bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximum Likelihood Analysis of Linear Mediation Models with Treatment–Mediator Interaction
Authors: Wang Kai
Published: May 2019

This research concerns a mediation model, where the mediator model is linear and the outcome model is also linear but with a treatment–mediator interaction term and a residual correlated with the residual of the mediator model. Assuming the treatment is randomly assigned, parameters in this mediation model are shown to be partially identifiable. Under the normality assumption on the residual of the mediator and the residual of the outcome, explicit full-information maximum likelihood estimates of model parameters are introduced given the correlation between the residual for the mediator and the residual for the outcome. A consistent variance matrix of these estimates is derived. Currently, the coefficients of this mediation model are estimated using the iterative feasible generalized least squares (IFGLS) method that is originally developed for seemingly unrelated regressions (SURs). We argue that this mediation model is not a system of SURs. While the IFGLS estimates are consistent, their variance matrix is not. Theoretical comparisons of the FIMLE variance matrix and the IFGLS variance matrix are conducted. Our results are demonstrated by simulation studies and an empirical study. The FIMLE method has been implemented in a freely available R package iMediate.
The 2-3-4 spike competition in the Rosensweig instability
Authors: Spyropoulos A. N. , Papathanasiou A. G. , Boudouvis A. G.
Published: May 2019

The horizontal free surface of a magnetic liquid (ferrofluid) pool turns unstable when the strength of a vertically applied uniform magnetic field exceeds a threshold. The instability, known as normal field instability or Rosensweig’s instability, is accompanied by the formation of liquid spikes either few, in small diameter pools, or many, in large diameter pools; in the latter case, the spikes are arranged in hexagonal or square patterns. In small pools where only few spikes – 2, 3 or 4 in this work – can be accommodated, their appearance/disappearance/re-appearance observed in experiments, as applied field strength varies, is investigated by computer-aided bifurcation and linear stability analysis. The equations of three-dimensional capillary magneto-hydrostatics give rise to a three-dimensional free boundary problem which is discretized by the Galerkin/finite element method and solved for multi-spike surface deformation coupled with magnetic field distribution simultaneously with a compact numerical scheme based on Newton iteration. Standard eigenvalue problems are solved in the course of parameter continuation to reveal the multiplicity and the stability of the emerging deformations. The computational predictions reveal selection mechanisms among equilibrium states and explain the corresponding experimental observations and measurements.
A latent variable approach to measuring and explaining peace agreement strength
Authors: Williams Rob , Gustafson Daniel J. , Gent Stephen E. , Crescenzi Mark J. C.
Published: May 2019

Much of the peace agreement durability literature assumes that stronger peace agreements are more likely to survive the trials of the post-conflict environment. This work does an excellent job identifying which provisions indicate that agreements are more likely to endure. However, there is no widely accepted way to directly measure the strength of agreements, and existing measures suffer from a lack of nuance or reliance on subjective weighting. We use a Bayesian item response theory model to develop a principled measure of the latent strength of peace agreements in civil conflicts from 1975 to 2005. We illustrate the measure's utility by exploring how various international factors such as sanctions and mediation contribute to the strength or weakness of agreements.
Deliberative Democracy in an Unequal World: AText-As-DataStudy of South India’s Village Assemblies
Authors: PARTHASARATHY RAMYA , RAO VIJAYENDRA , PALANISWAMY NETHRA
Published: May 2019

This paper opens the “black box” of real-world deliberation by usingtext-as-datamethods on a corpus of transcripts from the constitutionally mandatedgram sabhas, or village assemblies, of rural India. Drawing on normative theories of deliberation, we identify empirical standards for “good” deliberation based on one’s ability both to speak and to be heard, and use natural language processing methods to generate these measures. We first show that, even in the rural Indian context, these assemblies are not mere “talking shops,” but rather provide opportunities for citizens to challenge their elected officials, demand transparency, and provide information about local development needs. Second, we find that women are at a disadvantage relative to men; they are less likely to speak, set the agenda, and receive a relevant response from state officials. And finally, we show that quotas for women for village presidencies improve the likelihood that female citizens are heard.
Protein deficiency during pregnancy and lactation impairs glucose-induced insulin secretion but increases the sensitivity to insulin in weaned rats
Authors: Latorraca Márcia Q. , Carneiro Everardo M. , Boschero Antonio C. , Mello Maria A. R.
Published: May 2019

We studied glucose homeostasis in rat pups from dams fed on a normal-protein (170 g/kg) (NP) diet or a diet containing 60 g protein/kg (LP) during fetal life and the suckling period. At birth, total serum protein, serum albumin and serum insulin levels were similar in both groups. However, body weight and serum glucose levels in LP rats were lower than those in NP rats. At the end of the suckling period (28 d of age), total serum protein, serum albumin and serum insulin were significantly lower and the liver glycogen and serum free fatty acid levels were significantly higher in LP rats compared with NP rats. Although the fasting serum glucose level was similar in both groups, the area under the blood glucose concentration curve after a glucose load was higher for NP rats (859 (sem58) mmol/l per 120 min for NP ratsv.607 (sem52) mmol/l per 120 min for LP rats;P< 0.005). The mean post-glucose increase in insulin was higher for NP rats (30 (sem4.7) nmol/l per 120 min for NP ratsv.17 (sem3.9) nmol/l per 120 min for LP rats;P< 0.05). The glucose disappearance rate for NP rats (0.7 (sem0.1) %/min) was lower than that for LP rats (1.6 (sem0.2)%/min;P< 0.001). Insulin secretion from isolated islets (1 h incubation) in response to 16.7mmol glucose/l was augmented 14-fold in NP rats but only 2.6-fold in LP rats compared with the respective basal secretion (2.8 mmol/l;P< 0.001). These results indicate thatin vivoas well asin vitroinsulin secretion in pups from dams maintained on a LP diet is reduced. This defect may be counteracted by an increase in the sensitivity of target tissues to insulin.
Transfers of N metabolites across the ovine liver in response to short-term infusions of an amino acid mixture into the mesenteric vein
Authors: Lobley G. E. , Bremner D. M. , Nieto R. , Obitsu T. , Moore A. Hotston , Brown D. S.
Published: May 2019

The effect of acute (4.5 h) infusions into the mesenteric vein of an amino acid (AA) mixture, which simulated the composition of rumen microbial protein, on net transfers of NH3, urea and total AA across the portal-drained viscera (PDV) and liver in the ovine has been examined. Four wether sheep were surgically prepared with vascular catheters across the PDV and liver (Lobley et al. 1995) and were offered a basal diet of 1000 g grass pellets/d (approximately 1.4 × energy maintenance). Each animal was infused at weekly intervals with one of four dilutions of the AA mixture. These dilutions provided 0.44, 0.88, 1.32 and 1.84mmol AA-N/min infused, the lowest of which approximately doubled the net absorption of AA-N from the basal diet. Animals were treated with heparin to allow continuous collection of blood by peristaltic pump for 2 h preceding, and between 0.5–2.5 and 2.5–4.5 h after, the start of the AA infusions. Blood flow in the hepatic artery increased (100 v. 208 g/min; P = 0.002) in response to AA infusion, while hepatic portal venous flow decreased (2090 v. 1854 g/min; P = 0.006). The AA infusion also stimulated O2 uptake by the PDV (P < 0.001) and liver (P = 0.016). Absorption across the PDV and hepatic removal of NH3 were unchanged between basal and amino acid infusion conditions. Urea-N removal across the PDV was unaltered, but hepatic production increased (P < 0.001) with level of AA infusion. During infusions, net appearance of AA across the PDV was below the theoretical level. This may have been due to inhibition of AA uptake from the small intestine, and/or increased removal by the digestive tract of AA from the systemic circulation associated with greater arterial concentrations. Hepatic extraction of AA increased with level of infusion, both for total AA and those included in the infusate. Total hepatic urea-N production tended towards a maximum (estimated as 2 μmol N/g liver wet weight per min). The AA removed by the liver and not used for ureagenesis remained similar (170 μmol AA-N/min) between basal and AA infusions. This was presumed available for anabolic purposes (mainly synthesis of export proteins). The proportion of net AA-N appearance (absorption plus infused) across the PDV removed by the liver declined from 0.71 to 0.53 between basal and AA infusions. In contrast to findings from cattle (Wray-Cahen et al. 1997), increased AA infusion did not alter the net removal of glutamine across the liver. This may reflect differences between the studies in NH3: AA-N absorbed. Further differences between the cattle study and the current findings may relate to the different physiological state (pregnancy v. growth), which may alter the partition of AA between anabolic and catabolic fates.
Intestinal degradation in pigs of rye dietary fibre with different structural characteristics
Authors: Glitsø L. V. , Brunsgaard G. , Højsgaard S. , Sandström B. , Bach Knudsen K. E.
Published: May 2019

In order to investigate the effects of dietary fibre (DF) characteristics on carbohydrate degradation and the metabolism in the large intestine, pigs were fed on four rye-bread diets (based on whole rye, pericarp/testa, aleurone or endosperm) with differences in characteristics and amount of DF. The degradability of DF in the large intestine varied greatly between diets. The pericarp/testa DF was hardly degraded in the large intestine, whereas endosperm DF was extensively and rapidly degraded in the caecum. Caecal degradation of aleurone DF was also limited, leaving more material to be degraded in the colon. The undegradable pericarp/testa DF was characterized by high contents of lignin, cellulose, ferulic acids and highly substituted arabinoxylans (the major DF component in rye). Ingestion of this diet resulted in increased faecal bulk and reduced transit time, but with low colonic pH and the lowest concentrations of short-chain fatty acids (SCFA). The aleurone diet, on the other hand, led to a fermentation pattern which may be considered more optimal, with lower colonic pH and higher concentrations of SCFA, in particular butyric acid. Despite the large differences in carbohydrate fermentation only minor significant effects on the presence of protein degradation products and on histological measurements (height and diameter of colonic crypts and thickness of the muscularis externa) were observed.
Effects of simmondsin on food intake, growth, and metabolic variables in lean (+/?) and obese (fa/fa) Zucker rats
Authors: Flo G. , Vermaut S. , Darras V. M. , Van Boven M. , Decuypere E. , Kühn R. , Daenens P. , Cokelaere M.
Published: May 2019

Incorporation of 2·5 g/kg of the anorexigen, simmondsin, in the diet resulted in food intake reduction in both lean and obese Zucker rats; however, the obese rats were much more sensitive to the food intake-reducing activity of simmondsin. In both obese and lean simmondsin-treated Zucker rats, growth was slower than in control rats, but was the same as that in pair-fed animals. The 24 h heat production pattern showed a smaller diurnal variation and a lower mean in obese rats than in lean rats. Food intake reduction, as a result of either simmondsin treatment or pair feeding, caused a decrease in mean heat production. Simmondsin treatment, but not pair feeding, caused a decrease in the diurnal variation of heat production. Plasma total cholesterol levels were increased in both simmondsin-treated and pair-fed obese and lean Zucker rats compared with control animals; this increase was mainly due to an increase in HDL-cholesterol levels. Blood leptin levels in both obese and lean rats decreased with decreased food intake and decreased fat deposition, but in obese rats, simmondsin treatment resulted in an additional decrease in leptin levels. It is concluded that the food intake-reducing effect of simmondsin is more pronounced in obese Zucker rats than in their lean littermates, and except for the simmondsin-specific effects on leptin and total cholesterol values in obese littermates, the effects of simmondsin are related to food intake restriction in obese and lean Zucker rats.
Canadian Supreme Court: Delgamuukw V. British Columbia
Authors: Bell Catherine
Published: May 2019

Delgamuukw v. B.C. is a pivotal decision in the evolution of Canadian law on Aboriginal rights.Numerous meetings, round-tables, workshops and conferences have been held to discuss its potential impact on litigation and negotiation.1 Delgamuukw has also served as a vehicle for discussion of more fundamental issues such as the appropriateness of selecting the judicial forum to resolve Aboriginal title claims and the role of legal reasoning in furthering the process of colonization.2 Given the influence of British colonial law on the development of Aboriginal rights jurisprudence in former British colonies and the restrictions placed by evidentiary presumptions originating in English courts, Delgamuukw may also have persuasive precedential value outside of Canada. In particular, the Supreme Court's elaboration of the concept of Aboriginal rights and its discussion of the weight to be given to oral histories may influence other commonwealth courts which face the demanding task of accommodating the rights of colonized peoples within a contemporary political and legal rights regime.3
Japan's Liberal-Democratic Paradox of Refugee Admission
Authors: Kalicki Konrad
Published: May 2019

In-migration embodies the liberal-democratic paradox: the tension between the right of an individual and the collective will of a polity. This is well illustrated by escalating conflicts over admission of the “special category” of international migrants: refugees. Taking Japan as a notoriously difficult case, this paper analyzes recent developments in Japan's embattled refugee policy and argues that grassroots efforts by civil society provide a way to move beyond the current gridlock of the state-centric paradigm of refugee admission. Specifically, empirical evidence available to date suggests that private refugee sponsorship that enables individuals and community organizations to voluntarily sponsor the resettlement of UN-recognized refugees offers a viable policy instrument in Japan's context. While retaining the democratic communitarian outlook on admission of foreigners, the model injects liberal universalist qualities into immigration policy that are capable of motivating positive change domestically and, potentially, across East Asia at large.
How to Read a Sinographic Text in Eighteenth-Century Chosŏn Korea:Liuxi Waizhuanand Yi Tŏngmu's Compilation ofNoeroe Nangnak Sŏ
Authors: Son Suyoung
Published: May 2019

This paper examines the transnational literary interactions in the early modern Sinographic sphere by examining the late Chosŏn writer Yi Tŏngmu's reading of an early Qing text,Liuxi Waizhuan,and its resonance in his compilation ofNoeroe Nangnak Sŏ. Reconsidering the unmediated communicability of the Sinographic text, it demonstrates the ways in whichNoeroe Nangnak SŏdecoupledLiuxi Waizhuanfrom its local conditions of production and circulation and relocalized it to fit Chosŏn Korea's agenda of repositioning itself in the changing Sinocentric order after the downfall of the Ming. Between delocalizing and relocalizing the Sinographic text, the compilation ofNoeroe Nangnak Sŏparticipated in the constantly shifting meanings of loyalty to the fallen Ming, thereby diversifying the repertoire of the shared civilization in early modern East Asia.
Rejoinder to Michael Sandel
Authors: Dagger Richard
Published: May 2019

Michael Sandel's response to my critical essay is thoughtful, generous, and characteristically elegant. I am not the only one, I am sure, who will welcome this clarification of his views. Yet I am inclined to think that what he does not include in his response is as important as what he does.

What Professor Sandel's response does not include is any attempt to sort out, qualify, accept, or reject the criticisms advanced in the “Sandel and the Self” section of my essay. He says in his second sentence that I bring out “the continuities and differences between Democracy's Discontent and my earlier work with subtlety and care,” but he fails to note that most of those continuities concern the unencumbered self he attributes to liberalism. We are left to wonder, then, what he makes of the three charges that I bring against his account of this self: that he mistakes the point of the unencumbered self in Rawlsian liberalism; that he trades on a false dichotomy between the encumbered and the unencumbered self; and that he neglects to notice a distinction, implicit in his as much as in Rawls's thinking, between the self in the abstract, general sense and the self in the concrete, particular sense.
Multicultural Liberals and the Rushdie Affair: A Critique of Kymlicka, Taylor, and Walzer
Authors: O'Neill Daniel I.
Published: May 2019

This article critically analyzes the work of Will Kymlicka, Charles Taylor, and Michael Walzer, three of the most important contemporary political philosophers writing on issues of multiculturalism. It uses the Rushdie affair, and each theorist's interpretation of it, as the basis for an immanent critique of “multicultural liberalism,” a theory defined by the dual commitment to cultural rights for minority groups and certain core liberal principles, defended in different ways by Kymlicka, Taylor, and Walzer. It is principally concerned with Kymlicka, whose work is one of the most influential attempts to respond to communitarian criticisms that “atomistic” liberalism is inhospitable to community and culture. The article argues that Kymlicka's defense of “multicultural citizenship” is deeply problematic from the perspective of the Rushdie affair. It then considers Taylor and Walzer similarly, as representatives of the communitarian strain of multicultural liberal argument, and likewise finds their positions unconvincing. The article concludes with the suggestion that the Rushdie affair points to a potentially unresolvable tension at the heart of all three attempts to defend multicultural liberalism.
Rhetorics of “the People”: The Supreme Court, the Social Contract, and the Constitution
Authors: Mason Pamela A.
Published: May 2019

This article explores the federal judiciary's use of eighteenth–century social contract theory inUnited States v. Verdugo–Urquidez(494 US 259) to interpret the constitutional rhetoric of “the people” for our time. The principal version of social contract theory at play inVerdugorecalls a republican ideology which forms an old and volatile current in American political thought, an ideology which supports a far more exclusionary standard of membership in the nation than has obtained for most of this century, and which has important implications for the construction of political authority it is enlisted to support.
Judging the Past: The Prosecution of East German Border Guards and the GDR Chain of Command
Authors: Quint Peter E.
Published: May 2019

Transitions from dictatorship to democracy often raise the perplexing question of whether a new government may punish actions which, although reprehensible, were considered legal under the old regime. In these instances, the desire for condign punishment of evil acts confronts the principle that forbids retroactive criminal prosecutions. After German unification, problems of this type arose in trials of East German border guards for the use of deadly force at the Berlin Wall, along with prosecutions of military and civilian officials higher in the German Democratic Republic (GDR) chain of command. In this article, the author discusses these prosecutions and analyzes the response of the German courts to the difficult problems of retroactivity that the cases raise. In its concluding section, the article suggests that these cases may evoke issues concerning the legitimacy of the GDR that were the subject of bitter debates during Germany's divided past.
La responsabilité pénale individuelle pour violation du droit international humanitaire applicable en situation de conflit armé non international
Authors: Graditzky Thomas
Published: May 2019

Au milieu de notre siècle, deux événements majeurs ont marqué le droit pénal international. En premier lieu, les procès des grands criminels de guerre qui se sont déroulés à Nuremberg et à Tokyo suite au second conflit mondial jouent un rôle phare dans le domaine. La responsabilité pénale individuelle pour certains actes graves contraires aux normes du droit international applicable lors de conflits armés est mise au grand jour; les termes de «crimes contre la paix», «crimes de guerre» et «crimes contre l'humanité» trouvent leur consécration. Peu après, avec, l'adoption des quatre Conventions de Genève du 12 août 1949 pour la protection des victimes de la guerre, le deuxième événement fait son apparition.
La restauration d'un ordre de justice dans les situations postconflictuelles à la lumière de l'enseignement social de l'Église catholique
Authors: Filibeck Giorgio
Published: May 2019

Avant tout, il faut relever que les situations postconflictuelles, aujourd'hui encore, ne sont pas toutes caractérisées par le retour d'une paix véritable. Il s'agit souvent d'un état dans lequel le conflit se poursuit d'une façon plus ou moins larvée, allant d'actes d'hostilité isolés, parfois de type terroriste, jusqu'à des opérations militaires qui, tout en étant salutaires, entretiennent cependant un climat de belligérance. Dans un tel contexte, il apparaît difficile de garantir la sécurité qui est indispensable au fonctionnement de la justice.
Rice (Oryza sativa) response to clomazone
Authors: Jordan David L. , Bollich Patrick K. , Burns Ann B. , Walker Douglas M.
Published: May 2019

Experiments were conducted in 1993 and 1994 to determine if seed treated with disulfoton at 3, 6, or 12 g ai kg−1 reduced bleaching of rice foliage caused by clomazone applied delayed preemergence at 0.56, 1.1, 1.7, or 2.2 kg ai ha−1 on silt loam and silty clay soils. Clomazone injured rice more on silt loam soil than on silty clay soil. Disulfoton reduced bleaching caused by clomazone. In additional field experiments conducted during 1995 and 1996, clomazone at rates as high as 2.2 kg ha−1 did not affect grain yield in seven of 10 experiments. Clomazone at rates below 1.7 kg ha−1 did not reduce grain yield in any of the experiments.
Iron-enhanced remediation of water and soil containing atrazine
Authors: Singh Jasbir , Shea Patrick J. , Hundal Lakhwinder S. , Comfort Steve D. , Zhang Tian C. , Hage David S.
Published: May 2019

Atrazine is the most widely used herbicide in the U.S. and has been detected in surface water and groundwater. Technologies are needed for onsite and in situ remediation of water and soil containing atrazine. We investigated the potential of using fine-grained, zero-valent iron (Fe0) to remove atrazine and promote its degradation in contaminated water and soil. Atrazine loss from aqueous solution increased with increasing Fe0concentration (w/v). Agitating 20 μg14C-ring-labeled atrazine L−1with 10% Fe0(w/v) removed 92% of the14C from solution within 48 h. Only about 4% of the14C lost from solution was extractable from the iron with 3 mM CaCl2(readily available pool), 81% was extractable with CH3CN (potentially available pool), and 11% was unextractable residues. A companion experiment indicated that most of the14C extracted from the iron with 3 mM CaCl2after the 48-h Fe0treatment was unaltered atrazine, while the CH3CN extract contained approximately 33% atrazine and 48% was unidentified atrazine transformation products. Treating a highly contaminated solution (20 mg atrazine L−1) with 20% Fe0(w/v) removed 88% of the14C (added as14C-ring-labeled atrazine) from solution within 48 h. Deethylatrazine was the main atrazine transformation product detected in solution after treatment, but small amounts of deisopropylatrazine, didealkylatrazine, and hydroxyatrazine were also found. Treating Sharpsburg surface soil containing 1 mg atrazine kg−1with Fe0(2%, w/w) increased atrazine mineralization from 4.1 to 11.2% after 120 d. Pyrite (4% FeS2, w/w) also increased atrazine mineralization in surface soil, but was less effective in the presence of NO3−or SO42−(100 mg kg−1soil). Adding 2% Fe0(w/w) and 100 mg NO3−kg−1to contaminated subsurface soil increased atrazine mineralization from 0.4 to 8.2% within 120 d, and unextractable residues increased from 4.6 to 9.8%. These results indicate iron can sorb atrazine and promote its transformation in water and soil.
Is it unnatural to genetically engineer plants?
Authors: Comstock Gary
Published: May 2019

Author' note: This article is based on remarks made in February 1998 at the annual meeting of the Weed Science Society of America in Chicago. Those remarks were in turn based on an article, to be published in Spanish, titled “Es Antinatural la Manipulación Genética de los Animales?” The Spanish version will appear in the Proceedings of the Segundo Congreso Caribeno de Bioetica, University of Puerto Rico, Mayaguez, March 1998. It addresses the question of the engineering of animals; the focus here is the engineering of plants. Whether one considers flora or fauna, the unnaturalness objection raises the same cluster of concerns. Consequently, an assessment of those concerns need not vary significantly in turning from animals to plants.
Quinclorac belongs to a new class of highly selective auxin herbicides
Authors: Grossmann Klaus
Published: May 2019

Substituted quinolinecarboxylic acids, including quinclorac (BAS 514H), are a new class of highly selective auxin herbicides, which are chemically similar to naturally occurring compounds isolated from plants and soils. Quinclorac is used in rice to control important dicot and monocot weeds, particularly barnyardgrass. The herbicide has also been developed for application in turfgrass areas, spring wheat, and chemical fallow. Quinclorac is readily absorbed by germinating seeds, roots, and leaves and is translocated in the plant both acropetally and basipetally. By mimicking an auxin overdose, quinclorac affects the phytohormonal system in sensitive plants. The compound stimulates the induction of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activity and thus promotes ethylene biosynthesis. In susceptible dicots, increased levels of ethylene trigger an accumulation of abscisic acid (ABA), which, as part of the intrinsic auxin activity of quinclorac, plays a major role in growth inhibition and the induction of epinasty and senescence. In sensitive grasses, such as barnyardgrass species, large crabgrass, broadleaf signalgrass, and green foxtail, quinclorac leads particularly to an accumulation of tissue cyanide, formed as a co-product during increased ACC and ethylene synthesis. This causes phytotoxicity characterized by the inhibition of root and particularly shoot growth with tissue chlorosis and subsequent necrosis. These effects were not observed in tolerant rice and a resistant biotype of barnyardgrass. No significant differences in uptake, translocation, or metabolism of quinclorac between resistant and sensitive grasses were found. Hence, a target-site-based mechanism of selectivity is suggested. The induction process of the ACC synthase activity plays the primary role in the selective herbicide action of quinclorac. This is a common effect of auxin herbicides and auxins, which lead to the accumulation of cyanide and/or ABA depending on the plant species and tissues, the compound concentration in the tissue, and their biological activity.
Chlorophyll fluorescence for rapid detection of propanil-resistant barnyardgrass (Echinochloa crus-galli)
Authors: Norsworthy Jason K. , Talbert Ronald E. , Hoagland Robert E.
Published: May 2019

Repeated use of propanil to control barnyardgrass (BYG) and other weeds in rice has led to the development of propanil-resistant barnyardgrass (R-BYG). R-BYG possesses elevated aryl acylamidase activity levels, which cause rapid metabolism of propanil analogous to propanil degradation in rice. The current screening method for determining propanil resistance in BYG requires about 10 mo. The present study examined the use of chlorophyll fluorescence as a more rapid method to identify propanil resistance in BYG soon after it is suspected. Chlorophyll fluorescence data from excised BYG leaf tissue (R-BYG and susceptible-BYG [S-BYG]; 13- to 41-d-old) exposed to 100 μM propanil for 2 h indicated a 95 to 100% inhibition of electron transport (photosynthesis inhibition) in both R- and S-BYG. However, when incubated in water in the dark for 22 h after the initial 2-h treatment, metabolism in R-BYG was sufficient to reduce levels of absorbed propanil and facilitate recovery. Lack of metabolism of propanil prevented recovery in S-BYG, thus allowing the two biotypes to be distinguished easily by the chlorophyll fluorescence assay. Further studies using this 2-h exposure to 100 μM propanil followed by a 22-h recovery period evaluated several assay parameters. A longer recovery time and the effects of various propanil concentrations were also evaluated. A herbicide dose-response curve showed the greatest difference in photosynthesis inhibition for both biotypes at about 100 μM propanil, but both biotypes were inhibited > 95% when treated with 400 μM propanil. Inhibition of photosynthesis in both biotypes was greatest when the recovery incubation temperature was 35 C compared to 20, 25, and 30 C. Fluorescence data from harvested tissue stored moist in plastic bags at 23 C (to simulate shipment) showed that biotypes could be differentiated even when received as late as 4 d after harvest. Thus, samples can be harvested from the field soon after propanil failure and resistance or susceptibility to propanil determined after only a few days. This technique can greatly reduce the time, space, and labor currently required to determine propanil resistance in BYG.
Paraquat resistance in horseweed (Conyza canadensis) and Virginia pepperweed (Lepidium virginicum) from Essex County, Ontario
Authors: Smisek Alida , Doucet Colleen , Jones Martha , Weaver Susan
Published: May 2019

Populations of horseweed and Virginia pepperweed resistant to the herbicide paraquat were found in several fruit orchards in Essex County, Ontario, Canada, where paraquat had been applied four to five times per year for at least 10 yr. Dose–response experiments were conducted in the greenhouse for each species, using 2-to 4-mo-old plants from populations that had received repeated exposure to paraquat and those that had not. The paraquat dose that reduced shoot dry weight by 50% (ED50) was estimated for each population. Resistant populations of horseweed had ED50 values 25 to 35 times higher than susceptible populations. A resistant population of Virginia pepperweed had an ED50 10 times higher than susceptible populations.
Effects of mechanical damage on cheat (Bromus secalinus) caryopsis anatomy and germination
Authors: Gossen Reonna R. Slagell , Tyrl Ronald J. , Hauhouot Marilyne , Peeper Thomas F. , Claypool P. Larry , Solie John B.
Published: May 2019

A hammer mill removed most of the lemmas, paleas, and pericarps from cheat florets. Typically, the cuticular layer of the testa was the only remaining intact layer, and damage to the embryos and endosperm was severe. A roller mill disrupted tissue organization of lemmas, paleas, and outer layers of the caryopses primarily at the cuts. Large gaps between the aleurone layer and testa, between testa and pericarp, and between the scutellum and endosperm were created. In the field, germination of mill-damaged florets was reduced, and florets exhibited progressive degradation the longer they were buried. Nematodes and fungi penetrated the cuticular layer of mill-damaged seed. Attaching a hammer mill or a roller mill to a grain combine to treat cheat seed before it is returned to the field could provide a novel method of cheat control.
Absorption, translocation, and metabolism of primisulfuron and nicosulfuron in broadleaf signalgrass (Brachiaria platyphylla) and corn
Authors: Gallaher Kent , Mueller Thomas C. , Hayes Robert M. , Schwartz Otto , Barrett Michael
Published: May 2019

Broadleaf signalgrass is sensitive to nicosulfuron and resistant to primisulfuron, but corn is resistant to both. Research was conducted to determine the effect of varying light level and air temperature on absorption, translocation, and metabolism of nicosulfuron and primisulfuron in broadleaf signalgrass and corn. Corn absorbed between 60 and 85% of the applied nicosulfuron and primisulfuron within 72 h after treatment (HAT), depending on environmental treatment. Absorption, translocation, and metabolism all tended to be more rapid at higher temperature and light intensity. Nicosulfuron and primisulfuron translocation out of the treated leaf was < 4.5% of herbicide absorbed through 72 HAT. Corn rapidly metabolized both herbicides in both environments. However, primisulfuron was metabolized more rapidly (high = 99%, low = 92%) than nicosulfuron (high = 95%, low = 78%). Broadleaf signalgrass absorbed 20% more nicosulfuron than primisulfuron through 72 HAT. Nicosulfuron translocation out of the treated leaf in broadleaf signalgrass was ≤ 15% absorbed through 72 HAT, while primisulfuron translocation was ≤ 4% during the same time period. Primisulfuron metabolism was more rapid than nicosulfuron in broadleaf signalgrass. During the first 4 HAT, broadleaf signalgrass metabolized > 20 times more primisulfuron than nicosulfuron. By 72 HAT, broadleaf signalgrass under conditions of high light and temperature had metabolized nearly 90% of the primisulfuron absorbed but ≤ 7% of the nicosulfuron absorbed was metabolized during the same time. These results suggest that differential activity of nicosulfuron and primisulfuron on broadleaf signalgrass may be based on differential rates of metabolism to nonphytotoxic compounds; uptake and translocation differences agree with the differential broadleaf signalgrass activity. Additionally, environment has the potential to affect rates of sulfonylurea absorption, translocation, and metabolism.
Growth of field horsetail (Equisetum arvense) under low light and low nitrogen conditions
Authors: Andersson Torsten N. , Lundegårdh Bengt
Published: May 2019

Field horsetail was grown from rhizome segments for 28 and 52 d under 35, 60, 120, 170, and 320 μmol m–2s–1photosynthetic photon flux (PPF) and four continuous nitrogen (N) supply rates corresponding to a total of 1 to 6 kg N ha–128 d after planting (DAP) and 6 to 41 kg N ha–152 DAP. There was no response to the supply of N in the first growth period, probably due to the mobilization of nitrogen available in the planted rhizomes, and only dry weight (DW) of new belowground production, mostly roots, responded to increased light. Rhizomes were produced during the latter part of the 52-d period. Requirements for light and N during the 52-d period were low, because total new tissue production was only reduced at the lowest levels of light (35 μmol m–2s–1PPF) and the two lowest N supply rates (6 and 18 kg N ha–1). The ratio of shoot DW to belowground organ DW increased only as the N supply increased. Shoot height response to an increased N supply was also small. Field horsetail can therefore be considered tolerant of low levels of N but will be overtopped by fast-growing species when competing for increased supplies of N. Both an increase in N supply and a reduction in light increased the reduction of DW of the planted rhizomes, whereas tuber production was favored by low N supply and high light intensities. Field horsetail can tolerate low levels of N but is not likely to be competitive in a dense crop stand.
The implications of variable or constant expansion rates in invasive weed infestations
Authors: Smith H. Arlen , Johnson Wayne S. , Shonkwiler J. Scott , Swanson Sherm R.
Published: May 2019

Data on the spread of invasive weeds into arid western lands are used to evaluate the environmental and economic importance of controlling invasive weed infestations early. Variable rate and constant rate infestation expansion paths are estimated. The implications of variable vs. constant infestation growth rates for projecting both biophysical and economic effects are illustrated. The projections derived from both constant and variable growth rate expansion paths support the contention that it is expedient to control new infestations early.
Influence of velvetleaf (Abutilon theophrasti) and common sunflower (Helianthus annuus) density variation on weed management outcomes
Authors: Dieleman J. Anita , Mortensen David A. , Martin Alex R.
Published: May 2019

Interactions between initial weed seedling density and postemergence herbicide and mechanical weed control were studied in two field experiments conducted between 1994 and 1996. Increasing seedbank densities of velvetleaf (0 to 500 seed m–2) in soybean or common sunflower (250 to 2,500 seed 1.3 m–2) in corn or soybean were established at Lincoln and Mead, NE, respectively. Emerged seedlings were treated with increasing intensities of weed control from none to bentazon alone or with interrow cultivation. A positive linear relationship between initial seedling density and density of surviving seedlings was consistently observed. As initial seedling density increased, more survivors were present after treatment. As intensity of weed control increased, the number of seedling survivors decreased. Resulting reproductive fitness decreased with increasing management intensity but remained positive when regressed against surviving seedling densities. Weed management outcomes were dependent on initial seedling density, such that the absolute number of survivors increased, while proportion of survivors appeared constant within the density ranges studied. These research findings emphasize the need to account for weed infestation level when assessing efficacy of weed management systems and provide evidence that patchy weed distributions may persist in part because of the need for considerably higher management intensities in high density patch centers.
Estimated soybean (Glycine max) yield loss from herbicide damage using ground cover or rated stunting
Authors: Donald W. W.
Published: May 2019

The primary goal of this research was to determine whether crop damage from herbicides measured soon after treatment could estimate relative crop yield loss. Two to 4 wk after spraying soybeans with an unregisrered mixture of rhifensulfuron plus sethoxydim at various rates plus crop oil concentrate, percent stunting was visually rated and percent projected ground cover of soybeans was determined from photographs. In each of 3 yr, relative percent soybean yield was a negative linear function of relative herbicide rate from 0.25× to 2× the registered (1×) rate. The 1× rate of thifensulfuron and sethoxydim was 17.5 and 420 g ai ha−1, respectively. Relative soybean yield was also negatively related linearly to stunting but positively related linearly to soybean ground cover over 3 yr. Linear regression equation models of relative soybean yield versus percent soybean ground cover explained more model variability, more consistently (R2≥ 0.60 in two of 3 yr) than did either stunting (R2≥ 0.60 in one of 3 yr) or relative herbicide rate (R2= 0.37 to 0.48 over 3 yr). However, linear regression models for each independent variable differed from year to year and were related to differences in rainfall following treatment. Ways are suggested to increase regression model precision and between-year reproducibility.
Extractability and degradation of atrazine in a submerged sediment
Authors: Mersie Wondi , Liu Jianbo , Seybold Cathy , Tierney Dennis
Published: May 2019

A study was conducted to examine the effects of residence time and temperature on atrazine extractability and degradation in a sediment generated from Emporia sandy loam soil submerged under a water column. Sediments amended with 2.8 μg of atrazine were incubated at two temperatures (5 and 24 C), sampled at 0, 14, 28, 112, 168, 252, and 336 d, and then sequentially extracted once with 80 ml 0.01 M CaCl2 aqueous solution, three times with 25 ml of methanol/water mixture (4:1, v/v), and three times with 25 ml of methanol/water/formic acid (20:5:1, v/v pH 3.2) for a total of seven times. Extracts were analyzed for atrazine and metabolites using reverse phase high-performance liquid chromatography. The rate of bound residue formation was greater at 24 than at 5 C. About 30 and 60% of the 14C was bound (nonextractable) to sediments at 5 and 24 C, respectively. Water was less effective in extracting 14C residues from sediments incubated at 24 C than at 5 C. Acidification of the methanol/water mixture with formic acid during the last extraction step improved the removal of hydroxyatrazine from sediment. Atrazine degraded primarily to hydroxyatrazine (HA) and to a lesser extent to deethylatrazine (DEA). Although no DEA was found, HA at 43 μg kg−1 of sediment was detected 112 d after treatment at 5 C, indicating that chemical degradation could occur at a low temperature if sediments are incubated for extended periods of time. At 24 C, HA was found within 28 d and reached the maximum level at day 252. The results suggested that HA is the major metabolite of atrazine in the sediment; a significant fraction of the residue was unavailable for extraction, and this unextractable portion increased with residence time.
Comparison of chemical extraction and bioassay for measurement of metsulfuron in soil
Authors: Szmigielska Anna M. , Schoenau Jeff J. , Greer Ken
Published: May 2019

A new extraction method for the HPLC-UV determination of metsulfuron in soil was developed and compared with NaHCO3extraction and a lentil bioassay technique. The new procedure consisted of metsulfuron extraction using anion exchange membranes followed by a dichloromethane concentration of the membrane eluates. Three soils representing different landscape positions were spiked with metsulfuron to yield concentrations in the range of 0 to 40 μg kg−1dry soil and were analyzed by the above procedures. At a given spike rate, the efficiency of the anion exchange membrane extraction was highest for the soil from the upper slope position and lowest for the soil from the lower slope position, indicating that the amount of ion-exchangeable sulfonylurea was affected by soil properties. Similar trends in degree of root growth inhibition were observed for lentil response to metsulfuron presence in soil; percent root growth inhibition was related to the landscape position as the amount of membrane-extractable metsulfuron. The percent shoot growth inhibition was not soil dependent and did not differ among soils. The efficiency of NaHCO3extraction for metsulfuron did not vary with soil type; in the NaHCO3method, because of the buffered alkaline nature of the extraction, differences in soil properties, particularly soil pH, would have less effect on metsulfuron recovery. Because of similar trends for the results of the membrane extraction method and a lentil root bioassay, anion exchange membrane extraction may provide useful information on bioavailable fractions of sulfonylurea herbicides in soil.
AC 263,222 absorption and fate in leafy spurge (Euphorbia esula)
Authors: Thompson W. Mack , Nissen Scott J. , Masters Robert A.
Published: May 2019

Absorption, translocation, and metabolism of AC 263,222 by leafy spurge were studied over 8 d. Based on the amount of herbicide applied and recovered from the leaf surfaces, 40% of applied AC 263,222 was absorbed by leafy spurge 2 d after treatment (DAT), with no further absorption observed by 8 DAT. Eight DAT, 19% of applied [14C]-AC 263,222 had translocated to below-ground plant parts while 4% was exuded from the roots into the sand media. AC 263,222 was not metabolized 2 DAT in the crown, root, and root buds, but 42% was metabolized in the treated leaves. Only 17% of recovered [14C] was AC 263,222 in treated leaves 8 DAT (83% metabolized), while AC 263,222 accounted for 70% of recovered [14C] in the root and root buds. HPLC analysis indicated that the balance of [14C] was associated with a single, polar metabolite. Total recovery of [14C] was 88% at 8 DAT.
Light effects on rhizome morphogenesis in nutsedges (Cyperusspp.): implications for control by soil solarization
Authors: Chase Carlene A. , Sinclair Thomas R. , Shilling Donn G. , Gilreath James P. , Locascio Salvadore J.
Published: May 2019

Soil solarization is a process of soil disinfestation that involves solar heating of moist soil covered with transparent polyethylene film. This nonchemical approach to controlling soil-borne pests is being investigated as an alternative to methyl bromide fumigation. Summer solarization controlled annual weed species and suppressed purple nutsedge. Although some nutsedge tubers sprouted despite the solarization treatment, the resulting shoots were almost always trapped under the clear solarization film. Conversely, in rows that were mulched with black film, nutsedge rhizomes punctured the film so that leaf expansion occurred above the film. In controlled pot experiments conducted in darkness, yellow nutsedge rhizomes readily penetrated 19- and 30-μm clear films as effectively as opaque films. Thicker clear films and bubble film reduced nutsedge penetration. In the greenhouse and laboratory, nutsedge penetration of transparent polyethylene film was inversely related to irradiance levels when the film was in direct contact with the soil. However, when there was a 5- to 10-mm space between the soil and the film, the lowest irradiance level (30 μmol m−2s−1) was as effective as 320 μmol m−2s−1in reducing penetration by purple nutsedge. The film penetration by nutsedge rhizomes appears to be linked to a light-dependent morphological change from rhizome growth to leaf development, which occurs before film penetration with clear mulch and after film penetration with opaque mulch. The alternate sprouting and foliar scorching of nutsedge shoots trapped under clear films could potentially be exploited to deplete nutsedge tubers that occur at soil depths that do not develop lethal temperatures under soil solarization.