8,646 research outputs found
Insecticide and Growth Regulator Effects on the Leafminer, \u3ci\u3eLiriomyza Trifolii\u3c/i\u3e (Diptera: Agromyzidae), in Celery and Observations on Parasitism
The effects of different insecticides were compared on survival and development of the leafminer, L. trifolii, in celery in Michigan and parasitism was assessed in this non- resident population. Avermectin, thiocyclam, and cyromazine effectively controlled L. trifolii larvae or prevented successful emergence as adults. Moderate to high levels of resistance to permethrin and chlorpyrifos were present. Avermectin caused high mortality of all larval stages and no adults successfully emerged. Thiocyclam caused high mortality to all larval stages, but did not affect adult emergence from the surviving larvae. Cyromazine acted most strongly against early stage larvae before visible mines were present, caused little direct mortality of larger larvae, but prevented successful adult emergence. No parasitoids emerged from 2029 larvae collected and reared, in contrast to studies in sites where L. trifolii is a year-round resident
Sources, paths, and concepts for reduction of noise in the test section of the NASA Langley 4x7m wind tunnel
NASA is investigating the feasibility of modifying the 4x7m Wind Tunnel at the Langley Research Center to make it suitable for a variety of aeroacoustic testing applications, most notably model helicopter rotors. The amount of noise reduction required to meet NASA's goal for test section background noise was determined, the predominant sources and paths causing the background noise were quantified, and trade-off studies between schemes to reduce fan noise at the source and those to attenuate the sound generated in the circuit between the sources and the test section were carried out. An extensive data base is also presented on circuit sources and paths
Shoreline configuration and shoreline dynamics: A mesoscale analysis
The author has identified the following significant results. Atlantic coast barrier island shorelines are seldom straight, but rather sinuous. These shoreline curvatures range in size from cusps to capes. Significant relationships exist between the orientation of shoreline segments within the larger of these sinuous features and shoreline dynamics, with coefficients ranging up to .9. Orientation of the shoreline segments of Assateague Island (60 km) and the Outer Banks of North Carolina (130 km) was measured from LANDSAT 2 imagery (1:80,000) and high altitude aerial photography (1:120,000). Long term trends in shoreline dynamics were established by mapping shoreline and storm-surge penetration changes
PDEs with Compressed Solutions
Sparsity plays a central role in recent developments in signal processing,
linear algebra, statistics, optimization, and other fields. In these
developments, sparsity is promoted through the addition of an norm (or
related quantity) as a constraint or penalty in a variational principle. We
apply this approach to partial differential equations that come from a
variational quantity, either by minimization (to obtain an elliptic PDE) or by
gradient flow (to obtain a parabolic PDE). Also, we show that some PDEs can be
rewritten in an form, such as the divisible sandpile problem and
signum-Gordon. Addition of an term in the variational principle leads to
a modified PDE where a subgradient term appears. It is known that modified PDEs
of this form will often have solutions with compact support, which corresponds
to the discrete solution being sparse. We show that this is advantageous
numerically through the use of efficient algorithms for solving based
problems.Comment: 21 pages, 15 figure
LANDSAT application of remote sensing to shoreline-form analysis
The author has identified the following significant results. Orientation of the shoreline segments of Assateague Island (55 km) was measured from LANDSAT 2 imagery enlarged to 1:250,000 and 1:80,000. Long term trends in shoreline dynamics were established by mapping shoreline and storm-surge penetration changes from historical low altitude aerial photography spanning four decades
Sonic boom simulation by means of low-pressure sources
Sonic boom simulation by low pressure source
Entropy and Entanglement in Quantum Ground States
We consider the relationship between correlations and entanglement in gapped
quantum systems, with application to matrix product state representations. We
prove that there exist gapped one-dimensional local Hamiltonians such that the
entropy is exponentially large in the correlation length, and we present strong
evidence supporting a conjecture that there exist such systems with arbitrarily
large entropy. However, we then show that, under an assumption on the density
of states which is believed to be satisfied by many physical systems such as
the fractional quantum Hall effect, that an efficient matrix product state
representation of the ground state exists in any dimension. Finally, we comment
on the implications for numerical simulation.Comment: 7 pages, no figure
Multi-kilowatt modularized spacecraft power processing system development
A review of existing information pertaining to spacecraft power processing systems and equipment was accomplished with a view towards applicability to the modularization of multi-kilowatt power processors. Power requirements for future spacecraft were determined from the NASA mission model-shuttle systems payload data study which provided the limits for modular power equipment capabilities. Three power processing systems were compared to evaluation criteria to select the system best suited for modularity. The shunt regulated direct energy transfer system was selected by this analysis for a conceptual design effort which produced equipment specifications, schematics, envelope drawings, and power module configurations
On black hole thermalization, D0 brane dynamics, and emergent spacetime
When matter falls past the horizon of a large black hole, the expectation
from string theory is that the configuration thermalizes and the information in
the probe is rather quickly scrambled away. The traditional view of a classical
unique spacetime near a black hole horizon conflicts with this picture. The
question then arises as to what spacetime does the probe actually see as it
crosses a horizon, and how does the background geometry imprint its signature
onto the thermal properties of the probe. In this work, we explore these
questions through an extensive series of numerical simulations of D0 branes. We
determine that the D0 branes quickly settle into an incompressible symmetric
state -- thermalized within a few oscillations through a process driven
entirely by internal non-linear dynamics. Surprisingly, thermal background
fluctuations play no role in this mechanism. Signatures of the background
fields in this thermal state arise either through fluxes, i.e. black hole hair;
or if the probe expands to the size of the horizon -- which we see evidence of.
We determine simple scaling relations for the D0 branes' equilibrium size, time
to thermalize, lifetime, and temperature in terms of their number, initial
energy, and the background fields. Our results are consistent with the
conjecture that black holes are the fastest scramblers as seen by Matrix
theory.Comment: 43 pages, 12 figures; v2: added analysis showing that results are
consistent with and confirm Susskind conjecture on black hole thermalization.
Added clarification about strong coupling regime. Citation adde
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