1,285 research outputs found
Vacuum-UV spectroscopy of interstellar ice analogs. II. Absorption cross-sections of nonpolar ice molecules
Dust grains in cold circumstellar regions and dark-cloud interiors at 10-20 K
are covered by ice mantles. A nonthermal desorption mechanism is invoked to
explain the presence of gas-phase molecules in these environments, such as the
photodesorption induced by irradiation of ice due to secondary ultraviolet
photons. To quantify the effects of ice photoprocessing, an estimate of the
photon absorption in ice mantles is required. In a recent work, we reported the
vacuum-ultraviolet (VUV) absorption cross sections of nonpolar molecules in the
solid phase. The aim was to estimate the VUV-absorption cross sections of
nonpolar molecular ice components, including CH4, CO2, N2, and O2. The column
densities of the ice samples deposited at 8 K were measured in situ by infrared
spectroscopy in transmittance. VUV spectra of the ice samples were collected in
the 120-160 nm (10.33-7.74 eV) range using a commercial microwave-discharged
hydrogen flow lamp. We found that, as expected, solid N2 has the lowest
VUV-absorption cross section, which about three orders of magnitude lower than
that of other species such as O2, which is also homonuclear. Methane (CH4) ice
presents a high absorption near Ly-alpha (121.6 nm) and does not absorb below
148 nm. Estimating the ice absorption cross sections is essential for models of
ice photoprocessing and allows estimating the ice photodesorption rates as the
number of photodesorbed molecules per absorbed photon in the ice.Comment: 9 pages, 6 figures, 7 table
Suppressive impact of metronomic chemotherapy using UFT and/or cyclophosphamide on mediators of breast cancer dissemination and invasion
ProducciĂłn CientĂficaMetronomic chemotherapy using the 5-FU prodrug uracil-tegafur (UFT) and cyclophosphamide (CTX) was previously shown to only modestly delay primary tumor growth, but nevertheless markedly suppressed the development of micro-metastasis in an orthotopic breast cancer xenograft model, using the metastatic variant of the MDA-MB-231 cell line, 231/LM2-4. Furthermore, a remarkable prolongation of survival, with no toxicity, was observed in a model of postsurgical advanced metastatic disease. A question that has remained unanswered is the seemingly selective anti-metastatic mechanisms of action responsible for this treatment. We assessed the in vivo effect of metronomic UFT, CTX or their combination, on vascular density, collagen deposition and c-Met (cell mediators or modulators of tumor cell invasion or dissemination) via histochemistry/immunohistochemistry of primary tumor sections. We also assessed the effect of continuous exposure to low and non-toxic doses of active drug metabolites 5-fluorouracil (5-FU), 4-hydroperoxycyclophosphamide (4-HC) or their combination, on 231/LM2-4 cell invasiveness in vitro. In the in vivo studies, a significant reduction in vascular density and p-Met[Y1003] levels was associated with UFT+CTX treatment. All treatments reduced intratumoral collagen deposition. In the in vitro studies, a significant reduction of collagen IV invasion by all treatments was observed. The 3D structures formed by 231/LM2-4 on Matrigel showed a predominantly Mass phenotype under treated conditions and Stellate phenotype in untreated cultures. Taken together, the results suggest the low-dose metronomic chemotherapy regimens tested can suppress several mediators of tumor invasiveness highlighting a new perspective for the anti-metastatic efficacy of metronomic chemotherapy.Canadian Institutes of Health Research (grant 364411
Passive interferometric interrogation of a magnetic field sensor using an erbium doped fiber optic laser with magnetostrictive transducer
An erbium doped (Er3+) fiber optic laser is proposed for magnetic field measurement. A pair of FBGsglued onto a magnetostrictive material (Terfenol-D rod) modulates the laser wavelength operation whensubject to a static or a time dependent magnetic field. A passive interferometer is employed to measure thelaser wavelength changes due to the applied magnetic field. A data acquisition hardware and a LabVIEWsoftware measure three phase-shifted signals at the output coupler of the interferometer and processthem using two distinct demodulation algorithms. Results show that sensitivity to varying magneticfields can be tuned by introducing a biasing magnetic field. A maximum error of 0.79% was found, formagnetic fields higher than 2.26 mT-RMS
Health Promotion for Childhood Obesity: An Approach Based on Self-Tracking of Data
[EN]At present, obesity and overweight are a global health epidemic. Traditional interventions
for promoting healthy habits do not appear to be e ective. However, emerging technological solutions
based on wearables and mobile devices can be useful in promoting healthy habits. These applications
generate a considerable amount of tracked activity data. Consequently, our approach is based on
the quantified-self model for recommending healthy activities. Gamification can also be used as
a mechanism to enhance personalization, increasing user motivation. This paper describes the
quantified-self model and its data sources, the activity recommender system, and the PROVITAO
App user experience model. Furthermore, it presents the results of a gamified program applied for
three years in children with obesity and the process of evaluating the quantified-self model with
experts. Positive outcomes were obtained in children’s medical parameters and health habits
Agile human centered methodologies to develop educational software
This paper presents a methodological proposal that is based on powerful current approaches to the software development process: agile methodologies (SCRUM, Lean UX), user-centered design (UCD) and user experience design (UXD). Specifically, we have adapted some of the characteristics of the agile methodologies, which have allowed us to produce useful prototypes that are focused on the users while receiving constant feedback from them. The main goal of the proposed methodology is to identify usability problems and UX factors in the early stages of educational software development. Furthermore, we have also applied and validated the proposal during the framework development of an educational software project for users with special educational needs. A specific case taking into account key usability issues to support students with special education needs (SEN) is presented. In conclusion, we state that the proposed methodology could be a good design process philosophy to follow in the development of software projects in general, and in educational projects in particular
An in-depth view of the microscopic dynamics of Ising spin glasses at fixed temperature
Using the dedicated computer Janus, we follow the nonequilibrium dynamics of
the Ising spin glass in three dimensions for eleven orders of magnitude. The
use of integral estimators for the coherence and correlation lengths allows us
to study dynamic heterogeneities and the presence of a replicon mode and to
obtain safe bounds on the Edwards-Anderson order parameter below the critical
temperature. We obtain good agreement with experimental determinations of the
temperature-dependent decay exponents for the thermoremanent magnetization.
This magnitude is observed to scale with the much harder to measure coherence
length, a potentially useful result for experimentalists. The exponents for
energy relaxation display a linear dependence on temperature and reasonable
extrapolations to the critical point. We conclude examining the time growth of
the coherence length, with a comparison of critical and activated dynamics.Comment: 38 pages, 26 figure
Simulating spin systems on IANUS, an FPGA-based computer
We describe the hardwired implementation of algorithms for Monte Carlo
simulations of a large class of spin models. We have implemented these
algorithms as VHDL codes and we have mapped them onto a dedicated processor
based on a large FPGA device. The measured performance on one such processor is
comparable to O(100) carefully programmed high-end PCs: it turns out to be even
better for some selected spin models. We describe here codes that we are
currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication
Criterios para la instrumentaciĂłn de un magnetĂłmetro hall en corriente continua.
En este trabajo se presentan los criterios de diseño para la implementaciĂłn de un medidor de intensidad de campo magnĂ©tico, mediante un sensor Hall, es decir un magnetĂłmetro Hall, teniendo en cuenta criterios instrumentales y metrolĂłgicos. En el proceso de mediciĂłn de campo magnĂ©tico se presenta incertidumbre tipo B, debida a la transducciĂłn, amplificaciĂłn, filtrado y conversiĂłn A/D. Se incorporan consideraciones que el instrumentador debe tener en cuenta para reducir el Ăndice de incertidumbre, haciendo el proceso de mediciĂłn más eficiente. Se realizĂł la instrumentaciĂłn del magnetĂłmetro Hall y se redujo el Ăndice de incertidumbre en un 5%, correspondiente a uno de los factores de error
Matching microscopic and macroscopic responses in glasses
We first reproduce on the Janus and Janus II computers a milestone experiment
that measures the spin-glass coherence length through the lowering of
free-energy barriers induced by the Zeeman effect. Secondly we determine the
scaling behavior that allows a quantitative analysis of a new experiment
reported in the companion Letter [S. Guchhait and R. Orbach, Phys. Rev. Lett.
118, 157203 (2017)]. The value of the coherence length estimated through the
analysis of microscopic correlation functions turns out to be quantitatively
consistent with its measurement through macroscopic response functions.
Further, non-linear susceptibilities, recently measured in glass-forming
liquids, scale as powers of the same microscopic length.Comment: 6 pages, 4 figure
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