Fractional Rate Of Increase Research Articles

Sensitivities of Extreme Precipitation to Global Warming Are Lower over Mountains than over Oceans and Plains

Abstract Climate-model simulations predict an intensification of extreme precipitation in almost all areas of the world under global warming. Local variations in the magnitude of this intensification are evident in these simulations, but most previous efforts to understand the factors responsible for the changes in extreme precipitation focused on zonal averages and neglected zonal variations, leading to uncertainties in the understanding and estimation of regional responses. Here the spatial heterogeneity of the warming-induced response of midlatitude extreme precipitation is studied in climate-model simulations with idealized orography on the western margins of otherwise flat continents. It is shown that the sensitivity of extreme precipitation to warming (i.e., its fractional rate of increase in intensity with global-mean surface temperature) is ~3% K−1 lower over the mountains than the oceans and plains. This difference in sensitivity is primarily produced by differences in the dynamics governing vertical ascent over the three regions. In these extreme events, mountain-wave dynamics control the moist ascent over the mountains, and the sensitivity of this ascent to global warming is mainly controlled by changes in upper-level dry static stability and the cross-mountain winds. In contrast, midlatitude cyclone dynamics govern moist ascent over the oceans and plains. Ascending motions in intense midlatitude cyclones are sensitive to the ratio of the moist static stability in their saturated cores to the dry stability in surrounding regions. This ratio decreases in the warmer world, intensifying the maximum vertical velocities while reducing the horizontal extent of the regions of the rising air within the cyclone.

Scaling of Precipitation Extremes over a Wide Range of Climates Simulated with an Idealized GCM

Abstract Extremes of precipitation are examined in a wide range of climates simulated with an idealized aquaplanet GCM. The high percentiles of daily precipitation increase as the climate warms. Their fractional rate of increase with global-mean surface temperature is generally similar to or greater than that of mean precipitation, but it is less than that of atmospheric (column) water vapor content. A simple scaling is introduced for precipitation extremes that accounts for their behavior by including the effects of changes in the moist-adiabatic lapse rate, the circulation strength, and the temperature when the extreme events occur. The effects of changes in the moist-adiabatic lapse rate and circulation strength on precipitation extremes are important globally, whereas the difference in the mean temperature and the temperature at which precipitation extremes occur is important only at middle to high latitudes.

Noise shaping in neural populations

Many neurons display intrinsic interspike interval correlations in their spike trains. However, the effects of such correlations on information transmission in neural populations are not well understood. We quantified signal processing using linear response theory supported by numerical simulations in networks composed of two different models: One model generates a renewal process where interspike intervals are not correlated while the other generates a nonrenewal process where subsequent interspike intervals are negatively correlated. Our results show that the fractional rate of increase in information rate as a function of network size and stimulus intensity is lower for the nonrenewal model than for the renewal one. We show that this is mostly due to the lower amount of effective noise in the nonrenewal model. We also show the surprising result that coupling has opposite effects in renewal and nonrenewal networks: Excitatory (inhibitory coupling) will decrease (increase) the information rate in renewal networks while inhibitory (excitatory coupling) will decrease (increase) the information rate in nonrenewal networks. We discuss these results and their applicability to other classes of excitable systems.

Effect of Liquid Flavor Supplementation of the Diet on Dairy Cows in the Transition Period

A 9-wk trial was conducted to study the performance of 24 Holstein cows during the transition period (3wk prepartum to 6wk postpartum). Cows were assigned to either a control or liquid-flavored (0.52mL/kg of feed) total mixed ration in a randomized complete block design. The diets contained corn silage, alfalfa haylage, cottonseed, and a grain mix based on ground corn and soybean meal. Cows were fed to ensure 10% orts, and the diet provided (on a dry matter basis) 13% crude protein, 32% acid detergent fiber, 44% neutral detergent fiber, and 1.54Mcal/kg of NEL prepartum and 17.5% crude protein, 30% acid detergent fiber, 40% neutral detergent fiber, and 1.57Mcal/kg of NEL postpartum. An additional 2.3kg of alfalfa hay was fed during the first 5 d postpartum. Weekly means of dry matter intake (DMI), milk yield, milk protein, milk fat, SNF, somatic cell counts, and body weight (BW) were analyzed using a repeated measures procedure. There was no effect of treatment on these variables, and least squares means were 16.9 and 15.7kg/d for DMI, 38 and 35.3kg/d for milk yield, 3.10 and 3.11% for milk protein, 3.69 and 3.74% for milk fat, 8.37 and 8.16% for SNF, 1.99×105 and 4.33×105 for somatic cell count, and 631 and 651kg for BW for cows fed control and flavored diets, respectively. Individual cow daily DMI data were fitted to an exponential model describing pre- and postpartum feed consumption [DMI = a−b×e(−c×t), where DMI was measured in kg, a = asymptotic DMI, b = potential fractional increase in DMI, c = fractional rate of increase in DMI, and t = days prior to calving or days in milk]. Fractional rates of increase in DMI were similar: 0.139 and 0.123/d for control and flavored diets, respectively. Data for both groups were separately analyzed using multiple regression with 3.5% fat-corrected milk as the dependent variable and BW and DMI as independent variables. More BW was mobilized per unit increase in 3.5% fat-corrected milk in cows fed the control than in cows fed the flavored diet. Cows fed the control diet tended to be in more negative energy balance during early lactation than cows fed the flavored diet. It was concluded that feeding flavor improved energy balance of cows in early lactation and may reduce the risk of health or reproductive problems.

Transport characteristics related with microstructure of (Bi, Pb)-Sr-Ca-Cu-O superconductor prepared by the sol-gel method

Differences in the transport characteristics of Bi2Sr2Ca2Cu3Oy (high-T c phase) superconducting ceramics produced by two-step heat-treatment (calcination and reheating at various temperatures) of metal acetate-derived gels are discussed in relation to their microstructure. Variation of the volume fraction increase rate of the high-T c phase, which depends on the calcination temperature, results in much difference in the transport characteristics of the resultant samples. Superconducting bodies possessing a higher T c(end) and critical current density can be obtained at a lower volume fraction increase-rate of the high-T c phase. It is considered that the origin of the above results is an improvement of the weak-link structure.

Kinetics of Hydrolytic Aging of Polyester Urethane Elastomers

Abstract : The hydrolytic degradation of polyester urethane elastomers is due to the acid catalyzed hydrolysis of the ester group. Acid content (A) and the reciprocal of the number average molecular weight increase by equivalent amounts indicating that each molecular chain scission produces one acid group. The fractional rate of increase in acidity, k, is a pseudo first order rate constant because the ester and water contents change only slightly with degradation. Values of k at 85 C and 100% relative humidity are in the 15-20% per day for polyurethanes, based on polycaprolactone and polytetramethylene adipate diols. At 100% relative humidity k obeys the Arrhenius equation between 35 and 85 C with activation energies in the range 68-83 kJ/mol (16-20 kcal/mol). Values of k decrease with relative humidity, becoming zero in dry air.