COX-derived prostanoid pathways in gastrointestinal cancer development and progression : novel targets for prevention and intervention

Arachidonic acid metabolism through cyclooxygenase (COX) pathways leads to the generation of biologically active eicosanoids. Eicosanoid expression levels vary during development and progression of gastrointestinal (GI) malignancies. COX-2 is the major COX-isoform responsible for G.I. cancer development/progression. COX-2 expression increases during progression from a normal to cancerous state. Evidence from observational studies has demonstrated that chronic NSAID use reduces the risk of cancer development, while both incidence and risk of death due to G.I. cancers were significantly reduced by daily aspirin intake. A number of randomized controlled trials (APC trial, Prevention of Sporadic Adenomatous Polyps trial, APPROVe trial) have also shown a significant protective effect in patients receiving selective COX-2 inhibitors. However, chronic use of selective COX-2 inhibitors at high doses was associated with increased cardiovascular risk, while NSAIDs have also been associated with increased risk. More recently, downstream effectors of COX-signaling have been investigated in cancer development/progression. PGE 2, which binds to both EP and PPAR receptors, is the major prostanoid implicated in the carcinogenesis of G.I. cancers. The role of TXA 2 in G.I. cancers has also been examined, although further studies are required to uncover its role in carcinogenesis. Other prostanoids investigated include PGD 2 and its metabolite 15d-PGJ2, PGF 1α and PGI 2. Targeting these prostanoids in G.I. cancers has the promise of avoiding cardiovascular toxicity associated with chronic selective COX-2 inhibition, while maintaining anti-tumor reactivity.A progressive sequence from normal to pre-malignant to a malignant state has been identified in G.I. cancers. In this review, we will discuss the role of the COX-derived prostanoids in G.I. cancer development and progression. Targeting these downstream prostanoids for chemoprevention and/or treatment of G.I. cancers will also be discussed. Finally, we will highlight the latest pre-clinical technologies as well as avenues for future investigation in this highly topical research field. © 2011 Elsevier B.V.

Alcohol consumption in young adults : the role of multisensory imagery

Little is known about the subjective experience of alcohol desire and craving in young people. Descriptions of alcohol urges continue to be extensively used in the everyday lexicon of young, non-dependent drinkers. Elaborated Intrusion (EI) Theory contends that imagery is central to craving and desires, and predicts that alcohol-related imagery will be associated with greater frequency and amount of drinking. This study involved 1,535 age stratified 18–25 year olds who completed an alcohol–related survey that included the Imagery scale of the Alcohol Craving Experience (ACE) questionnaire. Imagery items predicted 12-16% of the variance in concurrent alcohol consumption. Higher total Imagery subscale scores were linearly associated with greater drinking frequency and lower self-efficacy for moderate drinking. Interference with alcohol imagery may have promise as a preventive or early intervention target in young people.

All-environment visual place recognition with SMART

This paper presents Sequence Matching Across Route Traversals (SMART); a generally applicable sequence-based place recognition algorithm. SMART provides invariance to changes in illumination and vehicle speed while also providing moderate pose invariance and robustness to environmental aliasing. We evaluate SMART on vehicles travelling at highly variable speeds in two challenging environments; firstly, on an all-terrain vehicle in an off-road, forest track and secondly, using a passenger car traversing an urban environment across day and night. We provide comparative results to the current state-of-the-art SeqSLAM algorithm and investigate the effects of altering SMART’s image matching parameters. Additionally, we conduct an extensive study of the relationship between image sequence length and SMART’s matching performance. Our results show viable place recognition performance in both environments with short 10-metre sequences, and up to 96% recall at 100% precision across extreme day-night cycles when longer image sequences are used.

Cultivation

The interest in potentially economically valuable plants (for food, timber, dyes, fabric, and drugs) was part of the concerted effort given by colonial governments towards providing botanic gardens in new colonies. While convicts and guards laboured in Brisbane Town from 1825 until 1849, botanists such as Alan Cunningham were discovering the delights of native plants in their numerous excursions. Their observations and collections of seeds were sent south (to the local botanic gardens at Melbourne and Sydney) and onward to the Royal Botanic Gardens in Britain (at Kew and Edinburgh). This set the local pattern for future exchanges among the global British Imperial botanic garden network...

Effects of pupil center shift on ocular aberrations

Purpose: To investigate effects of pupil shifts, occurring with changes in luminance and accommodation stimuli, on refraction components and higher-order aberrations. Method: Participants were young and older groups (n=20, 22±2 years, age range 18–25 years; n=19, 49±4 years, 45–58 years). Aberrations/refractions at 4 mm and 3 mm diameters were compared between centered and decentered pupils for low (background 0.01cd/m², 0D), and high (6100cd/m², 4D or 6D) stimuli. Decentration was the difference between pupil centers for low and high stimuli. Clinical important changes with decentration were: M ±0.50D or ±0.25D, J180 and J45 ±0.25D or ±0.125D, HORMS ±0.05m, C(3, 1) ±0.05m, C(4, 0) ±0.05m. Results: Because of small pupil shifts in most participants (mean 0.26mm), there were few important changes in most refraction components and higher-order aberration terms. However, M changed by >0.25 D for a third of participants with 4mm pupils. When determining refractions from 2nd-6th order aberration coefficients, the more stringent criteria gave 76/ 534 (14%) possible important changes. Some participants had large pupil shifts with considerable aberration changes. Comparisons at the high stimulus were possible for only 11 participants because of small pupils. When refractions were determined from 2nd order aberration coefficients only, there were only 35 (7%) important changes for the more stringent criteria. Conclusion: Usually pupil shifts with changes in stimulus conditions have little influence on aberrations, but they can with high shifts. The number of aberrations orders that are considered as contributing to refraction influences the proportion of cases that might be considered clinically important.

Importance of knowledge management processes in a project-based organization : a case study of research enterprise

Knowledge Management (KM) is vital factor to successfully undertake projects. The temporary nature of projects necessitates employing useful KM practices for tackling issues such as knowledge leakiness and rework. The Project Management Office (PMO) is a unit within organizations to facilitate and oversee organizational projects. Project Management Maturity Models (PMMM) shows the development of PMOs from immature to mature levels. The existing PMMMs have focused on discussing Project Management (PM) practices, however, the management of project knowledge is yet to be addressed, at various levels of maturity. This research project was undertaken to investigate the mentioned gap for addressing KM practices at the existing PMMMs. Due to the exploratory and inductive nature of this research, qualitative methods were chosen as the research methodology. In total, three cases selected from different industries: research; mining and government organizations, to provide broad categories for research and research questions were examined using the developed framework. This paper presents the partial findings of undertaken investigation of the research organisation with the lowest level of maturity. The result shows that knowledge creation and capturing are the most important processes, while knowledge transferring and reusing are not as important as the other two processes. In addition, it was revealed that provision of “knowledge about client” and “project management knowledge” are the most important types of knowledge that are required at this level of maturity. In conclusion, the outcomes of this paper shall provide powerful guidance to PMOs at lowest level of maturity from KM point of view.

Origins of Australian Football: Victoria's Early History. Volume 3: Covert 'Professionalism': The Power of the Wealthy Clubs 1886 to 1890

This volume continues the story of football in Marvellous Melbourne during the 1880s. At this time the VFA continued to expand as Melbourne’s boom continued apace. In 1886 Port Melbourne, Prahran, St Kilda, Footscray and South Williamstown joined the competition, and the Ballarat clubs Ballarat, Ballarat Imperial and South Ballarat were also contending for the VFA premiership. In 1886 matches were divided into four quarters, goal umpires waved two flags to announce a goal, and time clocks and bells were employed to mark the end of quarters. Victoria also played inter-colonial matches against New South Wales, Tasmania and South Australia. VFA secretary T.S. Marshall was at the forefront of fighting the game’s turn towards professionalism, but although it was illegal to pay players, the practice continued. The period 1886 to 1890 also set the stage for the eventual formation of the Victorian Football League, for by the end of the 1880s the Victorian Football Association had become in effect a two-tier competition. The most popular clubs in the VFA, South Melbourne, Geelong, Carlton and Essendon collected the lion’s share of the gate money, which they used to build their wealth and entrench their position as the dominant Victorian teams. The lower tier clubs had to make do with paltry gate money and season fixtures that advantaged the strong clubs. In these fixtures the strong clubs elected to play each other first to increase their gate money, and only deemed to play the poorer clubs at the start of the season. This led to an increasing divide between the VFA’s rich and poor, and by 1890 South Williamstown and Prahran merged with Williamstown and St Kilda respectively, University dropped out of senior ranks, and the Ballarat clubs were excluded from competing for the VFA premiership, which left 12 senior clubs until Collingwood’s emergence in 1892. At this time, no team was as powerful as South Melbourne, which experienced the greatest success in the club’s VFA and VFL history when it collected triple premiership crowns in 1888, 1889, and 1890. South Melbourne was a most ambitious club and spearheaded the move towards professionalism, although this could not be made public. The fine teams it produced at this time contained some of the greatest players of the era, such as Peter Burns, “Sonny” Elms and “Dinny” McKay, and it looked after players with health insurance, jobs, inter-colonial trips, and other incentives. Geelong’s premiership in 1886 was perhaps its greatest triumph, but this success was followed by a premiership drought that would last for 39 years. Carlton remained one of Victorian football’s power clubs, and after securing the premiership in 1887 continued to compete for top honours. As always, the game became ever more popular and world record crowds of over 30,000 attended matches between South Melbourne, Carlton, Geelong and Essendon.

Decisions and actions of distracted drivers at the onset of yellow light

Driving on an approach to a signalized intersection while distracted is relatively risky, as potential vehicular conflicts and resulting angle collisions tend to be relatively more severe compared to other locations. Given the prevalence and importance of this particular scenario, the objective of this study was to examine the decisions and actions of distracted drivers during the onset of yellow lights. Driving simulator data were obtained from a sample of 69 drivers under baseline and handheld cell phone conditions at the University of Iowa – National Advanced Driving Simulator. Explanatory variables included age, gender, cell phone use, distance to stop-line, and speed. Although there is extensive research on drivers’ responses to yellow traffic signals, the examinations have been conducted from a traditional regression-based approach, which do not necessary provide the underlying relations and patterns among the sampled data. In this paper, we exploit the benefits of both classical statistical inference and data mining techniques to identify the a priori relationships among main effects, non-linearities, and interaction effects. Results suggest that the probability of yellow light running increases with the increase in driving speed at the onset of yellow. Both young (18–25 years) and middle-aged (30–45 years) drivers reveal reduced propensity for yellow light running whilst distracted across the entire speed range, exhibiting possible risk compensation during this critical driving situation. The propensity for yellow light running for both distracted male and female older (50–60 years) drivers is significantly higher. Driver experience captured by age interacts with distraction, resulting in their combined effect having slower physiological response and being distracted particularly risky.

The nature of non-equilibrium solidification of undercooled Agsingle bondCu alloys in contact with primary copper dendrites

Liquids of silver-copper alloys with near eutectic compositions embedded in a copper matrix were undercooled. The structural and microstructural investigations of these alloys solidified from undercooled temperature indicated the absence of both the eutectic reaction and diffusionless transformation below the equal free energy curve (T0). Instead the liquid maintained local equilibrium with the copper dendrites continuously until it intersected the extended solidus of the silver rich solid solution.

L'ecfrasis nel Piacere di Gabriele D'Annunzio

Tutkielman aiheena on ekfrasis Gabriele D'Annunzion romaanissa Il Piacere (1889). Lähtökohtana on selvittää, millaisissa muodoissa ekfrasis esiintyy romaanissa sekä miten ekfrasis vaikuttaa teoksen tulkintatradition esille tuomaan tematiikkaan. Pyrkimyksenä on myös selkeyttää ekfrasiksen käsitettä, jonka ongelmana ovat sanaan eri aikakausina liitetyt eri merkitykset. Tärkeimpiä lähdeteoksia ovat James A.W. Heffernanin Museum of Words (1993) ja W.J.T. Mitchellin Picture Theory (1994), Marinella Cantelmon Il Piacere dei leggitori: D'Annunzio e la comunicazione letteraria (1996) sekä John Hollanderin artikkeli "The Poetics of Ekphrasis" (1988). Tutkielman avainkäsitteenä on Heffernanin määritelmä, jonka mukaan ekfrasis on sanallinen esitys kuvallisesta esityksestä. Määritelmää sovellettaessa on otettu huomioon representaatiokäsityksen avautuminen, jolloin vastaanottaja, ympäristö etc. ovat osa esitystä. Korpuksen muodostavat tapahtumaympäristöä, taideteoksia, esineistöä ja henkilöhahmoja kuvaavat ekfrastiset katkelmat. Luokittelussa toimivat alakäsitteinä Valerie Robillardin kuvaileva, attributiivinen ja assosiatiivinen ekfrasis sekä Tamar Yacobin ekfrastinen vertaus. Analyysi osoittaa, että kuvaileva ekfrasis on yleisin, mutta vain kuvitteellisten teosten yhteydessä. Katkelmissa on näkyvissä ekfrasikselle luonteenomainen kerronnallinen impulssi. Ekfrasis osallistuu tunnetun ja uuden elementin vuoropuheluun ankkuroimalla kuvitteelliset taideteokset lukijalle tuttuun ympäristöön, jolloin myös uusi tulee toden kaltaiseksi. Attributiivinen ekfrasis takaa välittömän tunnistettavuuden. Henkilöhahmot, erityisesti keskeiset naishahmot, on määritelty ekfrastisten vertausten kautta. Ekfrasis ilmentää osaltaan naishahmojen vaihdettavuuden tematiikkaa. Kyseessä on myös toiseuden haltuunotto. Kuvallisen viittaussuhteen ansiosta ekfrasis toimii tehokeinona. Tekstuaalisena strategiana ekfrasis luo siteitä tapahtumien välille ja rytmittää teoksen vaiheita. Ekfrastiset katkelmat tarjoavat myös väylän vaihtoehtoiselle tulkinnalle haastamalla tekstin totuuskäsityksen. Kuvallinen ja sanallinen esitys tuovat tekstiin omat merkityksensä, jolloin merkityskenttä laajenee. Il Piacere on intertekstuaalinen kollaasi, jossa kokonaiskuva muodostuu eri elementtien vuorovaikutuksesta. D'Annunzion mielestä kauneus on taiteen ensisijainen tarkoitus, ja ekfrasis retorisena keinona on osa pyrkimystä tavoittaa täydellinen muoto.

Rikollisia sattumalta? : Naisten keskinäistä haureutta koskevat oikeudenkäynnit 1950-luvun Itä-Suomessa

The main focus of the research is on the genealogy of women's same-sex fornication in Finnish criminal law from 1889/1894 to 1971. Why were women included in the concept of same-sex fornication in Finland and why, where, and when was the law put into effect? Which women were tried, how did the trial proceedings evolve, and what kind of effects did the trials have afterwards? Which concepts were used? These questions have been approached through the analysis of the Finnish Penal Code, the criminal law science and four trial proceedings in Eastern Finland during the 1950s. The research draws on the epistemology of the closet and the concept of heteronormativity adapted from queer theories. It is method critical in utilising ethnography, micro history and feminist ethical self-reflection. The research consists of six scientific refereed articles (see appendix) and of a theoretical introduction. The main results of the research are: 1) The genealogy of Finnish decency [Sittlichkeit] can not be researched without oral histories, due to the late modernisation of Finnish society and the legal system, which does not follow the pattern of English, French and German societies. 2) The inclusion of women's same-sex fornication in the Finnish Penal Code is not incomprehensible when compared to the early modern European legislations and court practices. Women have been punished for the sins of Sodom, though not directly under the 1734 Swedish law. 3) Fornication and decency were ambivalent concepts in the 1889/1894 law, and juridical authorities offered controversial interpretations of them during the late 19th and early 20th centuries. 4) A peak in women's convictions occurred in the 1950s, and most of the trial proceedings took place in rural Eastern Finland. Neither the state nor the police were active in prosecuting; instead, the trial proceedings began "by accident". 5) From 1940 to 1960 police training lacked instructions concerning the interrogation of women suspected of same-sex fornication. 6) The figure of the penitent woman was produced in the chiasmic encounter of confession and police interrogation which moulded and was moulded by the epistemological matrix of shame, honour, and decency. Women's speech acts were judicialised as confessions which enabled the disciplinary tampering with the women's bodies. 7) Gender and personality, more than sexuality, or "criminality" defined the status of the convicted women in their village communities after the trials. 8) Relations between police training, sexuality, and decency have not been well researched in Finland. 9) Decriminalisation in 1971 did not mark the end of homophobic legal discourse, even though the 1999 reform of sexual crimes took the form of gender neutral conceptualisation

Complicated Presence : The Unity of Being in Parmenides and Heidegger

The attempt to refer meaningful reality as a whole to a unifying ultimate principle - the quest for the unity of Being - was one of the basic tendencies of Western philosophy from its beginnings in ancient Greece up to Hegel's absolute idealism. However, the different trends of contemporary philosophy tend to regard such a speculative metaphysical quest for unity as obsolete. This study addresses this contemporary situation on the basis of the work of Martin Heidegger (1889-1976). Its methodological framework is Heidegger's phenomenological and hermeneutical approach to the history of philosophy. It seeks to understand, in terms of the metaphysical quest for unity, Heidegger's contrast between the first (Greek) beginning or "onset" (Anfang) of philosophy and another onset of thinking. This other onset is a possibility inherent in the contemporary situation in which, according to Heidegger, the metaphysical tradition has developed to its utmost limits and thereby come to an end. Part I is a detailed interpretation of the surviving fragments of the Poem of Parmenides of Elea (fl. c. 500 BC), an outstanding representative of the first philosophical beginning in Heidegger's sense. It is argued that the Poem is not a simple denial of apparent plurality and difference ("mortal acceptances," doxai) in favor of an extreme monism. Parmenides' point is rather to show in what sense the different instances of Being can be reduced to an absolute level of truth or evidence (aletheia), which is the unity of Being as such (to eon). What in prephilosophical human experience is accepted as being is referred to the source of its acceptability: intelligibility as such, the simple and undifferentiated presence to thinking that ultimately excludes unpresence and otherness. Part II interprets selected key texts from different stages in Heidegger's thinking in terms of the unity of Being. It argues that one aspect of Heidegger's sustained and gradually deepening philosophical quest was to think the unity of Being as singularity, as the instantaneous, context-specific, and differential unity of a temporally meaningful situation. In Being and Time (1927) Heidegger articulates the temporal situatedness of the human awareness of meaningful presence. His later work moves on to study the situational correlation between presence and the human awareness. Heidegger's "postmetaphysical" articulation seeks to show how presence becomes meaningful precisely as situated, in an event of differentiation from a multidimensional context of unpresence. In resigning itself to this irreducibly complicated and singular character of meaningful presence, philosophy also faces its own historically situated finitude. This resignation is an essential feature of Heidegger's "other onset" of thinking.

Herakleitos, filosofia ja metafysiikka : Collin ja Heideggerin tulkintojen valossa

Tutkielmani aiheena on noin 2500 vuotta sitten Efesoksen kaupungissa eläneen Herakleitoksen ajattelu. Selvitän, mikä suhde Herakleitoksen ajattelulla on filosofiaan ja metafysiikkaan. Lähestyn tätä kysymystä pääasiassa kahden uuden ajan filosofin italialaisen Giorgio Collin (1917-1979) ja saksalaisen Martin Heideggerin (1889-1976) esittämien tulkintojen pohjalta. Osoitan, että Herakleitoksen ajattelu eroaa olennaisesti Platonin ja Aristoteleen jälkeisestä filosofisesta ja metafyysisestä ajattelusta. Perusteluna tarkastelen Herakleitoksen ajattelua neljästä näkökulmasta: 1) historiallisesti filosofian syntyä edeltäneen viisauden ja uskonnollisen ajattelun edustajana, 2) loogisesti olevan käsitteeseen keskittyvästä metafysiikasta poikkeavana ajatteluna, 3) välittömän kokemuksen ajatteluna ja 4) fenomenologisena ilmiön ja kätkeytymättömyyden ajatteluna. Ensimmäinen ja kolmas näkökulma edustavat Collin tulkintaa, toinen ja neljäs näkökulma puolestaan Heideggerin tulkintaa. Tärkeimpinä lähteinäni ovat Collin teokset Filosofian synty (1975), Filosofia dell'espressione (1969) ja La sapienza greca (1977-80) sekä Heideggerin teokset Oleminen ja aika (1927), Einführung in die Metaphysik (1935/53), Aletheia (1951), Logos (1951) ja Heraklit Seminar (1966-67).

Papin pojasta suurteollisuusmieheksi : Alfred Kihlman ja nousevan keskiluokan sosiaaliset verkostot 1800-luvun Suomessa

Tutkimuksen tavoitteena on hahmottaa 1800-luvulla tapahtunutta keskiluokan sosiaalista nousua pohjalaissyntyisen papin, opettajan, liikemiehen ja valtiopäiväedustajan Alfred Kihlmanin (1825-1904) elämänvaiheiden kautta. Kyseessä ei ole perinteinen elämäkerta, vaan työn pyrkimyksenä on mikrotason tarkan analyysin kautta päästä käsiksi laajempiin yhteiskunnallisiin muutosprosesseihin. Erityisen kiinnostuksen kohteena ovat erilaiset sosiaaliset verkostot sekä niiden merkitys Kihlmanin kaltaisen keskiluokkaisen yksilön sosiaaliselle nousulle. Tutkimus jakautuu kahteen pääosaan, joista ensimmäinen käsittelee heränneiden pappien verkostoja 1840-luvulla ja 1850-luvun alussa ja jälkimmäinen liikemiesverkostoja 1850-luvun jälkipuolelta 1870-luvun alkuun. Pääasiallisena lähdeaineistona on Alfred Kihlmanin laaja kirjeenvaihto. Alfred Kihlman liittyi kouluvuosinaan 1840-luvun alussa nuorison piirissä nopeasti levinneeseen herännäisyyteen. Nuoret heränneet papit muodostivat tiiviin sosiaalisen verkoston, joka perustui jaetulle uskonnolliselle ideologialle sekä pappisperheiden välisille avioliittositeille. Lisäksi verkostoa pidettiin yllä yhteisillä kokoontumisilla, vierailuilla, kirjeenvaihdolla sekä palvelusten vaihtamisella. Verkoston välityksellä saatiin tehokkaasti mm. informaatiota sekä rahalainoja. Herännäisyys nousi nuoren keskiluokkaisen papiston omaa yhteiskunnallista voimattomuuttaan kohtaan tuntemasta tyytymättömyydestä. Kun sivistyneistön mahdollisuudet menestyä perinteisillä foorumeilla olivat autonomian alkupuolella heikot, nuoret heränneet kielsivät uskonnollisessa ideologiassaan arvon maalliselta menestykseltä ja rakensivat oman verkostonsa, jonka sisällä he saattoivat toteuttaa pätemisentarvettaan. Yhteiskunnallisen tilanteen muututtua verkosto muuttui 1850-luvun alussa hyödystä rasitteeksi, minkä seurauksena heränneiden pappien rivit hajaantuivat. Irtauduttuaan herännäisyydestä Alfred Kihlman siirtyi opettajan uralle. Heränneeltä vaimoltaan perimänsä varallisuuden sekä nuoruus- ja herännäisvuosinaan solmimiensa ystävyyssuhteiden ansiosta hän ajatui 1850-luvun kuluessa yhä enemmän myös liike-elämään. Hänen merkittävimmäksi toimintakentäkseen muodostuivat Suomen Yhdyspankki sekä Tampereen Pellava- ja Rautateollisuus, jonka johtajana hän toimi vuodesta 1866 lähtien. 1860-luvulla liikemiesverkostot perustuivat suurelta osin sukulaisuuteen, mutta yhä enenevässä määrin myös ystävyys-, kollega- ja liikekumppanuussuhteisiin. Kun pankkilaitos oli vielä hyvin kehittymätön, verkostot olivat etenkin pääomien hankinnassa avainasemassa. Tiiviit lainaverkostot olivat huonojen suhdanteiden aikana toisaalta myös vaaraksi, sillä yksi suuri konkurssi saattoi vetää mukanaan joukoittain liikemiehiä. Verkostojen kautta voitiin välittää ja saada myös suosituksia sekä sisäpiiritietoa, jota ei ollut saatavissa muista lähteistä. Yhteiskunnan muuttuminen ja henkilösuhteet mahdollistivat Alfred Kihlmanin sosiaalisen nousun. Teollistuminen ja liike-elämän vapautuminen tarjosivat uusia mahdollisuuksia keskiluokan yritteliäille yksilöille. Ylempien yhteiskuntaluokkien välisten säätyjen välisten raja-aitojen tasaantuminen tekivät 1850-luvun puolivälissä mahdolliseksi myös papin osallistumisen liike-elämään. Avainsanat: sosiaaliset verkostot - Suomi - 1800-luku - herännäisyys - kirkkohistoria - taloushistoria

Resilience of a high-conservation-value, semi-arid grassland on fertile clay soils to burning, mowing and ploughing.

In grassland reserves, managed disturbance is often necessary to maintain plant species diversity. We carried out experiments to determine the impact of fire, kangaroo grazing, mowing and disc ploughing on grassland species richness and composition in a nature reserve in semi-arid eastern Australia. Vegetation response was influenced by winter-spring drought after establishment of the experiments, but moderate rainfall followed in late summer-autumn. Species composition varied greatly between sampling times, and the variability due to rainfall differences between seasons and years was greater than the effects of fire, kangaroo grazing, mowing or disc ploughing. In the fire experiment, species richness and composition recovered more rapidly after spring than autumn burning. Species richness and composition were similar to control sites within 12 months of burning and mowing, suggesting that removal of the dominant grass canopy is unnecessary to enhance plant diversity. Two fires (separated by 3 years) and post-fire kangaroo grazing had only minor influence on species richness and composition. Even disc ploughing caused only a small reduction in native richness. The minor impact of ploughing was explained by the small areas that were ploughed, the once-off nature of the treatment, and the high degree of natural movement and cracking in these shrink-swell soils. Recovery of the composition and richness of these grasslands was rapid because of the high proportion of perennial species that resprout vegetatively after fire and mowing. There appears to be little conservation benefit from fire, mowing or ploughing ungrazed areas, as we could identify no native plant species dependent on frequent disturbance for persistence in this grassland community. However, the ability of the Astrebla- and Dichanthium-dominated grasslands to recover quickly after disturbance, given favourable seasonal conditions, suggests that they are well adapted to natural disturbances (e.g. droughts, fire, flooding and native grazing).