14 research outputs found
Factors Contributing to SARS-CoV-2 Vaccine Hesitancy of Hispanic Population in Rio Grande Valley
Hispanic communities have been disproportionately affected by economic disparities. These inequalities have put Hispanics at an increased risk for preventable health conditions. In addition, the CDC reports Hispanics to have 1.5× COVID-19 infection rates and low vaccination rates. This study aims to identify the driving factors for COVID-19 vaccine hesitancy of Hispanic survey participants in the Rio Grande Valley. Our analysis used machine learning methods to identify significant associations between medical, economic, and social factors impacting the uptake and willingness to receive the COVID-19 vaccine. A combination of three classification methods (i.e., logistic regression, decision trees, and support vector machines) was used to classify observations based on the value of the targeted responses received and extract a robust subset of factors. Our analysis revealed different medical, economic, and social associations that correlate to other target population groups (i.e., males and females). According to the analysis performed on males, the Matthews correlation coefficient (MCC) value was 0.972. An MCC score of 0.805 was achieved by analyzing females, while the analysis of males and females achieved 0.797. Specifically, several medical, economic factors, and sociodemographic characteristics are more prevalent in vaccine-hesitant groups, such as asthma, hypertension, mental health problems, financial strain due to COVID-19, gender, lack of health insurance plans, and limited test availability
Aspects of Discrete Breathers and New Directions
We describe results concerning the existence proofs of Discrete Breathers
(DBs) in the two classes of dynamical systems with optical linear phonons and
with acoustic linear phonons. A standard approach is by continuation of DBs
from an anticontinuous limit. A new approach, which is purely variational, is
presented. We also review some numerical results on intraband DBs in random
nonlinear systems. Some non-conventional physical applications of DBs are
suggested. One of them is understanding slow relaxation properties of glassy
materials. Another one concerns energy focusing and transport in biomolecules
by targeted energy transfer of DBs. A similar theory could be used for
describing targeted charge transfer of nonlinear electrons (polarons) and, more
generally, for targeted transfer of several excitations (e.g. Davydov soliton).Comment: to appear in the Proceedings of NATO Advanced Research Workshop
"Nonlinearity and Disorder: Theory and Applications",
Tashkent,Uzbekistan,October 1-6, 200
Fractal entropy of a chain of nonlinear oscillators
We study the time evolution of a chain of nonlinear oscillators. We focus on
the fractal features of the spectral entropy and analyze its characteristic
intermediate timescales as a function of the nonlinear coupling. A Brownian
motion is recognized, with an analytic power-law dependence of its diffusion
coefficient on the coupling.Comment: 6 pages, 3 figures, revised version to appear in Phys. Rev.
Asymptotic Dynamics of Breathers in Fermi-Pasta-Ulam Chains
We study the asymptotic dynamics of breathers in finite Fermi-Pasta-Ulam
chains at zero and non-zero temperatures. While such breathers are essentially
stationary and very long-lived at zero temperature, thermal fluctuations tend
to lead to breather motion and more rapid decay
Enhanced Pulse Propagation in Non-Linear Arrays of Oscillators
The propagation of a pulse in a nonlinear array of oscillators is influenced
by the nature of the array and by its coupling to a thermal environment. For
example, in some arrays a pulse can be speeded up while in others a pulse can
be slowed down by raising the temperature. We begin by showing that an energy
pulse (1D) or energy front (2D) travels more rapidly and remains more localized
over greater distances in an isolated array (microcanonical) of hard springs
than in a harmonic array or in a soft-springed array. Increasing the pulse
amplitude causes it to speed up in a hard chain, leaves the pulse speed
unchanged in a harmonic system, and slows down the pulse in a soft chain.
Connection of each site to a thermal environment (canonical) affects these
results very differently in each type of array. In a hard chain the dissipative
forces slow down the pulse while raising the temperature speeds it up. In a
soft chain the opposite occurs: the dissipative forces actually speed up the
pulse while raising the temperature slows it down. In a harmonic chain neither
dissipation nor temperature changes affect the pulse speed. These and other
results are explained on the basis of the frequency vs energy relations in the
various arrays
Energy Relaxation in Nonlinear One-Dimensional Lattices
We study energy relaxation in thermalized one-dimensional nonlinear arrays of
the Fermi-Pasta-Ulam type. The ends of the thermalized systems are placed in
contact with a zero-temperature reservoir via damping forces. Harmonic arrays
relax by sequential phonon decay into the cold reservoir, the lower frequency
modes relaxing first. The relaxation pathway for purely anharmonic arrays
involves the degradation of higher-energy nonlinear modes into lower energy
ones. The lowest energy modes are absorbed by the cold reservoir, but a small
amount of energy is persistently left behind in the array in the form of almost
stationary low-frequency localized modes. Arrays with interactions that contain
both a harmonic and an anharmonic contribution exhibit behavior that involves
the interplay of phonon modes and breather modes. At long times relaxation is
extremely slow due to the spontaneous appearance and persistence of energetic
high-frequency stationary breathers. Breather behavior is further ascertained
by explicitly injecting a localized excitation into the thermalized array and
observing the relaxation behavior
Monomers, materials and energy from coffee by-products: A review
In recent years, the circular economy and sustainability have gained attention in the food industry aimed at recycling food industrial waste and residues. For example, several plant-based materials are nowadays used in packaging and biofuel production. Among them, by-products and waste from coffee processing constitute a largely available, low cost, good quality resource. Coffee production includes many steps, in which by-products are generated including coffee pulp, coffee husks, silver skin and spent coffee. This review aims to analyze the reasons why coffee waste can be considered as a valuable source in recycling strategies for the sustainable production of bio-based chemicals, materials and fuels. It addresses the most recent advances in monomer, polymer and plastic filler productions and applications based on the development of viable biorefinery technologies. The exploration of strategies to unlock the potential of this biomass for fuel productions is also revised. Coffee by-products valorization is a clear example of waste biorefinery. Future applications in areas such as biomedicine, food packaging and material technology should be taken into consideration. However, further efforts in techno-economic analysis and the assessment of the feasibility of valorization processes on an industrial scale are needed
Dynamical properties of discrete breathers in curved chains with first and second neighbor interaction
We present the study of discrete breather dynamics in curved polymerlike chains consisting of masses connected via nonlinear springs. The polymer chains are one dimensional but not rectilinear and their motion takes place on a plane. After constructing breathers following numerically accurate procedures, we launch them in the chains and investigate properties of their propagation dynamics. We find that breather motion is strongly affected by the presence of curved regions of polymers, while the breathers themselves show a very strong resilience and remarkable stability in the presence of geometrical changes. For chains with strong angular rigidity we find that breathers either pass through bent regions or get reflected while retaining their frequency. Their motion is practically lossless and seems to be determined through local energy conservation. For less rigid chains modeled via second neighbor interactions, we find similarly that chain geometry typically does not destroy the localized breather states but, contrary to the angularly rigid chains, it induces some small but constant energy loss. Furthermore, we find that a curved segment acts as an active gate reflecting or refracting the incident breather and transforming its velocity to a value that depends on the discrete breathers frequency. We analyze the physical reasoning behind these seemingly general breather properties
Interaction of a discrete breather with a lattice junction
We study the scattering of a moving discrete breather (DB) on a junction in a Fermi-Pasta-Ulam chain consisting of two segments with different masses of the particles. We consider four distinct cases: (i) a light-heavy (abrupt) junction in which the DB impinges on the junction from the segment with lighter mass, (ii) a heavy-light junction, (iii) an up mass ramp in which the mass in the heavier segment increases continuously as one moves away from the junction point, and (iv) a down mass ramp. Depending on the mass difference and DB characteristics (frequency and velocity), the DB can either reflect from, or transmit through, or get trapped at the junction or on the ramp. For the heavy-light junction, the DB can even split at the junction into a reflected and a transmitted DB. The latter is found to subsequently split into two or more DBs. For the down mass ramp the DB gets accelerated in several stages, with accompanying radiation (phonons). These results are rationalized by calculating the Peierls-Nabarro barrier for the various cases. We also point out implications of our results in realistic situations such as electron-phonon coupled chains