Increase In Qp Research Articles

Effect of Pressure and Turbulence Intensity on the Heat Flux During Flame Wall Interaction (FWI)

Combustion applications such as internal combustion engines are a major source of power generation. Renewable alternative fuels like hydrogen and ammonia promise the potential of combustion in future power applications. Most power applications encounter flame wall interaction (FWI) during which high heat losses occur. Investigating heat loss during FWI has the potential to identify parameters that could lead to decreasing heat losses and possibly increasing the efficiency of combustion applications. In this work, a study of FWI (CH4-air mixture) in a constant volume chamber, with a head-on quenching configuration, at high pressure in both laminar and turbulent conditions is presented. High-speed surface temperature measurement using thin junction thermocouples coupled with high-speed flow field characterization using particle image velocimetry (PIV) are used simultaneously to investigate the effect of pressure during FWI (Pint) and turbulence intensity (q) on the heat flux peak (QP). In laminar combustion regimes, it is found that QP is proportional to Pint0.35. The increase in q is shown to affect both Pint and QP. Finally, comparing QP versus Pint for both laminar and turbulent combustion regimes, it is found that an increase in q leads to an increase in QP (b = 0.76).

High light stress under phosphorus limitation in summer may accelerate diatom shift from Skeletonema to Chaetoceros in an oligotrophic coastal area of Japan

In the Seto Inland Sea, the largest semi-enclosed sea in Japan, the most dominant diatom in the past, Skeletonema spp., has been replaced by another diatom Chaetoceros spp. since the 1980s, and this shift is often explained as the result of oligotrophication. Based on previous observations of a shift from Skeletonema spp. to Chaetoceros spp. under prolonged sunny conditions, the recent increase in solar insolation over the last 30 years might have also accelerated the replacement of Skeletonema by Chaetoceros, especially during the summer when nutrient levels are relatively low and solar insolation is high. In our experiments, culture strains of Skeletonema costatum and Chaetoceros lorenzianus under severely nitrogen-limited conditions exhibited less non-photochemical quenching (NPQ) under prolonged exposure (1 h) to high light (800 µmol-photons m-2 s-1) and a decrease in photochemical quenching (qP) which was especially notable in S. costatum. Conversely, marked increases in NPQ were observed under severely phosphorus-limited conditions, even under short time exposure (30 s) to high light, even though the increase in NPQ could not relieve the decrease in qP, which was more apparent in S. costatum. These trends in NPQ and qP were attributed to the limited nutrients because replenishment of the nutrients led to a decrease in NPQ and an increase in qP. Interestingly, this recovery was faster in C. lorenzianus than S. costatum. The results showed that phosphorus depletion caused severe photoinhibition especially in S. costatum, irrespective of active NPQ induction. Further, given the severe phosphorus-limited conditions in the Seto Inland Sea for an extended period, we conducted competition experiments using continuous coculture of both species to simulate the typical summer environment where severe phosphorus limitation and high light occur. The results showed that the shift from S. costatum to C. lorenzianus was accelerated by continuous exposure to high light, which could explain the recent shift in the dominant species in the summer in the study area.

Low specific growth rate and temperature in fed-batch cultures of a beta-propeller phytase producing Pichia pastoris strain under GAP promoter trigger increased KAR2 and PSA1-1 gene expression yielding enhanced extracellular productivity

Previously, we showed that the methylotrophic yeast Pichia pastoris (syn. Komagataella phaffii) could produce and secrete the beta-propeller phytase FTEII in an active form under the control of the AOX1 promoter and methanol as the inductor. In this work, we engineered P. pastoris strains to construct a constitutive P. pastoris expression system (GAP promoter) and extracellularly produce the phytase FTEII. We optimized the culture conditions to increase the extracellular volumetric phytase productivity (Qp) and evaluated the impact of the optimization process on the physiological response of the host. Moreover, we analyzed the expression levels of the FTEII gene and endogenous genes for P. pastoris cells in cultures with the lowest and highest Qp to understand which processes (from heterologous gene expression to protein secretion) might be responsible for the increase in Qp. The results indicate that a low specific growth rate and temperature in the fed-batch phase increases the Qp, which was correlated with an upregulation of the KAR2 and PSA1–1/MPG1 genes rather than increased heterologous gene transcription.

Pulmonary vascular resistance and compliance in pulmonary blood flow alterations in children with congenital heart disease.

There is a unique hyperbolic relationship between pulmonary vascular resistance (Rp) and compliance (Cp); however, the characteristics of this coupling curve in pulmonary blood flow alterations remains unknown in children with congenital heart disease. We aimed to explore the Rp-Cp coupling and resistant-compliance (RC) time among them. We retrospectively reviewed catheterization data and calculated Rp and Cp in 217 subjects with ventricular septal defect. Median age and weight at catheterization were 2.8 (1.7-4.4) months and 4.3 (3.7-5.3) kg, respectively. Pulmonary hemodynamic parameters were as follows: mean pulmonary arterial pressure: 36 (28-43) mmHg; the amount of pulmonary blood flow (Qp): 14.2 (11.6-17.6) L/min/m2; Rp: 1.95 (1.38-2.59) Wood unit m2; Cp: 2.98 (2.42-3.88) mmHg/mL/m2; and RC time: 0.35 (0.30-0.40) s. RC time remained unchanged according to alterations in Qp (P = 0.206); however, the relationship between logarithm transformations of Rp and Cp showed more steeper according to an increase in Qp. The pulmonary circulation depends upon Cp rather than Rp according to the degree of Qp despite the constancy in RC time. We should take both Rp and Cp into consideration when evaluating the pulmonary circulation among children with congenital heart disease.

Perfusion process combining low temperature and valeric acid for enhanced recombinant factor VIII production.

Perfusion operation mode remains the preferred platform for production of labile biopharmaceuticals (e.g., blood factors) and is also being increasingly adopted for production of stable products (e.g., monoclonal antibodies). Regardless of the product, process development typically aims at maximizing production capacity. In this work, we investigated the impact of perfusion cultivation conditions on process productivity for production of human factor VIII (FVIII). Recombinant CHO cells were cultivated in bioreactors coupled to inclined settlers and the effects of reducing the temperature to 31°C with or without valeric acid (VA) supplementation were evaluated. Increases in cell specific productivity (qp ) up to 2.4-fold (FVIII concentration) and up to 3.0-fold (FVIII biological activity) were obtained at 31°C with VA compared to the control at 37°C. Biological activity is the most important quality attribute for FVIII and was positively affected by mild hypothermia in combination with the chemical inducer. The low temperature conditions resulted in enhanced product transcript levels, suggesting that the higher qp is related to the increased mRNA levels. Furthermore, a high-producer subclone was evaluated under the perfusion conditions optimized for the parental clone (31°C with VA), yielding increases in qp of 6-fold and 15-fold compared to the parental clone cultivated under the same condition and at 37°C, respectively. The proposed perfusion strategy enables increased product formation without increasing production costs, being potentially applicable to perfusion production of other CHO-derived biopharmaceuticals. To the best of our knowledge, this is the first report showing the benefits of perfusion combining mild hypothermia with VA supplementation.

Zinc supplementation increases protein titer of recombinant CHO cells.

In order to study the impact of zinc and copper on the titer levels of mAb and recombinant protein in CHO cells, the IgG-expressing (DP12) and EPO-expressing (SK15) cell lines were cultured in chemically defined media with increasing concentrations of either metal. Supplementation with 25mg/l in CDM media resulted in a significant increase in EPO (1.7-fold) and IgG (2.6-fold) titers compared to control (no added zinc). Titers at this Zn concentration in CDM containing the insulin replacing agent aurintricarboxylic acid (ATA) (CDM + A) showed a 1.8-fold (EPO) and 1.2-fold (IgG) titers increase compared to control. ATA appeared to also reduce the specific productivity (Qp) enhancement induced by Zn-25, with up to 4.9-fold (DP12) and 1.9-fold (SK15) Qp increase in CDM compared to the 1.6-fold (DP12) and 1.5-fold (SK15) Qp increase observed in CDM + A. A 31% reduced Viable Cell Density (VCD) in DP12 was observed in both Zn-supplemented media (3 × 106 cells/ml vs 4.2 × 106 cells/ml, day 5), whereas SK15 Zn-25 cultures displayed a 24% lower peak only in CDM + A (2.2 × 106 cells/ml vs 3.2 × 106 cells/ml, day 5). Supplementation with copper at 13.7-20mg/l resulted in less significant cell line/product-type dependent effects on titer, VCD and Viability. Analysis of the energetic phenotype of both cell lines in 25mg/l Zn-supplemented CDM media revealed a twofold increase in the oxygen consumption rate (OCR) compared to non-supplemented cells. Together, these data suggest that high zinc supplementation may induce an increase in oxidative respiration metabolism that results in increased Qp and titers in suspension CHO cultures.

Pulmonary to Systemic Flow Ratio (Qp/Qs) in Dilated Cardiomyopathy, Mitral Valve Disease and Patent Ductus Arteriosus Affected Dog

The study was designed to determine pulmonary to systemic flow ratio (Qp/Qs) by Doppler echocardiography in Dilated Cardiomyopathy (DCM), Mitral valve disease (MVD) and Patent ductus arteriosus (PDA) affected dogs. Dilated cardiomyopathy, Mitral valve disease and Patent ductus arteriosus were diagnosed by Doppler echocardiography and these affected dogs Pulmonary artery diameter, , Peak pulmonary artery velocity, pulmonary velocity time interval, aortic diameter, peak aortic flow, aortic velocity time interval were recorded. The mean values of Qp/Qs ratio in DCM and MVD were 1.16±0.21 and 0.72±0.31 respectively. The mean values of Qp, Qs and Qp/Qs ratio was 25.62±4.47, 14.99±5.02 and 1.2±0.16 respectively in PDA affected dogs. Increase in Qp may be observed due to pulmonary over circulation, these leading to an increase in Qp/Qs ratio. Left to right shunting associated with intracardiac shunts in PDA leads to above mentioned condition. The combination of pulmonary to systemic flow ratio (Qp/Qs) with Doppler parameters, offers a striking approach for the assessment of intra cardiac shunt severity in dogs. Further, the present method is rapid, easy and non-invasive and aids in early diagnosis.

All-trans retinoic acid in combination with sodium butyrate enhances specific monoclonal antibody productivity in recombinant CHO cell line.

The effects of all-trans retinoic acid (RA) and sodium butyrate (NaBu) on growth, viability and antibody production of two types of transfected Chinese hamster ovary cell lines (CHO-K1 and CHO-S) were investigated using a batch mode cell culture. By adding 0.5mM NaBu in the CHO-K1 cell culture, the cell specific productivity (Qp) and antibody concentration increased by five- and threefold, respectively. The optimal concentration of RA was 100nM which resulted in twofold increase in antibody production. In a combination model, RA applied at early growth phase of CHO-K1 cells followed by addition of NaBu with lowering culture temperature at the end of stationary phase resulted in two- and threefold increase in Qp and final antibody concentration, respectively. The latter strategy was also applied on suspended CHO-S cells with enhanced Qp and antibody concentration, but to a lesser extent than the CHO-K1 cells. In conclusion, our results demonstrate that the addition of RA and NaBu along with lowering the culture temperature can increase cell culture period as well as Qp and the final concentration of recombinant monoclonal antibody in both CHO-K1 and CHO-S cells without any significant change in binding affinity of the mAb.

Exploring cellular behavior under transient gene expression and its impact on mAb productivity and Fc-glycosylation.

Transient gene expression (TGE) is a methodology employed in bioprocessing for the fast provision of recombinant protein material. Mild hypothermia is often introduced to overcome the low yield typically achieved with TGE and improve specific protein productivity. It is therefore of interest to examine the impact of mild hypothermic temperatures on both the yield and quality of transiently expressed proteins and the relationship to changes in cellular processes and metabolism. In this study, we focus on the ability of a Chinese hamster ovary cell line to galactosylate a recombinant monoclonal antibody (mAb) product. Through experimentation and flux balance analysis, our results show that TGE in mild hypothermic conditions led to a 76% increase in qP compared to TGE at 36.5°C in our system. This increase is accompanied by increased consumption of nutrients and amino acids, together with increased production of intracellular nucleotide sugar species, and higher rates of mAb galactosylation, despite a reduced rate of cell growth. The reduction in biomass accumulation allowed cells to redistribute their energy and resources toward mAb synthesis and Fc‐glycosylation. Interestingly, the higher capacity of cells to galactosylate the recombinant product in TGE at 32°C appears not to have been assisted by the upregulation of galactosyltransferases (GalTs), but by the increased expression of N‐acetylglucosaminyltransferase II (GnTII) in this cell line, which facilitated the production of bi‐antennary glycan structures for further processing.

Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses

This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Qp, of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, –0.3 and −0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Qp from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress.

MiR-92a enhances recombinant protein productivity in CHO cells by increasing intracellular cholesterol levels.

MicroRNAs (miRNAs) have emerged as promising targets for engineering of CHO cell factories to enhance recombinant protein productivity. Manipulation of miRNA levels in CHO cells have been shown to improve product yield by increasing proliferation and specific productivity (qP), resisting apoptosis and enhancing oxidative metabolism. The authors previously demonstrated that over-expressing miR-92a results in increases in qP and titer of CHO-IgG cells. However, the mechanisms by which miR-92a enhances qP in CHO cells are still uninvestigated. Here, the authors report the identification of insig1, a regulator of cholesterol biosynthesis, as a target of miR-92a using computational prediction. Both transient and stable over-expression of miR-92a decreased the expression levels of insig1. Insig1 was further validated as a target of miR-92a using 3' UTR reporter assay. Intracellular cholesterol concentration of two high-producing miR-92a clones were significantly increased by ≈30% compared to the blank-transfected pool. Relative Golgi surface area was also found to be 18-26% higher in these clones. Our findings suggest that miR-92a may affect cholesterol metabolism by repressing insig1, resulting in raised intracellular cholesterol levels and Golgi volume and hence enhanced protein secretion.

Investigation of relationship between EBNA-1 expression level and specific foreign protein productivity in transient gene expression of HEK293 cells

Abstract In an attempt to determine the relationship between the Epstein–Barr virus nuclear antigen-1 (EBNA-1) expression level and specific foreign protein productivity (qp), EBNA-1-amplifed HEK293 cells, which achieved a higher EBNA-1 expression level than that achieved by HEK293E cells, were established using dihydrofolate reductase (dhfr)-mediated gene amplification. Compared with a control culture in a null pool, Fc-fusion protein production by transient transfection in the EBNA-1-amplified pool showed a significant improvement. qp was linearly correlated with the EBNA-1 expression level in the transient transfection of EBNA-1-amplified clones, as indicated by the correlation coefficient (R2 = 0.7407). The Fc-fusion protein production and qp in a transient gene expression-based culture with EBNA-1-amplified HEK293 cells, E-amp-68, were approximately 2.0 and 3.2 times, respectively, higher than those in a culture with HEK293E cells. The increase in qp by EBNA-1 amplification mainly resulted from an enhancement in the amount of replicated DNA and level of mRNA expression but not an improved transfection efficiency. Taken together, it was found that EBNA-1 amplification could improve the therapeutic protein production in an HEK293 cell-based transient gene expression system.

Amplification of postwildfire peak flow by debris

AbstractIn burned steeplands, the peak depth and discharge of postwildfire runoff can substantially increase from the addition of debris. Yet methods to estimate the increase over water flow are lacking. We quantified the potential amplification of peak stage and discharge using video observations of postwildfire runoff, compiled data on postwildfire peak flow (Qp), and a physically based model. Comparison of flood and debris flow data with similar distributions in drainage area (A) and rainfall intensity (I) showed that the median runoff coefficient (C = Qp/AI) of debris flows is 50 times greater than that of floods. The striking increase in Qp can be explained using a fully predictive model that describes the additional flow resistance caused by the emergence of coarse‐grained surge fronts. The model provides estimates of the amplification of peak depth, discharge, and shear stress needed for assessing postwildfire hazards and constraining models of bedrock incision.

Novel cell engineering of the Unfolded Protein Response to achieve efficient therapeutic protein production cell line

Bioproduction of therapeutic proteins such as monoclonal antibodies (mAb) continues to be a fast growing sector of advanced manufacturing. An ever increasing repertoire of therapeutic proteins coupled with the emergence of biosimilars has led to increasing global demand for higher yielding, faster, and more cost-effective manufacturing process. Central to any good production platform is the capacity of the production cell line. A suitable production cell line exhibits physiological traits such as high specific productivity (qp), short doubling time, high peak cell density and efficient metabolism. The emergence of a suitable production cell line with all the aforementioned traits is an extremely rare event, as it requires that all facets of cellular transcription, translation, secretion and metabolic efficiency are both individually optimized and collectively synchronized into a system capable of high level protein expression. Cellular translation and secretion capacity is thought to be one of the major cellular bottlenecks limiting protein production in mammalian cells. The over-expression of complex recombinant proteins such as mAbs driven by strong viral promoters exerts considerable burden on the Endoplasmic Reticulum (ER) and Golgi apparatus. Increased ER stress triggers the Unfolded Protein Response (UPR), which may lead to cell apoptosis and thus elimination of cells with high expression of the Gene of Interest (GOI). In this thesis, we adopted a host cell engineering approach to expand cellular translation and secretion capacity prior to expressing the GOI, in order to increase the probability of isolating high producers. Through screening of a panel of mAb producing clonal cell lines using qPCR, the XBP1 mRNA splice ratio was identified as a suitable target to augment host cell translation and secretion machinery. A high ratio of spliced over unspliced XBP1 mRNA is required to overcome the negative regulatory effect of unspliced XBP1 protein. Spliced XBP1 mRNA translates into a potent transcription factor that up-regulates a wide range of folding, secretory and quality control proteins, which forms the cytoprotective branch of the UPR. A stable CHO host cell line engineered with a high splice ratio of XBP1 mRNA exhibited increased expression of various chaperone and secretary vesicle proteins without increasing UPR associated apoptotic markers. This engineered host cell line was compared against the parental cell line in transient mAb production studies. The XBP1 cell line displayed a 7.5 fold increase in qp over the control cell line and more than 4 fold increase in final volumetric productivity. Moreover, a 3-fold increase in the percentage of high producers was observed in the cell distributions post-transfection when using the XBP1 host cell line. mAb producing cells derived from the XBP1 host cell line also demonstrated competency in conventional stirred-tank bioreactors, showing promise of a commercially viable production platform. In conclusion, XBP1 mRNA splice ratio engineered host cells have expanded translation and secretion capacity to alleviate the ER stress experienced from mAb production. The augmented capacity enabled multi-fold improvements in qp and volumetric productivity and increased the frequency of high producers in the transformed pool. The engineered host cell line showed great promise to become a commercially viable production platform cell line to significantly reduce the time and resources associated with cell line development.

Microarray profiling of preselected CHO host cell subclones identifies gene expression patterns associated with increased production capacity.

Over the last three decades, product yields from CHO cells have increased dramatically, yet specific productivity (qP) remains a limiting factor. In a previous study, using repeated cell-sorting, we have established different host cell subclones that show superior transient qP over their respective parental cell lines (CHO-K1, CHO-S). The transcriptome of the resulting six cell lines in different biological states (untransfected, mock transfected, plasmid transfected) was first explored by hierarchical clustering and indicated that gene activity associated with increased qP did not stem from a certain cellular state but seemed to be inherent for a high qP host line. We then performed a novel gene regression analysis identifying drivers for an increase in qP. Genes significantly implicated were first systematically tested for enrichment of GO terms using a Bayesian approach incorporating the hierarchical structure of the GO term tree. Results indicated that specific cellular components such as nucleus, ER, and Golgi are relevant for cellular productivity. This was complemented by targeted GSA that tested functionally homogeneous, manually curated subsets of KEGG pathways known to be involved in transcription, translation, and protein processing. Significantly implicated pathways included mRNA surveillance, proteasome, protein processing in the ER and SNARE interactions in vesicular transport.

Optimum Conditions for the Efficacy and Safety of Cryofiltration Apheresis: An Analysis of Circuit Temperatures Depending on Plasma Flow Rate and Cooling Coil Lengths/Turns.

A system providing both appropriate cooling and warming are needed for the efficacy and safety of cryofiltration (CF) plasmapheresis. We measured some points of CF circuit temperatures with varying plasma flow rates (QP = 10-40 mL/min) and the numbers of connecting cooling coils (one or two) under the conditions of blood flow rate (QB ) 100 mL/min with 7700-mm coil length, 19 turns, and 50-mL priming volume. We measured the respective temperatures of each point of starting/returning for an extracorporeal circuit (TA /TV ), intracooling coil (TC ), and post-plasma fractionator (PF) (TPF ). The subtraction of TV from TA (ΔT) was used as an indicator of safe return. There were no significant differences in TC , TPF , or ΔT in accordance with each QP between that of one and two coils. All of the Tc values under the condition QP ≤ 20 mL/min achieved <4°C. The TPF under the condition QP ≥ 20 mL/min was not significantly different compared to that of QP 30 mL/min (the lowest condition). Although the ΔT increased depending on the QP increase, the ΔT under the condition QP ≤ 15 mL/min was not significantly different from that of the control (one-way double-filtration plasmapheresis [DFPP]) group. We conclude that (i) one coil is enough for effective cooling in CF, and (ii) an ideal QP that fulfills the required conditions for both effective cooling and sufficient warming of returning fluid does not exist, but QP from 15 to 20 mL/min may be a relevant range.

Effects of nasal continuous positive airway pressure on pulmonary and systemic output in preterm infants

Objective: Respiratory assistance with nasal continuous positive airway pressure (n-CPAP) is an effective treatment in premature newborns presenting respiratory distress. The aim of the study was to depict cardiac function, systemic (Qs) and pulmonary output (Qp) by echocardiography in stable premature infants requiring prolonged n-CPAP. Our hypothesis was that n-CPAP could reduce pulmonary blood flow. Patients and methods: All premature infants 7 days-old, requiring n-CPAP without severe respiratory compromise nor need for additional oxygen were prospectively included. Every patient had a first echocardiography while on n-CPAP. N-CPAP was then discontinued for two hours and a second echocardiography was performed. Results: 17 premature infants were included. Mean gestational age was 28 ± 2 weeks and mean weight 1.1 ± 0.3 kg. Following retrieval of n-CPAP we observed an increase in Qp of 53 ml/kg/min (95% CI 19-87 ml/kg/min), but no significant change in Qs. Consecutively a significant increase in Qp/Qs ratio of 16% was found (95% CI 7-29%). Conclusions: Nasal continuous positive airway pressure has hemodynamic effects in preterm infants in stable pulmonary and cardiac conditions. It reduces pulmonary output without interference with systemic output.

Modeling the growth response of Cladophora in a Laurentian Great Lake to the exotic invader Dreissena and to lake warming

A Cladophora growth model (CGM) is calibrated and validated here to simulate attached and sloughed Cladophora biomass in daily time‐steps in an urbanized location of Lake Ontario, using two years of collected input data and independent measurements of Cladophora biomass. The CGM is used to hindcast Cladophora growth using multiplicative factors of seasonal minimal tissue phosphorus concentrations (QP) and seasonal mean nearshore light attenuation (KdPAR) of the early 1970s and 1980s relative to modern data. The possible effects of climate on growth are also forecast using additive temperature increases. Cladophora QP in Lake Ontario has declined in parallel with decreasing pelagic P concentrations, resulting in reduced Cladophora biomass at all depths in the euphotic zone. KdPAR has also declined, most strongly since the mid‐1990s, following Dreissena mussel invasion, driving an increase in biomass between 3.5‐ and 10‐m depth. Combining these effects, the CGM predicts that biomass along shorelines today is lower in Lake Ontario than in the 1980s. However, any increases in QP in this post‐dreissenid‐mussel period will result in greater Cladophora proliferation than in previous decades due to increased nearshore water clarity. Cladophora QP, while still currently lower than in the early 1980s, may be rising due to P supply to the littoral zone by the invasive mussels. The surface water temperature of Lake Ontario indicates warming of 0.96°C decade‐1 from 1980 to 2006. With increasing surface water temperatures, the CGM predicts an earlier spring growth but only a marginal increase in peak Cladophora biomass.

MODEL SIMULATION OF WATER-IN-OIL XANTHAN FERMENTATION

ABSTRACT The W/O xanthan fermentation is simulated by integrating the microbial kinetic behaviors and the multiple-phase process characteristics. Model 1 assumes uniform redistribution of cells, substrates and product by frequent droplet breakup and coalescence. Model 2 simulates the system of viscous aqueous phase with minimal droplet breakup and component redistribution. The real fermentation should proceed within the bounds set by the two models. Effects of various parameters are evaluated. The aqueous-phase xanthan concentration (Xn) and volumetric productivity (QP) achieved at 200 h are used as the indicators. Xn and QP increase with nitrogen-source concentration (SNO) initially but plateau (Model 1) or decrease slightly (Model 2) at high SNO. Xn (at 200 h) decreases with increasing aqueous-phase volume fraction (f). QP, however, increases with f reflecting its basing on the total dispersion volume. Increasing agitation and aeration result in higher Xn and QP. The higher agitation enhances the G/O interfacial oxygen transfer and reduces the droplet size. Increasing aeration improves the G/O interfacial transfer but increases the droplet size. Its net positive effect implies a rate-limiting step at G/O interface. The W/O fermentation can produce far higher Xn (> 200 kg/m3) and QP( > 0.8 kg/m3-h) than the conventional fermentation (Xn ∼ 50 kg/m3, QP ∼ 0.5 kg/m3-h).

Effect of High Temperature on Photosynthesis in Beans (I. Oxygen Evolution and Chlorophyll Fluorescence).

We studied the effect of increasing temperature on photosynthesis in two bean (Phaseolus vulgaris L.) varieties known to differ in their resistance to extreme high temperatures, Blue Lake (BL), commercially available in the United Kingdom, and Barbucho (BA), noncommercially bred in Chile. We paid particular attention to the energy-transducing mechanisms and structural responses inferred from fluorescence kinetics. The study was conducted in non-photorespiratory conditions. Increases in temperature resulted in changes in the fluorescence parameters nonphotochemical quenching (qN) and photochemical quenching (qP) in both varieties, but to a different extent. In BL and BA the increase in qP and the decrease in qN were either completed at 30[deg]C or slightly changed following increases from 30 to 35[deg]C. No indication of photoinhibition was detected at any temperature, and the ratio of the quantum efficiencies of photosystem II (PSII) and O2 evolution remained constant from 20 to 35[deg]C. Measurements of 77-K fluorescence showed an increase in the photosystem I (PSI)/PSII ratio with temperature, suggesting an increase in the state transitions. In addition, measurements of fast-induction fluorescence revealed that the proportion of PSII[beta] centers increased with increasing temperatures. The extent of both changes were maximum at 30 to 35[deg]C, coinciding with the ratio of rates at temperatures differing by 10[deg]C for oxygen evolution.