635 research outputs found
Biomarkers in emergency medicine
Researchers navigate the ocean of biomarkers searching for proper targets and optimal utilization of them. Emergency medicine builds up the front line to maximize the utility of clinically validated biomarkers and is the cutting edge field to test the applicability of promising biomarkers emerging from thorough translational researches. The role of biomarkers in clinical decision making would be of greater significance for identification, risk stratification, monitoring, and prognostication of the patients in the critical- and acute-care settings. No doubt basic research to explore novel biomarkers in relation to the pathogenesis
is as important as its clinical counterpart. This special issue includes five selected research papers that cover a variety of biomarker- and disease-related topics
Spectral Gap Amplification
A large number of problems in science can be solved by preparing a specific
eigenstate of some Hamiltonian H. The generic cost of quantum algorithms for
these problems is determined by the inverse spectral gap of H for that
eigenstate and the cost of evolving with H for some fixed time. The goal of
spectral gap amplification is to construct a Hamiltonian H' with the same
eigenstate as H but a bigger spectral gap, requiring that constant-time
evolutions with H' and H are implemented with nearly the same cost. We show
that a quadratic spectral gap amplification is possible when H satisfies a
frustration-free property and give H' for these cases. This results in quantum
speedups for optimization problems. It also yields improved constructions for
adiabatic simulations of quantum circuits and for the preparation of projected
entangled pair states (PEPS), which play an important role in quantum many-body
physics. Defining a suitable black-box model, we establish that the quadratic
amplification is optimal for frustration-free Hamiltonians and that no spectral
gap amplification is possible, in general, if the frustration-free property is
removed. A corollary is that finding a similarity transformation between a
stoquastic Hamiltonian and the corresponding stochastic matrix is hard in the
black-box model, setting limits to the power of some classical methods that
simulate quantum adiabatic evolutions.Comment: 14 pages. New version has an improved section on adiabatic
simulations of quantum circuit
Parameter Estimation with Mixed-State Quantum Computation
We present a quantum algorithm to estimate parameters at the quantum
metrology limit using deterministic quantum computation with one bit. When the
interactions occurring in a quantum system are described by a Hamiltonian , we estimate by zooming in on previous estimations and by
implementing an adaptive Bayesian procedure. The final result of the algorithm
is an updated estimation of whose variance has been decreased in
proportion to the time of evolution under H. For the problem of estimating
several parameters, we implement dynamical-decoupling techniques and use the
results of single parameter estimation. The cases of discrete-time evolution
and reference-frame alignment are also discussed within the adaptive approach.Comment: 12 pages. Improved introduction and technical details moved to
Appendi
Necessary Condition for the Quantum Adiabatic Approximation
A gapped quantum system that is adiabatically perturbed remains approximately
in its eigenstate after the evolution. We prove that, for constant gap, general
quantum processes that approximately prepare the final eigenstate require a
minimum time proportional to the ratio of the length of the eigenstate path to
the gap. Thus, no rigorous adiabatic condition can yield a smaller cost. We
also give a necessary condition for the adiabatic approximation that depends on
local properties of the path, which is appropriate when the gap varies.Comment: 5 pages, 1 figur
Quantum Speedup by Quantum Annealing
We study the glued-trees problem of Childs et. al. in the adiabatic model of
quantum computing and provide an annealing schedule to solve an oracular
problem exponentially faster than classically possible. The Hamiltonians
involved in the quantum annealing do not suffer from the so-called sign
problem. Unlike the typical scenario, our schedule is efficient even though the
minimum energy gap of the Hamiltonians is exponentially small in the problem
size. We discuss generalizations based on initial-state randomization to avoid
some slowdowns in adiabatic quantum computing due to small gaps.Comment: 7 page
Importance of spinal deformity index in risk evaluation of VCF (vertebral compression fractures) in obese subjects: prospective study.
Introduction
Obesity and osteoporosis share many features and recent studies have identified many similarities suggesting common pathophysiological mechanisms. Obesity is associated with a higher risk of non-traumatic fractures despite bone mineral density (BMD) being normal or even increased.
Materials and methods
54 obese subjects were analyzed (51 ± 16 years, 10 males, 44 females). Spinal deformity index (SDI) is a semi-quantitative method that may be a surrogate index of bone microarchitecture. SDI index was higher in patients than in controls. In 87.5 % of patients and 10 % of controls we found morphometric vertebral fractures, despite a DEXA Tscore not diagnostic of osteoporosis.
Conclusion
The objective of this study was to assess in obese patients levels of 25OH vitamin D, parathyroid hormone, serum and urinary calcium (Ca) and phosphorus (P), BMD, and SDI. 87.5 % of the obese subjects present nontraumatic vertebral fractures and reduced bone quality as measured by SDI
A Quantum Approach to Classical Statistical Mechanics
We present a new approach to study the thermodynamic properties of
-dimensional classical systems by reducing the problem to the computation of
ground state properties of a -dimensional quantum model. This
classical-to-quantum mapping allows us to deal with standard optimization
methods, such as simulated and quantum annealing, on an equal basis.
Consequently, we extend the quantum annealing method to simulate classical
systems at finite temperatures. Using the adiabatic theorem of quantum
mechanics, we derive the rates to assure convergence to the optimal
thermodynamic state. For simulated and quantum annealing, we obtain the
asymptotic rates of and , for the temperature and magnetic field, respectively. Other
annealing strategies, as well as their potential speed-up, are also discussed.Comment: 4 pages, no figure
Obesity and sleep disturbance: the chicken or the egg?
Epidemiological studies suggested an association between obesity and sleep disturbances. Obstructive sleep apnea is the most prevalent type of obesity-related sleep disorder that lead to an increased risk for numerous chronic health conditions. In addition the increased visceral adipose tissue might be responsible for the secretion of inflammatory cytokines that could contribute to alter the sleep-wake rhythm. Unhealthy food characterized by high consumption of fat and carbohydrate seems to negatively influence the quality of sleep while diet rich of fiber is associated to more restorative and deeper sleep. Although obesity could cause through several pathogenetic mechanisms an alteration of sleep, it has been reported that subjects suffering from sleep disorders are more prone to develop obesity. Experimental laboratory studies have demonstrated that decreasing either the amount or quality of sleep increase the risk of developing obesity. Experimental sleep restriction also causes physiological, hormonal and food behavioral changes that promote a positive energy balance and a compensatory disproportionate increase in food intake, decrease in physical activity, and weight gain. Thus, the aim of this review is to provide observational evidence on the association of obesity with sleep disturbances and viceversa with emphasis on possible pathophysiological mechanisms (hormonal and metabolic) that link these two pathological conditions
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