First assessment of the plant phenology index (PPI) for estimating gross primary productivity in African semi-arid ecosystems

The importance of semi-arid ecosystems in the global carbon cycle as sinks for CO2 emissions has recently been highlighted. Africa is a carbon sink and nearly half its area comprises arid and semi-arid ecosystems. However, there are uncertainties regarding CO2 fluxes for semi-arid ecosystems in Africa, particularly savannas and dry tropical woodlands. In order to improve on existing remote-sensing based methods for estimating carbon uptake across semi-arid Africa we applied and tested the recently developed plant phenology index (PPI). We developed a PPI-based model estimating gross primary productivity (GPP) that accounts for canopy water stress, and compared it against three other Earth observation-based GPP models: the temperature and greenness model, the greenness and radiation model and a light use efficiency model. The models were evaluated against in situ data from four semi-arid sites in Africa with varying tree canopy cover (3 to 65 percent). Evaluation results from the four GPP models showed reasonable agreement with in situ GPP measured from eddy covariance flux towers (EC GPP) based on coefficient of variation, root-mean-square error, and Bayesian information criterion. The PPI-based GPP model was able to capture the magnitude of EC GPP better than the other tested models. The results of this study show that a PPI-based GPP model is a promising tool for the estimation of GPP in the semi-arid ecosystems of Africa.Comment: Accepted manuscript; 12 pages, 4 tables, 9 figure

Feed Quantity Effect on Carp Juveniles’ Plasma Protein and Immunoglobulin Levels

Plasma protein and immunoglobulin (Ig) levels in fish can be influenced by stress reaction, caused by some nutritional factors. This paper shows effects of different feed quantity on total protein and total Ig levels in blood of common carp (Cyprinus carpio) juveniles exposed to chronic stress conditions. The study was carried out in a recirculation aquaculture system (RAS) during 96 days. Carps (initial weight 6.43±0.02 g) were distributed into four groups in three replicate tanks, 40 fish per tank. The groups were formed according to the feed quantity applied: 2, 3, 4 and 5% of commercial extruded mixture in relation to the ichthyomass (i.e. groups I, II, III and IV respectively). According to the results, the mean values of total plasma proteins and Ig were highest in group IV and the lowest in group II (p<0.05). Total protein levels were influenced by feed quantity (p<0.05), and sampling time (p<0.001). Total Ig levels were influenced by duration of the experiment i.e. sampling time (p<0.001). In all groups the mean values of plasma proteins after two month of the experiment was increased (p<0.01), and the mean values of Ig in less fed groups I and II (p<0.05 and p<0.01, respectively). Total plasma proteins and Ig were not significantly affected by water quality parameters only in the group fed 2% of feed (group I). Significant positive correlation between total proteins and Ig was determined in each experimental group (p<0.01). In terms of reducing stress and ensuring welfare in carp juveniles, applied feed amount should match to the length of fish growing in the fish tanks, stocking density and capacity of the system for efficient water purification

Accounting for self-protective responses in randomized response data from a social security survey using the zero-inflated Poisson model

In 2004 the Dutch Department of Social Affairs conducted a survey to assess the extent of noncompliance with social security regulations. The survey was conducted among 870 recipients of social security benefits and included a series of sensitive questions about regulatory noncompliance. Due to the sensitive nature of the questions the randomized response design was used. Although randomized response protects the privacy of the respondent, it is unlikely that all respondents followed the design. In this paper we introduce a model that allows for respondents displaying self-protective response behavior by consistently giving the nonincriminating response, irrespective of the outcome of the randomizing device. The dependent variable denoting the total number of incriminating responses is assumed to be generated by the application of randomized response to a latent Poisson variable denoting the true number of rule violations. Since self-protective responses result in an excess of observed zeros in relation to the Poisson randomized response distribution, these are modeled as observed zero-inflation. The model includes predictors of the Poisson parameters, as well as predictors of the probability of self-protective response behavior.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS135 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Enhanced Stability and Efficiency for Photoelectrochemical Iodide Oxidation by Methyl Termination and Electrochemical Pt Deposition of n-Si Microwire Arrays

Arrays of Si microwires doped n-type (n-Si) and surface-functionalized with methyl groups have been used, with or without deposition of Pt electrocatalysts, to photoelectrochemically oxidize I–(aq) to I_3–(aq) in 7.6 M HI(aq). Under conditions of iodide oxidation, methyl-terminated n-Si microwire arrays exhibited stable short-circuit photocurrents over a time scale of days, albeit with low energy-conversion efficiencies. In contrast, electrochemical deposition of Pt onto methyl-terminated n-Si microwire arrays consistently yielded energy-conversion efficiencies of ∼2% for iodide oxidation, with an open-circuit photovoltage of ∼400 mV and a short-circuit photocurrent density of ∼10 mA cm^(–2) under 100 mW cm^(–2) of simulated air mass 1.5G solar illumination. Platinized electrodes were stable for >200 h of continuous operation, with no discernible loss of Si or Pt. Pt deposited using electron-beam evaporation also resulted in stable photoanodic operation of the methyl-terminated n-Si microwire arrays but yielded substantially lower photovoltages than when Pt was deposited electrochemically

Unassisted solar-driven photoelectrosynthetic HI splitting using membrane-embedded Si microwire arrays

Free-standing, membrane-embedded, Si microwire arrays have been used to affect the solar-driven, unassisted splitting of HI into H_2 and I_3−. The Si microwire arrays were grown by a chemical-vapor-deposition vapor–liquid–solid growth process using Cu growth catalysts, with a radial n+p junction then formed on each microwire. A Nafion proton-exchange membrane was introduced between the microwires and Pt electrocatalysts were then photoelectrochemically deposited on the microwires. The composite Si/Pt–Nafion membrane was mechanically removed from the growth substrate, and Pt electrocatalysts were then also deposited on the back side of the structure. The resulting membrane-bound Si microwire arrays spontaneously split concentrated HI into H_2(g) and I_3− under 1 Sun of simulated solar illumination. The reaction products (i.e. H_2 and I_3−) were confirmed by mass spectrometry and ultraviolet–visible electronic absorption spectroscopy

LitMiner: integration of library services within a bio-informatics application

BACKGROUND: This paper examines how the adoption of a subject-specific library service has changed the way in which its users interact with a digital library. The LitMiner text-analysis application was developed to enable biologists to explore gene relationships in the published literature. The application features a suite of interfaces that enable users to search PubMed as well as local databases, to view document abstracts, to filter terms, to select gene name aliases, and to visualize the co-occurrences of genes in the literature. At each of these stages, LitMiner offers the functionality of a digital library. Documents that are accessible online are identified by an icon. Users can also order documents from their institution's library collection from within the application. In so doing, LitMiner aims to integrate digital library services into the research process of its users. METHODS: Case study RESULTS: This integration of digital library services into the research process of biologists results in increased access to the published literature. CONCLUSION: In order to make better use of their collections, digital libraries should customize their services to suit the research needs of their patrons

Enhanced Stability and Efficiency for Photoelectrochemical Iodide Oxidation by Methyl Termination and Electrochemical Pt Deposition of n-Si Microwire Arrays

Arrays of Si microwires doped n-type (n-Si) and surface-functionalized with methyl groups have been used, with or without deposition of Pt electrocatalysts, to photoelectrochemically oxidize I–(aq) to I_3–(aq) in 7.6 M HI(aq). Under conditions of iodide oxidation, methyl-terminated n-Si microwire arrays exhibited stable short-circuit photocurrents over a time scale of days, albeit with low energy-conversion efficiencies. In contrast, electrochemical deposition of Pt onto methyl-terminated n-Si microwire arrays consistently yielded energy-conversion efficiencies of ∼2% for iodide oxidation, with an open-circuit photovoltage of ∼400 mV and a short-circuit photocurrent density of ∼10 mA cm^(–2) under 100 mW cm^(–2) of simulated air mass 1.5G solar illumination. Platinized electrodes were stable for >200 h of continuous operation, with no discernible loss of Si or Pt. Pt deposited using electron-beam evaporation also resulted in stable photoanodic operation of the methyl-terminated n-Si microwire arrays but yielded substantially lower photovoltages than when Pt was deposited electrochemically

Analysing cognitive test data: Distributions and non-parametric random effects

An important assumption in many linear mixed models is that the conditional distribution of the response variable is normal. This assumption is violated when the models are fitted to an outcome variable that counts the number of correctly answered questions in a questionnaire. Examples include investigations of cognitive decline where models are fitted to Mini Mental State Examination scores, the most widely used test to measure global cognition. Mini Mental State Examination scores take integer values in the 0–30 range, and its distribution has strong ceiling and floor effects. This article explores alternative distributions for the outcome variable in mixed models fitted to mini mental state examination scores from a longitudinal study of ageing. Model fit improved when a beta-binomial distribution was chosen as the distribution for the response variable

Observation of Photovoltaic Action from Photoacid-Modified Nafion Due to Light-Driven Ion Transport

Replacing passive ion-exchange membranes, like Nafion, with membranes that use light to drive ion transport would allow membranes in photoelectrochemical technologies to serve in an active role. Toward this, we modified perfluorosulfonic acid ionomer membranes with organic pyrenol-based photoacid dyes to sensitize the membranes to visible light and initiate proton transport. Covalent modification of the membranes was achieved by reacting Nafion sulfonyl fluoride poly(perfluorosulfonyl fluoride) membranes with the photoacid 8-hydroxypyrene-1,3,6-tris(2-aminoethylsulfonamide). The modified membranes were strongly colored and maintained a high selectivity for cations over anions. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ion-exchange measurements together provided strong evidence of covalent bond formation between the photoacids and the polymer membranes. Visible-light illumination of the photoacid-modified membranes resulted in a maximum power-producing ionic photoresponse of ∼100 μA/cm2 and ∼1 mV under 40 Suns equivalent excitation with 405 nm light. In comparison, membranes that did not contain photoacids and instead contained ionically associated RuII-polypyridyl coordination compound dyes, which are not photoacids, exhibited little-to-no photoeffects (∼1 μA/cm2). These disparate photocurrents, yet similar yields for nonradiative excited-state decay from the photoacids and the RuII dyes, suggest temperature gradients were not likely the cause of the observed photovoltaic action from photoacid-modified membranes. Moreover, spectral response measurements supported that light absorption by the covalently bound photoacids was required in order to observe photoeffects. These results represent the first demonstration of photovoltaic action from an ion-exchange membrane and offer promise for supplementing the power demands of electrochemical processes with renewable sunlight-driven ion transport