bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increase of ethanol productivity in an airlift reactor with a modified draught tube
Authors: Vicente António A. , Dluhý Marián , Teixeira José A. 
Published: March 2009

AbstractStatic mixers were introduced in the draught tube of a three‐phase, concentric tube type airlift bioreactor, resulting in a 30% increase in ethanol productivity during glucose fermentation with a highly flocculent strain ofSaccharomyces cerevisiae.Increased productivity was obtained as a consequence of the floe size reduction provoked by the new design of the draught tube and of the smaller applied aeration rates, allowing a higher dilution rate to be used. Steady state data at different dilution rates were measured for both systems and the results were compared in terms of specific consumption / production rates and ethanol productivity. An approach based on heterogeneous catalysis principles was used in order to consider the presence of porous yeast flocs. Total glucose conversion was achieved at a dilution rate of 0.34 h−1. The smaller floe size contributed to the higher observed reaction rates by reducing diffusional limitations inside the flocs. The respiratory quotient had a constant value (around 23) at all dilution rates, meaning that the metabolic state of the cells in the flocs remained constant, having a strong fermentative metabolism.
A note on the drag coefficient of a single gas bubble in a power‐law fluid
Authors: Rodrigue Denis , De Kee Daniel , Man Fong Chen Feng Chan 
Published: March 2009

AbstractThe motion of a single gas bubble is examined in the case of creeping flow where the exterior phase obeys the power‐law model. An expression is developed for the drag coefficient using a perturbation method up to the second order in the parameter α = (n‐1)/2. The relation obtained is compared with existing correlations and experimental data.
Agitator design for solids suspension under gassed conditions
Authors: Lehn Mary C. , Myers Kevin J. , Barker André 
Published: March 2009

AbstractDesign of mechanical agitators for solids suspension under gassed conditions can be achieved using a constant ungassed torque criterion if the solids suspension task is more difficult than the gas dispersion task. When gas dispersion is the more difficult task, design for complete gas dispersion will ensure solids suspension. Evidence supporting this approach is very strong for radial‐flow impellers, but less so for up‐pumping and down‐pumping axial‐flow impellers.
Pressure gradients, voidage and gas flow in the annulus of spouted beds
Authors: He Y.‐L. , Lim C. Jim , Grace John R. 
Published: March 2009

AbstractParallel measurements of pressure gradients with a differential pressure probe and voidage profiles with a fibre optic system have been carried out to study gas flow distributions in the annulus of spouted beds. The observation of Grbavcic et al. (1976) that for a given fluid‐solid combination and column geometry the annulus pressure gradient at any bed level is independent of bed depth was corroborated again. Calibration curves of pressure drops versus superficial gas velocities for beds of voidage higher than the loose‐packed voidage were obtained by applying the Ergun (1952) equation, making it possible to estimate superficial gas velocities in the annulus using the static pressure gradient method. The local superficial gas velocity in the annulus was found to be higher in a deep bed than in a shallow bed of the same material, contrary to the conclusion (Grbavcic et al., 1976) that, for a given fluid‐solid combination and column geometry, the annulus fluid velocity at any level is independent of bed depth. Theoretical models and equations which do not account for the conical geometry near the bottom were found to underpredict superficial gas velocities in the annulus. Increasing the spouting gas flow was found to increase the net gas flow through the annulus.
Hydrodynamics in a gravity settling vessel: CFD modelling with LDA validation
Authors: Wan M. H. , Bara B. , Hackman L. , Czarnecki J. , Afacan A. , Nandakumar K. , Masliyah J. H. 
Published: March 2009

AbstractVertical gravity settling vessels, usually referred to as primary separation vessels (PSV), are used in separating bitumen aggregates from slurry containing sand and fine clays. The hydrodynamics in the PSV influences the separation efficiency of recovered bitumen through the overall mean flow and turbulent interaction. In order to deepen our understanding of the hydrodynamic conditions in such vessels, this paper presents a combined study of the flow field using Laser Doppler Anemometry (LDA) to measure the velocity field, and computational fluid dynamics (CFD) simulations to validate the CFD model. The investigation shows that the flow geometry has a significant influence on the overall flow pattern in such vessels. It also demonstrates that the CFD simulation is a reliable tool in capturing the complex mean flow pattern observed in experiments. Use of different turbulent models such as the standard k‐ε model and Reynolds stress model has very little effect on the mean flow field.
Evaluation of radial voidage profiles in packed beds of low‐aspect ratios
Authors: Mariani Nestor J. , Mazza German D. , Martinez Osvaldo M. , Barreto Guillermo F. 
Published: March 2009

AbstractThe relationship between the radial voidage profile, ϵ(r), and the radial distribution of centres of mono‐sized spherical particles, f(r), is revised. A close expression is given for the section S(r1, rc), the area of the segment of a cylindrical surface of radius r intersected by a particle centred at rC. From this expression, ϵ(r) can be evaluated straightforwardly from the knowledge of f(r). The range 1≥ a ≥ 2 of aspect ratios (a = dT/dp is then analysed specifically. For this range, the distribution of spherical particles has been characterized theoretically (Govindarao et al., 1992) and a simple expression allows the evaluation of ϵ(r). The use of this expression for actual catalyst particles, imperfect spheres showing a distribution of sizes, in finally analyzed.
Parametric studies of carbon dioxide absorption into highly concentrated monoethanolamine solutions
Authors: Demontigny David , Tontiwachwuthikul Paitoon , Chakma Amit 
Published: March 2009

AbstractCarbon dioxide (CO2) absorption into highly concentrated solutions of monoethanolamine (MEA) was studied. The effect of operating parameters on the overall mass transfer coefficient (KGav) was determined in a pilot‐plant scale absorption unit. The (KGav) increased at low solution concentrations, decreased at intermediate concentrations, and increased as the concentration became high (54 wt%). The (KGav) increased with an increasing liquid flow rate, decreased with an increase in either the CO2 loading or the CO2 partial pressure, and was not affected by the inert gas flow rate. Finally, structured 4A Gempak packing produced (KGav) values twice as high as randomly packed IMTP#15 or 16‐mm Pall Ring systems.
Mathematical modelling and its use for design of feeding strategies for L‐Sorbose fermentation
Authors: Giridhar Raghavan Nair , Srivastava Ashok Kumar 
Published: March 2009

AbstractBatch sorbitol to sorbose bioconversion by Acetobacter suboxydans using initial sorbitol concentration (S0 = 100 g/L) yielded a productivity of 10.11 g/L‐h and 98.6% conversion in 10 h time. The batch kinetics was then used to develop an unstructured mathematical model. Model parameters were identified using a nonlinear regression technique assisted by a computer program which minimized the deviation between the model predictions and actual batch experimental data. F test indicated 99% confidence on the prediction of model using optimized parameters. The batch model was eventually extrapolated to identify nutrient feeding strategies to maintain constant noninhibitory sorbitol supply and eliminate substrate limitation for fed‐batch fermentation in order to improve the sorbose productivity. The adequacy of the fed‐batch model was established by excellent agreement between experimental data and model simulation (except towards the end of fermentation).
The activity coefficients of glycine, DL‐Serine and DL‐Valine in aqueous solutions containing nitrates at 298.15 K
Authors: Gao Chongxia , Vera Juan H. 
Published: March 2009

AbstractAn electrochemical method was used to measure the mean activity coefficients of amino acids in water‐electrolyte‐amino acid systems. The amino acids were glycine, DL‐serine and DL‐valine and the electrolytes were KNO3 and NaNO3. The activity coefficients of the electrolytes were obtained from the e.m.f measurements in an electrochemical cell with an anion and a cation ion‐selective electrodes, each measured versus a double junction reference electrode at 298.15 K. The activity coefficients of the amino acids in the ternary systems were obtained from those of the electrolyte according to the cross differential relation. A simple semi‐empirical model based on a modification of a more complex form, derived from perturbation theory, was used to correlate the activity coefficients in binary aqueous solutions and in ternary systems.
Axial liquid dispersion in a liquid–solid circulating fluidized bed
Authors: Zheng Ying 
Published: March 2009

AbstractAlthough axial liquid dispersion has been studied extensively in particulate fluidized beds, no data has been reported previously in a liquid–solid circulating fluidized bed (LSCFb). In this work, the axial liquid dispersions at various radial positions were measured in an LSCFB of 76 mm in diameter and 3.0 m in height using a dual conductivity probe. The results reveal that the axial liquid dispersion is affected not only by the operating conditions but by the radial positions as well. A local axial dispersion model is proposed to describe the axial liquid dispersion at various radial positions. The local axial liquid dispersion coefficients determined by the proposed model are greater at the axis than near the wall region of the riser. This nonuniformity of axial liquid dispersion is believed to be caused by the radial nonuniform distribution of liquid velocity, and bed voidage in the LSCFB can significantly affect the axial liquid dispersion.
In vitro breeding of grey poplar (Populus × canescens) for phytoremediation purposes
Authors: Bittsánszky András , Gyulai Gábor , Gullner Gábor , Kiss József , Szabó Zoltán , Kátay György , Heszky László , Kömíves Tamás 
Published: March 2009

AbstractBACKGROUND: Paraquat‐tolerant poplar (Populus × canescens) clones (PQT) were selected in in vitro nodal segment cultures at the sublethal paraquat concentration (0.4 µmol L−1). After testing on tissue culture media, regenerants were micropropagated, rooted and transplanted to a greenhouse followed by a field test at heavily contaminated fields of the Chemical Company Balatonfüzfö (Hungary).RESULTS: PQT clones showed significantly higher gst (glutathione S‐transferase) gene expression level than the wild type (WT) analyzed by qRT‐PCR (quantitative reverse transcriptase real time PCR). The expression level of gst gene in the PQT clones showed 70‐fold (without paraquat treatment), 4‐fold (at 0.1 µmol L−1 paraquat), 20‐fold (at 0.4 µmol L−1 paraquat) and 40‐fold (at 1 µmol L−1 paraquat) increments compared with WT. For functional analysis, enzyme activities of lipoxygenase (LOX; EC 1.13.11.12), glutathione S‐transferase (GST; EC 2.5.1.18), ascorbate peroxidase (APOX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) were determined. The enzyme activity of GR and LOX, and the glutathione content (GSH) were found to be significantly higher in PQT clones.CONCLUSIONS: Paraquat‐tolerant clones as powerful new stress tolerant and non‐GMO plants can provide an effective tool for phytoremediaton purposes where the pollutants cause oxidative stresses. Copyright © 2009 Society of Chemical Industry
Model Theory of Visco‐Elastic Properties and Relaxation Spectra of Two Different Interpenetrating Polymer Networks
Authors: Gotlib Yuli Ya. , Torchinskii Isaak A. , Toshchevikov Vladimir P. , Shevelev Vladimir A. 
Published: March 2009

AbstractDynamic viscoelastic models of the system of two different interpenetrating polymer networks with different topology and type of interactions were used for calculating spectra of relaxation times of the system under consideration. It was shown, that two branches of the relaxation spectrum appear for two models of interpenetrating networks with different components. One of the branches is the branch of the collective motion of double network consisting of two initial interacting networks. Parameters of this branch of relaxation spectrum are defined by both own elastic constants of each of interacting networks and by effective quasi‐elastic interactions between two networks. This branch is the low frequency one and is described by broad relaxation time spectrum. The second branch is the high frequency one and characterizes mutual local motions of two interacting networks. The relaxation spectrum of this branch is comparatively narrow and depends on the quasi‐elastic constants and mutual friction which is defined by the entanglements of the networks and by its effective rigidity. The second branch does not contain extremely large relaxation times for infinitely large networks.
2‐D DIGE identification of differentially expressed heterogeneous nuclear ribonucleoproteins and transcription factors during neural differentiation of human embryonic stem cells
Authors: Barthéléry Miguel , Jaishankar Amritha , Salli Ugur , Freeman Willard M. , Vrana Kent E. 
Published: March 2009

AbstractNeural stem cells (NSC) are progenitors that can give rise to all neural lineages. They are found in specific niches of fetal and adult brains and grow in vitro as non‐adherent colonies, the neurospheres. These cells express the intermediate filament nestin, commonly considered an NSC marker. NSC can be derived as neurospheres from human embryonic stem cells (hESC). The mechanisms of cellular programming that hESC undergo during differentiation remain obscure. To investigate the commitment process of hESC during directed neural differentiation, we compared the nuclear proteomes of hESC and hESC‐derived neurospheres. We used 2‐D DIGE to conduct a quantitative comparison of hESC and NSC nuclear proteins and detected 1521 protein spots matched across three gels. Statistical analysis (ANOVA n = 3 with false discovery correction) revealed that only 2.1% of the densitometric signal was significantly changed. The ranges of average ratios varied from 1.2‐ to 11‐fold at a statistically significant p‐value <0.05. MS/MS identified 15 regulated proteins previously shown to be involved in chromatin remodeling, mRNA processing and gene expression regulation. Notably, three members of the heterogeneous nuclear ribonucleoprotein family (AUF‐1, and FBP‐1 and FBP‐2) register a 54, 70 and 99% increased expression, highlighting them as potential markers for NSC in vitro derivation. By contrast, Cpsf‐6 virtually disappears with differentiation with an 11‐fold drop in NSC, highlighting this protein as a novel marker for undifferentiated ESC.
Development of AlGaN/GaN HEMTs with efficiencies above 60% up to 100 V for next generation mobile communication 100 W power bars
Authors: Waltereit P. , Bronner W. , Quay R. , Dammann M. , Müller S. , Musser M. , Mikulla M. , Ambacher O. , van Rijs F. , Rödle T. , Riepe K. 
Published: March 2009

AbstractWe present a systematic study of epitaxial growth, processing technology, device performance and reliability of our GaN HEMTs manufactured on 3‐inch SiC substrates. Epitaxy and processing are optimized for both performance and reliability. The deposition of the AlGaN/GaN HEMT epitaxial structures is designed for both low background carrier concentration and a low trap density in order to simultaneously achieve a high buffer isolation and low DC to RF dispersion. Device fabrication is performed using standard processing techniques involving both electron‐beam and stepper lithography. The developed HEMTs demonstrate excellent high‐voltage stability, high power performance and large power added efficiencies. Devices exhibit two‐terminal gate‐drain breakdown voltages in excess of 160 V (current criterion 1 mA/mm) across the entire 3‐inch wafer with parasitic gate and drain currents well below 1 mA/mm when biased up to 80 V drain bias under pinch‐off conditions. Load‐Pull measurements at 2 GHz on 800 μm gate periphery devices return both a well‐behaved relationship between bias‐voltage and output‐power as well as power‐added‐efficiencies beyond 60% up to UDS = 100 V. For a drain bias of 100 V an output‐power‐density around 22 W/mm with 26 dB linear gain is obtained. On large periphery devices (32 mm gate width packaged in industry‐standard ceramic packages) an output power beyond 100 W is achieved with a PAE above 50% and a linear gain around 15 dB. Reliability is tested on devices having a gate periphery of 8×60 μm at an operating bias of 50 V under both DC and RF conditions. About 10% drain‐current change under DC‐stress (50 mA/mm) is observed after more than 1000 h of operation with an extrapolated drain‐current degradation below 20% after 200,000 h (more than 20 years) of operation. Under RF stress (2 GHz, 1 dB compression) the observed change in output power density is below 0.2 dB after more than 1000 h. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design and analysis of high‐performance terahertz quantum cascade lasers
Authors: Sekine Norihiko , Hosako Iwao 
Published: March 2009

AbstractWe propose a new design for a high‐performance terahertz (THz) quantum cascade laser (QCL) and investigate the characteristics of the laser by using rate equation analysis. By comparing the four‐level system in our design with the three‐level system in the conventional THz QCL, it was found that both a lower threshold current and higher slope efficiency can be realized in the former. Furthermore, it was found that the four‐level system has higher operating temperature tolerance. These results are expected to contribute to the development of THz QCLs that can be operated at high temperatures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐resolved photoluminescence of type‐II InAs/GaAs quantum dots covered by a thin GaAs1–xSbx layer
Authors: Liao Yu‐An , Hsu Wei‐Ting , Lee Ming‐Chih , Chiu Pei‐Chin , Chyi Jen‐Inn , Chang Wen‐Hao 
Published: March 2009

AbstractWe investigate carrier lifetimes of InAs/GaAs quantum dots (QDs) covered by a thin GaAs1–xSbx layer by time‐resolved photoluminescence (PL). Both the power dependent PL peak shift and the longer decay time confirm the type‐II band alignments. Different recombination paths have been identified by temperature dependent measurements. At low temperatures, the long‐range recombination with holes trapped in the GaAsSb layer is significant, resulting in non‐single‐exponential decays. The short‐range recombination with holes confined in the band‐bending region surrounding the InAs QDs is important at higher temperatures. The variation in decay time across the ground‐state and the temporal PL peak redshift further confirm the localization of holes in the GaAsSb layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Firm and industry effects on firm performance: A generalization and extension for new ventures
Authors: Short Jeremy C. , McKelvie Alexander , Ketchen David J. , Chandler Gaylen N. 
Published: March 2009

AbstractOur study extends a long‐running debate into the domain of entrepreneurship by examining firm and industry effects on the performance of new ventures. We examine to what extent firm and industry levels explain sales, sales growth, and survival among 7,256 young Swedish firms over a five‐year period, and compare these findings to a sample of 12,692 established firms. We found that the industry level ‘matters’ little for the survival of either sample of firms, and industry membership matters less for the sales and sales growth of new ventures than for established firms. Post hoc analysis revealed that size affects new venture performance, and that new venture funding is related to both sales and survival. At a broad level, our findings shed new light on the roles of the liabilities of newness and smallness for the performance of new ventures. Copyright © 2009 Strategic Management Society.
On Ovariotomy in Sows with Observations on the Mammary Glands and the Internal Genital Organs
Authors: Mackenzie K. J. J. , Marshall F. H. A. 
Published: March 2009

(1) Distinct changes take place in the tissues of the mammary region in sows during the period of heat. These changes consist mainly of congestion of the glands. Moreover the part affected is in the pig of much commercial value.(2) The black pigment often found in the mammary tissue of black sows is not associated with the recurrence of heat, and the bacon manufacturer who wishes to differentiate between sows slaughtered at this period and other sows must not rely on this pigment as a guide.(3) Since ovulation occurs during oestrus and not during prooestrum it is advisable to “hog” the sow towards the end of her heat period.
The soil-point method for directly estimating the water-supplying power of a soil in the field
Authors: Hardy F. 
Published: March 2009

1. Attention is drawn to Mason's modification of Livingston's soilpoint method of directly estimating the water-supplying power of a soil in situ. Mason used ordinary lead writing pencils as soil-points.2. This method, heretofore tested only in the laboratory, has been employed by the writer in an ecological field study. Details of the procedure adopted are described, and the reliability of the method is indicated by the presentation of a series of mean results with their corresponding probable errors.3. It is concluded that the method is practicable; it should prove of considerable usefulness to workers in ecology.
The influence of the administration of certain oils on the nutritive value of the butter fat of cows on winter rations
Authors: Drummond Jack Cecil , Channon Harold John , Coward Katharine Hope , Golding John , Mackintosh James , Zilva Sylvester Solomon 
Published: March 2009

(1) Further experiments are described, the results of which support the relationship between the presence of vitamin A in the diet of the cow and its presence in milk fat.(2) The typical winter ration of concentrates, roots and hay may be adequate to maintain the vitamin A value of the milk fat for considerable periods provided that at least one of the components supplies adequate amounts of that dietary principle. Well cured green meadow hays are in this respect greatly superior to dry brown seeds hays.(3) The addition of cod liver oil to a winter ration deficient in vitamin A will induce a sharp rise in the vitamin A value of the milk fat of cows. No such effect is seen when oils deficient in this dietary factor (coconut oil, arachis oil) are given.(4) The administration of cod liver oil in doses from 1 to 8 ozs. daily to milking cows caused no “fishy” taint in the milk or butter-fat.(5) The administration of cod liver oil caused no appreciable change in the yield of milk but the higher doses appeared to cause a noticeable drop in the percentage of fat. Further experiments are required to throw more light on this observation.