Asymmetric periodic orbits in the photogravitational Copenhagen problem

AbstractIn this paper we study the Ox-asymmetric solutions of the planar photogravitational restricted three-body problem in the case of primaries with equal masses and equal values of the radiation pressure parameters. In particular, we are concerned with the families of asymmetric orbits which bifurcate from the well known families a, b, and c. Their evolution is examined via the numerical construction of series of the critical bifurcation points of a, b, and c with respect to the variation of the common radiation parameter q. We also present some illustrative cases of these families for several values of this parameter. In order to avoid the singularity due to binary collisions between the third body and one of the primaries, the equations of motion of the problem are regularized by using the Levi-Civita transformations

The scaling of X-ray variability with luminosity in Ultra-luminous X-ray sources

We investigated the relationship between the X-ray variability amplitude and X-ray luminosity for a sample of 14 bright Ultra-luminous X-ray sources (ULXs) with XMM-Newton/EPIC data, and compare it with the well established similar relationship for Active Galactic Nuclei (AGN). We computed the normalised excess variance in the 2-10 keV light curves of these objects and their 2-10 keV band intrinsic luminosity. We also determined model "variability-luminosity" relationships for AGN, under several assumptions regarding their power-spectral shape. We compared these model predictions at low luminosities with the ULX data. The variability amplitude of the ULXs is significantly smaller than that expected from a simple extrapolation of the AGN "variability-luminosity" relationship at low luminosities. We also find evidence for an anti-correlation between the variability amplitude and L(2-10 keV) for ULXs. The shape of this relationship is consistent with the AGN data but only if the ULXs data are shifted by four orders of magnitudes in luminosity. Most (but not all) of the ULXs could be "scaled-down" version of AGN if we assume that: i) their black hole mass and accretion rate are of the order of ~(2.5-30)x 10E+03 Msolar and ~ 1-80 % of the Eddington limit, and ii) their Power Spectral Density has a doubly broken power-law shape. This PDS shape and accretion rate is consistent with Galactic black hole systems operating in their so-called "low-hard" and "very-high" states.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in A&

Linear Stability of Equilibrium Points in the Generalized Photogravitational Chermnykh's Problem

The equilibrium points and their linear stability has been discussed in the generalized photogravitational Chermnykh's problem. The bigger primary is being considered as a source of radiation and small primary as an oblate spheroid. The effect of radiation pressure has been discussed numerically. The collinear points are linearly unstable and triangular points are stable in the sense of Lyapunov stability provided $\mu< \mu_{Routh}=0.0385201$. The effect of gravitational potential from the belt is also examined. The mathematical properties of this system are different from the classical restricted three body problem

The Elastic Moduli of Thick Composites

Thick composites are in use in critical applications and are proposed for still others. It is important to measure the elastic moduli of thick composites for two reasons: (1) for design data on stiffness, and (2) for prediction of feasible wave paths for ultrasonic waves for NDE. Previously only relatively thin composites of relatively simple symmetries have been measured for their elastic moduli. Now, it is becoming necessary to measure thick composites of feasible engineering lay-ups. These generally provide the complexity of orthorhombic symmetry locally in a specimen combined with curvature in the gross structure. In this work, specimens cut from thick structures will be treated in the same way as crystals to measure the elastic moduli by means of ultrasonic wave velocities. Results on one structure will be presented. Difficulties will be analyzed

Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks

(Abridged) Many classes of active galactic nuclei (AGN) have been defined entirely throughout optical wavelengths while the X-ray spectra have been very useful to investigate their inner regions. However, optical and X-ray results show many discrepancies that have not been fully understood yet. The aim of this paper is to study the "synapses" between the X-ray and optical classifications. For the first time, the new EFLUXER task allowed us to analyse broad band X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB), transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2). The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components. We suggest that this is related to a large degree of obscuration at X-rays. The S1, S1.8, S2, L1.8, L2/T2/SB-AGN (SB with indications of AGN), and SB classes have similar average X-ray spectra within each class, but these average spectra can be distinguished from class to class. The S2 (L1.8) class is linked to the S1.8 (S1) class with larger SB-like component than the S1.8 (S1) class. The L2, T2, and SB-AGN classes conform a class in the X-rays similar to the S2 class albeit with larger fractions of SB-like component. This SB-like component is the contribution of the star-formation in the host galaxy, which is large when the AGN is weak. An AGN-like component seems to be present in the vast majority of the ELN, attending to the non-negligible fraction of S1-like or S1.8-like component. This trained ANN could be used to infer optical properties from X-ray spectra in surveys like eRosita.Comment: 15 pages, 7 figures, accepted for publication in A&A. Appendix B only in the full version of the paper here: https://dl.dropboxusercontent.com/u/3484086/AGNSynapsis_OGM_online.pd

Spin-valley phase diagram of the two-dimensional metal-insulator transition

Using symmetry breaking strain to tune the valley occupation of a two-dimensional (2D) electron system in an AlAs quantum well, together with an applied in-plane magnetic field to tune the spin polarization, we independently control the system's valley and spin degrees of freedom and map out a spin-valley phase diagram for the 2D metal-insulator transition. The insulating phase occurs in the quadrant where the system is both spin- and valley-polarized. This observation establishes the equivalent roles of spin and valley degrees of freedom in the 2D metal-insulator transition.Comment: 4 pages, 2 figure

Highly anisotropic g-factor of two-dimensional hole systems

Coupling the spin degree of freedom to the anisotropic orbital motion of two-dimensional (2D) hole systems gives rise to a highly anisotropic Zeeman splitting with respect to different orientations of an in-plane magnetic field B relative to the crystal axes. This mechanism has no analogue in the bulk band structure. We obtain good, qualitative agreement between theory and experimental data, taken in GaAs 2D hole systems grown on (113) substrates, showing the anisotropic depopulation of the upper spin subband as a function of in-plane B.Comment: 4 pages, 3 figure

The Benefit of Menopausal Hormone Therapy on Bone Density and Microarchitecture Persists After its Withdrawal.

Menopausal hormone therapy (MHT) favorably affects bone mineral density (BMD). Whether MHT also affects bone microarchitecture, as assessed by trabecular bone score (TBS), has never been evaluated. Our objective was to assess the effect of MHT on TBS and BMD before and after its withdrawal. This was a cross-sectional study. This study included the general community. Data were collected from the OsteoLaus cohort (1500 women aged 50-80 years). After exclusion of women with bone-modulating treatments, 1279 women were categorized according to MHT status into current (CU), past (PU), and never (NU) users. Spine TBS and BMD at lumbar spine, femoral neck, and total hip were assessed by dual X-ray absorptiometry. Age- and body mass index-adjusted analysis showed higher TBS values in CU vs PU or NU (1.31 ± 0.01, 1.29 ± 0.01, and 1.27 ± 0.01, respectively; P &lt; .001). All BMD values were significantly higher in CU vs PU or NU. Compared to NU, PU exhibited higher lumbar spine (0.94 ± 0.01 vs 0.91 ± 0.01 g/cm(2); P = .017) and total hip (0.86 ± 0.01 vs 0.84 ± 0.01 g/cm(2); P = .026) BMD and a trend for higher TBS (P = .066). The 10-year loss of TBS and BMD at lumbar spine and total hip was significantly lower for both CU and PU vs NU. MHT duration had no effect on bone parameters. In PU, the residual effect on TBS and BMD was significantly more prominent in early discontinuers (&lt;2 years). MHT is associated with bone microarchitecture preservation, as assessed by TBS. The effect of MHT on TBS and BMD persists at least 2 years after withdrawal

The Effect of Sleep Quality and Being Physically Active on Developing Mental Toughness

Mental toughness (MT) has been increasingly associated with successful performance in several stressful and competitive environments (e.g. the military, business, academics, medicine, sports). Being physically active (PA) may compromise sleep quality (SQ). Research has reported conflicting associations regarding PA and MT. Regarding SQ and MT, a bidirectional association has been reported. However, research has not yet focused on the combined effects of PA and SQ on MT. PURPOSE: To characterize the association and the effects of PA and SQ on MT. The authors hypothesized that: (a) PA and SQ are negatively associated; (b) PA and MT are positively associated; (c) SQ and MT are negatively associated; and (d) the interaction effect of PA and SQ on MT will be buffering. METHODS: Sixty-two participants (age 25.4 6.0 SD) completed inventories related to SQ (Pittsburgh Sleep Quality Index) and MT (Mental Toughness Index). PA data were collected according to American College of Sports Medicine guidelines. Main and interaction effects of the responses were analyzed using factorial ANOVA. Significance was set at p \u3c 0.05. All analyses were performed using SPSS. RESULTS: PA was positively correlated with SQ (r = .009, p =.473) and with MT (r = .246, p = .027). SQ was negatively correlated with MT (r = -.470, p = .000). PA (F1,58 = 10.939, p = .002, η2 = .159) and QS (F1,58 = 23.051, p = .000, η2 = .284) had a main effect on MT. The interaction of PA and QS had a buffering moderating effect on MT (F1,58 = 12.394, p = .001, η2 = .176). CONCLUSION: Evidence was found for all but the first hypothesis. PA-participants tending to be mentally tougher than the non-PA ones. Poor sleepers, on average, were mentally tougher than the good sleepers. The buffering effect indicates that the non-PA individuals with poor quality of sleep are the mentally toughest ones, followed by PA individuals with poor quality of sleep. Non-PA individuals with good quality of sleep present the lowest MT levels. In regards to developing mental toughness the authors suggest that: a) PA should be prescribed to good quality of sleepers and b) in poor quality sleepers focus should be placed on sleep before PA. Such findings may be useful to exercise and health-related practitioners when prescribing PA in a wide variety of individuals that report sleep quality issues in relation to MT capacities