4,536 research outputs found
-algebras and quantum dynamics: some existence results
We discuss the possibility of defining an algebraic dynamics within the
settings of -algebras. Compared with our previous results on this
subject, the main improvement here is that we are not assuming the existence of
some hamiltonian for the {\em full} physical system. We will show that, under
suitable conditions, the dynamics can still be defined via some limiting
procedure starting from a given {\em regularized sequence}
Note on the Relativistic Thermodynamics of Moving Bodies
We employ a novel thermodynamical argument to show that, at the macroscopic
level,there is no intrinsic law of temperature transformation under Lorentz
boosts. This result extends the corresponding microstatistical one of earlier
works to the purely macroscopic regime and signifies that the concept of
temperature as an objective entity is restricted to the description of bodies
in their rest frames. The argument on which this result is based is centred on
the thermal transactions between a body that moves with uniform velocity
relative to a certain inertial frame and a thermometer, designed to measure its
temperature, that is held at rest in that frame.Comment: To be published in J. Phys. A. A few minor corrections have been made
to the earlier version of this articl
Designing probiotic therapies with broad-spectrum activity against a wildlife pathogen
Host-associated microbes form an important component of immunity that protect
against infection by pathogens. Treating wild individuals with these protective microbes,
known as probiotics, can reduce rates of infection and disease in both wild and captive
settings. However, the utility of probiotics for tackling wildlife disease requires that
they offer consistent protection across the broad genomic variation of the pathogen
that hosts can encounter in natural settings. Here we develop multi-isolate probiotic
consortia with the aim of effecting broad-spectrum inhibition of growth of the lethal
amphibian pathogen Batrachochytrium dendrobatidis (Bd) when tested against nine
Bd isolates from two distinct lineages. Though we achieved strong growth inhibition
between 70 and 100% for seven Bd isolates, two isolates appeared consistently
resistant to inhibition, irrespective of probiotic strategy employed. We found no evidence
that genomic relatedness of the chytrid predicted similarity of inhibition scores, nor that
increasing the genetic diversity of the bacterial consortia could offer stronger inhibition
of pathogen growth, even for the two resistant isolates. Our findings have important
consequences for the application of probiotics to mitigate wildlife diseases in the face of
extensive pathogen genomic variation
Assessment of quality indicators among nurse practitioners performing upper endoscopy.
Background and study aimsâLimited international data have shown that non-physicians can safely perform upper endoscopy, but no such study has been performed in the United States. Our aim was to assess the quality of outpatient upper endoscopies performed by nurse practitioners (NPs).Patients and methodsâRetrospective chart review of upper endoscopies performed by 3 NPs between 2010 and 2013 was performed. Comparisons among all NPs performing upper endoscopy and assessment of individual NP performance over time with respect to quality indicators were performed.ResultsâThree NPs performed 333 upper endoscopies (distribution of 166, 44, and 123, respectively). Of the cases, 98.2â%s were successfully completed to the second portion of the duodenum. In most cases, photo-documentation of required anatomical landmarks was performed: GE junction (84.2â%), GE junction in retroflexed view (84.2â%), antrum (82.1â%) and duodenum (80.9â%). Photo-documentation improved with increasing experience. NPs appropriately performed biopsies for specific medical conditions: 10/11 (90.9â%) gastric ulcers were biopsied and 63/66 (95.5) of patients with iron deficiency had duodenal biopsies performed for celiac disease. A physician endoscopist was required during the procedure 22.5â% of the time. Important parameters such as documenting informed consent (100â%) and documenting a discharge plan (99.4â%) in the procedure reports were overwhelming present. There was a single adverse event during the study period.ConclusionâIn the first US study of NPs performing upper endoscopy, they were able to perform high-quality and safe upper endoscopies. These findings support incorporation of non-physicians alongside physicians to help meet the growing demand for endoscopic services across the United States
Seismic response to evolving injection at the Rotokawa geothermal field, New Zealand
Catalogs of microseismicity are routinely compiled at geothermal reservoirs and provide valuable insights into reservoir structure and fluid movement. Hypocentral locations are typically used to infer the orientations of structures and constrain the extent of the permeable reservoir. However, frequency-magnitude distributions may contain additional, and underused, information about the distribution of pressure. Here, we present a four-year catalog of seismicity for the Rotokawa geothermal field in the central TaupĆ Volcanic Zone, New Zealand starting two years after the commissioning of the 140 MWe Nga Awa Purua power station. Using waveform-correlation-based signal detection we double the size of the previous earthquake catalog, refine the location and orientation of two reservoir faults and identify a new structure. We find the rate of seismicity to be insensitive to major changes in injection strategy during the study period, including the injectivity decline and shift of injection away from the dominant injector, RK24. We also map the spatial distribution of the earthquake frequency-magnitude distribution, or b-value, and show that it increases from âŒ1.0 to âŒ1.5 with increasing depth below the reservoir. As has been proposed at other reservoirs, we infer that these spatial variations reflect the distribution of pressure in the reservoir, where areas of high b-value correspond to areas of high pore-fluid pressure and a broad distribution of activated fractures. This analysis is not routinely conducted by geothermal operators but shows promise for using earthquake b-value as an additional tool for reservoir monitoring and management
Observer based feedback control of 3rd order LCC resonant converters
The paper considers specific issues related to the design and realisation of observer-based feedback of isolated output voltage for resonant power converters. To provide a focus to the study, a 3rd order LCC converter is employed as a candidate topology. It is shown that whilst resonant converters nominally operate at high switching frequencies to facilitate the use of small reactive components, by appropriate pre-conditioning of non-isolated resonant-tank voltages and currents, the resulting observer can be implemented at relatively low sampling frequencies, and hence, take advantage of low-cost digital hardware.
Experimental results are used to demonstrate the accuracy of observer estimates under both transient and steady-state operating conditions, and to show operation of the observer as part of a closed-loop feedback system where the LCC resonant converter is used as a regulated power supply
Quantum control of spin-correlations in ultracold lattice gases
We demonstrate that it is possible to prepare a lattice gas of ultracold
atoms with a desired non-classical spin-correlation function using atom-light
interaction of the kind routinely employed in quantum spin polarization
spectroscopy. Our method is based on quantum non-demolition (QND) measurement
and feedback, and allows in particular to create on demand exponentially or
algebraically decaying correlations, as well as a certain degree of
multi-partite entanglement.Comment: 2 figure
Certified quantum non-demolition measurement of material systems
An extensive debate on quantum non-demolition (QND) measurement, reviewed in
Grangier et al. [Nature, {\bf 396}, 537 (1998)], finds that true QND
measurements must have both non-classical state-preparation capability and
non-classical information-damage tradeoff. Existing figures of merit for these
non-classicality criteria require direct measurement of the signal variable and
are thus difficult to apply to optically-probed material systems. Here we
describe a method to demonstrate both criteria without need for to direct
signal measurements. Using a covariance matrix formalism and a general noise
model, we compute meter observables for QND measurement triples, which suffice
to compute all QND figures of merit. The result will allow certified QND
measurement of atomic spin ensembles using existing techniques.Comment: 11 pages, zero figure
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