The rupture of oil gland reservoirs housed near the outer surface of the citrus exocarp is a common experience to the discerning citrus consumer and bartenders the world over. These reservoirs often rupture outwardly in response to bending the peel, which compresses the soft material surrounding the reservoirs, the albedo, increasing fluid pressure in the reservoir. Ultimately, fluid pressure exceeds the failure strength of the outermost membrane, the flavedo. The ensuing high-velocity discharge of oil and exhaustive emptying of oil gland reservoirs creates a method for jetting small quantities of the aromatic oil. We compare this jetting behavior across five citrus hybrids through high-speed videography. The jetting oil undergoes an extreme acceleration to reach velocities in excess of 10 m/s. Through material characterization and finite element simulations, we rationalize the combination of tuned material properties and geometries enabling the internal reservoir pressures that produce explosive dispersal, finding the composite structure of the citrus peel is critical for microjet production.

Groups of organisms such as flocks, swarms, herds, and schools form for a variety of motivations linked to survival and proliferation. Their size, locomotive domain, population, and the environmental stimuli guiding motion make challenging the study of member interactions and global behaviors. In this review, we borrow principles and analogies from fluids to describe the characteristics of organismal aggregations, which may inspire new tools for the analysis of collective motion. Examples of fluid resemblance include open channel flow, droplet formation, and particleladen flow. We show how the properties of density, viscosity, and surface tension have strong parallels in the structure and behavior of aggregations of contrasting scale and domain. In certain cases, aggregations are sufficiently fluid-like that values can be assigned to such properties. We highlight how organisms engaging in collective motion can flow, roll, and change phase. Finally, we present limitations and exceptions for the application of fluidic principles to the motion of living groups.

Insects perform takeoffs from a nearly unquantifiable number of surface permutations and many use their legs to initiate upward movement prior to the onset of wingbeats, including the mosquito. In this study we examine the unprovoked pre-takeoff mechanics of Aedes aegypti mosquitoes from two surfaces of contrasting roughness, one with roughness similar to polished glass and the other comparable to the human forearm. Using high-speed videography, we find mosquitos exhibit two distinct leg actions prior to takeoff, the widely observed push and a previously undocumented leg-strike, where one of the rearmost legs is raised and strikes the ground. Across 106 takeoff sequences we observe a greater incidence of leg-strikes from the smoother surface, and rationalize this observation by comparing the characteristic size of surface features on the mosquito tarsi and each test surface. Measurements of pre-takeoff kinematics reveal both strategies remain under the mechanosensory detection threshold of mammalian hair and produce nearly identical vertical body velocities. Lastly, we develop a model that explicates the measured leg velocity of striking legs utilized by mosquitoes, 0.59 m s −1 .

The over-all efficiency of a counter circuit embodying a scaling circuit to reduce the rate of recording is investigated. The probability of detecting counts (G(n, r)) of a scaling circuit and recorder fed with random impulses is shown to be: 1 -J(jur, n), where n is the scale of the circuit, r the resolving time of the recorder, n the statistical average of incoming counts, and where I for, n) is the ratio of the incomplete gamma-function with upper limit \XT of n to the complete gamma-function of n. Efficiency curves (100 G(n, r)) are plotted showing that the distribution in time of the impulses leaving the scaling circuit is no longer random, but is a distribution in which the extreme short and long intervals between impulses are averaged out. The average rate of recording counts (fj, n ) is {fx/n)G(n, r). The analysis is extended to include the effect of the finite resolving time of the amplifier (r/a and the scaling circuit and recorder will operate with 100 percent efficiencv.

^> The development of certain aspects of a physically interpretable geometry defined over a finite field is presented. The concepts of order, norm, metric, inner product, etc. are developed over a subset of the total field. It is found that the finite discrete space behaves ..locally, not globally, like the conventional "continuous" spaces. The implications of this behavior for mathematical induction and the limit procedure are discussed, and certain radical conclusions are reached. Among these are: (a) mathematical induction ultimately fails for. a finite system and further extension leads to the introduction of formal indeterminancy; (b) finite space-time operations have inherent formal properties like those heretofore attributed to the substantive physical universe, and (c) certain formal properties attributed to continuous spaces cannot be developed from successive embedding in finite space of finer resolution-but must be based on indc7c: lent axiomatic (nontestable) assumptions. It is suggested that a finite field representation should be used as the fundamental basis of a physical representation. Jj ■ ; i ; ' , i Rapioduod by NATIONAL TECHNICAL .NFORMATION SERVICE Sprin»fl.W. V.. MtSI DISTRIBUTION STATEMENT Thi* document ha« been approved (or public reloam« and sole; its distribution is unlimited. Dm-2 ~i to 200 x 10 and declare the answer to be Ik x 10. In this way, replacement permits our mathematical operations to continue and avoids cessation due to uncomputability or lack of performable instructions. One couid also construct his system to reset itself to some arbitrary point-say zero-whenever an impasse is reached. However, the rationale for replacement is clearly preferable because it seeks a "nearby" problem and we shall adopt it.