Anatomical adaptations for peripheral oxygen transport at high and low temperatures

On acute cold exposure most animals show a reduction in cardiac output and increased blood viscosity that may seriously impair oxygen supply to peripheral tissue. The apparent increase in capillarisation in response to chronic low temperature may be accompanied by significant muscle atrophy in hibernating mammals, and a rise in capillary density (CD) may then simply reflect a reduced fibre diameter. When hamsters were exposed to reduced temperature and photoperiod, capillary to fibre ratio (C:F) of the tibialis anterior muscle was unchanged (at 2.7) and CD increased by 30% (to 1538 mm−2) following a similar decrease in fibre size. A measure of local C:F decreased around glycolytic fibres, but increased around both oxidative fibre types. When corrected for changes in fibre size, local CD increased around all fibre types in the cold. Fishes are particularly sensitive to fluctuations in environmental temperature, but in contrast to mammals often maintain activity and undergo muscle hypertrophy. Slow (aerobic) muscle from striped bass and goldfish held for eight weeks at seasonal extremes of 5 and 25°C had a higher C:F in cold vs. warm animals. However, increased fibre size meant that the functional capacity of the microcirculation was maintained rather than increased. Seasonal acclimatisation of trout induced an inverse relationship between environmental temperature and C:F, increasing 40% from summer (18°C) to winter (4°C). However, extensive hypertrophy at 4°C meant that the size of the capillary bed was maximal at 11°C, corresponding to the point of highest muscle blood flow and greatest scope for aerobic swimming, reflecting an optimised aerobic performance at intermediate temperatures. The consequence of altered fibre composition and capillarisation is calculated as an increase in mean fibre PO2 from 1.9 to 4.6 kPa, and in minimum PO2 from 0.6 to 4.2 kPa in 25° v. 5°C-acclimated striped bass, respectively. However, the most dramatic effect on intracellular oxygenation results from an altered capillary supply with the capillary supply becoming increasingly inadequate at high temperatures

Keep It Real!: A Real-time UK Macro Data Set

In this paper, we present a real-time macro data set for the UK. Each variable has many different vintages---reflecting the revisions that occur in real time. Our aim is to provide a resource that allows researchers to assess the robustness of their results to data revisions. We illustrate the importance of this issue by analysing the impact of real-time data on UK inflation forecasts.

"Keep it real!": A real-time UK macro data set

We present a real-time macro data set for the UK. Each variable has many different vintages - reflecting the revisions and s that occur over time. Our aim is to provide a resource for researchers evaluating UK forecasting performance and policy-making in real time. We illustrate the importance of these data by analysing their impacts on UK inflation forecasts and monetary policy in the late 1980s. We find that, contrary to the view of contemporary policy-makers, the initial measurements of demand-side macro variables did not disguise inflationary pressures.

Local capillary supply in muscle is not determined by local oxidative capacity

It is thought that the prime determinant of global muscle capillary density is the mean oxidative capacity. However, feedback control during maturational growth or adaptive remodelling of local muscle capillarisation is likely to be more complex than simply matching O2 supply and demand in response to integrated tissue function. We tested the hypothesis that the maximal oxygen consumption (MO2,max) supported by a capillary is relatively constant, and independent of the volume of tissue supplied (capillary domain). We demonstrate that local MO2,max assessed by succinate dehydrogenase histochemistry: (1) varied more than 100-fold between individual capillaries and (2) was positively correlated to capillary domain area in both human vastus lateralis (R=0.750, P<0.001) and soleus (R=0.697, P<0.001) muscles. This suggests that, in contrast to common assumptions, capillarisation is not primarily dictated by local oxidative capacity, but rather by factors such as fibre size, or consequences of differences in fibre size such as substrate delivery and metabolite removal

Denitrification in a pasture soil

The effect of multiple applications of cow slurry or inorganic nitrogen fertiliser (calcium nitrate) on the composition of the soil atmosphere was studied over three years, in an imperfectly drained pasture soil. Irrespective of fertiliser treatments concentrations of oxygen (‎O2) decreased and carbon dioxide (CC^) increased during the winter months, but remained near ambient levels during the summer. Slurry decreased 02 concentrations temporarily, especially following applications in the autumn and in the spring. Concentrations of nitrous oxide (N20) remained close to ambient during the summer under all treatments but increased over the autumn, winter and spring,especially in the few weeks following fertiliser applications. Enhanced N20 concentrations were significantly related to decreases in O2.The relative diffusivity of soil cores from the field site was determined from the rate of diffusion of 85Kr through the cores. From this, the diffusion coefficient for N2O was calculated and used to estimate the flux of N2O from the field plot. Losses from plots receiving inorganic fertiliser were up to 6kg N ha-1 a-1 but lower than this from control plots and plots receiving slurry.In the 3rd year acetylene (C2H2) was used to inhibit the reduction of N2O to N2 in microplots enclosed by plastic cylinders driven into the soil, so that total gaseous losses could be measured. These were low during the summer and in the winter in all treatments, but increased during the autumn and spring. Losses of N were highest in the inorganic fertiliser treatment: 10 and 21% of the N applied in the autumn and spring, respectively. Fluxes of up to 115g N ha-1 h-1 were recorded. Losses from the slurried plots were only slightly higher than from the control plots. When fluxes were low, most loss of N was as N2O, but the proportion lost as N2 increased as the total flux increased. The highest ratio of (N2 + N20) :N20 recorded was 25.In laboratory experiments C2H2 was found to inhibit nitrification totally at a concentration of 0.04ml ml-1 but the effect was found to be reversible. Acetylene also inhibited N2O reduction. In aerobic conditions C2H2 increased soil respiration, some of the C2H2 being consumed in the process. Several colonies of bacteria were isolated from the soil able to use C2H2 as their sole carbon source

Three Essays on Quote Stuffing, Dealer Liquidity and Stub Quoting

This dissertation consists of three essays on quote stuffing, dealer provided liquidity, and stub quoting. The first essay examines the impact that intense episodic spikes in quoting activity (frequently referred to as quote stuffing ) has on market conditions. We find that quote stuffing is pervasive with several hundred events occurring each trading day and that over 74% of US exchange traded securities experience at least one episode during 2010. We find that during periods of intense quoting activity stocks experience decreased liquidity, higher trading cost, and increased short term volatility. In the second we examine the role of the NASDAQ market marker over time. Specifically, we study the liquidity providing behavior of NASDAQ market markers in the trading environment in 2010 compared to 2004. We examine the frequency with which market makers are at the inside quote, the market and stock specific factors that influence market maker participation, changes in the number of market makers over time, and the relation between market maker participation and intraday bid-ask spread patterns. We find that the role of NASDAQ market makers declines over time. In 2004, the percentage of the trading day that market makers quote at the inside bid (ask) is 60% (62%) compared to 2010 when NASDAQ dealers quote at the inside bid (ask) just 12% (11%). The number of market makers declines. We also find evidence that the influence market makers have on intraday variations in the bid-ask declines over time. Finally in the third essay, we examine the liquidity providing behavior of NASDAQ market makers surrounding two periods of changing dealer obligation. The first period is the relaxation of Rule 4613 in November of 2007 which required NASDAQ market makers to place two-sided quotes that must be reasonably related to the current best bid and offer. This rule change permitted NASDAQ market makers to post quotes far away from the prevailing market (frequently referred to as a Stub Quote ). The second is the Securities and Exchange Commission ban on stub quoting in December 2010 which requires that market makers quote within a predefined distance from market prices. We find evidence in both the 2007 and 2010 rule change periods that placing restrictions on stub quoting alters market makers liquidity providing behavior. Stub quote restrictions increase the time that market makers quote at the NBBO. We also find evidence that stub quoting restrictions increase the percent of daily volume executed by market makers. However, we find little evidence that stub quoting rules impact the participation of market makers during days with excessive volatility

Environmental stress influences mitochondrial metabolism in vascular cells: consequences for angiogenesis

While the important and varied roles that vascular cells play in both health and disease is well recognised, the focus on potential therapeutic targets continually shifts as new players emerge. Here, we outline how mitochondria may be viewed as more than simply energygenerating organelles, but instead as important sentinels of metabolic health and effectors of appropriate responses to physiological challenges

The Robust Maximum Daily Return Effect as Demand for Lottery and Idiosyncratic Volatility Puzzle

We form indexes of overpriced and underpriced stocks by ranking stocks based on the disposition effect and anchoring bias. We document the negative relation between maximum daily return and future returns (MAX effect) is confined to overpriced stocks which make up about half the entire sample. We find that the average cross-sectional correlation between maximum daily return and idiosyncratic volatility is nearly 90%. Consistent with prior studies the idiosyncratic volatility puzzle disappears after controlling for the MAX effect. However, when using a sample with a $5 price breakpoint and controlling for overpriced stocks the idiosyncratic volatility puzzle and the MAX effect are economically and statistically significant