Context. The Rosetta spacecraft made continuous measurements of the coma of comet 67P/Churyumov-Gerasimenko (67P) for more than two years. The plasma in the coma appeared very dynamic, and many ...factors control its variability. Aims. We wish to identify the effects of solar flares on the comet plasma and also their effect on the measurements by the Langmuir Probe Instrument (LAP). Methods. To identify the effects of flares, we proceeded from an existing flare catalog of Earth-directed solar flares, from which a new list was created that only included Rosetta-directed flares. We also used measurements of flares at Mars when at similar longitudes as Rosetta. The flare irradiance spectral model (FISM v.1) and its Mars equivalent (FISM-M) produce an extreme-ultraviolet (EUV) irradiance (10–120 nm) of the flares at 1 min resolution. LAP data and density measurements obtained with the Mutual Impedence Probe (MIP) from the time of arrival of the flares at Rosetta were examined to determine the flare effects. Results. From the vantage point of Earth, 1504 flares directed toward Rosetta occurred during the mission. In only 24 of these, that is, 1.6%, was the increase in EUV irradiance large enough to cause an observable effect in LAP data. Twenty-four Mars-directed flares were also observed in Rosetta data. The effect of the flares was to increase the photoelectron current by typically 1–5 nA. We find little evidence that the solar flares increase the plasma density, at least not above the background variability. Conclusions. Solar flares have a small effect on the photoelectron current of the LAP instrument, and they are not significant in comparison to other factors that control the plasma density in the coma. The photoelectron current can only be used for flare detection during periods of calm plasma conditions.
SrTiO3 exhibits a superconducting dome upon doping with Nb, with a maximum critical temperature Tc≈0.4 K. Using microwave stripline resonators at frequencies from 2 to 23 GHz and temperatures down to ...0.02 K, we probe the low-energy optical response of superconducting SrTiO3 with a charge carrier concentration from 0.3 to 2.2×1020 cm−3, covering the majority of the superconducting dome. We find single-gap electrodynamics even though several electronic bands are superconducting. This is explained by a single energy gap 2Δ due to gap homogenization over the Fermi surface consistent with the low level of defect scattering in Nb-doped SrTiO3. Furthermore, we determine Tc, 2Δ, and the superfluid density as a function of charge carrier concentration, and all three quantities exhibit the characteristic dome shape.
Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ...ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.
Thrombolytic therapy and mortality Thiemann, David R; Coresh, Josef; Schulman, Steven P ...
The Lancet (British edition),
04/2001, Letnik:
357, Številka:
9265
Journal Article
Abstract
Coronary computed tomography angiography (CCTA) offers high-resolution anatomic characterization of the coronary vasculature but may be suboptimal for lesions dependent on real-time ...visualization of flow including chronic total occlusion (CTO). In CTOs, heavy calcification and distal vessel opacification from collateralization may confound luminal assessment. Several studies have examined the role of CCTA in characterizing known CTOs to guide percutaneous coronary intervention (PCI). However, the efficacy of CCTA in the de novo diagnosis of CTOs prior to coronary angiography (CAG) has not been demonstrated. A total of 233 consecutive patients who presented for CAG within a 3-month period of having CCTA were retrospectively reviewed. Those patients with prior diagnosis of CTO or prior bypass of the occluded vessels were excluded. Sensitivity and specificity analysis of CCTA in identifying CTOs using CAG as the gold standard was performed. The prevalence of CTO was 21.11% in the population that met criteria for analysis (
n
= 199). The sensitivity of CCTA in predicting CTO was 57.1%, while the specificity was 96.8%. The positive predictive value and negative predictive value of CCTA in detection of CTO were 82.8 and 89.4%, respectively. Our study shows that CCTA has excellent specificity but poor sensitivity in the detection of CTO thus limiting its clinical use in de novo diagnosis. Further studies to determine the effect of de novo CTO diagnosis on clinically important procedural factors, such as radiation exposure, contrast use, and need for repeat procedures, are warranted and may implicate a role for CCTA in this setting.
Many studies using mammalian cellular and subcellular systems have demonstrated that polycyclic aromatic hydrocarbons, including benzoapyrene (BaP), are metabolically activated by cytochrome P450s ...(CYPs). In order to evaluate the role of hepatic versus extra-hepatic metabolism of BaP and its pharmacokinetics, we used the hepatic cytochrome P450 reductase null (HRN) mouse model, in which cytochrome P450 oxidoreductase, the unique electron donor to CYPs, is deleted specifically in hepatocytes, resulting in the loss of essentially all hepatic CYP function. HRN and wild-type (WT) mice were treated intraperitoneally (i.p.) with 125 mg/kg body wt BaP daily for up to 5 days. Clearance of BaP from blood was analysed by high-performance liquid chromatography with fluorescence detection. DNA adduct levels were measured by 32P-post-labelling analysis with structural confirmation of the formation of 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzoapyrene by liquid chromatography–tandem mass spectrometry analysis. Hepatic microsomes isolated from BaP-treated and untreated mice were also incubated with BaP and DNA in vitro. BaP–DNA adduct formation was up to 7-fold lower with the microsomes from HRN mice than with that from WT mice. Most of the hepatic microsomal activation of BaP in vitro was attributable to CYP1A. Pharmacokinetic analysis of BaP in blood revealed no significant differences between HRN and WT mice. BaP–DNA adduct levels were higher in the livers (up to 13-fold) and elevated in several extra-hepatic tissues of HRN mice (by 1.7- to 2.6-fold) relative to WT mice. These data reveal an apparent paradox, whereby hepatic CYP enzymes appear to be more important for detoxification of BaP in vivo, despite being involved in its metabolic activation in vitro.
PDF
