9,571 research outputs found
Inhalation therapy during acute asthma : the role of a combined steroid and beta-stimulant preparation
CITATION: Joubert, J. R., Burger, G. & Shephard, E. 1985. Inhalation therapy during acute asthma : the role of a combined steroid and beta-stimulant preparation. South African Medical Journal, 68:381-384.The original publication is available at http://www.samj.org.zaA compound consisting of a ÎČ-stimulant, salbutamol (100 ÎŒg/puff), and a steroid, beclomethasone diproprionate (50 ÎŒg/puff), was studied to test the hypothesis that the corticosteroid could enhance the bronchodilator proporties of the ÎČ-stimulant during chronic asthma and simulated acute attacks (antigen challenge). Conventional doses (200 ÎŒg and 100 ÎŒg of salbutamol and beclomethasone respectively) were compared using a schedule which included a second administration 1 hour later. The results obtained on the baseline bronchial responsiveness of chronic asthmatics and during the delayed asthmatic response (simulated acute asthma) were similar. The compound was as effective as salbutamol alone but not more so. A significantly greater bronchodilator response was recorded in all patients after the second administration of both the compound and salbutamol alone. The practical advantages of having one rather than two inhalers are evident, but the appropriate application of this compound agent, probably in a prophylactic role, must be defined.Publisherâs versio
The effect of fruit maturity and storage duration on friction discolouration of Packham's Triumph and Doyenne du Comice pears
The original publication is available at http://www.actahort.org/books/671/671_53.htmFriction discolouration (FD) is causing the South African pear industry
multi-million rand losses due to blemished fruit being rejected for the export market
and being sold locally. The occurrence of FD was studied over two seasons using
âPackhamâs Triumphâ and âDoyenne du Comiceâ (Pyrus communis) fruit. The
influence of fruit maturity and storage duration were investigated by harvesting
over three maturities and storing fruit for up to three months. FD was induced using
a modified laboratory shaker that was shown to closely mimic pack line damage.
Polyphenol oxidase (PPO) activity and total phenolics (TP) content were also
evaluated. âDoyenne du Comiceâ was more prone to FD than âPackhamâs Triumphâ.
Harvest maturity significantly influenced FD susceptibility, with the middle picking
maturity generally giving higher FD ratings. Increasing storage duration generally
increased FD ratings, although not consistently. PPO activity was not influenced by
harvest maturity, but was influenced by storage duration. In âPackhamâs Triumphâ,
the TP content was not affected by harvest maturity or storage duration, whereas
both these factors significantly influenced TP content in âDoyenne du Comiceâ.
Susceptibility to development of FD symptoms is not easily linked to either PPO
activity or TP content, and seasonal differences in susceptibility make prediction of
possible levels of FD very difficult
Factors affecting shrivelling and friction discolouration of pears (Pyrus communis L. )
Thesis (MScAgric)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Shrivelling and friction discolouration (FD), as postharvest disorders, negatively influence
the marketability and potential shelf life of pears. By investigating the contributing factors in
each of the disorders, the potential involvement of handling and storage variables were
determined. This allowed for a better understanding of the responsible factors that create
susceptible environments for these disorders to occur.
From the moment that pears are harvested they lose weight by means of transpiration and, to
a lesser extent, respiration. When excessive losses are experienced, the fruit will appear
shrivelled and the marketability and shelf life are negatively influenced. By minimizing the
rates of weight loss, the occurrence of shrivelling among pears during the postharvest
handling can be lessened. The periods that proved to be most conducive to shrivelling (during
a simulated postharvest handling duration) were where temperatures above 0 °C were
experienced. These short periods proved more perilous for shrivelling than lengthy storage
durations at low temperatures. This influenced the transpiration rate in such a way that the
driving force accelerated the rate of weight loss in all the cultivars that were studied.
Removing field heat from fresh produce and maintaining the cold chain reduces the driving
force behind the transpiration of the pears.
In all the cultivars studied, âPackhamâs Triumphâ, âBeurrĂš Boscâ and âForelleâ, smaller and
less mature fruit were more inclined to appear shrivelled. The surface area to volume ratio is
fundamental in determining the rate of weight loss. This was most evident in âBeurrĂš Boscâ.
Although no reproducible results could be obtained from the morphological studies, literature
has attributed this phenomenon to the composition and quantity of the cuticle layer.
Reduction of weight loss was obtained by sealing of the fruit stem. This obstructed water
movement from the fruit through the xylem conducting tissue to the surrounding atmosphere.
Not only did the stem appear greener and fresher, but less weight loss and subsequent shrivel
was noticeable in the treated fruit. This effect was most evident in âPackhamâs Triumphâ and
âBeurrĂš Boscâ, but not in âForelleâ. âForelleâ typically has a very short, thin stem in
comparison to the other two cultivars.All the cultivars showed visual shrivel symptoms after 11 days at 18 °C. Rate of weight loss
was the lowest in âPackhamâs Triumphâ, but due to its prominent dimensions, it appeared
shrivelled before any of the other cultivars. âBeurrĂš Boscâ lost weight at the highest rate
(0.42%.day-1).
As fruit injury, in the presence of oxygen, is inevitable, the oxidative enzymatic browning of
pears will always be troublesome. This defensive mechanism partially prevents the infection
of the fruit where epidermal cells are injured. To minimize FD, impact and frictional forces
need to be lower during both harvesting and handling practices.
A laboratory scale method was developed through which reproduceable treatments could be
performed, thereby subjecting the fruit to industry related friction, rather than impact, injury.
By assessing the discolouration in terms of both extent and intensity, the influence of
variables could be determined on both âPackhamâs Triumphâ and âDoyenne du Comiceâ
pears. As also found in practice, âDoyenne du Comiceâ proved to be far more susceptible to
FD than âPackhamâs Triumphâ, although the activity of the enzyme, polyphenol oxidase
(PPO) was found to be higher in the latter.
Although no significant difference was found between the FD encountered at fruit
temperature of 3 °C and 15 °C, discolouration was greater at the higher temperature. This
might be attributed to a greater degree of water loss, lower cell turgidity or higher enzyme
activity. Thus, fruit taken from storage and sorted directly thereafter will exhibit less FD. The
contribution of condensation forming on the fruit, acting as lubrication, cannot be ignored.
Such fruit, with high turgor pressure, might again be more susceptible to bruising which will
only be revealed well after the injury. Since enzymes, which include PPO, catalyse
biochemical reactions, the availability of sufficient substrate most probably regulates the
extent of this biochemical discolouration.
Harvesting at optimum maturity and preventing any unnecessary friction will most definitely
reduce the occurrence of FD. The ultimate challenge remains to optimize sorting and packing
conditions without compromising on fruit quality.AFRIKAANSE OPSOMMING: Verrimpeling en friksie verbruining (FV), as na-oes defekte, het ân negatiewe invloed op die
bemarkbaarheid en potensiële raklewe van pere. Hierdie studie het die bydraende faktore vir
elkeen van die defekte ondersoek. Daar is gepoog om die effek van verskillende hanteringsen
opbergingsmetodes op bogenoemde defekte te bepaal. ân Beter begrip is verkry van die
oorsaaklike faktore wat bydra tot die ontstaan van die betrokke defekte.
Direk na die oes van pere, begin die vrug gewig verloor as gevolg van veral transpirasie.
Oormatige verliese sal lei tot ân vrug wat verrimpeld voorkom, met ân negatiewe invloed op
die bemarkbaarheid en raklewe daarvan. Die voorkoms van die verrimpeling van pere tydens
die na-oes hantering van die vrugte, kan verminder word deur vermindering van die tempo
van gewigsverlies. Die periodes waartydens die verrimpeling veral voorgekom het, (soos
gevind in ân gesimuleerde na-oes hanteringsmodel) was wanneer temperature bo 0 °C
ondervind is. Sulke kort periodes was meer geneig om aanleiding te gee tot verrimpeling as
die verlengde periodes van opberging by lae temperature. Sulke periodes van hoër
temperature het gelei tot versnelde transpirasie en ân versnelde tempo van gewigsverlies in al
die kultivars wat ondersoek is. Die transpirasietempo van pere kan verlaag word deur die
verwydering van veld-hitte en deur die streng behoud van die koue-ketting.
In al die kultivars wat ondersoek is, âPackhamâs Triumphâ, âBeurrĂš Boscâ en âForelleâ, is
gevind dat die kleiner en minder volwasse vrugte meer geneig was tot verrimpeling. Die
oppervlak area tot volume verhouding is krities in die bepaling van die tempo van
gewigsverlies. Hierdie bevinding was die prominentste in âBeurrĂš Boscâ. Alhoewel geen
beduidende resultate verkry kon word van die morfologiese studies nie, is daar verskeie
verwysings in die literatuur wat hierdie verskynsel toeskryf aan die samestelling en
hoeveelheid van die kutikula laag.
Vermindering van gewigsverlies is verkry deur verseëling van die vrugtestingel. Hierdie
tegniek het gelei tot ân blokkering van die watervloei van die vrug na die omgewing deur die
xileem weefsel. Verseëling van die stingel het dit groener en varser laat voorkom, en het ook
ân merkbare vermindering in gewigsverlies en die daaropvolgende verrimpeling tot gevolg
gehad. Die effek van stingel-verseĂ«ling was die prominentste in âPackhamâs Triumphâ enâBeurrĂš Boscâ. Dit was minder duidelik in âForelleâ wat tipies gekenmerk word deur ân baie
korter, dun stingel in vergelyking met die ander twee kultivars.
Al die kultivars het makroskopiese verrimpeling getoon na ân opbergingperiode van 11 dae
by 18 °C. Die tempo van gewigsverlies was die laagste in âPackhamâs Triumphâ alhoewel dit
eerste verrimpeld voorgekom het. Dit kan toegeskryf word aan die spesifieke afmetings van
hierdie betrokke kultivar. âBeurrĂš Boscâ het vinnigste gewig verloor (0.42%.dag-1).
Aangesien die besering van vrugte, in die aanwesigheid van suurstof, onvermydelik is, sal
oksidatiewe, ensiematiese verbruining van pere altyd problematies wees. Hierdie
verdedigingsmeganisme voorkom tot ân mate die infeksie van die vrug wanneer epidermale
selle beskadig word. FV kan beperk word deur die vrugte tydens oes en hanteringsprosedures
so min as moontlik bloot te stel aan impak en friksie kragte.
ân Laboratorium-model is ontwikkel ter nabootsing van die omstandighede in die industrie.
Die vrugte is aan friksie, eerder as impak, onderwerp, soos ondervind in die industrie. Die
omvang asook die intensiteit van die verbruining is gemeet in beide âPackhamâs Triumphâ en
âDoyenne du Comiceâ pere. Op hierdie wyse kon die invloed van die onderskeie
veranderlikes in elke kultivar bepaal word. Alhoewel die ensiematiese aktiwiteit van die
polifenol oksidase ensiem (PFO) die hoogste in âPackhamâs Triumphâ was, is gevind dat
âDoyenne du Comiceâ veel meer geneig was tot FV as âPackhamâs Triumphâ. Hierdie
bevinding bevestig die verskynsel soos in die praktyk gevind.
Alhoewel geen betekenisvolle verskil gevind is tussen FV by vrug temperatuur van 3 °C en
15 °C nie, was daar meer verbruining by die hoër temperatuur. Hierdie verskynsel kan
toegeskryf word aan ân groter mate van waterverlies, laer sel turgiditeit en hoĂ«r ensiem
aktiwiteit. Dus sal vrugte wat direk na opberging gesorteer word, minder FV toon. Die bydrae
van die kondensasie wat op die vrug vorm, en as ân smeermiddel dien, kan nie geĂŻgnoreer
word nie. Sulke vrugte met hoër turgiditeit, mag egter meer vatbaar wees vir kneusing, wat
egter eers ân geruime tyd na die kneusing tevoorverskyn mag kom. Aangesien ensieme, wat
PFO insluit, as katalis dien in biochemiese reaksies, sal die beskikbaarheid van voldoende
substraat, na alle waarskynlikheid die omvang van die biochemiese verkleuring reguleer.Die oes van pere tydens optimum volwassenheid, en die voorkoming van onnodige friksie sal
definitief die voorkoms van FV verminder. Die uitdaging is steeds om sortering- en
verpakkingstegnieke verder te verfyn sonder om ân negatiewe invloed op vrugtekwaliteit te
hĂȘ
Pattern Forming Dynamical Instabilities of Bose-Einstein Condensates: A Short Review
In this short topical review, we revisit a number of works on the
pattern-forming dynamical instabilities of Bose-Einstein condensates in one-
and two-dimensional settings. In particular, we illustrate the trapping
conditions that allow the reduction of the three-dimensional, mean field
description of the condensates (through the Gross-Pitaevskii equation) to such
lower dimensional settings, as well as to lattice settings. We then go on to
study the modulational instability in one dimension and the snaking/transverse
instability in two dimensions as typical examples of long-wavelength
perturbations that can destabilize the condensates and lead to the formation of
patterns of coherent structures in them. Trains of solitons in one-dimension
and vortex arrays in two-dimensions are prototypical examples of the resulting
nonlinear waveforms, upon which we briefly touch at the end of this review.Comment: 28 pages, 9 figures, publishe
Das bandkeramische GrĂ€berfeld vom âViesenhĂ€user Hofâ bei Stuttgart-MĂŒhlhausen: Neue Untersuchungsergebnisse zum Migrationsverhalten im frĂŒhen Neolithikum
Einleitung: Gegenstand des vorliegenden Beitrags ist die Rolle der MobilitĂ€t im Leben der frĂŒhen Ackerbauern
und ViehzĂŒchter in SĂŒdwestdeutschland. Seit Jahrzehnten werden wissenschaftliche Auseinandersetzungen
ĂŒber die Bedeutung von Wanderungsbewegungen bei der Ausbreitung der produzierenden Wirtschaftsweise in Europa zwischen 7000 und 4000 v. Chr. gefĂŒhrt. Dabei gehen traditionelle Ăberlegungen davon aus, dass die ersten Ackerbauern in Mitteleuropa Zuwanderer waren, die ein
âPaketâ neuer Errungenschaften und Ideen mit sich fĂŒhrten, das u. a. Haustiere, dauerhafte Siedlungen, Keramik und den Ackerbau enthielt.1 Neuere Untersuchungen und Ăberlegungen gestehen dagegen der einheimischen Bevölkerung eine maĂgebliche Bedeutung bei der Ăbernahme der neolithischen
Wirtschaftsweise zu.2 Die MobilitĂ€t des Menschen ist aber nicht nur fĂŒr die ErklĂ€rung des Neolithisierungsprozesses, sondern auch fĂŒr das VerstĂ€ndnis der Lebens- und Wirtschaftsweise der Menschen in den mittleren und spĂ€teren Abschnitten der Linearbandkeramik von höchstem
Interesse.
Die bisherige Forschungsdiskussion basierte in diesem Zusammenhang ĂŒberwiegend auf indirekten Argumenten, d. h. auf Artefakten, die auch getauscht oder gestohlen worden sein konnten, aber nicht auf den Ăberresten der potenziellen Zuwanderer selbst, die in Form von Knochen und ZĂ€hnen erhalten sind.
Die vorliegende Studie bedient sich der direkten Analyse menschlicher Skelettreste der bandkeramischen GrĂ€ber vom âViesenhĂ€user Hofâ, Stuttgart-MĂŒhlhausen, mittels anthropologischer Untersuchungen und Strontiumisotopenanalysen. Nachfolgend werden der Fundplatz in seinem archĂ€ologischen Kontext der Linearbandkeramik sowie die Ergebnisse der anthropologischen Untersuchungen
und Strontiumisotopenanalysen vorgestellt und dann die Rolle der MobilitĂ€t im Leben der frĂŒhen Ackerbauern und ViehzĂŒchter sowie fĂŒr die Ausbreitung der neolithischen Wirtschaftsweise diskutiert.
Stuttgart-MĂŒhlhausen ist eines der Ă€ltesten bandkeramischen GrĂ€berfelder, die bislang fĂŒr derartige Untersuchungen zur VerfĂŒgung standen
Serogrouping and sulphonamide sensitivity of Neisseria meningitidis isolates from the south-western Cape
CITATION: Donald, P.R. et al. 1989. Serogrouping and sulphonamide sensitivity of Neisseria meningitidis isolates from the south-western Cape. S Afr Med J, 76:453.The original publication is available at http://www.samj.org.zaNeisseria meningitidis infections were first reported
from the south-western Cape Province in 1883. Since then, against a backdrop of a relatively low incidence with winter exacerbation, epidemic periods have occurred at 10 - IS-year intervals. During the 1978 - 1979 epidemic more than 95% of
isolates at Tygerberg Hospital were of serogroup B and only 5% were resistant to sulphonamides. Seventy-seven per cent of patients notified as suffering from meningococcal infections were
under 4 years of age.3 In this report we briefly describe the pattern of serogrouping and sulphonamide resistance of N. meningitidis for the period 1980 - 1987.Publisherâs versio
Fixed points and amenability in non-positive curvature
Consider a proper cocompact CAT(0) space X. We give a complete algebraic
characterisation of amenable groups of isometries of X. For amenable discrete
subgroups, an even narrower description is derived, implying Q-linearity in the
torsion-free case.
We establish Levi decompositions for stabilisers of points at infinity of X,
generalising the case of linear algebraic groups to Is(X). A geometric
counterpart of this sheds light on the refined bordification of X (\`a la
Karpelevich) and leads to a converse to the Adams-Ballmann theorem. It is
further deduced that unimodular cocompact groups cannot fix any point at
infinity except in the Euclidean factor; this fact is needed for the study of
CAT(0) lattices.
Various fixed point results are derived as illustrations.Comment: 33 page
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