448 research outputs found

    A Hierarachy of Residential Neighborhoods Determined by Blight Conditions: The Case of Council Bluffs, Iowa

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    The purpose of this study is twofold. In the first place, there is a relative lack of geographical research devoted to the residential sections of cities. This is regretable since residential land-use is predominant in most urban areas. Secondly, there has been very little study of blighted areas by geographers. The majority of the work carried out on this subject has been mainly the product of sociologists and land economists

    Eastern Beringia and beyond: Late Wisconsinan and Holocene landscape dynamics along the Yukon Coastal Plain, Canada

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    Terrestrial permafrost archives along the Yukon Coastal Plain (northwest Canada) have recorded landscape development and environmental change since the Late Wisconsinan at the interface of unglaciated Beringia (i.e. Komakuk Beach) and the northwestern limit of the Laurentide Ice Sheet (i.e. Herschel Island). The objective of this paper is to compare the late glacial and Holocene landscape development on both sides of the former ice margin based on permafrost sequences and ground ice. Analyses at these sites involved a multi-proxy approach including: sedimentology, cryostratigraphy, palaeoecology of ostracods, stable water isotopes in ground ice, hydrochemistry, and AMS radiocarbon and infrared stimulated luminescence (IRSL) dating. AMS and IRSL age determinations yielded full glacial ages at Komakuk Beach that is the northeastern limit of ice-free Beringia. Herschel Island to the east marks the Late Wisconsinan limit of the northwest Laurentide Ice Sheet and is composed of ice-thrust sediments containing plant detritus as young as 16.2 cal ka BP that might provide a maximum age on ice arrival. Late Wisconsinan ice wedges with sediment-rich fillings on Herschel Island are depleted in heavy oxygen isotopes (mean δ18O of −29.1‰); this, together with low dexcess values, indicates colder-than-modern winter temperatures and probably reduced snow depths. Grain-size distribution and fossil ostracod assemblages indicate that deglaciation of the Herschel Island icethrust moraine was accompanied by alluvial, proluvial, and eolian sedimentation on the adjacent unglaciated Yukon Coastal Plain until ~11 cal ka BP during a period of low glacio-eustatic sea level. The late glacial–Holocene transition was marked by higher-than-modern summer temperatures leading to permafrost degradation that began no later than 11.2 cal ka BP and caused a regional thaw unconformity. Cryostructures and ice wedges were truncated while organic matter was incorporated and soluble ions were leached in the thaw zone. Thermokarst activity led to the formation of ice-wedge casts and deposition of thermokarst lake sediments. These were subsequently covered by rapidly accumulating peat during the early Holocene Thermal Maximum. A rising permafrost table, reduced peat accumulation, and extensive ice-wedge growth resulted from climate cooling starting in the middle Holocene until the late 20th century. The reconstruction of palaeolandscape dynamics on the Yukon Coastal Plain and the eastern Beringian edge contributes to unraveling the linkages between ice sheet, ocean, and permafrost that have existed since the Late Wisconsinan

    RELACIÓN ENTRE EL RENDIMIENTO ACADÉMICO DE LOS INGRESANTES Y EL ABANDONO DE LOS ESTUDIOS UNIVERSITARIOS: COMPARACIÓN ENTRE CARRERAS DE INGENIERÍA Y ECONOMICAS

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    La preocupación por orientar adecuadamente los recursos que se afectan a los programas de apoyo a los estudiantes de primer año de las carreras, nos llevó a trabajar intentando generar un modelo que sea capaz de determinar, anticipadamente, que estudiantes se encontrarían en situación de abandonar sus estudios. En una primera aplicación del modelo, se analizó la correlación entre el rendimiento académico y el abandono para diez cohortes de ingresantes, de las dos carreras de Ingeniería que ofrece la Universidad Nacional de Luján, observándose una significativa correlación entre el rendimiento académico del estudiante en el primer cuatrimestre y el abandono de los estudios durante el segundo, tercero y cuarto cuatrimestre. En este trabajo, presentamos los resultados que se alcanzaron al aplicar el mismo modelo a las diez cohortes, equivalentes, de estudiantes de las dos carreras del campo de las Ciencias Económicas que se ofrecen en la misma Institución: Licenciatura en Administración y Licenciatura en Comercio Internacional. Las principales conclusiones a las que arribamos es que el modelo se valida positivamente al cambiar el origen disciplinar de las carreras en las que se aplica. Por otra parte, existe mayor correlación entre el rendimiento académico en el primer cuatrimestre y el momento en que se abandonan los estudios para los estudiantes de carreras de Ciencias Económicas que la observada en los de Ingeniería. Se repite el fenómeno observado para las carreras de Ingeniería, de disminuir la correlación entre el rendimiento académico y el abandono para la cohorte 2002. También se detecta una diferencia significativa respecto de la moda para la cantidad de asignaturas aprobadas durante el primer cuatrimestre para las cuatro carreras

    Non-Lethal Management to Reduce Conflicts with Winter Urban Crow Roosts in New York: 2002 - 2007

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    American crow populations have increased steadily since 1966 in many parts of the U.S. Large winter congregations of crows in urban environments have resulted in an increased number of requests for assistance in managing nocturnal roosts in New York. In 2002, the USDA APHIS Wildlife Services program initiated a large-scale non-lethal winter roost dispersal program in Troy, New York. Since that time, similar programs have been implemented in 4 other cities in New York to manage crow roosts ranging in size from 8,000 - 63,000 individuals. The goals of the programs were to minimize noise, accumulations of crow feces around residences, strong odors associated with droppings, property damage, clean-up costs, and potential threats to human health and safety. The primary management strategy relied on dispersing concentrated crow populations from high-impact high-conflict areas, to low-impact low-conflict areas. An integrated management program using pyrotechnics, amplified recorded crow distress calls, and hand-held lasers was implemented to successfully disperse local crow roosts, reducing populations at the majority of core roost sites each year by more than 98%. In some instances, significant reductions in crow numbers and associated damage persisted \u3e8 weeks after management without additional interventions, although most sites required multiple additional “spot treatments.” High-profile urban wildlife management projects of this type require multiple meetings with key stakeholders and the public and often attract intense media interest, adding complexity to these programs. We provide summary information from 5 cities in New York documenting crow management techniques, intensity of effort, number of interventions required to relocate crow populations, and key lessons learned regarding science-based project documentation, project transparency, communication, and the need for long-term adaptive management strategies to meet project goals

    A LEED structural analysis of the Co(100) surface

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    The structure of the clean Co(1010) surface has been analysed by LEED. Application of a recently developed computational scheme reveals the prevalence of the termination A in which the two topmost layers exhibit a narrow spacing of 0.62 Å, corresponding to a 12.8(±0.5)% contraction with respect to the bulk value, while the spacing between the second and third layer is slightly expanded by 0.8(±0.2)%

    Rinikerfeld Palaeolake (Northern Switzerland) – a sedimentary archive of landscape and climate change during the penultimate glacial cycle

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    While timing and ice extent of the last glacial maximum are generally well known, the courses of earlier glaciations have remained poorly constrained, with one of the main reasons being the scarcity of sedimentary archives. This study introduces a new palaeolake record from a Mid‐Pleistocene glaciofluvial channel system in the Lower Aare Valley (Northern Switzerland). The record of Rinikerfeld comprises a >40 m long succession of Quaternary deposits that are targeted by multi‐method sedimentological analysis. Sedimentary facies together with geochemical and geotechnical parameters, pollen content, as well as luminescence ages allow the reconstruction of the establishment, evolution and infilling of the early Marine Isotope Stage 6‐aged Rinikerfeld Palaeolake. A drastic change in lake sediment composition and structure indicates cessation of the initial glacially derived input, which is explained by landscape modification and drainage rerouting during the Penultimate (Beringen) Glaciation. Geochemical and palynological data further reveal cold, initially periglacial but slightly ameliorating, climate conditions, while the lake was progressively filled up by local runoff, before being buried by periglacial colluvial diamicts, and potentially overridden by ice. It is therefore concluded that the onset of the Beringen Glaciation was an environmentally as well as geomorphically dynamic time period in the Northern Alpine Foreland

    Leptomeningeal metastasis from solid tumours: EANO-ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up

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    • This Clinical Practice Guideline provides recommendations for managing leptomeningeal metastases from solid tumours. • The guideline covers clinical, imaging and cytological diagnosis, staging and risk assessment, treatment and follow-up. • A treatment and management algorithm is provided. • The author panel encompasses a multidisciplinary group of experts from different institutions and countries in Europe. • Recommendations are based on available scientific data and the authors’ collective expert opinion
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