Bis(4-methyl-3,5-diphenyl-1H-pyrazole-κN 2)silver(I) nitrate

In the title complex, [Ag(C16H14N2)2]NO3, the geometry around the AgI ion is T-shaped with two short Ag—N bonds to the pyrazole ligand and one long Ag—O bond to the nitrate anion. The crystal structure is stabilized by inter­molecular N—H⋯O, C—H⋯O and C—H⋯π inter­actions

Experimental study into the effect of the closed discontinuity dip angle on the particle acceleration resulted from explosion

The most important effect of a discontinuity when encountered with a wave is the division of wave energy. This process is conducted in the form of dividing the input waves to the reflection and transmission waves. Several researchers have studied the effect of physical and mechanical properties of these discontinuities on waves division. In this study, the effect of the closed discontinuity dip angle has been investigated in the form of experimental tests in scale model. Accordingly, the effect of discontinuity dip from 60 to 120 degrees at 10 degree steps was investigated on particle acceleration of the waves. The results indicated that by increasing the discontinuity dip, the reflection of the waves increase and the vibration is enhanced. On dips greater than 90 degrees, the amount of wave reflection is more than the transmission and at dip angles less than 90 degrees, it is opposite. It was also found that on dips greater than 90 degrees, the ratio of reflection was three times more than the 90 degrees dip and the ratio of reflection is approximately 6 to 7 times more than the transmission of waves. By increasing the angle of discontinuity dip, the attenuation rate of particle acceleration increases where this amount at an angle of 100 degrees is about 30 percent more than that of 90 degrees. Some empirical models for the reflection ratio and the attenuation of the particle acceleration were obtained in terms of the dip angle of discontinuity dip with a high determination coefficient.Keywords: Blast-induced particle acceleration, closed discontinuity, reflection and transmission of waves, scale model tes

Impact of deep convection and dehydration on bromine loading in the upper troposphere and lower stratosphere

Stratospheric bromine loading due to very short-lived substances is investigated with a three-dimensional chemical transport model over a period of 21 years using meteorological input data from the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis from 1989 to the end of 2009. Within this framework we analyze the impact of dehydration and deep convection on the amount of stratospheric bromine using an idealized and a detailed full chemistry approach. We model the two most important brominated short-lived substances, bromoform (CHBr<sub>3</sub>) and dibromomethane (CH<sub>2</sub>Br<sub>2</sub>), assuming a uniform convective detrainment mixing ratio of 1 part per trillion by volume (pptv) for both species. The contribution of very short-lived substances to stratospheric bromine varies drastically with the applied dehydration mechanism and the associated scavenging of soluble species ranging from 3.4 pptv in the idealized setup up to 5 pptv using the full chemistry scheme. In the latter case virtually the entire amount of bromine originating from very short-lived source gases is able to reach the stratosphere thus rendering the impact of dehydration and scavenging on inorganic bromine in the tropopause insignificant. Furthermore, our long-term calculations show that the mixing ratios of very short-lived substances are strongly correlated to convective activity, i.e. intensified convection leads to higher amounts of very short-lived substances in the upper troposphere/lower stratosphere especially under extreme conditions like El Niño seasons. However, this does not apply to the inorganic brominated product gases whose concentrations are anti-correlated to convective activity mainly due to convective dilution and possible scavenging, depending on the applied approach

Atmospheric impacts of chlorinated very short-lived substances over the recent past – Part 2: Impacts on ozone

Depletion of the stratospheric ozone layer remains an ongoing environmental issue, with increasing stratospheric chlorine from very short-lived substances (VSLS) recently emerging as a potential but uncertain threat to its future recovery. Here the impact of chlorinated VSLS (Cl-VSLS) on past ozone is quantified, for the first time, using the UM–UKCA (Unified Model–United Kingdom Chemistry and Aerosol) chemistry-climate model. Model simulations nudged to reanalysis fields show that in the second decade of the 21st century Cl-VSLS reduced total column ozone by, on average, ∼ 2–3 DU (Dobson unit) in the springtime high latitudes and by ∼0.5 DU in the annual mean in the tropics. The largest ozone reductions were simulated in the Arctic in the springs of 2011 and 2020. During the recent cold Arctic winter of 2019/20 Cl-VSLS resulted in local ozone reductions of up to ∼7 % in the lower stratosphere and of ∼7 DU in total column ozone by the end of March. Despite nearly doubling of Cl-VSLS contribution to stratospheric chlorine over the early 21st century, the inclusion of Cl-VSLS in the nudged simulations does not substantially modify the magnitude of the simulated recent ozone trends and, thus, does not help to explain the persistent negative ozone trends that have been observed in the extra-polar lower stratosphere. The free-running simulations, on the other hand, suggest Cl-VSLS-induced amplification of the negative tropical lower-stratospheric ozone trend by ∼20 %, suggesting a potential role of the dynamical feedback from Cl-VSLS-induced chemical ozone loss. Finally, we calculate the ozone depletion potential of dichloromethane, the most abundant Cl-VSLS, at 0.0107. Our results illustrate a so-far modest but nonetheless non-negligible role of Cl-VSLS in contributing to the stratospheric ozone budget over the recent past that if continues could offset some of the gains achieved by the Montreal Protocol.</p

Modelling marine emissions and atmospheric distributions of halocarbons and dimethyl sulfide: the influence of prescribed water concentration vs. prescribed emissions

Marine-produced short-lived trace gases such as dibromomethane (CH2Br2), bromoform (CHBr3), methyliodide (CH3I) and dimethyl sulfide (DMS) significantly impact tropospheric and stratospheric chemistry. Describing their marine emissions in atmospheric chemistry models as accurately as possible is necessary to quantify their impact on ozone depletion and Earth's radiative budget. So far, marine emissions of trace gases have mainly been prescribed from emission climatologies, thus lacking the interaction between the actual state of the atmosphere and the ocean. Here we present simulations with the chemistry climate model EMAC (ECHAM5/MESSy Atmospheric Chemistry) with online calculation of emissions based on surface water concentrations, in contrast to directly prescribed emissions. Considering the actual state of the model atmosphere results in a concentration gradient consistent with model real-time conditions at the ocean surface and in the atmosphere, which determine the direction and magnitude of the computed flux. This method has a number of conceptual and practical benefits, as the modelled emission can respond consistently to changes in sea surface temperature, surface wind speed, sea ice cover and especially atmospheric mixing ratio. This online calculation could enhance, dampen or even invert the fluxes (i.e. deposition instead of emissions) of very short-lived substances (VSLS). We show that differences between prescribing emissions and prescribing concentrations (−28 % for CH2Br2 to +11 % for CHBr3) result mainly from consideration of the actual, time-varying state of the atmosphere. The absolute magnitude of the differences depends mainly on the surface ocean saturation of each particular gas. Comparison to observations from aircraft, ships and ground stations reveals that computing the air–sea flux interactively leads in most of the cases to more accurate atmospheric mixing ratios in the model compared to the computation from prescribed emissions. Calculating emissions online also enables effective testing of different air–sea transfer velocity (k) parameterizations, which was performed here for eight different parameterizations. The testing of these different k values is of special interest for DMS, as recently published parameterizations derived by direct flux measurements using eddy covariance measurements suggest decreasing k values at high wind speeds or a linear relationship with wind speed. Implementing these parameterizations reduces discrepancies in modelled DMS atmospheric mixing ratios and observations by a factor of 1.5 compared to parameterizations with a quadratic or cubic relationship to wind spee

Length frequency, length -weight relationship and gonad development status of silver pomfret, Pampus argenteus, in Khouzestan (Iran) and Kuwait coastal waters, Persian Gulf

Data used in this publication is a part of a comprehensive study was carried out jointly between South Aquaculture Research Center (SIARC) and Kuwait Institute for Scientific Research (KISR) on silver pomfret (Pampus argenteus) in 2003 to 2005. The study was aimed to collect efficient data from two regions from biological and population parameters of this economically important fish to properly explain its stock situation and ultimately leads to improve a better management program for conservation of stock and yield sustainability. Monthly data collection on length and biology, started since May 2003 and ended by December 2005. Shrimp trawl and gill nets were used for sample collection from the predicted areas in both sea regions. FL of the fish was within the range of 12-34cm, with the dominant length of 18-25cm in Kuwaiti waters. In Khouzestan waters fork length was ranged 14-22cm for the years of 2003 and 2004 but 14-26cm for 2005. Strong relationship between length and weight in both countries with a scanty difference was observed for this species (R2 =0.989 for Khouzestn, R^2=0.947 for Kuwait). The findings of present study are suggesting that silver pomfret is following an allometric growth pattern in studied area. Spawning of silver pomfert begin in July and continue till October in Kuwaiti waters but in Khouzestan waters the heights spawning of this fish started in end of May till October. Length at first maturity of this species in the studied area of Kuwait was found to be 19.6cm FL based on Spearman-Karber method but 23.3cm (FL) based on the logistic model. The parameter was estimated 20.0 cm (FL) in Khouzestan waters according to the logistic model

Bis[bis­(3,5-dimethyl-1H-pyrazol-1-yl)­borato]cobalt(II)

The asymmetric unit of the title compound, [Co(C10H16BN4)2], comprises one unit of the complex. The geometry around the CoII ion is a distorted tetra­hedron. The dihedral angles between the pyrazole rings in the two ligands are 47.19 (15) and 47.20 (16)°, while that between the coordination planes is 79.77 (7)°

Revisiting the hemispheric asymmetry in mid-latitude ozone changes following the Mount Pinatubo eruption: A 3-D model study

Following the eruption of Mt. Pinatubo, satellite and in-situ measurements showed a large enhancement in stratospheric aerosol in both hemispheres, but significant mid-latitude column O3 depletion was observed only in the north. We use a three-dimensional chemical transport model to determine the mechanisms behind this hemispheric asymmetry. The model, forced by European Centre for Medium-Range Weather Forecasts ERA-Interim reanalyses and updated aerosol surface area density, successfully simulates observed large column NO2 decreases and the different extents of ozone depletion in the two hemispheres. The chemical ozone loss is similar in the northern (NH) and southern hemispheres (SH), but the contrasting role of dynamics increases the depletion in the NH and decreases it in the SH. The relevant SH dynamics are not captured as well by earlier ERA-40 reanalyses. Overall the smaller SH column O3 depletion can be attributed to dynamical variability and smaller SH background lower stratosphere O3 concentrations

Recent Trends in Stratospheric Chlorine From Very Short‐Lived Substances

Very short‐lived substances (VSLS), including dichloromethane (CH2Cl2), chloroform (CHCl3), perchloroethylene (C2Cl4), and 1,2‐dichloroethane (C2H4Cl2), are a stratospheric chlorine source and therefore contribute to ozone depletion. We quantify stratospheric chlorine trends from these VSLS (VSLCltot) using a chemical transport model and atmospheric measurements, including novel high‐altitude aircraft data from the NASA VIRGAS (2015) and POSIDON (2016) missions. We estimate VSLCltot increased from 69 (±14) parts per trillion (ppt) Cl in 2000 to 111 (±22) ppt Cl in 2017, with \u3e80% delivered to the stratosphere through source gas injection, and the remainder from product gases. The modeled evolution of chlorine source gas injection agrees well with historical aircraft data, which corroborate reported surface CH2Cl2 increases since the mid‐2000s. The relative contribution of VSLS to total stratospheric chlorine increased from ~2% in 2000 to ~3.4% in 2017, reflecting both VSLS growth and decreases in long‐lived halocarbons. We derive a mean VSLCltot growth rate of 3.8 (±0.3) ppt Cl/year between 2004 and 2017, though year‐to‐year growth rates are variable and were small or negative in the period 2015–2017. Whether this is a transient effect, or longer‐term stabilization, requires monitoring. In the upper stratosphere, the modeled rate of HCl decline (2004–2017) is −5.2% per decade with VSLS included, in good agreement to ACE satellite data (−4.8% per decade), and 15% slower than a model simulation without VSLS. Thus, VSLS have offset a portion of stratospheric chlorine reductions since the mid‐2000s