Found 9941 publications. Showing page 293 of 398:
Polycyclic Aromatic Hydrocarbons Not Declining in Arctic Air Despite Global Emission Reduction
Two decades of atmospheric measurements of polycyclic aromatic hydrocarbons (PAHs) were conducted at three Arctic sites, i.e., Alert, Canada; Zeppelin, Svalbard; and Pallas, Finland. PAH concentrations decrease with increasing latitude in the order of Pallas > Zeppelin > Alert. Forest fire was identified as an important contributing source. Three representative PAHs, phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) were selected for the assessment of their long-term trends. Significant decline of these PAHs was not observed contradicting the expected decline due to PAH emission reductions. A global 3-D transport model was employed to simulate the concentrations of these three PAHs at the three sites. The model predicted that warming in the Arctic would cause the air concentrations of PHE and PYR to increase in the Arctic atmosphere, while that of BaP, which tends to be particle-bound, is less affected by temperature. The expected decline due to the reduction of global PAH emissions is offset by the increment of volatilization caused by warming. This work shows that this phenomenon may affect the environmental occurrence of other anthropogenic substances, such as more volatile flame retardants and pesticides.
2019
2008
2007
POP model intercomparison study. Stage 1. Comparison of descriptions of main processes determining POP behaviour in various environmental compartments. EMEP MSC-E Technical Report, 1/2004
2004
POP model intercomparison study. Stage II. Comparison of mass balance estimates and sensitivity studies. EMEP/MSC-E Technical Report, 5/2006
2006
POP model intercomparison study. Stage II. Comparison of mass balance estimates and sensitivity studies. DRAFT. EMEP/MSC-E Technical Report, 4/2005
2005
2001
2004
2005
2004
Background
Quantitative measurements of cerebrospinal fluid to blood clearance has previously not been established for neurological diseases. Possibly, variability in cerebrospinal fluid clearance may affect the underlying disease process and may possibly be a source of under- or over-dosage of intrathecally administered drugs. The aim of this study was to characterize the cerebrospinal fluid to blood clearance of the intrathecally administered magnetic resonance imaging contrast agent gadobutrol (Gadovist, Bayer Pharma AG, GE). For this, we established a population pharmacokinetic model, hypothesizing that cerebrospinal fluid to blood clearance differs between cerebrospinal fluid diseases.
Methods
Gadobutrol served as a surrogate tracer for extra-vascular pathways taken by several brain metabolites and drugs in cerebrospinal fluid. We estimated cerebrospinal fluid to blood clearance in patients with different cerebrospinal fluid disorders, i.e. symptomatic pineal and arachnoid cysts, as well as tentative spontaneous intracranial hypotension due to cerebrospinal fluid leakage, idiopathic intracranial hypertension, or different types of hydrocephalus (idiopathic normal pressure hydrocephalus, communicating- and non-communicating hydrocephalus). Individuals with no verified cerebrospinal fluid disturbance at clinical work-up were denoted references.
Results
Population pharmacokinetic modelling based on 1,140 blood samples from 161 individuals revealed marked inter-individual variability in pharmacokinetic profiles, including differences in absorption half-life (time to 50% of tracer absorbed from cerebrospinal fluid to blood), time to maximum concentration in blood and the maximum concentration in blood as well as the area under the plasma concentration time curve from zero to infinity. In addition, the different disease categories of cerebrospinal fluid diseases demonstrated different profiles.
Conclusions
The present observations of considerable variation in cerebrospinal fluid to blood clearance between individuals in general and across neurological diseases, may suggest that defining cerebrospinal fluid to blood clearance can become a useful diagnostic adjunct for work-up of cerebrospinal fluid disorders. We also suggest that it may become useful for assessing clearance capacity of endogenous brain metabolites from cerebrospinal fluid, as well as measuring individual cerebrospinal fluid to blood clearance of intrathecal drugs.
BioMed Central (BMC)
2022
2013
2002
2017
2007
Possible future petroleum activity around Jan Mayen. Consequences of emissions to air. NILU OR
Norwegian Institute for Air Research (NILU), Norwegian Institute for Water Research (NIVA) and the Norwegian Institute for Nature Research (NINA) have concidered the effects on the environment of emissions of NOx, SO2 and particulate matter into the air from any future petroleum activity in the waters around Jan Mayen. It is estimated deposition of nitrogen, sulfur and particulates - also formation of ozone is calculated. It is also considered what effect it has on nature. Calculations indicate that emissions most likely will not lead to negative effects on vegetation and fauna of the terrestrial impact area.
2012
Norwegian Institute for Air Research (NILU), Norwegian Institute for Water Research (NIVA) and the Norwegian Institute for Nature Research (NINA) have concidered the effects on the environment of emissions of NOx, SO2 and particulate matter into the air from any future petroleum activity in Barents-sea. It is estimated deposition of nitrogen, sulfur and particulates - also formation of ozone is calculated. It is also considered what effect it has on nature. Calculations indicate that emissions most likely will not lead to negative effects on vegetation and fauna of the terrestrial impact area.
2012
2002