Circulating PACAP levels are associated with altered imaging measures of entorhinal cortex neurite density in posttraumatic stress disorder.

Introduction: Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates plasticity in brain systems underlying arousal and memory and is associated with posttraumatic stress disorder (PTSD). Research in animal models suggests that PACAP modulates entorhinal cortex (EC) input to the hippocampus, contributing to impaired contextual fear conditioning. In PTSD, PACAP is associated with higher activity of the amygdala to threat stimuli and lower functional connectivity of the amygdala and hippocampus. However, PACAP-affiliated structural alterations of these regions have not been investigated in PTSD. Here, we examined whether peripheral PACAP levels were associated with neuronal morphology of the amygdala and hippocampus (primary analyses), and EC (secondary) using Neurite Orientation Dispersion and Density Imaging.Methods: Sixty-four (44 female) adults (19 to 54 years old) with DSM-5 Criterion A trauma exposure completed the Clinician-Administered PTSD Scale (CAPS-5), a blood draw, and magnetic resonance imaging. PACAP38 radioimmunoassay was performed and T1-weighted and multi-shell diffusion-weighted images were acquired. Neurite Density Index (NDI) and Orientation Dispersion Index (ODI) were quantified in the amygdala, hippocampus, and EC. CAPS-5 total score and anxious arousal score were used to test for clinical associations with brain structure.Results: Higher PACAP levels were associated with greater EC NDI (ß = 0.0099, q = 0.032) and lower EC ODI (ß = -0.0073, q = 0.047), and not hippocampal or amygdala measures. Neither EC NDI nor ODI was associated with clinical measures.Conclusions: Circulating PACAP levels were associated with altered neuronal density of the EC but not the hippocampus or amygdala. These findings strengthen evidence that PACAP may impact arousal-associated memory circuits in PTSD.

PACAP was associated with altered entorhinal cortex neurite density in PTSD.PACAP was not associated with altered neurite density in amygdala or hippocampus.PACAP may impact arousal-associated memory circuits.

Circulating PACAP levels are associated with altered imaging measures of entorhinal cortex neurite density in posttraumatic stress disorder.

Background: Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates plasticity in brain systems underlying arousal and memory and is associated with posttraumatic stress disorder (PTSD). Research in animal models suggests that PACAP modulates entorhinal cortex (EC) input to the hippocampus, contributing to impaired contextual fear conditioning. In PTSD, PACAP is associated with higher activity of the amygdala to threat stimuli and lower functional connectivity of the amygdala and hippocampus. However, PACAP-affiliated structural alterations of these regions have not been reported. Here, we examined whether peripheral PACAP levels were associated with neuronal morphology of the amygdala and hippocampus (primary analysis), and EC (secondary analysis) using Neurite Orientation Dispersion and Density Imaging. Methods: Sixty-four (44 female) adults (19 to 54 years old) with DSM-5 Criterion A trauma exposure completed the Clinician-Administered PTSD Scale (CAPS-5), a blood draw, and magnetic resonance imaging. PACAP38 radioimmunoassay was performed and T1-weighted and multi-shell diffusion- weighted images were acquired. Neurite Density Index (NDI) and Orientation Dispersion Index (ODI) were quantified in the amygdala, hippocampus, and EC. CAPS-5 total score and anxious arousal score were used to test for clinical associations with brain structure. Results: Higher PACAP levels in blood were associated with greater EC NDI (ß=0.31, q=0.034) and lower EC ODI (ß=-0.30, q=0.042) and not hippocampal or amygdala measures. Neither EC NDI nor ODI was associated with clinical measures. Conclusions: Circulating PACAP levels were associated with altered neuronal density of the EC but not hippocampus or amygdala. These findings strengthen evidence that PACAP may impact arousal- associated memory circuits.

A twenty year record of greenhouse gases in the Eastern Mediterranean atmosphere.

Twenty years of CO2, CH4 and CO greenhouse gas atmospheric concentration measurements at Finokalia station on Crete in the Eastern Mediterranean region are presented. This dataset is the longest in the Eastern Mediterranean, based on bi-weekly grab sampling since 2002 and continuous observations since June 2014. CO2 concentrations increase by 2.4 ppm·y-1 since 2002, in agreement with the general north hemisphere trend as derived by worldwide NOAA observations. CH4 showed a mean increasing trend of 7.5 ppb·y-1 since 2002, a rate that has accelerated since 2018 (12.4 ppb·y-1). In contrast, CO has decreased by 1.6 ppb·y-1 since 2002, which resulted from a strong decrease until 2017 (2.5 ppb·y-1), followed by a small increase in the last 3 years (0.2 ppb·y-1). Both CO2 and CH4 present maxima during winter and minima during summer, in general agreement with the observations at the ICOS stations in Europe. CO also presents the highest values in winter and the lowest values in summer during June, while a secondary maximum is seen in August, which can be attributed to open fires that often occur in the area during this period. The mean summertime diurnal cycles of CH4 and CO agree with a 24-h mean OH radical concentration of the order of 0.3-1 × 107 molecules·cm-3 over the region, in general agreement with the only existing in-situ observations at Finokalia for 2001.

Impact of shipping emissions on air pollution and pollutant deposition over the Barents Sea.

Arctic warming leading to reduced summertime sea-ice is likely to lead to increased local shipping especially along the Northeast Passage near the northern coasts of Norway and Russia, which are shorter than the traditional southerly routes. Here, the regional chemistry-transport model WRF-Chem is used to examine the effects of shipping emissions on levels of air pollutants and deposition fluxes over the Barents Sea both for present-day and future conditions, based on a high growth scenario. Present-day shipping emissions are found to have already substantial effects on ozone concentrations, but limited effects on sulphate and nitrate aerosols. Predicted future changes in ozone are also important, particularly in regions with low nitrogen oxide concentrations, and results are sensitive to the way in which diversion shipping is distributed due to non-linear effects on photochemical ozone production. Whilst modest future increases in sulphate and nitrate aerosols are predicted, large enhancements in dry deposition of sulphur dioxide and wet deposition of nitrogen compounds to the Barents Sea are predicted. Such levels of future nitrogen deposition would represent a significant atmospheric source of oceanic nitrogen affecting sensitive marine ecosystems.

Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation.

A total of 16 global chemistry transport models and general circulation models have participated in this study; 14 models have been evaluated with regard to their ability to reproduce the near-surface observed number concentration of aerosol particles and cloud condensation nuclei (CCN), as well as derived cloud droplet number concentration (CDNC). Model results for the period 2011-2015 are compared with aerosol measurements (aerosol particle number, CCN and aerosol particle composition in the submicron fraction) from nine surface stations located in Europe and Japan. The evaluation focuses on the ability of models to simulate the average across time state in diverse environments and on the seasonal and short-term variability in the aerosol properties. There is no single model that systematically performs best across all environments represented by the observations. Models tend to underestimate the observed aerosol particle and CCN number concentrations, with average normalized mean bias (NMB) of all models and for all stations, where data are available, of -24% and -35% for particles with dry diameters > 50 and > 120nm, as well as -36% and -34% for CCN at supersaturations of 0.2% and 1.0%, respectively. However, they seem to behave differently for particles activating at very low supersaturations (< 0.1 %) than at higher ones. A total of 15 models have been used to produce ensemble annual median distributions of relevant parameters. The model diversity (defined as the ratio of standard deviation to mean) is up to about 3 for simulated N3 (number concentration of particles with dry diameters larger than 3 nm) and up to about 1 for simulated CCN in the extra-polar regions. A global mean reduction of a factor of about 2 is found in the model diversity for CCN at a supersaturation of 0.2% (CCN0.2) compared to that for N3, maximizing over regions where new particle formation is important. An additional model has been used to investigate potential causes of model diversity in CCN and bias compared to the observations by performing a perturbed parameter ensemble (PPE) accounting for uncertainties in 26 aerosol-related model input parameters. This PPE suggests that biogenic secondary organic aerosol formation and the hygroscopic properties of the organic material are likely to be the major sources of CCN uncertainty in summer, with dry deposition and cloud processing being dominant in winter. Models capture the relative amplitude of the seasonal variability of the aerosol particle number concentration for all studied particle sizes with available observations (dry diameters larger than 50, 80 and 120 nm). The short-term persistence time (on the order of a few days) of CCN concentrations, which is a measure of aerosol dynamic behavior in the models, is underestimated on average by the models by 40% during winter and 20% in summer. In contrast to the large spread in simulated aerosol particle and CCN number concentrations, the CDNC derived from simulated CCN spectra is less diverse and in better agreement with CDNC estimates consistently derived from the observations (average NMB -13% and -22% for updraft velocities 0.3 and 0.6 ms-1, respectively). In addition, simulated CDNC is in slightly better agreement with observationally derived values at lower than at higher updraft velocities (index of agreement 0.64 vs. 0.65). The reduced spread of CDNC compared to that of CCN is attributed to the sublinear response of CDNC to aerosol particle number variations and the negative correlation between the sensitivities of CDNC to aerosol particle number concentration (∂N d/∂N a) and to updraft velocity (∂N d/∂w). Overall, we find that while CCN is controlled by both aerosol particle number and composition, CDNC is sensitive to CCN at low and moderate CCN concentrations and to the updraft velocity when CCN levels are high. Discrepancies are found in sensitivities ∂N d/∂N a and ∂N d/∂w; models may be predisposed to be too "aerosol sensitive" or "aerosol insensitive" in aerosol-cloud-climate interaction studies, even if they may capture average droplet numbers well. This is a subtle but profound finding that only the sensitivities can clearly reveal and may explain inter-model biases on the aerosol indirect effect.

Observation- and Model-Based Estimates of Particulate Dry Nitrogen Deposition to the Oceans.

Anthropogenic nitrogen (N) emissions to the atmosphere have increased significantly the deposition of nitrate (NO3-) and ammonium (NH4+) to the surface waters of the open ocean, with potential impacts on marine productivity and the global carbon cycle. Global-scale understanding of the impacts of N deposition to the oceans is reliant on our ability to produce and validate models of nitrogen emission, atmospheric chemistry, transport and deposition. In this work, ~2900 observations of aerosol NO3- and NH4+ concentrations, acquired from sampling aboard ships in the period 1995 - 2012, are used to assess the performance of modelled N concentration and deposition fields over the remote ocean. Three ocean regions (the eastern tropical North Atlantic, the northern Indian Ocean and northwest Pacific) were selected, in which the density and distribution of observational data were considered sufficient to provide effective comparison to model products. All of these study regions are affected by transport and deposition of mineral dust, which alters the deposition of N, due to uptake of nitrogen oxides (NOx) on mineral surfaces. Assessment of the impacts of atmospheric N deposition on the ocean requires atmospheric chemical transport models to report deposition fluxes, however these fluxes cannot be measured over the ocean. Modelling studies such as the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), which only report deposition flux are therefore very difficult to validate for dry deposition. Here the available observational data were averaged over a 5° × 5° grid and compared to ACCMIP dry deposition fluxes (ModDep) of oxidised N (NOy) and reduced N (NHx) and to the following parameters from the TM4-ECPL (TM4) model: ModDep for NOy, NHx and particulate NO3- and NH4+, and surface-level particulate NO3- and NH4+ concentrations. As a model ensemble, ACCMIP can be expected to be more robust than TM4, while TM4 gives access to speciated parameters (NO3- and NH4+) that are more relevant to the observed parameters and which are not available in ACCMIP. Dry deposition fluxes (CalDep) were calculated from the observed concentrations using estimates of dry deposition velocities. Model - observation ratios, weighted by grid-cell area and numbers of observations, (RA,n) were used to assess the performance of the models. Comparison in the three study regions suggests that TM4 over-estimates NO3- concentrations (RA,n = 1.4 - 2.9) and under-estimates NH4+ concentrations (RA,n = 0.5 - 0.7), with spatial distributions in the tropical Atlantic and northern Indian Ocean not being reproduced by the model. In the case of NH4+ in the Indian Ocean, this discrepancy was probably due to seasonal biases in the sampling. Similar patterns were observed in the various comparisons of CalDep to ModDep (RA,n = 0.6 - 2.6 for NO3-, 0.6 - 3.1 for NH4+). Values of RA,n for NHx CalDep - ModDep comparisons were approximately double the corresponding values for NH4+ CalDep - ModDep comparisons due to the significant fraction of gas-phase NH3 deposition incorporated in the TM4 and ACCMIP NHx model products. All of the comparisons suffered due to the scarcity of observational data and the large uncertainty in dry deposition velocities used to derive deposition fluxes from concentrations. These uncertainties have been a major limitation on estimates of the flux of material to the oceans for several decades. Recommendations are made for improvements in N deposition estimation through changes in observations, modelling and model - observation comparison procedures. Validation of modelled dry deposition requires effective comparisons to observable aerosol-phase species concentrations and this cannot be achieved if model products only report dry deposition flux over the ocean.

Analysis of the latitudinal variability of tropospheric ozone in the Arctic using the large number of aircraft and ozonesonde observations in early 2008.

The goal of the paper are to: (1) present tropospheric ozone (O3) climatologies in summer 2008 based on a large amount of measurements, during the International Polar Year when the Polar Study using Aircraft, Remote Sensing, Surface Measurements, and Models of Climate Chemistry, Aerosols, and Transport (POLARCAT) campaigns were conducted (2) investigate the processes that determine O3 concentrations in two different regions (Canada and Greenland) that were thoroughly studied using measurements from 3 aircraft and 7 ozonesonde stations. This paper provides an integrated analysis of these observations and the discussion of the latitudinal and vertical variability of tropospheric ozone north of 55°N during this period is performed using a regional model (WFR-Chem). Ozone, CO and potential vorticity (PV) distributions are extracted from the simulation at the measurement locations. The model is able to reproduce the O3 latitudinal and vertical variability but a negative O3 bias of 6-15 ppbv is found in the free troposphere over 4 km, especially over Canada. Ozone average concentrations are of the order of 65 ppbv at altitudes above 4 km both over Canada and Greenland, while they are less than 50 ppbv in the lower troposphere. The relative influence of stratosphere-troposphere exchange (STE) and of ozone production related to the local biomass burning (BB) emissions is discussed using differences between average values of O3, CO and PV for Southern and Northern Canada or Greenland and two vertical ranges in the troposphere: 0-4 km and 4-8 km. For Canada, the model CO distribution and the weak correlation (< 30%) of O3 and PV suggests that stratosphere-troposphere exchange (STE) is not the major contribution to average tropospheric ozone at latitudes less than 70°N, due to the fact that local biomass burning (BB) emissions were significant during the 2008 summer period. Conversely over Greenland, significant STE is found according to the better O3 versus PV correlation (> 40%) and the higher 75th PV percentile. A weak negative latitudinal summer ozone gradient -6 to -8 ppbv is found over Canada in the mid troposphere between 4 and 8 km. This is attributed to an efficient O3 photochemical production due to the BB emissions at latitudes less than 65°N, while STE contribution is more homogeneous in the latitude range 55°N to 70°N. A positive ozone latitudinal gradient of 12 ppbv is observed in the same altitude range over Greenland not because of an increasing latitudinal influence of STE, but because of different long range transport from multiple mid-latitude sources (North America, Europe and even Asia for latitudes higher than 77°N).

Linking 31P magnetic shielding tensors to crystal structures: experimental and theoretical studies on metal(II) aminotris(methylenephosphonates).

The (31)P chemical shift tensor of the phosphonate group [RC-PO(2)(OH)](-) is investigated with respect to its principal axis values and its orientation in a local coordinate system (LCS) defined from the P atom and the directly coordinated atoms. For this purpose, six crystalline metal aminotris(methylenephosphonates), MAMP·xH(2)O with M = Zn, Mg, Ca, Sr, Ba, and (2Na) and x = 3, 3, 4.5, 0, 0, and 1.5, respectively, were synthesized and identified by diffraction methods. The crystal structure of water-free BaAMP is described here for the first time. The principal components of the (31)P shift tensor were determined from powders by magic-angle-spinning NMR. Peak assignments and orientations of the chemical shift tensors were established by quantum-chemical calculations from first principles using the extended embedded ion method. Structure optimizations of the H-atom positions were necessary to obtain the chemical shift tensors reliably. We show that the (31)P tensor orientation can be predicted within certain error limits from a well-chosen LCS, which reflects the pseudosymmetry of the phosphonate environment.

Investigation of the inhibitory effects of heavy metals on heterotrophic biomass activity and their mitigation through the use of natural minerals.

This study examined the inhibitory effects of lead, copper, nickel and zinc on heterotrophic biomass and their potential mitigation through the use of low-cost, natural minerals. Activated sludge was placed in batch reactors and specific heavy metal concentrations were added. Subsequently, the biomass specific oxygen uptake rate (sOUR) was determined to assess the level of biomass inhibition. Biomass inhibition by heavy metals followed the order Cu(2+)>Pb(2+)>Zn(2+)>Ni(2+), with copper being the most toxic metal, causing high inhibition of heterotrophic biomass even at relatively low concentrations (i.e. 10 mg·L(-1)). Zn had very small toxic effect at 10 mg·L(-1), while at 40 mg·L(-1) the level of biomass inhibition reached 80%. Nickel stimulated activated sludge activity at concentrations of the order of 10 mg·L(-1). The addition of 10 g·L(-1) bentonite and zeolite in activated sludge resulted in the decrease of the inhibitory effect of heavy metals on biomass respiratory activity. In some cases, mineral addition was very favorable as inhibition was reduced from 69-90% to less than 55% and even up to 12%. The beneficial action of minerals is attributed both to the adsorption of heavy metals on the mineral and on the potential aggregation between mineral and sludge particles.