11,717 research outputs found
Inertial and dimensional effects on the instability of a thin film
We consider here the effects of inertia on the instability of a flat liquid
film under the effects of capillary and intermolecular forces (van der Waals
interaction). Firstly, we perform the linear stability analysis within the long
wave approximation, which shows that the inclusion of inertia does not produce
new regions of instability other than the one previously known from the usual
lubrication case. The wavelength, , corresponding to he maximum
growth, , and the critical (marginal) wavelength do not change at
all. The most affected feature of the instability under an increase of the
Laplace number is the noticeable decrease of the growth rates of the unstable
modes. In order to put in evidence the effects of the bidimensional aspects of
the flow (neglected in the long wave approximation), we also calculate the
dispersion relation of the instability from the linearized version of the
complete Navier-Stokes (N-S) equation. Unlike the long wave approximation, the
bidimensional model shows that can vary significantly with inertia
when the aspect ratio of the film is not sufficiently small. We also perform
numerical simulations of the nonlinear N-S equations and analyze to which
extent the linear predictions can be applied depending on both the amount of
inertia involved and the aspect ratio of the film
From car to bike. Marketing and dialogue as a driver of change
The Paris Climate Agreement has sent a key message to the international community regarding the need to increase efforts to move towards a low-carbon economy and help slow climate change, while underpinning global long-term economic growth and sustainable development. COP 21 recognizes the social, economic and environmental value of voluntary mitigation actions and their co-benefits for adaptation, health and sustainable development. In this framework, the PTP Cycle project, running from 2013 to 2016 and funded by the European Commission through the Intelligent Energy Europe program, introduces a non-market approach through voluntary participation in the adoption of sustainable transport modes such as cycling, based on marketing to potential customers through Personalized Travel Plans. The medium-sized city of Burgos (Spain) and the cities of Ljubljana, Riga, Antwerp and London
(boroughs of Haringey and Greenwich) developed a new policy instrument (Personalized Travel Plans) in order to increase bike patronage. Beyond potential savings of CO2, the results show that PTP as a form of Active Mobility Consultancy is a suitable instrument to influence modal shift to public transport, walking and cycling, and to address the challenges of climate change, while fostering sustainable transportation by changing mobility behaviour. These results, matching with the state-of-the-art of studies and pilot applications in other countries, allows deriving differentiated results for medium-size and large urban areas
Pilot study of vegetation in the Alchichica-Perote region by remote sensing
A study of the application of satellite images to the identification of vegetation in a small area corresponding to the arid zone of Veracruz and part of Puebla is presented. This study is accomplished by means of images from the LANDSAT satellite obtained on January 19 and May 23, 1973. The interpretation of the different maps is made on the basis of information from the data bank of the Flora de Veracruz program, and various surveys made by land and air
Topologically protected charge transfer along the edge of a chiral -wave superconductor
The Majorana fermions propagating along the edge of a topological
superconductor with pairing deliver a shot noise power of
per eV of voltage bias. We calculate the full
counting statistics of the transferred charge and find that it becomes
trinomial in the low-temperature limit, distinct from the binomial statistics
of charge- transfer in a single-mode nanowire or charge- transfer
through a normal-superconductor interface. All even-order correlators of
current fluctuations have a universal quantized value, insensitive to disorder
and decoherence. These electrical signatures are experimentally accessible,
because they persist for temperatures and voltages large compared to the
Thouless energy.Comment: 5 pages, 4 figures. v3 [post-publication]: added an appendix on the
effect of a tunnel barrier at the normal-superconductor contac
The Feasibility of Laparoscopic Cholecystectomy in Patients with Previous Abdominal Surgery
A retrospective study was carried in 1500 patients submitted to elective laparoscopic cholecystectomy to ascertain its feasibility in patients with previous abdominal surgery. In 411 patients (27.4%) previous infraumbilical intraperitoneal surgery had been performed, and 106 of them (7.06%) had 2 or more operations. Twenty five patients (1.66%) had previous supraumbilical intraperitoneal operations (colonic resection, hydatid liver cysts, gastrectomies, etc.) One of them had been operated 3 times. In this group of 25 patients the first trocar and pneumoperitoneum were performed by open laparoscopy. In 2 patients a Marlex mesh was present from previous surgery for supraumbilical hernias. Previous infraumbilical intraperitoneal surgery did not interfere with laparoscopic cholecystectomy, even in patients with several operations. There was no morbidity from Verres needle or trocars. In the 25 patients with supraumbilical intraperitoneal operations, laparoscopic cholecystectomy was completed in 22. In 3, adhesions prevented the visualization of the gallbladder and these patients were converted to an open procedure. In the 2 patients Marlex mesh prevented laparoscopic cholecystectomy because of adhesions to abdominal organs. We conclude that in most instances previous abdominal operations are no contraindication to laparoscopic cholecystectomy
Drops with non-circular footprints
In this paper we study the morphology of drops formed on partially wetting
substrates, whose footprint is not circular. This type of drops is a
consequence of the breakup processes occurring in thin films when anisotropic
contact line motions take place. The anisotropy is basically due to hysteresis
effects of the contact angle since some parts of the contact line are wetting,
while others are dewetting. Here, we obtain a peculiar drop shape from the
rupture of a long liquid filament sitting on a solid substrate, and analyze its
shape and contact angles by means of goniometric and refractive techniques. We
also find a non--trivial steady state solution for the drop shape within the
long wave approximation (lubrication theory), and compare most of its features
with experimental data. This solution is presented both in Cartesian and polar
coordinates, whose constants must be determined by a certain group of measured
parameters. Besides, we obtain the dynamics of the drop generation from
numerical simulations of the full Navier--Stokes equation, where we emulate the
hysteretic effects with an appropriate spatial distribution of the static
contact angle over the substrate
Training experience as a limiting factor in master long distance runners
En las últimas décadas ha aumentado el número de atletas veteranos en
carreras populares de resistencia. El estudio, que incluyó 103 atletas, tuvo el
objetivo de analizar cómo influye la edad y los años de experiencia en el
rendimiento de corredores veteranos en largas distancias. Para ello se elaboró
un cuestionario ad hoc. El análisis de los años de experiencia muestra
correlaciones significativas (p<0,05) en todas las distancias de la categorÃa de
35-39 años, asà como en la distancia de 21,1 km en categorÃa 40-44 años. Por
otro lado, en la comparación entre categorÃas relacionados con el tiempo total,
se encontraron diferencias significativas en la distancia de 21,1 km para los
grupos de edad de 35-39/45-49 (p=0,014) y 35-39/50-54 (p=0,014) asà como en
la distancia de 42,2 km para los grupos de edad de 35-39/45-49 (p=0,022) y 45-
49/50-54 (p=0,050). Los años de experiencia parecen ser un factor limitante del
rendimientoIn the last decades, the number of recreational master runners in long-distance
running events has increased. This study, which included 103 runners, aimed to
analyze the influence of age and training experience on master runners'
performance over long distances. An ad hoc questionnaire was used. Training
experience analysis showed significant correlations (p<0.05) in all distances in
the 35-39 years category, as well as in the distance of 21.1 km in the 40-44
years category. Furthermore, in the comparison between categories related to
the total time, significant differences were found in 21.1 km distance for age
groups of 35-39 / 45-49 (p=0.014) and 35-39 / 50-54 (p= 0.014) as well as in
42.2 km distance for the age groups of 35-39 / 45-49 (p=0.022) and 45-49 / 50-
54 (p=0.050). Training experience appears to be a limiting factor for
performance in recreational master runner
Micro Electro Kinetic Actuator (MEKA) arrays for active sublayer control of turbulent boundary layers
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77296/1/AIAA-2002-267-217.pd
Phase-locked magnetoconductance oscillations as a probe of Majorana edge states
We calculate the Andreev conductance of a superconducting ring interrupted by
a flux-biased Josephson junction, searching for electrical signatures of
circulating edge states. Two-dimensional pair potentials of spin-singlet d-wave
and spin-triplet p-wave symmetry support, respectively, (chiral) Dirac modes
and (chiral or helical) Majorana modes. These produce h/e-periodic
magnetoconductance oscillations of amplitude \simeq (e^{2}/h)N^{-1/2}, measured
via an N-mode point contact at the inner or outer perimeter of the grounded
ring. For Dirac modes the oscillations in the two contacts are independent,
while for an unpaired Majorana mode they are phase locked by a topological
phase transition at the Josephson junction.Comment: 10 pages, 6 figures. New appendix on the gauge invariant
discretization of the Bogoliubov-De Gennes equation. Accepted for publication
in PR
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