Ozonation of bromide-containing drinking waters:a delicate balance between disinfection and bromate formation

2000 ◽  
Vol 41 (7) ◽  
pp. 53-59 ◽  
Author(s):  
U. von Gunten ◽  
U. Pinkernell
Keyword(s):  
Temperature Dependence ◽  
Low Temperatures ◽  
The Other ◽  
Ozone Exposure ◽  
Oh Radicals ◽  
Strong Temperature Dependence ◽  
Control Options ◽  
The One ◽  
Kinetics Of ◽  
Ozonation Process

The occurrence of Cryptosporidium in raw waters and bromate formation during ozonation of bromide-containing waters leads to a difficult optimisation of ozonation processes. On the one hand inactivation of Cryptosporidium requires high ozone exposures, on the other hand under these conditions bromate formation is favored. In order to overcome this problem we need information about (i) the oxidant concentrations (ozone and OH radicals) during an ozonation process, (ii) kinetics of the inactivation of Cryptosporidium, (iii) kinetics and mechanism of bromate formation, and (iv) the reactor hydraulics. The strong temperature dependence of the inactivation of Cryptosporidium which results in a higher ozone exposure (time-integrated action of ozone) at low temperatures makes it more difficult to fulfil disinfection and bromate standards at low temperatures. Underthese conditions control options for bromate formation can be applied. Depressionof pH and addition of ammonia have been selected to be the best options. For a given ozone exposure both measures lead to a reduction of bromate formation in the order of 50%.

scholarly journals The principal magnetic susceptibilities of neodymium sulphate octahydrate at low temperatures

1939 ◽  
Vol 170 (941) ◽  
pp. 266-271 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Energy Levels ◽  
Constant Factor ◽  
The Other ◽  
Crystalline Field ◽  
Cubic Symmetry ◽  
The Subject ◽  
The Difference ◽  
The One

The magnetic and other related properties of neodymium sulphate have been the subject of numerous investigations in recent years, but there is still a remarkable conflict of evidence on all the essential points. The two available determinations of the susceptibility of the powdered salt at low temperatures, those of Gorter and de Haas (1931) from 290 to 14° K and of Selwood (1933) from 343 to 83° K both fit the expression X ( T + 45) = constant over the range of temperature common to both, but the constants are not the same and the susceptibilities at room temperature differ by 11%. The fact that the two sets of results can be converted the one into the other by multiplying throughout by a constant factor suggested that the difference in the observed susceptibilities was due to some error of calibration. It could, however, also be due to the different purity of the samples examined though the explanation of the occurrence of the constant factor is then by no means obvious. From their analysis of the absorption spectrum of crystals of neodymium sulphate octahydrate Spedding and others (1937) conclude that the crystalline field around the Nd+++ ion is predominantly cubic in character since they find three energy levels at 0, 77 and 260 cm. -1 .* Calculations of the susceptibility from these levels reproduce Selwood’s value at room temperature but give no agreement with the observations-at other temperatures. On the other hand, Penney and Schlapp (1932) have shown that Gorter and de Haas’s results fit well on the curve calculated for a crystalline field of cubic symmetry and such a strength that the resultant three levels lie at 0, 238 and 834 cm. -1 , an overall spacing almost three times as great as Spedding’s.

scholarly journals Rare temperature histories and cirrus ice number density in a parcel and a one-dimensional model

2014 ◽  
Vol 14 (23) ◽  
pp. 13013-13022 ◽  
Author(s):  
D. M. Murphy
Keyword(s):  
Temperature Dependence ◽  
Low Temperatures ◽  
Ice Crystals ◽  
Strong Increase ◽  
Number Density ◽  
Dimensional Model ◽  
One Dimensional ◽  
Slow Growth Rate ◽  
Wide Range ◽  
The One

Abstract. A parcel and a one-dimensional model are used to investigate the temperature dependence of ice crystal number density. The number of ice crystals initially formed in a cold cirrus cloud is very sensitive to the nucleation mechanism and the detailed history of cooling rates during nucleation. A possible small spread in the homogeneous freezing threshold due to varying particle composition is identified as a sensitive nucleation parameter. In a parcel model, the slow growth rate of ice crystals at low temperatures inherently leads to a strong increase in ice number density at low temperatures. This temperature dependence is not observed. The model temperature dependence occurs for a wide range of assumptions and for either homogeneous or, less strongly, heterogeneous freezing. However, the parcel model also shows that random temperature fluctuations result in an extremely wide range of ice number densities. A one-dimensional model is used to show that the rare temperature trajectories resulting in the lowest number densities are disproportionately important. Low number density ice crystals sediment and influence a large volume of air. When such fall streaks are included, the ice number becomes less sensitive to the details of nucleation than it is in a parcel model. The one-dimensional simulations have a more realistic temperature dependence than the parcel mode. The one-dimensional model also produces layers with vertical dimensions of meters even if the temperature forcing has a much broader vertical wavelength. Unlike warm clouds, cirrus clouds are frequently surrounded by supersaturated air. Sedimentation through supersaturated air increases the importance of any process that produces small numbers of ice crystals. This paper emphasizes the relatively rare temperature trajectories that produce the fewest crystals. Other processes are heterogeneous nucleation, sedimentation from the very bottom of clouds, annealing of disordered to hexagonal ice, and entrainment.

scholarly journals Adipo-Myokines: Two Sides of the Same Coin—Mediators of Inflammation and Mediators of Exercise

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Silja Raschke ◽  
Jürgen Eckel
Keyword(s):  
Skeletal Muscle ◽  
Mrna Level ◽  
Cell Types ◽  
The Other ◽  
Target Tissue ◽  
Beneficial Effects ◽  
Mediators Of Inflammation ◽  
The One ◽  
Two Sides ◽  
Kinetics Of

This review summarizes the current literature regarding the most discussed contraction-regulated moykines like IL-6, IL-15, irisin, BDNF, ANGPTL4, FGF21, myonectin and MCP-1. It is suggested that the term myokine is restricted to proteins secreted from skeletal muscle cells, excluding proteins that are secreted by other cell types in skeletal muscle tissue and excluding proteins which are only described on the mRNA level. Interestingly, many of the contraction-regulated myokines described in the literature are additionally known to be secreted by adipocytes. We termed these proteins adipo-myokines. Within this review, we try to elaborate on the question why pro-inflammatory adipokines on the one hand are upregulated in the obese state, and have beneficial effects after exercise on the other hand. Both, adipokines and myokines do have autocrine effects within their corresponding tissues. In addition, they are involved in an endocrine crosstalk with other tissues. Depending on the extent and the kinetics of adipo-myokines in serum, these molecules seem to have a beneficial or an adverse effect on the target tissue.

A New Method and Device for Temperature Measurement Using One-Dimensional Heat Equation

1994 ◽  
Author(s):  
Nicolae A. Damean
Keyword(s):  
Heat Equation ◽  
Temperature Measurement ◽  
Low Temperatures ◽  
Principal Component ◽  
The Other ◽  
New Method ◽  
Gradient Algorithm ◽  
One Dimensional ◽  
The One ◽  
The Mathematical Model

Abstract A new method and device for temperature measurement are presented. The method reduces the measurement of the unknown temperature to the solving of an optimal control problem, using a numerical computer. The device consists of a hardware part including some conventional transducers and a software one. The problem of temperature measurement, according to this method, is mathematically modelled by means of the one-dimensional heat equation, describing the heat transfer through the device. The principal component of the device is a rod. The variation of the temperature which is produced near one end of the rod is determined using some temperature measurements in the other end of the rod, the mathematical model and a type of gradient algorithm. This device works as an attenuator of high temperatures and as an amplifier of low temperatures.

scholarly journals A study of catalytic actions at solid surfaces. X. -The interaction of carbon monoxide and hydrogen as conditioned by nickel at relatively low temperatures. -A practical synthesis of methane

1923 ◽  
Vol 103 (720) ◽  
pp. 25-34 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Low Temperatures ◽  
Solid Surfaces ◽  
The Other ◽  
Theoretical Interest ◽  
Primary Object ◽  
Pure Methane ◽  
Practical Synthesis ◽  
The One ◽  
Water Gas

The investigation described in this communication had for its primary object the production of formaldehyde or methyl alcohol. In this aim we have been so far unsuccessful, but our results have led to the discovery of an action, Apart from theoretical interest the method would appear to have important technical possibilities, either as a means of producing pure methane is formed from water-gas than by other methods. In order to make clear the course of the action about to be described it will be well briefly to enumerate some of the known interactions of carbon monoxide and hydrogen on the one hand, and of the former gas and steam on the other.

The Kinetics of Polymerization Reactions

1945 ◽  
Vol 18 (2) ◽  
pp. 223-235 ◽  
Author(s):  
G. Gee ◽  
H. W. Melville
Keyword(s):  
Half Life ◽  
Molecular Size ◽  
The Other ◽  
Chain Growth ◽  
Extreme Conditions ◽  
Kinetics Of Polymerization ◽  
Molecular Sizes ◽  
Mathematical Difficulties ◽  
The One ◽  
Kinetics Of

Abstract A general treatment of the kinetics of polymerization reactions is given to cover the two extreme conditions in which the lifetime of chain growth is (1) small, and (2) large compared with the half life of the monomer. Case (1) is considered on the basis of the assumption that the velocity coefficients do not depend on molecular size. Case (2) is considered for propagation coefficients which are on the one hand independent, and on the other hand dependent on molecular size. In addition, the distribution of molecular sizes is computed in those cases where the mathematical difficulties are not insurmountable. The application of these results to the analysis of polymerization reactions is discussed. The work described in this paper was completed when war broke out, and was to have been published as part of a book on polymerization processes. In view of the interest and development in these matters, it was felt desirable to give this account of these ideas now.

Vulcanization of Elastomers. 12. Perbunan with Thiuram Monosulfide and Sulfur. I

1959 ◽  
Vol 32 (1) ◽  
pp. 128-138 ◽  
Author(s):  
Walter Scheele ◽  
Horst-Eckart Toussaint
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Induction Period ◽  
Rate Constants ◽  
The Other ◽  
Tetramethylthiuram Disulfide ◽  
First Order ◽  
The One ◽  
Limiting Value

Abstract The vulcanization of Perbunan 2818 by tetramethylthiuram monsulfide plus sulfur (1 mole monosulfide per gram-atom S) was thoroughly studied. The following results were shown: The limiting value for dithiocarbamate formation is 66 mole per cent of the initial thiuram monosulfide, indicating a two-thirds transformation. The limiting value is practically independent of temperature. The formation of dithiocarbamate can be described as a reaction of the first order. The formation of dithiocarbamate is characterized by an induction period which grows longer with lowering of the temperature, and at 100° C it amounts to about 100 minutes. The rate constants for dithiocarbamate formation were calculated, and it was shown that they were practically the same as those for the vulcanization of Perbunan with tetramethylthiuram disulfide. The activation energies as derived from the temperature dependence of the rate constants for dithiocarbamate formation in the vulcanization of Perbunan by thiuram monosulfide plus sulfur on the one hand and with thiuram disulfide on the other, are only very slightly different and are practically the same as the activation energy for dithiocarbamate formation during the vulcanization of natural rubber with thiuram monosulfide plus sulfur. The results were thoroughly discussed in light of the present conceptions of the course of thiuram vulcanizations.

scholarly journals Disentangling Dynamical Quantum Coherences in the Fenna-Matthews-Olson Complex

2021 ◽  
Author(s):  
Hong-Guang Duan ◽  
Ajay Jha ◽  
Lipeng Chen ◽  
Vandana Tiwari ◽  
Richard Cogdell ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Reaction Center ◽  
Low Temperatures ◽  
Quantum Coherence ◽  
Energy Transport ◽  
Light Harvesting ◽  
Quantum Decoherence ◽  
Strong Temperature Dependence ◽  
Temperature Dependent ◽  
Electronic Coherence

Abstract In the primary step of natural light-harvesting, the energy of a solar photon is captured in antenna chlorophyll as a photoexcited electron-hole pair, or an exciton. Its efficient conversion to stored chemical potential occurs in the special pair reaction center, which has to be reached by down-hill ultrafast excited state energy transport. Key to this process is the degree of interaction between the chlorophyll chromophores that can lead to spatial delocalization and quantum coherence effects. The importance of quantum contributions to energy transport depends on the relative coupling between the chlorophylls in relation to the intensity of the fluctuations and reorganization dynamics of the surrounding protein matrix, or bath. The latter induce uncorrelated modulations of the site energies, resulting in quantum decoherence, and localization of the spatial extent of the exciton. The current consensus is that under physiological conditions quantum decoherence occurs on the 10 fs time scale, and quantum coherence plays little role for the observed picosecond energy transfer dynamics. In this work, we reaffirm this from a different point of view by finding that the true onset of important electronic quantum coherence only occurs at extremely low temperatures of ~20 K. We have directly determined the exciton coherence times using two-dimensional (2D) electronic spectroscopy of the Fenna-Matthew-Olson (FMO) complex over an extensive temperature range. At 20 K, we show that electronic coherences persist out to 200 fs (close to the antenna) and marginally up to 500 fs at the reaction-center side. The electronic coherence is found to decay markedly faster with modest increases in temperature to become irrelevant above 150 K. This temperature dependence also allows disentangling the previously reported long-lived beatings thought to be evidence for electronic quantum coherence contributions. We show that they result from mixing vibrational coherences in the electronic ground state. We also uncover the relevant electronic coherence between excited electronic states and examine the temperature-dependent non-Markovianity of the transfer dynamics to show that the bath involves uncorrelated motions even to low temperatures. The observed temperature dependence allows a clear separation of the fragile electronic coherence from the robust vibrational coherence. The specific details of the critical bath interaction are treated through a theoretical model based on measured bath parameters that reproduces the temperature dependent dynamics. By this, we provide a complete picture of the bath interaction which places these systems in the regime of strong bath coupling. We believe this main conclusion to be generically valid for light harvesting systems. This principle makes the systems robust against otherwise fragile quantum effects as evidenced by the strong temperature dependence. We conclude that nature explicitly exploits decoherence or dissipation in engineering site energies to yield downhill energy gradients to unerringly direct energy, even on the fastest time scales of biological processes.

Kinetics of Reactions of 8-Quinolinol and Acetate with Hydroxyaluminum Species in Aqueous Solutions. 2. Initial Solid Phases

1971 ◽  
Vol 49 (10) ◽  
pp. 1688-1690 ◽  
Author(s):  
R. C. Turner
Keyword(s):  
Aqueous Solutions ◽  
Solid Phase ◽  
The Other ◽  
Rate Determining Step ◽  
Rate Of Dissolution ◽  
Effects Of Ph ◽  
Solid Phases ◽  
The One ◽  
Kinetics Of ◽  
As If

The effects of pH and concentrations of 8-quinolinol and acetate on the rate of release of mononuclear Al from an initial solid phase formed by the rapid precipitation of mononuclear Al cations and from another formed by the precipitation of polynuclear hydroxyaluminum cations with NaOH were determined. With the solid formed by precipitation of the mononuclear Al cations, the rate was governed by the rate of dissolution of the solid. Dissolution occurred because the solution was undersaturated with respect to the solid. With the solid formed by the precipitation of the polynuclear cations the reaction behaved as if the rate determining step in the release of the mononuclear Al was the decomposition of the polynuclear cations after dissolution of the solid, indicating that the polynuclear cations persisted as such in the precipitate.Independent evidence that the two initial solid phases were entirely different was indicated by the fact that the one formed by precipitation of mononuclear cations developed into gibbsite in a few days whereas the other did not.

Sign in / Sign up

Export Citation Format

Share Document