12 research outputs found
The Miscible-Immiscible Quantum Phase Transition in Coupled Two-Component Bose-Einstein Condensates in 1D Optical Lattices
Using numerical techniques, we study the miscible-immiscible quantum phase
transition in a linearly coupled binary Bose-Hubbard model Hamiltonian that can
describe low-energy properties of a two-component Bose-Einstein condensate in
optical lattices. With the quantum many-body ground state obtained from density
matrix renormalization group algorithm, we calculate the characteristic
physical quantities of the phase transition controlled by the linear coupling
between two components. Furthermore we calculate the Binder cumulant to
determine the critical point and draw the phase diagram. The strong-coupling
expansion shows that in the Mott insulator regime the model Hamiltonian can be
mapped to a spin 1/2 XXZ model with a transverse magnetic field.Comment: 10 pages, 10 figures, submitted to Phys. Rev.
Phase separation and pattern formation in a binary Bose-Einstein condensate
The miscibility-immiscibility phase transition in binary Bose-Einstein condensates (BECs) can be controlled by a coupling between the two components. Here we propose a new scheme that uses coupling-induced pattern formation to test the Kibble-Zurek mechanism (KZM) of topological-defect formation in a quantum phase transition. For a binary BEC in a ring trap we find that the number of domains forming the pattern scales as a function of the coupling quench rate with an exponent as predicted by the KZM. For a binary BEC in an elongated harmonic trap we find a different scaling law due to the transition being spatially inhomogeneous. We perform a “quantum simulation” of the harmonically trapped system in a ring trap to verify the scaling exponent
Quantum enhanced measurement of rotations with a spin-1 Bose-Einstein condensate in a ring trap
We present a model of a spin-squeezed rotation sensor utilizing the Sagnac effect in a spin-1 Bose-Einstein condensate in a ring trap. The two input states for the interferometer are seeded using Raman pulses with Laguerre-Gauss beams and are amplified by the bosonic enhancement of spin-exchange collisions, resulting in spin-squeezing and potential quantum enhancement of the interferometry. The ring geometry has an advantage over separated beam path atomic rotation sensors due to the uniform condensate density. We model the interferometer both analytically and numerically for realistic experimental parameters and find that significant quantum enhancement is possible, but this enhancement is partially degraded when working in a regime with strong atomic interactions
Causality and defect formation in the dynamics of an engineered quantum phase transition in a coupled binary Bose-Einstein condensate
Continuous phase transitions occur in a wide range of physical systems, and
provide a context for the study of non-equilibrium dynamics and the formation
of topological defects. The Kibble-Zurek (KZ) mechanism predicts the scaling of
the resulting density of defects as a function of the quench rate through a
critical point, and this can provide an estimate of the critical exponents of a
phase transition. In this work we extend our previous study of the
miscible-immiscible phase transition of a binary Bose-Einstein condensate (BEC)
composed of two hyperfine states in which the spin dynamics are confined to one
dimension [J. Sabbatini et al., Phys. Rev. Lett. 107, 230402 (2011)]. The
transition is engineered by controlling a Hamiltonian quench of the coupling
amplitude of the two hyperfine states, and results in the formation of a random
pattern of spatial domains. Using the numerical truncated Wigner phase space
method, we show that in a ring BEC the number of domains formed in the phase
transitions scales as predicted by the KZ theory. We also consider the same
experiment performed with a harmonically trapped BEC, and investigate how the
density inhomogeneity modifies the dynamics of the phase transition and the KZ
scaling law for the number of domains. We then make use of the symmetry between
inhomogeneous phase transitions in anisotropic systems, and an inhomogeneous
quench in a homogeneous system, to engineer coupling quenches that allow us to
quantify several aspects of inhomogeneous phase transitions. In particular, we
quantify the effect of causality in the propagation of the phase transition
front on the resulting formation of domain walls, and find indications that the
density of defects is determined during the impulse to adiabatic transition
after the crossing of the critical point.Comment: 23 pages, 10 figures. Minor corrections, typos, additional referenc
Inter-rater agreement of CDC criteria and ASEPSIS score in assessing surgical site infections after cesarean section: a prospective observational study
ObjectiveTo assess and compare the inter-rater agreement of the CDC criteria and the ASEPSIS score in identifying surgical site infections after cesarean section.MethodsProspective observational study including 110 patients subjected to a cesarean section at our institution. Surgical wounds were managed according to standard care and were photographed on the third, seventh, and thirtieth postoperative day or during any evaluation in case of complications. Three expert surgeons reviewed the prospectively gathered data and photographs and classified each wound using CDC criteria and the ASEPSIS score. The inter-rater agreements of CDC criteria and ASEPSIS score were determined with Krippendorff's Alpha with linear weights and compared with a confidence interval approach.ResultsThe weighted α coefficient for CDC criteria was 0.587 (95%CI, 0.411–0.763, p < 0.001, “moderate” agreement according to Altman's interpretation of weighted agreement coefficient), while the weighted α coefficient for the ASEPSIS score was 0.856 (95%CI, 0.733–0.980, p < 0.001, “very good” agreement).ConclusionASEPSIS score presents a “very good” inter-rater agreement for surgical site infections identification after cesarean, resulting in a more objective method than CDC criteria (“moderate” inter-rater agreement). ASEPSIS score could represent an objective tool for managing and monitoring surgical site infections after cesarean section, also by photographic evaluation
Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study
: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI
Diel behavior from temporally scheduled hauling of the red shrimps Aristeus antennatus and Aristaeomorpha foliacea in the Spartivento Canyon (Southern Sardinia, Italy)
The Crustacean Society Summer Meeting (TCSSM) - 10th Colloquium Crustacea Decapoda Mediterranea (CCDM), 3-7 June 2012, Athens, GreeceThe red shrimp Aristeus antennatus (Risso 1816) and the giant red shrimp Aristaeomorpha foliacea (Risso 1827) are one of the most important and exploited demersal (400-800 m) resources in the Western Mediterranean Sea1. Although their bathymetric distribution has been investigated, information on its variation over the 24-h scale as result of rhythmic nektobenthic displacements on population is scarce2. In this context, we carried out a temporally scheduled hauling within different depths strata in order to characterize the displacement rhythms of both species, in relation to the local topographic and oceanographic conditionsPeer Reviewe