Miracle-dz/UniFAR-FTUs huggingface dataset:
A geochronological and petrological study of anatectic paragneiss and associated granite dykes from the Day Nui Con Voi metamorphic core complex, North Vietnam: constraints on the timing of metamorphism within the Red River shear zone

The Red River shear zone (RRSZ) is a major left‐lateral strike‐slip shear zone, containing a ductilely deformed metamorphic core bounded by brittle strike‐slip and normal faults, which stretches for >1000 km from Tibet through Yunnan and North Vietnam to the South China Sea. The RRSZ exposes four high‐grade metamorphic core complexes along its length. Various lithologies from the southernmost core complex, the Day Nui Con Voi (DNCV), North Vietnam, provide new constraints on the tectonic and metamorphic evolution of this region prior to and following the initial India–Asia collision. Analysis of a weakly deformed anatectic paragneiss using P–T pseudosections constructed in the MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O (MnNCKFMASHTO) system provides prograde, peak and retrograde metamorphic conditions, and in situ U–Th–Pb geochronology of metamorphic monazite yields texturally controlled age constraints. Tertiary metamorphism and deformation, overprinting earlier Triassic metamorphism associated with the Indosinian orogeny and possible Cretaceous metamorphism, are characterized by peak metamorphic conditions of ~805 °C and ~8.5 kbar between c. 38 and 34 Ma. Exhumation occurred along a steep retrograde P–T path with final melt crystallizing at the solidus at ≥~5.5 kbar at ~790 °C. Further exhumation at ~640–700 °C and ~4–5 kbar at c. 31 Ma occurred at subsolidus conditions. U–Pb geochronological analysis of monazite from a strongly deformed pre‐kinematic granite dyke from the flank of the DNCV provides further evidence for exhumation at this time. Magmatic grains suggest initial emplacement at 66.0 ± 1.0 Ma prior to the India–Asia collision, whereas grains with metamorphic characteristics indicate later growth at 30.6 ± 0.4 Ma. Monazite grains from a cross‐cutting post‐kinematic dyke within the core of the DNCV antiform provide a minimum age constraint of 25.2 ± 1.4 Ma for the termination of fabric development. A separate and significant episode of monazite growth at c. 83–69 Ma is suggested to be the result of fluid‐assisted recrystallization following the emplacement of magmatic units.
Morphological segmentation of x-ray images

X-ray images are the essential aiding means in clinical diagnosis of fracture all along. According to the characteristic of X-ray images, a novel improving strategy based on homotopy modification of gradients is proposed. Opening-by-reconstruction and closing-by-reconstruction are used to smooth the images. Top-hat transformation and bottom-hat transformation are used to enhance contrast. Combination of top-hat-reconstruction and opening-by-reconstruction is employed to remove complex muscle background. Extended minima transformation, area opening operation, image addition, complement of image, distance transformation and watershed transformation are together employed to compute internal and external markers. Using the markers to modify gradients ensures that the regional minima exactly occur in the bones objects and the muscle background. Correct watershed ridge lines are obtained by applying watershed transform to the modified gradients. Experimental results show that a good segmentation effect can be achieved using the proposed algorithm, and the algorithm is suitable for segmenting X-ray images in interactive fracture diagnosis systems.
Global-Scale Drought Caused Atmospheric CO2 Increase

Identifying the mechanisms driving interannual fluctuations of atmospheric carbon dioxide is necessary for predicting future CO2 concentrations and climate change [Prentice et al., 2001]. A possible clue comes from a well-established positive correlation between atmospheric CO2 growth rates and the El Nino-Southern Oscillation phenomenon [Keeling et al., 1989; Bousquet et al., 2000]. Most tropical droughts are also linked to El Nino [Lyon, 2004], suggesting carbon losses from drought as a major cause for interannual CO2 variations. A lag correlation between 7-month running means (see Figure 1) of monthly atmospheric CO2 concentrations [Cooperative Atmospheric Data Integration Project, 2004] and Nino 3 sea surface temperatures (available at http://www.cpc.noaa.gov/data/indices/) for the period 1979–2003 peaks at a lag of four months with a correlation of 0.49, and a significance level above 99.9% (assuming 42 independent measurements).
Tropospheric NO x and O3 budgets in the equatorial Pacific

By combining the results of model calculations and simultaneous measurements of O3, NO, HNO3, particulate NO3−, and meteorological parameters in the mid-Pacific, we have investigated the budget and photochemistry of near surface atmospheric ozone and odd nitrogen. The observed decrease of O3 toward the Intertropical Convergence Zone is consistent with the transport of O3 from higher latitude and a photochemical sink for O3 by the reaction between H2O and O(1D). The total deposition flux of odd nitrogen deduced from the data is about 1.3×109 cm−2 s−1, or 5 MT(N)/yr averaged globally. Most of the deposition flux is due to HNO3 and particulate NO3−. This deposition flux is probably representative of values over most of the Pacific because the HNO3 and particulate NO3− densities measured over the Pacific during the GAMETAG experiments are consistent with our values. Since the residence time of odd nitrogen in the lower troposphere is short, a widely distributed, diffuse source of odd nitrogen is required to balance the deposition flux. It seems that the NO formed by cloud to cloud lightning in the tropical upper troposphere is the most likely source.
Rainfall induced instability of mechanically stabilized earth embankments

A 10.4-m high highway embankment retained behind mechanically stabilized earth (MSE) walls is under construction in the northeastern part of the Indian state of Bihar. The structure is constructed with compacted, micaceous, grey, silty sand, reinforced with polyester (PET) geogrids, and faced with reinforced cement concrete fascia panels. The connections between the fascia panels and the geogrids failed on several occasions during the monsoon seasons of 2007 and 2008 following episodes of heavy rainfall, when the embankment was still under construction. However, during these incidents the MSE embankment itself remained by and large stable and the collateral damages were minimal. The observational data during these incidents presented an opportunity to develop and calibrate a simple procedure for estimating rainfall induced pore water pressure development within MSE embankments constructed with backfill materials that do not allow unimpeded seepage. A simple analytical finite element model was developed for the purpose. The modeling results were found to agree with the observational and meteorological records from the site. These results also indicated that the threshold rainwater infiltration flux needed for the development of pore water pressure within an MSE embankment is a monotonically increasing function of the hydraulic conductivity of backfill. Specifically for the MSE embankment upon which this study is based, the analytical results indicated that the instabilities could have been avoided by having in place a chimney drain immediately behind the fascia panels.
Spectral characteristics of the microwave emission from a wind-driven foam-covered sea

Aircraft observations of the microwave emission from the Bering Sea show that the spectral character of brightness temperature variation with wind speed in a fully developed sea is due to a combination of surface roughness and a surface layer with varying dielectric constant over a physical depth of a few millimeters. The varying dielectric layer is identified with cusps formed by the bubbles associated with thin foam streaks. Computations of the radiative transfer through such a layer show that the change in microwave emissivity due to the presence of that layer decreases as microwave wavelength increases. Since foam streak coverage on the ocean surface increases with surface wind speed, the increase in microwave brightness temperature with increasing wind speed will be less at longer wavelengths, a characteristic that is observed in the experimental results presented. In addition, it has been observed that in fetch-limited situations the microwave brightness temperature depends in the same way on surface wind speed but is essentially independent of varying foam coverage, the implication being that the surface wave structure becomes more important in determining the microwave brightness temperatures as fetch approaches zero. It appears that microwave brightness temperatures are directly related to ocean surface wind speeds, regardless of fetch.
Aerosol retrieval with satellite image and correlation analyses between aerosol distribution and urban underlaying surface

Human activity is one of the most important aerosol sources. Because the underlaying surface feature records most human activities, it is important to recognize the correlation between aerosol distribution and the underlaying surface. In this research, the dark object algorithm and a second-generation operational algorithm of Moderate-Resolution Imaging Spectroradiometer (MODIS) aerosol retrieval are used to estimate aerosol optical depth from Enhanced Thematic Mapper Plus (ETM+) images acquired by the Landsat 7 satellite system in urban regions, and the correlations between aerosol distribution and urban underlaying surface features (including landform, land cover and urbanization level) is analysed. Results show that (1) it is feasible to apply a second-generation algorithm to retrieve aerosol optical depth with ETM+ images. When a validation is performed with the ground observation meteorological range converted into aerosol optical depth with the correlation model acquired by a Moderate-Resolution Atmospheric Transmission (MODTRAN) simulation, the retrieval error is about 0.0094. For higher spatial resolution of an ETM+ image, it is better to study the aerosol distribution features in the urban regions. Additionally, (2) there are obvious variations in spatial distribution of aerosol over the different features of the underlaying surface. For the landform, aerosol optical depth is mountain < hill < plain; for the land cover, aerosol optical depth is dense vegetation < sparse vegetation < water < bare soil < residential area; for the different urbanization-level regions, there is bigger and bigger aerosol optical depth with increasing of the urbanization level. On the whole, as human activities increase, so too does the aerosol optical depth.
Seismic displacements near a fault

Ground motion at only 80 meters from the San Andreas fault was recorded during the Parkfield earthquake of June 28, 1966, by the accelerographs of the U.S. Coast and Geodetic Survey. Seismic displacements obtained from the accelerograms are compared with synthetic seismograms calculated for a moving dislocation model. An excellent agreement was obtained between the observed and theoretical seismograms. The dislocation is the only important source parameter that controls the seismic motion at such short distances. Other parameters such as the fault length and depth show negligible effect of the motion. The rupture velocity is a significant but not dominant factor. From the comparison of observed and theoretical seismograms, it was concluded that the fault dislocation was about 60 cm. This value is an order of magnitude greater than the fault offset observed at the surface. This discrepancy was attributed to the decoupling of a thin surface layer (probably less than 100 meters from the surface). The fault depth was estimated by combining the estimated dislocation with the seismic moment obtained from long-period surface waves. The fault depth within the basement rock was found to be about 3 km, which is significantly smaller than the depth (15 km) of the aftershock zone. This discrepancy was attributed to the effect of increasing friction with depth which momentarily prevented downward extension of rupture during the main shock.
The importance of flow in the Mozambique Channel to seasonality in the Greater Agulhas Current System

The temporal variability of the greater Agulhas Current system has important climatological consequences. Some recent results have suggested that this variability contains a large seasonal component, due to changes in the circulation at latitudes poleward of Madagascar only. A model simulation shows that the contribution of Tropical Surface Water to Agulhas Current waters, via the Mozambique Channel, also has a distinct seasonal characteristic that is brought about by the seasonal wind stress over the tropical Indian Ocean. This simulated flow through the Channel contributes substantially to the seasonality of the Agulhas Current. This model result is shown to be not inconsistent with available hydrographic observations.
Background aerosol concentration derived from the atmospheric electric conductivity measurements made over the Indian Ocean during INDOEX

Measurements of the atmospheric electric conductivity on board ORV Sagarkanya during her three cruises over the Indian Ocean (17°N to 20°S, 57°E to 79°E) during the periods of December to March 1996–1997, 1998, and 1999 are reported. The results show that the values of atmospheric conductivity over the southern hemisphere are 2 to 3 times ofthat over the northern Indian Ocean and the north-to-south gradients extend up to the Intertropical Convergence Zone (ITCZ) and have large interseasonal and intraseasonal variations. The values of electric conductivity have been used to calculate the aerosol concentrations. The latitudinal variations of the aerosol concentration have been observed to have positive gradients from the Indian coastline to the ITCZ, and the gradients are different during the three cruises. The aerosol concentrations attain their pristine level only at 15°–20°S in this season. Because of the large interseasonal variability of the aerosol concentration observed over the northern Indian Ocean, it is concluded that estimating any secular change in the background aerosol pollution may be a futile exercise in this area.
Ecological controls on methane emissions from a Northern Peatland Complex in the zone of discontinuous permafrost, Manitoba, Canada

Methane emissions were measured by a static chamber technique in a diverse peatland complex in the Northern Study Area (NSA) of the Boreal Ecosystem Atmosphere Study (BOREAS). Sampling areas represented a wide range of plant community and hydrochemical gradients (pH 3.9–7.0). Emissions were generally larger than those reported from other boreal wetland environments at similar latitude. Seasonal average fluxes from treed peatlands (including palsas) ranged from 0 to 20 mg CH4 m−2 d−1 compared with 92 to 380 mg CH4 m−2 d−1 in open graminoid bogs and fens (with maximum single fluxes up to 1355 mg CH4 m−2 d−1). Permafrost-related collapse scars had similarly high CH4 emissions, particularly in the lag areas where continuous measurements of water table, peat surface elevation, and peat temperature showed that the peat surface adjusted to a falling water table in the abnormally dry 1994 season, maintaining warm, saturated conditions and high CH4 flux later into the season than nonfloating sites. A predictive model for CH4 flux and environmental variables was developed using multiple stepwise regression. A combined variable of mean seasonal peat temperature at the average position of the water table explained most of the spatial variability in log CH4 flux (r2 = 0.64), with height above mean water table (HMWT), water chemistry (Kcorr, pH, Ca), tree cover, and herbaceous plant cover explaining additional variance (r2 = 0.81). Canonical correspondence analysis (CCA) of combined vascular and bryophyte data with environmental variables showed that CH4 flux was negatively correlated with HMWT, the second axis of vegetation variability, and was only weakly correlated with chemistry, the first axis. Sedge and tree cover were correlated with high and low CH4 fluxes, respectively, while shrub cover was of less predictive value. Microtopographic groupings of hummocks and hollows were separated in terms of CH4 flux at the intermediate ranges of the moisture gradient. These data show that multivariate vegetation analyses may provide a useful framework for integrating the complex environmental controls on CH4 flux and extrapolating single point chamber measurements to the landscape scale using remote sensing. (Key words: CH4 flux, peatland, vegetation, and remote sensing.)
Late Quaternary Palaeoichnological Sites from the Southern Atlantic Coast of Buenos Aires Province, Argentina: Mammal, Bird and Hominid Evidence

Palaeontological and palaeoichnological studies were made along the southeastern coast of Buenos Aires province, Argentina. Continental Late Pleistocene and continental, transitional and marine Holocene stratigraphic units were identified. The former are represented by fossil mammal bones and ichnites dated from 16,000 to 12,000 y. B.P. Continental Early Holocene beds dated circa 8,100 years B.P. contain fish, rodent and bird remains. Middle Holocene sediments 6,930 to 6,570 years B.P. are recorded by deposits bioturbated by estuarine crabs. During the Late Holocene, between 5,000 and 4,800 B.P., a marine transgression is recorded by a very rich mollusc fauna. The palaeoenvironmental variety recorded along a few tens of kilometers of the coast is a distinctive feature of this part of the Argentine coastal region. At Monte Hermoso beach, in the eastern part of the studied zone, archaeological materials were dated 7,300 years B.P., and human footprints dated 7,125 years B.P. were also recorded. In January 2005 some isolated human footprints were found at Pehuen-Co palaeoichnological site, which are older than those found at Monte Hermoso beach and of the same age as the oldest human archaeological findings in Patagonia, that is about 12,000 yeas B.P.
A Numerical Technique for Calculating the Transient Position of the Saltwater Front

The movement of the saltwater front in coastal aquifers, including the effect of dispersion, can be determined by using numerical methods. The method of characteristics is used to solve the solute transport equation, and the alternating direction iterative procedure is used to solve the groundwater flow equation for the two-dimensional problem. This approach permits the treatment of transient flow in nonhomogeneous aquifers with irregular geometry.
Evaluation of the Apollo Asteroids as Sources of Stone Meteorites

Calculation of the secular perturbations of the earth-crossing (Apollo) asteroids shows that the node of one body, 1948 EA, seldom, if ever, crosses the earth's orbit and probably should not be included with the Apollo asteroids. Another object, 1580 Betulia, will cross the earth's orbit, although its present perihelion lies beyond the orbit of the earth. The hypothesis that chondritic meteorites are produced in earth-crossing orbits as collision fragments of these Apollo asteroids has the attractive feature that the short (∼107 years) cosmic-ray ages, characteristic of such an initial orbit, are in agreement with measured ages. A quantitative study of this hypothesis indicates difficulties that must be overcome before this hypothesis may be considered plausible. (1) If the Apollos are ordinary asteroids, gravitationally perturbed into earth-crossing orbits, the steady-state ratio of falls from fragments of Apollo asteroids to falls from fragments of other asteroids will be to a good approximation R = TA/TC ∼ 0.01 to 0.1, where TA is the lifetime of Apollo asteroids (∼107 years) and Tc is the collision lifetime (108 – 109 years) of meteorites in the asteroid belt. In the steady state, long exposure ages should predominate. (2) The expected mass yield of meteorites from the known Apollo asteroids is too small by a factor of about 500. Although there are certainly many undiscovered Apollo asteroids, it is unlikely that they are sufficiently numerous or sufficiently massive to produce the observed meteorite flux of ∼109 g/yr. Effects of the ∼104-year periodic variations in eccentricity and inclination do not change this conclusion. These difficulties are in part avoidable if, as proposed by Opik, the Apollo asteroids are cometary cores, especially if there also exist numerous fragmented cores within cometary nuclei.
Structural Heterogeneity in Northeast Japan and Its Implications for the Genesis of the 2004 and 2007 Niigata Earthquakes

Abstract We utilized 188,766 P -wave and 179,328 S -wave high-quality arrival-time data from 14,666 local earthquakes to determine the three-dimensional (3D) seismic velocity ( V P , V S ), V P / V S ratio, crack density ( e ), and bulk velocity ( V ϕ ) structures in and around the source areas of the 2004 and 2007 Niigata earthquakes (Japan Meteorological Agency magnitude [ M J ] 6.8) in Japan in order to understand the generation mechanisms of the Niigata mainshocks. The aftershock hypocenters were relocated by applying the double-difference location method simultaneously with the tomographic inversion, indicating a complicated fault system that includes not only two parallel dominant faults dipping to the northeast but also some conjugate faults crossing the Niigata mainshock hypocenters. In general, high velocity ( V P , V S ) with low e at 11 km depth is visible in the southeastern part of this area in contrast to anomalous low velocity with high crack density in the northwestern part along the Niigata-Kobe tectonic zone (NKTZ). These characteristics of the velocity and crack density are consistent with the spatial distribution of active faults along the NKTZ. The surface geological features that indurated pre-Neogene rock outcrops were observed in the southeastern area, whereas deep sedimentary basins were observed on the opposite side. Low V P and low V S zones with high V P / V S anomalies were imaged in and/or under the source areas, showing agreement with those revealed by previous studies. All the features of the velocity and V P / V S structures, together with the images of the crack density and bulk velocity, suggest the presence of fluids under the source areas. Such fluids might have weakened the mechanical strength of the fault zone of the source areas, thus triggering the 2004 and 2007 Niigata earthquakes. Our present study, together with other recent tomographic images, reveals that fluids penetrated into the source rocks from the lower crust and uppermost mantle as a result of dehydration of the subducting Pacific slab and thus may play a key role in the genesis of these large crustal earthquakes.
A test of (Ge/Si)opal as a paleorecorder of (Ge/Si)seawater

Late Pleistocene variations of germanium to silicon ratios in marine diatom shells from sediment cores, (Ge/Si)opal, are coherent with the global isotope record of glacial to interglacial climate change. These variations are thought to reflect changes in (Ge/Si)seawater driven by climate-modulated alterations in oceanic Ge/Si sources and sinks. However, an important criterion for interpreting (Ge/Si)opal as a monitor of whole ocean (Ge/Si)seawater is that the opal burial ratio be insensitive both to local diatom production and surface ocean silica concentrations (so-called biological fractionation effects) and to differential dissolution artifacts (so-called diagenesis offsets). Here we test these assumptions by comparing model ocean sediment (Ge/Si)opal distributions with data from Holocene and glacial sediments across the high-latitude Indian-Antarctic Ocean siliceous ooze belt. In contrast to the model, the data show no gradients in either Holocene or glacial (Ge/Si)opal values across productivity zones displaying dramatic changes in biosiliceous production, opal burial, and dissolution. This evidence supports the contention that fractionation effects are small and that observed down-core variations in (Ge/Si)opal faithfully record secular changes in (Ge/Si)seawater.