2,073 research outputs found

    A critical revision of the fossil record, stratigraphy and diversity of the Neogene seal genus Monotherium (Carnivora, Phocidae)

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    Historically, Monotherium had been one of the few genera of extinct Phocidae (true seals) that served as a wastebin taxon. Consequently, it did neither aid in understanding phylogenetic relationships of extinct Phocidae, nor in understanding seal diversity in deep time. This urged the reassessment of the genus. Before our review, Monotherium included five different species: Monotherium aberratum, Monotherium affine, and Monotherium delognii from Belgium; Monotherium gaudini from Italy; and Monotherium? wymani from the east coast USA. In this work we redescribe the fossil record of the genus, retaining the type species M. delognii. Monotherium aberratum and M. affine are reassigned to the new phocine genus Frisiphoca. Monotherium gaudini is renamed and considered a stem-monachine (Noriphoca gaudini). The holotype of the monachine M.? wymani requires further study pending the discovery of new fossil material that could be attributed to the same taxon. Reinvestigating the stratigraphic context reveals that N. gaudini most likely represents one of the two oldest named phocid seals, or even the oldest, dated to the late Oligocene-earliest Miocene. Our results allow questioning the widespread idea that Phocidae originated in the western Atlantic and better appreciate their palaeobiogeography during the late Oligocene-Miocene interval in the North Atlantic realm

    On Prophoca and Leptophoca (Pinnipedia, Phocidae) from the Miocene of the North Atlantic realm : redescription, phylogenetic affinities and paleobiogeographic implications

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    Background: Prophoca and Leptophoca represent the oldest known genera of phocine seals, dating from the latest early to middle Miocene. Originally, Prophoca rousseaui and Prophoca proxima were described based on fragmentary remains from the Miocene of Belgium. However, several researchers contested the union of Prophoca rousseaui and Prophoca proxima into one genus, without providing evidence. The stratigraphic context of Prophoca remained poorly constrained due to the lack of precise data associated with the original specimens collected in the area of Antwerp (north of Belgium). Methods: Prophoca and Leptophoca are redescribed and their phylogenetic position among Phocidae is reassessed using PAUP. Dinoflagellate biostratigraphy has been carried out on sediment samples associated with specimens from Prophoca and Leptophoca to elucidate their approximate ages. Results: Whereas the species Prophoca rousseaui is redescribed, Prophoca proxima is considered synonymous to Leptophoca lenis, with the proposal of a new combination Leptophoca proxima (Van Beneden, 1877). Sediment samples from specimens of both taxa have been dated to the late Langhian-early Serravallian (middle Miocene). Following a reinvestigation of Leptophoca amphiatlantica, characters from the original diagnosis are questioned and the specimens of Leptophoca amphiatlantica are considered Leptophoca cf. L. proxima. In a phylogenetic analysis, Prophoca rousseaui and Leptophoca proxima constitute early branching stem-phocines. Discussion: Leptophoca proxima from the North Sea Basin is younger than the oldest known find of Leptophoca proxima from North America, which does not contradict the hypothesis that Phocinae originated along the east coast of North America during the late early Miocene, followed by dispersal to Europe shortly after. Morphological features of the appendicular skeleton indicate that Prophoca rousseaui and Leptophoca proxima have archaic locomotory modes, retaining a more prominent use of the fore flipper for aquatic propulsion than extant Phocidae

    Nearly magnitude‐invariant stress drops in simulated crack‐like earthquake sequences on rate‐and‐state faults with thermal pressurization of pore fluids

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    Stress drops, inferred to be magnitude‐invariant, are a key characteristic used to describe natural earthquakes. Theoretical studies and laboratory experiments indicate that enhanced dynamic weakening, such as thermal pressurization of pore fluids, may be present on natural faults. At first glance, magnitude invariance of stress drops and enhanced dynamic weakening seem incompatible since larger events may experience greater weakening and should thus have lower final stresses and higher stress drops. We hypothesize that enhanced dynamic weakening can be reconciled with magnitude‐invariant stress drops due to larger events having lower average prestress when compared to smaller events. We conduct numerical simulations of long‐term earthquake sequences in fault models with rate‐and‐state friction and thermal pressurization, and in the parameter regime that results mostly in crack‐like ruptures, we find that such models can explain both the observationally inferred stress drop invariance and increasing breakdown energy with event magnitude. Smaller events indeed have larger average initial stresses than medium‐sized events, and we find nearly constant stress drops for events spanning up to two orders of magnitude in average slip, comparable to approximately six orders of magnitude in seismic moment. Segment‐spanning events have more complex behavior, which depends on the properties of the arresting velocity‐strengthening region at the edges of the faults

    Two inscribed documents of the Athenian Empire: the Chalkis decree and the tribute reassessment decree

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    This paper discusses two important inscriptions for the history of the Athenian Empire, the Chalkis decree of 446/5 (or 424/3?) BC (IG I3 40) and the tribute reassessment decree (“Thoudippos’ decree”) of 425/4 BC (IG I3 71). Based on English translations of the most up-to-date and authoritative Greek texts, the paper sets out to explain the inscriptions in historical context, without assuming prior knowledge of ancient Greek or of the history of Athens and the Athenian Empire. To help the reader new to the study of Athenian inscriptions, the Paper includes an introduction to inscribed Athenian decrees of the fifth century BC. This paper will be useful for researchers, teachers and learners of Greek History at University level, but is also designed to help 6th-form teachers and students in the UK with the study of these two inscriptions, which are set as source material for the “Relations between Greek states and between Greek and non-Greek states, 492-404 BC” period study under the OCR specification for A-level Ancient History (H407, for first assessment in 2019; LACTOR4 1.78 and 138). Note: minor corrections were incorporated on 28 June 2017

    Attic Inscriptions in UK Collections 1 (Petworth House)

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    This, the inaugural volume of AIUK, publishes the important hellenistic inscription in Petworth House. Dating to 108/7 BC it honours the maidens who worked on the robe (peplos) for the statue of Athena. Another small fragment of the same inscription is in the Epigraphical Museum, Athens. It is one of three similar inscriptions which date to around the same decade and seem to reflect a revival or reform of the arrangements for making the peplos, which was carried in procession and presented to the goddess at the Panathenaia festival. The names of the maidens are listed in a “roll of honour” at the bottom of the inscription. This and the lists of maidens in the other two inscriptions supply us with much of our information on the female members of elite Athenian families at this period

    357/6 BC: A significant year in the development of Athenian honorific practice

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    The main purpose of this short paper is to draw attention to the significance of 357/6 BC as the year that dedications by Athenian officials begin to refer to the crowning of officials by the Council and/or People (section 2). It also makes a case for lowering the accepted date at which the Athenians began honouring more than one Council prytany per year from ca. 340 BC to after 307/6 BC (section 3) and proposes consequential changes to the editions of some relevant inscriptions in IG II3 4 fasc. 1, mainly to dates (section 4). The paper concludes with a brief note on historical context (section 5)

    The challenges and resolutions of moving middle curriculum managers on to principalship

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    Frearson (2003), Clancy (2005) and Colinson and Colinson (2006) all argue that there is a chronic shortage of suitably experienced candidates pursuing principalship, a situation which is being made worse by an ageing workforce amongst currently serving principals. Hargreaves and Fink (2005) suggest that this is a result of the principals’ role becoming increasingly complex and demanding which has deterred potential candidates from pursuing principalship. At the same time Hargreaves and Fink (2005) and Davies (2009) argue that sustainable leadership offers a viable mechanism for developing individuals and organisational capacity resulting in a greater pool of suitably experienced and skilled candidates. This research reviews current literature on sustainable leadership and argues for an alternative framework for further education colleges. It also considers the current challenges faced by principals and middle curriculum managers and the resolutions which need to be put into place in order to develop individuals capable of becoming the next generation of principals.The research was achieved through a three phase design: phase one was a questionnaire to principals of all general further education colleges in the south east of England, including London; phase two was a series of interviews with principals and phase three were focus groups with middle curriculum managers.The research demonstrates that the role of the modern principal encompassed three main elements: public; internal private and internal public, all of which need to be balanced by incumbents in order to fulfil their duties effectively to both stakeholders and spectators. The research also suggests that the development of future principals should take place prior to commencing the post and rather than focusing on knowledge as per existing approaches, there is overwhelming support from participants for an evidence based approach

    Attic Inscriptions in UK Collections: British Museum, Decrees of the Council and Assembly

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    This, the second part of our publication of the Attic inscriptions in the British Museum, contains new editions of the seventeen decrees of the Council and Assembly in the collection. All were acquired in Athens by UK aristocrats in the early 19th century and are published here in most cases together with other fragments of the same inscriptions still in Athens. The inscriptions offer a series of illuminating snapshots of the policy preoccupations of Athenian citizens across the entire span of Athenian decree-inscribing, from the early 5th century BC to the early 3rd century AD, and include important documents of the Eleusinian Mysteries and the Athenian Empire as well as characteristic inscriptions of the 4th century BC and Hellenistic and Roman Athens. Introductory sections discuss the history of the collection and locate the inscriptions in the context of Athenian decree-inscribing and Athenian history more broadly. In addition to significant new epigraphical findings this edition includes reassessments of several major inscriptions

    Mean Curvature Flow with a Neumann Boundary Condition in Flat Spaces

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    In this thesis I study mean curvature flow in both Euclidean and Minkowski space with a Neumann boundary condition. In Minkowski space I show that for a convex timelike cone boundary condition, with compatible spacelike initial data, mean curvature flow with a perpendicular Neumann boundary condition exists for all time. Furthermore, by a blowdown argument I show convergence as t →∞ to a homothetically expanding hyperbolic hyperplane. I also study the case of graphs over convex domains in Minkowski space. I obtain long time existence for spacelike initial graphs which are taken by mean curvature flow with a Neumann boundary condition to a constant function as t →∞. In Euclidean space I consider boundary manifolds that are rotational tori where I write t for the unit vector field in the direction of the rotation. If the initial manifold M₀ is compatible with the boundary condition, and at no point has t as a tangent vector, then mean curvature flow with a perpendicular Neumann boundary condition exists for all time and converges to a flat cross-section of the boundary torus. I also discuss other constant angle boundary conditions

    Combating occupational apartheid plaguing internationally trained professionals: A mixed methods description of activist entrepreneurship in cross-sector partnerships

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    Individuals that were born in a foreign country, have a bachelor’s degree or higher from a foreign post-secondary education institution, and are not working at their full level of expertise, are referred to more concisely as “internationally trained professionals” (ITPs). Social workers have called becoming informed about immigrants’ integration needs a new frontier of social service and professional development. All fields of human services will benefit from any data resulting from descriptive exploration of the ITP integration issue. The bounded system that serves for this case study is the current limited response to the ITP issue seen in Virginia, USA. In the North of the state we see a mature, urban response by the local state-run community college and various community-based organizations. In the West we see an emergent, rural response by a community coalition of service providers and interested parties from all three sectors of society. Detailed in the case is the acting of leaders to address the marginalization of ITPs. Using the theoretical lens of activist entrepreneurship, the case illustrates the necessity that activist entrepreneurs feel in their work for marginalized peoples, the internal and external environmental opportunities that these leaders identify as facilitating their inner drive, and the broad social needs underpinning the opportunities and necessities. Both qualitative and quantitative data are used to describe Virginia’s response to the ITP issue. A threshold for service entry is established across three ITP variables. A snapshot of the impact of a coalition in its formation stage is explicated. Cross-sector partnerships are key tools in responding to the ITP issue. Several ideas for both quantitative and qualitative follow-up research are generated. Examining ITP variables for relationships and more fully describing the essence and process of activist entrepreneurship are among the proposals
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