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.     

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.     

Optimal use of solar collectors for residential buildings

Solar radiation is an abundant free resource which may be used in the form of solar heated water. This is achieved in solar collectors which, unfortunately, are expensive devices and, further, the warm water must be stored in accumulators—items which also cost money. This paper shows how we have optimized the situation for a block‐of‐flats in Sweden. In order to find this point we have used the minimum life‐cycle cost (LCC) concept as a criterion. The best solution is therefore found when that cost finds its lowest value. It is also examined under which conditions solar collectors are part of the optimal solution and further it is calculated what happens if this optimal point is abandoned, i.e. how much will the LCC increase if other than optimal solutions are chosen. LCC optimization for multi‐family buildings almost always results in a heating system with low operating costs such as district heating or dual‐fuel systems where a heat pump takes care of the base load and an oil boiler the peak. The installation cost must, however, be kept to a reasonable level. Expensive solar panel systems are therefore normally avoided if the lowest LCC shall be reached, at least for Swedish conditions. This is so even if the solar system has a very low operating cost. For buildings where the only alternative energy source is electricity, solar collectors seem to be on the rim of profitability, i.e. for an energy price of about 0.6 SEK kWh^?1. Copyright © 2001 John Wiley & Sons, Ltd.     

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.     

Bovine Satellite Cells Isolated after 2 and 5 Days of Tissue Storage Maintain the Proliferative and Myogenic Capacity Needed for Cultured Meat Production

Cultured meat is an emerging alternative food technology which aims to deliver a more ethical, sustainable, and healthy muscle-tissue-derived food item compared to conventional meat. As start-up companies are rapidly forming and accelerating this technology, many aspects of this multi-faceted science have still not been investigated in academia. In this study, we investigated if bovine satellite cells with the ability to proliferate and undergo myogenic differentiation could be isolated after extended tissue storage, for the purpose of increasing the practicality for cultured meat production. Proliferation of bovine satellite cells isolated on the day of arrival or after 2 and 5 days of tissue storage were analyzed by metabolic and DNA-based assays, while their myogenic characteristics were investigated using RT-qPCR and immunofluorescence. Extended tissue storage up to 5 days did not negatively affect proliferation nor the ability to undergo fusion and create myosin heavy chain-positive myotubes. The expression patterns of myogenic and muscle-specific genes were also not affected after tissue storage. In fact, the data indicated a positive trend in terms of myogenic potential after tissue storage, although it was non-significant. These results suggest that the timeframe of which viable myogenic satellite cells can be isolated and used for cultured meat production can be greatly extended by proper tissue storage.     

A language for describing boundary scan devices

Boundary scan (IEEE Standard 1149.1-1990) technology is beginning to be embraced in chip and board designs. One key need is a way to simply and effectively describe the feature set of a boundary scan compliant device in a manner both user friendly and suitable for software to utilize. A language subset of VHDL is proposed here for this purpose. As with any new standard, the industry is learning how to apply its rules and mistakes will occur. A derivative effect of the language proposed here is that if a device is not describable by the language, then that device does not comply with the 1149.1 standard. While the converse is not true, the language still allows a syntactic check for compliance as well as a number of semantic checks.     

On the modelling of multicomponent acid extraction with long-chain aliphatic amines

The solvent extraction of phosphoric, hydrochloric, sulphuric, hydrofluosilicic and hydrofluoric acids with long-chain aliphatic amins is modelled. Pure acid equilibria are based on existing isotherms or calculated extraction constants when only experimental data are available. For binary mixtures binary combinations of acid complexes are added. In the aqueous phase Bromley's model for electrolytes is used for calculation of ionic activity coefficients and the appropriate association/dissociation equilibria taken into account for calculation of ionic strength. For the organic phase an empirical model for the non-ideal behaviour of phosphoric acid is used. For multicomponent mixtures at low acid concentrations the model calculates the extraction of phosphoric, hydrochloric and sulphuric acid almost quantitatively. For hydrofluosilicic and hydrofluoric acid the calculations are less precise and further information is needed about the different fluoride exchange equilibria involved.     

Considerations on System Design, Implementation and Computer Processing in SPECT

The application of SPECT as an alternative and/or a complement to other excisting imaging methods in nuclear medicine is being increasingly frequent. Specially designed devices have been developed as well as systems based on conventional devices, such as rotating gamma cameras.     

Skin cancer identification using multifrequency electrical impedance--a potential screening tool

Electrical bio-impedance can be used to assess skin cancers and other cutaneous lesions. The aim of this study was to distinguish skin cancer from benign nevi using multifrequency impedance spectra. Electrical impedance spectra of about 100 skin cancers and 511 benign nevi were measured. Impedance of reference skin was measured ipsi-laterally to the lesions. The impedance relation between lesion and reference skin was used to distinguish the cancers from the nevi. It was found that it is possible to separate malignant melanoma from benign nevi with 75% specificity at 100% sensitivity, and to distinguish nonmelanoma skin cancer from benign nevi with 87% specificity at 100% sensitivity. The power of skin cancer detection using electrical impedance is as good as, or better than, conventional visual screening made by general practitioners.     

Implementing enterprise content management: from evolution through strategy to contradictions out-of-the-box

This study examines a strategic development and implementation process of enterprise content management (ECM) in a large oil company. In view of the framework of four motors of development and change in organizations, this study represents a revelatory case of a hybrid development approach to ECM that involves the teleological, life-cycle, and dialectical motors of development. This is in contrast to the evolutionary development motor, which has prevailed in the hitherto reported content management research. The case study also complements process-based research on enterprise system implementations in general. We suggest that research and practice on large-scale ECM implementations should acknowledge all the four motors of change.