1,658 research outputs found
The long-term effect of radio sources on the ICM
We have performed 3D hydrodynamical simulations of FR-II radio sources in
beta-profile cooling-flow clusters. The effects of cooling of the cluster gas
were incorporated into a modified version of the ZEUS-MP code. The simulations
followed not only the active phase of the radio source, but also the long term
behaviour for up to 2 Gyr after the jets of the radio source were switched off.
We find as expected that the radio source has a significant effect on the
cooling flow while it is active, however we also find that the effects of the
radio source on the cluster are long-lived. A buoyancy driven convective flow
is established as the remnants of the radio source rise through the cluster
dragging material from the cluster core. Although the central Mpc of the
cluster reverts to having a cooling flow, this asymmetric convective flow is
able to remove the cool gas accumulating at the cluster core and indeed there
is a net outflow persisting for timescales of about an order of magnitude
longer than the time for which the source is active or longer. The convective
flow may also provide a mechanism to enhance the metallicity of the cluster gas
at large cluster radii.Comment: 7 pages, 13 figures; minor addition
The assimilation of church members into the local faith community
The assimilation of church members into the local faith community
In this article, the assimilation of members into the faith community is discussed. When a church
has found its identity in being a ‘missional faith community’, the outcome is growth. Growth
cannot take place if the church is unable to assimilate new members into church life. People are
only assimilated into the faith community when they are interconnected through relationships,
and experience a fundamental sense of belonging. This article discusses aspects of membership
assimilation, namely intention, active participation, and culture. A model is proposed whereby
leaders can evaluate the functional worth of people for the faith community at any level of
assimilation. This model can also assist leaders in creating processes to assimilate members more
effectively.Hierdie artikel handel oor die problematiek van die assimilasie (oftewel opneming) van nuwe lidmate
in die plaaslike geloofsgemeenskap. Assimilasie verwys na die geloofsgemeenskap se vermoë om nuwe
lidmate by die gemeenskap te integreer, en hulle in liefdevolle verhoudings aan mekaar te verbind. Dit
dui dus op ‘n verskeidenheid formele en informele prosesse wat mense in staat stel om deel te word
van die geloofsgemeenskap (Dudley 1998:114). Wanneer ‘n geloofsgemeenskap ‘n missionale identiteit
ontdek, is groei die uitkoms (Basson 2006:37). Groei kan egter nie doeltreffend plaasvind as daar nie ‘n
effektiewe assimilasieproses in die geloofsgemeenskap bestaan nie (Ford 2007:49). Hierdie artikel wys
op verskillende noodsaaklike aspekte ten opsigte van die assimilasie van nuwe lidmate, en stel ‘n model
voor wat die grondslag vir toekomstige assimilasieprosesse in geloofsgemeenskappe kan uitmaak.http://www.hts.org.zahb201
A spatial decision support system for groundwater abstraction impact assessment and licensing
Thesis (MSc)--Stellenbosch University, 2005.ENGLISH ABSTRACT: Water resources in South Africa are limited and groundwater plays an important role in
supporting basic human needs, sustaining ecosystems and enabling industrial and agricultural
development. Sound management practices are necessary to ensure sustainable development
of water resources. All groundwater usage must be licensed in compliance with the National
Water Act of 1998. A Spatial Decision Support System (SDSS) can be used to assist in the
groundwater usage licensing process of the Department of Water Affairs and Forestry
(DWAF).
The main aim of this study was to develop a SDSS, named Groundwater Abstraction &
Licence Evaluation Tool (GALET), that could assist in the process of allocating water use
licences and determining the local impact of abstraction, based on existing theory and data.
The development was done within ArcView 3.2 using the scripting language Avenue. The
Sandveld, an arid stretch of land along the west coast of South Africa that is heavily impacted
by groundwater abstraction, was the chosen study area. The data collected for this study
included existing borehole, recharge, rainfall and geological information.
GALET proved to be capable of calculating essential information needed to evaluate
groundwater abstraction, which included drawdown in the water table, zone of influence and
the possible effects on features such as rivers and wetlands. Targeted potential users regarded
GALET as a useful tool in the process of licensing and groundwater abstraction impact
assessment and plans are under way to implement GALET or a derivative thereof at the
DWAF regional offices.AFRIKAANSE OPSOMMING: Waterhulpbronne in Suid-Afrika is beperk en grondwater speel 'n belangrike rol in die
ondersteuning van basiese menslike behoeftes, volhouding van ekosisteme asook industriële
en landbou-ontwikkeling. Betroubare bestuurspraktyke is noodsaaklik om die volhoubare
ontwikkeling van waterhulpbronne te verseker. Alle grondwatergebruik moet volgens die
Nasionale Waterwet van 1998 gelisensieer word. 'n Ruimtelike Besluitnemings
Ondersteuning Stelsel (RBOS) kan as 'n hulpmiddel gebruik word in die lisensiëringsproses
van die Departement van Waterwese en Bosbou.
Die hoofdoel van hierdie studie was om 'n RBOS, genoem Groundwater Abstraction &
Licence Evaluation Tool (GALET), te ontwikkel wat as hulpmiddel gebruik kan word in die
allokeringsproses van watergebruiklisensies en die bepaling van die impak van
grondwateronttrekking op die omgewing, gebaseer op bestaande teorie en data. Die
ontwikkeling is in ArcView 3.2 met die programmeringstaal Avenue gedoen. Die Sandveld,
'n ariede streek aan die weskus van Suid-Afrika wat onderhewig is aan grootskaalse
grondwateronttrekking, is gekies as die studie area. Die data wat vir hierdie studie ingesamel
is sluit bestaande boorgat, grondwateraanvulling, reënval en geologiese inligting in.
GALET was in staat om belangrike inligting aangaande die evaluering van
grondwateronttrekking te bereken, o.a. die daling van die grondwatervlak, die impaksone en
die moontlike effekte op landvorms soos riviere en vleilande. Die teikengroep potensiële
gebruikers het GALET as 'n nuttige hulpmiddel in die proses van lisensiëring en
grondwateronttrekking impakbepaling beskou en planne is onderweg om dit of 'n aangepaste
program by die streekskantore van die Departement van Waterwese en Bosbou te
implementeer
Trichodina colisae (Ciliophora: Trichodinidae): new parasite records for two freshwater fish species farmed in Brazil
AGN effect on cooling flow dynamics
We analyzed the feedback of AGN jets on cooling flow clusters using
three-dimensional AMR hydrodynamic simulations. We studied the interaction of
the jet with the intracluster medium and creation of low X-ray emission
cavities (Bubbles) in cluster plasma. The distribution of energy input by the
jet into the system was quantified in its different forms, i.e. internal,
kinetic and potential. We find that the energy associated with the bubbles, (pV
+ gamma pV/(gamma-1)), accounts for less than 10 percent of the jet energy.Comment: "Accepted for publication in Astrophysics & Space Science
Association of radial longitudinal deficiency and thumb hypoplasia: An update using the CoULD registry
BACKGROUND: Deficiency of the radial aspect of the forearm and hand is the most common congenital longitudinal deficiency of the upper limb. Radial longitudinal deficiency is associated with several named syndromes. The purpose of the present study was to explore patterns of radial longitudinal deficiency and thumb hypoplasia in syndromes and to examine the severity of these differences across various syndromes.
METHODS: Data were collected from the Congenital Upper Limb Differences (CoULD) registry. Congenital differences are classified in the registry with use of the Oberg-Manske-Tonkin (OMT) classification system. Diagnosis of a syndrome by a physician as noted in the CoULD registry was recorded. Thumb deficiency and radial deficiency were classified according to the modified versions of the Blauth criteria and the Bayne and Klug criteria, respectively.
RESULTS: We identified 259 patients with 383 affected limbs with radial deficiency. Eighty-three of these patients had a diagnosed syndrome. The severity of radial deficiency was correlated with the severity of thumb deficiency. The Kendall tau coefficient indicated significant correlation between radial severity and thumb severity (tau = 0.49 [95% confidence interval = 0.40 to 0.57]; p \u3c 0.05). Subjects with a syndrome were twice as likely to have bilateral deficiency and 2.5 times more likely to have both radial and thumb deficiency compared with subjects without a syndrome. Subjects with VACTERL syndrome (vertebral defects, anal atresia, cardiac anomalies, tracheoesophageal fistula, renal anomalies, and limb defects) had patterns of thumb and radial deficiency similar to the general cohort, whereas subjects with Holt-Oram syndrome, TAR (thrombocytopenia absent radius) syndrome, and Fanconi anemia demonstrated varied presentations of thumb and radial deficiency.
CONCLUSIONS: The present study investigated the characteristics of patients with radial longitudinal deficiency and thumb hypoplasia. Our results support the findings of previous research correlating the severity of radial deficiency with the severity of thumb deficiency. Furthermore, we identified characteristic features of patients with radial longitudinal deficiency and associated syndromes
The association between environmental exposures during childhood and the subsequent development of Crohn's Disease: A score analysis approach
Background Environmental factors during childhood are thought to play a role in the aetiology of Crohn's Disease (CD). In South Africa, recently published work based on an investigation of 14 childhood environmental exposures during 3 age intervals (0-5, 6-10 and 11-18 years) has provided insight into the role of timing of exposure in the future development of CD. The 'overlapping' contribution of the investigated variables however, remains unclear. The aim of this study was to perform a post hoc analysis using this data and investigate the extent to which each variable contributes to the subsequent development of CD relative to each aforementioned age interval, based on a score analysis approach. Methods Three methods were used for the score analysis. Two methods employed the subgrouping of one or more (similar) variables (methods A and B), with each subgroup assigned a score value weighting equal to one. For comparison, the third approach (method 0) involved no grouping of the 14 variables. Thus, each variable held a score value of one. Results Results of the score analysis (Method 0) for the environmental exposures during 3 age intervals (0-5, 6-10 and 11-18 years) revealed no significant difference between the case and control groups. By contrast, results from Method A and Method B revealed a significant difference during all 3 age intervals between the case and control groups, with cases having significantly lower exposure scores (approximately 30% and 40% lower, respectively). Conclusion Results from the score analysis provide insight into the 'compound' effects from multiple environmental exposures in the aetiology of CD.IS
Uniform regularity for the Navier-Stokes equation with Navier boundary condition
We prove that there exists an interval of time which is uniform in the
vanishing viscosity limit and for which the Navier-Stokes equation with Navier
boundary condition has a strong solution. This solution is uniformly bounded in
a conormal Sobolev space and has only one normal derivative bounded in
. This allows to get the vanishing viscosity limit to the
incompressible Euler system from a strong compactness argument
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