Late movement of basin-edge lobate scarps on Mercury

Basin-edge lobate scarps are a sub-type of tectonic shortening structure on the surface of Mercury that have formed at the edge of volcanic units that fill or partly fill impact basins. We have performed a global survey of these features and find that they are widespread in basins across the planet. We obtained model ages from crater size–frequency distribution analysis for a subset of our surveyed basins, for both the smooth plains infill and for the last resolvable tectonic activity on the associated basin-edge scarps. Our results indicate that some of these lobate scarps were still accumulating strain in the late Mansurian (approximately 1 Ga). From a photogeological assessment, we find that the orientations of these basin-edge lobate scarps are similar to those reported for the global population of lobate scarps in earlier studies, appearing to align ∼north–south at low latitudes and ∼east–west at higher latitudes. However, reassessing these landforms’ orientation with artificially illuminated topographic data does not allow us to rule out the effect of illumination bias. We propose that these landforms, the result of crustal shortening in response to global contraction, formed along the interface between the basin floor and the smooth plains unit, which acted as a mechanical discontinuity along which shortening strains were concentrated

Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. II. Optical and Near Infrared Star Formation History of the Starburst Cluster NGC 2070 in 30 Doradus

We present a study of the recent star formation of 30 Doradus in the Large Magellanic Cloud (LMC) using the panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). In this paper we focus on the stars within 20 pc of the center of the massive ionizing cluster of 30 Doradus, NGC 2070. We recovered the star formation history by comparing deep optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PARSEC models, which include all stellar phases from pre-main sequence to post- main sequence. For the first time in this region we are able to measure the star formation using intermediate and low mass stars simultaneously. Our results suggest that NGC2070 experienced a prolonged activity. In particular, we find that the star formation in the region: i) exceeded the average LMC rate ~ 20 Myr ago; ii) accelerated dramatically ~ 7 Myr ago; and iii) reached a peak value 1-3 Myr ago. We did not find significant deviations from a Kroupa initial mass function down to 0.5 Msun. The average internal reddening E(B-V) is found to be between 0.3 and 0.4 mag.Comment: Submitted to Ap

Insights on the paleoepidemiology of ancient tuberculosis from the structural analysis of postcranial remains from the Ligurian Neolithic (northwestern Italy)

The aim of this research is to gain insights on the progression timeline of osteoarticular tuberculosis (TB) in people from the Neolithic period by using skeletal traits that are independent of the bony lesions. The body proportions and postcranial mechanical strength of bones from two individuals from Liguria in northwestern Italy (Arene Candide 5, adolescent, and Arma dell’Aquila 1, adult), were compared with the rest ofthe Ligurian Neolithic skeletal series (45 individuals). If TB led to wasting ofthe skeleton and lack of normal function that endured for years, as often happens today, a clear signature of postcranial gracility and disruption of development should be apparent. Conversely, rapid progress of the disease would leave little systemic macroscopic change in the skeleton, except for the bony lesions directly caused by the TB pathogen, suggesting a different level of bacterial virulence in the past. The extreme biomechanical gracility observed in the lower limb of Arene Candide 5 suggests a period of compromised diaphyseal periosteal apposition during ontogeny due to metabolic disturbances likely linked to TB. Results suggest that, in Neolithic Liguria, TB in humans saw a slow, chronic progression, which is characteristic of diseases with long histories of host-pathogen co-evolution

Contribution of White Dwarfs to Cluster Masses

I present a literature search through 31 July 1997 of white dwarfs (WDs) in open and globular clusters. There are 36 single WDs and 5 WDs in binaries known among 13 open clusters, and 340 single WDs and 11 WDs in binaries known among 11 globular clusters. From these data I have calculated WD mass fractions for four open clusters (the Pleiades, NGC 2168, NGC 3532, and the Hyades) and one globular cluster (NGC 6121). I develop a simple model of cluster evolution that incorporates stellar evolution but not dynamical evolution to interpret the WD mass fractions. I augment the results of my simple model with N-body simulations incorporating stellar evolution (Terlevich 1987; de la Feunte Marcos 1996; Vesperini & Heggie 1997). I find that even though these clusters undergo moderate to strong kinematical evolution the WD mass fraction is relatively insensitive to kinematical evolution. By comparing the cluster mass functions to that of the Galactic disk, and incorporating plausibility arguments for the mass function of the Galactic halo, I estimate the WD mass fraction in these two populations. I assume the Galactic disk is ~10 Gyrs old (Winget et al. 1987; Liebert, Dahn, & Monet 1988; Oswalt et al. 1996) and that the Galactic halo is ~12 Gyrs old (Reid 1997b; Gratton et al. 1997; Chaboyer et al. 1998), although the WD mass fraction is insensitive to age in this range. I find that the Galactic halo should contain 8 to 9% (alpha = -2.35) or perhaps as much as 15 to 17% (alpha = -2.0) of its stellar mass in the form of WDs. The Galactic disk WD mass fraction should be 6 to 7% (alpha = -2.35), consistent with the empirical estimates of 3 to 7% (Liebert, Dahn, & Monet 1988; Oswalt et al. 1996). (abridged)Comment: 20 pages, uuencoded gunzip'ed latex + 3 postscrip figures, to be published in AJ, April, 199

The Evolution of Globular Clusters in the Galaxy

We investigate the evolution of globular clusters using N-body calculations and anisotropic Fokker-Planck (FP) calculations. The models include a mass spectrum, mass loss due to stellar evolution, and the tidal field of the parent galaxy. Recent N-body calculations have revealed a serious discrepancy between the results of N-body calculations and isotropic FP calculations. The main reason for the discrepancy is an oversimplified treatment of the tidal field employed in the isotropic FP models. In this paper we perform a series of calculations with anisotropic FP models with a better treatment of the tidal boundary and compare these with N-body calculations. The new tidal boundary condition in our FP model includes one free parameter. We find that a single value of this parameter gives satisfactory agreement between the N-body and FP models over a wide range of initial conditions. Using the improved FP model, we carry out an extensive survey of the evolution of globular clusters over a wide range of initial conditions varying the slope of the mass function, the central concentration, and the relaxation time. The evolution of clusters is followed up to the moment of core collapse or the disruption of the clusters in the tidal field of the parent galaxy. In general, our model clusters, calculated with the anisotropic FP model with the improved treatment for the tidal boundary, live longer than isotropic models. The difference in the lifetime between the isotropic and anisotropic models is particularly large when the effect of mass loss via stellar evolution is rather significant. On the other hand the difference is small for relaxation- dominated clusters which initially have steep mass functions and high central concentrations.Comment: 36 pages, 11 figures, LaTeX; added figures and tables; accepted by Ap

Local Simulation Algorithms for Coulomb Interaction

Long ranged electrostatic interactions are time consuming to calculate in molecular dynamics and Monte-Carlo simulations. We introduce an algorithmic framework for simulating charged particles which modifies the dynamics so as to allow equilibration using a local Hamiltonian. The method introduces an auxiliary field with constrained dynamics so that the equilibrium distribution is determined by the Coulomb interaction. We demonstrate the efficiency of the method by simulating a simple, charged lattice gas.Comment: Last figure changed to improve demonstration of numerical efficienc

Reservas de amido em sarmentos de videira 'Isabel precoce' submetida a diferentes épocas de poda e duas safras no ciclo.

Na região sul do Brasil, onde o clima é temperado, tradicionalmente colhe-se apenas uma safra/ciclo por ano. Alguns locais, como na Depressão Central do RS estão adotando manejo de dupla poda a fim de obter duas safras e oferecendo uma maior viabilidade financeira para o produtor que além de obter uma segunda safra, poderá ofertar em um período de baixa oferta de uva no mercado, recebendo mais pela produção. O objetivo deste trabalho foi avaliar as reservas de amido em sarmentos que se desenvolveram a partir de distintas datas de poda e em videiras com ou sem a prática de dupla colheita. O vinhedo de Isabel Precoce onde foi realizado o experimento está localizado no município de Eldorado do Sul-RS. A quantificação do amido foi por processo enzimático com posterior leitura em espectrofotômetro. Concluiu-se que a precocidade na poda de inverno auxilia no acúmulo de reservas de amido em sarmentos da videira por aumentar o ciclo vegetativo fotossinteticamente ativo das plantas e a dupla poda/colheita reduz os conteúdos de amido presentes no sarmento, principalmente no segundo período de crescimento, podendo debilitar a planta caso esta prática seja associada a podas tardias e realizada em anos sucessivos

In situ observations on the dentition and oral cavity of the Neanderthal skeleton from Altamura (Italy)

The Neanderthal specimen from Lamalunga Cave, near Altamura (Apulia, Italy), was discovered during a speleological survey in 1993. The specimen is one of the most complete fossil hominins in Europe and its state of preservation is exceptional, although it is stuck in calcareous concretions and the bones are mostly covered by calcite depositions. Nevertheless, it is possible to carry out some observations on craniodental features that have not previously been described. In this work, we present an account of the oral cavity, made possible by the use of a videoscope, which allowed us to reach some hidden parts of the mandible and palate. This is the first detailed overview of the teeth and maxillary bones of the Neanderthal skeleton from Altamura. The dentition is almost complete. However, two teeth (upper right P3 and upper left M1) were lost ante mortem and four teeth (lower right I1 and P3 and lower left I1 and I2) were lost most probably post mortem. Dental wear is marked. The erupted M3s and the inversion of the compensating curve of Wilson in the M1s and M2s but not in the M3s suggest that the individual is fully adult, but not old. Although most of the teeth have their roots exposed for several millimeters, the periodontal bone appears to be in good condition overall, except in correspondence of the two ante-mortem tooth losses. X-rays of the anterior teeth show a periapical lesion, probably linked to the advanced dental wear. We also observed a weak expression of taurodontism in the posterior dentition and the presence of a retromolar space, features consistent with an attribution to the Neanderthal hypodigm; this attribution is also supported by aspects of the cranial morphology, the morphometric analysis of the scapula and preliminary mtDNA data. There is also a well-developed palatine torus, to the best of our knowledge a feature not previously described in Neanderthals

WIYN Open Cluster Study 1: Deep Photometry of NGC 188

We have employed precise V and I photometry of NGC 188 at WIYN to explore the cluster luminosity function (LF) and study the cluster white dwarfs (WDs). Our photometry is offset by V = 0.052 (fainter) from Sandage (1962) and Eggen & Sandage (1969). All published photometry for the past three decades have been based on these two calibrations, which are in error by 0.05 +- 0.01. We employ the Pinsonneault etal (1998) fiducial main sequence to derive a cluster distance modulus of 11.43 +- 0.08. We report observations that are >= 50% complete to V = 24.6 and find that the cluster central-field LF peaks at M_I ~ 3 to 4. This is unlike the solar neighborhood LF and unlike the LFs of dynamically unevolved portions of open and globular clusters, which rise continuously until M_I ~ 9.5. Although we find that >= 50% of the unresolved cluster objects are multiple systems, their presence cannot account for the shape of the NGC 188 LF. For theoretical reasons (Terlevich 1987; Vesperini & Heggie 1997) having to do with the survivability of NGC 188 we believe the cluster is highly dynamically evolved and that the missing low luminosity stars are either in the cluster outskirts or have left the cluster altogether. We identify nine candidate WDs, of which we expect three to six are bona fide cluster WDs. The luminosities of the faintest likely WD indicates an age (Bergeron, Wesemael, & Beauchamp 1995) of 1.14 +- 0.09 Gyrs. This is a lower limit to the cluster age and observations probing to V = 27 or 28 will be necessary to find the faintest cluster WDs and independently determine the cluster age. While our age limit is not surprising for this ~6 Gyr old cluster, our result demonstrates the value of the WD age technique with its very low internal errors. (abridged)Comment: 26 pages, uuencoded gunzip'ed latex + 16 postscrip figures, to be published in A