Near resonance acoustic scattering from organized schools of juvenile Atlantic bluefin tuna (Thunnus thynnus)

Schools of Atlantic bluefin tuna (Thunnus thynnus) can exhibit highly organized spatial structure within the school. This structure was quantified for dome shaped schools using both aerial imagery collected from a commercial spotter plane and 400 kHz multibeam echo sounder data collected on a fishing vessel in 2009 in Cape Cod Bay, MA. Observations from one school, containing an estimated 263 fish within an approximately ellipsoidal volume of 1900 m3, were used to seed an acoustic model that estimated the school target strength at frequencies between 10 and 2000 Hz. The fish\u27s swimbladder resonance was estimated to occur at approximately 50 Hz. The acoustic model examined single and multiple scattering solutions and also a completely incoherent summation of scattering responses from the fish. Three levels of structure within the school were examined, starting with fish locations that were constrained by the school boundaries but placed according to a Poisson process, then incorporating a constraint on the distance to the nearest neighbor, and finally adding a constraint on the bearing to the nearest neighbor. Results suggest that both multiple scattering and spatial organization within the school should be considered when estimating the target strength of schools similar to the ones considered here

Some subnormal operators not in A2

AbstractBercovici, Foias, and Pearcy have defined a decreasing sequence of classes of operators, An, 1 ⩽ n < ℵ0. If A denotes area measure on the disc D and if S = Mz on P2(dA) then S ϵ Aℵ0; on the other hand, if μ = ¦dz¦Γ + dA for some arc Γ on ∂D, we show Mz on P2(μ) is an element of A1/A2, while its minimal normal extension, Mz on L2(μ), is in Aℵ0. Let S be a subnormal operator whose minimal normal extension has scalar valued spectral measure μ such that P∞(μ) = H∞(D). If there exist λ ϵ D and ƒ ϵH∞(D) so that ¦ƒ(λ)¦ > ∥ƒ∥μD we give a condition sufficient for S to be a member of A1A2

NASA's rotorcraft icing research program

The objective of the NASA aircraft icing research program is to develop and make available icing technology to support the needs and requirements of industry for all weather aircraft designs. While a majority of the technology being developed is viewed to be generic (i.e., appropriate to all vehicle classes), vehicle specific emphasis is being placed on the helicopter due to its unique icing problems. In particular, some of the considerations for rotorcraft icing are indicated. The NASA icing research program emphasizes technology development in two key areas: ice protection concepts and icing simulation (analytical and experimental). The NASA research efforts related to rotorcraft icing in these two technology areas will be reviewed

A Two-Coordinate Nickel Imido Complex That Effects C−H Amination

An exceptionally low coordinate nickel imido complex, (IPr*)Ni═N(dmp) (2) (dmp = 2,6-dimesitylphenyl), has been prepared by the elimination of N_2 from a bulky aryl azide in its reaction with (IPr*)Ni(η^6-C_7H_8) (1). The solid-state structure of 2 features two-coordinate nickel with a linear C−Ni−N core and a short Ni−N distance, both indicative of multiple-bond character. Computational studies using density functional theory showed a Ni═N bond dominated by Ni(dπ)−N(pπ) interactions, resulting in two nearly degenerate singly occupied molecular orbitals (SOMOs) that are Ni−N π* in character. Reaction of 2 with CO resulted in nitrene-group transfer to form (dmp)NCO and (IPr*)Ni(CO)_3 (3). Net C−H insertion was observed in the reaction of 2 with ethene, forming the vinylamine (dmp)NH(CH═CH_2) (5) via an azanickelacyclobutane intermediate, (IPr*)Ni{N,C:κ^2-N(dmp)CH_2CH_2} (4)

Icing research tunnel test of a model helicopter rotor

An experimental program has been conducted in the NASA Lewis Research Center Icing Research Tunnel (IRT) in which an OH-58 tail rotor assembly was operated in a horizontal plane to simulate the action of a typical main rotor. Ice was accreted on the blades in a variety of rotor and tunnel operating conditions and documentation of the resulting shapes was performed. Rotor torque and vibration are presented as functions of time for several representative test runs, and the effects of various parametric variations on the blade ice shapes are shown. This OH-58 test was the first of its kind in the United States and will encourage additional model rotor icing tunnel testing. Although not a scaled representative of any actual full-scale main rotor system, this rig has produced torque and vibration data which will be useful in assessing the quality of existing rotor icing analyses

Integration of ethics into a forestry curriculum

Following a comprehensive review of their forestry curriculum in 1995, the Oklahoma State University Forestry Faculty elected to modify the way professional ethics are formally addressed. The modifications involve three courses. An introduction of ethics and their role in natural resource management is presented to freshman in an introductory course. This provides a framework for learning and applying the science and practices of the Forestry Profession in the context of an ethical philosophy. Students address ethics a second time between their sophomore and junior years. This happens during the initial summer camp course where students are exposed to philosophical and policy differences between natural resource management agencies. Ethics are formally reintroduced in two senior courses that are usually taken concurrently. One of these courses is a capstone experience where students address real natural resource management problems. The second is a course in forest administration and natural resource policy. In these two courses the instructors cooperate to require the students to consider professional ethics in a philosophical framework for decision making as well as an applied standard for real decisions in the execution of professional work. This is accomplished through discussions of the Ethical Canons of the Society of American Foresters in the forest administration and policy course. These discussions are followed by group presentations to the class of ethical considerations associated with projects from the student’s capstone experience