314 research outputs found
The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions
Interacting fermions are ubiquitous in nature and understanding their
thermodynamics is an important problem. We measure the equation of state of a
two-component ultracold Fermi gas for a wide range of interaction strengths at
low temperature. A detailed comparison with theories including Monte-Carlo
calculations and the Lee-Huang-Yang corrections for low-density bosonic and
fermionic superfluids is presented. The low-temperature phase diagram of the
spin imbalanced gas reveals Fermi liquid behavior of the partially polarized
normal phase for all but the weakest interactions. Our results provide a
benchmark for many-body theories and are relevant to other fermionic systems
such as the crust of neutron stars.Comment: 28 pages, 7 figure
Bose-Hubbard physics in synthetic dimensions from interaction Trotterization
Activating transitions between a set of atomic internal states has emerged as
an elegant scheme by which lattice models can be designed in ultracold atomic
gases. In this approach, the internal states can be viewed as fictitious
lattice sites defined along a synthetic dimension, hence offering a powerful
method by which the spatial dimensionality of the system can be extended.
Inter-particle collisions generically lead to infinite-range interactions along
the synthetic dimensions, which a priori precludes the design of
Bose-Hubbard-type models featuring on-site interactions. In this article, we
solve this obstacle by introducing a protocol that realizes strong and tunable
"on-site" interactions along an atomic synthetic dimension. Our scheme is based
on pulsing strong intra-spin interactions in a fast and periodic manner, hence
realizing the desired "on-site" interactions in a digital (Trotterized) manner.
We explore the viability of this protocol by means of numerical calculations,
which we perform on various examples that are relevant to ultracold-atom
experiments. This general method, which could be applied to various atomic
species by means of fast-response protocols based on Fano-Feshbach resonances,
opens the route for the exploration of strongly-correlated matter in synthetic
dimensions.Comment: 9 pages, 6 figure
Fossiliferous Cretaceous Amber from Myanmar (Burma): Its Rediscovery, Biotic Diversity, and Paleontological Significance
The termites of Early Eocene Cambay amber, with the earliest record of the Termitidae (Isoptera)
This is the publisher's version, also available electronically from http://www.pensoft.net.The fauna of termites (Isoptera) preserved in Early Eocene amber from the Cambay Basin (Gujarat, India) are described and figured. Three new genera and four new species are recognized, all of them Neoisoptera – Parastylotermes krishnai Engel & Grimaldi, sp. n. (Stylotermitidae); Prostylotermes kamboja Engel & Grimaldi, gen. et sp. n. (Stylotermitidae?); Zophotermes Engel, gen. n., with Zophotermes ashoki Engel & Singh, sp. n. (Rhinotermitidae: Prorhinotermitinae); and Nanotermes isaacae Engel & Grimaldi, gen. et sp. n. (Termitidae: Termitinae?). Together these species represent the earliest Tertiary records of the Neoisoptera and the oldest definitive record of Termitidae, a family that comprises >75% of the living species of Isoptera. Interestingly, the affinities of the Cambay amber termites are with largely Laurasian lineages, in this regard paralleling relationships seen between the fauna of bees and some flies. Diversity of Neoisoptera in Indian amber may reflect origin of the amber deposit in Dipterocarpaceae forests formed at or near the paleoequator
Exploring patterns of beta-diversity to test the consistency of biogeographical boundaries: A case study across forest plant communities of Italy
Aim: To date, despite their great potential biogeographical regionalization models have been mostly developed on descriptive and empirical bases. This paper aims at applying the beta-diversity framework on a statistically representative data set to analytically test the consistency of the biogeographical regionalization of Italian forests. Location: Italy. Taxon: Vascular plants. Methods: Forest plant communities were surveyed in 804 plots made in a statistically representative sample of forest communities made by 201 sites of Italian forests across the three biogeographical regions of the country: Alpine, Continental, and Mediterranean. We conducted an ordination analysis and an analysis of beta-diversity, decomposing it into its turnover and nestedness components. Results: Our results provide only partial support to the consistency of the biogeographical regionalization of Italy. While the differences in forest plant communities support the distinction between the Alpine and the other two regions, differences between Continental and Mediterranean regions had lower statistical support. Pairwise beta-diversity and its turnover component are higher between- than within-biogeographical regions. This suggests that different regional species pools contribute to assembly of local communities and that spatial distance between-regions has a stronger effect than that within-regions. Main conclusions: Our findings confirm a biogeographical structure of the species pools that is captured by the biogeographical regionalization. However, nonsignificant differences between the Mediterranean and Continental biogeographical regions suggest that this biogeographical regionalization is not consistent for forest plant communities. Our results demonstrate that an analytical evaluation of species composition differences among regions using beta-diversity analysis is a promising approach for testing the consistency of biogeographical regionalization models. This approach is recommended to provide support to the biogeographical regionalization used in some environmental conservation polices adopted by EU
Superfluid fraction in an interacting spatially modulated Bose-Einstein condensate
At zero temperature, a Galilean-invariant Bose fluid is expected to be fully
superfluid. Here we investigate theoretically and experimentally the quenching
of the superfluid density of a dilute Bose-Einstein condensate due to the
breaking of translational (and thus Galilean) invariance by an external 1D
periodic potential. Both Leggett's bound fixed by the knowledge of the total
density and the anisotropy of the sound velocity provide a consistent
determination of the superfluid fraction. The use of a large-period lattice
emphasizes the important role of two-body interactions on superfluidity
Improved outcomes in the treatment of post-myocardial infarction ventricular septal defect with percutaneous TandemHeart left ventricular mechanical circulatory support
Background
Post-myocardial infarction (MI) ventricular septal defect (VSD) is associated with 40% - 50% of peri-procedural mortalities; however, it is amenable to catheter-based therapies. We retrospectively investigated the impact of state-of-the-art bridging percutaneous left ventricular mechanical circulatory support (MCS) using the TandemHeart® (TH) ventricular assist device (VAD) on a patient with post-MI VSD.
Results
From July 2008 to March 2014, 23 patients were referred for treatment of post-MI VSD. Initially, 18/23 patients required MCS; 12 received an intra-aortic balloon pump (IABP), while 6 received initial TH support. Seven of the IABP patients later required TH support. Catheter-based device VSD closure was performed in 18 of the patients; however, three patients required conversion to conventional open cardiac surgical repair via VSD patch closure due to failure of the catheter-based approach. Five patients with TH underwent planned open cardiac surgical repair due to an anticipated lack of suitability for catheter-based treatment. Results revealed that delayed closure after MI correlated with improved survival. Overall, 30-day and 6-month survival rates were 83% (19/23) and 70% (16/23), respectively.
Conclusions
Further, Qp/Qs ratios of \u3c2.4 correlated with successful percutaneous VSD repair, and this assessment should be further explored as an assessment to inform clinical judgment in patients with post-MI VSD treatment
Global and Regional IUCN Red List Assessments: 15
In this contribution, the conservation status assessment of three vascular plants are presented according to IUCN categories and criteria. It includes the assessment of Oryza rhizomatis D.A.Vaughan and Saxifraga facchinii W.D.J.Koch at a global level and Helianthemum caput-felis Boiss. at a regional level
Factors influencing epiphytic bryophyte and lichen species richness at different spatial scales in managed temperate forests
The effect of management related factors on species richness of epiphytic
bryophytes and lichens was studied in managed deciduous-coniferous mixed
forests in Western-Hungary. At the stand level, the potential explanatory
variables were tree species composition, stand structure, microclimate and
light conditions, landscape and historical variables; while at tree level host
tree species, tree size and light were studied. Species richness of the two
epiphyte groups was positively correlated. Both for lichen and bryophyte plot
level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for
bryophytes the presence of large trees, while for lichens amount and
heterogeneity of light were important. Tree level richness was mainly
determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size
generally increased tree level species richness, except on pine for bryophytes
and on hornbeam for lichens.
The key variables for epiphytic diversity of the region were directly
influenced by recent forest management; historical and landscape variables
were not influential. Forest management oriented to the conservation of
epiphyte s should focus on: (i) the maintenance of tree species diversity in
mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks);
(iii) conserving large trees within the stands; (iv) providing the presence of
shrub and regeneration layer; (v) creating heterogeneous light conditions. For
these purposes tree selection and selective cutting management seem more
appropriate than shelterwood system
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