Context. The electron temperature of the plasma is one important aspect of the environment. Electrons created by photoionization or impact ionization of atmospheric gas have energies ~10 eV. In an ...active comet coma, the gas density is high enough for rapid cooling of the electron gas to the neutral gas temperature (a few hundred kelvin). How cooling evolves in less active comets has not been studied before. Aims. We aim to investigate how electron cooling varied as comet 67P/Churyumov-Gerasimenko changed its activity by three orders of magnitude during the Rosetta mission. Methods. We used in situ data from the Rosetta plasma and neutral gas sensors. By combining Langmuir probe bias voltage sweeps and mutual impedance probe measurements, we determined at which time cold electrons formed at least 25% of the total electron density. We compared the results to what is expected from simple models of electron cooling, using the observed neutral gas density as input. Results. We demonstrate that the slope of the Langmuir probe sweep can be used as a proxy for the presence of cold electrons. We show statistics of cold electron observations over the two-year mission period. We find cold electrons at lower activity than expected by a simple model based on free radial expansion and continuous loss of electron energy. Cold electrons are seen mainly when the gas density indicates that an exobase may have formed. Conclusions. Collisional cooling of electrons following a radial outward path is not sufficient to explain the observations. We suggest that the ambipolar electric field keeps electrons in the inner coma for a much longer time, giving them time to dissipate energy by collisions with the neutrals. We conclude that better models are required to describe the plasma environment of comets. They need to include at least two populations of electrons and the ambipolar field.
ABSTRACT We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. ICRF2 ...contains precise positions of 3414 compact radio astronomical objects and has a positional noise floor of ∼40 as and a directional stability of the frame axes of ∼10 as. A set of 295 new "defining" sources was selected on the basis of positional stability and the lack of extensive intrinsic source structure. The positional stability of these 295 defining sources and their more uniform sky distribution eliminates the two greatest weaknesses of the first realization of the International Celestial Reference Frame (ICRF1). Alignment of ICRF2 with the International Celestial Reference System was made using 138 positionally stable sources common to both ICRF2 and ICRF1. The resulting ICRF2 was adopted by the International Astronomical Union as the new fundamental celestial reference frame, replacing ICRF1 as of 2010 January 1.
Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims. Our aim is to ...demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma. Methods. In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas. Results. LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5–10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order − 10 V. Conclusions. The warm (5–10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.
We present Rosetta RPC case study from four events at various radial distance, phase angle and local time from autumn 2015, just after perihelion of comet 67P/Churyumov-Gerasimenko. Pulse like (high ...amplitude, up to minutes in time) signatures are seen with several RPC instruments in the plasma density (LAP, MIP), ion energy and flux (ICA) as well as magnetic field intensity (MAG). Furthermore the cometocentric distance relative to the electron exobase is seen to be a good organizing parameter for the measured plasma variations. The closer Rosetta is to this boundary, the more pulses are measured. This is consistent with the pulses being filaments of plasma originating from the diamagnetic cavity boundary as predicted by simulations.
We use data from several instruments on board Cassini to determine the characteristics of the plasma and dust regions around Saturn׳s moon Enceladus. For this we utilize the Langmuir probe and the ...electric antenna connected to the wideband receiver of the radio and plasma wave science (RPWS) instrument package as well as the magnetometer (MAG). We show that there are several distinct plasma and dust regions around Enceladus. Specifically they are the plume filled with neutral gas, plasma, and charged dust, with a distinct edge boundary region. Here we present observations of a new distinct plasma region, being a dust trail on the downstream side. This is seen both as a difference in ion and electron densities, indicating the presence of charged dust, and directly from the signals created on RPWS antennas by the dust impacts on the spacecraft. Furthermore, we show a very good scaling of these two independent dust density measurement methods over four orders of magnitude in dust density, thereby for the first time cross-validating them. To establish equilibrium with the surrounding plasma the dust becomes negatively charged by attracting free electrons. The dust distribution follows a simple power law and the smallest dust particles in the dust trail region are found to be 10nm in size as well as in the edge region around the plume. Inside the plume the presence of even smaller particles of about 1nm is inferred. From the magnetic field measurements we infer strong field-aligned currents at the geometrical edge of Enceladus.
•Different regions with specific plasma structure and B-field configurations.•The dust is in equilibrium with the surrounding plasma (collective behavior).•Minimum dust sizes: 1 nm (plume) and 10 nm (plume edge and dust trail).•Overview of 20 flybys in dust and plasma densities, B-field and currents.•We show strong field-aligned edge currents.
Although conservation-minded researchers advocate that growers use a variety of methods to defend crops from wildlife, we know little about the effects of such methods on the targeted species. We ...assessed effects of nonlethal crop defense (CD) methods used in Tangkoko Reserve, Sulawesi, Indonesia, on potentially stress-related behavior of Critically Endangered (CR) wild, crested macaques (
Macaca nigra
). We examined responses of three groups exposed to different amounts of CD, both immediately after being targeted and when only exposed to cues of targeting elsewhere in the forest. We analyzed 630 h of data from 33 adults of both sexes by using Generalized Linear Mixed Models. When not targeted, all groups and both sexes displayed fewer self-directed behaviors, males showed fewer affiliative behaviors, and two groups decreased aggression in months with more CD. When we compared behavior immediately after targeting with behavior unassociated with targeting, males in the most frequently targeted group showed increased aggression, whereas both sexes in the moderately frequently targeted group showed increased self-directed behaviors. We suggest that when not targeted, groups show a degree of behavioral inhibition during months in which CD targeting is relatively frequent. When targeted, the two regularly targeted groups displayed behavior consistent with increased stress. However, the groups appeared to respond in qualitatively different ways. We tentatively suggest that the macaques’ behavioral responses to CD (inhibition in low-risk conditions and signs of stress and/or motivational conflict in moderate-risk conditions) resemble typical responses of primates to perceived predators posing varying degrees of risk.
Abstract
In 2015 August, comet 67P/Churyumov–Gerasimenko, the target comet of the ESA Rosetta mission, reached its perihelion at ∼1.24 au. Here, we estimate for a three-day period near perihelion, ...effective ion speeds at distances ∼200–250 km from the nucleus. We utilize two different methods combining measurements from the Rosetta Plasma Consortium (RPC)/Mutual Impedance Probe with measurements either from the RPC/Langmuir Probe or from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Comet Pressure Sensor (COPS) (the latter method can only be applied to estimate the effective ion drift speed). The obtained ion speeds, typically in the range 2–8 km s−1, are markedly higher than the expected neutral outflow velocity of ∼1 km s−1. This indicates that the ions were de-coupled from the neutrals before reaching the spacecraft location and that they had undergone acceleration along electric fields, not necessarily limited to acceleration along ambipolar electric fields in the radial direction. For the limited time period studied, we see indications that at increasing distances from the nucleus, the fraction of the ions’ kinetic energy associated with radial drift motion is decreasing.
Aim
Downregulated in adenoma (DRA, Slc26a3) is a member of the solute carrier family 26 (SLC26), family of anion transporters, which is mutated in familial chloride‐losing diarrhoea (CLD). Besides ...Cl−‐rich diarrhoea, CLD patients also have a higher‐than‐average incidence of intestinal inflammation. In a search for potential explanations for this clinical finding, we investigated colonic electrolyte transport, the mucus layer and susceptibility against dextran sodium sulphate (DSS)‐induced colitis in Slc26a3−/− mice.
Methods
HCO3− secretory (JHCO3−) and fluid absorptive rates were measured by single‐pass perfusion in vivo and in isolated mid‐distal colonic mucosa in Ussing chambers in vitro. Colonocyte intracellular pH (pHi) was assessed fluorometrically, the mucus layer by immunohistochemistry and colitis susceptibility by the addition of DSS to the drinking water.
Results
HCO3− secretory (JHCO3‐) and fluid absorptive rates were strongly reduced in Slc26a3−/− mice compared to wild‐type (WT) littermates. Despite an increase in sodium/hydrogen exchanger 3 (NHE3) mRNA and protein expression, and intact acid‐activation of NHE3, the high colonocyte pH in Slc26a3−/− mice prevented Na+/H+ exchange‐mediated fluid absorption in vivo. Mucin 2 (MUC2) immunohistochemistry revealed the absence of a firm mucus layer, implying that alkaline secretion and/or an absorptive flux may be necessary for optimal mucus gel formation. Slc26a3−/− mice were highly susceptible to DSS damage.
Conclusions
Deletion of DRA results in severely reduced colonic HCO3− secretory rate, a loss of colonic fluid absorption, a lack of a firmly adherent mucus layer and a severely reduced colonic mucosal resistance to DSS damage. These data provide potential pathophysiological explanations for the increased susceptibility of CLD patients to intestinal inflammation.
Summary There is a paucity of therapies for most neurological disorders—from rare lysosomal storage diseases to major public health concerns such as stroke and Alzheimer's disease. Advances in the ...targeting of drugs to the CNS are essential for the future success of neurotherapeutics; however, the delivery of many potentially therapeutic and diagnostic compounds to specific areas of the brain is restricted by the blood–brain barrier, the blood–CSF barrier, or other specialised CNS barriers. These brain barriers are now recognised as a major obstacle to the treatment of most brain disorders. The challenge to deliver therapies to the CNS is formidable, and the solution will require concerted international efforts among academia, government, and industry. At a recent meeting of expert panels, essential and high-priority recommendations to propel brain barrier research forward in six topical areas were developed and these recommendations are presented here.
Patient 4 (sibling to patient 3) was well until he presented with inflammatory colitis and Hodgkin lymphoma (inguinal and para-aortic region) at age 16 years. Because of his sibling's history, CTLA4 ...haploinsufficiency was confirmed by both genetic and protein level testing, the only patient in this cohort to have an identified mutation before HSCT. In summary, 4 of 8 patients experienced GvHD despite having well-matched donors and receiving alemtuzumab in 3 out of 4 cases.\n9 (5.4-16.8)IgA 0.27 (0.74-2.61)IgM 0.84 (0.40-1.95)Preimmunoglobulin therapyPre-RTX 23 y Interstitial lung disease ("nodular lymphoid hyperplasia") Transverse myelitis Recurrent white matter and brainstem lesions with oligoclonal bands and elevated IgG index Arthritis Father:ITPSister:Patient no. 7 Table I Patients' characteristics ABVD, Adriamcyin (Doxorubicin), bleomycin, vinblastine, dacarbazine; naive CD4, CD3+CD4+CD27+CD45RA+; naive CD8, CD3+CD4-CD27+CD45RA+; Euronet PHL-C1, Euronet pediatric Hodgkin lymphoma-C1; F, female; IDDM, insulin-dependent diabetes mellitus; ITP, idiopathic thrombocytopenic purpura; M, male; NK, natural killer; PN, parenteral nutrition; RTX, rituximab.
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