119 research outputs found
MID-IR LED-based, Photoacoustic CO2 Sensor
AbstractThe technology used to implement CO2 sensors depends on the requirements in terms of sensitivity, price and robustness. The most common technology for highly sensitive tasks are based on tunable diode laser spectroscopy, while so-called non-dispersive infrared (NDIR) photometers [2] are used in less demanding scenarios such as control air conditioning systems. Most NDIR systems use thermal emitters as light source which are readily available at low cost but require compensation for cross-sensitivities toward other gas species. The detector technology employed in these systems ranges from photodiodes to thermopiles and pyroelectric detectors, all of which require the use of spectral filters to avoid cross sensitivities. Here we present a low-cost photoacoustic-based detector comprised of a microphone in a hermetically sealed chamber filled with CO2. To excite sound waves a MID-IR LED emitting radiation in the strong CO2 absorption region around 4.2μm is used for the first time
Gas sensors for climate research
The availability of datasets providing information on the spatial and
temporal evolution of greenhouse gas concentrations is of high relevance for
the development of reliable climate simulations. However, current gas
detection technologies do not allow for obtaining high-quality data at
intermediate spatial scales with high temporal resolution. In this regard the
deployment of a wireless gas sensor network equipped with in situ gas
analysers may be a suitable approach. Here we present a novel, non-dispersive
infrared absorption spectroscopy (NDIR) device that can possibly act as a
central building block of a sensor node to provide high-quality data of
carbon dioxide (CO2) concentrations under field conditions at a
high measurement rate. Employing a gas-based, photoacoustic detector we
demonstrate that miniaturized, low-cost, and low-power consuming
CO2 sensors may be built. The performance is equal to that of
standard NDIR devices but at a much reduced optical path length. Because of
the spectral properties of the photoacoustic detector, no cross-sensitivities
to humidity exist.</p
Descriptive analyses of maternally-derived antibody levels against porcine circovirus 2 (PCV-2) in 3-and 21-day-old piglets from farms of four European countries using different vaccination protocols in sows
Background
Up to now, information on the levels of maternally-derived antibodies (MDA) against PCV-2 in suckling piglets born to sows vaccinated with different strategies is scarce in the literature. In the present observational study, the PCV-2-specific MDA titres from piglets from 109 farms (thirty 3-day-old and thirty 21-day-old piglets per farm) across four different European countries (France n = 30, Germany n = 27, Italy n = 22 and Spain n = 30) using different sow vaccination strategies (during gestation, as a gilt, as a piglet or never) were assessed.
Results
In all four countries, mean log PCV-2 MDA titres were higher in 3-day-old piglets than in the 3-week-old ones, being significant in most of all the comparisons performed. Within each country, the highest PCV-2-specific MDA titres were observed in the 3-day-old piglets born to sows vaccinated during gestation. Indeed, in the four countries, more than 60% of this subpopulation (3-day-old piglets from sows vaccinated during pregnancy) had the highest log PCV-2 titres detectable with the ELISA technique used in this study. The lowest MDA titres were more variable. Whereas in France and Germany the lowest titres corresponded to 21-day-old piglets born from sows vaccinated as a piglet, in Italy, they corresponded to 21-day-old piglets derived from sows vaccinated as a gilt and in Spain to 21-day-old piglets born from non-vaccinated sows. In this study, PCV-2-specific MDA titres at 3 and 21 days of age were not affected by sow parity.
Conclusions
Data obtained could be considered as a European global overview of PCV-2-specific MDA titres present in the pre-vaccinated piglet populations in different European countries, with titres tending to be higher in younger piglets, but with values variable among countries and sow vaccination strategies.info:eu-repo/semantics/publishedVersio
Descriptive analyses of maternally-derived antibody levels against porcine circovirus 2 (PCV-2) in 3- and 21-day-old piglets from farms of four European countries using different vaccination protocols in sows
Background Up to now, information on the levels of maternally-derived antibodies (MDA) against PCV-2 in suckling piglets born to sows vaccinated with different strategies is scarce in the literature. In the present observational study, the PCV-2-specific MDA titres from piglets from 109 farms (thirty 3-day-old and thirty 21-day-old piglets per farm) across four different European countries (France n = 30, Germany n = 27, Italy n = 22 and Spain n = 30) using different sow vaccination strategies (during gestation, as a gilt, as a piglet or never) were assessed. Results In all four countries, mean log PCV-2 MDA titres were higher in 3-day-old piglets than in the 3-week-old ones, being significant in most of all the comparisons performed. Within each country, the highest PCV-2-specific MDA titres were observed in the 3-day-old piglets born to sows vaccinated during gestation. Indeed, in the four countries, more than 60% of this subpopulation (3-day-old piglets from sows vaccinated during pregnancy) had the highest log PCV-2 titres detectable with the ELISA technique used in this study. The lowest MDA titres were more variable. Whereas in France and Germany the lowest titres corresponded to 21-day-old piglets born from sows vaccinated as a piglet, in Italy, they corresponded to 21-day-old piglets derived from sows vaccinated as a gilt and in Spain to 21-day-old piglets born from non-vaccinated sows. In this study, PCV-2-specific MDA titres at 3 and 21 days of age were not affected by sow parity. Conclusions Data obtained could be considered as a European global overview of PCV-2-specific MDA titres present in the pre-vaccinated piglet populations in different European countries, with titres tending to be higher in younger piglets, but with values variable among countries and sow vaccination strategies
On the Efetov-Wegner terms by diagonalizing a Hermitian supermatrix
The diagonalization of Hermitian supermatrices is studied. Such a change of
coordinates is inevitable to find certain structures in random matrix theory.
However it still poses serious problems since up to now the calculation of all
Rothstein contributions known as Efetov-Wegner terms in physics was quite
cumbersome. We derive the supermatrix Bessel function with all Efetov-Wegner
terms for an arbitrary rotation invariant probability density function. As
applications we consider representations of generating functions for Hermitian
random matrices with and without an external field as integrals over
eigenvalues of Hermitian supermatrices. All results are obtained with all
Efetov-Wegner terms which were unknown before in such an explicit and compact
representation.Comment: 23 pages, PACS: 02.30.Cj, 02.30.Fn, 02.30.Px, 05.30.Ch, 05.30.-d,
05.45.M
Alpha-Amino-Beta-Carboxy-Muconate-Semialdehyde Decarboxylase Controls Dietary Niacin Requirements for NAD+ Synthesis
NAD+ is essential for redox reactions in energy metabolism and necessary for DNA repair and epigenetic modification. Humans require sufficient amounts of dietary niacin (nicotinic acid, nicotinamide, and nicotinamide riboside) for adequate NAD+ synthesis. In contrast, mice easily generate sufficient NAD+ solely from tryptophan through the kynurenine pathway. We show that transgenic mice with inducible expression of human alpha-amino-beta-carboxy-muconate-semialdehyde decarboxylase (ACMSD) become niacin dependent similar to humans when ACMSD expression is high. On niacin-free diets, these acquired niacin dependency (ANDY) mice developed reversible, mild-to-severe NAD+ deficiency, depending on the nutrient composition of the diet. NAD deficiency in mice contributed to behavioral and health changes that are reminiscent of human niacin deficiency. This study shows that ACMSD is a key regulator of mammalian dietary niacin requirements and NAD+ metabolism and that the ANDY mouse represents a versatile platform for investigating pathologies linked to low NAD+ levels in aging and neurodegenerative diseases
Theory of superfluidity and drag force in the one-dimensional Bose gas
The one-dimensional Bose gas is an unusual superfluid. In contrast to higher
spatial dimensions, the existence of non-classical rotational inertia is not
directly linked to the dissipationless motion of infinitesimal impurities.
Recently, experimental tests with ultracold atoms have begun and quantitative
predictions for the drag force experienced by moving obstacles have become
available. This topical review discusses the drag force obtained from linear
response theory in relation to Landau's criterion of superfluidity. Based upon
improved analytical and numerical understanding of the dynamical structure
factor, results for different obstacle potentials are obtained, including
single impurities, optical lattices and random potentials generated from
speckle patterns. The dynamical breakdown of superfluidity in random potentials
is discussed in relation to Anderson localization and the predicted
superfluid-insulator transition in these systems.Comment: 17 pages, 12 figures, mini-review prepared for the special issue of
Frontiers of Physics "Recent Progresses on Quantum Dynamics of Ultracold
Atoms and Future Quantum Technologies", edited by Profs. Lee, Ueda, and
Drummon
Quantum flutter of supersonic particles in one-dimensional quantum liquids
The non-equilibrium dynamics of strongly correlated many-body systems
exhibits some of the most puzzling phenomena and challenging problems in
condensed matter physics. Here we report on essentially exact results on the
time evolution of an impurity injected at a finite velocity into a
one-dimensional quantum liquid. We provide the first quantitative study of the
formation of the correlation hole around a particle in a strongly coupled
many-body quantum system, and find that the resulting correlated state does not
come to a complete stop but reaches a steady state which propagates at a finite
velocity. We also uncover a novel physical phenomenon when the impurity is
injected at supersonic velocities: the correlation hole undergoes long-lived
coherent oscillations around the impurity, an effect we call quantum flutter.
We provide a detailed understanding and an intuitive physical picture of these
intriguing discoveries, and propose an experimental setup where this physics
can be realized and probed directly.Comment: 13 pages, 9 figure
Quantum dynamics of a single, mobile spin impurity
Quantum magnetism describes the properties of many materials such as transition metal oxides and cuprate superconductors. One of its elementary processes is the propagation of spin excitations. Here we study the quantum dynamics of a deterministically created spin-impurity atom, as it propagates in a one-dimensional lattice system. We probe the full spatial probability distribution of the impurity at different times using single-site-resolved imaging of bosonic atoms in an optical lattice. In the Mott-insulating regime, a post-selection of the data allows to reduce the effect of temperature, giving access to a space- and time-resolved measurement of the quantum-coherent propagation of a magnetic excitation in the Heisenberg model. Extending the study to the bath's superfluid regime, we determine quantitatively how the bath strongly affects the motion of the impurity. The experimental data shows a remarkable agreement with theoretical predictions allowing us to determine the effect of temperature on the coherence and velocity of impurity motion. Our results pave the way for a new approach to study quantum magnetism, mobile impurities in quantum fluids, and polarons in lattice systems
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