Generation Of Uniform Droplets Research Articles

Microdroplet application for determination of comparative topical and residual efficacy of formulated permethrin to two populations of diamond back moth (plutella xylostella L.)

AbstractAn on‐demand, uniform droplet generator was used to apply 120 μm diameter drops of formulated permethrin either directly onto 3rd‐instar Plutella xylostella, of two Ohio populations, or onto the abaxial surface of leaf discs (1‐1000 drops cm−2) to which those larvae were subsequently exposed. Incorporating a fluorescent tracer (Saturn Yellow GT‐17N) in the spray mixture confirmed that „direct hit”︁ larvae had received a topical dose from a single droplet. There was little difference in the LC50/LD50 for either population of P. xylostella when 24 and 48 h mortality assessments from direct hits were compared, but the LD50 of Celeryville larvae was 6‐8 times greater than that of Fremont larvae. Residual deposits of 120 μm drops containing approximately the LC50, based on the topical assays, revealed that a droplet density providing a dose per cm2 leaf surface of more than 1000 times the LD50 was required to cause median mortality. The efficiency of utilisation, based on the topical LD95 values, was 0.0006% and 0.072% for Fremont and Celeryville larvae, respectively.

Influence of bifenthrin spray deposit quality on the mortality of Trichoplusia ni (Lepidoptera: Noctuidae) on cabbage

A uniform droplet generator was used to apply precise deposits of aqueous bifenthrin to the abaxial surface of cabbage leaf sections. These deposits were defined in terms of droplet size, droplet density (drops/cm 2), concentration of active ingredient (a.i.) and quantity of a.i./cm 2. Three droplet sizes (60 μm, 90 μm and 120 μm in-flight diameter) were examined at bifenthrin concentrations between 0·0075 and 7·5 g a.i./l. Cabbage looper ( Trichoplusia ni Hübner) first-instar larvae were exposed to the dried deposit and, 24 h later, mortality and the location of the larvae were recorded. Significant reductions ( P < 0·01) in dose/cm 2 for median mortality (LQ 50) were associated with decreasing concentration. At each concentration, doubling the droplet diameter, from 60 μm to 120 μm, also doubled the LQ 50. The insecticide utilization efficiency extremes were represented by 60 μm drops at 0·0075 g a.i./l where 0·3 ng/cm 2 (374 drops/cm 2) caused 50% mortality, compared with 15·8 ng/cm 2 in two drops, 120 μm diameter, containing 7·5 g a.i./l.

Morphological Investigation of Solute Particles Trapped from an Air-Acetylene Flame

A uniform-droplet generator has been employed to produce individual desolvated KCl particles in a laminar air-acetylene flame. The resulting particles were collected on various surfaces and at different points in their vaporization history. Morphological studies were then conducted on the trapped particles in order to better characterize the structural changes which occur during desolvation and vaporization. Particles collected early in their vaporization exhibited strong crystalline structure characteristic of KCl, whereas particles gathered later in their volatilization history showed evidence of fusion and, in some cases, the formation of hollow spheres. In addition to the morphological studies, the various collection surfaces and the collection technique itself were assessed. Direct collection on scanning-electron microscopy specimen stubs was judged to be best.

Effect of droplet size on the phosphine depression of calcium atomic emission signals in flame spectrometry

The effect of the droplet size on the magnitude of the phosphine depression of calcium signals is discussed. The droplet size governs the time required for droplet desolvation in the flame. It is during the desolvation process that the combustion products of phosphine, PO x , diffuse into the droplet and form a refractory compound with the analyte. The longer the desolvating droplet resides in the PO x -contaminated flame, the more severe the depression. A uniform droplet generator, a pneumatic nebulizer spray chamber system, and a glass-frit nebulizer spray chamber system were the sample introduction systems studied. Droplet sizes of (55 μm, 0.5–10 μm (2 μm mean), and <0.1–2 μm (0.1 μm mean) were produced by these systems, respectively, and depressions of the calcium signals of 57%, 55%, and 4% were noted. These results suggest that the phosphine depression on calcium signals may be alleviated by using a glass-frit nebulizer (or modifying a commercial nebulizer) to remove droplets greater than 2 μm in diameter.

Phosphine depression of calcium in flame atomic emission spectrometry with a uniform droplet generator

Phosphine depression of calcium in flame atomic emission spectrometry with a uniform droplet generator

Enhancement of titanium, zirconium, and uranium flame spectrometric signals by aluminum and explosive fragmentation of solute particles

In a nitrous oxide-acetylene flame, the atomic absorption signals for Ti, Zr, and U were enhanced 100, 200, and 400%, respectively, when 800 ..mu..g of Al was added per milliliter of solution. Parameters affecting the extent of the Al enhancement of Ti were investigated and optimum analysis conditions were determined. The dependence of the Ti enhancement on the Al/Ti molar ratio indicated a possible stoichiometric reaction. Emission due to TiO was also enhanced to a similar extent by Al, indicating that the mechanism of enhancement was not a simple competition for oxygen in the flame. By use of a uniform droplet generator, explosive fragmentation of solute particles was observed for Ti, Zr, and U when Al was added but not for Al or the other elements alone. By greatly increasing the solute particle surface area, making vaporization more rapid, this explosive fragmentation could account for the Al enhancement of these elements. 8 figures.

Effects of Spray Droplet Size, Dosage, and Solution per ha Rates on Mortality of Twospotted Spider Mite123

Controlled sizes of droplets were combined with dosages of formetanate at various solution rates per ha to evaluate effects on the mortality of Tetranychus urticae Koch in the laboratory, An experimental uniform droplet generator produced uniform droplets of 100, 150, 200, 250, and 300 μ m diam. An equation was developed to show the effect of droplet size, dosage, and solution application rates on mite mortality. Dosage could be reduced, if the solution rate were reduced, without decreasing the mortality. When all other factors were equal, different droplet sizes had little ellect on the mortality rate.

Validation of Two-Dimensional Droplet Deposition Models

ABSTRACT AN open circuit windtunnel, a two-dimensional rec-tangular target, and a uniform droplet generator were used to obtain experimental data for comparison with an existing simulation model. Trajeactory data were obtained by using a camera to observe and record the path of the droplets as they approached the target. The distance the target had to be moved to find the top and bottom limiting trajectories was carefully measured and compared with the predicted values from the model. Four wind velocities and a range of droplet sizes from 113 to 338 jLtm were used in the experimental portion of this study. The two-dimensional simulation model showed good agreement with experimental data for velocities below 0.65 m/s. The two-dimensional model consistently over-predicted velocities above 1 m/s: i.e., for cell Reynolds numbers greater than 175. The amount of overprediction increased with increasing wind velocities. This error in prediction is attributed primarily to the relatively large cell size used to solve the Navier-Stokes equations for flow around a rectangular object.

Ink jet printing

Several basically different nonimpact printing processes have been developed in the last several years using modulated or deflected ink jets. This review paper describes these processes, which are also applicable to the accurate dispensing of fluids, particle sorting, the generation of uniform droplets for research purposes, and other applications.