Evaluación de la eficacia cosmética de cremas elaboradas con aceites extraídos de especies vegetales Amazónicas: Mauritia Flexuosa (Morete), Plukenetia Volubilis (Sacha Inchi) y Oenocarpus Bataua (Ungurahua)

Investigaciones anteriores demuestran la actividad antioxidante de los aceites de Mauritua flexuosa (Morete), Plukenetia volubilis (Sacha inchi) y Oenocarpus bataua (Ungurahua), se realizaron formulaciones de cremas de aplicación cosmética y emulsiones básicas, evitando que el uso de demasiados ingredientes puedan interferir en lo que se consideran como “activos” dentro de la formulación cosmética (aceites con potencial antioxidante). Las muestras fueron evaluadas en un estudio in vivo no invasivo, utilizando una muestra de 30 mujeres que presentaban cierto grado de fotoenvejecimiento. Se realizó una evaluación clínica dermatológica y una evaluación instrumental utilizando el Cutometer MPA580, equipo que permite visualizar las modificaciones en la elasticidad y firmeza cutánea. La evaluación se la hizo al inicio y luego de cuatro semanas de utilizar el producto y los datos fueron sometidos al análisis de varianza. Los resultados del estudio demuestran que a los 28 días de tratamiento, la evaluación clínica las cremas muestran una mejorara significativa en la luminosidad y suavidad de la piel, y la evaluación instrumental indica que se logró una mejoría en la firmeza y elasticidad de la piel.

Determinación experimental del coeficiente de fricción empleando sensores movimiento

El objetivo de este artículo es mostrar una alternativa en la medición del coeficiente de fricción estático y dinámico entre dos superficies sólidas cuando se emplea el método del plano inclinado. La medición es realizada por medio de sensores de movimiento, aplicando los circuitos de acondicionamiento de señal los cuales son necesarios en su implementación. Los resultados muestran que los instrumentos empleados pueden ser adecuados en el cálculo de estos coeficientes

Crossover in the nature of the metallic phases in the perovskite-type RNiO_3

We have measured the photoemission spectra of Nd$_{1-x}$Sm$_{x}$NiO$_{3}$, where the metal-insulator transition and the N\'{e}el ordering occur at the same temperature for $x \lesssim 0.4$ and the metal-insulator transition temperature ($T_{MI}$) is higher than the N\'{e}el temperature for $x \gtrsim 0.4$. For $x \le 0.4$, the spectral intensity at the Fermi level is high in the metallic phase above $T_{MI}$ and gradually decreases with cooling in the insulating phase below $T_{MI}$ while for $x > 0.4$ it shows a pseudogap-like behavior above $T_{MI}$ and further diminishes below $T_{MI}$. The results clearly establish that there is a sharp change in the nature of the electronic correlations in the middle ($x \sim 0.4$) of the metallic phase of the $R$NiO$_3$ system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.

Dimensions of professional competences for interventions towards sustainability

This paper investigates sustainability competences through the eyes of professional practitioners in the field of sustainability and presents empirical data that have been created using an action research approach. The design of the study consists of two workshops, in which professional practitioners in interaction with each other and the facilitators are invited to explore and reflect on the specific knowledge, skills, attitudes and behaviours necessary to conduct change processes successfully towards sustainability in a variety of business and professional contexts. The research focuses on the competences associated with these change processes to devise, propose and conduct appropriate interventions that address sustainability issues. Labelled ‘intervention competence’, this ability comprises an interlocking set of knowledge, skills, attitudes and behaviours that include: appreciating the importance of (trying to) reaching decisions or interventions; being able to learn from lived experience of practice and to connect such learning to one’s own scientific knowledge; being able to engage in political-strategic thinking, deliberations and actions, related to different perspectives; the ability for showing goal-oriented, adequate action; adopting and communicating ethical practices during the intervention process; being able to cope with the degree of complexity, and finally being able to translate stakeholder diversity into collectively produced interventions (actions) towards sustainability. Moreover, this competence has to be practised in contexts of competing values, non-technical interests and power relations. The article concludes with recommendations for future research and practice

Renormalization group flow of SU(3) lattice gauge theory - Numerical studies in a two coupling space

We investigate the renormalization group (RG) flow of SU(3) lattice gauge theory in a two coupling space with couplings $\beta_{11}$ and $\beta_{12}$ corresponding to $1\times 1$ and $1\times 2$ loops respectively. Extensive numerical calculations of the RG flow are made in the fourth quadrant of this coupling space, i.e., $\beta_{11}>0$ and $\beta_{12}<0$. Swendsen's factor two blocking and the Schwinger-Dyson method are used to find an effective action for the blocked gauge field. The resulting renormalization group flow runs quickly towards an attractive stream which has an approximate line shape. This is numerical evidence of a renormalized trajectory which locates close to the two coupling space. A model flow equation which incorporates a marginal coupling (asymptotic scaling term), an irrelevant coupling and a non-perturbative attraction towards the strong coupling limit reproduces qualitatively the observed features. We further examine the scaling properties of an action which is closer to the attractive stream than the currently used improved actions. It is found that this action shows excellent restoration of rotational symmetry even for coarse lattices with $a \sim 0.3$ fm.Comment: 18 pages with 9 eps figures psfig.sty, typos correcte

Kiloparsec-scale star formation law in M81 and M101 based on AKARI far-infrared observations

We assess the relationships between the surface densities of the gas and star formation rate (SFR) within spiral arms of the nearby late-type spiral galaxies M81 and M101. By analyzing these relationships locally, we derive empirically a kiloparsec scale Kennicutt-Schmidt Law. Both M81 and M101 were observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared bands at 65, 90, 140, and 160 um. The spectral energy distributions of the whole galaxies show the presence of the cold dust component (Tc~20 K) in addition to the warm dust component (Tw~60 K). We deconvolved the cold and warm dust emission components spatially by making the best use of the multi-band photometric capability of the FIS. The cold and warm dust components show power-law correlations in various regions, which can be converted into the gas mass and the SFR, respectively. We find a power-law correlation between the gas and SFR surface densities with significant differences in the power law index N between giant HII regions (N=1.0) and spiral arms (N=2.2) in M101. The power-law index for spiral arms in M81 is similar (N=1.9) to that of spiral arms in M101. Conclusions: The power-law index is not always constant within a galaxy. The difference in the power-law index can be attributed to the difference in the star formation processes on a kiloparsec scale. N~2 seen in the spiral arms in M81 and M101 supports the scenario of star formation triggered by cloud-cloud collisions enhanced by spiral density wave, while N~1 derived in giant HII regions in M101 suggests the star formation induced by the Parker instability triggered by high velocity HI gas infall. The present method can be applied to a large galaxy sample for which the AKARI All Sky Survey provides the same 4 far-infrared band data.Comment: 12 pages, 8 figures, accepted for publication in A&

Density functional study of Aun_n (n=2-20) clusters: lowest-energy structures and electronic properties

We have investigated the lowest-energy structures and electronic properties of the Au$_n$(n=2-20) clusters based on density functional theory (DFT) with local density approximation. The small Au$_n$ clusters adopt planar structures up to n=6. Tabular cage structures are preferred in the range of n=10-14 and a structural transition from tabular cage-like structure to compact near-spherical structure is found around n=15. The most stable configurations obtained for Au$_{13}$ and Au$_{19}$ clusters are amorphous instead of icosahedral or fcc-like, while the electronic density of states sensitively depend on the cluster geometry. Dramatic odd-even alternative behaviors are obtained in the relative stability, HOMO-LUMO gaps and ionization potentials of gold clusters. The size evolution of electronic properties is discussed and the theoretical ionization potentials of Au$_n$ clusters compare well with experiments.Comment: 6 pages, 7 figure

Morphology and Size Differences between Local & High Redshift Luminous Infrared Galaxies

We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z ~ 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z ~ 1 and a lensed galaxy at z ~ 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z > 1 for a given IR luminosity compared to their local counterparts.Comment: Accepted for publication in The Astrophysical Journal; 13 pages, 7 figures; Online materials available at http://inthanon.as.arizona.edu/~wiphu/Rujopakarn_2010

BUCK CONVERTER LOSSES-BASED MODEL FOR SIMULATION AND PID CONTROL STRATEGY

Este artículo presenta un modelo en forma canónica de un convertidor Buck considerando las pérdidas originadas por los elementos de conmutación (diodo y MOSFET) y la resistencia del devanado del inductor. Adicionalmente, se muestra la comparación en simulación del circuito convencional con semiconductores y de un circuito equivalente propuesto, en el que se remplazan los elementos de conmutación por fuentes dependientes. Los resultados se basan en la simulación de los modelos de estudio controlados mediante un PID que tiene como objetivo la regulación del voltaje de salida del convertidor ante cambios en la carga y en la fuente de alimentación. Para el diseño del controlador se utilizan los parámetros de la tarjeta de desarrollo de Microchip dsPICDEM.This paper presents a canonical model for the Buck converter taking intoaccount the losses of the switching devices in the circuit (diode and mosfet) and the coil resistance. Moreover, a comparison between the simulations of the standard semiconductor-based model and the proposed model is presented. In the proposed model, the switching devices are replaced by dependent sources. Obtained results are based on simulations of the target models, which are controlled by mean a PID controller aimed to improve the output voltage regulation for changes in the load and the power supply. For the controller design, parameters of a Microchip dsPICDEM development board are used