4,691 research outputs found
Shock Waves in Nanomechanical Resonators
The dream of every surfer is an extremely steep wave propagating at the
highest speed possible. The best waves for this would be shock waves, but are
very hard to surf. In the nanoscopic world the same is true: the surfers in
this case are electrons riding through nanomechanical devices on acoustic waves
[1]. Naturally, this has a broad range of applications in sensor technology and
for communication electronics for which the combination of an electronic and a
mechanical degree of freedom is essential. But this is also of interest for
fundamental aspects of nano-electromechanical systems (NEMS), when it comes to
quantum limited displacement detection [2] and the control of phonon number
states [3]. Here, we study the formation of shock waves in a NEMS resonator
with an embedded two-dimensional electron gas using surface acoustic waves. The
mechanical displacement of the nano-resonator is read out via the induced
acoustoelectric current. Applying acoustical standing waves we are able to
determine the anomalous acoustocurrent. This current is only found in the
regime of shock wave formation. We ontain very good agreement with model
calculations.Comment: 14 Pages including 4 figure
Yersinia ruckeri isolates recovered from diseased Atlantic Salmon (Salmo salar) in Scotland are more diverse than those from Rainbow Trout (Oncorhynchus mykiss) and represent distinct subpopulations
Yersinia ruckeri is the etiological agent of enteric redmouth (ERM) disease of farmed salmonids. Enteric redmouth disease is traditionally associated with rainbow trout (Oncorhynchus mykiss, Walbaum), but its incidence in Atlantic salmon (Salmo salar) is increasing. Yersinia ruckeri isolates recovered from diseased Atlantic salmon have been poorly characterized, and very little is known about the relationship of the isolates associated with these two species. Phenotypic approaches were used to characterize 109 Y. ruckeri isolates recovered over a 14-year period from infected Atlantic salmon in Scotland; 26 isolates from infected rainbow trout were also characterized. Biotyping, serotyping, and comparison of outer membrane protein profiles identified 19 Y. ruckeri clones associated with Atlantic salmon but only five associated with rainbow trout; none of the Atlantic salmon clones occurred in rainbow trout and vice versa. These findings suggest that distinct subpopulations of Y. ruckeri are associated with each species. A new O serotype (designated O8) was identified in 56 biotype 1 Atlantic salmon isolates and was the most common serotype identified from 2006 to 2011 and in 2014, suggesting an increased prevalence during the time period sampled. Rainbow trout isolates were represented almost exclusively by the same biotype 2, serotype O1 clone that has been responsible for the majority of ERM outbreaks in this species within the United Kingdom since the 1980s. However, the identification of two biotype 2, serotype O8 isolates in rainbow trout suggests that vaccines containing serotypes O1 and O8 should be evaluated in both rainbow trout and Atlantic salmon for application in Scotland
Infant feeding knowledge, attitudes,and beliefs predict antenatal intention among first-time mothers in Queensland
Aim: This study assessed infant feeding knowledge, attitudes, and beliefs among women from Queensland,
Australia, in their first pregnancy. Antenatal feeding intention in this group was described, and the hypothesis
was tested that antenatal knowledge, attitudes, and beliefs about infant feeding are associated with antenatal
intention for the duration and exclusivity of breastfeeding for the infant’s first year.
Subjects and Methods: The Feeding Queensland Babies Study is a prospective survey of infant feeding
attitudes and behaviors among first-time mothers in Queensland, Australia. Data on infant feeding knowledge,
attitudes, beliefs, and intention were collected antenatally, and an Infant Feeding Attitudes Score was
calculated.
Results: Although 85% of respondents endorsed breastfeeding as most appropriate for infants, 11% valued
formula feeding equally. Intention to give any breastmilk during the first weeks was 98%, but it fell to 18%
during the second year. More than one-quarter of women reported intention to introduce foods other than
breastmilk before 5 months of infant age. The infant feeding attitudes and beliefs score correlated positively
with feeding intention for breastfeeding and the introduction of complementary solids.
Conclusions: Enhancing women’s knowledge of recommendations and their understanding of breastfeeding’s
specific benefits and the reasons for recommended scheduling of feeding transitions may positively impact
breastfeeding exclusivity and duration and the age-appropriate introduction of complementary solids. Communication
of detailed feeding recommendations for the infant’s first year and specific information about the
health benefits of breastfeeding should be a goal of healthcare providers working with pregnant women
Cooling of cryogenic electron bilayers via the Coulomb interaction
Heat dissipation in current-carrying cryogenic nanostructures is problematic
because the phonon density of states decreases strongly as energy decreases. We
show that the Coulomb interaction can prove a valuable resource for carrier
cooling via coupling to a nearby, cold electron reservoir. Specifically, we
consider the geometry of an electron bilayer in a silicon-based
heterostructure, and analyze the power transfer. We show that across a range of
temperatures, separations, and sheet densities, the electron-electron
interaction dominates the phonon heat-dissipation modes as the main cooling
mechanism. Coulomb cooling is most effective at low densities, when phonon
cooling is least effective in silicon, making it especially relevant for
experiments attempting to perform coherent manipulations of single spins.Comment: 9 pages, 5 figure
Effects of mixing red clover and maize silages on milk production and whole-body N partitioning in dairy cows
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