We describe a nearly explicit chemical mechanism for isoprene photooxidation guided by chamber studies that include time-resolved observation of an extensive suite of volatile compounds. We provide ...new constraints on the chemistry of the poorly-understood isoprene δ-hydroxy channels, which account for more than one third of the total isoprene carbon flux and a larger fraction of the nitrate yields. We show that the cis branch dominates the chemistry of the δ-hydroxy channel with less than 5% of the carbon following the trans branch. The modelled yield of isoprene nitrates is 12±3% with a large difference between the δ and β branches. The oxidation of these nitrates releases about 50% of the NOx. Methacrolein nitrates (modelled yield ~15±3% from methacrolein) and methylvinylketone nitrates (modelled yield ~11±3% yield from methylvinylketone) are also observed. Propanone nitrate, produced with a yield of 1% from isoprene, appears to be the longest-lived nitrate formed in the total oxidation of isoprene. We find a large molar yield of formic acid and suggest a novel mechanism leading to its formation from the organic nitrates. Finally, the most important features of this mechanism are summarized in a condensed scheme appropriate for use in global chemical transport models.
Atmospheric field measurements and models of the stratospheric sulfate aerosol layer led to the suggestion that sulfuric acid (H2SO4) must photolyze at high altitudes. We propose that excitation of ...vibrational overtones of H2SO4and its hydrate in the near-infrared and visible leads to photolysis, forming sulfur trioxide ($SO_3$) and water. On the basis of absorption cross sections calculated with ab initio methods calibrated to experimental measurements, we estimated J values that are sufficient to explain stratospheric and mesospheric sulfur dioxide (SO2) concentrations and the observation of the sulfate layer.
Peroxy radical reactions (RO2 + RO2 ) from the NO3 -initiated oxidation of isoprene are studied with both gas chromatography and a chemical ionization mass spectrometry technique that allows for more ...specific speciation of products than in previous studies of this system. We find high nitrate yields (~ 80%), consistent with other studies. We further see evidence of significant hydroxyl radical (OH) formation in this system, which we propose comes from RO2 + HO2 reactions with a yield of ~38-58%. An additional OH source is the second generation oxidation of the nitrooxyhydroperoxide, which produces OH and a dinitrooxyepoxide with a yield of ~35%. The branching ratio of the radical propagating, carbonyl- and alcohol-forming, and organic peroxide-forming channels of the RO2 + RO2 reaction are found to be ~18-38%, ~59-77%, and ~3-4%, respectively. HO2 formation in this system is lower than has been previously assumed. Addition of RO2 to isoprene is suggested as a possible route to the formation of several isoprene C10 -organic peroxide compounds (ROOR). The nitrooxy, allylic, and C5 peroxy radicals present in this system exhibit different behavior than the limited suite of peroxy radicals that have been studied to date.
Humic-like substances (HULIS) comprise a significant fraction of the organic compounds in aerosol particles. In the present study we report the chemical properties of HULIS samples originating from ...urban (Copenhagen, Denmark), rural (Melpitz, Germany) and remote (Storm Peak Laboratory, CO, USA) environments. Suwannee River Fulvic Acid Standard (SRFA) was included in the study as a reference. Raman, Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy were used together with high performance liquid chromatography-mass spectrometry (HPLC-MS) for characterisation of the samples. The same main functional groups were present in all samples, but the relative abundance of functional groups varied among the studied samples, which was mainly evident from the FTIR spectra. The urban and rural samples were found to be very similar with respect to the relative abundance of functional groups. The remote sample contained relatively more C=O and COOH groups, which may be due to the remote environment. Organonitrates appeared to be present in the three atmospheric samples, while it did not appear to be present in the SRFA. The SRFA sample comprised significantly larger amounts of aromatic groups relative to the atmospheric samples in line with previous findings. All the obtained mass spectra showed clear periods of 14-16 Da in line with previous studies. The estimated average molecular weight (AMW) was comparable for the atmospheric samples within the errors - while the AMW of SRFA was higher. In general the atmospheric HULIS samples from different environments were rather similar with respect to the properties investigated.
The primary results from the Vasopressin and Methylprednisolone for In-Hospital Cardiac Arrest (VAM-IHCA) trial have previously been reported. The objective of the current manuscript is to report ...long-term outcomes.
The VAM-IHCA trial was a multicenter, randomized, double-blind, placebo-controlled trial conducted at ten hospitals in Denmark. Adult patients (age ≥ 18 years) were eligible for the trial if they had an in-hospital cardiac arrest and received at least one dose of epinephrine during resuscitation. The trial drugs consisted of 40 mg methylprednisolone (Solu-Medrol®, Pfizer) and 20 IU of vasopressin (Empressin®, Amomed Pharma GmbH) given as soon as possible after the first dose of epinephrine. This manuscript report outcomes at 6 months and 1 year including survival, survival with favorable neurological outcome, and health-related quality of life.
501 patients were included in the analysis. At 1 year, 15 patients (6.3%) in the intervention group and 22 patients (8.3%) in the placebo group were alive corresponding to a risk ratio of 0.76 (95% CI, 0.41–1.41). A favorable neurologic outcome at 1 year, based on the Cerebral Performance Category score, was observed in 14 patients (5.9%) in the intervention group and 20 patients (7.6%) in the placebo group (risk ratio, 0.78 95% CI, 0.41–1.49. No differences existed between groups for favorable neurological outcome and health-related quality of life at either 6 months or 1 year.
Administration of vasopressin and methylprednisolone, compared with placebo, in patients with in-hospital cardiac arrest did not improve long-term outcomes in this trial.
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•Electron delocalization between Ph and chelated rings of Cu(dbm)2 is confirmed.•M–L bond strength in target complexes are theoretically and experimentally studied.•Raman spectrum for ...Cu(dbm)2 is reported for the first time, besides its IR spectrum.•Full and detailed vibrational assignment for Cu(dbm)2 complex is presented.
There are some discrepancies in both the vibrational assignments and in the metal–ligand (M–L) bond strengths predicted in the previous studies on the copper (II) chelated complex of dibenzoylmethane, Cu(dbm)2. Also, there is a lack of theoretical structure, Raman spectrum and full vibrational assignment for Cu(dbm)2 in the literatures. Density functional theory (DFT) at the B3LYP level and also MP2 calculations using different basis sets, besides Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) analyses, have been employed to investigate the effect of methyl substitution with the phenyl group on the stabilities of bis(acetylacetonate) copper (II), Cu(acac)2, and Cu(dbm)2 complexes and the electron delocalization in their chelated rings. Measured solid phase infrared and Raman bands for Cu(dbm)2 complex have been interpreted in terms of the calculated vibrational modes and detailed assignment has been presented. We concluded that, theoretically, the results of charge transfer studies, and experimentally, in-phase symmetric OCuO stretching mode of these complexes are very useful measures for M–L bond strength. The electron delocalization in the chelated rings and the M–L bond strength in Cu(dbm)2 are concluded to be higher than those in Cu(acac)2. The calculated geometries and vibrational results are in good agreement with the experimental data.
Vapor phase OH-stretching overtone spectra of ethylene glycol were recorded to investigate weak intramolecular hydrogen bonding. The spectra were recorded with conventional absorption spectroscopy ...and laser photoacoustic spectroscopy in the first to fourth OH-stretching overtone regions. The room-temperature spectra are dominated by two conformers that show weak intramolecular hydrogen bonding. A less abundant third conformer, with no sign of hydrogen bonding, is also observed. Vapor phase spectra of the ethylene-d 4 glycol isotopomer were also recorded and used to identify an interfering resonance between CH-stretching and OH-stretching states in the fourth overtone. Anharmonic oscillator local mode calculations of the OH-stretching transitions have provided an accurate simulation of the observed spectra. The local mode parameters were calculated with coupled cluster ab initio methods. The calculations facilitate assignment of the different conformers in the spectra and illustrate the effect of the intramolecular hydrogen bonding.
Lipophilic monocations can pass through phospholipid bilayers and accumulate in negatively-charged compartments such as the mitochondrial matrix, driven by the membrane potential. This property is ...used to visualize mitochondria, to deliver therapeutic molecules to mitochondria and to measure the membrane potential. In theory, lipophilic dications have a number of advantages over monocations for these tasks, as the double charge should lead to a far greater and more selective uptake by mitochondria, increasing their therapeutic potential. However, the double charge might also limit the movement of lipophilic dications through phospholipid bilayers and little is known about their interaction with mitochondria. To see whether lipophilic dications could be taken up by mitochondria and cells, we made a series of bistriphenylphosphonium cations comprising two triphenylphosphonium moieties linked by a 2-, 4-, 5-, 6- or 10-carbon methylene bridge. The 5-, 6- and 10-carbon dications were taken up by energized mitochondria, whereas the 2- and 4-carbon dications were not. The accumulation of the dication was greater than that of the monocation methyltriphenylphosphonium. However, the uptake of dications was only described by the Nernst equation at low levels of accumulation, and beyond a threshold membrane potential of 90-100 mV there was negligible increase in dication uptake. Interestingly, the 5- and 6-carbon dications were not accumulated by cells, due to lack of permeation through the plasma membrane. These findings indicate that conjugating compounds to dications offers only a minor increase over monocations in delivery to mitochondria. Instead, this suggests that it may be possible to form dications within mitochondria that then remain within the cell.
Accumulation of phosphorus (P) in agricultural topsoils can contribute to leaching of P which may cause eutrophication of surface waters. An understanding of P mobilization processes in the plough ...layer is needed to improve agricultural management strategies. We compare leaching of total dissolved and particulate P through the plough layer of a typical Danish sandy loam soil subjected to three different P fertilizer regimes in a long‐term field experiment established in 1975. The leaching experiment used intact soil columns (20 cm diameter, 20 cm high) during unsaturated conditions. The three soils had small to moderate labile P contents, expressed by water‐extractable P (3.6–10.7 mg/kg), Olsen P (11–28 mg/kg) and degree of P saturation (DPS) (25–34%). Mobilization of total dissolved P (TDP) increased significantly (P < 0.05) from the intact soil columns with increasing labile P, whereas the increase in particulate P (PP) with increasing labile P content was modest and statistically insignificant. We found concentrations up to 1.5 mg TP/L for the plough layer of this typical Danish sandy loam soil. This highlights that even a moderate labile P content can be a potential source of TDP from the plough layer, and that a lower concentration margin of optimum agronomic P levels should be considered.
The transport of phosphorus (P) from agricultural land has led to the eutrophication of surface waters worldwide, especially in areas with intensive animal production. In this research, we ...investigated the role of bacteria in the leaching of P through three agricultural soils with different textures, before and after the surface application of dairy slurry manure (Bos taurus L.). Leachates of intact soil columns (diameter 20 cm, height 20 cm) of loamy sand, sandy loam and loam were analysed for total bacterial cells measured by universal 16S rRNA genes, and compared with the P content of leachates. The number of 16S rRNA genes per bacterial cell was validated by real‐time polymerase chain reaction (PCR) with a universal 16S rRNA gene primer set. Enumeration of bacterial cells by DAPI staining of cells extracted by density gradient centrifugation of the sandy loam estimated 4.6 16S rRNA genes cell⁻¹. Leaching of bacteria was in the range of 2.5–4.5 × 10⁵ cells ml⁻¹ prior to application of slurry to the three soil textures. After slurry application, leaching increased to 1.1 × 10⁶ cells ml⁻¹ in the loamy sand, 4.9 × 10⁶ cells ml⁻¹ in the sandy loam and 5.0 × 10⁶ cells ml⁻¹ in the loam. Based on the reported P content of soil bacteria, 0.3–1.8% of the total P leached was present in the bacterial biomass when no slurry was applied, whereas slurry application increased the leaching of P from the bacterial biomass to 3−7.9% of total P leached. Bacterial leaching was related to the particulate P fraction of leachates of the loamy sand and sandy loam, but was also related to both dissolved and particulate leachate fractions of the loam. These results indicate that bacterial transport might play a role in the leaching of P from soil where manure has been applied, but this mechanism of transport is generally not addressed when considering the leaching of P.
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