Bacteriological and epidemiological studies of campylobacter spp. in Swedish broilers

Campylobacter jejuni is the most frequently reported cause of bacterial gastrointestinal illness in humans in Sweden. Chicken products are considered an important risk factor for human infection. This thesis analyses and identifies sources and risk factors for colonisation of Campylobacter spp. in broilers at both farm level and slaughter. Slaughter groups with a low within-group prevalence were identified, split slaughter was confirmed as a risk factor and contamination of carcasses was shown to occur both during transport and during the slaughter process. Environmental campylobacter load was comparable on high and low incidence farms, indicating that hygiene regime is of greater importance than environmental load. Slaughter groups with a high within-flock prevalence had significantly higher campylobacter load in carcasses at slaughter than slaughter groups with a low degree of colonisation Campylobacter jejuni is the Campylobacter sp. predominantly found in broilers. Strain characterisation below species level, so-called subtyping, is a helpful tool in epidemiological studies, e.g. in determination of transmission routes. Certain subtypes were shown to be common in Sweden and may have a higher ability to survive in the environment around broiler houses. The results from phylogenetic analysis indicated that typing based on 16S rRNA sequencing is not always sufficient for differentiating between C. jejuni and C. coli. However, nine different 16S rRNA types were identified among 47 Swedish campylobacter isolates from broilers. About one-third of Swedish broiler producers seldom deliver any campylobacter-positive broilers to slaughter, demonstrating that it is possible to produce campylobacter-free chickens in Sweden. The factors identified as carrying the highest risk of producing campylobacter-positive broilers in Sweden were (i) insufficient general tidiness on the farm, (ii) split slaughter, (iii) an in-line position of the doors between the outside and access into broiler houses instead of an angled position. Furthermore, (iv) high risk farms often had other livestock such as cattle and pigs, and (v) high risk farms were more frequently situated in groves than in forest. Reducing the proportion of campylobacter-infected broiler flocks and the numbers of campylobacter on broiler carcasses would considerably lower the risk for consumers

"Quantum machine" to solve quantum "measurement problem"?

Recently a study of the first superposed mechanical quantum object ("machine") visible to the naked eye was published. However, as we show, it turns out that if the object would actually be observed, i.e. would interact with an optical photon, the quantum behavior should vanish. This, the actual observation, has long been suspected in many interpretations of quantum mechanics to be what makes the transition quantum $\rightarrow$ classical, but so far it has not been available for direct experimental study in a mechanical system. We show how any interaction, even a purely quantum one, of sufficient strength can constitute a physical "measurement" - essentially the emergence of an effectively classical object - active observation thus being a sufficient but not necessary criterion. So it seems we have in this case of the "quantum machine" a unique possibility to study, and possibly solve, the long-standing "measurement problem" of quantum mechanics.Comment: 4 page

A simple solution to color confinement

We show that color confinement is a direct result of the nonabelian, i.e. nonlinear, nature of the color interaction in quantum chromodynamics. This makes it in general impossible to describe the color field as a collection of elementary quanta (gluons). A quark cannot be an elementary quanta of the quark field, as the color field of which it is the source is itself a source hence making isolated (noninteracting) quarks impossible. In geometrical language, the impossibility of quarks and gluons as physical particles arises due to the fact that the color Yang-Mills space does not have a constant trivial curvature.Comment: 6 pages, LaTe

Aspects of nonrelativistic quantum gravity

A nonrelativistic approach to quantum gravity is studied. At least for weak gravitational fields it should be a valid approximation. Such an approach can be used to point out problems and prospects inherent in a more exact theory of quantum gravity, yet to be discovered. Nonrelativistic quantum gravity, e.g., shows promise for prohibiting black holes altogether (which would eliminate singularities and also solve the black hole information paradox), gives gravitational radiation even in the spherically symmetric case, and supports non-locality (quantum entanglement). Its predictions should also be testable at length scales well above the "Planck scale", by high-precision experiments feasible with existing technology.Comment: Accepted for publicatio

The Bruhat order on conjugation-invariant sets of involutions in the symmetric group

Let $I_n$ be the set of involutions in the symmetric group $S_n$, and for $A \subseteq \{0,1,\ldots,n\}$, let $$F_n^A=\{\sigma \in I_n \mid \text{$\sigma$ has $a$ fixed points for some $a \in A$}\}.$$ We give a complete characterisation of the sets $A$ for which $F_n^A$, with the order induced by the Bruhat order on $S_n$, is a graded poset. In particular, we prove that $F_n^{\{1\}}$ (i.e., the set of involutions with exactly one fixed point) is graded, which settles a conjecture of Hultman in the affirmative. When $F_n^A$ is graded, we give its rank function. We also give a short new proof of the EL-shellability of $F_n^{\{0\}}$ (i.e., the set of fixed point-free involutions), which was recently proved by Can, Cherniavsky, and Twelbeck. Keywords: Bruhat order, symmetric group, involution, conjugacy class, graded poset, EL-shellabilityComment: 12 pages, 3 figure

Nonlinear gauge interactions: a possible solution to the "measurement problem" in quantum mechanics

Two fundamental, and unsolved problems in physics are: i) the resolution of the "measurement problem" in quantum mechanics ii) the quantization of strongly nonlinear (nonabelian) gauge theories. The aim of this paper is to suggest that these two problems might be linked, and that a mutual, simultaneous solution to both might exist. We propose that the mechanism responsible for the "collapse of the wave function" in quantum mechanics is the nonlinearities already present in the theory via nonabelian gauge interactions. Unlike all other models of spontaneous collapse, our proposal is, to the best of our knowledge, the only one which does not introduce any new elements into the theory. A possible experimental test of the model would be to compare the coherence lengths - here defined as the distance over which quantum mechanical superposition is still valid - for, \textit{e.g}, electrons and photons in a double-slit experiment. The electrons should have a finite coherence length, while photons should have a much longer coherence length (in principle infinite, if gravity - a very weak effect indeed unless we approach the Planck scale - is ignored).Comment: 11 pages, Accepted for publicatio

Reply to comment on ``A simple explanation of the non-appearance of physical gluons and quarks"

This is the reply to a comment by Andreas Aste [hep-th/0302103] on a previous article of mine in Can.J.Phys. The counter-arguments used by Aste utilize a mathematical limit without physical meaning. We still contend that in QCD, the particles ``gluons'' and ``quarks'' are merely artifacts of an approximation method (the perturbative expansion) and are simply absent in the exact theory.Comment: 2 pages, to appear in Can.J.Phy

The "proton spin crisis" - a quantum query

The "proton spin crisis" was introduced in the late 1980s, when the EMC-experiment revealed that little or nothing of a proton's spin seemed to be carried by its quarks. The main objective of this paper is to point out that it is wrong to assume that the proton spin, measured by completely different experimental setups, should be the same in all circumstances.Comment: 5 page

The Moral Significance of Indetectable Effects

A reassessment of Parfit\u27s fifth mistake in moral mathematics