Hartree-Fock-Bogoliubov theory versus local-density approximation for superfluid trapped fermionic atoms

We investigate a gas of superfluid fermionic atoms trapped in two hyperfine states by a spherical harmonic potential. We propose a new regularization method to remove the ultraviolet divergence in the Hartree-Fock-Bogoliubov equations caused by the use of a zero-range atom-atom interaction. Compared with a method used in the literature, our method is simpler and has improved convergence properties. Then we compare Hartree-Fock-Bogoliubov calculations with the semiclassical local-density approximation. We observe that for systems containing a small number of atoms shell effects, which cannot be reproduced by the semiclassical calculation, are very important. For systems with a large number of atoms at zero temperature the two calculations are in quite good agreement, which, however, is deteriorated at non-zero temperature, especially near the critical temperature. In this case the different behavior can be explained within the Ginzburg-Landau theory.Comment: 12 pages, 8 figures, revtex; v2: references and clarifying remarks adde

Analyzing a Bose polaron across resonant interactions

Recently, two independent experiments reported the observation of long-lived polarons in a Bose-Einstein condensate, providing an excellent setting to study the generic scenario of a mobile impurity interacting with a quantum reservoir. Here, we expand the experimental analysis by disentangling the effects of trap inhomogeneities and the many-body continuum in one of these experiments. This makes it possible to extract the energy of the polaron at a well-defined density as a function of the interaction strength. Comparisons with quantum Monte-Carlo as well as diagrammatic calculations show good agreement, and provide a more detailed picture of the polaron properties at stronger interactions than previously possible. Moreover, we develop a semi-classical theory for the motional dynamics and three-body loss of the polarons, which partly explains a previously unresolved discrepancy between theory and experimental observations for repulsive interactions. Finally, we utilize quantum Monte-Carlo calculations to demonstrate that the findings reported in the two experiments are consistent with each other

Spin Excitations in a Fermi Gas of Atoms

We have experimentally investigated a spin excitation in a quantum degenerate Fermi gas of atoms. In the hydrodynamic regime the damping time of the collective excitation is used to probe the quantum behavior of the gas. At temperatures below the Fermi temperature we measure up to a factor of 2 reduction in the excitation damping time. In addition we observe a strong excitation energy dependence for this quantum statistical effect.Comment: 4 pages, 3 figure

Density wave instabilities of tilted fermionic dipoles in a multilayer geometry

We consider the density wave instability of fermionic dipoles aligned by an external field, and moving in equidistant layers at zero temperature. Using a conserving Hartree-Fock approximation, we show that correlations between dipoles in different layers significantly decrease the critical coupling strength for the formation of density waves when the distance between the layers is comparable to the inter-particle distance within each layer. This effect, which is strongest when the dipoles are oriented perpendicular to the planes, causes the density waves in neighboring layers to be in-phase for all orientations of the dipoles. We furthermore demonstrate that the effects of the interlayer interaction can be understood from a classical model. Finally, we show that the interlayer correlations are important for experimentally relevant dipolar molecules, including the chemically stable $^{23}$Na$^{40}$K and $^{40}$K$^{133}$Cs, where the density wave regime is within experimental reach.Comment: 18 pages, 11 figures; new version with expanded discussion on experimental relevance including one new figur

Direct identification and susceptibility testing of enteric bacilli from positive blood cultures using VITEK (GNI+/GNS-GA)

AbstractObjective To study the possibility of reporting results of identification and susceptibility testing of Gram-negative bacilli the same day as bacteremia is detected by using direct inoculation from positive blood cultures (Bactec 9240) into VITEK GNI+ and GNS-GA cards.Methods All blood cultures with Gram-negative enteric bacillus-like morphology on microscopy found to be positive on workdays between 15 June 1999 and 29 February 2000 were included. Identification and susceptibility testing were done by three methods: the direct method using a suspension made by differential centrifugation of positive blood culture broth for inoculation of the VITEK cards; the standard method using an inoculum made from an overnight culture on a solid media; and the routine method (reference method) using conventional testing.Results Of 169 isolates, the direct method resulted in 75% correct identifications, 9% misidentifications and 17% non-identifications. All misidentified isolateswere Escherichia coli, of which 80% were reported as Salmonella arizonae. Five biochemical tests yielded most of the aberrant results; correcting the citrate and malonate reactions in most cases led to correct identification by the VITEK database. Despite a negative H2S reaction, 11 E. coli isolates were reported as S. arizonae. Two-thirds (69%) of identifications were reported within 6 h, and 95% of these were correct. The direct susceptibility testing method was assessable for 140 isolates. Correct results were found in 99% of isolate-antimicrobial combinations, and 85% were reported within 6 h.Conclusion The direct VITEK method could correctly report identifications and susceptibility patterns within 6 h, making same-day reporting possible for almost two-thirds (63%) of bacteremic episodes with Gram-negative bacilli. These results could probably be improved by modification of the identification algorithms of the VITEK software

Endo-sinus bone gain following osteotome-mediated sinus floor elevation with Bio-Oss Collagen compared with no grafting material: a one-year single-blind randomized controlled trial

The objective of this study was to assess endo-sinus bone gain (ESBG) following osteotome-mediated sinus floor elevation with Bio-Oss Collagen (test) compared with no grafting material (control) using two- and three-dimensional radiographic methods, as part of a randomized controlled trial (ClinicalTrials.gov, NCT04618900). Forty healthy patients who met the necessary eligibility criteria were allocated by block randomization to either the test group (20 patients) or control group (20 patients). Cone beam computed tomography scans were obtained at enrolment (T0), immediately after surgery (T1), at delivery of the prosthetic rehabilitation (T2), and 1 year after functional implant loading (T3). Mean differences were expressed with the 95% confidence interval; significance was set at P &lt; 0.05. ESBG was significantly increased with Bio-Oss Collagen compared with no grafting material at T1, T2, and T3 (P &lt; 0.001). A gradual decrease in ESBG was observed over time with both treatment modalities (P &lt; 0.001), which diminished the difference between the test and control groups at T2 and T3. ESBG was observed to be positively correlated with implant protrusion length and negatively correlated with the residual bone height. In osteotome-mediated sinus floor elevation, the application of Bio-Oss Collagen underneath the elevated Schneiderian membrane improved ESBG significantly when compared with no grafting material. However, the increased ESBG seems not to have positively improved the treatment outcomes in terms of the implant stability quotient or the survival of the implants or suprastructures.</p

Husdyrbruget i Danmark 1886.

Husdyrbruget i Danmark 1886