24 research outputs found
Particle statistics and lossy dynamics of ultracold atoms in optical lattices
Experimental control over ultracold quantum gases has made it possible to investigate low-dimensional systems of both bosonic and fermionic atoms. In closed one-dimensional systems there are many similarities in the dynamics of local quantities for spinless fermions and strongly interacting "hard-core" bosons, which on a lattice can be formalized via a Jordan-Wigner transformation. In this study, we analyze the similarities and differences for spinless fermions and hard-core bosons on a lattice in the presence of particle loss. The removal of a single fermion causes differences in local quantities compared with the bosonic case because of the different particle exchange symmetry in the two cases. We identify deterministic and probabilistic signatures of these dynamics in terms of local particle density, which could be measured in ongoing experiments with quantum gas microscopes
Metal--topological-insulator transition in the quantum kicked rotator with Z2 symmetry
The quantum kicked rotator is a periodically driven dynamical system with a
metal-insulator transition. We extend the model so that it includes phase
transitions between a metal and a topological insulator, in the universality
class of the quantum spin Hall effect. We calculate the Z2 topological
invariant using a scattering formulation that remains valid in the presence of
disorder. The scaling laws at the phase transition can be studied efficiently
by replacing one of the two spatial dimensions with a second incommensurate
driving frequency. We find that the critical exponent does not depend on the
topological invariant, in agreement with earlier independent results from the
network model of the quantum spin Hall effect.Comment: 5 figures, 6 page
Modern applications of machine learning in quantum sciences
In these Lecture Notes, we provide a comprehensive introduction to the most recent advances in the application of machine learning methods in quantum sciences. We cover the use of deep learning and kernel methods in supervised, unsupervised, and reinforcement learning algorithms for phase classification, representation of many-body quantum states, quantum feedback control, and quantum circuits optimization. Moreover, we introduce and discuss more specialized topics such as differentiable programming, generative models, statistical approach to machine learning, and quantum machine learning
Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model
Recycled aggregate concrete (RAC) has emerged as a viable solution for
solving some of the environmental problems of concrete production.
However, design guidelines for deflection control of reinforced RAC
members have not yet been proposed. This study presents a
comprehensive analysis of the applicability of the fib Model Code 2010
(MC2010) deflection control model to reinforced RAC beams. Three
databases of long-term studies on natural aggregate concrete (NAC) and
RAC beams were compiled and meta-analyses of deflection predictions
by MC2010 were performed. First, the MC2010 deflection control model
was tested against a large database of long-term tests on NAC beams.
Second, a database of RAC and companion NAC beams was compiled
and initial and long-term deflections were calculated using the MC2010
model. It was shown that deflections of RAC beams are significantly
underestimated relative to NAC beams. Previously proposed
modifications for MC2010 equations for shrinkage strain and creep
coefficient were used, and new modifications for the modulus of elasticity
and empirical coefficient β were proposed. The improved MC2010
deflection control model on RAC beams was shown to have equal
performance to that on companion NAC beams. The proposals presented
in this paper can help engineers to more reliably perform deflection
control of reinforced RAC members.This is the peer-reviewed version of the article:
N. Tošić, S. Marinković, and J. de Brito, ‘Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model’, Structural Concrete, vol. 20, no. 6, pp. 2015–2029, 2019 [https://doi.org/10.1002/suco.201900035
Accuracy of H. pylori fecal antigen test using fecal immunochemical test (FIT)
Background: Gastric and colorectal cancer (CRC) are both one of the most common cancers worldwide. In many countries fecal immunochemical tests (FIT)-based CRC screening has been implemented. We investigated if FIT can also be applied for detection of H. pylori, the main risk factor for gastric cancer. Methods: This prospective study included participants over 18 years of age referred for urea breath test (UBT). Patients were excluded if they had used antibiotics/bismuth in the past 4 weeks, or a proton pomp inhibitor (PPI) in the past 2 weeks. Participants underwent UBT, ELISA stool antigen test in standard feces tube (SAT), ELISA stool antigen test in FIT tube (Hp-FIT), and blood sampling, and completed a questionnaire on user friendliness. UBT results were used as reference. Results: A total of 182 patients were included (37.4% male, median age 52.4 years (IQR 22.4)). Of these, 60 (33.0%) tested H. pylori positive. SAT and Hp-FIT showed comparable overall accuracy 71.1% (95%CI 63.2–78.3) vs. 77.6% (95%CI 70.4–83.8), respectively (p = 0.97). Sensitivity of SAT was 91.8% (95%CI 80.4–97.7) versus 94.2% (95%CI 84.1–98.9) of Hp-FIT (p = 0.98). Serology scored low with an overall accuracy of 49.7% (95%CI 41.7–57.7). Hp-FIT showed the highest overall user convenience. Conclusions: FIT can be used with high accuracy and sensitivity for diagnosis of H. pylori and is rated as the most convenient test. Non-invasive Hp-FIT test is highly promising for combined upper and lower gastrointestinal (pre-) cancerous screening. Further research should investigate the clinical implications, benefits and cost-effectiveness of such an approach