Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer

We present a method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer. The purpose of GRANIT is to improve the accuracy of measurement of the quantum states parameters by several orders of magnitude, taking advantage of long storage of Ultracold neutrons at specula trajectories. The transitions could be excited using a periodic spatial variation of a magnetic field gradient. If the frequency of such a perturbation (in the frame of a moving neutron) coincides with a resonance frequency defined by the energy difference of two quantum states, the transition probability will sharply increase. The GRANIT experiment is motivated by searches for short-range interactions (in particular spin-dependent interactions), by studying the interaction of a quantum system with a gravitational field, by searches for extensions of the Standard model, by the unique possibility to check the equivalence principle for an object in a quantum state and by studying various quantum optics phenomena

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

Visual demonstration of growth hormone receptors on human growth plate chondrocytes

The sites of action of GH in the human infant remain unclear; recent evidence in animals suggests direct actions on growth plate and other tissues. We have used a monoclonal antibody recognizing the human GH receptor to visually identify and localize GH receptors in the human infant growth plate. Sternochondral cartilage was obtained at postmortem from infants dying of sudden infant death (n = 20), and either decalcified, fixed, and cut into longitudinal sections or digested with collagenase for monolayer culture of chondrocytes. Sections of cultured chondrocytes were stained immunocytochemically with a monoclonal antibody recognizing human GH receptor (MAb 263), using an avidin-biotin system. Sternochondral cartilage was also obtained at operation from adolescents undergoing sternochondroplasty. In infant tissue, GH receptor was identified in sections in chondrocytes of the proliferative and hypertrophic layers, in perichondrium, in osteocytes in new bone, and in hemopoietic precursor cells in marrow. Cultured chondrocytes showed heterogeneous staining for GH receptor. With prolonged culture from 5–8 days, the pattern of staining changed from individual cells to groups of cells. [125I]Human (h)GH showed specific binding to chondrocyte monolayer (0.6 ± 0.3%), confirmed visually on emulsion autoradiography. In support of specificity of MAb263, it was able to displace [125I]hGH from monolayers by 35%. Adolescent cultured chondrocytes failed to demonstrate specific binding of [125I]hGH. We conclude that GH receptors are widely distributed in a range of mesenchyme cells in the human infant growth plate, including bone and hemopoietic precursors. The expression of these receptors appears to be maturation dependent in both intact tissue and culture, while they may no longer be expressed after the peak growth phase of puberty

In vivo fatty acid analysis in humans and animals using carbon-13 nuclear magnetic resonance spectroscopy

The signals observed in in vivo carbon-13 nuclear magnetic resonance (13C NMR) spectra are from ‘mobile’ molecules, i.e. those with relatively unrestricted motion. In practice, this eliminates virtually all 13C present in proteins and other macromolecules. Because of sensitivity limitations, mobile molecules present at low concentrations are also not detectable. As a result, 13C NMR mainly detects ‘mobile’ fatty acids, i.e. free fatty acids and triglycerides. Fatty acids in phospholipids are considered to be largely ’invisible’by 13C NMR. For measurements done in vivo, the main signal observed is from adipose tissue triglycerides because the trunk and limbs are surrounded by varying thicknesses of adipose tissue