The 2019 surface acoustic waves roadmap Delsing, Per; Cleland, Andrew N; Schuetz, Martin J A ...
Journal of physics. D, Applied physics,
08/2019, Volume:
52, Issue:
35
Journal Article
Peer reviewed
Open access
Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these ...nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applications in life sciences and microfluidics for sensing and mixing of tiny amounts of liquids. In addition to this continuously growing number of applications, SAWs are ideally suited to probe and control elementary excitations in condensed matter at the limit of single quantum excitations. Even collective excitations, classical or quantum are nowadays coherently interfaced by SAWs. This wide, highly diverse, interdisciplinary and continuously expanding spectrum literally unites advanced sensing and manipulation applications. Remarkably, SAW technology is inherently multiscale and spans from single atomic or nanoscopic units up even to the millimeter scale. The aim of this Roadmap is to present a snapshot of the present state of surface acoustic wave science and technology in 2019 and provide an opinion on the challenges and opportunities that the future holds from a group of renown experts, covering the interdisciplinary key areas, ranging from fundamental quantum effects to practical applications of acoustic devices in life science.
Nanotechnology applications can be found in agricultural production, animal feed, food processing, food additives and food contact materials (hereinafter referred to as agri/feed/food). A great ...diversity of nanomaterials is reported to be currently used in various applications, while new nanomaterials and applications are reported to be in development.
It is expected that applications of nanomaterials in agri/feed/food will increase in the future and thereby increase the human and environmental exposure to such materials. To gain up-to-date knowledge we explored and reviewed the already marketed and in-development applications of nanomaterials in the agri/feed/food sectors upon the request of the European Food Safety Authority (EFSA). In this paper the results of the project are highlighted and discussed in more detail.
The majority of the applications of nanomaterials that we identified concerned application in food as food additives and food contact materials, while much fewer applications seem to be developed for agriculture and feed. Nano-encapsulates, silver, titanium dioxide and silica are the most often mentioned nanomaterials in the literature. About half of the identified applications are claimed to be already in use. In-development applications are found for nano-encapsulates and nano-composites in novel foods, food and feed additives, biocides, pesticides and food contact materials.
•Nanotechnology is applied in agricultural production, animal feed, food processing, - additives and food contact materials.•Nano-encapsulates, silver, titanium dioxide and silica are the most often mentioned nanomaterials in the literature.•A comparison between marketed and in-development applications indicates a trend moving from inorganic to organic NM.•Nanotechnology is an enabling technology, therefore product description should contain the function of a NM in the product.
Context.
β
Pictoris is arguably one of the most studied stellar systems outside of our own. Some 30 yr of observations have revealed a highly-structured circumstellar disk, with rings, belts, and a ...giant planet:
β
Pictoris b. However very little is known about how this system came into being.
Aims.
Our objective is to estimate the C/O ratio in the atmosphere of
β
Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry.
Methods.
We used the GRAVITY instrument with the four 8.2 m telescopes of the Very Large Telescope Interferometer to obtain
K
-band spectro-interferometric data on
β
Pic b. We extracted a medium resolution (
R
= 500)
K
-band spectrum of the planet and a high-precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio.
Results.
Our new astrometry disfavors a circular orbit for
β
Pic b (
e
= 0.15
−0.04
+0.05
). Combined with previous results and with H
IPPARCOS
/
Gaia
measurements, this astrometry points to a planet mass of
M
= 12.7 ± 2.2
M
Jup
. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of
β
Pic b. In particular, the C/O ratios derived with the two codes are identical (0.43 ± 0.05 vs. 0.43
−0.03
+0.04
). We argue that if the stellar C/O in
β
Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment.
Aims
. To date, infrared interferometry at best achieved contrast ratios of a few times 10
−4
on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, ...enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets.
Methods
. We used the GRAVITY fringe tracker to lock the fringes on the central star, and integrated off-axis on the HR 8799 e planet situated at 390 mas from the star. Data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. The inferred
K
band spectrum of the planet has a spectral resolution of 500. We also derive the astrometric position of the planet relative to the star with a precision on the order of 100
μ
as.
Results
. The GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital solutions. A small adjustment of a few degrees to the orbital inclination of HR 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. The spectrum, with a signal-to-noise ratio of ≈5 per spectral channel, is compatible with a late-type L brown dwarf. Using Exo-REM synthetic spectra, we derive a temperature of 1150 ± 50 K and a surface gravity of 10
4.3 ± 0.3
cm s
2
. This corresponds to a radius of 1.17
−0.11
+0.13
R
Jup
and a mass of 10
−4
+7
M
Jup
, which is an independent confirmation of mass estimates from evolutionary models. Our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars.
Many microbial symbionts have multiple phenotypic consequences for their animal hosts. However, the ways in which different symbiont-mediated phenotypes combine to affect fitness are not well ...understood. We investigated whether there are correlations between different symbiont-mediated phenotypes. We used the symbiont
Spiroplasma
, a striking example of a bacterial symbiont conferring diverse phenotypes on insect hosts. We took 11 strains of
Spiroplasma
infecting pea aphids (
Acyrthosiphon pisum
) and assessed their ability to provide protection against the fungal pathogen
Pandora neoaphidis
and the parasitoids
Aphidius ervi
and
Praon volucre
. We also assessed effects on male offspring production for five of the
Spiroplasma
strains. All but one of the
Spiroplasma
strains provided very strong protection against the parasitoid
P. volucre
. As previously reported, variable protection against
P. neoaphidis
and
A. ervi
was also present; male-killing was likewise a variable phenotype. We find no evidence of any correlation, positive or negative, between the different phenotypes, nor was there any evidence of an effect of symbiont phylogeny on protective phenotype. We conclude that multiple symbiont-mediated phenotypes can evolve independently from one another without trade-offs between them.
Dual‐Lobe Reconnection and Horse‐Collar Auroras Milan, S. E.; Carter, J. A.; Bower, G. E. ...
Journal of geophysical research. Space physics,
October 2020, 2020-10-00, 20201001, Volume:
125, Issue:
10
Journal Article
Peer reviewed
Open access
We propose a mechanism for the formation of the horse‐collar auroral configuration during periods of strongly northward interplanetary magnetic field (IMF), invoking the action of dual‐lobe ...reconnection (DLR). Auroral observations are provided by the Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP). We also use ionospheric flow measurements from DMSP and polar maps of field‐aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Sunward convection is observed within the dark polar cap, with antisunward flows within the horse‐collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR. We suggest that newly closed flux is transported antisunward and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes. Horse‐collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northward IMF. The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low‐latitude boundary layer and cold, dense plasma sheet. We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse‐collar auroras being an intermediate step.
Plain Language Summary
During quiet geomagnetic conditions, the global distribution of auroras can acquire a “horse‐collar” configuration, in which regions of weak auroral emission appear at dawn and dusk poleward of the main auroral oval. We propose a new model to explain the formation of this configuration, which provides new insights into magnetospheric dynamics during periods of northward‐directed interplanetary magnetic field. To support our proposal, we use observations of the auroras, ionospheric convection, and estimations of the pattern of electrical currents flowing between the ionosphere and magnetosphere from a suite of spacecraft. Our proposed model resolves a 40‐year‐old question regarding the nature of the horse‐collar auroras and many other aspects of magnetospheric dynamics.
Key Points
We propose that horse‐collar auroras, which occur during prolonged periods of northward IMF, are a signature of dual‐lobe reconnection
The dayside polar cap is eroded and replaced by magnetic flux newly closed by dual‐lobe reconnection, filled with sun‐aligned arcs
We discuss the implications for NBZ phenomena, including solar wind capture, the low‐latitude boundary layer and cold, dense plasma sheet
The GRAVITY Young Stellar Object survey Perraut, K.; Labadie, L.; Lazareff, B. ...
Astronomy and astrophysics (Berlin),
12/2019, Volume:
632
Journal Article
Peer reviewed
Open access
Context.
The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. Terrestrial planets form or migrate within the innermost regions of these ...protoplanetary disks and so, the processes of disk evolution and planet formation are intrinsically linked. Studies of the dust distribution, composition, and evolution of these regions are crucial to understanding planet formation.
Aims.
We built a homogeneous observational dataset of Herbig Ae/Be disks with the aim of spatially resolving the sub au-scale region to gain a statistical understanding of their morphological and compositional properties, in addition to looking for correlations with stellar parameters, such as luminosity, mass, and age.
Methods.
We observed 27 Herbig Ae/Be stars with the GRAVITY instrument installed at the combined focus of the Very Large Telescope Interferometer (VLTI) and operating in the near-infrared
K
-band, focused on the
K
-band thermal continuum, which corresponds to stellar flux reprocessed by the dust grains. Our sample covers a large range of effective temperatures, luminosities, masses, and ages for the intermediate-mass star population. The circumstellar disks in our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data.
Results.
Our best-fit models correspond to smooth and wide rings that support previous findings in the
H
-band, implying that wedge-shaped rims at the dust sublimation edge are favored. The measured closure phases are generally non-null with a median value of ~10°, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20–25° but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to ~10
4
L
⊙
luminosity values and confirm the significant spread around the mean relation observed by PIONIER in the
H
-band. Gapped sources exhibit a large
N
-to-
K
band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the mass range of 2
M
⊙
, we do observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the
N
-to-
K
size ratio. However, the size of the current sample does not yet permit us to invoke a clear, universal evolution mechanism across the Herbig Ae/Be mass range. The measured locations of the
K
-band emission in our sample suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation.
Multicloud attains a larger momentum by gratifying the needs of the more number of heterogeneous cloud users. The inherent parts that are used in the multicloud systems are analogous, scheduling and ...rescheduling. In the analogous aspect, requests from the first user are given more priority and tasks are delegated to the virtual machines. In the scheduling phase, round robin based mechanism is used to accomplish the tasks in all the clouds. Rescheduling is a mechanism of shifting the executed tasks of one cloud to the another cloud. The expenditure of exceution of the tasks around 15 % are merely reduced in the rescheduling phase. This article is merely focused to dwindle the exceution costs of the VMs in the clouds. The denouement of the propounded algorithm manifests better when it is compared with conventional min-min algorithm.
Wastewater monitoring of SARS-CoV-2 enables early detection and monitoring of the COVID-19 disease burden in communities and can track specific variants of concern. We determined proportions of the ...Omicron and Delta variants across 30 municipalities covering >75% of the province of Alberta (population 4.5 million), Canada, during November 2021–January 2022. Larger cities Calgary and Edmonton exhibited more rapid emergence of Omicron than did smaller and more remote municipalities. Notable exceptions were Banff, a small international resort town, and Fort McMurray, a medium-sized northern community that has many workers who fly in and out regularly. The integrated wastewater signal revealed that the Omicron variant represented close to 100% of SARS-CoV-2 burden by late December, before the peak in newly diagnosed clinical cases throughout Alberta in mid-January. These findings demonstrate that wastewater monitoring offers early and reliable population-level results for establishing the extent and spread of SARS-CoV-2 variants.
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