Molecular vibrations in a solution-phase reaction are detected at a level of detail rivaling that of gas-phase studies.

Vibrational energy flow into reactants, and out of products, plays a key role in chemical reactivity, so understanding the microscopic detail of the pathways and rates associated with this phenomenon is of considerable interest. Here, we use molecular dynamics simulations to model the vibrational relaxation that occurs during the reaction CN + c-C(6)H(12) → HCN + c-C(6)H(11) in CH(2)Cl(2), which produces vibrationally hot HCN. The calculations reproduce the observed energy distribution, and show that HCN relaxation follows multiple timescales. Initial rapid decay occurs through energy transfer to the cyclohexyl co-product within the solvent cage, and slower relaxation follows once the products diffuse apart. Re-analysis of the ultrafast experimental data also provides evidence for the dual timescales. These results, which represent a formal violation of conventional linear response theory, provide a detailed picture of the interplay between fluctuations in organic solvent structure and thermal solution-phase chemistry.

Tian N, Gu JW, Jordan S, Rose RA, Hughson MD, Manning RD Jr. Immune suppression prevents renal damage and dysfunction and reduces arterial pressure in salt-sensitive hypertension. Am J Physiol Heart Circ Physiol 292: H1018 -H1025, 2007. First published October 13, 2006; doi:10.1152/ajpheart.00487.2006.-The goal of this study was to test the hypothesis that renal infiltration of immune cells in Dahl S rats on increased dietary sodium intake contributes to the progression of renal damage, decreases in renal hemodynamics, and development of hypertension. We specifically studied whether anti-immune therapy, using mycophenolate mofetil (MMF), could help prevent increases in renal NF-B activation, renal infiltration of monocytes/macrophages, renal damage, decreases in glomerular filtration rate (GFR) and renal plasma flow, and increases in arterial pressure. Seventy-four 7-to 8-wk-old Dahl S, Rapp strain rats were maintained on an 8% Na, 8% Na ϩ MMF (20 mg ⅐ kg Ϫ1 ⅐ day Ϫ1 ), 0.3% Na, or 0.3% Na ϩ MMF diet for 5 wk. Arterial and venous catheters were implanted at day 21. By day 35, renal NF-B in 8% Na rats was 47% higher than in 0.3% Na rats and renal NF-B was 41% lower in 8% Na ϩ MMF rats compared with the 8% Na group. MMF treatment significantly decreased renal monocyte/macrophage infiltration and renal damage and increased GFR and renal plasma flow. In high-NA Dahl S rats mean arterial pressure increased to 182 Ϯ 5 mmHg, and MMF reduced this arterial pressure to 124 Ϯ 3 mmHg. In summary, in Dahl S rats on high sodium intake, treatment with MMF decreases renal NF-B and renal monocyte/macrophage infiltration and improves renal function, lessens renal injury, and decreases arterial pressure. This suggests that renal infiltration of immune cells is associated with increased arterial pressure and renal damage and decreasing GFR and renal plasma flow in Dahl salt-sensitive hypertension. renal failure; macrophages; renal hemodynamics; nuclear factor-B SEVERAL MECHANISMS have been found to contribute to the etiology of salt-sensitive hypertension, including reduced levels of NO (7) and elevated oxidative stress (12,29). In addition to these factors, there is emerging evidence indicating that the immune system may play an important role in salt-sensitive hypertension.In several models of hypertension, renal tubulointerstitial infiltration of macrophages and lymphocytes occurs. Renal immunocompetent cells have been found in DOCA hypertension (27), post-angiotensin II (ANG) salt-sensitive hypertension (21), hypertension following NO inhibition (20), protein overload nephropathy (1), the spontaneously hypertensive rate (SHR) (22) and the double-transgenic rat (dTGR) that has human renin and angiotensinogen genes (18). Anti-immune therapy administered to each of the above models of hypertension successfully decreased arterial pressure (24).Dahl salt-sensitive hypertension is characterized by increases in oxidative stress, severe renal damage, and decreases in renal hemodynamics (29); however, the role of renal immune cell infil...

The impact of air pollution on human health and the associated external costs in Europe and the United States (US) for the year 2010 are modeled by a multi-model ensemble of regional models in the frame of the third phase of the Air Quality Modelling Evaluation International Initiative (AQMEII3). The modeled surface concentrations of O3, CO, SO2 and PM2.5 are used as input to the Economic Valuation of Air Pollution (EVA) system to calculate the resulting health impacts and the associated external costs from each individual model. Along with a base case simulation, additional runs were performed introducing 20 % anthropogenic emission reductions both globally and regionally in Europe, North America and east Asia, as defined by the second phase of the Task Force on Hemispheric Transport of Air Pollution (TF-HTAP2).Health impacts estimated by using concentration inputs from different chemistry–transport models (CTMs) to the EVA system can vary up to a factor of 3 in Europe (12 models) and the United States (3 models). In Europe, the multi-model mean total number of premature deaths (acute and chronic) is calculated to be 414 000, while in the US, it is estimated to be 160 000, in agreement with previous global and regional studies. The economic valuation of these health impacts is calculated to be EUR 300 billion and 145 billion in Europe and the US, respectively. A subset of models that produce the smallest error compared to the surface observations at each time step against an all-model mean ensemble results in increase of health impacts by up to 30 % in Europe, while in the US, the optimal ensemble mean led to a decrease in the calculated health impacts by ~ 11 %.A total of 54 000 and 27 500 premature deaths can be avoided by a 20 % reduction of global anthropogenic emissions in Europe and the US, respectively. A 20 % reduction of North American anthropogenic emissions avoids a total of ~ 1000 premature deaths in Europe and 25 000 total premature deaths in the US. A 20 % decrease of anthropogenic emissions within the European source region avoids a total of 47 000 premature deaths in Europe. Reducing the east Asian anthropogenic emissions by 20 % avoids ~ 2000 total premature deaths in the US. These results show that the domestic anthropogenic emissions make the largest impacts on premature deaths on a continental scale, while foreign sources make a minor contribution to adverse impacts of air pollution.

Tian N, Moore RS, Braddy S, Rose RA, Gu JW, Hughson MD, Manning RD Jr. Interactions between oxidative stress and inflammation in salt-sensitive hypertension. Am J Physiol Heart Circ Physiol 293: H3388-H3395, 2007. First published October 5, 2007; doi:10.1152/ajpheart.00981.2007.-The goal of this study was to test the hypothesis that increases in oxidative stress in Dahl S rats on a high-salt diet help to stimulate renal nuclear factor-B (NF-B), renal proinflammatory cytokines, and chemokines, thus contributing to hypertension, renal damage, and dysfunction. We specifically studied whether antioxidant treatment of Dahl S rats on high Na intake would decrease renal inflammation and thus attenuate the hypertensive and adverse renal responses. Sixty-four 7-to 8-wk-old Dahl S or R/Rapp strain rats were maintained for 5 wk on high Na (8%) or high Na ϩ vitamins C (1 g/l in drinking water) and E (5,000 IU/kg in food). Arterial and venous catheters were implanted at day 21. By day 35 in the high-Na S rats, antioxidant treatment significantly increased the renal reduced-to-oxidized glutathione ratio and decreased renal cortical H 2O2 and O2•Ϫ release and renal NF-B. Antioxidant treatment with vitamins C and E in high-Na S rats also decreased renal monocytes/macrophages in the glomeruli, cortex, and medulla, decreased tumor necrosis factor-␣ by 39%, and decreased monocyte chemoattractant protein-1 by 38%. Vitamin-treated, high-Na S rats also experienced decreases in arterial pressure, urinary protein excretion, renal tubulointerstitial damage, and glomerular necrosis and increases in glomerular filtration rate and renal plasma flow. In conclusion, antioxidant treatment of high-Na Dahl S rats decreased renal inflammatory cytokines and chemokines, renal immune cells, NF-B, and arterial pressure and improved renal function and damage. renal failure; cytokines; chemokines; renal hemodynamics; salt-sensitivity; nuclear factor-B STUDIES IN HUMAN AND EXPERIMENTAL HYPERTENSION have shown that increases in oxidative stress may play an important role in the etiology and maintenance of increased blood pressure. Increased oxidative stress has been found in the spontaneously hypertensive rat (SHR), the stroke-prone SHR, DOCA-salt hypertensive rats, and the Dahl salt-sensitive (S) rat (5,6,10,21,22,41,49). In addition, evidence for increased renal oxidative stress has been found in lead-induced hypertension (48), coarctation of the aorta (3), and in the Dahl S rat (22, 43).There is considerable evidence for the involvement of the immune system in hypertension. Studies in several models of experimental hypertension have found renal invasion of lymphocytes and macrophages (24,29,31,40,45). Anti-immune therapy administered to these models of hypertension successfully decreased arterial pressure (32) and renal levels of immunocompetent cells.Our laboratory has shown that the Dahl S rat, when challenged with a high-salt diet, experiences both oxidative stress and inflammation (45), and this is associated with hypertension and considerable r...

Link to publication record in Explore Bristol Research PDF-documentThe following article has been submitted to/accepted by Journal of Chemical Physics. After it is published, it will be found at 10.1063/1.3603966 University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above.

Diesel-powered road vehicles are important sources for nitrogen oxide (NO x ) emissions, and the European passenger fleet is highly dieselised, which has resulted in many European roadside environments being noncompliant with legal air quality standards for nitrogen dioxide (NO2). On the basis of vehicle emission remote sensing data for 300000 light-duty vehicles across the United Kingdom, light-duty diesel NO x emissions were found to be highly dependent on ambient temperature with low temperatures resulting in higher NO x emissions, i.e., a “low temperature NO x emission penalty” was identified. This feature was not observed for gasoline-powered vehicles. Older Euro 3 to 5 diesel vehicles emitted NO x similarly, but vehicles compliant with the latest Euro 6 emission standard emitted less NO x than older vehicles and demonstrated less of an ambient temperature dependence. This ambient temperature dependence is overlooked in current emission inventories but is of importance from an air quality perspective. Owing to Europe’s climate, a predicted average of 38% more NO x emissions have burdened Europe when compared to temperatures encountered in laboratory test cycles. However, owing to the progressive elimination of vehicles demonstrating the most severe low temperature NO x penalty, light-duty diesel NO x emissions are likely to decrease more rapidly throughout Europe than currently thought.

Transient, broadband infra-red absorption spectroscopy with picosecond time resolution has been used to study the dynamics of reactions of CN radicals with tetrahydrofuran (THF) and d(8)-THF in liquid solutions ranging from neat THF to 0.5 M THF in chlorinated solvents (CDCl(3) and CD(2)Cl(2)). HCN and DCN products were monitored via their v(1) (C≡N stretching) and v(3) (C-H(D) stretching) vibrational absorption bands. Transient spectral features indicate formation of vibrationally excited HCN and DCN, and the onsets of absorption via the fundamental bands of HCN and DCN show short (5-15 ps) delays consistent with vibrational relaxation within the nascent reaction products. This interpretation is confirmed by non-equilibrium molecular dynamics simulations employing a newly derived analytic potential energy surface for the reaction in explicit THF solvent. The rate coefficient for reactive formation of HCN (as determined from measurements on both the 1(1)(0) and 3(1)(0) fundamental bands) decreases with increasing dilution of the THF in CDCl(3) or CD(2)Cl(2), showing pseudo-first order kinetic behaviour for THF concentrations in the range 0.5-4.5 M, and a bimolecular rate coefficient of (1.57 ± 0.12) × 10(10) M(-1) s(-1) is derived. Simultaneous analysis of time-dependent HCN 1(1)(0) and 3(1)(0) band intensities following reaction of CN with THF (3.0 M) in CD(2)Cl(2) suggests that C-H stretching mode excitation is favoured, and this deduction is supported by the computer simulations. The results extend our recent demonstration of nascent vibrational excitation of the products of bimolecular reactions in liquid solution to a different, and more strongly interacting class of organic solvents. They serve to reinforce the finding that dynamics (and thus the topology of the reactive potential energy surface) play an important role in determining the nascent product state distributions in condensed phase reactions.