2063 research outputs found
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Hydrodynamics of spike proteins dictate a transport-affinity competition for SARS-CoV-2 and other enveloped viruses
Get PDFMany viruses, such as SARS-CoV-2 or Influenza, possess envelopes decorated with surface proteins (a.k.a. spikes). Depending on the virus type, a large variability is present in the surface-proteins number, morphology and reactivity, which remains generally unexplained. Since viruses’ transmissibility depends on features beyond their genetic sequence, new tools are required to discern the effects of spikes functionality, interaction, and morphology. Here, we postulate the relevance of hydrodynamic interactions in the viral infectivity of enveloped viruses and propose micro-rheological characterization as a platform for virus differentiation. To understand how the spikes affect virion mobility and infectivity, we investigate the diffusivity of spike-decorated structures using mesoscopic-hydrodynamic simulations. Furthermore, we explored the interplay between affinity and passive viral transport. Our results revealed that the diffusional mechanism of SARS-CoV-2 is strongly influenced by the size and distribution of its spikes. We propose and validate a universal mechanism to explain the link between optimal virion structure and maximal infectivity for many virus families.LCF/BQ/PI20/1176001
Zindler-type hypersurfaces in R^4
Get PDFIn this paper the definition of Zindler-type hypersurfaces is introduced in as a generalization of planar Zindler curves. After recalling some properties of planar Zindler curves, it is shown that Zindler hypersurfaces satisfy similar properties. Techniques from quaternions and symplectic geometry are used. Moreover, each Zindler hypersurface is fibrated by space Zindler curves that correspond, in the convex case, to some space curves of constant width lying on the associated hypersurface of constant width and with the same symplectic area
OSCILLATION INEQUALITIES IN ERGODIC THEORY AND ANALYSIS: ONE-PARAMETER AND MULTI-PARAMETER PERSPECTIVES
Get PDFIn this survey we review useful tools that naturally arise in the study of pointwise convergence problems in analysis, ergodic theory and probability. We will pay special attention to quantitative aspects of pointwise convergence phenomena from the point of view of oscillation estimates in both the single and several parameter settings. We establish a number of new oscillation inequalities and give new proofs for known results with elementary arguments
Some Non-standard Biparametric Poincaré Type Inequalities Through Harmonic Analysis
Get PDFWe show some non-standard Poincaré type estimates in the biparametric setting with appropriate weights. We will derive these results using variants from classical estimates exploiting the interplay between maximal functions and fractional integrals. We also provide a sharper result by using extrapolation techniques
Minimal conditions for BMO
Get PDFWe study minimal integrability conditions via Luxemburg- type expressions with respect to generalized oscillations that imply the membership of a given function f to the space BMO. Our method is simple, sharp and flexible enough to be adapted to several different settings, like spaces of homogeneous type, non doubling measures on Rn and also BMO spaces defined over more general bases than the basis of cubes
Influence of Random Telegraph Noise on Quantum Bit Gate Operation
Get PDFWe consider the problem of analyzing spin-flip qubit gate operation in the presence of Random Telegraph Noise (RTN). Our compressive approach is the following. By using the Feynman disentangling operators method, we calculate the spin-flip probability of qubit driven by different kinds of composite pulses, e.g., Constant pulse (C-pulse), Quantum Well pulse (QW-pulse), and Barrier Potential pulse (BP-pulse) in the presence of RTN. When composite pulses and RTN act in the x-direction and z-direction respectively, we calculate the optimal time to achieve perfect spin-flip probability of qubit. We report that the highest fidelity of spin-flip qubit can be achieved by using C-pulse, followed by BP-pulse and QW-pulse. For a more general case, we have tested several pulse sequences for achieving high fidelity quantum gates, where we use the pulses acting in different directions. From the calculations, we find that high fidelity of qubit gate operation in the presence of RTN is achieved when QW-pulse, BP-pulse, and C-pulse act in the x-direction, y-direction, and z-direction, respectively. We extend our investigations for multiple QW and BP pulses while choosing the C-pulse amplitude constant in the presence of RTN. The results of calculation show that 98.5 % fidelity can be achieved throughout the course of RTN that may be beneficial for quantum error correction
Comparing Two Samples Through Stochastic Dominance: A Graphical Approach
Get PDFNondeterministic measurements are common in real-world scenarios: the performance of a stochastic optimization algorithm or the total reward of a reinforcement learning agent in a chaotic environment are just two examples in which unpredictable outcomes are common. These measures can be modeled as random variables and compared among each other via their expected values or more sophisticated tools such as null hypothesis statistical tests. In this article, we propose an alternative framework to visually compare two samples according to their estimated cumulative distribution functions. First, we introduce a dominance measure for two random variables that quantifies the proportion in which the cumulative distribution function of one of the random variables stochastically dominates the other one. Then, we present a graphical method that decomposes in quantiles (i) the proposed dominance measure and (ii) the probability that one of the random variables takes lower values than the other. With illustrative purposes, we reevaluate the experimentation of an already published work with the proposed methodology and we show that additional conclusions—missed by the rest of the methods—can be inferred. Additionally, the software package RVCompare was created as a convenient way of applying and experimenting with the proposed framework.PID2019-106453GA-I00
BERC 2018-202
Sawyer-type inequalities for Lorentz spaces
Get PDFThe Hardy-Littlewood maximal operator M satisfies the classical Sawyer-type estimate ∥Mfv∥L1,∞(uv)≤Cu,v‖f‖L1(u),where u∈ A1 and uv∈ A∞. We prove a novel extension of this result to the general restricted weak type case. That is, for p> 1 , u∈ApR, and uvp∈ A∞, ∥Mfv∥Lp,∞(uvp)≤Cu,v‖f‖Lp,1(u).From these estimates, we deduce new weighted restricted weak type bounds and Sawyer-type inequalities for the m-fold product of Hardy-Littlewood maximal operators. We also present an innovative technique that allows us to transfer such estimates to a large class of multi-variable operators, including m-linear Calderón-Zygmund operators, avoiding the A∞ extrapolation theorem and producing many estimates that have not appeared in the literature before. In particular, we obtain a new characterization of ApR. Furthermore, we introduce the class of weights that characterizes the restricted weak type bounds for the multi(sub)linear maximal operator M, denoted by APR, establish analogous bounds for sparse operators and m-linear Calderón-Zygmund operators, and study the corresponding multi-variable Sawyer-type inequalities for such operators and weights. Our results combine mixed restricted weak type norm inequalities, ApR and APR weights, and Lorentz spaces
Shape matters: Competing mechanisms of particle shape segregation
Get PDFIt is well-known that granular mixtures that differ in size or shape segregate when sheared. In the
past, two mechanisms have been proposed to describe this effect, and it is unclear if both exist. To
settle this question, we consider a bidisperse mixture of spheroids of equal volume in a rotating drum,
where the two mechanisms are predicted to act in opposite directions. We present the first evidence
that there are two distinct segregation mechanisms driven by relative over-stress. Additionally, we
showed that for non-spherical particles, these two mechanisms can act in different directions leading
to a competition between the effects of the two. As a result, the segregation intensity varies nonmonotonically as a function of AR, and at specific points, the segregation direction changes for both
prolate and oblate spheroids, explaining the surprising segregation reversal previously reported.
Consistent with previous results, we found that the kinetic mechanism is dominant for (almost)
spherical particles. Furthermore, for moderate aspect ratios, the kinetic mechanism is responsible
for the spherical particles segregation to the periphery of the drum, and the gravity mechanism
plays only a minor role. Whereas, at the extreme values of AR, the gravity mechanism notably
increases and overtakes its kinetic counterpart
Algebraic equations for constant width curves and Zindler curves
Get PDFAn explicit method to compute algebraic equations of curves of constant width and Zindler curves generated by a family of middle hedgehogs is given thanks to a property of Chebyshev polynomials. This extends the methodology used by Rabinowitz and Martinez-Maure in particular constant width curves to generate a full family of algebraic equations, both of curves of constant width and Zindler curves, defined by trigonometric polynomials as support functions