Numerous bioactive compounds in plant-derived products are secondary toxic metabolites produced by plants as a mechanism of defence against herbivores and invading microbes. Among them, essential ...oils (EO), which are known for their antimicrobial effects have been proposed as modulators of rumen fermentation. However, there is little information on their dose–response effects on the rumen ecosystem. Using five natural EO from
Thymus vulgaris,
Origanum vulgare, thymol chemo-type of
O. vulgare,
Cinnamomum verum, and
Anethum graveolens, and three pure constituents thymol, carvacrol, and cinnamaldehyde, we examined the
in vitro response of the rumen microbial ecosystem evaluated through production curves of volatile fatty acids (VFA), ammonia, and gas. Three types of EO molecules were discriminated, being carvone (a terpene), thymol, and carvacrol (phenolic EO originated from the terpene pathway), and cinnamaldehyde (a phenolic EO originating from the phenyl-propane pathway). The carvone-based EO produced a linear non-threshold profile that negatively affected end-products of fermentation. A threshold profile, characterized by a virtual stop of fermentation when doses were higher than the threshold level, occurred for thymol/carvacrol-based EO. The effect of cinnamaldehyde-based EO was a negative sigmoid profile characterized by a reduction of protein degradation at low additive concentration, without changes in VFA production, and a negative effect on all fermentation variables at higher concentrations. Loss of the methanogenesis was a feature of the transition point in this profile. Results show that EO induces at least three types of dose–response in the rumen ecosystem. Knowing the type of response, as well as the effective dose, could help determine which compound would be most appropriate for a particular production objective, such as decreasing protein degradation. Results also highlight the toxic nature of EO upon rumen microbes, and that there is a narrow dose window for the successful adoption of this technology.
The white-bellied pangolin (
) is the world's most trafficked mammal and is at risk of extinction. Reducing the illegal wildlife trade requires an understanding of its origins. Using a genomic ...approach for tracing confiscations and analyzing 111 samples collected from known geographic localities in Africa and 643 seized scales from Asia between 2012 and 2018, we found that poaching pressures shifted over time from West to Central Africa. Recently, Cameroon's southern border has emerged as a site of intense poaching. Using data from seizures representing nearly 1 million African pangolins, we identified Nigeria as one important hub for trafficking, where scales are amassed and transshipped to markets in Asia. This origin-to-destination approach offers new opportunities to disrupt the illegal wildlife trade and to guide anti-trafficking measures.
Context. Astrophysical polarized foregrounds represent the most critical challenge in cosmic microwave background (CMB) B -mode experiments, requiring multifrequency observations to constrain ...astrophysical foregrounds and isolate the CMB signal. However, recent observations indicate that foreground emission may be more complex than anticipated. Not properly accounting for these complexities during component separation can lead to a bias in the recovered tensor-to-scalar ratio. Aims. In this paper we investigate how the increased spectral resolution provided by band-splitting in bolometric interferometry (BI) through a technique called spectral imaging can help control the foreground contamination in the case of an unaccounted-for Galactic dust frequency de-correlation along the line of sight (LOS). Methods. We focused on the next-generation ground-based CMB experiment CMB-S4 and compared its anticipated sensitivity, frequency, and sky coverage with a hypothetical version of the same experiment based on BI (CMB-S4/BI). We performed a Monte Carlo analysis based on parametric component separation methods (FGBuster and Commander) and computed the likelihood of the recovered tensor-to-scalar ratio, r . Results. The main result is that spectral imaging allows us to detect systematic uncertainties on r from frequency de-correlation when this effect is not accounted for in the component separation. Conversely, an imager such as CMB-S4 would detect a biased value of r and would be unable to spot the presence of a systematic effect. We find a similar result in the reconstruction of the dust spectral index, and we show that with BI we can more precisely measure the dust spectral index when frequency de-correlation is present and not accounted for in the component separation. Conclusions. The in-band frequency resolution provided by BI allows us to identify dust LOS frequency de-correlation residuals where an imager with a similar level of performance would fail. This creates the possibility of exploiting this potential in the context of future CMB polarization experiments that will be challenged by complex foregrounds in their quest for B -mode detection.
The Q&U Bolometric Interferometer for Cosmology (QL’BIC) is the first bolometric interferometer designed to measure the primordial B-mode polarization of the Cosmic Microwave Background (CMB). ...Bolometric interferometry is a novel technique that combines the sensitivity of bolometric detectors with the control of systematic effects that is typical of interferometry, both key features in the quest for the faint signal of the primordial B-modes. A unique feature is the so-called “spectral imaging”, i.e., the ability to recover the sky signal in several sub-bands within the physical band during data analysis. This feature provides an in-band spectral resolution of ∆v/v ~ 0.04 that is unattainable by a traditional imager. This is a key tool for controlling the Galactic foregrounds contamination. In this paper, we describe the principles of bolometric interferometry, the current status of the QU BIC experiment and future prospects.
QUBIC I: Overview and science program Mousset, L.; Battistelli, E.S.; de Bernardis, P. ...
Journal of Cosmology and Astroparticle Physics,
04/2022, Letnik:
2022, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Abstract
The Q & U Bolometric Interferometer for Cosmology (QUBIC) is a novel kind of polarimeter optimized for the measurement of the B-mode polarization of the Cosmic Microwave Background (CMB), ...which is one of the major challenges of observational cosmology. The signal is expected to be of the order of a few tens of nK, prone to instrumental systematic effects and polluted by various astrophysical foregrounds which can only be controlled through multichroic observations. QUBIC is designed to address these observational issues with a novel approach that combines the advantages of interferometry in terms of control of instrumental systematic effects with those of bolometric detectors in terms of wide-band, background-limited sensitivity. The QUBIC synthesized beam has a frequency-dependent shape that results in the ability to produce maps of the CMB polarization in multiple sub-bands within the two physical bands of the instrument (150 and 220 GHz). These features make QUBIC complementary to other instruments and makes it particularly well suited to characterize and remove Galactic foreground contamination. In this article, first of a series of eight, we give an overview of the QUBIC instrument design, the main results of the calibration campaign, and present the scientific program of QUBIC including not only the measurement of primordial B-modes, but also the measurement of Galactic foregrounds.
We give forecasts for typical observations and measurements: with three years of integration on the sky and assuming perfect foreground removal as well as stable atmospheric conditions from our site in Argentina, our simulations show that we can achieve a statistical sensitivity to the effective tensor-to-scalar ratio (including primordial and foreground B-modes)
σ
(
r
)=0.015.
Abstract
Bolometric interferometry is a novel technique that has the ability to perform spectral imaging. A bolometric interferometer observes the sky in a wide frequency band and can reconstruct sky ...maps in several sub-bands within the physical band in post-processing of the data. This provides a powerful spectral method to discriminate between the cosmic microwave background (CMB) and astrophysical foregrounds. In this paper, the methodology is illustrated with examples based on the Q & U Bolometric Interferometer for Cosmology (QUBIC) which is a ground-based instrument designed to measure the B-mode polarization of the sky at millimeter wavelengths. We consider the specific cases of point source reconstruction and Galactic dust mapping and we characterize the point spread function as a function of frequency. We study the noise properties of spectral imaging, especially the correlations between sub-bands, using end-to-end simulations together with a fast noise simulator. We conclude showing that spectral imaging performance are nearly optimal up to five sub-bands in the case of QUBIC.
Abstract
Setting an upper limit or detection of B-mode polarization
imprinted by gravitational waves from Inflation is one goal of
modern large angular scale cosmic microwave background (CMB)
...experiments around the world. A great effort is being made in the
deployment of many ground-based, balloon-borne and satellite
experiments, using different methods to separate this faint
polarized component from the incoming radiation. QUBIC exploits one
of the most widely-used techniques to extract the input Stokes
parameters, consisting in a rotating half-wave plate (HWP) and a
linear polarizer to separate and modulate polarization
components. QUBIC uses a step-by-step rotating HWP, with 15°
steps, combined with a 0.4°s
-1
azimuth sky scan
speed. The rotation is driven by a stepper motor mounted on the
cryostat outer shell to avoid heat load at internal cryogenic
stages. The design of this optical element is an engineering
challenge due to its large 370 mm diameter and the
8 K operation temperature that are unique features of
the QUBIC experiment. We present the design for a modulator
mechanism for up to 370 mm, and the first optical
tests by using the prototype of QUBIC HWP (180 mm
diameter). The tests and results presented in this work show that
the QUBIC HWP rotator can achieve a precision of 0.15°
in position by using the stepper motor and custom-made optical
encoder. The rotation induces <5.0 mW (95% C.L) of
power load on the 4 K stage, resulting in no thermal
issues on this stage during measurements. We measure a temperature
settle-down characteristic time of 28 s after a rotation
through a 15° step, compatible with the scanning
strategy, and we estimate a maximum temperature gradient within the
HWP of ≤ 10 mK. This was calculated by setting
up finite element thermal simulations that include the temperature
profiles measured during the rotator operations. We report
polarization modulation measurements performed at
150 GHz, showing a polarization efficiency >99%
(68% C.L.) and a median cross-polarization χ
Pol
of 0.12%, with 71% of detectors showing a
χ
Pol
+ 2
σ
upper limit <1%, measured using
selected detectors that had the best signal-to-noise ratio.
LiteBIRD is a planned JAXA-led cosmic microwave background (CMB)
B
-mode satellite experiment aiming for launch in the late 2020s, with a primary goal of detecting the imprint of primordial ...inflationary gravitational waves. Its current baseline focal-plane configuration includes 15 frequency bands between 40 and 402 GHz, fulfilling the mission requirements to detect the amplitude of gravitational waves with the total uncertainty on the tensor-to-scalar ratio,
δr
, down to
δr
< 0.001. A key aspect of this performance is accurate astrophysical component separation, and the ability to remove polarized thermal dust emission is particularly important. In this paper we note that the CMB frequency spectrum falls off nearly exponentially above 300 GHz relative to the thermal dust spectral energy distribution, and a relatively minor high frequency extension can therefore result in even lower uncertainties and better model reconstructions. Specifically, we compared the baseline design with five extended configurations, while varying the underlying dust modeling, in each of which the High-Frequency Telescope (HFT) frequency range was shifted logarithmically toward higher frequencies, with an upper cutoff ranging between 400 and 600 GHz. In each case, we measured the tensor-to-scalar ratio
r
uncertainty and bias using both parametric and minimum-variance component-separation algorithms. When the thermal dust sky model includes a spatially varying spectral index and temperature, we find that the statistical uncertainty on
r
after foreground cleaning may be reduced by as much as 30–50% by extending the upper limit of the frequency range from 400 to 600 GHz, with most of the improvement already gained at 500 GHz. We also note that a broader frequency range leads to higher residuals when fitting an incorrect dust model, but also it is easier to discriminate between models through higher
χ
2
sensitivity. Even in the case in which the fitting procedure does not correspond to the underlying dust model in the sky, and when the highest frequency data cannot be modeled with sufficient fidelity and must be excluded from the analysis, the uncertainty on
r
increases by only about 5% for a 500 GHz configuration compared to the baseline.
QUBIC VIII: Optical design and performance De Petris, M.; Amico, G.; Battistelli, E.S. ...
Journal of Cosmology and Astroparticle Physics,
04/2022, Letnik:
2022, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Abstract
The Q and U Bolometric Interferometer for Cosmology (QUBIC) is a ground-based experiment that aims to detect B-mode polarization anisotropies 1 in the CMB at angular scales around the
ℓ
≃100 ...recombination peak. Systematic errors make ground-based observations of B modes at millimetre wavelengths very challenging and QUBIC mitigates these problems in a somewhat complementary way to other existing or planned experiments using the novel technique of bolometric interferometry. This technique takes advantage of the sensitivity of an imager and the systematic error control of an interferometer. A cold reflective optical combiner superimposes the re-emitted beams from 400 aperture feedhorns on two focal planes. A shielding system composed of a fixed groundshield, and a forebaffle that moves with the instrument, limits the impact of local contaminants.
The modelling, design, manufacturing and preliminary measurements of the optical components are described in this paper.
