193 research outputs found
Potential of shrimp waste meal and insect exuviae as sustainable sources of chitin for fish feeds.
Aquaculture is one of the world’s fastest growing food-producing sectors, providing more than half of all fish
consumed globally for human nutrition. However, to maintain such growth and meet the increasing demand for
aquatic food, sustainable raw materials for fish feeds are needed. In this regard, insects represent one of the most
promising alternatives to fish meal (FM) protein source for use in aquafeeds. In addition to protein, insects
contain bioactive compounds, such as chitin, which is a natural polysaccharide abundantly present in the pupal
exuviae of some insects. Studies have shown that dietary chitin or its derivate chitosan acts as a prebiotic thus
modulating the gut microbial communities of fish. Accordingly, the present study aimed to evaluate the effect of
two waste products rich in chitin, i.e., shrimp head meal (SHM), and insect (Hermetia illucens) pupal exuviae on
the gut microbiota of rainbow trout (Oncorhynchus mykiss). Three isoproteic, isolipidic, and isoenergetic diets
containing either FM, SHD, or a combination of FM and 1.6% of pupal exuviae meal (PEM) were tested through a
91-day feeding trial. At the end of the experiment, no differences in final mean body weight, specific growth rate,
and feed conversion ratio values were observed between fish experimental groups. Mortality was <1% and it did
not correlate with diet for the entire duration of the trial. However, a modulatory effect of dietary pupal exuviae
on fish gut microbiota was detected. Indeed, gut bacterial species richness improved by including insect exuviae.
In particular, Firmicutes and Actinobacteria phyla, mainly represented by Bacillus, Facklamia, Brevibacterium, and
Corynebacterium genera, were enriched in trout receiving pupal exuviae. These genera are chitinolytic and shortchain fatty acids (SCFAs)-producing bacteria. SCFAs production was confirmed by gas chromatography analysis,
which detected the highest amount of butyrate in feces of trout fed with pupal exuviae meal. Functional inference
analysis of intestinal microbiota using PICRUST metagenome prediction tool, showed differences in response to
diet. In particular, eleven pathways were significantly different between control fish (FM) and fish fed the PEM
diet, whereas twenty functional traits were significantly different between the FM and SHM fish groups. Overall,
our data confirmed that chitin from insect’s pupal exuviae represents a promising functional ingredient, better
than SHM, for positively modulating gut microbiota communities of rainbow trout
Effect of partial substitution of fishmeal with insect meal (Hermetia illucens) on gut neuromuscular function in Gilthead sea bream (Sparus aurata)
Alternative nutrient sources to fishmeal for fish feed, such as insect meals, represent a promising sustainable supply. However, the consequences for fish digestive function have not been exhaustively investigated. In the present study we evaluated the effect of partial fishmeal substitution with 10% Hermetia illucens (Hi10) larvae meal on the neuromuscular function of proximal and distal intestine in gilthead sea bream. In animals fed with insect meal, weight and growth parameters were similar to controls fed with conventional fishmeal. In addition, no anomalies in intestinal gross morphology and no overt signs of inflammation were observed. The gastrointestinal transit was significantly reduced in Hi10 fed animals. In the proximal and distal intestine longitudinal muscle, Hi10 feeding downregulated the excitatory cholinergic and serotoninergic transmission. Sodium nitroprussideinduced inhibitory relaxations increased in the proximal intestine and decreased in the distal intestine after Hi10 meal. Changes in the excitatory and inhibitory components of peristalsis were associated with adaptive changes in the chemical coding of both proximal and distal intestine myenteric plexus. However, these neuromuscular function alterations were not associated with considerable variations in morphometric growth parameters, suggesting that 10% Hi meal may represent a tolerable alternative protein source for gilthead sea bream diets
Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets
The interaction of laser pulses with thin grating targets, having a periodic
groove at the irradiated surface, has been experimentally investigated.
Ultrahigh contrast () pulses allowed to demonstrate an enhanced
laser-target coupling for the first time in the relativistic regime of
ultra-high intensity >10^{19} \mbox{W/cm}^{2}. A maximum increase by a factor
of 2.5 of the cut-off energy of protons produced by Target Normal Sheath
Acceleration has been observed with respect to plane targets, around the
incidence angle expected for resonant excitation of surface waves. A
significant enhancement is also observed for small angles of incidence, out of
resonance.Comment: 5 pages, 5 figures, 2nd version implements final correction
Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments
Seismology of stars is strongly developing. To address this question we have
formed an international collaboration OPAC to perform specific experimental
measurements, compare opacity calculations and improve the opacity calculations
in the stellar codes [1]. We consider the following opacity codes: SCO,
CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large
differences for Fe and Ni in equivalent conditions of envelopes of type II
supernova precursors, temperatures between 15 and 40 eV and densities of a few
mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar
results and differ from OP ones for the lower temperatures and for spectral
interval values [3]. In this work we discuss the role of Configuration
Interaction (CI) and the influence of the number of used configurations. We
present and include in the opacity code comparisons new HULLAC-v9 calculations
[5, 6] that include full CI. To illustrate the importance of this effect we
compare different CI approximations (modes) available in HULLAC-v9 [7]. These
results are compared to previous predictions and to experimental data.
Differences with OP results are discussed.Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and
Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences
201
Extreme Ultraviolet Beam Enhancement by Relativistic Surface Plasmons
The emission of high-order harmonics in the extreme ultraviolet range from the interaction of a short, intense laser pulse with a grating target is investigated experimentally. When resonantly exciting a surface plasmon, both the intensity and the highest order observed for the harmonic emission along the grating surface increase with respect to a flat target. Harmonics are obtained when a suitable density gradient is preformed at the target surface, demonstrating the possibility to manipulate the grating profile on a nanometric scale without preventing the surface plasmon excitation. In support of this, the harmonic emission is spatiotemporally correlated to the acceleration of multi-MeV electron bunches along the grating surface. Particle-in-cell simulations reproduce the experimental results and give insight on the mechanism of high harmonic generation in the presence of surface plasmons
Theory of laser ion acceleration from a foil target of nanometers
A theory for laser ion acceleration is presented to evaluate the maximum ion
energy in the interaction of ultrahigh contrast (UHC) intense laser with a
nanometer-scale foil. In this regime the energy of ions may be directly related
to the laser intensity and subsequent electron dynamics. This leads to a simple
analytical expression for the ion energy gain under the laser irradiation of
thin targets. Significantly, higher energies for thin targets than for thicker
targets are predicted. Theory is concretized to the details of recent
experiments which may find its way to compare with these results.Comment: 22 pages 7 figures. will be submitted to NJ
A novel radio imaging method for physical spectral index modelling
We present a new method, called "forced-spectrum fitting", for
physically-based spectral modelling of radio sources during deconvolution. This
improves upon current common deconvolution fitting methods, which often produce
inaccurate spectra. Our method uses any pre-existing spectral index map to
assign spectral indices to each model component cleaned during the
multi-frequency deconvolution of WSClean, where the pre-determined spectrum is
fitted. The component magnitude is evaluated by performing a modified weighted
linear least-squares fit. We test this method on a simulated LOFAR-HBA
observation of the 3C196 QSO and a real LOFAR-HBA observation of the 4C+55.16
FRI galaxy. We compare the results from the forced-spectrum fitting with
traditional joined-channel deconvolution using polynomial fitting. Because no
prior spectral information was available for 4C+55.16, we demonstrate a method
for extracting spectral indices in the observed frequency band using
"clustering". The models generated by the forced-spectrum fitting are used to
improve the calibration of the datasets. The final residuals are comparable to
existing multi-frequency deconvolution methods, but the output model agrees
with the provided spectral index map, embedding correct spectral information.
While forced-spectrum fitting does not solve the determination of the spectral
information itself, it enables the construction of accurate multi-frequency
models that can be used for wide-band calibration and subtraction.Comment: 17 pages, 9 figures, 5 tables. Accepted for publication in MNRA
Assessing the impact of two independent direction-dependent calibration algorithms on the LOFAR 21-cm signal power spectrum
Detecting the 21-cm signal from the Epoch of Reionisation (EoR) is
challenging due to the strong astrophysical foregrounds, ionospheric effects,
radio frequency interference and instrumental effects. Understanding and
calibrating these effects are crucial for the detection. In this work, we
introduce a newly developed direction-dependent (DD) calibration algorithm
DDECAL and compare its performance with an existing algorithm, SAGECAL, in the
context of the LOFAR-EoR 21-cm power spectrum experiment. In our data set, the
North Celestial Pole (NCP) and its flanking fields were observed
simultaneously. We analyse the NCP and one of its flanking fields. The NCP
field is calibrated by the standard pipeline, using SAGECAL with an extensive
sky model and 122 directions, and the flanking field is calibrated by DDECAL
and SAGECAL with a simpler sky model and 22 directions. Additionally, two
strategies are used for subtracting Cassiopeia A and Cygnus A. The results show
that DDECAL performs better at subtracting sources in the primary beam region
due to the application of a beam model, while SAGECAL performs better at
subtracting Cassiopeia A and Cygnus A. This indicates that including a beam
model during DD calibration significantly improves the performance. The benefit
is obvious in the primary beam region. We also compare the 21-cm power spectra
on two different fields. The results show that the flanking field produces
better upper limits compared to the NCP in this particular observation. Despite
the minor differences between DDECAL and SAGECAL due to the beam application,
we find that the two algorithms yield comparable 21-cm power spectra on the
LOFAR-EoR data after foreground removal. Hence, the current LOFAR-EoR 21-cm
power spectrum limits are not likely to depend on the DD calibration method.Comment: 28 pages, 14 figures, accepted for publication in A&
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