bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in Soil Organic Carbon Contents and Nitrous Oxide Emissions after Introduction of No‐Till in Pampean Agroecosystems
Authors: Steinbach Haydée S. , Alvarez Roberto 
Published: January 2006

ABSTRACTWe reviewed published results to estimate no‐till effects on SOC and denitrification in the Argentine Pampas and the potential of no‐till to mitigate the global warming effect. On an equivalent mass basis, 42 paired data sets were used for SOC comparisons of no‐till vs. plow till (moldboard plow or disk plow), 18 paired data for comparison of no‐till vs. reduced till (chisel plow or harrow disk), and 20 paired data for comparison of plow till vs. reduced till. Twenty‐six denitrification data sets were used for evaluation of tillage system and fertilization effects on N2O emission. Changes in SOC under no‐till were not correlated to time since initiation of experiments. Averaged over years a 2.76 Mg ha−1 SOC increase (P = 0.01) was observed in no‐till systems compared with tilled systems, but no differences were detected between plow and reduced till. The SOC under tillage explained most of the SOC variation under no‐till (R2 = 0.94, P = 0.01). The model had a positive intercept and predicted a relatively higher increase of SOC in areas of low organic matter level. The conversion of the whole pampean cropping area to no‐till would increase SOC by 74 Tg C, about twice the annual C emissions from fossil fuel consumption of Argentina. Emissions of N2O were greater under no‐till with a mean increase of 1 kg N ha−1 yr−1 in denitrification rate for humid pampean scenarios. The increased emissions of N2O might overcome the mitigation potential of no‐till due to C sequestration in about 35 yr, and therefore no‐till might produce global warming.
Reduction of Stream Sediment Concentration by a Riparian Buffer: Filtering of Road Runoff in Disturbed Headwater Basins of Montane Mainland Southeast Asia
Authors: Ziegler Alan D. , Negishi Junjiro , Sidle Roy C. , Preechapanya Pornchai , Sutherland Ross A. , Giambelluca Thomas W. , Jaiaree Sathaporn 
Published: January 2006

ABSTRACTWe determined the extent that a riparian buffer reduces stream suspended sediment concentrations by filtering road runoff during 18 rain events in a 2.5‐ha, multi‐use watershed in northern Thailand. The dominant buffer species was the perennial sedge Fimbristylis aphylla Zoll. ex Steud. (Cyperaceae). We monitored stream sediment concentration for situations where road runoff either flowed into the riparian buffer or was diverted directly into the stream (buffer and no buffer scenarios). These data were used to develop the following relationships between instantaneous stream sediment concentration (Ci) and discharge (Qi): Ci = 28.329Qi0.851 (buffer scenario) and Ci = 22.265Qi1.579 (no buffer scenario). Using these functions to calculate total event suspended concentrations, we determined that the buffer reduced suspended sediment concentration by 34 to 87%, for the range of events monitored. Removal of sediment from runoff generated on a 2.4‐m‐wide, 165‐m‐long unpaved road section was achieved principally via ponding, which reduced the transport capacity as flow entered the relatively flat, saturated buffer. Sediment deposition occurred primarily within the first 10 m of the buffer. Some sediment was also deposited on the fillslope leading to the buffer. Maximum road sediment concentration during the largest buffer event approached 100 000 mg L−1 Meanwhile, the corresponding maximum stream suspended sediment concentration was <4000 mg L−1 In contrast, maximum stream concentrations when flow bypassed the buffer during smaller events were commonly 4000 to 7000 mg L−1 Naturally occurring buffers represent an economical means of mitigating road‐related impacts in upland basins in Southeast Asia, particularly if combined with measures limiting sediment and runoff production on contributing road sections.
Occurrence of Arsenic in Ground Water in the Choushui River Alluvial Fan, Taiwan
Authors: Liu Chen‐Wuing , Wang Sheng‐Wei , Jang Cheng‐Shin , Lin Kao‐Hong 
Published: January 2006

ABSTRACTAn investigation of shallow ground water quality revealed that high arsenic (As) concentrations were found in both aquifers and aquitards in the southern Choushui River alluvial fan of Taiwan. A total of 655 geological core samples from 13 drilling wells were collected and analyzed. High As contents were found primarily in aquitards, to a maximum of 590 mg/kg. The contents were correlated with the locations of the marine sequences. Additionally, strong correlations among the As concentrations of core samples, the clay, and the geological age of the Holocene transgression were identified. Most of the As in ground water originated from the aquitard of the marine sequence. The high As content in marine formations with high clay contents may be attributable to the bioaccumulation of As in the sea organisms, which accrued and were deposited in the formation. A preliminary geogenic model of the origin of the high As concentration in the shallow sedimentary basin of the Choushui River alluvial fan of Taiwan is proposed.
Instrumentation for Measuring Runoff, Sediment, and Chemical Losses from Agricultural Fields
Authors: Bonilla Carlos A. , Kroll David G. , Norman John M. , Yoder Daniel C. , Molling Christine C. , Miller Paul S. , Panuska John C. , Topel Jeffrey B. , Wakeman Peter L. , Karthikeyan K. G. 
Published: January 2006

ABSTRACTThis work describes a simple, passive sampling system for measuring runoff, sediment, and chemical losses from typical agricultural fields. The sampler consists of a 5 to 7 m wide runoff collector connected to a series of multislot divisors. These divisors split the flow into aliquots, providing a continuous sampling during the runoff event. Divisors were located in a wooden box below ground level. With an adequate pump, this system can operate in fields with a slope gradient as low as 2%, and can stay in the field during winter to record first snowmelt‐generated runoff. A radio transmitter reports by telemetry the occurrence and magnitude of any runoff event, and indicates when the system should be sampled and emptied. This article includes a description of the equipment, advantages, and disadvantages based on 2 yr of operation, and examples of data collected.
Phosphorus Sequestration by Chemical Amendments to Reduce Leaching from Wastewater Applications
Authors: Zvomuya Francis , Rosen Carl J. , Gupta Satish C. 
Published: January 2006

ABSTRACTPhosphorus‐immobilizing amendments can be useful in minimizing P leaching from high P soils that may be irrigated with wastewater. This study tested the P‐binding ability of various amendment materials in a laboratory incubation experiment and then tested the best amendment in a field setup using drainage lysimeters. The laboratory experiment involved incubating 100‐g samples of soil (72 mg kg−1 water‐extractable phosphorus, WEP) with various amendments at different rates for 63 d at field moisture capacity and 25°C. The amendments tested were alum [Al2(SO4)3·14H2O], ferric chloride (FeCl3), calcium carbonate (CaCO3), water treatment residual (WTR), and sugarbeet lime (SBL). Ferric chloride and alum at rates of 1.5 and 3.9 g kg−1, respectively, were the most effective amendments that decreased WEP to 20 mg kg−1, below which leaching has previously been shown to be low. Alum (1.3 kg m−2), which is less sensitive to redox conditions, was subsequently tested under field conditions, where it reduced WEP concentration in the 0‐ to 0.15‐m layer from 119 mg kg−1 on Day 0 to 36.1 mg kg−1 (85% decrease) on Day 41. Lysimeter breakthrough tests using tertiary‐treated potato‐processing wastewater (mean total phosphorus [TP] = 3.4 mg L−1) showed that alum application reduced leachate TP and soluble reactive phosphorus (SRP) concentrations by 27 and 25%, respectively. These results indicate that alum application may be an effective strategy to immobilize P in high P coarse‐textured soils. The relatively smaller decreases in TP and SRP in the leachate compared to WEP suggest some of the P may be coming from depths below 0.2 m. Thus, to achieve higher P sequestration, deeper incorporation of the alum may be necessary.
Temporal and Spatial Distributions of Sediment Total Organic Carbon in an Estuary River
Authors: Ouyang Y. , Zhang J. E. , Ou L.‐T. 
Published: January 2006

ABSTRACTUnderstanding temporal and spatial distributions of naturally occurring total organic carbon (TOC) in sediments is critical because TOC is an important feature of surface water quality. This study investigated temporal and spatial distributions of sediment TOC and its relationships to sediment contaminants in the Cedar and Ortega Rivers, Florida, USA, using three‐dimensional kriging analysis and field measurement. Analysis of field data showed that large temporal changes in sediment TOC concentrations occurred in the rivers, which reflected changes in the characteristics and magnitude of inputs into the rivers during approximately the last 100 yr. The average concentration of TOC in sediments from the Cedar and Ortega Rivers was 12.7% with a maximum of 22.6% and a minimum of 2.3%. In general, more TOC accumulated at the upper 1.0 m of the sediment in the southern part of the Ortega River although the TOC sedimentation varied with locations and depths. In contrast, high concentrations of sediment contaminants, that is, total polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), were found in sediments from the Cedar River. There was no correlation between TOC and PAHs or PCBs in these river sediments. This finding is in contradiction to some other studies which reported that the sorption of hydrocarbons is highly related to the organic matter content of sediments. This discrepancy occurred because of the differences in TOC and hydrocarbon source input locations. It was found that more TOC loaded into the southern part of the Ortega River, while almost all of the hydrocarbons entered into the Cedar River. This study suggested that the locations of their input sources as well as the land use patterns should also be considered when relating hydrocarbons to sediment TOC.
An Approach for Measuring Methane Emissions from Whole Farms
Authors: McGinn S. M. , Flesch T. K. , Harper L. A. , Beauchemin K. A. 
Published: January 2006

ABSTRACTEstimates of enteric methane (CH4) emissions from ruminants are typically measured by confining animals in large chambers, using head hoods or masks, or by a ratiometric technique involving sampling respired air of the animal. These techniques are not appropriate to evaluate large‐scale farm emissions and the variability between farms that may be partly attributed to different farm management. This study describes the application of an inverse‐dispersion technique to calculate farm emissions in a controlled tracer‐release experiment. Our study was conducted at a commercial dairy farm in southern Alberta, Canada (total of 321 cattle, including 152 lactating dairy cows). Sulfur hexafluoride (SF6) and CH4 were released from 10 outlet locations (barn and open pens) using mass‐flow controllers. A Lagrangian stochastic (LS) dispersion model was then used to infer farm emissions from downwind gas concentrations. Concentrations of SF6 and CH4 were measured by gas chromatography analysis and open path lasers, respectively. Wind statistics were measured with a three‐dimensional sonic anemometer. Comparing the inferred emissions with the known release rate showed we recovered 86% of the released CH4 and 100% of the released SF6 The location of the concentration observations downwind of the farm was critically important to the success of this technique.
Water‐in‐oil emulsion foaming by thiourea nitrosation: Reaction and mass transfer
Authors: da Silva Gabriel , Dlugogorski Bogdan Z. , Kennedy Eric M. 
Published: January 2006

AbstractA study has been undertaken into the chemical production of gas bubbles within a concentrated water‐in‐oil emulsion, typical of those used as emulsion explosives. Chemical foaming was initiated by the introduction of a concentrated sodium nitrite solution to the emulsion, and the measurement of the decreasing emulsion density with time served to estimate the rate of nitrogen production. A conversion of emulsion density to nitrite ion concentration facilitated a kinetic analysis of the data. The change in nitrite ion concentration follows a rate equation which indicates that the rate‐limiting reaction step corresponds to the N‐nitrosation of thiourea by ON+, with an apparent rate constant of 0.22 M−1 s−1 at 25 °C. Tests over a temperature range of 25 to 50 °C yielded an activation energy of 59 kJ mol−1. A mass‐transfer model describing the rate of diffusion between aqueous droplets is presented. This model suggests that chemical kinetics, rather than molecular diffusion, is the rate‐limiting phenomenon in the foaming of emulsions. Supporting this finding, the kinetic experiments in emulsion returned very similar results to previous experiments performed in aqueous media under similar conditions. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Agent distribution and water remaining of polyester nonwoven fabrics after‐treated with polyurethane–citric acid
Authors: Wang Chang 
Published: January 2006

AbstractPolyester nonwoven fabric samples were used to treat with aqueous solutions of water‐soluble polyurethane (PU) containing the foaming agent, citric acid, or the mixtures of foaming agent and citric acid to examine the water remaining and the degradation of PU under the simulative condition of under ground. The results reveal that the viscosity of PU solutions could affect the values of pickup and add‐on. The water remaining values for PU containing citric acid are higher than those for PU containing the foaming agent and PU containing the foaming agent and citric acid. The pore structures, nonwoven construction, and the pores caused by the aggregation of PU within/on the treated nonwoven fabrics can affect the water remaining. From the observation of SEM and the comparison of FTIR, the degradation of water‐soluble PU resin is proved, which could form the rough porous surface of PU resin on the fiber surface as a factor improving the water remaining. The value of water remaining for PU containing citric after 60 weeks' treatment is significantly higher than the pristine nonwoven fabric (control). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 47–56, 2006
New technologies, new findings, and new concepts in the study of vertebrate cis‐regulatory sequences
Authors: Gómez‐Skarmeta José Luis , Lenhard Boris , Becker Thomas S. 
Published: January 2006

AbstractAll vertebrates share a similar early embryonic body plan and use the same regulatory genes for their development. The availability of numerous sequenced vertebrate genomes and significant advances in bioinformatics have resulted in the finding that the genomic regions of many of these developmental regulatory genes also contain highly conserved noncoding sequence. In silico discovery of conserved noncoding regions and of transcription factor binding sites as well as the development of methods for high throughput transgenesis in Xenopus and zebrafish are dramatically increasing the speed with which regulatory elements can be discovered, characterized, and tested in the context of whole live embryos. We review here some of the recent technological developments that will likely lead to a surge in research on how vertebrate genomes encode regulation of transcriptional activity, how regulatory sequences constrain genomic architecture, and ultimately how vertebrate form has evolved. Developmental Dynamics 235:870–885, 2006. © 2006 Wiley‐Liss, Inc.
Spatial relations between avian craniofacial neural crest and paraxial mesoderm cells
Authors: Evans Darrell J.R. , Noden Drew M. 
Published: January 2006

AbstractFate maps based on quail–chick grafting of avian cephalic neural crest precursors and paraxial mesoderm cells have identified the majority of derivatives from each population but have not unequivocally resolved the precise locations of and population dynamics at the interface between them. The relation between these two mesenchymal tissues is especially critical for the development of skeletal muscles, because crest cells play an essential role in their differentiation and subsequent spatial organization. It is not known whether myogenic mesoderm and skeletogenic neural crest cells establish permanent relations while en route to their final destinations, or later at the sites where musculoskeletal morphogenesis is completed. We applied β‐galactosidase‐encoding, replication‐incompetent retroviruses to paraxial mesoderm, to crest progenitors, or at the interface between mesodermal and overlying neural crest as both were en route to branchial or periocular regions in chick embryos. With respect to skeletal structures, the results identify the avian neural crest:mesoderm boundary at the junction of the supraorbital and calvarial regions of the frontal bone, lateral to the hypophyseal foramen, and rostral to laryngeal cartilages. Therefore, in the chick embryo, most of the frontal and the entire parietal bone are of mesodermal, not neural crest, origin. Within paraxial mesoderm, the progenitors of each lineage display different behaviors. Chondrogenic cells are relatively stationary and intramembranous osteogenic cells move only in transverse planes around the brain. Angioblasts migrate invasively in all directions. Extraocular muscle precursors form tightly aggregated masses that en masse cross the crest:mesoderm interface to enter periocular territories, while branchial myogenic lineages shift ventrally coincidental with the movements of corresponding neural crest cells. En route to the branchial arches, myogenic mesoderm cells do not maintain constant, nearest‐neighbor relations with adjacent, overlying neural crest cells. Thus, progenitors of individual muscles do not establish stable, permanent relations with their connective tissues until both populations reach the sites of their morphogenesis within branchial arches or orbital regions. Developmental Dynamics 235:1310–1325, 2006. © 2006 Wiley‐Liss, Inc.
Sister chromatid exchange analysis in smelting plant workers exposed to arsenic
Authors: Paiva Leiliane , Martínez Valeria , Creus Amadeu , Quinteros Domingo , Marcos Ricardo 
Published: January 2006

AbstractThere are many studies documenting the genotoxic effects of environmental exposure to arsenic. Nevertheless, few data are available on the genotoxic risks of occupational arsenic exposure. In the present study, we have evaluated whether or not occupational exposure to arsenic in a copper smelting plant results in a significant increase in the frequency of sister chromatid exchange (SCE). SCE frequencies, proliferation rate index (PRI), and high frequency cells (HFCs) were evaluated in peripheral blood lymphocytes from a group of 105 arsenic‐exposed workers from a Chilean smelting plant (exposed group). Similar assays were conducted on a group of 55 workers employed at the same mine but involved in administrative jobs (internal control), and on 48 workers of another mine, with no significant levels of arsenic (external control). Small but significant increases in SCE frequency were observed in the arsenic‐exposed workers compared with the external control group (6.28 ± 0.09 vs. 5.84 ± 0.14 SCE/cell; P < 0.01). Also, significantly higher frequencies of HFCs were observed in the exposed group (2.21% ± 0.20%) than in either the external control group (1.20 ± 0.23; P = 0.002) or the internal control group (1.30 ± 0.24; P = 0.008). However, there was no relationship between arsenic levels in the urine of the subjects and SCE or HFC frequency. The results of the study indicate that copper smelting results in slightly increased levels of DNA damage. However, our data were not consistent with arsenic exposure being the cause of the increase. Environ. Mol. Mutagen., 2006. © 2006 Wiley‐Liss, Inc.
Mechanisms of genotoxicity of nucleoside reverse transcriptase inhibitors
Authors: Olivero Ofelia A. 
Published: January 2006

AbstractNucleoside analogs were first approved by the U.S. Food and Drug Administration for use against HIV‐AIDS in 1987. Since then, these agents, now commonly referred to as nucleoside reverse transcriptase inhibitors (NRTIs), have become essential components of the Highly Active Antiretroviral Therapy (HAART) drug combinations used for treatment of Human Immunodeficiency Virus‐1 (HIV‐1) infections. Their antiretroviral activity is likely two‐fold: incorporation of the drug into viral DNA and inhibition of the viral reverse transcriptase. However, incorporation of the drug into host nuclear and mitochondrial DNA may be largely responsible for dose‐limiting toxicities. Azidothymidine (AZT, 3′‐azido‐3′‐deoxythymidine, zidovudine), the first NRTI approved for the therapy of HIV‐1, is incorporated into DNA, causes mutations in the hypoxanthine‐guanine phosphoribosyl‐transferase (HPRT) and thymidine kinase (TK) genes, and induces micronuclei, chromosomal aberrations, sister chromatid exchange, shortened telomeres, and other genotoxic effects in cultured cells. Genomic instability would be predicted as a consequence of these events. Metabolic pathways that result in the phosphorylation of AZT play a crucial role in AZT‐DNA incorporation, and may be altered after prolonged treatment. For example, thymidine kinase 1, the enzyme responsible for AZT mono‐phosphorylation, is down‐regulated during long‐term exposure and appears to be associated with AZT‐induced replication inhibition and the accumulation of cells in S‐phase. Detailed information on the mechanisms underlying NRTI‐associated antiretroviral efficacy, toxicity, and metabolic resistance were not available when AZT was first approved for use as an antiretroviral agent. Current insights, based on 15 years of research, may lead to intervention strategies to attenuate toxicity without altering drug efficacy. Environ. Mol. Mutagen., 2006. Published 2006 Wiley‐Liss, Inc.
Real‐time detection of epidermal growth factor receptor expression in fresh oral cavity biopsies using a molecular‐specific contrast agent
Authors: Hsu Elizabeth R. , Gillenwater Ann M. , Hasan M. Qasim , Williams Michelle D. , El‐Naggar Adel K. , Richards‐Kortum Rebecca R. 
Published: January 2006

AbstractEarly diagnosis of individuals with high risk of developing head and neck squamous carcinoma should lead to decreased morbidity and increased survival. To aid in noninvasive early detection of oral neoplasia in vivo, we have developed a molecular‐specific fluorescent contrast agent, consisting of a far‐red fluorescent dye coupled to a monoclonal antibody targeted against the epidermal growth factor receptor. In our study, we used organ cultures of normal and neoplastic human oral tissue to evaluate the capabilities of using this contrast agent to enhance clinical diagnosis. Fresh tissue sections were prepared from 34 biopsies of clinically normal and abnormal oral mucosa from 17 consenting patients. Samples were exposed to contrast agent, rinsed and the presence of bound agent was detected using fluorescence confocal microscopy. Simple assays to assess cytotoxicity of the dye used in the agent and to determine labeling efficacy at physiologic temperatures were also performed. Results indicate that the mean fluorescence intensity (MFI) of samples with dysplasia and cancer are higher than that of the normal sample from the same patient, and that this increase in fluorescence could potentially be used in the early detection and delineation of premalignant lesions. Normal tissue could be distinguished from cancer or moderate dysplasia, using either the ratio of the MFI of abnormal to normal tissue or the MFI obtained from the epithelial surface. No detrimental effects from the dye were observed over a 4‐day period. These results indicate that the use of this optical contrast agent could yield important clinical advantages for noninvasive early detection and molecular characterization of oral mucosa. © 2006 Wiley‐Liss, Inc.