Home About us Contact
|
Home About us Contact | ||
|
|
||
Transfer Capacity (transfer + capacity)
Selected AbstractsRegulated cross-border transmission investment in EuropeEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2006Leonardo Meeus Abstract In a liberalized market, generation and transmission investment decisions are decoupled, so that a more elaborated grid is necessary. The European transmission grid has to ensure security of supply, facilitate the market and integrate renewables. Transmission grid investments are clearly needed, especially to increase the scarcely available cross-border transfer capacities. The regulatory framework in which these investments have to take place is discussed in this paper. It is stated that this framework does not ensure that congestion revenues are used for transmission investments that are in the long-term benefit of the market, because regulators are biased towards a short-term tariff reduction. The authors conclude that more coordination is clearly necessary, either pushed by European regulation or driven by coordinated regulatory actions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Analysis of the parameters of the sintered loop heat pipeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2004K.J. Zan Abstract The purpose of this paper is to establish an experimental formula for sintered dendritic nickel powder. For this reason, wick structures with different porosity ranging from 65 to 80% were fabricated by cold pressing sintering process at fixed porosity and their parameters that included porosity, pore radius, and permeability were also measured. According to both the capillary limitation and the present experimental formula of the sintered dendritic nickel powder, the wick structure parameters that would affect the heat transfer capacity of the loop heat pipe (LHP) were analyzed theoretically and then investigated experimentally. The results showed that there exists an optimal combination of wick structure parameters by which the performance of the LHP would achieve optimization. The maximum heat transfer capacity was up to 500 W and the thermal resistance was 0.12°C/W at the allowable working temperature 80°C. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 515,526, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20034 [source] Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit areaPLANT CELL & ENVIRONMENT, Issue 3 2002P. Meir Abstract The observation of acclimation in leaf photosynthetic capacity to differences in growth irradiance has been widely used as support for a hypothesis that enables a simplification of some soil-vegetation-atmosphere transfer (SVAT) photosynthesis models. The acclimation hypothesis requires that relative leaf nitrogen concentration declines with relative irradiance from the top of a canopy to the bottom, in 1 : 1 proportion. In combination with a light transmission model it enables a simple estimate of the vertical profile in leaf nitrogen concentration (which is assumed to determine maximum carboxylation capacity), and in combination with estimates of the fraction of absorbed radiation it also leads to simple ,big-leaf' analytical solutions for canopy photosynthesis. We tested how forests deviate from this condition in five tree canopies, including four broadleaf stands, and one needle-leaf stand: a mixed-species tropical rain forest, oak (Quercus petraea (Matt.) Liebl), birch (Betula pendula Roth), beech (Fagus sylvatica L.) and Sitka spruce (Picea sitchensis (Bong.) Carr). Each canopy was studied when fully developed (mid-to-late summer for temperate stands). Irradiance (Q, µmol m,2 s,1) was measured for 20 d using quantum sensors placed throughout the vertical canopy profile. Measurements were made to obtain parameters from leaves adjacent to the radiation sensors: maximum carboxylation and electron transfer capacity (Va, Ja, µmol m,2 s,1), day respiration (Rda, µmol m,2 s,1), leaf nitrogen concentration (Nm, mg g,1) and leaf mass per unit area (La, g m,2). Relative to upper-canopy values, Va declined linearly in 1 : 1 proportion with Na. Relative Va also declined linearly with relative Q, but with a significant intercept at zero irradiance (P < 0·01). This intercept was strongly related to La of the lowest leaves in each canopy (P < 0·01, r2 = 0·98, n= 5). For each canopy, daily lnQ was also linearly related with lnVa(P < 0·05), and the intercept was correlated with the value for photosynthetic capacity per unit nitrogen (PUN: Va/Na, µmol g,1 s,1) of the lowest leaves in each canopy (P < 0·05). Va was linearly related with La and Na(P < 0·01), but the slope of the Va : Na relationship varied widely among sites. Hence, whilst there was a unique Va : Na ratio in each stand, acclimation in Va to Q varied predictably with La of the lowest leaves in each canopy. The specific leaf area, Lm(cm2 g,1), of the canopy-bottom foliage was also found to predict carboxylation capacity (expressed on a mass basis; Vm, µmol g,1 s,1) at all sites (P < 0·01). These results invalidate the hypothesis of full acclimation to irradiance, but suggest that La and Lm of the most light-limited leaves in a canopy are widely applicable indicators of the distribution of photosynthetic capacity with height in forests. [source] Adaptations in placental nutrient transfer capacity to meet fetal growth demands depend on placental size in miceTHE JOURNAL OF PHYSIOLOGY, Issue 18 2008P. M. Coan Experimental reduction in placental growth often leads to increased placental efficiency measured as grams of fetus produced per gram of placenta, although little is known about the mechanisms involved. This study tested the hypothesis that the smallest placenta within a litter is the most efficient at supporting fetal growth by examining the natural intra-litter variation in placental nutrient transfer capacity in normal pregnant mice. The morphology, nutrient transfer and expression of key growth and nutrient supply genes (Igf2P0, Grb10, Slc2a1, Slc2a3, Slc38a1, Slc38a2 and Slc38a4) were compared in the lightest and heaviest placentas of a litter at days 16 and 19 of pregnancy, when mouse fetuses are growing most rapidly in absolute terms. The data show that there are morphological and functional adaptations in the lightest placenta within a litter, which increase active transport of amino acids per gram of placenta and maintain normal fetal growth close to term, despite the reduced placental mass. The specific placental adaptations differ with age. At E16, they are primarily morphological with an increase in the volume fraction of the labyrinthine zone responsible for nutrient exchange, whereas at E19 they are more functional with up-regulated placental expression of the glucose transporter gene, Slc2a1/GLUT1 and one isoform the System A family of amino acid transporters, Slc38a2/SNAT2. Thus, this adaptability in placental phenotype provides a functional reserve capacity for maximizing fetal growth during late gestation when placental growth is compromised. [source] Construction and Performance of a Minibioreactor Suitable as Experimental Bioartificial LiverARTIFICIAL ORGANS, Issue 4 2008Joaquķn V. Rodriguez Abstract:, This work deals with the construction and performance of a hollow fiber-based minibioreactor (MBR). Due to its simple design and the utilization of standard materials, it could serve as a suitable tool to evaluate the behavior and performance of cold preserved or cultured hepatocytes in bioartificial liver devices. The system consists of 140 fiber capillaries through which goat blood is pumped at a flow of 9 mL/min. The cell compartment contains 90 × 106 rat hepatocytes (volume 10 mL) and an internal oxygenator made of silicone tubing. To test the in vitro function of the system, 2-h perfusion experiments were performed, the evolution of hematocrit, plasma and extra-fiber fluid osmolality, and plasma urea and creatinine concentrations were evaluated. The detoxication efficiency of an ammonia overload was tested, showing that the system has enough capacity to remove ammonium. Also, the MBR oxygen transfer capacity to hepatocytes was tested, showing that the cells received an adequate oxygen supply. [source] Development of a Novel Membrane Aerated Hollow-Fiber MicrobioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2008Louis Villain A new challenge in biotechnological processes is the development of flexible bioprocessing platforms, allowing strain selection, facilitating scale-up and integrating separation steps. Miniaturization of such a cultivation system allows parallel use and the saving of resources but makes the supply of oxygen to the cells difficult. In this work we present a membrane aerated hollow-fiber microbioreactor (HFMBR) which consists of an acrylic glass module equipped with two different types of membrane fibers. Fibers of polyethersulfone and polyvinyldifluoride were used for substrate and oxygen supply, respectively. Cultivation of E. coli as model organism and production of His-tagged GFP were carried out in the extracapillary space of the membrane aerated HFMBR and compared with cultivations in shaking flask which are commonly used for screening experiments. The measurement of the oxygen transfer capacity and the online monitoring of the dissolved oxygen during the cultivation were performed using a fiber optic oxygen sensor. Online measurement of the optical density was also integrated to the bioreactor. Due to efficient oxygen transfer, a better cell growth than in the shaking flask experiments was achieved, while no negative influence on the GFP productivity was observed in the membrane aerated bioreactor. Thus the feasibility of a future integrated downstreaming could also be demonstrated. [source] | |||||||||||||