Evolution of a localized thermal explosion in a reactive gas

Experimental observations of ignition in premixed gaseous reactants indicate that perfectly homogeneous initiation is practically unrealizable. Instead, combustion first sets in, as a rule, at small, discrete sites where inherent inhomogeneities cause chemical activity to proceed preferentially and lead to localized explosions. Combustion waves propagating away from these hot spots or reaction centers eventually envelop the remaining bulk. This study examines the spatial structure and temporal evolution of a hot spot for a model involving Arrhenius kinetics. The hot spot, characterized by peaks in pressure and temperature with little diminution in local density, is shown to have one of two possible self-similar structures. The analysis employs a combination of asymptotics and numerics, and terminates when pressure and temperature in the explosion have peaked

Multiple Differentiation Capacity of STRO-1+/CD146+ PDL Mesenchymal Progenitor Cells

Although mesenchymal progenitor cells can be isolated from periodontal ligament (PDL) tissues using stem cell markers STRO-1 and CD146, the proportion of these cells that have the capacity to differentiate into multiple cell lineages remains to be determined. This study was designed to quantify the proportions of primary human PDL cells that can undergo multilineage differentiation and to compare the magnitude of these capabilities relative to bone marrow-derived mesenchymal stem cells (MSCs) and parental PDL (PPDL) cells. PDL mesenchymal progenitor (PMP) cells were isolated from PPDL cells using the markers STRO-1 and CD146. The colony-forming efficiency and multilineage differentiation potential of PMP, PPDL, and MSCs under chondrogenic, osteogenic, and adipogenic conditions were determined. Flow cytometry revealed that on average 2.6% of PPDL cells were STRO-1+/CD146+, whereas more than 63% were STRO-1/CD146. Colony-forming efficiency of STRO-1+/CD146+ PMP cells (19.3%) and MSCs (16.7%) was significantly higher than that of PPDL cells (6.8%). Cartilage-specific genes, early markers of osteoblastic differentiation, and adipogenic markers were significantly upregulated under appropriate conditions in PMP cells and MSCs compared to either their noninduced counterparts or induced PPDL cells. Consistent with these findings, immunohistochemistry revealed substantial accumulation of cartilaginous macromolecules, mineralized calcium nodules, and lipid vacuoles under chondrogenic, osteogenic, or adipogenic conditions in PMP and MSC cultures, respectively, compared to noninduced controls or induced PPDL cells. Thus STRO-1+/CD146+ PMP cells demonstrate multilineage differentiation capacity comparable in magnitude to MSCs and could potentially be utilized for regeneration of the periodontium and other tissues.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78113/1/scd.2008.0113.pd

Blockchain application in supply chain chemical substance reporting

Cryptocurrencies have gained prominence in recent years due to: (1) potential large increase in values; (2) transferability between different users, and (3) security and; (4) traceability of data enabled by blockchain methods. Blockchains utilize an underlying digital ledger system which enables data to be encrypted, recorded and traced in a more efficient manner than traditional paper and electronic based systems. Chemical regulations impose the need on industry to record the use of hazardous chemicals, which can vary from: (1) simple reporting, through to; (2) permits to continue the use substances, until alternative substances are identified; or even (3) substances become restricted for use, within specific use cases, or restricted from use outright. The importance of obtaining supply chain chemical substance reporting cannot be understated, without accurate supply chain data, and concise internal product definitions, the process of identifying chemical substances: (1) where used; (2) if they appear on the finished part, or; (3) only used in the process of manufacture, or (4) used in maintenance and repair of parts. The process of collating supply chain chemical substance reporting is lengthy process as data needs to be requested, collated, checked, verified and rolled up to assess potential business continuity risks, as well as varying levels of reporting activity back to employees, consumers and chemical regulators.N/

IDRC and the interdisciplinary research process

Spanish version available in IDRC Digital Library: CIID y el processo de investigación interdisciplinari

CIID y el proceso de investigación interdisciplinaria

Vensión inglés en la biblioteca: IDRC and the interdisciplinary research processPublicado también en: Conocimiento sin barreras : propuestas, discusión y síntesi

Interdisciplinarity in INTESEP : a paper presented at the Africa INTESEP Meeting, 7-10 June, 1994, Abidjan, Côte d'Ivoire

French version available in IDRC Digital Library: L'interdisciplinarité dans l'IPESE : document présenté à la rencontre d'Afrique sur l'IPESE, du 7 au 10 juin 1994, Abidjan, Côte d'Ivoir

Research issues in science, technology and education in East, Central and Southern Africa

Meeting: IDRC Seminar on Education, Science Policy, Research and Action, 10-13 Jan. 1984, New Delhi, I

Robust H Stabilization via Parameterized Lyapunov Bounds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57850/1/RobustHinfStabilizationTAC1997.pd

Evaluation of Combustion Processes for Production of Feedstock Chemicals from Ammonium Sulfate and Ammonium Bisulfate

The combustion of ammonium bisulfate and ammonium sulfate solutions in hydrocarbon/air flames was studied under varied flame conditions. The objective of the study was to optimize the recovery of sulfur value from aqueous waste streams containing these salts. Combustion of ammonium sulfates yielded different sulfur species such as sulfur dioxide (SO2 ), hydrogen sulfide (H2S), and carbonyl sulfide (COS). The types of sulfur species obtained and their yields were dependent on the flame stoichiometry. When combustion was carried out in stochiometric flames or in flames with excess oxygen, the sulfur present in the salts was quantitatively converted to SO2 . However, these flames also produced nitrogen oxides (NOx ) above the 200ppm level. Combustion of ammonium sulfates in the sub-stoichiometric (oxygen-deficient) flames resulted in the formation of reduced sulfur species, particularly H2S. This species accounted for nearly 90% of the total sulfur present in the salts. Introduction of a secondary air stream in cooler regions of the combustor led to quantitative oxidation of H2 S and other reduced species such as COS to SO2. The SO2 obtained through the secondary oxidation contained nitrogen oxides at comparably lower levels

Robust Controller Synthesis via Shifted Parameter-Dependent Quadratic Cost Bounds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57848/1/ShiftedParDepTAC1998.pd