Integrated weed management practices that reduce selection for resistance on herbicides are critical to delay resistance. To quantify the reduction in selection for resistance placed on Palmer amaranth from 2,4-D applied postemergence in cotton, an experiment was conducted three times in Georgia during 2020 and 2021 evaluating the benefits of (i) a cover crop, (ii) preemergence herbicides, and (iii) timeliness of applications. When a timely total-postemergence program of glyphosate + 2,4-D was applied three times over the season in a conventionally tilled system, 281,690 glyphosate-resistant Palmer amaranth plants ha–1 were exposed to 2,4-D. Over 61,500 of these plants were exposed to multiple 2,4-D applications. Altering the production system to conservation tillage, and including a rolled-rye cover crop, reduced the total number of plants exposed to 2,4-D for the season by 72% and the number of plants exposed multiple times by 60%. Even more effective, including a mixture of residual preemergence herbicides reduced the number of plants exposed to 2,4-D at least once over 99.9%, and reduced multiple exposures over 99.3% for the season; this benefit was observed for both conventional and conservation tillage systems. Delaying the initial application of the total-postemergence program did not influence the number of Palmer amaranth plants treated at least once but increased the number of plants treated multiple times by a factor of 3.7 times. As a result of early-season weed competition, cotton height and yield reductions were also associated with both lack of preemergence residuals and delayed postemergence applications. When considering the goal of minimizing the number of Palmer amaranth treated with a postemergence application of 2,4-D in a cotton system, the preemergence was the most effective option followed by (fb) the cover crop fb making timely postemergence applications. However, the most effective approach was to utilize each of these tactics in the same growing season.

Cover crops are increasingly being included in crop rotations as a mechanism to promote diversity and provide agroecosystem services, including weed suppression. Recently, cover crop mixtures have increased in popularity in an attempt to provide a greater diversity in ecological services as compared with monocultures. Several recent studies, however, have failed to detect a positive effect of cover crop diversity on biomass production or weed suppression. Here we assessed biomass productivity and weed suppression in 19 cover crops seeded as monocultures and 19 mixtures of varying species composition and functional richness (two- and three-species mixtures) of full-season cover crops in Atlantic Canada. Cover crop biomass production and weed suppression varied by species identity, functional diversity, and species richness. As cover crop biomass increased regardless of diversity, weed biomass declined. Highly productive forbs and grasses provided the greatest weed suppression in monoculture. In line with previous observations, mixtures were not more productive or weed suppressive on average than the most productive monocultures. We observed that the inclusion of the highly productive species buckwheat (Fagopyrum esculentum Moench) and sorghum–sudangrass [Sorghum × drummondi (Nees ex Steud.) Millsp. & Chase] in a mixture increased stand evenness, productivity, weed suppression, and spatiotemporal stability. Taken together, our results suggest that effects of diversity on mixture productivity and weed suppression are species specific. This further demonstrates the importance of species selection in cover crop mixture design.

A field study was conducted in 2017 and 2018 at the Louisiana State University Agricultural Center H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha−1. Control of barnyardgrass, red rice, and two non-acetyl-CoA carboxylase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all mixtures containing halosulfuron and halosulfuron plus thifensulfuron resulted in antagonism with an observed control of 79% to 90%, compared with an expected control of 96% to 99%. At 28 DAT, all mixtures containing halosulfuron resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

Few options are available for controlling bermudagrass invasion of seashore paspalum. Bermudagrass and seashore paspalum tolerance to topramezone, triclopyr, or the combination of these two herbicides were evaluated in both greenhouse and field conditions. Field treatments included two sequential applications of topramezone (15.6 g ai ha−1) alone and five rates of topramezone + triclopyr (15.6 + 43.2, 15.6 + 86.3, 15.6 + 172.6, 15.6 + 345.2, or 15.6 g ai ha−1 + 690.4 g ae ha−1). Secondary greenhouse treatments included a single application of topramezone (20.8 g ha−1) or triclopyr (258.9 g ha−1) alone, or in combination at 20.8 + 258.9 or 20.8 + 517.8 g ha−1, respectively. Greenhouse and field results showed that topramezone applications in combination with triclopyr present opposite responses between bermudagrass and seashore paspalum. Topramezone increased bermudagrass injury and decreased seashore paspalum bleaching injury compared to topramezone alone. In field evaluations, topramezone + triclopyr at 15.6 + 690.4 g ha−1 used in sequential applications resulted in >90% injury to bermudagrass, however, injury decreased over time. Furthermore, sequential applications of topramezone + triclopyr at 15.6 + 690.4 g ha−1 resulted in >50% injury to seashore paspalum. Application programs including topramezone plus triclopyr should increase bermudagrass suppression and reduce seashore paspalum injury compared to topramezone alone. However, additional studies are needed because such practices will likely require manipulation of topramezone rate, application timing, application interval, and number of applications in order to maximize bermudagrass control and minimize seashore paspalum injury.

A field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station near Crowley, Louisiana, to evaluate the interactions of quizalofop and a mixture of propanil plus thiobencarb applied sequentially or mixed to control weedy rice and barnyardgrass. Visual weed control evaluations occurred at 14, 28, and 42 d after treatment (DAT). Quizalofop was applied at 120 g ai ha−1 at 7, 3, and 1 d before and after propanil plus thiobencarb were each applied at 3,360 g ai ha−1. In addition, quizalofop was applied alone and in a mixture with propanil plus thiobencarb at day 0. Control of red rice ‘CL-111’ and ‘CLXL-745’ was greater than 91% when quizalofop was applied alone at day 0, similar to control for quizalofop applied 7, 3, and 1 d prior to propanil plus thiobencarb at all evaluation dates. Control of the same weeds treated with quizalofop plus propanil plus thiobencarb applied in a mixture at day 0 was 70% to 76% at each evaluation date, similar to quizalofop applied 1 or 3 d after propanil plus thiobencarb. A similar trend in control of barnyardgrass by 88% to 97% occurred when quizalofop was applied alone and by 48% to 53% at 14, 28, and 42 DAT when the mixture was used. ‘PVL01’ rough rice yield was 4,060 kg ha−1 when treated with quizalofop alone; however, yield was reduced to 3,180 kg ha−1 when it was treated with quizalofop mixed with propanil plus thiobencarb at day 0, similar to PVL01 rice treated with quizalofop 1 or 3 d following the propanil plus thiobencarb application.

This study investigated the effect of production and curing parameters on the mechanical performance of compressed earth blocks (CEBs) stabilized with 0-20 wt % CCR (calcium carbide residue). Kaolinite (K) and quartz (Q)-rich earthen materials were mixed with the CCR and used to mould CEBs at optimum moisture content (OMC) and OMC+2 % of the dry mixtures, cured at 20 °C, ambient temperature in the lab (30±5 °C) and 40 °C for 0-90 days. After curing, the reactivity of the materials and compressive strength of dry CEBs were tested. Increasing the moulding moisture from OMC to OMC+2 decreased the compressive strength 0.3 times (4.4 to 3.3 MPa) for the CEBs stabilized with 20 % CCR cured at 30±5 °C for 45 days. Similarly, the compressive strength (4.4 MPa) was reached by CEBs stabilized with 10 and 20 % CCR after 28 and 45 days of curing, respectively. At 40 °C, the compressive strength increased 3.3 times (1.1 to 4.7 MPa with 0 to 20 % CCR) for K-rich and 2.5 times (2 to 7.1 MPa) for Q˗rich materials. At 20 °C, the compressive strength increased only 1.3 times (1.1 to 2.5 MPa) for K˗rich and barely 0.7 times (2 to 3.4 MPa) for Q-rich materials. These suggest that CCR is useful for stabilization and improving the performances of CEBs in hot regions.

A field study was conducted in 2015 and 2016 near Crowley, LA, to evaluate antagonistic, synergistic, or neutral interactions of quizalofop when mixed with contact herbicides labeled for use in rice production. Quizalofop was applied at 120 g ai ha−1. Mixture herbicides included bentazon at 1,050 g ai ha−1, carfentrazone at 18 g ai ha−1, propanil at 3,360 g ai ha−1, saflufenacil at 25 g ai ha−1, and thiobencarb at 3,360 g ai ha−1. A second application of quizalofop at 120 g ha−1 was made at 28 d after the initial application (DAIT) to evaluate control of weeds escaping the initial treatment. At 14 and 28 DAIT, red rice, ‘CLXL-745’, and ‘CL-111’ treated with quizalofop plus propanil indicated an antagonistic response with an observed control of 69% to 71% compared with an expected control of 92% to 94%. Barnyardgrass treated with the same mixture also indicated an antagonistic response at 14 and 28 DAIT with an observed control of 16% compared with an expected control of 94%. Barnyardgrass treated with quizalofop plus saflufenacil indicated an antagonistic response at 14 DAIT; however, the same mixture produced a neutral response by 28 DAIT. In addition, a second application of quizalofop was not able to overcome the antagonism observed with a quizalofop plus propanil mixture at 14 and 28 DAIT for red rice, CLXL-745, CL-111, or barnyardgrass control. Quizalofop mixed with carfentrazone or thiobencarb produced a neutral response for all weeds evaluated at each evaluation date.

Field and greenhouse studies were conducted to evaluate the antagonism potential of glufosinate applied sequentially or mixed with graminicides on barnyardgrass control. Applications of glufosinate alone provided variable control throughout the growing season in both field and greenhouse experiments. In the field, barnyardgrass control was not adversely affected by glufosinate- and clethodim-mix applications or sequential applications of glufosinate before or after clethodim. Soybean yield was not affected by application timing or clethodim rate, with yield ranging from 1,748 to 2,733 kg ha−1. In the greenhouse, glufosinate applied 1 and 3 d before graminicides generally reduced barnyardgrass control compared with the graminicides applied alone. The response with quizalofop-P was not as dramatic as with the other graminicides. Although significant visual barnyardgrass control differences were detected due to application timing of glufosinate, barnyardgrass biomass with fluazifop-P and quizalofop-P did not differ between the application timings of glufosinate. However, glufosinate applied 1 and 3 d before clethodim had significantly greater biomass compared with glufosinate applied 1 and 3 d after clethodim. The differences in environmental conditions and growth stages at the time of application may have contributed to barnyardgrass control response differences between the field and greenhouse experiments. Although barnyardgrass control in the field was not affected by glufosinate application timing, data from the greenhouse indicate potential exists for reduced control if glufosinate is applied 1 or 3 d before graminicides.

Conductive composites are being considered for use in applications such as electromagnetic shielding. Prior work has shown correlation of electrical conductivity to the microstructure of corresponding composite. In the present paper, composites consisting of polyurethane acrylic and dispersed nickel nanoparticles were fabricated, and tested for their electrical conductivity. In the fabrication process, half of the suspensions were agitated by sonication and half were not. Correlations between electrical conductivity and composite microstructural details are presented. These correlations show an optimum concentration of nickel nanoparticles that result in maximum conductivity enhancement. In addition, sonicating the suspensions increased conductivity of resulting nanocomposites. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) images were used to estimate surface concentration and distribution of Nickel nanoparticles, and were correlated to electrical conductivity measurements. Parameters such as number of particles in contact and junction distance between the nano particles in the composites are suggested as a way of enhancing electrical conductivity.

A field study was conducted in 2015 and 2016 at the H. Rouse Caffey Rice Research Station (RRS) to evaluate antagonistic, synergistic, or neutral interactions of quizalofop when mixed with ALS-inhibiting herbicides labeled in rice production. Quizalofop was applied at 120 g ai ha−1. Mixture herbicides included penoxsulam at 40 g ai ha−1, penoxsulam+triclopyr at 352 g ai ha−1, halosulfuron at 53 g ai ha−1, bispyribac at 34 g ai ha−1, orthosulfamuron+halosulfuron at 94 g ai ha−1, orthosulfamuron+quinclorac at 491 g ai ha−1, imazosulfuron at 211 g ai ha−1, and bensulfuron at 43 g ai ha−1. All ALS herbicides mixed with quizalofop indicated antagonistic responses for red rice, CL-111, CLXL 745, or barnyardgrass control at either 14 or 28 days after treatment (DAT). At 28 DAT, quizalofop mixed with penoxsulam or bispyribac controlled barnyardgrass 34 to 38%, compared with an expected control of 97%. In addition, these same mixtures controlled red rice, CL-111, and CLXL-745 61 to 67% at 28 DAT compared with an expected control of 96 to 97%. A second application of quizalofop at 120 g ha−1 was applied at 28 DAT. At 42 DAT, neutral responses were indicated for all mixtures except with quizalofop mixed with penoxsulam containing products.

Earth stabilization, using two by-products available in Burkina Faso: Calcium Carbide Residue (CCR) and Rice Husk Ash (RHA), improved the performance of compressed earth blocks (CEBs). The effect of adding CCR or CCR: RHA (in various ratios) to the clayey earth was investigated. CEBs were molded by manually compressing moisturized mixtures of earthen materials and 0-15 % CCR or CCR: RHA (various ratios) with respect to the weight of earthen material. The results showed that, with 15 % CCR: RHA in 7: 3 ratio, the compressive strength of CEBs (6.6 MPa) is three times that of the CEBs containing 15 % CCR alone (2.2 MPa). This improvement was related to the pozzolanic reaction between CCR, clay and RHA. These CEBs comply with the requirement for wall construction of two-storey housing.

We elucidate the long-term behavior of failure rates for a broad class of frailty models in survival analysis. The class properly includes the proportional hazard frailty model, the additive frailty model, and the accelerated failure time frailty model. A complete asymptotic expansion is derived and compared with the corresponding result for the limiting behavior obtained by Finkelstein and Esaulova (2006a). Several examples are provided to facilitate the comparison and to illustrate both the applicability and the limitations of our approach.

In situ and ex situ neutron reflectivity is used to characterize annealed regioregular-P3HT/PCBM bilayers. In situ annealing of a 20 nm PCBM/35 nm P3HT bilayer at 170 °C reveals rapid mixing of PCBM and P3HT to produce a polymer-rich layer that contains around 18–20% PCBM. Samples with three different thicknesses of P3HT layer are ex situ annealed at 140 °C. This again reveals migration of PCBM into the P3HT and vice versa, with the polymer-rich layer in the 20 nm PCBM/35 nm P3HT sample containing 19% PCBM. Complete migration of the entire PCBM layer into the P3HT layer is observed for a 20 nm PCBM/80 nm P3HT bilayer. The robustness of fitted model composition profiles, in comparison with real-space imaging of sample surface morphology and previous work on annealed P3HT/PCBM bilayer compositions, is discussed in detail.

We discuss recent literature data on the relaxation times (the primary tα), viscosity, and self-diffusion in water-glycerol and water-methanol mixtures across a wide temperature range from the stable water phase to the deep supercooled regime (373–147K). In particular, to clarify the role of hydrophilicity interactions (the hydrogen bonds) and hydrophobic interactions we study the mixture in terms of the water molar fraction (XW) with fixed temperatures at 5K steps across the entire composition range, and we find a marked deviation from the ideal thermodynamic behavior of the transport functions. This deviation is strongly T and XW dependent and spans values that range from two orders of magnitude at the highest temperature to more than five in the deeply supercooled regime (more precisely, at ≃200K). We analyze these deviations in terms of how the measured values differ from ideal values and find that the hydrogen-bonding water network dominates system properties up to XW = 0.3. We also examine an Arrhenius plot of the maximum excess value (Δtα(T) vs. 1/T) and find two significant changes due to water: one at the dynamical crossover temperature (TL ≃ 225K, i.e., the locus of the Widom line), and one at T ≃ 315K (the water isothermal compressibility χT minimum).