Disturbance in weak measurements and the difference between quantum and classical weak values

The role of measurement induced disturbance in weak measurements is of central importance for the interpretation of the weak value. Uncontrolled disturbance can interfere with the postselection process and make the weak value dependent on the details of the measurement process. Here we develop the concept of a generalized weak measurement for classical and quantum mechanics. The two cases appear remarkably similar, but we point out some important differences. A priori it is not clear what the correct notion of disturbance should be in the context of weak measurements. We consider three different notions and get three different results: (1) For a `strong' definition of disturbance, we find that weak measurements are disturbing. (2) For a weaker definition we find that a general class of weak measurements are non-disturbing, but that one gets weak values which depend on the measurement process. (3) Finally, with respect to an operational definition of the `degree of disturbance', we find that the AAV weak measurements are the least disturbing, but that the disturbance is always non-zero.Comment: v2: Many minor changes. Additional references. One additional appendix and another appendix rewritte

Infusion pasteurization of milk: Influence on the viscosity and casein micelle size

Milk is normally heat treated in order to obtain safe dairy products with an elongated shelf life as compared to raw milk. New methods, such as infusion pasteurization, for heat treatment of milk are currently being developed. This provides an opportunity for treating milk in a manner that creates different or improved functional properties compared to traditional indirect pasteurization. Infusion pasteurization has a time-temperature profile characterized by very rapid heating to relatively high temperatures, short holding times and very rapid cooling, which may lead to products with different properties as compared to products subjected to the standard low pasteurization at 72°C for 15s. Infusion pasteurization was performed on raw milk with two different holding times (0.1s and 0.7s) and for each holding time samples were drawn at three different temperatures (80°C, 100°C, and 120°C). Samples were compared to raw milk and to milk from the same batch subjected to a standard pasteurization at 72°C for 15s. The size of the casein micelles and the viscosity were measured in skimmed milk samples, using dynamic light scattering and capillary viscometri, respectively. The results showed a broadening of the size distributions of the casein micelles as the temperature of the infusion pasteurization increased from 80°C to 120°C with no marked difference between the two holding times. The viscosity also increased with increasing intensity of the infusion pasteurization treatment. Little or no difference was seen between the raw milk, the standard pasteurization and the infusion treatments at 80°C regarding both casein micelle size and viscosity. The observed changes in the investigated physical properties of the infusion pasteurization treated milk indicate that this novel pasteurization process might result in milk with altered functionality when used in the production of dairy products. This is currently under investigation

Infusion pasteurization of whole milk and skim milk: Influence on viscosity and particle size

Infusion pasteurization was performed on both whole milk and skim milk and at different temperatures in the range 72°C-120°C. The skim milk was prepared at a commercial dairy and had been heated to approx. 60°C during the separation process. The whole milk was skimmed by centrifugation prior to the analyses. In the analyses, the infusion pasteurized samples were compared to a standard low pasteurization on the same batches of milk and samples of the raw milks. Particle sizes were analyzed using dynamic light scattering, and the viscosity of the samples were measured with a capillary viscometer. The viscosity measurements showed no significant changes in viscosity after infusion pasteurization of skim milk, nor did the particle sizes change. On the other hand, when whole milk was infusion pasteurized an increase in viscosity of the skim milk fraction was seen as treatment temperature increased, and an increase in the z-average diameter of particles and broadening of the size distributions was observed. These observations were quite surprising and might be the result of influence of several different processes during and after infusion pasteurization

Probabilistic Modelling of Liquid Chromatography Time-of-Flight Mass Spectrometry

Liquid Chromatography Time-of-Flight Mass Spectrometry (LC-TOFMS) is an analytical platform that is widely used in the study of biological mixtures in the rapidly growing fields of proteomics and metabolomics. The development of statistical methods for the analysis of the very large data-sets that are typically produced in LC-TOFMS experiments is a very active area of research. However, the theoretical basis on which these methods are built is currently rather thin and as a result, inferences regarding the samples analysed are generally drawn in a somewhat qualitative fashion. This thesis concerns the development of a statistical formalism that can be used to describe and analyse the data produced in an LC-TOFMS experiment. This is done through the derivation of a number of probability distributions, each corresponding to a different level of approximation of the distribution of the empirically obtained data. Using such probabilistic models, statistically rigorous methods are developed and validated which are designed to address some of the central problems encountered in the practical analysis of LC-TOFMS data, most notably those related to the identification of unknown metabolites. Unlike most existing bioinformatics techniques, this work aims for rigour rather than generality. Consequently the methods developed are closely tailored to a particular type of TOF mass spectrometer, although they do carry over to other TOF instruments, albeit with important restrictions. And while the algorithms presented may constitute useful analytical tools for the mass spectrometers to which they can be applied, the broader implications of the general methodological approach that is taken are also of central importance. In particular, it is arguable that the main value of this work lies in its role as a proof-of-concept that detailed probabilistic modelling of TOFMS data is possible and can be used in practice to address important data analytical problems in a statistically rigorous manner