Note on clock synchronization and Edwards transformations

Edwards transformations relating inertial frames with arbitrary clock synchronization are reminded and put in more general setting. Their group theoretical context is described.Comment: 11 pages, no figures; final version, to appear in Foundations of Physics Letter

Sideband cooling while preserving coherences in the nuclear spin state in group-II-like atoms

We propose a method for laser cooling group-II-like atoms without changing the quantum state of their nuclear spins, thus preserving coherences that are usually destroyed by optical pumping. As group-II-like atoms have a $^1S_0$ closed-shell ground state, nuclear spin and electronic degrees of freedom are decoupled, allowing for independent manipulation. The hyperfine interaction that couples these degrees of freedom in excited states can be suppressed through the application of external magnetic fields. Our protocol employs resolved-sideband cooling on the forbidden clock transition, $^1S_0 \to {}^3P_0$, with quenching via coupling to the rapidly decaying $^1P_1$ state, deep in the Paschen-Back regime. This makes it possible to laser cool neutral atomic qubits without destroying the quantum information stored in their nuclear spins, as shown in two examples, $^{171}$Yb and $^{87}$Sr.Comment: 4 pages, 3 figures v4: minor changes in text, changes in the references, published versio

Aspekte der Mast- und Schlachtleistung sowie Wirtschaftlichkeit von Schweinen bei 100% Biofütterung

In an organic fattening trial 62 pigs of the genotype (PixHa)x(DuxGLR) were divided into 2 groups which were fed during finishing period with a ration containing soy prod-ucts or farm grown grain legumes, respectively. The Methionin deficit of the second group did not affect negatively the fattening performance, whereas lean meat content decreased significantly. In spite of lower feed costs of the second group the profitabil-ity was lower

Temporal evolution of spatial computations for visuomotor control

Goal-directed reaching movements are guided by visual feedback from both target and hand. The classical view is that the brain extracts information about target and hand positions from a visual scene, calculates a difference vector between them, and uses this estimate to control the movement. Here we show that during fast feedback control, this computation is not immediate, but evolves dynamically over time. Immediately after a change in the visual scene, the motor system generates independent responses to the errors in hand and target location. Only about 200 ms later, the changes in target and hand positions are combined appropriately in the response, slowly converging to the true difference vector. Therefore, our results provide evidence for the temporal evolution of spatial computations in the human visuomotor system, in which the accurate difference vector computation is first estimated by a fast approximation

Memorization in trumpet pedagogy: A qualitative case study of its integration in the college-level applied studio

Memorization is an important component in the education of many classical musicians, but it is infrequently addressed in pedagogical literature for trumpet players. Furthermore, the area of memorization has undergone very little systematic investigation in the pedagogy of trumpeters and others for whom notation is almost exclusively relied upon in formal education. This study employed qualitative instrumental case study methods in order to describe the teaching and learning of memorization in the studios at Boston University (BU) and University of California, Los Angeles (UCLA). These studios under the leadership of Terry Everson (BU) and Jens Lindemann (UCLA) were purposefully selected based upon the teachers’ reputations for performing from memory as well as their use of memorization within their teaching. The scarcity of literature on memorization suggests that it may rarely be an intentional part of trumpet pedagogy, even while performing from memory has been and is currently practiced by some of the most elite trumpet soloists and chamber ensembles. In an effort to broaden the discussion surrounding memorization, the literature review presents a survey of various interrelated topics from the perspective of music educators, cognitive psychologists, and others. Existing literature demonstrates that emphasis is too often given to the retrieval of memory at the expense of the other two parts of the memorization process: encoding and storage. Framing this study, then, is an understanding of memorization as a process rather than simply an end goal of performance without music. Following a preliminary questionnaire administered to student participants at each site, trumpet lessons were observed and interviews were conducted with the teachers and fifteen student participants. A description of the teaching and learning of memorization within the studios is presented in order to consider what might be gained through the inclusion of memorization and the challenges it presented for both students and teachers. The values, strategies, and practices of teachers passed on in the apprentice-like relationship of the studio and exchanged among students in a community of aspiring musicians are described. The student participants at both sites exhibited a variety of inclinations and attitudes towards memorization, ranging from full embrace to a near complete aversion to the practice. Students at BU reported personal progress in memorization skills while memorization experiences were uneven for students at UCLA. Both teachers and students considered the relationship between anxiety and memorization as well as the role that the studio community may serve in developing such skills. The benefits, challenges, and methods of memorization are discussed, including Everson’s emphasis on aural and analytical strategies for memorization that evolve from a desire for students to know the entire piece, not just the trumpet part. Lindemann’s belief that performing from memory can be a tool for empowering students and effectively communicating with audiences is also described. Several areas of commonality and contrast between the teachers’ performing and teaching philosophies are discussed. Significantly, both teachers believed that memorization could be an important pedagogical tool for overcoming technical challenges, but only the students at BU were consistently required to memorize repertoire. Implications for teaching, practice, and performance are provided along with suggestions for future research

Effects and Propositions

The quantum logical and quantum information-theoretic traditions have exerted an especially powerful influence on Bub's thinking about the conceptual foundations of quantum mechanics. This paper discusses both the quantum logical and information-theoretic traditions from the point of view of their representational frameworks. I argue that it is at this level, at the level of its framework, that the quantum logical tradition has retained its centrality to Bub's thought. It is further argued that there is implicit in the quantum information-theoretic tradition a set of ideas that mark a genuinely new alternative to the framework of quantum logic. These ideas are of considerable interest for the philosophy of quantum mechanics, a claim which I defend with an extended discussion of their application to our understanding of the philosophical significance of the no hidden variable theorem of Kochen and Specker.Comment: Presented to the 2007 conference, New Directions in the Foundations of Physic

Noise and Correlations in a Spatial Population Model with Cyclic Competition

Noise and spatial degrees of freedom characterize most ecosystems. Some aspects of their influence on the coevolution of populations with cyclic interspecies competition have been demonstrated in recent experiments [e.g. B. Kerr et al., Nature {\bf 418}, 171 (2002)]. To reach a better theoretical understanding of these phenomena, we consider a paradigmatic spatial model where three species exhibit cyclic dominance. Using an individual-based description, as well as stochastic partial differential and deterministic reaction-diffusion equations, we account for stochastic fluctuations and spatial diffusion at different levels, and show how fascinating patterns of entangled spirals emerge. We rationalize our analysis by computing the spatio-temporal correlation functions and provide analytical expressions for the front velocity and the wavelength of the propagating spiral waves.Comment: 4 pages of main text, 3 color figures + 2 pages of supplementary material (EPAPS Document). Final version for Physical Review Letter

Tissue-specific and minor inter-individual variation in imprinting of <i>IGF2R</i> is a common feature of <i>Bos taurus</i> concepti and not correlated with fetal weight

The insulin-like growth factor 2 receptor (IGF2R) is essential for prenatal growth regulation and shows gene dosage effects on fetal weight that can be affected by in-vitro embryo culture. Imprinted maternal expression of murine Igf2r is well documented for all fetal tissues excluding brain, but polymorphic imprinting and biallelic expression were reported for IGF2R in human. These differences have been attributed to evolutionary changes correlated with specific reproductive strategies. However, data from species suitable for testing this hypothesis are lacking. The domestic cow (Bos taurus) carries a single conceptus with a similar gestation length as human. We identified 12 heterozygous concepti informative for imprinting studies among 68 Bos taurus fetuses at Day 80 of gestation (28% term) and found predominantly maternal IGF2R expression in all fetal tissues but brain, which escapes imprinting. Inter-individual variation in allelic expression bias, i.e. expression of the repressed paternal allele relative to the maternal allele, ranged from 4.6−8.9% in heart, 4.3−10.2% in kidney, 6.1−11.2% in liver, 4.6−15.8% in lung and 3.2−12.2% in skeletal muscle. Allelic bias for mesodermal tissues (heart, skeletal muscle) differed significantly (P&lt;0.05) from endodermal tissues (liver, lung). The placenta showed partial imprinting with allelic bias of 22.9−34.7% and differed significantly (P&lt;0.001) from all other tissues. Four informative fetuses were generated by in-vitro fertilization (IVF) with embryo culture and two individuals displayed fetal overgrowth. However, there was no evidence for changes in imprinting or DNA methylation after IVF, or correlations between allelic bias and fetal weight. In conclusion, imprinting of Bos taurus IGF2R is similar to mouse except in placenta, which could indicate an effect of reproductive strategy. Common minor inter-individual variation in allelic bias and absence of imprinting abnormalities in IVF fetuses suggest changes in IGF2R expression in overgrown fetuses could be modulated through other mechanisms than changes in imprinting

Coexistence versus extinction in the stochastic cyclic Lotka-Volterra model

Cyclic dominance of species has been identified as a potential mechanism to maintain biodiversity, see e.g. B. Kerr, M. A. Riley, M. W. Feldman and B. J. M. Bohannan [Nature {\bf 418}, 171 (2002)] and B. Kirkup and M. A. Riley [Nature {\bf 428}, 412 (2004)]. Through analytical methods supported by numerical simulations, we address this issue by studying the properties of a paradigmatic non-spatial three-species stochastic system, namely the `rock-paper-scissors' or cyclic Lotka-Volterra model. While the deterministic approach (rate equations) predicts the coexistence of the species resulting in regular (yet neutrally stable) oscillations of the population densities, we demonstrate that fluctuations arising in the system with a \emph{finite number of agents} drastically alter this picture and are responsible for extinction: After long enough time, two of the three species die out. As main findings we provide analytic estimates and numerical computation of the extinction probability at a given time. We also discuss the implications of our results for a broad class of competing population systems.Comment: 12 pages, 9 figures, minor correction