Efficient water management practices

Presented at Competing interests in water resources - searching for consensus: proceedings from the USCID water management conference held on December 5-7, 1996 in Las Vegas, Nevada.In September 1990, AB 3616, "The Agricultural Water Suppliers Act," became law in California. This law required the Department of Water Resources (DWR) to establish an advisory committee to review and study potential Efficient Water Management Practices (EWMPs) and to determine which were feasible for achieving water conservation. The advisory committee was comprised of representatives of the California farming community, agricultural water suppliers, the Department of Food and Agriculture, the University of California, the California State University, public interest groups, and other interested parties. During 1992, the last year of California's six year drought, Governor Wilson, in a speech discussing California's water needs, referred to the many water conservation practices developed by California's farmers and expressed his support for the development of EWMPs for agricultural water use. He further emphasized the AB 3616 Advisory Committee should develop a strategy for implementing these practices. An Urban Memorandum of Understanding (MOU) had recently been signed by urban water suppliers and public interest groups (environmentalists). The urban signatories committed to implement certain Best Management Practices during a specific time frame to help reduce future demand and conserve water supplies. The Governor was hopeful a similar MOU could be developed for agricultural water suppliers which would encourage further improvements in water management. The Governor's directive changed the purpose of the AB 3616 Advisory Committee. Not only was a list of efficient water management practices to be prepared, but a document was also needed which outlined a reasonable implementation plan acceptable to both agricultural and environmental representatives. Since 1992, the Advisory Committee members have been working to develop an acceptable MOU. There have been many meetings, disagreements, and at times uncertainty over whether a workable product could be developed. The Advisory Committee approved the Final Draft MOU on October 15, 1996. Can it work and will it be effective in further improving agricultural water management or is it just another layer of bureaucracy? This paper will discuss the process followed, areas of disagreement, and what steps were taken to reach a consensus

Nodal inhibits differentiation of human embryonic stem cells along the neuroectodermal default pathway

AbstractGenetic studies in fish, amphibia, and mice have shown that deficiency of Nodal signaling blocks differentiation into mesoderm and endoderm. Thus, Nodal is considered as a major inducer of mesendoderm during gastrulation. On this basis, Nodal is a candidate for controlling differentiation of pluripotent human embryonic stem cells (hESCs) into tissue lineages with potential clinical value. We have investigated the effect of Nodal, both as a recombinant protein and as a constitutively expressed transgene, on differentiation of hESCs. When control hESCs were grown in chemically defined medium, their expression of markers of pluripotency progressively decreased, while expression of neuroectoderm markers was strongly upregulated, thus revealing a neuroectodermal default mechanism for differentiation in this system. hESCs cultured in recombinant Nodal, by contrast, showed prolonged expression of pluripotency marker genes and reduced induction of neuroectoderm markers. These Nodal effects were accentuated in hESCs expressing a Nodal transgene, with striking morphogenetic consequences. Nodal-expressing hESCs developing as embryoid bodies contained an outer layer of visceral endoderm-like cells surrounding an inner layer of epiblast-like cells, each layer having distinct gene expression patterns. Markers of neuroectoderm were not upregulated during development of Nodal-expressing embryoid bodies, nor was there induction of markers for definitive mesoderm or endoderm differentiation. Moreover, the inner layer expressed markers of pluripotency, characteristic of undifferentiated hESCs and of epiblast in mouse embryos. These results could be accounted for by an inhibitory effect of Nodal-induced visceral endoderm on pluripotent cell differentiation into mesoderm and endoderm, with a concomitant inhibition of neuroectoderm differentiation by Nodal itself. There could also be a direct effect of Nodal in the maintenance of pluripotency. In summary, analysis of the Nodal-expressing phenotype suggests a function for the transforming growth factor-beta (TGF-β) growth factor superfamily in pluripotency and in early cell fate decisions leading to primary tissue layers during in vitro development of pluripotent human stem cells. The effects of Nodal on early differentiation illustrate how hESCs can augment mouse embryos as a model for analyzing mechanisms of early mammalian development

In situ colorimetric and composite coloration efficiency measurements for electrochromic Prussian blue

An in situ colorimetric method, based on the CIE (Commission Internationale de l’Eclairage) system of colorimetry, has been successfully applied to the study of electrochromism in electrochemically deposited films of Prussian blue (iron(III) hexacyanoferrate(II), PB) on transmissive ITO/glass substrates for the first time. On electrochemical reduction of PB to Prussian white (iron(II) hexacyanoferrate(II), PW), sharp and reversible changes in the hue and saturation occur, as shown by the track of the CIE 1931 xy chromaticity coordinates. For PB, the CIELAB 1976 colour space coordinates were L* 5 73, a*5226 and b*5233, with a dominant wavelength calculated as 488 nm. Concurrently, as the intensely absorbing PB mixed-valence chromophore is ‘bleached’ to the transparent PW, a large increase in the relative luminance of the electrochromic film is observed. On oxidation of PB, the CIELAB 1976 colour space coordinates show the transition through intermediate green to the Prussian yellow (iron(III) hexacyanoferrate(III), PY) state (L* 5 94, a* 5 2 and b* 5 18), with a steady increase in relative luminance. To reliably compare the power requirement of PB films with other electrochromic systems, composite coloration efficiencies (CCE’s) have been calculated, using a tandem chronoabsorptometry/chronocoulometry method, as previously developed for organic polymer systems. Using 95% of the total transmittance change at lmax as reference point, coloration efficiencies, g 5 DA(lmax)/Q, were calculated as 143 and 150 cm2 C21 respectively for the PB/PW and PW/PB electrochromic transitions