Public concern regarding the use of herbicides in urban areas (e.g., golf courses, parks, lawns) is increasing. Thus, there is a need for alternative methods for weed control that are safe for the public, effective against weeds, and yet selective to turfgrass and other desirable species. New molecular tools such as ribonucleic acid interference (RNAi) have the potential to meet all those requirements, but before these technologies can be implemented, it is critical to understand the perceptions of key stakeholders to facilitate adoption as well as regulatory processes. With this in mind, turfgrass system managers, such as golf course superintendents and lawn care providers, were surveyed to gain insight into the perception and potential adoption of RNAi technology for weed management. Based on survey results, turfgrass managers believe that cost of weed management and time spent managing weeds are the main challenges faced in their fields. When considering new weed management tools, survey respondents were most concerned about cost, efficacy, and efficiency of a new product. Survey respondents were also optimistic toward RNAi for weed management and would either use this technology in their own fields or be willing to conduct research to develop RNAi herbicides. Although respondents believed that the general public would have some concerns about this technology, they did not believe this to be the most important factor for them when choosing new weed management tools. The need for new herbicides to balance weed control challenges and public demands is a central factor for turfgrass managers’ willingness to use RNAi-based weed control in turfgrass systems. They believe their clientele will be accepting of RNAi tools, although further research is needed to investigate how a wider range of stakeholders perceive RNAi tools for turfgrass management more broadly.

Competition between genotypes within a plant population can result in the displacement of the least competitive by more competitive genotypes. Although evolutionary processes in plants may occur over thousands and millions of years, it has been suggested that changes in key fitness traits could occur in as little as decades, with herbicide resistance being a common example. However, the rapid evolution of complex traits has not been proven in weeds. We hypothesized that changes in weed growth and competitive ability can occur in just a few years because of selection in agroecosystems. Seed of multiple generations of a single natural population of the grassy weed giant foxtail (Setaria faberi Herrm.) were collected during 34 yr (i.e., 1983 to 2017). Using a “resurrection” approach, we characterized life-history traits of the different year-lines under noncompetitive and competitive conditions. Replacement-series experiments comparing the growth of the oldest year-line (1983) versus newer year-lines (1991, 1996, 1998, 2009, and 2017) showed that plant competitive ability decreased and then increased progressively in accordance with oscillating selection. The adaptations in competitive ability were reflected in dynamic changes in leaf area and biomass when plants were in competition. The onset of increased competitive ability coincided with the introduction of herbicide-resistant crops in the landscape in 1996. We also conducted a genome-wide association study and identified four loci that were associated with increased competitive ability over time, confirming that this trait changed in response to directional selection. Putative transcription factors and cell wall–associated enzymes were linked to those loci. This is the first study providing direct in situ evidence of rapid directional evolution of competitive ability in a plant species. The results suggest that agricultural systems can exert enough pressure to cause evolutionary adaptations of complex life-history traits, potentially increasing weediness and invasiveness.

High crop densities are valuable to increase weed suppression, but growers might be reluctant to implement this practice due to increased seed cost. Because it is also possible to lower planting densities in areas with no or low weed interference risk, the area allocated to each planting density must be optimized considering seed cost and productivity per plant. In this study, the growth and yield of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] were characterized in response to low planting densities and arrangements. The results were used to develop a bioeconomic model to optimize the area devoted to high- and low-density plantings to increase weed suppression without increasing seed cost. Physiological differences seen in each crop varied with the densities tested; however, maize was the only crop that had differences in yield (per area) between densities. When a model to optimize low and high planting densities was used, maize and cotton showed the most plasticity in yield per planted seed (g seed−1) and area of low density to compensate for high-density area unit. Maize grown at 75% planting density compared with the high-planting density (200%) increased yield (g seed−1) by 229%, return by 43%, and profit by 79% while decreasing the low-density area needed to compensate for high-density area. Cotton planted at 25% planting density compared with the 200% planting density increased yield (g seed−1) by 1,099%, return by 46%, and profit by 62% while decreasing the low-density area needed to compensate for high-density area. In contrast, the high morphological plasticity of soybean did not translate into changes in area optimization, as soybean maintained return, profit, and a 1:1 ratio for area compensation. This optimization model could allow for the use of variable planting at large scales to increase weed suppression while minimizing costs to producers.

Castration of male piglets in the United States is conducted without analgesics because no Food and Drug Administration (FDA) approved products are labeled for pain control in swine. The absence of approved products is primarily due to a wide variation in how pain is measured in suckling piglets and the lack of validated pain-specific outcomes individually indistinct from other biological responses, such as general stress or inflammation responses with cortisol. Simply put, to measure pain mitigation, measurement of pain must be specific, quantifiable, and defined. Therefore, given the need for mitigating castration pain, a consortium of researchers, veterinarians, industry, and regulatory agencies was formed to identify potential animal-based outcomes and develop a methodology, based on the known scientific research, to measure pain and the efficacy of mitigation strategies. The outcome-based measures included physiological, neuroendocrine, behavioral, and production parameters. Ultimately, this consortium aims to provide a validated multimodal methodology to demonstrate analgesic drug efficacy for piglet castration.

Measurable outcomes were selected based on published studies suggesting their validity, reliability, and sensitivity for the direct or indirect measurement of pain associated with surgical castration in piglets. Outcomes to be considered are observation of pain behaviors (i.e. ethogram defined behaviors and piglet grimace scale), gait parameters measured with a pressure mat, infrared thermography of skin temperature of the cranium and periphery of the eye, and blood biomarkers. Other measures include body weight and mortality rate.

This standardized measurement of the outcome variable's primary goal is to facilitate consistency and rigor by developing a research methodology utilizing endpoints that are well-defined and reliably measure pain in piglets. The resulting methodology will facilitate and guide the evaluation of the effectiveness of comprehensive analgesic interventions for 3- to 5-day-old piglets following surgical castration.

Respiratory distress syndrome results from inadequate functional pulmonary surfactant and is a significant cause of mortality in preterm infants. Surfactant is essential for regulating alveolar interfacial surface tension, and its synthesis by Type II alveolar epithelial cells is stimulated by leptin produced by pulmonary lipofibroblasts upon activation by peroxisome proliferator-activated receptor γ (PPARγ). As it is unknown whether PPARγ stimulation or direct leptin administration can stimulate surfactant synthesis before birth, we examined the effect of continuous fetal administration of either the PPARγ agonist, rosiglitazone (RGZ; Study 1) or leptin (Study 2) on surfactant protein maturation in the late gestation fetal sheep lung. We measured mRNA expression of genes involved in surfactant maturation and showed that RGZ treatment reduced mRNA expression of LPCAT1 (surfactant phospholipid synthesis) and LAMP3 (marker for lamellar bodies), but did not alter mRNA expression of PPARγ, surfactant proteins (SFTP-A, -B, -C, and -D), PCYT1A (surfactant phospholipid synthesis), ABCA3 (phospholipid transportation), or the PPARγ target genes SPHK-1 and PAI-1. Leptin infusion significantly increased the expression of PPARγ and IGF2 and decreased the expression of SFTP-B. However, mRNA expression of the majority of genes involved in surfactant synthesis was not affected. These results suggest a potential decreased capacity for surfactant phospholipid and protein production in the fetal lung after RGZ and leptin administration, respectively. Therefore, targeting PPARγ may not be a feasible mechanistic approach to promote lung maturation.

Soil and surface residues from cotton field studies in Stoneville, MS (1994 through 1996) and Florence, SC (1995 through 1996) were sampled to evaluate effects of cover crop and tillage on herbicide dissipation. Mississippi treatments included tillage (conventional [CT]; none [NT]) and cover crop (ryegrass; none [NC]). South Carolina treatments included tillage (CT; reduced tillage [RT]) and cover crop (rye; NC). Fluometuron was applied preemergence (PRE) in both Mississippi and South Carolina, and norflurazon was applied PRE in Mississippi. Soils were sampled various times during the growing season (depths: 0 to 2 cm, 2 to 10 cm). Cover crop residues were sampled from RT or NT cover crop areas. Soil and cover crop sample extracts were analyzed for herbicides. Soil organic carbon tended to increase with tillage reduction and presence of cover crop and was positively correlated with herbicide sorption, especially in the surface. Across locations, herbicide half-lives ranged from 7 to 15 d in the soil surface. Tillage had mixed effects on herbicide persistence in surface soil, with higher herbicide concentrations in CT at early samplings, but differences were insignificant later on. The most consistent effects were observed in RT/NT with cover crops, where cover crop residues intercepted applied herbicide, impeding subsequent movement into soil. Herbicide dissipation in cover crop residues was often more rapid than in soil, with half-lives from 3 to 11 d. Herbicide retention in cover crop residues and rapid dissipation were attributed to strong herbicide affinity to cover crop residues (e.g., fluometuron Kd = 7.1 [in rye]; Kd = 1.65 [in Mississippi Dundee soil CT, NC]) and herbicide co-metabolism as cover crop residues decomposed. A fluometuron metabolite, desmethyl-fluometuron, was observed in most soil and cover crop samples after 1 wk. Only minimal herbicide or metabolite moved into the subsurface, and little treatment effect could be ascribed to herbicide or metabolite movement below 2 cm.

Western ragweed is problematic in Oklahoma pasture and rangeland. There are no labeled PRE herbicides for western ragweed control in pastures to allow ranchers the flexibility of extending the spray season or the ability to spray before emergence of sensitive crops in bordering fields. Field studies were conducted in four locations during a 2-yr period to determine the effects of applying aminopyralid PRE for control of western ragweed. Good to excellent control of western ragweed was obtained when aminopyralid rates of 89 g ae ha−1 or greater were applied PRE. Control was season long and equal to that obtained with a formulated mixture of 2,4-D and aminopyralid applied POST at a rate of 457 + 57 g ae ha−1. Sward height at time of PRE application had little to no effect on the efficacy of the treatment, but time after application before a significant rainfall event did influence the aminopyralid rate needed to achieve acceptable PRE control.

The late Pleistocene Big Timber glacier of west-central Montana was used as the test case for a model which calculates the mass balance of a paleoglacier using glacial flow theory. Application of Glen’s flow law to a detailed reconstruction of the glacier provided an estimate of the component of mass flux due to internal deformation. Assuming basal slip to be zero where mass flux due to deformation was a maximum, the mass flux at the equilibrium-line altitude (ELA) an ablation gradient of 3.0 ± 0.6 mm/m, and an accumulation gradient of 1.0 ± 0.2 mm/m were determined. Application of the continuity model above and below the ELA generated a second estimate of mass flux at discrete points along the glacier. The difference between deformation flux and continuity flux yields a first approximation of slip, which is highly variable along the glacier. Since the mass-balance gradients are climatically controlled, this model provides information on the paleoclimatic setting of the glacier. The low gradients indicate that, during the last glacial maximum, the east side of the central Rocky Mountains experienced a cold, dry environment much like that of modern-day glaciers in the Brooks Range of Alaska.

Luminescent paints allow non-intrusive measurement of pressure and temperature at high spatial resolution without prior knowledge of the flow-field. Experiments have demonstrated that a ‘standard’ luminescent paint technique, developed by BAE Systems, can simultaneously measure steady pressure and temperature. This is achieved through knowledge of the paint phosphorescence lifetime rather than the absolute intensity, which increases the measurement accuracy. In addition, a new ‘fast’ paint has been calibrated at the University of Bath for the measurement of unsteady pressure using a variable frequency pulsing air jet. Pressure measurements were made with both paints in the wake of various excrescences, sized to produce vortex shedding in the frequency range 500–4,200Hz, in a transonic tunnel. The extent of the wakes was determined from a flow visualisation technique. Time-averaged measurements, using both luminescent paints, and transient measurements of the unsteady pressure field, made with the fast paint, were compared with transducer data. For all cases the luminescent paint data compared well with the conventional measurements and the Strouhal number agreed well with data from the literature. The use of luminescent paint for the simultaneous measurement of pressure and temperature over a NACA 0012 aerofoil, as well as the quantification of convective heat transfer is examined in Part 2.

The idea of sweeping the wings of an aeroplane in order to delay or reduce the transonic drag rise is of course an old one, dating from at least 20 years ago. At subsonic speeds the art of swept wing design is now highly developed, largely due to research at the RAE under Küchemann on the three-dimensional aspects of the subject, and at the NPL, notably by Pearcey and Holder, on two-dimensional section design. It was soon realised that, at least in principle, the same ideas could be carried over some way into the supersonic speed range—how far still remains to be seen.

A review is given of current methods in theoretical aerodynamics which are useful in the design of aircraft wings for subsonic and transonic speeds. These are of two basic types:

• (A) direct methods for calculating the flow over a givenwing shape. In the design process, these can be used to obtain a rapid estimate of the effect of a specified change in wing shape. The most practical methods of this type make use of the viscous/inviscid interaction technique; some recent methods are described and examples are given of their use, both in two and three dimensions, including comparisons with experiment.

• (B) inverse methods in which the shape is calculated explicitly, as a result of either (a) specifying the surface pressure distribution on the wing, or (b) requiring that some suitable ‘target’ function, usually the drag/lift ratio, shall be a minimum.At present, these methods are restricted to inviscid flow.

Several examples of both ‘pressure’ and ‘optimisation’ methods are discussed, and their advantages and limitations considered.

Research is in progress to assess, and if possible improve, the accuracy of a widely-used method for calculating the pressure distribution on swept wings in subsonic attached (inviscid) flow. Ref. 1 does not make specific recommendations on how to deal with wings having “cranked” planforms (i.e. wings with discontinuous changes in the sweep angle of the leading or trailing edges, other than at the central “kink” fundamental to the swept wing concept); but it implies (section 8.3) that the method of ref. 2 could be used for this purpose. A re-examination of this problem, in connection with the programme of work of the Transonic Aerodynamics Committee of the Royal Aeronautical Society, has revealed errors, which could be seriously misleading, in that part of ref. 2 dealing with the thickness effect. The object of the present note is to present the corrected formulae for the basic streamwise and span-wise components of perturbation velocity due to the thickness, at and near the crank, in the simplified example consisting of two semi-infinite wing panels of different sweep angles joined together; to examine the possible singularities in the flow field in the neighbourhood of the crank; and finally to discuss qualitatively the implications of these formulae on the magnitude of the “crank effect”, including the influence of free-stream Mach number.

A heat transfer measurement technique has been developed, which utilised a laser to heat a spot of the ‘standard’ luminescent paint on an insulated metal wind tunnel model. The convective heat transfer coefficient was determined from the experimental quasi steady-state surface temperature, and solutions obtained from radial and axial conduction in a numerical heat transfer model. The convective heat transfer coefficient variation over both a flat plate and a NACA 0012 aerofoil have been measured in transonic flow. Measurements obtained from the flat plate were seen to agree well with correlation data from the literature. Measurements on the NACA 0012 aerofoil indicated the point of transition from laminar to turbulent boundary layer as well as the location of shock boundary layer interaction. The luminescent paint provided simultaneous measurements of pressure and temperature (see Part 1). The distribution of pressure over the NACA 0012 aerofoil was shown to be in excellent agreement with conventional transducer data, although the luminescent paint data provided greater spatial resolution. The position of the shock determined from the heat transfer measurements was shown to be in excellent agreement with the pressure measurements.

A method for providing lateral control at supersonic speeds by means of control surfaces located on nacelles or on the fuselage is described. These surfaces are arranged so that they affect the pressures over adjacent wings, and hence produce a rolling moment. The note includes the results of calculations and of a limited number of measurements which enable the effectiveness of such controls to be estimated.

After a brief discussion of alternative ways in which the drag of an aircraft wing can be derived theoretically, attention is focused on a technique whereby the separate ‘far-field’ components of drag — viscous, trailing-vortex (induced) and wave — are calculated separately. In particular, a new approximate method is described for estimating the wave drag. Based on an exact two-dimensional analysis involving the flow conditions just upstream of the shock wave, a simple formula is derived which, to first order, involves only a knowledge of the Mach number distribution on the surface of the aerofoil ahead of the shock and of the surface geometry at its foot. The accuracy of this formula is assessed for aerofoils by comparison with more exact theoretical results and with experiment. A ‘strip theory’ extension to swept wings is proposed and illustrated by applying it to a particular transport-type wing body combination. Using experimental pressure measurements as input, all three components of drag are estimated theoretically, and by adding their sum to separate balance measurements of the body drag comparisons between ‘theory’ and experiment for the overall drag can be made. These show a satisfactory standard of accuracy, the error varying between —5% and — 1% of the total drag over a wide range of Mach number and lift coefficient.