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At least 127 records · Page 7Linked to original sources
PubMed1998

Artificial cells with emphasis on cell encapsulation of genetically engineered cells.

Artificial cells are prepared in the laboratory for medical and biotechnological applications. Encapsulated cells are being studied for the treatment of diabetes, liver failure, and other conditions. More recently, there have been extensive studies into the use of encapsulated genetically engineered cells for gene therapy. We recently found that daily orally administered artificial cells, each containing a genetically engineered microorganism, can lower the elevated urea level in uremic rats to normal levels. This may solve the final obstacle of the lack of an effective oral urea removal system for the simple and inexpensive oral treatment of uremia. This is important because 85% of the world's uremic population cannot afford standard dialysis. Other areas of artificial cell application include use in hemoperfusion. Red blood cell substitutes based on modified hemoglobin are already in Phase 3 clinical trials in patients. Artificial cells containing enzymes are being developed for clinical trial in hereditary enzyme deficiency disease and other diseases. They are also being investigated for drug delivery and for use in other applications in biotechnology, chemical engineering, and medicine.

Administration, Oral↗
PubMed2005

Electrochemical removal of metal ions from aqueous solution: a student workshop.

An environmental electrochemistry workshop program on metal ion removal is described. The program was designed for undergraduate students in chemistry, chemical engineering or environmental science and teaches environmental electrochemistry through a combination of hands-on experiments, understanding of research concepts, completion of project reports and in class discussion. The students are encouraged to quantitatively describe the performance of the electrochemical cells (containing 2-D and 3-D carbon cathodes) and to consider the advantages and shortcomings of electrochemical routes to environmental treatment.

Cations↗
PubMed1999

An information theoretic approach for combining neural network process models.

Typically neural network modelers in chemical engineering focus on identifying and using a single, hopefully optimal, neural network model. Using a single optimal model implicitly assumes that one neural network model can extract all the information available in a given data set and that the other candidate models are redundant. In general, there is no assurance that any individual model has extracted all relevant information from the data set. Recently, Wolpert (Neural Networks, 5(2), 241 (1992)) proposed the idea of stacked generalization to combine multiple models. Sridhar, Seagrave and Barlett (AIChE J., 42, 2529 (1996)) implemented the stacked generalization for neural network models by integrating multiple neural networks into an architecture known as stacked neural networks (SNNs). SNNs consist of a combination of the candidate neural networks and were shown to provide improved modeling of chemical processes. However, in Sridhar's work SNNs were limited to using a linear combination of artificial neural networks. While a linear combination is simple and easy to use, it can utilize only those model outputs that have a high linear correlation to the output. Models that are useful in a nonlinear sense are wasted if a linear combination is used. In this work we propose an information theoretic stacking (ITS) algorithm for combining neural network models. The ITS algorithm identifies and combines useful models regardless of the nature of their relationship to the actual output. The power of the ITS algorithm is demonstrated through three examples including application to a dynamic process modeling problem. The results obtained demonstrate that the SNNs developed using the ITS algorithm can achieve highly improved performance as compared to selecting and using a single hopefully optimal network or using SNNs based on a linear combination of neural networks.

Journal Article↗
PubMed1978

The hazards of a chemical laboratory environment--a study of the mortality in two cohorts of swedish chemists.

The causes of death among the 93 chemists belonging to a cohort of 857 men, who graduated from the Schools of Chemical Engineering at the Royal Institute of Technology (KTH), Stockholm, and the Chalmers Institute of Technology (CTH), Gothenburg, Sweden, during the years 1930 to 1950, were studied. The group was followed until the end of 1974. There was a significant increase of cancer, particularly of leukemias/malignant lymphomas and of urogenital tumors. The study indicated that chemists, who continued with laboratory work for at least a few years after graduation and specifically worked with organic compounds, displayed an increased frequency of death from cancer.

Adult↗
PubMed1995

Engineering membrane proteins.

Much of the research on integral membrane proteins mirrors that on soluble proteins; however, membrane protein engineering also has its own ends and means, many of which take advantage of the peculiar situation of membrane proteins, whose chains are distributed between one lipidic and two aqueous phases. Extramembrane loops have been shortened, cut, or elongated with segments forming proteolytic cleavage sites, foreign epitopes, extra transmembrane segments, or even whole proteins, with the aim of facilitating purification, biochemical/biophysical studies, or crystallogenesis. Transmembrane alpha-helices have been deleted, duplicated, exchanged, transported into a foreign context or replaced with synthetic peptides, in order to both understand their integration into, and assembly in, the membrane and unravel their functional role. Insertion of cysteine residues has been the basis for a great diversity of experiments, ranging from the exploration of secondary, tertiary and quaternary structures of the transmembrane region to the creation of anchoring points for reporter molecules. Chemical engineering--the synthesis of protein fragments or even of whole proteins--offers particularly exciting new prospects, given the small size of folding domains in alpha-helical membrane proteins. Membrane protein engineering is rapidly developing its own agenda of questions and tool chest of techniques.

Bacteriorhodopsins↗
PubMed2005

Dynamic adsorption of radon by activated carbon.

The adsorption of radon on activated carbon has been used in or considered for a number of applications, including in situ decay beds, cyclic decontamination systems, and diffusive samplers. And although there are numerous measurements of the adsorption coefficients of specific activated carbons for radon, each of these applications depends on knowing, in addition to the adsorption coefficient for radon, the mass transfer factors describing its dynamic adsorption. Here we used a standard procedure in gas chromatography and chemical engineering, the spreading of a pulse as it passes through a bed of adsorbent, to determine these mass transfer factors. For this application, this procedure is developed further to correct the radon adsorption data for distortions caused by the decay of radon and by the presence of radon decay products in the detector. The results from eight activated carbons show a wide variation in the mass transfer coefficients for radon, which could affect significantly the suitability of adsorbents, as demonstrated here by the effect that mass transfer has on the performance of in situ decay beds.

Adsorption↗
PubMed2006

[Regenerating agents (RGTAs): a new therapeutic approach].

RGTAs, or ReGeneraTing Agents constitute a new class of medicinal substance that enhance both speed and quality of tissue healing and leading in some case to a real tissue regenerating process. RGTAs consist of chemically engineered polymers adapted to interact with and protect against proteolytic degradation of cellular signaling proteins known as growth factors, cytokines, interleukins, colony stimulating factors, chemokines, neurotrophic factors etc. Indeed almost all these proteins of cellular communication are naturally stored in the extra cellular matrix interacting specifically with the heparan sulfates or HS. After tissue injury of any cause, cells die liberating glycanases and proteases inducing first HS degradation then liberation of the cytokines which in turn are susceptible to degradation as they are no longer protected. By replacing the natural HS, RGTAs will protect cytokines from proteolyses as they are liberated from the matrix compartment matter in the wound. This spatio-temporal selective protection of cytokines results in a preservation of the natural endogenous signaling of a tissue and is reflected by spectacular tissue regeneration or by a very greatly improved tissue repair. These observations indicate that mammals have an unexpected ability to regenerate and that RGTA helps to reveal this capacity. The aim of OTR3 is to develop RGTA into a drug to treat specific tissue lesions.

Animals↗
PubMed1998

High resolution electron microscopy investigations of interface and other structure defects in some ceramics.

Interface, grain boundary, and other structure defects are the most important structural factors to affect the properties of ceramics materials. The present paper shows the relationship between the properties and those structure features such as grain boundaries, phase boundaries, interfaces, twins, intergrowths, dislocations, point defect aggregates, order-disorder, and other structure defects in different kinds of ceramics materials. At present this research covers: C60, sialon-based ceramics (alpha-sialon/SiC(w) composite, Y-alpha-sialon/beta-sialon composite), high Tc superconductors (YBa2Cu3O7, YBa2Cu4O8, Bi2Sr2CaCu2O8, Bi2Sr2Ca2Cu3O10), and bioceramics (hydroxyapatite, chlorapatite) and so on. The structure features mentioned above were characterized by high-resolution electron microscopy; so the structure details are at an atomic level and the related physical, chemical, engineering, even biological phenomena can be understood at an atomic and molecular level.

Biocompatible Materials↗
PubMed1998

Malcolm Lilly.

Explore the source record for details and available documents.

Biomedical Engineering↗
PubMed2000

Commentary: using the convection-dispersion model and transit time density functions in the analysis of organ distribution kinetics.

The convection-dispersion model and its extended form have been used to describe solute disposition in organs and to predict hepatic availabilities. A range of empirical transit-time density functions has also been used for a similar purpose. The use of the dispersion model with mixed boundary conditions and transit-time density functions has been queried recently by Hisaka and Sugiyama in this journal. We suggest that, consistent with soil science and chemical engineering literature, the mixed boundary conditions are appropriate providing concentrations are defined in terms of flux to ensure continuity at the boundaries and mass balance. It is suggested that the use of the inverse Gaussian or other functions as empirical transit-time densities is independent of any boundary condition consideration. The mixed boundary condition solutions of the convection-dispersion model are the easiest to use when linear kinetics applies. In contrast, the closed conditions are easier to apply in a numerical analysis of nonlinear disposition of solutes in organs. We therefore argue that the use of hepatic elimination models should be based on pragmatic considerations, giving emphasis to using the simplest or easiest solution that will give a sufficiently accurate prediction of hepatic pharmacokinetics for a particular application.

Algorithms↗
PubMedDate not supplied

In memoriam Dr Marlene DeLuca. 1987 O. M. Smith Lecture. Firefly luciferase: mechanism of action, cloning and expression of the active enzyme.

The untimely death of Marlene DeLuca in 1987 has deprived the scientific community of an outstanding expert on bioluminescence. Earlier in that year she was honoured as the thirty-ninth recipient of the Otto Mitchell Smith Lectureship Award at Oklahoma State University, Stillwater, Oklahoma. On 20 March 1987 Dr DeLuca presented a scientific lecture entitled 'Firefly Luciferase--Mechanism of Action, Cloning, and Expression of the Active Enzyme' and a popular lecture at the banquet that evening entitled 'Light and Life'. She was selected for her excellence in research, her oral presentation ability, and her personableness. Marlene was the first woman so honoured. To honour Dr Otto M. Smith the Alpha Delta Chapter of Phi Lambda Upsilon, a national chemistry honorary organization, inaugurated The Otto Mitchell Smith Lectureship in 1948 at Oklahoma State University. Former awardees include Nobel Laureates H. C. Brown, Stanford Moore, and Arthur Kornberg and the following prominent biochemists/molecular biologists: Robert A. Alberty, University of Wisconsin; Daniel E. Koshland, Brookhaven National Laboratory; Sol Spiegelman, University of Illinois; Carl Djerassi, Stanford University; and John T. Edsall, Harvard University. The lectureship honours Dr O. M. Smith, who was Director of the Research Foundation, professor, and Head of the Departments of Chemistry and Chemical Engineering. As a tribute to Dr DeLuca's outstanding contribution to bioluminescence we reproduce here the edited text of her Otto Mitchell Smith Lectureship and a selected bibliography of her work on firefly bioluminescence.

Awards and Prizes↗
PubMed2003

Continuous flow techniques in organic synthesis.

As part of the dramatic changes associated with the need for preparing compound libraries in pharmaceutical and agrochemical research laboratories, the search for new technologies that allow automation of synthetic processes has become one of the main topics. Despite this strong trend for automation high-throughput chemistry is still carried out in batches, whereas flow-through processes are rather restricted to production processes. This is far from understandable because the main advantages of that approach are facile automation, reproducibility, safety, and process reliability, because constant reaction parameters can be assured. Indeed, methods and technologies are missing that allow rapid transfer from the research level to process development without time-consuming adaptation and optimization of methods from the laboratory scale to production plant scale. Continuous-flow processes are considered as a universal lever to overcome these restrictions and, only recently, joint efforts between synthetic and polymer chemists and chemical engineers have resulted in the first continuous-flow devices and microreactors; these allow rapid preparation of compounds with minimum workup. Many of these approaches use immobilized reagents and catalysts, which are embedded in a structured flow-through reactor. It is generally accepted, that for achieving best reaction and kinetic parameters for convective-flow processes monolithic materials are ideally suited as solid phases or polymer supports. In addition, immobilization techniques have to be developed that allow facile regeneration of the active species in the reactor.

Journal Article↗
PubMed2006

Combining enabling techniques in organic synthesis: continuous flow processes with heterogenized catalysts.

The concepts article describes enabling techniques (solid-phase assisted synthesis, new reactor design, microwave irradiation and new solvents) in organic chemistry and emphasizes the combination of several of them for creating new synthetic technology platforms. Particular focus is put on the combination of immobilized catalysts as well as biocatalysts with continuous flow processes. In this context, the PASSflow continuous flow technique fulfils both chemical as well as chemical engineering requirements. It combines reactor design with optimized, monolithic solid phases as well as reversible immobilization techniques for performing small as well as large scale synthesis with heterogenized catalysts under continuous flow conditions.

Journal Article↗
PubMed1990

Preparative free-flow isoelectric focusing: modeling and experiments.

Free-flow isoelectric focusing was adapted to preparative scale separations and chemical engineering methods were used to describe the main mechanisms operating in the apparatus. A mixture of human serum albumin (pI 4.6) and beta-lactoglobulin (pI 5.22) was separated in pH gradients, generated with carrier ampholytes of different origin and covering the pH ranges 4-6.5, 3.5-5, 4-5.5 and 4.5-5.0. Best results were obtained in the pH 4-5.5 range. The experimental results have validated the results obtained with a numerical model.

Ampholyte Mixtures↗
PubMed2004

Quantitative assessment of fibrinogen cross-linking by epsilon aminocaproic acid in patients with end-stage liver disease.

Analysis of the effectiveness of antifibrinolytic therapy for liver transplant recipients is hampered by lack of quantitative assays for assessing drug effects. We adapted chemical engineering tools used in polymerization studies to quantify fibrinogen cross-linking by plasma from liver transplant patients obtained before and after epsilon aminocaproic acid (EACA) therapy. A target fluorescein isothiocyanate-fibrinogen (FITC-fibrinogen) molecule was constructed; it fluoresces in a quantifiable pattern when in solution, and undergoes cross-linking in the presence of plasmin inhibitors. Cross-linking quenches the fluorescent signal, and the quenching is a quantifiable endpoint. Thus fluorescence from this reporter molecule can be used to assess functional improvement in fibrinogen cross-linking as a result of antifibrinolytic therapies, and it is sensitive to picomolar amounts of plasmin inhibitors and activators. Cross-linking of FITC-fibrinogen by patient plasma, before and after EACA therapy, was assessed using fluorescence spectrometry. Fluorescence patterns from FITC-fibrinogen indicated no significant cross-linking of the target fibrinogen as a consequence of EACA in posttreatment plasma. When the fibrinogen-FITC target was assayed without plasma in the presence of EACA at concentrations that bracket therapeutic levels (100 and 400 microg/ml), significant fluorescence quenching (target FITC-fibrinogen cross-linking) was achieved. These results suggest that fibrinogen-FITC fluorescence is sensitive enough to detect EACA activity in clinically relevant ranges, but that EACA given in usual doses is insufficient to promote fibrinogen cross-linking in patients with end-stage liver disease.

Adult↗
PubMed2004

Quantifying arbitrary magnetic susceptibility distributions with MR.

Magnetic susceptibility, as a physical property of materials, plays important roles in many physical, chemical, engineering, and medical applications. Its quantification becomes of significant interest when MRI becomes a commonly used technique in biomedical applications. A general method is presented here for quantifying arbitrary magnetic susceptibility distributions in a localized region on the basis of first principles of magnetic induction field distributions in space. A proof of the concept was demonstrated by computer simulations. The study establishes the methodological basis for quantitative magnetic susceptibility imaging with MR.

Computer Simulation↗