Searching for criteria for the selection of efficient tree species for fallow improvement, with special reference to carbon and nitrogen

Planted fallows are a potential means for regenerating soil fertility in the humid tropics. N-fixing leguminous trees are often recommended for this purpose, but precise criteria for efficient fallow trees do not exist. A combined field and laboratory study was undertaken, including 9 tree species of five years age, of which 6 were N-fixing, and a spontaneous fallow dominated byChromolaena odorata on a Ferralic Cambisol in the Central Côte d'Ivoire. Although the trees differed widely in growth, litterfall and root mass, differences in total soil C and N were small. Soil respiration and N-mineralization were measured by incubating topsoil in the laboratory. The initial CO₂-flush after rewetting differed significantly between species, but non-significant differences afterwards indicated comparable stability and size of the labile C pools of the soils. Total N-mineralization differed significantly between species, with highest values for the control. There was no relationship between the ability of the plants to fix N and N-mineralization or total N-accumulation in the soils. To test the effect of the trees on a subsequent crop, rice was grown in pots filled with topsoil from all plots. Total above-ground dry matter of the rice differed significantly between species and was significantly correlated with N-mineralization in the soil and N-concentration in the rice leaves. N-mineralization was closely related to the amount of litterfall for 7 of the 9 tree species, and to root-mass for the 6 N-fixing tree species. Litterfall and root mass are identified as potential criteria for fallow tree efficiency, but the long-term effect of high N-mineralization rates on available soil-N pools needs further investigation. The importance of soil biological measurements in comparison to chemical soil tests for the assessment of fallow effects is stressed.     

Apolipoprotein B metabolism in hypertriglyceridemic diabetic patients administered either a fish oil- or vegetable oil-enriched diet

The effect on apolipoprotein B kinetics of a diet enriched in either fish oil or safflower oil was investigated in five hypertriglyceridemic (HTG), non-insulin-dependent diabetic subjects. The fish oil diet decreased plasma triglycerides and VLDL-apoB but increased LDL-apoB and LDL-cholesterol. Total plasma apoB concentration did not change, nor did the increased VLDL-apoB secretion present in these HTG subjects, which, accompanied by impaired lipolysis, accounted for their elevated VLDL. The fish oil-induced fall in VLDL resulted from a decrease in secretion without a change in residence time. The IDL fraction, which also contained small VLDL, was the primary site for the secretion of apoB particles in the HTG subjects. On the fish oil diet there was a further, compensatory increase in the secretion of these lipoproteins such that the transport of apoB in IDL remained the same, as did its mass. In the HTG subjects the major portion of IDL lipoproteins was catabolized, with LDL-apoB production comprising the lesser quantity. On the fish oil diet, a shift in the channeling of the lipoprotein output from IDL resulted in a decrease in the catabolic pathway and an increase in conversion to LDL. As the residence time of LDL did not change, this increased input gave rise to the larger mass of LDL-apoB seen in these hypertriglyceridemic subjects when receiving a fish oil diet.     

Fieldbus brings protocol to process control

Recognizing the harvest to be reaped from a standardized interface for interconnecting their wares, the makers of electronic test and measuring instruments long ago devised the arrangement now known as the Standard Digital Interface for Programmable Instrumentation, or IEEE Standard 488. Movers and shakers in the world of process control saw things differently, as a consequence, that industry still lacks a common digital interface for connecting field devices (pumps, valves, temperature transmitters, and so on) to a system controller. This state of affairs is about to change. For a variety of business reasons, companies now appear ready to embrace an industry-wide standard for what has become known as a fieldbus-an all-digital communication network for connecting process instrumentation to controllers. Many candidate systems are under development, indeed some are in use outside the formal standards process. One bus, however, looks well positioned to become an industry standard-the Foundation fieldbus (trade-marked as the FOUNDATION fieldbus). Still under development by the Fieldbus Foundation, Austin, Texas, it has a particular focus on interoperability. Key functional aspects of the Foundation fieldbus ensure that compliant field devices can easily share data and execute standard functions in a control system     

Measurement of cofactor distances between P700.+ and A1.- in native and quinone-substituted photosystem I using pulsed electron paramagnetic resonance spectroscopy

The radical pair P700.+Q.- (P700 = primary electron donor, Q = quinone acceptor) in native photosystem I and in preparations in which the native acceptor (vitamin K1) is replaced by different quinones is investigated by pulsed EPR spectroscopy. In a two-pulse experiment, the light-induced radical pair causes an out-of-phase electron spin echo, showing an envelope modulation. From the modulation frequency, the dipolar coupling, and therefore the distance between the two cofactors, can be derived. The observation of nearly identical distances of about 25.4 A between P700.+ and Q.- in all preparations investigated here leads to the conclusion that the reconstituted quinones are bound to the native A1 binding pocket. Since the orientation of the reconstituted naphthoquinone relative to the axis joining P700.+ and Q*- differs drastically from that of the native vitamin K1, it cannot be bonded to the protein in the same way as the native acceptor. This implies that the function of A1 as an electron acceptor does not depend on the orientation or hydrogen bonding of the quinone.     

Dam Break in Channels with 90° Bend

In practice, dam-break modeling is generally performed using a one-dimensional (1D) approach for its limited requirements in data and computation. However, for valleys with multiple sharp bends, such a 1D model may fail for predicting as well the maximum water level as the wave arrival time. This paper presents an experimental study of a dam-break flow in an initially dry channel with a 90° bend, with refined measurements of water level and velocity field. The measured data are compared to some numerical results computed with finite-volume schemes associated with Roe-type flux calculation. The 1D approach reveals the expected limits, while a full two-dimensional (2D) approach provides fine level prediction and rather satisfactory information about the arrival time. A hybrid approach is now proposed, mixing the 1D model for the straight reaches and local 2D models for the bends. The compatibility of the Roe fluxes at the interfaces requires a careful formulation, but the resulting scheme seems able to capture reflection and diffraction processes in such a way that the results are really good in what concerns the water level.     

Untersuchung von gefriervorgǎngen in zementstein mit hilfe der DTA.

Freezing phenomena in hardened cement paste (hcp) were investigated by DTA. On cooling at least two phase transitions have been observed in the temperature range betwenn -10°C and -25°C and near -43°C respectively. Also a hysteresis between cooling and heating has been found. The phase transitions are correlated to the radius of the water-filled pores and so to relative humidity and water content. Comparable results were obtained in different kinds of hcp. These findings can be explained by the specific properties of water in porous systems induced by surface interaction.     

Overbank Flow in Symmetrically Narrowing Floodplains

Experimental data are presented for flow in compound channels with symmetrically narrowing floodplains. In such a geometry, the flow behavior presents similarities with the more complex flow in a meandering compound channel, yet without the curvature effects, because of mass transfers between the floodplains and the main channel, and secondary currents induced in the main channel. An estimation of the momentum transfer generated by the mass transfer is found significant compared to the frictional losses. It mainly depends on the geometrical parameters and is practically independent of the friction slope. Free-surface profile computations are performed with the exchange discharge model (EDM) to incorporate the effects of the momentum transfer in terms of an additional head loss. Agreement was found between measured and computed water surfaces, thus validating the EDM approach.