Models of the equilibrium distribution of organic chemicals between water and solid phases of environmental media

2014 ◽  
Vol 22 (4) ◽  
pp. 430-444 ◽  
Author(s):  
Eva M. Webster
Keyword(s):  
Organic Phase ◽  
Solid Phase ◽  
Ion Pairs ◽  
Chemical Environment ◽  
Individual Species ◽  
Linear Free Energy Relationship ◽  
Organic Chemicals ◽  
Equilibrium Models ◽  
Adsorption Models

Water–solid phase equilibrium distributions are foundational to multimedia environmental fate models of anthropogenic organic chemicals. This contextual review of equilibrium models of ionizing organics in aqueous–solids systems highlights the broad range of modeling assumptions and paradigms that have been employed. The complexity of soils and sediment, especially the organic phase, is provided as background along with a description of equilibrium models for nonpolar, nonionizing organics. The ways in which these single-species models have been modified and adapted for application to ionizing organics is detailed. The individual species proposed as contributing to observed distributions include the neutral parent, ions, and ion pairs. The debate over the role of the organic phase in soil and sediment solids is presented. Both absorption and surface adsorption models are described. Organic carbon (OC)-dependent models range from the simple Karickhoff equation to complex molecular connectivity indices models and polyparameter linear free energy relationship (pp-LFER) models. Adsorption models are derived from inorganic interaction chemistry. They include the early Langmuir model and Freundlich equation and continue to the modern Model VI and the NICA-Donnan model. Adsorption models focus on the mineral phase, but the role of the organic phase is not entirely dismissed. Dual mode models seek to combine absorption to OC with adsorption interactions. Conclusions drawn from studies of acid behavior do not predict the sorption of bases; bases are described separately. No single explanation and accompanying model of the distribution behavior of ionizing organics has emerged as the clear choice for regulatory use. The complexity of chemical–environment interactions is such that models are either challenging to parameterize and understand or they fail to capture key aspect(s) of the system critical to understanding of one or more classes of chemical or environmental medium. Future research directions are suggested including the possible benefit of removing sorbate–sorbent or chemical–environment distinctions.

The influence of chemical environment on the infrared spectra of embedded molecules in astrophysical ices

2017 ◽  
Vol 13 (S332) ◽  
pp. 346-352 ◽  
Author(s):  
Victor S. Bonfim ◽  
Sergio Pilling
Keyword(s):  
Dielectric Constant ◽  
Cross Section ◽  
Continuum Model ◽  
Solid Phase ◽  
Chemical Environment ◽  
Effect Of Temperature ◽  
Individual Species ◽  
Polarized Continuum Model ◽  
Different Types ◽  
Astrophysical Ices

AbstractIn this work, one intends to computationally simulate and investigate, via thermochemical calculations, how the chemical environment influences some molecular properties, such as IR spectra and absorption cross section, of individual species embedded in the solid phase employing the Polarized Continuum Model (PCM) approach. The trial molecules used here to check these effects are CO, CO2 and H2O. The solid phase (bulk ice) is simulated using different dielectric constant values representing different types of astrophysical ice at PCM approach. The effect of temperature is also investigated since it is known it affects the dielectric constant of the solvent medium.

Europium and cerium extraction by the nitrobenzene solution of dicarbolide in the presence of polyethylene glycols

1986 ◽  
Vol 51 (3) ◽  
pp. 498-515 ◽  
Author(s):  
Emanuel Makrlík ◽  
Petr Vaňura
Keyword(s):  
Molecular Weight ◽  
Polyethylene Glycol ◽  
Organic Phase ◽  
Perchloric Acid ◽  
Equilibrium Constants ◽  
Polyethylene Glycols ◽  
Individual Species ◽  
Nitrobenzene Solution ◽  
Separation Factors ◽  
Equilibrium Data

Extraction of Eu3+ and Ce3+ microamounts from 0.1-0.4M perchloric acid by the nitrobenzene solution of dicarbolide H+[Co(C2B9H11)2]- in the presence of polyethylene glycols (Mr = 200, 300, 400) has been studied. The equilibrium data and the typical maxima on the dependence of the metal distribution ratio on the total analytical concentration of polyethylene glycol in the system can be explained assuming that the species ML3+org, ML3+2org, ML3+3org, MLH2+-1org, and HL+org (where M3+ = Eu3+, Ce3+; L = polyethylene glycol) are extracted into the organic phase. The values of extraction and equilibrium constants in the organic phase were determined and the effect of the polyethylene glycol molecular weight on the equilibrium constants and on the abundances of individual species in the organic phase is discussed. It has been found that the addition of polyethylene glycol to the acid - nitrobezene - dicarbolide system increases the values of the separation factors αCe/Eu.

Introduction to geomicrobiology

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Fossil Fuels ◽  
Solid Phase ◽  
Direct Reduction ◽  
Iron Oxidation ◽  
Mineral Dissolution ◽  
Precipitation Process ◽  
Soluble Ions ◽  
Chemolithoautotrophic Bacteria ◽  
The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

scholarly journals The Role of Electric Pressure/Stress Suppressing Pinhole Defect on Coalescence Dynamics of Electrified Droplet

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 503
Author(s):  
Jaehyun Lee ◽  
Ehsan Esmaili ◽  
Giho Kang ◽  
Baekhoon Seong ◽  
Hosung Kang ◽  
...  
Keyword(s):  
Solid Phase ◽  
Critical Factor ◽  
Air Pressure ◽  
Conical Shape ◽  
Electric Stress ◽  
Bottom Interface ◽  
Electric Pressure ◽  
Pressure Stress ◽  
Air Film

The dimple occurs by sudden pressure inversion at the droplet’s bottom interface when a droplet collides with the same liquid-phase or different solid-phase. The air film entrapped inside the dimple is a critical factor affecting the sequential dynamics after coalescence and causing defects like the pinhole. Meanwhile, in the coalescence dynamics of an electrified droplet, the droplet’s bottom interfaces change to a conical shape, and droplet contact the substrate directly without dimple formation. In this work, the mechanism for the dimple’s suppression (interfacial change to conical shape) was studied investigating the effect of electric pressure. The electric stress acting on a droplet interface shows the nonlinear electric pressure adding to the uniform droplet pressure. This electric stress locally deforms the droplet’s bottom interface to a conical shape and consequentially enables it to overcome the air pressure beneath the droplet. The electric pressure, calculated from numerical tracking for interface and electrostatic simulation, was at least 108 times bigger than the air pressure at the center of the coalescence. This work helps toward understanding the effect of electric stress on droplet coalescence and in the optimization of conditions in solution-based techniques like printing and coating.

scholarly journals Molecular analysis of the microflora in chronic venous leg ulceration

2003 ◽  
Vol 52 (4) ◽  
pp. 365-369 ◽  
Author(s):  
K.E. Hill ◽  
C.E. Davies ◽  
M.J. Wilson ◽  
P. Stephens ◽  
K.G. Harding ◽  
...  
Keyword(s):  
Individual Species ◽  
Venous Leg Ulcer ◽  
Bacterial Populations ◽  
Cultural Methods ◽  
Rdna Sequences ◽  
Oral Microflora ◽  
16S Rdna Sequences ◽  
First Time

There is growing evidence to suggest that the resident microflora of chronic venous leg ulcers impairs cellular wound-healing responses, thereby playing an important role in maintaining the non-healing phenotype of many of these wounds. The significance of individual species of bacteria will remain unclear until it is possible to characterize fully the microflora of such lesions. The limitations and biases of culture-based microbiology are being realized and the subsequent application of molecular methods is revealing greater diversity within mixed bacterial populations than that demonstrated by culture alone. To date, this approach has been limited to a small number of systems, including the oral microflora. Here, for the first time, the comprehensive characterization of the microflora present in the tissue of a chronic venous leg ulcer is described by the comparison of 16S rDNA sequences amplified directly from the wound tissue with sequences obtained from bacteria that were isolated by culture. The molecular approach demonstrated significantly greater bacterial diversity than that revealed by culture. Furthermore, sequences were retrieved that may possibly represent novel species of bacteria. It is only by the comprehensive analysis of the wound microflora by both molecular and cultural methods that it will be possible to further our understanding of the role of bacteria in this important condition.

scholarly journals The role of Th1/Th2 disbalanced immune response in the determination of clinical features of autoimmune diabetes mellitus

2011 ◽  
Vol 14 (2) ◽  
pp. 12-17 ◽  
Author(s):  
Tatiana Vladimirovna Saprina ◽  
F E Lazarenko ◽  
T S Prokhorenko ◽  
N V Ryazantseva ◽  
Irina Nikolaevna Vorozhtsova
Keyword(s):  
Immune Response ◽  
Beta Cell ◽  
Cell Function ◽  
Solid Phase ◽  
Autoimmune Diabetes ◽  
Mononuclear Leukocytes ◽  
Diagnostic Strategy ◽  
C Peptide ◽  
Significant Difference

Aim. To elucidate the role of Th1/Th2 polarization of immune response in LADA patients in the realization of the clinical phenotype of the disease. Materials and methods. 70 patients aged 21-61 (mean 41.3?1.0 yr) with DM diagnosed based on WHO criteria (1999). Groups 1 and 2 included 13 DM1and 57 DM2 patients (34.6?7.2 and 43.6?7.6 yr respectively). 27 DM2 patients (41.2?1.6 yr) presumably had LADA (P. Zimmet's criteria).Serum anti-GAD65, ICA, and IAA antibodies along with C-peptide were measured in fasting sera and 120 min after GTT by solid phase immunoenzymeassays following manufacturer's instructions with the use of a photometer for Multiscan EX microplates (ThermoLabSystems, Finland) at405 nm (for GAG and ICA) and 450 nm (for IAA and C-peptide). GAD, IAA, and C-peptides levels were calculated automatically from calibrationcurves. Mononuclear leukocytes were isolated by centrifugation in the ficoll-verographin density gradient. The cells thus obtained were resuspendedin the complete nutritient medium reducing their concentration to 2.0x10^6/ml. Phytohemagglutinin (Difco, Germany) was added (10 mcg/1 ml) tothe samples to stimulate mononuclear leukocytes; cell suspensions were further incubated for 24 hr. Initial and PGA-induced levels of IL-2, 4, 10 insupernatants of cell cultures were measured by solid phase immunoassay at 450 nm. Results. At least one type of autoantibodies (GAD, ICA or IAA) was identified in 24.3% of all DM patients (17/70) and in 18% of the DM2 patients(10/57). The level of anti-GAD and ICA ABs and percentage of AB-positive patients were higher in the LADA group while that of anti-IAA ABs amongDM1 patients without LADA. Two AB types at a time were found in 17% (4/23) of the patients with autoimmune DM in the absence of significantdifference between LADA and DM1. Patients with LADA had a significantly lower basal C-peptide level than DM2 patients. The was a tendencytoward lower level of stimulated C-peptide secretion in LADA patients compared with DM2 ones. It suggests impairment of beta-cell secretory functionaffected by the autoimmune process. We observed enhanced basal production of IFN-y by blood mononuclear leukocytes in all DM patients in theabsence of significant difference between the groups. Mitogen-activated production in all CD patients was lower than normal without inter-groupdifferences. Patients with DM2 had the inverted type of IL-2 secretion unlike those with autoimmune diabetes. In both cases it was significantly differentfrom normal values. There was a tendency toward higher basal production of IL-4 by mononuclear leukocytes in LADA and DM2 comparedwith CD1 which reflects pathogenetic peculiarities of beta-cell function in LADA differing from those in DM1 and responsible for slower impairment ofbeta-cell function in this condition. Basal and PGA- induced production of IL-10 was higher in LADA and DM2 than in DM1. It suggests enhancedsuppressor activity of leukocytes that may protect beta-cells from autoimmune destruction and determines gradual development of clinical symptoms ofinsulin deficiency. In contrast, low production of IL-10 in DM1 gives evidence of polarization of the immune response. Conclusion. The loss of functional parenchyma and manifestation of insulin deficiency in LADA occur at a relatively low rate due to the peculiarcharacter of cytokine-mediated cell interactions. It suggests the necessity of an active and careful diagnostic strategy with the use of immunologicalmethods for examination of elder patients presenting with a variety of pathogenetic variants of DM.

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