Modelling organic material in activated sludge systems

A simple predictive model for the activated sludge reactor inorganic suspended solids (ISS) concentration is presented. It is based on the accumulation of influent ISS in the reactor and an ordinary heterotrophic organism (OHO) ISS content (fiOHO) of 0.15 mg ISS/mgOHOVSS and a variable phosphate accumulating organism (PAO) ISS content (fiPAO) proportional to their P content (fXBGP). The model is validated with data from 21 investigations conducted over the past 15 years on 30 aerobic and anoxic-aerobic nitrification denitrification (ND) systems and 18 anaerobic-anoxic-aerobic ND biological excess P removal (BEPR) systems variously fed artificial and real wastewater and operated from 3 to 20 d sludge age. The predicted reactor VSS/TSS ratio reflects the observed relative sensitivity to sludge age, which is low, and to BEPR, which is high. For effective use of the model for design, two significant issues require attention: measurement of the influent ISS concentration, which is not commonly done in wastewater characterisation analyses; and estimating a priori the P content of PAOs (fXBGP), which can vary considerably depending on the extent of anoxic P uptake BEPR that takes place in the system. Some guidance on selection of the mixed liquor VSS/TSS ratio for design is given

Relationships Between Gender and Alberta Diploma Scores

The purpose of this study was to investigate relationships between gender and Alberta diploma examination and school-awarded scores. Weak relationships between gender and scores were found both on Alberta diploma examination scores and on school-awarded scores. These relationships tended to be relatively greater in magnitude for school-awarded scores than for diploma examination scores, with girls generally attaining higher school-awarded scores than boys. Effect sizes of all correlations between scores and gender were in the small range. R² values showed that the overall statistical effect of gender on students' schoolawarded scores was greater than the effect on students' diploma examination scores. The greatest statistical effect for gender was on the difference between school-awarded scores and diploma examination scores, with girls having larger differences than boys.Le but de cette recherche est d'étudier le rapport entre le sexe et les notes aux examens du ministère menant à l'obtention du diplôme du secondaire en Alberta et celles découlant des examens gérés par les écoles. La corrélation entre le sexe et les notes était faible pour les deux types d'examens. Les résultats ont révélé une tendance selon laquelle la corrélation était plus importante pour les notes découlant des examens gérés par l'école, où les notes des filles étaient généralement plus élevées que celles des garçons. L'ampleur de l'effet pour toutes les corrélations entre les notes et le sexe était limitée. Les valeurs R² ont indiqué que l'effet statistique global du sexe sur la performance des élèves était plus important pour les notes découlant d'examens administrés par l'école que pour celles des examens du ministère. L'effet statistique le plus important sur le sexe consistait en la différence entre les notes aux examens administrés par l'école et les notes aux examens gérés par le ministre. Les différences les plus importantes se retrouvaient chez les filles

TeV blazar variability: the firehose instability?

Recently observed minute timescale variability of blazar emission at TeV energies has imposed severe constraints on jet models and TeV emission mechanisms. We focus on a robust jet instability to explain this variability. As a consequence of the bulk outflow of the jet plasma, the pressure is likely to be anisotropic, with the parallel pressure $P_{||}$ in the forward jet direction exceeding the perpendicular pressure $P_{\perp}$. Under these circumstances, the jet is susceptible to the firehose instability, which can cause disruptions in the large scale jet structure and result in variability of the observed radiation. For a realistic range of parameters, we find that the growth timescale of the firehose instability is $\approx$ a few minutes, in good agreement with the observed TeV variability timescales for Mrk 501 (Albert et al. 2007) and PKS 2155-304 (Aharonian et al. 2007).Comment: Accepted for publication, MNRA

The WKB Approximation without Divergences

In this paper, the WKB approximation to the scattering problem is developed without the divergences which usually appear at the classical turning points. A detailed procedure of complexification is shown to generate results identical to the usual WKB prescription but without the cumbersome connection formulas.Comment: 13 pages, TeX file, to appear in Int. J. Theor. Phy

A Modified Synchrotron Model for Knots in the M87 Jet

For explaining the broadband spectral shape of knots in the M87 jet from radio through optical to X-ray, we propose a modified synchrotron model that considers the integrated effect of particle injection from different acceleration sources in the thin acceleration region. This results in two break frequencies at two sides of which the spectral index of knots in the M87 jet changes. We discuss the possible implications of these results for the physical properties in the M87 jet. The observed flux of the knots in the M87 jet from radio to X-ray can be satisfactorily explained by the model, and the predicted spectra from ultraviolet to X-ray could be further tested by future observations. The model implies that the knots D, E, F, A, B, and C1 are unlikely to be the candidate for the TeV emission recently detected in M87.Comment: 12 pages, 1 figure, 2 tables, Accepted for publication in ApJ Letter

The Effect of Feeding Strategy on Butanol Production by Clostridium beijerinckii NCIMB 8052 Using Glucose and Xylose

We performed fed-batch fermentations of glucose and xylose mixtures producing butanol. Our aim was to develop a feeding strategy for coping with carbon catabolite repression (CCR) and sequential utilization problems as well as understanding the effect of feeding strategy on fermentation kinetics. Experimental results showed that fermenter 1 with only xylose as the initial carbon source could co-utilize sugars for all mixed sugar feeds. On the other hand, fermenter 2 with only glucose as the initial sugar showed sequential utilization. Xylose in fermenter 2 accumulated while glucose was present; it was only utilized after the glucose was completely exhausted. Besides the sugar utilization profile, the feeding strategy had an impact on the fermentation kinetics. Maximum specific growth rates were 0.68 h-1 and 0.94 h-1, for fermenter 1 and 2,respectively. Fermenter 1 produced 4.98 g/l butanol and yield was 0.28 g/g, while fermenter 2 produced 0.5 g/l butanol with a yield value of 0.05 g/g. Total sugar utilization was also higher for fermenter 1, 81 % and 46 % for fermenter 2. The feeding strategy we proposed showed that wild type Clostridium beijerinckii NCIMB 8052 can co-utilize glucose and xylose, and produce butanol. Our observation suggests that we can tackle sequential utilization problem and enhance fermentation process with the proposed feeding strategy without having to manipulate the strain.publishedVersio

Response Surface Methodology for Understanding Glucose and Xylose Utilization by Clostridium beijerinckii NCIMB 8052

We applied response surface methodology to understand the effect and extend of carbon catabolite repression (CCR) on growth of Clostridium beijerinckii NCIMB 8052 using xylose and glucose as representative lignocellulosic sugars. We performed batch growth experiments based on the central composite design with different concentrations of glucose and xylose, and estimated the respective growth rates as the response. Fitting the quadratic model with interaction coefficient to experimental data gave a good quality of fit (R-squared=0.939). We found that glucose is the most significant factor affecting the growth rate. Interaction between glucose and xylose is another highly significant factor. Response surface illustrated that increasing or decreasing both sugar concentrations at the same time results in a decreasing growth rate, and increasing either sugar concentration while decreasing the other sugar increases the growth rate. It is an important finding as it suggests that CCR can be not only from glucose on xylose but also from xylose on glucose. A transcriptional study will be necessary to understand the repression mechanism and to improve the utilization of sugars in mixed form, thus lignocellulosic fermentation processes.publishedVersio

Instanton approach to the Langevin motion of a particle in a random potential

We develop an instanton approach to the non-equilibrium dynamics in one-dimensional random environments. The long time behavior is controlled by rare fluctuations of the disorder potential and, accordingly, by the tail of the distribution function for the time a particle needs to propagate along the system (the delay time). The proposed method allows us to find the tail of the delay time distribution function and delay time moments, providing thus an exact description of the long-time dynamics. We analyze arbitrary environments covering different types of glassy dynamics: dynamics in a short-range random field, creep, and Sinai's motion.Comment: 4 pages, 1 figur

Heritability and expression of selected mixograph parameters in progeny of parents varying for mixing time

The mixograph performs certain rheological measurements during dough mixing and is a good predictor of wheat end-use quality. The aim of this study was to determine the expression and the heritability of mixing characteristics measured with Mixsmart® software and some quality characteristics in hard red spring wheat parents and their F1 progeny. Six parents varying in midline peak time and envelope peak time were crossed in a half diallel design. Parents and progeny were planted in three different environments. General combining ability (GCA) was a significant source of variation for the measured characteristics, and parents differed widely in terms of GCA effects. Midline-development time, -peak integral and -peak time showed high narrow sense heritability. Envelope peak-integral and -tail width displayed high narrow sense heritability for some, but not all locations. High GCA:SCA (specific combining ability) ratios indicated the prevalence of additive gene effects for midline-development time, -peak integral and -peak time, indicating that these characteristics are largely genetically determined, and that selection for them should lead to genetic gain

A model for community physiotherapy from the perspective of newly graduated physiotherapists as a guide to curriculum revision

Background. Limitations in physiotherapy curricula have been reported. Work-based experiences, especially during compulsory community service, could inform curricula. Objective. To develop a model of community service physiotherapy to guide curriculum reform. Methods. In this appreciative inquiry, trained physiotherapy students conducted tele-interviews with newly graduated physiotherapists. Twelve recently graduated community-service physiotherapists – heterogeneous in gender, mother tongue, university attended and work setting – were purposively recruited. Two coders applied Tesch’s coding technique to the transcripts; one did paper-based work and the other used AtlasTi software. Consensus was reached and a member check done. Results. Four themes identified were: (i) the essence of community physiotherapy; (ii) the collaborative nature of community physiotherapy; (iii) prerequisites for a positive practice environment; and (iv) community physiotherapy as a gateway to personal growth and professional development. Physiotherapists consult clients from varied cultural backgrounds, ages and health and disease profiles. Health education is a key intervention, but clients emphasised therapeutic touch. Team work enhances services, especially within a context of poverty, and prevents isolation. New graduates have to deal with inefficient management, lack of transport, inadequate equipment and needs resilience. They want discipline-specific supervision. Conclusion. Community physiotherapy makes specific demands, especially for novice therapists. Service-learning in authentic diverse contexts would foster professional development and cultural competence. Clinical competency should remain the backbone of the curriculum, complemented by competency in health education. Different ways of reflection would facilitate lifelong learning and growth in attributes such as resilience, which is necessary for dealing with sub-optimal practice environments