2,973 research outputs found
Selection of teachers in Cambridge
Thesis (Ed.M.)--Boston University, 1938. This item was digitized by the Internet Archive
A comparison of pilot-scale supersonic direct steam injection to conventional steam infusion and tubular heating systems for the heat treatment of protein-enriched skim milk-based beverages
peer-reviewedDirect supersonic steam injection, direct steam infusion, and indirect tubular heating were each applied to protein-enriched skim milk-based beverages with 4, 6 and 8% (w/w) total protein, and the effect of final heat temperature on the physical properties of these beverages was investigated. Supersonic steam injection resulted in significantly lower levels of denaturation of β-lactoglobulin (34.5%), compared to both infusion (76.3%) and tubular (97.1%) heating technologies. Viscosity, particle size and accelerated physical stability of formulations did not differ significantly between the heating technologies, while noticeable colour differences due to heat treatment (mainly attributed to increasing b* value) were observed, particularly for tubular heating. Overall, the extent of protein denaturation in high-protein dairy products was significantly influenced by the particular heating technology applied. The application of supersonic steam injection technology, with rapid heating and high shear characteristics, may enable differenciated product characteristics for ready-to-drink ambient-delivery high-protein dairy beverages.
Industrial relevance:
The design and application of novel direct supersonic steam injection technology was comprehensively studied and found to provide significant benefits over direct steam infusion and indirect tubular heating technologies for skim milk-based protein beverages. This type of injection heating system resulted in heat-treated formulations with lower levels of denatured whey proteins, compared to tubular and infusion heating, offering an alternative opportunity to the industry in terms of producing shelf-stable dairy protein beverages
Characterizing the Youngest Herschel-detected Protostars I. Envelope Structure Revealed by CARMA Dust Continuum Observations
We present CARMA 2.9 mm dust continuum emission observations of a sample of
14 Herschel-detected Class 0 protostars in the Orion A and B molecular clouds,
drawn from the PACS Bright Red Sources (PBRS) sample (Stutz et al.). These
objects are characterized by very red 24 \micron\ to 70 \micron\ colors and
prominent submillimeter emission, suggesting that they are very young Class 0
protostars embedded in dense envelopes. We detect all of the PBRS in 2.9 mm
continuum emission and emission from 4 protostars and 1 starless core in the
fields toward the PBRS; we also report 1 new PBRS source. The ratio of 2.9 mm
luminosity to bolometric luminosity is higher by a factor of 5 on
average, compared to other well-studied protostars in the Perseus and Ophiuchus
clouds. The 2.9 mm visibility amplitudes for 6 of the 14 PBRS are very flat as
a function of uv-distance, with more than 50\% of the source emission arising
from radii 1500 AU. These flat visibility amplitudes are most consistent
with spherically symmetric envelope density profiles with
~~R. Alternatively, there could be a massive unresolved
structure like a disk or a high-density inner envelope departing from a smooth
power-law. The large amount of mass on scales 1500 AU (implying high
average central densities) leads us to suggest that that the PBRS with flat
visibility amplitude profiles are the youngest PBRS and may be undergoing a
brief phase of high mass infall/accretion and are possibly among the youngest
Class 0 protostars. The PBRS with more rapidly declining visibility amplitudes
still have large envelope masses, but could be slightly more evolved.Comment: Accepted to ApJ, 40 pages, 9 Figures, 4 Table
High Resolution 8 mm and 1 cm Polarization of IRAS 4A from the VLA Nascent Disk and Multiplicity (VANDAM) Survey
Magnetic fields can regulate disk formation, accretion and jet launching.
Until recently, it has been difficult to obtain high resolution observations of
the magnetic fields of the youngest protostars in the critical region near the
protostar. The VANDAM survey is observing all known protostars in the Perseus
Molecular Cloud. Here we present the polarization data of IRAS 4A. We find that
with ~ 0.2'' (50 AU) resolution at {\lambda} = 8.1 and 10.3 mm, the inferred
magnetic field is consistent with a circular morphology, in marked contrast
with the hourglass morphology seen on larger scales. This morphology is
consistent with frozen-in field lines that were dragged in by rotating material
entering the infall region. The field morphology is reminiscent of rotating
circumstellar material near the protostar. This is the first polarization
detection of a protostar at these wavelengths. We conclude from our
observations that the dust emission is optically thin with {\beta} ~ 1.3,
suggesting that mm/cm-sized grains have grown and survived in the short
lifetime of the protostar.Comment: Accepted to ApJL. 13 pages, 4 figure
Evolution of Mass Outflow in Protostars
We have surveyed 84 Class 0, Class I, and flat-spectrum protostars in
mid-infrared [Si II], [Fe II] and [S I] line emission, and 11 of these in
far-infrared [O I] emission. We use the results to derive their mass outflow
rates. Thereby we observe a strong correlation of mass outflow rates with
bolometric luminosity, and with the inferred mass accretion rates of the
central objects, which continues through the Class 0 range the trend observed
in Class II young stellar objects. Along this trend from large to small
mass-flow rates, the different classes of young stellar objects lie in the
sequence Class 0 -- Class I/flat-spectrum -- Class II, indicating that the
trend is an evolutionary sequence in which mass outflow and accretion rates
decrease together with increasing age, while maintaining rough proportionality.
The survey results include two which are key tests of magnetocentrifugal
outflow-acceleration mechanisms: the distribution of the outflow/accretion
branching ratio b, and limits on the distribution of outflow speeds. Neither
rule out any of the three leading outflow-acceleration,
angular-momentum-ejection mechanisms, but they provide some evidence that disk
winds and accretion-powered stellar winds (APSWs) operate in many protostars.
An upper edge observed in the branching-ratio distribution is consistent with
the upper bound of b = 0.6 found in models of APSWs, and a large fraction
(0.31) of the sample have branching ratio sufficiently small that only disk
winds, launched on scales as large as several AU, have been demonstrated to
account for them.Comment: Version submitted to ApJ: 36 pages, 3 tables, 8 figure
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