Chaos motion in robot manipulators

It is shown that a simple two-link planar manipulator exhibits a phenomenon of global instability in a subspace of its configuration space. A numerical example, as well as results of a graphic simulation, is given

Gender and poverty : a life cycle approach to the analysis of the differences in gender outcomes

The authors study complex interactions between gender and poverty in postwar Bosnia and Herzegovina. The goal of their analysis is to uncover how a spectrum of gender differentials at different parts of the life cycle varies across income groups. Using the data from the 2001 Bosniaand Herzegovina Living Standards Measurement Study, the authors find strong gender-poverty interaction in the patterns of labor force participation, gender gap in earnings, individuals'school finances, and school attendance. The main source of gender inequality seems to come from differences in investments in girls'and boys'educations that increase with declines in income levels. Short-term income shocks could lead to long-term increases in gender inequality in households with school age children, unless there is ready access to credit markets. The authors also find that the magnitude of the impact of economic development on gender differences in Bosnia will depend on where the growth is concentrated. If the poor capture at least some benefits of economic growth, the gender differences in household investment in human capital of their children will decline. If, on the other hand, growth is concentrated among the richest, then important gender disparities could remain pervasive.Health Monitoring&Evaluation,Economic Theory&Research,Environmental Economics&Policies,Labor Policies,Public Health Promotion,Health Monitoring&Evaluation,Inequality,Housing&Human Habitats,Economic Theory&Research,Environmental Economics&Policies

Spin Excitations in BaFe1.84Co0.16As2 Superconductor Observed by Inelastic Neutron Scattering

Superconductivity appears to compete against the spin-density-wave in Fe pnictides. However, optimally cobalt doped samples show a quasi-two-dimensional spin excitation centered at the (0.5, 0.5, L) wavevector, "the spin resonance peak", that is strongly tied to the onset of superconductivity. By inelastic neutron scattering on single crystals we show the similarities and differences of the spin excitations in BaFe1.84Co0.16As2, with respect to the spin excitations in the high-temperature superconducting cuprates. As in the cuprates the resonance occurs as an enhancement to a part of the spin excitation spectrum which extends to higher energy transfer and higher temperature. However, unlike in the cuprates, the resonance peak in this compound is asymmetric in energy.Comment: 12 pages, 6 figures; PACS # 74.70.-b, 74.20.Mn, 78.70.Nx, 74.25.Ha; corrected discussion of figures in tex

High pressure effects in fluorinated HgBa2Ca2Cu3O(8+d)

We have measured the pressure sensitivity of Tc in fluorinated HgBa2Ca2Cu3O(8+d) (Hg-1223) ceramic samples with different F contents, applying pressures up to 30 GPa. We obtained that Tc increases with increasing pressure, reaching different maximum values, depending on the F doping level, and decreases for a further increase of pressure. A new high Tc record (166 K +/- 1 K) was achieved by applying pressure (23 GPa) in a fluorinated Hg-1223 sample near the optimum doping level. Our results show that all our samples are at the optimal doping, and that fluorine incorporation decreases the crystallographic $a$-parameter concomitantly increasing the maximum attainable Tc. This effect reveals that the compression of the $a$ axes is one of the keys that controls the Tc of high temperature superconductors.Comment: 4 pages, 4 figures, submitted to Phys. Rev.

Synthesis of Single Phase Hg-1223 High Tc Superconducting Films With Multistep Electrolytic Process

We report the multistep electrolytic process for the synthesis of high Tc single phase HgBa2Ca2Cu3O8+ (Hg-1223) superconducting films. The process includes : i) deposition of BaCaCu precursor alloy, ii) oxidation of BaCaCu films, iii) electrolytic intercalation of Hg in precursor BaCaCuO films and iv) electrochemical oxidation and annealing of Hg-intercalated BaCaCuO films to convert into Hg1Ba2Ca2Cu3O8+ (Hg-1223). Films were characterized by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrolytic intercalation of Hg in BaCaCuO precursor is proved to be a novel alternative to high temperature-high pressure mercuration process. The films are single phase Hg-1223 with Tc = 121.5 K and Jc = 4.3 x 104 A/cm2.Comment: 17 Pages, 10 Figures. Submitted to Superconductor Science and Technolog

Inflammatory signaling compromises cell responses to interferon alpha.

Interferon alpha (IFNα) is widely used for treatment of melanoma and certain other malignancies. This cytokine as well as the related IFNβ exerts potent anti-tumorigenic effects; however, their efficacy in patients is often suboptimal. Here, we report that inflammatory signaling impedes the effects of IFNα/β. Melanoma cells can secrete pro-inflammatory cytokines that inhibit cellular responses to IFNα/β via activating the ligand-independent pathway for the phosphorylation and subsequent ubiquitination and accelerated degradation of the IFNAR1 chain of type I IFN receptor. Catalytic activity of the p38 protein kinase was required for IFNAR1 downregulation and inhibition of IFNα/β signaling induced by proinflammatory cytokines such as interleukin 1 (IL-1). Activation of p38 kinase inversely correlated with protein levels of IFNAR1 in clinical melanoma specimens. Inhibition of p38 kinase augmented the inhibitory effects of IFNα/β on cell viability and growth in vitro and in vivo. The roles of inflammation and p38 protein kinase in regulating cellular responses to IFNα/β in normal and tumor cells are discussed