Yellow | EPFL Graph Search

Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the RGB color model, used to create colors on television and computer screens, yellow is a secondary color made by combining red and green at equal intensity. Carotenoids give the characteristic yellow color to autumn leaves, corn, canaries, daffodils, and lemons, as well as egg yolks, buttercups, and bananas. They absorb light energy and protect plants from photo damage in some cases. Sunlight has a slight yellowish hue when the Sun is near the horizon, due to atmospheric scattering of shorter wavelengths (green, blue, and violet). Because it was widely available, yellow ochre pigment was one of the first colors used in art; the Lascaux cave in France has a painting of a yellow horse 17,000 years old. Ochre and orpiment pigments were used to represent

Soil-vegetation patterns in secondary slash and burn successions in Central Menabe, Madagascar

Alexandre Buttler, Jean-Michel Gobat

Slash and burn agriculture is a traditional and predominant land use practice in Madagascar and its relevance in the context of forest preservation is significant. At the end of a cycle of culture, the fields become mostly weed covered and the soil fertility starts to drop. As a consequence, these fields are abandoned (they are called “monka”) and the farmers, in the best case, re-use old surfaces where the vegetation has recovered to some extent. Nevertheless, some of the farmers continue to extend part of their cultures into the natural forest. In order to decrease deforestation, the paper focuses on the potential for agricultural re-use of monkas. To do so, we present the soil–vegetation pattern along a slash and burn successional gradient from newly cultivated surfaces to surfaces abandoned for 40 years. Vegetation relevés were carried out on 61 plots sampled on yellow and red soils, and soil variables such as loss of ignition, pH, total carbon content and total nitrogen content were measured. Results show that: (1) by the 10th year of abandonment woody species are increasing, and after 21–30 years herbaceous plants become less dominant, (2) the species richness increases with age of abandonment, but flattens out by 40 years, (3) by 20 years of fallow, the loss of ignition, total carbon and total nitrogen show similar values or even higher values than in cultivated surfaces, (4) the yellow soils are related to higher pH more than the red soils and are preferred for cultivation, but the higher pH of yellow soils is not associated with higher species richness. Given these results, we conclude that fields older than 20 years have recovered sufficient fertility to be re-used as agricultural land. This re-use would decrease impacts on natural forests. But beyond the nutrient perspective, critical problems remain, including the growing demand for arable land and the need for cultivation to control invasive weeds.

2010

Potential Direct Regulators of the Drosophila yellow Gene Identified by Yeast One-Hybrid and RNAi Screens

Bart Deplancke

The regulation of gene expression controls development, and changes in this regulation often contribute to phenotypic evolution. Drosophila pigmentation is a model system for studying evolutionary changes in gene regulation, with differences in expression of pigmentation genes such as yellow that correlate with divergent pigment patterns among species shown to be caused by changes in cis- and trans-regulation. Currently, much more is known about the cis-regulatory component of divergent yellow expression than the trans-regulatory component, in part because very few trans-acting regulators of yellow expression have been identified. This study aims to improve our understanding of the trans-acting control of yellow expression by combining yeast-one-hybrid and RNAi screens for transcription factors binding to yellow cis-regulatory sequences and affecting abdominal pigmentation in adults, respectively. Of the 670 transcription factors included in the yeast-one-hybrid screen, 45 showed evidence of binding to one or more sequence fragments tested from the 5 intergenic and intronic yellow sequences from D. melanogaster, D. pseudoobscura, and D. willistoni, suggesting that they might be direct regulators of yellow expression. Of the 670 transcription factors included in the yeast-one-hybrid screen, plus another TF previously shown to be genetically upstream of yellow, 125 were also tested using RNAi, and 32 showed altered abdominal pigmentation. Nine transcription factors were identified in both screens, including four nuclear receptors related to ecdysone signaling (Hr78, Hr38, Hr46, and Eip78C). This finding suggests that yellow expression might be directly controlled by nuclear receptors influenced by ecdysone during early pupal development when adult pigmentation is forming.

Genetics Society of America2016

Structure and characterization of CI3+[Al{OC(CF3)3}4]-; Lewis acidities of CX3+ and BX3

Ines Raabe, Nils Trapp

Prepn. of the title compd. (I) from starting materials CI4 and AgAl{OC(CF3)3}4 was performed with the complete exclusion of light and with carefully purified diiodine-free CI4, since CI4 decomps. within minutes in soln. in light with formation of I2 and other carbon iodides, and II reacts immediately with I2 to give yet unidentified decompn. products. With these precautions I was prepd. in quant. yield. According to calcns. at the MP2/TZVPP level and estn. of the sublimation and lattice enthalpies in a suitable cycle, we est. that the reaction is exothermic by -33 kJmol-1 in the gas phase and by -127 kJmol-1 in the solid state. In CH2Cl2 soln., I is dark blood red and in situ NMR reactions show only resonance signals for the CI3+ ion (d(13C)= 97 ppm; in SO2ClF: d(13C) = 95 ppm; calcd. value: d(13C) = 106 ppm) and the anion (d(13C) = 121.5 ppm (q); d(27A1)= 38.0 ppm). A CH2Cl2 soln. of I is stable for about 8 to 12 h at ambient temp. and much longer if stored at -30 or -78 DegC. Single crystals that appeared yellow as thin plates but black when thicker were grown at -78 DegC from cooled concd. CH2Cl2 solns. of I. The crystal structure detn. of a dark orthorhombic block of I showed that it contained isolated trigonal-planar CI3+ ions with a sum of I-C-I bond angles of 360.0 Deg (range: 118.8-122.1 Deg0) and Al{OC(CF3)3}4 ions. [on SciFinder (R)]

2003

Soil-vegetation patterns in secondary slash and burn successions in Central Menabe, Madagascar

Alexandre Buttler, Jean-Michel Gobat

2010