Let
Λ
π
(
n
)
denote the
n
th coefficient in the Dirichlet series expansion of the logarithmic derivative of
L
(
s
,
π
)
associated with an automorphic irreducible cuspidal representation of
GL
m
...over
Q
. In this paper, for all
α
of irrational type 1 lying in the interval
0
,
1
, we investigate the best possible estimate for the sum
∑
n
≤
x
Λ
π
(
n
)
e
(
n
α
)
under a certain assumption. And we consider the metric result on the exponential sum involving automorphic
L
-functions without any assumptions. Let
Λ
(
n
)
be the von Mangoldt function. Then as an application, for
ε
>
0
and all
0
<
α
<
1
in a set of full Lebesgue measure (depending on
π
), we obtain
∑
n
≤
x
Λ
(
n
)
λ
π
(
n
)
e
(
n
α
)
=
O
(
x
5
6
+
ε
)
.
Background
The aim of this study was to investigate the prevalence of epidemiologic and physician‐diagnosed pollen‐induced AR (PiAR) in the grasslands of northern China and to study the impact of the ...intensity and time of pollen exposure on PiAR prevalence.
Methods
A multistage, clustered and proportionately stratified random sampling with a field interviewer‐administered survey study was performed together with skin prick tests (SPT) and measurements of the daily pollen count.
Results
A total of 6043 subjects completed the study, with a proportion of 32.4% epidemiologic AR and 18.5% PiAR. The prevalence was higher in males than females (19.6% vs 17.4%, P = .024), but no difference between the two major residential and ethnic groups (Han and Mongolian) was observed. Subjects from urban areas showed higher prevalence of PiAR than rural areas (23.1% vs 14.0%, P < .001). Most PiAR patients were sensitized to two or more pollens (79.4%) with artemisia, chenopodium, and humulus scandens being the most common pollen types, which were similarly found as the top three sensitizing pollen allergens by SPT. There were significant regional differences in the prevalence of epidemiologic AR (from 18.6% to 52.9%) and PiAR (from 10.5% to 31.4%) among the six areas investigated. PiAR symptoms were positively associated with pollen counts, temperature, and precipitation (P < .05), but negatively with wind speed and pressure P < .05).
Conclusion
Pollen‐induced AR (PiAR) prevalence in the investigated region is extremely high due to high seasonal pollen exposure, which was influenced by local environmental and climate conditions.
Four extreme haze episodes occurred in October 2014 in the North China Plain (NCP). To clarify the formation mechanism of hazes in autumn, strengthened observations were conducted in Beijing from 5 ...October to 2 November. The meteorological parameters, satellite data, chemical compositions and optical properties of aerosols were obtained. The hazes originated from the NCP, developing in the southwest and northeast directions, with the highest concentration of PM2.5 of 469 mu g m-3 in Beijing. The NCP was dominated by a weak high pressure system during the haze episode, which resulted in low surface wind speed and relatively stagnant weather. Moreover, the wind slowed down around Beijing city. The secondary aerosols NO3- was always higher than that of SO42-, which indicated the motor vehicles played a more important part in the hazes in October 2014, even though the oxidation rate from SO2 to SO42- was faster than that of NOx to NO3-. Sudden increases of the concentrations of organic matter, Cl- and BC (black carbon) before each haze episode implied that regional transport of pollutants by biomass burning was important for haze formation during autumn. A satellite map of fire points and the backward trajectories of the air masses also indicated this pollution source. The distinct decrease in the PBL (planetary boundary layer) height during four haze episodes restrained the vertical dispersion of the air pollutants. Water vapor also played a vital role in the formation of hazes by accelerating the chemical transformation of secondary pollutants, leading to hygroscopic growth of aerosols and altering the thermal balance of the atmosphere.
► Biochar from sugar beet tailing effectively removed Cr(VI) from solution. ► Most of the Cr on the biochar was Cr(III). ► Cr(VI) removal was via electrostatic attraction to biochar. ► Reduction of ...Cr(VI) to Cr(III) ion and complexation between Cr(III) ion and biochar function groups were also important. ► The maximum sorption capacity of biochar for Cr(VI) was123
mg/g.
Removal of Cr(VI) from aqueous solutions using biochar from sugar beet tailing (SBT) was investigated as a function of pH, contact time, and biochar mass via batch experiments. The surface characteristics of SBT biochar before and after Cr(VI) sorption was investigated with scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Desorption and X-ray photoelectron spectroscopy studies showed that most of the Cr bound to SBT biochar was Cr(III). These results indicated that the electrostatic attraction of Cr(VI) to positively charged biochar surface, reduction of Cr(VI) to Cr(III) ion, and complexation between Cr(III) ion and SBT's function groups were probably responsible for Cr(VI) removal by SBT biochar. An initial solution with a pH of 2.0 was most favorable for Cr(VI) removal. The sorption process can be described by the pseudo-second order equation and Langmuir isotherm. The maximum sorption capacity for Cr(VI) was 123
mg/g under an acidic medium, which was comparable to other low-cost sorbents.
Biochar produced by thermal decomposition of biomass under oxygen-limited conditions has received increasing attention as a cost-effective sorbent to treat metal-contaminated waters. However, there ...is a lack of information on the roles of different sorption mechanisms for different metals and recent development of biochar modification to enhance metal sorption capacity, which is critical for biochar field application. This review summarizes the characteristics of biochar (e.g., surface area, porosity, pH, surface charge, functional groups, and mineral components) and main mechanisms governing sorption of As, Cr, Cd, Pb, and Hg by biochar. Biochar properties vary considerably with feedstock material and pyrolysis temperature, with high temperature producing biochars with higher surface area, porosity, pH, and mineral contents, but less functional groups. Different mechanisms dominate sorption of As (complexation and electrostatic interactions), Cr (electrostatic interactions, reduction, and complexation), Cd and Pb (complexation, cation exchange, and precipitation), and Hg (complexation and reduction). Besides sorption mechanisms, recent advance in modifying biochar by loading with minerals, reductants, organic functional groups, and nanoparticles, and activation with alkali solution to enhance metal sorption capacity is discussed. Future research needs for field application of biochar include competitive sorption mechanisms of co-existing metals, biochar reuse, and cost reduction of biochar production.
Display omitted
•Biochar properties varied with increasing pyrolysis temperature.•Complexation and electrostatic interaction are important mechanisms for As sorption.•Complexation and reduction are important mechanisms for Cr and Hg sorption.•Cation exchange and precipitation are important mechanisms for Cd and Pb sorption.•Biochar have been modified to enhance its metal sorption capacity.
We investigate how whole populations of 2–6 MeV electrons can be quickly lost from the Earth's outer radiation belt at L= 3–6 through precipitation into the atmosphere due to quasi‐linear pitch angle ...scattering by combined electromagnetic ion cyclotron (EMIC) and whistler mode waves of realistic intensities occurring at the same or different local times. We provide analytical estimates of the corresponding relativistic electron lifetimes, emphasizing that the combined effects of both waves can lead to very fast (2–10 h) dropouts. Scaling laws for the loss timescales are derived, allowing us to determine the various plasma and wave parameter domains potentially leading to strong and fast dropouts. The analysis reveals that the fastest MeV electron dropouts occur at approximately the same rate over some high energy range and almost independently of EMIC wave amplitudes above a certain threshold. These results should help to better understand the dynamic variability of the radiation belts.
Key Points
Combined EMIC and chorus or hiss scattering can cause fast and strong MeV electron dropouts
Comprehensive parametric study of this dropout mechanism based on analytical estimates
Dropout timescales become independent of electron energy and EMIC intensity for sufficiently high EMIC to chorus wave intensity ratio
Quantifying Radiation Belt Electron Loss Processes at L < 4 Claudepierre, S. G.; Ma, Q.; Bortnik, J.
Journal of geophysical research. Space physics,
October 2022, 2022-Oct, 2022-10-00, 20221001, Letnik:
127, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We present a comprehensive analysis of the processes that lead to quasilinear pitch‐angle‐scattering loss of electrons from the L < 4 region of the Earth's inner magnetosphere during geomagnetically ...quiet times. We consider scattering via Coulomb collisions, hiss waves, lightning‐generated whistler (LGW) waves, waves from ground‐based very‐low‐frequency (VLF) transmitters, and electromagnetic ion cyclotron (EMIC) waves. The amplitude, frequency, and wave normal angle spectra of these waves are parameterized with empirical wave models, which are then used to compute pitch‐angle diffusion coefficients. From these coefficients, we estimate the decay timescales, or lifetimes, of 30 keV to 4 MeV electrons and compare the results with timescales obtained from in‐situ observations. We demonstrate good quantitative agreement between the two over most of the L and energy range under investigation. Our analysis suggests that the electron decay timescales are very sensitive to the choice of plasmaspheric density model. At L < 2, where our theoretical lifetimes do not agree well with the observations, we show that including Coulomb energy drag (ionization energy loss) in our calculations significantly improves the quantitative agreement with the observed decay timescales. We also use an accurate model of the geomagnetic field to provide an estimate of the effect that the drift‐loss cone has on the theoretically calculated electron lifetimes, which are usually obtained using an axisymmetric dipole field.
Key Points
Coulomb energy drag is an important electron loss process at L ≤ 2 and should not be neglected in theoretical and numerical treatments
Electron decay timescales in the L < 4 region are very sensitive to the choice of plasmaspheric density model
Explicitly incorporating lightning‐generated whistler waves into our lifetime calculations improves the quantitative agreement with the observations at L ≈ 1.8, 3.2
We use measurements from NASA's Van Allen Probes to calculate the decay time constants for electrons over a wide range of energies (30 keV to 4 MeV) and
L values (
L = 1.3–6.0) in the Earth's ...radiation belts. Using an automated routine to identify flux decay events, we construct a large database of lifetimes for near‐equatorially mirroring electrons over a 5‐year interval. We provide the first accurate estimates of the long decay timescales in the inner zone (
∼100 days), which are highly resolved in energy and free from proton contamination. In the slot region and outer zone, we compare our lifetime calculations with prior empirical estimates and find good quantitative agreement (lifetimes
∼1–20 days). The comparisons suggest that some prior estimates may overestimate electron lifetimes between
L≈ 2.5–4.5 due to instrumental effects and/or background contamination. Previously reported two‐stage decays are explicitly demonstrated to be a consequence of using integral fluxes.
Plain Language Summary
The Earth is surrounded by two invisible, donut‐shaped belts of charged particle radiation (think electrons and protons) called the Van Allen belts. The particles in these belts orbit rapidly around the Earth in the same region where spacecraft fly, like GPS and weather satellites. Since the particles in the belts can damage satellites, we need to understand what specific processes make the intensity of the belts go up and down. Knowing which processes are important for changing the belt intensity helps us build better computer models that can be used to predict the future state of the belts (much like weather prediction models). This letter uses spacecraft observations to estimate the loss timescales in the radiation belt region, which are then used in a companion paper to better understand the processes that make the belt intensity go down.
Key Points
A large database of radiation belt electron decay timescales is calculated from Van Allen Probes MagEIS measurements
We provide the first accurate estimates of these timescales over a wide range of energies in the inner zone, free from proton contamination
Outer zone decay timescales generally agree well with prior estimates; some differences exist and may be due to instrumental effects
PDF
