Miracle-dz/UniFAR-FTUs huggingface dataset:
Mixing states of individual aerosol particles in spring Arctic troposphere during ASTAR 2000 campaign

[1] The present study mainly focuses on the mixing states of aerosol constituents and their vertical distribution in spring Arctic troposphere during the ASTAR 2000 campaign (T. Yamanouchi et al., Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) campaign: An overview and first results, submitted to Bulletin of the American Meteorological Society, 2002) (hereinafter referred to as Yamanouchi et al., submitted manuscript, 2002). Sulfate and soot were identified as major aerosol under both Arctic haze and background conditions, and sea-salts are major only in lower troposphere (<3 km above sea level). Mineral/dusts and unknown species were obtained as minor constituents during the ASTAR 2000 campaign. Airborne aerosol measurements were carried out under the Arctic haze (23 March), and aerosol-enriched (20 March and 12 April) conditions. The highest relative abundance of soot (∼94.7%) was observed in free troposphere on 23 March, when the heaviest Arctic haze condition during the ASTAR 2000 campaign (Yamanouchi et al., submitted manuscript, 2002) was transported directly from Russian industrial regions to the measuring area for several days. Moreover, whereas the external mixing of soot and sulfate dominated under the Arctic haze and aerosol enriched conditions, in the background conditions the internal mixing is dominant. On the other hand, most of aerosol particles containing sulfate had the external mixing states with soot and other aerosol constituents in the free troposphere under both the Arctic haze and background conditions. Sea-salts are dominant only in the lower troposphere (<3 km asl), although a few sea-salt particles were observed in the middle-upper troposphere (3–7 km). Some sea-salt particles were modified (Cl− depleted) in the lower troposphere (<3 km) during the ASTAR 2000 campaign.
Monitoring secondary tropical forests using space-borne data: Implications for Central America

Tropical secondary forests, which play an important role in carbon sequestration, may be monitored using space-borne sensors. Secondary forest biomass or age estimation from space-borne data may be used to quantify the carbon sink these forests represent. At current capabilities, roughly three successional stages up to 15 years of age may be identified from Landsat TM data. Using synthetic aperture radar, reliable biomass estimates may be made up to approximately 60 tons/ha. The potential for overcoming these limitations is reviewed, including the synergy of radar and optical imagery and the unprecedented spatial and spectral resolutions of new sensors. Most of the available literature to date is from the Amazon; in this paper, applicability to Central America is considered, which has a much more heterogeneous landscape and the dynamics of secondary growth have a special significance in the framework of conservation biology and carbon sequestration. We conclude that critical issues in this region will be topographical correction and stratification according to ecological and site quality variables.
Numerical Modeling of Spudcan Deep Penetration in Three-Layer Clays

AbstractThis paper reports the results from numerical modeling of spudcan deep penetration through three-layer clays. Two typical seabed strength profiles commonly encountered in the field, and identified as critical for potential punch-through failure, were considered: (1) uniform stiff-soft-stiff clay and (2) nonuniform clay with an interbedded stiff clay layer. Three-dimensional large deformation finite-element (LDFE) analyses were carried out with and without simulating strain softening and strain rate dependency of the shear strength. The results were compared with previously published LDFE results and centrifuge test data. A detailed parametric study was undertaken, varying the relevant range of layer thicknesses (relative to the spudcan diameter), strength ratios, normalized strength, and strength nonhomogeneity. Punch-through and rapid leg penetration (for stiff-over-soft) and squeezing (for the reverse) were demonstrated by the penetration resistance profiles and associated soil failure mechanism.
Subglacial recharge into the Western Canada Sedimentary Basin—Impact of Pleistocene glaciation on basin hydrodynamics

Brine springs discharging from Devonian carbonates of the Western Canada Sedimentary Basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin. Stable isotope data suggest that the brine springs originated as Pleistocene meltwater. These waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin-scale flow system, caused by the overriding ice sheet. Esker distribution shows a notable relationship between shield and sedimentary rocks. An integrated sedimentary basin/ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development. The fluid flow history of the Western Canada Sedimentary Basin is characterized by back-and-forth movement through geological time in response to changing boundary conditions. Modern-day flow systems may not then be indicative of historic movement of economic fluids through the basin.
Equatorial ionosphere responses to two magnetic storms of moderate intensity from conjugate point observations in Brazil

[1] Equatorial ionospheric responses during two magnetic storms of moderate intensity are investigated, for the first time, by conjugate point observations in Brazil. The study focuses on storm-induced changes in the evening prereversal vertical drift, thermospheric trans-equatorial winds, spread F/plasma bubble irregularity development, electron density/plasma frequency heights, the EIA strength, and zonal plasma drifts. It is based on data obtained from five Digisondes operated in Brazil, three of them being part of a conjugate point equatorial experiment (COPEX) involving a dip equatorial and two magnetic conjugate sites at ±12°. The other two were operated at the equatorial ionization anomaly (EIA) trough and crest locations at nearby magnetic meridians. The results bring out, and clarify, many outstanding aspects of the strong influence of storm time electric fields on the equatorial ionosphere at different phases of the two long lasting storm sequences. During both storms prompt penetration electric fields dominated the ionospheric response features as compared to the disturbance wind dynamo effects that were not very conspicuous. An under-shielding (over-shielding) electric field occurring in the evening hours causes enhancement (suppression) of the prereversal vertical drift and post sunset spread F/plasma bubble generation. The same electric fields cause post sunset EIA enhancement and suppression, respectively. Post sunset (post midnight) spread F can develop from under-shielding (over-shielding) electric fields, while it can be disrupted by over-shielding (under-shielding) electric field. Trans-equatorial winds are found to be ineffective to stabilize the post sunset F region against the destabilizing effect of strong prereversal vertical drift. Storm time westward plasma drifts are found to be driven by prompt penetration eastward electric fields (through their effect of inducing vertical Hall electric fields), rather than by a disturbance westward thermospheric wind during these storms.
Seismicity at intersections of spreading centers and transform faults

Ocean-bottom seismographs were used in a microearthquake monitoring experiment at the eastern junction of the Oceanographer transform with the mid-Atlantic ridge at 35°N. Microearthquake activity at the junction occurred over a broad area (>7 km). These microearthquakes ‘cut across’ the corner between the transform and median valley and are associated with fault scarps that form the inner walls on the west and north sides of the median and transform valleys. At intersections of other major fracture zones (>100-km offset) and slow to moderate spreading centers microearthquake activity is also diffuse and cuts across the corner between the spreading center and transform fault. The narrow zone of decoupling (∼1 km) observed between spreading center and transform boundaries by detailed geological studies at the Tamayo/East Pacific Rise and Vema/mid-Atlantic Ridge intersections suggest that the diffuse seismicity (20 to 30 km in width) does not reflect a diffuse plate boundary at the transition from rift to transform valley. Instead, the faulting probably reflects internal deformation of the corner by secondary faults off of the plate boundary.
Short-term effects of three animal manures on soil pH and Al solubility

A short-term (3-day) equilibration experiment was carried out to determine the effects of 3 animal manures (poultry, pig, and cattle) added at a rate of 20 mg/g to an Oxisol on pH and the concentrations of total (Al-T) and monomeric (Al-Mono) Al in solution. The pH of equilibrium solutions from the control, cattle, pig, and poultry manure treatments were 4.0, 4.6, 5.2, and 6.3, respectively. AlMono concentrations decreased progressively as pH increased but concentrations of AlT were similar in the pig and poultry manure treatments. Subsequent equilibration experiments examined the solubility of AlMono and AlT when the 3 manures were added to the Oxisol or a 40uM AlCl3 solution and pH was maintained at 4.0, 4.5, 5.0, 5.5, 6.0, and 6.5. In both experiments, addition of manures generally tended to reduce the concentration of AlT in the lower pH range ( 4.0 and 4.5) but increase it in the higher range ( pH 5.5 or 6.0 and above). Concentrations of AlMono, and the proportion of AlT present as AlMono, were reduced over the whole pH range. Results were explained in terms of the strong bonding ability of organic matter in both the solid and solution phases for Al. At lower pH, where Al is highly soluble, complexation by solid-phase organic matter results in a reduction in both Al-T and Al-Mono. However, at higher pH, where Al solubility becomes limited, complexation of Al by soluble organic matter becomes an important mechanism and this results in an elevation in AlT, while concentrations of AlMono remain very low. It was concluded that the effects of manures in reducing concentrations of AlMono in soil solution are attributable to both an increase in pH and the complexing ability of organic matter for Al.
Seismic detection of marine methane hydrate

As offshore petroleum exploration and development move into deeper water, industry must contend increasingly with gas hydrate, a solid compound that binds water and a low-molecular-weight gas (usually methane). Gas hydrate has been long studied in industry from an engineering viewpoint, due to its tendency to clog gas pipelines. However, hydrate also occurs naturally wherever there are high pressures, low temperatures, and sufficient concentrations of gas and water. These conditions prevail in two natural environments, both of which are sites of active exploration: permafrost regions and marine sediments on continental slopes. In this article we discuss seismic detection of gas hydrate in marine sediments. Gas hydrate in deepwater sediments poses both new opportunities and new hazards. An enormous quantity of natural gas, likely far exceeding the global inventory of conventional fossil fuels, is locked up worldwide in hydrates. Ex-traction of this unconventional resource presents unique exploration, engineering, and economic challenges, and several countries, including the United States, Japan, Canada, India, and Korea, have initiated joint industry-academic-governmental programs to begin studying those challenges. Hydrates also constitute a potential drilling hazard. Because hydrates are only stable in a restricted range of pressure and temperature, any activity that sufficiently raises temperature or lowers pressure could destabilize them, releasing potentially large volumes of gas and decreasing the shear strength of the host sediments. Assessment of the opportunities and hazards associated with hydrates requires reliable methods of detecting hydrate and accurate maps of their distribution and concentration. Hydrate may occur only within the upper few hundred meters of deepwater sediment, at any depth between the seafloor and the base of the stability zone, which is controlled by local pressure and temperature. Hydrate is occasionally exposed at the seafloor, where it can be detected either visually or acoustically by strong seismic reflection amplitudes or high backscatter …
Migration and Children's School and Labor: Evidence from El Salvador

This paper examines the impact of parental migration on schooling outcomes for children left behind in El Salvador. Using cross sectional data collected in 2012, outcomes for children are observed for children with migrant parents; the outcomes are also analyzed by gender of the migrant parent who left his or her child behind. With instrumental variables estimations, as well as a seemingly unrelated regression to estimate the impact of migration on a child's time allocation, observations are also compared by subsample to examine the impact of the presence or absence of remittances in the household when a parent has migrated. Results show that children with a migrant parent will complete more years of school, more so if the migrant is a mother. Migration has no significant influence on time allocation, except in the absence of remittances, which can cause a child to work more and study less. This paper studies the impact of both migration and remittances on a child's schooling behavior. Results suggest that the same factors that affect schooling may have strong correlation with the propensity to migrate as well.
Failure behavior of single sand grains: Theory versus experiment

Grain-scale brittle fracture and grain rearrangement play an important role in controlling the compaction behavior of reservoir rocks during the early stages of burial. Therefore, the understanding of single-grain failure is important. We performed constant displacement rate crushing tests carried out on selected, wellrounded, single sand grains and on randomly sampled grains from different grain size (d) batches of pure quartz sand. Applying a Hertzian fracture mechanics model for grain crushing, the critical load at failure (Fc) data obtained for the selected grains were converted into an accurate estimate of the size of flaws associated with failure (cf). Similarly, the distributed Fc data obtained from the different batch samples were converted into distributions of grain failure stress. Weibull weakest link theory could not explain the observed grain failure behavior. On the contrary, the Hertzian grain failure criterion enabled the conversion of the distributed Fc data, for the batch samples, into distributions of cf, assuming spherical grains, or of "effective" radius of curvature (rg), characterizing contact surface asperities in the case of non-spherical
Differential Preservation of Gravel-sized Bioclasts in Alpheid- versus Callianassid-Bioturbated Muddy Reefal Sediments

Abstract Infaunal bivalve shells were extracted from sediment cores taken in shallow seas off Phuket, South Thailand, and were scored for four types of taphonomic degradation to assess the effect that different types of bioturbation have on the preservation of such bioclasts. This gravel-sized fraction of off-reef biogenic (bivalve) sediments showed variation in the extent of degradation, depending on whether it was found in an area bioturbated by callianassid or alpheid shrimps. Cores taken in the alpheid area have a higher proportion of grains with poorly defined shape and ornamentation, a loss of surface luster and high levels of microbioerosion. In contrast, those from the callianassid area have a higher proportion of shiny, sharply defined fragments and a lower level of microbioerosion than those from the alpheid area. It is concluded that the different nature of bioturbation in the two areas accounts for the difference in preservation. In working the sediment, callianassids bury the gravel fraction, while alpheids repeatedly bring it to the sediment surface, thus exposing it to higher levels of physical and microbiological erosion. The shrimps' activities result in a difference in preservation potential of fine and coarse sediments, and this taphonomic bias will affect taphofacies interpretation. Rapid burial of gravel by callianassids also has implications for time-averaging, as a shell fragment's condition is more indicative of its residence time at the surface-water interface than its age.
Has the NFL’s Rooney Rule Efforts ‘‘Leveled the Field’’ for African American Head Coach Candidates?

Madden provides evidence that African American head coaches in the National Football League (NFL) significantly outperformed whites between 1990 and 2002. She concludes that this evidence is consistent with African Americans being required to be better to be hired as head coaches. In 2002, the NFL promulgated the Rooney Rule requiring that NFL teams make various affirmative efforts when hiring coaches. This article finds that the performance advantage of African American head coaches has been eliminated since the Rooney Rule but finds no similar time trends in racial differentials in performance for other NFL coaching positions.
Coupling of air and sea surface temperatures in the eastern Fram Strait during the last 2000 years

The Arctic has undergone significant changes in the last 20–30 years. The understanding of these changes is limited by the time span or resolution of existing climate records. The main gateway of heat to the Arctic Ocean is the Fram Strait, between Greenland and Svalbard. We have reconstructed past air and sea surface temperatures and relative variations in freshwater extent in a marine core from eastern Fram Strait which spans the last 2000 years. The results show a progressive increase in air temperature and a decrease in the upper mixed water layer temperature, together with an increase in freshwater content during the last 1000 years. Considering the oceanographic features of the eastern Fram Strait, these results suggest that there might have been a progressive increase in the inflow of Atlantic water during the last 1000 years, accompanied by an increase in atmospheric heat transport, causing progressive sea-ice melting and subsequent cooling and freshening of the upper mixed water layer in this area. We suggest that our data show long-scale average changes in the modes of positive and negative Arctic multidecadal variability over the last 2000 years.
How ubiquitous is the dipole relationship in tropical Atlantic sea surface temperatures

Several kinds of analysis are applied to sea surface temperature anomalies (SSTA) (1856–1991) to determine the degree to which SSTA of opposite sign in the tropical North and South Atlantic occur. Antisymmetric (“dipole”) configurations of SSTA on basin scales are not ubiquitous in the tropical Atlantic. Unless the data are stratified by both season and frequency, inherent dipole behavior cannot be demonstrated. Upon removing the global El Nino-Southern Oscillation signal in SSTA (which is symmetric between the North and South Atlantic) from the data, the regions north or south of the Intertropical Convergence Zone have qualitatively different temporal variabilities and are poorly correlated. Dipole configurations do occur infrequently (12–15% of the time), but no more so than expected by chance for stochastically independent variables. Nondipole configurations that imply significant meridional SSTA gradients occur much more frequently, nearly half of the time. Cross-spectral analysis of seasonally averaged SSTA indices for the North and South Atlantic show marginally significant coherence with antisymmetric phase in two period bands: 8–12 years for the boreal winter-spring and 2.3 years for the boreal summer-fall. Antisymmetric coherence is optimal for a small subregion west of Angola in the South Atlantic, with respect to SSTA of basin scale in the tropical North Atlantic. Dipole variability, even where optimal, explains only a small fraction of the total variance in tropical Atlantic SSTA (<7%).
Financial and environmental consequences of a voluntary farm environmental assurance program in Michigan

The Michigan Agriculture Environmental Assurance Program is a voluntary environmental management program for Michigan farms. The Michigan Agriculture Environmental Assurance Program encourages farm managers to become better environmental stewards through writing Comprehensive Nutrient Management Plans and incorporating changes to comply with regulations as well as generally accepted management practices and recommendations. Early-adopting livestock producers with verified operations were interviewed to identify and measure costs incurred, environmental outcomes achieved, and producer attitudes and perceptions as a result of verification. The average total cost to become verified was $120,600 per farm, of which the average producer paid $104,423, with the remaining $16,177 provided through cost-share funds. Much of this cost was for long-term investments such as manure storage and facilities improvements. Producers realized an average postverification annual cost savings of $2,792 by curtailing unnecessary use of commercial fertilizer. The financial values had large amounts of variation in every case. The per animal unit costs of verification were generally in the same range as the US Environmental Protection Agency estimates for cost of compliance with similar (but mandatory) proposed regulations. With respect to environmental outcome, after verification, average operation mass balance improved. The primary motivation to participate in the program stemmed from existing or potential environmental regulations.
The Blake Geomagnetic Polarity Episode recorded in Chinese loess

A geomagnetic anomaly consisting of three clearly defined periods of reverse polarity separated by two short intervals of normal polarity has been documented in a loess section near Xining, western China. On the basis of previous studies of Chinese loess stratigraphy, we correlate this geomagnetic polarity episode with the Blake event. While more research is needed to improve our understanding of the exact process of remanence acquisition of loess deposits, this study shows that loess may provide records of fast geomagnetic events and lends further support to the global nature of the Blake geomagnetic event.