Miracle-dz/UniFAR-FTUs huggingface dataset:
Interrelations between Si and P biogeochemical cycles—a new approach to the solution of the eutrophication problem

Because the biogeochemical cycles of P and Si in temperate lakes are strongly connected by the dynamics of primary producers, it should be possible to influence the former cycle by causing changes in the latter. It is shown using the mathematical model ‘Rostherne’ that winter levels of ambient Si have a major influence both on spring levels of ambient P and on the summer cyanobacterial maxima. Additions of Si to the lakes could be used for the fine regulation of the biogeochemical balance and may prescribe a recipe for improvement of water quality, as well as a new solution to the problem of eutrophication. Copyright © 2000 John Wiley & Sons, Ltd.
Litter input controls on soil carbon in a temperate deciduous forest

Above- and belowground litter inputs in a temperate deciduous forest were altered for 20 yr to determine the importance of leaves and roots on soil C and soil organic matter (SOM) quantity and quality. Carbon and SOM quantity and quality were measured in the O horizon and mineral soil to 50 cm in five treatments (control, double litter [DL], no litter [NL], no roots [NR], no inputs [NI]). After two decades of doubled litter addition, soil C and SOM did not increase. However, leaf litter exclusions reduced soil C (O and mineral horizons combined) by 24% in NL and 33% in NI treatments. In the mineral soil, the largest declines occurred in the 0- to 10-cm depth (0.93–2.01 kg C m⁻²), although losses were observed throughout the entire solum. The NR treatments showed no losses of C. Thermal characterization of SOM quality differed among treatments in the 0- to 10-cm depth. Patterns of CO₂ evolution during SOM combustion revealed differences in SOM quality between surface and deeper horizons. Our work shows that the sources of litter are important in controlling soil C. Leaf litter made important contributions to maintaining current stocks of soil C; increased leaf litter did not increase soil C, but decreases in litter inputs resulted in rapid soil C declines. Root litter may ultimately provide more stable sources of soil C. Management activities or environmental alterations that decrease litter inputs in mature forests can lower soil C content; however, increases in forest productivity and the resulting increased litter production seem unlikely to increase soil C sequestration.
Rhaxellid sponge microscleres from the Portlandian of Dorset, UK

Three previously described species and two new species of rhaxellid microscleres, Rhaxella winspitensis sp. nov. and R. elongata sp. nov., are described from cherts collected from the Cherty Series of the Portlandian of Dorset. The classification of Rhaxella is reviewed, retaining the genus within the family Geodiidae Gray. The results of this study suggest that three time-dependent rhaxellid assemblages can be recognized which, despite being restricted to certain depositional environments, may have biostratigraphic applications. A Portlandian assemblage described here is species-rich in comparison with known Oxfordian-Kimmeridgian assemblages. Bajocian-Callovian assemblages contain only R. sorbyana. The increased faunal diversity with time is speculatively described by an evolving Rhaxella lineage.
Deformation of clinopyroxenite: Evidence for a transition in flow mechanisms and semibrittle behavior

A systematic suite of constant strain rate experiments was performed on a vacuum-dried, high-purity, fine-grained clinopyroxenite using NaCl and NaF as confining media in a Griggs-type piston-cylinder apparatus. The experiments were carried out over a range of temperatures from 400° to 1100°C, strain rates from 10−3 to 10−7 s−1, and confining pressures from 170 to 1990 MPa. At T = 600°C and e˙ = 1.1 × 10−5 s−1, three modes of deformation occur with increasing confining pressure: (1) Macroscopic faulting associated with low strength and stress drops, (2) stable microfracturing and plastic deformation associated with pressure-dependent strength, and (3) plastic deformation (mechanical twinning and 〈001〉 slip) with high strengths which are insensitive to pressure variations. In experiments at P = 1500 MPa, within this high-pressure plastic mode, two regimes of flow are clearly defined. At low to intermediate temperatures and high strain rates, flow strengths are insensitive to changes in strain rate and temperature. Optical and transmission electron microscope observations indicate that plastic strain is accomplished by mechanical twinning on (100) and (001) and by {100}〈001〉 slip. In contrast, at high temperatures and low strain rates the flow stress is strongly dependent on temperature and strain rate. Specimens deformed in this regime show evidence of recovery, multiple slip, and recrystallization; and plastic strain is much more homogeneous. The flow data within each regime can be satisfactorily fit to thermally activated power laws. In the low-temperature regime n (the stress exponent) = 83 ± 16 and E* (the activation energy for flow) = 220 ± 40 kJ/mol. We believe that these parameters reflect flow dominated by the kinetics of dislocation glide associated with mechanical twinning and (100)〈001〉 slip. In the high-temperature regime, n = 5.3 ± 1.1 and E* = 380 ± 30 kJ/mol. These parameters describe creep by multiple slip accompanied by increased rates of diffusion and recovery.
A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles

A review of remote sensing technology for lower tropospheric thermodynamic (TD) profiling is presented with focus on high accuracy and high temporal‐vertical resolution. The contributions of these instruments to the understanding of the Earth system are assessed with respect to radiative transfer, land surface‐atmosphere feedback, convection initiation, and data assimilation. We demonstrate that for progress in weather and climate research, TD profilers are essential. These observational systems must resolve gradients of humidity and temperature in the stable or unstable atmospheric surface layer close to the ground, in the mixed layer, in the interfacial layer—usually characterized by an inversion—and the lower troposphere. A thorough analysis of the current observing systems is performed revealing significant gaps that must be addressed to fulfill existing needs. We analyze whether current and future passive and active remote sensing systems can close these gaps. A methodological analysis and demonstration of measurement capabilities with respect to bias and precision is executed both for passive and active remote sensing including passive infrared and microwave spectroscopy, the global navigation satellite system, as well as water vapor and temperature Raman lidar and water vapor differential absorption lidar. Whereas passive remote sensing systems are already mature with respect to operational applications, active remote sensing systems require further engineering to become operational in networks. However, active remote sensing systems provide a smaller bias as well as higher temporal and vertical resolutions. For a suitable mesoscale network design, TD profiler system developments should be intensified and dedicated observing system simulation experiments should be performed.
Ground‐based determination of the spectral ultraviolet extraterrestrial solar irradiance: Providing a link between space‐based and ground‐based solar UV measurements

The extraterrestrial solar spectrum between 295 and 355 nm has been determined from direct irradiance measurements made with a Brewer double spectrophotometer, using the Langley method. The measurements in this study consist of 449 half days of data collected during 1998 at Mauna Loa Observatory, Hawaii. The ±2.3% accuracy of this extraterrestrial solar spectrum is obtained by a careful investigation of the instrument calibration and the systematic errors that can arise because of atmospheric and instrument instabilities as well as finite slit width effects and is limited by the uncertainty of the absolute irradiance scale transfer between the standard laboratory and the instrument. A comparison between this extraterrestrial solar spectrum measured from the ground with the mean UARS and ATLAS-1 spectrum show an agreement better than 3%. The mean ratios are 1.002 for the mean UARS spectrum, 1.003 for the mean ATLAS-1 spectrum, 1.013 for the SOLSPEC spectrum, and 1.017 for the ATLAS-3 spectrum.
Geochemistry of the Yandal belt metavolcanic rocks, Eastern Goldfields Province, Western Australia

Archaean felsic metavolcanic rocks occur throughout the Yandal belt in the north of the Eastern Goldfields of Western Australia where they are most abundant in the higher parts of the stratigraphy. With the exception of the Spring Well Sequence at the southern end of the belt, these rocks are typically dacites showing geochemical affinities with Archaean high‐Al trondhjemite‐tonalite‐dacite (TTD) suites. They have high Sr, Al2O3, and (La/Yb)N; low Y, Nb, Zr and heavy rare‐earth elements (HREE); and lack a significant Eu anomaly. In contrast, broadly coeval mafic volcanic rocks have flat REE patterns and trace‐element compositions more typical of modern backarc basin basalts. The Spring Well Sequence is readily distinguished lithologically and geochemically from the remainder of the Yandal belt. Spring Well basaltic andesites are geochemically similar to modern calc‐alkaline arc magmas, i.e. negative Nb–Ta anomalies and enrichment of both large‐ion lithophile elements (LILE) and light rare‐earth elements (LREE). Andesites and rhyolites, both abundant in the Spring Well Sequence, have elevated LILE relative to high field strength elements, and moderate to strong negative Nb, Ta, Sr and Ti anomalies. Rhyolites have low Sr/Y and relatively flat REE patterns ((La/Yb)N = 4.2–5.0). The chemistry and lithostratigraphic associations of the Yandal belt, with the exception of the Spring Well area, suggest a similarity with the Kalgoorlie Terrane, which is supported by published geochronological data. In contrast, the abundance of rhyolite, distinctive calc‐alkaline chemistry and ca2690 Ma age of the Spring Well Sequence suggests a possible association with ca2692 Ma bimodal calc‐alkaline arc‐rift sequence at Teutonic Bore and similar rocks at Melita and Jeedamya, 150 km south of Spring Well. The abundance of TTD dacite and tholeiitic basalt throughout the Yandal belt suggests magma generation from both decompression partial melting of mantle peridotite to produce backarc tholeiitic magma, and partial melting of subducted oceanic lithosphere to produce high‐Al dacite‐tonalite magma. Based on field relationships of the lithological associations, spatial geochemical patterns and published geochronological data, a shallow, west‐dipping subduction model is postulated for the Yandal belt. In this model, widespread tholeiitic basalt and TTD dacite volcanic sequences are thought to have formed in a backarc basin west of a predominantly submerged continental margin volcanic arc. The dominance of dacite in the upper stratigraphy of the Yandal belt could indicate the development of a secondary volcanic ridge or arc in this basin. The Spring Well Sequence is interpreted to occupy the northern preserved portion of the primary arc, remnants of which now extend south through Teutonic Bore to the Melita and Jeedamya volcanic centres. South of Spring Well, volcanic sequences become distinctly bimodal with basalt and high silica rhyolite suggesting an increasing influence of arc extension toward the south.
The Çubukludağ graben, south of İzmir: its tectonic significance in the Neogene geological evolution of the western Anatolia

Abstract Field studies on the Neogene successions in south of İzmir reveal that subsequent Neogene continental basins were developed in the region. Initially a vast lake basin was formed during the early-Middle Miocene period. The lacustrine sediments underwent an approximately N-S shortening deformation to the end of Middle Miocene. A small portion of the basin fill was later trapped within the N-S-trending, fault-bounded graben basin, the Çubukludağ graben, opened during the Late Miocene. Oblique-slip normal faults with minor sinistral displacement are formed possibly under N–S extensional regime, and controlled the sediment deposition. Following this the region suffered a phase of denudation which produced a regionwide erosional surface suggesting that the extension interrupted to the end of Late Miocene–Early Pliocene period. After this event the E–W-trending major grabens and horsts of western Anatolia began to form. The graben bounding faults cut across the Upper Miocene–Pliocene lacustrine sediments and fragmented the erosional surface. The Çubukludağ graben began to work as a cross garden between the E–W grabens, since that period. © 2001 Éditions scientifiques et médicales Elsevier SAS
Monthly mean wind stress and Sverdrup transport in the North Atlantic: A comparison of the Hellerman-Rosenstein and Isemer-Hasse climatologies

The monthly mean wind stress climatology of Hellerman and Rosenstein (HR) is compared with the climatology of Isemer and Hasse (IH), which represents a version of the Bunker atlas (BU) for the North Atlantic based on revised parameterizations. The drag coefficients adopted by IH are 21% smaller than the values of BU and HR, and the calculation of wind speed from marine estimates of Beaufort force (Bft) is based on a revised Beaufort equivalent scale similar to the scientific scale recommended by WMO. The latter choice significantly increases wind speed below Bft 8, and effectively counteracts the reduction of the drag coefficients. Comparing the IH stresses with HR reveals substantially enhanced magnitudes in the trade wind region throughout the year. At 15°N the mean easterly stress increases from about 0.9 (HR) to about 1.2 dyn cm−1 (IH). Annual mean differences are smaller in the region of the westerlies. In winter, the effect due to the reduced drag coefficient dominates and leads to smaller stress values in IH; during summer season the revision of the Beaufort equivalents is more effective and leads to increased stresses. Implications of the different wind stress climatologies for forcing the large-scale ocean circulation are discussed by means of the Sverdrup transport streamfunction (ψs): Throughout the subtropical gyre a significant intensification of ψs takes place with IH. At 27°N, differences of more than 10 Sv (1 Sv ≡ 106 m3 s−1) are found near the western boundary. Differences in the seasonality of ψs are more pronounced in near-equatorial regions where IH increase the amplitude of the annual cycle by about 50%. An eddy-resolving model of the North Atlantic circulation is used to examine the effect of the different wind stresses on the seasonal cycle of the Florida Current. The transport predicted by the numerical model is in much better agreement with observations when the circulation is forced by IH than by HR, regarding both the annual mean (29.1 Sv vs 23.2 Sv) and the seasonal range (6.3 Sv vs 3.4 Sv).
ENSO, volcanoes and record‐breaking temperatures

Monthly‐mean, near‐surface temperatures are examined for records and trends after accounting for the influences of ENSO and the volcanic eruptions of Agung, El Chichón and Pinatubo. Of the 16 consecutive record‐breaking months in 1997–98, at least six can be attributed to ENSO‐associated warmth. The period is still unusual, but no more unusual than 1990–91 when an equal number of records occurred in the ENSO‐adjusted data. The warming trend over the past two decades is also shown to be unusual, but is found (in the raw data) to be not significantly different from the warming trend of the 1910s–1930s. When ENSO and volcanic effects are removed, however, the recent warming trend increases (to 0.25°C/decade) and becomes highly significant compared to the earlier period.
The Flattening Firm and Product Market Competition: The Effect of Trade Liberalization on Corporate Hierarchies

This paper establishes a causal effect of product market competition on various characteristics of organizational design. Using a unique panel-dataset on firm hierarchies of large U.S. firms (1986-1999) and a quasi-natural experiment (trade liberalization), we find that competition leads firms to flatten their hierarchies: (i) firms reduce the number of positions between the CEO and division managers and (ii) increase the number of positions reporting directly to the CEO. The results illustrate how firms redesign their organizational structure through a set of complementary choices in response to changes in their environment. We discuss several possible interpretations of these changes.
Relative contributions of H+ and O+ to the ring current energy near magnetic storm maximum

[1] Close to the peak of a magnetic storm, the ratio of the O+ to the H+ contribution to the ring current energy, U(O+)/U(H+), depends on both solar EUV flux and storm size. This ratio provides a lower limit on the importance of the ionospheric plasma source compared to the solar wind source since only the ionosphere supplies O+ while both the solar wind and the ionosphere supply H+. We have used measurements from the CHEM ion spectrometer on the Active Magnetospheric Particle Tracer Explorers (AMPTE) CCE spacecraft to assess U(O+)/U(H+) near storm maximum. CHEM measured equatorial ion composition over the energy per charge range 1.5–300 keV/e for more than 4 years, from solar minimum through much of the rising phase of Solar Cycle 22. Thus our data set is large, including 67 magnetic storms with minimum Dst values less than −50 nT. To estimate the O+ and H+ contributions to the ring current energy, we have multiplied local measurements of each ion's energy density along the CCE trajectory by the appropriate dipole L shell volume and summed over L values from two to seven. We have used a bilinear regression to assess the dependence of U(O+)/U(H+) on solar EUV flux, parameterized by F10.7, and storm size, parameterized by minimum Dst value Dstmin. We have found that both F10.7 and Dstmin are important (and nearly independent) predictors of U(O+)/U(H+). Only four storms of 67 had U(O+)/U(H+) > 1. Two of the four were fairly small, with |Dstmin| < 100 nT but with high F10.7 values. This shows that O+ can sometimes contribute the majority of the ring current energy during small storms when the solar EUV flux is high (i.e., near solar maximum) as well as during very large storms throughout the solar cycle.
The Mesolithic-Neolithic Transition in Portugal: Isotopic and Dental Evidence of Diet

Paired radiocarbon (AMS) and stable isotope (δ13C and δ15N) analyses of human bone collagen from Mesolithic and Neolithic Portuguese skeletons suggest a marked change of diet just prior to 7000 BP at the Mesolithic-Neolithic transition. The Mesolithic diet was based on foods of both marine and terrestrial origins, while the Neolithic diet was more dependent on terrestrial food sources. A linear correlation trend between δ13C and δ15N for the Mesolithic samples implies that the marine component of their diet was isotopically homogeneous, and consisted either of a well-defined mixture of several species, or a single species that was consistently exploited. Changes in the rate and type of dental attrition and differences in dental pathology confirm that a change of diet was established by 7000 BP, but suggest that the trend had been initiated soon after 8000 BP.
Fluoride contamination mapping of groundwater in Northern India integrated with geochemical indicators and GIS

There are many incidents of increasing fluoride concentrations observed in India's groundwater. In the present study, the fluoride content was chemically analysed and integrated with geochemical model WATEQ4F sampled from Allahabad district, Northern India, with other water quality parameters. Geospatial technique was employed to depict the spatial distribution of fluoride concentrations, over this plain, normalized with WHO (World Health Organization) and BIS (Bureau of Indian Standards) standards represented in the form of spatially interpolated maps. Hydro-geological conditions, such as weathering, geochemical reactions, alkaline nature of water, ion-exchange and high variability in temperature range, were taken into account in describing the geo or anthropogenic contributions to fluoride in groundwater. A large database of available ancillary information on related factors, such as soil properties, geological settings and climatic and topographical information, on a local scale, were also taken into account to rationalize the results. The analysis implies that post-monsoon samples have elevated concentration of fluoride compared with the pre-monsoon samples, with several zones found severely contaminated with fluoride as compared with the set standards in both seasons. The correlation analysis revealed a high correlation of fluoride, with fluorite mineral saturation index, followed by calcite and magnesite, indicating that these minerals could be used as geochemical indicators for fluoride contaminated areas.
The changing characteristics of monsoon rainfall in India during 1971–2005 and links with large scale circulation

This study examines the changes in monsoon rainfall of India using a suite of extreme indices defined by the Expert Team on Climate Change Detection Monitoring and Indices (ETCCDMI) to make the Indian results comparable internationally, in addition to the use of some relevant indices particularly developed for the Indian climate. To this end, the recently developed high resolution daily gridded (0.5° × 0.5°) rainfall dataset for the period 1971–2005 has been analysed using robust nonparametric techniques. Despite the high interannual variability and spatial diversity of the Indian climatology, the results reveal signal of changes for several extreme rainfall indices, generally consistent with the simulated outcome of an intensified Indian monsoon rainfall in the context of global warming. A predominant decrease in wet days, moderate and total rainfall is observed in the high rainfall regions of northeast, central and southwest India. In the active monsoon months of July and August, the dry spells defined by the maximum length of consecutive dry days (CDD) have increased significantly over the north and central regions of India, suggesting a serious threat to the Indian agriculture. Simultaneously, the extreme rainfall indices, based on the percentile and absolute values, show increasing trends over large parts of the country. The probability density function (PDF) of several indices show noticeable changes since the 1990s over the homogeneous central and northeast parts of India. The indices representing the total monsoon rainfall and dry spells are better correlated with the El Niño–Southern Oscillation (NINO3.4), compared to that of the Indian Ocean Dipole Mode Index (IODMI). The mapping of the observed rainfall trends and their correspondence to the large scale circulation modes is expected to assist the policy makers to prioritize the mitigation and adaptation strategies.