Slow light in moving media

We review the theory of light propagation in moving media with extremely low group velocity. We intend to clarify the most elementary features of monochromatic slow light in a moving medium and, whenever possible, to give an instructive simplified picture

Production, Competition Indices, and Nutritive Values of Setaria Splendida, Centrosema Pubescens, and Clitoria Ternatea in Mixed Cropping Systems in Peatland

This research was conducted to evaluate production, different competition indices and nutritive value of Setaria splendida, Centrosema pubescens, and Clitoria ternatea in monoculture and mix cropping system on peat soil land. The experiment was set up in a randomized complete block design with five treatments and three replications. The five treatments were: S. splendida sole cropping (SS), C. pubescens sole cropping (CP), C. ternatea sole cropping (CT), S. splendida and C. pubescens mix cropping (SS/CP) and S. splendida/C. ternatea mix cropping (SS/CT). The DM yield of S. splendida in mixed cropping with C. pubescens increased 43.4% and in mix cropping with C. ternatea increased 15.7% compared to sole S. splendida. The value of land equivalent ratio of SS/CP (LERSS/CP) was >1. The LERSS/CT value was <1. The crowding coefficient value of S. splendida (KSS) was higher than KCP and KCT. The total value of KSS/CP and KSS/CT were >1. The competition ratio (CR) values of S. splendida in both mix cropping were >1. The agressivity (A) values of S. splendida in both mix cropping were positive. The crude protein, NDF and ADF content of forage were not affected by mix cropping system. In conclusion, mix cropping in peatland do not affect productivity and nutritive value of S. splendida, C. pubescens, and C. ternatea. S. splendida is more effective in exploiting environmental resources when intercropped with C. pubescens compared to C. ternatea on peatland

Monopoles without magnetic charges: Finite energy monopole-antimonopole configurations in CP1 model and restricted QCD

We propose a new type of regular monopole-like field configuration in quantum chromodynamics (QCD) and CP^1 model. The monopole configuration can be treated as a monopole-antimonopole pair without localized magnetic charges. An exact numeric solution for a simple monopole-antimonopole solution has been obtained in CP^1 model with an appropriate potential term. We suppose that similar monopole solutions may exist in effective theories of QCD and in the electroweak standard model.Comment: 8 pages, 8 figures, 1 table, final version accepted by Phys. Lett.

Dynamics of the Young Binary LMC Cluster NGC 1850

In this paper we have examined the age and internal dynamics of the young binary LMC cluster NGC 1850 using BV CCD images and echelle spectra of 52 supergiants. Isochrone fits to a BV color-magnitude diagram revealed that the primary cluster has an age of $\tau = 90 \pm 30$ Myr while the secondary member has $\tau = 6 \pm 5$ Myr. BV surface brightness profiles were constructed out to R $>$ 40 pc, and single-component King-Michie (KM) models were applied. The total cluster luminosity varied from L$_B$ = 2.60 - 2.65 $\times 10^6$ L$_B$\sol\ and L$_V$ = 1.25 - 1.35 $\times 10^6$ as the anisotropy radius varied from infinity to three times the scale radius with the isotropic models providing the best agreement with the data. Of the 52 stars with echelle spectra, a subset of 36 were used to study the cluster dynamics. The KM radial velocity distributions were fitted to these velocities yielding total cluster masses of 5.4 - 5.9 $\pm 2.4 \times 10^4$ M\sol\ corresponding to M/L$_B$ = 0.02 $\pm 0.01$ M\sol/L$_B$\sol\ or M/L$_V$ = 0.05 $\pm 0.02$ M\sol/L$_V$\sol. A rotational signal in the radial velocities has been detected at the 93\% confidence level implying a rotation axis at a position angle of 100\deg. A variety of rotating models were fit to the velocity data assuming cluster ellipticities of $\epsilon = 0.1 - 0.3$. These models provided slightly better agreement with the radial velocity data than the KM models and had masses that were systematically lower by a few percent. The preferred value for the slope of a power-law IMF is a relatively shallow, x = 0.29 \pmm{+0.3}{-0.8} assuming the B-band M/L or x = 0.71 \pmm{+0.2}{-0.4} for the V-band.Comment: 41 pages (figures available via anonymous FTP as described below

On the interactions between molecules in an off-resonant laser beam:Evaluating the response to energy migration and optically induced pair forces

Electronically excited molecules interact with their neighbors differently from their ground-state counterparts. Any migration of the excitation between molecules can modify intermolecular forces, reflecting changes to a local potential energy landscape. It emerges that throughput off-resonant radiation can also produce significant additional effects. The context for the present analysis of the mechanisms is a range of chemical and physical processes that fundamentally depend on intermolecular interactions resulting from second and fourth-order electric-dipole couplings. The most familiar are static dipole-dipole interactions, resonance energy transfer (both second-order interactions), and dispersion forces (fourth order). For neighboring molecules subjected to off-resonant light, additional forms of intermolecular interaction arise in the fourth order, including radiation-induced energy transfer and optical binding. Here, in a quantum electrodynamical formulation, these phenomena are cast in a unified description that establishes their inter-relationship and connectivity at a fundamental level. Theory is then developed for systems in which the interplay of these forms of interaction can be readily identified and analyzed in terms of dynamical behavior. The results are potentially significant in Förster measurements of conformational change and in the operation of microelectromechanical and nanoelectromechanical devices. © 2009 American Institute of Physics

Thermodynamics of Two Dimensional Magnetic Nanoparticles

A two dimensional magnetic particle in the presence of an external magnetic field is studied. Equilibrium thermodynamical properties are derived by evaluating analytically the partition function. When the external field is applied perpendicular to the anisotropy axis the system exhibits a second order phase transition with order parameter being the magnetization parallel to the field. In this case the system is isomorph to a mechanical system consisting in a particle moving without friction in a circle rotating about its vertical diameter. Contrary to a paramagnetic particle, equilibrium magnetization shows a maximum at finite temperature. We also show that uniaxial anisotropy in a system of noninteracting particles can be missinterpreted as a ferromagnetic or antiferromagnetic coupling among the magnetic particles depending on the angle between anisotropy axis and magnetic field.Comment: 4 pages 6 figures 19 reference

FIP Bias Evolution in a Decaying Active Region

Solar coronal plasma composition is typically characterized by first ionization potential (FIP) bias. Using spectra obtained by Hinode's EUV Imaging Spectrometer (EIS) instrument, we present a series of large-scale, spatially resolved composition maps of active region (AR) 11389. The composition maps show how FIP bias evolves within the decaying AR from 2012 January 4-6. Globally, FIP bias decreases throughout the AR. We analyzed areas of significant plasma composition changes within the decaying AR and found that small-scale evolution in the photospheric magnetic field is closely linked to the FIP bias evolution observed in the corona. During the AR's decay phase, small bipoles emerging within supergranular cells reconnect with the pre-existing AR field, creating a pathway along which photospheric and coronal plasmas can mix. The mixing time scales are shorter than those of plasma enrichment processes. Eruptive activity also results in shifting the FIP bias closer to photospheric in the affected areas. Finally, the FIP bias still remains dominantly coronal only in a part of the AR's high-flux density core. We conclude that in the decay phase of an AR's lifetime, the FIP bias is becoming increasingly modulated by episodes of small-scale flux emergence, i.e. decreasing the AR's overall FIP bias. Our results show that magnetic field evolution plays an important role in compositional changes during AR development, revealing a more complex relationship than expected from previous well-known Skylab results showing that FIP bias increases almost linearly with age in young ARs (Widing $\&$ Feldman, 2001, ApJ, 555, 426)