Maxwell's theory on a post-Riemannian spacetime and the equivalence principle

The form of Maxwell's theory is well known in the framework of general relativity, a fact that is related to the applicability of the principle of equivalence to electromagnetic phenomena. We pose the question whether this form changes if torsion and/or nonmetricity fields are allowed for in spacetime. Starting from the conservation laws of electric charge and magnetic flux, we recognize that the Maxwell equations themselves remain the same, but the constitutive law must depend on the metric and, additionally, may depend on quantities related to torsion and/or nonmetricity. We illustrate our results by putting an electric charge on top of a spherically symmetric exact solution of the metric-affine gauge theory of gravity (comprising torsion and nonmetricity). All this is compared to the recent results of Vandyck.Comment: 9 pages, REVTeX, no figures; minor changes, version to be published in Class. Quantum Gra

The Constitutive Relations and the Magnetoelectric Effect for Moving Media

In this paper the constitutive relations for moving media with homogeneous and isotropic electric and magnetic properties are presented as the connections between the generalized magnetization-polarization bivector $$ and the electromagnetic field F. Using the decompositions of F and $\mathcal{M}$, it is shown how the polarization vector P(x) and the magnetization vector M(x) depend on E, B and two different velocity vectors, u - the bulk velocity vector of the medium, and v - the velocity vector of the observers who measure E and B fields. These constitutive relations with four-dimensional geometric quantities, which correctly transform under the Lorentz transformations (LT), are compared with Minkowski's constitutive relations with the 3-vectors and several essential differences are pointed out. They are caused by the fact that, contrary to the general opinion, the usual transformations of the 3-vectors $$, $\mathbf{B}$, $\mathbf{P}$, $\mathbf{M}$, etc. are not the LT. The physical explanation is presented for the existence of the magnetoelectric effect in moving media that essentially differs from the traditional one.Comment: 18 pages, In Ref. [10] here, which corresponds to Ref. [18] in the published paper in IJMPB, Z. Oziewicz's published paper is added. arXiv admin note: text overlap with arXiv:1101.329

Corrections to Sirlin's Theorem in O(p6)O(p^6) Chiral Perturbation Theory

We present the results of the first two-loop calculation of a form factor in full $SU(3) \times SU(3)$ Chiral Perturbation Theory. We choose a specific linear combination of $\pi^+, K^+, K^0$ and $K\pi$ form factors (the one appearing in Sirlin's theorem) which does not get contributions from order $p^6$ operators with unknown constants. For the charge radii, the correction to the previous one-loop result turns out to be significant, but still there is no agreement with the present data due to large experimental uncertainties in the kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure

Semirelativistic stability of N-boson systems bound by 1/r pair potentials

We analyze a system of self-gravitating identical bosons by means of a semirelativistic Hamiltonian comprising the relativistic kinetic energies of the involved particles and added (instantaneous) Newtonian gravitational pair potentials. With the help of an improved lower bound to the bottom of the spectrum of this Hamiltonian, we are able to enlarge the known region for relativistic stability for such boson systems against gravitational collapse and to sharpen the predictions for their maximum stable mass.Comment: 11 pages, considerably enlarged introduction and motivation, remainder of the paper unchange

Preschool/Kindergarten teachers' conceptions of standardised testing

Standardised tests play an important role in early childhood (EC) education in many countries. Although teachers' conceptions largely determine whether and how these instruments are used, research on this topic is scarce. As a result, factors that influence conceptions of standardised testing have remained largely unexplored. To examine teachers' conceptions of standardised testing and aspects that may influence these conceptions, Brown's CoA-III-A questionnaire was distributed to 97 EC educators. Based on their responses, a selection of six preschool/kindergarten teachers participated in a series of semi-structured interviews. Analyses of the questionnaire and the interviews indicated that the teachers did not see these tests solely as instruments for accountability or improvement. While some perceived the test as pleasant confirmation, others perceived the results as negative opposition to their own observations. The teachers' conceptions were influenced by classroom population, management team, and the ascribed purpose of the test

Role of lipoxygenase products in the effects of angiotensin II in the isolated aorta and perfused heart of the rat

The objective of this study was to determine whether arachidonate metabolites are involved in the vasoconstrictive effects of angiotensin II in rats. In the isolated perfused heart, dexamethasone (4 mg/kg) significantly suppressed the maximal decreases in coronary flow induced by angiotensin II and vasopressin (reference drug). In the heart, the nonselective lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 1 μM) markedly suppressed the angiotensin II-induced decreases in coronary flow. NDGA (10 μM) inhibited both angiotensin II- and methoxamine- (reference drug) induced contractions in aortic rings with (in the presence of L-NAME) and without endothelium. In the heart, the leukotriene synthesis inhibitor MK-886 (0.3 μM) significantly reduced the maximal effects to angiotensin II, but the leukotriene antagonist FPL 55712 (0.1 and 0.3 μM) had no effect. We conclude that in the isolated perfused rat heart angiotensin II-induced decreases in coronary flow are in part mediated by Hpoxygenase products, which might be derived from the 5-Hpoxygenase pathway, but are probably not leukotrienes. Furthermore, endothelium independent Hpoxygenase products mediate part of the contractile responses to angiotensin II in the isolated rat aorta

Labour and Neonatal Outcome in Small for Gestational Age Babies Delivered Beyond 36+0 Weeks: A Retrospective Cohort Study

Objective. Small for gestational age (SGA) is associated with increased neonatal morbidity and mortality. At present, evidence on whether these pregnancies should be managed expectantly or by induction is lacking. To get insight in current policy we analysed data of the National Dutch Perinatal Registry (PRN). Methods. We used data of all nulliparae between 2000 and 2005 with a singleton in cephalic presentation beyond 36+0 weeks, with a birth weight below the 10th percentile. We analysed two groups of pregnancies: (I) with isolated SGA and (II) with both SGA and hypertensive disorders. Onset of labour was related to route of delivery and neonatal outcome. Results. Induction was associated with a higher risk of emergency caesarean section (CS), without improvement in neonatal outcome. For women with isolated SGA the relative risk of emergency CS after induction was 2.3 (95% Confidence Interval [CI] 2.1 to 2.5) and for women with both SGA and hypertensive disorders the relative risk was 2.7 (95% CI 2.3 to 3.1). Conclusion. Induction in pregnancies complicated by SGA at term is associated with a higher risk of instrumental deliveries without improvement of neonatal outcome. Prospective studies are needed to determine the best strategy in suspected IUGR at term

Formation of Structure in Snowfields: Penitentes, Suncups, and Dirt Cones

Penitentes and suncups are structures formed as snow melts, typically high in the mountains. When the snow is dirty, dirt cones and other structures can form instead. Building on previous field observations and experiments, this work presents a theory of ablation morphologies, and the role of surface dirt in determining the structures formed. The glaciological literature indicates that sunlight, heating from air, and dirt all play a role in the formation of structure on an ablating snow surface. The present work formulates a mathematical model for the formation of ablation morphologies as a function of measurable parameters. The dependence of ablation morphologies on weather conditions and initial dirt thickness are studied, focusing on the initial growth of perturbations away from a flat surface. We derive a single-parameter expression for the melting rate as a function of dirt thickness, which agrees well with a set of measurements by Driedger. An interesting result is the prediction of a dirt-induced travelling instability for a range of parameters.Comment: 28 pages, 13 figure