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Institution

University of Los Andes

EducationBogotá, Colombia
About: University of Los Andes is a education organization based out in Bogotá, Colombia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 17616 authors who have published 25555 publications receiving 413463 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a linear correlation between the formulation variables, which are characteristic parameters of the substances as well as the temperature, is used to determine an optimum formulation and to characterize unknown surfactants and oils.
Abstract: Enhanced recovery of crude oil by surfactant flooding requires the attainment of an ultralow interfacial tension. Since Winsor’s work in the 1950s it has been known that a minimum interfacial tension and a concomitant three-phase behavior of a surfactant–oil–water system occurs when the interactions of the surfactant and the oil and water phases are exactly equal. It has been known since the 1970s that these conditions are attained when a linear correlation is satisfied between the formulation variables, which are characteristic parameters of the substances as well as the temperature. This first part of our review on how to attain ultralow interfacial tension for enhanced oil recovery shows how formulation scan techniques using these correlations are used to determine an optimum formulation and to characterize unknown surfactants and oils. The physicochemical significance of the original empirical correlation is reported as the surfactant affinity difference or hydrophilic–lipophilic deviation model. We report the range of accurate validity of, and how to test, this simple model with four variables.

175 citations

Journal ArticleDOI
TL;DR: A 24-hour waist-worn accelerometry protocol implemented in U.S. children may produce an important increase in wear time compliance that also provides an opportunity to study the total sleep episode time separate and distinct from physical activity and sedentary time detected during waking-hours.
Abstract: We compared 24-hour waist-worn accelerometer wear time characteristics of 9–11 year old children in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) to similarly aged U.S. children providing waking-hours waist-worn accelerometer data in the 2003–2006 National Health and Nutrition Examination Survey (NHANES). Valid cases were defined as having ≥4 days with ≥10 hours of waking wear time in a 24-hour period, including one weekend day. Previously published algorithms for extracting total sleep episode time from 24-hour accelerometer data and for identifying wear time (in both the 24-hour and waking-hours protocols) were applied. The number of valid days obtained and a ratio (percent) of valid cases to the number of participants originally wearing an accelerometer were computed for both ISCOLE and NHANES. Given the two surveys’ discrepant sampling designs, wear time (minutes/day, hours/day) from U.S. ISCOLE was compared to NHANES using a meta-analytic approach. Wear time for the 11 additional countries participating in ISCOLE were graphically compared with NHANES. 491 U.S. ISCOLE children (9.92±0.03 years of age [M±SE]) and 586 NHANES children (10.43 ± 0.04 years of age) were deemed valid cases. The ratio of valid cases to the number of participants originally wearing an accelerometer was 76.7% in U.S. ISCOLE and 62.6% in NHANES. Wear time averaged 1357.0 ± 4.2 minutes per 24-hour day in ISCOLE. Waking wear time was 884.4 ± 2.2 minutes/day for U.S. ISCOLE children and 822.6 ± 4.3 minutes/day in NHANES children (difference = 61.8 minutes/day, p < 0.001). Wear time characteristics were consistently higher in all ISCOLE study sites compared to the NHANES protocol. A 24-hour waist-worn accelerometry protocol implemented in U.S. children produced 22.6 out of 24 hours of possible wear time, and 61.8 more minutes/day of waking wear time than a similarly implemented and processed waking wear time waist-worn accelerometry protocol. Consistent results were obtained internationally. The 24-hour protocol may produce an important increase in wear time compliance that also provides an opportunity to study the total sleep episode time separate and distinct from physical activity and sedentary time detected during waking-hours. ClinicalTrials.gov NCT01722500 .

175 citations

Journal ArticleDOI
TL;DR: NIV improves hypoxemia and the signs and symptoms of acute respiratory failure and seems to afford these patients protection from endotracheal intubation.
Abstract: Outcomes:To compare the benefits of noninvasive ventilation (NIV) plus standard therapy vs. standard therapy alone in children with acute respiratory failure; assess method effectiveness in improving gas exchange and vital signs; and assess method safety.Design:Prospective, randomized, controlled st

174 citations

Journal ArticleDOI
TL;DR: In this paper, the decay of the coherences of the quantum register is shown to strongly depend on the input states, and it is shown that this sensitivity is a characteristic of both types of coupling and not only of collective coupling.
Abstract: The dynamical evolution of a quantum register of arbitrary length coupled to an environment of arbitrary coherence length is predicted within a relevant model of decoherence. The results are reported for quantum bits (qubits) coupling individually to different environments (``independent decoherence'') and qubits interacting collectively with the same reservoir (``collective decoherence''). In both cases, explicit decoherence functions are derived for any number of qubits. The decay of the coherences of the register is shown to strongly depend on the input states: We show that this sensitivity is a characteristic of both types of coupling (collective and independent) and not only of the collective coupling, as has been reported previously. A nontrivial behavior (``recoherence'') is found in the decay of the off-diagonal elements of the reduced density matrix in the specific situation of independent decoherence. Our results lead to the identification of decoherence-free states in the collective decoherence limit. These states belong to subspaces of the system's Hilbert space that do not get entangled with the environment, making them ideal elements for the engineering of ``noiseless'' quantum codes. We also discuss the relations between decoherence of the quantum register and computational complexity based on the dynamical results obtained for the register density matrix.

173 citations

Proceedings ArticleDOI
07 Jun 2015
TL;DR: In this article, a Moving Objectness Detector (MOD) is trained on image and motion fields to detect moving objects and discard over/under segmentations or background parts of the scene.
Abstract: We segment moving objects in videos by ranking spatio-temporal segment proposals according to “moving objectness”; how likely they are to contain a moving object. In each video frame, we compute segment proposals using multiple figure-ground segmentations on per frame motion boundaries. We rank them with a Moving Objectness Detector trained on image and motion fields to detect moving objects and discard over/under segmentations or background parts of the scene. We extend the top ranked segments into spatio-temporal tubes using random walkers on motion affinities of dense point trajectories. Our final tube ranking consistently outperforms previous segmentation methods in the two largest video segmentation benchmarks currently available, for any number of proposals. Further, our per frame moving object proposals increase the detection rate up to 7% over previous state-of-the-art static proposal methods.

173 citations


Authors

Showing all 17748 results

NameH-indexPapersCitations
Alexander Belyaev1421895100796
Sarah Catherine Eno1411645105935
Mitchell Wayne1391810108776
Kaushik De1391625102058
Pierluigi Paolucci1381965105050
Randy Ruchti1371832107846
Gabor Istvan Veres135134996104
Raymond Brock135146897859
Harrison Prosper1341587100607
J. Ellison133139292416
Gyorgy Vesztergombi133144494821
Andrew Brandt132124694676
Scott Snyder131131793376
Shuai Liu129109580823
C. A. Carrillo Montoya128103378628
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202334
2022205
20211,504
20201,645
20191,563
20181,599