2,506 research outputs found
Sulfites in beer: reviewing regulation, analysis and role
Beer is an extremely complex mixture of more than 3,000 different compounds in an aqueous environment. Thus, it is perhaps not surprising that the maintenance of beer quality throughout its lifetime has been a considerable challenge for brewers. Whilst it is inevitable that chemical changes will occur in beer with the passage of time, it is the formation of flavor-active components which is of immediate concern to an overview of beer shelf life stability. Sulfur dioxide has long been recognized by brewers as the most important factor in delaying flavor staling, and prolonging the shelf life of beer. However, nowadays, sulfur dioxide and sulfites are considered allergens and concerns about the safety of their use as food additives have been on the increase. The present review is structured into three main parts. Firstly, the chemical properties of sulfur dioxide are presented, along with the toxic effects and maximum legal levels permitted according to U.S. and EU legislation. As the accurate determination of the free, bound and total sulfur dioxide in beer is essential to ensuring regulatory compliance, several methods have been developed for analyzing sulfur dioxide in beer. Thus, secondly, various types of methods are reported and compared with the officially recommended ones. Finally, the crucial role of sulfite in the control of flavor instability of beer is discussed in light of the current data. Two courses of action have been proposed, which are elucidated in detail relating firstly to the fact that sulfite inhibits beer oxidation during storage by acting as an antioxidant and, secondly, sulfite reacts with the carbonyl staling compounds in beer, and thereby masks stale flavors
Regional Knowledge and the Emergence of an Industry: Laser Systems Production in West Germany, 1975-2005
We analyze the emergence and spatial evolution of the German laser systems industry. Regional knowledge in the related field of laser sources, as well as the presence of universities with physics or engineering departments, is conducive to the emergence of laser systems suppliers. The regional presence of source producers is also positively related to entry into laser systems. One important mechanism behind regional entry is the diversification of upstream laser source producers into the downstream systems market. Entry into the materials processing submarket appears to be unrelated to academic knowledge in the region, but the presence of laser source producers and the regional stock of laser knowledge are still highly predictive in this submarket.Innovation, regional knowledge, laser technology, emerging industries, diversification
High Angular Resolution Observations of the Collimated Jet Source Associated with a Massive Protostar in IRAS 16547-4247
A triple radio source recently detected in association with the luminous
infrared source IRAS 16547-4247 has been studied with high angular resolution
and high sensitivity with the Very Large Array at 3.6 and 2 cm. Our
observations confirm the interpretation that the central object is a thermal
radio jet, while the two outer lobes are most probably heavily obscured HH
objects. The thermal radio jet is resolved angularly for the first time and
found to align closely with the outer lobes. The opening angle of the thermal
jet is estimated to be , confirming that collimated outflows can
also be present in massive protostars. The proper motions of the outer lobes
should be measurable over timescales of a few years. Several fainter sources
detected in the region are most probably associated with other stars in a young
cluster.Comment: 9 pages, 2 figure
VLA observations of candidate high-mass protostellar objects at 7 mm
We present radio continuum observations at 7 mm made using the Very Large
Array towards three massive star forming regions thought to be in very early
stages of evolution selected from the sample of Sridharan et al. (2002).
Emission was detected towards all three sources (IRAS 18470-0044, IRAS
19217+1651 and IRAS 23151+5912). We find that in all cases the 7 mm emission
corresponds to thermal emission from ionized gas. The regions of ionized gas
associated with IRAS 19217+1651 and IRAS 23151+5912 are hypercompact with
diameters of 0.009 and 0.0006 pc, and emission measures of 7.0 x 10^8 and 2.3 x
10^9 pc cm^(-6), respectively.Comment: 17 pages, 5 figures, accepted by The Astronomical Journa
An Asymmetric Keplerian Disk Surrounding the O-type Protostar IRAS 16547-4247
For the past few decades, there has been great interest in determining if even the most massive stars in our galaxy (namely the spectral O-type stars) are formed in a similar manner as the low- and intermediate-mass stars, that is, through the presence of accreting disks and powerful outflows. Here, using sensitive observations of the Atacama Large Millimeter/Submillimeter Array, we report a resolved Keplerian disk (with 15 synthesized beams across its major axis) surrounding the deeply embedded O-type protostar IRAS 16547-4247. The disk shows some asymmetries that could arise because the disk is unstable and fragmenting or because of different excitation conditions within the disk. The enclosed mass estimated from the disk Keplerian radial velocities is 25 -3 M . The molecular disk is at the base of an ionized thermal radio jet and is approximately perpendicular to the jet axis orientation. We additionally find the existence of a binary system of compact dusty objects at the center of the accreting disk, which indicates the possible formation of an O-type star and a companion of lower mass. This is not surprising due to the high binary fraction reported in massive stars. Subtracting the contribution of the dusty disk plus the envelope and the companion, we estimated a mass of 20 M for the central star.Fil: Zapata, Luis A.. Universidad Nacional Autónoma de México; MéxicoFil: Garay, Guido. Universidad de Chile; ChileFil: Palau, Aina. Universidad Nacional Autónoma de México; MéxicoFil: RodrÃguez, Luis F.. Universidad Nacional Autónoma de México; MéxicoFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaFil: Estalella, Robert. Universidad de Barcelona; EspañaFil: Guzmán, Andres. National Astronomical Observatory of Japan; Japó
Techniques for Extraction of Brewer’s Spent Grain Polyphenols: a Review
Million tons of brewer’s spent grain (BSG) are annually produced worldwide as brewing industry by-products.
BSG represents a valuable source of phenolic compounds, which have attracted much attention due to their diverse health benefits. Relevant strategies have been developed for their efficient extraction, in order to commercially exploit these resources. This review focuses on the current extraction methods used to obtain phenolic compounds from BSG, ranging from more traditional to advanced techniques. The commonly used methods are the conventional solid–liquid extractions, employing organic solvents, alkaline, and enzymatic reactions. However, the inherent difficulties in screening and obtaining these compounds have led to the development of advanced extraction techniques. Pressurized fluid extraction, supercritical extractions, and microwave-assisted and ultrasound-assisted extractions are some of the novel extraction techniques that have been recently explored. These techniques have been mostly applied for phenolic recovery from barley and malt, as well as other types of cereals. In this review, it is shown that these novel techniques may provide an innovative approach to extract phenolics from BSG or related products, following an in-depth discussion on the major strengths and weaknesses identified in each technique.info:eu-repo/semantics/publishedVersio
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The Collimated Jet Source in IRAS 16547-4247: Time Variation, Possible Precession, and Upper Limits to the Proper Motions along the Jet Axis
The triple radio source detected in association with the luminous infrared source IRAS 16547-4247 has previously been studied with high angular resolution and high sensitivity with the Very Large Array at 3.6 cm wavelength. In this paper, we present new 3.6 cm observations taken 2.68 years after the first epoch that allow a search for variability and proper motions, as well as the detection of additional faint sources in the region. We do not detect proper motions along the axis of the outflow in the outer lobes of this source at a 4σ upper limit of ~160 . This suggests that these lobes are probably working surfaces where the jet is interacting with a denser medium. However, the brightest components of the lobes show evidence of precession, at a rate of clockwise in the plane of the sky. It may be possible to understand the distribution of almost all the identified sources as the result of ejecta from a precessing jet. The core of the thermal jet shows significant variations in flux density and morphology. We compare this source with other jets in low- and high-mass young stars and suggest that the latter can be understood as a scaled-up version of the former.Astronom
The Collimated Jet Source in IRAS 16547-4247: Time Variation, Possible Precession, and Upper Limits to the Proper Motions Along the Jet Axis
The triple radio source detected in association with the luminous infrared
source IRAS 16547-4247 has previously been studied with high angular resolution
and high sensitivity with the Very Large Array (VLA) at 3.6-cm wavelength. In
this paper, we present new 3.6 cm observations taken 2.68 years after the first
epoch that allow a search for variability and proper motions, as well as the
detection of additional faint sources in the region. We do not detect proper
motions along the axis of the outflow in the outer lobes of this source at a
4- upper limit of 160 km s. This suggests that these lobes
are probably working surfaces where the jet is interacting with a denser
medium. However, the brightest components of the lobes show evidence of
precession, at a rate of yr clockwise in the plane of
the sky. It may be possible to understand the distribution of almost all the
identified sources as the result of ejecta from a precessing jet. The core of
the thermal jet shows significant variations in flux density and morphology. We
compare this source with other jets in low and high mass young stars and
suggest that the former can be understood as a scaled-up version of the latter.Comment: 26 pages, 9 figure
The Rotating Molecular Structures and the Ionized Outflow Associated with IRAS 16547-4247
We present VLA 1.3 cm radio continuum and water maser observations as well as
SMA SO (226.300 GHz) and 1.3 mm dust continuum observations toward the
massive star formation region IRAS 16547-4247. We find evidence of multiple
sources in the central part of the region. There is evidence of a rotating
structure associated with the most massive of these sources, traced at small
scales (~50 AU) by the water masers. At large scales (~1000 AU) we find a
velocity gradient in the SO2 molecular emission with a barely resolved
structure that can be modeled as a rotating ring or two separate objects. The
velocity gradients of the masers and of the molecular emission have the same
sense and may trace the same structure at different size scales. The position
angles of the structures associated with the velocity gradients are roughly
perpendicular to the outflow axis observed in radio continuum and several
molecular tracers. We estimate the mass of the most massive central source to
be around 30 solar masses from the velocity gradient in the water maser
emission. The main source of error in this estimate is the radius of the
rotating structure. We also find water masers that are associated with the
large scale molecular outflow of the system, as well as water masers that are
associated with other sources in the region. Our results suggest that the
formation of this source, one of the most luminous protostars or protostellar
clusters known, is taking place with the presence of ionized jets and disk-like
structures.Comment: 26 pages, 7 figure
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The rotating molecular structures and the ionized outflow associated with IRAS 16547-4247
We present Very Large Array 1.3 cm radio continuum and water maser observations as well as Submillimeter Array SO 2 (226.300 GHz) and 1.3 mm dust continuum observations toward the massive star formation region IRAS 16547−4247. We find evidence of multiple sources in the central part of the region. There is evidence of a rotating structure associated with the most massive of these sources, traced at small scales (∼50 AU) by the water masers. At large scales (∼1000 AU), we find a velocity gradient in the SO 2 molecular emission with a barely resolved structure that can be modeled as a rotating ring or two separate objects. The velocity gradients of the masers and of the molecular emission have the same sense and may trace the same structure at different size scales. The position angles of the structures associated with the velocity gradients are roughly perpendicular to the outflow axis observed in radio continuum and several molecular tracers. We estimate the mass of the most massive central source to be around 30 solar masses from the velocity gradient in the water maser emission. The main source of error in this estimate is the radius of the rotating structure. We also find water masers that are associated with the large-scale molecular outflow of the system, as well as water masers that are associated with other sources in the region. Our results suggest that the formation of this source, one of the most luminous protostars or protostellar clusters known, is taking place with the presence of ionized jets and disk-like structures.Astronom
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