50 research outputs found
Estimation of speciated and total mercury dry deposition at monitoring locations in eastern and central North America
Dry deposition of speciated mercury, i.e., gaseous oxidized mercury (GOM), particulate-bound mercury (PBM), and gaseous elemental mercury (GEM), was estimated for the year 2008–2009 at 19 monitoring locations in eastern and central North America. Dry deposition estimates were obtained by combining monitored two- to four-hourly speciated ambient concentrations with modeled hourly dry deposition velocities (<i>V</i><sub>d</sub>) calculated using forecasted meteorology. Annual dry deposition of GOM+PBM was estimated to be in the range of 0.4 to 8.1 μg m<sup>−2</sup> at these locations with GOM deposition being mostly five to ten times higher than PBM deposition, due to their different modeled <i>V</i><sub>d</sub> values. Net annual GEM dry deposition was estimated to be in the range of 5 to 26 μg m<sup>−2</sup> at 18 sites and 33 μg m<sup>−2</sup> at one site. The estimated dry deposition agrees very well with limited surrogate-surface dry deposition measurements of GOM and PBM, and also agrees with litterfall mercury measurements conducted at multiple locations in eastern and central North America. This study suggests that GEM contributes much more than GOM+PBM to the total dry deposition at the majority of the sites considered here; the only exception is at locations close to significant point sources where GEM and GOM+PBM contribute equally to the total dry deposition. The relative magnitude of the speciated dry deposition and their good comparisons with litterfall deposition suggest that mercury in litterfall originates primarily from GEM, which is consistent with the limited number of previous field studies. The study also supports previous analyses suggesting that total dry deposition of mercury is equal to, if not more important than, wet deposition of mercury on a regional scale in eastern North America
Nested-grid simulation of mercury over North America
We have developed a new nested-grid mercury (Hg) simulation over North
America with a 1/2° latitude by 2/3° longitude
horizontal resolution employing the GEOS-Chem global chemical transport
model. Emissions, chemistry, deposition, and meteorology are self-consistent
between the global and nested domains. Compared to the global model
(4° latitude by 5° longitude), the nested model shows
improved skill at capturing the high spatial and temporal variability of Hg
wet deposition over North America observed by the Mercury Deposition Network
(MDN) in 2008–2009. The nested simulation resolves features such as
higher deposition due to orographic precipitation, land/ocean contrast and
and predicts more efficient convective rain scavenging of Hg over the
southeast United States. However, the nested model overestimates Hg wet
deposition over the Ohio River Valley region (ORV) by 27%. We modify
anthropogenic emission speciation profiles in the US EPA National Emission
Inventory (NEI) to account for the rapid in-plume reduction of reactive to
elemental Hg (IPR simulation). This leads to a decrease in the model bias to
−2.3% over the ORV region. Over the contiguous US, the correlation
coefficient (<i>r</i>) between MDN observations and our IPR simulation increases
from 0.60 to 0.78. The IPR nested simulation generally reproduces the
seasonal cycle in surface concentrations of speciated Hg from the
Atmospheric Mercury Network (AMNet) and Canadian Atmospheric Mercury Network
(CAMNet). In the IPR simulation, annual mean gaseous and particulate-bound
Hg(II) are within 140% and 11% of observations, respectively. In
contrast, the simulation with unmodified anthropogenic Hg speciation
profiles overestimates these observations by factors of 4 and 2 for gaseous
and particulate-bound Hg(II), respectively. The nested model shows improved
skill at capturing the horizontal variability of Hg observed over California
during the ARCTAS aircraft campaign. The nested model suggests that North
American anthropogenic emissions account for 10–22% of Hg wet deposition
flux over the US, depending on the anthropogenic emissions speciation
profile assumed. The modeled percent contribution can be as high as 60%
near large point sources in ORV. Our results indicate that the North
American anthropogenic contribution to dry deposition is 13–20%
Cerebral activations during viewing of food stimuli in adult patients with acquired structural hypothalamic damage: A functional neuroimaging study
BACKGROUND/OBJECTIVES: Obesity is common following hypothalamic damage due to tumours. Homeostatic and non-homeostatic brain centres control appetite and energy balance but their interaction in the presence of hypothalamic damage remains unknown. We hypothesized that abnormal appetite in obese patients with hypothalamic damage results from aberrant brain processing of food stimuli. We sought to establish differences in activation of brain food motivation and reward neurocircuitry in patients with hypothalamic obesity (HO) compared with patients with hypothalamic damage whose weight had remained stable. SUBJECTS/METHODS: In a cross-sectional study at a University Clinical Research Centre, we studied 9 patients with HO, 10 age-matched obese controls, 7 patients who remained weight-stable following hypothalamic insult (HWS) and 10 non-obese controls. Functional magnetic resonance imaging was performed in the fasted state, 1 h and 3 h after a test meal, while subjects were presented with images of high-calorie foods, low-calorie foods and non-food objects. Insulin, glucagon-like peptide-1, Peptide YY and ghrelin were measured throughout the experiment, and appetite ratings were recorded. RESULTS: Mean neural activation in the posterior insula and lingual gyrus (brain areas linked to food motivation and reward value of food) in HWS were significantly lower than in the other three groups (P=0.001). A significant negative correlation was found between insulin levels and posterior insula activation (P=0.002). CONCLUSIONS: Neural pathways associated with food motivation and reward-related behaviour, and the influence of insulin on their activation may be involved in the pathophysiology of HO.International Journal of Obesity advance online publicatio
Prader-Willi syndrome: A primer for clinicians
The advent of sensitive genetic testing modalities for the diagnosis of Prader-Willi syndrome has helped to define not only the phenotypic features of the syndrome associated with the various genotypes but also to anticipate clinical and psychological problems that occur at each stage during the life span. With advances in hormone replacement therapy, particularly growth hormone children born in circumstances where therapy is available are expected to have an improved quality of life as compared to those born prior to growth hormone
Field Measurements of the Atmospheric Dry Deposition Fluxes and Velocities of Polycyclic Aromatic Hydrocarbons to the Global Oceans
Impact of sex and depressed mood on the central regulation of cardiac autonomic function
Cardiac autonomic dysregulation has been implicated in the comorbidity of major psychiatric disorders and cardiovascular disease, potentially through dysregulation of physiological responses to negative stressful stimuli (here, shortened to stress response). Further, sex differences in these comorbidities are substantial. Here, we tested the hypothesis that mood- and sex-dependent alterations in brain circuitry implicated in the regulation of the stress response are associated with reduced peripheral parasympathetic activity during negative emotional arousal. Fifty subjects (28 females) including healthy controls and individuals with major depression, bipolar psychosis and schizophrenia were evaluated. Functional magnetic resonance imaging and physiology (cardiac pulse) data were acquired during a mild visual stress reactivity challenge. Associations between changes in activity and functional connectivity of the stress response circuitry and variations in cardiovagal activity [normalized high frequency power of heart rate variability (HFn)] were evaluated using GLM analyses, including interactions with depressed mood and sex across disorders. Our results revealed that in women with high depressed mood, lower cardiovagal activity in response to negative affective stimuli was associated with greater activation of hypothalamus and right amygdala and reduced connectivity between hypothalamus and right orbitofrontal cortex, amygdala, and hippocampus. No significant associations were observed in women with low levels of depressed mood or men. Our results revealed mood- and sex-dependent interactions in the central regulation of cardiac autonomic activity in response to negative affective stimuli. These findings provide a potential pathophysiological mechanism for previously observed sex differences in the comorbidity of major depression and cardiovascular disease
Proactive Transparency and Open Data : A Tentative Analysis
Part 6: Open GovernmentInternational audienceIn this paper, we discuss the topic of governmental transparency, and more specifically in relation to Open Data. We look at governmental transparency in terms of channels, benefits, context, directions, etc., and we argue that there is an emergence of new intermediaries in the domain of governmental transparency, made possible mainly through information and communication technology. We then use the concept of public utility to integrate transparency and open data in a larger governmental perspective and we give a few examples of the use of open data to that effect. We propose an approach to support proactive transparency based on Open Data, based on a “lens” to be used to analyse transparency and open data in given contexts
Plasma-Based Water Treatment: Efficient Transformation of Perfluoroalkyl Substances in Prepared Solutions and Contaminated Groundwater
A process
based on electrical discharge plasma was tested for the
transformation of perfluorooctanoic acid (PFOA). The plasma-based
process was adapted for two cases, high removal rate and high removal
efficiency. During a 30 min treatment, the PFOA concentration in 1.4
L of aqueous solutions was reduced by 90% with the high rate process
(76.5 W input power) and 25% with the high efficiency process (4.1
W input power). Both achieved remarkably high PFOA removal and defluorination
efficiencies compared to leading alternative technologies. The high
efficiency process was also used to treat groundwater containing PFOA
and several cocontaminants including perfluorooctanesulfonate (PFOS),
demonstrating that the process was not significantly affected by cocontaminants
and that the process was capable of rapidly degrading PFOS. Preliminary
investigation into the byproducts showed that only about 10% of PFOA
and PFOS is converted into shorter-chain perfluoroalkyl acids (PFAAs).
Investigation into the types of reactive species involved in primary
reactions with PFOA showed that hydroxyl and superoxide radicals,
which are typically the primary plasma-derived reactive species, play
no significant role. Instead, scavenger experiments indicated that
aqueous electrons account for a sizable fraction of the transformation,
with free electrons and/or argon ions proposed to account for the
remainder