bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluidized‐Bed Bioreactors
Authors: Gòdia Francesc , Solà Caries 
Published: March 2005

AbstractFluidized‐bed reactors present a number of advantages that make them an attractive alternative in processes involving biocatalysts. However, fluidized‐bed bioreactors are also realtively complex, basically for two reasons. First, their use requires the biocatalyst, commonly cells or enzymes, to be immobilized into or onto a solid support. Second, the hydrodynamic characterization is difficult, especially in those systems where three phases (gas—liquid—solid) are involved. The mathematical model of a fluidized‐bed bioreactor needs to take into account those hydrodynamic aspects that will determine the flux model in the reactor. Moreover, the description of other aspects is also required: the mechanisms of transport between the different phases, the kinetic equations for the phenomena taking place in the biocatalytic particles, such as cell growth, product formation, substrate consumption, enzyme deactivation, and the mass balance equations in the reactor. In addition to these aspects, the application of fluidized‐bed bioreactors to different kind of processes is also discussed. The potential of this type of bioreactor is also emphasized from the point of view of the different number of possible modifications in the design both of the bioreactor and the biocatalyst particles, in order to enhance its operation.
Phosphorescence Probes of the Glassy State in Amorphous Sucrose
Authors: Shahs Naina K. , Ludescher Richard D. 
Published: March 2005

AbstractWe have used phosphorescence from the luminescent chromophores N‐acetyltryp‐tophanamide (NATA) and erythrosin B (Ery B) to probe the molecular dynamics of the glassy state and the glass‐to‐rubber transition in amorphous sucrose. These measurements exploit the known sensitivity of phosphorescence intensity to the rate and extent of molecular collisions with the local environment. Both probes exhibit intense, well‐defined phosphorescence emission spectra in the glassy sugar matrix. Time‐resolved phosphorescence intensity decays for each probe were multiexponential both above and below the glass transition temperature, indicating that the sucrose matrix is heterogeneous on the molecular level; local microviscosities around the NATA probe were estimated in the range from 104 to 5 × 107 Pa·s in the glassy state at 25 °C. Plots of phosphorescence lifetime versus temperature for both probes are linear above and below the glass transition temperature of sucrose (62 °C), but exhibit a break in slope near approximately 50 °C characteristic of a dramatic change in the rate of molecular collision between the probe and the local environment. The similar sensitivity of two chemically different spectroscopic probes (the indole ring of NATA and the xanthene ring of Ery B) to molecular changes near the glass transition in this sugar indicates that phosphorescence may provide a generally applicable, site‐specific probe of the glassy state and changes in it in biological materials.
Comparative Enzyme Biodegradability of Xylan, Cellulose, and Starch Derivatives†
Authors: Glasser Wolfgang G. , Ravindran G. , Jain Rajesh K. , Samaranayake Gamini , Todd Jason 
Published: March 2005

AbstractThe enzyme biodegradability of xylan and of two of its prominent derivatives, (hydroxypropyl)xylan and xylan acetate, were examined comparatively vis‐à‐vis similar cellulose and starch derivatives, using a commercially available xylanase‐rich enzyme preparation. The results indicate that xylan, like cellulose and its derivatives, is subject to enzymatic depolymerization in relation to degree of substitution. Degradation paralleled the presence of unmodified xylose units in the polysaccharide. Degradation proceeded rapidly, with greater than 80% of total degradation being complete after only 1 day. A comparison with starch and cellulose derivatives revealed that hydroxypropyl xylan suffers less biodegradability loss as substitution rises to 0.25 or 0.4, after which loss of degradability parallels that of the corresponding cellulose and starch derivatives. This apparent tolerance to low degrees of substitution is attributed to molecular heterogeneity which suggests that constituents other than xylose become propoxylated initially. Xylan acetate was found to lose enzymatic biodegradability at a rate which parallels that of cellulose acetate, and this is 35% slower (with respect to DS) than corresponding starch acetates. Size exclusion chromatography results suggest that xylan degrades to monosaccharides, that xylan derivatives degrade to monosaccharides and oligosaccharides, and that substitution with lignin prevents xylan from being recognized by xylanolytic enzymes, resulting in loss of degradability.
Mathematical Model for Analysis of Mass Transfer for Immobilized Cells in Lactic Acid Fermentation
Authors: Wang Henian , Seki Minoru , Furusaki Shintaro 
Published: March 2005

AbstractA new mathematical model is proposed to analyze the mass transfer behavior in lactic acid fermentation using immobilized cells entrapped in calcium alginate. The model is comprised of material balance equations for glucose, free lactic acid, and several ions. The dissociation rate of lactic acid (rdiss) is involved in the proposed equations. To solve the equations numerically, a modified calculating method is proposed. Through model analysis, the possible mass transfer behavior in the gel bead was discussed. The model is validated by comparisons with the experimental results obtained from batch and continuous fermentation. The simulations using the model were made to investigate the mass transfer limitation in the gel beads. The results showed that the cell density gradient was formed in the gel beads and it was caused by the accumulation of the inhibitory product (free lactic acid), not by substrate starvation. Moreover, unusual mass transfer behavior of lactate ion in the immobilization support was pointed out.
Development of a Continuous Lactulose Process: Separation and Purification
Authors: Kozempel Michael F. , Kurantz Michael J. , Craig Jr. James C. , Hicks Kevin B. 
Published: March 2005

AbstractWe developed a continuous pilot plant process to produce lactulose from lactose using boric acid to boost the conversion to about 75%. The process consists of three reactors (two continuous stirred tank reactors followed by a tubular reactor), pH adjustment, a crystallizer—filter—evaporator recycle initial separation section, and a chromatographic purification system to produce lactulose containing less than 1–5 ppm of boric acid. The continuous process operates at 0.53 kg/min (20% solids) through the reactors and about 0.3 kg/min (55% solids) out of the initial separation section. The chromatographic separation is at the prep scale with a flow rate of 2.0 mL/min. The final product is a 55% solids syrup containing no detectable boric acid.
Studies of High Solidity Ratio Hydrofoil Impellers for Aerated Bioreactors. 1. Review
Authors: Mcfarlane Caroline M. , Nienow Alvin W. 
Published: March 2005

AbstractThis first part of a four‐part series of papers presents a review of the literature on high solidity ratio axial flow hydrofoil impellers. Interest in the application of high‐flow, low power number, hydrofoil impellers, such as the Prochem Maxflo T and the Lightnin A315, has developed over recent years and has largely been stimulated by reports of improved fermentation performance relative to the Rushton disc turbine. Initially, the review briefly examines the characteristics of the radial flow Rushton turbine, as traditionally used in fermenters, with particular reference to its weaknesses. It also discusses the use of pitched blade turbines (mixed flow impellers) for air dispersion since these show some characteristics similar to those of the axial flow hydrofoils. The consideration of these two impeller types provides the background to explain the advantages and potential problems associated with high solidity ratio, axial flow, downward pumping hydrofoils. These aspects are discussed in relation to existing literature which is still relatively scarce. Finally, the advantages of retrofitting are introduced. Parts 2–4 report on a recent, detailed, fluid dynamic study of the Prochem Maxflo T and Lightnin A315 hydrofoil impellers which extends our knowledge of these important impeller types.
Conditions Promoting Metal‐Catalyzed Oxidations during Immobilized Cu—Iminodiacetic Acid Metal Affinity Chromatography
Authors: Krishnamurthy Rajesh , Madurawe Rapti D. , Bush Kristen D. , Lumpkin Janice A. 
Published: March 2005

AbstractMany solutions that contain oxygen and/or hydrogen peroxide, transition metals, and reductants undergo metal‐catalyzed oxidation (MCO) reactions. These reactions produce highly reactive radical intermediates which can cause damage to a variety of biomolecules. Some of the types of damage caused by MCO reactions to proteins are activity losses, irreversible amino acid modifications, increased susceptibility to proteolysis, and/or fragmentation. The occurrence of such reactions in immobilized metal affinity chromatography (IMAC) systems has not been reported, nor has it been well studied. We report here enzyme activity studies of lactate dehydrogenase (LDH) during chromatography on an immobilized Cu2+‐‐iminodiacetic acid (IDA) metal affinity column and document the occurrence of MCO reactions under various chromatography conditions. Chromatography in the presence of the reducing agent ascorbate or the oxidant hydrogen peroxide caused LDH inactivation, and the presence of both reagents greatly enhanced the loss of activity. Increasing concentrations of reducing agent or hydrogen peroxide led to increased levels of damage. Chromatography under anaerobic conditions reduced LDH inactivation. Enzyme inactivation on the column was consistent with activity losses observed in solutions containing dissolved Cu2+‐‐IDA. Other reducing agents such as glutathione, β‐mercaptoethanol, and cysteine also caused LDH inactivation during chromatography. During chromatography in the presence of a reducing agent and/or peroxide, Cu+ and hydroxyl radicals were generated on the column and metal ions were removed from the column. Studies with the Cu+‐specific chelator bicinchoninic acid indicated that Cu+ was an essential component for the observed protein inactivation. The loss of enzyme activity in the presence of ascorbate and/or peroxide is most likely due to the occurrence of MCO reactions on the column. During chromatography in the absence of added reagents, the loss of LDH activity and the occurrence of MCO reactions were not detected over the chromatography times used in this study. However, LDH inactivation did occur in solutions containing dissolved Cu2+‐‐IDA. An understanding of the conditions under which MCO reactions occur during IMAC would aid the design of better downstream processing operations utilizing metal affinity methods.
Hollow Fiber Array Affinity Chromatography
Authors: Schisla D. K. , Carr P. W. , Cussler E. L. 
Published: March 2005

AbstractPreparative separations of creatine phosphokinase and bovine albumin are carried out by hollow fiber liquid chromatography. The hollow fibers used are poly(propylene), 240μm in diameter. They are uniformly coated with cross‐linked poly(vinyl alcohol) and then reacted with the triazine dye Procion Blue MX‐R. Experiments with these fibers show good protein separations, including those of the phosphokinase from the rabbit heart and the rabbit brain. Other experiments show that overloading can be successfully predicted. In terms of resolution at low sample loads, hollow fiber chromatography is currently inferior to analytical columns, though it is potentially superior for preparative separations.
Effective Bioconversion with Continuous Product Recovery Using AOT/Lecithin Mixed Reverse Micellar Systems and Centrifugal Partition Chromatography as a Novel Bioreactor
Authors: Yamada Yasushi , Kuboi Ryoichi , Komasawa Isao 
Published: March 2005

AbstractThe application of reverse micellar micro‐bioreactor systems for enzymatic conversion with continuous recovery of water‐soluble products was demonstrated, based on the production of galactose by micelles containing β‐galactosidase (β‐gal). The β‐gal was firmly encapsulated in AOT (bis(2‐ethylhexyl)sodium sulfosuccinate)/Lecithin mixed micelles. The addition of lecithin to the AOT reverse micelles stabilized the micellar interface, and the leakage of the encapsulated β‐gal to the bulk aqueous phase was therefore negligible, while substrate and product were free to transfer and partition owing to their low molecular weights. The stability of the solubilized β‐gal was also increased in the AOT/Lecithin mixed micelles as compared to the conventional AOT micelles. A considerably higher activity was observed in the present systems than in the bulk buffer solution. Enzymatic conversion and product recovery was carried out in a continuous operation mode by use of centrifugal partition chromatography (CPC), employing the reverse micellar solution with encapsulated β‐gal as the stationary phase and the substrate aqueous solution as the mobile phase. Use of the CPC contactor eliminated any mass transfer limitation on the substrate and the product, and galactose was continuously recovered in the effluent. The recovery of galactose continued for a period of 5 h with more than a 85% conversion at the optimum operating condition. This reverse micellar micro‐bioreactor system was thus found to be very effective for the continuous production and recovery of hydrophilic products.
Kinetics of bidirectional H+ and substrate transport by the proton-dependent amino acid symporter PAT1
Authors: FOLTZ Martin , MERTL Manuela , DIETZ Veronika , BOLL Michael , KOTTRA Gabor , DANIEL Hannelore 
Published: March 2005

PAT1 is a recently identified member of the PAT family of proton/amino acid co-transporters with predominant expression in the plasma membrane of enterocytes and in lysosomal membranes of neurons. Previous studies in Xenopus oocytes expressing PAT1 established proton/substrate co-transport associated with positive inward currents for a variety of small neutral amino acids. Here we provide a detailed analysis of the transport mode of the murine PAT1 in oocytes using the two-electrode voltage-clamp technique to measure steady-state and pre-steady-state currents. The GPC (giant patch clamp) technique and efflux studies were employed to characterize the reversed transport mode. Kinetic parameters [Km (Michaelis constant) and Imax (maximum current)] for transport of various substrates revealed a dependence on membrane potential: hyperpolarization increases the substrate affinity and maximal transport velocity. Proton affinity for interaction with PAT1 is almost 100 nM, corresponding to a pH of 7.0 and is independent of substrate. Kinetic analysis revealed that binding of proton most likely occurs before substrate binding and that the proton and substrate are translocated in a simultaneous step. No evidence for a substrate-uncoupled proton shunt was observed. As shown by efflux studies and current measurements by the GPC technique, PAT1 allows bidirectional amino acid transport. Surprisingly, PAT1 exhibits no pre-steady-state currents in the absence of substrate, even at low temperatures, and therefore PAT1 takes an exceptional position among the ion-coupled co-transporters.
Elicited and spontaneous communicative functions and stability of conversational measures with children who have pragmatic language impairments
Authors: Adams Catherine , Lloyd Julian 
Published: March 2005

AbstractBackground: The preliminary phase of a project aimed at establishing appropriate outcome measures for intervention with children who have pragmatic language impairments (PLI) is reported. Assessment methods for children with PLI are considered in the context of developing outcome measures for intervention studies. Communicative function assessments in elicitation and conversational contexts are compared. The stability of measures derived from conversational profiling is also considered.Aims: To investigate the utility of an elicited communicative function assessment in discriminating the pragmatic characteristics of children with PLI and to compare this method to conversational profiling. An additional aim was to estimate the degree of variation on conversational indices derived from interactions with children with PLI.Methods & Procedures: Fifteen children with PLI (mean age 9;5 years) and an age‐matched control group were assessed on two occasions on a new communicative function elicitation task and on a conversation task. A checklist of communicative functions was employed in analysing the elicitation and the conversation tasks. An analysis of conversation was carried out to derive conversational indices such as verbosity and meshing.Outcomes & Results: The elicitation task failed to discriminate between the PLI and control groups and showed a strong ceiling effect. Significant between‐group differences were found for both communicative function in conversation measures and on conversational indices. The variation in conversation indices is relatively small compared with the baseline measures.Conclusions: A more representative picture of communicative function ability arises from unstructured tasks rather than from structured elicitation tasks for the age group of children with PLI. The elicitation procedure outlined in this paper might be better suited to a younger age group. Differences between communicative function performance on elicitation and conversation situations suggest a strong effect of context on the pragmatic performance of children with PLI. The conversational indices reported show sufficient stability to be employed in an outcome measure provided the minor variations indicated are factored into estimates of change.
Personal photon dosemeter trial—Devonport Royal Dockyard
Authors: Collison Roger 
Published: March 2005

To establish an understanding of the operational responses of various personal dosemeters employed at Devonport and to assess new types of dosemeters, a photon dosemeter trial was conducted. Most day-to-day exposure is to relatively low dose rates. Therefore the suitability of each dosemeter for use within the relatively low Devonport dose rate environment has been assessed.The Panasonic TLD demonstrated a good representation of the dose within the medium to higher gamma energy ranges with an unexpected under-response at lower energies.The optically stimulated luminescent dosemeter showed a varied response within a degraded60Co environment.With consistent under-response, the NRPB TLD and film badge were found to generally be unsuitable for sites such as Devonport.The Harshaw TLD demonstrated a good representation of the dose.The RADOS RAD80 and QFD fail to meet current best industry standards. However, the QFD is the only direct reading dosemeter suitable for use where intrinsically safe equipment is required.The RADOS RAD52 and SAIC PD 2i show a reasonable representation of the dose received but should be adjusted to read within an operational60Co environment.Direct ion storage and Thermos electronic personal dosemeters showed good representations of the dose. Inherent characteristics combined with the associated systems led to the conclusion that these dosemeters should be employed for preference.
Lymphangioma‐like Kaposi sarcoma
Authors: Ramirez James A. , Laskin William B. , Guitart Joan 
Published: March 2005

Background:  Lymphangioma‐like Kaposi's sarcoma (LLKS) is a rare morphologic expression of Kaposi's sarcoma (KS) that occurs in virtually all of the well‐recognized clinical subtypes of the disease and has the potential to mimic other pathologic processes. In this study, we present the clinical and pathological features of four patients with LLKS.Methods:  Four cases of LLKS were retrieved from the dermatopathology files of our institution. All four tumours were tested immunohistochemically with anti‐human herpesvirus‐8 (HHV‐8) latent nuclear antigen‐1 (LNA‐1) and anti‐CD34 antibodies.Results:  Clinically, each patient presented with violaceous patches, papules or plaques; one patient presented with bullous lesions. All of the LLKS biopsy specimens revealed areas with characteristic light microscopic features of KS. Lymphangioma‐like foci consisted of ectatic, irregularly shaped vascular spaces lined by mildly atypical endothelial cells. All tumour cells, including those associated with LLKS foci, showed a strong and diffuse reactivity for anti‐HHV‐8 LNA‐1 and anti‐CD34. KS progressed slowly in two patients with adequate follow‐up.Conclusions:  As LLKS can mimic other disease processes, the correct diagnosis relies heavily on the recognition of salient clinical and histological features of conventional KS, including a strong immunohistochemical expression of HHV‐8‐associated LNA‐1 in lesional cells.
Structure Change of Ca2SiO4 Solid Solutions with Ba Concentration
Authors: Fukuda Koichiro , Maki Iwao , Adachi Keisuke 
Published: March 2005

A series of Ba‐bearing Ca2SiO4 solid solutions (C2S(ss)), (BaxCa1−x)2SiO4 with 0.075 x 0.30, were prepared and examined by X‐ray and electron beam diffraction. They are all made up of orthorhombic domains 120° different in orientation around the common c axis of the former α phase. The C2S solid solution with x= 0.075 shows a superstructure incommensurate along the a axis with λ (modulation wavelength) = 3.5 and commensurate along the c axis with Δ= 3. With x= 0.15, modulation is observed only along the a axis and Δ= 3.4. No evidence of superstructure is found with x= 0.24; the space group and cell dimensions are comparable with those of pure α’H‐C2S. The C2S(ss) with x= 0.30 gives a superlattice with the cell‐edge length of 3b. All the C2S(ss), when reheated at 1000°C for 24 h, produced lamellae of the trigonal phase T nearly in parallel with (001) of the host α’L phase. The crystallographic orientation between the two phases is
image
This indicates that the above Ba‐bearing C2S(ss) phases occur as precursors to the thermodynamically more stable two‐phase mixtures.
Acquired APC resistance and oral contraceptives: differences between two functional tests
Authors: Curvers Joyce , Thomassen M. Christella L. G. D. , Nicolaes Gerry A. F. , Van Oerle Rene , Hamulyak Karly , Coenraad HEMKER H. , Tans Guido , Rosing Jan 
Published: March 2005

Resistance to activated protein C (APC) is often associated with a mutation in factor V (factor VLeiden). Individuals without factor VLeiden who exhibit a response in functional APC‐resistance tests similar to that of carriers of factor VLeiden are considered to be acquired APC resistant. This phenomenon is particularly observed in women using oral contraceptives (OC).In the present study we compared the response to APC in plasma from normal individuals, carriers of factor VLeiden and women who use OC using functional tests that either quantify the effect of APC on the endogenous thrombin potential (ETP) or on the activated partial thromboplastin time (aPTT).Both tests discriminated equally well between individuals with and without factor VLeiden who were not using OC. In contrast to the aPTT‐based test, the ETP‐based assay yielded significant differences in sensitivity to APC between non‐OC users and OC users and between users of second and third generation OC. Since there was no correlation between APC‐sensitivity determined with both assays in non‐carriers of factor VLeiden and in women who use OC and a poor correlation in carriers of factor VLeiden, we propose that other plasma components differentially modulate the response to APC in the aPTT‐ and ETP‐based APC‐resistance tests and that OC change the level of plasma protein(s) that modulate the effect of APC on thrombin formation initiated via the extrinsic coagulation pathway.