1,668 research outputs found
Effect of high frequency ultrasounds on lycopene and total phenolic concentration, antioxidant properties and α-glucosidase inhibitory activity of tomato juice
Tomato juice was subjected to high frequency ultrasounds(378 and 583 kHz)at increasing energy densities (up to 250 MJ/m3). Results relevant to the treatments at high frequency providing an energy density of 250 MJ/m3 were compared with those obtained at 24 kHz delivering the same energy density. Lycopene and total phenolic concentration, as well as the α-glucosidase inhibitory activityof tomato juice, were not affected by ultrasound regardless the frequency and energy density. However, the antioxidant properties were negatively affected by high frequency ultrasounds
Dynamical energy analysis on mesh grids: a new tool for describing the vibro-acoustic response of complex mechanical structures
We present a new approach for modelling noise and vibration in complex mechanical structures in the mid-to-high frequency regime. It is based on a dynamical energy analysis (DEA) formulation which extends standard techniques such as statistical energy analysis (SEA) towards non-diffusive wave fields. DEA takes into account the full directionality of the wave field and makes sub-structuring obsolete. It can thus be implemented on mesh grids commonly used, for example, in the finite element method (FEM). The resulting mesh based formulation of DEA can be implemented very efficiently using discrete flow mapping (DFM) as detailed in [1] and described here for applications in vibro-acoustics
Mortality rates and division of labor in the leaf-cutting ant, Atta colombica
Division of labor in social groups is affected by the relative costs and benefits of conducting different tasks. However, most studies have examined the dynamics of division of labor, rather than the costs and benefits that presumably underlie the evolution of such systems. In social insects, division of labor may be simplistically described as a source-sink system, with external tasks, such as foraging, acting as sinks for the work force. The implications of two distinct sinks â foraging and waste-heap working â for division of labor were examined in the leaf-cutting ant Atta colombica. Intrinsic mortality rates were similar across external task groups. Exposure to waste (a task-related environment) led to a 60% increase in the mortality rate of waste-heap workers compared to workers not exposed to waste. Given the small number of workers present in the waste-heap task group, such increases in mortality are unlikely to affect division of labor and task allocation dramatically, except perhaps under conditions of stress
Hierarchical progressive surveys. Multi-resolution HEALPix data structures for astronomical images, catalogues, and 3-dimensional data cubes
Scientific exploitation of the ever increasing volumes of astronomical data
requires efficient and practical methods for data access, visualisation, and
analysis. Hierarchical sky tessellation techniques enable a multi-resolution
approach to organising data on angular scales from the full sky down to the
individual image pixels. Aims. We aim to show that the Hierarchical progressive
survey (HiPS) scheme for describing astronomical images, source catalogues, and
three-dimensional data cubes is a practical solution to managing large volumes
of heterogeneous data and that it enables a new level of scientific
interoperability across large collections of data of these different data
types. Methods. HiPS uses the HEALPix tessellation of the sphere to define a
hierarchical tile and pixel structure to describe and organise astronomical
data. HiPS is designed to conserve the scientific properties of the data
alongside both visualisation considerations and emphasis on the ease of
implementation. We describe the development of HiPS to manage a large number of
diverse image surveys, as well as the extension of hierarchical image systems
to cube and catalogue data. We demonstrate the interoperability of HiPS and
Multi-Order Coverage (MOC) maps and highlight the HiPS mechanism to provide
links to the original data. Results. Hierarchical progressive surveys have been
generated by various data centres and groups for ~200 data collections
including many wide area sky surveys, and archives of pointed observations.
These can be accessed and visualised in Aladin, Aladin Lite, and other
applications. HiPS provides a basis for further innovations in the use of
hierarchical data structures to facilitate the description and statistical
analysis of large astronomical data sets.Comment: 21 pages, 6 figures. Accepted for publication in Astronomy &
Astrophysic
Submillimeter to centimeter excess emission from the Magellanic Clouds. II. On the nature of the excess
Dust emission at submm to cm wavelengths is often simply the Rayleigh-Jeans
tail of dust particles at thermal equilibrium and is used as a cold mass tracer
in various environments including nearby galaxies. However, well-sampled
spectral energy distributions of the nearby, star-forming Magellanic Clouds
have a pronounced (sub-)millimeter excess (Israel et al., 2010). This study
attempts to confirm the existence of such a millimeter excess above expected
dust, free-free and synchrotron emission and to explore different possibilities
for its origin. We model NIR to radio spectral energy distributions of the
Magellanic Clouds with dust, free-free and synchrotron emission. A millimeter
excess emission is confirmed above these components and its spectral shape and
intensity are analysed in light of different scenarios: very cold dust, Cosmic
Microwave Background (CMB) fluctuations, a change of the dust spectral index
and spinning dust emission. We show that very cold dust or CMB fluctuations are
very unlikely explanations for the observed excess in these two galaxies. The
excess in the LMC can be satisfactorily explained either by a change of the
spectral index due to intrinsic properties of amorphous grains, or by spinning
dust emission. In the SMC however, due to the importance of the excess, the
dust grain model including TLS/DCD effects cannot reproduce the observed
emission in a simple way. A possible solution was achieved with spinning dust
emission, but many assumptions on the physical state of the interstellar medium
had to be made. Further studies, using higher resolution data from Planck and
Herschel, are needed to probe the origin of this observed submm-cm excess more
definitely. Our study shows that the different possible origins will be best
distinguished where the excess is the highest, as is the case in the SMC.Comment: 7 pages, 6 figures; accepted in A&
Dust emission at 8-mic and 24-mic as Diagnostics of HII Region Radiative Transfer
We use the Spitzer SAGE survey of the Magellanic Clouds to evaluate the
relationship between the 8-mic PAH emission, 24-mic hot dust emission, and HII
region radiative transfer. We confirm that in the higher-metallicity Large
Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in
the nebular Lyman continuum: objects identified as optically thin candidates
based on nebular ionization structure show 6 times lower median 8-mic surface
brightness (0.18 mJy arcsec^-2) than their optically thick counterparts (1.2
mJy arcsec^-2). The 24-mic surface brightness also shows a factor of 3 offset
between the two classes of objects (0.13 vs 0.44 mJy arcsec^-2, respectively),
which is driven by the association between the very small dust grains and
higher density gas found at higher nebular optical depths. In contrast, PAH and
dust formation in the low-metallicity Small Magellanic Cloud is strongly
inhibited such that we find no variation in either 8-mic or 24-mic emission
between our optically thick and thin samples. This is attributable to extremely
low PAH and dust production together with high, corrosive UV photon fluxes in
this low-metallicity environment. The dust mass surface densities and
gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey
data support this interpretation.Comment: Accepted to ApJ, May 15, 2017. 10 pages, 9 figure
The remnant of SN1987A revealed at (sub-)mm wavelengths
Context: Supernova 1987A (SN1987A) exploded in the Large Magellanic Cloud
(LMC). Its proximity and rapid evolution makes it a unique case study of the
early phases in the development of a supernova remnant. One particular aspect
of interest is the possible formation of dust in SN1987A, as SNe could
contribute significantly to the dust seen at high redshifts. Aims: We explore
the properties of SN1987A and its circumburst medium as seen at mm and sub-mm
wavelengths, bridging the gap between extant radio and infrared (IR)
observations of respectively the synchrotron and dust emission. Methods:
SN1987A was observed with the Australia Telescope Compact Array (ATCA) at 3.2
mm in July 2005, and with the Atacama Pathfinder EXperiment (APEX) at 0.87 mm
in May 2007. We present the images and brightness measurements of SN1987A at
these wavelengths for the first time. Results: SN1987A is detected as an
unresolved point source of 11.2 +/- 2.0 mJy at 3.2 mm (5" beam) and 21 +/- 4
mJy at 0.87 mm (18" beam). These flux densities are in perfect agreement with
extrapolations of the powerlaw radio spectrum and modified-blackbody dust
emission, respectively. This places limits on the presence of free-free
emission, which is similar to the expected free-free emission from the ionized
ejecta from SN1987A. Adjacent, fainter emission is observed at 0.87 mm
extending ~0.5' towards the south-west. This could be the impact of the
supernova progenitor's wind when it was still a red supergiant upon a dense
medium. Conclusions: We have established a continuous spectral energy
distribution for the emission from SN1987A and its immediate surroundings,
linking the IR and radio data. This places limits on the contribution from
ionized plasma. Our sub-mm image reveals complexity in the distribution of cold
dust surrounding SN1987A, but leaves room for freshly synthesized dust in the
SN ejecta.Comment: Accepted for publication in Astronomy and Astrophysics Letters on 28
April 2011. A better quality figure 1 can be had from
http://www.astro.keele.ac.uk/~jacco/research/SN1987A087mm.ep
Colloidal, tribological and sensory properties of oral nutritional supplements
This study aims to evaluate the physicochemical and sensory properties of oral nutritional supplements (ONSs). High physical stability was measured in ONSs with mean particle sizes <0.33 !m and viscosity >19.3 mPa·s. ONSs formulated with dairy-soy protein mixtures displayed low friction coefficients, whereas ONSs containing dairy proteins alone had high friction coefficient values in the boundary regime. Sensory analysis revealed low to medium liking across the products and the highest preference was found in samples with the highest perceived 'sweetness', 'vanilla aroma' and 'thickness'. The results will underpin the formulation of novel ONSs with good physical stability and sensory acceptability
High-resolution Manometry Findings in Patients After Sclerotherapy for Esophageal Varices
Background/Aims Endoscopic therapy for esophageal varices may lead to esophageal dysmotility. High-resolution manometry is probably the more adequate tool to measure esophageal motility in these patients. This study aimed to evaluate esophageal motility using high resolution manometry following eradication of esophageal varices by endoscopic sclerotherapy. Methods We studied 21 patients (11 women, age 52 [45-59] years). All patients underwent eradication of esophageal varices with endoscopic sclerotherapy and subsequent high resolution manometry. Results A significant percentage of defective lower esophageal sphincter (basal pressure 14.3 [8.0-20.0] mmHg43% hypertonic) and hypocontractility (distal esophageal amplitude 50 [31-64] mmHgproximal esophageal amplitude 40 [31-61] mmHgdistal contractile integral 617 [403-920] mmHg center dot sec center dot cm48% ineffective) was noticed. Lower sphincter basal pressure and esophageal amplitude correlated inversely with the number of sessions (P < 0.001). No manometric parameter correlated with symptoms or interval between last endoscopy and manometry. Conclusions Esophageal motility after endoscopic sclerotherapy is characterized by: (1) defective lower sphincter and (2) defective and hypotensive peristalsis. Esophageal dysmotility is associated to an increased number of endoscopic sessions, but manometric parameters do not predict symptoms.Univ Fed Sao Paulo, Escola Paulista Med, Dept Surg, Sao Paulo, BrazilUniv Chicago, Dept Surg, 5841 S Maryland Ave, Chicago, IL 60637 USAUniv Fed Sao Paulo, Escola Paulista Med, Dept Surg, Sao Paulo, BrazilWeb of Scienc
- âŠ