Mercury's Weather-Beaten Surface: An Examination of the Relevant Processes Through Comparisons and Contrasts with the Moon and Asteroids

We examine global color properties of Mercury and their correlations to the predicted trends due to particle bombardment and thermal processing. Color ratio and spectral slope analyzes are interpreted relative to lunar and asteroid studies

Young people's perceptions of youth-oriented health services in urban Soweto, South Africa: a qualitative investigation.

BACKGROUND: In 2006, the South African Department of Health adopted and scaled-up loveLife's Youth Friendly Services (YFS) initiative to a national policy to improve youth utilization of health programmes by strengthening community sensitisation and counselling services. As these services roll-out, alternative services to target young people are also becoming more popular. Success of any of these services, however, is dependent upon young people's perceptions of these health services as a whole. This paper aims to examine the knowledge and perceptions of current health services oriented towards young people and examine potential alternative approaches to health service delivery. METHODS: The study was conducted in urban Soweto, South Africa. Twenty-five in-depth interviews were conducted between May-July 2012. Twenty-three of these were analysed according to modified grounded theory. RESULTS: Knowledge of YFS was very low with no thorough knowledge of the programme's purpose or activities. In general, young people were dissatisfied with the current health services in Soweto citing a lack of resources, long waiting times, and poor quality of care heightened by an underlying lack of choice and perceived inequity. When compared to alternative models of service delivery, no particular model was preferred over another. CONCLUSIONS: Greater knowledge of whether and to what extent local clinics in Soweto are implementing YFS standards is needed. If implemented, improved outreach and advertisement is suggested. In-service training of nurses should be prioritized with a focus on sensitivity and equitable treatment to all

Interpreting ~1 Hz magnetic compressional waves in Mercury's inner magnetosphere in terms of propagating ion‐Bernstein waves

We show that ~1 Hz magnetic compressional waves observed in Mercury's inner magnetosphere could be interpreted as ion‐Bernstein waves in a moderate proton beta ~0.1 plasma. An observation of a proton distribution with a large planetary loss cone is presented, and we show that this type of distribution is highly unstable to the generation of ion‐Bernstein waves with low magnetic compression. Ray tracing shows that as these waves propagate back and forth about the magnetic equator; they cycle between a state of low and high magnetic compression. The group velocity decreases during the high‐compression state leading to a pileup of compressional wave energy, which could explain the observed dominance of the highly compressional waves. This bimodal nature is due to the complexity of the index of refraction surface in a warm plasma whose upper branch has high growth rate with low compression, and its lower branch has low growth/damping rate with strong compression. Two different cycles are found: one where the compression maximum occurs at the magnetic equator and one where the compression maximum straddles the magnetic equator. The later cycle could explain observations where the maximum in compression straddles the equator. Ray tracing shows that this mode is confined within ±12° magnetic latitude which can account for the bulk of the observations. We show that the Doppler shift can account for the difference between the observed and model wave frequency, if the wave vector direction is in opposition to the plasma flow direction. We note that the Wentzel‐Kramers‐Brillouin approximation breaks down during the pileup of compressional energy and that a study involving full wave solutions is required.Key PointsThe ion‐Bernstein (IB) mode is highly unstable to proton loss cones at MercuryThe IB mode can become highly compressional as it propagatesRay tracing of the IB mode predicts compression peaking the off equatorPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112180/1/jgra51808.pd

The crystal structures of two isomers of 5-(phenyl- isothiazolyl)-1,3,4-oxathiazol-2-one

Published VersionThe syntheses and crystal structures of two isomers of phenyl iso­thia­zolyl oxa­thia­zolone, C11H6N2O2S2, are described [systematic names: 5-(3-phenyl­iso­thia­zol-5-yl)-1,3,4-oxa­thia­zol-2-one, (I), and 5-(3-phenyl­iso­thia­zol-4-yl)-1,3,4-oxa­thia­zol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) mol­ecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetra­mers linked by strong S...N [3.072 (2) Å] and S...O contacts [3.089 (1) Å]. The tetra­mers are π-stacked parallel to the a-axis direction. The single mol­ecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central iso­thia­zolyl ring and the pendant oxa­thia­zolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic iso­thia­zoloyl ring and the non-aromatic oxa­thia­zolone heterocycle. In the crystal of isomer (II), the strong S...O [3.020 (1) Å] and S...C contacts [3.299 (2) Å] and the non-planar structure of the mol­ecule lead to a form of π-stacking not observed in isomer (I) or other oxathiazolone derivatives

Crystal structure determination as part of an ongoing undergraduate organic laboratory project: 5-[(<i>E</i>)-styryl]-1,3,4-oxathiazol-2-one

Published versionThe title compound, C10H7NO2S, provides the first structure of an &alpha;-alkenyl oxathiazolone ring. The phenyl ring and the oxa&shy;thia&shy;zolone groups make dihedral angles of 0.3 (3) and &minus;2.8 (3)&deg;, respectively, with the plane of the central alkene group; the dihedral angle between the rings is 2.68 (8)&deg;. A careful consideration of bond lengths provides insight into the electronic structure and reactivity of the title compound. In the crystal, extended &Pi;-stacking is observed parallel to the a-axis direction, consisting of cofacial head-to-tail dimeric units [centroid&ndash;centroid distance of 3.6191 (11) &Aring;]. These dimeric units are separated by a slightly longer centroid&ndash;centroid distance of 3.8383 (12) &Aring;, generating infinite stacks of mol&shy;ecules

Messenger Observations of Mercury's Bow Shock and Magnetopause

The MESSENGER spacecraft made the first of three flybys of Mercury on January 14.2008 (1). New observations of solar wind interaction with Mercury were made with MESSENGER'S Magnetometer (MAG) (2.3) and Energetic Particle and Plasma Spectrometer (EPPS) - composed of the Energetic Particle Spectrometer (EPS) and Fast Imaging Plasma Spectrometer (FIPS) (3,4). These MESSENGER observations show that Mercury's magnetosphere has a large-scale structure that is distinctly Earth-like, but it is immersed in a comet-like cloud of planetary ions [5]. Fig. 1 provides a schematic view of the coupled solar wind - magnetosphere - neutral atmosphere - solid planet system at Mercury

MESSENGER Detection of Electron-Induced X-Ray Fluorescence from Mercury's surface

The X-Ray Spectrometer (XRS) on the MESSENGER spacecraft measures elemental abundances on the surface of Mercury by detecting fluorescent X-ray emissions induced on the planet's surface by the incident solar X-ray flux. The XRS began orbital observations on 23 March 2011 and has observed X-ray fluorescence (XRF) from the surface of the planet whenever a sunlit portion of Mercury has been within the XRS field of view. Solar flares are generally required to provide sufficient signal to detect elements that fluoresce at energies above ∼2 keV, but XRF up to the calcium line (3.69 keV) has been detected from Mercury's surface at times when the XRS field of view included only unlit portions of the planet. Many such events have been detected and are identified as electron-induced X-ray emission produced by the interaction of ∼1-10 keV electrons with Mercury's surface. Electrons in this energy range were detected by the XRS during the three Mercury flybys and have also been observed regularly in orbit about Mercury. Knowledge of the energy spectrum of the electrons precipitating at the planet's surface makes it possible to infer surface composition from the measured fluorescent spectra, providing additional measurement opportunities for the XRS. Abundance results for Mg, Al, and Si are in good agreement with those derived from solar-induced XRF data, providing independent validation of the analysis methodologies. Derived S and Ca abundances are somewhat higher than derived from the solar-induced fluorescence data, possibly reflecting incomplete knowledge of the energy spectra of electrons impacting the planet

ARTEMIS Science Objectives

NASA's two spacecraft ARTEMIS mission will address both heliospheric and planetary research questions, first while in orbit about the Earth with the Moon and subsequently while in orbit about the Moon. Heliospheric topics include the structure of the Earth's magnetotail; reconnection, particle acceleration, and turbulence in the Earth's magnetosphere, at the bow shock, and in the solar wind; and the formation and structure of the lunar wake. Planetary topics include the lunar exosphere and its relationship to the composition of the lunar surface, the effects of electric fields on dust in the exosphere, internal structure of the Moon, and the lunar crustal magnetic field. This paper describes the expected contributions of ARTEMIS to these baseline scientific objectives

Mycorrhizas and biomass crops: opportunities for future sustainable development

Central to soil health and plant productivity in natural ecosystems are in situ soil microbial communities, of which mycorrhizal fungi are an integral component, regulating nutrient transfer between plants and the surrounding soil via extensive mycelial networks. Such networks are supported by plant-derived carbon and are likely to be enhanced under coppiced biomass plantations, a forestry practice that has been highlighted recently as a viable means of providing an alternative source of energy to fossil fuels, with potentially favourable consequences for carbon mitigation. Here, we explore ways in which biomass forestry, in conjunction with mycorrhizal fungi, can offer a more holistic approach to addressing several topical environmental issues, including ‘carbon-neutral’ energy, ecologically sustainable land management and CO2 sequestration

Work functions, ionization potentials, and in-between: Scaling relations based on the image charge model

We revisit a model in which the ionization energy of a metal particle is associated with the work done by the image charge force in moving the electron from infinity to a small cut-off distance just outside the surface. We show that this model can be compactly, and productively, employed to study the size dependence of electron removal energies over the range encompassing bulk surfaces, finite clusters, and individual atoms. It accounts in a straightforward manner for the empirically known correlation between the atomic ionization potential (IP) and the metal work function (WF), IP/WF$\sim$2. We formulate simple expressions for the model parameters, requiring only a single property (the atomic polarizability or the nearest neighbor distance) as input. Without any additional adjustable parameters, the model yields both the IP and the WF within $\sim$10% for all metallic elements, as well as matches the size evolution of the ionization potentials of finite metal clusters for a large fraction of the experimental data. The parametrization takes advantage of a remarkably constant numerical correlation between the nearest-neighbor distance in a crystal, the cube root of the atomic polarizability, and the image force cutoff length. The paper also includes an analytical derivation of the relation of the outer radius of a cluster of close-packed spheres to its geometric structure.Comment: Original submission: 8 pages with 7 figures incorporated in the text. Revised submission (added one more paragraph about alloy work functions): 18 double spaced pages + 8 separate figures. Accepted for publication in PR