Modelling effects of prolonged conditioning on dormancy and germination of Striga hermonthica

The impact of environment on the germination biology of the parasite was studied in the laboratory with seeds conditioned at various water potentials, urea concentrations and at 17.5 to 37.5°C for up to 133 days. Maximum germination was observed at 20 to 25°C. Water stress and urea suppressed maximum germination. The final percentage germination response to period of conditioning showed a non-linear relationship and suggests the release of seeds from dormancy during the initial period and later on dormancy induction. Germination percentage increased with increase in conditioning period to a threshold and remained stable for variable periods followed by a decline with further extension of conditioning time. The decline in germination finally terminated in zero germination in most treatments before the end of experimentation. The investigated factors of temperature, water potential and urea showed clear effects on the expression of dormancy pattern of the parasite. The effects of water potential and urea were viewed as modifying a primary response of seeds to temperature during conditioning. The changes in germinability potential during conditioning were consistent with the hypothesis that dormancy periods are normally distributed within seed populations and that loss of primary dormancy precedes induction of secondary dormancy. Hence an additive mathematical model of loss of primary dormancy and induction of secondary as affected by environment was developed as: G = {[Φ-1 (Kp+ (po+pnN+pwW) (T-Tb) t)]-[Φ-1 (Ks+ ((swW+sa)+sorT)t)]}[Φ-1(aT2+bT+c+cwW)].

Impact of Bt cotton on farmer livelihoods in South Africa

The economic benefits of Genetically Modified (GM) crops in developing countries have been well documented, but little research has been undertaken to date on the impacts of GM adoption on household livelihoods. The research reported here aimed to assess the livelihood impacts of the adoption of Bt cotton in South Africa., and involved 100 interviews of resource-poor farmers growing Bt cotton in Makhathini Flats, South Africa. Some 88% of respondents reported a higher income from Bt compared to non-Bt varieties previously grown by them, and this higher income was used primarily for greater education of their children (76%), more investment in growing cotton (46%), repaying debt (28%), investment in other crops (20%) and spending money on themselves. Some 89% had increased their asset base due to Bt cotton, primarily by increasing their cultivable land. These benefits of Bt adoption appeared widespread regardless of gender or farm size.

Phylogenomics of eukaryotes: Impact of missing data on large alignments

Resolving the relationships between Metazoa and other eukaryotic groups as well as between metazoan phyla is central to the understanding of the origin and evolution of animals. The current view is based on limited data sets, either a single gene with many species (e.g., ribosomal RNA) or many genes but with only a few species. Because a reliable phylogenetic inference simultaneously requires numerous genes and numerous species, we assembled a very large data set containing 129 orthologous proteins (similar to30,000 aligned amino acid positions) for 36 eukaryotic species. Included in the alignments are data from the choanoflagellate Monosiga ovata, obtained through the sequencing of about 1,000 cDNAs. We provide conclusive support for choanoflagellates as the closest relative of animals and for fungi as the second closest. The monophyly of Plantae and chromalveolates was recovered but without strong statistical support. Within animals, in contrast to the monophyly of Coelomata observed in several recent large-scale analyses, we recovered a paraphyletic Coelamata, with nematodes and platyhelminths nested within. To include a diverse sample of organisms, data from EST projects were used for several species, resulting in a large amount of missing data in our alignment (about 25%). By using different approaches, we verify that the inferred phylogeny is not sensitive to these missing data. Therefore, this large data set provides a reliable phylogenetic framework for studying eukaryotic and animal evolution and will be easily extendable when large amounts of sequence information become available from a broader taxonomic range.

The impact of parents' expectations on parenting behaviour: an experimental investigation

Over-involved parenting is commonly hypothesized to be it risk factor for the development of anxiety disorders in childhood. This parenting style may result from parental attempts to prevent child distress based on expectations that the child will be unable to cope in a challenging situation. Naturalistic studies are limited in their ability to disentangle the overlapping contribution of child and parent factors in driving parental behaviours. To overcome this difficulty, an experimental study was conducted in which parental expectations of child distress were manipulated and the effects on parent behaviour and child mood were assessed. Fifty-two children (aged 7 - 11 years) and their primary caregiver participated. Parents were allocated to either a "positive" or a "negative" expectation group. Observations were made of the children and their parents interacting whilst completing a difficult anagram task. Parents given negative expectations of their child's response displayed higher levels of involvement. No differences were found on indices of child mood and behaviour and possible explanations for this are considered. The findings are consistent with suggestions that increased parental involvement may be a "natural" reaction to enhanced perceptions of child vulnerability and an attempt to avoid child distress.

Impact of stratospheric variability on tropospheric climate change

An improved stratospheric representation has been included in simulations with the Hadley Centre HadGEM1 coupled ocean atmosphere model with natural and anthropogenic forcings for the period 1979–2003. An improved stratospheric ozone dataset is employed that includes natural variations in ozone as well as the usual anthropogenic trends. In addition, in a second set of simulations the quasi biennial oscillation (QBO) of stratospheric equatorial zonal wind is also imposed using a relaxation towards ERA-40 zonal wind values. The resulting impact on tropospheric variability and trends is described. We show that the modelled cooling rate at the tropopause is enhanced by the improved ozone dataset and this improvement is even more marked when the QBO is also included. The same applies to warming trends in the upper tropical troposphere which are slightly reduced. Our stratospheric improvements produce a significant increase of internal variability but no change in the positive trend of annual mean global mean near-surface temperature. Warming rates are increased significantly over a large portion of the Arctic Ocean. The improved stratospheric representation, especially the QBO relaxation, causes a substantial reduction in near-surface temperature and precipitation response to the El Chichón eruption, especially in the tropical region. The winter increase in the phase of the northern annular mode observed in the aftermath of the two major recent volcanic eruptions is partly captured, especially after the El Chichón eruption. The positive trend in the southern annular mode (SAM) is increased and becomes statistically significant which demonstrates that the observed increase in the SAM is largely subject to internal variability in the stratosphere. The possible inclusion in simulations for future assessments of full ozone chemistry and a gravity wave scheme to internally generate a QBO is discussed.

Simulating the impact of regulation changes on the market for prostitution services

The paper draws on recent research on the economics of prostitution focussing on the role of stigma in shaping the interaction between demand and supply and the resulting sub-markets in which this activity is typically organised. Here we extend the framework to consider the role of reputation and stigma in determining policy decisions regarding the regulation of prostitution and show how sub-optimal outcomes (from the point of view of the welfare of sex workers) may prevail.

An analysis of the impact of R&D on productivity using Bayesian model averaging with a reversible jump algorithm.

A Bayesian Model Averaging approach to the estimation of lag structures is introduced, and applied to assess the impact of R&D on agricultural productivity in the US from 1889 to 1990. Lag and structural break coefficients are estimated using a reversible jump algorithm that traverses the model space. In addition to producing estimates and standard deviations for the coe¢ cients, the probability that a given lag (or break) enters the model is estimated. The approach is extended to select models populated with Gamma distributed lags of di¤erent frequencies. Results are consistent with the hypothesis that R&D positively drives productivity. Gamma lags are found to retain their usefulness in imposing a plausible structure on lag coe¢ cients, and their role is enhanced through the use of model averaging.

A human volunteer study to assess the impact of confectionery sweeteners on the gut microbiota composition.

Sweeteners are being sourced to lower the energetic value of confectionery including chocolates. Some, especially non-digestible carbohydrates, may possess other benefits for human health upon their fermentation by the colonic microbiota. The present study assessed non-digestible carbohydrate sweeteners, selected for use in low-energy chocolates, for their ability to beneficially modulate faecal bacterial profiles in human volunteers. Forty volunteers consumed a test chocolate (low-energy or experimental chocolate) containing 22·8 g of maltitol (MTL), MTL and polydextrose (PDX), or MTL and resistant starch for fourteen consecutive days. The dose of the test chocolates was doubled every 2 weeks over a 6-week period. Numbers of faecal bifidobacteria significantly increased with all the three test treatments. Chocolate containing the PDX blend also significantly increased faecal lactobacilli (P = 0·00 001) after the 6 weeks. The PDX blend also showed significant increases in faecal propionate and butyrate (P = 0·002 and 0·006, respectively). All the test chocolates were well tolerated with no significant change in bowel habit or intestinal symptoms even at a daily dose of 45·6 g of non-digestible carbohydrate sweetener. This is of importance not only for giving manufacturers a sugar replacement that can reduce energetic content, but also for providing a well-tolerated means of delivering high levels of non-digestible carbohydrates into the colon, bringing about improvements in the biomarkers of gut health.

The impact of country risk on international real estate returns

Commercial real estate investors have well-established methods to assess the risks of a property investment in their home country. However, when the investment decision is overseas another dimension of uncertainty overlays the analysis. This additional dimension, typically called country risk, encompasses the uncertainty of achieving expected financial results solely due to factors relating to the investment’s location in another country. However, very little has been done to examine the effects of country risk on international real estate returns, even though in international investment decisions considerations of country risk dominate asset investment decisions. This study extends the literature on international real estate diversification by empirically estimating the impact of country risk, as measured by Euromoney, on the direct real estate returns of 15 countries over the period 1998-2004, using a pooled regression analysis approach. The results suggest that country risk data may help investor’s in their international real estate decisions since the country risk data shows a significant and consistent impact on real estate return performance.

The impact of exchanges rates on international real estate portfolio allocation

This paper, examines whether the asset holdings and weights of an international real estate portfolio using exchange rate adjusted returns are essentially the same or radically different from those based on unadjusted returns. The results indicate that the portfolio compositions produced by exchange rate adjusted returns are markedly different from those based on unadjusted returns. However following the introduction of the single currency the differences in portfolio composition are much less pronounced. The findings have a practical consequence for the investor because they suggest that following the introduction of the single currency international investors can concentrate on the real estate fundamentals when making their portfolio choices, rather than worry about the implications of exchange rate risk.