41 research outputs found
Levels of lipid-derived gut microbial metabolites differ among plant matrices in an in vitro model of colon fermentation
This study explored differences in microbial lipid metabolites among sunflower seeds, soybeans, and walnuts. The matrices were subjected to in vitro digestion and colonic fermentation. Defatted digested materials and fiber/phenolics extracted therefrom were added to sunflower oil (SO) and also fermented. Targeted and untargeted lipidomics were employed to monitor and tentatively identify linoleic acid (LA) metabolites. Walnut fermentation produced the highest free fatty acids (FFAs), LA, and conjugated LAs (CLAs). Defatted digested walnuts added to SO boosted FFAs and CLAs production; the addition of fibre boosted CLAs, whereas the addition of phenolics only increased 9e,11z-CLA and 10e,12z-CLA. Several di-/tri-hydroxy-C18-FAs, reported as microbial LA metabolites for the first time, were annotated. Permutational multivariate analysis of variance indicated significant impacts of food matrix presence and type on lipidomics and C18-FAs. Our findings highlight how the food matrices affect CLA production from dietary lipids, emphasizing the role of food context in microbial lipid metabolism
Double-domed temperature-pressure phase diagram found for CePd3S4
CePd3S4 exhibits interplay between ferromagnetism (FM), quadrupolar order,
and the Kondo effect at low temperatures with a FM transition temperature that
is much higher than the value expected from the de Gennes scaling of the
heavier RPd3S4 compounds. In this work, we investigated the electrical
transport and magnetic properties of CePd3S4 under pressure up through 12 GPa
so as to better understand the interplay between electronic and magnetic phases
in this material. Our findings show that the low pressure FM state is suddenly
replaced by a new magnetically ordered phase that is most likely
antiferromagnetic that spans from ~ 7 GPa to ~ 11 GPa. Whereas this could be
described as an example of avoided quantum criticality, given that clear
changes in resistance and Hall data are detected near 6.3 GPa for all
temperatures below 300 K, it is also possible that the change in ground state
is a response to a pressure induced change in structure. The lack of any
discernible change in the pressure dependence of the room temperature unit cell
parameter/volume across this whole pressure range suggests that this change in
structure is either more subtle than could be detected by our measurements
(i.e. development of weak, new wave vector) or the transition is electronic
(such as a Lifshitz transition).Comment: 16 pages, 16 figures, 74 reference
Suppression of metal-to-insulator transition and stabilization of superconductivity by pressure in Re3Ge7
The effect of pressure on the low-temperature states of the Re3Ge7 is
investigated by both electrical and Hall resistance and magnetization
measurements. At ambient pressure, the temperature dependent resistance of
Re3Ge7 behaves quasi-linearly from room temperature down to 60 K, then
undergoes a two-step metal-to-insulator transitions (MIT) at temperatures T1 =
59.4 K and T2 = 58.7 K which may be related to a structural phase transition or
occurrence of charge density wave ordering. Upon applying pressure, the
two-step (T1, T2) MIT splits into three steps (T1, T2 and T3) above 1 GPa, and
all traces of MITs are fully suppressed by ~8 GPa. Subsequently, the onset of
bulk superconductivity (SC) occurs between 10.8 and 12.2 GPa and persists to
our highest pressure of 26.8 GPa. At 12.2 GPa the superconducting transition
temperature, Tc, and upper critical field, Hc2 reach the maximum of Tc (onset)
~5.9 K and Hc2 (1.8 K) ~ 14 kOe. Our results not only present the observation
of SC under high pressure in Re3Ge7 but also delineate the interplay between SC
and other competing electronic states by creating a T - p phase diagram for
this potentially topologically nontrivial system Re3Ge7.Comment: 11 pages, 12 figures, and 37 reference
Strong enhancement of magnetic ordering temperature and structural/valence transitions in EuPd3S4 under high pressure
We present a comprehensive study of the mixed valent compound, EuPd3S4, by
electrical transport, X-ray diffraction, time-domain 151Eu synchrotron
M\"ossbauer spectroscopy, and X-ray absorption spectroscopy measurements under
high pressure. The electrical transport measurements show that the
antiferromagnetic ordering temperature, TN, increases rapidly from 2.8 K at
ambient pressure to 23.5 K at ~19 GPa and plateaus between ~19 and ~29 GPa
after which no anomaly associated with TN is detected. A pressure-induced first
order structural transition from cubic to tetragonal is observed, with a rather
broad coexistence region (~20 GPa to ~32 GPa) that corresponds to the TN
plateau. M\"ossbauer spectroscopy measurements show a clear valence transition
from approximately 50:50 Eu2+:Eu3+ to fully Eu3+ at ~28 GPa, consistent with
the vanishing of the magnetic order at the same pressure. X-ray absorption data
show a transition to a fully trivalent state at a similar pressure. Our results
show that pressure first greatly enhances TN, most likely via enhanced
hybridization between the Eu 4f states and the conduction band, and then,
second, causes a structural phase transition that coincides with the conversion
of the europium to a fully trivalent state.Comment: 28 pages, 6 figures in main manuscript, 10 figures in S
Viterbi decoding of CRES signals in Project 8
Cyclotron radiation emission spectroscopy (CRES) is a modern approach for determining charged particle energies via high-precision frequency measurements of the emitted cyclotron radiation. For CRES experiments with gas within the fiducial volume, signal and noise dynamics can be modelled by a hidden Markov model. We introduce a novel application of the Viterbi algorithm in order to derive informational limits on the optimal detection of cyclotron radiation signals in this class of gas-filled CRES experiments, thereby providing concrete limits from which future reconstruction algorithms, as well as detector designs, can be constrained. The validity of the resultant decision rules is confirmed using both Monte Carlo and Project 8 data
SYNCA: A Synthetic Cyclotron Antenna for the Project 8 Collaboration
Cyclotron Radiation Emission Spectroscopy (CRES) is a technique for measuring the kinetic energy of charged particles through a precision measurement of the frequency of the cyclotron radiation generated by the particle\u27s motion in a magnetic field. The Project 8 collaboration is developing a next-generation neutrino mass measurement experiment based on CRES. One approach is to use a phased antenna array, which surrounds a volume of tritium gas, to detect and measure the cyclotron radiation of the resulting β-decay electrons. To validate the feasibility of this method, Project 8 has designed a test stand to benchmark the performance of an antenna array at reconstructing signals that mimic those of genuine CRES events. To generate synthetic CRES events, a novel probe antenna has been developed, which emits radiation with characteristics similar to the cyclotron radiation produced by charged particles in magnetic fields. This paper outlines the design, construction, and characterization of this Synthetic Cyclotron Antenna (SYNCA). Furthermore, we perform a series of measurements that use the SYNCA to test the position reconstruction capabilities of the digital beamforming reconstruction technique. We find that the SYNCA produces radiation with characteristics closely matching those expected for cyclotron radiation and reproduces experimentally the phenomenology of digital beamforming simulations of true CRES signals
Tritium Beta Spectrum and Neutrino Mass Limit from Cyclotron Radiation Emission Spectroscopy
The absolute scale of the neutrino mass plays a critical role in physics at
every scale, from the particle to cosmological. Measurements of the tritium
endpoint spectrum have provided the most precise direct limit on the neutrino
mass scale. In this Letter, we present advances by Project 8 to the Cyclotron
Radiation Emission Spectroscopy (CRES) technique culminating in the first
frequency-based neutrino mass limit. With only a cm-scale physical
detection volume, a limit of <180 eV is extracted from the
background-free measurement of the continuous tritium beta spectrum. Using
Kr calibration data, an improved resolution of 1.660.16 eV
(FWHM) is measured, the detector response model is validated, and the
efficiency is characterized over the multi-keV tritium analysis window. These
measurements establish the potential of CRES for a high-sensitivity
next-generation direct neutrino mass experiment featuring low background and
high resolution.Comment: 7 pages, 5 figures, for submission to PR