The influence of added saccharide, protein and lipid on the sedimentation of E. coli bacteria using aluminium sulphate and polyacrylamides

The chemical sedimentation of E. coli bacteria has been studied in the presence of polymeric impurities such as occur in domestic waste-water (proteins, lipids, saccharides).Chemical sedimentation was carried out at pH 7 using aluminium sulphate and various polyacrylamides. Sedimentation was followed from the turbidity of samples from a sedimentation vessel as a function of time after polyacrylamide addition.The results show that protein and lipid increase, whilst polysaccharide reduces the sedimentation rate to extents that depend on the dosages and types of polyacrylamides used. In particular, at a fixed dosage level of a given polyacrylamide, variations in concentrations of polymeric impurities may lead to variations in sedimentation rate of ca. 30 per cent. In order to obtain reproducible sedimentation, it is therefore necessary to vary the polyacrylamide dosage to compensate for changes in the levels of protein, lipid and polysaccharide which occur in domestic waste-water.     

Flood Response Using Complementary Early Warning Information

The objective of this comparative case study was to investigate and compare how Swedish municipalities gather and use warning information from official and unofficial sources at the municipal level, as well as the circumstances under which that process has a chance to succeed. The overall conclusions of the study are that official and unofficial warnings have the potential to play complementary roles for municipalities making decisions about flood response, giving the municipalities a wider perspective and better opportunity to assess risk and to act appropriately. The required resources for using official warnings and getting access to unofficial warning sources are not evenly distributed among municipalities, and a lack of systematization of access to warning information hinders the flood response potential.     

Temperature dependence of the solubility areas for W/O microemulsions with nonionic/anionic surfactants

The solubitity areas were determined at 30, 50 and 75 C for W/O microemulsions of water and decane stabilized by sodium dodecyl sulfate or hexaethylene glycol dodecyl ether in combination with pentanol. The results showed no pronounced changes when the ionic surfactant was partly replaced with the nonionic one and revealed an excellent temperature stability in the range 30–75 C for the W/O microemulsions.     

Spectral decomposition of the Lindblad operator

Abstract

We discuss the mathematical structure of quantum states on which the master equation generates a semigroup of irreversible time evolution. As an illustration of an open system we choose to treat the harmonic oscillator, in which case we can perform the construction of a complete set of eigenelements describing both the attenuator and the amplifier. We show that the corresponding eigenelements belong to adjoint spaces, and their orthogonality and completeness is shown explicitly. We also show that our results are in agreement with earlier work by Briegel and Englert. We illustrate the use of our results by deriving previously known time-dependent results for some simple cases.     

States prepared by decay

Abstract

We consider the time evolution of a discrete state embedded in a continuum. Results from scattering theory can be utilized to solve the initial value problem and to discuss the system as a model of wave packet preparation. Extensive use is made of the analytic properties of the propagators, and simple model systems are evaluated to illustrate the argument. We verify the exponential appearence of the continuum state and its propagation as a localized wave packet.     

Study of the OH and Cl-initiated oxidation, IR absorption cross-section, radiative forcing, and global warming potential of four C4-hydrofluoroethers

Infrared absorption cross-sections and OH and Cl reaction rate coefficients for four C4-hydrofluoroethers (CF3)2CHOCH3, CF3CH2OCH2CF3, CF3CF2CH2OCH3, and CHF2CF2CH2OCH3 are reported. Relative rate measurements at 298 K and 1013 hPa of OH and Cl reaction rate coefficients give k(OH+(CF3)2CHOCH3) = (1.27+/-0.13) x 10(-13), k(OH+CF3CH2OCH2CF3) = (1.51+/-0.24) x 10(-13), k(OH+CF3CF2CH2OCH3) = (6.42+/-0.33) x 10(-13), k(OH+CHF2CF2CH2OCH3) = (8.7 +/-0.5) x 10(-13), k(Cl+(CF3)2CHOCH3) = (8.4+/-1.3) x 10(-12), k(Cl+CF3CH2OCH2CF3) = (6.5+/-1.7) x 10(-13), k(Cl+CF3CF2CH2OCH3) = (4.0+/-0.8) x 10(-11), and k(Cl+CHF2CF2CH2OCH3) = (2.65+/-0.17) x 10(-11) cm3 molecule(-1) s(-1). The primary products of the OH and Cl reactions with the fluorinated ethers have been identified as esters, and OH and Cl reaction rate coefficients for one of these, CF3CH2OCHO, are reported: k(OH+CF3CH2OCHO) = (7.7+/-0.9) x 10(-14) and kCl+CF3CH2OCHO) = (6.3+/-1.9) x 10(-14) cm3 molecule(-1) s(-1) The rate coefficient for the Cl-atom reaction with CHF2CH2F is derived as k(Cl+CHF2CH2F) = (3.0+/-0.9) x 10(-14) cm3 molecule(-1) s(-1) at 298 K. The error limits include 3sigma from the statistical data analyses as well as the errors in the rate coefficients of the reference compounds employed. The tropospheric lifetimes of the hydrofluoroethers are estimated to be short tauOH((CF3)2CHOCH3) approximately 100 days, tauOH(CF3CH2OCH2CF3) approximately 80 days, tauOH(CF3CF2CH2OCH3) approximately 20 days, and tauOH(CHF2CF2CH2OCH3) approximately 14 days, and their global warming potentials are small compared to CFC-11.     

TIM—a test improvement model

The software testing state of practice is not as good as it ought to be. To reduce the gap between the state of practice and the state of the art, improvement in software testing is necessary. Existing improvement models focus too little on, or lack important aspects of, software testing. Therefore a new model is required. This paper describes a test improvement model called TIM. The model functions as a guidebook for test improvement. It is mainly inspired by SEI's Capability Maturity Model and Gelperin's Testability Maturity Model. TIM introduces new perspectives to test improvement, with explicit focus on cost-effectiveness and risk management. The model addresses five ‘key areas’ of testing: organization, planning and tracking, test cases, testware and reviews. TIM also includes an assessment procedure. The model is continuously revised as knowledge is gained through research and experience of use. This paper presents results from three applications of TIM. © 1997 John Wiley & Sons, Ltd.