1,170 research outputs found

    Control over phase separation and nucleation using a laser-tweezing potential

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    Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid‚Äďliquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter

    Calidad de vida en asistentes a un programa de actividad física en Bogotá, Colombia

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    The rise of chronic noncommunicable diseases in older adults is a global public health challenge, so actions to prevent or mitigate them are necessary to improve population health but quality of life. The objective focused on and rated the quality of life in users who regularly attend the Recreov√≠a program. Non-experimental study with descriptive cross-sectional design, conducted in 280 adult women with an average age of 56.71 ¬Ī to 10.79 years, inhabitants of the city of Bogot√°, who attend the Recreov√≠a program 3 times a week. Quality of life was evaluated with WHOQOL-BREF. A statistically significant relationship was found between quality of life and socioeconomic stratum (p=0,002), between quality of life and physical health (p<0,001) and quality of life and hypertension (p=0,003). The perception of quality of life was weighted as good as referred to by the participants; as there is a relationship between intermediate and structural determinants, it encourages decision-making that actions in the population must transcend beyond collective programs but affect the living and health conditions of the population.El aumento de Enfermedades cr√≥nicas no transmisibles en los adultos mayores es un reto en salud p√ļblica a nivel mundial, por lo que las acciones que se hagan para prevenir o mitigar estas son necesarias para mejorar la salud de la poblaci√≥n sino la calidad de vida. El objetivo se centr√≥ en evaluar la calidad de vida en las usuarias que asisten de manera regular al programa de Recreov√≠a. Estudio no experimental con dise√Īo descriptivo de corte transversal, realizado en 280 mujeres adultas con una edad promedio de 56.71 ¬Ī 10.79 a√Īos, habitantes de la ciudad de Bogot√°, que asisten 3 veces por semana al programa de Recreov√≠a. Se eval√ļo la calidad de vida con el WHOQOL-BREF. Se encontr√≥ relaci√≥n estad√≠sticamente significativa entre la calidad de vida y el estrato socioecon√≥mico (p=0.002), entre la calidad de vida y la salud f√≠sica (p<0.001) y la calidad de vida e Hipertensi√≥n (p=0.003). La percepci√≥n de calidad de vida fue ponderada como buena de acuerdo con lo referido por las participantes; al existir relaci√≥n entre determinantes intermedios y estructurales, alienta a tomadores de decisi√≥n que las acciones en la poblaci√≥n deben trascender m√°s all√° de programas colectivos, sino que afecten las condiciones de vida y salud de la poblaci√≥n

    Effects of web-based electrocardiography simulation on strategies and learning styles

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    Objective: To identify the association between the use of web simulation electrocardiography and the learning approaches, strategies and styles of nursing degree students. Method: A descriptive and correlational design with a one-group pretest‚Äď posttest measurement was used. The study sample included 246 students in a Basic and Advanced Cardiac Life Support nursing class of nursing degree. Results: No significant differences between genders were found in any dimension of learning styles and approaches to learning. After the introduction of web simulation electrocardiography, significant differences were found in some item scores of learning styles: theorist (p < 0.040), pragmatic (p < 0.010) and approaches to learning. Conclusion: The use of a web electrocardiogram (ECG) simulation is associated with the development of active and reflexive learning styles, improving motivation and a deep approach in nursing students

    Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

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    The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of ‚ąös = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT‚Č•20 GeV and pseudorapidities {pipe}ő∑{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}ő∑{pipe}<0. 8) for jets with 60‚ȧpT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2‚ȧ{pipe}ő∑{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. ¬© 2013 CERN for the benefit of the ATLAS collaboration

    Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector