The warming events were carried out in climate chambers on tree seedlings of
Betula pendula
and
Fagus sylvatica
in October, January, and February. Control seedlings were kept at photoperiod and temperature matching the daily fluctuating field conditions. Warmed seedlings were kept 10°C warmer than the control seedlings for 10 days during the respective warming periods. Warming in October increased bud dormancy depth and decreased spring leaf-out rate only for
F. sylvatica
, whereas warming in February reduced bud dormancy depth and advanced spring leaf-out rate only for
B. pendula
. Neither bud dormancy depth nor spring leaf out rate were affected by January warming. The results indicate that warming-induced changes in bud dormancy depth may explain species- and timing-specific warming effects on spring phenology. The extent to which the timing of bud dormancy phases is species-specific will influence among-species variation in future spring leaf out times.
We address new optical nanoantenna systems with tunable highly directional radiation patterns. The antenna comprises a regular linear array of metal nanoparticles in the proximity of an interface ...with high dielectric contrast. We show that the radiation pattern of the system can be controlled by changing parameters of the excitation, such as the polarization and/or incidence angles. In the case of excitation under the total reflection condition, the system operates as a nanoscopic source of radiation, converting the macroscopic incident plane wavefront into a narrow beam of light with adjustable characteristics. We derive also simple analytical formulas which give an excellent description of the radiation pattern and provide a useful tool for analysis and antenna design.
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IJS, KILJ, NUK, PNG, UL, UM
We study theoretically the optical response of graded linear arrays of noble metal nanospheres in which the center-to-center distances and/or the radii of the spheres change linearly along the chain. ...A strong asymmetry of the system response with respect to the direction of incidence of the incoming light is revealed. We show that for light propagating from smaller to larger spheres the optical signal can be localized in a controlled way at an arbitrary subset of a few neighboring spheres by adjusting the wavelength of the incoming field. This opens new opportunities to control the flow of electromagnetic energy at the nanometer scale.
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Key plant traits affecting growth performance can differ among and within species, influencing competitive plant community dynamics. We determined the intra-specific variability of germination base ...temperature among 13 arable weed species and the seedlings' early post-emergence relative growth rate among 21 species in climate chamber and green house experiments. Intra-specific variability was quantified with two seed populations (originating from contrasting climate in Germany & France) for the germination base temperature of 6 species and for the early growth rate of 16 species. Inter-specific variability for both traits was always higher than intra-specific variability. Within a given species, we found that germination base temperatures were higher in seeds stemming from colder climate populations. Seedling relative growth rates did not differ between seed populations. Models simulating weed growth should reflect these differences in germination traits among populations, especially when they are used for weed community assembly studies in a local to regional extent.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Updated results of experimental studies of the thermophysical properties of uranium hexafluoride (UF
6
) in the rarefied-gas region in the temperature range from 287 to 368 K, the range of pressures ...from 53 to 750 Torr, and the range of gas densities from 0.00188 to 0.0118 g/cm
3
were obtained by processing the author’s previous data using the Origin-8 graphic-mathematical program. Updated UF
6
state parameter values in the region of vapor-solid equilibrium and updated data for the heat of sublimation were obtained. On the basis of
P‒V‒T
data, an equation of state for UF
6
was constructed that provides twice the approximation to the experimental pressure data with a standard deviation of 0.53 Torr as compared to the previous equation and 0.12% over the entire range of state parameters studied. Data were updated for the second virial coefficient. We used uranium hexafluoride with a natural content of uranium isotopes and a purity of 99.98 vol %. A description of the experimental equipment and methods of research and processing of experimental data are given.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Updated results of experimental studies of the thermophysical properties of uranium hexafluoride (UF
6
) were obtained by processing the author’s data using the Origin-8 program. Updated UF
6
state ...para-meter values in the area of vapor−liquid equilibrium and updated data for the heat of vaporization were obtained. A physical and mathematical method for determining the critical temperature from experimental data on the boundary curve (binodal) has been developed, which made it possible to refine the critical para-meters of UF
6
:
T
c
= 504.6 ± 0.5 K, ρ
c
= 1.385 ± 0.0015 g/cm
3
,
P
c
= 45.5 ± 0.3 bar. Using
P–V–T
data two virial equations of state for a dense and highly compressed UF
6
gas were constructed. One of them describes the experimental data for a dense gas in the entire studied range of state parameters with a standard deviation
MSD
of 0.47 bar and 0.56%. The second equation provides the definition of pressure for UF
6
with
MSD
= 0.16 bar and 0.36% in the entire subcritical region. The data for the second virial coefficient for UF
6
in the temperature range 310–592 K were updated. The equation of state for liquid UF
6
is presented for the first time, which describes the experimental data with
MSD
less than 7 bar and 6% in the temperature range 453–493 K, density from ρ
l
at the phase boundary up to 2.9–3.1 g/cm
3
and pressures up to 200–240 bar. The description of the experimental high-pressure equipment and the methodology for conducting research and determining the parameters of the state of UF
6
is given.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The nuclear recoil effect on the g factor of Li-like ions is evaluated. The one-electron recoil contribution is treated within the framework of the rigorous QED approach to the first order in the ...electron-to-nucleus mass ratio m/M and to all orders in the parameter αZ. These calculations are performed in a range Z=3-92. The two-electron recoil term is calculated for low- and middle-Z ions within the Breit approximation using a four-component approach. The results for the two-electron recoil part obtained in the Letter strongly disagree with the previous calculations performed using an effective two-component Hamiltonian. The obtained value for the recoil effect is used to calculate the isotope shift of the g factor of Li-like ^{A}Ca^{17+} with A=40 and A=48 which was recently measured. It is found that the new theoretical value for the isotope shift is closer to the experimental one than the previously obtained value.
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The strong mixing of close levels with two valence electrons in Be-like xenon greatly complicates ab initio QED calculations beyond the first-order approximation. Because of a strong interplay ...between the electron-electron correlation and QED effects, the standard single-level perturbative QED approach may fail, even if it takes into account the second-order screened QED diagrams. In the present Letter, the corresponding obstacles are overcome by working out the QED perturbation theory for quasidegenerate states. The contributions of all the Feynman diagrams up to the second order are taken into account. The many-electron QED effects are rigorously evaluated in the framework of the extended Furry picture to all orders in the nuclear-strength parameter αZ. The higher-order electron-correlation effects are considered within the Breit approximation. The nuclear recoil effect is accounted for as well. The developed approach is applied to high-precision QED calculations of the ground and singly excited energy levels in Be-like xenon. The most accurate theoretical predictions for the binding and excitation energies are obtained. These results deviate from the most precise experimental value by 3σ but perfectly agree with a more recent measurement.
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A comparative analysis of areal and profile measurements of magnetic susceptibility was carried out on the plots pf 100 m
2
in order to improve methods of surface soil sounding for mapping purposes ...and for identification of anomalies associated with anthropogenic pollution or disturbance of the surface soil layer. Two sites with Haplic Chernozems and one site with Haplic Kastanozem (Endosalic, Cambic) were studied. Additionally, a catena on the Yergeni Upland with different landscape positions (eluvial, transeluvial, transeluvial–accumulative) was studied. A comparison of the areal and profile magnetic susceptibility measured to a depth of 30 cm showed a direct correlation (
R
2
= 0.7). The areal survey was found to correctly determine the volumetric magnetic susceptibility (
) to a depth of 30 cm. The
variation at sites with different types of soils reflects soil–climatic zonality and spatial lithological heterogeneity expressed in different textures and mineralogical compositions of the upper (0–30 cm) soil layer within the test area of 10 × 10 m. The areal magnetic susceptibility of soils can be an important additional indicator capable of reflecting the features of soil-forming, lithological, and geochemical processes occurring in the upper soil layer. The
variation at sites in different landscape positions is due to the development of sheet erosion and changes in the direction of iron oxidogenesis depending on the position of the soil profile in the relief. The set of areal and profile magnetic susceptibility measurements can be used to study soil inhomogeneities caused by anthropogenic, paleocryogenic, geomorphological, and lithogenic factors. In particular, this approach can be applied to the study of polluted soils and monitoring of agricultural lands.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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