Spatial variability of the green water footprint using a medium-resolution remote sensing technique: The case of soybean production in the Southeast Argentine Pampas.

Agriculture accounts for about 70% of the fresh water use in the world, dominating rainfed production systems. As meeting future food demand will require an increase in crop production, new techniques are necessary to monitor the spatial variability of agricultural water use. However, the use of remote sensing for the water footprint estimation is limited. This study aims at evaluating the spatial variability of the soil-water consumption in soybean crops, also termed as green water footprint (WFgreen), in a sector of the Argentine Pampas using satellite data. WFgreen was evaluated at spatial resolution of 250 m, estimating the soil water availability through the evaporative fraction and crop yield from Moderate-Resolution Imaging Spectroradiometer (MODIS/Aqua) data. In the analysed soybean plots, the WFgreen varied from 900 m3 t-1 to 1800 m3 t-1. The preliminary comparison of the method with field measurements showed a RMSE = 494 m3 t-1 and Bias = -410 m3 t-1, respectively. The high spatial variability reflected the heterogeneity of soil-water use efficiency. The proposed technique can be useful to obtain WFgreen maps at medium spatial resolutions (250 m-1000 m). Also, it can be applied in regions with poor ground data coverage to estimate the WFgreen, after a parameterization of the model. The contribution to our understanding of the relationship between soil-water availability, rainfed-crop productivity and then WFgreen is expected.

Effects of Steroid Hormone in Avian Follicles.

The aim of the present study was to examine the effects of testosterone (T) and estradiol-17ß (E2) on the production of progesterone (P4) by granulosa cells, and of the E2 on the production of P4 and T by theca internal cells. In the first experiment, granulosa cells isolated from the largest (F1) and third largest (F3) preovulatory follicle were incubated for 4 h in short-term culture system, P4 production by granulosa cells of both F1 and F3 was increased in a dose-dependent manner by ovine luteinizing hormone (oLH), but not T or E2. In the second experiment, F1 and F3 granulosa cells cultured for 48 h in the developed monolayer culture system were recultured for an additional 48 h with increasing doses of various physiological active substances existing in the ovary, including T and E2. Basal P4 production for 48 h during 48 to 96 h of the cultured was about nine fold greater by F1 granulosa cells than by F3 granulosa cells. In substances examined oLH, chicken vasoactive intestinal polypeptide (cVIP) and T, but not E2, stimulated in a dose-dependent manner P4 production in both F1 and F3 granulosa cells. In addition, when the time course of P4 production by F1 granulosa cells in response to oLH, cVIP, T and E2 was examined for 48 h during 48 to 96 h of culture, although E2 had no effect on P4 production by granulosa cells of F1 during the period from 48 to 96 h of culture, P4 production with oLH was found to be increased at 4 h of the culture, with a maximal 9.14 fold level at 6 h. By contrast, P4 production with cVIP and T increased significantly (p<0.05) from 8 and 12 h of the culture, respectively, with maximal 6.50 fold response at 12 h and 6, 48 fold responses at 36 h. Furthermore, when F1 granulosa cells were precultured with E2 for various times before 4 h culture with oLH at 96 h of culture, the increase in P4 production in response to oLH with a dose-related manner was only found at a pretreatment time of more than 12 h. In the third experiment, theca internal cells of F1, F2 and the largest third to fifth preovulatory follicles (F3-5) were incubated for 4 h in short-term culture system with increasing doses of E2. The production of P4 and T by theca internal cells were increased with the addition of E2 of 10(-6) M. These increases were greater in smaller follicles. These results indicate that, in granulosa cells of the hen, T may have a direct stimulatory action in the long term on P4 production, and on E2 in long-term action which may enhance the sensitivity to LH for P4 production, and thus, in theca internal cells, E2 in short term action may stimulate the production of P4 and T.

Liquid-phase microextraction with solidification of the organic floating drop for the preconcentration and determination of mercury traces by electrothermal atomic absorption spectrometry.

A procedure for the determination of traces of mercury by liquid-phase microextraction based on solidification of a floating organic droplet for separation and electrothermal atomic absorption spectrometry for final measurement has been developed. For this purpose, 50 microL of pre-heated (50 degrees C) undecanoic acid (UA), are added to 25 mL of aqueous sample solution at pH 5. The mixture, maintained at 50 degrees C, is stirred for 10 min using a high stirring rate in order to fragment the UA drop into droplets, thus favoring the extraction process. Next, the vial is immersed in an ice bath, which results in the solidification of the UA drop that is easily separated. Injection into the atomizer is carried out after gentle heating. The pyrolytic atomizers are coated with electrolytically reduced palladium that acts as an effective chemical modifier for more than 500 firings. Under the optimized conditions, the detection limit was 70 ng L(-1) mercury with an enrichment factor of 430. The relative standard deviation of the measurements was in the 2.1-3.5% range. Recovery studies applied to the determination of mercuric ions in bottled and tap water samples were in the 92-104% range.