6,301 research outputs found
Individual and Collective Behavior of Small Vibrating Motors Interacting Through a Resonant Plate
We report on experiments of many small motors -- cell phone vibrators --
glued to and interacting through a resonant plate. We find that individual
motors interacting with the plate demonstrate hysteresis in their steady-state
frequency due to interactions with plate resonances. For multiple motors
running simultaneously, the degree of synchronization between motors increases
when the motors' frequencies are near a resonance of the plate, and the
frequency at which the motors synchronize shows a history dependence.Comment: 7 pages, 8 figure
Dynamics of Large Fragments in the Tail of Active Asteroid P/2010 A2
We examine the motions of large fragments at the head of the dust tail of
active asteroid P/2010 A2. In previous work we showed that these fragments were
ejected from the primary nucleus in early 2009, either following a
hypervelocity impact or by rotationally induced break-up. Here, we follow their
positions through a series of Hubble Space Telescope images taken during the
first half of 2010. The orbital evolution of each fragment allows us to
constrain its velocity relative to the main nucleus after leaving its sphere of
gravitational influence. We find that the fragments constituting a prominent
X-shaped tail feature were emitted in a direction opposite to the motion of the
asteroid and towards the south of its orbital plane. Derived emission
velocities of these primary fragments range between 0.02 and 0.3 m/s,
comparable to the ~0.08 m/s gravitational escape speed from the nucleus. Their
sizes are on the order of decimeters or larger. We obtain the best fits to our
data with ejection velocity vectors lying in a plane that includes the nucleus.
This may suggest that the cause of the disruption of P/2010 A2 is rotational
break-up.Comment: 30 pages, 8 figures, accepted for publication by The Astrophysical
Journa
Periodic 2-graphs arising from subshifts
Higher-rank graphs were introduced by Kumjian and Pask to provide models for
higher-rank Cuntz-Krieger algebras. In a previous paper, we constructed
2-graphs whose path spaces are rank-two subshifts of finite type, and showed
that this construction yields aperiodic 2-graphs whose -algebras are
simple and are not ordinary graph algebras. Here we show that the construction
also gives a family of periodic 2-graphs which we call \emph{domino graphs}. We
investigate the combinatorial structure of domino graphs, finding interesting
points of contact with the existing combinatorial literature, and prove a
structure theorem for the -algebras of domino graphs.Comment: 17 page
A comparison of refined models for flexible subassemblies
Interactions between structure response and control of large flexible space systems have challenged current modeling techniques and have prompted development of new techniques for model improvement. Due to the geometric complexity of envisioned large flexible space structures, finite element models (FEM's) will be used to predict the dynamic characteristics of structural components. It is widely accepted that these models must be experimentally 'validated' before their acceptance as the basis for final design analysis. However, predictions of modal properties (natural frequencies, mode shapes, and damping ratios) are often in error when compared to those obtained from Experimental Modal Analysis (EMA). Recent research efforts have resulted in the development of algorithmic approaches for model improvement, also referred to as system or structure identification
Perspective: Melanoma diagnosis and monitoring: Sunrise for melanoma therapy but early detection remains in the shade
Last revised 25 Jul 2016.Melanoma is one of the most dangerous forms of cancer. The five-year survival rate is 98% if it is detected early. However, this rate plummets to 63% for regional disease and 17% when tumors have metastasized, that is, spread to distant sites. Furthermore, the incidence of melanoma has been rising by about 3% per year, whereas the incidence of cancers that are more common is decreasing. A handful of targeted therapies have recently become available that have finally shown real promise for treatment, but for reasons that remain unclear only a fraction of patients respond long term. These drugs often increase survival by only a few months in metastatic patient groups before relapse occurs. More effective treatment may be possible if a diagnosis can be made when the tumor burden is still low. Here, an overview of the current state-of-the-art is provided along with an argument for newer technologies towards early point-of-care diagnosis of melanoma
Johne's disease or paratuberculosis (1993)
Johne's disease (pronounced "Yone-es") or paratuberculosis is an incurable wasting disease of adult cattle that is being increasingly recognized in the United States. Since prevalence rates in U.S.-slaughtered cows range from 2 to 18 percent, Johne's disease is now considered a major problem. It is of more concern in dairy herds than beef operations since there is a larger percentage of cases in the dairy cattle population than in beef.Reviewed October 1993 -- Extension website
The balancing act
Nutrient management is as much a global issue as a local one with a balance required between economics and environment, inherent biological limitations and expectations of nutrient use efficiency, and traditional fertiliser practices and actual enterprise nutrient requirements. The concept of nutrient balance depends on context and scale. Nutrient balance can be considered at a global scale, where issues of nutrient stocks, cycles, depletion and transfer of a particular element are important. For a single farm enterprise, nutrient balance might be considered in terms of phosphorus (P) inputs into and outputs from the enterprise. This is commonly known as a farm-gate nutrient balance, where the difference between inputs and outputs is nutrient surplus, and the conversion of inputs to outputs is nutrient use efficiency. Equally, a farm might consider nutrient balance in terms of the balance of nutrients within a particular soil, paddock, or crop where some nutrients are in sufficient supply and others are deficient. This paper will consider these aspects of nutrient balance, and will indicate where these imbalances exist as a basis for improvement
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