Capillary waves control the ejection of bubble bursting jets

Here we provide a theoretical framework describing the generation of the fast jet ejected vertically out of a liquid when a bubble, resting on a liquid–gas interface, bursts. The self-consistent physical mechanism presented here explains the emergence of the liquid jet as a consequence of the collapse of the gas cavity driven by the low capillary pressures that appear suddenly around its base when the cap, the thin film separating the bubble from the ambient gas, pinches. The resulting pressure gradient deforms the bubble which, at the moment of jet ejection, adopts the shape of a truncated cone. The dynamics near the lower base of the cone, and thus the jet ejection process, is determined by the wavelength λ∗ of the smallest capillary wave created during the coalescence of the bubble with the atmosphere which is not attenuated by viscosity. The minimum radius at the lower base of the cone decreases, and hence the capillary suction and the associated radial velocities increase, with the wavelength λ∗ . We show that λ∗ increases with viscosity as λ∗∝Oh1/2 for Oh≲O(0.01) , with Oh=μ/ρRσ−−−−√ the Ohnesorge number, R the bubble radius and ρ , μ and σ indicating respectively the liquid density, viscosity and interfacial tension coefficient. The velocity of the extremely fast and thin jet can be calculated as the flow generated by a continuous line of sinks extending along the axis of symmetry a distance proportional to λ∗ . We find that the jet velocity increases with the Ohnesorge number and reaches a maximum for Oh=Ohc , the value for which the crest of the capillary wave reaches the vertex of the cone, and which depends on the Bond number Bo=ρgR2/σ . For Oh>Ohc , the jet is ejected after a bubble is pinched off; in this regime, viscosity delays the formation of the jet, which is thereafter emitted at a velocity which is inversely proportional to the liquid viscosity

La oportunidad de saneamiento del incumplimiento del vendedor en el régimen de vicios materiales

El presente escrito pretende demostrar, con base en el estudio de la reforma alemana sobre la compraventa, la Convención de Viena sobre contratos de compraventa internacional de mercaderías y otros modelos del derecho comparado, que el régimen de vicios materiales contenido en los códigos Civil y de Comercio colombianos, moldeado sobre las acciones edilicias del derecho romano, probablemente comienza a revelar algunas deficiencias, dado que si bien dichas acciones respondían a la realidad socioeconómica de aquel momento histórico, en el cual los vicios por su naturaleza eran físicamente insubsanables y los bienes vendidos estaban determinados como cosa cierta, hoy en cambio la producción en masa conduce a que los productos disponibles en el mercado sean en gran parte reemplazables y, debido a su complejidad técnica y tecnológica, también reparables; de donde se sigue que, en caso de vicios de la cosa vendida, un remedio más conforme con la sociedad actual pudiera ser el de conceder, como primera opción, un derecho al vendedor de corregir su incumplimiento, lo cual se verificaría, a elección del comprador, mediante la sustitución del bien defectuoso o mediante la reparación del defecto, frustrado lo cual el comprador podría pasar a ejercer las llamadas pretensiones “secundarias”, esto es, la resolución del contrato, la reducción del precio o el denominado resarcimiento de daños. En la consecución de tal objetivo, se expondrán los rasgos característicos del nuevo esquema alemán sobre la materia, así como algunos de los problemas más relevantes que éste ha traído consigo, intentando brindar elementos sobre los fundamentos y las técnicas que se encuentran detrás de las decisiones tomadas, que serán luego comparadas con las adoptadas por la Convención de Viena sobre contratos de compraventa internacional de mercaderías y otros modelos del derecho comparado, para concluir con una reflexión sobre algunos aspectos relevantes con los cuales esos modelos podrían contribuir para un análisis de la disciplina en Colombia.

Diversity in mobile communications for blind detection of block-coded modulations

Spatial, temporal, and frequency diversity structures are analyzed to address the blind equalization problem in the presence of time-variant frequency selective channels. The aim of the paper is to present equalization schemes useful in front of fast changing channel responses. The best solution is a deterministic blind criterion that allows direct channel equalization and symbol detection. The main contribution of this paper is to present deterministic blind equalization schemes in CDMA systems (frequency diversity) to reduce the impact of the time-variant frequency selective channel.Peer ReviewedPostprint (published version

Herpetofauna of Cayo Carenas, Cienfuegos Bay, south-central Cuba

The herpetofauna inhabiting the keys in Cienfuegos Bay in south-central Cuba is virtually unknown. Herein we provide the results of the first rapid inventory performed on Cayo Carenas during the summer of 2016. We found 12 reptilian species in seven families on the key. We also discuss the ecology and the most plausible biogeographic origins for some of the species

Physical consequences of P≠\neqNP and the DMRG-annealing conjecture

Computational complexity theory contains a corpus of theorems and conjectures regarding the time a Turing machine will need to solve certain types of problems as a function of the input size. Nature {\em need not} be a Turing machine and, thus, these theorems do not apply directly to it. But {\em classical simulations} of physical processes are programs running on Turing machines and, as such, are subject to them. In this work, computational complexity theory is applied to classical simulations of systems performing an adiabatic quantum computation (AQC), based on an annealed extension of the density matrix renormalization group (DMRG). We conjecture that the computational time required for those classical simulations is controlled solely by the {\em maximal entanglement} found during the process. Thus, lower bounds on the growth of entanglement with the system size can be provided. In some cases, quantum phase transitions can be predicted to take place in certain inhomogeneous systems. Concretely, physical conclusions are drawn from the assumption that the complexity classes {\bf P} and {\bf NP} differ. As a by-product, an alternative measure of entanglement is proposed which, via Chebyshev's inequality, allows to establish strict bounds on the required computational time.Comment: Accepted for publication in JSTA

Reconstruction of the second layer of Ag on Pt(111)

The reconstruction of an Ag monolayer on Ag/Pt(111) is analyzed theoretically, employing a vertically extended Frenkel-Kontorova model whose parameters are derived from density functional theory. Energy minimization is carried out using simulated quantum annealing techniques. Our results are compatible with the STM experiments, where a striped pattern is initially found which transforms into a triangular reconstruction upon annealing. In our model we recognize the first structure as a metastable state, while the second one is the true energy minimum

A single scaling parameter as a first approximation to describe the rainfall pattern of a place: application on Catalonia

As well as in other natural processes, it has been frequently observed that the phenomenon arising from the rainfall generation process presents fractal self-similarity of statistical type, and thus, rainfall series generally show scaling properties. Based on this fact, there is a methodology, simple scaling, which is used quite broadly to find or reproduce the intensity–duration–frequency curves of a place. In the present work, the relationship of the simple scaling parameter with the characteristic rainfall pattern of the area of study has been investigated. The calculation of this scaling parameter has been performed from 147 daily rainfall selected series covering the temporal period between 1883 and 2016 over the Catalonian territory (Spain) and its nearby surroundings, and a discussion about the relationship between the scaling parameter spatial distribution and rainfall pattern, as well as about trends of this scaling parameter over the past decades possibly due to climate change, has been presented.Peer ReviewedPostprint (author's final draft

HST emission-line images of nearby 3CR radio galaxies: two photoionization, accretion and feedback modes

We present HST/ACS narrow-band images of a low-z sample of 19 3C radio galaxies to study the H$\alpha$ and [OIII] emissions from the narrow-line region (NLR). Based on nuclear emission line ratios, we divide the sample into High and Low Excitation Galaxies (HEGs and LEGs). We observe different line morphologies, extended line emission on kpc scale, large [OIII]/H$\alpha$ scatter across the galaxies, and a radio-line alignment. In general, HEGs show more prominent emission line properties than LEGs: larger, more disturbed, more luminous, and more massive regions of ionized gas with slightly larger covering factors. We find evidence of correlations between line luminosities and (radio and X-ray) nuclear luminosities. All these results point to a main common origin, the active nucleus, which ionize the surrounding gas. However, the contribution of additional photoionization mechanism (jet shocks and star formation) are needed to account for the different line properties of the two classes. A relationship between the accretion, photoionization and feedback modes emerges from this study. For LEGs (hot-gas accretors), the synchrotron emission from the jet represents the main source of ionizing photons. The lack of cold gas and star formation in their hosts accounts for the moderate ionized-gas masses and sizes. For HEGs (cold-gas accretors), an ionizing continuum from a standard disk and shocks from the powerful jets are the main sources of photoionization, with the contribution from star formation. These components, combined with the large reservoir of cold/dust gas brought from a recent merger, account for the properties of their extended emission-line regions.Comment: accepted for publication on ApJ (22 pages, 12 figures