A delay differential model of ENSO variability: Parametric instability and the distribution of extremes

We consider a delay differential equation (DDE) model for El-Nino Southern Oscillation (ENSO) variability. The model combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. We perform stability analyses of the model in the three-dimensional space of its physically relevant parameters. Our results illustrate the role of these three parameters: strength of seasonal forcing $b$, atmosphere-ocean coupling $\kappa$, and propagation period $\tau$ of oceanic waves across the Tropical Pacific. Two regimes of variability, stable and unstable, are separated by a sharp neutral curve in the $(b,\tau)$ plane at constant $\kappa$. The detailed structure of the neutral curve becomes very irregular and possibly fractal, while individual trajectories within the unstable region become highly complex and possibly chaotic, as the atmosphere-ocean coupling $\kappa$ increases. In the unstable regime, spontaneous transitions occur in the mean ``temperature'' ({\it i.e.}, thermocline depth), period, and extreme annual values, for purely periodic, seasonal forcing. The model reproduces the Devil's bleachers characterizing other ENSO models, such as nonlinear, coupled systems of partial differential equations; some of the features of this behavior have been documented in general circulation models, as well as in observations. We expect, therefore, similar behavior in much more detailed and realistic models, where it is harder to describe its causes as completely.Comment: 22 pages, 9 figure

Teachers’ Expectations of Educational Leaders’ Leadership Approach and Perspectives on the Principalship: Identifying Critical Leadership Paradigms for the 21st Century

Using an exploratory design, with a sample of 97 teachers, this research sought to ascertain teachers’ perspectives on the behaviours and approaches that educational leaders, particularly their principals, should display. This exploration was done against the backdrop of the attitudes to, and expectations of, leaders that are deemed to be characteristics 21st century perspectives on leadership. The research uncovered four main behaviours that teachers expected their principals and other educational leaders to employ in their leadership approaches. These behaviours are: recognition of staff’s commitment, facilitation of participation in decision-making, embrace of teachers’ diverse strengths, and openness to criticism. The four behaviours are captured under the acronym RePaDo and designated “Paradigm RePaDo”. The factors account for 54.53% of the variation in the data which were extracted from a 33-item self-designed instrument. The data analysis was conducted using SPSS V 22. The study makes four recommendations for how principals and other educational leaders may improve their leadership practice

Development of ‘RL Plus’: winter wheat variety performance in relation to site characteristics (HGCA Project Report No. 365)

This project developed RL Plus, an augmented version of the Recommended Lists for Cereals and Oilseeds, published by the HGCA on CD and the internet (http://www.hgca.com) to provide the cereals and oilseeds industry with means of interrogating and analysing data from HGCA-funded variety trials. Given that RL Plus is fully documented and published in electronic form, it is not described further here. This report is confined to additional research analysing relative variety performance of winter wheat in terms of site characteristics. A spreadsheet was constructed of treated yields of winter wheat from 43 varieties across 506 trials (Recommended List, National List or BSPB trials) in the UK from harvests during 1992-2002. This included site information collected from the trials, and supplemented with the site location (OS coordinates), soil types, meteorological data and drought index derived during the project. Complete, or nearcomplete, data existed for 249 trials from harvests during 1993-2003. These data were used to investigate factors associated with site variation in variety yields. Data-mining techniques were used to identify site variables that explained variation in variety yields between sites. This information was used to build models to describe and predict patterns of variety variability due to site differences. Variation in variety yields could be modelled in terms of overall variety differences (43% variety variation accounted for), and variety interactions with large-scale trend due to geographic location (general climate, 16%), small-scale location trend specific to years (micro-climates, 14%), expected site yield (2%), late sown crops (crops sown on/after 30 October, 0.4%), sites with sandy or shallow soil (0.5%), sites with low soil K index (0.4%), differences between years (4.5%), differences between sites (unexplained by site variables, 2%), and other unexplained variation (18%). Further investigation suggested that other site variables, such as previous cropping, might also influence variety variability but that the relationship was local (differed between regions). The results of the statistical analysis can be used to optimise use of the ‘Varieties on your Farm’ module of RL Plus. In general, geographic location appears to be the most important site variable influencing variation in variety yields across the UK. However, for particular varieties, the expected site yield, soil type or soil K index may be equally important

Lack of analgesic efficacy in female rats of\ud the commonly recommended oral dose of\ud buprenorphine

Previous work in our laboratory showed that the recommended oral dose of buprenorphine (0.5 mg/kg) was not as effective\ud as the standard therapeutic subcutaneous dose for postoperative analgesia in male Long-Evans (hooded) and Sprague-Dawley (albino) rats. The aim of the current study was to extend this analysis to female rats. We measured the pain threshold in adult female rats in diestrus or proestrus before and 30 and 60 min after oral buprenorphine (0.5 mg/kg,), the standard subcutaneous dose of buprenorphine (0.05 mg/kg), or vehicle only (1 ml/kg each orally and subcutaneously). Female rats showed an increased pain threshold (analgesia) after subcutaneous buprenorphine but no change in pain threshold after either oral buprenorphine or vehicle only. Estrous cycle stage (proestrus versus diestrus) did not affect the analgesic effects of buprenorphine, but rats in proestrus showed significantly lower pain thresholds (less tolerance to pain) than did those in diestrus. These results show that the oral dose of buprenorphine recommended for postoperative analgesic care does not induce significant analgesia in female rats and therefore is not as effective as the standard subcutaneous dose

Nitrogen uptake strategies of edaphically specialized Bornean tree species

The association of tree species with particular soil types contributes to high b diversity in forests, but the mechanisms producing such distributions are still debated. Soil nitrogen (N) often limits growth and occurs in differentially available chemical forms. In a Bornean forest where tree species composition changes dramatically along a soil gradient varying in supplies of different N-forms, we investigated whether tree species’ N-uptake and soil specialization strategies covaried. We analyzed foliar 15N natural abundance for a total of 216 tree species on clay or sandy loam (the soils at the gradient’s extremes) and conducted a 15N-tracer experiment with nine specialist and generalist species to test whether species displayed flexible or differential uptake of ammonium and nitrate. Despite variation in ammonium and nitrate supplies and nearly 4 % difference in foliar δ15N between most soil specialists and populations of generalists on these soils, our 15N tracer experiment showed little support for the hypothesis that soil specialists vary in N-form use or the ratios in which they use these forms. Instead, our results indicate that these species possess flexible capacities to take up different inorganic N forms. Variation between soil specialists in uptake of different N forms is thus unlikely to cause the soil associations of tree species and high b diversity characteristic of this Bornean rain forest. Flexible uptake strategies would facilitate N-acquisition when supply rates of N-forms exhibit spatiotemporal variation and suggest that these species may be functionally redundant in their responses to N gradients and influences on ecosystem N-cycles

Intragenic repeat expansion in the cell wall protein gene HPF1 controls yeast chronological aging

Aging varies among individuals due to both genetics and environment, but the underlying molecular mechanisms remain largely unknown. Using a highly recombined Saccharomyces cerevisiae population, we found 30 distinct quantitative trait loci (QTLs) that control chronological life span (CLS) in calorie-rich and calorie-restricted environments and under rapamycin exposure. Calorie restriction and rapamycin extended life span in virtually all genotypes but through different genetic variants. We tracked the two major QTLs to the cell wall glycoprotein genes FLO11 and HPF1. We found that massive expansion of intragenic tandem repeats within the N-terminal domain of HPF1 was sufficient to cause pronounced life span shortening. Life span impairment by HPF1 was buffered by rapamycin but not by calorie restriction. The HPF1 repeat expansion shifted yeast cells from a sedentary to a buoyant state, thereby increasing their exposure to surrounding oxygen. The higher oxygenation altered methionine, lipid, and purine metabolism, and inhibited quiescence, which explains the life span shortening. We conclude that fast-evolving intragenic repeat expansions can fundamentally change the relationship between cells and their environment with profound effects on cellular lifestyle and longevity

Shared and selective neural correlates of inhibition, facilitation, and shifting processes during executive control

A network of prefrontal and parietal regions has been implicated in executive control processes. However, the extent to which individual regions within this network are engaged in component control processes, such as inhibition of task-irrelevant stimulus attributes or shifting (switching) between attentional foci, remains controversial. Participants (N = 17) underwent functional magnetic resonance imaging while performing a global–local task in which the global and local levels could facilitate or interfere with one another. Stimuli were presented in blocks in which participants either constantly shifted between the global and local levels, or consistently responded to one level only. Activations related to inhibition and shifting processes were observed in a large network of bilateral prefrontal, parietal, and basal ganglia regions. Region of interest analyses were used to classify each region within this network as being common to inhibition and shifting, or preferential to one component process. Several regions were classified as being preferential to inhibition, including regions within the dorsolateral and ventrolateral prefrontal cortex, the parietal lobes, and the temporal–parietal junction. A limited set of regions in the parietal lobes and left dorsolateral prefrontal cortex were classified as preferential to shifting. There was a very large set of regions displaying activation common to both inhibition and shifting processes, including regions within the dorsolateral prefrontal cortex, anterior cingulate, and basal ganglia. Several of these common regions were also involved during facilitation, suggesting that they are responsive to the number of task-salient channels of information, rather than purely to demands on control processes.National Institute of Mental Health (U.S.) (MH061426)National Institute on Aging (AG021847

Geometric matrix midranges

We define geometric matrix midranges for positive definite Hermitian matrices and study the midrange problem from a number of perspectives. Special attention is given to the midrange of two positive definite matrices before considering the extension of the problem to $N > 2$ matrices. We compare matrix midrange statistics with the scalar and vector midrange problem and note the special significance of the matrix problem from a computational standpoint. We also study various aspects of geometric matrix midrange statistics from the viewpoint of linear algebra, differential geometry and convex optimization.ECH2020 EUROPEAN RESEARCH COUNCIL (ERC) (670645

Staging for prostate cancer

BACKGROUND. The American Joint Committee on Cancer (AJCC) staging system for prostate cancer is based primarily based on clinical tumor (T) classification. In this article, the authors summarize arguments for incorporating additional pretreatment parameters and creating a new staging system for prostate cancer. METHODS. Men with localized prostate cancer who received treatment with external beam radiation alone were analyzed using the 1997 AJCC staging system compared with a system that included pretreatment prostate-specific antigen (pPSA) level and Gleason score (GS). Multivariate analyses using a Cox proportional-hazards model were carried out to evaluate T classification, GS, and pPSA as predictors of overall survival (OS), disease-specific survival (DSS), and freedom from PSA failure (FFPF). RESULTS. Based on pretreatment characteristics in a series of contemporary patients, only 0.6% of patients were classified with AJCC stage I disease, 16.0% were classified with AJCC stage III disease, and 83.4% were classified with AJCC stage II disease. Multivariate analyses indicated the independent statistical significance of T classification, GS, and pPSA in predicting OS, DSS, and FFPF (model chi-square value, P < .0001 for each). Using these 3 predictors, subsets of patients who had similar outcomes were combined to provide examples of the insensitivity of the AJCC system for predicting outcomes. Incorporating pPSA and GS allowed the identification of differences in OS, DSS, and FFPF for subsets of patients with AJCC stage II disease ( P < .0001, P = .005, and P < .0001, respectively). CONCLUSIONS. The current AJCC staging system does not divide contemporary patients with prostate cancer into prognostic subgroups and does not identify patients who have comparable biochemical control and survival. The AJCC staging system for prostate cancer should be changed to incorporate pPSA, GS, and risk stratification. Cancer 2007. © 2006 American Cancer Society.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55927/1/22403_ftp.pd

Microblogging, constituency service and impression management – UK MPs and the use of Twitter

Twitter, a microblogging site which allows users to deliver statements, thoughts and links in 140 characters to followers as well as a wider Internet audience, is the latest online communications technology adopted by MPs. Assessing the use of early adopters, this article considers which MPs are most likely to use Twitter (e.g. tweeting), and how. Content analysis of tweeting MPs was conducted, and identified personal and political characteristics which may influence use. The data suggested that of the six characteristics tested, gender, party and seniority had most impact on adoption. Applying Jones and Pittman’s (1982) typology there is clear evidence that MPs use Twitter as a tool of impression management. Constituency service is a secondary function of the use of Twitter by MPs. Where MPs use Twitter as part of their constituency role it is to promote their local activity. We note that a small group of MPs use Twitter as a regular communication channel, but most are only occasionally dipping their toe into the microbloggersphere