The impact of historical land use change from 1850 to 2000 on particulate matter and ozone

Anthropogenic land use change (LUC) since pre-industrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation. The general trend of expansion of managed ecosystems (croplands and pasturelands) at the expense of natural ecosystems has led to an 11 % decline in global mean biogenic volatile organic compound emissions. Concomitant growth in agricultural activity has more than doubled ammonia emissions and increased emissions of nitrogen oxides from soils by more than 50 %. Conversion to croplands has also led to a widespread increase in ozone dry deposition velocity. Together these changes in biosphere-atmosphere exchange have led to a 14 % global mean increase in biogenic secondary organic aerosol (BSOA) surface concentrations, a doubling of surface aerosol nitrate concentrations, and local changes in surface ozone of up to 8.5 ppb. We assess a global mean LUC-DRF of +0.017 Wm−2, −0.071 Wm−2, and −0.01 Wm−2 for BSOA, nitrate, and tropospheric ozone, respectively. We conclude that the DRF and the perturbations in surface air quality associated with LUC are substantial and should be considered alongside changes in anthropogenic emissions and climate feedbacks in chemistry-climate studies.https://www.atmos-chem-phys.net/16/14997/2016/acp-16-14997-2016.pdfhttps://www.atmos-chem-phys.net/16/14997/2016/acp-16-14997-2016.pdfPublished versio

Compositional nanodomain formation in hybrid formate perovskites

We report the synthesis and structural characterisation of three mixed-metal formate perovskite families [C(NH$_2$)$_3$]M$_{1-x}$Cu$_x$(HCOO)$_3$ (M = Mn, Zn, Mg). Using a combination of infrared spectroscopy, non-negative matrix factorization, and reverse Monte Carlo refinement, we show that the Mn- and Zn-containing compounds support compositional nanodomains resembling the polar nanoregions of conventional relaxor ferroelectrics. The M = Mg family exhibits a miscibility gap that we suggest reflects the limiting behaviour of nanodomain formation.Comment: 4 pages, 3 figure

A New Technique for Repeated Measurement of Cardiac Output During Cardiopulmonary Resuscitation

We have developed a method for measurement of cardiac output during CPR with ventricular fibrillation. The method avoids the problems encountered when conventional techniques are used under the conditions of very low cardiac output. The method consists of injecting 5% saline as the indicator into the left ventricle and detecting its appearance in the descending aorta by withdrawing blood through an electrically calibrated conductivity cell. The adequacy of indicator mixing has been verified by obtaining dilutions curves simultaneously from the brachial and femoral arteries. Cardiac output can be determined even when output is as low as 7 ml/min/kg during CPR with ventricular fibrillation. Repeated determinations can be made as often as every minute. This method offers promise as a practical research tool which can be used with dye indicators also

Potassium Efflux from Myocardial Cells Induced by Defibrillator Shock

A transient, dose-dependent cardiac depression was produced by defibrillator shocks in an isolated, working canine heart preparation perfused with oxygenated arterial blood from a support dog. Accompanying this depression was an efflux of potassium (K+ ), forced out of the myocardial cells by the passage of defibrillating current. The transient increase in extracellular K + concentration was recorded graphically in the venous outflow. It was found that 5-msec rectangular wave shocks, from three to ten times defibrillatory current threshold, released doserelated pulses of K+ . We conclude that because extracellular K + is a myocardial depressant, at least part of the myocardial depression after defibrillation is caused by the release of K+ from the myocardial cells

Lightweight foamed geopolymer

Foamed cementitious materials are becoming more commonly used as an alternative to organic polymer foams in the insulation of buildings. Foamed geopolymers are a promising alternative to other foamed cement-based materials, potentially offering attractive performance with reduced environmental footprint in both manufacturing and operational phases of the material lifecycle. To produce a geopolymer foam derived from metakaolin with a very high strength/density ratio, flash calcined metakaolin was mixed with a sodium silicate activator solution, foamed using aluminum powder and with the addition of polyethylene glycol (PEG) as a bubble stabilising agent. After curing, the densities of the obtained materials ranged from approx. 997 kg/m3 to 1016 kg/m3, with 7-day compressive strengths of up to 14 MPa. The foamed geopolymers produced here have desirable mechanical properties and performance as a construction product, and could potentially be used as a lightweight material for walls or partitions

Cardiac output during CPR: a comparison of two methods

Simultaneous Fick and saline dilution methods were compared for measuring cardiac output during experimental cardiac arrest and resuscitation in anesthetized dogs. During cardiopulmonary resuscitation (CPR) cardiac output averaged 53 ± 30 ml/min-kg (42% of pre-arrest values). Values obtained using the Fick vs. saline methods were highly correlated (r = 0.96), and were not statistically different (t = 1.47, df = 16)

Relationships of Native and Exotic Strains of Phragmites australis to Wetland Ecosystem Properties

Invasions by exotic plant species like Phragmites australis can affect wetlands and the services they provide, including denitrification. Native and exotic Phragmites strains were genetically verified in 2002 but few studies have compared their ecosystem effects. We compared relationships between native and exotic Phragmites and environmental attributes, soil nutrient concentrations, and abundance and activity of soil denitrifying bacteria. There were no significant differences for any measured variables between sites with exotic and native strains. However, there were significant positive correlations between native Phragmites stem density and soil nutrient concentrations and denitrification rates. Furthermore, denitrifying bacterial abundance was positively correlated with nitrate concentration and denitrification rates. Additionally, there were significant negative correlations between water levels in native Phragmites sites and native stem density, nutrient concentrations, and denitrification rates. Surprisingly, we found no significant relationships between exotic stem density or water level and measured variables. These results suggest 1) the native strain may have important ecosystem effects that had only been documented for exotic Phragmites, and 2) abiotic drivers such as water level may have mediated this outcome. Further work is needed to determine if the stem density gradients were a consequence, rather than a cause, of pre-existing gradients of abiotic factors

Effect of calcination method and clay purity on the performance of metakaolin-based geopolymers

The calcination of kaolinite clay to produce metakaolin can be achieved using a range of processes, including rotary, fluidised bed and flash calcination. Rotary calcination was the most popular of these processes for many years as it takes place in a rotary kiln, which is readily available, at easily attainable temperatures of 650 – 800 °C. However, in recent years’ flash calcination processes have become more widely used, and the technology has advanced to a point where commercial flash metakaolin-based geopolymers are now available. Flash calcination involves the rapid heating of clay at temperatures of around 1000 °C for less than a few seconds. The differences in these calcination methods can have a notable effect on the structural ordering of the metakaolin itself, as well as playing an important role in defining the chemical and physical properties of metakaolin-based geopolymers. The purity of the clay also plays a key role in the chemistry of the geopolymers produced. Calcined clay-based geopolymers can be used as construction materials or for the immobilisation of problematic wastes, among other applications, as they can offer desirable performance characteristics. The chemical and physical properties of these geopolymers, and thus the influence of the clay source on key performance parameters, will need to be fully understood when deciding how they can be used for many different applications. This study demonstrates the effect of the calcination method on the properties of calcined metakaolin geopolymer systems for waste immobilisation applications. A main focus of this study is the rheological properties, as the flow properties of these systems are one of the most important parameters for many geopolymer applications. The porosity, heat evolution and mineralogical development of these systems is also presented, with a view towards assessing performance in targeted applications for the immobilisation of nuclear waste

Transchest defibrillation under conditions of hypothermia

This study was conducted to determine whether or not hypothermia changes ventricular defibrillation threshold. Ventricular fibrillation was induced by electrical stimulation of the endocardium in pentobarbital anesthetized dogs, both during normothermia and hypothermia produced by circulating 8 °C water through a rubber bladder implanted in the peritoneal cavity. Defibrillation threshold was determined as the shock strength needed to defibrillate the ventricles and differing no more than 10 percent from a shock strength that failed to defibrillate. Defibrillation threshold current was stable for body temperatures ranging from 37 oC to 22 oC. Threshold energy increased linearly with decreasing temperature in keeping with the expected temperature-dependent changes in body fluid resistance. Normothermic electrical doses are probably appropriate for defibrillation of hypothermic children

Electroventilation

Electroventilation is a term used to describe the production of inspiration by applying rhythmic bursts of short duration stimuli to extrathoracic electrodes to stimulate motor nerves to the inspiratory muscles. In the dog, the optimum site for the electrodes was found to be on the upper chest wall, bilaterally. The inspired volume increased with increasing current intensity. The maximum tidal volume attainable was about four times resting tidal volume. The ability of electroventilation to maintain arterial blood oxygen saturation without the production of cardiac arrhythmias was demonstrated in pentobarbital-anesthetized dogs. The technique has several potential applications and offers promise in emergency and critical-care medicine