bluuebunny/crossref_metadata_2025 huggingface dataset:
The Economics of Spam
Authors: Rao Justin M , Reiley David H
Published: August 2012

We estimate that American firms and consumers experience costs of almost $20 billion annually due to spam. Our figure is more conservative than the $50 billion figure often cited by other authors, and we also note that the figure would be much higher if it were not for private investment in anti-spam technology by firms, which we detail further on. Based on the work of crafty computer scientists who have infiltrated and monitored spammers' activity, we estimate that spammers and spam-advertised merchants collect gross worldwide revenues on the order of $200 million per year. Thus, the “externality ratio” of external costs to internal benefits for spam is around 100:1. In this paper, we start by describing the history of the market for spam, highlighting the strategic cat-and-mouse game between spammers and email providers. We discuss how the market structure for spamming has evolved from a diffuse network of independent spammers running their own online stores to a highly specialized industry featuring a well-organized network of merchants, spam distributors (botnets), and spammers (or “advertisers”). We then put the spam market's externality ratio of 100 into context by comparing it to other activities with negative externalities. Lastly, we evaluate various policy proposals designed to solve the spam problem, cautioning that these proposals may err in assuming away the spammers' ability to adapt.
Genre trends at the US box office, 1991 to 2010
Authors: Redfern Nick
Published: August 2012

This article examines genre trends in the top 50 grossing films at the US box office each year from 1991 to 2010, focusing on the frequency and rank of different genres, the box office gross and release patterns of films in different genres, and the release profile of Hollywood studios.
The results show a narrowing of the range of genres at the highest rankings, with fantasy/science fiction movies coming to dominate at the expense of comedy, crime/thriller and drama films. There are also marginal increases in action/adventure and family films. Analysis of the opening and
total gross for each film reveals that different genres are characterized by different release patterns, and noted the importance of awards in contributing to the box office gross of drama films. With one notable exception, there is no evidence of genre specialization among film studios in
contemporary Hollywood cinema.
Video exposé: Metafiction and message in Nigerian films
Authors: McCain Carmen
Published: August 2012

In this article, I discuss how Nigerian film-makers respond to discourses surrounding film-making in Nigeria through using techniques of metafiction to theorize their roles as professionals and cultural mediators. Dividing my analysis into two sections, first on the English-language
'Nollywood' and second on the Hausa-language 'Kannywood', I examine self-reflexive techniques by which film-makers draw attention to their roles as truth-tellers and message-bearers and how metafictions about the film industries illustrate tensions between a junk-journalist expos aesthetic
and a celebrity culture concerned with image. While there are many similarities in how film-makers in both 'Nollywood' and 'Kannywood' respond to criticism, I argue that these metafictions reveal differences in economic and cultural context that have resulted in an increasingly upwardly mobile
Nollywood, while Kannywood has remained closer to the grass roots. Ultimately, these films express on a smaller scale the film-maker's theories about what the film industry as a whole does for the nation.
Hustlers, home-wreckers and homoeroticism: Nollywood's Beautiful Faces
Authors: Green-Simms Lindsey
Published: August 2012

This article examines the ways that Nollywood films are involved in the moral policing of the postcolonial subject both by challenging the state's moral failings and by enacting its ideological violence. I argue that although it is necessary to acknowledge how Nigerian video-films reflect
the struggles, anxieties and instability of ordinary Nigerians, it is also crucial to examine the ways that they deflect various concerns about everyday life on to certain bodies. Through a close reading of Kabat Esosa Egbon's film Beautiful Faces (2004), a film about female campus cults,
I demonstrate that while the film grapples with issues of violence and corruption on university campuses, it does so by channeling fears about students' educational opportunities into anxiety about women's sexual transgressions. In this way, I suggest that Beautiful Faces is typical of many
Nollywood films that simultaneously challenge corrupt and wizened government institutions while also reproducing their normative and violent hetero-patriarchal position.
The capital gap: Nollywood and the limits of informal trade
Authors: McCall John C.
Published: August 2012

This article examines Nollywood as a creative industry based in Africa's informal sector. By definition, the informal sector produces no financial records, so no quantitative economic data are presented. This research utilizes ethnographic methods and anthropological analysis to highlight
the importance of the video movie industry to Nigerian people, its place in their economic life and its integral role in their culture. Nollywood's intimacy with Nigerians has been achieved by way of the industry's distinctive informal system of production and distribution. This same informality
prevents the video industry from establishing financial legitimacy. Without the ability to generate capital, the industry is straining against its economic limits. Thus, the cultural success of Nollywood pushes it towards inevitable formalization and uncertain consequences.
Determination of Thiencarbazone in Soil by Oriental Mustard Root Length Bioassay
Authors: Szmigielski Anna M. , Schoenau Jeff J. , Johnson Eric N. , Holm Frederick A. , Sapsford Ken L.
Published: August 2012

Using an oriental mustard root length bioassay, thiencarbazone bioavailability and dissipation in five Saskatchewan soils was investigated under laboratory conditions. Thiencarbazone bioavailability was assessed at 0 to 3.9 µg ai kg−1. Thiencarbazone concentrations corresponding to 50% inhibition (I50values) obtained from dose-response curves varied from 0.56 to 1.71 µg kg−1. Multiple regression analysis indicated that organic carbon content (P = 0.018) and soil pH (P = 0.017) predicted thiencarbazone bioavailability. Thiencarbazone dissipation was examined in soils incubated at 23 C and moisture content of 85% field capacity. Thiencarbazone half-lives estimated from dissipation curves were 9 to 50 d, and organic carbon content (P = 0.002) and soil pH (P = 0.008) were significant factors affecting thiencarbazone dissipation. Thiencarbazone bioavailability decreases and dissipation rate is slower in Canadian prairie soils of high organic matter content and low soil pH. Because root length of oriental mustard plants also was reduced by ammonium, therefore ammonium-containing or -producing fertilizers can cause false positive results for thiencarbazone soil residues. Canaryseed roots had the same sensitivity to ammonium as oriental mustard roots but were not inhibited by thiencarbazone. Therefore canaryseed root length bioassay was effective in identifying inhibition caused by ammonium toxicity. Use of oriental mustard root and canaryseed root bioassays together can aid in interpreting bioassay results for detection of thiencarbazone residues.
Effect of Tuber Density and Trifloxysulfuron Application Timing on Purple Nutsedge (Cyperus rotundus) Control
Authors: Lati Ran Nisim , Filin Sagi , Eizenberg Hanan
Published: August 2012

Herbicides are the basis for conventional management of purple nutsedge, one of the world's most troublesome weeds. However, as concern rises over their environmental impact, farmers are being required to reduce herbicide usage. Herbicide efficacy is strongly affected by weed growth stage and density at application, and when herbicides are applied under optimal conditions, low rates can provide maximal control efficacy (CE). Therefore, this study aimed to determine the time window for control of purple nutsedge using a low rate of herbicide, based on an effective degree days (EDDs) model, at low (one tuber) and high (10 tubers) densities. Two experiments were performed under field conditions, in the summers of 2009 and 2010. Rate of 3.75 g a.i. ha−1trifloxysulfuron was applied once on each of five individual application dates. The growth of both treated and untreated plots was evaluated by means of leaf cover area (LCA) and biomass, which were then used to establish the time window for control. Results showed differences in both growth parameters between low and high tuber densities. The high-density patches reached LCA and fresh biomass values of 1,367 g and 1.12 m2, respectively, compared to 604 g and 0.69 m2, respectively, in the lower density patches. The favorable control periods based on biomass and LCA for the lower density patches were set to later dates than those for the higher density patches, 626 EDD compared to 483 EDD for biomass, and 786 EDD compared to 502 EDD for LCA, respectively. Although differences between the biomass- and LCA-based favorable control periods were observed at both tuber densities, the computed linear relations between the two growth parameters enabled adjusting them and setting the appropriate control period.
Rigid Ryegrass (Lolium rigidum) Populations Containing a Target Site Mutation in EPSPS and Reduced Glyphosate Translocation Are More Resistant to Glyphosate
Authors: Bostamam Yazid , Malone Jenna M. , Dolman Fleur C. , Boutsalis Peter , Preston Christopher
Published: August 2012

Glyphosate is widely used for weed control in the grape growing industry in southern Australia. The intensive use of glyphosate in this industry has resulted in the evolution of glyphosate resistance in rigid ryegrass. Two populations of rigid ryegrass from vineyards, SLR80 and SLR88, had 6- to 11-fold resistance to glyphosate in dose-response studies. These resistance levels were higher than two previously well-characterized glyphosate-resistant populations of rigid ryegrass (SLR77 and NLR70), containing a modified target site or reduced translocation, respectively. Populations SLR80 and SLR88 accumulated less glyphosate, 12 and 17% of absorbed glyphosate, in the shoot in the resistant populations compared with 26% in the susceptible population. In addition, a mutation within the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) where Pro106had been substituted by either serine or threonine was identified. These two populations are more highly resistant to glyphosate as a consequence of expressing two different resistance mechanisms concurrently.
Genetic Analysis of Atypical U.S. Red Rice Phenotypes: Indications of Prior Gene Flow in Rice Fields?
Authors: Gealy David H. , Agrama Hesham , Jia Melissa H.
Published: August 2012

Weedy red rice is a troublesome weed problem in rice fields of the southern United States. Typically, red rice plants are much taller than rice cultivars, and most biotypes are either awnless with straw-colored hulls (strawhull) or have long awns with black-colored hulls (blackhull). Outcrossing between rice and red rice occurs at low rates, resulting in a broad array of plant types. Simple sequence repeat (SSR) markers were used to evaluate the genetic backgrounds of atypical red rice types obtained from rice farms in Arkansas, Louisiana, Missouri, and Mississippi, in comparison to standard red rice types and rice cultivars. Principal coordinates analysis (PCoA) and population structure analysis of atypical red rice accessions suggested that short-stature awnless (LhtsA−) and awned (LhtsA+) types, each representing a total of about 5% of a 460-accession collection, usually were closely genetically related to their normal-sized counterparts, and not with cultivated rice. A short-awned, intermediate height type, ‘Sawn’, representing about 4% of the accessions was genetically distinct from all of the other types. Key alleles in Sawn types appeared to be shared by both standard awnless (StdRRA−) and awned (StdRRA+) red rice, suggesting that Sawn types could have arisen from gene flow between awned and awnless red rice types.
Germination and Emergence Characteristics of Common Beggar's-Tick (Bidens alba)
Authors: Ramirez Analiza H. M. , Jhala Amit J. , Singh Megh
Published: August 2012

Common beggar's-tick is an annual weed commonly found in citrus groves in Florida. A series of laboratory and greenhouse experiments were conducted to determine the germination response of common beggar's-tick to various environmental factors that influence seed survival, germination, and dormancy. The results suggest that common beggar's-tick germinated over a wide range of temperatures (15 to 40 C) and in both alternating light and dark and dark conditions. New seeds (collected in 2010) germinated better than the old seeds (collected in 2007) at 15/10 C; however, at temperatures above 35 C, the old seeds germinated better. The highest germination was 95% at 25 to 30 C with old seeds compared to 78 to 86% at 20 to 30 C with new seeds. Germination of common beggar's-tick was inhibited at osmotic potential above −0.6 MPa and salt concentrations of 320 mM. Highest germination in common beggar's-tick was found under neutral conditions (pH 7); germination decreased sharply under increasing acidity and alkalinity. Emergence decreased as depth of sowing increased, with greatest germination (89 to 91%) occurring when sown at the surface (0 cm) regardless of seed age. No germination was observed when seeds were buried at 10 cm. Results of this study suggest that favorable temperature and soil pH, and adequate moisture in Florida ensures the germination and continued presence of common beggar's-tick.
Nitrogen-Enhanced Efficacy of Mesotrione and Topramezone for Smooth Crabgrass (Digitaria ischaemum) Control
Authors: Elmore Matthew T. , Brosnan James T. , Kopsell Dean A. , Breeden Gregory K.
Published: August 2012

The herbicides mesotrione and topramezone inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) and have efficacy against smooth crabgrass. Research was conducted to determine the impacts of soil-applied nitrogen (N) fertilizer on the effectiveness of single applications of mesotrione and topramezone for postemergence smooth crabgrass control. Field experiments in 2010 and 2011 evaluated the efficacy of mesotrione (280 g a.i. ha−1) and topramezone (9 g a.i. ha−1) for control of multitiller smooth crabgrass subjected to five N fertility treatments (0, 12, 25, 37, or 49 kg N ha−1). Greenhouse experiments evaluated the response of smooth crabgrass to mesotrione (0, 70, 140, 280, 560, and 1,120 g ha−1) and topramezone (0, 4.5, 9, 18, 36, and 72 g ha−1) with 0 or 49 kg N ha−1. Further research evaluated changes in smooth crabgrass leaf tissue pigment concentrations following treatment with mesotrione (280 g ha−1) and topramezone (18 g ha−1) with 0 or 49 kg N ha−1. In field experiments, N increased smooth crabgrass control with mesotrione and topramezone for 8 wk; however, increasing N rate above 25 kg ha−1did not improve control on any rating date. In dose-response experiments, N application reduced I50values for mesotrione and topramezone by 67 and 53%, respectively, 21 d after treatment (DAT). Reductions in aboveground biomass with both herbicides were greater when applied following N treatment as well. In leaf-response experiments, N decreased new leaf chlorophyll and carotenoid concentrations and new leaf production after treatment with topramezone. Future research should investigate whether increased translocation of these herbicides to meristimatic regions contribute to N-enhanced efficacy.
A Waterhemp (Amaranthus tuberculatus) Population Resistant to 2,4-D
Authors: Bernards Mark L. , Crespo Roberto J. , Kruger Greg R. , Gaussoin Roch , Tranel Patrick J.
Published: August 2012

A waterhemp population from a native-grass seed production field in Nebraska was no longer effectively controlled by 2,4-D. Seed was collected from the site, and dose-response studies were conducted to determine if this population was herbicide resistant. In the greenhouse, plants from the putative resistant and a susceptible waterhemp population were treated with 0, 18, 35, 70, 140, 280, 560, 1,120, or 2,240 g ae ha−12,4-D. Visual injury estimates (I) were made 28 d after treatment (DAT), and plants were harvested and dry weights (GR) measured. The putative resistant population was approximately 10-fold more resistant to 2,4-D (R:S ratio) than the susceptible population based on both I50(50% visual injury) and GR50(50% reduction in dry weight) values. The R:S ratio increased to 19 and 111 as the data were extrapolated to I90and GR90estimates, respectively. GR50doses of 995 g ha−1for the resistant and 109 g ha−1for the susceptible populations were estimated. A field dose-response study was conducted at the suspected resistant site with 2,4-D doses of 0, 140, 280, 560, 1,120, 2,240, 4,480, 8,960, 17,920, and 35,840 g ha−1. At 28 DAT, visual injury estimates were 44% in plots treated with 35,840 g ha−1. Some plants treated with the highest rate recovered and produced seed. Plants from the resistant and susceptible populations were also treated with 0, 9, 18, 35, 70, 140, 280, 560, or 1,120 g ae ha−1dicamba in greenhouse bioassays. The 2,4-D resistant population was threefold less sensitive to dicamba based on I50estimates but less than twofold less sensitive based on GR50estimates. The synthetic auxins are the sixth mechanism-of-action herbicide group to which waterhemp has evolved resistance.
How Important are Crop Spatial Pattern and Density for Weed Suppression by Spring Wheat?
Authors: Olsen Jannie Maj , Griepentrog Hans-Werner , Nielsen Jon , Weiner Jacob
Published: August 2012

Previous research has shown that both the density and spatial pattern of wheat have an influence on crop growth and weed suppression, but it is not clear what degree of uniformity is necessary to achieve major improvements in weed suppression. Field experiments were performed over 3 yr to investigate the effects of crop density and different spatial distributions on weed suppression. The spatial pattern of spring wheat sown in five patterns and three densities in small weed-infested plots were analyzed with the use of digitized photographs of field plots to describe the locations of individual wheat plants asxandycoordinates. We used a simple quantitative measure, Morisita's index, to measure the degree of spatial uniformity. Increased crop density resulted in reduced weed biomass and increased crop biomass every year, but crop pattern had significant effects on weed and crop biomass in the first year only. Weather conditions during the second and third years were very dry, resulting in very low weed biomass production. We hypothesize that water deficiency increased the importance of belowground relative to aboveground competition by reducing biomass production, making competition more size symmetric, and reducing the effect of crop spatial pattern on weed growth. The results indicate that increased crop density in cereals can play an important role in increasing the crop's competitive advantage over weeds, and that spatial uniformity maximizes the effect of density when low resource levels or abiotic stress do not limit total biomass production.
Why Early Season Weed Control Is Important in Maize
Authors: Page Eric R. , Cerrudo Diego , Westra Philip , Loux Mark , Smith Kenneth , Foresman Chuck , Wright Harold , Swanton Clarence J.
Published: August 2012

Control of early-emerging weeds is essential to protect the yield potential of maize. An understanding of the physiological changes that occur as a result of weed interference is required to address variability in yield loss across sites and years. Field trials were conducted at the University of Guelph (UG), the Ohio State University (OSU), and Colorado State University (CSU) during 2009 and 2010. There were six treatments (season-long weedy and weed-free, and weed control at the 1st-, 3rd-, 5th-, and 10th-leaf-tip stages of maize development) and 20 individual plants per plot were harvested at maturity. We hypothesized that, as weed control was delayed, weed interference in the early stages of maize development would increase plant-to-plant variability in plant dry-matter accumulation, which would result in a reduction of grain yield at maturity. The onset of the critical period for weed control (CPWC) occurred on average between the third and fifth leaf tip stages of development (i.e., V1 to V3, respectively). Rate of yield loss following the onset of the CPWC ranged from 0.05 MG ha−1d−1at UG 2009 to 0.22 MG ha−1d−1at CSU 2010 (i.e., 0.5 and 1.6% d−1, respectively). On average, reductions in kernel number per plant accounted for approximately 65% of the decline in grain yield as weed control was delayed. Biomass partitioning to the grain was stable through early weed removal treatments, increased and peaked at the 10th-leaf-tip time of control, and decreased in the season-long weedy treatment. Plant-to-plant variability in dry matter at maturity and incidence of bareness increased as weed control was delayed. As weed control was delayed, the contribution of plant-to-plant variability at maturity to the overall yield loss was small, relative to the decline of mean plant dry matter.
Variation in Pathogenicity and Host Range ofBipolarissp. Causing Leaf Blight Disease on the Invasive GrassMicrostegium vimineum
Authors: Kleczewski N. M. , Flory S. L. , Clay K.
Published: August 2012

Microstegium vimineumis a widespread invasive grass that poses significant threats to forests and disturbed areas throughout the United States. Often, the large-scale, rapid spread ofMicrostegiumprohibits management by traditional methods. Control ofMicrostegiummay be possible through the use of a pathogen (referred to here asBipolarisMv) that causes leaf blight onMicrostegium. Members of the fungal genusBipolarisare known pathogens of many plants, including important agronomic crops. However, little is known about the biology and host range ofBipolarisMv. We used a series of growth chamber and light bank experiments to determine the variation inBipolarisMv from different geographic origins and its ability to cause foliar lesions and chlorosis onMicrostegium. We used petri plate and soil infestation assays to determine the effects ofBipolarisMv onMicrostegiumemergence from seed, biomass, and root necrosis. Finally, we tested the host range of these fungi on economically and ecologically important plant species. All isolates increased disease onMicrostegiumfoliage relative to controls, although the effects varied among isolates. Isolates increased root necrosis by 97% in petri plate assays and by 4% in soil infestation trials compared to controls. Infestation of soils withBipolarisMv reduced emergence ofMicrostegiumfrom seed by 31% compared to controls, but did not affect root or stand biomass.BipolarisMv produced lesions on a range of grasses, including corn, sorghum, rye, and wheat, although lesion size varied with isolate. These results indicate thatBipolarisMv may be an effective pathogen onMicrostegium, but its use as a bioherbicide may be impractical because of its effects on a wide range of grasses.
The Influence of Nitrogen Application Timing and Rate on Volunteer Corn Interference in Hybrid Corn
Authors: Terry Ryan M. , Marquardt Paul T. , Camberato James J. , Johnson William G.
Published: August 2012

Volunteer corn (VC) in hybrid corn has become more prevalent in recent years and can reduce grain yield. Nitrogen (N) management can influence VC interference in corn. Field experiments were established to determine the effects of N fertilizer management and VC interference on hybrid corn growth and grain yield. Treatments consisted of three VC densities (control, 0 plants m−2; low density, 1 plant m−2; high density, 4 plants m−2) and six N fertilizer treatments (0 kg N ha−1, 67 kg N ha−1 at planting, 67 kg N ha−1 at planting + 133 kg N ha−1 at V5 corn growth stage, 67 kg N ha−1 at planting + 133 kg N ha−1 at V10 corn growth stage, 200 kg N ha−1 at V5 corn growth stage, and 200 kg N ha−1 at V10 corn growth stage). The effect of VC on hybrid corn was dependent on N rate. When 200 kg N ha−1 was applied, regardless of application timing, hybrid corn dry weight, hybrid corn N content, and hybrid corn grain yield were reduced by the high VC density. However, when VC grain yield was added to hybrid corn grain yield, VC density did not affect total grain yield. When 0 and 67 kg N ha−1 were applied, neither hybrid corn dry weight nor hybrid corn N content was affected by either VC density, but the high VC density reduced hybrid corn grain yield for both N rates by 19% and total grain yield by 9 and 10%, respectively. Application timing of N fertilizer had no effect on hybrid corn dry weight, N content, or grain yield. However, late N fertilizer applications (200 kg N ha−1 at V10 and 67 kg N ha−1 at planting +133 kg N ha−1 at V10) resulted in greater VC N content, VC grain yield, and total yield. Assuming the harvestability of VC, the ability of a late N treatment (V10) to maximize total grain yield allows growers to use a late N application to reduce the competitive effects of VC in hybrid corn.
Phenotypic Plasticity in the Invasion of Crofton Weed (Eupatorium adenophorum) in China
Authors: Zhao Yujie , Yang Xuejun , Xi Xinqiang , Gao Xianming , Sun Shucun
Published: August 2012

Phenotypic plasticity and rapid evolution are two important strategies by which invasive species adapt to a wide range of environments and consequently are closely associated with plant invasion. To test their importance in invasion success of Crofton weed, we examined the phenotypic response and genetic variation of the weed by conducting a field investigation, common garden experiments, and intersimple sequence repeat (ISSR) marker analysis on 16 populations in China. Molecular markers revealed low genetic variation among and within the sampled populations. There were significant differences in leaf area (LA), specific leaf area (SLA), and seed number (SN) among field populations, and plasticity index (PIv) for LA, SLA, and SN were 0.62, 0.46 and 0.85, respectively. Regression analyses revealed a significant quadratic effect of latitude of population origin on LA, SLA, and SN based on field data but not on traits in the common garden experiments (greenhouse and open air). Plants from different populations showed similar reaction norms across the two common gardens for functional traits. LA, SLA, aboveground biomass, plant height at harvest, first flowering day, and life span were higher in the greenhouse than in the open-air garden, whereas SN was lower. Growth conditions (greenhouse vs. open air) and the interactions between growth condition and population origin significantly affect plant traits. The combined evidence suggests high phenotypic plasticity but low genetically based variation for functional traits of Crofton weed in the invaded range. Therefore, we suggest that phenotypic plasticity is the primary strategy for Crofton weed as an aggressive invader that can adapt to diverse environments in China.
Triazine-Resistant Annual Bluegrass (Poa annua) Populations with Ser264Mutation Are Resistant to Amicarbazone
Authors: Perry D. H. , McElroy J. S. , Dane F. , van Santen E. , Walker R. H.
Published: August 2012

Amicarbazone is a photosystem II (PSII)-inhibiting herbicide in the triazolinone family, which is similar in mode of action to the triazines. Annual bluegrass is a cool-season weed and has shown resistance to some PSII-inhibiting herbicides. The objective was to evaluate triazine-resistant and -susceptible annual bluegrass populations for potential cross-resistance to amicarbazone. Two triazine-resistant (MS-01, MS-02) and triazine-susceptible (AL-01, COM-01) annual bluegrass populations were treated with amicarbazone, atrazine, and simazine at 0.26, 1.7, and 1.7 kg ai ha−1, respectively. All herbicide treatments controlled the susceptible populations greater than 94% 2 wk after treatment (WAT). No visual injury of MS-01 and MS-02 was observed at any time following herbicide treatment. Quantum yield (ΦPSII) of annual bluegrass was measured 0 to 72 h after application (HAA) to determine the photochemical effects of amicarbazone compared to other PSII inhibitors. ΦPSIIof triazine-susceptible populations was reduced at all measurement times by all three herbicides. However, amicarbazone decreased ΦPSIIof susceptible populations faster and greater than atrazine and simazine at most measurement times. Amicarbazone did not reduce ΦPSIIof the MS-01 population. Amicarbazone significantly reduced ΦPSIIof the MS-02 population during several measurement timings; however, these reductions were short-lived compared to the susceptible populations and no trend in ΦPSIIreduction was observed. Sequencing of thepsbAgene revealed a Ser to Gly substitution at amino acid position 264 known to confer resistance to triazine herbicides. These data indicate amicarbazone efficiently inhibited PSII of susceptible annual bluegrass populations; however, triazine-resistant annual bluegrass populations with Ser264to Gly mutations are cross-resistant to amicarbazone.
Weedy rice (Oryza sativa) II. Response of Weedy Rice to Seed Burial and Flooding Depth
Authors: Chauhan Bhagirath Singh
Published: August 2012

Weedy rice is a serious problem of cultivated rice in most of the rice-growing areas in Asia, causing increased production costs and yield losses in rice. A study was conducted to determine the response of weedy rice accessions from India (IWR), Malaysia (MWR), Thailand (TWR), and Vietnam (VWR) to seed burial and flooding depths. The greatest emergence for each weedy rice accession (97% for IWR, 82% for MWR, 97% for TWR, and 94% for VWR) was observed in seeds placed on the soil surface. Seedling emergence decreased with increase in burial depth. For the IWR accession, 0.5% of the seedlings emerged from 8-cm depth, whereas for the other three weedy rice accessions, no seedlings emerged from this depth. When seeds were sown on the soil surface, flooding depth ranging from 0 to 8 cm had no or very little effect on seedling emergence of different weedy rice accessions. On the other hand, flooding decreased seedling emergence in all weedy rice accessions when seeds were sown at 1 cm deep into the soil. Compared with seedling emergence, flooding had a more pronounced effect on seedling biomass for all weedy rice accessions. A flooding depth of 2 cm reduced seedling biomass by an amount greater than 85% of each weedy rice accession. The results of this study suggest that emergence and growth of weedy rice could be suppressed by deep tillage that buries seeds below their maximum depth of emergence (i.e., > 8 cm for the accessions studied) and by flooding fields as early as possible. The information gained from this study may help design cultural management strategies for weedy rice in Asia.
Uncertainty in Fluid Substitution using Gassmann's Equation and Implication for DHI analysis and Time-lapse Monitoring
Authors: Ileka Okey
Published: August 2012

Gassmann's equation may not be directly applicable for amplitude variation with offset (AVO) modeling due to the violation of its assumptions (low permeability, highly compressible mineral components, invasion and dispersion), the high sensitivity to input parameters which may be in error, the variations in rock frame porosity and compressibility between gas and brine saturated rocks due to the lateral or vertical geological variability or differences in digenesis or cementation due to different pore fluids, the chemical effects at very low effective stress, frame hardening or softening and the heterogeneous fluid distribution spatially and between pores of various sizes and shapes, possible in applicability of wood's equation.

This study investigates the uncertainty in gassmann's equation and the implication in direct hydrocarbon indicator (DHI) analysis and time lapse monitoring. Gassmann's equations are only applicable to clean, highly permeable reservoir rocks. When gas is substituted for brine using gassmann's equations, predicted compressional wave velocity exhibits a wide range of possible values. This range is larger than the expected change in velocity. A single deterministic gassmann result is only one of many possible stochastic realizations. The maximum, mean, median, modal and minimum values of the many stochastic realization of fluid modulus, fluid density, bulk modulus, compressional wave velocity, acoustic impedance, shear impedance and fluid factor can be used in the interpretation.

The resulting range of possible stochastic realizations of modelled compressional wave velocity ratio between the two bounding media, possible stochastic realizations of modelled density ratio between the two bounding media, possible stochastic realizations of poisson's ratio in the upper medium and possible stochastic realizations of poisson's ratio in the lower media gives rise to various possible stochastic realizations for direct hydrocarbon indicator (DHI) prestack data and time lapse post stack data.
Case Study: Numerical Simulation of a Tight Gas Reservoir with Multifractured Horizontal Wells
Authors: Feng Yang , Zhengfu Ning , Xinwei Liao , Huiqing Liu , Hongmei Liao
Published: August 2012

Tight gas reservoirs have amounted to almost 50% of the newly proved natural gas reserves of PetroChina Co., Ltd. in the past five years. Horizontal wells with multiple hydraulically fractures have been proved an effective method to promote the development performance in tight gas reservoirs, which can extend the reservoir contact, reduce the flow resistance, and enhance the well deliverability. This paper summarizes the design, optimization, results, and reservoir modeling of a tight gas reservoir with fractured horizontal wells. A 3-D reservoir model by using multi-scale data is established to optimize future field development performance. Numerical simulation combining well test interpretation and dynamic analysis results is the primary method to define the various impacting factors, such as orientation of horizontal well, hydraulic fracture spacing, number of fractures along the horizontal well, fracture length, etc. Pilot results have been history matched with a numerical model to reconcile reservoir characterization interpretations and provide prediction of ultimate recovery. The simulation results show that with the average productivity of 5.52×104m3/d of a single fractured horizontal well, the tight gas reservoir can product stably for 3 years, and the periodical recovery will be 16.85%, the ultimate cumulative gas production will be 25.52×108m3.
Re-defining The Refusal Standard For Stovepipe Installation
Authors: Alabi Tunde , Iyua Donald
Published: August 2012

The installation of stovepipe is necessary to provide a circulating system for the drilling fluid, prevent incompetent surface soils from being eroded by drilling fluid, and guide drill string and other casing strings into the hole. It is an integral and routine part of the well construction process. The stovepipe also bears much of the loads of the subsequent casing strings that are installed in the well. To be able to withstand the loads it bears, the stovepipe needs to be driven to a competent refusal depth. For a number of decades, SPDC drilling standard for onshore well construction required stovepipes to be driven with a Delmag D22 hammer to a defined refusal blow count of 110 blows/ft. Most of the time, a satisfactory competent formation was reached. At that time 26" OD, ¾" thickness stovepipes were used. Over time, however, changes were made to the hammer specifications. Also, the sizes of stovepipes were changed. Albeit there was no corresponding engineered translation to new refusal standards for the revised stovepipe and drive hammer specifications. Though the equipment changes did not prompt a return to first principles to re-define the standards, the resulting challenges, particularly in the GB field, did

This paper presents the engineering principles used to derive the new standard and the results achieved in applying the standard.
How Economic is Steam-Assisted Gravity Drainage for the In-situ Development of the Nigerian Bitumen Deposit?
Authors: Lawal Kazeem A.
Published: August 2012

This paper details a preliminary evaluation of the economics and commercial risks of deploying the steam-assisted gravity drainage (SAGD) technique for the in-situ extraction of the oil component of the Nigerian tar sands. The workflow consists of parameter screening, experimental design, response-surface generation and Monte-Carlo simulation. With the net present value (NPV) as the objective function, we evaluate the impacts of the reservoir models (oil production and steam-injection profiles), project costs, hydrocarbon (oil and gas) price and the fiscal regime on project economics and commerciality.

Within the range of parameters investigated, the uncertainties associated with the reservoir model, oil price, operating expenditure (OPEX) and capital expenditure (CAPEX) are found to be the main determinants of the commercial risks of the project. The fiscal policies do not appear to have much impact, at least within the parameter space examined.

Overall, it is estimated that SAGD has more than 60% chance of economic success (NPV > 0), suggesting that this recovery technique is commercially attractive for the in-situ exploitation of the Nigerian bitumen deposit. The commercial prospects of this technique notwithstanding, the potential risks are highlighted, while options for mitigating such risks within the Nigerian context are discussed.
The Effectiveness of Root-Mean-Square in Sensitivity Analysis of Produced Water
Authors: Adeniyi A. T. , Adewole E. S , Olafuyi O.
Published: August 2012

This study examined impacts of successive iteration of root-mean-square values on matching historical data with data obtained from simulator. Root-Mean-Square (RMS) is simply the magnitude of a set of numbers. The magnitude is a difference between two data sets, which was reduced. An RMS value of 24.389 was reduced to 20.788 and then to an acceptable value of 11.72. A match obtained was used to make 10 years forecast with a fluid rate of 500stb/day and 1500stb/day for two predictions. Results obtained from one of the simulator's predictions were compared with a third-order degree polynomial. It is required to identify regions whose faults have significant contribution to produced water volume. This is necessary because some faults do have zero transmissibility. Region with zero transmissibility sealing fault cannot be produced by flooding across the region. Inactive faults were identified through sensitivity analysis; it was discovered that bottom and flank water entered the region through the left flank and vertically upward from the bottom.

Historical data of produced water were eventually matched with that simulated at an RMS value of 11.72 to generate future data for Sagbama. Sagbama is a name given to a hydrocarbon reservoir with the following characteristics: 16,404.2ft by 16,404.2ft by 197.85ft, gridded into 1,640.42ft in x-direction, 1,642.42ft in y-direction, and 49.212ft in z-direction. It consists of live oil and gas with unknown volume of bottom water drive. Densities of oil, water, and gas under consideration are 749.389 kg/m3, 1000 kg/m3 and 1.11242 kg/m3 respectively. Reference pressure was 400bar and rock compressibility took a value of 4.0E-5/bar. Datum depth of 3000m with 331.65bar as it the pressure at the datum, depth to gas-oil contact was 3000m without capillary pressure.
Determination of Abandonment Reservoir Pressure, GOR and BSW for Well Performance Evaluation
Authors: Dike Francis , Aboaja Ugochukwu , Ogunlade Kayode , Kefe Amrasa , Osho Rotimi
Published: August 2012

Well performance evaluation and prediction via decline curve analysis (DCA) requires defined abandonment conditions (Abandonment BSW and oil rate) to estimate the developed ultimate recovery (DUR) of a drainage point. Abandonment BSW and oil rate are derived from well models which require abandonment reservoir pressure and Gas-oil-ratio (GOR) among others as inputs. Good understanding of the performance of a reservoir is necessary for the prediction of abandonment GOR, and this prediction requires a systematic approach. The assumed value of producing GOR has a direct impact on the magnitude of the hydrostatic and dynamic pressure loss in a production tubular and hence it is a very important parameter in the vertical lift performance of a well. Similarly, the the reservoir pressure at abandonment is an indication of the energy available from the reservoir for lift hydrocarbon fluid s from the bottom of the producing wells. This paper illustrates the methodology employed for the estimation of abandonment reservoir pressure, GOR and BSW in support of well performance evaluation and reservoir management. Case studies for saturated and undersaturated reservoirs with weak-to moderate aquifers are considered.
Understanding Crude Oil Price Variation Using Time Series Analysis
Authors: Torkowei Biu Victor , Ikiensikimama Sunday Sunday
Published: August 2012

Historically crude oil prices show characteristics of seasonality, fat tails, time-variant volatilities and asymmetric distributions. Irrespective of its volatility, the single point value approach is the most widely used in evaluating profitable prospect which do not give a clear understanding of some of the key historical parameters driving its constant swings.

This work is to model oil price variation using time series analysis in order to explore whether the stochastic oil prices exhibit similar ARIMA model with the dependant parameters. This provides a clear understanding of the intrusive characteristics of the stochastic oil price in relation with the dependent parameters. The Akaike's Information Criterion (AIC)/ residual variance was used to select the ARIMA models for the dependent parameters investigated in comparison with the oil price before subsequent forecasting.

Result using the AIC/variance indicates ARIMA (1, 0, 0) with constant as the likely model for the volatile oil price, oil demand, production, world rig count, OECD consumption and population depicting their interdependent. However the likely model for the cost oil, non-OECD consumption and population differ completely which indicates that they are spot price independent. Estimated derivative instrument i.e. actual and optimistic value show a continuous rise in crude oil price of 4% annually (average oil price of $85 and demand 91 million bbls forecasted) which is a more realistic baseline for investment decision when compared to the single point value used.
Challenges, Risks and Opportunities of Mature Field Further Development: A Niger Delta Case Study
Authors: Sarkar A. , Nanpan M. , Peacock A. , Ebufegha A.
Published: August 2012

Identifying further development opportunities in terms of infill well drilling targets to improve recovery in matured Niger Delta fields pose significant challenges. The remaining unswept oil targets carry large uncertainties and risks associated with many sub-surface complexities and often limited and/or inconsistent surveillance data. This paper presents a case study of identifying infill opportunities in the 35-year old Niger Delta A1 field and describes how a pragmatic approach to integrated modeling and uncertainty management resulted in a robust phased further development plan which attempts to mitigate risks.

Niger Delta A1 field is a vertically stacked sequence of reservoirs. Production has occurred from nine oil bearing sands, in the depth range 6,400 to 8,400 ftss, which have strong aquifer support. The average porosities vary from 23-30% and permeabilities from 1000-5800 mD. The oil densities vary from 20-27° API. The current (Dec., 2011) recovery factors range from 25-56%.

Integrated static and dynamic reservoir modeling indicated further development opportunities in five of the vertically stacked reservoirs. The key uncertainties were the top structure of the reservoirs, current oil-water contacts, sand qualities and aquifer definitions. History matching of production data were carried out to narrow down the location of unswept oil, however, large uncertainties remained. Modeling indicated that the overall recovery from the field could potentially be increase by 6% from drilling four infill wells with 7 drainage targets. Risk mitigation measures include a focused data acquisition plan to calibrate the current fluid contacts and drilling wells targeting two sub-surface locations with dual or sequential phased development. Production data analysis indicates that the recovery factors and well recoverable volumes are highly correlated to average net oil pay. The correlations may be used for reserve QC.
Hydraulics Optimization For Efficient Hole Cleaning in Deviated and Horizontal Wells
Authors: Ogunrinde J. O. , Dosunmu A.
Published: August 2012

Efficient cuttings transport and hole cleaning is a very important factor that must be considered during drilling operations. In inclined and horizontal drilling, hole cleaning is a common issue since there is high tendency for formation of cuttings bed in the hole which can lead to several complex problems. The optimization of cuttings transport depends on so many factors like hole angle, cutting size, drill string rotation, drill pipe eccentricity, bit hydraulics etc.

This paper is designed to examine critical factors that affect the efficient cleaning/transport of cuttings and bit hydraulics in inclined wells with a view to understanding how to minimize drilling difficulties thereby reducing non producing time (NPT) during drilling operations.

The developed model ensures proper hole cleaning in the critical hole angle (between 45° and 60°) as well as horizontal wells and determining the optimum flowrate and rate of penetration (ROP) that will ensure successful drilling. The model also helps to save time wasted when we encounter problems of high concentrations of cuttings which causes high Equivalent circulation density (ECD) that can result in lost circulation problem amongst others.

Finally, the developed model is validated using field data and graphs showing how the penetration rate increases as cuttings concentration in the annulus reduces thereby optimizing drilling operations.
Estimating the Effects of Ethane and Heavier Components Recovery on the Heat Content of Residue Gas
Authors: Bahadori Alireza
Published: August 2012

Recovery of natural gas liquids (NGL) components in gas not only may be required for hydrocarbon dew point control in a natural gas stream (to avoid the unsafe formation of a liquid phase during transport), but also yields a source of revenue, as NGLs normally have significantly greater value as separate marketable products than as part of the natural gas stream. One of the key parameters in the recovery of ethane and heavier products from natural gas is the effect of the extraction on the heat content of the residue gas. In this work a simple-to-use generalized correlation is developed for the ethane recovery limit to attain a minimum higher heating value (HHV) for various feed gas compositions. As can be seen from this correlation results, the quantity of inerts in the feed gas has an impact on the ethane recovery level which can be targeted in a plant design. A simple correlation is also developed here to estimate the propane and butanes recovery percent as a function of ethane recovery percent. The tool developed in this study can be of immense practical value for petroleum and gas engineers to have a quick check of the heat content of the residue gas after recovery of ethane and heavier components from natural gas at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.