Determination of external and internal mass transfer limitation in nitrifying microbial aggregates

In this article we present a study of the effects of external and internal mass transfer limitation of oxygen in a nitrifying system. The oxygen uptake rates (OUR) were measured on both a macro-scale with a respirometric reactor using off-gas analysis (Titrimetric and Off-Gas Analysis (TOGA) sensor) and on a micro-scale with microsensors. These two methods provide independent, accurate measurements of the reaction rates and concentration profiles around and in the granules. The TOGA sensor and micro-sensor measurements showed a significant external mass transfer effect at low dissolved oxygen (DO) concentrations in the bulk liquid while it was insignificant at higher DO concentrations. The oxygen distribution with anaerobic or anoxic conditions in the center clearly shows major mass transfer limitation in the aggregate interior. The large drop in DO concentration of 22 - 80% between the bulk liquid and aggregate surface demonstrates that the external mass transfer resistance is also highly important. The maximum OUR even for floccular biomass was only attained at much higher DO concentrations ( approximate to 8 mg/L) than typically used in such systems. For granules, the DO required for maximal activity was estimated to be > 20mg/L, clearly indicating the effects of the major external and internal mass transfer limitations on the overall biomass activity. Smaller aggregates had a larger volumetric OUR indicating that the granules may have a lower activity in the interior part of the aggregate. (C) 2004 Wiley Periodicals, Inc.

Tertiapin-Q blocks recombinant and native large conductance K+ channels in a use-dependent manner

Tertiapin, a short peptide from honey bee venom, has been reported to specifically block the inwardly rectifying K+ (Kir) channels, including G protein-coupled inwardly rectifying potassium channel (GIRK) 1 + GIRK4 heteromultimers and ROMK1 homomultimers. In the present study, the effects of a stable and functionally similar derivative of tertiapin, tertiapin-Q, were examined on recombinant human voltage-dependent Ca2+-activated large conductance K+ channel (BK or MaxiK; alpha-subunit or hSlo1 homomultimers) and mouse inwardly rectifying GIRK1 + GIRK2 (i.e., Kir3.1 and Kir3.2) heteromultimeric K+ channels expressed in Xenopus oocytes and in cultured newborn mouse dorsal root ganglion (DRG) neurons. In two-electrode voltage-clamped oocytes, tertiapin-Q (1-100 nM) inhibited BK-type K+ channels in a use- and concentration-dependent manner. We also confirmed the inhibition of recombinant GIRK1 + GIRK2 heteromultimers by tertiapin-Q, which had no effect on endogenous depolarization- and hyperpolarization-activated currents sensitive to extracellular divalent cations (Ca2+, Mg2+, Zn2+, and Ba2+) in defolliculated oocytes. In voltage-clamped DRG neurons, tertiapin-Q voltage- and use-dependently inhibited outwardly rectifying K+ currents, but Cs+-blocked hyperpolarization-activated inward currents including I-H were insensitive to tertiapin-Q, baclofen, barium, and zinc, suggesting absence of functional GIRK channels in the newborn. Under current-clamp conditions, tertiapin-Q blocked the action potential after hyperpolarization (AHP) and increased action potential duration in DRG neurons. Taken together, these results demonstrate that the blocking actions of tertiapin-Q are not specific to Kir channels and that the blockade of recombinant BK channels and native neuronal AHP currents is use-dependent. Inhibition of specific types of Kir and voltage-dependent Ca2+-activated K+ channels by tertiapin-Q at nanomolar range via different mechanisms may have implications in pain physiology and therapy.

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87-0.97 g/g starch associated with 1.5-2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.

Simultaneous saccharification and fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of simultaneous saccharification and fermentation (SSF) for lactic acid production by fungal species of Rhizopus arrhizus 36017 and Rhizopus oryzae 2062 was studied with respect to growth pH, temperature and substrate. Both R. arrhizus 36017 and R. oryzae 2062 had a capacity to carry out a single stage SSF process for lactic acid production from potato starch wastewater. The kinetic characteristics, termed as starch hydrolysis, accumulation of reducing sugars, lactic acid production and fungal biomass formation, were affected with variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.85-0.92 g/g associated with 1.5-3.5 g/l fungal biomass produced in 36-48 h fermentation. R. arrhizus 36017 had a higher capacity to produce lactic acid, while R. oryzae 2062 produced more fungal biomass under similar conditions. (c) 2005 Elsevier B.V. All rights reserved.

Uptake and metabolism of ginsenoside Rh2 and its aglycon protopanaxadiol by Caco-2 cells

The uptake and metabolism profiles of ginsenoside Rh2 and its aglycon protopanaxadiol (ppd) were studied in the human epithelial Caco-2 cell line. High-performance liquid chromatography-mass spectrometry was applied to determine Rh2 and its aglycon ppd concentration in the cells at different pH, temperature, concentration levels and in the presence or absence of inhibitors. Rh2 uptake was time and concentration dependent, and its uptake rates were reduced by metabolic inhibitors and influenced by low temperature, thus indicating that the absorption process was energy-dependent. Drug uptake was maximal when the extracellular pH was 7.0 for Rh2 and 8.0 for ppd. Rh2 kinetic analysis showed that a non-saturable component (K-d 0.17 nmol (.) h(-1) (.) mg(-1) protein) and an active transport system with a K-m of 3.95 mumol (.) l(-1) and a V-max of 4.78 nmol(.)h(-1) (.)mg(-1) protein were responsible for the drug uptake. Kinetic analysis of ppd showed a non-saturable component (K-d 0.78 nmol (.) h(-1) (.) mg(-1) protein). It was suggested that active extrusion of P-glycoprotein and drug degradation in the intestine may influence Rh2 bioavailability.

Dispersion and size control of layered double hydroxide nanoparticles in aqueous solutions

We report a simple but efficient method to prepare stable homogeneous suspensions containing monodispersed MgAl layered double hydroxide (LDH) nanoparticles that have wide promising applications in cellular drug ( gene) delivery, polymer/LDH nanocomposites, and LDH thin films for catalysis, gas separation, sensing, and electrochemical materials. This new method involves a fast coprecipitation followed by controlled hydrothermal treatment under different conditions and produces stable homogeneous LDH suspensions under variable hydrothermal treatment conditions. Moreover, the relationship between the LDH particle size and the hydrothermal treatment conditions ( time, temperature, and concentration) has been systematically investigated, which indicates that the LDH particle size can be precisely controlled between 40 and 300 nm by adjusting these conditions. The reproducibility of making the identical suspensions under identical conditions has been confirmed with a number of experiments. The dispersion of agglomerated LDH aggregates into individual LDH crystallites during the hydrothermal treatment has been further discussed. This method has also been successfully applied to preparing stable homogeneous LDH suspensions containing various other metal ions such as Ni2+, Fe2+, Fe3+, Co2+, Cd2+, and Gd3+ in the hydroxide layers and many inorganic anions such as Cl-, CO32-, NO3-, and SO42-.

Physical activity and strength of the femoral neck during the adolescent growth spurt: A longitudinal analysis

Loading of the femoral neck (FN) is dominated by bending and compressive stresses. We hypothesize that adaptation of the FN to physical activity would be manifested in the cross-sectional area (CSA) and section modulus (Z) of bone, indices of axial and bending strength, respectively. We investigated the influence of physical activity on bone strength during adolescence using 7 years of longitudinal data from 109 boys and 121 girls from the Saskatchewan Paediatric Bone and Mineral Accrual Study (PBMAS). Physical activity data (PAC-Q physical activity inventory) and anthropometric measurements were taken every 6 months and DXA bone scans were measured annually (Hologic QDR2000, array mode). We applied hip structural analysis to derive strength and geometric indices of the femoral neck using DXA scans. To control for maturation, we determined a biological maturity age defined as years from age at peak height velocity (APHV). To account for the repeated measures within individual nature of longitudinal data, multilevel random effects regression analyses were used to analyze the data. When biological maturity age and body size (height and weight) were controlled, in both boys and girls, physical activity was a significant positive independent predictor of CSA and Z of the narrow region of the femoral neck (P < 0.05). There was no independent effect of physical activity on the subperiosteal width of the femoral neck. When leg length and leg lean mass were introduced into the random effects models to control for size and muscle mass of the leg (instead of height and weight), all significant effects of physical activity disappeared. Even among adolescents engaged in normal levels of physical activity, the statistically significant relationship between physical activity and indices of bone strength demonstrate that modifiable lifestyle factors like exercise play an important role in optimizing bone strength during the growing years. Physical activity differences were explained by the interdependence between activity and lean mass considerations. Physical activity is important for optimal development of bone strength. (c) 2005 Elsevier Inc. All rights reserved.

EFFECT OF FORMULATION ON PHYSICO-CHEMICAL PROPERTIES, WATER STATUS AND STABILITY OF PASTA, TOMATO SAUCE AND READY TO EAT PASTA MEALS

Ready to eat pasta meals are an important segment of convenience food, but these products are subjected to significant changes in physico-chemical properties during storage, which reduce their acceptability at the time of consumption. A deep understanding of the properties of the single phases, their dependence upon formulation, and the changes they undergo during storage is very important to intelligently intervene on products properties to improve their quality at the time of consumer’s consumption. This work has focused on the effect of formulation on physico-chemical properties of pasta and tomato sauce with a special focus on mechanical/rheological attributes and water status. Variable considered in pasta formulation were gluten, glycerol and moisture content and their effect was studied in both freshly cooked or shelf-stable cooked pasta. The effect of multiple hydrocolloids (at different levels) was considered in the case of tomato sauce. In the case of pasta, it was found that water content was indeed a very important variable in defying pasta mechanical properties and water status. Higher moisture contents in pasta resulted in softer samples and reduced the changes in physico-chemical parameters during storage. Glycerol was found to favor water uptake and to soften the pasta matrix, acting as plasticizer and increasing molecular mobility. The addition of gluten hardened pasta but did not affect the water status. The combination of higher amount of gluten (15%, g gluten / 100 g product) with higher moisture content (59-65%, g water / 100 g product) were found to minimize the physico-chemical changes occurring in RTE pasta meals during storage, improving quality at longer storage times. Hydrocolloids added into tomato sauce modulated its mechanical attributes and water status in very different manner, depending on hydrocolloid type and concentration. This may allow to produce tomato sauce for different applications and that are expected to have different performance if placed in contact with pasta in a RTE meal. Future work should include an investigation of how the interaction between the two phases (pasta and sauce) can be modulated and controlled by controlling the properties of the single phases with the goal of obtaining highly acceptable products also at longer storage times.

Children's attentional skills and road behavior

Switching attention and concentration, 2 skills expected to be used by skillful pedestrians, were studied. A sample of 160 children (aged 4 years 3 months-10 years) played a computer game involving attention switching. To examine concentration, a subset of the children was distracted with a cartoon video while they attempted a difficult task that required matching familiar figures. The same subset was also observed crossing roads. Older children switched faster and were less distracted. Children who were better at switching were more likely to show awareness of traffic when about to cross a road. Children who maintained concentration when challenged by a distracting event crossed the road in a less reckless manner. Parents and educators designing safety programs should take into account the development of these skills.

Mathematical modelling and control of agitated extraction columns

Liquid-liquid extraction has long been known as a unit operation that plays an important role in industry. This process is well known for its complexity and sensitivity to operation conditions. This thesis presents an attempt to explore the dynamics and control of this process using a systematic approach and state of the art control system design techniques. The process was studied first experimentally under carefully selected. operation conditions, which resembles the ranges employed practically under stable and efficient conditions. Data were collected at steady state conditions using adequate sampling techniques for the dispersed and continuous phases as well as during the transients of the column with the aid of a computer-based online data logging system and online concentration analysis. A stagewise single stage backflow model was improved to mimic the dynamic operation of the column. The developed model accounts for the variation in hydrodynamics, mass transfer, and physical properties throughout the length of the column. End effects were treated by addition of stages at the column entrances. Two parameters were incorporated in the model namely; mass transfer weight factor to correct for the assumption of no mass transfer in the. settling zones at each stage and the backmixing coefficients to handle the axial dispersion phenomena encountered in the course of column operation. The parameters were estimated by minimizing the differences between the experimental and the model predicted concentration profiles at steady state conditions using non-linear optimisation technique. The estimated values were then correlated as functions of operating parameters and were incorporated in·the model equations. The model equations comprise a stiff differential~algebraic system. This system was solved using the GEAR ODE solver. The calculated concentration profiles were compared to those experimentally measured. A very good agreement of the two profiles was achieved within a percent relative error of ±2.S%. The developed rigorous dynamic model of the extraction column was used to derive linear time-invariant reduced-order models that relate the input variables (agitator speed, solvent feed flowrate and concentration, feed concentration and flowrate) to the output variables (raffinate concentration and extract concentration) using the asymptotic method of system identification. The reduced-order models were shown to be accurate in capturing the dynamic behaviour of the process with a maximum modelling prediction error of I %. The simplicity and accuracy of the derived reduced-order models allow for control system design and analysis of such complicated processes. The extraction column is a typical multivariable process with agitator speed and solvent feed flowrate considered as manipulative variables; raffinate concentration and extract concentration as controlled variables and the feeds concentration and feed flowrate as disturbance variables. The control system design of the extraction process was tackled as multi-loop decentralised SISO (Single Input Single Output) as well as centralised MIMO (Multi-Input Multi-Output) system using both conventional and model-based control techniques such as IMC (Internal Model Control) and MPC (Model Predictive Control). Control performance of each control scheme was. studied in terms of stability, speed of response, sensitivity to modelling errors (robustness), setpoint tracking capabilities and load rejection. For decentralised control, multiple loops were assigned to pair.each manipulated variable with each controlled variable according to the interaction analysis and other pairing criteria such as relative gain array (RGA), singular value analysis (SVD). Loops namely Rotor speed-Raffinate concentration and Solvent flowrate Extract concentration showed weak interaction. Multivariable MPC has shown more effective performance compared to other conventional techniques since it accounts for loops interaction, time delays, and input-output variables constraints.

The isolation and identification of dermatologically active constituents of coal tar

The production and uses of coal tar are reviewed as are the uses of steroids and cytotoxic agents in the treatment of psoriasis with a review of the condition also. An attempt was made to improve the efficaciousness and cosmetic acceptability of a low temperature tar, by screening fractions of this tar, derived from a variety of separation procedures. The most efficacious fraction was the highest boiling acid fraction, which is believed to consist mainly of mono- and di-hydric phenols. A time and concentration study showed that the optimum regime was the application of a 10% concentration in 5% wool fat in soft, yellow paraffin daily for 21 days. The mouse tail skin was selected as an experimental model, to ascertain the efficaciousness of fractions, because of the similarities between this skin and the psoriatic lesion. The activity of a fraction was monitored by the inducement of a granular layer in the mouse tail epidermis. Because coal tar is not an easy medium to work with, and the active fractions showed no increase in cosmetic acceptability over the parent coal tar, likely coal tar constituents were selected for screening on the basis of phenolic character, and the molecular weight range elucidated by mass spectroscopy. 32 potential anti-psoriatic agents were screened on mouse tail. Two catechols, 3,5-di-t-butyl and 4-t-butyl catechols were active. Other structures showed little or no activity. 24 catechols were screened and two extremely active catechols were discovered, 3-methyl-5-t-octyl and 5-methyl-3-t-octyl catechols. The screening of catechol-rich coal tar fractions and a coal tar fraction which had had the catechols removed by oxidation, showed that some anti-psoriatic activity was contained in the catechol fraction of coal tar. Attempts to elucidate the mode of action of these two compounds met with little success, but two modes of action are suggested.

Investigation of the role of protein kinase C (PKC) in cytostasis induced by tumour promoting phorbol esters and related compounds

Protein kinase C (PKC) is considered to be the major receptor for tumour promoting phorbol esters such as 12-0- tetradecanoylphorbol-13-acetate (TPA). These agents evoke a plethora of biological effects on cells in culture. The growth of A549 human lung carcinoma cells maintained in medium fortified with 10% foetal calf serum (FCS) is arrested for 6 days by TPA and other biologically active phorbol esters. In the work described in this thesis, the hypothesis was tested that modulation of PKC activity is closely related to events pivotal for cytostasis to occur. The effect of several phorbol esters, of newly synthesized analogues of diacylglycerols (DAG) and of bryostatins (bryos) on cell growth and ability to modulate activity of PKC has been investigated.Determination of the subcellular distribution of PKC following treatment of cells with TPA and partial enzyme purification by non-denaturing poly-acrylamide gel electrophoresis revealed translocation of enzyme activity from cytosoUc to paniculate fraction. Chronic exposure of cells to TPA resulted in a time and concentration dependent degradation of enzyme activity. Synthetic DAG and DAG analogues, unable to arrest the growth of cells at non-toxic concentrations, were neither able to affect subcellular PKC distribution nor compete effectively for phorbol ester binding sites at physiologically relevant concentrations. Bryos 1,2,4 and 5, natural products, possessing antineoplastic activity in mice, elicited transient arrest of A549 cell growth in vitro. They successfully competed for phorbol ester receptors in A549 cells with exquisite affinity and induced a shift in sub-cellular PKC distribution, though not to the same extent as PTA. Enzyme down-regulation resulted from prolonged exposure of cells to nanomolar concentrations of bryos. In vivo studies demonstrated that neither PDBu nor bryo 1 was able to inhibit A549 xenograft growth in athymic mice. The growth of A549 cell populations cultured under conditions of serum-deprivation was inhibited only transiently by biologically active phorbol esters. Fortification of serum-free medium with EGF or fetuin was able to partially restore sensitivity to maintained growth arrest by PTA. PKC translocation to the paniculate cellular fraction and subsequent enzyme down-regulation, induced by TPA, occurred in a manner similar to that observed in serum-supplemented cells. However, total PKC activity and cytosolic phorbol ester binding potential were greatly reduced in the serum-deprived cell population. Western blot analysis using monospecific monoclonal antibodies revealed the presence of PKC-a in both A549 cell populations, with significantly reduced protein levels in serum- deprived cells. PKC-/9 was not detected in either cell population.

Investigation of the antiproliferative properties of tumour promoting phorbol esters and related compounds

Tumour promoting phorbol esters such as 12-0-tetradecanoylphorbol-13-acetate (TPA) exert a multitude of biological effects on many cellular systems, many of which are believed to be mediated via the activation of the enzyme protein kinase C (PKC). TPA and other biologically active phorbol esters inhibited the proliferation of the A549 human lung carcinoma cell line. However, after 5-6 days culture in the continued presence of the phorbol ester cells began to proliferate at a rate similar to that of untreated cells. Resistance to TPA was lost following subculturing, although subculture in the presence of 10 nM TPA for more than 9 weeks resulted in a more resistant phenotype. The selection of a TPA-resistant subpopulation was not responsible for the observed resistance. The antiproliferative properties of other PKC activators were investigated. Mezerein induced the same antiproliferative effects as TPA but synthetic diacylglycerols (DAGs), the presumed physiological ligands of PKC, exerted only a non-specific cytotoxic influence on growth. Bryostatins 1 and 2 were able to induce transient growth arrest of A549 cells in a manner similar to phorbol esters at nanomolar concentrations, but at higher concentrations blocked both their own antiproliferative action and also that of phorbol esters and mezerein. Fourteen compounds synthesized to mimic features of the phorbol ester pharmacophore and/or DAGs did not mimic the antiproliferative properties of TPA in A549 cells and exerted only a DAG-like non-specific cytotoxicity at high concentrations. The subcellular distribution and activity of PKC was determined following partial purification by non-denaturing polyacrylamide gel electrophoresis. Treatment with TPA, mezerein or bryostatins resulted in a concentration-dependent shift of PKC activity from the cytosol to cellular membranes within 30 min. Significant translocation was not observed on treatment with DAGs. Chronic exposure of cells to TPA caused a time- and concentration dependent down-regulation of functional PKC activity. A complete loss of PKC activity was also observed on treatment with growth-inhibitory concentrations of bryostatins. No PKC activity was detected in cells resistant to the growth-inhibitory influence of TPA. Measurement of intracellular Ca2+ concentrations using A549 cells cultured on Cytodex 1 microcarrier beads revealed that TPA, mezerein and the bryostatins induced a similar rapid rise in intracellular Ca2+ levels.

The need for and improvement of budgetary planning in a multinational corporation

The aim of this research is to improve the planning methodology of Dunlop via an analysis of their annual planning system. This was approached via an investigation of how the plans were developed; extensive interviews, which analysed divisional attitudes and approaches to planning; an analysis of forecast accuracy; and participation in the planning system itself. These investigations revealed certain deficiencies in the operating of the system. In particular, little evidence of formal planning could be found, and some divisions were reacting ex post to the market, rather than planning ex ante. The resulting plans tended to lack resilience and were generally unrealistic, partly because of imposed targets. Similarly, because the links between the elements of the system were often inefficient, previously agreed strategies were not always implemented. The analysis of forecast accuracy in the plans revealed divisions to be poor at most aspects of forecasting. Simple naive models often outperformed divisional forecasts, and much of the error was attributed to systematic, and therefore eliminable factors. These analyses suggested the need for a new system which is proposed in the form of Budgetary Planning. This system involves conceptual changes within the current planning framework. Such changes aim to revise tactical planning in order to meet the needs placed on it by. in particular, strategic planning. Budgetary Planning is an innovation in terms of the current planning literature. It is a total system of annual planning aimed at implementing and controlling the iteratively agreed strategies within the current environment. This is achieved by the generation of tactical alternatives, variable funding and concentration of forecast credibility, all of which aid both the realism and the resilience of planning.

Tacit collusion, firm asymmetries and numbers:evidence from EC merger cases

The purpose of this paper is to identify empirically the implicit structural model, especially the roles of size asymmetries and concentration, used by the European Commission to identify mergers with coordinated effects (i.e. collective dominance). Apart from its obvious policy-relevance, the paper is designed to shed empirical light on the conditions under which tacit collusion is most likely. We construct a database relating to 62 candidate mergers and find that, in the eyes of the Commission, tacit collusion in this context virtually never involves more than two firms and requires close symmetry in the market shares of the two firms.