363 research outputs found
Foundational Checklist of the Amphibians of Wise County, Virginia
The Appalachian Mountains are arguably home to the highest degree of amphibian diversity in the world, particularly caudate (salamander) biodiversity. Despite the high degree of amphibian endemism in the Appalachians, several regions remain unsurveyed for amphibian species. In addition to this knowledge gap, we are in the midst of alarming amphibian biodiversity loss. Thus, it is of the utmost importance to bridge this knowledge gap by conducting surveys before some of these amphibian species are lost. We surveyed Wise County (previously unsurveyed county in the Appalachian Mountains with no records existing in the primary literature) over two years to assess amphibian species presence. We found 23 different species of amphibians (eight species of frogs and toads; 15 species of salamanders). In addition, we report five new amphibian species occurrences previously unreported in the primary literature within Wise County. However, not all amphibian species expected to occur in Wise County were observed. The primary suspected reason for their lack of occurrence involves habitat loss and/or modification, since the region is heavily exploited for coal and lumber. Overall, our study provides invaluable data in current times of amphibian biodiversity concern as they clarify and expand our knowledge of known amphibian species within the area. Using our work as a foundation, future surveying could assess whether amphibian biodiversity of Wise County are experiencing growth, stability, or decline
Non-linear instability of Kerr-type Cauchy horizons
Using the general solution to the Einstein equations on intersecting null
surfaces developed by Hayward, we investigate the non-linear instability of the
Cauchy horizon inside a realistic black hole. Making a minimal assumption about
the free gravitational data allows us to solve the field equations along a null
surface crossing the Cauchy Horizon. As in the spherical case, the results
indicate that a diverging influx of gravitational energy, in concert with an
outflux across the CH, is responsible for the singularity. The spacetime is
asymptotically Petrov type N, the same algebraic type as a gravitational shock
wave. Implications for the continuation of spacetime through the singularity
are briefly discussed.Comment: 11 pages RevTeX, two postscript figures included using epsf.st
Повернення в Ніжин (корпус документів з епістолярію І.Г. Спаського)
Підготовка до друку та переднє слово Наталії ДМИТРЕНКО (Ніжин), коментарі Сергія ЗОЗУЛІ (Київ–Ніжин):
Уперше вводиться до наукового обігу корпус джерел з епістолярію українського та російського радянського історика-нумізмата, музейника І.Г. Спаського. Корпус джерел який містить кореспонденцію, отриману відомим науковцем від кореспондентів-ніжинців, і де, здебільшого, відображена “ніжинська тематика” – проблеми збереження культурної спадщини Ніжина, післявоєнного розвитку міста тощо.Подготовка к печати и предисловие Наталии ДМИТРЕНКО (Нежин), комментарии Сергея ЗОЗУЛИ (Киев–Нежин):
Впервые вводится в научный оборот корпус источников из эпистолярия украинского и российского советского историка-нумизмата, музейщика И.Г. Спасского. Корпус источников содержит корреспонденцию, полученную известным ученым от корреспондентов-нежинцев, и в котором преимущественно отображена “нежинская тематика” – проблемы сохранения культурного наследия Нежина, послевоенного развития города и т.п.Preparation to the print and preface of Nataliya DMYTRENKO (Nizhyn), comments of Serhiy ZOZULYA (Kyiv–Nizhyn):
The corps of sources from the epistolary legacy of the Ukrainian and Russian soviet historiannumismatist and museum worker I.G. Spas’kiy is entered to the scientific appeal in the first time. This corps of sources contains correspondence got the known scientist from Nizhynians and contains mostly “Nizhyn themes” – problems of protect of Nizhyn’s cultural legacy, post-war development of this town etc
Challenges in monitoring and managing engineered slopes in a changing climate
Geotechnical asset owners need to know which parts of their asset network are vulnerable to climate change induced failure in order to optimise future investment. Protecting these vulnerable slopes requires monitoring systems capable of identifying and alerting to asset operators changes in the internal conditions that precede failure. Current monitoring systems are heavily reliant on point sensors which can be difficult to interpret across slope scale. This paper presents challenges to producing such a system and research being carried out to address some of these using electrical resistance tomography (ERT). Experimental results show that whilst it is possible to measure soil water content indirectly via resistivity the relationship between resistivity and water content will change over time for a given slope. If geotechnical parameters such as pore water pressure are to be estimated using this method then ERT systems will require integrating with more conventional geotechnical instrumentation to ensure correct representative information is provided. The paper also presents examples of how such data can be processed and communicated to asset owners for the purposes of asset management
First Principles Calculations of Fe on GaAs (100)
We have calculated from first principles the electronic structure of 0.5
monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We
find the Fe magnetic moment to be determined by the Fe-As distance. As
segregates to the top of the Fe film, whereas Ga most likely is found within
the Fe film. Moreover, we find an asymmetric in-plane contraction of our
unit-cell along with an expansion perpendicular to the surface. We predict the
number of Fe 3d-holes to increase with increasing Fe thickness on -doped
GaAs.Comment: 9 pages, 14 figures, submitted to PR
The Relativistic Factor in the Orbital Dynamics of Point Masses
There is a growing population of relativistically relevant minor bodies in
the Solar System and a growing population of massive extrasolar planets with
orbits very close to the central star where relativistic effects should have
some signature. Our purpose is to review how general relativity affects the
orbital dynamics of the planetary systems and to define a suitable relativistic
correction for Solar System orbital studies when only point masses are
considered. Using relativistic formulae for the N body problem suited for a
planetary system given in the literature we present a series of numerical
orbital integrations designed to test the relevance of the effects due to the
general theory of relativity in the case of our Solar System. Comparison
between different algorithms for accounting for the relativistic corrections
are performed. Relativistic effects generated by the Sun or by the central star
are the most relevant ones and produce evident modifications in the secular
dynamics of the inner Solar System. The Kozai mechanism, for example, is
modified due to the relativistic effects on the argument of the perihelion.
Relativistic effects generated by planets instead are of very low relevance but
detectable in numerical simulations
Research-informed design, management and maintenance of infrastructure slopes: development of a multi-scalar approach
The UK’s transport infrastructure is one of the most heavily used in the world. The performance of these networks is critically dependent on the performance of cutting and embankment slopes which make up £20B of the £60B asset value of major highway infrastructure alone. The rail network in particular is also one of the oldest in the world: many of these slopes are suffering high incidents of instability (increasing with time). This paper describes the development of a fundamental understanding of earthwork material and system behaviour, through the systematic integration of research across a range of spatial and temporal scales. Spatially these range from microscopic studies of soil fabric, through elemental materials behaviour to whole slope modelling and monitoring and scaling up to transport networks. Temporally, historical and current weather event sequences are being used to understand and model soil deterioration processes, and climate change scenarios to examine their potential effects on slope performance in futures up to and including the 2080s. The outputs of this research are being mapped onto the different spatial and temporal scales of infrastructure slope asset management to inform the design of new slopes through to changing the way in which investment is made into aging assets. The aim ultimately is to help create a more reliable, cost effective, safer and more resilient transport system
Domain Wall Spacetimes: Instability of Cosmological Event and Cauchy Horizons
The stability of cosmological event and Cauchy horizons of spacetimes
associated with plane symmetric domain walls are studied. It is found that both
horizons are not stable against perturbations of null fluids and massless
scalar fields; they are turned into curvature singularities. These
singularities are light-like and strong in the sense that both the tidal forces
and distortions acting on test particles become unbounded when theses
singularities are approached.Comment: Latex, 3 figures not included in the text but available upon reques
A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3π Survey
We present the discovery of a faint Milky Way satellite, Laevens 2/Triangulum II, found in the Panoramic Survey Telescope And Rapid Response System (Pan-STARRS 1) 3 pi imaging data and confirmed with follow-up wide-field photometry from the Large Binocular Cameras. The stellar system, with an absolute magnitude of M_V=-1.8 +/-0.5, a heliocentric distance of 30 +2/-2 kpc, and a half-mass radius of 34 +9/-8 pc, shows remarkable similarity to faint, nearby, small satellites such as Willman 1, Segue 1, Segue 2, and Bo\"otes II. The discovery of Laevens 2/Triangulum II further populates the region of parameter space for which the boundary between dwarf galaxies and globular clusters becomes tenuous. Follow-up spectroscopy will ultimately determine the nature of this new satellite, whose spatial location hints at a possible connection with the complex Triangulum-Andromeda stellar structures
Small Polarons in Transition Metal Oxides
The formation of polarons is a pervasive phenomenon in transition metal oxide
compounds, with a strong impact on the physical properties and functionalities
of the hosting materials. In its original formulation the polaron problem
considers a single charge carrier in a polar crystal interacting with its
surrounding lattice. Depending on the spatial extension of the polaron
quasiparticle, originating from the coupling between the excess charge and the
phonon field, one speaks of small or large polarons. This chapter discusses the
modeling of small polarons in real materials, with a particular focus on the
archetypal polaron material TiO2. After an introductory part, surveying the
fundamental theoretical and experimental aspects of the physics of polarons,
the chapter examines how to model small polarons using first principles schemes
in order to predict, understand and interpret a variety of polaron properties
in bulk phases and surfaces. Following the spirit of this handbook, different
types of computational procedures and prescriptions are presented with specific
instructions on the setup required to model polaron effects.Comment: 36 pages, 12 figure
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