340 research outputs found
The Role of Cooperative in The Milk Value Chain in West Bandung Regency, West Java Province
The objective of the study was to evaluate the capacity of Northern Bandung Dairy Farmer Cooperative (KPSBU) to support farmers in producing good quality milk within the milk value chain in West Bandung Regency, West Java. The study used qualitative research strategies including desk study, case study, and focus group discussions. The study compared the involvement of three milk collecting actors that were classified into large cooperative (KPSBU), small cooperative (KUD Puspa Mekar), and private company (Bina Kitri Bersama). A total of 18 dairy farmers, 3 milk collecting actors, 2 milk processors, and one livestock officer were interviewed. Three focus group discussions were conducted. The large cooperative performed better in services, milk collection, and milk quality assessment compared to other milk collecting actors. Membersâ commitment, inconsistent milk quality, and shortage of good quality fodder were the hindering factors that influenced the collection of good quality milk in the large cooperative. In conclusion, the large cooperative had better performance in service provision, it also had better infrastructures in milk collection and milk quality assessment compared to other milk collecting actors. Increasing the milk quality standard by milk processing companies affected the milk price since 2000.
On the Exchange of Kinetic and Magnetic Energy Between Clouds and the Interstellar Medium
We investigate, through 2D MHD numerical simulations, the interaction of a
uniform magnetic field oblique to a moving interstellar cloud. In particular we
explore the transformation of cloud kinetic energy into magnetic energy as a
result of field line stretching. Some previous simulations have emphasized the
possible dynamical importance of a ``magnetic shield'' formed around clouds
when the magnetic field is perpendicular to the cloud motion (Jones et al.
1996, Miniati et al. 1998). It was not clear, however, how dependent those
findings were to the assumed field configuration and cloud properties. To
expand our understanding of this effect, we examine several new cases by varing
the magnetic field orientation angle with respect to the cloud motion (\theta),
the cloud-background density contrast, and the cloud Mach number.
We show that in 2D and with \theta large enough, the magnetic field tension
can become dominant in the dynamics of the motion of high density contrast, low
Mach number clouds. In such cases a significant fraction of cloud kinetic
energy can be transformed into magnetic energy with the magnetic pressure at
the cloud nose exceeding the ram pressure of the impinging flow. We derive a
characteristic timescale for this process of energy ``conversion''. We find
also that unless the cloud motion is highly aligned to the magnetic field,
reconnection through tearing mode instabilities in the cloud wake limit the
formation of a strong flux rope feature following the cloud. Finally we attempt
to interpret some observational properties of the magnetic field in view of our
results.Comment: 24 pages in aaspp4 Latex and 7 figures. Accepted for publication in
The Astrophysical Journa
Sky maps without anisotropies in the cosmic microwave background are a better fit to WMAP's uncalibrated time ordered data than the official sky maps
The purpose of this reanalysis of the WMAP uncalibrated time ordered data
(TOD) was two fold. The first was to reassess the reliability of the detection
of the anisotropies in the official WMAP sky maps of the cosmic microwave
background (CMB). The second was to assess the performance of a proposed
criterion in avoiding systematic error in detecting a signal of interest. The
criterion was implemented by testing the null hypothesis that the uncalibrated
TOD was consistent with no anisotropies when WMAP's hourly calibration
parameters were allowed to vary. It was shown independently for all 20 WMAP
channels that sky maps with no anisotropies were a better fit to the TOD than
those from the official analysis. The recently launched Planck satellite should
help sort out this perplexing result.Comment: 11 pages with 1 figure and 2 tables. Extensively rewritten to explain
the research bette
A Super-Alfvenic Model of Dark Clouds
Supersonic random motions are observed in dark clouds and are traditionally
interpreted as Alfven waves, but the possibility that these motions are
super-Alfvenic has not been ruled out. In this work we report the results of
numerical experiments in two opposite regimes; M_a ~ 1 and M_a >> 1, where M_a
is the initial Alfvenic Mach number --the ratio of the rms velocity to the
Alfven speed. Our results show that models with M_a >> 1 are consistent with
the observed properties of molecular clouds that we have tested --statistics of
extinction measurements, Zeeman splitting measurements of magnetic field
strength, line width versus integrated antenna temperature of molecular
emission line spectra, statistical B-n relation, and scatter in that relation--
while models with M_a ~ 1 have properties that are in conflict with the
observations. We find that both the density and the magnetic field in molecular
clouds may be very intermittent. The statistical distributions of magnetic
field and gas density are related by a power law, with an index that decreases
with time in experiments with decaying turbulence. After about one dynamical
time it stabilizes at B ~ n^{0.4}. Magnetically dominated cores form early in
the evolution, while later on the intermittency in the density field wins out,
and also cores with weak field can be generated, by mass accretion along
magnetic field lines.Comment: 10 figures, 2 tables include
High-resolution imaging of compact high-velocity clouds (II)
We have imaged five compact high-velocity clouds in HI with arcmin angular-
and km/s spectral-resolution using the WSRT. Supplementary total-power data,
which is fully sensitive to both the cool and warm components of HI, is
available for comparison for all the sources, albeit with angular resolutions
that vary from 3' to 36'. The fractional HI flux in compact CNM components
varies from 4% to 16% in our sample. All objects have at least one local peak
in the CNM column which exceeds about 10^19 cm^-2 when observed with arcmin
resolution. It is plausible that a peak column density of 1-2x10^19 cm^-2 is a
prerequisite for the long-term survival of these sources. One object in our
sample, CHVC120-20-443 (Davies' cloud), lies in close projected proximity to
the disk of M31. This object is characterized by exceptionally broad linewidths
in its CNM concentrations (more than 5 times greater than the median value).
These CNM concentrations lie in an arc on the edge of the source facing the M31
disk, while the diffuse HI component of this source has a position offset in
the direction of the disk. All of these attributes suggest that CHVC120-20-443
is in a different evolutionary state than most of the other CHVCs which have
been studied. Similarly broad CNM linewidths have only been detected in one
other object, CHVC111-07-466, which also lies in the Local Group barycenter
direction and has the most extreme radial velocity known. A distinct
possibility for Davies' cloud seems to be physical interaction of some type
with M31. The most likely form of this interaction might be the ram-pressure or
tidal- stripping by either one of M31's visible dwarf companions, M32 or
NGC205, or else by a dark companion with an associated HI condensation.Comment: 12 pages, 11 (low res.) png figs, accepted for pub. in A&
Introduction to Magnetic Monopoles
One of the most basic properties of magnetism is that a magnet always has two
poles, north and south, which cannot be separated into isolated poles, i.e.,
magnetic monopoles. However, there are strong theoretical arguments why
magnetic monopoles should exist. In spite of extensive searches they have not
been found, but they have nevertheless played a central role in our
understanding of physics at the most fundamental level.Comment: 22 pages, 7 figures. To be published in Contemporary Physic
A Very Sensitive 21cm Survey for Galactic High-Velocity HI
Very sensitive HI 21cm observations have been made in 860 directions at dec
>= -43deg in search of weak, Galactic, high-velocity HI emission lines at
moderate and high Galactic latitudes. One-third of the observations were made
toward extragalactic objects. The median 4-sigma detection level is NHI =
8x10^{17} cm^-2 over the 21' telescope beam. High-velocity HI emission is
detected in 37% of the directions; about half of the lines could not have been
seen in previous surveys. The median FWHM of detected lines is 30.3 km/s. High-
velocity HI lines are seen down to the sensitivity limit of the survey implying
that there are likely lines at still lower values of NHI. The weakest lines
have a kinematics and distribution on the sky similar to that of the strong
lines, and thus do not appear to be a new population. Most of the emission
originates from objects which are extended over several degrees; few appear to
be compact sources. At least 75%, and possibly as many as 90%, of the lines are
associated with one of the major high-velocity complexes. The Magellanic Stream
extends at least 10 deg to higher Galactic latitude than previously thought and
is more extended in longitude as well. Although there are many lines with low
column density, their numbers do not increase as rapidly as NHI^-1, so most of
the HI mass in the high-velocity cloud phenomenon likely resides in the more
prominent clouds. The bright HI features may be mere clumps within larger
structures, and not independent objects.Comment: 88 pages includes 22 figures Accepted for Publication in ApJ Suppl.
June 200
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