Hypervirulent disease due to group A Streptococcus (GAS) can result from strains with mutations that enhance virulence gene expression but reduce subsequent transmission. We used whole-genome ...sequencing to investigate intrafamilial spread among 4 siblings of infection due to a hypervirulent GAS strain that resulted in a fatality. All invasive and pharyngeal GAS isolates had an identical mutation in a gene encoding a key regulatory protein that yielded a hyperinvasive phenotype. These data challenge the prevailing theory of reduced transmission induced by mutations that lead to hypervirulent GAS by showing that spread of hypervirulent GAS may lead to clusters of invasive disease.
We consider two one-dimensional harmonic chains coupled along their length via linear springs. Casting the elastic wave equation for this system in a Dirac-like form reveals a directional ...representation. The elastic band structure, in a spectral representation, is constituted of two branches corresponding to symmetric and antisymmetric modes. In the directional representation, the antisymmetric states of the elastic waves possess a plane wave orbital part and a 4x1 spinor part. Two of the components of the spinor part of the wave function relate to the amplitude of the forward component of waves propagating in both chains. The other two components relate to the amplitude of the backward component of waves. The 4x1 spinorial state of the two coupled chains is supported by the tensor product Hilbert space of two identical subsystems composed of a non-interacting chain with linear springs coupled to a rigid substrate. The 4x1 spinor of the coupled system is shown to be in general not separable into the tensor product of the two 2x1 spinors of the uncoupled subsystems in the directional representation.
Abstract
We calibrate spectrophotometric optical spectra of 32 stars commonly used as standard stars, referenced to 14 stars already on the Hubble Space Telescope–based CALSPEC flux system. ...Observations of CALSPEC and non-CALSPEC stars were obtained with the SuperNova Integral Field Spectrograph over the wavelength range 3300–9400 Å as calibration for the Nearby Supernova Factory cosmology experiment. In total, this analysis used 4289 standard-star spectra taken on photometric nights. As a modern cosmology analysis, all presubmission methodological decisions were made with the flux scale and external comparison results blinded. The large number of spectra per star allows us to treat the wavelength-by-wavelength calibration for all nights simultaneously with a Bayesian hierarchical model, thereby enabling a consistent treatment of the Type Ia supernova cosmology analysis and the calibration on which it critically relies. We determine the typical per-observation repeatability (median 14 mmag for exposures ≳5 s), the Maunakea atmospheric transmission distribution (median dispersion of 7 mmag with uncertainty 1 mmag), and the scatter internal to our CALSPEC reference stars (median of 8 mmag). We also check our standards against literature filter photometry, finding generally good agreement over the full 12 mag range. Overall, the mean of our system is calibrated to the mean of CALSPEC at the level of ∼3 mmag. With our large number of observations, careful cross-checks, and 14 reference stars, our results are the best calibration yet achieved with an integral-field spectrograph, and among the best calibrated surveys.
•Coarse particle liberation to flotation ocurred by replacing cyclones with screens.•The heuristic of an unchanged constant liberation by size in grinding is challenged.•Comminution circuit design ...should also aim to maximizing downstream mineral recovery.
The heuristic of a constant liberation by size independent of the degree of comminution has been established as a robust assumption over time. Therefore, when assessing the comminution circuit performance, achieving a final target P80 size at the lowest possible energy and cost seems to be the only concern. The introduction of higher capacity fine screening to replace hydrocyclones challenges this fixed approach due to the inherent difference in classification principles between the technologies. The impact of classification efficiency and mode on the liberation properties of a polymetallic ore ground in a production ball mill circuit are presented. It was found that the liberation properties remained constant across the comminution device but were significantly different across the circuit. The circuit closed with screens was found to improve the coarse particle liberation in comparison to the hydrocyclones. The liberation data is presented and implications for circuit performance are discussed. It is postulated that the assessment of comminution circuit design and performance should be based on the ultimate objective, recovery of the valuable minerals, and thus be based on the ore- and process-specific recovery window, not on a fixed ‘grind size’.
It is shown that multiple logical phi-bit large-scale unitary operations analogous to quantum circuits can be realized by design. Logical phi-bits are nonlinear acoustic analogues of qubits which ...arise when elastic waveguides are coupled and driven at multiple frequencies in the presence of non-linearities. The contribution presents an approach that maps both the state of multiple phi-bits in their supporting nonlinear acoustic metastructure and their representations as complex state vectors in exponentially scaling Hilbert spaces. Upon physically actuating
π
changes in phi-bit phases and by engineering appropriate multiple phi-bits representations, one can realize a scalable phi-bit-based quantum Fourier transform.
Type Ia Supernova Carbon Footprints Thomas, R. C; Aldering, G; Antilogus, P ...
The Astrophysical journal,
12/2011, Letnik:
743, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present convincing evidence of unburned carbon at photospheric velocities in new observations of five Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory. These SNe are identified ...by examining 346 spectra from 124 SNe obtained before +2.5 days relative to maximum. Detections are based on the presence of relatively strong C II lambda 6580 absorption 'notches' in multiple spectra of each SN, aided by automated fitting with the SYNAPPS code. Four of the five SNe in question are otherwise spectroscopically unremarkable, with ions and ejection velocities typical of SNe Ia, but spectra of the fifth exhibit high-velocity (v > 2,000 km s super(-1)) Si II and Ca II features. On the other hand, the light curve properties are preferentially grouped, strongly suggesting a connection between carbon-positivity and broadband light curve/color behavior: three of the five have relatively narrow light curves but also blue colors and a fourth may be a dust-reddened member of this family. Accounting for signal to noise and phase, we estimate that 22 super(+)10 sub(-)6% of SNe Ia exhibit spectroscopic C II signatures as late as -5 days with respect to maximum. We place these new objects in the context of previously recognized carbon-positive SNe Ia and consider reasonable scenarios seeking to explain a physical connection between light curve properties and the presence of photospheric carbon. We also examine the detailed evolution of the detected carbon signatures and the surrounding wavelength regions to shed light on the distribution of carbon in the ejecta. Our ability to reconstruct the C II lambda 6580 feature in detail under the assumption of purely spherical symmetry casts doubt on a 'carbon blobs' hypothesis, but does not rule out all asymmetric models. A low volume filling factor for carbon, combined with line-of-sight effects, seems unlikely to explain the scarcity of detected carbon in SNe Ia by itself.
•Confirmed water recovery in flotation is a strong function of froth residence time.•Showed water recovery is affected by variables that change water flow into a froth.•Proposed a new empirical water ...recovery model incorporating two primary mechanisms.
The entrainment of fine gangue particles has become a critical issue in flotation nowadays when low quality and complex ores are processed. Water recovery contributes significantly to gangue entrainment and greatly affects concentrate grade. In this study, a factorial batch flotation experiment was performed to investigate the main and combined effects of gas flowrate, froth height, impeller speed and gangue particle density on water recovery using a mixture of liberated chalcopyrite and gangue minerals in a 3.5L batch flotation cell.
Results show that water recovery was significantly affected by (1) froth height, (2) gas flowrate, (3) impeller speed, (4) the interaction between impeller speed and particle density, and (5) the interaction between gas flowrate and froth height (in the order of reducing effects). Interestingly, water recovery was less sensitive to gas flowrate as froth height was increased, and more sensitive to froth height as gas flowrate was increased. There was an increase in the amount of water entering the froth phase from the pulp when increasing impeller speed, especially in the context of high-density gangue mineral systems.
The identified effects and interactions and the effect of froth residence time on water recovery suggest that water recovery could be predicted effectively if both water drainage and water entering the froth from the pulp are considered. A model based on these two parameters was proposed in this paper.
We illustrate the concept of geometric phase in the case of two prototypical elastic systems, namely the one-dimensional harmonic oscillator and a one-dimensional binary superlattice. We demonstrate ...formally the relationship between the variation of the geometric phase in the spectral and wave number domains and the parallel transport of a vector field along paths on curved manifolds possessing helicoidal twists which exhibit non-conventional topology.
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