6,122 research outputs found
Application of membrane separation in biotechnology
Membrane technology emerges as one of the most important separation methods, which have captured the attention of industries, related to biochemical, pharmaceutical, biomedical, and food industries. Due to the current intensive development and expansion, membrane technology is also rapidly gaining market recognition and application in Malaysia. Factors accelerating the positive growth of membrane market in Malaysia include economic factors, technology, support industries and awareness in environmental safety and health. Therefore, this paper seeks to review the separation mechanism, advantages and applications of synthetic polymeric membranes in biotechnology
Disentangling the entangled: Observations and analysis of the triple non-coeval protostellar system VLA1623
Commonplace at every evolutionary stage, Multiple Protostellar Systems (MPSs)
are thought to be formed through fragmentation, but it is unclear when and how.
The youngest MPSs, which have not yet undergone much evolution, provide
important constraints to this question. It is then of interest to disentangle
early stage MPSs. In this letter we present the results of our work on VLA1623
using our observations and archival data from the Submillimeter Array (SMA).
Our continuum and line observations trace VLA1623's components, outflow and
envelope, revealing unexpected characteristics. We construct the SED for each
component using the results of our work and data from literature, as well as
derive physical parameters from continuum and perform a simple kinematical
analysis of the circumstellar material. Our results show VLA1623 to be a triple
non-coeval system composed of VLA1623A, B & W, with each source driving its own
outflow and unevenly distributed circumstellar material. From the SED, physical
parameters and IR emission we conclude that VLA1623A & W are Class 0 and I
protostars, respectively, and together drive the bulk of the observed outflow.
Furthermore, we find two surprising results, first the presence of a rotating
disk-like structure about VLA1623A with indications of pure Keplerian rotation,
which, if real, would make it one of the first evidence of Keplerian disk
structures around Class 0 protostars. Second, we find VLA1623B to be a bonafide
extremely young protostellar object between the starless core and Class 0
stages.Comment: 22 pages, 4 figures, 1 Table, Accepted to Ap
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Widening of Protostellar Outflows: an Infrared Outflow Survey in Low Luminosity Objects
We present an outflow survey toward 20 Low Luminosity Objects (LLOs), namely
protostars with an internal luminosity lower than 0.2 Lsun. Although a number
of studies have reported the properties of individual LLOs, the reasons for
their low luminosity remain uncertain. To answer this question, we need to know
the evolutionary status of LLOs. Protostellar outflows are found to widen as
their parent cores evolve, and therefore, the outflow opening angle could be
used as an evolutionary indicator. The infrared scattered light escapes out
through the outflow cavity and highlights the cavity wall, giving us the
opportunity to measure the outflow opening angle. Using the
Canada-France-Hawaii Telescope, we detected outflows toward eight LLOs out of
20 at Ks band, and based on archival Spitzer IRAC1 images, we added four
outflow-driving sources from the remaining 12 sources. By fitting these images
with radiative transfer models, we derive the outflow opening angles and
inclination angles. To study the widening of outflow cavities, we compare our
sample with the young stellar objects from Arce & Sargent 2006 and Velusamy et
al. 2014 in the plot of opening angle versus bolometric temperature taken as an
evolutionary indicator.Our LLO targets match well the trend of increasing
opening angle with bolometric temperature reported by Arce & Sargent and are
broadly consistent with that reported by Velusamy et al., suggesting that the
opening angle could be a good evolutionary indicator for LLOs. Accordingly, we
conclude that at least 40% of the outflow-driving LLOs in our sample are young
Class 0 objects.Comment: Accepted for publication in AJ, 13 pages, 9 figure
On the Public Economics of Casino Gambling
This paper studies casino-style gambling from the public economics point of view in a jurisdiction populated by oligopolistically competitive legal casinos. We consider three different regimes: laissez-faire, entry regulation and tax regulation. The model highlights three important external effects from casino-style gambling: non-casino income creation, social disorder costs, and casino exporting to other jurisdictions. In the generalized case with an endogenously-determined ratio of local to total gamblers, we allow the configuration of casinos to be centralized or jurisdiction-wide dispersed. A complete comparison between equilibrium and command optimum outcomes is provided, and the welfare consequences under the three regimes and two casino configurations are examined.Casino gambling, externalities, oligopoly pricing, entry, tax regulation
Multi-wavelength Stellar Polarimetry of the Filamentary Cloud IC5146: I. Dust Properties
We present optical and near-infrared stellar polarization observations toward
the dark filamentary clouds associated with IC5146. The data allow us to
investigate the dust properties (this paper) and the magnetic field structure
(Paper II). A total of 2022 background stars were detected in -, -,
-, and/or -bands to mag. The ratio of the polarization
percentage at different wavelengths provides an estimate of ,
the wavelength of peak polarization, which is an indicator of the small-size
cutoff of the grain size distribution. The grain size distribution seems to
significantly change at 3 mag, where both the average and dispersion
of decrease. In addition, we found
0.6-0.9 m for mag, which is larger than the 0.55 m
in the general ISM, suggesting that grain growth has already started in low
regions. Our data also reveal that polarization efficiency (PE ) decreases with as a power-law in -, -, and
-bands with indices of -0.710.10, -1.230.10 and -0.530.09.
However, -band data show a power index change; the PE varies with
steeply (index of -0.950.30) when mag but softly
(index of -0.250.06) for greater values. The soft decay of PE in
high regions is consistent with the Radiative Aligned Torque model,
suggesting that our data trace the magnetic field to mag.
Furthermore, the breakpoint found in -band is similar to the where we
found the dispersion significantly decreased. Therefore, the
flat PE- in high regions implies that the power index changes result
from additional grain growth.Comment: 31 pages, 17 figures, and 3 tables; accepted for publication in Ap
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