A connection between the morphology of the X-ray emission and rotation for solar-type stars in open clusters

It is suggested that the three-segmented morphology of the soft X-ray emission from cluster and field stars may be understood in terms of the recent classification of rotating stars into three kinds: those lying on the convective sequence, on the interface sequence, or in the gap between them.Comment: 7 pages, 1 (color) figure, accepted by ApJ Letter

Current-spin coupling for ferromagnetic domain walls in fine wires

The coupling between a current and a domain wall is examined. In the presence of a finite current and the absence of a potential which breaks the translational symmetry, there is a perfect transfer of angular momentum from the conduction electrons to the wall. As a result, the ground state is in uniform motion. This remains the case when relaxation is accounted for. This is described by, appropriately modified, Landau-Lifshitz-Gilbert equations.Comment: 4 pqges, no figure

Hadron Loops: General Theorems and Application to Charmonium

In this paper we develop a formalism for incorporating hadron loops in the quark model. We derive expressions for mass shifts, continuum components and mixing amplitudes of "quenched" quark model states due to hadron loops, as perturbation series in the valence-continuum coupling Hamiltonian. We prove three general theorems regarding the effects of hadron loops, which show that given certain constraints on the external "bare" quark model states, the valence-continuum coupling, and the hadrons summed in the loops, the following results hold: (1) The loop mass shifts are identical for all states within a given N,L multiplet. (2) These states have the same total open-flavor decay widths. (3) Loop-induced valence configuration mixing vanishes provided that {\L}_i \neq \L_f or $\S_i \neq \S_f$. The charmonium system is used as a numerical case study, with the $^3\P_0$ decay model providing the valence-continuum coupling. We evaluate the mass shifts and continuum mixing numerically for all 1S, 1P and 2S charmonium valence states due to loops of D, D$^*$, D$_s$ and D$_s^*$ meson pairs. We find that the mass shifts are quite large, but are numerically similar for all the low-lying charmonium states, as suggested by the first theorem. Thus, loop mass shifts may have been "hidden" in the valence quark model by a change of parameters. The two-meson continuum components of the physical charmonium states are also found to be large, creating challenges for the interpretation of the constituent quark model.Comment: 10 pages, 1 ps figure. Typos corrected; discussion of psi-eta_c mass splitting added, published versio

Bi-layer splitting in overdoped high TcT_{c} cuprates

Recent angle-resolved photoemission data for overdoped Bi2212 are explained. Of the peak-dip-hump structure, the peak corresponds the $\vec q =0$ component of a hole condensate which appears at $T_c$. The fluctuating part of this same condensate produces the hump. The bilayer splitting is large enough to produce a bonding hole and an electron antibonding quasiparticle Fermi surface. Smaller bilayer splittings observed in some experiments reflect the interaction of the peak structure with quasiparticle states near, but not at, the Fermi surface.Comment: 4 pages with 2 figures - published versio

Health outcomes of children born to mothers with chronic kidney disease: a pilot study

This study aimed to study the health of children born to mothers with chronic kidney disease. Twenty-four children born to mothers with chronic kidney disease were compared with 39 matched control children born to healthy mothers without kidney disease. The well-being of each child was individually assessed in terms of physical health, neurodevelopment and psychological health. Families participating with renal disease were more likely to be from lower socio-economic backgrounds. Significantly fewer vaginal deliveries were reported for mothers with renal disease and their infants were more likely to experience neonatal morbidity. Study and control children were comparable for growth parameters and neurodevelopment as assessed by the Griffiths scales. There was no evidence of more stress amongst mothers with renal disease or of impaired bonding between mother and child when compared to controls. However, there was evidence of greater externalizing behavioral problems in the group of children born to mothers with renal disease. Engaging families in such studies is challenging. Nonetheless, families who participated appreciated being asked. The children were apparently healthy but there was evidence in this small study of significant antenatal and perinatal morbidity compared to controls. Future larger multi-center studies are required to confirm these early findings

Ferromagnetic resonance with a magnetic Josephson junction

We show experimentally and theoretically that there is a coupling via the Aharonov-Bohm phase between the order parameter of a ferromagnet and a singlet, s-wave, Josephson supercurrent. We have investigated the possibility of measuring the dispersion of such spin waves by varying the magnetic field applied in the plane of the junction and demonstrated the electromagnetic nature of the coupling by the observation of magnetic resonance side-bands to microwave induced Shapiro steps.Comment: 6 pages, 5 figure

On the Symmetries of the Edgar-Ludwig Metric

The conformal Killing equations for the most general (non-plane wave) conformally flat pure radiation field are solved to find the conformal Killing vectors. As expected fifteen independent conformal Killing vectors exist, but in general the metric admits no Killing or homothetic vectors. However for certain special cases a one-dimensional group of homotheties or motions may exist and in one very special case, overlooked by previous investigators, a two-dimensional homethety group exists. No higher dimensional groups of motions or homotheties are admitted by these metrics.Comment: Plain TeX, 7 pages, No figure

Ages for illustrative field stars using gyrochronology: viability, limitations and errors

We here develop an improved way of using a rotating star as a clock, set it using the Sun, and demonstrate that it keeps time well. This technique, called gyrochronology, permits the derivation of ages for solar- and late-type main sequence stars using only their rotation periods and colors. The technique is clarified and developed here, and used to derive ages for illustrative groups of nearby, late-type field stars with measured rotation periods. We first demonstrate the reality of the interface sequence, the unifying feature of the rotational observations of cluster and field stars that makes the technique possible, and extends it beyond the proposal of Skumanich by specifying the mass dependence of rotation for these stars. We delineate which stars it cannot currently be used on. We then calibrate the age dependence using the Sun. The errors are propagated to understand their dependence on color and period. Representative age errors associated with the technique are estimated at ~15% (plus possible systematic errors) for late-F, G, K, & early-M stars. Ages derived via gyrochronology for the Mt. Wilson stars are shown to be in good agreement with chromospheric ages for all but the bluest stars, and probably superior. Gyro ages are then calculated for each of the active main sequence field stars studied by Strassmeier and collaborators where other ages are not available. These are shown to be mostly younger than 1Gyr, with a median age of 365Myr. The sample of single, late-type main sequence field stars assembled by Pizzolato and collaborators is then assessed, and shown to have gyro ages ranging from under 100Myr to several Gyr, and a median age of 1.2Gyr. Finally, we demonstrate that the individual components of the three wide binaries XiBooAB, 61CygAB, & AlphaCenAB yield substantially the same gyro ages.Comment: 58 pages, 18 color figures, accepted for publication in The Astrophysical Journal; Age uncertainties slightly modified upon correcting an algebraic error in Section