Affine Symmetries of Orbit Polytopes

An orbit polytope is the convex hull of an orbit under a finite group $G \leq \operatorname{GL}(d,\mathbb{R})$. We develop a general theory of possible affine symmetry groups of orbit polytopes. For every group, we define an open and dense set of generic points such that the orbit polytopes of generic points have conjugated affine symmetry groups. We prove that the symmetry group of a generic orbit polytope is again $G$ if $G$ is itself the affine symmetry group of some orbit polytope, or if $G$ is absolutely irreducible. On the other hand, we describe some general cases where the affine symmetry group grows. We apply our theory to representation polytopes (the convex hull of a finite matrix group) and show that their affine symmetries can be computed effectively from a certain character. We use this to construct counterexamples to a conjecture of Baumeister et~al.\ on permutation polytopes [Advances in Math. 222 (2009), 431--452, Conjecture~5.4].Comment: v2: Referee comments implemented, last section updated. Numbering of results changed only in Sections 9 and 10. v3: Some typos corrected. Final version as published. 36 pages, 5 figures (TikZ

Strangeness from 20 AGeV to 158 AGeV

New results from the energy scan programme of NA49, in particular kaon production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters are constant at SPS energies. Both findings support the scenario of a phase transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly with beam energy, showing an energy dependence similar to K-/pi-. The measured particle yields can be reproduced by a hadron gas model, with chemical freeze-out parameters on a smooth curve in the T-muB plane. The transverse spectra can be understood as resulting from a rapidly expanding, locally equilibrated source. No evidence for an earlier kinetic decoupling of heavy hyperons is found

Management of skin-sparing mastectomy: Results of a survey of German Hospitals

Background: The aim of this study was to evaluate the current management of skin-sparing mastectomy in German hospitals and to determine its oncologic safety. For this purpose, 100 surgeons were surveyed regarding their use of skin-sparing mastectomy. Results: Almost all surveyed hospitals performed skin-sparing mastectomy. Most of them believe that the recurrence rate is equal to that of conventional mastectomy. 95% regard inflammatory cancer as a contraindication to skin-sparing surgery. Most of the hospitals thin out the skin without leaving any macroscopic glandular tissue behind, and 73% leave the nipple-areola complex (NAC) on the basis of frozen sections. Volume replacement is most commonly done with latissimus dorsi muscle flaps and pedicled TRAM flaps. In 76% of the surveyed hospitals, reconstruction after mastectomy is performed by the gynecological department. Conclusion: Skin-sparing mastectomy is considered to be the best cosmetic option for breast reconstruction in selected breast cancer patients. At present, statistical proof of its oncologic safety is lacking. The surgical techniques used for skin-sparing mastectomy have not yet been standardized. In order to achieve standardization, careful discussion-making and evaluation remain important

Optical alignment and spinning of laser-trapped microscopic particles

Light-induced rotation of absorbing microscopic particles by transfer of angular momentum from light to the material raises the possibility of optically driven micromachines. The phenomenon has been observed using elliptically polarized laser beams or beams with helical phase structure. But it is difficult to develop high power in such experiments because of overheating and unwanted axial forces, limiting the achievable rotation rates to a few hertz. This problem can in principle be overcome by using transparent particles, transferring angular momentum by a mechanism first observed by Beth in 1936, when he reported a tiny torque developed in a quartz waveplate due to the change in polarization of transmitted light. Here we show that an optical torque can be induced on microscopic birefringent particles of calcite held by optical tweezers. Depending on the polarization of the incident beam, the particles either become aligned with the plane of polarization (and thus can be rotated through specified angles) or spin with constant rotation frequency. Because these microscopic particles are transparent, they can be held in three-dimensional optical traps at very high power without heating. We have observed rotation rates in excess of 350 Hz.Comment: 4 pages, 4 figure

Computer-assisted grounded theory analysis with ATLAS.ti

In this paper I show how the various steps of a Grounded Theory analysis can be conducted in a computer-assisted environment. As the Grounded Theory approach was developed before the event of CAQDAS, the various steps and procedures have been described for manual ways of analysis. In newer books one finds references that this can of course also be accomplished in CAQDAS, but little detail is provided on the practical aspects, as if the process were self-explanatory. Based on my experience, it is not, and this applies to the application of any methodological approach in CAQDAS. Learning the various tools and features in a software does not automatically teach the user which tool is the best fit for a particular process given a particular methodological framework. In this paper I want to show how the various steps and procedures of the Strauss and Corbin approach to Grounded Theory can be translated for use in ATLAS.ti

Methods and methodologies for qualitative data analysis

The main aim of this paper is to introduce the contributions that are published in the proceedings. As a side-line, I follow up on an observation that I made (not only) at the conference – which is the distinction between methods and methodology. I hope that you will enjoy and benefit from reading the articles in the proceedings and watching the corresponding videos of the original presentations on the conference YouTube channel (http://www.youtube.com/user/ATLASticonference)

Apidae aus Süd-Ost-Afrika gesammelt von Missionar Henri A. Junod Dr. phil. h. c. (1863-1934) (Hym. Apid.)

Dem grossen Interesse, welches Herr Missionar Junod während seiner amtlichen Tätigkeit in N.-Transvaal und der Delagoa Bai der Insektenwelt schenkte, verdanken wir höchst wertvolle Funde, die im folgenden zusammengestellt wurden.Peer reviewe