bluuebunny/crossref_metadata_2025 huggingface dataset:
Biotechnological approaches for plant viruses resistance: from general to the modern RNA silencing pathway
Authors: Rodrigues Silas Pessini , Lindsey George G. , Fernandes Patricia Machado Bueno
Published: September 2009

Virus diseases are significant threats to modern agriculture and their control remains a challenge to the management of cultivation. The main virus resistance strategies are based on either natural resistance or engineered virus-resistant plants. Recent progress in understanding the molecular mechanisms underlying the roles of resistance genes has promoted the development of new anti-virus strategies. Engineered plants, in particular plants expressing RNA-silencing nucleotides, are becoming increasingly important and are likely to provide more effective strategies in future. A general discussion on the biotechnology of plant responses to virus infection is followed by recent advances in engineered plant resistance.
Effect of mannitol on the pharmacokinetics of amikacin in wistar rats
Authors: Olguín Hugo Juárez , Portugal Miriam Carrasco , Pérez Janett Flores , Vieyra Angélica Camacho , Pérez Carmen Flores , Rodríguez Alfonso Alfaro
Published: September 2009

The study analyzed the effect of mannitol on the pharmacokinetics (PK) of amikacin. Adult Wistar rats were treated as follows: Group 1 (G1) received mannitol for three days, Group 2 (G2) received mannitol plus 10 mg/kg of amikacin simultaneously, and Group 3 only amikacin. The PK study was conducted on the 4th day. For which, blood samples were drawn at fixed times during 24 h and immunoenzymatically analyzed. Results revealed significant differences (p<0.05) between the groups, e.g. Cmax were 62.26 ± 15.75 µg/ml for G1, 72.63 ± 24.80 µg/ml for G2 and 68.61 ± 27.40 µg/ml for G3. The AUC also differed in the three groups, being largest for G2, 222.52 ± 47.30 µg/ml/h, and smallest for G1, 135.59 ± 39.00 µg/ml/h. Alteration of the PK parameters observed between the groups must be considered when both drugs are prescribed, although human studies are necessary to confirm the results.
Evaluation of protein quality from genetically modified and organic soybean in two consecutives generations of wistar rats
Authors: Daleprane Julio Beltrame , Pacheco Juliana Tomaz , Boaventura Gilson Teles
Published: September 2009

The aim of this study was to evaluate the cumulative effects of using genetically modified and organic soybean in two generations of rats. Two consecutive generations of 64 Wistar rats denominated F0 and F1 were used. The animals from each generation were divided into three groups (n=8) and fed chow made of organic soybean, genetically modified soybean and casein. The PER, NPR and CAE were determined. ANOVA was applied to the results. In both the generations, a statistically significant (p<0.05) difference was found between the experimental groups and the control group. The organic soybean supplement with L-cystine provided a better use of this protein in comparison to the genetically modified soybean protein, which demonstrated that the soybean maintained its protein use, although always inferior to casein. Thus, soybean should be used with caution during the growth stages because even with supplements, it remained inferior in relation to the casein group.
Threat of an influenza panzooty: a review based on conservation medicine
Authors: Caron Luiz Felipe , Soccol Vanete Thomaz
Published: September 2009

Among reemerging illnesses, influenza constitutes one of the main concerns. The avian influenza has recently demonstrated the strong transmission capacity of the etiological agent -a virus from the Orthomyxoviridae family - associated to high pathogenic manifestations of the illness. The strong mutation capacity of this virus, through different hosts, reveals how important integrated actions aiming at monitoring its presence in different species are. The swine infection represents an additional concern not only in relation to that species but also in relation to the possibility of the virus to mutate and adapt to humans. The elements that determine the pathogenicity of the various viral subtypes must be well understood, for the tools used to control the illness - such as vaccination - may promote viral mutation and thus render the control even more difficult instead of favoring it. The present review aims at characterizing various components involved in the virus maintenance in different species as well as the determinant elements involved in its evolution, from the point of view of Conservation Medicine, which is the branch of science that deals exactly with the interaction among the environment, human beings, and animals, thus creating a holistic vision not only of the problem but also of the coherent and effective actions involved in their solution.
Cytogenetic characterization of Aloysia virgata Ruiz and Pavan (Verbenaceae)
Authors: Brandão Aline Dias , Viccini Lyderson Facio , Recco-Pimentel Shirlei Maria
Published: September 2009

Since previous cytogenetic reports of Aloysia have only described the meiotic behavior and chromosomal number of some species, the aim of this work was to provide detailed cytogenetic description of Aloysia virgata that would contribute to the understanding of the taxonomical organization of the Verbenaceae. Aloysia virgata had a karyotype with 2n = 36 metacentric chromosomes, all with similar size. The large amount of heterochromatin seen after Giemsa staining was confirmed by C-banding. Four nucleolar organizer regions (NORs) were detected with an rDNA 45S probe in two homologous pairs and two sites of 5S rDNA located on one chromosomal pair were detected by fluorescence in situ hybridization. The interphase nucleus was classified as semi-reticulate. Meiotic analysis showed a normal chromosomal behavior, with 18 bivalents in some parts of prophase I and in metaphase I. The number of chromosomes, NORs and 5S rDNA segments did not exclude a possible polyploid origin.
The influence of caffeine and thymol on the survival, growth and reproduction of Subulina octona (Brugüière, 1789) (Mollusca, Subulinidae)
Authors: Ferreira Paula , Soares Geraldo Luiz Gonçalves , D'ávila Sthefane , Bessa Elisabeth Cristina de Almeida
Published: September 2009

Subulina octona is a terrestrial snail which serves as an intermediate host for the parasites. It is also an agricultural pest. The aim of this work was to assess, during 120 days, the effects of caffeine and thymol at 2.5 g/L and 5 g/L on the hatchability, survival after hatching, growth and reproduction of S. octona under the laboratory conditions. A total of 240 eggs, 240 juveniles aged 10-day-old, and 240 aged 30-day-old were tested. The results showed that thymol (at 2.5 g/L and 5 g/L) and caffeine (at 5 g/L) acted as ovicides. In the 10-day-old juveniles, caffeine at 5 g/L caused 25% mortality and at 2.5 g/L it caused 30% mortality. Thymol at 2.5 and 5 g/L caused 20 and 22.5% mortality, respectively. In the 30-day-old juveniles, caffeine at 5 g/L caused 47.5% mortality.
Analysis of Mercury-Rich plants and mine tailings using the Hydride-Generation AAS method
Authors: Moreno Fábio Netto , Anderson Christopher , Stewart Robert , Robinson Brett
Published: September 2009

A hydride-generation atomic absorption spectroscopy (AAS) method was developed for the analysis of total Hg in liquid matrices of mercury-rich plants and mine tailings samples. The detection limit for this method was as low as 11.4 ng/mL. The reproducibility of the mercury signals (in terms of relative standard deviation) was 4.6%. Accuracy of the method was verified by analyses of deionised water samples spiked with HgCl2 and HgNO3. Recovery values for total mercury ranged from 88.5 to 94.3% for both mercury species added. An external certified laboratory validated the analytical method with a maximum discrepancy of 15 %. Optimal analytical response of the equipment for Hg analysis of plant samples was achieved when the sample volume added to the reaction vessel was 0.25 mL.
Neural network based control of an absorption column in the process of bioethanol production
Authors: Eyng Eduardo , Silva Flávio Vasconcelos da , Palú Fernando , Fileti Ana Maria Frattini
Published: September 2009

Gaseous ethanol may be recovered from the effluent gas mixture of the sugar cane fermentation process using a staged absorption column. In the present work, the development of a nonlinear controller, based on a neural network inverse model (ANN controller), was proposed and tested to manipulate the absorbent flow rate in order to control the residual ethanol concentration in the effluent gas phase. Simulation studies were carried out, in which a noise was applied to the ethanol concentration signals from the rigorous model. The ANN controller outperformed the dynamic matrix control (DMC) when step disturbances were imposed to the gas mixture composition. A security device, based on a conventional feedback algorithm, and a digital filter were added to the proposed strategy to improve the system robustness when unforeseen operating and environmental conditions occured. The results demonstrated that ANN controller was a robust and reliable tool to control the absorption column.
Physico-chemical quality changes in mangaba (hancornia speciosa gomes) fruit stored at different temperatures
Authors: Carnelossi Marcelo Augusto Gutierrez , Sena Hildo Costa de , Narain Narendra , Yaguiu Paula , Silva Gabriel Francisco da
Published: September 2009

The physical-chemical quality changes in mangaba fruit were studied. The fruit which attained full development at half-ripe stage were harvested and initially stored at 6, 8, 10 and 12±1ºC for four days. After this period, the fruit were transferred to an acclimatized room (24±2ºC) and maintained for five days. For control purposes, recently harvested fruit were stored directly in an acclimatized room (24±2ºC) for six days. After the transfer and storage at 24ºC, fruit were analyzed daily for their vitamin-C, soluble solids (ºBrix), titratable acidity, pH and firmness contents. In fruit directly stored at 24ºC, there was a sharp fall in vitamin C and acid contents. The fruit firmness decrease, after four days of storage, and they turned totally ripe. The fruit which were initially maintained at 6 or 8ºC did not show any significative difference in physical-chemical quality during the storage.
Iron Metabolism, Iron Deficiency, Thrombocytosis, and the Cardiorenal Anemia Syndrome
Authors: Besarab Anatole , Hörl Walter Hermann , Silverberg Donald
Published: September 2009

In treating moderate to severe anemia of chronic kidney disease (CKD), oral iron is effective only in a minority of nondialysis patients. Intravenous iron is more effective and can raise levels of hemoglobin even without the use of erythropoiesis-stimulating agents (ESAs). Unfortunately, the current assays of iron status that are presently widely available are not especially helpful in predicting response. In patients on dialysis, i.v. iron is effective over a wide range of serum ferritin from <100 ng/ml to 800 ng/ml. None of the three available randomized controlled trials comparing oral with i.v. iron showed evidence of nephrotoxicity caused by i.v. iron.

Iron deficiency is a risk factor for thrombocytosis and should, wherever possible, be avoided. Optimal coadministration of iron may reduce the risk for ESA-driven cardiovascular events. Increased total body iron stores (imperfectly reflected by serum ferritin levels in CKD) do not appear to be related to such events or hospitalization in CKD; it is unclear what other risk factors and mechanisms need to be considered.

In the appreciable proportion of patients with both renal and cardiac dysfunction, management is further complicated by a vicious circle (which can be characterized as cardiorenal anemia syndrome) in which CKD, heart failure, and anemia exacerbate each other. In such patients, correction of anemia appears to improve cardiac function and quality of life without a greater risk for adverse events.
Examining the Involvement of Erythropoiesis-Stimulating Agents in Tumor Proliferation (Erythropoietin Receptors, Receptor Binding, Signal Transduction), Angiogenesis, and Venous Thromboembolic Events
Authors: Fandrey Joachim , Dicato Mario
Published: September 2009

Safety concerns have arisen about the possibility of erythropoiesis-stimulating agents (ESAs) promoting tumor growth and increasing the incidence of venous thromboembolic events (VTEs). Because of the reported presence of erythropoietin receptors (EPORs) on tumor cells, it was questioned if ESAs had the potential for promoting tumor growth through stimulation of EPORs and tumor vessels and/or enhanced tumor oxygenation. Studies have shown that EPOR mRNA can be isolated from tumor cells, but the presence of EPOR protein has not yet been proven because of a lack of specific antibodies against EPORs. It is questionable whether EPORs on tumor cells are functional and there is no evidence that ESAs (within the approved indication in patients receiving chemotherapy) can stimulate EPORs on tumor cells in vivo. VTEs are frequent in cancer patients, resulting from the effects of malignant disease, cancer treatments, and comorbidities. VTEs are a leading cause of death in cancer patients. There are concerns about ESAs and a possible higher risk for VTEs and shorter survival in cancer patients. The higher risk for VTEs associated with ESAs appears to be a class effect, but the risk may be particularly pronounced when ESAs are used off label, as seen in clinical trials that targeted hemoglobin levels higher than those recommended by current ESA labeling and trials that enrolled patients who were not anemic at baseline. ESA treatment should be used within labeling confines.
Anemia Management in Oncology and Hematology
Authors: Spivak Jerry L. , Gascón Pere , Ludwig Heinz
Published: September 2009

Anemia is frequent in cancer patients and its incidence increases with chemotherapy. The probability of requiring transfusions also increases with chemotherapy. Anemia negatively impacts survival and accentuates fatigue in cancer patients. Cancer promotes inflammatory cytokine production, which suppresses erythropoiesis and erythropoietin (EPO) production. Erythropoiesis-stimulating agents (ESAs) improve erythropoiesis and reduce transfusion needs in anemic cancer patients receiving chemotherapy. However, meta-analyses have shown an increased risk of thromboembolic (TE) events with ESA use during chemotherapy, but not increased on-study mortality or reduced overall survival. Three reasons have been proposed to explain why ESAs might have adverse effects in anemic cancer patients: tumor progression due to stimulation of tumor cell EPO receptors; increased risk of TE; and reduced survival. However, erythropoietin is not an oncogene, nor is the EPO receptor. It has also been demonstrated that erythropoietin does not stimulate tumor proliferation. Increased TE risk associated with ESAs is probably a consequence of increased blood viscosity due to excessive RBC mass elevation with concomitant plasma volume contraction, nitric oxide scavenging, and endothelial cell activation. Increased ESA dosing may also impact survival negatively because EPO contracts the plasma volume and stimulates inflammatory cytokine production independently of increasing erythropoiesis. Furthermore, transfusions themselves are associated with an increase in TE and plasma volume contraction, and these events are potentiated when ESAs are given with transfusions. An update on the management of anemia in oncology, the potential adverse events of ESAs, the benefits and risks of transfusions, and QoL are discussed in this paper.
Is Nephrology More at Ease Than Oncology with Erythropoiesis-Stimulating Agents? Treatment Guidelines and an Update on Benefits and Risks
Authors: Locatelli Francesco , Gascón Pere
Published: September 2009

Erythropoiesis-stimulating agents (ESAs), which promote RBC production, have been extensively used to reduce transfusion requirements and improve quality of life (QoL) in both cancer patients and those with chronic kidney disease (CKD). However, the likelihood of response and duration of treatment differ in the two settings. In renal anemia, ESAs act straightforwardly as hormone-replacement therapy. The anemia of cancer, however, relates not to a lack of endogenous erythropoietin production but to diverse aspects of the disease (including a relevant inflammatory component) and chemotherapy. Response to ESAs is slower and less certain than in nephrology. In both settings, early studies showed that reversal of severe anemia was accompanied by substantial improvement in QoL. However, again in both settings, subsequent studies indicated that efforts to normalize hemoglobin might worsen outcome. In the context of cancer, this concern was reinforced by the suggestion that malignant cells had erythropoietin receptors and that its administration might therefore accelerate tumor growth, and moreover that cancer patients are more susceptible to venous thrombosis. The absence of these concerns for nephrologists, and their greater experience in managing ESAs and patients’ iron status, may make them more at ease with ESAs than their counterparts in oncology. However, both groups of specialists have had to deal with reversals in recommended thresholds for intervention and restrictions imposed by regulatory authorities. In both specialties, the broad consensus now emerging is that the optimum balance of benefits and risks lies in using ESAs aimed at a hemoglobin level in the range of 11–12 g/dl, although for CKD patients there is still room for an individualized approach.
Update on Erythropoiesis-Stimulating Agents and Clinical Trials in Oncology
Authors: Aapro Matti , Spivak Jerry L.
Published: September 2009

Anemia commonly occurs among cancer patients receiving chemotherapy. In these patients, erythropoiesis-stimulating agents (ESAs) are effective in managing anemia but there is an increased risk for thrombovascular events. In more recent randomized clinical trials, there have been differing results regarding the impact of ESAs on overall survival and mortality. The balance between studies that show higher ESA-associated mortality and those that don’t show ESA-associated mortality is examined in this review. This review discusses where we stand today on anemia management in cancer patients. Preliminary results from a recent independent patient data meta-analysis for on-study deaths and overall survival in patients receiving chemotherapy (the only oncology population for which ESA treatment is currently indicated) showed no statistically significant difference between the ESA and control groups (on-study deaths hazard ratio [HR], 1.10; 95% confidence interval [CI], 0.98–1.24; overall survival HR, 1.04; 95% CI, 0.97–1.11, compared with controls). Possible factors that could influence study results are discussed in this review. There are no convincing data to support ESA-induced tumor stimulation in patients. ESAs decrease RBC transfusion needs and sustain targeted hemoglobin levels, and this ESA response does not significantly impact overall survival or mortality when ESAs are used within guidelines and labeling. However, based on the currently available data and meta-analysis, the use of ESAs has to be carefully balanced against any possible risk for higher mortality.
A fence line in time demonstrates grazing‐induced vegetation shifts and dynamics in the semiarid Succulent Karoo
Authors: Todd Simon W. , Hoffman M. Timm
Published: September 2009

The mediterranean ecosystems of the world harbor exceptional biodiversity, and factors such as livestock grazing which may negatively affect biodiversity are of global concern. The mediterranean ecosystems of southern Africa have only sporadically been exposed to high densities of indigenous herbivores and may not be as typically resilient to livestock grazing pressure as the savannah and grassland ecosystems of semiarid Africa. We investigate this issue by assessing the impacts of two contrasting livestock grazing intensities associated with communal and commercial ranching systems on the dwarf succulent shrublands of the Succulent Karoo in Namaqualand, South Africa. We interpret the results in terms of vegetation dynamics and the implications for the current debate on nonequilibrium rangelands. The results demonstrate that the relative extent of plant community divergence between the communal and commercial rangeland has been maintained over the past 10 years, overall and within different plant growth forms. Recruitment of certain palatable shrub species occurred on the heavily grazed communal rangeland, indicating that a further decline in their populations is not inevitable. Recruitment of the unpalatable shrub Galenia africana on the communal rangeland was disproportionately greater than that of the palatable species, reenforcing the dominance of this species. Due to the longevity of woody shrubs, short‐term vegetation shifts are small, limiting the potential for the recovery of overgrazed shrublands during periods of low grazing pressure. The shift on the communal rangeland toward annuals and geophytes has increased the variability of forage production and contrasts with the dominance of dwarf shrubs on the commercial rangeland. Shrub‐dominated ecosystems create the potential for forage storage and inter‐annual transfer of excess production, buffering livestock numbers in the face of a fluctuating environment. Despite the semiarid nature of the area and contrary to the predictions of the nonequilibrium theory, livestock and vegetation in Namaqualand interact strongly, and a close relationship between livestock numbers and primary production persists over the long‐term on the communal rangeland.
Riparian bird response to vegetation structure: a multiscale analysis using LiDAR measurements of canopy height
Authors: Seavy Nathaniel E. , Viers Joshua H. , Wood Julian K.
Published: September 2009

The ability to measure vegetation structure at spatial scales that are biologically meaningful for wildlife is often limited because information about the spatial scale of habitat selection is lacking and there are logistical constraints to measuring vegetation structure at ever larger spatial scales. To address this challenge, we used LiDAR‐derived measurements of vegetation canopy height to quantify habitat associations of riparian birds at the Cosumnes River Preserve in central California, USA. Our objectives were (1) to evaluate the utility of LiDAR (light detection and ranging) measurements for describing habitat associations of riparian passerine birds, and (2) to capitalize on the ease with which LiDAR measurements can be summarized at multiple spatial scales to evaluate the predictive performance of vegetation measurements across spatial scales from 0.2 to 50 ha. At each location where we conducted point‐count surveys of the avian community, we summarized the mean and coefficient of variation of canopy height measured at five spatial scales (0.2, 0.8, 3.1, 12.6, and 50.2 ha). For each of these spatial scales, we used stepwise model selection to identify the best logistic‐regression model describing patterns of occurrence for 16 species of passerine birds that were sufficiently abundant for analysis. We then used area‐under‐the‐curve (AUC) values to identify models that performed well (AUC >0.75) on a temporally independent data set. Of the 16 species, 10 species had logistic‐regression models with AUC values >0.75. For six of these species, AUC values were highest for the models with vegetation measurements at the 0.2–3 ha scale. For the other four species, AUC values were highest for the model with vegetation variables measured at the 50‐ha scale. These results illustrate the utility of using LiDAR‐derived measurements of vegetation to understand habitat associations of riparian birds and underscore the importance of using multiscale approaches to modeling wildlife habitat use.
A unifying approach for evaluating the condition of wetland plant communities and identifying related stressors
Authors: Johnston Carol A. , Zedler Joy B. , Tulbure Mirela G. , Frieswyk Christin B. , Bedford Barbara L. , Vaccaro Lynn
Published: September 2009

Assessment of vegetation is an important part of evaluating wetland condition, but it is complicated by the variety of plant communities that are naturally present in freshwater wetlands. We present an approach to evaluate wetland condition consisting of: (1) a stratified random sample representing the entire range of anthropogenic stress, (2) field data representing a range of water depths within the wetlands sampled, (3) nonmetric multidimensional scaling (MDS) to determine a biological condition gradient across the wetlands sampled, (4) hierarchical clustering to interpret the condition results relative to recognizable plant communities, (5) classification and regression tree (CART) analysis to relate biological condition to natural and anthropogenic environmental drivers, and (6) mapping the results to display their geographic distribution. We applied this approach to plant species data collected at 90 wetlands of the U.S. Great Lakes coast that support a variety of plant communities, reflecting the diverse physical environment and anthropogenic stressors present within the region. Hierarchical cluster analysis yielded eight plant communities at a minimum similarity of 25%. Wetlands that clustered botanically were often geographically clustered as well, even though location was not an input variable in the analysis. The eight vegetation clusters corresponded well with the MDS configuration of the data, in which the first axis was strongly related (R2 = 0.787, P < 0.001) with floristic quality index (FQI) and the second axis was related to the Great Lake of occurrence. CART models using FQI and the first MDS axis as the response variables explained 75% and 82% of the variance in the data, resulting in 6–7 terminal groups spanning the condition gradient. Initial CART splits divided the region based on growing degree‐days and cumulative anthropogenic stress; only after making these broad divisions were wetlands distinguished by more local characteristics. Agricultural and urban development variables were important correlates of wetland biological condition, generating optimal or surrogate splits at every split node of the MDS CART model. Our findings provide a means of using vegetation to evaluate a range of wetland condition across a broad and diverse geographic region.
The importance of multimodel projections to assess uncertainty in projections from simulation models
Authors: Valle Denis , Staudhammer Christina L. , Cropper Wendell P. , Gardingen Paul Rvan
Published: September 2009

Simulation models are increasingly used to gain insights regarding the long‐term effect of both direct and indirect anthropogenic impacts on natural resources and to devise and evaluate policies that aim to minimize these effects. If the uncertainty from simulation model projections is not adequately quantified and reported, modeling results might be misleading, with potentially serious implications. A method is described, based on a nested simulation design associated with multimodel projections, that allows the partitioning of the overall uncertainty in model projections into a number of different sources of uncertainty: model stochasticity, starting conditions, parameter uncertainty, and uncertainty that originates from the use of key model assumptions. These sources of uncertainty are likely to be present in most simulation models. Using the forest dynamics model SYMFOR as a case study, it is shown that the uncertainty originated from the use of alternate modeling assumptions, a source of uncertainty seldom reported, can be the greatest source of uncertainty, accounting for 66–97% of the overall variance of the mean after 100 years of stand dynamics simulation. This implicitly reveals the great importance of these multimodel projections even when multiple models from independent research groups are not available. Finally, it is suggested that a weighted multimodel average (in which the weights are estimated from the data) might be substantially more precise than a simple multimodel average (equivalent to equal weights for all models) as models that strongly conflict with the data are given greatly reduced or even zero weights. The method of partitioning modeling uncertainty is likely to be useful for other simulation models, allowing for a better estimate of the uncertainty of model projections and allowing researchers to identify which data need to be collected to reduce this uncertainty.
Dispersal polymorphism in an invasive forest pest affects its ability to establish
Authors: Robinet Christelle , Liebhold Andrew M.
Published: September 2009

Given the increasing number of biological invasions, there is a crucial need to identify life history traits that promote invasion. Invasiveness reflects capabilities for both establishment after introduction and spread following establishment. In this paper, we explore, via simulation, the interacting effects of dispersal and Allee effects on both invasion processes. Dispersal capability is a trait that has been widely recognized to facilitate invasions. However, dispersal dilutes local population densities in isolated populations and this could strengthen Allee effects, ultimately promoting extinction of invading populations. A spatially explicit, stochastic individual‐based model was used to simulate dispersal, mating, and growth in isolated, newly arrived invading populations. We used the invasion of North America by the gypsy moth, Lymantria dispar, as a case study because: (1) a great amount of biological data on the species is available; (2) Allee effects caused by mate location failure are known to play an important role in its establishment and spread; and (3) a dispersal polymorphism has previously been identified (i.e., in some populations adult females are fully capable of flight, but in other populations females are not able to fly). We considered the introduction of a hypothetical number of eggs at a single location, originating from populations with varying female dispersal capabilities, and we then used simulation models to evaluate the population growth rate over two generations as well as spread distance. Nondispersing populations had the highest growth rates and inclusion of even limited dispersal capabilities caused population growth rates to be greatly diminished. The Allee threshold was 700 eggs for nondispersing populations and 1400 eggs for the long‐distance dispersing populations. Thus, for an intermediate number of eggs initially introduced, nondispersing populations would most likely establish, whereas dispersing populations would likely become extinct. Spread distance increased linearly with the number of eggs initially introduced in both dispersing and nondispersing populations but rapidly reached a limit for nondispersing populations. Though species capable of long‐distance dispersal may invade a larger area than nondispersing species, their growth rates are likely to be considerably lower, and eradication should be easier. Following these results, strategies for managing invasions should be adjusted for the interactions between Allee effects and dispersal.
An Optimized Method To Remove Filter Cake Formed by Formate-Based Drill-In Fluid in Extended-Reach Wells
Authors: Alotaibi M.B.. B. , Nasr-El-Din H.A.. A. , Hill A.D.. D. , Al Moajil A.M.. M.
Published: September 2009

Smart, horizontal, and multilateral wells provide an attractive option for maximizing reservoir contact in both oil and gas fields in Saudi Arabia. Formate drill-in fluid has been selected lately for drilling gas wells because of its ability to preserve conventional polymers at high temperatures. The formate salts also can reduce the rate of hydrolytic and oxidative degradation of many viscosifiers and fluid loss agents at high temperatures.

Drilling fluid filter cake can reduce the flow efficiency of cased or openhole wells. Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimize the leakoff. Such solids become consolidated and trapped in the polymeric material and this makes the filter cake a strong permeability barrier.

The conventional method for cleaning the filter cake is by circulating solids-free formate brines at a high flow rate. This mechanical technique removes only the external drilling fluid damage. Chemical fluids like acids, oxidizers, or chelating agents are usually used as an alternative method for dissolving both the external and internal filter cake. Most of these fluids cannot give a full coverage to the wellbore because of the formation heterogeneity.

A new class of esters can generate an acid downhole at a low rate and distribute it uniformly through the wellbore. Fluid compatibility and thermal stability tests were studied in detail. Return permeability experiments were conducted by using high-pressure/ high-temperature (HPHT) dynamic fluid loss cells. The ester solution was effective in cleaning the filter cake in comparison to the formate brines completion fluid and other organic acids results. Also, circulating formate brine to restore the wellbore permeability or remove the internal filter-cake damage was found to be insufficient. Surface tension measurements indicated that the generated alcohol and lactic acid from the ester solution had lowered the surface tension more than the formate brines.
New Effective-Stress Law for Predicting Perforation Depth at Downhole Conditions
Authors: Grove B. , Heiland J. , Walton I. , Atwood D.
Published: September 2009

For natural completions, well productivity is proportional to the depth of the perforation tunnels extending beyond the drilling damage (all other things being equal). Perforation depth, in turn, is generally inversely related to the formation effective stress. Accurate productivity modeling, therefore, requires accurate knowledge of the relationship between the downhole stress environment and perforation depth.

A comprehensive experimental effort was recently conducted to evaluate the penetration performance of shaped charges into stressed Berea sandstone cores. Rock confining stress (σc) and pore fluid pressure (Pp) were varied from ambient to 10,000 psi to simulate a range of downhole stress environments. This current work featured a broader and more systematic investigation of the influence of pore pressure than previous studies.

Our experiments yielded the expected inverse correlation between penetration depth and effective stress (σeff). However, the data suggest a new definition of effective stress. Historically, the perforating community has defined σeff = σc − Pp, but a new treatment (σeff = σc − aPp; a = 0.5) better fits present data. Furthermore, this new effective stress law better fits published historical penetration results. Pore pressure's influence on penetration depth is, therefore, weaker than previously thought; for a given confining stress, increasing pore pressure does increase penetration but to a lesser extent than conventional models would indicate. The present work suggests that all shaped charges would be similarly affected.

These findings are relevant to penetration modeling, and in turn to well productivity modeling and prediction. Further implications are to laboratory testing, regarding scaling of parameters to accurately simulate field conditions.

This work culminates an initial application of combined penetration mechanics and geomechanics analyses to the investigation of shaped charge penetration into geologic materials. Future work will address different rock types, additional poroelastic quantities, and dynamic effects as they contribute to pressure-induced strengthening of reservoir rock.
Evaluation of the Gray Model GM(1,1) Applied to Soil Particle Distribution
Authors: Wu Cheng-Mau , Wen Jet-Chau , Chang Kou-Chiang
Published: September 2009

Particle size distribution (PSD) is a fundamental soil physical property. The conventional approaches for representing PSD use empirical models with two to four parameters. We developed an alternative way to predict PSD that differs from conventional approaches by using the gray model GM(1,1), which does not depend on the model shape as empirical approaches do. The performance of GM(1,1) was compared with Skaggs model by using four statistical criteria. From nine textures of soil samples in our study, the results reveal that the GM(1,1) is superior for making PSD predictions. The results show that for the overall textures, the GM(1,1) model makes better predictions than the Skaggs model except for sand. Therefore, the performance of the GM(1,1) is fairly reliable and efficient and is not affected by soil textures in general.
Aggregate‐Associated Carbon and Nitrogen in Reclaimed Sandy Loam Soils
Authors: Wick Abbey F. , Stahl Peter D. , Ingram Lachlan J.
Published: September 2009

Minimal research has been conducted on aggregate, C, and N in coarse‐textured soils used to reclaim surface coal mine lands. Furthermore, little is known about the contribution different plant communities make to the recovery of aggregation in these soils. Two chronosequences of semiarid reclaimed sites with sandy loam soils were sampled under shrub‐ and grass‐dominated communities. Aggregation, aggregate fractions, and associated C and N were measured. No definitive trends of increasing macroaggregates between sites were observed under shrubs; however, macro‐ and microaggregation was greater in the 16‐yr‐old (0.20 and 0.23 kg aggregate kg−1soil, respectively) than in the 5‐yr‐old soils (0.02 and 0.08 kg aggregate kg−1soil, respectively) under grasses. Although C and N concentrations were drastically reduced (50–75%) with mining activity between the <1‐yr‐old and native soils, aggregate C and N concentrations under shrubs and grasses were similar to each other and to the native soils in the 5‐yr‐old site. Soils under grass in the 16‐yr‐old site had lower available and aggregate‐occluded C and N concentrations than the 5‐yr‐old site, while C and N concentrations did not change between 5‐ and 16‐yr‐old soils under shrubs. Conversely, aggregate C and N pool sizes under shrubs and grasses both increased with site age to conditions similar to those observed in the native soil. Reclaimed shrub site soils had consistently higher C concentrations in the older reclaimed sites (10 and 16 yr old) than the soils under grasses, indicating greater accumulation and retention of C and N in organic material under shrub than grass communities in semiarid reclaimed sites.
Near‐Infrared Reflectance Spectroscopy Prediction of Soil Properties: Effects of Sample Cups and Preparation
Authors: Nduwamungu Cargèle , Ziadi Noura , Tremblay Gaëtan F. , Parent Léon-Étienne
Published: September 2009

Most methods for soil analysis are based on wet chemistry. Near infrared reflectance spectroscopy (NIRS) is a cost‐effective and environmentally sound alternative technique. This study evaluated the effect of sample fineness (0.2, 0.5, 1, and 2 mm) and sample cups (transport versus spinning) on the accuracy of NIRS predictions of soil texture, cation‐exchange capacity, pH, total C and N, organic C, and potentially mineralizable N (Nmin) using 150 air‐dried samples collected from a 15‐ha site dominated by Humaquept, Endoaquept, and Dystrochrept soils. The best spectral pretreatment was determined for each property. Principal component analysis (PCA) was used to select samples in calibration and validation sets. Calibration equations were developed using the modified partial least square regression. The accuracy of NIRS prediction was evaluated using three statistics for the prediction set: coefficient of determination (R2), ratio of performance deviation (RPD), and ratio error range (RER). Across the factorial designed treatments, successful calibrations were observed for clay, sand, and Nmin (R2 ≥ 0.90, RPD ≥ 3, RER ≥ 15). Prediction accuracy of pH was poor (0.51 ≤ R2 ≤ 0.74, 1.39 ≤ RPD ≤ 1.92, 6.13 ≤ RER ≤ 8.33), while it was intermediate for remaining properties. Sample fineness of 2 mm appeared to be sufficient since finenesses of 0.2, 0.5, or 1.0 mm did not improve calibration accuracy. These findings at small scale should not be extrapolated and further investigations are required to validate them at a larger scale.
Reduction of Ammonia Volatilization from Urea by a Floating Duckweed in Flooded Rice Fields
Authors: Li Hua , Liang Xinqiang , Lian Yanfeng , Xu Lei , Chen Yingxu
Published: September 2009

Effective nutrient management to reduce high N losses and to improve N use efficiency has been an important focus of agricultural and environmental science research. Understanding the influence of duckweed (Lemna minor L.), a common floating macrophyte in flooded rice (Oryza sativa L.) fields, on NH3 volatilization and grain yield is required for better management of applied N fertilizer. We conducted an on‐farm experiment with three levels of urea (0, 90, 180 kg urea N ha−1) applied alone or in combination with duckweed. Our results indicate that total ammoniacal‐N concentration, pH, and temperature of the floodwater were significantly lower in the plots with a duckweed cover. As a consequence, NH3 volatilization rates were reduced by duckweed from 20.0 to 53.7% and from 19.0 to 33.2% in plots supplied with 90 and 180 kg urea‐N ha−1, respectively. Duckweed increased rice grain yields by approximately 0.7 and 0.7 Mg ha−1 (9.8 and 9.4%) in plots supplied with 90 and 180 kg urea N ha−1, respectively. Ammonia losses from urea‐N applications can be reduced and N use efficiencies can be improved by the presence of duckweed in flooded rice fields.
Soil Properties Controlling the Adsorption of Dissolved Organic Carbon to Mineral Soils
Authors: Kothawala D. N. , Moore T. R. , Hendershot W. H.
Published: September 2009

Dissolved organic C (DOC) is the most reactive and mobile component of soil C and can be retained within mineral soils by adsorption. We determined the adsorption characteristics for 52 mineral soil samples from 17 temperate and boreal soil profiles, using a modified Langmuir equation. The DOC solution used for batch experiments was derived from the organic horizons of a Spodosol. We analyzed the extent to which soil properties, such as the sum of poorly crystalline Fe and Al (Fepc+ Alpc), texture, and soil C, are related to DOC adsorption to mineral soils. Sorption characteristics including the maximum adsorption capacity (Qmax), and the null point (np), where adsorption equals desorption, were best explained by Fepc+ Alpc(R2= 0.55 and 0.28, respectively). The Alpcexerted a stronger influence than FepconQmaxA simple method for estimatingQmaxwas developed whereby the change in pOH after treatment with NaF is well correlated to Fepc+ Alpc(R2= 0.71,P< 0.0001) andQmax(R2= 0.50,P< 0.0001). The influence of clay content onQmaxwas of secondary importance and was largely masked by the dominant influence of Fepc+ AlpcSoil C did not have any influence onQmax, but a slight negative influence on np. The B horizons of Spodosols and volcanic soils had the greatestQmax, while large levels of soil C in Spodosols produced a high desorption potential. Results from this study emphasize the importance of considering the adsorption potential in conjunction with the desorption potential for better prediction of changes to the size of mineral soil C pools and DOC export to aquatic systems.
Measurement of Steady‐State Soil Water Flux across a Soil Horizon Interface
Authors: Dyck M. F. , Kachanoski R. G.
Published: September 2009

Soil horizon interfaces have been shown to be focal points for localized, three‐dimensional redistribution of water and solutes in field soils. Therefore, understanding of the physics of water flow and transport in layered soils requires experimental observations of the magnitude and variability of local soil water flux under a variety of well‐defined boundary conditions. We developed a time domain reflectometry (TDR) method to measure the spatial pattern of steady‐state, local soil water flux density above and below a soil horizon interface under quasi‐steady surface water application and implemented it in laboratory and field experiments. Time series of TDR‐measured bulk soil electrical conductivity and TDR‐measured soil volumetric water content at each location are used to quantify the solute travel time under steady‐state flow conditions, which is then used to quantify steady‐state, local soil water flux density. Results from laboratory and field experiments showed that the proposed methodology yielded local soil water flux density estimates that were, on average, 104% of the applied surface water flux density (i.e., mass recovery = 104%), which is consistent with transient, local soil water flux density estimates from a previous study. For the field experiments, steady‐state, local soil water flux density estimates above and below an A/B horizon interface (measured across the length of a 6.75‐m transect) were negatively correlated to each other. The strength of the negative correlation, however, decreased with increasing surface water application rate, suggesting that the hydrologic response of the soil horizon interface is flux‐dependent. This flux‐dependent correlation between A and B horizon steady‐state soil water flux density is probably attributable to the spatial covariance between A and B horizon soil hydraulic properties.
Water Treatment Residuals and Biosolids Long‐Term Co‐Applications Effects to Semi‐Arid Grassland Soils and Vegetation
Authors: Ippolito J. A. , Barbarick K. A. , Stromberger M. E. , Paschke M. W. , Brobst R. B.
Published: September 2009

Water treatment residuals (WTRs) and biosolids are byproducts from municipal water treatment processes. Both byproducts have been studied separately for land application benefits. There are possible environmental benefits of WTRs and biosolids co‐application but these studies are limited. Our objectives were to determine relative long‐term (13–15 yr) effects of a single and short‐term (2–4 yr) effects of repeated WTR‐biosolids co‐applications on soil chemistry, microbiology, and plant community structure in a Colorado semiarid grassland. Only relative changes associated between co‐applications were studied, as we assumed WTR application would only occur if used as a management practice. Three WTR rates (5, 10, and 21 Mg ha−1) were surface co‐applied (no incorporation) with a single biosolids rate (10 Mg ha−1) once in 1991 (long‐term plots) and again in 2002 (short‐term plots). Soil 0‐ to 8‐, 8‐ to 15‐, and 15‐ to 30‐cm depth pH, electrical conductivity (EC), NO3–N, NH4–N, total C, and total N were not affected by WTR application in 2004, 2005, or 2006. Ammonium‐bicarbonate diethylenetriaminepentaacetic acid (AB‐DTPA)‐ extractable soil Al was unaffected by WTR application, but extractable P and Mo decreased with increasing WTR rate because of WTR adsorption. Plant tissue P and Mo content decreased with specific plant species and years due to adsorption to WTR; no deficiency symptoms were observed. Plant community composition and cover were largely unaffected by WTR application. Soil microbial community structure was unaffected by WTR co‐application rate (total ester‐linked fatty acid methyl ester [EL‐FAME] concentrations ranged from 33.4 to 54.8 nmol g−1 soil), although time since biosolids‐WTR application affected a subset of microbial community fatty acids including markers for Gram‐positive and Gram‐negative bacteria. Overall, WTR‐biosolids co‐applications did not adversely affect semiarid grassland ecosystem dynamics.