6,331 research outputs found
Unusual sub-genus associations of fecal Prevotella and Bacteroides with specific dietary patterns
Background: Diet has a recognized effect in shaping gut microbiota. Many studies link an increase in Prevotella to high-fibre diet, while Bacteroides abundance is usually associated with the consumption of animal fat and protein-rich diets. Nevertheless, closely related species and strains may harbour different genetic pools; therefore, further studies should aim to understand whether species of the same genus are consistently linked to dietary patterns or equally responsive to diet variations. Here, we used oligotyping of 16S rRNA gene sequencing data to exploit the diversity within Prevotella and Bacteroides genera in faecal samples of omnivore and non-omnivore subjects from a previously studied cohort.
Results: A great heterogeneity was found in oligotype composition. Nevertheless, different oligotypes within the same genus showed distinctive correlation patterns with dietary components and metabolome. We found that some Prevotella oligotypes are significantly associated with the plant-based diet but some are associated with animal-based nutrients, and the same applies to Bacteroides. Therefore, an indiscriminate association of Bacteroidetes genera with specific dietary patterns may lead to an oversimplified vision that does not take into account sub-genus diversity and the different possible responses to dietary components.
Conclusions: We demonstrated that Prevotella and Bacteroides oligotypes show distinctive correlation patterns with dietary components and metabolome. These results substantiate a current oversimplification of diet-dependent microbe-host associations and highlighted that sub-genus differences must be taken into account when planning gut microbiota modulation for health benefits
Sharp transition for single polarons in the one-dimensional Su-Schrieffer-Heeger model
We study a single polaron in the Su-Schrieffer-Heeger (SSH) model using four
different techniques (three numerical and one analytical). Polarons show a
smooth crossover from weak to strong coupling, as a function of the
electron-phonon coupling strength , in all models where this coupling
depends only on phonon momentum . In the SSH model the coupling also depends
on the electron momentum ; we find it has a sharp transition, at a critical
coupling strength , between states with zero and nonzero momentum of
the ground state. All other properties of the polaron are also singular at
, except the average number of phonons in the polaronic
cloud. This result is representative of all polarons with coupling depending on
and , and will have important experimental consequences (eg., in ARPES
and conductivity experiments)
Interplay between charge-lattice interaction and strong electron correlations in cuprates: phonon anomaly and spectral kinks
We investigate the interplay between strong electron correlations and
charge-lattice interaction in cuprates. The coupling between half breathing
bond stretching phonons and doped holes in the t-t'-J model is studied by
limited phonon basis exact diagonalization method. Nonadiabatic electron-phonon
interaction leads to the splitting of the phonon spectral function at half-way
to the zone boundary at and
to low energy kink feature in the electron dispersion, in agreement with
experimental observations. Another kink due to strong electron correlation
effects is observed at higher energy, depending on the strength of the
charge-lattice coupling.Comment: 4 pages, 3 figure
Measuring the Three-Dimensional Structure of Galaxy Clusters. II. Are clusters of galaxies oblate or prolate?
The intrinsic shape of galaxy clusters can be obtained through a combination
of X-ray and Sunyaev-Zeldovich effect observations once cosmological parameters
are assumed to be known. In this paper we discuss the feasibility of modelling
galaxy clusters as either prolate or oblate ellipsoids. We analyze the
intra-cluster medium distribution for a sample of 25 X-ray selected clusters,
with measured Sunyaev-Zeldovich temperature decrements. A mixed population of
prolate and oblate ellipsoids of revolution fits the data well, with prolate
shapes preferred on a 60-76% basis. We observe an excess of clusters nearly
aligned along the line of sight, with respect to what is expected from a
randomly oriented cluster population, which might imply the presence of a
selection bias in our sample. We also find signs that a more general triaxial
morphology might better describe the morphology of galaxy clusters. Additional
constraints from gravitational lensing could disentangle the degeneracy between
an ellipsoidal and a triaxial morphology, and could also allow an unbiased
determination of the Hubble constant.Comment: 9 pages, 8 figures, accepted for publication in Astrophys.
Polaron features for long-range electron-phonon interaction
The polaron features for long-range electron-phonon interaction are
investigated by extending a variational approach previously proposed for the
study of systems with local coupling. The ground-state spectral weight, the
average kinetic energy, the mean number of phonons, and the electron-lattice
correlation function are discussed for a wide range of model parameters
focusing on the adiabatic regime and comparing the results with the short-range
case (Holstein model). A strong mixing of electronic and phononic degrees of
freedom for small values of the electron-phonon coupling constant is found in
the adiabatic case due to the long-range interaction. Finally a polaron "phase
diagram" is proposed.Comment: 4 figs., to appear in J. Phys.:Condens. Matte
Ultramicronized palmitoylethanolamide reduces viscerovisceral hyperalgesia in a rat model of endometriosis plus ureteral calculosis: role of mast cells.
The effects of ultramicronized palmitoylethanolamide were evaluated on pain behaviours and markers of mast cell (MC) activity in 'a rat model of endometriosis plus ureteral calculosis (ENDO+STONE)-induced viscerovisceral hyperalgesia (VVH). Female Sprague-Dawley rats that underwent surgical induction of endometriosis were randomly assigned to receive active (ultramicronized palmitoylethanolamide 10 mg·kg-1 ·d-1, orally) or placebo treatment for 25 days. At day 21, they underwent ureteral stone formation and were video-recorded till day 25 to evaluate ureteral and uterine pain behaviours. At autopsy (day 25), ureteral condition and number and diameter of endometrial cysts were evaluated. The following were then measured: number and percentage of degranulating MCs, number of vessels, chymase, nerve growth factor (NGF), vascular endothelial growth factor (VEGF), and Flk-1 (VEGF receptor) in cysts, and NGF in dorsal root ganglia (DRG). Ultramicronized palmitoylethanolamide-treated vs placebo-treated rats showed significantly lower number, duration and complexity of ureteral crises, shorter duration of uterine pain, and smaller cyst diameter (0.0001 < P < 0.004); a significantly higher percentage of expelled stones (P < 0.0001); significantly lower MC number (P<0.01), vessel number (P< 0.01), chymase (P< 0.05), NGF (P<0.05), VEGF (P< 0.01), and Flk-1 (P< 0.01) expression in cysts and NGF expression in DRG (P< 0.01). In all animals, the global duration of ureteral crises correlated linearly and directly with cyst diameter, MC number and chymase in cysts, and NGF in cysts and DRG (0.02 < P < 0.0002). Ultramicronized palmitoylethanolamide significantly reduces VVH from ENDO+STONE, probably by modulating MC expression/activity in cysts, thus reducing central sensitization due to noxious signals from endometriotic lesions. The results suggest potential utility of the compound for VVH in clinics
Taking screenshots of the invisible: A study on bacterial contamination of mobile phones from university students of healthcare professions in Rome, Italy
Mobile phones (MPs) are commonly used both in the personal and professional life. We assessed microbiological contamination of MPs from 108 students in healthcare professions (HPs), in relation to their demographic characteristics and MPs handling habits, collected by means of a questionnaire. Cultural and biochemical tests were performed, and statistical analyses were carried out. Staphylococci were present in 85% of MPs, Enterococci in 37%, Coliforms in 6.5%; E. coli was never detected. Staphylococcus epidermidis was the most frequently isolated staphylococcal species (72% of MPs), followed by S. capitis (14%), S. saprophyticus, S. warneri, S. xylosus (6%), and by S. aureus (4%). Heterotrophic Plate Counts (HPC) at 37◦C, ranged from 0 to 1.2 × 104 CFU/dm2 (mean = 362 CFU/dm2). In univariate analysis, the male gender only was significantly associated with higher HPCs and enterococcal contamination. Multiple linear regression models explained only 17% and 16% of the HPC 37◦C and staphylococcal load variability, respectively. Developing specific guidelines for a hygienic use of MPs in clinical settings, for preventing cross-infection risks, is advisable, as well as introducing specific training programs to HP students. MPs decontamination procedures could also be implemented in the community
Animal rennets as sources of dairy lactic acid bacteria
The microbial composition of artisan and industrial animal rennet pastes was studied by using both culture-dependent and -independent
approaches. Pyrosequencing targeting the 16S rRNA gene allowed to identify 361 operational taxonomic units
(OTUs) to the genus/species level. Among lactic acid bacteria (LAB), Streptococcus thermophilus and some lactobacilli, mainly
Lactobacillus crispatus and Lactobacillus reuteri, were the most abundant species, with differences among the samples. Twelve
groups of microorganisms were targeted by viable plate counts revealing a dominance of mesophilic cocci. All rennets were able
to acidify ultrahigh-temperature-processed (UHT) milk as shown by pH and total titratable acidity (TTA). Presumptive LAB
isolated at the highest dilutions of acidified milks were phenotypically characterized, grouped, differentiated at the strain level
by randomly amplified polymorphic DNA (RAPD)-PCR analysis, and subjected to 16S rRNA gene sequencing. Only 18 strains
were clearly identified at the species level, as Enterococcus casseliflavus, Enterococcus faecium, Enterococcus faecalis, Enterococcus
lactis, Lactobacillus delbrueckii, and Streptococcus thermophilus, while the other strains, all belonging to the genus Enterococcus,
could not be allotted into any previously described species. The phylogenetic analysis showed that these strains might
represent different unknown species. All strains were evaluated for their dairy technological performances. All isolates produced
diacetyl, and 10 of them produced a rapid pH drop in milk, but only 3 isolates were also autolytic. This work showed that animal
rennet pastes can be sources of LAB, mainly enterococci, that might contribute to the microbial diversity associated with dairy
productions
Free energy of the Fr\"ohlich polaron in two and three dimensions
We present a novel Path Integral Monte Carlo scheme to solve the Fr\"ohlich
polaron model. At intermediate and strong electron-phonon coupling, the polaron
self-trapping is properly taken into account at the level of an effective
action obtained by a preaveraging procedure with a retarded trial action. We
compute the free energy at several couplings and temperatures in three and two
dimensions. Our results show that the accuracy of the Feynman variational upper
bound for the free energy is always better than 5% although the thermodynamics
derived from it is not correct. Our estimates of the ground state energies
demonstrate that the second cumulant correction to the variational upper bound
predicts the self energy to better than 1% at intermediate and strong coupling.Comment: RevTeX 7 pages 3 figures, revised versio
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