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The end Ordovician (Hirnantian) extinction was the first of the five big Phanerozoic extinction events, and the first that involved metazoan-based communities. It comprised two discrete pulses, both linked in different ways to an intense but short-lived glaciation at the South Pole. The first, occurring at, or just below, the Normalograptus extraordinarius graptolite Biozone, mainly affected nekto
The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations ∼2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.
Elevated molybdenum (Mo) contents in organic-rich sediments are indicative of deposition from an anoxic and sulfide-rich (euxinic) water-column. This can be used for tracing past euxinic conditions in ancient oceans from sedimentary archives. Conventional analytical detection of elevated molybdenum levels is, however, expensive and cannot be directly performed in the field. Here, we show that hand
Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization by investigating environmental, depositional and diagenetic conditions in beds with and without soft-tissue pre
The end-Ordovician extinction consisted of two discrete pulses, both linked, in various ways, to glaciation at the South Pole. The first phase, starting just below the Normalograptus extraordinarius Zone, particularly affected nektonic and planktonic species, while the second pulse, associated with the Normalograptus persculptus Zone, was less selective. Glacially induced cooling and oxygenation a
Burgess Shale-type biotas occur globally in the Cambrian record and offer unparalleled insight into the Cambrian explosion, the initial Phanerozoic radiation of the Metazoa. Deposits bearing exceptionally preserved soft-bodied fossils are unusually common in Cambrian strata; more than 40 are now known. The well-documented decline of soft-bodied preservation following the Middle Cambrian represents
To explore how seawater chemistry might influence exceptional Burgess Shale-type preservation, freshly-killed shrimp and annelids were covered in clay and exposed to high and low sulfate concentrations for up to six weeks of anaerobic decay. Decay was monitored by carbon mass balance calculations and non-destructive imaging. Decay rates and visual distortion of shrimp cuticle and muscle appear slo
Most organisms that ever lived on Earth lacked skeletons and have therefore escaped preservation in the geological record. This fact makes it hard to accurately trace the evolution of multicellular organisms and the tree of life. However a handful faunas did get exceptionally well-preserved, including their soft-bodied members, just when complex lifeforms diverged 550 million years ago. Geochemica
PURPOSE: To investigate the contents of green- and blue-sensitive cone photoreceptors in laminated rabbit retinal transplants.METHODS: Eleven rabbits each received a sheet of embryonic neuroretina into the subretinal space in one eye. Vitrectomy was used in the procedure and properly polarized flat transplants were placed on the host pigment epithelium. After 17-309 days the transplants were exami
Embryonic full-thickness rabbit neuroretinal sheets were transplanted to the subretinal space of adult hosts. This was accomplished by using a new transplantation technique involving vitrectomy and retinotomy. The grafts were followed from 10 to 306 days after surgery and were then examined by different histological techniques. In the light microscope, the transplants were seen to develop the norm
BACKGROUND: The study was carried out to evaluate the expression of major histocompatibility complex (MHC) molecules in retinal transplants with different tissue integrity.METHODS: Twelve adult rabbits received an allogeneic subretinal neuroretinal transplant, in the form of either fragmented embryonic cells or a complete full-thickness embryonic retina. A controlled transvitreal approach was used
PURPOSE: To establish neuronal connections in the rod and cone pathway between laminated rabbit retinal transplants and the host retina.METHODS: Fourteen adult rabbits received a complete full-thickness embryonic transplant. After survival times of 3 to 10 months, the retinas were studied under light microscope and with immunohistochemistry. Antibodies against protein kinase C (PKC), parvalbumin,
PURPOSE: To examine immunohistochemical markers in straight, well-laminated retinal transplants with special attention paid to the interphotoreceptor matrix, the Müller cells and the ganglion cells as these three retinal components have been abnormal in transplants produced by previous methods.METHODS: Nine rabbits underwent subretinal transplantation of a complete full-thickness embryonic neurore
PURPOSE: To establish the light and electron microscopic morphology of long-term full-thickness embryonic rabbit retinal transplants, with special attention paid to graft- host integration.METHODS: Eighteen rabbits received a complete embryonic neuroretina 19 days after conception. The transplants were positioned under the host retina, flat against the host retinal pigment epithelium with proper p
Adult and embryonic rabbit retinal sheets were transplanted into the subretinal space of adult rabbits. The transplants were either full-thickness with intact layering, or gelatin embedded and vibratome sectioned with the inner retina removed. The full-thickness grafts were positioned subretinally by means of a glass capillary in which they were partially folded. The vibratome sectioned ones were
PURPOSE: To develop an improved surgical technique making full-thickness retinal transplant possible, thereby achieving a normal laminated transplant with minimal rosette formation.METHODS: A total of 23 rabbits underwent vitrectomy, retinotomy, and subsequent subretinal transplant of a complete embryonic neuroretina using a specially crafted glass cannula. Of the 23 animals, 15 received a prenata
This study delineates the permissible scope for compulsory mental health interventions under the Convention on the Rights of Persons with Disabilities (CRPD). It was initially triggered by two competing positions within the current debate over the future of coercive psychiatry; a practice that is still omnipresent among states worldwide. According to one position, defended by the CRPD Committee amThis study delineates the permissible scope for compulsory mental health interventions under the Convention on the Rights of Persons with Disabilities (CRPD). It was initially triggered by two competing positions within the current debate over the future of coercive psychiatry; a practice that is still omnipresent among states worldwide. According to one position, defended by the CRPD Committee am
This thesis delves into two ‘edge areas’ located in and around East Jerusalem. It attempts to unfold and analyze the dynamics in these edge areas, while investigating the agency of the people present there through their own perceptions and practices towards the land, the urbanization processes, the power circulation and the structural impositions. Squeezed by a settler-colonial domination that con
