Crystal structure of the high-pressure phase of the oxonitridosilicate chloride Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃0.2

The structural compression mechanism of Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃ 0.2, was investigated by in situ single-crystal synchrotron X-ray diffraction at pressures of 3.0, 8.5 and 8.6 GPa using the diamond–anvil cell technique. On increasing pressure the low-pressure cubic structure first undergoes only minor structural changes. Between 8.5 and 8.6 GPa a first-order phase transition occurs, accompanied by a change of the single-crystal colour from light orange to dark red. The main structural mechanisms, leading to a volume reduction of about 5% at the phase transition, are an increase in and a rearrangement of the Ce coordination, the loss of the Ce2, Ce3 split position, and a bending of some of the inter-polyhedral Si—N—Si angles in the arrangement of the corner-sharing Si tetrahedra. The latter is responsible for the short c axis of the orthorhombic high-pressure structure compared with the cell parameter of the cubic low-pressure structure

KLUM@LPJ: Integrating dynamic land-use decisions into a dynamic global vegetation and crop growth model to assess the impacts of a changing climate. A feasibility study for Europe

We test the hypothesis that models should be coupled to accurately project the impacts of climate change on the agro-economic and agro-environmental system. We couple the LPJ-C global dynamic vegetation model for crops to the global agricultural land-use model KLUM. Potential crop yields, from LPJ-C, and crop prices drive the land-use decisions; cropland allocation from KLUM scale the carbon entering the soil litter pool in LPJ-C. Through the crop prices, economic effects are projected directly on the carbon cycle. Global change impacts are projected on the agricultural sector and can be economically assessed. The coupled model performs reasonably well for the observed climate and prices for 6 crops in Europe on a 0.5x0.5 longitude-latitude grid. We estimate the impact of climate change on agriculture in Europe for A1 and B2 scenarios of the IPCC. The coupled model reproduces the essential processes and interactions of the modeled system. Simulations with the uncoupled models are used to estimate the accuracy added by the model coupling. Sign and size of the biases from ignoring the feedbacks are substantial for some parameters, and particularly their spatial pattern, while for other parameters (e.g., the European total of soil organic carbon) biases are negligible. The answer to the question “Should models be coupled?” is “It depends on what you’re interested in”.Climate change, land use, soil carbon, model coupling

Contribution of the adrenal gland to the production of androstenedione and testosterone during the first two years of life

Androstenedione and testosterone were measured in whole adrenal glands of 56 previously healthy boys who died suddenly between birth and 2 yr of age. In each adrenal gland, the concentration of androstenedione considerably exceeded that of testosterone. The highest concentrations were found during the first week of life (median, 295 ng/g; range, 98- 320 ng/g). Thereafter, values decreased rapidly until the end of the first year of life (median, 10 ng/g; range, 4.4-22.7 ng/g). Adrenal testosterone concentrations averaged 15% of those of androstenedione in the same gland and similarly decreased until the end of the first year. The decrease of adrenal androgen concentrations paralleled the involution of the fetal adrenal zone. A close correlation existed between the concentration of androstenedione in adrenal tissue and plasma. However, no correlation existed between adrenal and plasma testosterone. When the adrenals and testes of the same infant were compared, there was 10 times more androstenedione in the adrenals than in the testes during the first 2 yr of life. The testes contained more testosterone than the adrenals only during the first 4 months. Thus, in infant boys the adrenals are the main source of androstenedione during the first 2 yr. After the sixth month of life, they also are the main source of testosterone

Testosterone and androstenedione concentrations in human testis and epididymis during the first two years of life

Testosterone and androstenedione were measured in testicular and epididymal tissue of 37 previously healthy infants between 1 and 24 months of age who died suddenly. In half of the patients elevated plasma levels of cortisol and androstenedione suggested preterminal stress. Plasma testosterone levels, however, did not differ from those in healthy infants. Testicular testosterone concentrations were maximal in boys from 1-3 months of age (median, 36.6 ng/g; range, 7-380 ng/g) with peak values similar to those found in pubertal or even adult testes. Thereafter testicular testosterone concentrations decreased and after the age of 6 months all values were below 12.5 ng/g, which corresponds to the low normal range of older prepubertal boys. Plasma testosterone and testicular testosterone correlated significantly (P less than 0.001). On average the testicular concentrations were 36.4 times higher than the corresponding plasma concentrations. Testicular androstenedione was low but correlated significantly with testicular testosterone (P less than 0.001). Epididymal testosterone concentrations were surprisingly high (1-3 months: median, 10.3 ng/g; range, 4-42.7 ng/g) and averaged 30% of the testicular testosterone concentration. Thus, epididymal testosterone concentrations were significantly higher than the circulating plasma testosterone levels, indicating the capacity of the infant epididymis to accumulate androgens. These findings suggest that high local testosterone concentrations during early infancy are important not only for the testis itself but particularly for the developing epididymi

Estrone and estradiol concentrations in human ovaries, testes, and adrenals during the first two years of life

To determine the origin of estrogens in infant blood, we measured estrone (E1) and estradiol (E2) in the gonads of 50 girls and 64 boys who died suddenly between birth and 2 yr of age as well as in the adrenals of 18 of these infant girls and 16 of the boys. In the adrenals, E1 [median, 2.8 ng/g (10.4 pmol/g); range, 1.1-4.8 ng/g (4.1- 17.8 pmol/g)] and E2 [median, 3.0 ng/g (10.9 pmol/g); range, 1.2-5.3 ng/g (4.4-19.5 pmol/g)] were found in similar concentrations and were independent of age and sex. In the gonads, E2 was the major estrogen, but the concentrations differed markedly between the sexes; E2 exceeded E1 almost 10-fold in the ovaries and 2-fold in the testes. On the average, the gonads of the infant girls had 5 times more E2 and 2 times more E1 than those of the boys. As in plasma, E2 concentrations were highest in the ovaries of 1- to 6-month-old girls [median, 10.5 ng/g (38.5 pmol/g); range, 1.1-55.1 ng/g (4.0-202.0 pmol/g)] and in testes of 1- to 3-month-old boys [median, 1.8 ng/g (6.6 pmol/g); range, 0.6- 6.4 ng/g (2.3-23.5 pmol/g)]. Ovarian E2 concentrations declined to less than 3.0 ng/g (11.0 pmol/g) by the end of the first year of life, and testicular E2 declined to less than 1.0 ng/g (3.7 pmol/g) after only 6 months of age. Gonadal estrogen concentrations paralleled changes in gonadal morphology. Ovarian weights varied in a pattern of rise and fall similar to that of ovarian E2 concentrations; the biggest ovaries contained multiple macroscopic cysts. Testicular E2 closely correlated with Leydig cell development and testicular testosterone concentrations. We infer, therefore, that the surge of plasma E2 in infant girls originates from ovarian follicles and that of boys from testicular Leydig cells, and that these both occur as a result of the postnatal surge in gonadotropin secretion. The basal plasma E1 and E2 pool, however, is derived from the adrenals and remains at a comparatively constant level in both sexe

High-Pressure Phase Transition of the Oxonitridosilicate Chloride Ce4[Si4O3+xN7-x]Cl1-xOx with x = 0.12 and 0.18

The high-pressure behaviour of the oxonitridosilicate chlorides Ce4[Si4O3þxN7-x]Cl1-xOx, x = 0.12 and 0.18, is investigated by in situ powder synchrotron X-ray diffraction. Pressures up to 28 GPa are generated using the diamond-anvil cell technique. A reversible phase transition of first order occurs at pressures between 8 and 10 GPa. Within this pressure range the high- and the low-pressure phases are observed concomitantly. At the phase transition the unit cell volume is reduced by about 5%, and the cubic symmetry (space group P213) is reduced to orthorhombic (space group P212121) following a translationengleiche group-subgroup relationship of index 3. A fit of a third-order Birch-Murnaghan equation of state to the p-V data results in a bulk modulus B0 = 124(5) GPa with its pressure derivative B0 = 5(1) at V0 = 1134.3(4) Å3 for the low-pressure phase and in B0 = 153(10) GPa with B0 = 3.0(6) at V0 = 1071(3) Å3 for the high-pressure phase. The orthorhombic phase shows an anisotropic axial compression with the a axis (which is the shortest axis) being more compressible (k(a) = 0.0143(4) 1/GPa) than the b and c axes (k(b) = 0.0045(2), k(c) = 0.0058(2) 1/GPa). The experimental results confirm an earlier prediction of the pressureinduced instability of isotypic Ce4[Si4O4N6]O, and also show that the bulk modulus was predicted reasonably well

Combined use of weather forecasting and satellite remote sensing information for fire risk, fire and fire impact monitoring

The restoration of fire-affected forest areas needs to be combined with their future protection from renewed catastrophic fires, such as those that occurred in Greece during the 2007 summer season. The present work demonstrates that the use of various sources of satellite data in conjunction with weather forecast information is capable of providing valuable information for the characterization of fire danger with the purpose of protecting the Greek national forest areas. This study shows that favourable meteorological conditions have contributed to the fire outbreak during the days of the unusually damaging fires in Peloponnese as well as Euboia (modern Greek: Evia) at the end of August 2007. During those days, Greece was located between an extended high pressure system in Central Europe and a low pressure system in the Middle East. Their combination resulted in strong north-northeasterly winds in the Aegean Sea. As a consequence, strong winds were also observed in the regions of Evia and Peloponnese, especially in mountainous areas. The analysis of satellite images showing smoke emitted from the fires corroborates the results from the weather forecasts. A further analysis using the Fraction of Absorbed Photosyntetically Active Radiation (FAPAR) as an indicator of active vegetation shows the extent of the destruction caused by the fire. The position of the burned areas coincides with that of the active fires detected in the earlier satellite image. Using the annual maximum FAPAR as an indicator of regional vegetation density, it was found that only regions with relatively high FAPAR were burned

Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−xAlxOxN7−x] (x = 2; M = Sr, Ba)

The compressibilities of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−xAlxOxN7−x] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42 GPa were generated using the diamond–anvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order Birch–Murnaghan equation-of-state to the p–V data results in V0 = 302.91 (6) Å3, B0 = 176 (2) GPa and B′ = 4.4 (2) for SrYb[Si4N7]; V0 = 310.4 (1) Å3, B0 = 161 (2) GPa and B′ = 4.6 (2) for SrYb[Si4−xAlxOxN7−x]; and V0 = 317.3 (5) Å3, B0 = 168 (2) GPa and B′ = 4.7 (2) for BaYb[Si4−xAlxOxN7−x]. While the linear compressibilities of the a and c axes of BaYb[Si4−xAlxOxN7−x] are very similar up to 30 GPa, distinct differences were observed for SrYb[Si4N7] and SrYb[Si4−xAlxOxN7−x], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role

Coupled Al/Si and O/N order/disorder in BaYb[Si4–xAlxOxN7–x]sialon

The fractions of aluminium, [Al]/[Al + Si], and oxygen, [O]/[O + N], in crystallographically distinct sites of BaYb[Si4–xAlxOxN7–x] oxonitridoaluminosilicate (space group P63mc, No. 186) were refined based on the results of neutron powder diffraction for a synthetic sample with the composition of x = 2.2(2) and simulated as functions of temperature for the compositions x = 2 and x = 2.3 using a combination of static lattice energy calculations (SLEC) and Monte Carlo simulations. The SLEC calcu lations have been performed on a set of 800 structures differing in the distribution of Al/Si and O/N within the 2 × 2 × 2 supercell containing 36 formula units of BaYb[Si4–xAlxOxN7–x]. The SLEC were based on a transferable set of empirical interatomic potentials developed within the present study. The static lattice energies of these structures have been expanded in the basis set of pair-wise ordering energies and on-site chemical potentials. The ordering energies and the chemical potentials have been used to calculate the configuration energies of the oxonitridoaluminosilicates (so-called sialons) using a Monte Carlo algorithm. The simulations suggest that Al and O are distributed unevenly over two non-equivalent T(Si/Al) and three L(N/O) sites, respectively, and the distribution shows strong dependence both on the temperature and the composition. Both simulated samples exhibit order/disorder transitions in the temperature range 500–1000 K to phases with partial long-range order below these temperatures. Above the transition temperatures the Si/Al and N/O distributions are affected by short-range ordering. The predicted site occupancies are in a qualitative agreement with the neutron diffraction results