scholarly journals Charging and coagulation of radioactive and nonradioactive particles in the atmosphere

2016 ◽  
Vol 16 (5) ◽  
pp. 3449-3462 ◽  
Author(s):  
Yong-ha Kim ◽  
Sotira Yiacoumi ◽  
Athanasios Nenes ◽  
Costas Tsouris
Keyword(s):  
Atmospheric Particles ◽  
The Other ◽  
Urban Atmosphere ◽  
Balance Model ◽  
Charge Accumulation ◽  
Charge Balance ◽  
Charge Distributions ◽  
Coagulation Kinetics ◽  
Balance Charge ◽  
Kinetics Of

Abstract. Charging and coagulation influence one another and impact the particle charge and size distributions in the atmosphere. However, few investigations to date have focused on the coagulation kinetics of atmospheric particles accumulating charge. This study presents three approaches to include mutual effects of charging and coagulation on the microphysical evolution of atmospheric particles such as radioactive particles. The first approach employs ion balance, charge balance, and a bivariate population balance model (PBM) to comprehensively calculate both charge accumulation and coagulation rates of particles. The second approach involves a much simpler description of charging, and uses a monovariate PBM and subsequent effects of charge on particle coagulation. The third approach is further simplified assuming that particles instantaneously reach their steady-state charge distributions. It is found that compared to the other two approaches, the first approach can accurately predict time-dependent changes in the size and charge distributions of particles over a wide size range covering from the free molecule to continuum regimes. The other two approaches can reliably predict both charge accumulation and coagulation rates for particles larger than about 0.04 micrometers and atmospherically relevant conditions. These approaches are applied to investigate coagulation kinetics of particles accumulating charge in a radioactive neutralizer, the urban atmosphere, and an atmospheric system containing radioactive particles. Limitations of the approaches are discussed.

scholarly journals Charging and coagulation of radioactive and nonradioactive particles in the atmosphere

2015 ◽  
Vol 15 (17) ◽  
pp. 23795-23840
Author(s):  
Y.-H. Kim ◽  
S. Yiacoumi ◽  
A. Nenes ◽  
C. Tsouris
Keyword(s):  
Atmospheric Particles ◽  
The Other ◽  
Urban Atmosphere ◽  
Balance Model ◽  
Charge Accumulation ◽  
Charge Balance ◽  
Charge Distributions ◽  
Coagulation Kinetics ◽  
Balance Charge ◽  
Kinetics Of

Abstract. Charging and coagulation influence one another and impact the particle charge and size distributions in the atmosphere. However, few investigations to date have focused on the coagulation kinetics of atmospheric particles accumulating charge. This study presents three approaches to include mutual effects of charging and coagulation on the microphysical evolution of atmospheric particles such as radioactive particles. The first approach employs ion balance, charge balance, and a bivariate population balance model (PBM) to comprehensively calculate both charge accumulation and coagulation rates of particles. The second approach involves a much simpler description of charging, and uses a monovariate PBM and subsequent effects of charge on particle coagulation. The third approach is further simplified assuming that particles instantaneously reach their steady-state charge distributions. It is found that compared to the other two approaches, the first approach can accurately predict time-dependent changes in the size and charge distributions of particles over a wide size range covering from the free molecule to continuum regimes. The other two approaches can reliably predict both charge accumulation and coagulation rates for particles larger than about 40 nm and atmospherically relevant conditions. These approaches are applied to investigate coagulation kinetics of particles accumulating charge in a radioactive neutralizer, the urban atmosphere, and a radioactive plume. Limitations of the approaches are discussed.

scholarly journals Effects of Heme Modulation on Ovophis and Trimeresurus Venom Activity in Human Plasma

Toxins ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 322 ◽  
Author(s):  
Vance G. Nielsen ◽  
Nathaniel Frank ◽  
Ryan W. Matika
Keyword(s):  
Carbon Monoxide ◽  
Enzymatic Activity ◽  
Human Plasma ◽  
The Other ◽  
Geographic Isolation ◽  
Diverse Species ◽  
Fibrinogenolytic Activity ◽  
Coagulation Kinetics ◽  
Kinetics Of ◽  
Coagulation Kinetic

Geographic isolation and other factors result in evolution-driven diversity of the enzymatic composition of venom of pit vipers in the same genus. The present investigation sought to characterize venoms obtained from such genetically diverse Ovophis and Trimeresurus pit vipers utilizing thrombelastographic coagulation kinetic analyses. The coagulation kinetics of human plasma were assessed after exposure to venom obtained from two Ovophis and three Trimeresurus species. The potency of each venom was defined (µg/mL required to equivalently change coagulation); additionally, venoms were exposed to carbon monoxide (CO) or a metheme-inducing agent to modulate any enzyme-associated heme. All venoms had fibrinogenolytic activity, with four being CO-inhibitable. While Ovophis venoms had similar potency, one demonstrated the presence of a thrombin-like activity, whereas the other demonstrated a thrombin-generating activity. There was a 10-fold difference in potency and 10-fold different vulnerability to CO inhibition between the Trimeresurus species. Metheme formation enhanced fibrinogenolytic-like activity in both Ovophis species venoms, whereas the three Trimeresurus species venoms had fibrinogenolytic-like activity enhanced, inhibited, or not changed. This novel “venom kinetomic” approach has potential to identify clinically relevant enzymatic activity and assess efficacy of antivenoms between genetically and geographically diverse species.

Impact Of Synthesis Route on the Water Oxidation Kinetics of Hematite Photoanodes

2020 ◽  
Author(s):  
Camilo A. Mesa ◽  
Ludmilla Steier ◽  
Benjamin Moss ◽  
Laia Francàs ◽  
James E. Thorne ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Reaction Kinetics ◽  
Water Oxidation ◽  
Oxidation Kinetics ◽  
Oxidation Reaction ◽  
Charge Accumulation ◽  
Optical Signals ◽  
Current Voltage ◽  
Voltage Performance ◽  
Kinetics Of

<p><i>Operando</i> spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. Whilst these photoanodes exhibit very different current / voltage performance, their underlying water oxidation kinetics are found to be almost invariant. Lower photoanode performance was found to correlate with the observation of optical signals indicative of charge accumulation in mid-gap oxygen vacancy states, indicating these states do not contribute directly to water oxidation.</p>

The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

1992 ◽  
Vol 57 (11) ◽  
pp. 2302-2308
Author(s):  
Karel Mocek ◽  
Erich Lippert ◽  
Emerich Erdös
Keyword(s):  
Thermal Decomposition ◽  
Liquid Phase ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Sodium Carbonate ◽  
Room Temperature ◽  
Active Form ◽  
The Other ◽  
Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

On the kinetics of Hadamard-type fractional differential systems

2020 ◽  
Vol 23 (2) ◽  
pp. 553-570 ◽  
Author(s):  
Li Ma
Keyword(s):  
Differential Operator ◽  
Numerical Simulations ◽  
Type Inequality ◽  
The Other ◽  
Differential Systems ◽  
Fractional Differential Systems ◽  
Fractional Differential Operator ◽  
Fractional Differential ◽  
Kinetics Of ◽  
Theoretical Results

AbstractThis paper is devoted to the investigation of the kinetics of Hadamard-type fractional differential systems (HTFDSs) in two aspects. On one hand, the nonexistence of non-trivial periodic solutions for general HTFDSs, which are considered in some functional spaces, is proved and the corresponding eigenfunction of Hadamard-type fractional differential operator is also discussed. On the other hand, by the generalized Gronwall-type inequality, we estimate the bound of the Lyapunov exponents for HTFDSs. In addition, numerical simulations are addressed to verify the obtained theoretical results.

scholarly journals Characterization of the Two Mycobacterium tuberculosis recA Promoters

2003 ◽  
Vol 185 (20) ◽  
pp. 6005-6015 ◽  
Author(s):  
Krishna K. Gopaul ◽  
Patricia C. Brooks ◽  
Jean-François Prost ◽  
Elaine O. Davis
Keyword(s):  
Escherichia Coli ◽  
Dna Damage ◽  
Mycobacterium Tuberculosis ◽  
Promoter Activity ◽  
The Other ◽  
Expression Level ◽  
Promoter Elements ◽  
Kinetics Of

ABSTRACT The recA gene of Mycobacterium tuberculosis is unusual in that it is expressed from two promoters, one of which, P1, is DNA damage inducible independently of LexA and RecA, while the other, P2, is regulated by LexA in the classical way (E. O. Davis, B. Springer, K. K. Gopaul, K. G. Papavinasasundaram, P. Sander, and E. C. Böttger, Mol. Microbiol. 46:791-800, 2002). In this study we characterized these two promoters in more detail. Firstly, we localized the promoter elements for each of the promoters, and in so doing we identified a mutation in each promoter which eliminates promoter activity. Interestingly, a motif with similarity to Escherichia coli σ70 −35 elements but located much closer to the −10 element is important for optimal expression of P1, whereas the sequence at the −35 location is not. Secondly, we found that the sequences flanking the promoters can have a profound effect on the expression level directed by each of the promoters. Finally, we examined the contribution of each of the promoters to recA expression and compared their kinetics of induction following DNA damage.

scholarly journals Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3396
Author(s):  
Luboš Běhálek ◽  
Jan Novák ◽  
Pavel Brdlík ◽  
Martin Borůvka ◽  
Jiří Habr ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
Structural Changes ◽  
The Other ◽  
Half Time ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Melt Crystallisation ◽  
Kinetics Of ◽  
Crystallisation Rate

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

Reactions of hydrogen atoms with hexafluoroacetone

1978 ◽  
Vol 56 (20) ◽  
pp. 2638-2645 ◽  
Author(s):  
D. W. Grattan ◽  
K. O. Kutschke
Keyword(s):  
Rate Constant ◽  
Cross Sections ◽  
The Other ◽  
Hydrogen Atoms ◽  
Kinetics Of

Attempts were made to study the kinetics of the reaction of atomic H with (CF3)2CO vapour (HFA). Atomic H was generated from H2 by mercury photosensitization in the presence of C2H4 and HFA but the system was complicated by the loss of C2H5 radicals by addition to HFA and the kinetic results were intractable. When atomic H was generated from C3H8, the kinetics again were obscured by some unidentified reaction(s) which became more important at higher [HFA]/[C3H8]. An estimate of the rate constant for the addition of H to HFA obtained at low [HFA]/[C3H8] yielded k9 = 8.5 × 105 l mol−1 s−1. Trifluoroacetaldehyde was identified with some reliability but many of the other heavier products formed in the H2 + HFA reaction could not be identified. Quenching cross-sections were determined for C2H4, C3H8, C4H10, and HFA relative to that for N2O.

Acetylcholinesterase in Human Erythroid Cells

1973 ◽  
Vol 12 (3) ◽  
pp. 911-923
Author(s):  
R. J. SKAER
Keyword(s):  
Endoplasmic Reticulum ◽  
Nervous System ◽  
Golgi Apparatus ◽  
Red Cells ◽  
The Other ◽  
Red Cell ◽  
Erythroid Cells ◽  
Cell Replacement ◽  
Kinetics Of ◽  
Human Red Cells

Acetylcholinesterase is present in human red cells but cannot be demonstrated by the copper thiocholine test. The enzyme is revealed, however, in the perinuclear cisterna, endoplasmic reticulum and Golgi apparatus of red cell precursors. It is suggested that 2 forms of the enzyme are present, one of which can be demonstrated by the copper thiocholine test, the other cannot; one form may be the precursor of the other. These observations may cast light on the kinetics of red cell replacement and on the interpretation of the results from the copper thiocholine test on other tissues such as the nervous system.

Kinetics of Fertilization in the Sea Urchin: A Comparison of Methods

1970 ◽  
Vol 52 (2) ◽  
pp. 455-468
Author(s):  
R. PRESLEY ◽  
P. F. BAKER
Keyword(s):  
Sea Urchin ◽  
Uranyl Nitrate ◽  
Sea Water ◽  
Fertilization Rate ◽  
The Other ◽  
Jelly Coat ◽  
Cortical Responses ◽  
Direct Counting ◽  
Further Development ◽  
Kinetics Of

1. A method is described for the direct counting of male pronuclei in recently fertilized sea-urchin eggs. 2. Using this method, fertilization rate determinations were made to compare 30% artificial sea water (A.S.W.), isotonic KCl, sea water containing lauryl sulphate, calcium-free and magnesium-free A.S.W. containing EDTA, and sea water containing uranyl nitrate, as agents blocking fertilization but permitting further development of previously fertilized eggs. 3. 30% A.S.W. was found to be less satisfactory than the other agents, lacking instant effect, and tending to promote polyspermy. The other agents all gave sigmoid rate curves, that of uranyl nitrate lagging 15-25 sec. behind the others. 4. Evidence was found that uranyl nitrate acts at a later stage in fertilization than the other agents. 5. Sigmoid rate curves were found, except with 30% A.S.W., when eggs with the bulk of the jelly coat removed, and nicotine-treated eggs, were fertilized. 6. Analysis of sperm distribution among eggs from samples fertilized for more than 40 sec. confirmed that re-fertilization takes place at a lower rate than primary fertilization. 7. The processes blocked by KCl and uranyl nitrate were found to precede the cortical responses to fertilization, and the termination of nicotine sensitivity.

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