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Anaerobic 4-hydroxyproline utilization: Discovery of a new glycyl radical enzyme in the human gut microbiome uncovers a widespread microbial metabolic activity.
The discovery of enzymes responsible for previously unappreciated microbial metabolic pathways furthers our understanding of host-microbe and microbe-microbe interactions. We recently identified and characterized a new gut microbial glycyl radical enzyme (GRE) responsible for anaerobic metabolism of trans-4-hydroxy-l-proline (Hyp). Hyp dehydratase (HypD) catalyzes the removal of water from Hyp to generate Δ1-pyrroline-5-carboxylate (P5C). This enzyme is encoded in the genomes of a diverse set of gut anaerobes and is prevalent and abundant in healthy human stool metagenomes. Here, we discuss the roles HypD may play in different microbial metabolic pathways as well as the potential implications of this activity for colonization resistance and pathogenesis within the human gut. Finally, we present evidence of anaerobic Hyp metabolism in sediments through enrichment culturing of Hyp-degrading bacteria, highlighting the wide distribution of this pathway in anoxic environments beyond the human gut
The Euler-Betti Algorithm to identify foliations in Hilbert Scheme
Foliations in the complex projective plane are uniquely determined by their
singular locus, which is in correspondence with a zero-dimensional ideal.
However, this correspondence is not surjective. We give conditions to determine
whether an ideal arises as the singular locus of a foliation or not.
Furthermore, we give an effective method to construct the foliation in the
positive case
Diffraction in time of a confined particle and its Bohmian paths
Diffraction in time of a particle confined in a box which its walls are
removed suddenly at is studied. The solution of the time-dependent
Schr\"{o}dinger equation is discussed analytically and numerically for various
initial wavefunctions. In each case Bohmian trajectories of the particles are
computed and also the mean arrival time at a given location is studied as a
function of the initial state.Comment: 8 pages, 6 figure
Disclosing hidden information in the quantum Zeno effect: Pulsed measurement of the quantum time of arrival
Repeated measurements of a quantum particle to check its presence in a region
of space was proposed long ago [G. R. Allcock, Ann. Phys. {\bf 53}, 286 (1969)]
as a natural way to determine the distribution of times of arrival at the
orthogonal subspace, but the method was discarded because of the quantum Zeno
effect: in the limit of very frequent measurements the wave function is
reflected and remains in the original subspace. We show that by normalizing the
small bits of arriving (removed) norm, an ideal time distribution emerges in
correspondence with a classical local-kinetic-energy distribution.Comment: 5 pages, 4 figures, minor change
Open inflationary universes in a brane world cosmology
In this paper, we study a type of one-field model for open inflationary
universe models in the context of the brane world models. In the scenario of a
one-bubble universe model, we determine and characterize the existence of the
Coleman-De Lucia instanton, together with the period of inflation after
tunneling has occurred. Our results are compared to those found in the Einstein
theory of Relativistic Models.Comment: 8 pages, 4 Figures, accepted in Physical Review
Supranutritional doses of vitamin E to improve lamb meat quality
Vitamin E is a fat-soluble antioxidant, therefore, it can be stored in any fat depot in the body, where it exerts a potent chain-breaking antioxidant effect. Moreover, the antioxidant activity of vitamin E-like compounds is also present in meat post mortem. The deposition of tocopherol in the muscle depends on the dosage, the source, and the period of supplementation, so different dosage-time combinations have been developed. Vitamin E does not affect production parameters if minimum requirements for function and growth are satisfied, but it could influence lamb fatty acid profile. During display, it protects PUFA from degradation, reducing lipid oxidation and, therefore, delaying discolouration. Furthermore, vitamin E would indirectly affect the development of lamb aroma by reducing protein and lipid oxidation. To facilitate optimal supplementation rates by producers and retailers, the present paper reviews vitamin E chemistry, biochemistry, nutrition and its ability to maintain lamb quality
An accelerated closed universe
We study a model in which a closed universe with dust and quintessence matter
components may look like an accelerated flat Friedmann-Robertson-Walker (FRW)
universe at low redshifts. Several quantities relevant to the model are
expressed in terms of observed density parameters, and
, and of the associated density parameter related
to the quintessence scalar field .Comment: 11 pages. For a festschrift honoring Alberto Garcia. To appear in
Gen. Rel. Gra
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