Showing papers by "University of Peradeniya published in 2010"

Acute human lethal toxicity of agricultural pesticides: a prospective cohort study

Abstract: Background: Agricultural pesticide poisoning is a major public health problem in the developing world, killing at least 250,000–370,000 people each year. Targeted pesticide restrictions in Sri Lanka over the last 20 years have reduced pesticide deaths by 50% without decreasing agricultural output. However, regulatory decisions have thus far not been based on the human toxicity of formulated agricultural pesticides but on the surrogate of rat toxicity using pure unformulated pesticides. We aimed to determine the relative human toxicity of formulated agricultural pesticides to improve the effectiveness of regulatory policy. Methods and Findings: We examined the case fatality of different agricultural pesticides in a prospective cohort of patients presenting with pesticide self-poisoning to two clinical trial centers from April 2002 to November 2008. Identification of the pesticide ingested was based on history or positive identification of the container. A single pesticide was ingested by 9,302 patients. A specific pesticide was identified in 7,461 patients; 1,841 ingested an unknown pesticide. In a subset of 808 patients, the history of ingestion was confirmed by laboratory analysis in 95% of patients. There was a large variation in case fatality between pesticides—from 0% to 42%. This marked variation in lethality was observed for compounds within the same chemical and/or WHO toxicity classification of pesticides and for those used for similar agricultural indications. Conclusion: The human data provided toxicity rankings for some pesticides that contrasted strongly with the WHO toxicity classification based on rat toxicity. Basing regulation on human toxicity will make pesticide poisoning less hazardous, preventing hundreds of thousands of deaths globally without compromising agricultural needs. Ongoing monitoring of patterns of use and clinical toxicity for new pesticides is needed to identify highly toxic pesticides in a timely manner. Please see later in the article for the Editors’ Summary.

seL4: formal verification of an operating-system kernel

Abstract: We report on the formal, machine-checked verification of the seL4 microkernel from an abstract specification down to its C implementation. We assume correctness of compiler, assembly code, hardware, and boot code. seL4 is a third-generation microkernel of L4 provenance, comprising 8700 lines of C and 600 lines of assembler. Its performance is comparable to other high-performance L4 kernels. We prove that the implementation always strictly follows our high-level abstract specification of kernel behavior. This encompasses traditional design and implementation safety properties such as that the kernel will never crash, and it will never perform an unsafe operation. It also implies much more: we can predict precisely how the kernel will behave in every possible situation.

A systematic review of oral fungal infections in patients receiving cancer therapy

Abstract: The aims of this systematic review were to determine, in patients receiving cancer therapy, the prevalence of clinical oral fungal infection and fungal colonization, to determine the impact on quality of life and cost of care, and to review current management strategies for oral fungal infections. Thirty-nine articles that met the inclusion/exclusion criteria were independently reviewed by two calibrated reviewers, each using a standard form. Information was extracted on a number of variables, including study design, study population, sample size, interventions, blinding, outcome measures, methods, results, and conclusions for each article. Areas of discrepancy between the two reviews were resolved by consensus. Studies were weighted as to the quality of the study design, and recommendations were based on the relative strength of each paper. Statistical analyses were performed to determine the weighted prevalence of clinical oral fungal infection and fungal colonization. For all cancer treatments, the weighted prevalence of clinical oral fungal infection was found to be 7.5% pre-treatment, 39.1% during treatment, and 32.6% after the end of cancer therapy. Head and neck radiotherapy and chemotherapy were each independently associated with a significantly increased risk for oral fungal infection. For all cancer treatments, the prevalence of oral colonization with fungal organisms was 48.2% before treatment, 72.2% during treatment, and 70.1% after treatment. The prophylactic use of fluconazole during cancer therapy resulted in a prevalence of clinical fungal infection of 1.9%. No information specific to oral fungal infections was found on quality of life or cost of care. There is an increased risk of clinically significant oral fungal infection during cancer therapy. Systemic antifungals are effective in the prevention of clinical oral fungal infection in patients receiving cancer therapy. Currently available topical antifungal agents are less efficacious, suggesting a need for better topical agents.

Thermal conductivity in metallic nanostructures at high temperature: Electrons, phonons, and the Wiedemann-Franz law

Abstract: The Boltzmann transport equation is used to calculate thermal and electrical conductivity of metal nanostructures with characteristic dimensions in the 25--500 nm range, near to and above the Debye temperature. Thermal conductivity contributions from phonons and electrons are considered. The intrinsic effects of electron-phonon, phonon-phonon, and phonon-electron scattering, and grain boundary and surface interactions are addressed. Excellent agreement is found between model results and available data reporting direct measurements of thermal conductivity of nanowires, ribbons, and thin films in Al, Pt, and Cu, respectively. The Wiedemann-Franz (W-F) law and Lorenz factor are examined with decreasing size; their applicability is found to degrade in nanowires due mainly to increased relative phonon contribution. The effect of differences in the electron mean-free path for thermal gradient versus electrical field is also examined. A modified version of W-F is presented, corrected for these two factors and valid from macroscale to nanoscale provided characteristic sizes exceed the phonon mean-free path.

Pathogenomics of Culex quinquefasciatus and Meta-Analysis of Infection Responses to Diverse Pathogens

Abstract: The mosquito Culex quinquefasciatus poses a substantial threat to human and veterinary health as a primary vector of West Nile virus (WNV), the filarial worm Wuchereria bancrofti, and an avian malaria parasite. Comparative phylogenomics revealed an expanded canonical C. quinquefasciatus immune gene repertoire compared with those of Aedes aegypti and Anopheles gambiae. Transcriptomic analysis of C. quinquefasciatus genes responsive to WNV, W. bancrofti, and non-native bacteria facilitated an unprecedented meta-analysis of 25 vector-pathogen interactions involving arboviruses, filarial worms, bacteria, and malaria parasites, revealing common and distinct responses to these pathogen types in three mosquito genera. Our findings provide support for the hypothesis that mosquito-borne pathogens have evolved to evade innate immune responses in three vector mosquito species of major medical importance.

Multiseason Recoveries of Organic and Inorganic Nitrogen-15 in Tropical Cropping Systems

Abstract: In tropical agroecosystems, limited N availability remains a major impediment to increasing yield. A 15N-recovery experiment was conducted in 13 diverse tropical agroecosystems. The objectives were to determine the total recovery of one single 15N application of inorganic or organic N during three to six growing seasons and to establish whether the losses of N are governed by universal principles. Between 7 and 58% (average of 21%) of crop N uptake duringthe first growing season was derived from fertilizer. On average, 79% of crop N was derived from the soil. When 15N-labeled residues were applied, in the first growing season 4% of crop N was derived from the residues. Average recoveries of 15N- labeled fertilizer and residue in crops after the first growing season were 33 and 7%, respectively. Corresponding recoveries in the soil were 38 and 71 %. An additional 6% of the fertilizer and 9.1 % of the residue was recovered by crops during subsequent growing seasons. There were no significant differences in total 15N recovery (average 54%) between N from fertilizer and N from residue. After five growing seasons, more residue N (40%) than fertilizer N (18%) was recovered in the soil, better sustaining the soil organic matter N content. Long-term total recoveries of 15N-labeled fertilizer or residue in the crop and soil were similar. Soil N remained the primary source of N for crops. As higher rainfall and temperature tend to cause higher N losses, management practices to improve N use efficiency and reduce losses in wet tropical regions will remain a challenge.

Comparison of lossless data compression algorithms for text data

Abstract: Data compression is a common requirement for most of the computerized applications. There are number of data compression algorithms, which are dedicated to compress different data formats. Even for a single data type there are number of different compression algorithms, which use different approaches. This paper examines lossless data compression algorithms and compares their performance. A set of selected algorithms are examined and implemented to evaluate the performance in compressing text data. An experimental comparison of a number of different lossless data compression algorithms is presented in this paper. The article is concluded by stating which algorithm performs well for text data.

Enterprise Recovery Following Natural Disasters

Abstract: Using data from surveys of enterprises in Sri Lanka after the December 2004 tsunami, the authors undertake the first microeconomic study of the recovery of the private firms in a developing country following a major natural disaster. Disaster recovery in low-income countries is characterized by the prevalence of relief aid rather than of insurance payments; the data show this distinction has important consequences. The data indicate that aid provided directly to households correlates reasonably well with reported losses of household assets, but is uncorrelated with reported losses of business assets. Business recovery is found to be slower than commonly assumed, with disaster-affected enterprises lagging behind unaffected comparable firms more than three years after the disaster. Using data from random cash grants provided by the project, the paper shows that direct aid is more important in the recovery of enterprises operating in the retail sector than for those operating in the manufacturing and service sectors.

A prospective observational study of the clinical toxicology of glyphosate-containing herbicides in adults with acute self-poisoning

Abstract: Context. The case fatality from acute poisoning with glyphosate-containing herbicides is approximately 7.7% from the available studies but these have major limitations. Large prospective studies of patients with self-poisoning from known formulations who present to primary or secondary hospitals are needed to better describe the outcome from acute poisoning with glyphosate-containing herbicides. Furthermore, the clinical utility of the glyphosate plasma concentration for predicting clinical outcomes and guiding treatment has not been determined. Objective. To describe the clinical outcomes, dose–response, and glyphosate kinetics following self-poisoning with glyphosate-containing herbicides. Methods. This prospective observational case series was conducted in two hospitals in Sri Lanka between 2002 and 2007. We included patients with a history of acute poisoning. Clinical observations were recorded until discharge or death. During a specified time period, we collected admission (n = 216, including five de...

Ageing of silicone rubber insulators in coastal and inland tropical environment

Abstract: This paper presents investigations on the performance of 33 kV silicone rubber insulators characterized by different creepage lengths, which aimed to find out whether the insulators could permanently work when electrically stressed beyond the recommended limits in polluted and clean tropical environments. The study was performed under natural field and laboratory conditions. The insulators tested included eight types of silicone rubber composite insulators, one type of hybrid silicone-ceramic insulator and one semi-conducting glazed porcelain insulator, while ordinary porcelain and glass insulators were used as reference. During the field investigation, two sets of the insulators were separately installed and energized in coastal and inland parts of Sri Lanka, being by that exposed to marine and clean tropical environments. Their performances were periodically evaluated by visual inspections and measurements of hydrophobicity class. After five years of field exposure, the insulator performances were evaluated in laboratory by measurements of leakage currents under clean fog conditions and of wet flashover voltage. A third set of the insulators was aged in laboratory for 1000 hours inside a salt fog chamber where the insulators were continuously energized and daily sprayed with salt solution for eight hours and left to rest for remaining 16 hours. This treatment represented conditions similar as those in the field i.e. insulators exposed to salt sprays during monsoons. The insulator performances were investigated by measurements of leakage currents and classifying their patterns into different categories, i.e. capacitive, resistive, non-linear, discharge and strong discharge types, by means of fast Fourier transform and short time Fourier transform analyses. It was found that the long-term field exposure yielded weaker insulator deterioration than the salt fog chamber ageing, which indicated for a possibility to increase the electric stress on silicone rubber insulators to levels higher than the ones used today on glass and porcelain counterparts.

Natural radionuclides and trace elements in rice field soils in relation to fertilizer application: study of a chronic kidney disease area in Sri Lanka

Abstract: The rising number of chronic kidney disease patients with no identifiable cause (CKD of uncertain aetiology), prevalent in some areas of the dry zone of Sri Lanka is suspected to be related to the environmental exposure to heavy metals. Agricultural soils are well recognized as being contaminated with potentially toxic metals from various forms of fertilizers and agro-chemicals, which could easily enter the human body through the food chain. The objective of this paper is to determine the content of heavy metals and activity concentration of background radionuclides such as K-40, Ra-226 and Th-232, in rice field soils. Rice farming is the most common agricultural practice in the affected region and possible heavy metal sources such as fertilizers are applied in abundance in the rice fields. Soils collected from a rice field in a non-CKD region was used for the comparison. In dry zone soils, Ca, K, Ba, Pb and Zr contents were higher and Fe, Mn, Cr, Ni and Zn contents were lower compared to that of soils from the wet zone non-CKD region. However, the activity concentration of soils was mostly the same in all samples, except for the K-40 contents of the soils, which were higher in the rice field soils compared to the undisturbed forest soils and also to the world averages. The mean U content was 3.6 mg/kg in the studied soils, although extremely high uranium contents were found in some fertilizer samples particularly in the triple superphosphates. Most uranium applied via fertilizer could contaminate the drinking water sources and even low uranium concentrations in drinking water may cause nephrotoxic effects.

Autonomous distributed V2G (vehicle-to-grid) considering charging request and battery condition

Abstract: Integration of large scale renewable energy sources into power grid, battery energy storage performs an important role for smoothing their natural intermittency and ensuring grid-wide frequency stability. Plug-in hybrid electric vehicle and electric vehicle have potential of alternative of the battery because of its high performance lithiumion battery and longer plug-in time than driving time. Therefore, vehicle-to-grid is expected to be one of the key technologies for smart grids integrating renewable energy sources. In this paper, an autonomous distributed vehicle-to-grid control scheme is proposed. Grid-connected electric vehicles contribute frequency regulation and spinning reserve triggered by self-terminal frequency, which is a signal of supply and demand balance in the power grid. Proposed scheme also consider charging request for the next drive and battery condition during the vehicle-to-grid. Satisfaction of vehicle user convenience and effect load frequency control is evaluated through coupled analysis of vehicle-to-grid model and typical power grid model.

A single-electron reducing quinone oxidoreductase is necessary to induce haustorium development in the root parasitic plant Triphysaria

Abstract: Parasitic plants in the Orobanchaceae develop haustoria in response to contact with host roots or chemical haustoria-inducing factors. Experiments in this manuscript test the hypothesis that quinolic-inducing factors activate haustorium development via a signal mechanism initiated by redox cycling between quinone and hydroquinone states. Two cDNAs were previously isolated from roots of the parasitic plant Triphysaria versicolor that encode distinct quinone oxidoreductases. QR1 encodes a single-electron reducing NADPH quinone oxidoreductase similar to ζ-crystallin. The QR2 enzyme catalyzes two electron reductions typical of xenobiotic detoxification. QR1 and QR2 transcripts are upregulated in a primary response to chemical-inducing factors, but only QR1 was upregulated in response to host roots. RNA interference technology was used to reduce QR1 and QR2 transcripts in Triphysaria roots that were evaluated for their ability to form haustoria. There was a significant decrease in haustorium development in roots silenced for QR1 but not in roots silenced for QR2. The infrequent QR1 transgenic roots that did develop haustoria had levels of QR1 similar to those of nontransgenic roots. These experiments implicate QR1 as one of the earliest genes on the haustorium signal transduction pathway, encoding a quinone oxidoreductase necessary for the redox bioactivation of haustorial inducing factors.

Excessive ovarian stimulation up-regulates the Wnt-signaling molecule DKK1 in human endometrium and may affect implantation: an in vitro co-culture study

Abstract: background: High serum estradiol (E2) levels following ovarian stimulation lead to reduced implantation and pregnancy rates, yet the underlying mechanisms remain unknown. We investigated if aberrant expression of genes in the Wnt-signaling pathway may be involved. methods: Microarray and real-time PCR analysis were performed to analyze gene expression profiles of endometrial samples taken at day hCG þ 7 in stimulated cycles, and days LH þ 7 and LH þ 10 in natural cycles. Expression of several Wnt-signaling transcripts, including Dickkopf homolog 1 (DKK1), DKK2 and secreted frizzled-related protein 4 (sFRP4), was analyzed throughout the menstrual cycle. JAr spheroid/Ishikawa endometrial cell co-culture experiments were established to study effects of DKK1 on spheroid attachment in vitro. results: We identified 351 differentially expressed genes. Endometrial samples taken at hCG þ 7 had similar expression profiles to those at LH þ 10. DKK1 transcripts were up-regulated and DKK2 and sFRP4 were down-regulated in the stimulated compared with LH þ 7 group (all P , 0.05). DKK1 transcripts were low in proliferative phase (PS) and increased in late-secretory phase (LS, P , 0.05), although DKK2 peaked in mid-secretory phase (P , 0.05). sFRP4 transcripts were high in PS. Treatment of spheroid with recombinant human DKK-1 protein dose-dependently suppressed (P , 0.05 versus control) spheroids attachment onto endometrial cells (associated with decreased b-catenin protein): this suppression was nullified by anti-DKK1 antibody. conclusion: Gene expression patterns in stimulated cycles resembled those of LS in natural cycles, when the implantation window is about to close, suggesting high serum E2 and/or progesterone concentrations may advance endometrial development, altering the implantation window and possibly decreasing pregnancy rate. Aberrant expression of DKK1 might impair embryo attachment and implantation in vivo.

Suppression of NF-κB Increases Bone Formation and Ameliorates Osteopenia in Ovariectomized Mice

Abstract: Bone degenerative diseases, including osteoporosis, impair the fine balance between osteoclast bone resorption and osteoblast bone formation. Single-agent therapy for anabolic and anticatabolic effects is attractive as a drug target to ameliorate such conditions. Inhibition of nuclear factor (NF)-κB reduces the osteoclast bone resorption. The role of NF-κB inhibitors on osteoblasts and bone formation, however, is minimal and not well investigated. Using an established NF-κB inhibitor named S1627, we demonstrated that inhibition of NF-κB increases osteoblast differentiation and bone formation in vitro by up-regulating the mRNAs of osteoblast-specific genes like type I collagen, alkaline phosphatase, and osteopontin. In addition, S1627 was able to increase bone formation and repair bone defect in a murine calvarial defect model. To determine the effect of NF-κB on a model of osteoporosis, we injected two doses of inhibitor (25 and 50 mg/kg · d) twice a day in sham-operated or ovariectomized 12-wk-old mice a...

The gift of disaster: the commodification of good intentions in post-tsunami Sri Lanka.

Abstract: This paper analyses the commodification of post-tsunami aid in Sri Lanka, a process that ‘contaminated’ the ‘purity’ of good intentions with the politics of patronage and international aid. It argues that gifts are not just material transfers of ‘aid’, but also embodiments of cultural symbolism, social power, and political affiliations. The tsunami gift re-enforced and reconfigured exchange relationships among different patrons and clients in Sri Lankan communities, perpetuating the political economy that has driven social conflict and discontent in the post-independence years. Beyond dominant rationales of ethnic or political party patronage, the paper finds that gifts by disingenuous patrons not only became patrimonial, but that the patrimonial rationale emerged as much from above as from below—a dynamic that became nearly inescapable and self-reinforcing. Through three case studies, we explore the intricate chain of relations, obligations, and expectations pertinent in the co-evolving, but often contradictory, gift rationales that permeate the practices, performances, and discourses of tsunami aid.

A modified low-cost colorimetric method for paracetamol (acetaminophen) measurement in plasma.

Abstract: Background. Despite a significant increase in the number of patients with paracetamol poisoning in the developing world, plasma paracetamol assays are not widely available. The purpose of this study was to assess a low-cost modified colorimetric paracetamol assay that has the potential to be performed in small laboratories with restricted resources. Methods. The paracetamol assay used in this study was based on the Glynn and Kendal colorimetric method with a few modifications to decrease the production of nitrous gas and thereby reduce infrastructure costs. Preliminary validation studies were performed using spiked aqueous samples with known concentrations of paracetamol. Subsequently, the results from the colorimetric method for 114 stored clinical samples from patients with paracetamol poisoning were compared with those from the current gold-standard high-performance liquid chromatography method. A prospective survey, assessing the clinical use of the paracetamol assay, was performed on all patients with paracetamol poisoning attending the Peradeniya General Hospital, Sri Lanka, over a 10-month period. Results. The recovery study showed an excellent correlation (r 2 > 0.998) for paracetamol concentrations from 25 to 400 mg/L. The final yellow color was stable for at least 10 min at room temperature. There was also excellent correlation with the high-performance liquid chromatography method (r 2 = 0.9758). In the clinical cohort study, use of the antidote N-acetylcysteine was avoided in over a third of patients who had the plasma paracetamol concentration measured. The cost of consumables used per assay was $0.50 (US). Conclusions .T his colorimetric paracetamol assay is reliable and accurate and can be performed rapidly, easily, and economically. Use of this assay in resourcepoor clinical settings has the potential to have a significant clinical and economic impact on the management of paracetamol poisoning.

Y-chromosomal variation confirms independent domestications of swamp and river buffalo.

Abstract: Y-chromosomal variation in the water buffalo was analysed by sequencing of DBY, ZFY and SRY gene segments. A clear separation of the paternal lineages of the river and swamp types parallels the differences between their maternal lineages and nuclear DNA. Sequence divergence was found to be comparable to the divergence of taurine cattle and zebu, and this divergence predated domestication, confirming that river and swamp buffalo originated from different wild populations. Within a sample of 23 Thai swamp buffaloes, we identified four haplotypes with different geographical distributions, two of which were shared by Thai wild buffaloes.

Young patients with colorectal cancer have poor survival in the first twenty months after operation and predictable survival in the medium and long-term: Analysis of survival and prognostic markers

Abstract: This study compares clinico-pathological features in young ( 50 years) with colorectal cancer, survival in the young and the influence of pre-operative clinical and histological factors on survival. A twelve year prospective database of colorectal cancer was analysed. Fifty-three young patients were compared with forty seven consecutive older patients over fifty years old. An analysis of survival was undertaken in young patients using Kaplan Meier graphs, non parametric methods, Cox's Proportional Hazard Ratios and Weibull Hazard models. Young patients comprised 13.4 percent of 397 with colorectal cancer. Duration of symptoms and presentation in the young was similar to older patients (median, range; young patients; 6 months, 2 weeks to 2 years, older patients; 4 months, 4 weeks to 3 years, p > 0.05). In both groups, the majority presented without bowel obstruction (young - 81%, older - 94%). Cancer proximal to the splenic flexure was present more in young than in older patients. Synchronous cancers were found exclusively in the young. Mucinous tumours were seen in 16% of young and 4% of older patients (p < 0.05). Ninety four percent of young cancer deaths were within 20 months of operation. At median follow up of 50 months in the young, overall survival was 70% and disease free survival 66%. American Joint Committee on Cancer (AJCC) stage 4 and use of pre-operative chemoradiation in rectal cancer was associated with poor survival in the young. If patients, who are less than 40 years old with colorectal cancer, survive twenty months after operation, the prognosis improves and their survival becomes predictable.

An assessment of the human-elephant conflict in Sri Lanka

Abstract: The association between man and elephant in Sri Lanka is ancient. Elephants being the largest terrestrial herbivores require relatively large areas and diversity of environments to forage. With the increase in human population density and changes in the land-use patterns, elephant habitat is being continuously reduced. As a result, much of the present day elephant range extends into and overlaps with agricultural lands resulting in conflict with man. The assessment of the human-elephant conflict was carried out from January to March 2008 through the use of a questionnaire in 100 villages selected randomly from five provinces whose combined extent is 42,559 km2 which amounts roughly to 65% of the total land area of Sri Lanka. 65% of the respondents identified crop depredations with bull elephants, both young and old. At least 13 food items have been identified by the villagers as preferred by wild elephants in agricultural areas. Crop damage to paddy accounted for 69% of the complaints. At the same time, most of the farmers identified citrus trees as the most likely crop to be avoided by elephants. Failure to recognize the significance of the human-elephant conflict can result in a negative attitude to elephants and apathy or indifference to conservation initiatives. Although it is unlikely that the human-elephant conflict can be eliminated altogether, yet every effort must be taken to reduce it to tolerable levels. Key words : Asian elephant; Elephas maximus ; crop depredations; mortality DOI: 10.4038/cjsbs.v39i1.2350 Cey. J. Sci. (Bio. Sci.) 39 (1): 21-33, 2010

Students Usage of an Academic Library: a user survey conducted at the Main Library University of Peradeniya

Abstract: Since the university library is committed to provide an excellent service for its users, it has to develop an on-going dialog with the users. One of the main tools that can be used to assess the library services is the user surveys. This study was undertaken to assess library user satisfaction with current information services and resources while identifying user needs. A questionnaire based survey was used for data collection. The questionnaires were distributed among 800 undergraduates who visit the library. It was found that the undergraduates are overall satisfied with available library resources, services and facilities. But it further found that library resources and services are not being fully utilized by undergraduates. Based on these findings, it was recommended that a comprehensive information literacy program should be conducted to promote awareness and use of electronic information resources. It was also recommended that the library should increase the acquisition of electronic information sources while continuing to acquire general and reference materials to fulfill the current research needs of the users. Key words: User studies; User needs; User assessment; University library use; academic library use; undergraduate library use doi: 10.4038/jula.v14i1.2687 Journal of the University Librarians Association of Sri Lanka . Vol.14 (Issue 1). 2010 43-60

Barriers to tree seedling emergence on human-induced grasslands in Sri Lanka

Abstract: Summary 1. Colonization by woody plants is often very slow or absent on grasslands occupying degraded land in the tropics. Seed dispersal limitation is widely reported, but the constraints to forest succession imposed by barriers to seedling establishment are poorly understood. We tested the hypotheses that seedling emergence of woody plants is limited by interactions of anthropogenic fire, vertebrate herbivory and competition with the dominant grass sward in human-induced montane grasslands in Sri Lanka. 2. Seedling emergence was determined fortnightly for 18 months in response to experimental manipulation of fire regimes, access by vertebrate herbivores and competition from the dominant grass canopy at the forest/grassland edge and at 10, 20 and 40 m from the edge into four blocks of grassland. Seedling emergence was also monitored in the absence of any experimental manipulation at 10, 20 and 40 m into adjacent blocks of lower montane rainforest. 3. Emergence of seedlings of woody plants was much lower in the grassland (mean <0·1 seedlings m−2 year−1) than in natural forest patches (mean 6·0 seedlings m−2 year−1), but was maximal at the forest/grassland edge (mean 9·5 m−2 year−1). In the grassland, fire reduced seedling emergence by 36% in fenced vertebrate exclosures but increased seedling emergence by 68% in unfenced plots. Exclusion of vertebrate herbivores had no impact on seedling emergence at the forest/grassland edge. Removal of the grass canopy by clipping or tilling increased seedling emergence at the edge, but had no effect in the grassland. Seedlings of the woody pioneer species Macaranga indica dominated the community of emergents in the grassland and at the edge. 4. Synthesis and applications. Although dispersal limitation represents the primary constraint to forest succession on degraded montane grasslands in Sri Lanka, management of fire regimes, vertebrate herbivory and competition from the dominant grasses would influence the abundance and composition of tree seedling emergents. Tilling in narrow strips, 2–5 m wide and within 10 m of the forest edge, would facilitate the emergence and establishment of early successional trees in the grassland, but the strips would require protection from fire for at least 2 years. Within the interior of grassland patches, a combination of controlled burning and short-term access to vertebrate dispersers would promote tree seedling emergence, but the burned patches would then require long-term protection from fire and grazing subsequently to allow the emergents to establish and catalyse forest succession.

The phylogeography of Indoplanorbis exustus (Gastropoda: Planorbidae) in Asia

Abstract: The freshwater snail Indoplanorbis exustus is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. Indoplanorbis is of economic importance in that it is responsible for the transmission of several species of the genus Schistosoma which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that Indoplanorbis includes only a single species. The aims of the present study were to date the radiation of Indoplanorbis across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that I. exustus might be polyphyletic. The results indicated a radiation beginning in the late Miocene with a divergence of an ancestral bulinine lineage into Assam and peninsular India clades. A Southeast Asian clade diverged from the peninsular India clade late-Pliocene; this clade then radiated at a much more rapid pace to colonize all of the sampled range of Indoplanorbis in the mid-Pleistocene. The phylogenetic depth of divergences between the Indian clades and Southeast Asian clades, together with habitat and parasitological differences suggest that I. exustus may comprise more than one species. The timescale estimated for the radiation suggests that the dispersal to Arabia and to Southeast Asia was facilitated by palaeogeographical events and climate change, and did not require human involvement. Further samples from Afghanistan, Africa and western India are required to refine the phylogeographical hypothesis and to include the African Recent dispersal.

Changes in achievement goals and competence perceptions across the college semester

Abstract: We investigated the relationship between changes in perceptions of competence and changes in achievement goals across a college semester for students enrolled in an introductory psychology course. Two types of competence perceptions were examined: self-efficacy for learning and normative perceived ability. Changes in normative perceived ability were predicted to relate to changes in performance goals, but not mastery goals. Because mastery goals rely on self-referent standards to evaluate ability, we predicted changes in self-efficacy for learning would relate to changes in mastery goals. We also expected changes in self-efficacy for learning to relate to changes in performance goals because learning can lead to the demonstration of superior competence. The predictions were supported for mastery and performance-approach goals, but not for performance-avoidance goals. Very little change in performance-avoidance goals was observed. Scores on the first course exam also predicted change in performance-approach goals, with this effect partially mediated by competence perceptions.