575 research outputs found
A Pathway From Porous Particle Technology Toward Tailoring Aerogels for Pulmonary Drug Administration
Pulmonary drug delivery has recognized benefits for both local and systemic treatments. Dry powder inhalers (DPIs) are convenient, portable and environmentally friendly devices, becoming an optimal choice for patients. The tailoring of novel formulations for DPIs, namely in the form of porous particles, is stimulating in the pharmaceutical research area to improve delivery efficiency. Suitable powder technological approaches are being sought to design such formulations. Namely, aerogel powders are nanostructured porous particles with particularly attractive properties (large surface area, excellent aerodynamic properties and high fluid uptake capacity) for these purposes. In this review, the most recent development on powder technologies used for the processing of particulate porous carriers are described via updated examples and critically discussed. A special focus will be devoted to the most recent advances and uses of aerogel technology to obtain porous particles with advanced performance in pulmonary delivery.Work carried out in the framework of COST Action CA18125 “Advanced Engineering and Research of aeroGels for Environment and Life Sciences” (AERoGELS), funded by the European Commission. This work was also supported by Xunta de Galicia [ED431C 2020/17], MCIUN [RTI2018-094131-AI00], Agencia Estatal de Investigación [AEI], and FEDER funds. CG-G acknowledges to MINECO for a Ramón y Cajal Fellowship [RYC2014-15239]
Enhanced Piezoelectricity of Electrospun Polyvinylidene Fluoride Fibers for Energy Harvesting
Piezoelectric polymers are promising energy materials for wearable and implantable applications for replacing bulky batteries in small and flexible electronics. Therefore, many research studies are focused on understanding the behavior of polymers at a molecular level and designing new polymer-based generators using polyvinylidene fluoride (PVDF). In this work, we investigated the influence of voltage polarity and ambient relative humidity in electrospinning of PVDF for energy-harvesting applications. A multitechnique approach combining microscopy and spectroscopy was used to study the content of the β-phase and piezoelectric properties of PVDF fibers. We shed new light on β-phase crystallization in electrospun PVDF and showed the enhanced piezoelectric response of the PVDF fiber-based generator produced with the negative voltage polarity at a relative humidity of 60%. Above all, we proved that not only crystallinity but also surface chemistry is crucial for improving piezoelectric performance in PVDF fibers. Controlling relative humidity and voltage polarity increased the d33 piezoelectric coefficient for PVDF fibers by more than three times and allowed us to generate a power density of 0.6 μW·cm-2 from PVDF membranes. This study showed that the electrospinning technique can be used as a single-step process for obtaining a vast spectrum of PVDF fibers exhibiting different physicochemical properties with β-phase crystallinity reaching up to 74%. The humidity and voltage polarity are critical factors in respect of chemistry of the material on piezoelectricity of PVDF fibers, which establishes a novel route to engineer materials for energy-harvesting and sensing applications
Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
HII regions are the birth places of stars, and as such they provide the best
measure of current star formation rates (SFRs) in galaxies. The close proximity
of the Magellanic Clouds allows us to probe the nature of these star forming
regions at small spatial scales. We aim to determine the monochromatic IR band
that most accurately traces the bolometric IR flux (TIR), which can then be
used to estimate an obscured SFR. We present the spatial analysis, via
aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using
the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are
also included. We find that nearly all of the LMC and SMC HII region SEDs peak
around 70um, from ~10 to ~400 pc from the central sources. As a result, the
sizes of HII regions as probed by 70um is approximately equal to the sizes as
probed by TIR (about 70 pc in radius); the radial profile of the 70um flux,
normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma
standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction
of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um
normalized fluxes (0.12 to 0.52); and these results are invariant between the
LMC and SMC. From these results, we argue that 70um is the most suitable IR
band to use as a monochromatic obscured star formation indicator because it
most accurately reproduces the TIR of HII regions in the LMC and SMC and over
large spatial scales. We also explore the general trends of the 8, 24, 70, and
160um bands in the LMC and SMC HII region SEDs, radial surface brightness
profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an
obscured SFR equation that is modified from the literature to use 70um
luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable
from 10 to 300 pc distance from the center of an HII region.Comment: 21 pages, 12 figures, 4 tables. Will be published in ApJ
A systematic fitting scheme for caustic-crossing microlensing events
We outline a method for fitting binary-lens caustic-crossing microlensing
events based on the alternative model parameterisation proposed and detailed in
Cassan (2008). As an illustration of our methodology, we present an analysis of
OGLE-2007-BLG-472, a double-peaked Galactic microlensing event with a source
crossing the whole caustic structure in less than three days. In order to
identify all possible models we conduct an extensive search of the parameter
space, followed by a refinement of the parameters with a Markov Chain-Monte
Carlo algorithm. We find a number of low-chi2 regions in the parameter space,
which lead to several distinct competitive best models. We examine the
parameters for each of them, and estimate their physical properties. We find
that our fitting strategy locates several minima that are difficult to find
with other modelling strategies and is therefore a more appropriate method to
fit this type of events.Comment: 12 pages, 11 figure
OGLE-2005-BLG-153: Microlensing Discovery and Characterization of A Very Low Mass Binary
The mass function and statistics of binaries provide important diagnostics of
the star formation process. Despite this importance, the mass function at low
masses remains poorly known due to observational difficulties caused by the
faintness of the objects. Here we report the microlensing discovery and
characterization of a binary lens composed of very low-mass stars just above
the hydrogen-burning limit. From the combined measurements of the Einstein
radius and microlens parallax, we measure the masses of the binary components
of and . This discovery
demonstrates that microlensing will provide a method to measure the mass
function of all Galactic populations of very low mass binaries that is
independent of the biases caused by the luminosity of the population.Comment: 6 pages, 3 figures, 1 tabl
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