Showing papers by "Lehigh University published in 1984"

Characterization of the secreted cellulases of Trichoderma reesei wild type and mutants during controlled fermentations

Abstract: The cellulases produced under pH controlled fermentation conditions with 5% Solka Floc and cornsteep liquor as substrates by Trichoderma reesei wild type QM6a and two mutants, Rut-C30 and RL-P37, have been separated by isoelectric focusing in polyacrylamide gels. The total complement of secreted proteins of the two mutants was distinct from the parent. However, the number and isoelectric points of the various enzymes in the cellulase complex were unchanged in the mutants. All secreted proteins stained with Schiff's reagent which indicated they were glycoproteins. One mutant, Rut-C30, exhibited a dramatic shift in the CBH I proteins during the course of the fermentation. RL-P37 showed a two-fold increase in the specific activity of both the total cellulase complex and endoglucanase. In addition a productivity on the order of 100 IU/l/h was achieved. Co-produced with the cellulases were at least two acid proteases with differential activity towards azocoll and azocasein.

Acid–base complexes of polymers

Abstract: Les polymeres acides (chlorure polyvinylique surchlore, fluorure de polyvinyle, fluorure de polyvinylidene, polybutyral vinylique) absorbent fortement les vapeurs de solvants basiques et les polymeres basiques (PMMA) absorbent fortement les vapeurs de solvants acides. Importance des proprietes acidobasiques des polymeres dans l'adherence au verre

The boundary layer induced by a convected two-dimensional vortex

Abstract: The response of a wall boundary layer to the motion of a convected vortex is investigated. The principal cases considered are for a rectilinear filament of strength –κ located a distance a above a plane wall and convected to the right in a uniform flow of speed U∞*. The inviscid solution predicts that such a vortex will remain at constant height a above the wall and be convected with constant speed αU∞*. Here α is termed the fractional convection rate of the vortex, and cases in the parameter range 0 [les ] α < 1 are considered. The motion is initiated at time t* = 0 and numerical calculations of the developing boundary-layer flow are carried out for α = 0, 0.2, 0.4, 0.55, 0.7, 0.75 and 0.8. For α < 0.75, a rapid lift-up of the boundary-layer streamlines and strong boundary-layer growth occurs in the region behind the vortex; in addition an unusual separation phenomenon is observed for α [les ] 0.55. For α [ges ] 0.75, the boundary-layer development is more gradual, but ultimately substantial localized boundary-layer growth also occurs. In all cases, it is argued that a strong inviscid–viscous interaction will take place in the form of an eruption of the boundary-layer flow. The generalization of these results to two-dimensional vortices with cores of finite dimension is discussed.

The effect of organosolv pretreatment on the enzymatic hydrolysis of poplar

Abstract: The use of alcohol/water/catalyst mixtures to delignify wood allows the lignin to be recovered in a usable form while leaving the carbohydrate fraction relatively intact. The effects of temperature, reaction time, and the type of solvent and catalyst on the delignification of milled poplar wood were investigated. The lignin, cellulose, and hemicellulose composition of the pretreated material was measured for each treatment condition. In addition, the pretreated samples were subjected to enzymatic hydrolysis using the cellulases produced by the thermophilic bacterium Thermomonospora sp. YX. The extent of enzymatic hydrolysis was characterized using an empirical model, and the results were used to examine the effectiveness of the pretreatment.

Preparation of large-particle-size monodisperse latexes in space: polymerization kinetics and process development

Abstract: Monodisperse polystyrene latexes are prepared by seeded emulsion polymerization; however, sizes larger than 2 microns are difficult to prepare because of the creaming and settling of the particles and their sensitivity to mechanical shear. Preparation in space would obviate the creaming and settling, and allow agitation just sufficient for good heat transfer and mixing. Three polymerizations yielding 3-5 micron size particles were carried out successfully on the third flight of the 'Columbia' launched Mar. 22, 1982; however, four polymerizations yielding sizes up to 10 microns on the fourth flight launched June 27, 1982 were incomplete owing to apparatus malfunction. The results of these polymerizations and the prospects of developing a preparative space process are reviewed.

The HCH‐1 model of enzymatic cellulose hydrolysis

Abstract: Solka Floc BW200 was enzymatically hydrolyzed in a batch reactor using a commercial cellulase preparation. A total of 50 different hydrolysis conditions were run within a 10-fold range in enzyme concentration and a 30-fold range in cellulose concentration. The data were evaluated in three ways using five different models. Previous literature models were not as successful in correlating the data as the HCH-1 Model derived in this work.

Variability of the Sr/Ti Ratio in SrTiO3

Abstract: TiO2 is observed as a second phase in SrTiO3 having Sr/Ti ≤ 0.995 (≥0.5 mol% excess TiO2). The effect of excess TiO2 on the equilibrium electrical conductivity at 1000°C is consistent with a solubility of <0.1 mol% TiO2 with the formation of unassociated oxygen vacancies. More Ti02 is retained in solid solution when samples are quenched from the sintering temperature rather than furnace-cooled. The effect of excess SrO on the equilibrium electrical conductivity also indicates some solid solubility.

A degree of controllability definition - Fundamental concepts and application to modal systems

Abstract: Starting from basic physical considerations, this paper develops a concept of the degree of controllability of a control system, and then develops numerical methods to generate approximate values of the degree of controllability for any linear time-invariant system. In many problems, such as the control of future, very large, flexible spacecraft and certain chemical process control problems, the question of how to choose the number and locations of the control system actuators is an important one. The results obtained here offer the control system designer a tool which allows him to rank the effectiveness of alternative actuator distributions, and hence to choose the actuator locations on a rational basis. The degree of controllability is shown to take a particularly simple form when the dynamic equations of a satellite are in second-order modal form. The degree of controllability concept has still other fundamental uses - it allows one to study the system structural relations between the various inputs and outputs of a linear system, which has applications to decoupling and model reduction.

A simulation-based experimental investigation of supply/timing uncertainty in MRP systems

Abstract: SUMMARY The uncertainty inherent in material requirements planning (MRP) systems is of two general types: demand uncertainty and supply uncertainty. Supply uncertainty is a result of late deliveries (timing) or order shrinkage (quantity) or both. The purpose of this paper is to examine the impact of operating policies on an MRP system given supply uncertainty resulting from timing factors, specifically the uncertainty caused by variability in the lead time of purchased parts. Experiments arc conducted to assess the impact of four factors: the amount of lead time variability, the amount of safety stock or safety lead time, the lot-size rule, and the holding cost and lateness penalty, on the total cost of the MRP system given supply/timing uncertainty. An MRP/Production simulator is employed to perform the experiments. Practical guidelines for the manager of an MRP system with supply/timing uncertainty are presented.

cooperation, competition, and synergy: information‐sharing groups among Southeast Alaskan salmon seiners

Abstract: The salmon seine fishery of Southeast Alaska is a tightly regulated and very competitive commercial enterprise. Despite relations marked by competition, small groups of skippers cooperate with one another to the extent of sharing information as they scout for salmon just in advance of legal seine periods. This paper analyzes these voluntary action groups in terms of the role they play in helping skippers to discharge their most important responsibility: deciding where to fish. The size, timing of activities, and limited purpose of the groups are then explicated with respect to the cultural ecology of the seine fishery. [maritime anthropology, voluntary action, cultural ecology, decision processes]

Theory of off-center impurities in silicon: Substitutional nitrogen and oxygen

Abstract: The single-particle electronic structures and atomic displacements of substitutional nitrogen and oxygen in silicon are treated theoretically in a cluster representation using both the scattered-wave $X\ensuremath{\alpha}$ ($\mathrm{S}\mathrm{W}\ensuremath{-}X\ensuremath{\alpha}$) and modified neglect of diatomic overlap (MNDO) electronic-structure methods. Substitutional carbon and sulfur are treated to a lesser degree for the purpose of comparison. The impurity $X$ and its environment are simulated by the clusters $X{\mathrm{Si}}_{4}{\mathrm{H}}_{12}$ ($\mathrm{S}\mathrm{W}\ensuremath{-}X\ensuremath{\alpha}$ and MNDO) and $X{\mathrm{Si}}_{16}{\mathrm{H}}_{36}$ (MNDO only). In all cases, we find a localized occupied ${a}_{1}$ state in the gap with a localized unoccupied ${t}_{2}$ state above it when the impurity atoms are on center. Using computed MNDO total energies for $X{\mathrm{Si}}_{4}{H}_{12}$ as a function of impurity displacement, we find spontaneous displacement directions correctly predicted for neutral carbon, nitrogen, oxygen, and sulfur, and for negative oxygen. By monitoring the single-particle energies and eigenvectors, we identify the driving force for the spontaneous asymmetric displacements as a pseudo\char22{}Jahn-Teller effect. We further explore the total energy with respect to simultaneous impurity and near-neighbor-silicon displacements, where the effect of the host outside the cluster is simulated by "external springs" connected to the four silicon atoms of the cluster. We find that it is necessary to use effective springs that are quite different from those which follow from a valence-force treatment in order to reproduce the observed spontaneous displacements of the substitutional nitrogen and oxygen impurities. This failure of the simple valence-force treatment is discussed. Our results also suggest a model for the "thermal donor" in silicon, whereby a substitutional oxygen is pushed "on center" by the strain field due to surrounding oxygen interstitials.

Experimental and theoretical determination of kAFe factors for quantitative X‐ray microanalysis in the analytical electron microscope

Abstract: SUMMARY Quantitative X-ray microanalysis in the analytical electron microscope involves the se of Gliff—Lorimer kA3 factors to relate measured X-ray intensities from elements A and B to their composition. This study has generated a wide range of these factors for both K and L )-ray lines. The values of the k factor for each element is ratioed to Fe, rather than to Si as has been - ., common practice to date. The use of kAFe rather than kASi factors reduces the uncert1ntY in the values due to variations in the efficiency of individual energy dispersive spectromters, thus making the values more universally applicable. New calculations of the value of kAFe have been made from first principles, encompaSing all of the most recent values of the cross-section for X-ray ionization. Comparison of the exeri mental results with both the calculations and existing k factor data has been made. Qlose attention has been paid to minimizing the errors in both the experimental and theoretica1 calculations to reduce the overall error in quantification of X-ray energy dispersive spectra in the analytical electron microscope.

A comparison of two empirical models for the enzymatic hydrolysis of pretreated poplar wood.

Abstract: Two empirical models for the enzymatic hydrolysis of cellulose are used to analyze the same set of experimental data to determine if one model is superior to the other. Both models adequately describe the data. The parameters in both models may be correlated to the hydrolysis conditions of enzyme, substrate, and product inhibitor concentrations. Both empirical models have features which are consistent with theoretical models of cellulose hydrolysis.

Parent-Child Interactions in Abusive and Nonabusive Families

Abstract: Parent-child interactions of 439 parent-child dyads were studied. These included 182 interactions with maltreated children, 199 interactions with maltreating adults, with the remaining interactions from control families served by child welfare agencies, day-care programs, Head Start, and private nursery schools. Income was found to be a significant determinant with parental behavior being more child-centered and supportive at the upper income level, and more parent-centered and child rejecting at the lower income level. Maltreatment was found to be associated with more parental rejection and less child warmth, over and above the effects of income level. The results are discussed in terms of an ecological model of child maltreatment and developmental implications for the victims of maltreatment.

Microbial oxidation of dibenzothiophene by the thermophilic organism Sulfolobus acidocaldarius

Abstract: The refractory organic sulfur compound dibenzothiophene (DBT) has been oxidized by the thermophilic, sulfur oxidizing organism Sulfolobus acidocaldarius. Sulfate ions were released into the medium as the oxidation product. The kinetics of this oxidation have been investigated on the basis of sulfate released as a result of oxidation. Dibenzothiophene was found to be inhibitory to the organisms for initial concentrations over 500 mg/L. The organism may prove to be capable of oxidizing thiophene compounds present in oil refinery wastewater, coal, and crude oil.

Crack growth in a single crystal superalloy at elevated temperature

Abstract: The influence of temperature and frequency on the crack propagation behavior of a single crystal superalloy has been investigated. At applied stress intensities approaching the fracture toughness, failure at all temperatures is associated with the fracture of script carbides ahead of the crack tip. At low and intermediate levels of ΔK the fatigue crack growth behavior is influenced by the temperature and frequency. At room temperature crack growth is found to occur by failure on {111} planes; at 600 °C and 850 °C crack growth is parallel to {100} . It has been shown that this behavior is not attributable to environmental interactions but arises from the morphology and distribution of the strengthening γ’ precipitate. Dislocations within the crack tip plastic zone are contained within the matrix, and crack propagation occurs primarily within the γ matrix by plasticity-controlled failure.

Acid-Base Contributions to Polymer-Filler Interactions

Abstract: 1. Acid-base interactions determine adsorption and bonding of polymers to fillers. 2. Quantitative predictability of the enthalpy of such bonding is attainable from the Drago C and E equation once the C and E constants are determined for polymers and fillers. 3. Infrared and calorimetric methods are discussed for determining the C and E constants for polymers and fillers. 4. For the case of poly(methylmethacrylate) filled with silica, the enthalpy of bonding has been determined by FTIR spectroscopy. 5. Acid-base interactions between polymers and fillers generate high zeta-potentials which tend to eliminate filler flocculation and reduce viscosity of filled polymer melts.

Core‐shell emulsion copolymerization of styrene and acrylonitrile on polystyrene seed particles

Abstract: Seeded emulsion copolymerization of an azeotropic composition of styrene (St) and an acrylinitrile (AN) comonomer mixture in polystyrene (PS) seed at different polymerization temperature of 55–75°C were investigated. The kinetic data showed a transition temperature at 65°C, above which the activation energy of polymerization is low, 6.1 Kcal/mol, compared with 9.8 Kcal/mol below it. The particle-size results and thin layer chromatographic (TLC) data showed two types of particle of different composition and morphology in the final latex system: a smaller size of (St–AN) copolymer and a larger size of core-PS and (St–AN) copolymer shell, with a zone of PS grafted (St–AN) copolymer in between. Various polymerization parameters, that is emulsifier concentration, type of seed particle and its size, and monomer/polymer ratio, were studied and their effects on particle size and particle morphology were examined. The percent of grafted core-PS was 10% below a polymerization temperature of 65°C and 40% above that temperature. By adjusting the size and number of the seed particles, monomer-polymer ratio, and emulsifier concentration conditions were established in which a final copolymer latex with “perfect” core-shell morphology was achieved.

Inverse emulsion polymerization of acrylamide: polymerization kinetics and process development

Abstract: Inverse emulsion polymerization confers the benefits of emulsion polymerization kinetics — rapid polymerization rates combined with high polymer molecular weights — on water-soluble polymers, particularly polyacrylamide and its copolymers and derivatives, and allows easy dissolution of the polymer in water by inversion of the latex. The mechanism and kinetics of the inverse emulsion polymerization of acrylamide in o-xylene containing Tetronic 1102 emulslfier and benzoyl peroxide initiator are described, particularly the formation of 10-200nm multiple emulsion droplets resulting from the particulate emulsifier, and their effect on the polymerization process

Dynamics of flexible bodies in tree topology - A computer oriented approach

Abstract: An approach suited for automatic generation of the equations of motion for large mechanical systems (i.e., large space structures, mechanisms, robots, etc.) is presented. The system topology is restricted to a tree configuration. The tree is defined as an arbitrary set of rigid and flexible bodies connected by hinges characterizing relative translations and rotations of two adjoining bodies. The equations of motion are derived via Kane's method. The resulting equation set is of minimum dimension. Dynamical equations are imbedded in a computer program called TREETOPS. Extensive control simulation capability is built in the TREETOPS program. The simulation is driven by an interactive set-up program resulting in an easy to use analysis tool.