10,321 research outputs found
Application of remote sensing to study nearshore circulation
Immediate use of drogued buoy tracking was made when the Virginia State Highway Department requested assistance in selecting the best route for a new bridge-tunnel complex across the James River at Newport News. The result was that the Highway Department acted and chose a preferred route from several alternatives. It was also observed that the drogues did not follow the channel as predicted by the James River hydraulic model. This permitted telling the Navy why it is that part of their channel always silts up. The Hampton Roads Sanitation District asked help locate the best route and position of an ocean sewer outfall. Biological activities are focused primarily on delineating biological interaction between the marsh and continental shelf waters on Virginia's Eastern Shore. Information derived is helpful in categorizing the relative biological value of different marsh areas so that meaningful use and management decisions can be made concerning their eventual disposition
Neuromuscular control of wingbeat kinematics in Anna's hummingbirds (Calypte anna)
Hummingbirds can maintain the highest wingbeat frequencies of any flying vertebrate – a feat accomplished by the large pectoral muscles that power the wing strokes. An unusual feature of these muscles is that they are activated by one or a few spikes per cycle as revealed by electromyogram recordings (EMGs). The relatively simple nature of this activation pattern provides an opportunity to understand how motor units are recruited to modulate limb kinematics. Hummingbirds made to fly in low-density air responded by moderately increasing wingbeat frequency and substantially increasing the wing stroke amplitude as compared with flight in normal air. There was little change in the number of spikes per EMG burst in the pectoralis major muscle between flight in normal and low-density heliox (mean=1.4 spikes cycle^(–1)). However the spike amplitude, which we take to be an indication of the number of active motor units, increased in concert with the wing stroke amplitude, 1.7 times the value in air. We also challenged the hummingbirds using transient load lifting to elicit maximum burst performance. During maximum load lifting, both wing stroke amplitude and wingbeat frequency increased substantially above those values during hovering flight. The number of spikes per EMG burst increased to a mean of 3.3 per cycle, and the maximum spike amplitude increased to approximately 1.6 times those values during flight in heliox. These results suggest that hummingbirds recruit additional motor units (spatial recruitment) to regulate wing stroke amplitude but that temporal recruitment is also required to maintain maximum stroke amplitude at the highest wingbeat frequencies
Application of remote sensing to study nearshore circulation
The research to use remote sensing techniques for studying the continental shelf is reported. The studies reported include: (1) nearshore circulation in the vincinity of a natural tidal inlet; (2) identification of indicators of biological activity; (3) remote navigation system for tracking free drifting buoys; (4) experimental design of an estuaring tidal circulation; and (5) Skylab support work
Solid friction between soft filaments
Any macroscopic deformation of a filamentous bundle is necessarily
accompanied by local sliding and/or stretching of the constituent filaments.
Yet the nature of the sliding friction between two aligned filaments
interacting through multiple contacts remains largely unexplored. Here, by
directly measuring the sliding forces between two bundled F-actin filaments, we
show that these frictional forces are unexpectedly large, scale logarithmically
with sliding velocity as in solid-like friction, and exhibit complex dependence
on the filaments' overlap length. We also show that a reduction of the
frictional force by orders of magnitude, associated with a transition from
solid-like friction to Stokes' drag, can be induced by coating F-actin with
polymeric brushes. Furthermore, we observe similar transitions in filamentous
microtubules and bacterial flagella. Our findings demonstrate how altering a
filament's elasticity, structure and interactions can be used to engineer
interfilament friction and thus tune the properties of fibrous composite
materials
BIMA and Keck Imaging of the Radio Ring PKS 1830-211
We discuss BIMA (Berkeley Illinois Maryland Association) data and present new
high quality optical and near-IR Keck images of the bright radio ring PKS
1830-211. Applying a powerful new deconvolution algorithm we have been able to
identify both images of the radio source. In addition we recover an extended
source in the optical, consistent with the expected location of the lensing
galaxy. The source counterparts are very red, I-K=7, suggesting strong Galactic
absorption with additional absorption by the lensing galaxy at z=0.885, and
consistent with the detection of high redshift molecules in the lens.Comment: To be published in the ASP Conference Proceedings, 'Highly Redshifted
Radio Lines', Greenbank, W
OA16.01. Patients, physicians, and CAM providers regard communication as central for integrating conventional and CAM therapies for chronic pain
- …