Single Catastrophic Event Research Articles

Massive Genomic Rearrangement Acquired in a Single Catastrophic Event during Cancer Development

SummaryCancer is driven by somatically acquired point mutations and chromosomal rearrangements, conventionally thought to accumulate gradually over time. Using next-generation sequencing, we characterize a phenomenon, which we term chromothripsis, whereby tens to hundreds of genomic rearrangements occur in a one-off cellular crisis. Rearrangements involving one or a few chromosomes crisscross back and forth across involved regions, generating frequent oscillations between two copy number states. These genomic hallmarks are highly improbable if rearrangements accumulate over time and instead imply that nearly all occur during a single cellular catastrophe. The stamp of chromothripsis can be seen in at least 2%–3% of all cancers, across many subtypes, and is present in ∼25% of bone cancers. We find that one, or indeed more than one, cancer-causing lesion can emerge out of the genomic crisis. This phenomenon has important implications for the origins of genomic remodeling and temporal emergence of cancer.PaperClip

Size variation of conodont elements of the Hindeodus–Isarcicella clade during the Permian–Triassic transition in South China and its implication for mass extinction

Based on the analysis of thousands of conodont specimens from the Permian –Triassic (P–T) transition at Meishan (the GSSP of P–T Boundary) and Shangsi sections in South China, this study investigates the size variation of Hindeodus and Isarcicella P1 elements during the mass extinction interval. The results demonstrate that Hindeodus– Isarcicella underwent 4 episodes of distinct size reduction during the P–T transition at the Meishan Section and 2 episodes of size reduction in the earliest Triassic at Shangsi. The size reductions at Meishan took place at the junctions of beds 24d/24e, 25/26, 27b/27c and 28/29, and at the junctions of beds 28/29c and 30d/31a at Shangsi. The two earliest Triassic size reduction episodes were correlative between the two sections. These changes coincide with some important geological events such as eustatic sea-level changes, anoxic events, carbon isotope oscillations, miniaturization of brachiopods and microbial changes. Through detailed investigation of the palaeoenvironment and the palaeoecology of Hindeodus– Isarcicella, the authors propose that the main causes of the size reduction was a sharp decline of food availability because of the mass extinction and the anoxic event during the P/T transition. The pattern of size reduction supports suggestions that the end-Permian mass extinction was multi-episodal, consisting of 3 extinction events rather than a single catastrophic event.

Fluvial-controlled metal and As mobilisation, dispersal and storage in the Río Guadiamar, SW Spain and its implications for long-term contaminant fluxes to the Doñana wetlands

Flood-related contaminant (As, Cd, Cu, Pb, Zn) remobilisation, dispersal and storage in the Río Guadiamar was investigated following the 1998 Aznalcóllar tailings dam failure, along with records of floodplain contaminant loading in the decades preceding the tailings release. A series of post-spill floods resulted in the transfer of vast quantities of sediment-borne heavy metals and As towards the lower reaches of the Guadiamar and the borders of the Doñana National Park, but over-bank flood deposits collected between May 1999 and March 2002 show a systematic fall in contaminant concentrations following successive flood events. Geochemical improvements can largely be attributed to sediment mixing of contaminated and ‘clean’ material derived from calcareous catchment soils. Longer-term contaminant patterns in floodplain sediment cores show higher heavy metal and As loading rates operating before the opening of the Aznalcóllar pit in 1979 and in some instances pre-dating 1954. The remobilization and dispersal of historically contaminated alluvium in the upper Guadiamar means that the post-clean-up contaminant signature in flood-transported sediments largely reflects chronic, long-term metal mining in the Guadiamar catchment, rather than the acute effects of the Aznalcóllar spill. Generally results present a cautiously optimistic prognosis for the sensitive wetlands of Doñana, but high dissolved (aqueous) heavy metal (especially Cu and Zn) concentrations in the upper Guadiamar emphasise the need for addressing contaminant ‘hotspots’ in the region and for maintaining flow requirements for aquatic ecosystems. This study illustrates the importance of establishing antecedent geomorphological–geochemical conditions in a spill-impacted river system, both for assessing the impacts of a single catastrophic pollution event and for developing appropriate strategies for remediation.

Environmental Health Impacts of CAFOs

I am concerned about the development and content of the Mini-Monograph on Environmental Health Impacts of Concentrated Animal Feeding Operations (CAFOs) (Bunton et al. 2007; Burkholder et al. 2007; Donham et al. 2007; Gilchrist et al. 2007; Heederik et al. 2007; Thorne et al. 2007). Although I believe that the process of developing these reports was flawed, I will limit my comments to the content of the reports. It is difficult to comment on six separate articles within the word limitations of a letter; therefore, I will make some general comments followed by a few specific examples. Overall, there was a wide variation between the six articles (Bunton et al. 2007; Burkholder et al. 2007; Donham et al. 2007; Gilchrist et al. 2007; Heederik et al. 2007; Thorne et al. 2007) in both tone and scientific rigor. However, generally the authors did not differentiate between potential risks associated with general animal production—regardless of facility type—and risks associated with CAFOs. Their default was to assign any potential risk to the attribute “CAFO” rather than the attribute “animal.” For example, Burkholder et al. (2007) gave the impression that pathogens in manure would not exist in manure from animals raised in facilities that do not meet the definition of a CAFO. The authors of these articles generally referred to risk as the presence of potential pathogens or toxic substances. A true assessment of potential risk requires an assessment of exposure as well as volume or presence (National Research Council 1994), something that was not addressed to any extent in these reports. Additionally, Burkholder et al. (2007) did not in any way differentiate between the normal operation of a CAFO and potential impacts on water quality versus the results of a single catastrophic event, such as failure of a lagoon wall. Repeated reference to a single catastrophic event involving a single lagoon does not aid scientists or the public in understanding how CAFOs are operated on a daily basis, or how the typical handling of manure under daily operation may impact water quality. The authors did not attempt to document regulatory oversight or best management practices that have been implemented to minimize potential negative impacts on the environment (U.S. Environmental Protection Agency 2002). Indeed, there was no mention of the relative rarity of lagoon failure, leaving the impression that this is a common event. In some cases, where the authors attempted to assign risk to CAFOs rather than to animals, they presented biased opinion rather than fact. For example, Gilchrist et al. (2007) stated that Pathogens tend to be amplified in animals raised in CAFOs and, thus, are more difficult to eliminate in meat packing processes. This blanket statement does not specify a type of pathogen, but studies indicate that—among the more important pathogens—this is an inaccurate statement. For example, pathogens such as Trichinella spiralis, formerly one of the most prominent pork-associated pathogens, have largely disappeared with the movement of pigs to indoor production (Roy 2003). Furthermore, pork carcass contamination with bacterial pathogens such as Salmonella is consistently lowest in the large packing plants, which because of the large volume of production are most likely to acquire animals from large producers (U.S. Department of Agriculture, Food Safety and Inspection Service 2006). This clearly invalidates the argument that these pathogens are more difficult to eliminate in the packing process. Gilchrist et al. (2007) also referred to Denmark as a country that has experienced a successful transition to antibiotic-free production. This is incorrect, and indeed the latest DANMAP report (Danish Integrated Antimicrobial Resistance Monitoring and Research Program 2006) indicates that therapeutic antibiotic use in agriculture now exceeds the amount of antibiotics that were used to promote feed conversion before a ban on antibiotic growth promotion. Additionally, pig mortality in Denmark has risen 25% in the last 10 years (Agence France-Presse 2005). Gilchrist et al. (2007) suggest that industry leaders should take a leadership role in antibiotic use, but they apparently were unaware or intentionally overlooked the fact that the American Veterinary Medical Association, the American Association of Swine Veterinarians (2004), and the National Pork Board (2000) have had prudent use guidelines for 7 years, and that in 2005 the pork industry launched the Take Care — Use Antibiotics Responsibly program (National Pork Board 2005). More than 50 million pigs are marketed each year by producers who recognize the importance of protecting public health and animal health and welfare through the responsible use of antibiotics by pledging their support for the Take Care program. The topics covered by EHP are important and worthy of public discussion and scientific investigation. However, we do the public, producers, and the research community a disservice when that discussion is driven by misinformation and subjective opinion.

Organisations in Disaster

In the event of a disaster, communities become the targets of specialist organisations and a concentration of activities. The complex unstructured activities and routines of daily life are disrupted and even totally overwhelmed by a single catastrophic event that requires a redirection of priorities, resources and people to deal with all aspects of the disaster impact as rapidly as possible. The whole community must be mobilised to restore functions and meet needs, to return to the normality of the pre-disaster state. This latter purpose is least likely to be achieved, as the destroyed community can seldom rebuild to the same complex, but randomly haphazard state that existed before the disaster. The mobilisation of the whole community to the single purpose of recovery requires a high level of organisation. Response to a disaster demands that there be purposeful organisations ready to provide leadership and action. Emergency management is predicated for the existence of such purposeful organisations. However, while organisations are at the core of emergency management response and recovery, they are by no means simple or singular. Disaster generates a plethora of organisations, which interact with the community rather than simply organising disaster response. The community also organises itself, re-assigning priorities and using existing organisations and networks.

Anisotropy of magnetic susceptibility (AMS) analysis of basalt dikes at Cathedral Cliffs, WY: implications for Heart Mountain faulting

Mafic dikes pervade the upper plate of the Heart Mountain Detachment (HMD), yet the dike concentration in the lower plate is sparse. Previous workers interpreted that these dikes were emplaced either coeval with or subsequent to the emplacement of the upper plate. The magnetic fabrics of 32 mafic dikes at Cathedral Cliffs were analyzed using low-field anisotropy of magnetic susceptibility (AMS) as a proxy for flow. These dikes intrude Ordovician–Mississippian carbonate and overlying Eocene volcanic rocks and are truncated along the nearly horizontal HMD. The dikes trend between N10°W and N20°E, are all steeply dipping, and range in width between 0.5 and 3 m. Flow directions for the dikes were determined by the bearing and plunge of the K max (maximum principal susceptibility) axes relative to the dike orientation. About 66% of the dikes sampled show typical dike AMS patterns with K max and K int in the plane of the dike and K min normal to the dike plane. About 66% of the dikes sampled have K max inclinations >45° and thus were emplaced upward; 16% of the dikes have K max inclinations of <10° and thus were emplaced laterally. The remaining dikes have intermediate K max inclinations. With numerous dikes showing vertical to sub-vertical emplacement directions and with no magmatic source immediately below the detachment the dikes must predate emplacement of the upper plate. Therefore, upper plate dilation by dike intrusion could not be a driving force for protracted extension. Our date is consistent with a single catastrophic emplacement event, and inconsistent with an extensional allochthon model of incremental emplacement over long intervals of time.

Editorial Epilogue: Education after September 11

It was, I believe, the Danish philosopher Soren Kierkegaard who noted that single catastrophic event of monumental import is enough to call things into question ever after. If we are to take this pronouncement to heart, we must do much more than state the obvious when we speak about the tragedy of September 11. Yes, the world has changed. But I realize now that the very way in which this phrase has been repeated over and over deadens our understanding of it and fosters a cultural loss of memory that extends beyond the problem so easy to identify in our students: a lack of a sense of history. The assumption is that, in light of this national tragedy, the words speak for themselves. Initially, of course, they did. But without reflection, without context, without memory, the further we are removed from the event itself, the more these words become a passive observation of what we know, what we have always known to be true: when tragedy happens, we are forever altered. Most of the changes that come to mind when we hear this phrase have to do with a sobering of spirit-certainly with interruptions to our way of life-regarding the assumptions that we make about travel, and about trust. The question is how do we reflect on and learn from September 11 in a way that will allow us to fundamentally redirect how we live, think, and teach? Can we begin to imagine a response, a change so powerful that each and every social institution is permeated with new courage? The courage to look into the suffering we have met as well as that which we ourselves inflict-not only as a nation, but as a member of this race of human beings, fraught as we are with our prejudices, our fanatacisms, our fear, our greed? How do we begin to actualize and make visible the deeper changes that I believe Kierkegaard is referring to, changes born out of our conscious commitment to the never again that we so bravely hold to in the aftermath of grief? The truth is, the world is always different when violence of unprecedented magnitude is wrought. Did the world not change after Auschwitz, Hiroshima, and Vietnam? Was this nation not permanently altered after the assassinations of our presidents, of our political and social leaders? Is it enough to say the world has changed-we have changed-without wanting to know what, if anything, sets one tragedy apart from the suffering of countless numbers throughout history? What, beyond the personal experience of it, makes it ours? I do not mean to suggest that there is nothing unique about what happened with September 11, nor to diminish the personal loss and meaning of each life, of each family, of this country. But when, as an educator, I bemoan the lack of historical memory of my students, I must ask, where is our memory as a society, as a culture? Where is the evidence that we have made fundamental changes to our social-particularly our educational - institutions as a result of any of these tragic events of history? Now, three years since the attacks on the World Trade Center, I wonder: What has changed for our students, for us? Beyond our reactions, which include heightened vigilance, renewed patriotic fervor, a rush to engage our students in civic responsibility, a terrifying kind of knowing that anything can happen, even here in the United States-beyond all of this, what has changed substantively in the choices we make, the politics we play, the truths we teach? It is interesting that when things go wrong, we turn to our educational institutions to see what we can do differently, and well we should. We look to them too because we know that how we educate today will determine who we will become tomorrow. We look to our schools because we understand that, counter to the view that education is about facts, objective truths of knowledge, and better jobs, our schools are always fundamentally about values, about what is important to know and to become as human beings. Far from the myth of objective facts, we know that our curriculum is very much a value-informed and political issue. …

Faulting and effects of earthquakes on Minoan archaeological sites in Crete (Greece)

Examination of damages affecting the buildings of the archaeological sites of Phaistos and Agia Triada (southern Crete) suggests that these Minoan settlements were probably destroyed by two major seismic events characterized by MKS intensities of IX–X and occurred at the end of the Protopalatial (1700 BC) and the Neopalatial (1450 BC) periods. Geological and morphological studies carried out in the neighbouring areas show the occurrence of E–W trending Quaternary normal fault segments (Spili and Agia Galini faults) that control the present topography and morphology, and exhibit steep young scarps mostly Holocene in age. These fault segments are related to a NW–SE extension direction, which is consistent with that indicated by the available focal mechanisms of the earthquakes occurring in this area in the last 50 years. Combining structural and seismic data we can infer that the Spili and Agia Galini fault segments could represent good candidates to be considered active faults generating large earthquakes ( M≅6.5) that were responsible for the damages of Phaistos and Agia Triada. This hypothesis suggests that the Minoan palatial centres were destroyed by several large earthquakes related to ruptures along distinct fault segments rather than by a single catastrophic event that caused the abrupt destruction of the Minoan civilisation in the eastern Mediterranean.

Institutions and the precautionary principle: the case of mad cow disease

In the presence of scientific uncertainty, many actions may end up in a catastrophic event. Many argue that in such cases the precautionary principle should be adopted. Unfortunately this principle is not clear cut. The main purpose of this paper is to set up a model, which allows establishing the determinants and consequently the level of the precautionary acceptable cost. The model allows treating in a single framework ambiguity, catastrophic events, and agency problem. The acceptable cost will be essentially determined as the amount of transfers or subsidy that the public body should direct to the agents in order to elicit the level of effort that, on the basis of the principal's most pessimistic forecasts, has the higher chances of maximizing the principal welfare and preventing the catastrophic event. The model refers to the bovine spongiform encephalopathy(BSE or mad cow disease, ModCo Dist) epidemic but it could be easily applied to other situations in which Knightian uncertainty (ambiguity) makes catastrophic events quite likely.

Institutions and the Precautionary Principle: The Case of Mad Cow Disease

In the presence of scientific uncertainty many actions may end up in a catastrophic event. Many argue that in such cases the precautionary principle should be adopted. Unfortunately this principle is not clear-cut. The main purpose of this paper is to set up a model, which allows establishing the determinants and consequently the level of the precautionary acceptable cost. The model allows treating in a single framework ambiguity, catastrophic events and agency problem. The acceptable cost will be essentially determined as the amount of transfers or subsidy that the public body should direct to the agents in order to elicit the level of effort which - on the basis of the principalis most pessimistic forecasts - has the higher chances of maximizing the principal welfare and preventing the catastrophic event. The model refers to the BSE epidemic but it could be easily applied to other situations in which Knightian uncertainty (ambiguity) makes catastrophic events quite likely.

Pole tip recession and staining at the head to tape interface of linear tape recording systems

The tribology of the head to tape interface (HTI) of two linear tape recording systems, Travan™ NS20 and OnStream ADR™ are studied from the viewpoint of pole tip recession (PTR) and stain transferred from the tape. Heads tested in humid conditions (60% RH) show the highest PTR increase with deep and wide grooves forming on the pole surface, presumably ploughed by large fragments pulled out from the ceramic in a single catastrophic event. Smaller pullouts are likely to sediment within the recessed poles and increase the PTR acting as three-body abrasive particles. Both the recession of the TiC phase in respect to the Al 2O 3 phase over the Al 2O 3–TiC ceramic used as tape bearing surface (TBS) and the detection of Ti over the pole tip area by Auger electron spectroscopy (AES) identify the pullouts as being TiC fragments. XPS analysis shows a partial oxidation of the TiC phase, however, too superficial to account for the TiC pullout. Stain is detected on the heads either as discrete or restrained deposits (at high humidity) or as a continuous film, forming preferentially over the pole tip surface. The transfer films arises from the recessed pole edge at low humidity (10% RH) and centre at higher humidity (>35% RH), then gradually covers the remaining pole surface within 100 h in both cases. Finally, a preferential transfer is observed over the pole tip area and the TiC phase of the TBS surface, and may relate to their metal-like nature, as opposed to the insulating nature of the other materials.

Inherited neurodegenerative diseases: the one-hit model of neurodegeneration.

The clinical manifestations of inherited neurodegenerative diseases are often delayed for periods from years to decades. This observation has led to the idea that, in these disorders, neurons die from cumulative damage. A critical prediction of the cumulative damage hypothesis is that the probability of neuronal death increases with age. However, we recently demonstrated, in 17 examples of neurodegeneration, that the kinetics of neuronal death appear to be exponential. These examples include both monogenic disorders, such as photoreceptor degenerations, as well as others that are partly or entirely acquired (such as the clinical phase of parkinsonism and retinal detachment). Exponential kinetics indicate that (i) the risk of death is constant, (ii) death occurs randomly in time and (iii) the death of each neuron is independent of other neurons. We use the term 'one-hit model' to refer to the single catastrophic intracellular biochemical event, analogous to radioactive decay, which leads to neuronal death in the diseases we analyzed. Here, we examine the major features and implications of the one-hit model and provide preliminary evidence that amyotrophic lateral sclerosis also appears to fit this model. We also discuss a testable biochemical hypothesis, the mutant steady-state hypothesis, that we proposed to account for the one-hit model. Finally, we explore six unresolved issues that appear to challenge this model. The one-hit model appears to capture a novel principle underlying many neurodegenerations. Our findings suggest that any consideration of the biochemical basis of neurodegeneration must include a meticulous examination of the kinetics of cell death.

Boulders transport by catastrophic waves along the Ionian coast of Apulia (southern Italy)

Several tracts of the Ionian coast of Apulia (southern Italy) are characterized by large boulders, up to 80 t in weight, scattered some meters above present sea level. The largest boulder is about 80 t in weight and slid for about 40 m from the mean sea level up to about 1.8 m of altitude. Elongated boulders show a remarkably narrow range of orientation of the long axis as well as of the imbrication axis, suggesting that they had been transported by a single catastrophic event, most likely a tsunami, connected to a wave train approaching the coast from the South. Stratigraphic, morphological and historical data suggest that this event occurred during the late Holocene. Conventional radiocarbon age determination performed on Lithophag shells collected from a large boulder yielded a calibrated age between 1421 and 1568 A.D. Then, the catastrophic wave train, probably a tsunami, could be a local effect of the strong earthquake which hit southern Italy on December 5th, 1456.

Taphonomy of a Petrified Forest in the Two Medicine Formation (Campanian), Northwest Montana: Implications for Palinspastic Restoration of the Boulder Batholith and Elkhorn Mountains Volcanics

Abstract The taphonomy of a newly discovered petrified forest in the Two Medicine Formation, south of Choteau, Montana, provides new constraints on the pre-thrusting position of the Boulder batholith and Elkhorn Mountains Volcanics. The petrified forest consists of more than 200 charcoalified, subaligned trees encased in an ash flow tuff and an immediately overlying bentonite. The ash flow tuff has been dated at 80.002± 0.114Ma (39Ar/40Ar on plagioclase). The ash flow and bentonite are interpreted to record a single catastrophic eruptive event that toppled and entombed the forest. The mean azimuth of the prostrate trunks, which are interpreted as the direction of travel of the ash flow, is 037° (2σ = 35°). Based upon age, mineralogy, and the absence of other contemporaneous volcanic centers, it is concluded that the Late Cretaceous Elkhorn Mountains Volcanics were the most likely source of the tuff and bentonite that encase the trees. The mean azimuth of the tree trunks is consistent with palinspastic res...

Threatened Fishes of the World: Gymnocharacinus bergi Steindachner, 1903 (Characidae)

Common names: Mojarra desnuda, mojarra bronceada (spanish), naked characin (E). Conservation status: ‘Endangered’, Red Data Book (IUCN 1996). Identification: Robust and small characin (up to 100 mm TL) that belongs to a monotypic subfamily Gymnocharacininae. The fin rays are D 12, A 19, the caudal fin (P14-M1-R17(9/8)M1-P12) is forked with rounded lobes and lacks the adipose fin. The mouth is terminal with a slight superior prognatism. In adults, the lips do not cover the external series of pentacuspidal teeth. Each premaxillae and dentaries bear two rows of teeth. The maxillae bear two pentacuspidal teeth. The continuous lateral line is straight. Juveniles between 33–36.3 mm TL begin to reabsorb the scales and adults greater than 50 mm TL only show scales on the lateral line and posterior to the opercula. The colour is dark brown, greenish, the belly is creamish and present a band copper-coloured on the flanks, beneath the lateral line. The opercular zone shows golden reflections (Ringuelet et al. 1967, Miquelarena & Aramburu 1983, Ortubay 1998). Drawing by Ortubay (1998). Distribution: Endemic to the Somuncura Plateau at the NE of Argentinean Patagonia, restricted to the thermal headwaters of the two branches, ‘Frio’ and ‘Caliente’, of the Valcheta Stream (500–900 m altitude), an endorheic system of 100 km which disappears in the patagonian esteppe (Luling 1978). Abundance: Fish are scarce at the Frio branch and abundant at the Caliente branch (Ortubay 1998). Habitat and ecology: water temperature has a range of 21.5–26◦C. Ortubay (1998) summarises water chemistry and habitat description. Gymnocharacinus bergi has gregarian habits. Larvae feed on ostracods, chironomid larvae and acari. Juveniles and adults, with a grinding feeding apparatus, feed on periphitic algae. Reproduction: Maturity is reached at 37 mm TL in males and 38 mm TL in females, the breeding season occurs during later winter and early spring (August–October). Females present up to 200 oocytes (1.4-mm diameter) rich in yolk. Threats: In 1941, Oncorhynchus mykiss and Salvelinus fontinalis were introduced in the stream; in the colder Frio branch headwater, O. mykiss preys upon G. bergi and in winter months trout ascend the Caliente branch (Ortubay 1998). Nevertheless, the thermal barrier protects G. bergi at the warmer headwaters of Valcheta Stream. There, the mayor problems are the goat and cattle, pollution and catches for illegal sale of this species to collectors. The Frio branch is easily accessible by road. A single catastrophic event could eliminate the entire subfamily. Conservation actions: The Somuncura Plateau, of 15 000 km, was declared a Reserve Area in 1986 because of the presence of numerous endemics. Up to date, the limits are not established and there is no effective protection. In 1994, G. bergi was declared Natural Monument and catalogued as ‘Endangered’ (IUCN 1996). Conservation recommendations: Resettle two humans from the Caliente branch, educate the local people from the Frio branch, control the use of waters for cultivation and bathing, eradicate the salmonids from the headwaters, and construct a definitive barrier at the confluence of the two branches where the temperatures are extreme and out of the thermal tolerance for G. bergi (Ortubay et al. 1997, Ortubay 1998).

Stratified granular media beneath large slide blocks: Implications for mode of emplacement

Research Article| November 01, 2000 Stratified granular media beneath large slide blocks: Implications for mode of emplacement Mark H. Anders; Mark H. Anders 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar Einat Aharonov; Einat Aharonov 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar John J. Walsh John J. Walsh 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (11): 971–974. https://doi.org/10.1130/0091-7613(2000)28<971:SGMBLS>2.0.CO;2 Article history received: 19 May 2000 rev-recd: 01 Aug 2000 accepted: 07 Aug 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark H. Anders, Einat Aharonov, John J. Walsh; Stratified granular media beneath large slide blocks: Implications for mode of emplacement. Geology 2000;; 28 (11): 971–974. doi: https://doi.org/10.1130/0091-7613(2000)28<971:SGMBLS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We have examined the bottoms of many large slide blocks and found basal layers of well-rounded, fine- to coarse-grained, granular material that typically has the appearance of stratified, stream-deposited sandstone or conglomerate. Stratification is subparallel to the basal surface (detachment) and is typically inversely graded, although normal grading and banding of material are present in some samples. The sandstone-conglomerate–like material of the basal layer can be traced continuously from the detachment surface directly into the upper plate, where it is localized within clastic dikes. Although many of the physical characteristics of these basal layers appear to be those associated with water-laid stream deposits, there is no direct evidence of fluid involvement. We interpret the sandstone-conglomerate–like material in the basal layer to be produced by mechanical sieving in a high-energy fluidized environment under a rapidly moving rock mass during a single catastrophic emplacement event. These sandstone-conglomerate layers found along detachment surfaces may prove to be important in determining whether a detached block is simply a gravity slide or the upper-plate remnant of a low-angle normal fault associated with significant crustal extension. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Genetic variation within and among populations of the threatened lichen Lobaria pulmonaria in Switzerland and implications for its conservation.

The foliose epiphytic lichen Lobaria pulmonaria has suffered a significant decline in European lowlands during the last decades and therefore is considered as endangered throughout Europe. An assessment of the genetic variability is necessary to formulate biologically sound conservation recommendations for this species. We investigated the genetic diversity of the fungal symbiont of L. pulmonaria using 143 specimens sampled from six populations (two small, one medium, three large) in the lowland, the Jura Mountains, the pre-Alps and the Alps of Switzerland. Among all nuclear and mitochondrial regions sequenced for this study, variability was found only in the internal transcribed spacer (ITS I), with three polymorphic sites, and in the nuclear ribosomal large subunit (nrLSU), with four polymorphic sites. The variable sites in the nrLSU are all located within a putative spliceosomal intron. We sequenced these two regions for 81 specimens and detected six genotypes. Two genotypes were common, two were found only in the more diverse populations and two were found only in one population each. There was no correlation between population size and genetic diversity. The highest genetic diversity was found in populations where the fungal symbiont is reproducing sexually. Populations with low genetic diversity included only the two same common genotypes. Our study provides evidence suggesting that L. pulmonaria is self-incompatible and heterothallic. Based on our results we give populations with sexually reproducing individuals a higher rank in terms of conservation priority than strictly asexual populations. The remaining lowland populations are so small, that one single catastrophic event such as a windthrow might destroy the entire population. Hence we suggest augmenting such populations in size and genetic diversity using small thallus fragments or vegetative diaspores collected in other populations. As we did not detect any locally adapted genotypes, these transplants can be taken from any other genetically diverse population in Switzerland.

Kurtosis as a Metric in the Assessment of Gear Damage

Gear diagnostics is becoming an important area of research, especially in critical applications such as rotorcraft propulsion where safety is paramount. Many rotorcraft statistics illustrate the need for dedicated monitoring systems to reliably diagnose the faults. A gear system fails when it ceases to efficiently perform the function for which it was designed. This can be the result of a single catastrophic event or an accumulation of initially undetected and rather innocuous events in the gear system. It is well known that evaluation of statistical properties will give reasonable diagnostic indication of gear damage. Although there are a large number of such statistical attributes such as root mean square value, crest factor, skewness, kurtosis, and so on, kurtosis has emerged as a single number metric and one of the good indicators of damage of gears. Kurtosis can be estimated in both the time domain and the frequency domain. This paper discusses various variants of the kurtosis parameter such as FM4, NA4, NA4 * , NB4, and NB4 * , as well as their relative importance. The ability to use kurtosis beta distribution to detect toothwise gear faults is also discussed.

Early evolution of the Earth and Moon: new constraints from Hf-W isotope geochemistry

The W isotopic composition of the bulk silicate Earth (BSE) is chondritic within current analytical uncertainties, indicating that terrestrial core formation commenced more than 50 Myr after the differentiation of the earliest planetesimals in the solar system. This is consistent with U Pb data and holds true whether core formation is modelled as a single catastrophic event or as a continuous process that started late, unless accretion was more than about twice as slow as recently estimated. The chondritic W isotopic composition of the BSE provides support for the assumption that the overall lithophile/siderophile refractory element ratio of the Earth is close to chondritic, but requires mixing to remove early heterogeneities introduced by the accretion of any planetesimals already segregated into silicate and metallic portions with distinct W isotopic compositions. The same applies to any later accreted material, such as the putative Moon-forming giant impactor. Many models of terrestrial accretion and core formation involve a core that developed during the first 90% of accretion history, generally considered to correspond to a time span significantly shorter than that permitted by the W isotopic data. These models are difficult to reconcile with the W isotopic data unless the proto-Earth was re-homogenized by a major impactor, or accretion took longer than currently estimated. The W isotopic compositions of early lunar rocks provide the best hope of determining which model of accretion and core formation is correct for the Earth. A conservative assessment of isotopic ages for lunar highlands rocks, combined with the constraints from W isotopic data, indicate that the onset of major terrestrial core segregation, the formation of the Moon and the development of a lunar magma ocean all took place within < 80 Myr at 4.47 ± 0.04 Ga. Certain isotopic ages for lunar rocks would be consistent with a more restricted time window of 4.50 ± 0.01 Ga. Potassium and Cr isotopic data indicate early volatile depletion of the material from which the Earth and Moon formed and constrain models of pre-core Pb isotopic evolution. The various estimates for the Pb isotopic composition of the BSE seem best explained by strong U/Pb fractionation accompanying terrestrial core formation. Using the 4.47 ± 0.04 Ga age of the core, the second stage Pb isotopic evolution reproduces reasonable estimates for the present day BSE Pb isotopic composition if the second stage 238U 204Pb (μ) is in the range of 8.9 ± 0.5. The ‘lead paradox’ is entirely predictable from the 4.47 ± 0.04 Ga age of the core. The similarities between the late ages of the Earth's core, the Moon and the degassing of Xe from the terrestrial mantle are consistent with an accretion history which is more protracted than currently modelled. Alternatively, late impacts may have triggered all of these events. If a single late impact is invoked as an explanation, the Moon must have been derived primarily from the silicate portion of the impactor. Otherwise, the Hf-W data may define the age of a core that formed as a result of another impact, shortly prior to that which formed the Moon.

Dependence of the spectral evolution of γ-ray bursts on their photon fluence

THE nature of γ-ray bursts remains one of the great mysteries of modern astronomy1,2. Although the spatial distribution of these high-energy sources is tightly constrained (they are distributed isotropically across the sky3), the same cannot be said of their spectral and temporal properties, for which few clear trends have been identified1,2. But it is from such properties that important clues about the physical mechanisms underlying the bursts are likely to be derived4,5. Here we show that for a sample of bursts consisting of well resolved, isolated energy pulses, and for which the spectra are sufficiently clean to allow their temporal evolution to be modelled, the photon energy at which the power output is maximum for each pulse decreases exponentially with photon fluence (that is, running time integral of photon flux). We find that for many multi-pulse bursts, the exponential decay constant is invariant from pulse to pulse. This property favours models in which the pulses arise from a regenerative source, rather than as a consequence of a single catastrophic event.