104 research outputs found
Estimation of turbulent proton and electron heating rates via Landau damping constrained by Parker Solar Probe observations
The heating of ions and electrons due to turbulent dissipation plays a
crucial role in the thermodynamics of the solar wind and other plasma
environments. Using magnetic field and thermal plasma observations from the
first two perihelia of the Parker Solar Probe (PSP), we model the relative
heating rates as a function of radial distance, magnetic spectra, and plasma
conditions, enabling us to better characterize the thermodynamics of the inner
heliosphere. We employ the Howes et al. 2008 steady-state cascade model, which
considers the behavior of turbulent, low-frequency, wavevector-anisotropic,
critically balanced Alfv\'enic fluctuations that dissipate via Landau damping
to determine proton-to-electron heating rates . We distinguish
ion-cyclotron frequency circularly polarized waves from low-frequency
turbulence and constrain the cascade model using spectra constructed from the
latter. We find that the model accurately describes the observed energy
spectrum from over 39.4 percent of the intervals from Encounters 1 and 2,
indicating the possibility for Landau damping to heat the young solar wind. The
ability of the model to describe the observed turbulent spectra increases with
the ratio of thermal-to-magnetic pressure, , indicating that the model
contains the necessary physics at higher . We estimate high magnitudes
for the Kolmogorov constant which is inversely proportional to the non-linear
energy cascade rate. We verify the expected strong dependency of on
and the consistency of the critical balance assumption
Antioxidant Capacity and Corrosion Inhibition Efficiency of Sambucus nigra L. Extract
The cyclic voltammogram recorded in the potential range between 0 V and 800 mV with scan rate of 100 mV s−1 was used to determine the measure of antioxidants content (antioxidant capacity) present in Sambucus nigra L. extract. The antioxidant capacity of the extract was 4.06 mg GAE g −1 fw (mg of gallic acid equivalents per gram of fresh weight of the extract). The corrosion inhibition efficiency of Sambucus nigra L. extract on aluminium, copper, and bronze in 3 % NaCl solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy. Polarization data showed that extract acted as a mixed-type inhibitor, that the corrosion inhibition process was spontaneous physical adsorption (ΔG ≈ –16 kJ mol–1) of the extract molecules on metals surfaces and followed Freundlich isotherm. Impedance spectroscopy studies revealed that increasing the concentration of extract reduced the double-layer capacitance and increased the charge transfer resistance. The highest inhibition efficiencies (Cu: ~ 57 %, CuSn14: ~74 % and Al: ~58 %) were achieved for an extract concentration of 1.0 g L–1
Support for collective action against refugees: The role of national, European, and global identifications, and autochthony beliefs
To understand recent anti-refugee protests in Europe, we examined how different levels of inclusiveness of group identities (national, European, and global) are related to intentions to protest among native Europeans. We focused on the mediating role of autochthony (a belief that the first inhabitants of a territory are more entitled) and the moderating role of threat. Survey data from 11 European countries (N=1909) showed that national identification was positively associated with autochthony, and therefore, with the intention to protest against refugees. In contrast, global identification was related to lower protest intentions via lower autochthony. These paths were found only among Europeans who perceived refugees as a threat. European identification was not related to the endorsement of autochthony or to collective action. These findings indicate why and when majority members are willing to participate in collective action against refugees, and underscore the importance of global identification in the acceptance of refugees
Long-term Effects of Oxidative Stress in Volleyball Players
The aim of this study was to determine the impact of long-term training on elite female volleyball players and to determine parameters that could discriminate them according to the level of oxidative stress-associated adaptation. Fifty-four elite female volleyball players were divided into 3 groups (1: below-average training experience lt 8.0 years, 2: average training experience between 8.0 and 10.5 years and 3: above-average training experience > 10.5 years). The measured parameters were reactive oxygen metabolites, biological anti-oxidative potential, superoxide anion, malondialdehyde, advanced oxidation protein products, lipid hydroperoxides, paraoxonase activity, superoxide-dismutase activity and sulphydryl groups. Multiple discriminant analysis of the oxidative stress status parameters between the three groups of athletes indicated a statistically significant difference (Wilks' lambda=0.458, X-2=35.898, p=0.031). The most important discriminant variables, superoxide-dismutase and superoxide anion, were the best indicators of differences between groups with different training experience. The significantly higher values were found in Group 3 compared with Group 1 in superoxide-dismutase activity (141 +/- 32 vs. 86 +/- 46; p=0.002), sulphydryl groups (p=0.031), and reactive oxygen metabolites (p = 0.042). The significantly lower superoxide anion was found between Group 3 and Group 1 (377 +/- 187 vs. 1183 +/- 905; p=0.001). Oxidative stress status parameters adequately discriminated 68.5% of athletes with different training experience
Rubbery taproot disease of sugar beet in Serbia associated with 'Candidatus phytoplasma solani'
Rubbery taproot disease (RTD) of sugar beet was observed in Serbia for the first time in the 1960s. The disease was already described in neighboring Bulgaria and Romania at the time but it was associated with abiotic factors. In this study on RTD of sugar beet in its main growing area of Serbia, we provide evidence of the association between 'Candidatus Phytoplasma solani' (stolbur phytoplasma) infection and the occurrence of typical RTD symptomatology. 'Ca. P. solani' was identified by PCR and the sequence analyses of 16S ribosomal RNA, tuf, secY, and stamp genes. In contrast, the causative agent of the syndrome “basses richesses” of sugar beet-namely, 'Ca. Arsenophonus phytopathogenicus'-was not detected. Sequence analysis of the stolbur strain's tuf gene confirmed a previously reported and a new, distinct tuf stolbur genotype (named 'tuf d') that is prevalent in sugar beet. The sequence signatures of the tuf gene as well as the one of stamp both correlate with the epidemiological cycle and reservoir plant host. This study provides knowledge that, for the first time, enables the differentiation of stolbur strains associated with RTD of sugar beet from closely related strains, thereby providing necessary information for further epidemiological work seeking to identify insect vectors and reservoir plant hosts. The results of this study indicate that there are differences in hybrid susceptibility. Clarifying the etiology of RTD as a long-known and economically important disease is certainly the first step toward disease management in Serbia and neighboring countries.This is the peer reviewed version of the following article: Ćurčić Ž., Stepanović J., Zübert C., Taški-Ajduković K., Kosovac A., Rekanović E., Kube M., Duduk B. Rubbery taproot disease of sugar beet in Serbia associated with 'Candidatus phytoplasma solani'. Plant Disease 2021, 105 (2), 255 – 263. [https://doi.org/10.1094/PDIS-07-20-1602-RE]
The Structure and Origin of Switchbacks: Parker Solar Probe Observations
Switchbacks are rapid magnetic field reversals that last from seconds to
hours. Current Parker Solar Probe (PSP) observations pose many open questions
in regards to the nature of switchbacks. For example, are they stable as they
propagate through the inner heliosphere, and how are they formed? In this work,
we aim to investigate the structure and origin of switchbacks. In order to
study the stability of switchbacks, we suppose the small scale current sheets
therein may work to braid and stabilize the switchbacks. Thus, we use the
partial variance of increments method to identify the small scale current
sheets, and then compare their distributions in switchbacks. With more than one
thousand switchbacks identified with PSP observations in seven encounters, we
find many more current sheets inside than outside switchbacks, indicating that
these micro-structures should work to stabilize the S-shape structures of
switchbacks. Additionally, with the helium measurements, we study the
variations of helium abundance ratios and alpha-proton differential speeds to
trace switchbacks to their origins. We find both helium-rich and helium-poor
populations in switchbacks, implying the switchbacks could originate from both
closed and open magnetic field regions in the Sun. Moreover, we observe that
the alpha-proton differential speeds also show complex variations as compared
to the local Alfv\'en speed. The joint distributions of both parameters show
that low helium abundance together with low differential speed is the dominant
state in switchbacks. The presence of small scale current sheets in switchbacks
along with the helium features are in line with the hypothesis that switchbacks
could originate from the Sun via interchange reconnection process. However,
other formation mechanisms are not excluded
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