56 research outputs found
Mid-Infrared Observations of Planetary Nebulae detected in the GLIMPSE 3D Survey
We present mapping, profiles and photometry for 24 planetary nebulae (PNe)
detected in the GLIMPSE 3D mid-infrared (MIR) survey of the Galactic plane. The
PNe show many of the properties observed in previous studies of these sources,
including evidence for longer wave emission from outside of the ionised zones,
a likely consequence of emission from polycyclic aromatic hydrocarbons (PAHs)
within the nebular photo-dissociation regimes (PDRs). We also note variations
in 5.8/4.5 and 8.0/4.5 microns flux ratios with distance from the nuclei;
present evidence for enhanced MIR emission in the halos of the sources; and
note evidence for variations in colour with nebular evolution.Comment: 35 pages, 28 figures, Accepted for publication in Revista Mexicana de
Astronomia y Astrofisica (RevMexAA). 61 pages in arXi
The “tattoo” speckle pattern: fabrication and application
Digital Image Correlation (DIC) is widely used in experimental mechanics for full field measurement of displacements and strains. The application of this technique, normally requires the preparation of specimens with a random speckle pattern, via spray painting, stamping, manual patterning, etc. The applicability of most techniques to create random patterns is still limited. For instance, traditional methods such as airbrush painting are not suitable when time available to produce the speckle pattern is limited. The development and application of a novel technique to address this problem is presented in this paper. The developed technique makes use of commercially available temporary tattoo paper, adhesives, and paint. The presented technique showed to be quick, repeatable, consistent, and stable even under impact loads and large deformations. Additionally, they offer the possibility to optimise and customise the speckle pattern
A comprehensive investigation on the temperature and strain rate dependent mechanical response of three polymeric syntactic foams for thermoforming and energy absorption applications
Polymeric syntactic foams (PSF) are a kind of composite material, which consists of a polymer matrix reinforced by hollow thin wall glass micro-spheres. Because of their low density, low moisture absorption, relatively high specific strength and stiffness, PSF are often employed in aerospace and submarine applications in which they are subjected to a wide range of temperature conditions. Due to the temperature sensitivity of the polymer matrix, the physical and mechanical behaviour of PSFs is highly sensitive to temperature variations. Besides, their dynamic response is significantly affected by the strain rate. This research investigates the temperature and strain rate dependence of the mechanical behaviour of polyurethane, epoxy and nylon syntactic foams under compressive and tensile loads. The selected materials have in common that their mechanical characteristics, thermal properties, and dimensional stability make them suitable for both impact engineering and thermoforming applications. The experimental results, acquired over a temperature range from −25 °C to 100 °C at low and high strain rates, reveal a clear interplay between temperature and strain rate effects on the mechanical behaviour of the materials under investigation. This synergy is observed to vary based on both the matrix material and the loading mode. Notably, the rate dependency of polyurethane and nylon syntactic foams is significantly influenced by the testing temperature during compression, while in tension the influence of the temperature on the rate dependency is moderate or negligible. In contrast, the rate dependency of the epoxy syntactic foam remains largely unaffected by the testing temperature. Deformation and failure mechanisms were analysed by examining the failure surface of the tested samples using SEM micrographs
Examining the quasi-static uniaxial compressive behaviour of commercial high-performance epoxy matrices
Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM®890, CYCOM®977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM®977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM®890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material. The PRISM EP2400 resin, with combined toughening agents, led to true axial stress values across the entire plastic region of the stress-strain curve, which were in line with the stress values observed with the CYCOM®890 material. Interestingly, for all formulations, the dilation angles (associated with the volume change during plastic deformation), recorded at 0.3 plastic strain, were close to 0°, with the variations reflecting the polymer structure. Compression data collected for this series of commercial epoxy resins are in broad agreement with a selection of model epoxy resins based on di- and tetra-functional monomers, cured with polyamines or dicarboxylic anhydrides. However, the fully formulated resins demonstrate a significantly higher compressive modulus than the model resins, albeit at the expense of yield stress
Unveiling the stellar origin of the Wolf-Rayet nebula NGC6888 through infrared observations
We present a comprehensive infrared (IR) study of the iconic Wolf-Rayet (WR)
wind-blown bubble NGC6888 around WR136. We use Wide-field Infrared Survey
Explorer (WISE), Spitzer IRAC and MIPS and Herschel PACS IR images to produce a
sharp view of the distribution of dust around WR136. We complement these IR
photometric observations with Spitzer IRS spectra in the 5-38 m wavelength
range. The unprecedented high-resolution IR images allowed us to produce a
clean spectral energy distribution, free of contamination from material along
the line of sight, to model the properties of the dust in NGC6888. We use the
spectral synthesis code Cloudy to produce a model for NGC6888 that consistently
reproduces its optical and IR properties. Our best model requires a double
distribution with the inner shell composed only of gas, whilst the outer shell
requires a mix of gas and dust. The dust consists of two populations of grain
sizes, one with small sized grains =[0.002-0.008] m and
another one with large sized grains =[0.05-0.5] m. The
population of big grains is similar to that reported for other red supergiants
stars and dominates the total dust mass, which leads us to suggest that the
current mass of NGC6888 is purely due to material ejected from WR136, with a
negligible contribution of swept up interstellar medium. The total mass of this
model is 25.5 M, a dust mass of
0.14 M, for a dust-to-gas ratio
of . Accordingly, we suggest that the initial stellar mass of
WR136 was 50 M, consistent with current single stellar
evolution models.Comment: 13 pages, 11 figures, 6 tables; Accepted to MNRA
Desarrollo de Videojuego de Carreras Utilizando al Smartphone como Timón
Uno de los géneros más populares de videojuegos han sido los de carreras. Aquí hay una fuerte demanda por controladores con diseño de timón que hacen de la experiencia de juego más inmersiva y entretenida. No obstante, estos controladores suelen ser caros y no todos los jugadores pueden adquirirlos. En el afán de encontrar una alternativa más accesible que ofrezca la misma inmersión a los jugadores de este género se implementó SmartDrive, un videojuego de carreras para Android programado en Unity 3D. SmartDrive utiliza dos smartphones Android 5.0 o superior conectados vía un hotspot WiFi, uno se usa como pantalla del juego y otro como un timón gracias a sus sensores de movimiento. La validación contó con 30 participantes que jugaron y brindaron sus valoraciones mediante una encuesta. Los resultados finales destacaron la aceptación de SmartDrive en los participantes al ofrecer una experiencia inmersiva con una mecánica de juego novedosa e intuitiva, e implementada con recursos más económicos. Este estudio mostró el potencial de SmartDrive como una alternativa accesible y sin perder el grado de entretenimiento
Experimental characterisation of the dilation angle of polymers
Despite the wide use of Drucker-Prager plasticity-based models on polymers, the experimental measurement of the dilation angle, a critical parameter to fully describe the plastic potential, has been rarely reported in existing literature. This paper shows, for the first time, the experimental characterisation of the dilation angle of polymers over a wide range of plastic strain. These measurements were obtained from uniaxial compression experiments conducted on poly(methyl methacrylate) (PMMA) and an untoughened epoxy resin. The calculation of the dilation angle relied on the measurements of the compressive force and the strain components obtained via Digital Image Correlation (DIC). Lower values of dilation angle were obtained for the epoxy resin, suggesting that resistance to volumetric change during plastic deformation could be associated to molecular structure and internal forces. The methodology and results presented in this study can be applied to different types of materials and employed for developing and validating constitutive models that incorporate plastic dilation
Speckle patterns for DIC in challenging scenarios: rapid application and impact endurance
Digital image correlation (DIC) is a widely used technique in experimental mechanics for full field measurement of displacements and strains. The subset matching based DIC requires surfaces containing a random pattern. Even though there are several techniques to create random speckle patterns, their applicability is still limited. For instance, traditional methods such as airbrush painting are not suitable in the following challenging scenarios: (i) when time available to produce the speckle pattern is limited and (ii) when dynamic loading conditions trigger peeling of the pattern. The development and application of some novel techniques to address these situations is presented in this paper. The developed techniques make use of commercially available materials such as temporary tattoo paper, adhesives and stamp kits. The presented techniques are shown to be quick, repeatable, consistent and stable even under impact loads and large deformations. Additionally, they offer the possibility to optimise and customise the speckle pattern. The speckling techniques presented in the paper are also versatile and can be quickly applied in a variety of materials
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Development and application of genetic ancestry reconstruction methods to study diversity of patient-derived models in the NCI PDXNet Consortium
Precision medicine holds great promise for improving cancer outcomes. Yet, there are large inequities in the demographics of patients from whom genomic data and models, including patient-derived xenografts (PDX), are developed and for whom treatments are optimized. In this study, we developed a genetic ancestry pipeline for the Cancer Genomics Cloud, which we used to assess the diversity of models currently available in the National Cancer Institute-supported PDX Development and Trial Centers Research Network (PDXNet). We showed that there is an under-representation of models derived from patients of non-European ancestry, consistent with other cancer model resources. We discussed these findings in the context of disparities in cancer incidence and outcomes among demographic groups in the US, as well as power analyses for biomarker discovery, to highlight the immediate need for developing models from minority populations to address cancer health equity in precision medicine. Our analyses identified key priority disparity-associated cancer types for which new models should be developed.SignificanceUnderstanding whether and how tumor genetic factors drive differences in outcomes among U.S. minority groups is critical to addressing cancer health disparities. Our findings suggest that many additional models will be necessary to understand the genome-driven sources of these disparities
Optical and Infrared Imaging and Spectroscopy of the Multiple-Shell Planetary Nebula NGC 6369
NGC 6369 is a double-shell planetary nebula (PN) consisting of a bright
annular inner shell with faint bipolar extensions and a filamentary envelope.
We have used ground- and space-based narrow-band optical and near-IR images,
broad-band mid-IR images, optical long-slit echelle spectra, and mid-IR spectra
to investigate its physical structure. These observations indicate that the
inner shell of NGC 6369 can be described as a barrel-like structure shape with
polar bubble-like protrusions, and reveal evidence for H2 and strong polycyclic
aromatic hydrocarbons (PAHs) emission from a photo-dissociative region (PDR)
with molecular inclusions located outside the bright inner shell.
High-resolution HST narrow-band images reveal an intricate excitation structure
of the inner shell and a system of "cometary" knots. The knotty appearance of
the envelope, the lack of kinematical evidence for shell expansion and the
apparent presence of emission from ionized material outside the PDR makes us
suggest that the envelope of NGC 6369 is not a real shell, but a flattened
structure at its equatorial regions. We report the discovery of irregular knots
and blobs of diffuse emission in low-excitation and molecular line emission
that are located up to 80" from the central star, well outside the main nebular
shells. We also show that the filaments associated to the polar protrusions
have spatial extents consistent with post-shock cooling regimes, and likely
represent regions of interaction of these structures with surrounding material.Comment: 14 pages, 13 figures. Accepted for publication in MNRA
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