Search results for "Potential"
showing 10 items of 3348 documents
Aircraft-based observation of meteoric material in lower-stratospheric aerosol particles between 15 and 68° N
2021
We analyse aerosol particle composition measurements from five research missions between 2014 and 2018 to assess the meridional extent of particles containing meteoric material in the upper troposphere and lower stratosphere (UTLS). Measurements from the Jungfraujoch mountaintop site and a low-altitude aircraft mission show that meteoric material is also present within middle- and lower-tropospheric aerosol but within only a very small proportion of particles. For both the UTLS campaigns and the lower- and mid-troposphere observations, the measurements were conducted with single-particle laser ablation mass spectrometers with bipolar-ion detection, which enabled us to measure the chemical c…
Synoptic-scale variability of the polar and subpolar tropopause: Data analysis and idealized PV inversions
2002
The synoptic-scale variability of the polar and subpolar tropopause is investigated based on radiosonde and European Centre for Medium-Range Weather Forecasts Reanalysis data in combination with idealized potential vorticity (PV) inversions. A regression analysis is performed to examine the relationship between the relative vorticity at tropopause level, the tropopause displacement, the static stability above the tropopause, and the anomalies of tropopause temperature and potential temperature. The results are compared with regression coefficients computed from a large number of PV inversions. Generally, a cyclonically influenced tropopause is lower, warmer and potentially colder than avera…
Potential Vorticity Dynamics of Forecast Errors: A Quantitative Case Study
2018
Abstract Synoptic-scale error growth near the tropopause is investigated from a process-based perspective. Following previous work, a potential vorticity (PV) error tendency equation is derived and partitioned into individual contributions to yield insight into the processes governing error growth near the tropopause. Importantly, we focus here on the further amplification of preexisting errors and not on the origin of errors. The individual contributions to error growth are quantified in a case study of a 6-day forecast. In this case, localized mesoscale error maxima have formed by forecast day 2. These maxima organize into a wavelike pattern and reach the Rossby wave scale around forecast…
Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition
2019
The sources, chemical transformations and removal mechanisms of aerosol transported to the Arctic are key factors that control Arctic aerosol–climate interactions. Our understanding of sources and processes is limited by a lack of vertically resolved observations in remote Arctic regions. We present vertically resolved observations of trace gases and aerosol composition in High Arctic springtime, made largely north of 80∘ N, during the NETCARE campaign. Trace gas gradients observed on these flights defined the polar dome as north of 66–68∘ 30′ N and below potential temperatures of 283.5–287.5 K. In the polar dome, we observe evidence for vertically varying source…
Temperature changes in the mid- and high- latitudes of the Southern Hemisphere
2012
A Hierarchical Ascending Classification is used to regionalize monthly temperature anomalies measured at 24 weather stations in Antarctica and the Sub-Antarctic and mid-latitude southern islands from 1973 to 2002. Three principal regions are identified that are geographically coherent: Eastern Antarctica, the Antarctic Peninsula and the Sub-Antarctic and mid-latitude islands. Within each region, consistent trends are observed: namely, stationary temperatures in ‘East-Antarctica’; a robust warming in the ‘Sub-Antarctic and mid-latitude islands’, most pronounced in austral summer (nearly 0.5 °C per decade); and a strong but more recent warming in the ‘Antarctic Peninsula’. Austral summer temp…
The electron affinity of astatine
2020
One of the most important properties influencing the chemical behavior of an element is the electron affinity (EA). Among the remaining elements with unknown EA is astatine, where one of its isotopes, 211At, is remarkably well suited for targeted radionuclide therapy of cancer. With the At− anion being involved in many aspects of current astatine labeling protocols, the knowledge of the electron affinity of this element is of prime importance. Here we report the measured value of the EA of astatine to be 2.41578(7) eV. This result is compared to state-of-the-art relativistic quantum mechanical calculations that incorporate both the Breit and the quantum electrodynamics (QED) corrections and…
Argon broadening of the 13CO R(0) and R(7) transitions in the fundamental band at temperatures between 80 and 297K: comparison between experiment and…
2003
We present measurements of Ar-broadening parameters for the R(0) and R(7) lines in the fundamental band of13CO at eight temperatures from 80 to 297 K. The broadening parameters are determined by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The comparison of the broadening parameter values for R(7) derived at room temperature and different pressures from different line profiles shows that an empirical line profile, which takes into account narrowing effects (Dicke narrowing and absorber speed dependence) but neglects any correlation between collisions, is able to describe the observed lines with constant values of the narrowing…
Full configuration interaction calculation of singlet excited states of Be3
2004
The full configuration interaction (FCI) study of the singlets vertical spectrum of the neutral beryllium trimer has been performed using atomic natural orbitals [3s2p1d] basis set. The FCI triangular equilibrium structure of the ground state has been used to calculate the FCI vertical excitation energies up to 4.8 eV. The FCI vertical ionization potential for the same geometry and basis set amounts to 7.6292 eV. The FCI dipole and quadrupole transition moments from the ground state are reported as well. The FCI electric quadrupole moment of the X (3)A(1) (') ground state has been also calculated with the same basis set (Theta(zz)=-2.6461 a.u., Theta(xx)=Theta(yy)=-1/2Theta(zz)). Twelve of …
EMG activity of pigeon oesophagus in vivo.
1982
At rest, the pigeon cervical oesophagus, which is entirely smooth muscle, shows electric activity. This activity consists of bursts of spikes with frequency increasing in the oral-aboral direction. The bursts are un-phase locked, and there are no slow waves (E.C.A.). The surgical transection of the oesophageal muscular wall does not affect the electric activity even in a disconnected segment. After asphyxia electric activity persists, whereas the aboral gradient of frequency disappears. Therefore, the electric activity is thought to be myogenic in origin, and the frequency gradient nervous in origin. Atropine and neostigmine administration suggests that the cholinergic system modulates the …
Involvement of purinergic nerves in the NANC inhibitory junction potentials in pigeon oesophageal smooth muscle.
2004
1. Electrical field stimulation (EFS) (0.5 ms in train of 2-32 Hz for 300 ms) in smooth muscle of pigeon oesophagus, in the presence of atropine (1 microm) and guanethidine (1 microm), elicited an inhibitory response consisting of a transient hyperpolarization (inhibitory junction potential, IJP) associated with muscle relaxation. 2. Sodium nitroprusside (SNP, 100 microm) induced hyperpolarization correlated to mechanical relaxation. 3. The nitric oxide (NO) synthase inhibitor N(omega)-nitro-l-arginine (from 0.1 to 100 microm) caused a concentration-dependent reduction of electromechanical response to EFS indicating a role for NO in this response. 4. Apamin (1 microm) reduced both IJP and r…