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Grenci J, Todd DB. Effect of Conversion on Chain Addition Copolymerizations Performed in a Backmixed Drag Flow Extruder Reactor. INT POLYM PROC 2022. [DOI: 10.1515/ipp-2000-0006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The use of a drag flow device such as a twin screw extruder for polymerization and/or copolymerization processes has been studied extensively over the years. Due to the high viscosities (100 to 100 000 poise) that are produced, poor backmixing is experienced in these drag flow devices. As a result, these studies have shown the extruder reactor to exhibit a ‘‘plug flow’’ behavior. A drag flow device has been developed that achieves good backmixing with high viscosity materials. This device incorporates two counter-rotating, nonintermeshing, screws; one screw conveying material forward, while the other conveying material backward.
Theory suggests that in a plug flow reactor the copolymer composition varies (drifts) as a function of time (position) in the reactor in most cases. Conversely in a micromixed continuous stirred tank reactor (CSTR) the copolymer produced does not drift as a function with position in the reactor. It has also been shown that this drift in copolymer composition becomes more pronounced at higher conversion. Experiments were performed in a counter-rotating nonintermeshing twin screw extruder using the ‘‘backmixed’’ configuration and a ‘‘conventional’’ configuration. Two copolymer systems were investigated; butyl acrylate/styrene and butyl acrylate/butyl methacrylate. The copolymerizations were conducted at three residence times for each system and configuration to provide materials of a wide variety of conversions (13 to 97 %). Monomer samples were taken at two ports in the extruder and at the die. Samples were analyzed for composition by two methods; FTIR and refractive index (RI).
It was shown that the copolymer composition of samples produced in the backmixed extruder reactor does not change significantly as a function of position in the reactor. This is an indication that the copolymer composition does not drift in the reactor. Theoretically this is the behavior that exists with a chain addition copolymerization that occurs in a CSTR. Two methods (RI, FTIR) were used in the copolymer formulation (BA/Sty) and one method (FTIR) was used in the other copolymer formulation (BA/BMA). It was further shown that the difference in copolymer compositions in the two extruder reactors is more pronounced at higher conversions than at lower conversions.
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Affiliation(s)
- J. Grenci
- Polymer Processing Institute , Newark , NJ USA
| | - D. B. Todd
- Polymer Processing Institute , Newark , NJ USA
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Todd DB, Miller DM, Gordon JR. Field Evaluations of Sulfuryl Fluoride Fumigation for Control of the Common Bed Bug (Hemiptera: Cimicidae), Using a 1.9× Dosage Factor in Motor Vehicles and Filled Cargo Trailers. J Econ Entomol 2021; 114:857-867. [PMID: 33704428 DOI: 10.1093/jee/toab033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Indexed: 06/12/2023]
Abstract
This study investigated the efficacy of using Vikane gas fumigant (sulfuryl fluoride) at the 1.9× dosage rate for eliminating bed bugs (Cimex lectularius L.) in two challenging infestation situations: personal vehicles, and confined spaces densely packed with personal belongings. The vehicles used in this study were large minivans with seating that folded into the floor. The confined spaces were cargo trailers filled to 85% capacity with books, furniture, and other household items. Each van and trailer was equipped with ~90 sentinel bed bugs consisting of three groups of 9-11 bed bug eggs, 10 nymphs, and 10 adults. The Vikane Fumiguide calculator was used to determine the target dosage (g-h/m3) to apply in each replicate (e.g., one van or trailer). Sulfuryl fluoride concentrations were measured throughout the fumigation process using a Spectros SF-ReportIR. Concentration readings were input into the Fumiguide to determine when the accumulated dosage (g-h/m3) was achieved, and when aeration should be initiated. After aeration was complete, the sentinel bed bugs were removed from the replicates and bed bug nymph and adult mortality was recorded. Bed bug eggs were monitored for 23 d to determine latent mortality. Fumigated bed bug mortality for each replication was 100% regardless of life stage. Latent mortality was observed in a single bed bug egg, but the first instar never fully eclosed. This study determined that fumigation with sulfuryl fluoride at the 1.9× dosage factor is an effective method for eliminating resistant bed bugs from vehicles and personal belongings in densely packed situations.
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Affiliation(s)
- D B Todd
- Department of Entomology, Virginia Tech University, Blacksburg, VA, USA
| | - D M Miller
- Department of Entomology, Virginia Tech University, Blacksburg, VA, USA
| | - J R Gordon
- Douglas Products and Packaging Company, LLC, Liberty, MO, USA
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Butler JA, Slate AJ, Todd DB, Airton D, Hardman M, Hickey NA, Scott K, Venkatraman PD. A traditional Ugandan Ficus natalensis bark cloth exhibits antimicrobial activity against methicillin-resistant Staphylococcus aureus. J Appl Microbiol 2020; 131:2-10. [PMID: 33247525 DOI: 10.1111/jam.14945] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/05/2020] [Accepted: 11/14/2020] [Indexed: 12/28/2022]
Abstract
AIMS Surgical site, soft tissue and wound infections are some of the most prominent causes of healthcare-associated infections (HCAIs). Developing novel antimicrobial textiles and wound dressings may help alleviate the risk of developing HCAIs. We aimed to determine the antimicrobial efficacy of natural Ugandan bark cloth derived exclusively from the Ficus natalensis tree. METHODS AND RESULTS Antimicrobial contact and disc diffusion assays, coupled with time-kill kinetic assays, demonstrated that bark cloth inhibited the growth of a clinically relevant methicillin-resistant Staphylococcus aureus (MRSA) strain and acted as a bactericidal agent causing a seven-log reduction in bacterial viability. Scanning electron microscopy was used to reveal morphological changes in the bacterial cell ultrastructure when exposed to bark cloth, which supported a proposed mechanism of antimicrobial activity. CONCLUSIONS The observed antimicrobial properties, combined with the physical characteristics elicited by bark cloth, suggest this product is ideally suited for wound and other skin care applications. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first report where a whole bark cloth product made by traditional methods has been employed as an antimicrobial fabric against MRSA. Bark cloth is a highly sustainable and renewable product and this study presents a major advance in the search for natural fabrics which could be deployed for healthcare applications.
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Affiliation(s)
- J A Butler
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester, UK
| | - A J Slate
- Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - D B Todd
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester, UK
| | - D Airton
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester, UK
| | - M Hardman
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester, UK
| | - N A Hickey
- Faculty of Science and Engineering, Manchester Metropolitan University, Manchester, UK
| | - K Scott
- Istituto Marangoni, London, UK
| | - P D Venkatraman
- School of Fashion, Faculty of Arts and Humanities, Manchester Metropolitan University, Manchester, UK
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Choudhary M, Delaviz Y, Loh R, Polasky M, Wan C, Todd DB, Hyun KS, Dey S, Wu F. Measurement of Shear Viscosity and Solubility of Polystyrene Melts Containing Various Blowing Agents. J CELL PLAST 2016. [DOI: 10.1177/0021955x05059036] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This article presents measured data on shear viscosity and solubility of HCFC-142b and HFC-134a/ethanol blowing agent laden polystyrene melts at different temperatures. This study establishes the baseline for more novel and innovative blowing agent systems to replace HCFC-142b. The shear viscosity is measured using a helical barrel rheometer. Apparent solubility is determined by observing the onset of gas bubble presence or absence in a specially designed optical cell with sapphire windows using a microscope–CCD camera–monitor/recorder system. The article presents a selection of viscosity and solubility data and, where possible, compares them with measurements carried out by others. The dynamic methods of measuring solubility and viscosity of gas laden polymer melts used in this study are closer to the polymer foam manufacturing practice.
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Affiliation(s)
- M. Choudhary
- Owens Corning Science & Technology, Granville, OH, USA
| | - Y. Delaviz
- Owens Corning Science & Technology, Granville, OH, USA
| | | | - M. Polasky
- Owens Corning Foam Technology Center, Tallmadge, OH, USA
| | | | | | - K. S. Hyun
- Polymer Processing Institute, Newark, NJ, USA
| | - S. Dey
- SONOCO, Hartsville, SC, USA
| | - F. Wu
- National Institute of Standards and Technology, Gaithersburg, MD, USA
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Abstract
Abstract
The flow behavior of a Newtonian fluid through special mixing enhancers in a modular intermeshing co-rotating twin screw extruder has been examined. The mixing enhancers are slotted screws and gear mixing elements. Particular attention has been directed to drag and pressure flow characteristics and residence time distribution in such devices. The data obtained are useful for guidance in the selection of appropriate mixing elements and validation of flow simulation models for twin screw extruders.
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Affiliation(s)
- T. Brouwer
- Polymer Processing Institute, New Jersey Institute of Technology, Newark, New Jersey, USA
| | - D. B. Todd
- Polymer Processing Institute, New Jersey Institute of Technology, Newark, New Jersey, USA
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Abstract
Abstract
Staggered arrays of kneading paddles in co-rotating intermeshing twin screw extruders have drag and pressure characteristics similar to those in conventional screws. The pressure flow term was determined by measuring pressure drop as a function of flow rate in a non-rotating configuration. The drag flow per revolution was estimated as half of the product of lead length and open barrel cross section. The preliminary determinations were subsequently confirmed in a flooded operating extruder.
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Affiliation(s)
- D. B. Todd
- Polymer Processing Institute at Stevens Hobokeu, U.S.A
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Abstract
Abstract
Melting of plastics in intermeshing co-rotating twin screw extruders is known to occur over very short barrel lengths. The melting phenomenon has been studied for both pellets and powder in a readily opened clam shell barrel. The melting mechanism is attributed mainly to the dissipation of the energy imparted in interparticle friction as a consequence of the unique kneading action of this type extruder.
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Affiliation(s)
- D. B. Todd
- Polymer Processing Institute, Stevens Institute of Technology, Hoboken, U.S.A
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Singer E, Todd DB, Guinn VP. USE OF TRACERS IN REFINERY STUDIES Catalyst Mixing Patterns in Commercial Catalytic Cracking Units. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/ie50565a017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Grenci J, Todd DB. Effect of Conversion on Chain Addition Copolymerizations Performed in a Backmixed Drag Flow Extruder Reactor. INT POLYM PROC 2000. [DOI: 10.3139/217.1591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Todd DB. Histamine release by neuromuscular blocking agents. Br J Anaesth 1996; 76:471. [PMID: 8785157 DOI: 10.1093/bja/76.3.471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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Todd DB. Management of ventricular fibrillation by doctors in cardiac arrest teams. Guidelines do not discount change according to clinical circumstance. BMJ 1995; 310:1265. [PMID: 7767206 PMCID: PMC2549603 DOI: 10.1136/bmj.310.6989.1265b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Lillehei CW, Todd DB, Levy MJ, Ellis RJ. Partial cardiopulmonary bypass, hypothermia, and total circulatory arrest. A lifesaving technique for ruptured mycotic aortic aneurysms, ruptured left ventricle, and other complicated cardiac pathology. J Thorac Cardiovasc Surg 1969; 58:530-44. [PMID: 5394448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Long DM, Todd DB, Indeglia RA, Varco RL, Lillehei CW. Clinical use of dextran-40 in extracorporeal circulation--a summary of 5 years' experience. Transfusion 1966; 6:401-19. [PMID: 5965712 DOI: 10.1111/j.1537-2995.1966.tb04814.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Indeglia RA, Levy MJ, Lillehei RC, Todd DB, Lillehei CW. Correlation of plasma catecholamines, renal function, and the effects of dibenzyline on cardiac patients undergoing corrective surgery. J Thorac Cardiovasc Surg 1966; 51:244-57. [PMID: 5903634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Peterson TA, Todd DB, Edwards JE. Supravalvular aortic stenosis. J Thorac Cardiovasc Surg 1965; 50:734-41. [PMID: 5845458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Affiliation(s)
- D. B. Todd
- Podbielniak, Inc.; Franklin Park Illinois
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