Global and local cutoff frequencies for transverse waves propagating along solar magnetic flux tubes

The propagation of linear transverse waves along a thin isothermal magnetic flux tube is affected by a global cutoff frequency that separates propagating and non-propagating waves. In this paper, wave propagation along a thin but non-isothermal flux tube is considered and a local cutoff frequency is derived. The effects of different temperature profiles on this local cutoff frequency are studied by considering different power-law temperature distributions as well as the semi-empirical VAL C model of the solar atmosphere. The results show that the conditions for wave propagation strongly depend on the temperature gradients. Moreover, the local cutoff frequency calculated for the VAL C model gives constraints on the range of wave frequencies that are propagating in different parts of the solar atmosphere. These theoretically predicted constraints are compared to observational data and are used to discuss the role played by transverse tube waves in the atmospheric heating and dynamics, and in the excitation of solar atmospheric oscillations.Comment: To be publishd in ApJ Vol. 763. 10 pages, 3 Postscript figure

Helmholtz solver with transparent influx boundary conditions and nonuniform exterior

Boundary conditions for a 2D finite element Helmholtz solver are derived, which allow scattered light to leave the calculation domain in the presence of outgoing waveguides. Influx of light, through a waveguide or otherwise, can be prescribed at any boundary

A combination of Dirichlet to Neumann operators and perfectly matched layers as boundary conditions for optical finite element simulations

By combining Dirichlet to Neumann (DtN) operators and Perfectly Matched Layers (PML’s) as boundary conditions on a rectangular domain on which the Helmholtz equation is solved, the disadvantages of both methods are greatly diminished. Due to the DtN operators, light may be accurately fluxed into the domain, while the PML’s absorb light that is reflected from the corners of the domain when only DtN boundaries are used

Orthogonality relations for triple modes at dielectric boundary surfaces

We work out the orthogonality relations for the set of Carniglia-Mandel triple modes which provide a set of normal modes for the source-free electromagnetic field in a background consisting of a passive dielectric half-space and the vacuum, respectively. Due to the inherent computational complexity of the problem, an efficient strategy to accomplish this task is desirable, which is presented in the paper. Furthermore, we provide all main steps for the various proofs pertaining to different combinations of triple modes in the orthogonality integral.Comment: 15 page

'It Has to Go Down A Little, In Order to Go Around'- Following Feynman on the Gyroscope

In this paper we show that with the help of accessible, teaching quality equipment, some interesting details of the motion of a gyroscope, typically overlooked in introductory courses, can be measured and compared to theory. We begin by deriving a simple relation between the asymptotic dip angle of a gyroscope released from rest and its precession velocity. We then describe an experiment which measures these parameters. The data gives excellent agreement with the model. The idea for this project was suggested by the discussion of gyroscopic motion in The Feynman Lectures on Physics. Feynman's conclusion (stated in colloquial terms and quoted in the title) is confirmed and, in addition, conservation of angular momentum, which underlies this effect, is quantitatively demonstrated.Comment: 6 pages, 4 figure

Flight Gate Assignment with a Quantum Annealer

Optimal flight gate assignment is a highly relevant optimization problem from airport management. Among others, an important goal is the minimization of the total transit time of the passengers. The corresponding objective function is quadratic in the binary decision variables encoding the flight-to-gate assignment. Hence, it is a quadratic assignment problem being hard to solve in general. In this work we investigate the solvability of this problem with a D-Wave quantum annealer. These machines are optimizers for quadratic unconstrained optimization problems (QUBO). Therefore the flight gate assignment problem seems to be well suited for these machines. We use real world data from a mid-sized German airport as well as simulation based data to extract typical instances small enough to be amenable to the D-Wave machine. In order to mitigate precision problems, we employ bin packing on the passenger numbers to reduce the precision requirements of the extracted instances. We find that, for the instances we investigated, the bin packing has little effect on the solution quality. Hence, we were able to solve small problem instances extracted from real data with the D-Wave 2000Q quantum annealer.Comment: Updated figure

Slimy and ropy milk

A study of slimy and ropy milk sent for examination to the dairy bacteriological laboratories of Iowa State College has shown the following: 1. Cultures of organisms secured from slimy starters, apparently typical Streptococcus lacticus forms, sometimes showed marked capacity to produce ropiness when inoculated into sterile milk. This slime producing power is evidently a variable characteristic, appearing and disappearing without apparent cause. 2. Associative action of organisms in some cases is responsible for ropiness. Two organisms, neither of which alone can cause ropiness, may, when grown together, cause the medium to become slimy. 3. Bacterium (lactis) viscosum is one common cause of slimy milk. 4. Certain peptonizing bacteria, as Bact. peptogenes, produce a very slimy residuum after digestion of the casein. 5. Bacterium bulgaricum and certain related high acid organisms frequently produce marked viscosity in milk. Sliminess in milk is apparently due to different causes with different organisms: 1. Gum and gum-like capsular materials partially soluble, or at least swelling in water, al\u27e frequently the same. 2. In many cases there seems to be a direct relationship between chain formation of streptococcus and the development of ropiness, likewise between the numbers of bacteria and ropiness. 3. Associative action between two distinct organisms resulting in great increases in number of each is not uncommon as a cause of ropiness. Methods of control and prevention of slimy milk are discussed. Keys to the organisms that have been described as responsible for slimy production in milk are presented. An attempt has been made to clear up synonymy. Descriptions of thirty-three species of bacteria that have been found associated with milk are given, and the literature reviewed

Recent Developments in the Nuclear Many-Body Problem

The study of quantum chromodynamics (QCD) over the past quarter century has had relatively little impact on the traditional approach to the low-energy nuclear many-body problem. Recent developments are changing this situation. New experimental capabilities and theoretical approaches are opening windows into the richness of many-body phenomena in QCD. A common theme is the use of effective field theory (EFT) methods, which exploit the separation of scales in physical systems. At low energies, effective field theory can explain how existing phenomenology emerges from QCD and how to refine it systematically. More generally, the application of EFT methods to many-body problems promises insight into the analytic structure of observables, the identification of new expansion parameters, and a consistent organization of many-body corrections, with reliable error estimates.Comment: 15 pages, 10 figures, plenary talk at the 11th Conference on Recent Progress in Many-Body Theories (MB 11), Manchester, England, 9-13 Jul 200

Reinventing College Physics for Biologists: Explicating an epistemological curriculum

The University of Maryland Physics Education Research Group (UMd-PERG) carried out a five-year research project to rethink, observe, and reform introductory algebra-based (college) physics. This class is one of the Maryland Physics Department's large service courses, serving primarily life-science majors. After consultation with biologists, we re-focused the class on helping the students learn to think scientifically -- to build coherence, think in terms of mechanism, and to follow the implications of assumptions. We designed the course to tap into students' productive conceptual and epistemological resources, based on a theoretical framework from research on learning. The reformed class retains its traditional structure in terms of time and instructional personnel, but we modified existing best-practices curricular materials, including Peer Instruction, Interactive Lecture Demonstrations, and Tutorials. We provided class-controlled spaces for student collaboration, which allowed us to observe and record students learning directly. We also scanned all written homework and examinations, and we administered pre-post conceptual and epistemological surveys. The reformed class enhanced the strong gains on pre-post conceptual tests produced by the best-practices materials while obtaining unprecedented pre-post gains on epistemological surveys instead of the traditional losses.Comment: 35 pages including a 15 page appendix of supplementary material

Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M_UV = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha = -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of ~ -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M_UV ~ -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M*=10^8 Msun. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.Comment: accepted for publication in Ap