3,971 research outputs found
Influence of human pressures on large river structure and function
A large river study was conducted as part of the Cross Departmental Research Pool (CDRP) ecological integrity project to (i) provide an overview of the macroinvertebrate faunas of large rivers, including those in deep-water habitats, and (ii) to elucidate links between these faunas, river function and anthropogenic stressors. Eleven sites on 6th-order or 7th-order rivers were sampled; four in the South Island and seven in the North Island. We measured (i) macroinvertebrate communities colonising wood, riffles (where present), littoral habitats (1.5 m deep) (ii) ecosystem metabolism using a single-station open-channel approach based on natural changes in dissolved oxygen concentration over a 24-hour period, and (iii) wood and cellulose breakdown. Relationships were investigated between these response variables and reach-scale assessments of habitat quality, underlying upstream and segment environmental variables provided in the Freshwater Environments of New Zealand (FWENZ) database, and anthropogenic pressure variables provided by the Waters of National Importance (WONI) database
Streaming quantum gate set tomography using the extended Kalman filter
Closed-loop control algorithms for real-time calibration of quantum
processors require efficient filters that can estimate physical error
parameters based on streams of measured quantum circuit outcomes. Development
of such filters is complicated by the highly nonlinear relationship
relationship between observed circuit outcomes and the magnitudes of elementary
errors. In this work, we apply the extended Kalman filter to data from quantum
gate set tomography to provide a streaming estimator of the both the system
error model and its uncertainties. Our numerical examples indicate extended
Kalman filtering can achieve similar performance to maximum likelihood
estimation, but with dramatically lower computational cost. With our methods, a
standard laptop can process one- and two-qubit circuit outcomes and update gate
set error model at rates comparable with current experimental execution.Comment: 11 pages, 9 Figure
Enabling III-V-based optoelectronics with low-cost dynamic hydride vapor phase epitaxy
Silicon is the dominant semiconductor in many semiconductor device
applications for a variety of reasons, including both performance and cost.
III-V materials have improved performance compared to silicon, but currently
they are relegated to applications in high-value or niche markets due to the
absence of a low-cost, high-quality production technique. Here we present an
advance in III-V materials synthesis using hydride vapor phase epitaxy that has
the potential to lower III-V semiconductor deposition costs by orders of
magnitude while maintaining the requisite optoelectronic material quality that
enables III-V-based technologies to outperform Si. We demonstrate the impacts
of this advance by addressing the use of III-Vs in terrestrial photovoltaics, a
highly cost-constrained market. The emergence of a low-cost III-V deposition
technique will enable III-V electronic and opto-electronic devices, with all
the benefits that they bring, to permeate throughout modern society.Comment: pre-prin
The Mid-IR Spectral Effects of Darkening Agents and Porosity on the Silicate Surface Features of Airless Bodies
We systematically measured the mid-IR spectra of different mixtures of three silicates (antigorite, lizardite, and pure silica) with varying effective porosities and amounts of darkening agent (iron oxide and carbon). These spectra have broad implications for interpretation of current and future mission data for airless bodies, as well as for testing the capabilities of new instruments. Serpentines, such as antigorite and lizardite, are common to airless surfaces, and their mid-IR spectra in the presence of darkening agents and different surface porosities would be typical for those measured by spacecraft. Silica has only been measured in the plumes of Enceladus and presents exciting possibilities for other Saturn-system surfaces due to long range transport of E-ring material. Results show that the addition of the IR-transparent salt, KBr, to simulate surface porosity affected silicate spectra in ways that were not predictable from linear mixing models. The strengthening of silicate bands with increasing pore space, even when only trace amounts of KBr were added, indicates that spectral features of porous surfaces are more detectable in the mid-IR. Combining iron oxide with the pure silicates seemed to flatten most of the silicate features, but strengthened the reststrahlen band of the silica. Incorporating carbon with the silicates weakened all silicate features, but the silica bands were more resistant to being diminished, indicating silica may be more detectable in the mid-IR than the serpentines. We show how incorporating darkening agents and porosity provides a more complete explanation of the mid-IR spectral features previously reported on worlds such as Iapetus
Quantum non-demolition measurements of single donor spins in semiconductors
We propose a technique for measuring the state of a single donor electron
spin using a field-effect transistor induced two-dimensional electron gas and
electrically detected magnetic resonance techniques. The scheme is facilitated
by hyperfine coupling to the donor nucleus. We analyze the potential
sensitivity and outline experimental requirements. Our measurement provides a
single-shot, projective, and quantum non-demolition measurement of an
electron-encoded qubit state.Comment: 8+ pages. 4 figures. Published versio
Conserved but flexible modularity in the zebrafish skull: implications for craniofacial evolvability
Morphological variation is the outward manifestation of development and provides fodder for adaptive evolution. Because of this contingency, evolution is often thought to be biased by developmental processes and functional interactions among structures, which are statistically detectable through forms of covariance among traits. This can take the form of substructures of integrated traits, termed modules, which together comprise patterns of variational modularity. While modularity is essential to an understanding of evolutionary potential, biologists currently have little understanding of its genetic basis and its temporal dynamics over generations. To address these open questions, we compared patterns of craniofacial modularity among laboratory strains, defined mutant lines and a wild population of zebrafish ( ). Our findings suggest that relatively simple genetic changes can have profound effects on covariance, without greatly affecting craniofacial shape. Moreover, we show that instead of completely deconstructing the covariance structure among sets of traits, mutations cause shifts among seemingly latent patterns of modularity suggesting that the skull may be predisposed towards a limited number of phenotypes. This new insight may serve to greatly increase the evolvability of a population by providing a range of 'preset' patterns of modularity that can appear readily and allow for rapid evolution
Metabolic engineering of high-productivity CHO host lines for biomanufacturing
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