Venturi drift reduction nozzles : spray pattern characteristics, efficacy of postemergence herbicides, and accuracy of herbicide placement

Laboratory and field studies were conducted to evaluate the drift potential and efficacy of commonly used postemergence herbicides applied through venturi-type drift reduction nozzles as compared to a standard flat fan nozzle. Laboratory studies were conducted utilizing a Malvem laser droplet/particle size analyzer to determine the droplet spectra produced by a given nozzle. Spray solutions of glufosinate, glyphosate, and paraquat were applied through all combinations of five nozzle types (four venturi), three tip sizes, and four application pressures. Nozzles were also evaluated for pattern uniformity utilizing water plus surfactant at one pressure. When averaged over herbicide, tip size, and pressure the venturi nozzles collectively produced larger volume median diameter droplets than the standard nozzle. The percent of spray volume in droplets \u3c 205 pm was less for the venturi nozzles (17%) than for the standard nozzle (65%) when averaged across all factors. The order of herbicides producing the largest droplets was paraquat (470 µm) \u3e glyphosate (460 µm) \u3e glufosinate (400 µm), as measured by volume median diameter. The venturi nozzles were more variable in their spray volume distribution than the standard nozzle. Field studies were conducted to compare nozzle effects on the efficacy of postemergence herbicides applied to common cocklebur (Xanthium strumarium) and broadleaf signalgrass (Brachiaria platyphylla). Spray solutions of commercial formulations of glufosinate, glyphosate, and paraquat were applied through all combinations of three nozzles (two venturi) and two application volumes. Nozzle type had the most consistent effect on common cocklebur control. The Delavan Raindrop Ultra venturi nozzle provided the least control (≤ 93%) and least biomass reduction (87%). The Spraying Systems AI Teejet venturi nozzle and the Spraying Systems XR Teejet flat fan nozzle provided similar levels of control (94 to 96%) and biomass reduction (92 and 93%). Nozzle type also affected broadleaf signalgrass control, but herbicide had the most consistent effect. Glyphosate controlled broadleaf signalgrass less (≤ 88%) than either glufosinate or paraquat (92 to 98%). Field studies were conducted to measure nozzle effects on the accuracy of herbicide deposition in a target area and to identify the nozzle parameters responsible for accurate herbicide placement. The Delavan Raindrop Ultra and Spraying Systems AI Teejet venturi nozzles deposited a larger percentage of applied herbicide in the target area than the flat fan nozzle. However, the uniformity of herbicide deposition was similar for the venturi and flat fan nozzles. Increasing application volume increased the uniformity of herbicide deposition in the target area with all nozzles. Correlation analysis indicated that the percentage of spray volume contained in droplets smaller than approximately 200 µm was most important in determining herbicide deposition. Venturi nozzles produce larger droplets which are less susceptible to drift than droplets produced by conventional flat fan nozzles. However, venturi nozzles vary in the size of droplets produced and the level of weed control they provide. Venturi nozzles which produce droplets of approximately 450 µm can provide weed control similar to that provided by a flat fan nozzle, whereas, venturi nozzles which produce 650 µm droplets provide less weed control than a flat fan nozzle. Venturi nozzles can reduce the drift potential of herbicide sprays and, depending on the specific nozzle, can be as effective as flat fan nozzles with a variety of postemergence herbicides. Due to their overall reduction in drift potential of herbicide sprays, venturi nozzles can provide producers with increased flexibility with respect to the timing and location of herbicide applications. Also, utilization of venturi nozzles will allow producers to tailor herbicide application parameters, such as herbicide choice and application volume, to optimize weed control while minimizing drift potential

A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behaviour at eleven polar sites

Insoluble trace gases are trapped in polar ice at the firn-ice transition, at approximately 50 to 100 m below the surface, depending primarily on the site temperature and snow accumulation. Models of trace gas transport in polar firn are used to relate firn air and ice core records of trace gases to their atmospheric history. We propose a new model based on the following contributions. First, the firn air transport model is revised in a poromechanics framework with emphasis on the non-homogeneous properties and the treatment of gravitational settling. We then derive a nonlinear least square multi-gas optimisation scheme to calculate the effective firn diffusivity (automatic diffusivity tuning). The improvements gained by the multi-gas approach are investigated (up to ten gases for a single site are included in the optimisation process). We apply the model to four Arctic (Devon Island, NEEM, North GRIP, Summit) and seven Antarctic (DE08, Berkner Island, Siple Dome, Dronning Maud Land, South Pole, Dome C, Vostok) sites and calculate their respective depth-dependent diffusivity profiles. Among these different sites, a relationship is inferred between the snow accumulation rate and an increasing thickness of the lock-in zone defined from the isotopic composition of molecular nitrogen in firn air (denoted d15N). It is associated with a reduced diffusivity value and an increased ratio of advective to diffusive flux in deep firn, which is particularly important at high accumulation rate sites. This has implications for the understanding of d15N of N2 records in ice cores, in relation with past variations of the snow accumulation rate. As the snow accumulation rate is clearly a primary control on the thickness of the lock-in zone, our new approach that allows for the estimation of the lock-in zone width as a function of accumulation may lead to a better constraint on the age difference between the ice and entrapped gases

Extreme 13C depletion of CCl2F2 in firn air samples from NEEM, Greenland

A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than d13C = -80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near -40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to -120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change is likely to have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological advances in the CFC production process over the last 80 yr, though direct evidence is lacking

Taxonomic history of the iguanian lizard Liolaemus Pictus major Boulenger, with a revalidation of Liolaemus capillitas Hulse

Núñez (2004) examined the syntypes of Liolaemus pictus major Boulenger in the British Museum of Natural History and concluded, without supporting data, that this taxon is a senior synonym of Liolaemus capillitas Hulse. We show that the evidence does not support Núñez’s (2004) proposal. We first document the complex taxonomic history of L. p. major, the lack of a precise or even definitive type locality, and the implications of the latter on subsequent checklists and research. Second, we note differences between Boulenger’s (1885) type description of L. p. major and Hulse’s (1979) type description of L. capillitas. Third, we show that the syntypes of L. p. major photographed by Núñez (2004) do not exhibit the character states of L. capillitas. We conclude that L. capillitas is not a synonym of L. p. major. Based on the available evidence, the syntypes of L. p. major are probably assignable to Liolaemus elongatus from populations occurring in Patagonia (southern Argentina or adjacent Chile). However, the precise identity of the syntypes requires additional study and perhaps a type locality restriction or redefinition of L. elongatus, which is itself in a state of flux.Núñez (2004) examinó los sintipos de Liolaemus pictus major Boulenger en el Museo Británico de Historia Naturale y concluyó, sin datos que lo sostengan, que este taxón es un sinónimo señor de Liolaemus capillitas Hulse. Nosotros mostramos que la evidencia disponible no apoya la propuesta de Núñez (2004). Primero documentamos la compleja historia de L. p. major, la carencia de una localidad tipo o la restricción de una, y las implicancias de esto último en subsecuentes checklists e investigaciones. Segundo, notamos diferencias entre la descripción tipo de Boulenger (1885) de L. p. major y la descripción tipo de L. capillitas de Hulse (1979). Tercero, mostramos que los sintipos de L. p. major fotografiados por Núñez (2004) no exhiben los caracteres presentes en L. capillitas. Concluimos que L. capillitas no es un sinónimo L. p. major. Basados en la evidencia disponible, los sintipos de L. p. major son aparentemente asignables a Liolaemus elongatus de poblaciones que se encuentran en la Patagonia (sur de Argentina o adyacentes en Chile). De todos modos, la identidad precisa de los sintipos requerirá de estudio adicional y quizás la restricción de una localidad o la redefinición de L. elongatus, especie que por sí misma se encuentra pobremente definida.Fil: Espinoza, Robert E.. California State University; Estados UnidosFil: Lobo Gaviola, Fernando Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Bio y Geociencias del Noroeste Argentino; Argentina; Argentina. Universidad Nacional de Salta. Facultad de Cs.naturales. Catedra de Anatomia Comparada; ArgentinaFil: Etheridge, Richard. San Diego State University; Estados Unido

Urban community land trusts in Boston

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1981.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.Includes bibliographical references.by Thelma E. Pittman Etheridge.M.C.P

Clustering, advection and patterns in a model of population dynamics with neighborhood-dependent rates

We introduce a simple model of population dynamics which considers birth and death rates for every individual that depend on the number of particles in its neighborhood. The model shows an inhomogeneous quasistationary pattern with many different clusters of particles. We derive the equation for the macroscopic density of particles, perform a linear stability analysis on it, and show that there is a finite-wavelength instability leading to pattern formation. This is the responsible for the approximate periodicity with which the clusters of particles arrange in the microscopic model. In addition, we consider the population when immersed in a fluid medium and analyze the influence of advection on global properties of the model.Comment: Some typos and some problems with the figures correcte

Winter barley : a new factor in Missouri agriculture

Cover title.Includes bibliographical references

An all-year pasture system for Missouri

Caption title.Digitized 2006 AES MoU

An all-year pasture system for Missouri

Caption title.Digitized 2006 AES MoU

Domestic ventilation rates, indoor humidity and dust mite allergens : are our homes causing the asthma pandemic?

This paper is concerned with historical changes in domestic ventilation rates, relative humidity and the associated risk of house dust mite colonization. A controlled trial evaluated allergen and water vapour control measures on the level of house dust mite (HDM) Der p1 allergen and indoor humidity, concurrently with changes in lung function in 54 subjects who completed the protocol. Mechanical heat recovery ventilation units significantly reduced moisture content in the active group, while HDM allergen reservoirs in carpets and beds were reduced by circa 96%. Self reported health status confirmed a significant clinical improvement in the active group. The study can form the basis for assessing minimum winter ventilation rates that can suppress RH below the critical ambient equilibrium humidity of 60% and thus inhibit dust mite colonization and activity in temperate and maritime in' uenced climatic regions