593 research outputs found
Characteristics of near surface circulation patterns in the Benguela as derived from the ADCP(Acoustic Doppler Current Profiler).
Bibliography: leaves 63-73.This study forms part of one of the Benguela Environment Fisheries Interaction and Training (BENEFIT) program projects, whose main objective is to implement effective and quality ADCP data collection in the Benguela region. The thesis has two main components, firstly it undertook to investigate and assess the data quality, processing methods and software of ADCP data that are used to collect and process the ADCP data available in the Benguela region. An inter-comparison was made between the two different formats for data collection, i.e. raw and RDI proprietary "TRANSECT"processed data (which is more readily available in South Africa), to evaluate their respective accuracy in depicting current flow. The raw data were validated (edited and calibrated) using the CODAS software package before the current vectors could be drawn. TRANSECT -processed data could not be validated therefore vectors were drawn from the un-validated data. Data used here was collected during a monthly monitoring survey on 06-08 August 2001 on board one of the South African research vessel Algoa. The comparison results showed that TRANSECT -processed data includes unedited errors, noise and biases, which are already averaged into the data by the program and that the raw data presented a more realistic current flow. Secondly, the study undertook to apply the ADCP data collected to describe the state of oceanography of the Benguela region during the survey periods. Data from monitoring survey in 06-08 August 2001 was used to describe the southern Benguela while the second data set from a cruise conducted off Namibia in October 2000 was used to describe the oceanography of the central and northern Benguela. Most of the structures observed were in support of the literature and confirming previous studies of the region. In the southern region, the equator ward shelf jet off Cape Peninsula was observed to be forced offshore and entrained in an anticyclonic-like feature, which appeared to be part of a wann Agulhas filament. In northern Nambia, a strong poleward movement of the wann Angolan water was measured
Unveiling the nature and interaction of the intermediate/high-mass YSOs in IRAS 20343+4129
In order to elucidate the nature of the brightest infrared sources associated
with IRAS 20343+4129, IRS1 and IRS3, we observed with the Submillimeter Array
(SMA) the 1.3 mm continuum and CO(2-1) emission of the region. Faint millimeter
dust continuum emission was detected toward IRS1, and we derived an associated
gas mass of ~0.8 Msun. The IRS1 spectral energy distribution agrees with IRS1
being an intermediate-mass Class I source of about 1000 Lsun, whose
circumstellar material is producing the observed large infrared excess. We have
discovered a high-velocity CO bipolar outflow in the east-west direction, which
is clearly associated with IRS1, and the outflow parameters are similar to
those of intermediate-mass young stellar objects. Associated with the blue
large scale CO outflow lobe, detected with single-dish observations, we only
found two elongated low-velocity structures on either side of IRS3. The
large-scale outflow lobe is almost completely resolved out by the SMA. Our
detected low-velocity CO structures are coincident with elongated H2 emission
features. The strongest millimeter continuum condensations in the region are
found on either side of IRS3, where the infrared emission is extremely weak,
and the CO and H2 elongated structures follow the border of the millimeter
continuum emission that is facing IRS3. All these results suggest that the dust
is associated with the walls of an expanding cavity driven by IRS3, estimated
to be a B2 star. Within and beyond the expanding cavity, the millimeter
continuum sources can be sites of future low-mass star formation.Comment: 12 pages, 7 figures, accepted for publication in A&
Resolving the chemical substructure of Orion-KL
The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a
high-mass star-forming environment. For the first time, we complemented 1.3 mm
Submillimeter Array (SMA) interferometric line survey with IRAM 30 m
single-dish observations of the Orion-KL region. Covering a 4 GHz bandwidth in
total, this survey contains over 160 emission lines from 20 species (25
isotopologues), including 11 complex organic molecules (COMs).
At a spatial resolution of 1200 AU, the continuum substructures are resolved.
Extracting the spectra from individual substructures and providing the
intensity-integrated distribution map for each species, we studied the
small-scale chemical variations in this region. Our main results are: (1) We
identify lines from the low-abundance COMs CH3COCH3 and CH3CH2OH, as well as
tentatively detect CH3CHO and long carbon-chains C6H and HC7N. (2) We find that
while most COMs are segregated by type, peaking either towards the hot core
(e.g., N-bearing species) or the compact ridge (e.g., O-bearing species like
HCOOCH3 and CH3OCH3), while the distributions of others do not follow this
segregated structure (e.g., CH3CH2OH, CH3OH, CH3COCH3). (3) We find a second
velocity component of HNCO, SO2, 34SO2, and SO lines, which may be associated
with a strong shock event in the low-velocity outflow. (4) Temperatures and
molecular abundances show large gradients between central condensations and the
outflow regions, illustrating a transition between hot molecular core and
shock-chemistry dominated regimes.
Our observations of spatially resolved chemical variations in Orion-KL
provide the nearest reference source for hot molecular core and outflow
chemistry, which will be an important example for interpreting the chemistry of
more distant HMSFRs.Comment: 51 pages, 17 figures, accepted on 12 March 2015 Dashed lines in
Figure 10 of the published paper was missin
A line confusion-limited millimeter survey of Orion KL. III. Sulfur oxide species
We present a study of the sulfur-bearing species detected in a line
confusion-limited survey towards Orion KL performed with the IRAM 30m telescope
in the range 80-281 GHz. The study is part of an analysis of the line survey
divided into families of molecules. Our aim is to derive accurate physical
conditions and molecular abundances in the different components of Orion KL
from observed SO and SO2 lines. First we assumed LTE conditions obtain
rotational temperatures. We then used a radiative transfer model, assuming
either LVG or LTE excitation to derive column densities of these molecules in
the different components of Orion KL. We have detected 68 lines of SO, 34SO,
33SO, and S18O and 653 lines of SO2, 34SO2, 33SO2, SO18O and SO2 v2=1. We
provide column densities for all of them and also upper limits for the column
densities of S17O, 36SO, 34S18O, SO17O and 34SO2 v2=1 and for several
undetected sulfur-bearing species. In addition, we present 2'x2' maps around
Orion IRc2 of SO2 transitions with energies from 19 to 131 K and also maps with
four transitions of SO, 34SO and 34SO2. We observe an elongation of the gas
along the NE-SW direction. An unexpected emission peak appears at 20.5 km/s in
most lines of SO and SO2. A study of the spatial distribution of this emission
feature shows that it is a new component ~5" in diameter, which lies ~4" west
of IRc2. We suggest the emission from this feature is related to shocks
associated to the BN object. The highest column densities for SO and SO2 are
found in the high-velocity plateau (a region dominated by shocks) and in the
hot core. These values are up to three orders of magnitude higher than the
results for the ridge components. We also find high column densities for their
isotopologues in both components. Therefore, we conclude that SO and SO2 are
good tracers, not only of regions affected by shocks, but also of regions with
warm dense gas.Comment: Paper (ref AA/2013/21285) accepted for publication by A&A. 52 Pages,
26 figures, 13 table
Extended warm gas in Orion KL as probed by methyl cyanide
In order to study the temperature distribution of the extended gas within the
Orion Kleinmann-Low nebula, we have mapped the emission by methyl cyanide
(CH3CN) in its J=6_K-5_K, J=12_K-11_K, J=13_K-12_K, and J=14_K-13_K transitions
at an average angular resolution of ~10 arcsec (22 arcsec for the 6_K-5_K
lines), as part of a new 2D line survey of this region using the IRAM 30m
telescope. These fully sampled maps show extended emission from warm gas to the
northeast of IRc2 and the distinct kinematic signatures of the hot core and
compact ridge source components. We have constructed population diagrams for
the four sets of K-ladder emission lines at each position in the maps and have
derived rotational excitation temperatures and total beam-averaged column
densities from the fitted slopes. In addition, we have fitted LVG model spectra
to the observations to determine best-fit physical parameters at each map
position, yielding the distribution of kinetic temperatures across the region.
The resulting temperature maps reveal a region of hot (T > 350 K) material
surrounding the northeastern edge of the hot core, whereas the column density
distribution is more uniform and peaks near the position of IRc2. We attribute
this region of hot gas to shock heating caused by the impact of outflowing
material from active star formation in the region, as indicated by the presence
of broad CH3CN lines. This scenario is consistent with predictions from C-shock
chemical models that suggest that gas-phase methyl cyanide survives in the
post-shock gas and can be somewhat enhanced due to sputtering of grain mantles
in the passing shock front.Comment: 24 pages, 20 figures, accepted for publication in A&
Phytopharmacotherapeutic and Antimicrobial Attributes of Bitter Apple (Citrullus colocynthis) - A Review
Emergence of drug-resistant microorganisms over the past few decades has resulted in the search for bioactive compounds potent against these microorganisms. Phytochemicals derived from plants have shown positive curative properties and can be extracted from any part of the plant such as the roots, stem or flower. Bitter apple (Citrullus colocynthis) has been used traditionally for the treatment of infectious diseases and this has stimulated pharmacological interest in the active ingredients responsible for its medicinal properties. The plant also possesses several biological and pharmacological activities including anti-inflammatory, antidiabetic, antimicrobial, anticancer, and antioxidant. This review discussed the phytochemicals present in C. colocynthis, their mode of action and their antimicrobial attributes
Phytopharmacotherapeutic and Antimicrobial Attributes of Bitter Apple (Citrullus colocynthis) - A Review
Emergence of drug-resistant microorganisms over the past few decades has resulted in the search for bioactive compounds potent against these microorganisms. Phytochemicals derived from plants have shown positive curative properties and can be extracted from any part of the plant such as the roots, stem or flower. Bitter apple (Citrullus colocynthis) has been used traditionally for the treatment of infectious diseases and this has stimulated pharmacological interest in the active ingredients responsible for its medicinal properties. The plant also possesses several biological and pharmacological activities including anti-inflammatory, antidiabetic, antimicrobial, anticancer, and antioxidant. This review discussed the phytochemicals present in C. colocynthis, their mode of action and their antimicrobial attributes
Scientific Advancement in Contemporary Society: The Interface between Technology, Science and Law
This article is premised on the relation of technology and applied sciences with law. The three subjects are not only interwoven but cannot be protected and regulated without the viable use of law. The unprecedented advancement ofscientific innovations has far-reaching implication in virtually all ramifications of human endeavour. Technology is an invention created using science, which needs to be sustained by prudent management and law. The research goal is to narrow down a middle ground where all these independent fields can meet and share a symbiotic relationship without stifling each other. The research seeks to ascertain the knowledge and perception of selected university students of Nigeria and India, about Science, Law and Technology. The authors adopted the doctrinal and empirical research methodology coupled with the use of cases and legislations as source of information. The research revealed that majority of the participants has knowledge about the co-existence and impact of Science, Technology and Law in the society. However, the attitude and perception of the participants constitute a fundamental influence on the degree to which technological orientations occur during learning process. Also, 85% of 200 participants agreed that there is need for frequent education and legislation as science and technology evolves in the society. Hence, this article recommends the implementation and frequent modifications of law to continually protect, encourage and ensure the societal sustainability of ethical standards
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