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Sample records for extinction spontaneous recovery

  1. Extinction and spontaneous recovery of spatial behavior in pigeons.

    Science.gov (United States)

    Leising, Kenneth J; Wong, Jared; Blaisdell, Aaron P

    2015-10-01

    We investigated extinction and spontaneous recovery of spatial associations using a landmark-based appetitive search task in a touchscreen preparation with pigeons. Four visual landmarks (A, B, C, and D) were separately established as signals of a hidden reinforced target among an 8 × 7 array of potential target locations. The target was located above landmarks (LM) A and C and below B and D. After conditioning, A and B were extinguished. Responding to A and C was assessed on probe tests 2 days following extinction, whereas, B and D were tested 14 days after extinction. We observed spontaneous recovery from spatial extinction following a 14-day, but not a 2-day, postextinction retention interval. Furthermore, by plotting the spatial distribution of responding across the X and Y axes during testing, we found that spontaneous recovery of responding to the target in our task was due to enhanced spatial control (i.e., a change in the overall distribution of responses) following the long delay to testing. These results add spatial extinction and spontaneous recovery to the list of findings supporting the assertion that extinction involves new learning that attenuates the originally acquired response, and that original learning of the spatial relationship between paired events survives extinction. (PsycINFO Database Record

  2. Spontaneous recovery from extinction in the infant rat.

    Science.gov (United States)

    Revillo, D A; Paglini, M G; Arias, C

    2014-11-01

    Within the Pavlovian conditioning framework, extinction is a procedure in which, after conditioning, the conditioned stimulus (CS) is repeatedly presented without the unconditioned stimulus (US). During this procedure the conditioned response (CR) is gradually attenuated. It has been suggested that extinction during the early stages of ontogeny is a qualitatively different process from extinction in adulthood: during infancy, extinction may result in erasure of the memory, while during adulthood extinction involves new learning. This conclusion was supported by studies showing that renewal, reinstatement or spontaneous recovery procedures were not effective during infancy for recovering the CR once it had been extinguished. These studies used the freezing response as the only behavioral index, although some recent evidence indicates that the absence of freezing after conditioning or after extinction does not necessarily imply a deficit in memory, and that other behavioral indexes may be more sensitive to detecting conditioning effects. The goal of the present study was to analyze extinction in preweanling rats by examining the possibility of the spontaneous recovery of a conditioned fear response, measured through a different set of mutually-exclusive behaviors that constitute an exhaustive ethogram, and including control groups (Experiment 1: US-Only and CS-Only; Experiment 2: US-Only, CS-Only and Unpaired) in order to examine whether non-associative learning may explain quantitative or qualitative changes in the frequency of specific responses during extinction or recovery. Extinction produced changes in the expression of freezing, grooming and exploration, and the clearest evidence of spontaneous recovery came from the analysis of freezing behavior. The pattern of behavior observed during extinction is compatible with theoretical approaches which consider different dynamic behavioral systems, and it also fit in well with a molar approach to the analysis of

  3. Compound Stimulus Extinction Reduces Spontaneous Recovery in Humans

    Science.gov (United States)

    Coelho, Cesar A. O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately…

  4. Compound stimulus extinction reduces spontaneous recovery in humans

    Science.gov (United States)

    Coelho, Cesar A.O.; Dunsmoor, Joseph E.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design (“deepened extinction”) shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and nonextinguished CSB. Recovery of conditioned skin conductance responses to CSA was reduced 24 h after compound extinction, as compared with a group who received an equal number of extinction trials to the CSA alone. PMID:26572649

  5. Compound stimulus extinction reduces spontaneous recovery in humans

    OpenAIRE

    Coelho, Cesar A.O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design (“deepened extinction”) shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and nonextinguished CSB. Reco...

  6. Inhibition of Spontaneous Recovery of Fear by mGluR5 after Prolonged Extinction Training

    OpenAIRE

    Sheng-Chun Mao; Chih-Hua Chang; Chia-Chen Wu; M. Juliana Orejarena; Manzoni, Olivier J.; Po-Wu Gean

    2013-01-01

    Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged e...

  7. Inhibition of Spontaneous Recovery of Fear by mGluR5 after Prolonged Extinction Training

    OpenAIRE

    Sheng-Chun Mao; Chih-Hua Chang; Chia-Chen Wu; M Juliana Orejarena; Manzoni, Olivier J.; Po-Wu Gean

    2013-01-01

    Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged e...

  8. Inhibition of spontaneous recovery of fear by mGluR5 after prolonged extinction training.

    Directory of Open Access Journals (Sweden)

    Sheng-Chun Mao

    Full Text Available Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged extinction training causes greater reduction in both fear-potentiated startle and spontaneous recovery. This effect was specifically blocked by metabotropic glutamate receptor 5 (mGluR5, but not by mGluR1 antagonists and by a protein synthesis inhibitor. Similar inhibition of memory recovery following prolonged extinction training was also observed in mice. In agreement with the instrumental role of mGluR5 in the prolonged inhibition of fear recovery, we found that FMR1-/- mice which exhibit enhanced mGluR5-mediated signaling exhibit lower spontaneous recovery of fear after extinction training than wild-type littermates. At the molecular level, we discovered that prolonged extinction training reversed the fear conditioning-induced increase in surface expression of GluR1, AMPA/NMDA ratio, postsynaptic density-95 (PSD-95 and synapse-associated protein-97 (SAP97. Accordingly, delivery of Tat-GluR2(3Y, a synthetic peptide that blocks AMPA receptor endocytosis, inhibited prolonged extinction training-induced inhibition of fear recovery. Together, our results demonstrate that prolonged extinction training results in the mGluR5-dependent long-term inhibition of fear recovery. This effect may involve the degradation of original memory and may explain the beneficial effects of prolonged exposure therapy for the treatment of phobias.

  9. Inhibition of spontaneous recovery of fear by mGluR5 after prolonged extinction training.

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    Mao, Sheng-Chun; Chang, Chih-Hua; Wu, Chia-Chen; Orejarena, M Juliana; Orejanera, Maria Juliana; Manzoni, Olivier J; Gean, Po-Wu

    2013-01-01

    Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged extinction training causes greater reduction in both fear-potentiated startle and spontaneous recovery. This effect was specifically blocked by metabotropic glutamate receptor 5 (mGluR5), but not by mGluR1 antagonists and by a protein synthesis inhibitor. Similar inhibition of memory recovery following prolonged extinction training was also observed in mice. In agreement with the instrumental role of mGluR5 in the prolonged inhibition of fear recovery, we found that FMR1-/- mice which exhibit enhanced mGluR5-mediated signaling exhibit lower spontaneous recovery of fear after extinction training than wild-type littermates. At the molecular level, we discovered that prolonged extinction training reversed the fear conditioning-induced increase in surface expression of GluR1, AMPA/NMDA ratio, postsynaptic density-95 (PSD-95) and synapse-associated protein-97 (SAP97). Accordingly, delivery of Tat-GluR2(3Y), a synthetic peptide that blocks AMPA receptor endocytosis, inhibited prolonged extinction training-induced inhibition of fear recovery. Together, our results demonstrate that prolonged extinction training results in the mGluR5-dependent long-term inhibition of fear recovery. This effect may involve the degradation of original memory and may explain the beneficial effects of prolonged exposure therapy for the treatment of phobias.

  10. Reducing spontaneous recovery and reinstatement of operant performance through extinction-cues.

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    Bernal-Gamboa, Rodolfo; Gámez, A Matías; Nieto, Javier

    2017-02-01

    It has been argued that the response recovery effects share a common mechanism. A possible way to test it is evaluating whether the techniques that impaired renewal would impair the other recovery effects as well. Two experiments with rats used a free operant procedure to explore whether an extinction-cue could prevent the spontaneous recovery and reinstatement of an extinguished lever-pressing. Both experiments consisted of four phases: Acquisition, Extinction and Test 1 and Test 2. First, all rats were trained to perform one instrumental response (R1) for food in context A, and a different instrumental response (R2) for food in context B. Then, responses were extinguished within the same context: R1 in context A and R2 in context B. Throughout this phase all rats received brief presentations of a tone (extinction-cue). In both experiments animals were tested twice. The first test was conducted immediately after the last extinction session. In this test, rats received the extinction-cue for both responses. During the second test, rats experienced the tone only for R1. In Experiment 1 rats were tested after 5days, while for Experiment 2 test 2 took place after a single session of re-exposure to the food. Both experiments showed a recovery effect (spontaneous recovery in Experiment 1 and reinstatement in Experiment 2) for both responses. However, a cue featured in extinction attenuated recovery of R1 in both experiments when presented on the test. The findings suggest that spontaneous recovery, reinstatement and renewal might share a common mechanism. In addition, the present data shows that using an extinction-cue could help to reduces relapsing of voluntary behaviors.

  11. Spontaneous Recovery

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    Rescorla, Robert A.

    2004-01-01

    Spontaneous recovery from extinction is one of the most basic phenomena of Pavlovian conditioning. Although it can be studied by using a variety of designs, some procedures are better than others for identifying the involvement of underlying learning processes. A wide range of different learning mechanisms has been suggested as being engaged by…

  12. Extinction, Spontaneous Recovery and Renewal of Flavor Preferences Based on Taste-Taste Learning

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    Diaz, Estrella; De la Casa, L. G.

    2011-01-01

    This paper presents evidence of extinction, spontaneous recovery and renewal in a conditioned preferences paradigm based on taste-taste associations. More specifically, in three experiments rats exposed to a simultaneous compound of citric acid-saccharin solution showed a preference for the citric solution when the preference was measured with a…

  13. Extinction, Spontaneous Recovery and Renewal of Flavor Preferences Based on Taste-Taste Learning

    Science.gov (United States)

    Diaz, Estrella; De la Casa, L. G.

    2011-01-01

    This paper presents evidence of extinction, spontaneous recovery and renewal in a conditioned preferences paradigm based on taste-taste associations. More specifically, in three experiments rats exposed to a simultaneous compound of citric acid-saccharin solution showed a preference for the citric solution when the preference was measured with a…

  14. Acute, but not chronic, exposure to d-cycloserine facilitates extinction and modulates spontaneous recovery of a conditioned taste aversion.

    Science.gov (United States)

    Mickley, G Andrew; Remus, Jennifer L; Ramos, Linnet; Wilson, Gina N; Biesan, Orion R; Ketchesin, Kyle D

    2012-01-18

    D-cycloserine, the glutamate N-methyl-D-aspartate receptor partial agonist, has been reported to facilitate the extinction of learned fears acquired in both naturalistic and laboratory settings. The current study extended this literature by evaluating the ability of either chronic or acute administrations of DCS to modulate the extinction and spontaneous recovery of a conditioned taste aversion (CTA). Twenty-three hour fluid-deprived Sprague-Dawley rats acquired a strong CTA following 3 pairings of a conditioned stimulus (CS; 0.3% oral saccharin)+unconditioned stimulus [US; 81 mg/kg (i.p.) lithium chloride (LiCl)]. In separate groups of rats, we then employed 2 different extinction paradigms: (1) CS-only (CSO-EXT) in which saccharin was presented every-other day, or (2) Explicitly Unpaired (EU-EXT) in which both saccharin and LiCl were presented but on alternate days. Previous studies have indicated that the EU-EXT procedure speeds up the extinction process. Further, spontaneous recovery of a CTA emerges following CSO-EXT but the EU-EXT paradigm causes a suppression of spontaneous recovery. DCS (15 mg/kg, i.p.) was administered immediately after daily liquid presentations (saccharin or water, alternate days) during the extinction period. In an acute drug manipulation, DCS (15 mg/kg, i.p.) or saline control injections were administered for 4 days only. This was done during one of 3 different phases of extinction [i.e., static (2-5%), early dynamic (8-16%), or middle dynamic (20-40%) saccharin reacceptance]. Other animals assigned to the chronic DCS condition received daily DCS (15 mg/kg, i.p.) throughout extinction. Changes in saccharin drinking in these animals were compared to the data from rats that received no drug (saline controls). Once rats met our criterion for asymptotic extinction (90% reacceptance of the CS) they entered a 30-day latency period during which they received water for 1 h/day. The day after the completion of the latency period, a final

  15. Spontaneous Recovery of Previously Extinguished Behavior as an Alternative Explanation for Extinction-Related Side Effects

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    Waller, Raymond J.; Mays, Nicole M.

    2007-01-01

    Extinction is accepted as a viable intervention for behaviors that are hypothesized to be maintained by contingent attentional reinforcement. However, it is frequently acknowledged that extinction has potential numerous side effects, including the generation of aggressive behavior. This explanation does not provide a behavioral conceptualization…

  16. Spontaneous recovery from acalculia.

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    Basso, Anna; Caporali, Alessandra; Faglioni, Pietro

    2005-01-01

    A topic much considered in research on acalculia was its relationship with aphasia. Far less attention has been given to the natural course of acalculia. In this retrospective study, we examined the relationship between aphasia and acalculia in an unselected series of 98 left-brain-damaged patients and the spontaneous recovery from acalculia in 92 acalculic patients with follow-up. There was a significant association between aphasia and acalculia although 19 participants exhibited aphasia with no acalculia and six acalculia with no aphasia. We observed significant improvement between a first examination carried out between 1 and 5 months post-onset and a second examination carried out between 3 and 11 months later (mean: 5 months). The mechanisms of spontaneous recovery are discussed.

  17. Explicit Disassociation of a Conditioned Stimulus and Unconditioned Stimulus during Extinction Training Reduces Both Time to Asymptotic Extinction and Spontaneous Recovery of a Conditioned Taste Aversion

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    Mickley, G. Andrew; DiSorbo, Anthony; Wilson, Gina N.; Huffman, Jennifer; Bacik, Stephanie; Hoxha, Zana; Biada, Jaclyn M.; Kim, Ye-Hyun

    2009-01-01

    Conditioned taste aversions (CTAs) may be acquired when an animal consumes a novel taste (CS) and then experiences the symptoms of poisoning (US). This aversion may be extinguished by repeated exposure to the CS alone. However, following a latency period in which the CS is not presented, the CTA will spontaneously recover (SR). In the current…

  18. Spontaneous recovery in dynamical networks

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    Majdandzic, Antonio; Podobnik, Boris; Buldyrev, Sergey V.; Kenett, Dror Y.; Havlin, Shlomo; Eugene Stanley, H.

    2014-01-01

    Much research has been carried out to explore the structural properties and vulnerability of complex networks. Of particular interest are abrupt dynamic events that cause networks to irreversibly fail. However, in many real-world phenomena, such as brain seizures in neuroscience or sudden market crashes in finance, after an inactive period of time a significant part of the damaged network is capable of spontaneously becoming active again. The process often occurs repeatedly. To model this marked network recovery, we examine the effect of local node recoveries and stochastic contiguous spreading, and find that they can lead to the spontaneous emergence of macroscopic `phase-flipping' phenomena. As the network is of finite size and is stochastic, the fraction of active nodes z switches back and forth between the two network collective modes characterized by high network activity and low network activity. Furthermore, the system exhibits a strong hysteresis behaviour analogous to phase transitions near a critical point. We present real-world network data exhibiting phase switching behaviour in accord with the predictions of the model.

  19. Temporal Dynamics of Recovery from Extinction Shortly after Extinction Acquisition

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    Archbold, Georgina E.; Dobbek, Nick; Nader, Karim

    2013-01-01

    Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition…

  20. Renewal and spontaneous recovery, but not latent inhibition, are mediated by gamma-aminobutyric acid in appetitive conditioning.

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    Delamater, Andrew R; Campese, Vincent; Westbrook, R Frederick

    2009-04-01

    Previous research has reported a role for the neurotransmitter gamma-aminobutyric acid (GABA) in the extinction and renewal of conditioned fear. Here, the authors examine whether GABA is involved in the acquisition, extinction, renewal, spontaneous recovery, and latent inhibition of appetitive conditioning. Using Long-Evans rats, systemic injection of the GABA A receptor inverse agonist FG 7142 was shown to eliminate ABA renewal (Experiment 1) and spontaneous recovery (Experiment 4) of appetitive responding by selectively reducing the recovery of extinguished magazine approach. Furthermore, treatment with FG 7142 had no effects on acquisition or single-session extinction (Experiment 3) or on the context-specific expression of latent inhibition (Experiment 2). These data suggest that ABA renewal and spontaneous recovery, but not latent inhibition or responding during acquisition and an initial extinction session, are mediated by GABAergic mechanisms in appetitive Pavlovian conditioning. They provide support for the view that renewal and spontaneous recovery share a common psychological mechanism.

  1. Spontaneous Recovery of Consummatory Behavior, But Not of Consummatory Successive Negative Contrast

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    Norris, Jacob N.; Daniel, Alan M.; Papini, Mauricio R.

    2008-01-01

    Five experiments were designed to study spontaneous recovery (SR) in two situations involving consummatory behavior: consummatory successive negative contrast (cSNC) and consummatory extinction (cE). SR of consummatory suppression should occur if incentive downshift induces an egocentric memory encoding information about the emotional reaction to…

  2. Long-Term Maintenance of Immediate or Delayed Extinction Is Determined by the Extinction-Test Interval

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    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively…

  3. Long-term maintenance of immediate or delayed extinction is determined by the extinction-test interval

    OpenAIRE

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively long extinction-test interval was used; a relatively short extinction-test interval yielded the opposite result (Experiment 2). Previous data appear co...

  4. Recovery from the most profound mass extinction of all time.

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    Sahney, Sarda; Benton, Michael J

    2008-04-07

    The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.

  5. Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans

    NARCIS (Netherlands)

    Norrholm, S.D.; Vervliet, B.; Jovanovic, T.; Boshoven, W.; Myers, K.M.; Davis, M.; Rothbaum, B.O.; Duncan, E.J.

    2008-01-01

    Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occu

  6. Spontaneous Recovery But Not Reinstatement of the Extinguished Conditioned Eyeblink Response in the Rat

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    Thanellou, Alexandra; Green, John T.

    2011-01-01

    Reinstatement, the return of an extinguished conditioned response (CR) after reexposure to the unconditioned stimulus (US), and spontaneous recovery, the return of an extinguished CR with the passage of time, are two of four well-established phenomena which demonstrate that extinction does not erase the conditioned stimulus (CS)-US association. However, reinstatement of extinguished eyeblink CRs has never been demonstrated and spontaneous recovery of extinguished eyeblink CRs has not been systematically demonstrated in rodent eyeblink conditioning. In Experiment 1, US reexposure was administered 24 hours prior to a reinstatement test. In Experiment 2, US reexposure was administered 5 min prior to a reinstatement test. In Experiment 3, a long, discrete cue (a houselight), present in all phases of training and testing, served as a context within which each trial occurred to maximize context processing, which in other preparations has been shown to be required for reinstatement. In Experiment 4, an additional group was included that received footshock exposure, rather than US reexposure, between extinction and test, and contextual freezing was measured prior to test. Spontaneous recovery was robust in Experiments 3 and 4. In Experiment 4, context freezing was strong in a group given footshock exposure but not in a group given eyeshock US reexposure. There was no reinstatement observed in any experiment. With stimulus conditions that produce eyeblink conditioning and research designs that produce reinstatement in other forms of classical conditioning, we observed spontaneous recovery but not reinstatement of extinguished eyeblink CRs. This suggests that reinstatement, but not spontaneous recovery, is a preparation- or substrate-dependent phenomenon. PMID:21517145

  7. Memory Retrieval before or after Extinction Reduces Recovery of Fear in Adolescent Rats

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    Baker, Kathryn D.; McNally, Gavan P.; Richardson, Rick

    2013-01-01

    Adolescent rats exhibit impaired extinction retention compared to pre-adolescent and adult rats. A single nonreinforced exposure to the conditioned stimulus (CS; a retrieval trial) given shortly before extinction has been shown in some circumstances to reduce the recovery of fear after extinction in adult animals. This study investigated whether a…

  8. Memory Retrieval before or after Extinction Reduces Recovery of Fear in Adolescent Rats

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    Baker, Kathryn D.; McNally, Gavan P.; Richardson, Rick

    2013-01-01

    Adolescent rats exhibit impaired extinction retention compared to pre-adolescent and adult rats. A single nonreinforced exposure to the conditioned stimulus (CS; a retrieval trial) given shortly before extinction has been shown in some circumstances to reduce the recovery of fear after extinction in adult animals. This study investigated whether a…

  9. High Reported Spontaneous Stuttering Recovery Rates: Fact or Fiction?

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    Ramig, Peter R.

    1993-01-01

    Contact after 6 to 8 years with families of 21 children who were diagnosed as stuttering but did not receive fluency intervention services found that almost all subjects still had a stuttering problem. Results dispute the high spontaneous recovery rates reported in the literature and support the value of early intervention. (Author/DB)

  10. Early MR abnormality indicating functional recovery from spontaneous intracerebral hemorrhage

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    Fumeya, Hiroshi; Hideshima, Hiroshi (Hideshima Hospital, Musashino, Tokyo (Japan))

    1991-10-01

    Magnetic resonance (MR) imaging as an indicator of recovery from hemiparesis was evaluated in 60 patients with spontaneous intracerebral hemorrhage. T{sub 2}-weighted MR images revealed early MR abnormality (EMA) of the corticospinal tract within 1 week of ictus. Most patients without EMA recovered beyond Brunnstrom's Recovery Stage 3 while only a few patients with EMA did so. Patients with EMA cannot regain motor function because EMA is almost always followed by complete tract degeneration. EMA in the brainstem and poor motor function recovery are closely correlated. (author).

  11. Mercury anomalies and the timing of biotic recovery following the end-Triassic mass extinction.

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    Thibodeau, Alyson M; Ritterbush, Kathleen; Yager, Joyce A; West, A Joshua; Ibarra, Yadira; Bottjer, David J; Berelson, William M; Bergquist, Bridget A; Corsetti, Frank A

    2016-04-06

    The end-Triassic mass extinction overlapped with the eruption of the Central Atlantic Magmatic Province (CAMP), and release of CO2 and other volcanic volatiles has been implicated in the extinction. However, the timing of marine biotic recovery versus CAMP eruptions remains uncertain. Here we use Hg concentrations and isotopes as indicators of CAMP volcanism in continental shelf sediments, the primary archive of faunal data. In Triassic-Jurassic strata, Muller Canyon, Nevada, Hg levels rise in the extinction interval, peak before the appearance of the first Jurassic ammonite, remain above background in association with a depauperate fauna, and fall to pre-extinction levels during significant pelagic and benthic faunal recovery. Hg isotopes display no significant mass independent fractionation within the extinction and depauperate intervals, consistent with a volcanic origin for the Hg. The Hg and palaeontological evidence from the same archive indicate that significant biotic recovery did not begin until CAMP eruptions ceased.

  12. Increased spontaneous recovery with increases in conditioned stimulus alone exposures.

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    Leung, Hiu Tin; Westbrook, R Frederick

    2010-07-01

    A series of experiments used the compound test procedure (Rescorla, 2002) to measure the size of spontaneous recovery of freezing responses by rats to a latently inhibited and/or extinguished conditioned stimulus (CS). The size of recovery was greater: to a pre-exposed and conditioned CS than to a CS just conditioned or just pre-exposed; to an extensively pre-exposed or extinguished CS than to a moderately pre-exposed or extinguished CS; and to a pre-exposed and extinguished CS than to a CS just pre-exposed or just extinguished. These results show that the size of recovery is proportional to the size of the depression produced by CS-alone exposures regardless of whether they occurred before, after, or both before and after conditioning. The results are discussed in terms of some contemporary models of recovery and of the inferences permitted by the use of the compound assessment technique.

  13. Spontaneous recovery of effects of contrast adaptation without awareness

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    Gaoxing eMei

    2015-09-01

    Full Text Available Prolonged exposure to a high contrast stimulus reduces the neural sensitivity to subsequent similar patterns. Recent work has disclosed that contrast adaptation is controlled by multiple mechanisms operating over differing timescales. Adaptation to high contrast for a relatively longer period can be rapidly eliminated by adaptation to a lower contrast (or meanfield in the present study. Such rapid deadaptation presumably causes a short-term mechanism to signal for a sensitivity increase, cancelling ongoing signals from long-term mechanisms. Once deadaptation ends, the short-term mechanism rapidly returns to baseline, and the slowly decaying effects in the long-term mechanisms reemerge, allowing the perceptual aftereffects to recover during continued testing. Although this spontaneous recovery effect is considered strong evidence supporting the multiple mechanisms theory, it remains controversial whether the effect is mainly driven by visual memory established during the initial longer-term adaptation period. To resolve this debate, we used a modified Continuous Flash Suppression (CFS and visual crowding paradigms to render the adapting stimuli invisible, but still observed the spontaneous recovery phenomenon. These results exclude the possibility that spontaneous recovery found in the previous work was merely the consequence of explicit visual memory. Our findings also demonstrate that contrast adaptation, even at the unconscious processing levels, is controlled by multiple mechanisms.

  14. Spontaneous splenic rupture during the recovery phase of dengue fever.

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    de Silva, W T T; Gunasekera, M

    2015-07-02

    Spontaneous splenic rupture is a rare but known complication of dengue fever. Previously reported cases have occurred early during the course of the disease and most cases have led to a fatal outcome. Here we report a case of spontaneous splenic rupture in a patient with dengue fever, which occurred during the recovery phase of the illness. A 28-year-old Sinhalese, Sri Lankan man presented with a history of fever, myalgia and vomiting of 4 days duration. Investigations revealed a diagnosis of dengue fever with no signs of plasma leakage. He was managed in the ward as per local protocol. During the recovery phase the patient developed severe abdominal distention with circulatory failure. Radiology revealed splenic rupture with massive amounts of abdominal free fluid. The patient was resuscitated and Emergency laparotomy with splenectomy was performed. The outcome was excellent with the patient making a complete recovery. Although splenic rupture is a known complication of dengue fever it may be manifested late in the disease process. A high degree of suspicion should be maintained and patients must be monitored even during the recovery phase of dengue fever. Early diagnosis and intervention can prevent mortality.

  15. Self-change in eating disorders: is "spontaneous recovery" possible?

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    Vandereycken, Walter

    2012-01-01

    A limited series of community studies including non-treatment-seekers has shown that a considerable number of eating disorder patients do not enter the health care system but can be considered "clinically recovered" (remission of major symptoms) if followed up long enough. The possibility of "spontaneous recovery" (overcoming an eating disorder without professional treatment or formal help) often faces scepticism on the part of professionals. Clearly, self-change is an underestimated pathway to recovery from an eating disorder, but open-minded clinicians can learn a lot from it. Active coping and making use of one's "recovery capital" are key features of self-change even if maintenance of change is associated with social support and positive life changes.

  16. Subsequent biotic crises delayed marine recovery following the late Permian mass extinction event in northern Italy.

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    Foster, William J; Danise, Silvia; Price, Gregory D; Twitchett, Richard J

    2017-01-01

    The late Permian mass extinction event was the largest biotic crisis of the Phanerozoic and has the longest recovery interval of any extinction event. It has been hypothesised that subsequent carbon isotope perturbations during the Early Triassic are associated with biotic crises that impeded benthic recovery. We test this hypothesis by undertaking the highest-resolution study yet made of the rock and fossil records of the entire Werfen Formation, Italy. Here, we show that elevated extinction rates were recorded not only in the Dienerian, as previously recognised, but also around the Smithian/Spathian boundary. Functional richness increases across the Smithian/Spathian boundary associated with elevated origination rates in the lower Spathian. The taxonomic and functional composition of benthic faunas only recorded two significant changes: (1) reduced heterogeneity in the Dienerian, and (2) and a faunal turnover across the Smithian/Spathian boundary. The elevated extinctions and compositional shifts in the Dienerian and across the Smithian/Spathian boundary are associated with a negative and positive isotope excursion, respectively, which supports the hypothesis that subsequent biotic crises are associated with carbon isotope shifts. The Spathian fauna represents a more advanced ecological state, not recognised in the previous members of the Werfen Formation, with increased habitat differentiation, a shift in the dominant modes of life, appearance of stenohaline taxa and the occupation of the erect and infaunal tiers. In addition to subsequent biotic crises delaying the recovery, therefore, persistent environmental stress limited the ecological complexity of benthic recovery prior to the Spathian.

  17. Extinction of the Discriminative Stimulus Effects of Nicotine with a Devalued Reinforcer: Recovery Following Revaluation

    Science.gov (United States)

    Troisi, Joseph R., II; Bryant, Erin; Kane, Jennifer

    2012-01-01

    Extinction and recovery of the discriminative stimulus effects of nicotine (0.3 mg/kg) was investigated with a devalued food reinforcer (rats sated). Sixteen rats were trained in a counterbalanced one manipulandum (nose-poke) drug discrimination procedure with the roles of nicotine and saline counterbalanced as S[superscript D] and S[superscript…

  18. Behavior of lophophorates during the end-Permian mass extinction and recovery

    Science.gov (United States)

    Powers, Catherine M.; Bottjer, David J.

    2009-11-01

    The end-Permian mass extinction devastated most marine communities and the recovery was a protracted event lasting several million years into the Early Triassic. Environmental and biological processes undoubtedly controlled patterns of recovery for marine invertebrates in the aftermath of the extinction, but are often difficult to single-out. The global diversity and distribution of marine lophophorates during the aftermath of the end-Permian mass extinction indicates that stenolaemate bryozoans, rhynchonelliform brachiopods, and lingulid brachiopods displayed distinct recovery patterns. Bryozoans were the most susceptible of the lophophorates, experiencing relatively high rates of extinction at the end of the Permian, and becoming restricted to the Boreal region during the Early Triassic. The recovery of bryozoans was also delayed until the Late Triassic and characterized by very low diversity and abundance. Following the final disappearance of Permian rhynchonelliform brachiopod survivors, Early Triassic rhynchonelliform brachiopod abundance remained suppressed despite a successful re-diversification and a global distribution, suggesting a decoupling between global taxonomic and ecological processes likely driven by lingering environmental stress. In contrast with bryozoans and rhynchonelliforms, lingulid brachiopods rebounded rapidly, colonizing shallow marine settings left vacant by the extinction. Lingulid dominance, characterized by low diversity but high numerical abundance, was short-lived and they were once again displaced back into marginal settings as environmental stress changed through the marine recovery. The presence in lingulid brachiopods of the respiratory pigment hemerythrin, known to increase the efficacy of oxygen storage and transport, when coupled with other morphological and physiological adaptations, may have given lingulids a survival advantage in environmentally stressed Early Triassic settings.

  19. Biotic recovery from the Late Devonian F-F mass extinction event in China

    Institute of Scientific and Technical Information of China (English)

    廖卫华

    2002-01-01

    The Frasnian-Famennian (F-F) mass extinction is one of the five great extinctions of marine life during the Phanerozoic. The F-F event killed most of the Devonian reefs, the characteristic Devonian corals, stromatoporoids, bryozoans, nearly all tentaculites, a few superfamilies of brachiopods, such as Atrypacea and Pentameracea and some important elements of goniatites, such as Manticoceras.``The end-Frasnian was a phase of mass extinction. A large number of shelly benthos were killed by the F-F event. Early and middle Famennian was the survival interval. The marine faunas were very rare at that time. The late Famennian was the recovery interval. There appeared to have many new taxa in the Strunian stage. It lacked a radiation interval in Late Devonian Famennian because another event (the D-C mass extinction) happened at the Devonian-Carboniferous boundary.``Several causes for the F-F mass extinction have been proposed by some geologists, which have been grouped into two broad types, terrestrial and extraterrestrial. The former is related to sea level changes, climate changes and anoxic water event. The latter is linked with some forms of meteorite impact.``A large-scale eustatic change of sea level and black shales representing an anoxic environment has been invoked to explain one of the causes for the F-F mass extinction.``

  20. Large perturbations of the carbon cycle during recovery from the end-permian extinction.

    Science.gov (United States)

    Payne, Jonathan L; Lehrmann, Daniel J; Wei, Jiayong; Orchard, Michael J; Schrag, Daniel P; Knoll, Andrew H

    2004-07-23

    High-resolution carbon isotope measurements of multiple stratigraphic sections in south China demonstrate that the pronounced carbon isotopic excursion at the Permian-Triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the Early Triassic before ending abruptly early in the Middle Triassic. The unusual behavior of the carbon cycle coincides with the delayed recovery from end-Permian extinction recorded by fossils, suggesting a direct relationship between Earth system function and biological rediversification in the aftermath of Earth's most devastating mass extinction.

  1. Chief sources of brachiopod recovery from the end Ordovician mass extinction with special references to progenitors

    Institute of Scientific and Technical Information of China (English)

    戎嘉余; 詹仁斌

    1999-01-01

    Survivor, Lazarus and progenitor taxa are sources of biotic recovery following mass extinction. Investigations of the benthic brachiopods through the latest Ordovician mass extinction shows that progenitors developed many evolutionary novelties and successful surviving mechanisms. They are superior to survivors and Lazarus taxa in their ability to adapt to environmental changes. They are the primary source of macroevolution and the ancestors of a number of new taxa. Three kinds of progenitors are recognized based on the Ordovician-Silurian brachiopods from South China: survivor-progenitors, crisis-progenitors and Lazarus-progenitors; the last has the strongest ability to resist adverse environments, and is the most diverse and abundant.

  2. S-R Associations, Their Extinction, and Recovery in an Animal Model of Anxiety: A New Associative Account of Phobias Without Recall of Original Trauma

    Science.gov (United States)

    Laborda, Mario A.; Miller, Ralph R.

    2012-01-01

    Associative accounts of the etiology of phobias have been criticized because of numerous cases of phobias in which the client does not remember a relevant traumatic event (i.e., Pavlovian conditioning trial), instructions, or vicarious experience with the phobic object. In three lick suppression experiments with rats as subjects, we modeled an associative account of such fears. Experiment 1 assessed stimulus-response (S-R) associations in first-order fear conditioning. After behaviorally complete devaluation of the unconditioned stimulus, the target stimulus still produced strong conditioned responses, suggesting that an S-R association had been formed and that this association was not significantly affected when the outcome was devalued through unsignaled presentations of the unconditioned stimulus. Experiments 2 and 3 examined extinction and recovery of S-R associations. Experiment 2 showed that extinguished S-R associations returned when testing occurred outside of the extinction context (i.e., renewal) and Experiment 3 found that a long delay between extinction and testing also produced a return of the extinguished S-R associations (i.e., spontaneous recovery). These experiments suggest that fears for which people cannot recall a cause are explicable in an associative framework, and indicate that those fears are susceptible to relapse after extinction treatment just like stimulus-outcome (S-O) associations. PMID:21496503

  3. Marine anoxia and delayed Earth system recovery after the end-Permian extinction.

    Science.gov (United States)

    Lau, Kimberly V; Maher, Kate; Altiner, Demir; Kelley, Brian M; Kump, Lee R; Lehrmann, Daniel J; Silva-Tamayo, Juan Carlos; Weaver, Karrie L; Yu, Meiyi; Payne, Jonathan L

    2016-03-01

    Delayed Earth system recovery following the end-Permian mass extinction is often attributed to severe ocean anoxia. However, the extent and duration of Early Triassic anoxia remains poorly constrained. Here we use paired records of uranium concentrations ([U]) and (238)U/(235)U isotopic compositions (δ(238)U) of Upper Permian-Upper Triassic marine limestones from China and Turkey to quantify variations in global seafloor redox conditions. We observe abrupt decreases in [U] and δ(238)U across the end-Permian extinction horizon, from ∼3 ppm and -0.15‰ to ∼0.3 ppm and -0.77‰, followed by a gradual return to preextinction values over the subsequent 5 million years. These trends imply a factor of 100 increase in the extent of seafloor anoxia and suggest the presence of a shallow oxygen minimum zone (OMZ) that inhibited the recovery of benthic animal diversity and marine ecosystem function. We hypothesize that in the Early Triassic oceans-characterized by prolonged shallow anoxia that may have impinged onto continental shelves-global biogeochemical cycles and marine ecosystem structure became more sensitive to variation in the position of the OMZ. Under this hypothesis, the Middle Triassic decline in bottom water anoxia, stabilization of biogeochemical cycles, and diversification of marine animals together reflect the development of a deeper and less extensive OMZ, which regulated Earth system recovery following the end-Permian catastrophe.

  4. Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery

    Science.gov (United States)

    Clarkson, M. O.; Wood, R. A.; Poulton, S. W.; Richoz, S.; Newton, R. J.; Kasemann, S. A.; Bowyer, F.; Krystyn, L.

    2016-07-01

    The end-Permian mass extinction, ~252 million years ago, is notable for a complex recovery period of ~5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe-S-C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota.

  5. A Case of Dengue Maculopathy with Spontaneous Recovery

    Directory of Open Access Journals (Sweden)

    Fiona Oi-jing Luk

    2013-06-01

    Full Text Available Purpose: To report a case of dengue maculopathy, which resolved spontaneously without treatment. Methods: A 25-year-old female patient with good past health was admitted to a general hospital in Hong Kong with fever of unknown origin after traveling to Indonesia. Based on the clinical features and a positive real-time polymerase chain reaction for dengue virus type 1, she was diagnosed with dengue fever. The patient developed dengue maculopathy mainly affecting the vision of her left eye. Abnormalities on a multifocal electroretinogram showed bilateral involvement. Results: As there is no proven treatment for dengue maculopathy, the patient opted for observation. Her vision returned to normal within 3 weeks. Conclusion: Dengue maculopathy can cause severe visual loss and may resolve without treatment.

  6. Deepened Extinction following Compound Stimulus Presentation: Noradrenergic Modulation

    Science.gov (United States)

    Janak, Patricia H.; Corbit, Laura H.

    2011-01-01

    Behavioral extinction is an active form of new learning involving the prediction of nonreward where reward has previously been present. The expression of extinction learning can be disrupted by the presentation of reward itself or reward-predictive stimuli (reinstatement) as well as the passage of time (spontaneous recovery) or contextual changes…

  7. Extinction and recovery patterns in benthic foraminiferal paleocommunities across the Cretaceous/Paleogene and Paleocene/Eocene boundaries

    NARCIS (Netherlands)

    Speijer, R.P.

    1994-01-01

    In this thesis Late Cretaceous to Early Paleogene (66-54 Ma) benthic foraminiferal distribution patterns in the southern Tethys (northern margin of Africa) are discussed. We focus in particular on extinction and recovery patterns in middle neritic (50-100 m) to upper bathyal (200-600 m) benthic fora

  8. Spontaneous Recovery of Human Spatial Memory in a Virtual Water Maze

    Science.gov (United States)

    Luna, David; Martínez, Héctor

    2015-01-01

    The occurrence of spontaneous recovery in human spatial memory was assessed using a virtual environment. In Experiment 1, spatial memory was established by training participants to locate a hidden platform in a virtual water maze using a set of four distal landmarks. In Experiment 2, after learning about the location of a hidden platform, the…

  9. Improved Oil Recovery in Chalk. Spontaneous Imbibition affected by Wettability, Rock Framework and Interfacial Tension

    Energy Technology Data Exchange (ETDEWEB)

    Milter, J.

    1996-12-31

    The author of this doctoral thesis aims to improve the oil recovery from fractured chalk reservoirs, i.e., maximize the area of swept zones and their displacement efficiencies. In order to identify an improved oil recovery method in chalk, it is necessary to study wettability of calcium carbonate and spontaneous imbibition potential. The thesis contains an investigation of thin films and wettability of single calcite surfaces. The results of thin film experiments are used to evaluate spontaneous imbibition experiments in different chalk types. The chalk types were described detailed enough to permit considering the influence of texture, pore size and pore throat size distributions, pore geometry, and surface roughness on wettability and spontaneous imbibition. Finally, impacts of interfacial tension by adding anionic and cationic surfactants to the imbibing water phase are studied at different wettabilities of a well known chalk material. 232 refs., 97 figs., 13 tabs.

  10. Delayed recovery of non-marine tetrapods after the end-Permian mass extinction tracks global carbon cycle.

    Science.gov (United States)

    Irmis, Randall B; Whiteside, Jessica H

    2012-04-07

    During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects. In contrast, the terrestrial record of extinction and recovery is less clear; the effects and magnitude of the end-Permian extinction on non-marine vertebrates are particularly controversial. We use specimen-level data from southern Africa and Russia to investigate the palaeodiversity dynamics of non-marine tetrapods across the Permo-Triassic boundary by analysing sample-standardized generic richness, evenness and relative abundance. In addition, we investigate the potential effects of sampling, geological and taxonomic biases on these data. Our analyses demonstrate that non-marine tetrapods were severely affected by the end-Permian mass extinction, and that these assemblages did not begin to recover until the Middle Triassic. These data are congruent with those from land plants and marine invertebrates. Furthermore, they are consistent with the idea that unstable low-diversity post-extinction ecosystems were subject to boom-bust cycles, reflected in multiple Early Triassic perturbations of the carbon cycle.

  11. Rapid demise and recovery of plant ecosystems across the end-Permian extinction event

    Science.gov (United States)

    Hochuli, Peter A.; Hermann, Elke; Vigran, Jorunn Os; Bucher, Hugo; Weissert, Helmut

    2010-12-01

    activity of the Siberian Traps. Gymnosperms recovered prior to the major isotopic shift. The fast recovery of terrestrial ecosystem explains why all major plant groups survived the end-Permian extinction event while the majority of marine organisms were wiped out. The concordance of pattern of the δ 13C org in globally distributed marine and terrestrial sequences enables us to link turnovers in the terrestrial environment with marine extinction events. It demonstrates that the demise and the onset of the recovery of the terrestrial ecosystems was a global phenomenon and occurred prior to the major isotopic shift. The successive negative shifts in δ 13C org isotope values are thought to reflect CO 2 input into the atmosphere by multiphase volcanic activity (Siberian Traps) or other consecutive events (e.g. methane release).

  12. Recovery and diversification of marine communities following the late Permian mass extinction event in the western Palaeotethys

    Science.gov (United States)

    Foster, William J.; Sebe, Krisztina

    2017-08-01

    The recovery of benthic invertebrates following the late Permian mass extinction event is often described as occurring in the Middle Triassic associated with the return of Early Triassic Lazarus taxa, increased body sizes, platform margin metazoan reefs, and increased tiering. Most quantitative palaeoecological studies, however, are limited to the Early Triassic and the timing of the final phase of recovery is rarely quantified. Here, quantitative abundance data of benthic invertebrates were collected from the Middle Triassic (Anisian) succession of the Mecsek Mountains (Hungary), and analysed with univariate and multivariate statistics to investigate the timing of recovery following the late Permian mass extinction. These communities lived in a mixed siliciclastic-carbonate ramp setting on the western margin of the Palaeotethys Ocean. The new data presented here is combined with the previously studied Lower Triassic succession of the Aggtelek Karst (Hungary), which records deposition of comparable facies and in the same region of the Palaeotethys Ocean. The Middle Triassic benthic fauna can be characterised by three distinct ecological states. The first state is recorded in the Viganvár Limestone Formation representing mollusc-dominated communities restricted to above wave base, which are comparable to the lower and mid-Spathian Szin Marl Formation faunas. The second state is recorded in the Lapis Limestone Formation and records extensive bioturbation that is not limited to wave base and is comparable to the upper Spathian Szinpetri Limestone Formation. The third ecological state occurs in the Zuhánya Limestone Formation which was deposited in the Pelsonian Binodosus Zone, and has a more 'Palaeozoic' structure with sessile brachiopods dominating assemblages for the first time in the Mesozoic. The return of community-level characteristics to pre-extinction levels and the diversification of invertebrates suggests that the final stages of recovery and the radiation

  13. Spontaneous recovery of cochlear fibrocytes after severe degeneration caused by acute energy failure

    Directory of Open Access Journals (Sweden)

    Kunio eMizutari

    2014-08-01

    Full Text Available Cochlear fibrocytes in the lateral wall region play a critical role in the regulation of inner ear ion and fluid homeostasis, although these are nonsensory cells. Along with other nonsensory cells, fibrocytes in the spiral ligament have been reported to repopulate themselves after damage. However, the studies of regeneration of cochlear fibrocytes have been difficult because a suitable fibrocyte-specific degeneration model did not exist. Therefore, we analyzed cochlear fibrocytes using a rat model of acute cochlear energy failure induced by a mitochondrial toxin. This model is unique because hearing loss is caused by apoptosis of fibrocytes in the cochlear lateral wall not by damage to sensory cells. Although this model involves severe damage to the cochlear lateral wall, delayed spontaneous regeneration occurs without any treatment. Moreover, partial hearing recovery is accompanied by morphological remodeling of the cochlear lateral wall. Two hypotheses are conceivable regarding this spontaneous recovery of cochlear fibrocytes. One is that residual cochlear fibrocytes proliferate spontaneously, followed by remodeling of the functional region of the lateral wall. Another is that some foreign cells such as bone marrow-derived cells promote morphological and functional recovery of the lateral wall. Acceleration of the lateral wall recovery promoted by these mechanisms may be a new therapeutic strategy against hearing loss.

  14. Electrophysiological characterization of spontaneous recovery in deep dorsal horn interneurons after incomplete spinal cord injury.

    Science.gov (United States)

    Rank, M M; Flynn, J R; Galea, M P; Callister, R; Callister, R J

    2015-09-01

    In the weeks and months following an incomplete spinal cord injury (SCI) significant spontaneous recovery of function occurs in the absence of any applied therapeutic intervention. The anatomical correlates of this spontaneous plasticity are well characterized, however, the functional changes that occur in spinal cord interneurons after injury are poorly understood. Here we use a T10 hemisection model of SCI in adult mice (9-10 wks old) combined with whole-cell patch clamp electrophysiology and a horizontal spinal cord slice preparation to examine changes in intrinsic membrane and synaptic properties of deep dorsal horn (DDH) interneurons. We made these measurements during short-term (4 wks) and long-term (10 wks) spontaneous recovery after SCI. Several important intrinsic membrane properties are altered in the short-term, but recover to values resembling those of uninjured controls in the longer term. AP discharge patterns are reorganized at both short-term and long-term recovery time points. This is matched by reorganization in the expression of voltage-activated potassium and calcium subthreshold-currents that shape AP discharge. Excitatory synaptic inputs onto DDH interneurons are significantly restructured in long-term SCI mice. Plots of sEPSC peak amplitude vs. rise times suggest considerable dendritic expansion or synaptic reorganization occurs especially during long-term recovery from SCI. Connectivity between descending dorsal column pathways and DDH interneurons is reduced in the short-term, but amplified in long-term recovery. Our results suggest considerable plasticity in both intrinsic and synaptic mechanisms occurs spontaneously in DDH interneurons following SCI and takes a minimum of 10 wks after the initial injury to stabilize.

  15. Characteristics and Spontaneous Recovery of Tinnitus Related to Idiopathic Sudden Sensorineural Hearing Loss

    OpenAIRE

    Mühlmeier, Guido; Baguley, David; Cox, Tony; Suckfüll, Markus; De Meyer, Thomas

    2016-01-01

    Objective: To evaluate the characteristics and spontaneous recovery of tinnitus related to idiopathic sudden sensorineural hearing loss (ISSNHL). Study Design: Retrospective analysis from two randomized placebo-controlled clinical trials for treatment of ISSNHL within 48 hours from onset (Study A), or of tinnitus related to ISSNHL within 3 months from onset (Study B). Setting: Forty-eight European sites (academic tertiary referral centers, private ENT practices). Patients: One hundred thirtee...

  16. Extinction and renewal of conditioned sexual responses

    NARCIS (Netherlands)

    Brom, M.; Laan, E.; Everaerd, W.; Spinhoven, P.; Both, S.

    2014-01-01

    INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as

  17. Extinction and renewal of conditioned sexual responses

    NARCIS (Netherlands)

    Brom, M.; Laan, E.; Everaerd, W.; Spinhoven, P.; Both, S.

    2014-01-01

    INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as addictions

  18. Attentional, Associative, and Configural Mechanisms in Extinction

    Science.gov (United States)

    Larrauri, Jose A.; Schmajuk, Nestor A.

    2008-01-01

    The participation of attentional and associative mechanisms in extinction, spontaneous recovery, external disinhibition, renewal, reinstatement, and reacquisition was evaluated through computer simulations with an extant computational model of classical conditioning (N. A. Schmajuk, Y. Lam, & J. A. Gray, 1996; N. A. Schmajuk & J. A. Larrauri,…

  19. Anatomical mechanism of spontaneous recovery in regions caudal to thoracic spinal cord injury lesions in rats

    Science.gov (United States)

    Li, Lu-sheng; Yu, Hao; Raynald, Raynald; Wang, Xiao-dong; Dai, Guang-hui; Cheng, Hong-bin; Liu, Xue-bin

    2017-01-01

    Background The nerve fibre circuits around a lesion play a major role in the spontaneous recovery process after spinal cord hemisection in rats. The aim of the present study was to answer the following question: in the re-control process, do all spinal cord nerves below the lesion site participate, or do the spinal cord nerves of only one vertebral segment have a role in repair? Methods First we made a T7 spinal cord hemisection in 50 rats. Eight weeks later, they were divided into three groups based on distinct second operations at T7: ipsilateral hemisection operation, contralateral hemisection, or transection. We then tested recovery of hindlimbs for another eight weeks. The first step was to confirm the lesion had role or not in the spontaneous recovery process. Secondly, we performed T7 spinal cord hemisections in 125 rats. Eight weeks later, we performed a second single hemisection on the ipsilateral side at T8–T12 and then tested hindlimb recovery for another six weeks. Results In the first part, the Basso, Beattie, Bresnahan (BBB) scores and the electrophysiology tests of both hindlimbs weren’t significantly different after the second hemisection of the ipsilateral side. In the second part, the closer the second hemisection was to T12, the more substantial the resulting impairment in BBB score tests and prolonged latency periods. Conclusions The nerve regeneration from the lesion area after hemisection has no effect on spontaneous recovery of the spinal cord. Repair is carried out by all vertebrae caudal and ipsilateral to the lesion, with T12 being most important. PMID:28097067

  20. Recovery from prolonged deep rocuronium-induced neuromuscular blockade: A randomized comparison of sugammadex reversal with spontaneous recovery.

    Science.gov (United States)

    Rahe-Meyer, N; Berger, C; Wittmann, M; Solomon, C; Abels, E A M; Rietbergen, H; Reuter, D A

    2015-07-01

    Deep neuromuscular blockade (NMB) may not always be maintained to the end of surgery and the depth of block may be allowed to gradually diminish over time, particularly if reversal of NMB is not routinely performed. The current study aimed to assess recovery from deep rocuronium-induced NMB with sugammadex compared with placebo, provide data regarding the extent of residual blockade after deep rocuronium-induced NMB (placebo group), and to determine whether complete and reliable recovery could be provided by sugammadex (sugammadex group). This was a randomized, placebo-controlled, safety-assessor-blinded study in adult patients of American Society of Anesthesiologists Class I to III. Patients with clinically relevant kidney or liver insufficiency were excluded. Anesthesia was administered as routinely practiced at each study site. Rocuronium 0.6 mg/kg was administered for intubation, with maintenance doses of 0.1-0.2 mg/kg as needed. After the last rocuronium dose, at deep NMB (target depth 1-2 post-tetanic counts), patients received a single dose of sugammadex 4.0 mg/kg or placebo as randomized. The primary endpoint was time from sugammadex or placebo administration to recovery of the train-of-four (TOF) ratio to 0.9. Safety was assessed through monitoring of adverse events, vital signs and physical examination. Patients were also assessed for evidence of residual or recurrence of NMB. With this design, the study will provide data regarding the extent of residual blockade under these conditions (placebo group), and determine whether complete and reliable recovery could be provided by sugammadex (sugammadex group). Recovery to a TOF ratio of ≥ 0.9 with sugammadex was significantly faster (~ 40 times) than spontaneous recovery: geometric mean (95 % confidence interval) times were 2.2 (1.9-2.5) and 89.8 (80.1-100.7) min, respectively (p sugammadex, with median time to recovery > 1.5 h in the placebo group and one patient taking 4.8 h to achieve a

  1. Extinction learning, which consists of the inhibition of retrieval, can be learned without retrieval.

    Science.gov (United States)

    de Carvalho Myskiw, Jociane; Furini, Cristiane Regina Guerino; Schmidt, Bianca; Ferreira, Flávia; Izquierdo, Ivan

    2015-01-13

    In the present study we test the hypothesis that extinction is not a consequence of retrieval in unreinforced conditioned stimulus (CS) presentation but the mere perception of the CS in the absence of a conditioned response. Animals with cannulae implanted in the CA1 region of hippocampus were subjected to extinction of contextual fear conditioning. Muscimol infused intra-CA1 before an extinction training session of contextual fear conditioning (CFC) blocks retrieval but not consolidation of extinction measured 24 h later. Additionally, this inhibition of retrieval does not affect early persistence of extinction when tested 7 d later or its spontaneous recovery after 2 wk. Furthermore, both anisomycin, an inhibitor of ribosomal protein synthesis, and rapamycin, an inhibitor of extraribosomal protein synthesis, given into the CA1, impair extinction of CFC regardless of whether its retrieval was blocked by muscimol. Therefore, retrieval performance in the first unreinforced session is not necessary for the installation, maintenance, or spontaneous recovery of extinction of CFC.

  2. The Luoping biota: exceptional preservation, and new evidence on the Triassic recovery from end-Permian mass extinction.

    Science.gov (United States)

    Hu, Shi-xue; Zhang, Qi-yue; Chen, Zhong-Qiang; Zhou, Chang-yong; Lü, Tao; Xie, Tao; Wen, Wen; Huang, Jin-yuan; Benton, Michael J

    2011-08-07

    The timing and nature of biotic recovery from the devastating end-Permian mass extinction (252 Ma) are much debated. New studies in South China suggest that complex marine ecosystems did not become re-established until the middle-late Anisian (Middle Triassic), much later than had been proposed by some. The recently discovered exceptionally preserved Luoping biota from the Anisian Stage of the Middle Triassic, Yunnan Province and southwest China shows this final stage of community assembly on the continental shelf. The fossil assemblage is a mixture of marine animals, including abundant lightly sclerotized arthropods, associated with fishes, marine reptiles, bivalves, gastropods, belemnoids, ammonoids, echinoderms, brachiopods, conodonts and foraminifers, as well as plants and rare arthropods from nearby land. In some ways, the Luoping biota rebuilt the framework of the pre-extinction latest Permian marine ecosystem, but it differed too in profound ways. New trophic levels were introduced, most notably among top predators in the form of the diverse marine reptiles that had no evident analogues in the Late Permian. The Luoping biota is one of the most diverse Triassic marine fossil Lagerstätten in the world, providing a new and early window on recovery and radiation of Triassic marine ecosystems some 10 Myr after the end-Permian mass extinction.

  3. Partial Recovery of Audiological, Vestibular, and Radiological Findings following Spontaneous Intralabyrinthine Haemorrhage

    Directory of Open Access Journals (Sweden)

    Thomas Pézier

    2013-01-01

    Full Text Available The diagnosis, work-up, and treatment of sudden sensorineural hearing loss and sudden vestibular loss vary widely between units. With the increasing access to both magnetic resonance imaging and objective vestibular testing, our understanding of the various aetiologies at hand is increasing. Despite this, the therapeutic options are limited and without a particularly strong evidence base. We present a rare, yet increasingly diagnosed, case of intralabyrinthine haemorrhage (ILH together with radiological, audiological, and vestibular test results. Of note, this occurred spontaneously and has shown partial recovery in all the mentioned modalities.

  4. Recovery of prolactin function following spontaneous pregnancy in a woman with Sheehan's syndrome.

    Science.gov (United States)

    Laway, Bashir A; Mir, Shahnaz A; Zargar, Abdul H

    2013-12-01

    Sheehan's syndrome (SS) presents with hypopituitarism after parturition, usually preceded by postpartum hemorrhage. The first symptom of the disorder is lactation failure because of lactotroph cell necrosis. Recovery of lactotroph function after initial insult has not been reported in the literature. We describe the evaluation of a case of SS in whom lactotroph function recovered after the second pregnancy. A young woman delivered her first child at the age of 25 years; delivery was followed by severe postpartum hemorrhage and required blood transfusion. Sheehan's syndrome was diagnosed because of lactotroph, corticotroph, thyrotroph and somatotroph failure and empty sella on MRI. She conceived twice spontaneously and had normal lactation after the second delivery; investigations confirmed the normal basal and stimulable prolactin levels. We presume that recovery of lactotroph function after the second pregnancy in a patient with SS is possibly because of stimulatory effect of estrogen and progesterone on residual lactotroph cells.

  5. Recovery of prolactin function following spontaneous pregnancy in a woman with Sheehan′s syndrome

    Directory of Open Access Journals (Sweden)

    Bashir A Laway

    2013-01-01

    Full Text Available Sheehan′s syndrome (SS presents with hypopituitarism after parturition, usually preceded by postpartum hemorrhage. The first symptom of the disorder is lactation failure because of lactotroph cell necrosis. Recovery of lactotroph function after initial insult has not been reported in the literature. We describe the evaluation of a case of SS in whom lactotroph function recovered after the second pregnancy. A young woman delivered her first child at the age of 25 years; delivery was followed by severe postpartum hemorrhage and required blood transfusion. Sheehan′s syndrome was diagnosed because of lactotroph, corticotroph, thyrotroph and somatotroph failure and empty sella on MRI. She conceived twice spontaneously and had normal lactation after the second delivery; investigations confirmed the normal basal and stimulable prolactin levels. We presume that recovery of lactotroph function after the second pregnancy in a patient with SS is possibly because of stimulatory effect of estrogen and progesterone on residual lactotroph cells.

  6. Eccentricity and obliquity paced carbon cycling in the Early Triassic and implications for post-extinction ecosystem recovery

    Science.gov (United States)

    Fu, Wanlu; Jiang, Da-Yong; Montañez, Isabel P.; Meyers, Stephen R.; Motani, Ryosuke; Tintori, Andrea

    2016-06-01

    The timing of marine ecosystem recovery following the End Permian Mass Extinction (EPME) remains poorly constrained given the lack of radiometric ages. Here we develop a high-resolution carbonate carbon isotope (δ13Ccarb) record for 3.20 million years of the Olenekian in South China that defines the astronomical time-scale for the critical interval of major evolutionary and oceanic events in the Spathian. δ13Ccarb documents eccentricity modulation of carbon cycling through the period and a strong obliquity signal. A shift in phasing between short and long eccentricity modulation, and amplification of obliquity, is nearly coincident with a 2% decrease in seawater δ13CDIC, the last of a longer-term stepped decrease through the Spathian. The mid-Spathian shift in seawater δ13CDIC to typical thermocline values is interpreted to record a major oceanic reorganization with global climate amelioration. Coincidence of the phasing shift with the first occurrence of marine reptiles (248.81 Ma), suggests that their invasion into the sea and the onset of a complex ecosystem were facilitated by restoration of deep ocean ventilation linked mechanistically to a change in the response of the oceanic carbon reservoir to astronomical forcing. Together these records place the first constraints on the duration of the post-extinction recovery to 3.35 myr.

  7. Protein supplementation may enhance the spontaneous recovery of neurological alterations in patients with ischaemic stroke.

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    Aquilani, Roberto; Scocchi, Marco; Iadarola, Paolo; Franciscone, Piero; Verri, Manuela; Boschi, Federica; Pasini, Evasio; Viglio, Simona

    2008-12-01

    To determine whether protein supplementation could enhance neurological recovery in subacute patients with ischaemic stroke. Alimentation-independent patients with ischaemic stroke were randomly allocated to either 21 days of protein supplementation (protein-supplemented group; n=20) or to a spontaneous diet only (control group; n=21) in order to investigate the recovery of neurological changes (measured using the National Institute of Health (NIH) Stroke Scale). Tertiary care rehabilitation in Italy. Forty-two patients (27 male and 15 female; 66.4 +/- 11 years) 16 +/-2 days after the acute event. Supplementation with a hyperproteic nutritional formula (10% protein). NIH Stroke Scale and protein intake. At admission to rehabilitation, both groups of patients were homogeneous for demographic, clinical and functional characteristics. After 21 days from the start of the protocol, the NIH Stroke Scale was found to be enhanced in the group with supplemental proteins (-4.4 +/- 1.5 score versus -3 +/- 1.4 of control group; P<0.01). When expressed as difference (triangle up) between baseline and 21 days, the NIH Stroke Scale correlated negatively with change in protein intake (g/day) (r=-0.50, P= 0.001) and positively with change in carbohydrate/protein ratio (r = +0.40, P=0.01) Protein supplementation may enhance neurological recovery in subacute patients with ischaemic stroke.

  8. Characteristics and Spontaneous Recovery of Tinnitus Related to Idiopathic Sudden Sensorineural Hearing Loss

    Science.gov (United States)

    Mühlmeier, Guido; Baguley, David; Cox, Tony; Suckfüll, Markus; Meyer, Thomas

    2016-01-01

    Objective: To evaluate the characteristics and spontaneous recovery of tinnitus related to idiopathic sudden sensorineural hearing loss (ISSNHL). Study Design: Retrospective analysis from two randomized placebo-controlled clinical trials for treatment of ISSNHL within 48 hours from onset (Study A), or of tinnitus related to ISSNHL within 3 months from onset (Study B). Setting: Forty-eight European sites (academic tertiary referral centers, private ENT practices). Patients: One hundred thirteen adult patients of which 65 with hearing loss ≥30 dB (Study A) and 48 with persistent acute tinnitus (Study B) at baseline. Interventions: Intratympanic (i.t.) injection of placebo gel in single dose or in triple dose during 3 consecutive days. Main Outcome Measures: Frequency of tinnitus, subjective tinnitus loudness, rates of complete tinnitus remission, and complete hearing recovery during 3 months follow-up. Results: In acute ISSNHL, tinnitus loudness decreased rapidly in cases of mild-moderate hearing loss, and tinnitus had completely resolved in two-thirds of patients after 3 months. Hearing recovery preceded tinnitus resolution. When associated with severe-profound hearing loss, tinnitus improved significantly less. Complete hearing recovery and full tinnitus remission were both about three times more frequent in mild-moderate hearing loss patients than in severe-profound cases. Improvement in tinnitus loudness over time can be approximated by a negative exponential function. Conclusions: Prognosis for ISSNHL-related tinnitus is relatively poor in case of severe-profound hearing loss and the longer it has persisted. Alleviation or management of tinnitus should be a key therapeutic objective especially in pronounced ISSNHL cases. PMID:27228021

  9. Enhanced Oil Recovery from Oil-wet Carbonate Rock by Spontaneous Imbibition of Aqueous Surfactant Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Standnes, Dag Chun

    2001-09-01

    The main theme of this thesis is an experimental investigation of spontaneous imbibition (SI) of aqueous cationic surfactant solution into oil-wet carbonate (chalk- and dolomite cores). The static imbibition process is believed to represent the matrix flow of oil and water in a fractured reservoir. It was known that aqueous solution of C{sub 12}-N(CH{sub 3}){sub 3}Br (C12TAB) was able to imbibe spontaneously into nearly oil-wet chalk material, but the underlying mechanism was not understood. The present work was therefore initiated, with the following objectives: (1) Put forward a hypothesis for the chemical mechanism underlying the SI of C12TAB solutions into oil-wet chalk material based on experimental data and (2) Perform screening tests of low-cost commercially available surfactants for their ability to displace oil by SI of water into oil-wet carbonate rock material. It is essential for optimal use of the surfactant in field application to have detailed knowledge about the mechanism underlying the SI process. The thesis also discusses some preliminary experimental results and suggests mechanisms for enhanced oil recovery from oil-wet carbonate rock induced by supply of thermal energy.

  10. Psychological and neural mechanisms of experimental extinction: a selective review.

    Science.gov (United States)

    Delamater, Andrew R; Westbrook, R Frederick

    2014-02-01

    The present review examines key psychological concepts in the study of experimental extinction and implications these have for an understanding of the underlying neurobiology of extinction learning. We suggest that many of the signature characteristics of extinction learning (spontaneous recovery, renewal, reinstatement, rapid reacquisition) can be accommodated by the standard associative learning theory assumption that extinction results in partial erasure of the original learning together with new inhibitory learning. Moreover, we consider recent behavioral and neural evidence that supports the partial erasure view of extinction, but also note shortcomings in our understanding of extinction circuits as these relate to the negative prediction error concept. Recent work suggests that common prediction error and stimulus-specific prediction error terms both may be required to explain neural plasticity both in acquisition and extinction learning. In addition, we suggest that many issues in the content of extinction learning have not been fully addressed in current research, but that neurobiological approaches should be especially helpful in addressing such issues. These include questions about the nature of extinction learning (excitatory CS-No US, inhibitory CS-US learning, occasion setting processes), especially as this relates to studies of the micro-circuitry of extinction, as well as its representational content (sensory, motivational, response). An additional understudied problem in extinction research is the role played by attention processes and their underlying neural networks, although some research and theory converge on the idea that extinction is accompanied by attention decrements (i.e., habituation-like processes).

  11. Redox chemistry changes in the Panthalassic Ocean linked to the end-Permian mass extinction and delayed Early Triassic biotic recovery.

    Science.gov (United States)

    Zhang, Guijie; Zhang, Xiaolin; Hu, Dongping; Li, Dandan; Algeo, Thomas J; Farquhar, James; Henderson, Charles M; Qin, Liping; Shen, Megan; Shen, Danielle; Schoepfer, Shane D; Chen, Kefan; Shen, Yanan

    2017-02-21

    The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian-Lower Triassic deep-sea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ(33)S with either positive δ(34)S or negative δ(34)S that implies mixing of sulfide sulfur with different δ(34)S before, during, and after the end-Permian mass extinction. The precise coincidence of the negative Δ(33)S anomaly with the extinction horizon in western Canada suggests that shoaling of H2S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem.

  12. microRNAs Involved in Regulating Spontaneous Recovery in Embolic Stroke Model.

    Directory of Open Access Journals (Sweden)

    Fu Jia Liu

    Full Text Available To date, miRNA expression studies on cerebral ischemia in both human and animal models have focused mainly on acute phase of ischemic stroke. In this study, we present the roles played by microRNAs in the spontaneous recovery phases in cerebral ischemia using rodent stroke models. Brain tissues were harvested at different reperfusion time points ranging from 0-168 hrs after middle cerebral artery occlusion using homologous emboli. MiRNA and mRNA expression profiles were investigated by microarray followed by multiple statistical analysis. Candidate transcripts were also validated by quantitative RT-PCR. Three specific groups of miRNAs were observed among a total of 346 differentially expressed miRNAs. miRNAs, miR-21, -142-3p, -142-5p, and -146a displayed significant upregulation during stroke recovery (48 hrs to 168 hrs compared with those during acute phases (0 hrs to 24 hrs. On the other hand, an opposite trend was observed in the expression of miR-196a/b/c, -224 and -324-3p. Interestingly, miR-206, -290, -291a-5p and -30c-1*, positively correlated with the infarct sizes, with an initial increase up to 24hrs followed by a gradual decrease from 48 hrs to 168 hrs (R = 0.95. Taken together with the expression levels of corresponding mRNA targets, we have also found that Hedgehog, Notch, Wnt and TGF-β signaling pathways could play significant roles in stroke recovery and especially in neuronal repair.

  13. Rapid recovery from spontaneous and simultaneous bilateral quadriceps tendon rupture in an active, healthy individual.

    Science.gov (United States)

    Gaheer, Rajinder Singh; Hawkins, Amanda

    2010-07-13

    Bilateral spontaneous quadriceps rupture is an uncommon injury that is usually seen in association with multiple medical conditions and is frequently misdiagnosed. It is rarely seen in healthy, active individuals. This article presents a case of bilateral simultaneous and spontaneous rupture of the quadriceps tendon in a healthy, athletic, active and highly motivated patient with rapid recovery from injury and return to full sport activity within a relatively short period of time. A 65-year-old healthy man felt both knees give way while walking down stairs at home and collapsed, unable to bear weight. He was fit and well, not on any medications and basic laboratory screening was within normal limits. He was an active sportsman, horse rider, swimmer, and long-distance cyclist, and had completed a half marathon 1 month before his injury. He was diagnosed with bilateral quadriceps tendon ruptures. An ultrasound of both knees confirmed the diagnosis of full-thickness rupture. Surgical repair of both quadriceps tendons was performed 3 days after the injury. Bilateral locking brace in 10 degrees of flexion was used to immobilize both knees and protect the repair for 6 weeks. The patient remained nonweight bearing for 2 weeks, then gradual weight bearing was commenced, with full weight bearing at 6 weeks. Intensive isometric quadriceps exercises were started on the second postoperative day. Immobilization of both knees was maintained for 6 weeks, after which full active range of motion (ROM) was initiated. At 16 weeks after the injury he had bilateral ROM from 0 degrees to 120 degrees flexion, with no extension lag. He was horse riding, playing golf, swimming, and walking distances up to 2 miles at that time.

  14. Spontaneous electrochemical treatment for sulfur recovery by a sulfide oxidation/vanadium(V) reduction galvanic cell.

    Science.gov (United States)

    Kijjanapanich, Pimluck; Kijjanapanich, Pairoje; Annachhatre, Ajit P; Esposito, Giovanni; Lens, Piet N L

    2015-02-01

    Sulfide is the product of the biological sulfate reduction process which gives toxicity and odor problems. Wastewaters or bioreactor effluents containing sulfide can cause severe environmental impacts. Electrochemical treatment can be an alternative approach for sulfide removal and sulfur recovery from such sulfide rich solutions. This study aims to develop a spontaneous electrochemical sulfide oxidation/vanadium(V) reduction cell with a graphite electrode system to recover sulfide as elemental sulfur. The effects of the internal and external resistance on the sulfide removal efficiency and electrical current produced were investigated at different pH. A high surface area of the graphite electrode is required in order to have as less internal resistance as possible. In this study, graphite powder was added (contact area >633 cm(2)) in order to reduce the internal resistance. A sulfide removal efficiency up to 91% and electrical charge of more than 400 C were achieved when using five graphite rods supplemented with graphite powder as the electrode at an external resistance of 30 Ω and a sulfide concentration of 250 mg L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Spontaneous hematologic recovery from bone marrow aplasia after accidental tenfold overdosage with radiophosphorus

    Energy Technology Data Exchange (ETDEWEB)

    Gmuer, J.; Bischof, B.; Coninx, S.; Bucher, U.; Poretti, G.; Henrichs, K.; Kaul, A.; Roedler, H.D.; Buettner, K.; Frick, P.G.

    1983-04-01

    Two patients with polycythemia vera received intravenously an accidental tenfold overdosage of radiophosphorus therapy (60 and 50 mCi 32P, respectively). In both patients, the occurrence of hemorrhagic complications 3 wk after the 32P medication led to detection of the error and referral to our hospital. Upon admission they showed an agranulocytosis, severe thrombocytopenia, and bone marrow aplasia. In both cases, spontaneous recovery of the hematopoiesis was observed from day 40 posttreatment onward. In one patient, a slow but ultimately complete normalization of blood counts and marrow morphology took place, whereas in the other, a mild thrombocytopenia persists. Nearly 5 yr after the accidental overdosage, both patients are clinically well. Symptoms of polycythemia vera have not reappeared up to now. Attempts were made to evaluate the radiation dose absorbed by the bone marrow. In the first patient, the daily 32P excretion was determined from day 22 to day 60, whereas in the other patient a whole body count was performed on day 78 after administration. From these results, an approximate cumulative bone marrow dose of 10 Sv (1000 rem) could be calculated.

  16. Conodont body size and diversity trends after the end-Permian extinction: implications for the recovery of pelagic vs. benthic marine ecosystems

    Science.gov (United States)

    Schaal, E. K.; Morgan, D. J.; Clapham, M.; Rego, B. L.; Wang, S. C.; Payne, J.

    2012-12-01

    Many marine clades decreased in size across the end-Permian extinction horizon, but the pattern and timing of subsequent size increase during recovery is poorly constrained. The tempo of recovery from the end-Permian extinction is key to understanding the role of evolutionary and environmental constraints in the recovery of ecosystems. However, not all marine organisms share the same recovery pattern. In this study, we document Late Permian to Late Triassic trends in size distribution of conodonts, pelagic chordates that exhibit much more rapid diversification in the Early Triassic compared to benthic clades. Because tooth size correlates with body weight in chordates over many orders of magnitude and is commonly used to predict body size in fossils, conodont elements can serve as a proxy for the size of the conodont animal. Our dataset includes both specimens from high-resolution samples through an exceptionally exposed carbonate platform in south China and size measurements from the published literature for conodonts and seven other marine clades. In platform slope sections of south China, we observe a size decrease across the P/Tr boundary, but in platform interior sections, large conodonts are prolific in the earliest Triassic. Comparison with global data shows that while there is decrease in median conodont size across the P/Tr boundary, there is little change in maximum conodont size, and pre-extinction size distributions return by the Smithian. While benthic clades show Early Triassic size reduction and slow recovery, pelagic clades such as conodonts and ammonoids show large size and rapid diversification after the extinction event. This decoupling of recovery between benthic and pelagic marine ecosystems could reflect a depth gradient in environmental parameters such as oxygen availability or intrinsic differences in the evolutionary dynamics of these clades.

  17. Guanling Biota: A Marker of Triassic Biotic Recovery from the end-Permian Extinction in the Ancient Guizhou Sea

    Institute of Scientific and Technical Information of China (English)

    JIANG Dayong; Ryosuke MOTANI; LI Chun; HAO Weicheng; SUN Yuanlin; SUN Zuoyu; Lars SCHMITZ

    2005-01-01

    After a slow recovery from the end-Permian extinction during the Early Triassic and rapid radiation in the Middle Triassic, evolution of organisms reached a new peak phase in the Late Triassic. The Guanling Biota from the Wayao Member (conodont Paragondolella polygnathiformis Zone), Falang Formation, Xinpu, Guanling County, Guizhou Province, southwestern China corresponds to this peak that marks the full recovery from the end-Permian extinction of marine ecosystems. The biota is of high diversity, containing well preserved and completely articulated skeletons of vertebrates comprising marine reptiles, fishes, and invertebrates including crinoids, ammonites, bivalves, and other fossils,and is one of the best examples of marine ecosystem records in life history. The fossil marine reptiles and crinoids are most significant in this biota, especially the marine reptiles, which provide an important link between the Triassic Pacific and Tethys, and between Triassic basal forms and the Jurassic-Cretaceous marine top predators. The most remarkable fossils are the large completely articulated ichthyosaur skeletons up to and more than 10 m, and the first recorded thalattosaurs and placodonts in China. Following our review, of the 17 named reptilian taxa the eight listed here are considered to be valid: three ichthyosaurs (Qianichthyosaurus zhoui Li, 1999; Guizhouichthyosaurus tangae Cao and Luo in Yin et al.,2000, Guanlingsaurus liangae Yin in Yin et al., 2000), three thalattosaurs (Anshunsaurus huangguoshuensis Liu, 1999,Xinpusaurus suni Yin in Yin et al., 2000, Xinpusaurus kohi Jiang et al., 2004), and two placodonts (Sinocyamodus xinpuensis Li, 2000, Psephochelys polyosteoderma Li and Rieppel, 2002). Mixosaurus guanlingensis Cao in Yin et al.,2000 might be a junior synonym of Qianichthyosaurus zhoui Li, 1999, and Cymbospondylus asiaticus Li and You, 2002and Panjiangsaurus epicharis Chen and Cheng, 2003 might be junior synonyms of Guizhouichthyosaurus tangae Cao and Luo in

  18. Retention of perceptual generalization of fear extinction.

    Science.gov (United States)

    Pappens, Meike; Schroijen, Mathias; Van den Bergh, Omer; Van Diest, Ilse

    2015-12-01

    Fear reduction obtained during a fear extinction procedure can generalize from the extinction stimulus to other perceptually similar stimuli. Perceptual generalization of fear extinction typically follows a perceptual gradient, with increasing levels of fear reduction the more a stimulus resembles the extinction stimulus. The current study aimed to investigate whether perceptual generalization of fear extinction can be observed also after a retention interval of 24h. Fear was acquired to three geometrical figures of different sizes (CS(+), CS1(+) and CS2(+)) by consistently pairing them with a short-lasting suffocation experience (US). Three other geometrical figures that were never followed by the US served as control stimuli (CS(-), CS1(-), CS2(-)). Next, only the CS(+) was extinguished by presenting it in the absence of the US. One day later, fear responses to all stimuli were assessed without any US-presentation. Outcome measures included startle blink EMG, skin conductance, US expectancy, respiratory rate and tidal volume. On day 2 spontaneous recovery of fear was observed in US expectancy and tidal volume, but not in the other outcomes. Evidence for the retention of fear extinction generalization was present in US expectancy and skin conductance, but a perceptual gradient in the retention of generalized fear extinction could not be observed.

  19. Configurations of the interoceptive discriminative stimulus effects of ethanol and nicotine with two different exteroceptive contexts in rats: Extinction & recovery.

    Science.gov (United States)

    Troisi, Joseph R; Craig, Elizabeth M

    2015-06-01

    Interoceptive states interact with exteroceptive contexts in modulating operant behavior, which is maintained by its consequences. Evaluating discriminative stimulus control by overlapping interoceptive and exteroceptive configurations (gestalts) and the contribution of each modality may be clinically important for understanding aspects of relapsing behavior (e.g., drug abuse). With rats, the current investigation used a completely counterbalanced one-manipulandum operant drug discrimination procedure that established discriminative stimulus control between nicotine (0.3mg/kg) in one exteroceptive context and EtOH (1.0g/kg) in a differing exteroceptive context. One combined interoceptive-exteroceptive condition occasioned sessions of food reinforcement (S(D)) and the other counterbalanced condition occasioned sessions of non-reinforcement (S(Δ)). Each stimulus modality contributed to discriminative control, but to lesser extents than the combined intero-exteroceptive compound configurations (Experiments 1 & 2). In Experiment 1, responding was extinguished in the interoceptive stimulus conditions alone in a neutral exteroceptive context, but then renewed by reconfiguring the drugs with the exteroceptive contexts, and reversed in the opposing exteroceptive contexts. In Experiment 2, responding was extinguished in the interoceptive and exteroceptive contexts separately. Reconfiguration of the full intero-exteroceptive compound configurations did not promote recovery. These results suggest that interoceptive and exteroceptive discriminative control can be methodologically configured in modulating operant behavior during acquisition, extinction, and recovery of behavior; however, configuring interoceptive and exteroceptive discriminative stimuli do not appear to function as unique cues that differ from each stimulus modality alone. Clinical implications are discussed.

  20. Timing and duration of biotic extinction and recovery at the Cretaceous/Paleogene boundary in Texas and Alabama

    Science.gov (United States)

    Leighton, Andrew; Hart, Malcolm; Hampton, Matt; Leng, Melanie; Smart, Christopher

    2014-05-01

    The Cretaceous/Paleogene boundary successions in Texas and Alabama provide a sedimentary record of events relatively close to the Chicxulub impact site. Recent work in both areas has shown that there was a single 'impact' event that is coincident with extinctions of planktic foraminifera and calcareous nannofossil, although the dinoflagellate cyst community was little affected. The benthic foraminifera in the Texas successions are, remarkably, little affected with many taxa being found in both the Corsicana Mudstone Formation (uppermost Maastrichtian) and the Kincaid Mudstone Formation (lowermost Paleocene). In the sediments just above the erosive surface that marks the 'impact' event (and the K/Pg boundary) there are large benthic foraminifera, including nodosariids <1.5 mm in length and lenticulinids <1.5 mm in diameter. This assemblage is rather unusual, and we have been unable to determine any modern, or fossil, equivalent. As Lenticulina rotulata Lamarck occurs throughout the succession, this taxon has been used for stable isotope analysis (δ18O and δ13C) of a range of different size fractions. The results show both a variation in oxygen and carbon isotope values with size as well as a distinct cyclicity which, almost certainly, reflects astronomical tuning. It is possible, therefore, to use this cyclicity to determine the possible duration of zones P0 and Pα (80-100 kyrs), and the timing of biotic recovery following the 'impact' event. The size of the stable isotope excursions (close to the base of zone P1a) is indicative of the Dan-C2 and the Lower 29n hyperthermal events, allowing direct correlation with the two other locations where these have been described: most notably in the Gubbio succession where there is also a good record of the magnetostratigraphy and biostratigraphy.

  1. Extinction and renewal of conditioned sexual responses.

    Directory of Open Access Journals (Sweden)

    Mirte Brom

    Full Text Available INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as addictions. Research on these phenomena in the sexual domain is lacking, where it may help to explain the persistence of learned sexual responses. METHOD: Men (n = 40 and women (n = 62 participated in a differential conditioning paradigm, with genital vibrotactile stimulation as US and neutral pictures as conditional stimuli (CSs. Dependent variables were genital and subjective sexual arousal, affect, US expectancy, and approach and avoid tendencies towards the CSs. Extinction and renewal of conditioned sexual responses were studied by context manipulation (AAA vs. ABA condition. RESULTS: No renewal effect of genital conditioned responding could be detected, but an obvious recovery of US expectancy following a context change after extinction (ABA was demonstrated. Additionally, women demonstrated recovery of subjective affect and subjective sexual arousal. Participants in the ABA demonstrated more approach biases towards stimuli. CONCLUSIONS: The findings support the context dependency of extinction and renewal of conditioned sexual responses in humans. This knowledge may have implications for the treatment of disturbances in sexual appetitive responses such as hypo- and hypersexuality.

  2. Spontaneous diuresis and negative fluid balance predicting recovery and survival in patients with trauma-hemorragic shock

    Institute of Scientific and Technical Information of China (English)

    缑东元; 朱雅芳; 金燕; 陈丽英

    2003-01-01

    @@ Most patients with trauma-hemorragic shock, prior to ICU admission, have been resuscitated and stabilized in the emergency room (ER) and/or operation room (OR). Many of them suffer from systemic edema. This extra-vascular fluid is caused by massive infusion of fluid and blood for the maintenance of blood pressure. During the recovery stage, the patients exhibit spontaneous diuresis followed by negative fluid balance. Urine volumes of some patients are more than 10 000 ml/d. Do we need to maintain a balance between daily input and output of water at this situation?

  3. The Role of Survivor Incumbency on the Evolutionary Recovery of Calcareous Nannoplankton from the Cretaceous/Paleogene (K/Pg) Mass Extinction

    Science.gov (United States)

    Schueth, J.; Bralower, T. J.; Jiang, S.; Patzkowsky, M.

    2012-12-01

    The earliest Paleocene provides a unique opportunity to investigate the dynamics of survivorship and recovery following a mass extinction. We are interested in how the calcareous nannoplankton, which served a vital role at the base of the marine food chain, recovered from the K/Pg mass extinction. Little is known about how new Paleogene nannoplankton evolved, where diversification took place and what role biologic competition had in the diversification and dispersal of newly evolved taxa. Nannoplankton have a detailed fossil record over the boundary, and 93% of nannoplankton species went extinct at the K/Pg. We focus on the evolutionary history of the new Paleocene nannoplankton, constraining when new species originated and where they first appeared. Our goals are to understand the development of Paleogene nannoplankton assemblages and the role that survivors played in the recovery. This study uses data from five deep-sea sediment cores and one surface stratigraphic section. Two locations, the North Pacific and South Atlantic, have well-established orbital age models. After the K/Pg boundary, there is a gradual transition between ecosystems dominated by survivors and bloom taxa to a global new Paleogene assemblage. We determined that the key Paleogene lineages of Coccolithus, Cruciplacolithus and Prinsius originated and diversified in the North Pacific before the other oceans. Eutrophic survivors rapidly expanded in Southern Hemisphere sites, and diversity peaked within 20 thousand years after the extinction. We hypothesize that the survivors formed an incumbent assemblage in the Southern Hemisphere, which, in turn, increased biologic competition for resources and likely limited significant diversification in the South Atlantic. Because new Paleogene taxa became abundant in the North Pacific more than 200 thousand years before they did in the Southern Hemisphere, we suggest survivor incumbency also acted as a biotic barrier to the global expansion of the newly

  4. Preventing return of fear in an animal model of anxiety: additive effects of massive extinction and extinction in multiple contexts.

    Science.gov (United States)

    Laborda, Mario A; Miller, Ralph R

    2013-06-01

    Fear conditioning and experimental extinction have been presented as models of anxiety disorders and exposure therapy, respectively. Moreover, the return of fear serves as a model of relapse after exposure therapy. Here we present two experiments, with rats as subjects in a lick suppression preparation, in which we assessed the additive effects of two different treatments to attenuate the return of fear. First, we evaluated whether two phenomena known to generate return of fear (i.e., spontaneous recovery and renewal) summate to produce a stronger reappearance of extinguished fear. At test, rats evaluated outside the extinction context following a long delay after extinction (i.e., a delayed context shift) exhibited greater return of extinguished fear than rats evaluated outside the extinction context alone, but return of extinguished fear following a delayed context shift did not significantly differ from the return of fear elicited in rats tested following a long delay after extinction alone. Additionally, extinction in multiple contexts and a massive extinction treatment each attenuated the strong return of fear produced by a delayed context shift. Moreover, the conjoint action of these treatments was significantly more successful in preventing the reappearance of extinguished fear, suggesting that extensive cue exposure administered in several different therapeutic settings has the potential to reduce relapse after therapy for anxiety disorders, more than either manipulation alone.

  5. Leber's hereditary optic neuropathy masquerading as optic neuritis with spontaneous visual recovery.

    Science.gov (United States)

    Hsu, Tsui-Kang; Wang, An-Guor; Yen, May-Yung; Liu, Jorn-Hon

    2014-01-01

    We report a case of Leber's hereditary optic neuropathy (LHON) masquerading as optic neuritis with late visual recovery. A 28-year-old man had gradual visual loss in both eyes for two weeks. Visual acuity was 0.4 in the right eye and 0.7 in the left. Fundus examination revealed hyperaemic discs in each eye. Fluorescein angiography revealed dye leakage at both optic discs in the late phase. Static perimetry (Humphrey 30-2) revealed bilateral relative central scotomata. Magnetic resonance imaging of the optic nerves was normal and his lumbar puncture showed normal opening pressure. He received steroid pulse therapy for three days. Nevertheless, vision in his right eye deteriorated to 0.1 one month later and left vision worsened to 0.05 six months later. Fifteen months after onset, his vision began to improve. At 21 months, his vision recovered to 0.9 R and 1.0 L. Peripheral blood DNA sequencing revealed 14484 mutation of mitochondrial DNA (mtDNA). Visual recovery can occur in patients with Leber's hereditary optic neuropathy with mtDNA 14484 mutation. LHON could be misdiagnosed as optic neuritis in some cases. Molecular examination of mtDNA mutation can confirm the diagnosis of LHON in clinically controversial patients. We should keep in mind the diagnosis of LHON when optic neuritis shows poor response to pulse therapy.

  6. Acute Nicotine Enhances Spontaneous Recovery of Contextual Fear and Changes "c-fos" Early Gene Expression in Infralimbic Cortex, Hippocampus, and Amygdala

    Science.gov (United States)

    Kutlu, Munir G.; Tumolo, Jessica M.; Holliday, Erica; Garrett, Brendan; Gould, Thomas J.

    2016-01-01

    Exposure therapy, which focuses on extinguishing fear-triggering cues and contexts, is widely used to treat post-traumatic stress disorder (PTSD). Yet, PTSD patients who received successful exposure therapy are vulnerable to relapse of fear response after a period of time, a phenomenon known as spontaneous recovery (SR). Increasing evidence…

  7. Memory extinction entails the inhibition of the transcription factor NF-kappaB.

    Directory of Open Access Journals (Sweden)

    Emiliano Merlo

    Full Text Available In contextual memories, an association between a positive or negative reinforcement and the contextual cues where the reinforcement occurs is formed. The re-exposure to the context without reinforcement can lead to memory extinction or reconsolidation, depending on the number of events or duration of a single event of context re-exposure. Extinction involves the temporary waning of the previously acquired conditioned response. The molecular processes underlying extinction and the mechanisms which determine if memory will reconsolidate or extinguish after retrieval are not well characterized, particularly the role of transcription factors and gene expression. Here we studied the participation of a transcription factor, NF-kappaB, in memory extinction. In the crab context-signal memory, the activation of NF-kappaB plays a critical role in consolidation and reconsolidation, memory processes that are well characterized in this model. The administration of a NF-kappaB inhibitor, sulfasalazine prior to extinction session impeded spontaneous recovery. Moreover, reinstatement experiments showed that the original memory was not affected and that NF-kappaB inhibition by sulfasalazine impaired spontaneous recovery strengthening the ongoing memory extinction process. Interestingly, in animals with fully consolidated memory, a brief re-exposure to the training context induced neuronal NF-kappaB activation and reconsolidation, while prolonged re-exposure induced NF-kappaB inhibition and memory extinction. These data constitutes a novel insight into the molecular mechanisms involved in the switch between memory reconsolidation and extinction. Moreover, we propose the inhibition of NF-kappaB as the engaged mechanism underlying extinction, supporting a novel approach for the pharmacological enhancement of this memory process. The accurate description of the molecular mechanisms that support memory extinction is potentially useful for developing new strategies

  8. Differential spontaneous recovery across cognitive abilities during detoxification period in alcohol-dependence.

    Science.gov (United States)

    Petit, Géraldine; Luminet, Olivier; Cordovil de Sousa Uva, Mariana; Zorbas, Alexis; Maurage, Pierre; de Timary, Philippe

    2017-01-01

    There is a lack of consensus regarding the extent to which cognitive dysfunctions may recover upon cessation of alcohol intake by alcohol-dependents (AD), and the divergent findings are most likely due to methodological differences between the various studies. The present study was aimed at conducting a very strict longitudinal study of cognitive recovery in terms of assessment points, the duration of abstinence, control of age and duration of the addiction, and by use of individual analyses in addition to mean group comparisons. Our study further focused on the 2-3 week phase of alcohol detoxification that is already known to positively affect many biological, emotional, motivational, as well as neural variables, followed by longer-term therapies for which good cognitive functioning is needed. 41 AD inpatients undergoing a detoxification program, and 41 matched controls, were evaluated twice in terms of five cognitive functions (i.e., short-term memory, working memory, inhibition, cognitive flexibility, and verbal fluency) within a three-week interval [on the first day (T1) and the 18th day (T2) of abstinence for AD patients]. Emotional (positive and negative affectivity and depression) and motivational (craving) variables were also measured at both evaluation times. Although verbal fluency, short-term memory, and cognitive flexibility did not appear to be affected, the patients exhibited impaired inhibition and working memory at T1. While no recovery of inhibition was found to occur, the average working memory performance of the patients was comparable to that of the controls at T2. Improvements in emotional and motivational dimensions were also observed, although they did not correlate with the ones in working memory. Individual analysis showed that not all participants were impaired or recover the same functions. While inhibition deficits appear to persist after 18 days of detoxification, deficits in working memory, which is a central component of cognition

  9. Differential spontaneous recovery across cognitive abilities during detoxification period in alcohol-dependence

    Science.gov (United States)

    Petit, Géraldine; Luminet, Olivier; Cordovil de Sousa Uva, Mariana; Zorbas, Alexis; Maurage, Pierre; de Timary, Philippe

    2017-01-01

    Objective There is a lack of consensus regarding the extent to which cognitive dysfunctions may recover upon cessation of alcohol intake by alcohol-dependents (AD), and the divergent findings are most likely due to methodological differences between the various studies. The present study was aimed at conducting a very strict longitudinal study of cognitive recovery in terms of assessment points, the duration of abstinence, control of age and duration of the addiction, and by use of individual analyses in addition to mean group comparisons. Our study further focused on the 2–3 week phase of alcohol detoxification that is already known to positively affect many biological, emotional, motivational, as well as neural variables, followed by longer-term therapies for which good cognitive functioning is needed. Methods 41 AD inpatients undergoing a detoxification program, and 41 matched controls, were evaluated twice in terms of five cognitive functions (i.e., short-term memory, working memory, inhibition, cognitive flexibility, and verbal fluency) within a three-week interval [on the first day (T1) and the 18th day (T2) of abstinence for AD patients]. Emotional (positive and negative affectivity and depression) and motivational (craving) variables were also measured at both evaluation times. Results Although verbal fluency, short-term memory, and cognitive flexibility did not appear to be affected, the patients exhibited impaired inhibition and working memory at T1. While no recovery of inhibition was found to occur, the average working memory performance of the patients was comparable to that of the controls at T2. Improvements in emotional and motivational dimensions were also observed, although they did not correlate with the ones in working memory. Individual analysis showed that not all participants were impaired or recover the same functions. Conclusions While inhibition deficits appear to persist after 18 days of detoxification, deficits in working memory, which

  10. The effect of ZnO nanoparticles on improved oil recovery in spontaneous imbibition mechanism of heavy oil production

    Science.gov (United States)

    Tajmiri, M.; Ehsani, M. R.; Mousavi, S. M.; Roayaei, E.; Emadi, A.

    2015-07-01

    Spontaneous imbibition (SI) gets a controversial subject in oil- wet carbonate reservoirs. The new concept of nanoparticles applications in an EOR area have been recently raised by researches about oil viscosity reduction and generate emulsion without surfactant. But a lot of questions have been remained about which nanoparticles can alter wettability from oil- wet to water- wet to improve oil recovery. This study introduces the new idea of adding ZnO nanoparticles (0.2%wt concentration) by experimental work on oil recovery. The main goals of this research were to prove that ZnO nanoparticles have the ability to reduce viscosity and also alter wettability. The ultimate objective was to determine the potential of these nanoparticles to imbibe into and displace oil. Through the use of Amott- cell, laboratory tests were conducted in two experiments on four cylindrical core samples (three sandstones and one carbonate) were taken from real Iranian heavy oil reservoir. In the first experiment, core samples were saturated by crude oil and in the second experiment, nanoparticles were flooding into core samples and then saturated by crude oil for about two weeks and after that they were immersed in distilled water and the amount of recovery was monitored during 30 days for both tests. We expected that ZnO nanoparticles decreased the surface tension which reduced the capillary forces through SI and wettability alteration took place towards a more water-wet system and caused the oil relative permeability to increase which dominated the gravitational forces to pull out the oil. Our results proved this expectation from ZnO nanoparticles clearly because carbonate core was oil- wet and the capillary pressure was high and negative to push water into the core so the original oil in place (OOIP) was zero whereas by adding ZnO nanoparticles OOIP was increased to 8.89%. SI yielded recovery values from 17.3, 2 and 15 without nanoparticles to 20.68, 17.57 and 36.2 % OOIP with

  11. Stressor controllability modulates fear extinction in humans.

    Science.gov (United States)

    Hartley, Catherine A; Gorun, Alyson; Reddan, Marianne C; Ramirez, Franchesca; Phelps, Elizabeth A

    2014-09-01

    Traumatic events are proposed to play a role in the development of anxiety disorders, however not all individuals exposed to extreme stress experience a pathological increase in fear. Recent studies in animal models suggest that the degree to which one is able to control an aversive experience is a critical factor determining its behavioral consequences. In this study, we examined whether stressor controllability modulates subsequent conditioned fear expression in humans. Participants were randomly assigned to an escapable stressor condition, a yoked inescapable stressor condition, or a control condition involving no stress exposure. One week later, all participants underwent fear conditioning, fear extinction, and a test of extinction retrieval the following day. Participants exposed to inescapable stress showed impaired fear extinction learning and increased fear expression the following day. In contrast, escapable stress improved fear extinction and prevented the spontaneous recovery of fear. Consistent with the bidirectional controllability effects previously reported in animal models, these results suggest that one's degree of control over aversive experiences may be an important factor influencing the development of psychological resilience or vulnerability in humans.

  12. Stimulus Over-Selectivity and Extinction-Induced Recovery of Performance as a Product of Intellectual Impairment and Autism Severity

    Science.gov (United States)

    Kelly, Michelle P.; Leader, Geraldine; Reed, Phil

    2015-01-01

    The current experiment investigated the extent to which three variables (autism severity, nonverbal intellectual functioning, and verbal intellectual functioning) are associated with over-selective responding in a group of children with Autism Spectrum Disorder. This paper also analyzed the association of these three variables with the recovery of…

  13. [Effect of needling the mimetic muscle on recovery of mimetic function in the patient of spontaneous facial paralysis].

    Science.gov (United States)

    Chen, Ri-Han; Chen, Ri-Li

    2008-11-01

    To observe therapeutic effects of different acupuncture methods for recovery of mimetic function in the patient of spontaneous facial paralysis. One hundred and thirty-four cases of facial paralysis were randomly divided into a mimetic muscle acupuncture group (mimetic muscle group, n = 79) and a routine acupoint group (n = 55). The mimetic muscle group were treated by encircling needling frontal belly of epicranial muscle, orbicular muscle of eye, orbicular muscle of mouth and buccinator muscle, and the routine acupoint group with acupuncture at Dicang (ST 4), Jiache (ST 6), Yangbai (GB 14), Sibai (ST 2), Cuanzhu (BL 2), etc. on the affected side. Their therapeutic effects were compared after they were treated for 2 courses. The effective rate and the good rate were 94.9% and 92.4% in the mimetic muscle group and 70.9% and 52.7% in the routine acupoint group, respectively, with a significant difference between the two groups (P facial paralysis is superior to that of the routine acupuncture therapy.

  14. Sedimentology and ichnology of two Lower Triassic sections in South China: Implications for the biotic recovery following the end-Permian mass extinction

    Science.gov (United States)

    Luo, Mao; George, Annette D.; Chen, Zhong-Qiang

    2016-09-01

    Biotic recovery following the end-Permian mass extinction was investigated using trace fossil and facies analysis of two Lower-Middle Triassic sections in South China. The Susong section (Lower Yangtze Sedimentary Province) comprises a range of carbonate and mudstone facies that record overall shallowing from offshore to intertidal settings. The Tianshengqiao section (Upper Yangtze Sedimentary Province) consists of mixed carbonate and siliciclastic facies deposited in shallow marine to offshore settings. Griesbachian to Dienerian ichnological records in both sections are characterized by low ichnodiversity, low ichnofabric indices (1-2) and low bedding plane bioturbation indices (1-2). Higher ichnofabric indices (3 and 4), corresponding to a dense population of diminutive ichnotaxon, in the Tianshengqiao section suggest opportunistic infaunal biotic activity during the earliest Triassic. Ichnological data from the Susong section show an increase in ichnodiversity during the late Smithian with 11 ichnogenera identified and increased ichnofabric indices of 4-5 and bedding plane bioturbation indices of 3-5. Although complex traces such as Rhizocorallium are present in Spathian-aged strata in this section, low ichnodiversity and ichnofabric indices and diminutive Planolites suggest a decline in recovery. In the Tianshengqiao section, ichnofabric indices are moderate to high (3-5) although only six ichnogenera are present and Planolites burrows are consistently small in Smithian and Spathian strata. Complex traces, such as large Rhizocorallium and Thalassinoides, and large Planolites, did not appear until the Anisian. Ichnological results from both sections record the response of organisms to unfavourable environmental conditions although the Susong section shows earlier recovery during the Smithian prior to latest Smithian-Spathian decline. This decline may have resulted from a resurgence of euxinic to anoxic marine environment in various regions of South China

  15. Neuronal circuits of fear extinction.

    Science.gov (United States)

    Herry, Cyril; Ferraguti, Francesco; Singewald, Nicolas; Letzkus, Johannes J; Ehrlich, Ingrid; Lüthi, Andreas

    2010-02-01

    Fear extinction is a form of inhibitory learning that allows for the adaptive control of conditioned fear responses. Although fear extinction is an active learning process that eventually leads to the formation of a consolidated extinction memory, it is a fragile behavioural state. Fear responses can recover spontaneously or subsequent to environmental influences, such as context changes or stress. Understanding the neuronal substrates of fear extinction is of tremendous clinical relevance, as extinction is the cornerstone of psychological therapy of several anxiety disorders and because the relapse of maladaptative fear and anxiety is a major clinical problem. Recent research has begun to shed light on the molecular and cellular processes underlying fear extinction. In particular, the acquisition, consolidation and expression of extinction memories are thought to be mediated by highly specific neuronal circuits embedded in a large-scale brain network including the amygdala, prefrontal cortex, hippocampus and brain stem. Moreover, recent findings indicate that the neuronal circuitry of extinction is developmentally regulated. Here, we review emerging concepts of the neuronal circuitry of fear extinction, and highlight novel findings suggesting that the fragile phenomenon of extinction can be converted into a permanent erasure of fear memories. Finally, we discuss how research on genetic animal models of impaired extinction can further our understanding of the molecular and genetic bases of human anxiety disorders.

  16. Characterization of spontaneous bone marrow recovery after sublethal total body irradiation: importance of the osteoblastic/adipocytic balance.

    Directory of Open Access Journals (Sweden)

    Géraldine Poncin

    Full Text Available Many studies have already examined the hematopoietic recovery after irradiation but paid with very little attention to the bone marrow microenvironment. Nonetheless previous studies in a murine model of reversible radio-induced bone marrow aplasia have shown a significant increase in alkaline phosphatase activity (ALP prior to hematopoietic regeneration. This increase in ALP activity was not due to cell proliferation but could be attributed to modifications of the properties of mesenchymal stem cells (MSC. We thus undertook a study to assess the kinetics of the evolution of MSC correlated to their hematopoietic supportive capacities in mice treated with sub lethal total body irradiation. In our study, colony-forming units-fibroblasts (CFU-Fs assay showed a significant MSC rate increase in irradiated bone marrows. CFU-Fs colonies still possessed differentiation capacities of MSC but colonies from mice sacrificed 3 days after irradiation displayed high rates of ALP activity and a transient increase in osteoblastic markers expression while pparγ and neuropilin-1 decreased. Hematopoietic supportive capacities of CFU-Fs were also modified: as compared to controls, irradiated CFU-Fs significantly increased the proliferation rate of hematopoietic precursors and accelerated the differentiation toward the granulocytic lineage. Our data provide the first evidence of the key role exerted by the balance between osteoblasts and adipocytes in spontaneous bone marrow regeneration. First, (preosteoblast differentiation from MSC stimulated hematopoietic precursor's proliferation and granulopoietic regeneration. Then, in a second time (preosteoblasts progressively disappeared in favour of adipocytic cells which down regulated the proliferation and granulocytic differentiation and then contributed to a return to pre-irradiation conditions.

  17. Compound stimulus presentation and the norepinephrine reuptake inhibitor atomoxetine enhance long-term extinction of cocaine-seeking behavior.

    Science.gov (United States)

    Janak, Patricia H; Bowers, M Scott; Corbit, Laura H

    2012-03-01

    Drug abstinence is frequently compromised when addicted individuals are re-exposed to environmental stimuli previously associated with drug use. Research with human addicts and in animal models has demonstrated that extinction learning (non-reinforced cue-exposure) can reduce the capacity of such stimuli to induce relapse, yet extinction therapies have limited long-term success under real-world conditions (Bouton, 2002; O'Brien, 2008). We hypothesized that enhancing extinction would reduce the later ability of drug-predictive cues to precipitate drug-seeking behavior. We, therefore, tested whether compound stimulus presentation and pharmacological treatments that augment noradrenergic activity (atomoxetine; norepinephrine reuptake inhibitor) during extinction training would facilitate the extinction of drug-seeking behaviors, thus reducing relapse. Rats were trained that the presentation of a discrete cue signaled that a lever press response would result in cocaine reinforcement. Rats were subsequently extinguished and spontaneous recovery of drug-seeking behavior following presentation of previously drug-predictive cues was tested 4 weeks later. We find that compound stimulus presentations or pharmacologically increasing noradrenergic activity during extinction training results in less future recovery of responding, whereas propranolol treatment reduced the benefit seen with compound stimulus presentation. These data may have important implications for understanding the biological basis of extinction learning, as well as for improving the outcome of extinction-based therapies.

  18. Extinction of drug cue reactivity in methamphetamine-dependent individuals.

    Science.gov (United States)

    Price, Kimber L; Saladin, Michael E; Baker, Nathaniel L; Tolliver, Bryan K; DeSantis, Stacia M; McRae-Clark, Aimee L; Brady, Kathleen T

    2010-09-01

    Conditioned responses to drug-related environmental cues (such as craving) play a critical role in relapse to drug use. Animal models demonstrate that repeated exposure to drug-associated cues in the absence of drug administration leads to the extinction of conditioned responses, but the few existing clinical trials focused on extinction of conditioned responses to drug-related cues in drug-dependent individuals show equivocal results. The current study examined drug-related cue reactivity and response extinction in a laboratory setting in methamphetamine-dependent individuals. Methamphetamine cue-elicited craving was extinguished during two sessions of repeated (3) within-session exposures to multi-modal (picture, video, and in-vivo) cues, with no evidence of spontaneous recovery between sessions. A trend was noted for a greater attenuation of response in participants with longer (4-7 day) inter-session intervals. These results indicate that extinction of drug cue conditioned responding occurs in methamphetamine-dependent individuals, offering promise for the development of extinction- based treatment strategies. 2010 Elsevier Ltd. All rights reserved.

  19. Extinction of Drug Cue Reactivity in Methamphetamine-Dependent Individuals

    Science.gov (United States)

    Price, Kimber L.; Saladin, Michael E.; Baker, Nathaniel L.; Tolliver, Bryan K.; DeSantis, Stacia M.; McRae-Clark, Aimee L.; Brady, Kathleen T.

    2010-01-01

    Conditioned responses to drug-related environmental cues (such as craving) play a critical role in relapse to drug use. Animal models demonstrate that repeated exposure to drug-associated cues in the absence of drug administration leads to the extinction of conditioned responses, but the few existing clinical trials focused on extinction of conditioned responses to drug-related cues in drug-dependent individuals show equivocal results. The current study examined drug-related cue reactivity and response extinction in a laboratory setting in methamphetamine-dependent individuals. Methamphetamine cue-elicited craving was extinguished during two sessions of repeated (3) within-session exposures to multi-modal (picture, video, and in-vivo) cues, with no evidence of spontaneous recovery between sessions. A trend was noted for a greater attenuation of response in participants with longer (4-7 day) inter-session intervals. These results indicate that extinction of drug-cue conditioned responding occurs in methamphetamine-dependent individuals, offering promise for the development of extinction- based treatment strategies. PMID:20538262

  20. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow

    2004-07-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  1. Fundamentals of Reservoir Surface Energy as Related to Surface Properties, Wettability, Capillary Action, and Oil Recovery from Fractured Reservoirs by Spontaneous Imbibition

    Energy Technology Data Exchange (ETDEWEB)

    Norman Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Zhengxin Tong; Evren Unsal; Siluni Wickramathilaka; Shaochang Wo; Peigui Yin

    2008-06-30

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  2. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Peigui Yin; Shaochang Wo

    2005-02-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  3. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Peigui Yin; Shaochang Wo

    2004-10-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  4. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Peigui Yin; Shaochang Wo

    2005-04-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  5. Fundamentals of reservoir surface energy as related to surface properties, wettability, capillary action, and oil recovery from fractured reservoirs by spontaneous imbibition

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Jason Zhengxin Tong; Peigui Yin; Shaochang Wo

    2006-02-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  6. Rethinking Extinction.

    Science.gov (United States)

    Dunsmoor, Joseph E; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A

    2015-10-07

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Rethinking Extinction

    OpenAIRE

    Dunsmoor, Joseph E.; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A.

    2015-01-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavior...

  8. β-Adrenoceptor Blockade in the Basolateral Amygdala, But Not the Medial Prefrontal Cortex, Rescues the Immediate Extinction Deficit.

    Science.gov (United States)

    Giustino, Thomas F; Seemann, Jocelyn R; Acca, Gillian M; Goode, Travis D; Fitzgerald, Paul J; Maren, Stephen

    2017-05-02

    Early psychological interventions, such as exposure therapy, rely on extinction learning to reduce the development of stress- and trauma-related disorders. However, recent research suggests that extinction often fails to reduce fear when administered soon after trauma. This immediate extinction deficit (IED) may be due to stress-induced dysregulation of neural circuits involved in extinction learning. We have shown that systemic β-adrenoceptor blockade with propranolol rescues the IED, but impairs delayed extinction. Here we sought to determine the neural locus of these effects. Rats underwent auditory fear conditioning and then received either immediate (30 min) or delayed (24 h) extinction training. We used bilateral intracranial infusions of propranolol into either the infralimbic division of the medial prefrontal cortex (mPFC) or the basolateral amygdala (BLA) to examine the effects of β-adrenoceptor blockade on immediate and delayed extinction learning. Interestingly, intra-BLA, but not intra-mPFC, propranolol rescued the IED; animals receiving intra-BLA propranolol prior to immediate extinction showed less spontaneous recovery of fear during extinction retrieval. Importantly, this was not due to impaired consolidation of the conditioning memory. In contrast, neither intra-BLA nor intra-mPFC propranolol affected delayed extinction learning. Overall, these data contribute to a growing literature suggesting dissociable roles for key nodes in the fear extinction circuit depending on the timing of extinction relative to conditioning. These data also suggest that heightened noradrenergic activity in the BLA underlies stress-induced extinction deficits. Propranolol may be a useful adjunct to behavioral therapeutic interventions in recently traumatized individuals who are at risk for developing trauma-related disorders.Neuropsychopharmacology advance online publication, 31 May 2017; doi:10.1038/npp.2017.89.

  9. Lesions of Rat Infralimbic Cortex Enhance Recovery and Reinstatement of an Appetitive Pavlovian Response

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    Rhodes, Sarah E. V.; Kilcross, Simon

    2004-01-01

    The prefrontal cortex (PFC) has a well-established role in the inhibition of inappropriate responding, and evidence suggests that the infralimbic (IL) region of the rat medial PFC (MPFC) may be involved in some aspects of extinction of conditioned fear. MPFC lesions including, but not those sparing the IL cortex increase spontaneous recovery of…

  10. Early Silurian (Aeronian East Point Coral Patch Reefs of Anticosti Island, Eastern Canada: First Reef Recovery from the Ordovician/Silurian Mass Extinction in Eastern Laurentia

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    Jisuo Jin

    2012-05-01

    Full Text Available An extensive late Aeronian patch reef swarm outcrops for 60–70 km on Anticosti Island, eastern Canada, located in the inner to mid-shelf area of a prominent tropical carbonate platform of southeastern Laurentia, at 20°–25° S paleolatitude of the southern typhoon belt. This complex, described here for the first time, includes more than 100 patch reefs, up to 60–80 m in diameter and 10 m high. Reefs are exposed three-dimensionally on present-day tidal flats, as well as inland along roads and rivers. Down the gentle 1°–2° paleoslope, the reefs grade into coral-sponge biostromes, and westerly they grade into inter-reef or deeper ‘crinoidal meadow’ facies. The reef builders were dominantly tabulate and rugose corals, with lesser stromatoporoids. Other components include crinoids, brachiopods, green algae (especially paleoporellids, and encrusting cyanobacteria: reefs display some of the earliest known symbiotic intergrowths of corals and stromatoporoids. Reefs were variably built on a base of crinoidal grainstones, meadows of baffling tabulate corals, brachiopod shells, or chlorophytes. These reefs mark an early phase of reef recovery after a prominent reef gap of 5–6 million years following the Ordovician/Silurian mass extinction events. The reefs feature a maximal diversity of calcifying cyanobacteria, corals and stromatoporoids, but low diversity of brachiopods, nautiloids and crinoids. Following the North American Stratigraphic Code, we define herein the Menier Formation, encompassing the lower two members of the existing Jupiter Formation.

  11. From lab to clinic: Extinction of cued cravings to reduce overeating.

    Science.gov (United States)

    Jansen, Anita; Schyns, Ghislaine; Bongers, Peggy; van den Akker, Karolien

    2016-08-01

    Food cue reactivity is a strong motivation to eat, even in the absence of hunger. Therefore, food cue reactivity might sabotage healthy eating, induce weight gain and impede weight loss or weight maintenance. Food cue reactivity can be learned via Pavlovian appetitive conditioning: It is easily acquired but the extinction of appetitive responding seems to be more challenging. Several properties of extinction make it fragile: extinction does not erase the original learning and extinction is context-dependent. These properties threaten full extinction and increase the risk of full relapse. Extinction procedures are discussed to reduce or prevent the occurrence of rapid reacquisition, spontaneous recovery, renewal and reinstatement after extinction. A translation to food cue exposure treatment is made and suggestions are provided, such as conducting the exposure in relevant contexts, using occasional reinforcement and targeting expectancy violation instead of habituation. A new hypothesis proposed here is that the adding of inhibition training to strengthen inhibition skills that reduce instrumental responding, might be beneficial to improve food cue exposure effects.

  12. Extinction from a rationalist perspective.

    Science.gov (United States)

    Gallistel, C R

    2012-05-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: (1) the failure of partial reinforcement to increase reinforcements to acquisition; (2) the partial reinforcement extinction effect; (3) spontaneous recovery; (4) renewal; (5) reinstatement; (6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Extinction learning, reconsolidation and the internal reinforcement hypothesis.

    Science.gov (United States)

    Eisenhardt, Dorothea; Menzel, Randolf

    2007-02-01

    Retrieving a consolidated memory--by exposing an animal to the learned stimulus but not to the associated reinforcement--leads to two opposing processes: one that weakens the old memory as a result of extinction learning, and another that strengthens the old, already-consolidated memory as a result of some less well-understood form of learning. This latter process of memory strengthening is often referred to as "reconsolidation", since protein synthesis can inhibit this form of memory formation. Although the behavioral phenomena of the two antagonizing forms of learning are well documented, the mechanisms behind the corresponding processes of memory formation are still quite controversial. Referring to results of extinction/reconsolidation experiments in honeybees, we argue that two opposing learning processes--with their respective consolidation phases and memories--are initiated by retrieval trials: extinction learning and reminder learning, the latter leading to the phenomenon of spontaneous recovery from extinction, a process that can be blocked with protein synthesis inhibition.

  14. A novel UCS memory retrieval-extinction procedure to inhibit relapse to drug seeking

    Science.gov (United States)

    Luo, Yi-xiao; Xue, Yan-xue; Liu, Jian-feng; Shi, Hai-shui; Jian, Min; Han, Ying; Zhu, Wei-li; Bao, Yan-ping; Wu, Ping; Ding, Zeng-bo; Shen, Hao-wei; Shi, Jie; Shaham, Yavin; Lu, Lin

    2015-01-01

    We recently reported that a conditioned stimulus (CS) memory retrieval-extinction procedure decreases reinstatement of cocaine and heroin seeking in rats and heroin craving in humans. Here we show that non-contingent cocaine or methylphenidate injections (UCS retrieval) 1 h before the extinction sessions decreases cocaine-priming-induced reinstatement, spontaneous recovery, and renewal of cocaine seeking in rats. Unlike the CS-based memory retrieval-extinction procedure, the UCS memory retrieval manipulation decreases renewal and reinstatement of cocaine seeking in the presence of cocaine cues that were not present during extinction training and also decreases cocaine seeking when the procedure commences after 28 days of abstinence. The inhibitory effect of the UCS retrieval manipulation on cocaine-priming-induced reinstatement is mediated by regulation of AMPA-receptor endocytosis in the basolateral amygdala. The UCS memory retrieval-extinction procedure has superior relapse prevention characteristics than the CS memory retrieval-extinction procedure and could be a promising method for decreasing relapse in human addicts. PMID:26169171

  15. How Effective Is Therapy for Childhood Stuttering? Dissecting and Reinterpreting the Evidence in Light of Spontaneous Recovery Rates

    Science.gov (United States)

    Saltuklaroglu, Tim; Kalinowski, Joseph

    2005-01-01

    Background: Similar positive results (e.g. immediate decreases in stuttering frequency and a 60-80% recovery rate from stuttering) have been reported for numerous therapeutic protocols for treating childhood stuttering, many of which have been diametrically opposite in their orientations and implementations. For example, Johnson advocated indirect…

  16. Early endogenous activation of CB1 and CB2 receptors after spinal cord injury is a protective response involved in spontaneous recovery.

    Science.gov (United States)

    Arevalo-Martin, Angel; Garcia-Ovejero, Daniel; Sierra-Palomares, Yolanda; Paniagua-Torija, Beatriz; Gonzalez-Gil, Ines; Ortega-Gutierrez, Silvia; Molina-Holgado, Eduardo

    2012-01-01

    Spinal cord injury (SCI) induces a cascade of processes that may further expand the damage (secondary injury) or, alternatively, may be part of a safeguard response. Here we show that after a moderate-severe contusive SCI in rats there is a significant and very early increase in the spinal cord content of the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoyl ethanolamide (anandamide, AEA). Since 2-AG and AEA act through CB1 and CB2 cannabinoid receptors, we administered at 20 minutes after lesion a single injection of their respective antagonists AM281 and AM630 alone or in combination to block the effects of this early endocannabinoid accumulation. We observed that AM281, AM630 or AM281 plus AM630 administration impairs the spontaneous motor recovery of rats according to the Basso-Beattie-Bresnahan (BBB) locomotor scale. However, blockade of CB1, CB2 or both receptors produced different effects at the histopathological level. Thus, AM630 administration results at 90 days after lesion in increased MHC-II expression by spinal cord microglia/monocytes and reduced number of serotoninergic fibres in lumbar spinal cord (below the lesion). AM281 exerted the same effects but also increased oedema volume estimated by MRI. Co-administration of AM281 and AM630 produced the effects observed with the administration of either AM281 or AM630 and also reduced white matter and myelin preservation and enhanced microgliosis in the epicentre. Overall, our results suggest that the endocannabinoids acting through CB1 and CB2 receptors are part of an early neuroprotective response triggered after SCI that is involved in the spontaneous recovery after an incomplete lesion.

  17. Early endogenous activation of CB1 and CB2 receptors after spinal cord injury is a protective response involved in spontaneous recovery.

    Directory of Open Access Journals (Sweden)

    Angel Arevalo-Martin

    Full Text Available Spinal cord injury (SCI induces a cascade of processes that may further expand the damage (secondary injury or, alternatively, may be part of a safeguard response. Here we show that after a moderate-severe contusive SCI in rats there is a significant and very early increase in the spinal cord content of the endocannabinoids 2-arachidonoylglycerol (2-AG and arachidonoyl ethanolamide (anandamide, AEA. Since 2-AG and AEA act through CB1 and CB2 cannabinoid receptors, we administered at 20 minutes after lesion a single injection of their respective antagonists AM281 and AM630 alone or in combination to block the effects of this early endocannabinoid accumulation. We observed that AM281, AM630 or AM281 plus AM630 administration impairs the spontaneous motor recovery of rats according to the Basso-Beattie-Bresnahan (BBB locomotor scale. However, blockade of CB1, CB2 or both receptors produced different effects at the histopathological level. Thus, AM630 administration results at 90 days after lesion in increased MHC-II expression by spinal cord microglia/monocytes and reduced number of serotoninergic fibres in lumbar spinal cord (below the lesion. AM281 exerted the same effects but also increased oedema volume estimated by MRI. Co-administration of AM281 and AM630 produced the effects observed with the administration of either AM281 or AM630 and also reduced white matter and myelin preservation and enhanced microgliosis in the epicentre. Overall, our results suggest that the endocannabinoids acting through CB1 and CB2 receptors are part of an early neuroprotective response triggered after SCI that is involved in the spontaneous recovery after an incomplete lesion.

  18. Spontaneous recovery of memory functions in an untreated case of anti NMDAR encephalitis - a reason to maintain hope.

    Science.gov (United States)

    McIvor, Katherine; Moore, Perry

    2017-01-01

    Anti N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder that was only fully discovered recently and neuropsychological outcome data remains sparse. We present the case of BA, a 19-year-old male, which illustrates the cognitive outcome in an untreated case over a time period of over 2½ years. We conducted three cognitive assessments, including tests of memory and executive functioning, over this time period and considered the evidence for reliable change in memory function using the Wechsler Advanced Clinical Solutions (ACS) serial assessment package. Our findings revealed mild memory problems 6 months post-discharge with, at best, static and potentially declining memory functioning at follow-up assessment 12 months post-discharge. However, the results of testing at 30 months post-discharge revealed significant improvements in immediate and delayed memory index performances. Our report of a case of anti-NMDAR encephalitis provides evidence for spontaneous improvements in memory functioning occurring more than 2 years after initial assessment and also demonstrates both the utility and potential limitations of the ACS serial assessment software when used in a relatively typical clinical assessment situation.

  19. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction.

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    Andrew Z Krug

    Full Text Available Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL as a proxy for phylogenetic clustering, we find that A both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns.

  20. Isolated effects of number of acquisition trials on extinction of rat conditioned approach behavior.

    Science.gov (United States)

    Gottlieb, Daniel A; Prince, Emily B

    2012-05-01

    Four conditioned approach experiments with rats assessed for effects of number of acquisition trials on extinction of conditioned responding, when number of acquisition sessions and total acquisition time were held constant. In Experiment 1, 32 trials per acquisition session led to more extinction responding than did 1 or 2 trials per session but less than did 4 trials per session. In Experiment 2, 2 trials per acquisition session led to more spontaneous recovery than did 32 trials per session. These latter findings are reminiscent of the overtraining extinction effect (OEE). Experiment 3 attempted to reduce the OEE with a preconditioning phase of partial reinforcement. Experiment 4 attempted to reduce the beneficial within-subject effects of increasing the number of acquisition trials on extinction observed by Gottlieb and Rescorla (2010) by extinguishing stimuli in different sessions. Overall, results suggest a procedural asymmetry: between-subject, increasing the number of trials between any pair of trials does not lead to greater persistence of responding during extinction; within-subject, it does. Results are discussed from an associative perspective, with a focus on explanations involving either frustration or comparator mechanisms, and from an information processing perspective, with a focus on Rate Estimation Theory.

  1. Serotonin transporter polyadenylation polymorphism modulates the retention of fear extinction memory.

    Science.gov (United States)

    Hartley, Catherine A; McKenna, Morgan C; Salman, Rabia; Holmes, Andrew; Casey, B J; Phelps, Elizabeth A; Glatt, Charles E

    2012-04-01

    Growing evidence suggests serotonin's role in anxiety and depression is mediated by its effects on learned fear associations. Pharmacological and genetic manipulations of serotonin signaling in mice alter the retention of fear extinction learning, which is inversely associated with anxious temperament in mice and humans. Here, we test whether genetic variation in serotonin signaling in the form of a common human serotonin transporter polyadenylation polymorphism (STPP/rs3813034) is associated with spontaneous fear recovery after extinction. We show that the risk allele of this polymorphism is associated with impaired retention of fear extinction memory and heightened anxiety and depressive symptoms. These STPP associations in humans mirror the phenotypic effects of serotonin transporter knockout in mice, highlighting the STPP as a potential genetic locus underlying interindividual differences in serotonin transporter function in humans. Furthermore, we show that the serotonin transporter polyadenylation profile associated with the STPP risk allele is altered through the chronic administration of fluoxetine, a treatment that also facilitates retention of extinction learning. The propensity to form persistent fear associations due to poor extinction recall may be an intermediate phenotype mediating the effects of genetic variation in serotonergic function on anxiety and depression. The consistency and specificity of these data across species provide robust support for this hypothesis and suggest that the little-studied STPP may be an important risk factor for mood and anxiety disorders in humans.

  2. Interstellar Extinction

    Science.gov (United States)

    Gontcharov, G. A.

    2016-12-01

    This review describes our current understanding of interstellar extinction. This differ substantially from the ideas of the 20th century. With infrared surveys of hundreds of millions of stars over the entire sky, such as 2MASS, SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions of the interstellar medium at distances of a few kpc from the Sun. Observations at infrared and microwave wavelengths, where the bulk of the interstellar dust absorbs and radiates, have brought us closer to an understanding of the distribution of the dust particles on scales of the Galaxy and the universe. We are in the midst of a scientific revolution in our understanding of the interstellar medium and dust. Progress in, and the key results of, this revolution are still difficult to predict. Nevertheless, (a) a physically justified model has been developed for the spatial distribution of absorbing material over the nearest few kiloparsecs, including the Gould belt as a dust container, which gives an accurate estimate of the extinction for any object just by its galactic coordinates. It is also clear that (b) the interstellar medium contains roughly half the mass of matter in the galactic vicinity of the solar system (the other half is made up of stars, their remnants, and dark matter) and (c) the interstellar medium and, especially, dust, differ substantially in different regions of space and deep space cannot be understood by only studying near space.

  3. Neostigmine Administration after Spontaneous Recovery to a Train-of-Four Ratio of 0.9 to 1.0: A Randomized Controlled Trial of the Effect on Neuromuscular and Clinical Recovery.

    Science.gov (United States)

    Murphy, Glenn S; Szokol, Joseph W; Avram, Michael J; Greenberg, Steven B; Shear, Torin D; Deshur, Mark A; Benson, Jessica; Newmark, Rebecca L; Maher, Colleen E

    2017-09-27

    When a muscle relaxant is administered to facilitate intubation, the benefits of anticholinesterase reversal must be balanced with potential risks. The aim of this double-blinded, randomized noninferiority trial was to evaluate the effect of neostigmine administration on neuromuscular function when given to patients after spontaneous recovery to a train-of-four ratio of 0.9 or greater. A total of 120 patients presenting for surgery requiring intubation were given a small dose of rocuronium. At the conclusion of surgery, 90 patients achieving a train-of-four ratio of 0.9 or greater were randomized to receive either neostigmine 40 μg/kg or saline (control). Train-of-four ratios were measured from the time of reversal until postanesthesia care unit admission. Patients were monitored for postextubation adverse respiratory events and assessed for muscle strength. Ninety patients achieved a train-of-four ratio of 0.9 or greater at the time of reversal. Mean train-of-four ratios in the control and neostigmine groups before reversal (1.02 vs. 1.03), 5 min postreversal (1.05 vs. 1.07), and at postanesthesia care unit admission (1.06 vs. 1.08) did not differ. The mean difference and corresponding 95% CI of the latter were -0.018 and -0.046 to 0.010. The incidences of postoperative hypoxemic events and episodes of airway obstruction were similar for the groups. The number of patients with postoperative signs and symptoms of muscle weakness did not differ between groups (except for double vision: 13 in the control group and 2 in the neostigmine group; P = 0.001). Administration of neostigmine at neuromuscular recovery was not associated with clinical evidence of anticholinesterase-induced muscle weakness.

  4. Learning and the persistence of appetite: extinction and the motivation to eat and overeat.

    Science.gov (United States)

    Bouton, Mark E

    2011-04-18

    The modern world is saturated with highly palatable and highly available food, providing many opportunities to associate food with environmental cues and actions (through Pavlovian and operant or instrumental learning, respectively). Basic learning processes can often increase the tendency to approach and consume food, whereas extinction, in which Pavlovian and operant behaviors decline when the reinforcer is withheld, weakens but does not erase those tendencies. Contemporary research suggests that extinction involves an inhibitory form of new learning that appears fragile because it is highly dependent on the context for expression. These ideas are supported by the phenomena of renewal, spontaneous recovery, resurgence, reinstatement, and rapid reacquisition in appetitive learning, which together may help explain why overeating may be difficult to suppress permanently, and why appetitive behavior may seem so persistent.

  5. Effects of Recent Exposure to a Conditioned Stimulus on Extinction of Pavlovian Fear Conditioning

    Science.gov (United States)

    Chan, Wan Yee Macy; Leung, Hiu T.; Westbrook, R. Frederick; McNally, Gavan P.

    2010-01-01

    In six experiments we studied the effects of a single re-exposure to a conditioned stimulus (CS; "retrieval trial") prior to extinction training (extinction-reconsolidation boundary) on the development of and recovery from fear extinction. A single retrieval trial prior to extinction training significantly augmented the renewal and reinstatement…

  6. A potential recovery of a population of the sand lizard Liolaemus lutzae Mertens, 1938 in an area within its range: a lizard endemic and threatened with extinction

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    CFD. Rocha

    Full Text Available The endemic and threatened lizard Liolaemus lutzae has a relatively small geographic range restricted to only 200 km of along the coast of Rio de Janeiro State, Brazil, which are habitats under intensive anthropic disturbance. At the Barra da Tijuca beach, in Rio de Janeiro city an estimate of the population abundance made in 1991, compared to a previous estimate made in 1984, showed a considerable decrease (about 65%. Most of the decrease was attributed to anthropic disturbances that locally affected the beach vegetation, the species habitat. In this study we present estimates made in 2002 and in 2006 at the same area and compare them with the estimates of 1984 and 1991, using the same methodology in order to make comparable the data from different samplings years and to evaluate the present status of the local population. The estimated indexes of L. lutzae abundance in 2002 and in 2006 were higher than that of 1991. There was a significant increase in the mean number of recorded lizards in 2002 compared to 1991, but the mean number of lizards sighted in 2006 remained stable when compared with that of 2002. Our data based on the index of abundance recorded suggested that the number of L. lutzae at Barra da Tijuca beach recorded increased, which can be indicative of a potential recovery of the local population.

  7. Cannabinoid facilitation of fear extinction memory recall in humans

    Science.gov (United States)

    Rabinak, Christine A.; Angstadt, Mike; Sripada, Chandra S.; Abelson, James L.; Liberzon, Israel; Milad, Mohammed R.; Phan, K. Luan

    2012-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of the cannabinoid system during extinction learning enhances fear extinction and its retention. Specifically, CB1 receptor agonists, such as Δ9-tetrahydrocannibinol (THC), can facilitate extinction recall by preventing recovery of extinguished fear in rats. However, this phenomenon has not been investigated in humans. We conducted a study using a randomized, double-blind, placebo-controlled, between-subjects design, coupling a standard Pavlovian fear extinction paradigm and simultaneous skin conductance response (SCR) recording with an acute pharmacological challenge with oral dronabinol (synthetic THC) or placebo (PBO) 2 hours prior to extinction learning in 29 healthy adult volunteers (THC = 14; PBO = 15) and tested extinction retention 24 hours after extinction learning. Compared to subjects that received PBO, subjects that received THC showed low SCR to a previously extinguished CS when extinction memory recall was tested 24 hours after extinction learning, suggesting that THC prevented the recovery of fear. These results provide the first evidence that pharmacological enhancement of extinction learning is feasible in humans using cannabinoid system modulators, which may thus warrant further development and clinical testing. PMID:22796109

  8. Gradual extinction reduces Reinstatement

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    Youssef eShiban

    2015-09-01

    Full Text Available The current study investigated whether gradually reducing the frequency of aversive stimuli during extinction can prevent the return of fear. Thirty-one participants of a three-stage procedure (acquisition, extinction and a reinstatement test on day two were randomly assigned to a standard extinction (SE and gradual extinction (GE procedure. The two groups differed only in the extinction procedure. While the SE group ran through a regular extinction process without any negative events, the frequency of the aversive stimuli during the extinction phase was gradually reduced for the GE group. The unconditioned stimulus was an air blast (5 bar, 10 ms. A spider and a scorpion were used as conditioned stimuli. The outcome variables were contingency ratings and physiological measures (skin conductance response and startle response. There were no differences found between the two groups for the acquisition and extinction phases concerning contingency ratings, SCR, or startle response. Gradual extinction compared to standard extinction significantly reduced the return of fear in the reinstatement test for the startle response but not for skin conductance response or contingency ratings. This study was successful in translating the findings in rodent to humans. The results suggest that the gradual extinction process is suitable for increasing the efficacy of fear extinction.

  9. Spontaneous recovery and treatment effects in patients with homonymous visual field defects : A meta-analysis of existing literature in terms of the ICF framework

    NARCIS (Netherlands)

    de Haan, Gera A.; Heutink, Joost; Melis-Dankers, Bart; Tucha, Oliver; Brouwer, Wiebo H.

    2014-01-01

    Homonymous visual field defects (HVFDs) are a common consequence of posterior brain injury. Most patients do not recover spontaneously and require rehabiliation. To determine whether a certain intervention may help an individual patient, it is necessary to predict the patient's level of functioning

  10. Spontaneous recovery and treatment effects in patients with homonymous visual field defects : A meta-analysis of existing literature in terms of the ICF framework

    NARCIS (Netherlands)

    de Haan, Gera A.; Heutink, Joost; Melis-Dankers, Bart; Tucha, Oliver; Brouwer, Wiebo H.

    2014-01-01

    Homonymous visual field defects (HVFDs) are a common consequence of posterior brain injury. Most patients do not recover spontaneously and require rehabiliation. To determine whether a certain intervention may help an individual patient, it is necessary to predict the patient's level of functioning

  11. Is extinction forever?

    Science.gov (United States)

    Smith-Patten, Brenda D; Bridge, Eli S; Crawford, Priscilla H C; Hough, Daniel J; Kelly, Jeffrey F; Patten, Michael A

    2015-05-01

    Mistrust of science has seeped into public perception of the most fundamental aspect of conservation-extinction. The term ought to be straightforward, and yet, there is a disconnect between scientific discussion and public views. This is not a mere semantic issue, rather one of communication. Within a population dynamics context, we say that a species went locally extinct, later to document its return. Conveying our findings matters, for when we use local extinction, an essentially nonsensical phrase, rather than extirpation, which is what is meant, then we contribute to, if not create outright, a problem for public understanding of conservation, particularly as local extinction is often shortened to extinction in media sources. The public that receives the message of our research void of context and modifiers comes away with the idea that extinction is not forever or, worse for conservation as a whole, that an extinction crisis has been invented.

  12. Hypoxia, global warming, and terrestrial late Permian extinctions.

    Science.gov (United States)

    Huey, Raymond B; Ward, Peter D

    2005-04-15

    A catastrophic extinction occurred at the end of the Permian Period. However, baseline extinction rates appear to have been elevated even before the final catastrophe, suggesting sustained environmental degradation. For terrestrial vertebrates during the Late Permian, the combination of a drop in atmospheric oxygen plus climate warming would have induced hypoxic stress and consequently compressed altitudinal ranges to near sea level. Our simulations suggest that the magnitude of altitudinal compression would have forced extinctions by reducing habitat diversity, fragmenting and isolating populations, and inducing a species-area effect. It also might have delayed ecosystem recovery after the mass extinction.

  13. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    No species lives forever, and extinction is the ultimate fate of all living species. The fossil record indicates that a recent extinction wave affecting terrestrial vertebrates was parallel with the arrival of modern humans to areas formerly uninhabited by them. These modern instances of extinction...... started at around 40,000 years ago. On continents, large mammals (especially those >50 kg body mass) were affected, while on islands, the impacts were mainly felt by birds. The causes of these extinctions are not well known but hunting, habitat alteration and the introduction of non-native species...... reasons (certain groups do not fossilize) and methodological problems (methods of excavation and identification). Consequently, we can only crudely estimate the current rate of extinction. Nonetheless, it is evident that humans generated a new mass extinction, affecting all species in all habitats, and...

  14. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    No species lives forever, and extinction is the ultimate fate of all living species. The fossil record indicates that a recent extinction wave affecting terrestrial vertebrates was parallel with the arrival of modern humans to areas formerly uninhabited by them. These modern instances of extinction...... started at around 40,000 years ago. On continents, large mammals (especially those >50 kg body mass) were affected, while on islands, the impacts were mainly felt by birds. The causes of these extinctions are not well known but hunting, habitat alteration and the introduction of non-native species...... are the main causes of extinction. Our knowledge about extinctions is very incomplete, due to bias in research by taxonomy (vertebrate groups are better studied), geography (northern areas have received more attention), habitat (terrestrial habitats are better known than marine ones), as well as biological...

  15. Spontaneous pneumothorax

    Directory of Open Access Journals (Sweden)

    Davari R

    1996-07-01

    Full Text Available A case with bilateral spontaneous pneumothorax was presented. Etiology, mechanism, and treatment were discussed on the review of literature. Spontaneous Pneumothorax is a clinical entity resulting from a sudden non traumatic rupture of the lung. Biach reported in 1880 that 78% of 916 patients with spontaneous pneumothorax had tuberculosis. Kjergaard emphasized 1932 the primary importance of subpleural bleb disease. Currently the clinical spectrum of spontaneous pneumothorax seems to have entered a third era with the recognition of the interstitial lung disease and AIDS as a significant etiology. Standard treatment is including: observation, thoracocentesis, tube thoracostomy. Chemical pleurodesis, bullectomy or wedge resection of lung with pleural abrasion and occasionally pleurectomy. Little information has been reported regarding the efficacy of such treatment in spontaneous pneumothorax secondary to non bleb disease

  16. Mass extinction: a commentary

    Science.gov (United States)

    Raup, D. M.

    1987-01-01

    Four neocatastrophist claims about mass extinction are currently being debated; they are that: 1, the late Cretaceous mass extinction was caused by large body impact; 2, as many as five other major extinctions were caused by impact; 3, the timing of extinction events since the Permian is uniformly periodic; and 4, the ages of impact craters on Earth are also periodic and in phase with the extinctions. Although strongly interconnected the four claims are independent in the sense that none depends on the others. Evidence for a link between impact and extinction is strong but still needs more confirmation through bed-by-bed and laboratory studies. An important area for future research is the question of whether extinction is a continuous process, with the rate increasing at times of mass extinctions, or whether it is episodic at all scales. If the latter is shown to be generally true, then species are at risk of extinction only rarely during their existence and catastrophism, in the sense of isolated events of extreme stress, is indicated. This is line of reasoning can only be considered an hypothesis for testing. In a larger context, paleontologists may benefit from a research strategy that looks to known Solar System and Galactic phenomena for predictions about environmental effects on earth. The recent success in the recognition of Milankovitch Cycles in the late Pleistocene record is an example of the potential of this research area.

  17. First detection of Echinococcus multilocularis infection in two species of nonhuman primates raised in a zoo: a fatal case in Cercopithecus diana and a strongly suspected case of spontaneous recovery in Macaca nigra.

    Science.gov (United States)

    Yamano, Kimiaki; Kouguchi, Hirokazu; Uraguchi, Kohji; Mukai, Takeshi; Shibata, Chikako; Yamamoto, Hideaki; Takaesu, Noboru; Ito, Masaki; Makino, Yoshinori; Takiguchi, Mitsuyoshi; Yagi, Kinpei

    2014-08-01

    The causative parasite of alveolar echinococcosis, Echinococcus multilocularis, maintains its life cycle between red foxes (Vulpes vulples, the definitive hosts) and voles (the intermediate hosts) in Hokkaido, Japan. Primates, including humans, and some other mammal species can be infected by the accidental ingestion of eggs in the feces of red foxes. In August 2011, a 6-year-old zoo-raised female Diana monkey (Cercopithecus diana) died from alveolar echinococcosis. E. multilocularis infection was confirmed by histopathological examination and detection of the E. multilocularis DNA by polymerase chain reaction (PCR). A field survey in the zoo showed that fox intrusion was common, and serodiagnosis of various nonhuman primates using western blotting detected a case of a 14-year-old female Celebes crested macaque (Macaca nigra) that was weakly positive for E. multilocularis. Computed tomography revealed only one small calcified lesion (approximately 8mm) in the macaque's liver, and both western blotting and enzyme-linked immunosorbent assay (ELISA) showed a gradual decline of antibody titer. These findings strongly suggest that the animal had recovered spontaneously. Until this study, spontaneous recovery from E. multilocularis infection in a nonhuman primate had never been reported.

  18. An unconditioned stimulus retrieval extinction procedure to prevent the return of fear memory.

    Science.gov (United States)

    Liu, Jianfeng; Zhao, Liyan; Xue, Yanxue; Shi, Jie; Suo, Lin; Luo, Yixiao; Chai, Baisheng; Yang, Chang; Fang, Qin; Zhang, Yan; Bao, Yanping; Pickens, Charles L; Lu, Lin

    2014-12-01

    Conditioned fear memories can be updated by extinction during reconsolidation, and this effect is specific to the reactivated conditioned stimulus (CS). However, a traumatic event can be associated with several cues, and each cue can potentially trigger recollection of the event. We introduced a technique to target all diverse cues associated with an aversive event that causes fear. In human experiments, 161 subjects underwent modified fear conditioning, in which they were exposed to an unconditioned stimulus (US) or unreinforced CS to reactivate the memory and then underwent extinction, spontaneous recovery, and reinstatement. In animal experiments, 343 rats underwent contextual fear conditioning under a similar protocol as that used in the human experiments. We also explored the molecular alterations after US reactivation in rats. Presentation of a lower intensity US before extinction disrupted the associations between the different CS and reactivated US in both humans and rats. This effect persisted for at least 6 months in humans and was selective to the reactivated US. This procedure was also effective for remote memories in both humans and rats. Compared with the CS, the US induced stronger endocytosis of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid glutamate receptors 1 and 2 and stronger activation of protein kinase A, p70S6 kinase, and cyclic adenosine monophosphate response element binding protein in the dorsal hippocampus in rats. These findings demonstrate that a modified US retrieval extinction strategy may have a potential impact on therapeutic approaches to prevent the return of fear. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  19. High-precision timeline for Earth's most severe extinction.

    Science.gov (United States)

    Burgess, Seth D; Bowring, Samuel; Shen, Shu-zhong

    2014-03-04

    The end-Permian mass extinction was the most severe loss of marine and terrestrial biota in the last 542 My. Understanding its cause and the controls on extinction/recovery dynamics depends on an accurate and precise age model. U-Pb zircon dates for five volcanic ash beds from the Global Stratotype Section and Point for the Permian-Triassic boundary at Meishan, China, define an age model for the extinction and allow exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 Mya, an interval of 60 ± 48 ka. Onset of a major reorganization of the carbon cycle immediately precedes the initiation of extinction and is punctuated by a sharp (3‰), short-lived negative spike in the isotopic composition of carbonate carbon. Carbon cycle volatility persists for ∼500 ka before a return to near preextinction values. Decamillenial to millennial level resolution of the mass extinction and its aftermath will permit a refined evaluation of the relative roles of rate-dependent processes contributing to the extinction, allowing insight into postextinction ecosystem expansion, and establish an accurate time point for evaluating the plausibility of trigger and kill mechanisms.

  20. An asthma patient with steroid-resistant decrease in peak expiratory flow after the Great East Japan earthquake showing spontaneous recovery after 1 month.

    Science.gov (United States)

    Yanagimoto, Shintaro; Haida, Michiko; Suko, Matsunobu

    2012-01-01

    People living in Japan were affected in various ways after the Great East Japan earthquake of March 11, 2011. A 52-year-old female asthma patient not directly affected by the disaster experienced a decrease in peak expiratory flow (PEF) immediately after the earthquake. Despite increasing the inhaled and oral corticosteroid doses, her PEF did not recover. One month later, her PEF level abruptly returned to normal with minimal medications, which were previously ineffective, and the asthma-related symptoms vanished. The stabilization of her state of mind and actual social state seemed to be a part of the reason for the patient's recovery.

  1. Requirement for BDNF in the reconsolidation of fear extinction.

    Science.gov (United States)

    Radiske, Andressa; Rossato, Janine I; Köhler, Cristiano A; Gonzalez, Maria Carolina; Medina, Jorge H; Cammarota, Martín

    2015-04-22

    Therapies based on the impairment of reconsolidation or the enhancement of extinction offer the possibility of decreasing the persistent recollection of distressing memories. However, the direct interplay between reconsolidation and extinction has rarely been considered. Previously, we reported that reactivation induces reconsolidation of fear extinction memory. Here, using a step-down inhibitory avoidance learning paradigm in rats, we show that intrahippocampus infusion of function-blocking anti-BDNF antibody immediately or 6 h after extinction memory reactivation impairs the reconsolidation of extinction. Extinction memory reactivation increases proBDNF, BDNF, and tropomyosin receptor kinase B (TrkB) phosphorylation levels in dorsal CA1, while blocking BDNF maturation in the hippocampus with plasminogen activator inhibitor 1 hinders the persistence of extinction and induces the recurrence of fear. Moreover, coinfusion of recombinant BDNF (0.25 μg/side) after extinction memory reactivation impedes the recovery of the avoidance response induced by inhibiting gene expression and protein synthesis in the dorsal hippocampus. Our findings unravel a new role for BDNF, suggesting that this neurotrophin is necessary and sufficient to maintain the reactivated fear extinction engram.

  2. Spontaneous Pneumomediastinum in Labor

    Science.gov (United States)

    Benlamkadem, Said; Labib, Smael; Harandou, Mustapha

    2017-01-01

    Spontaneous pneumomediastinum and subcutaneous emphysema also known as Hamman's syndrome is a very rare complication of labor that is often related to the valsalva maneuver during the labor. In most case, Hamman's syndrome is a self-limiting condition, rarely complicated unless there are underlying respiratory diseases. Chest X-ray can be a useful early diagnostic technique in severe clinical presentation. We report an uneventful pregnancy in a primigravid parturient, which was complicated in the late second stage of labor by the development of subcutaneous emphysema, pneumomediastinum, and mild pneumothorax. Spontaneous recovery occurred after four days of conservative management. This condition shows the major interest of labor analgesia especially locoregional techniques. PMID:28316849

  3. Spontaneous deregulation

    NARCIS (Netherlands)

    Edelman, Benjamin; Geradin, Damien

    2016-01-01

    Platform businesses such as Airbnb and Uber have risen to success partly by sidestepping laws and regulations that encumber their traditional competitors. Such rule flouting is what the authors call “spontaneous private deregulation,” and it’s happening in a growing number of industries. The authors

  4. Spontaneous deregulation

    NARCIS (Netherlands)

    Edelman, Benjamin; Geradin, Damien

    2016-01-01

    Platform businesses such as Airbnb and Uber have risen to success partly by sidestepping laws and regulations that encumber their traditional competitors. Such rule flouting is what the authors call “spontaneous private deregulation,” and it’s happening in a growing number of industries. The authors

  5. Spontaneous deregulation

    NARCIS (Netherlands)

    Edelman, Benjamin; Geradin, Damien

    Platform businesses such as Airbnb and Uber have risen to success partly by sidestepping laws and regulations that encumber their traditional competitors. Such rule flouting is what the authors call “spontaneous private deregulation,” and it’s happening in a growing number of industries. The authors

  6. Recovery of motor spontaneous activity after intranasal delivery of human recombinant erythropoietin in a focal brain hypoxia model induced by CoCl2 in rats.

    Science.gov (United States)

    Merelli, Amalia; Caltana, Laura; Girimonti, Patricia; Ramos, Alberto Javier; Lazarowski, Alberto; Brusco, Alicia

    2011-08-01

    Stroke is a major human health problem inducing long-term disability without any efficient therapeutic option being currently available. Under hypoxia, hypoxia-inducible factor-1α (HIF-1α) activates several genes as erythropoietin receptor (Epo-R) related with O(2) supply, and the multidrug-resistance gene (MDR-1) related with drug-refractory phenotype. Brain cortical injection of CoCl(2) produces focal hypoxia-like lesion with neuronal and glial alterations, as well as HIF-1α stabilization and MDR-1 overexpression. Intranasal (IN) drug delivery can by-pass blood-brain barrier (BBB) where MDR-1 is normally expressed. We evaluated the effects of IN-rHu-Epo administration on spontaneous motor activity (SMA) and the brain pattern expression of HIF-1α, MDR-1, and Epo-R in our cobalt-induced hypoxia model. Adult male Wistar rats were injected by stereotaxic surgery in frontoparietal cortex, with CoCl(2) (2 μl-50 mM; n = 20) or saline (controls; n = 20). Ten rats of each group were treated with IN-rHu-Epo 24 U or IN-saline. In addition, erythropoietic stimulation was evaluated by reticulocytes (Ret) account during three consecutive days, after intraperitoneal (i.p.)-recombinant-human Epo (rHu-Epo) (950 U; n = 6) or IN-rHu-Epo (24 U; n = 6) administration. SMA was evaluated by open field and rotarod tests, before and after surgical procedures during five consecutive days. Histological and immunostaining studies of HIF-1α, MDR-1, and Epo-R were performed on brain slides. A significant difference in SMA was observed in the hypoxic rats of IN-rHu-Epo-administered group as compared with Co-Saline-treated subjects and controls (p < 0.001). HIF-1α, EPO-R, and MDR-1 were overexpressed in the hypoxic cortex areas, while in contralateral hemisphere or controls, they were negatives. Reticulocytes were only increased in intraperitoneal (i.p.)-rHu-Epo-administered group. In spite of MDR-1 overexpression being detected in neurons, the coexpression of Epo-R could

  7. Behavioral and neural bases of extinction learning in Hermissenda

    Directory of Open Access Journals (Sweden)

    Joel S. Cavallo

    2014-08-01

    Full Text Available Extinction of classical conditioning is thought to produce new learning that masks or interferes with the original memory. However, research in the nudibranch Hermissenda crassicornis (H.c. has challenged this view, and instead suggested that extinction erased the original associative memory. We have re-examined extinction in H.c. to test whether extinguished associative memories can be detected on the behavioral and cellular levels, and to characterize the temporal variables involved. Associative conditioning using pairings of light (CS and rotation (US produced characteristic suppression of H.c. phototactic behavior. A single session of extinction training (repeated light-alone presentations reversed suppressed behavior back to pre-training levels when administered 15 min after associative conditioning. This effect was abolished if extinction was delayed by 23 hr, and yet was recovered using extended extinction training (three consecutive daily extinction sessions. Extinguished phototactic suppression did not spontaneously recover at any retention interval tested (2-, 24-, 48-, 72-hr, or after additional US presentations (no observed reinstatement. Extinction training (single session, 15 min interval also reversed the pairing-produced increases in light-evoked spike frequencies of Type B photoreceptors, an identified site of associative memory storage that is causally related to phototactic suppression. These results suggest that the behavioral effects of extinction training are not due to temporary suppression of associative memories, but instead represent a reversal of the underlying cellular changes necessary for the expression of learning. In the companion article, we further elucidate mechanisms responsible for extinction-produced reversal of memory-related neural plasticity in Type B photoreceptors.

  8. Hybridization and extinction.

    Science.gov (United States)

    Todesco, Marco; Pascual, Mariana A; Owens, Gregory L; Ostevik, Katherine L; Moyers, Brook T; Hübner, Sariel; Heredia, Sylvia M; Hahn, Min A; Caseys, Celine; Bock, Dan G; Rieseberg, Loren H

    2016-08-01

    Hybridization may drive rare taxa to extinction through genetic swamping, where the rare form is replaced by hybrids, or by demographic swamping, where population growth rates are reduced due to the wasteful production of maladaptive hybrids. Conversely, hybridization may rescue the viability of small, inbred populations. Understanding the factors that contribute to destructive versus constructive outcomes of hybridization is key to managing conservation concerns. Here, we survey the literature for studies of hybridization and extinction to identify the ecological, evolutionary, and genetic factors that critically affect extinction risk through hybridization. We find that while extinction risk is highly situation dependent, genetic swamping is much more frequent than demographic swamping. In addition, human involvement is associated with increased risk and high reproductive isolation with reduced risk. Although climate change is predicted to increase the risk of hybridization-induced extinction, we find little empirical support for this prediction. Similarly, theoretical and experimental studies imply that genetic rescue through hybridization may be equally or more probable than demographic swamping, but our literature survey failed to support this claim. We conclude that halting the introduction of hybridization-prone exotics and restoring mature and diverse habitats that are resistant to hybrid establishment should be management priorities.

  9. Ecological model of extinctions

    CERN Document Server

    Abramson, G

    1997-01-01

    We present numerical results based on a simplified ecological system in evolution, showing features of extinction similar to that claimed for the biosystem on Earth. In the model each species consists of a population in interaction with the others, that reproduces and evolves in time. Each species is simultaneously a predator and a prey in a food chain. Mutations that change the interactions are supposed to occur randomly at a low rate. Extinctions of populations result naturally from the predator-prey dynamics. The model is not pinned in a fitness variable, and natural selection arises from the dynamics.

  10. Acute stress impairs the retrieval of extinction memory in humans.

    Science.gov (United States)

    Raio, Candace M; Brignoni-Perez, Edith; Goldman, Rachel; Phelps, Elizabeth A

    2014-07-01

    lower extinction retrieval (i.e., greater fear recovery) than those in the control group (n=25). Our results suggest that acute stress impairs the retrieval of extinction learning and offers insight into why treatment strategies used in the clinic may be challenging to recruit in daily life where stress is pervasive.

  11. Context, Learning, and Extinction

    Science.gov (United States)

    Gershman, Samuel J.; Blei, David M.; Niv, Yael

    2010-01-01

    A. Redish et al. (2007) proposed a reinforcement learning model of context-dependent learning and extinction in conditioning experiments, using the idea of "state classification" to categorize new observations into states. In the current article, the authors propose an interpretation of this idea in terms of normative statistical inference. They…

  12. Unexpectedly many extinct hominins.

    Science.gov (United States)

    Bokma, Folmer; van den Brink, Valentijn; Stadler, Tanja

    2012-09-01

    Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, while debate continues on the status of Homo floresiensis. The decade-long debate between "splitters," who recognize over 20 hominin species, and "lumpers," who maintain that all these fossils belong to just a few lineages, illustrates that we do not know how many extinct hominin species to expect. Here, we present probability distributions for the number of speciation events and the number of contemporary species along a branch of a phylogeny. With estimates of hominin speciation and extincton rates, we then show that the expected total number of extinct hominin species is 8, but may be as high as 27. We also show that it is highly unlikely that three very recent species disappeared due to natural, background extinction. This may indicate that human-like remains are too easily considered distinct species. Otherwise, the evidence suggesting that Neanderthal and the Denisova hominin represent distinct species implies a recent wave of extinctions, ostensibly driven by the only survivor, H. sapiens. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  13. Post-Learning Sleep Transiently Boosts Context Specific Operant Extinction Memory

    Directory of Open Access Journals (Sweden)

    Marion Inostroza

    2017-04-01

    Full Text Available Operant extinction is learning to supress a previously rewarded behavior. It is known to be strongly associated with the specific context in which it was acquired, which limits the therapeutic use of operant extinction in behavioral treatments, e.g., of addiction. We examined whether sleep influences contextual memory of operant extinction over time, using two different recall tests (Recent and Remote. Rats were trained in an operant conditioning task (lever press in context A, then underwent extinction training in context B, followed by a 3-h retention period that contained either spontaneous morning sleep, morning sleep deprivation, or spontaneous evening wakefulness. A recall test was performed either immediately after the 3-h experimental retention period (Recent recall or after 48 h (Remote, in the extinction context B and in a novel context C. The two main findings were: (i at the Recent recall test, sleep in comparison with sleep deprivation and spontaneous wakefulness enhanced extinction memory but, only in the extinction context B; (ii at the Remote recall, extinction performance after sleep was enhanced in both contexts B and C to an extent comparable to levels at Recent recall in context B. Interestingly, extinction performance at Remote recall was also improved in the sleep deprivation groups in both contexts, with no difference to performance in the sleep group. Our results suggest that 3 h of post-learning sleep transiently facilitate the context specificity of operant extinction at a Recent recall. However, the improvement and contextual generalization of operant extinction memory observed in the long-term, i.e., after 48 h, does not require immediate post-learning sleep.

  14. Pseudoarachnoiditis in Spontaneous Intracranial Hypotension

    Directory of Open Access Journals (Sweden)

    Özlem Alkan

    2011-03-01

    Full Text Available Spontaneous intracranial hypotension is an important cause of new daily persistent headaches in young and middle-aged individuals. The diagnosis is made based on low cerebrospinal fluid pressure with characteristic findings upon brain and spinal magnetic resonance imaging (MRI. We present the case of a 15-year-old boy with spontaneous intracranial hypotension. Although his brain MRI was normal, his lumbar spinal MRI showed clustering of the nerve roots characteristic of arachnoiditis. Radionuclide cisternography revealed an epidural leak, which was treated with an epidural blood patch. The patient reached a near-full recovery within 24 h, and the lumbar spinal MRI findings mimicking arachnoiditis disappeared.

  15. Ecology: Dynamics of Indirect Extinction.

    Science.gov (United States)

    Montoya, Jose M

    2015-12-01

    The experimental identification of the mechanism by which extinctions of predators trigger further predator extinctions emphasizes the role of indirect effects between species in disturbed ecosystems. It also has deep consequences for the hidden magnitude of the current biodiversity crisis.

  16. Mass Extinctions Past and Present.

    Science.gov (United States)

    Allmon, Warren Douglas

    1987-01-01

    Discusses some parallels that seem to exist between mass extinction recognizable in the geologic record and the impending extinction of a significant proportion of the earth's species due largely to tropical deforestation. Describes some recent theories of causal factors and periodicities in mass extinction. (Author/TW)

  17. Versatility of Fear-potentiated Startle Paradigms for Assessing Human Conditioned Fear Extinction and Return of Fear

    Directory of Open Access Journals (Sweden)

    Seth Davin Norrholm

    2011-11-01

    Full Text Available Fear conditioning methodologies have often been employed as testable models for assessing learned fear responses in individuals with anxiety disorders such as post-traumatic stress disorder (PTSD and specific phobia. One frequently used paradigm is measurement of the acoustic startle reflex under conditions that mimic anxiogenic and fear-related conditions. For example, fear-potentiated startle is the relative increase in the frequency or magnitude of the acoustic startle reflex in the presence of a previously neutral cue (e.g., colored shape; termed the conditioned stimulus or CS+ that has been repeatedly paired with an aversive unconditioned stimulus (e.g., airblast to the larynx. Our group has recently used fear-potentiated startle paradigms to demonstrate impaired fear extinction in civilian and combat populations with PTSD. In the current study, we examined the use of either visual or auditory CSs in a fear extinction protocol that we have validated and applied to human clinical conditions. This represents an important translational bridge in that numerous animal studies of fear extinction, upon which much of the human work is based, have employed the use of auditory CSs as opposed to visual CSs. Participants in both the visual and auditory groups displayed robust fear-potentiated startle to the CS+, clear discrimination between the reinforced CS+ and non-reinforced CS-, significant extinction to the previously reinforced CS+, and marked spontaneous recovery. We discuss the current results as they relate to future investigations of PTSD-related impairments in fear processing in populations with diverse medical and psychiatric histories.

  18. Effects of broken affordance on visual extinction.

    Science.gov (United States)

    Wulff, Melanie; Humphreys, Glyn W

    2015-01-01

    Previous studies have shown that visual extinction can be reduced if two objects are positioned to "afford" an action. Here we tested if this affordance effect was disrupted by "breaking" the affordance, i.e., if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006), extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool) and unrelated tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  19. Effects of broken affordance on visual extinction

    Directory of Open Access Journals (Sweden)

    Melanie eWulff

    2015-09-01

    Full Text Available Previous studies have shown that visual extinction can be reduced if two objects are positioned to afford an action. Here we tested if this affordance effect was disrupted by breaking the affordance – if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006, extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool and unrelated tool-tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  20. Effects of ibotenate and 192IgG-saporin lesions of the nucleus basalis magnocellularis/substantia innominata on spontaneous sleep and wake states and on recovery sleep after sleep deprivation in rats.

    Science.gov (United States)

    Kaur, Satvinder; Junek, Adrienne; Black, Michelle A; Semba, Kazue

    2008-01-09

    The basal forebrain (BF) is known for its role in cortical and behavioral activation, and has been postulated to have a role in compensatory mechanisms after sleep loss. However, specific neuronal phenotypes responsible for these roles are unclear. We investigated the effects of ibotenate (IBO) and 192IgG-saporin (SAP) lesions of the caudal BF on spontaneous sleep-waking and electroencephalogram (EEG), and recovery sleep and EEG after 6 h of sleep deprivation (SD). Relative to artificial CSF (ACSF) controls, IBO injections decreased parvalbumin and cholinergic neurons in the caudal BF by 43 and 21%, respectively, and cortical acetylcholinesterase staining by 41%. SAP injections nonsignificantly decreased parvalbumin neurons by 11%, but significantly decreased cholinergic neurons by 69% and cortical acetylcholinesterase by 84%. IBO lesions had no effect on sleep-wake states but increased baseline delta power in all states [up to 62% increase during non-rapid eye movement (NREM) sleep]. SAP lesions transiently increased NREM sleep by 13%, predominantly during the dark phase, with no effect on EEG. During the first 12 h after SD, animals with IBO and SAP lesions showed lesser rebound NREM sleep (32 and 77% less, respectively) and delta power (78 and 53% less) relative to ACSF controls. These results suggest that noncholinergic BF neurons promote cortical activation by inhibiting delta waves, whereas cholinergic BF neurons play a nonexclusive role in promoting wake. Intriguingly, these results also suggest that both types of BF neurons play important roles, probably through different mechanisms, in increased NREM sleep and EEG delta power after sleep loss.

  1. Resurrecting an Extinct Species: Archival DNA, Taxonomy, and Conservation of the Vegas Valley Leopard Frog

    Science.gov (United States)

    Suggestions that the extinct Vegas Valley leopard frog (Rana fisheri = Lithobates fisheri) may have been synonymous with one of several declining species has complicated recovery planning for imperiled leopard frogs in southwestern North America. To address this concern, we recon...

  2. Noradrenergic stimulation modulates activation of extinction-related brain regions and enhances contextual extinction learning without affecting renewal

    Directory of Open Access Journals (Sweden)

    Silke eLissek

    2015-02-01

    Full Text Available Renewal in extinction learning describes the recovery of an extinguished response if the extinction context differs from the context present during acquisition and recall. Attention may have a role in contextual modulation of behavior and contribute to the renewal effect, while noradrenaline is involved in attentional processing. In this functional magnetic resonance imaging (fMRI study we investigated the role of the noradrenergic system for behavioral and brain activation correlates of contextual extinction and renewal, with a particular focus upon hippocampus and ventromedial PFC, which have crucial roles in processing of renewal. Healthy human volunteers received a single dose of the NA reuptake inhibitor atomoxetine prior to extinction learning. During extinction of previously acquired cue-outcome associations, cues were presented in a novel context (ABA or in the acquisition context (AAA. In recall, all cues were again presented in the acquisition context. Atomoxetine participants (ATO showed significantly faster extinction compared to placebo (PLAC. However, atomoxetine did not affect renewal. Hippocampal activation was higher in ATO during extinction and recall, as was ventromedial PFC activation, except for ABA recall. Moreover, ATO showed stronger recruitment of insula, anterior cingulate, and dorsolateral/orbitofrontal PFC. Across groups, cingulate, hippocampus and vmPFC activity during ABA extinction correlated with recall performance, suggesting high relevance of these regions for processing the renewal effect. In summary, the noradrenergic system appears to be involved in the modification of established associations during extinction learning and thus has a role in behavioral flexibility. The assignment of an association to a context and the subsequent decision on an adequate response, however, presumably operate largely independently of noradrenergic mechanisms.

  3. Resurrecting extinct interactions with extant substitutes.

    Science.gov (United States)

    Griffiths, Christine J; Hansen, Dennis M; Jones, Carl G; Zuël, Nicolas; Harris, Stephen

    2011-05-10

    There is increasing evidence that restoration ecologists should be most concerned with restoring species interactions rather than species diversity per se [1]. Rewilding with taxon substitutes, the intentional introduction of exotic species to replace the ecosystem functions of recently extinct species, is one way to reverse ecosystem dysfunction following the loss of species interactions [2]. This is highly controversial [3], in part because of a lack of rigorous scientific studies [4]. Here we present the first empirical evidence of an in situ rewilding project undertaken as a hypothesis-driven ecosystem management option. On Ile aux Aigrettes, a 25-hectare island off Mauritius, the critically endangered large-fruited endemic ebony, Diospyros egrettarum (Ebenaceae), was seed-dispersal limited after the extinction of all native large-bodied frugivores, including giant tortoises. We introduced exotic Aldabra giant tortoises, Aldabrachelys gigantea, to disperse the ebony seeds. Not only did the tortoises ingest the large fruits and disperse substantial numbers of ebony seeds, but tortoise gut passage also improved seed germination, leading to the widespread, successful establishment of new ebony seedlings. Our results demonstrate that the introduction of these exotic frugivores is aiding the recovery of ebonies. We argue for more reversible rewilding experiments to investigate whether extinct species interactions can be restored.

  4. Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

    OpenAIRE

    Brackney Ryan J; Cheung Timothy HC; Herbst Katrina; Hill Jade C; Sanabria Federico

    2012-01-01

    Abstract Background Deficient operant extinction has been hypothesized to be constitutive of ADHD dysfunction. In order to elucidate the behavioral mechanisms underlying this deficit, the performance of an animal model of ADHD, the spontaneously hypertensive rat (SHR), was compared against the performance of a control strain, the Wistar-Kyoto rat (WKY) during extinction. Method Following extensive training of lever pressing under variable interval schedules of food reinforcement (reported pre...

  5. Extinction Events Can Accelerate Evolution

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific......Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate...... evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending...

  6. Extinction events can accelerate evolution.

    Directory of Open Access Journals (Sweden)

    Joel Lehman

    Full Text Available Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term.

  7. Extinction Events Can Accelerate Evolution

    Science.gov (United States)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term. PMID:26266804

  8. Polyandry prevents extinction.

    Science.gov (United States)

    Price, Tom A R; Hurst, Greg D D; Wedell, Nina

    2010-03-09

    Females of most animal species are polyandrous, with individual females usually mating with more than one male. However, the ubiquity of polyandry remains enigmatic because of the potentially high costs to females of multiple mating. Current theory to account for the high prevalence of polyandry largely focuses on its benefits to individual females. There are also higher-level explanations for the high incidence of polyandry-polyandrous clades may speciate more rapidly. Here we test the hypothesis that polyandry may also reduce population extinction risk. We demonstrate that mating with multiple males protects populations of the fruit fly Drosophila pseudoobscura against extinction caused by a "selfish" sex-ratio-distorting element. Thus, the frequency of female multiple mating in nature may be associated not only with individual benefits to females of this behavior but also with increased persistence over time of polyandrous species and populations. Furthermore, we show that female remating behavior can determine the frequency of sex-ratio distorters in populations. This may also be true for many other selfish genetic elements in natural populations.

  9. ¿Es posible la recuperación de especies silvestres extintas a través de la transferencia somática nuclear? Is the recovery of extinct wild species through somatic nuclear transfer possible?

    Directory of Open Access Journals (Sweden)

    Janet López-Saucedo

    2010-08-01

    Full Text Available El avance de las ciencias biomédicas está llegando a campos inexplorados y sorprendentes; en fecha reciente, se ponderó la posibilidad de "recuperar" especies extintas al publicarse la "resurrección" de la primera subespecie extinta: el bucardo. No obstante, la incorporación de técnicas reproductivas avanzadas en el mundo de la conservación biológica se mantiene hasta ahora limitada e incluso, en ocasiones, mal encaminada. Los factores involucrados en este pobre desarrollo son diversos, pero uno de los más importantes es el rechazo de la comunidad "conservacionista" a las estrategias de alta tecnología. Sin embargo, considerando que México es un país megadiverso, con un gran número de especies de mamíferos amenazados, es urgente la necesidad de que se incorporen herramientas biotecnológicas al estudio y conservación de las especies del país, y más aún, que sean las mismas comunidades científicas latinoamericanas quienes desarrollen y utilicen sus propias herramientas. En esta nota, se discuten los avances científicos que proponen la transferencia somática nuclear como una herramienta de conservación, sus posibilidades reales, las necesidades y sugerencias para su aplicación y desarrollo con el fin de convertir la biotecnología moderna en instrumento para la lucha por la conservación de las especies amenazadas de México y Latinoamérica.The advances in the world of the biomedical sciences are reaching unexplored and unexpected areas, such as the possibility of "recovering" extinct species. This has been highlighted by the recent publication of the "resurrection" of the first extinct subspecies: the Pyrenean ibex. Nevertheless, the incorporation of advanced reproductive techniques in the world of biological conservation has been limited until now and in occasions even misguided. The factors involved in this slow development are diverse but the most important one is the rejection by the "conservationist" community to high

  10. Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary

    Science.gov (United States)

    Longrich, Nicholas R.; Bhullar, Bhart-Anjan S.; Gauthier, Jacques A.

    2012-01-01

    The Cretaceous–Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification. PMID:23236177

  11. Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary.

    Science.gov (United States)

    Longrich, Nicholas R; Bhullar, Bhart-Anjan S; Gauthier, Jacques A

    2012-12-26

    The Cretaceous-Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.

  12. Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary

    Science.gov (United States)

    Longrich, Nicholas R.; Bhullar, Bhart-Anjan S.; Gauthier, Jacques A.

    2012-12-01

    The Cretaceous-Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.

  13. Stress enhances the consolidation of extinction memory in a predictive learning task

    Directory of Open Access Journals (Sweden)

    Tanja eHamacher-Dang

    2013-08-01

    Full Text Available Extinction is not always permanent, as indicated by several types of recovery effects, such as the renewal effect, which may occur after a context change and points towards the importance of contextual cues. Strengthening the retrieval of extinction memory is a crucial aim of extinction-based psychotherapeutic treatments of anxiety disorders to prevent relapse. Stress is known to modulate learning and memory, with mostly enhancing effects on memory consolidation. However, whether such a consolidation-enhancing effect of acute stress can also be found for extinction memory has not yet been examined in humans. In this study, we investigated the effect of stress after extinction learning on the retrieval of extinction memory in a predictive learning renewal paradigm. Participants took the part of being the doctor of a fictitious patient and learned to predict whether certain food stimuli were associated with ‘stomach trouble’ in two different restaurants (contexts. On the first day, critical stimuli were associated with stomach trouble in context A (acquisition phase. On the second day, these associations were extinguished in context B. Directly after extinction, participants were either exposed to a stressor (socially evaluated cold pressor test; n = 22 or a control condition (n = 24. On the third day, we tested retrieval of critical associations in contexts A and B. Participants exposed to stress after extinction exhibited a reduced recovery of responding at test in context B, suggesting that stress may context-dependently enhance the consolidation of extinction memory. Furthermore, the increase in cortisol in response to the stressor was negatively correlated with the recovery of responding in context A. Our findings suggest that in parallel to the known effects of stress on the consolidation of episodic memory, stress also enhances the consolidation of extinction memory, which might be relevant for potential applications in extinction

  14. Measuring Extinction with ALE

    Science.gov (United States)

    Zimmer, Peter C.; McGraw, J. T.; Gimmestad, G. G.; Roberts, D.; Stewart, J.; Smith, J.; Fitch, J.

    2007-12-01

    ALE (Astronomical LIDAR for Extinction) is deployed at the University of New Mexico's (UNM) Campus Observatory in Albuquerque, NM. It has begun a year-long testing phase prior deployment at McDonald Observatory in support of the CCD/Transit Instrument II (CTI-II). ALE is designed to produce a high-precision measurement of atmospheric absorption and scattering above the observatory site every ten minutes of every moderately clear night. LIDAR (LIght Detection And Ranging) is the VIS/UV/IR analog of radar, using a laser, telescope and time-gated photodetector instead of a radio transmitter, dish and receiver. In the case of ALE -- an elastic backscatter LIDAR -- 20ns-long, eye-safe laser pulses are launched 2500 times per second from a 0.32m transmitting telescope co-mounted with a 50mm short-range receiver on an alt-az mounted 0.67m long-range receiver. Photons from the laser pulse are scattered and absorbed as the pulse propagates through the atmosphere, a portion of which are scattered into the field of view of the short- and long-range receiver telescopes and detected by a photomultiplier. The properties of a given volume of atmosphere along the LIDAR path are inferred from both the altitude-resolved backscatter signal as well as the attenuation of backscatter signal from altitudes above it. We present ALE profiles from the commissioning phase and demonstrate some of the astronomically interesting atmospheric information that can be gleaned from these data, including, but not limited to, total line-of-sight extinction. This project is funded by NSF Grant 0421087.

  15. A Case of Spontaneously Resolved Bilateral Primary Spontaneous Pneumothorax

    Directory of Open Access Journals (Sweden)

    Hasan Kahraman

    2014-03-01

    Full Text Available A condition of intrapleural air-space accumulation in individuals without any history of trauma or lung disease is called as primary spontaneous pneumothorax (PSP. Sixteen-years-old male patient admitted with complains of chest pain and dyspnea beginning 3 day ago. On physical examination, severity of breath sounds decreased on right side. Chest radiograph was taken and right-sided pneumothorax was detected and tube thoracostomy was inserted. Two months ago the patient referred to a doctor with similar complaints and physical examination and chest radiograph were reported as normal. The radiograph was retrospectively examined and bilateral PSP was detected. We presented the case duo to spontaneous recovery of bilateral PSP is seen very rarely and so contributes data to the literature. In patients admitted to the clinic with chest pain and shortness of breath, pneumothorax should be considered at differential diagnosis.

  16. The end-Permian mass extinction: A complex, multicausal extinction

    Science.gov (United States)

    Erwin, D. H.

    1994-01-01

    The end-Permian mass extinction was the most extensive in the history of life and remains one of the most complex. Understanding its causes is particularly important because it anchors the putative 26-m.y. pattern of periodic extinction. However, there is no good evidence for an impact and this extinction appears to be more complex than others, involving at least three phases. The first began with the onset of a marine regression during the Late Permian and resulting elimination of most marine basins, reduction in habitat area, and increased climatic instability; the first pulse of tetrapod extinctions occurred in South Africa at this time. The second phase involved increased regression in many areas (although apparently not in South China) and heightened climatic instability and environmental degradation. Release of gas hydrates, oxidation of marine carbon, and the eruption of the Siberian flood basalts occurred during this phase. The final phase of the extinction episode began with the earliest Triassic marine regression and destruction of nearshore continental habitats. Some evidence suggests oceanic anoxia may have developed during the final phase of the extinction, although it appears to have been insufficient to the sole cause of the extinction.

  17. HOMONYMOUS HEMIANOPIA: RECOVERY OF VISUAL FIELDS IN ACUTE STROKE

    Directory of Open Access Journals (Sweden)

    Gopal Kishan

    2015-05-01

    Full Text Available Homonymous hemianopia the most common cause is stroke . The field defect of vascular origin the prognosis for spontaneous recovery is poor . The objective of this case was to describe the characteristics of spontaneous recovery of homonymous hemianopia . In this case left homonymous hemianopia . We have confirmed by formal visual field testing and CT scan was done which revealed right parietal infarct . Follow up of this case was done after 1 month visual field were analyzed spontaneous recovery was seen

  18. Functional Extinctions of Species in Ecological Networks

    OpenAIRE

    Säterberg, Torbjörn

    2016-01-01

    Current rates of extinctions are estimated to be around 1000 times higher than background rates that would occur without anthropogenic impacts. These extinction rates refer to the traditional view of extinctions, i.e. numerical extinctions. This thesis is about another type of extinctions: functional extinctions. Those occur when the abundance of a species is too small to uphold the species’ ecologically interactive role. I have taken a theoretical approach and used dynamical models to invest...

  19. Establishing endangered species recovery criteria using predictive simulation modeling

    Science.gov (United States)

    McGowan, Conor P.; Catlin, Daniel H.; Shaffer, Terry L.; Gratto-Trevor, Cheri L.; Aron, Carol

    2014-01-01

    Listing a species under the Endangered Species Act (ESA) and developing a recovery plan requires U.S. Fish and Wildlife Service to establish specific and measurable criteria for delisting. Generally, species are listed because they face (or are perceived to face) elevated risk of extinction due to issues such as habitat loss, invasive species, or other factors. Recovery plans identify recovery criteria that reduce extinction risk to an acceptable level. It logically follows that the recovery criteria, the defined conditions for removing a species from ESA protections, need to be closely related to extinction risk. Extinction probability is a population parameter estimated with a model that uses current demographic information to project the population into the future over a number of replicates, calculating the proportion of replicated populations that go extinct. We simulated extinction probabilities of piping plovers in the Great Plains and estimated the relationship between extinction probability and various demographic parameters. We tested the fit of regression models linking initial abundance, productivity, or population growth rate to extinction risk, and then, using the regression parameter estimates, determined the conditions required to reduce extinction probability to some pre-defined acceptable threshold. Binomial regression models with mean population growth rate and the natural log of initial abundance were the best predictors of extinction probability 50 years into the future. For example, based on our regression models, an initial abundance of approximately 2400 females with an expected mean population growth rate of 1.0 will limit extinction risk for piping plovers in the Great Plains to less than 0.048. Our method provides a straightforward way of developing specific and measurable recovery criteria linked directly to the core issue of extinction risk. Published by Elsevier Ltd.

  20. Mass Extinctions in Earth's History

    Science.gov (United States)

    Ward, P. D.

    2002-12-01

    Mass extinctions are short intervals of elevated species death. Possible causes of Earth's mass extinctions are both external (astronomical) and internal (tectonic and biotic changes from planetary mechanisms). Paleontologists have identified five "major" mass extinctions (>50 die-off in less than a million years) and more than 20 other minor events over the past 550 million years. Earlier major extinction events undoubtedly also occurred, but we have no fossil record; these were probably associated with, for example, the early heavy bombardment that cleared out the solar system, the advent of oxygen in the atmosphere, and various "snowball Earth" events. Mass extinctions are viewed as both destructive (species death ) and constructive, in that they allow evolutionary innovation in the wake of species disappearances. From an astrobiological perspective, mass extinctions must be considered as able both to reduce biodiversity and even potentially end life on any planet. Of the five major mass extinctions identified on Earth, only one (the Cretaceous/Tertiary event 65 million years ago that famously killed off the dinosaurs ) is unambiguously related to the impact of an asteroid or comet ( 10-km diameter). The Permian/Triassic (250 Myr ago) and Triassic/Jurassic (202 Myr ago) events are now the center of debate between those favoring impact and those suggesting large volume flooding by basaltic lavas. The final two events, Ordovician (440 Myr ago) and Devonian (370 Myr ago) have no accepted causal mechanisms.

  1. The learning of fear extinction.

    Science.gov (United States)

    Furini, Cristiane; Myskiw, Jociane; Izquierdo, Ivan

    2014-11-01

    Recent work on the extinction of fear-motivated learning places emphasis on its putative circuitry and on its modulation. Extinction is the learned inhibition of retrieval of previously acquired responses. Fear extinction is used as a major component of exposure therapy in the treatment of fear memories such as those of the posttraumatic stress disorder (PTSD). It is initiated and maintained by interactions between the hippocampus, basolateral amygdala and ventromedial prefrontal cortex, which involve feedback regulation of the latter by the other two areas. Fear extinction depends on NMDA receptor activation. It is positively modulated by d-serine acting on the glycine site of NMDA receptors and blocked by AP5 (2-amino-5-phosphono propionate) in the three structures. In addition, histamine acting on H2 receptors and endocannabinoids acting on CB1 receptors in the three brain areas mentioned, and muscarinic cholinergic fibers from the medial septum to hippocampal CA1 positively modulate fear extinction. Importantly, fear extinction can be made state-dependent on circulating epinephrine, which may play a role in situations of stress. Exposure to a novel experience can strongly enhance the consolidation of fear extinction through a synaptic tagging and capture mechanism; this may be useful in the therapy of states caused by fear memory like PTSD.

  2. Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

    Directory of Open Access Journals (Sweden)

    Brackney Ryan J

    2012-12-01

    Full Text Available Abstract Background Deficient operant extinction has been hypothesized to be constitutive of ADHD dysfunction. In order to elucidate the behavioral mechanisms underlying this deficit, the performance of an animal model of ADHD, the spontaneously hypertensive rat (SHR, was compared against the performance of a control strain, the Wistar-Kyoto rat (WKY during extinction. Method Following extensive training of lever pressing under variable interval schedules of food reinforcement (reported previously, SHR and WKY rats were exposed to two sessions of extinction training. Extinction data was analyzed using the Dynamic Bi-Exponential Refractory Model (DBERM of operant performance. DBERM assumes that operant responses are organized in bouts separated by pauses; during extinction, bouts may decline across multiple dimensions, including frequency and length. DBERM parameters were estimated using hierarchical Bayesian modeling. Results SHR responded more than WKY during the first extinction session. DBERM parameter estimates revealed that, at the onset of extinction, SHR produced more response bouts than WKY. Over the course of extinction, response bouts progressively shortened for WKY but not for SHR. Conclusions Based on prior findings on the sensitivity of DBERM parameters to motivational and schedule manipulations, present data suggests that (1 more frequent response bouts in SHR are likely related to greater incentive motivation, and (2 the persistent length of bouts in SHR are likely related to a slower updating of the response-outcome association. Overall, these findings suggest specific motivational and learning deficits that may explain ADHD-related impairments in operant performance.

  3. Colloquium paper: extinction as the loss of evolutionary history.

    Science.gov (United States)

    Erwin, Douglas H

    2008-08-12

    Current plant and animal diversity preserves at most 1-2% of the species that have existed over the past 600 million years. But understanding the evolutionary impact of these extinctions requires a variety of metrics. The traditional measurement is loss of taxa (species or a higher category) but in the absence of phylogenetic information it is difficult to distinguish the evolutionary depth of different patterns of extinction: the same species loss can encompass very different losses of evolutionary history. Furthermore, both taxic and phylogenetic measures are poor metrics of morphologic disparity. Other measures of lost diversity include: functional diversity, architectural components, behavioral and social repertoires, and developmental strategies. The canonical five mass extinctions of the Phanerozoic reveals the loss of different, albeit sometimes overlapping, aspects of loss of evolutionary history. The end-Permian mass extinction (252 Ma) reduced all measures of diversity. The same was not true of other episodes, differences that may reflect their duration and structure. The construction of biodiversity reflects similarly uneven contributions to each of these metrics. Unraveling these contributions requires greater attention to feedbacks on biodiversity and the temporal variability in their contribution to evolutionary history. Taxic diversity increases after mass extinctions, but the response by other aspects of evolutionary history is less well studied. Earlier views of postextinction biotic recovery as the refilling of empty ecospace fail to capture the dynamics of this diversity increase.

  4. The global vegetation pattern across the Cretaceous-Paleogene mass extinction interval: A template for other extinction events

    Science.gov (United States)

    Vajda, Vivi; Bercovici, Antoine

    2014-11-01

    Changes in pollen and spore assemblages across the Cretaceous-Paleogene (K-Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous-Paleogene boundary clay, associated with the Chicxulub asteroid impact event, constitutes a unique, global marker bed enabling comparison of the world-wide palynological signal spanning the mass extinction event. The data from both hemispheres are consistent, revealing diverse latest Cretaceous assemblages of pollen and spores that were affected by a major diversity loss as a consequence of the K-Pg event. Here we combine new results with past studies to provide an integrated global perspective of the terrestrial vegetation record across the K-Pg boundary. We further apply the K-Pg event as a template to asses the causal mechanism behind other major events in Earths history. The end-Permian, end-Triassic, and the K-Pg mass-extinctions were responses to different causal processes that resulted in essentially similar succession of decline and recovery phases, although expressed at different temporal scales. The events share a characteristic pattern of a bloom of opportunistic "crisis" tax followed by a pulse in pioneer communities, and finally a recovery in diversity including evolution of new taxa. Based on their similar extinction and recovery patterns and the fact that the Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K-Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.

  5. Recovery Swaps

    OpenAIRE

    Berd, Arthur M.

    2010-01-01

    We derive an arbitrage free relationship between recovery swap rates, digital default swap spreads and conventional CDS spreads, and argue that the fair forward recovery rate used in recovery swaps must contain a convexity premium over the expected recovery value.

  6. The Sixth Great Mass Extinction

    Science.gov (United States)

    Wagler, Ron

    2012-01-01

    Five past great mass extinctions have occurred during Earth's history. Humanity is currently in the midst of a sixth, human-induced great mass extinction of plant and animal life (e.g., Alroy 2008; Jackson 2008; Lewis 2006; McDaniel and Borton 2002; Rockstrom et al. 2009; Rohr et al. 2008; Steffen, Crutzen, and McNeill 2007; Thomas et al. 2004;…

  7. A Protection plan of wildlife in a danger of extinction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Don; Park, Yong Ha; Suh, Jung Soo [Korea Environment Institute, Seoul (Korea)

    1998-12-01

    This report collected data on the present situation of mammals, birds, amphibians, reptiles, fishes, insects, invertebrates, and 43 kinds of plants, which is in a danger of extinction, and their habitat, by the article 2 of 1998 Natural Environmental Conservation Act, as a part of 'Establishment of Biological diversity strategy'. This will utilize as a basic data for protection management to establish the recovery plan for each species. 358 refs., 43 figs., 3 tabs.

  8. Extinction, relapse, and behavioral momentum.

    Science.gov (United States)

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-05-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior.

  9. Thermal Transgressions and Phanerozoic Extinctions

    Science.gov (United States)

    Worsley, T. R.; Kidder, D. L.

    2007-12-01

    A number of significant Phanerozoic extinctions are associated with marine transgressions that were probably driven by rapid ocean warming. The conditions associated with what we call thermal transgressions are extremely stressful to life on Earth. The Earth system setting associated with end-Permian extinction exemplifies an end-member case of our model. The conditions favoring extreme warmth and sea-level increases driven by thermal expansion are also conducive to changes in ocean circulation that foster widespread anoxia and sulfidic subsurface ocean waters. Equable climates are characterized by reduced wind shear and weak surface ocean circulation. Late Permian and Early Triassic thermohaline circulation differs considerably from today's world, with minimal polar sinking and intensified mid-latitude sinking that delivers sulfate from shallow evaporative areas to deeper water where it is reduced to sulfide. Reduced nutrient input to oceans from land at many of the extinction intervals results from diminished silicate weathering and weakened delivery of iron via eolian dust. The falloff in iron-bearing dust leads to minimal nitrate production, weakening food webs and rendering faunas and floras more susceptible to extinction when stressed. Factors such as heat, anoxia, ocean acidification, hypercapnia, and hydrogen sulfide poisoning would significantly affect these biotas. Intervals of tectonic quiescence set up preconditions favoring extinctions. Reductions in chemical silicate weathering lead to carbon dioxide buildup, oxygen drawdown, nutrient depletion, wind and ocean current abatement, long-term global warming, and ocean acidification. The effects of extinction triggers such as large igneous provinces, bolide impacts, and episodes of sudden methane release are more potent against the backdrop of our proposed preconditions. Extinctions that have characteristics we call for in the thermal transgressions include the Early Cambrian Sinsk event, as well as

  10. The effects of extinction, noncontingent reinforcement and differential reinforcement of other behavior as control procedures.

    Science.gov (United States)

    Thompson, Rachel H; Iwata, Brian A; Hanley, Gregory P; Dozier, Claudia L; Samaha, Andrew L

    2003-01-01

    Several techniques have been used in applied research as controls for the introduction of a reinforcement contingency, including extinction, noncontingent reinforcement (NCR), and differential reinforcement of other behavior (DRO). Little research, however, has examined the relative strengths and limitations of these "reversal" controls. We compared the effects of extinction with those of NCR and DRO in both multi-element and reversal designs, with respect to (a) rate and amount of response decrement, (b) rate of response recovery following reintroduction of reinforcement, and (c) any positive or negative side effects associated with transitions. Results indicated that extinction generally produced the most consistent and rapid reversal effects, with few observed negative side effects.

  11. Genetic factors in Threatened Species Recovery Plans on three continents

    Science.gov (United States)

    Threatened species' recovery planning is applied globally to stem the current species extinction crisis. Evidence supports a key role of genetic processes, such as inbreeding depression, in determining species viability. We examined whether genetic factors are considered in threa...

  12. The extinction of the dinosaurs.

    Science.gov (United States)

    Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

    2015-05-01

    Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.

  13. Measuring Galactic Extinction A Test

    CERN Document Server

    Arce, H G; Arce, Hector G.; Goodman, Alyssa A.

    1999-01-01

    We test the recently published all-sky reddening map of Schlegel, Finkbeiner & Davis (1998 [SFD]) using the extinction study of a region in the Taurus dark cloud complex by Arce & Goodman (1999 [AG]). In their study, AG use four different techniques to measure the amount and structure of the extinction toward Taurus, and all four techniques agree very well. Thus we believe that the AG results are a truthful representation of the extinction in the region and can be used to test the reliability of the SFD reddening map. The results of our test show that the SFD all-sky reddening map, which is based on data from COBE/DIRBE and IRAS/ISSA, overestimates the reddening by a factor of 1.3 to 1.5 in regions of smooth extinction with A_V > 0.5 mag. In some regions of steep extinction gradients the SFD map underestimates the reddening value, probably due to its low spatial resolution. We expect that the astronomical community will be using the SFD reddening map extensively. We offer this Letter as a cautionary n...

  14. Preventing long-lasting fear recovery using bilateral alternating sensory stimulation: A translational study.

    Science.gov (United States)

    Wurtz, H; El-Khoury-Malhame, M; Wilhelm, F H; Michael, T; Beetz, E M; Roques, J; Reynaud, E; Courtin, J; Khalfa, S; Herry, C

    2016-05-03

    Posttraumatic stress disorder (PTSD) is a highly debilitating and prevalent psychological disorder. It is characterized by highly distressing intrusive trauma memories that are partly explained by fear conditioning. Despite efficient therapeutic approaches, a subset of PTSD patients displays spontaneous recurrence of traumatic memories after successful treatment. The development of animal behavioral models mimicking the individual variability in treatment outcome for PTSD patients represent therefore an important challenge as it allows for the identification of predicting factors of resilience or susceptibility to relapse. However, to date, only few animal behavioral models of long-lasting fear recovery have been developed and their predictive validity has not been tested directly. The objectives of this study were twofold. First we aimed to develop a simple animal behavioral model of long-lasting fear recovery based on auditory cued fear conditioning and extinction learning, which recapitulates the heterogeneity of fear responses observed in PTSD patients after successful treatment. Second we aimed at testing the predictive validity of our behavioral model and used to this purpose a translational approach based (i) on the demonstration of the efficiency of Eye Movement Desensitization and Reprocessing (EMDR) therapy to reduce conditioned fear responses in PTSD patients and (ii) on the implementation in our behavioral model of an electrical bilateral alternating stimulation of the eyelid which mimics the core feature of EMDR. Our data indicate that electrical bilateral alternating stimulation of the eyelid during extinction learning alleviates long-lasting fear recovery of conditioned fear responses and dramatically reduces inter-individual variability. These results demonstrate the face and predictive validity of our animal behavioral model and provide an interesting tool to understand the neurobiological underpinnings of long-lasting fear recovery.

  15. The atmospheric extinction of light

    CERN Document Server

    Hughes, Stephen W; Powell, Sean; Carroll, Joshua

    2015-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm^-1 respectively and 0.032, 0.037 and 0.092 cm^-1 for the Picotech Dr. DAQ ADC.

  16. Infectious Disease, Endangerment, and Extinction

    Directory of Open Access Journals (Sweden)

    Ross D. E. MacPhee

    2013-01-01

    Full Text Available Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters.

  17. Mass extinctions and supernova explosions

    CERN Document Server

    Korschinek, Gunther

    2016-01-01

    A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, or the direct exposure of lethal x-rays. Another indirect effect is cloud formation, induced by cosmic rays in the atmosphere which result in a drop in the Earth's temperature, causing major glaciations of the Earth. The discovery of highly intensive gamma ray bursts (GRBs), which could be connected to SNe, initiated further discussions on possible life-threatening events in Earth's history. The probability that GRBs hit the Earth is very low. Nevertheless, a past interaction of Earth with GRBs and/or SNe cannot be exclude...

  18. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, Kostas A.; Borges, Paulo A. V.; Ladle, Richard J.

    2010-01-01

    Habitat destruction is the leading cause of species extinctions. However, there is typically a time-lag between the reduction in habitat area and the eventual disappearance of the remnant populations. These "surviving but ultimately doomed" species represent an extinction debt. Calculating...... the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...... in the last 45 yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future...

  19. Habituation, latent inhibition, and extinction.

    Science.gov (United States)

    Jordan, Wesley P; Todd, Travis P; Bucci, David J; Leaton, Robert N

    2015-06-01

    In two conditioned suppression experiments with a latent inhibition (LI) design, we measured the habituation of rats in preexposure, their LI during conditioning, and then extinction over days. In the first experiment, lick suppression, the preexposed group (PE) showed a significant initial unconditioned response (UR) to the target stimulus and significant long-term habituation (LTH) of that response over days. The significant difference between the PE and nonpreexposed (NPE) groups on the first conditioning trial was due solely to the difference in their URs to the conditioned stimulus (CS)-a habituated response (PE) and an unhabituated response (NPE). In the second experiment, bar-press suppression, little UR to the target stimulus was apparent during preexposure, and no detectable LTH. Thus, there was no difference between the PE and NPE groups on the first conditioning trial. Whether the UR to the CS confounds the interpretation of LI (Exp. 1) or not (Exp. 2) can only be known if the UR is measured. In both experiments, LI was observed in acquisition. Also in both experiments, rats that were preexposed and then conditioned to asymptote were significantly more resistant to extinction than were the rats not preexposed. This result contrasts with the consistently reported finding that preexposure either produces less resistance to extinction or has no effect on extinction. The effect of stimulus preexposure survived conditioning to asymptote and was reflected directly in extinction. These two experiments provide a cautionary procedural note for LI experiments and have shown an unexpected extinction effect that may provide new insights into the interpretation of LI.

  20. Impact Crises, Mass Extinctions, and Galactic Dynamics: A Unified Theory

    Science.gov (United States)

    Rampino, M.R.

    1997-01-01

    recovery and radiation of new taxa. Isotopic and other geochemical signatures are also generally consistent with the expected after-effects of catastrophic impacts. Seven of the recognized extinction pulses are associated with concurrent (in some cases multiple) stratigraphic impact markers (e.g., layers with high Ir, shocked minerals, microtektites), and/or large, dated impact craters. Other less-well-studied crisis intervals show elevated Ir, still well below that of the K/T spike, which might be explained by low-Ir impactors, ejecta blowoff, or the sedimentary reworking and dilution of impact signatures. The best explanation for a possible periodic component of about 30 m.y. in mass extinctions and clusters of impacts is the modulation of the comet flux associated with the solar system's periodic passage through the plane of the Milky Way Galaxy. The quantitative agreement among paleontological, geological, and astronomical data suggests an important underlying unification of the processes involved.

  1. Extinction risk of soil biota.

    Science.gov (United States)

    Veresoglou, Stavros D; Halley, John M; Rillig, Matthias C

    2015-11-23

    No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology.

  2. Interstellar Grains: Effect of Inclusions on Extinction

    CERN Document Server

    Katyal, Nisha; Vaidya, D B

    2011-01-01

    A composite dust grain model which simultaneously explains the observed interstellar extinction, polarization, IR emission and the abundance constraints, is required. We present a composite grain model, which is made up of a host silicate oblate spheroid and graphite inclusions. The interstellar extinction curve is evaluated in the spectral region 3.4-0.1$\\mu m$ using the extinction efficiencies of the composite spheroidal grains for three axial ratios. Extinction curves are computed using the discrete dipole approximation (DDA). The model curves are subsequently compared with the average observed interstellar extinction curve and with an extinction curve derived from the IUE catalogue data.

  3. Interstellar grains: Effect of inclusions on extinction

    Science.gov (United States)

    Katyal, N.; Gupta, R.; Vaidya, D. B.

    2011-10-01

    A composite dust grain model which simultaneously explains the observed interstellar extinction, polarization, IR emission and the abundance constraints, is required. We present a composite grain model, which is made up of a host silicate oblate spheroid and graphite inclusions. The interstellar extinction curve is evaluated in the spectral region 3.4-0.1 μm using the extinction efficiencies of composite spheroidal grains for three axial ratios. Extinction curves are computed using the discrete dipole approximation (DDA). The model curves are subsequently compared with the average observed interstellar extinction curve and with an extinction curve derived from the IUE catalogue data.

  4. Spontaneous external gallbladder perforation

    Energy Technology Data Exchange (ETDEWEB)

    Noeldge, G.; Wimmer, B.; Kirchner, R.

    1981-04-01

    Spontaneous perforation of the gallbladder is one complication of cholelithiasis. There is a greater occurence of free perforation in the peritoneal cavity with bilary pertonitis, followed by the perforation into the stomach, small intestine and colon. A single case of the nowadays rare spontaneous perforation in and through the abdominal wall will be reported. Spontaneous gallbladder perforation appears nearly asymptomatic in its clinical course because of absent biliary peritonitis.

  5. Peritonitis - spontaneous bacterial

    Science.gov (United States)

    Spontaneous bacterial peritonitis (SBP); Ascites - peritonitis; Cirrhosis - peritonitis ... who are on peritoneal dialysis for kidney failure. Peritonitis may have other causes . These include infection from ...

  6. Endangered and Extinct Radioactivity

    Science.gov (United States)

    Leising, M. D.

    1993-07-01

    Gamma ray spectroscopy holds great promise for probing nucleosynthesis in individual nucleosynthesis events, via observations of short-lived radioactivity, and for measuring global galactic nucleosynthesis today with detections of longer-lived radioactivity. Many of the astrophysical issues addressed by these observations are precisely those that must be understood in order to interpret observations of extinct radioactivity in meteorites. It was somewhat surprising that the former case was realized first for a Type II supernova, when both 56Co [1] and 57Co [2] were detected in SN 1987A. These provide unprecedented constraints on models of Type II explosions. Live 26Al in the galaxy might come from Type II supernovae and their progenitors, and if this is eventually shown to be the case, can constrain massive star evolution, supernova nucleosynthesis, the galactic Type II supernova rate, and even models of the chemical evolution of the galaxy [3]. Titanium-44 is produced primarily in the alpha-rich freezeout from nuclear statistical equilibrium, possibly in Type Ia [4] and almost certainly in Type II supernovae [5]. The galactic recurrence time of these events is comparable to the 44Ti lifetime, so we expect to be able to see at most a few otherwise unseen 44Ti remnants at any given time. No such remnants have been detected yet [6]. Very simple arguments lead to the expectation that about 4 x 10^-4 M(sub)solar mass of 44Ca are produced per century. The product of the supernova frequency times the 44Ti yield per event must equal this number. Even assuming that only the latest event would be seen, rates in excess of 2 century^-1 are ruled out at >=99% confidence by the gamma ray limits. Only rates less than 0.3 century^-1 are acceptable at >5% confidence, and this means that the yield per event must be >10^-3 M(sub)solar mass to produce the requisite 44Ca. Rates this low are incompatible with current estimates for Type II supernovae and yields this high are also very

  7. A model of mass extinction

    CERN Document Server

    Newman, M E J

    1997-01-01

    A number of authors have in recent years proposed that the processes of macroevolution may give rise to self-organized critical phenomena which could have a significant effect on the dynamics of ecosystems. In particular it has been suggested that mass extinction may arise through a purely biotic mechanism as the result of so-called coevolutionary avalanches. In this paper we first explore the empirical evidence which has been put forward in favor of this conclusion. The data center principally around the existence of power-law functional forms in the distribution of the sizes of extinction events and other quantities. We then propose a new mathematical model of mass extinction which does not rely on coevolutionary effects and in which extinction is caused entirely by the action of environmental stresses on species. In combination with a simple model of species adaptation we show that this process can account for all the observed data without the need to invoke coevolution and critical processes. The model al...

  8. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, K.A.; Borges, Paulo A. V.; Ladle, R.J.;

    2010-01-01

    the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...

  9. Spontaneous intracranial hypotension.

    LENUS (Irish Health Repository)

    Fullam, L

    2012-01-31

    INTRODUCTION: Spontaneous\\/primary intracranial hypotension is characterised by orthostatic headache and is associated with characteristic magnetic resonance imaging findings. CASE REPORT: We present a case report of a patient with typical symptoms and classical radiological images. DISCUSSION: Spontaneous intracranial hypotension is an under-recognised cause of headache and can be diagnosed by history of typical orthostatic headache and findings on MRI brain.

  10. Interstellar Extinction by Spheroidal Dust Grains

    OpenAIRE

    Gupta, Ranjan; Mukai, Tadashi; Vaidya, D. B.; Sen, Asoke K.; Okada, Yasuhiko

    2005-01-01

    Observations of interstellar extinction and polarization indicate that the interstellar medium consists of aligned non-spherical dust grains which show variation in the interstellar extinction curve for wavelengths ranging from NIR to UV. To model the extinction and polarization, one cannot use the Mie theory which assumes the grains as solid spheres. We have used a T-matrix based method for computing the extinction efficiencies of spheroidal silicate and graphite grains of different shapes (...

  11. High-throughput culturing of fungi from plant litter by a dilution-to-extinction technique.

    Science.gov (United States)

    Collado, Javier; Platas, Gonzalo; Paulus, Barbara; Bills, Gerald F

    2007-06-01

    High-throughput bacterial cultivation has improved the recovery of slow-growing and previously uncultured bacteria. The most robust high-throughput methods are based on techniques of 'dilution to extinction' or 'extinction culturing'. The low-density partitioning of CFUs in tubes or microwells exploits the fact that the number of culturable species typically increases as inoculum density decreases. Bacterial high-throughput culturing methods were adapted to fungi to generate large numbers of fungal extinction cultures. The efficiency of extinction culturing was assessed by comparing it with particle filtration and automated plate-streaking. Equal volumes of particle suspension from five litter collections of the New Zealand forest tree Elaeocarpus dentatus were compared. Dilute particle suspensions of litter were pipetted into 48-well tissue culture plates containing 1 mL of agar medium per well. Particle volumes from the same samples were applied to continuous agar surfaces in Omnitray plates by automated streaking, and fungal diversity and richness were measured. The spectrum of isolates was assessed by microscopy and sequencing of the ITS or 28S region of the rRNA gene. Estimates of species diversity between the two methods were comparable, but extinction culturing increased species richness. Compared with plating methods using continuous surfaces, extinction culturing distributes fungal propagules over partitioned surfaces. Intercolony interactions are reduced, permitting longer incubation times, and colony initiation and recovery improved. Effort to evaluate and recover colonies from fungal isolation plates was substantially reduced.

  12. Further Evidence of Auditory Extinction in Aphasia

    Science.gov (United States)

    Marshall, Rebecca Shisler; Basilakos, Alexandra; Love-Myers, Kim

    2013-01-01

    Purpose: Preliminary research ( Shisler, 2005) suggests that auditory extinction in individuals with aphasia (IWA) may be connected to binding and attention. In this study, the authors expanded on previous findings on auditory extinction to determine the source of extinction deficits in IWA. Method: Seventeen IWA (M[subscript age] = 53.19 years)…

  13. Determining Extinction Ratio Of A Laser Diode

    Science.gov (United States)

    Unger, Glenn L.

    1992-01-01

    Improved technique to determine extinction ratio of pulsed laser diode based partly on definition of extinction ratio applicable to nonideal laser pulses. Heretofore, determinations involved assumption of ideal laser pulses, and neglected optical power from background light. Because power fluctuates during real pulse, more realistic to define extinction ratio in terms of energy obtained.

  14. Development of Extinction Imagers for the Determination of Atmospheric Optical Extinction

    Science.gov (United States)

    2014-08-01

    extinction coefficient > 0.4 km" ), the transmissometer tends to report higher values than the MSI. There are two possible reasons for this behavior ...REPORT TYPE Final Report 4. TITLE AND SUBTITLE Development of Extinction Imagers for the Determination of Atmospheric Optical Extinction 6. AUTHOR...further develop Extinction Imagers for use in the ocean environment, and to extend the capabilities into the Short Wave IR (SWIR). Extinction Imaging

  15. Forest succession and population viability of grassland plants: long repayment of extinction debt in Primula veris.

    Science.gov (United States)

    Lehtilä, Kari; Dahlgren, Johan P; Garcia, Maria Begoña; Leimu, Roosa; Syrjänen, Kimmo; Ehrlén, Johan

    2016-05-01

    Time lags in responses of organisms to deteriorating environmental conditions delay population declines and extinctions. We examined how local processes at the population level contribute to extinction debt, and how cycles of habitat deterioration and recovery may delay extinction. We carried out a demographic analysis of the fate of the grassland perennial Primula veris after the cessation of grassland management, where we used either a unidirectional succession model for forest habitat or a rotation model with a period of forest growth followed by a clear-cut and a new successional cycle. The simulations indicated that P. veris populations may have an extinction time of decades to centuries after a detrimental management change. A survey of the current incidence and abundance of P. veris in sites with different histories of afforestation confirmed the simulation results of low extinction rates. P. veris had reduced incidence and abundance only at sites with at least 100 years of forest cover. Time to extinction in simulations was dependent on the duration of the periods with favourable and unfavourable conditions after management cessation, and the population sizes and growth rates in these periods. Our results thus suggest that the ability of a species to survive is a complex function of disturbance regimes, rates of successional change, and the demographic response to environmental changes. Detailed demographic studies over entire successional cycles are therefore essential to identify the environmental conditions that enable long-term persistence and to design management for species experiencing extinction debts.

  16. High-precision geochronology confirms voluminous magmatism before, during, and after Earth's most severe extinction.

    Science.gov (United States)

    Burgess, Seth D; Bowring, Samuel A

    2015-08-01

    The end-Permian mass extinction was the most severe in the Phanerozoic, extinguishing more than 90% of marine and 75% of terrestrial species in a maximum of 61 ± 48 ky. Because of broad temporal coincidence between the biotic crisis and one of the most voluminous continental volcanic eruptions since the origin of animals, the Siberian Traps large igneous province (LIP), a causal connection has long been suggested. Magmatism is hypothesized to have caused rapid injection of massive amounts of greenhouse gases into the atmosphere, driving climate change and subsequent destabilization of the biosphere. Establishing a causal connection between magmatism and mass extinction is critically dependent on accurately and precisely knowing the relative timing of the two events and the flux of magma. New U/Pb dates on Siberian Traps LIP lava flows, sills, and explosively erupted rocks indicate that (i) about two-thirds of the total lava/pyroclastic volume was erupted over ~300 ky, before and concurrent with the end-Permian mass extinction; (ii) eruption of the balance of lavas continued for at least 500 ky after extinction cessation; and (iii) massive emplacement of sills into the shallow crust began concomitant with the mass extinction and continued for at least 500 ky into the early Triassic. This age model is consistent with Siberian Traps LIP magmatism as a trigger for the end-Permian mass extinction and suggests a role for magmatism in suppression of post-extinction biotic recovery.

  17. Neanderthal extinction by competitive exclusion.

    Directory of Open Access Journals (Sweden)

    William E Banks

    Full Text Available BACKGROUND: Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH. METHODOLOGY/PRINCIPAL FINDINGS: We apply a new methodology integrating archaeological and chronological data with high-resolution paleoclimatic simulations to define eco-cultural niches associated with Neanderthal and AMH adaptive systems during alternating cold and mild phases of Marine Isotope Stage 3. Our results indicate that Neanderthals and AMH exploited similar niches, and may have continued to do so in the absence of contact. CONCLUSIONS/SIGNIFICANCE: The southerly contraction of Neanderthal range in southwestern Europe during Greenland Interstadial 8 was not due to climate change or a change in adaptation, but rather concurrent AMH geographic expansion appears to have produced competition that led to Neanderthal extinction.

  18. Exploring co-extinction correlates

    DEFF Research Database (Denmark)

    Carpaneto, Giuseppe Maria; Mazziotta, Adriano; Pittino, Riccardo

    2011-01-01

    Co-extinction is a recurring topic in conservation biology. Quantification of co-extinction has been generally restricted to parasite-host, predator-prey and herbivore-host plant interactions. The loss of detritivorous insects upon the depletion of herbivore mammals has been poorly explored. Here...... of scarab beetle communities. Rarefaction curves estimated that a 50% reduction in the number of sample units where squirrel faecal pellets are the only available food resource accounts for a reduction of 28% of all the scarab species, and of 24% of the squirrel-linked species. The current decline of ground...... that the conservation of ground squirrels and their affiliate scarab species may be ensured by a moderate livestock grazing, owing to the higher ecological success of these rodents in the presence of large herbivores keeping low the grass cover. © 2011 Springer Science+Business Media B.V....

  19. Dissecting aneurysm of the middle cerebral artery treated with heparin infusion in a 6-year-old child; neurological recovery with delayed spontaneous thrombosis: case illustration and literature review.

    Science.gov (United States)

    Anichini, G; Passacantilli, E; Lenzi, J; Guidetti, G; Santoro, A

    2012-04-01

    Aneurysms in the pediatric population are a rare pathology with specific features which requires a deep knowledge of their pathogenesis for the best therapeutic choice; the authors report their experience with a patient presenting aneurysm of the middle cerebral artery (MCA) associated with proximal stenosis of the vessel. A six-year-old girl came to our observation after sudden onset of headache and left hemiparesis. Angio-MRI and angio-CT scan showed a right MCA dissecting aneurysms associated with proximal stenosis of the vessel. Patient started a therapy with low molecular weight heparin (LMWH), replaced, 15 days later, with acetyl-salicylic acid (ASA). Patient showed a rapid and almost complete neurological recovery, despite several radiological exams confirmed a complete occlusion of the right MCA. As many other authors noted, dissecting aneurysms in the pediatric population are probably due to a defect of the entire arterial wall. Combination of stenosis, turbulence and partial thrombosis of the aneurysm led to a complete occlusion of artery involved, leading to the formation of collateral circles. In our case, complete thrombosis was probably delayed with anticoagulant therapy and the progressive reinforcement of collateral circles lead to the patient's neurological recovery.

  20. A Reminder of Extinction Reduces Relapse in an Animal Model of Voluntary Behavior

    Science.gov (United States)

    Nieto, Javier; Uengoer, Metin; Bernal-Gamboa, Rodolfo

    2017-01-01

    One experiment with rats explored whether an extinction-cue prevents the recovery of extinguished lever-pressing responses. Initially, rats were trained to perform one instrumental response (R1) for food in Context A, and a different instrumental response (R2) in Context B. Then, responses were extinguished each in the alternate context (R1 in…

  1. Kappa Opioid Receptors Mediate where Fear Is Expressed Following Extinction Training

    Science.gov (United States)

    Cole, Sindy; Richardson, Rick; McNally, Gavan P.

    2011-01-01

    Six experiments used a within-subjects renewal design to examine the involvement of kappa opioid receptors (KORs) in regulating the expression and recovery of extinguished fear. Rats were trained to fear a tone conditioned stimulus (CS) via pairings with foot shock in a distinctive context (A). This was followed by extinction training of the CS in…

  2. Kappa Opioid Receptors Mediate where Fear Is Expressed Following Extinction Training

    Science.gov (United States)

    Cole, Sindy; Richardson, Rick; McNally, Gavan P.

    2011-01-01

    Six experiments used a within-subjects renewal design to examine the involvement of kappa opioid receptors (KORs) in regulating the expression and recovery of extinguished fear. Rats were trained to fear a tone conditioned stimulus (CS) via pairings with foot shock in a distinctive context (A). This was followed by extinction training of the CS in…

  3. Climatic and biotic upheavals following the end-Permian mass extinction

    NARCIS (Netherlands)

    Romano, C.; Goudemand, N.; Vennemann, T.W.; Ware, D.; Schneebeli-Hermann, E.; Hochuli, P.A.; Brühwiler, T.; Brinkmann, W.; Bucher, H.

    2013-01-01

    Recovery from the end-Permian mass extinction is frequently described as delayed, with complex ecological communities typically not found in the fossil record until the Middle Triassic epoch. However, the taxonomic diversity of a number of marine groups, ranging from ammonoids to benthic foraminifer

  4. A Reminder of Extinction Reduces Relapse in an Animal Model of Voluntary Behavior

    Science.gov (United States)

    Nieto, Javier; Uengoer, Metin; Bernal-Gamboa, Rodolfo

    2017-01-01

    One experiment with rats explored whether an extinction-cue prevents the recovery of extinguished lever-pressing responses. Initially, rats were trained to perform one instrumental response (R1) for food in Context A, and a different instrumental response (R2) in Context B. Then, responses were extinguished each in the alternate context (R1 in…

  5. Spontaneous rupture of pyometra

    National Research Council Canada - National Science Library

    Mallah, Fatemeh; Eftekhar, Tahere; Naghavi-Behzad, Mohammad

    2013-01-01

    Spontaneous perforation is a very rare complication of pyometra. The clinical findings of perforated pyometra are similar to perforation of the gastrointestinal tract and other causes of acute abdomen...

  6. Spontaneous Rupture of Pyometra

    OpenAIRE

    Fatemeh Mallah; Tahere Eftekhar; Mohammad Naghavi-Behzad

    2013-01-01

    Spontaneous perforation is a very rare complication of pyometra. The clinical findings of perforated pyometra are similar to perforation of the gastrointestinal tract and other causes of acute abdomen. In most cases, a correct and definite diagnosis can be made only by laparotomy. We report two cases of diffuse peritonitis caused by spontaneous perforated pyometra. The first case is a 78-year-old woman with abdominal pain for which laparotomy was performed because of suspected incarcerated he...

  7. The ethics of reviving long extinct species.

    Science.gov (United States)

    Sandler, Ronald

    2014-04-01

    There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable. © 2013 Society for Conservation Biology.

  8. Temporal properties of fear extinction--does time matter?

    Science.gov (United States)

    Golkar, Armita; Bellander, Martin; Öhman, Arne

    2013-02-01

    Fear extinction can be defined as the weakening of the expression of a conditioned response (CR) by extended experience of nonreinforcement. Conceptually, two distinct models have been invoked to account for extinction. R. A. Rescorla and A. R. Wagner (1972, A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement, in A. H. B. W. F. Prokasy (Ed.), Classical conditioning: II. Current research and theory, pp. 64-99, New York, NY, Appleton-Century-Crofts) postulated that the number of exposure trials is the primary determinant of CR decrement, whereas C. R. Gallistel and J. Gibbon (2000, Time, rate, and conditioning, Psychological Review, Vol. 107, pp. 289-344) proposed that the decisive event is the cumulated exposure time to the nonreinforced conditioned stimulus (CS) elapsed after the last CS reinforcement. We evaluated these two accounts in a human differential fear conditioning study in which CR was measured with the fear-potentiated startle response. Cumulated duration of nonreinforcement fails to explain our findings, whereas the number of trials appeared critical. In fact, many CS trials with a duration shorter than the acquisition CS duration facilitated within-session extinction, but this effect did not predict the recovery of fear.

  9. Resurrecting ancient animal genomes: the extinct moa and more.

    Science.gov (United States)

    Huynen, Leon; Millar, Craig D; Lambert, David M

    2012-08-01

    Recently two developments have had a major impact on the field of ancient DNA (aDNA). First, new advances in DNA sequencing, in combination with improved capture/enrichment methods, have resulted in the recovery of orders of magnitude more DNA sequence data from ancient animals. Second, there has been an increase in the range of tissue types employed in aDNA. Hair in particular has proven to be very successful as a source of DNA because of its low levels of contamination and high level of ancient endogenous DNA. These developments have resulted in significant advances in our understanding of recently extinct animals: namely their evolutionary relationships, physiology, and even behaviour. Hair has been used to recover the first complete ancient nuclear genome, that of the extinct woolly mammoth, which then facilitated the expression and functional analysis of haemoglobins. Finally, we speculate on the consequences of these developments for the possibility of recreating extinct animals. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A lesson in defining "extinct"

    OpenAIRE

    Asimow, Paul D.

    2014-01-01

    Toni Feder’s Issues and Events news item about the High-Altitude Water Cherenkov Gamma-Ray Observatory under construction in Mexico ( Physics Today, October 2013, page 22) begins by describing the site as “nestled at 4100 m on the slopes of Sierra Negra, an extinct volcano.” However, as the picture accompanying her piece or a cursory examination in Google Earth makes clear, the site is not on the slopes of Sierra Negra. It sits in the saddle between Sierra Negra and its much larger companion ...

  11. Molecular Dynamics Simulation of Spontaneous Imbibition in Nanopores and Recovery of Asphaltenic Crude Oils Using Surfactants for EOR Applications Simulations de dynamique moléculaire d’imbibition spontanée dans des nanopores et pour la récupération d’huiles brutes asphalténiques en utilisant des agents tensioactifs pour des applications d’EOR

    Directory of Open Access Journals (Sweden)

    Stukan M.R.

    2012-12-01

    Full Text Available We present Molecular Dynamics (MD simulations of the imbibition process in nanopores in case of two different mechanisms of the wettability modification. We compare the imbibition of an aqueous surfactant solution into an oil-wet pore driven by surfactant adsorption onto the oil-wet rock surface (coating mechanism and the imbibition of an aqueous surfactants solution driven by surfactants removing the contaminant molecules from the originally water-wet surface (cleaning mechanism. Our results show qualitative difference in the imbibition dynamics in these two cases and indicate that MD simulation is a useful tool to investigate details of the imbibition mechanisms at the pore scale with direct implications for Enhanced Oil Recovery (EOR operations. Nous presentons des simulations de Dynamique Moleculaire (DM du processus d’imbibition dans des nanopores dans le cas de deux mecanismes differents de modification de mouillabilite. Nous comparons l’imbibition d’une solution aqueuse d’agent tensioactif dans un pore mouille d’huile entrainee par une adsorption d’agent tensioactif sur la surface de roche mouillee d’huile (mecanisme de revetement et l’imbibition d’une solution aqueuse d’agent tensioactif entrainee par des agents tensioactifs eliminant les molecules contaminantes de la surface originellement mouillee d’eau (mecanisme de nettoyage. Nos resultats montrent une difference qualitative en matiere de dynamique d’imbibition dans ces deux cas et indiquent que la simulation de DM constitue un outil utile pour etudier les mecanismes d’imbibition a l’echelle des pores avec des implications directes pour des operations de recuperation renforcee d’huile (EOR, Enhanced Oil Recovery.

  12. Case of spontaneous ventriculocisternostomy

    Energy Technology Data Exchange (ETDEWEB)

    Yamane, Kanji; Yoshimoto, Hisanori; Harada, Kiyoshi; Uozumi, Tohru (Hiroshima Univ. (Japan). School of Medicine); Kuwabara, Satoshi

    1983-05-01

    The authors experienced a case of spontaneous ventriculocisternostomy diagnosed by CT scan with metrizamide and Conray. Patient was 23-year-old male who had been in good health until one month before admission, when he began to have headache and tinnitus. He noticed bilateral visual acuity was decreased about one week before admission and vomiting appeared two days before admission. He was admitted to our hospital because of bilateral papilledema and remarkable hydrocephalus diagnosed by CT scan. On admission, no abnormal neurological signs except for bilateral papilledema were noted. Immediately, right ventricular drainage was performed. Pressure of the ventricle was over 300mmH/sub 2/O and CSF was clear. PVG and PEG disclosed an another cavity behind the third ventricle, which was communicated with the third ventricle, and occlusion of aqueduct of Sylvius. Metrizamide CT scan and Conray CT scan showed a communication between this cavity and quadrigeminal and supracerebellar cisterns. On these neuroradiological findings, the diagnosis of obstructive hydrocephalus due to benign aqueduct stenosis accompanied with spontaneous ventriculocisternostomy was obtained. Spontaneous ventriculocisternostomy was noticed to produce arrest of hydrocephalus, but with our case, spontaneous regression of such symptoms did not appeared. By surgical ventriculocisternostomy (method by Torkildsen, Dandy, or Scarff), arrest of hydrocephalus was seen in about 50 to 70 per cent, which was the same results as those of spontaneous ventriculocisternostomy. It is concluded that VP shunt or VA shunt is thought to be better treatment of obstructive hydrocephalus than the various kinds of surgical ventriculocisternostomy.

  13. Extinction by the long dielectric needles

    CERN Document Server

    Cherkas, Nadejda L

    2016-01-01

    Electromagnetic wave extinction by the very long but finite dielectric needle is compared with that by the infinite dielectric cylinder for an oblique incidence of the electromagnetic wave. It is shown that the renormalized Hankel functions without the logarithmic terms should be used for the calculation of the extinction per unit length of the infinite dielectric cylinder to apply it for extinction calculations by the finite dielectric cylinder.

  14. Resistance to extinction and behavioral momentum

    OpenAIRE

    Nevin, John A.

    2012-01-01

    In the metaphor of behavioral momentum, reinforcement is assumed to strengthen discriminated operant behavior in the sense of increasing its resistance to disruption, and extinction is viewed as disruption by contingency termination and reinforcer omission. In multiple schedules of intermittent reinforcement, resistance to extinction is an increasing function of reinforcer rate, consistent with a model based on the momentum metaphor. The partial-reinforcement extinction effect, which opposes ...

  15. Mass Extinctions vs. Uniformitarianism in Biological Evolution

    OpenAIRE

    Bak, Per; Paczuski, Maya

    1996-01-01

    It is usually believed that Darwin's theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of coevolving species. The models exhibit self-organized criti...

  16. Extinction Maps in the WFAU Archives

    CERN Document Server

    Cross, Nicholas

    2015-01-01

    A brief set of notes about the database design for 3D maps of dust extinction in the WFAU Archives, which support data from UKIRT-WFCAM, VISTA and VST. The notes also detail typical use cases, such as getting colour-excesses, extinction-corrections, spectral energy distributions and colour-magnitude diagrams and demonstrate the SQL queries to return data, along with examples from VVV DR2 with bulge extinction maps from Chen et al. (2013).

  17. The Astronomical Pulse of Global Extinction Events

    Directory of Open Access Journals (Sweden)

    David F.V. Lewis

    2006-01-01

    Full Text Available The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

  18. The astronomical pulse of global extinction events.

    Science.gov (United States)

    Lewis, David F V; Dorne, Jean-Lou C M

    2006-06-23

    The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

  19. Mass extinctions vs. uniformitarianism in biological evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bak, P.; Paczuski, M.

    1995-12-31

    It is usually believed that Darwin`s theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of co-evolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.

  20. Enhancing Divergent Search through Extinction Events

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    A challenge in evolutionary computation is to create representations as evolvable as those in natural evolution. This paper hypothesizes that extinction events, i.e. mass extinctions, can significantly increase evolvability, but only when combined with a divergent search algorithm, i.e. a search...... for the capacity to evolve. This hypothesis is tested through experiments in two evolutionary robotics domains. The results show that combining extinction events with divergent search increases evolvability, while combining them with convergent search offers no similar benefit. The conclusion is that extinction...

  1. Secondary extinction in Pavlovian fear conditioning.

    Science.gov (United States)

    Vurbic, Drina; Bouton, Mark E

    2011-09-01

    Pavlov (1927/1960) reported that following the conditioning of several stimuli, extinction of one conditioned stimulus (CS) attenuated responding to others that had not undergone direct extinction. However, this secondary extinction effect has not been widely replicated in the contemporary literature. In three conditioned suppression experiments with rats, we further explored the phenomenon. In Experiment 1, we asked whether secondary extinction is more likely to occur with target CSs that have themselves undergone some prior extinction. A robust secondary extinction effect was obtained with a nonextinguished target CS. Experiment 2 showed that extinction of one CS was sufficient to reduce renewal of a second CS when it was tested in a neutral (nonextinction) context. In Experiment 3, secondary extinction was observed in groups that initially received intermixed conditioning trials with the target and nontarget CSs, but not in groups that received conditioning of the two CSs in separate sessions. The results are consistent with the hypothesis that CSs must be associated with a common temporal context during conditioning for secondary extinction to occur.

  2. Dust Extinction in Compact Planetary Nebulae

    OpenAIRE

    Lee, TH; Kwok, S.

    2005-01-01

    The effects of dust extinction on the departure from axisymmetry in the morphology of planetary nebulae (PNs) are investigated through a comparison of the radio free-free emission and hydrogen recombination line images. The dust extinction maps from five compact PNs are derived using high-resolution (̃0"1) Hα and radio maps of the HST and VLA. These extinction maps are then analyzed by an ellipsoidal shell ionization model including the effects of dust extinction to infer the nebulae's intrin...

  3. Climate predictors of late quaternary extinctions

    DEFF Research Database (Denmark)

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram

    2010-01-01

    Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...

  4. Constraints on Spontaneous Entrainment

    Directory of Open Access Journals (Sweden)

    Richardson Michael J.

    2011-12-01

    Full Text Available Past research has revealed that a person's rhythmic limb movements become spontaneously entrained to an environmental rhythm if a. visual information about the environmental rhythm is available and b. its frequency of the environmental rhythm is near that of the person's movements. Further, this research has demonstrated that if the eyes track the environmental stimulus, the spontaneous entrainment to the environmental rhythm is strengthened. Experiments were performed to investigate two hypotheses that could explain this eye-tracking enhancement of spontaneous entrainment. One hypothesis is that eye tracking allows for the pick up of important coordinative information at the turn-around points of a movement trajectory. Another hypothesis is that the limb movements entrain to the moving eyes through a neuromotor synergy linking the eyes and limb. Results of these experiments will help delineate the informational and dynamical constraints that can impact the acquisition of skilled actions.

  5. [Primary spontaneous pneumomediastinum].

    Science.gov (United States)

    Togashi, K; Hosaka, Y

    2007-12-01

    We report 5 cases of spontaneous pneumomediastinum. They were 4 men and 1 female with a mean age of 17 (14-25). Four patients developed sport-related pneumomediastinum and 1 patient had a karaoke-related condition. Primary spontaneous pneumomediasinum is a rare condition. In addition, there is no previous report describing karaoke-related spontaneous pneumomediastinum. Each of the patients experienced chest pain and/or neck pain before consulting our hospital. Chest roentgenogram and chest computed tomography showed pneumomediastinum without esophageal or tracheal injury. Four patients did not require hospitalization, but 1 patient was necessary to hospitalize for 7 days because of severe chest and neck pain. None of these 5 patients has had any recurrence for more than 1 year. Differentiating this entity from other diseases involving anterior chest pain is important.

  6. Spontaneous Perforation of Pyometra

    Directory of Open Access Journals (Sweden)

    Begüm Yildizhan

    2006-01-01

    Full Text Available Pyometra is the accumulation of purulent material in the uterine cavity. Its reported incidence is 0.01–0.5% in gynecologic patients; however, as far as elderly patients are concerned, its incidence is 13.6% [3]. The most common cause of pyometra is malignant diseases of genital tract and the consequences of their treatment (radiotherapy. Other causes are benign tumors like leiomyoma, endometrial polyps, senile cervicitis, cervical occlusion after surgery, puerperal infections, and congenital cervical anomalies. Spontaneous rupture of the uterus is an extremely rare complication of pyometra. To our knowledge, only 21 cases of spontaneous perforation of pyometra have been reported in English literature since 1980. This paper reports an additional case of spontaneous uterine rupture.

  7. Teens that fear screams: A comparison of fear conditioning, extinction, and reinstatement in adolescents and adults.

    Science.gov (United States)

    Den, Miriam Liora; Graham, Bronwyn M; Newall, Carol; Richardson, Rick

    2015-11-01

    This study investigated differences between adolescents and adults on fear conditioning, extinction, and reinstatement (i.e., the recovery of conditioned fear following re-exposure to the unconditioned stimulus [US] post-extinction). Participants underwent differential conditioning (i.e., the Screaming Lady) where one neutral face (CS+) was followed by the same face expressing fear and a loud scream (US) while another neutral face (CS-) remained neutral. Extinction involved non-reinforced presentations of both CSs, after which participants were reinstated (2xUSs) or not. On two self-report measures, both ages showed conditioning, good extinction learning and retention, and reinstatement-induced relapse. However, only adolescents showed conditioning, extinction, and reinstatement on the eye tracking measure; relapse on this measure could not be assessed in adults given they did not show initial conditioning. Lastly, higher levels of depression predicted stronger conditioning and weaker extinction in adolescents only. These findings are discussed in terms of their implications for adolescent anxiety disorders.

  8. Body size reductions in nonmammalian eutheriodont therapsids (Synapsida) during the end-Permian mass extinction.

    Science.gov (United States)

    Huttenlocker, Adam K

    2014-01-01

    The extent to which mass extinctions influence body size evolution in major tetrapod clades is inadequately understood. For example, the 'Lilliput effect,' a common feature of mass extinctions, describes a temporary decrease in body sizes of survivor taxa in post-extinction faunas. However, its signature on existing patterns of body size evolution in tetrapods and the persistence of its impacts during post-extinction recoveries are virtually unknown, and rarely compared in both geologic and phylogenetic contexts. Here, I evaluate temporal and phylogenetic distributions of body size in Permo-Triassic therocephalian and cynodont therapsids (eutheriodonts) using a museum collections-based approach and time series model fitting on a regional stratigraphic sequence from the Karoo Basin, South Africa. I further employed rank order correlation tests on global age and clade rank data from an expanded phylogenetic dataset, and performed evolutionary model testing using Brownian (passive diffusion) models. Results support significant size reductions in the immediate aftermath of the end-Permian mass extinction (ca. 252.3 Ma) consistent with some definitions of Lilliput effects. However, this temporal succession reflects a pattern that was underscored largely by Brownian processes and constructive selectivity. Results also support two recent contentions about body size evolution and mass extinctions: 1) active, directional evolution in size traits is rare over macroevolutionary time scales and 2) geologically brief size reductions may be accomplished by the ecological removal of large-bodied species without rapid originations of new small-bodied clades or shifts from long-term evolutionary patterns.

  9. Extinction-Optimized Volume Illumination.

    Science.gov (United States)

    Ament, Marco; Zirr, Tobias; Dachsbacher, Carsten

    2016-05-16

    We present a novel method to optimize the attenuation of light for the single scattering model in direct volume rendering. A common problem of single scattering is the high dynamic range between lit and shadowed regions due to the exponential attenuation of light along a ray. Moreover, light is often attenuated too strong between a sample point and the camera, hampering the visibility of important features. Our algorithm employs an importance function to selectively illuminate important structures and make them visible from the camera. With the importance function, more light can be transmitted to the features of interest, while contextual structures cast shadows which provide visual cues for perception of depth. At the same time, more scattered light is transmitted from the sample point to the camera to improve the primary visibility of important features. We formulate a minimization problem that automatically determines the extinction along a view or shadow ray to obtain a good balance between sufficient transmittance and attenuation. In contrast to previous approaches, we do not require a computationally expensive solution of a global optimization, but instead provide a closed-form solution for each sampled extinction value along a view or shadow ray and thus achieve interactive performance.

  10. Selectivity of terrestrial gastropod extinctions on an oceanic archipelago and insights into the anthropogenic extinction process

    OpenAIRE

    Chiba, Satoshi; Roy, Kaustuv

    2011-01-01

    Anthropogenic impacts have led to widespread extinctions of species on oceanic islands but the nature of many of these extinctions remains poorly known. Here we investigate extinction selectivities of terrestrial gastropods from the Ogasawara archipelago in the northwest Pacific, where anthropogenic threats have changed over time, shifting primarily from the effects of habitat loss to predation by a variety of different predators. Across all of the islands, extinct species had significantly s...

  11. Hume without Spontaneous Order

    Directory of Open Access Journals (Sweden)

    John Salter

    2015-01-01

    Full Text Available The question whether it is possible to be both a Humean and a contractarian arises from the interpretation of Hume as a theorist of spontaneous order, a theory that is usually taken to be incompatible with contractarianism. I argue that this interpretation is unconvincing and anachronistic. The real reason why it is problematic to view Hume as a contractarian is not because he is proponent of spontaneous order, but because he is a virtue-ethicist. I argue that Hume adopted and elaborated on the natural law account of the origins of property as conventional, but provided a different and separate account of the obligation to respect property rights.

  12. Spontaneous Atraumatic Mediastinal Hemorrhage

    Directory of Open Access Journals (Sweden)

    Morkos Iskander BSc, BMBS, MRCS, PGCertMedEd

    2013-04-01

    Full Text Available Spontaneous atraumatic mediastinal hematomas are rare. We present a case of a previously fit and well middle-aged lady who presented with acute breathlessness and an increasing neck swelling and spontaneous neck bruising. On plain chest radiograph, widening of the mediastinum was noted. The bruising was later confirmed to be secondary to mediastinal hematoma. This life-threatening diagnostic conundrum was managed conservatively with a multidisciplinary team approach involving upper gastrointestinal and thoracic surgeons, gastroenterologists, radiologists, intensivists, and hematologists along with a variety of diagnostic modalities. A review of literature is also presented to help surgeons manage such challenging and complicated cases.

  13. Constraints on Enhanced Extinction Resulting from Extinction Treatment in the Presence of an Added Excitor

    Science.gov (United States)

    Urcelay, Gonzalo P.; Lipatova, Olga; Miller, Ralph R.

    2009-01-01

    Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects…

  14. Temporal genetic analysis of the endangered tidewater goby: extinction-colonization dynamics or drift in isolation?

    Science.gov (United States)

    Kinziger, Andrew P; Hellmair, Michael; McCraney, W Tyler; Jacobs, David K; Goldsmith, Greg

    2015-11-01

    Extinction and colonization dynamics are critical to understanding the evolution and conservation of metapopulations. However, traditional field studies of extinction-colonization are potentially fraught with detection bias and have rarely been validated. Here, we provide a comparison of molecular and field-based approaches for assessment of the extinction-colonization dynamics of tidewater goby (Eucyclogobius newberryi) in northern California. Our analysis of temporal genetic variation across 14 northern California tidewater goby populations failed to recover genetic change expected with extinction-colonization cycles. Similarly, analysis of site occupancy data from field studies (94 sites) indicated that extinction and colonization are very infrequent for our study populations. Comparison of the approaches indicated field data were subject to imperfect detection, and falsely implied extinction-colonization cycles in several instances. For northern California populations of tidewater goby, we interpret the strong genetic differentiation between populations and high degree of within-site temporal stability as consistent with a model of drift in the absence of migration, at least over the past 20-30 years. Our findings show that tidewater goby exhibit different population structures across their geographic range (extinction-colonization dynamics in the south vs. drift in isolation in the north). For northern populations, natural dispersal is too infrequent to be considered a viable approach for recolonizing extirpated populations, suggesting that species recovery will likely depend on artificial translocation in this region. More broadly, this work illustrates that temporal genetic analysis can be used in combination with field data to strengthen inference of extinction-colonization dynamics or as a stand-alone tool when field data are lacking.

  15. Epidemic extinction in a generalized susceptible-infected-susceptible model

    Science.gov (United States)

    Chen, Hanshuang; Huang, Feng; Zhang, Haifeng; Li, Guofeng

    2017-01-01

    We study the extinction of epidemics in a generalized susceptible-infected-susceptible model, where a susceptible individual becomes infected at the rate λ when contacting m infective individual(s) simultaneously, and an infected individual spontaneously recovers at the rate μ. By employing the Wentzel-Kramers-Brillouin approximation for the master equation, the problem is reduced to finding the zero-energy trajectories in an effective Hamiltonian system, and the mean extinction time depends exponentially on the associated action S and the size of the population N, ˜ \\exp ≤ft(NS\\right) . Because of qualitatively different bifurcation features for m  =  1 and m≥slant 2 , we derive independently the expressions of S as a function of the rescaled infection rate λ /μ . For the weak infection, S scales to the distance to the bifurcation with an exponent 2 for m  =  1 and 3/2 for m≥slant 2 . Finally, a rare-event simulation method is used to validate the theory.

  16. Spontaneous closure of macular hole following blunt trauma

    Directory of Open Access Journals (Sweden)

    Clovis Arcoverde Freitas-Neto

    2016-01-01

    Full Text Available Ocular trauma can result in macular hole and it can lead to complete loss of central vision. We are reporting a case of traumatic macular hole associated with retinal hemorrhages and choroidal ruptures with spontaneous resolution and total vision recovery.

  17. Spontaneous resolution of a small extradural haematoma in a child.

    LENUS (Irish Health Repository)

    Sinha, A K

    2009-02-01

    We report the rapid spontaneous resolution of a small extradural haematoma (EDH) in a 19-month-old child. The haematoma was managed conservatively. The child went on to make a full recovery. The authors discuss the significance of this surprising clinical finding.

  18. Spontaneous rib fractures.

    Science.gov (United States)

    Katrancioglu, Ozgur; Akkas, Yucel; Arslan, Sulhattin; Sahin, Ekber

    2015-07-01

    Other than trauma, rib fracture can occur spontaneously due to a severe cough or sneeze. In this study, patients with spontaneous rib fractures were analyzed according to age, sex, underlying pathology, treatment, and complications. Twelve patients who presented between February 2009 and February 2011 with spontaneous rib fracture were reviewed retrospectively. The patients' data were evaluated according to anamnesis, physical examination, and chest radiographs. The ages of the patients ranged from 34 to 77 years (mean 55.91 ± 12.20 years), and 7 (58.4%) were male. All patients had severe cough and chest pain. The fractures were most frequently between 4th and 9th ribs; multiple rib fractures were detected in 5 (41.7%) patients. Eight (66.7%) patients had chronic obstructive pulmonary disease, 2 (16.7%) had bronchial asthma, and 2 (16.7%) had osteoporosis. Bone densitometry revealed a high risk of bone fracture in all patients. Patients with chronic obstructive pulmonary disease or bronchial asthma had been treated with high-dose steroids for over a year. Spontaneous rib fracture due to severe cough may occur in patients with osteoporosis, chronic obstructive pulmonary disease, or bronchial asthma, receiving long-term steroid therapy. If these patients have severe chest pain, chest radiography should be performed to check for bone lesions. © The Author(s) 2015.

  19. Spontaneous transverse colon volvulus.

    Science.gov (United States)

    Sana, Landolsi; Ali, Gassara; Kallel, Helmi; Amine, Baklouti; Ahmed, Saadaoui; Ali, Elouer Mohamed; Wajdi, Chaeib; Saber, Mannaï

    2013-01-01

    We report a case of spontaneous transverse colon volvulus in a young healthy woman. It constitutes an unusual case since it occurred in a young healthy woman with a subacute onset and no aetiological factor has been found. Its diagnosis is still challenging. Prompt recognition with emergency intervention constitutes the key to successful outcome.

  20. [Spontaneous bacterial peritonitis].

    Science.gov (United States)

    Velkey, Bálint; Vitális, Eszter; Vitális, Zsuzsanna

    2017-01-01

    Spontaneous bacterial peritonitis occurs most commonly in cirrhotic patients with ascites. Pathogens get into the circulation by intestinal translocation and colonize in peritoneal fluid. Diagnosis of spontaneous bacterial peritonitis is based on elevated polymorphonuclear leukocyte count in the ascites (>0,25 G/L). Ascites culture is often negative but aids to get information about antibiotic sensitivity in positive cases. Treatment in stable patient can be intravenous then orally administrated ciprofloxacin or amoxicillin/clavulanic acid, while in severe cases intravenous III. generation cephalosporin. Nosocomial spontaneous bacterial peritonitis often caused by Gram-positive bacteria and multi-resistant pathogens can also be expected thus carbapenem should be the choice of the empiric treatment. Antibiotic prophylaxis should be considered. Norfloxacin is used most commonly, but changes are expected due to increase in quinolone resistance. As a primary prophylaxis, a short-term antibiotic treatment is recommended after gastrointestinal bleeding for 5 days, while long-term prophylaxis is for patients with low ascites protein, and advanced disease (400 mg/day). Secondary prophylaxis is recommended for all patients recovered from spontaneous bacterial peritonitis. Due to increasing antibiotic use of antibiotics prophylaxis is debated to some degree. Orv. Hetil., 2017, 158(2), 50-57.

  1. On spontaneous scalarization

    CERN Document Server

    Salgado, M; Nucamendi, U; Salgado, Marcelo; Sudarsky, Daniel; Nucamendi, Ulises

    1998-01-01

    We study in the physical frame the phenomenon of spontaneous scalarization that occurs in scalar-tensor theories of gravity for compact objects. We discuss the fact that the phenomenon occurs exactly in the regime where the Newtonian analysis indicates it should not. Finally we discuss the way the phenomenon depends on the equation of state used to describe the nuclear matter.

  2. Failure and recovery in dynamical networks

    Science.gov (United States)

    Böttcher, L.; Luković, M.; Nagler, J.; Havlin, S.; Herrmann, H. J.

    2017-01-01

    Failure, damage spread and recovery crucially underlie many spatially embedded networked systems ranging from transportation structures to the human body. Here we study the interplay between spontaneous damage, induced failure and recovery in both embedded and non-embedded networks. In our model the network’s components follow three realistic processes that capture these features: (i) spontaneous failure of a component independent of the neighborhood (internal failure), (ii) failure induced by failed neighboring nodes (external failure) and (iii) spontaneous recovery of a component. We identify a metastable domain in the global network phase diagram spanned by the model’s control parameters where dramatic hysteresis effects and random switching between two coexisting states are observed. This dynamics depends on the characteristic link length of the embedded system. For the Euclidean lattice in particular, hysteresis and switching only occur in an extremely narrow region of the parameter space compared to random networks. We develop a unifying theory which links the dynamics of our model to contact processes. Our unifying framework may help to better understand controllability in spatially embedded and random networks where spontaneous recovery of components can mitigate spontaneous failure and damage spread in dynamical networks. PMID:28155876

  3. Extinction-Induced Variability in Human Behavior

    Science.gov (United States)

    Kinloch, Jennifer M.; Foster, T. Mary; McEwan, James S. A.

    2009-01-01

    Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996);…

  4. Periodicity of extinction: A 1988 update

    Science.gov (United States)

    Sepkowski, J. John, Jr.

    1988-01-01

    The hypothesis that events of mass extinction recur periodically at approximately 26 my intervals is an empirical claim based on analysis of data from the fossil record. The hypothesis has become closely linked with catastrophism because several events in the periodic series are associated with evidence of extraterrestrial impacts, and terrestrial forcing mechanisms with long, periodic recurrences are not easily conceived. Astronomical mechanisms that have been hypothesized include undetected solar companions and solar oscillation about the galactic plane, which induce comet showers and result in impacts on Earth at regular intervals. Because these mechanisms are speculative, they have been the subject of considerable controversy, as has the hypothesis of periodicity of extinction. In response to criticisms and uncertainties, a data base was developed on times of extinction of marine animal genera. A time series is given and analyzed with 49 sample points for the per-genus extinction rate from the Late Permian to the Recent. An unexpected pattern in the data is the uniformity of magnitude of many of the periodic extinction events. Observations suggest that the sequence of extinction events might be the result of two sets of mechanisms: a periodic forcing that normally induces only moderate amounts of extinction, and independent incidents or catastrophes that, when coincident with the periodic forcing, amplify its signal and produce major-mass extinctions.

  5. Can Parallelingualism Save Norwegian from Extinction?

    Science.gov (United States)

    Linn, Andrew R.

    2010-01-01

    Language extinction is one of the most pressing issues in linguistics today, and the literature is full of discussion about how to combat it. Statements that Norwegian is amongst the languages that are already extinct are merely examples of a widespread tendency in the literature towards erroneous information about Norwegian. Nonetheless, there is…

  6. Current extinction rates of reptiles and amphibians.

    Science.gov (United States)

    Alroy, John

    2015-10-20

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats.

  7. Synchronous extinction of North America's Pleistocene mammals

    Science.gov (United States)

    Faith, J. Tyler; Surovell, Todd A.

    2009-12-01

    The late Pleistocene witnessed the extinction of 35 genera of North American mammals. The last appearance dates of 16 of these genera securely fall between 12,000 and 10,000 radiocarbon years ago (≈13,800-11,400 calendar years B.P.), although whether the absence of fossil occurrences for the remaining 19 genera from this time interval is the result of sampling error or temporally staggered extinctions is unclear. Analysis of the chronology of extinctions suggests that sampling error can explain the absence of terminal Pleistocene last appearance dates for the remaining 19 genera. The extinction chronology of North American Pleistocene mammals therefore can be characterized as a synchronous event that took place 12,000-10,000 radiocarbon years B.P. Results favor an extinction mechanism that is capable of wiping out up to 35 genera across a continent in a geologic instant.

  8. Mass extinction in poorly known taxa.

    Science.gov (United States)

    Régnier, Claire; Achaz, Guillaume; Lambert, Amaury; Cowie, Robert H; Bouchet, Philippe; Fontaine, Benoît

    2015-06-23

    Since the 1980s, many have suggested we are in the midst of a massive extinction crisis, yet only 799 (0.04%) of the 1.9 million known recent species are recorded as extinct, questioning the reality of the crisis. This low figure is due to the fact that the status of very few invertebrates, which represent the bulk of biodiversity, have been evaluated. Here we show, based on extrapolation from a random sample of land snail species via two independent approaches, that we may already have lost 7% (130,000 extinctions) of the species on Earth. However, this loss is masked by the emphasis on terrestrial vertebrates, the target of most conservation actions. Projections of species extinction rates are controversial because invertebrates are essentially excluded from these scenarios. Invertebrates can and must be assessed if we are to obtain a more realistic picture of the sixth extinction crisis.

  9. Effects of standardized Ginkgo biloba extract on the acquisition, retrieval and extinction of conditioned suppression: Evidence that short-term memory and long-term memory are differentially modulated.

    Science.gov (United States)

    Zamberlam, C R; Vendrasco, N C; Oliveira, D R; Gaiardo, R B; Cerutti, S M

    2016-10-15

    Studies in our laboratory have characterized the putative neuromodulatory effects of a standardized extract of the green leaves of Ginkgo biloba (EGb), which comprises a formulation of 24% ginkgo-flavoglycosides and 6% ginkgo-terpenoid lactones, on conditioned suppression. This model comprises a suitable animal model for investigating the behavioral changes and pharmacological mechanisms that underlie fear memory and anxiety. The characterization of the effects on distinct stages of fear memory or fear extinction will help illustrate both the beneficial and harmful effects. Three hundred adult male Wistar rats were randomly assigned to 30 groups according to the treatment as follows: i-ii) control groups (CS-US and CSno-US); iii) vehicle group (12% Tween®80); and iv-vi) EGb groups (250, 500 and 1000mgkg(-1)); or experimental procedures designed to assess the effects of EGb treatment prior to the acquisition (n=20 per group) and retrieval of conditioned fear (n=10 per group) or prior to the extinction training (n=10 per group) and extinction retention test (n=10 per group). Furthermore, to better understand the effects of acute EGb treatment on fear memory, we conducted two additional analyses: the acquisition of within- and between-session extinction of fear memory (short- and long-term memory, respectively). No difference was identified between the control and treatment groups during the retention test (P>0.05), with the exception of the CSno-US group in relation to all groups (Pmemory, which was verified by the suppression ration in the first trial of extinction training (SR=0.39) and the extinction retention test session (SR=0.53, Pmemory acquisition, which were evaluated during the retention test (SR=0.79). Moreover, EGb administered at 1000mgkg(-1) prior to conditioning did not enhance the long-term extinction memory, i.e., it did not prevent the return of extinguished fear memory in the extinction retention test, in which the spontaneous recovery of fear was

  10. Trial Study of Vibration-Induced Effects on Spontaneous Potential

    Institute of Scientific and Technical Information of China (English)

    SunWeibin; QiuWeiting; HeZhanxiang

    2003-01-01

    Vibratory excitation generates not only reflections and refractions of wave fields on the subsurface interfaces but also electromagnetic waves with different frequencies. In this paper we address the vibration-induced effects on the spontaneous potential field. The effects of controllable vibration on the spontaneous potential field were studied under real field geologic conditions. Experimental data confirmed that the vibration-induced effects on the spontaneous potential field do exist under field conditions. Monitoring records over a long time interval showed that there existed three information zones in the vibration-induced effects on spontaneous potential field:These are the signal-variant zone, the extreme-stable zone and the relaxation-recovery zone. Combined with different well-site data, it was concluded that the time-variant features of the anomalies in the information zones was closely related to the properties of the subsurface liquid (oil and water).

  11. Backup & Recovery

    CERN Document Server

    Preston, W

    2009-01-01

    Packed with practical, freely available backup and recovery solutions for Unix, Linux, Windows, and Mac OS X systems -- as well as various databases -- this new guide is a complete overhaul of Unix Backup & Recovery by the same author, now revised and expanded with over 75% new material.

  12. Recovery Online

    Science.gov (United States)

    Clark, John R.

    2007-01-01

    Since the founding of Alcoholics Anonymous (AA) in 1935, programs offering opportunity for recovery from alcoholism and other addictions have undergone vast changes. The Internet has created nearly limitless opportunities for recovering people and those seeking recovery to find both meetings and places where they can gather virtually and discuss…

  13. Spontaneous shrinkage of vestibular schwannoma

    Directory of Open Access Journals (Sweden)

    Rossana Romani

    2016-01-01

    Conclusion: Early WWR management can be associated with spontaneous shrinkage of VS over time. Prospective clinical study of larger numbers of such cases using the UK VS database may help to identify predictive factors for the spontaneous regression of VS.

  14. Effect observation of rehabilitation on pelvic floor muscle recovery after forceps delivery and spontaneous labor%产钳助产和自然分娩经康复治疗后盆底肌恢复的效果观察

    Institute of Scientific and Technical Information of China (English)

    李庆梅; 鄂桂娟; 陈燕; 李丹彦; 苏园园

    2015-01-01

    Objective To observe the effect of rehabilitation on pelvic floor muscle recovery after forceps delivery and spontaneous labor. Methods 150 cases of primiparae delivered in our hospital from May 2011 to August 2013 were se-lected, and they were divided into forceps delivery group(n=78) and spontaneous labor group(n=72) by production mode. All participants were guided for Kegel training by specially-assigned persons in the second day after delivery,according to muscle strength recovery of pelvic floor,vaginal dumbbell or electrical stimulation with biological feedback was se-lected aiming at rehabilitation of pelvic floor muscle in 42 days after childbirth,1 course of treatment lasted 3 months. Muscle strength of pelvic floor, incidence of urinary incontinence and quality of sexual life at 42 days after childbirth and termination of rehabilitation training between two groups was compared. Results After early rehabilitation,pelvic floor muscle function muscle function,sexual satisfaction significantly higher of two groups.There was a statistical differ-ence in spontaneous recovery of pelvic floor muscle function before and after training in both groups (P0.05). Conclusion Pelvic floor muscle train-ing at an early stage after delivery can significantly strengthen pelvic floor muscle’s function and display no obvious difference in comparison with that in puerperae by spontaneous labor, which increases compliance of forceps delivery in these pregnant women, eliminates couple’s misgivings that forceps delivery has some influences on sexual life, improve quality of life, and promotes family harmony. Early-stage pelvic floor muscle training after delivery is worthy of expan-sion in clinic.%目的:探讨产钳助产和自然分娩经康复治疗后盆底肌恢复的效果。方法选择2011年5月~2013年8月在本院分娩的150例初产妇,按生产方式分为产钳助产组(n=78)和自然分娩组(n=72),所有产妇均于产后第2天开始由专人

  15. Crinoids from Svalbard in the aftermath of the end−Permian mass extinction

    Directory of Open Access Journals (Sweden)

    Salamon Mariusz A.

    2015-09-01

    Full Text Available The end-Permian mass extinction constituted a major event in the history of crinoids. It led to the demise of the major Paleozoic crinoid groups including cladids, disparids, flexibles and camerates. It is widely accepted that a single lineage, derived from a late Paleozoic cladid ancestor (Ampelocrinidae, survived this mass extinction. Holocrinid crinoids (Holocrinus, Holocrinida along with recently described genus Baudicrinus (Encrinida, the only crinoid groups known from the Early Triassic, are considered the stem groups for the post-Paleozoic monophyletic subclass Articulata. Here, we report preliminary data on unexpectedly diverse crinoid faunas comprising at least four orders from the Lower Triassic (Induan and Olenekian of Svalbard, extending their stratigraphic ranges deeper into the early Mesozoic. These findings strongly imply that the recovery of crinoids in the aftermath of the end-Permian extinction began much earlier at higher palaeolatitudes than in the central Tethys.

  16. Spontaneous healing of spontaneous coronary artery dissection.

    Science.gov (United States)

    Almafragi, Amar; Convens, Carl; Heuvel, Paul Van Den

    2010-01-01

    Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome and sudden cardiac death. It should be suspected in every healthy young woman without cardiac risk factors, especially during the peripartum or postpartum periods. It is important to check for a history of drug abuse, collagen vascular disease or blunt trauma of the chest. Coronary angiography is essential for diagnosis and early management. We wonder whether thrombolysis might aggravate coronary dissection. All types of treatment (medical therapy, percutaneous intervention or surgery) improve the prognosis without affecting survival times if used appropriately according to the clinical stability and the angiographic features of the involved coronary arteries. Prompt recognition and targeted treatment improve outcomes. We report a case of SCAD in a young female free of traditional cardiovascular risk factors, who presented six hours after thrombolysis for ST elevation myocardial infarction. Coronary angiography showed a dissection of the left anterior descending and immediate branch. She had successful coronary artery bypass grafting, with complete healing of left anterior descending dissection.

  17. Titan Extinction Profiles Observed by Cassini Radio Occultations and Implications

    Science.gov (United States)

    Marouf, Essam; French, Richard; Flasar, F. Michael; Schinder, Paul J.; Rappaport, Nicole J.

    Three monochromatic and phase-coherent radio signals of wavelength = 0.9, 3.6, and 13 cm (Ka-, X-, and S-bands), were propagated by Cassini through the neutral atmosphere of Titan and the refracted signals were observed on the Earth. Abel inversion of observed changes in the signal frequency is used to recover the refractivity profile of the atmosphere, hence estimate the expected loss in signal strength due to defocusing of the radio signal by differential refraction. The refractive defocusing component (wavelength independent, in principle) is then removed from the actual measured signal strength profiles yielding the "true" signal extinction due to absorption and scattering integrated along the propagation path. Abel inversion of the integrated intensity profiles, tempered to combat noise contribution, yields localized estimates of the extinction coefficient (absorbtivity) as a function of altitude, or the extinction profiles. The initial radio measurements are diffraction-limited. We extend Fresnel transform based diffraction reconstruction procedures developed for radio occultation observations of planetary rings to remove diffraction effects from the initial radio measurements. The procedures are tested using idealized models of simple isothermal atmospheric profile extending above a hard-limb (knife-edge) model. Reconstruction of the simulated "observed" diffraction-limited data shows good agreement with the assumed atmospheric profile and the location of the hard-limb for a range of model parameters. We then apply a similar approach to the actual measured data. Strong wavelength-dependent extinction coefficient profile behavior is observed. Its large-scale structure appears well modeled by predictions based on N2-N2 collision-induced gaseous absorption for Titan's physical conditions. Interesting localized features of yet unexplained origin are also observed. Because the spatial scales of the extinction profile features are relatively large compared with

  18. Spontaneous cervical epidural hematoma: Report of a case managed conservatively

    Directory of Open Access Journals (Sweden)

    Halim Tariq

    2008-01-01

    Full Text Available Spontaneous spinal epidural hematoma is a rare cause of acute spinal cord compression. A 25-year-old male presented with a history of sudden onset of complete quadriplegia with sensory loss below the neck along with loss of bowel and bladder control. He had no history of any constitutional symptoms. He reported 10 days later. He was managed conservatively and after two weeks of intensive rehabilitation he had complete neural recovery. The spontaneous recovery of neurological impairment is attributed to the spreading of the hematoma throughout the epidural space, thus decreasing the pressure with partial neural recovery. Conservative treatment is a fair option in young patients who present late and show neurological improvement. The neurological status on presentation will guide the further approach to management.

  19. Spontaneous Symmetry Probing

    CERN Document Server

    Nicolis, Alberto

    2011-01-01

    For relativistic quantum field theories, we consider Lorentz breaking, spatially homogeneous field configurations or states that evolve in time along a symmetry direction. We dub this situation "spontaneous symmetry probing" (SSP). We mainly focus on internal symmetries, i.e. on symmetries that commute with the Poincare group. We prove that the fluctuations around SSP states have a Lagrangian that is explicitly time independent, and we provide the field space parameterization that makes this manifest. We show that there is always a gapless Goldstone excitation that perturbs the system in the direction of motion in field space. Perhaps more interestingly, we show that if such a direction is part of a non-Abelian group of symmetries, the Goldstone bosons associated with spontaneously broken generators that do not commute with the SSP one acquire a gap, proportional to the SSP state's "speed". We outline possible applications of this formalism to inflationary cosmology.

  20. Spontaneous nephrocutaneous fistula

    Directory of Open Access Journals (Sweden)

    Alberto A. Antunes

    2004-08-01

    Full Text Available Spontaneous renal fistula to the skin is rare. The majority of cases develop in patients with antecedents of previous renal surgery, renal trauma, renal tumors, and chronic urinary tract infection with abscess formation. We report the case of a 62-year old woman, who complained of urine leakage through the skin in the lumbar region for 2 years. She underwent a fistulography that revealed drainage of contrast agent to the collecting system and images suggesting renal lithiasis on this side. The patient underwent simple nephrectomy on this side and evolved without intercurrences in the post-operative period. Currently, the occurrence of spontaneous renal and perirenal abscesses is extremely rare, except in patients with diabetes, neoplasias and immunodepression in general.

  1. Spontaneous Rupture of Pyometra

    Directory of Open Access Journals (Sweden)

    Fatemeh Mallah

    2013-01-01

    Full Text Available Spontaneous perforation is a very rare complication of pyometra. The clinical findings of perforated pyometra are similar to perforation of the gastrointestinal tract and other causes of acute abdomen. In most cases, a correct and definite diagnosis can be made only by laparotomy. We report two cases of diffuse peritonitis caused by spontaneous perforated pyometra. The first case is a 78-year-old woman with abdominal pain for which laparotomy was performed because of suspected incarcerated hernia. The second case is a 61-year-old woman with abdominal pain for which laparotomy was performed because of symptoms of peritonitis. At laparotomy of both cases, 1 liter of pus with the source of uterine was found in the abdominal cavity. The ruptured uterine is also detected. More investigations revealed no malignancy as the reason of the pyometra.

  2. [Spontaneous spinal cord herniation].

    Science.gov (United States)

    Rivas, J J; de la Lama, A; Gonza Lez, P; Ramos, A; Zurdo, M; Alday, R

    2004-10-01

    Spontaneous spinal cord herniation through a dural defect is an unusual condition. This entity has been probably underestimated before the introduction of MRI. We report a case of a 49-year-old man with a progressive Brown-Sequard syndrome. MRI and CT myelogram showed a ventrally displaced spinal cord at level T6-T7 and expansion of the posterior subarachnoid space. Through a laminectomy, a spinal cord herniation was identified and reduced. The anterior dural defect was repaired with a patch of lyophilized dura. The patient recovered muscle power but there was no improvement of the sensory disturbance. The diagnosis of spontaneous spinal cord herniation must be considered when progressive myelopathy occurs in middle-aged patients, without signs of spinal cord compression and typical radiological findings. Surgical treatment may halt the progressive deficits and even yield improvement in many cases.

  3. Spontaneous Perforation of Pyometra.

    Science.gov (United States)

    Sharma, Nalini; Singh, Ahanthem Santa; Bhaphiralyne, Wankhar

    2016-04-01

    Pyometra is collection of purulent material which occurs when there is interference with its normal drainage. It is an uncommon condition with incidence of 0.1 to 0.5% of all gynecological patients. Spontaneous rupture of uterus is an extremely rare complication of pyometra. A 65-year-old lady presented with pain abdomen and purulent vaginal discharge. Preoperative diagnosis of pyometra was made by magnetic resonance imaging (MRI). Laparotomy followed by peritoneal lavage and repair of perforation was performed. Although spontaneously perforated pyometra is rare, the condition must be borne in mind with regard to elderly women with acute abdominal pain. Preoperative diagnosis of perforated pyometra is absolutely essential. Computed tomography (CT) and MRI are diagnostic tools. In selected cases conservative approach at surgery can be opted.

  4. Spontaneous Rupture of Pyometra

    Science.gov (United States)

    Mallah, Fatemeh; Eftekhar, Tahere; Naghavi-Behzad, Mohammad

    2013-01-01

    Spontaneous perforation is a very rare complication of pyometra. The clinical findings of perforated pyometra are similar to perforation of the gastrointestinal tract and other causes of acute abdomen. In most cases, a correct and definite diagnosis can be made only by laparotomy. We report two cases of diffuse peritonitis caused by spontaneous perforated pyometra. The first case is a 78-year-old woman with abdominal pain for which laparotomy was performed because of suspected incarcerated hernia. The second case is a 61-year-old woman with abdominal pain for which laparotomy was performed because of symptoms of peritonitis. At laparotomy of both cases, 1 liter of pus with the source of uterine was found in the abdominal cavity. The ruptured uterine is also detected. More investigations revealed no malignancy as the reason of the pyometra. PMID:24024054

  5. Immediate extinction causes a less durable loss of performance than delayed extinction following either fear or appetitive conditioning

    OpenAIRE

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In all experiments, conditioning and extinction were accomplished in single sessions, and retention testing took place 24 h after extinction. In both f...

  6. Spontaneous bacterial peritonitis

    OpenAIRE

    Al Amri Saleh

    1995-01-01

    Spontaneous bacterial peritonitis (SBP) is an infection of the ascitic fluid without obvious intra-abdominal source of sepsis; usually complicates advanced liver disease. The pathogenesis of the disease is multifactorial: low ascitic protein-content, which reflects defi-cient ascitic fluid complement and hence, reduced opsonic activity is thought to be the most important pathogenic factor. Frequent and prolonged bacteremia has been considered as another pertinent cause of SBP. This disease is...

  7. [Spontaneous bilateral Petit hernia].

    Science.gov (United States)

    Fontoura, Rodrigo Dias; Araújo, Emerson Silveira de; Oliveira, Gustavo Alves de; Sarmenghi Filho, Deolindo; Kalil, Mitre

    2011-01-01

    Petit's lumbar hernia is an uncommon defect of the posterior abdominal wall that represents less than 1% of all abdominal wall hernias. It is more often unilateral and founded in young females, rarely containing a real herniated sac. There are two different approaches to repair: laparoscopy and open surgery. The goal of this article is to report one case of spontaneous bilateral lumbar Petit's hernia treated with open surgery.

  8. Spontaneous Flapping Flight

    Science.gov (United States)

    Vandenberghe, Nicolas; Zhang, Jun; Childress, Stephen

    2004-11-01

    As shown in an earlier work [Vandenberghe, et. al. JFM, Vol 506, 147, 2004], a vertically flapping wing can spontaneously move horizontally as a result of symmetry breaking. In the current experimental study, we investigate the dependence of resultant velocity on flapping amplitude. We also describe the forward thrust generation and how the system dynamically selects a Strouhal number by balancing fluid and body forces. We further compare our model system with examples of biological locomotion, such as bird flight and fish swimming.

  9. Spontaneous Perforation of Pyometra

    OpenAIRE

    Sharma, Nalini; Singh, Ahanthem Santa; Bhaphiralyne, Wankhar

    2016-01-01

    Pyometra is collection of purulent material which occurs when there is interference with its normal drainage. It is an uncommon condition with incidence of 0.1 to 0.5% of all gynecological patients. Spontaneous rupture of uterus is an extremely rare complication of pyometra. A 65-year-old lady presented with pain abdomen and purulent vaginal discharge. Preoperative diagnosis of pyometra was made by magnetic resonance imaging (MRI). Laparotomy followed by peritoneal lavage and repair of perfor...

  10. Spontaneous spinal epidural abscess.

    LENUS (Irish Health Repository)

    Ellanti, P

    2011-10-01

    Spinal epidural abscess is an uncommon entity, the frequency of which is increasing. They occur spontaneously or as a complication of intervention. The classical triad of fever, back pain and neurological symptoms are not always present. High index of suspicion is key to diagnosis. Any delay in diagnosis and treatment can have significant neurological consequences. We present the case of a previously well man with a one month history of back pain resulting from an epidural abscess.

  11. Resistance to extinction and behavioral momentum.

    Science.gov (United States)

    Nevin, John A

    2012-05-01

    In the metaphor of behavioral momentum, reinforcement is assumed to strengthen discriminated operant behavior in the sense of increasing its resistance to disruption, and extinction is viewed as disruption by contingency termination and reinforcer omission. In multiple schedules of intermittent reinforcement, resistance to extinction is an increasing function of reinforcer rate, consistent with a model based on the momentum metaphor. The partial-reinforcement extinction effect, which opposes the effects of reinforcer rate, can be explained by the large disruptive effect of terminating continuous reinforcement despite its strengthening effect during training. Inclusion of a term for the context of reinforcement during training allows the model to account for a wide range of multiple-schedule extinction data and makes contact with other formulations. The relation between resistance to extinction and reinforcer rate on single schedules of intermittent reinforcement is exactly opposite to that for multiple schedules over the same range of reinforcer rates; however, the momentum model can give an account of resistance to extinction in single as well as multiple schedules. An alternative analysis based on the number of reinforcers omitted to an extinction criterion supports the conclusion that response strength is an increasing function of reinforcer rate during training.

  12. Extinction as discrimination: the molar view.

    Science.gov (United States)

    Baum, William M

    2012-05-01

    The traditional molecular view of behavior explains extinction as the dissipation or inhibition of strength, formerly built up by contiguous reinforcement. In obstinate opposition to this explanation was the partial-reinforcement extinction effect: a partially reinforced response extinguishes more slowly than a continuously reinforced response. It suggests instead that extinction is discrimination. Four pigeons were exposed to daily sessions in which a variable period of food delivery, produced by pecking on a variable-interval schedule, was followed by extinction. The rate of food delivery was varied over a wide range across conditions. Varying the amount of food per delivery inversely with rate of delivery kept response rate from varying excessively. The results confirmed and extended the partial-reinforcement effect; persistence of pecking and time to extinction were inversely related to rate of obtaining food. The results support the molar view of extinction, not as loss of strength of a particular discrete response, but as a transition from one allocation of time among activities to another. Although molecular theories dismiss discrimination due to repeated training and extinction as an impurity or complication, repeated cycles of availability and privation are probably typical of the environment in which most vertebrate species evolved.

  13. Estimating extinction using unsupervised machine learning

    Science.gov (United States)

    Meingast, Stefan; Lombardi, Marco; Alves, João

    2017-05-01

    Dust extinction is the most robust tracer of the gas distribution in the interstellar medium, but measuring extinction is limited by the systematic uncertainties involved in estimating the intrinsic colors to background stars. In this paper we present a new technique, Pnicer, that estimates intrinsic colors and extinction for individual stars using unsupervised machine learning algorithms. This new method aims to be free from any priors with respect to the column density and intrinsic color distribution. It is applicable to any combination of parameters and works in arbitrary numbers of dimensions. Furthermore, it is not restricted to color space. Extinction toward single sources is determined by fitting Gaussian mixture models along the extinction vector to (extinction-free) control field observations. In this way it becomes possible to describe the extinction for observed sources with probability densities, rather than a single value. Pnicer effectively eliminates known biases found in similar methods and outperforms them in cases of deep observational data where the number of background galaxies is significant, or when a large number of parameters is used to break degeneracies in the intrinsic color distributions. This new method remains computationally competitive, making it possible to correctly de-redden millions of sources within a matter of seconds. With the ever-increasing number of large-scale high-sensitivity imaging surveys, Pnicer offers a fast and reliable way to efficiently calculate extinction for arbitrary parameter combinations without prior information on source characteristics. The Pnicer software package also offers access to the well-established Nicer technique in a simple unified interface and is capable of building extinction maps including the Nicest correction for cloud substructure. Pnicer is offered to the community as an open-source software solution and is entirely written in Python.

  14. Interstellar extinction by fractal polycrystalline graphite clusters?

    CERN Document Server

    Andersen, A C; Pustovit, V N; Niklasson, G A

    2001-01-01

    Certain dust particles in space are expected to appear as clusters of individual grains. The morphology of these clusters could be fractal or compact. To determine how these structural features would affect the interpretation of the observed interstellar extinction peak at $\\sim 4.6~\\mu$m, we have calculated the extinction by compact and fractal polycrystalline graphite clusters consisting of touching identical spheres. We compare three general methods for computing the extinction of the clusters, namely, a rigorous solution and two different discrete-dipole approximation methods.

  15. A model for evolution and extinction

    CERN Document Server

    Roberts, B W; Roberts, Bruce W

    1995-01-01

    We present a model for evolution and extinction in large ecosystems. The model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properties of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinctions and species lifetimes that we would expect to see in real ecosystems. It should be possible to test these predictions against the fossil record. The model indicates that a possible mechanism for mass extinction is the coincidence of a large coevolutionary avalanche in the ecosystem with a severe environmental disturbance.

  16. Volcanogenic Dark Matter and Mass Extinctions

    CERN Document Server

    Abbas, S; Abbas, Samar; Abbas, Afsar

    1996-01-01

    The passage of the Earth through dense clumps of dark matter, the presence of which are predicted by certain cosmologies, would produce large quantities of heat in the interior of this planet through the capture and subsequent annihilation of dark matter particles. This heat can cause large-scale volcanism which could in turn have caused the extinction of the dinosaurs and other mass extinctions. The periodicity of such volcanic outbursts agrees with the frequency of palaeontological mass extinctions as well as the observed periodicity in the occurrence of the largest flood basalt provinces on the globe.

  17. A mathematical model for Neanderthal extinction

    CERN Document Server

    Flores, J C

    1997-01-01

    A simple mathematical homogeneous model of competition is used to describe Neanderthal extinction in Europe. It considers two interacting species, Neanderthals and Early Modern Men, in the same ecological niche. Using paleontological data we claim that the parameter of similarity, between both species, fluctuates between 0.992 and 0.997. An extension of the model including migration (diffusion) is also discussed nevertheless, extinction of Neanderthal seems unavoidable. Numerical analysis of travelling wave solution (fronts) comfirms the extinction. The wave-front-velocity is estimated from linear analysis and numerical simulations confirm this estimation. We conjecture a mathematical formulation for the principle of exclusion between competitive interacting species (Gause).

  18. Functional diversity of marine ecosystems after the Late Permian mass extinction event

    Science.gov (United States)

    Foster, William J.; Twitchett, Richard J.

    2014-03-01

    The Late Permian mass extinction event about 252 million years ago was the most severe biotic crisis of the past 500 million years and occurred during an episode of global warming. The loss of around two-thirds of marine genera is thought to have had substantial ecological effects, but the overall impacts on the functioning of marine ecosystems and the pattern of marine recovery are uncertain. Here we analyse the fossil occurrences of all known benthic marine invertebrate genera from the Permian and Triassic periods, and assign each to a functional group based on their inferred lifestyle. We show that despite the selective extinction of 62-74% of these genera, all but one functional group persisted through the crisis, indicating that there was no significant loss of functional diversity at the global scale. In addition, only one new mode of life originated in the extinction aftermath. We suggest that Early Triassic marine ecosystems were not as ecologically depauperate as widely assumed. Functional diversity was, however, reduced in particular regions and habitats, such as tropical reefs; at these smaller scales, recovery varied spatially and temporally, probably driven by migration of surviving groups. We find that marine ecosystems did not return to their pre-extinction state, and by the Middle Triassic greater functional evenness is recorded, resulting from the radiation of previously subordinate groups such as motile, epifaunal grazers.

  19. Severe environmental effects of Chicxulub impact imply key role in end-Cretaceous mass extinction

    Science.gov (United States)

    Brugger, Julia; Feulner, Georg; Petri, Stefan

    2017-04-01

    66 million years ago, during the most recent of the five severe mass extinctions in Earth's history, non-avian dinosaurs and many other organisms became extinct. The cause of this end-Cretaceous mass extinction is seen in either flood-basalt eruptions or an asteroid impact. Modeling the climatic changes after the Chicxulub asteroid impact allow to assess its contribution to the extinction event and to analyze the short-term and long-term response of the climate and the biosphere to the impact. Existing studies either investigated the effect of dust, which is now believed to play a minor role, or used one-dimensional, non-coupled models. In contrast, we use a coupled climate model to explore the longer lasting cooling due to sulfate aerosols. Based on data from geophysical impact modeling, we set up simulations with different stratospheric residence times for sulfate aerosols. Depending on this residence time, global surface air temperature decreased by at least 26°C, with 3 to 16 years subfreezing temperatures and a recovery time larger than 30 years. Vigorous ocean mixing, caused by the fast cooling of the surface ocean, might have perturbed marine ecosystems by the upwelling of nutrients. The dramatic climatic changes seen in our simulations imply severe environmental effects and therefore a significant contribution of the impact in the end-Cretaceous mass extinction.

  20. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

    DEFF Research Database (Denmark)

    Finnegan, Seth; Mac Ørum Rasmussen, Christian; Harper, David A. T.

    2016-01-01

    The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician......–Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 35°) palaeolatitudinal ranges. This pattern is only observed...... in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions...

  1. Aerobic Marine Habitat Loss During the Late Permian Extinction

    Science.gov (United States)

    Penn, J. L.; Deutsch, C.; Payne, J.; Sperling, E. A.

    2016-12-01

    Rapid climate change at the end of the Permian is thought to have triggered the most severe mass extinction in Earth's history, but the precise mechanism of biodiversity loss is unknown. Geological evidence points to lethally hot equatorial temperatures and an expansion of anoxic ocean waters as likely culprits. However, previous climate model simulations of the warm Early Triassic exhibit weak tropical warming, and anoxic conditions require a massive and unconstrained increase in the ocean nutrient reservoir. Reconciling model predictions with the geologic record remains a key challenge to identifying the kill-mechanism, which must also take into account the role of animal physiology. Here we apply a recently developed index for the metabolic scope of marine animals to the first global climate simulations of the Permian-Triassic transition to quantify the effects of ocean warming and oxygen (O2) depletion on aerobic habitat availability. Forcing with extreme CO2 concentrations warms the surface ocean by over 10oC, consistent with paleoproxies for upper ocean temperature change. Warming depletes global O2, with greatest losses occuring in tropical deep waters as a result of their reduced ventilation. Together warming and deoxygenation would have constricted the occurrence of marine habitat by 80% globally, by decreasing the metabolic index of the Permian ocean. These changes are most pronounced in the tropics where the fossil record suggests recovery was severely inhibited. Fossil deposits also record changes in animal body size across the extinction. We find that adaptation via body size reductions can compensate for increasing hypoxia at high latitudes, and even prevent extinction there, but cannot maintain the habitability of the tropics.

  2. Epidemic extinction and control in heterogeneous networks

    CERN Document Server

    Hindes, Jason

    2016-01-01

    We consider epidemic extinction in finite networks with broad variation in local connectivity. Generalizing the theory of large fluctuations to random networks with a given degree distribution, we are able to predict the most probable, or optimal, paths to extinction in various configurations, including truncated power-laws. We find that paths for heterogeneous networks follow a limiting form in which infection first decreases in low-degree nodes, which triggers a rapid extinction in high- degree nodes, and finishes with a residual low-degree extinction. The usefulness of the approach is further demonstrated through optimal control strategies that leverage finite-size fluctuations. Interestingly, we find that the optimal control is a mix of treating both high and low-degree nodes based on large-fluctuation theoretical predictions.

  3. Protostars at Low Extinction in Orion A

    CERN Document Server

    Lewis, John Arban

    2016-01-01

    In the list of young stellar objects compiled by Megeath et al. (2012) for the Orion A molecular cloud, only 44 out of 1208 sources found projected onto low extinction (Ak<0.8 mag) gas are identified as protostars. These objects are puzzling because protostars are not typically expected to be associated with extended low extinction material. Here, we use high resolution extinction maps generated from Herschel data, optical/infrared and Spitzer Space Telescope photometry and spectroscopy of the low extinction protostellar candidate sources to determine if they are likely true protostellar sources or contaminants. Out of 44 candidate objects, we determine that 10 sources are likely protostars, with the rest being more evolved young stellar objects (18), galaxies (4), false detections of nebulosity and cloud edges (9), or real sources for which more data are required to ascertain their nature (3). We find none of the confirmed protostars to be associated with recognizable dense cores and we briefly discuss po...

  4. UV extinction properties of carina nebular dust

    Science.gov (United States)

    Massa, Derck

    1993-01-01

    I have performed an analysis of the UV extinction by dust along the line of sight to the young open cluster Tr 16. The observed curves are parameterized in order to extract quantitative information about the structure of the curves. Furthermore, by constructing differential extinction curves, obtained by differencing curves for stars which lie within a few arc seconds of each other on the sky, I was able to obtain a curve which is free of the effects of foreground extinction, and represents the extinction by the dust in the Tr 16 molecular cloud. I then show that this curve is nearly identical to one due to dust in the Orion molecular cloud. This result shows that dust in the Carina arm exhibits the same behavior as that in the local arm.

  5. Possible involvement of serotonin in extinction.

    Science.gov (United States)

    Beninger, R J; Phillips, A G

    1979-01-01

    In Experiment 1, rats were trained to leverpress for continuous reinforcement with food; half were then intubated with the serotonin synthesis inhibitor parachlorophenylalanine (PCPA: 400 mg/kg) and half with water. In extinction the PCPA-treated rats responded at a higher rate. In Experiment 2, rats were trained on a random interval schedule and then assigned to two groups, treated as in Experiment 1, and tested in extinction. There was no significant difference in the resistance to extinction of the two groups. In Experiment 3, the responding of rats trained in a punished stepdown response paradigm and then given an intragastric injection of PCPA took longer to recover than the responding of water-injected controls. These observations suggest that serotonergic neurons might play a role in extinction processes.

  6. Calibrating the end-Permian mass extinction.

    Science.gov (United States)

    Shen, Shu-zhong; Crowley, James L; Wang, Yue; Bowring, Samuel A; Erwin, Douglas H; Sadler, Peter M; Cao, Chang-qun; Rothman, Daniel H; Henderson, Charles M; Ramezani, Jahandar; Zhang, Hua; Shen, Yanan; Wang, Xiang-dong; Wang, Wei; Mu, Lin; Li, Wen-zhong; Tang, Yue-gang; Liu, Xiao-lei; Liu, Lu-jun; Zeng, Yong; Jiang, Yao-fa; Jin, Yu-gan

    2011-12-09

    The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ(13)C over 90,000 years, and coincided with a δ(13)C excursion of -5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.

  7. Periodicity of extinctions in the geologic past.

    Science.gov (United States)

    Raup, D M; Sepkoski, J J

    1984-02-01

    The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis. The analyzed record is based on variation in extinction intensity for fossil families of marine vertebrates, invertebrates, and protozoans and contains 12 extinction events. The 12 events show a statistically significant periodicity (P less than 0.01) with a mean interval between events of 26 million years. Two of the events coincide with extinctions that have been previously linked to meteorite impacts (terminal Cretaceous and Late Eocene). Although the causes of the periodicity are unknown, it is possible that they are related to extraterrestrial forces (solar, solar system, or galactic).

  8. Three Color Particle Optical Extinction Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design, build and test a multi-color (red, green, blue) particle optical extinction monitor suitable for use in either land or airborne applications....

  9. Optical atmospheric extinction over Cerro Paranal

    National Research Council Canada - National Science Library

    Patat, F; Moehler, S; O'Brien, K; Pompei, E; Bensby, T; Carraro, G; Ugarte Postigo, de, A; Fox, A; Gavignaud, I; James, G; Korhonen, H; Ledoux, C; Randall, S; Sana, H.A.A; Smoker, J; Stefl, S; Szeifert, T

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function...

  10. Extinction in the Lotka-Volterra model.

    Science.gov (United States)

    Parker, Matthew; Kamenev, Alex

    2009-08-01

    Birth-death processes often exhibit an oscillatory behavior. We investigate a particular case where the oscillation cycles are marginally stable on the mean-field level. An iconic example of such a system is the Lotka-Volterra model of predator-prey interaction. Fluctuation effects due to discreteness of the populations destroy the mean-field stability and eventually drive the system toward extinction of one or both species. We show that the corresponding extinction time scales as a certain power-law of the population sizes. This behavior should be contrasted with the extinction of models stable in the mean-field approximation. In the latter case the extinction time scales exponentially with size.

  11. Biomarker Records Associated with Mass Extinction Events

    Science.gov (United States)

    Whiteside, Jessica H.; Grice, Kliti

    2016-06-01

    The history of life on Earth is punctuated by a series of mass extinction episodes that vary widely in their magnitude, duration, and cause. Biomarkers are a powerful tool for the reconstruction of historical environmental conditions and can therefore provide insights into the cause and responses to ancient extinction events. In examining the five largest mass extinctions in the geological record, investigators have used biomarkers to elucidate key processes such as eutrophy, euxinia, ocean acidification, changes in hydrological balance, and changes in atmospheric CO2. By using these molecular fossils to understand how Earth and its ecosystems have responded to unusual environmental activity during these extinctions, models can be made to predict how Earth will respond to future changes in its climate.

  12. Anthropogenic stressors and riverine fish extinctions

    NARCIS (Netherlands)

    Dias, M.S.; Tedesco, P.A.; Hugueny, B.; Jézéquel, C.; Beauchard, O.; Brosse, S.; Oberdorff, T.

    2017-01-01

    Human activities are often implicated in the contemporary extinction of contemporary species. Concerningriverine fishes, the major biotic and abiotic threats widely cited include introduction of non-nativespecies, habitat fragmentation and homogenization in stream flow dynamics due to the damming

  13. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies: testing 'standard' extinction maps

    OpenAIRE

    Choloniewski, Jacek; Valentijn, Edwin A.

    2003-01-01

    The relative extinction in the Galaxy computed with our new method (Choloniewski and Valentijn 2003, CV) is compared with three patterns: Schlegel, Finkbeiner and Davis (1998, SFD), Burstein and Heiles (1978, BH) and the cosecans law. It is shown that extinction of SFD is more reliable then that of BH since it stronger correlates with our new extinction. The smallest correlation coeffcient have been obtained for the cosecans law. Linear regression analysis show that SFD overestimate the extin...

  14. An Analysis of the Shapes of Ultraviolet Extinction Curves. IV. Extinction without Standards

    OpenAIRE

    Fitzpatrick, Edward L.; Massa, Derck

    2005-01-01

    We present a new method for deriving UV-through-IR extinction curves, based on the use of stellar atmosphere models to provide estimates of the intrinsic (i.e., unreddened) stellar spectral energy distributions (SEDs), rather than unreddened (or lightly reddened) standard stars. We show that this ``extinction-without-standards'' technique greatly increases the accuracy of the derived extinction curves and allows realistic estimations of the uncertainties. An additional benefit of the techniqu...

  15. Deccan Volcanism likely cause for K-T Mass Extinction

    Science.gov (United States)

    Keller, G.; Reddy, A. N.; Jaiprakash, B. C.; Adatte, T.; Gertsch, B.; Bajpai, S.; Garg, R.; Prasad, V.; Upadhyay, H.; Bhowmick, P. K.

    2009-04-01

    -280 ky during which time a low diversity early Danian assemblage of small new species evolved globally. The last major Deccan volcanic pulses began at the C29R/C29N boundary and may have been the cause for the long delay in the full biotic recovery. These studies suggest that the real cause for the K-T mass extinction may have been the main phase of Deccan volcanic eruptions at the end of the Maastrichtian. In particular, the rapid succession of megaflows and the massive SO2 emissions estimated at least 10 to 30 times those from the Chicxulub impact may have caused a deadly runaway effect that lead to the K-T mass extinction. Chenet, A-L. et al. (2007) EPSL 263, 1-15; Chenet et al. (2008) JGR, 113, B04101; Keller, G. et al. (2008) EPSL 268, 293-311.

  16. Falling towards forgetfulness: synaptic decay prevents spontaneous recovery of memory.

    Directory of Open Access Journals (Sweden)

    James V Stone

    Full Text Available Long after a new language has been learned and forgotten, relearning a few words seems to trigger the recall of other words. This "free-lunch learning" (FLL effect has been demonstrated both in humans and in neural network models. Specifically, previous work proved that linear networks that learn a set of associations, then partially forget them all, and finally relearn some of the associations, show improved performance on the remaining (i.e., nonrelearned associations. Here, we prove that relearning forgotten associations decreases performance on nonrelearned associations; an effect we call negative free-lunch learning. The difference between free-lunch learning and the negative free-lunch learning presented here is due to the particular method used to induce forgetting. Specifically, if forgetting is induced by isotropic drifting of weight vectors (i.e., by adding isotropic noise, then free-lunch learning is observed. However, as proved here, if forgetting is induced by weight values that simply decay or fall towards zero, then negative free-lunch learning is observed. From a biological perspective, and assuming that nervous systems are analogous to the networks used here, this suggests that evolution may have selected physiological mechanisms that involve forgetting using a form of synaptic drift rather than synaptic decay, because synaptic drift, but not synaptic decay, yields free-lunch learning.

  17. Spontaneous Functional Recovery from Incomplete Spinal Cord Injury

    DEFF Research Database (Denmark)

    Rasmussen, Rune; Carlsen, Eva Maria Meier

    2016-01-01

    Our interactions with the world occur via precise coordination of our motor system. Even a movement as seemingly simple as reaching for an object is a complex motor behavior that requires precise neuronal activity in supraspinal areas (Lemon, 2008) and spinal areas (Azim et al., 2014). Motor...

  18. Biomarkers of Spontaneous Recovery from Traumatic Spinal Cord Injury

    Science.gov (United States)

    2016-10-01

    funding to NY State PIs who had at least 1 federally funded SCI research project, to expand aims or efforts towards the project. Support was used only...for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Immediately after SCI , a person confronts 3 major questions: (1) how...focuses on maximizing preserved function and managing medical complications of living with SCI . Currently, there is no FDA-approved drug to promote

  19. Demography and the extinction of European Neanderthals

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2011-01-01

    Causes previously suggested for the sudden extinction of Neanderthals (Homo neanderthalensis) in Europe, starting around 35,000 years ago, comprise food shortage, climatic effects and violence from Modern Humans. The aim here is to formulate a demographic model with reconstructed fertility and de...... Human newcomers during the last part of the period. The conclusion is that other reasons for extinction than climate or starvation must be sought....

  20. Software fires detection and extinction for forest

    Directory of Open Access Journals (Sweden)

    Juan Carlos García Seco

    2008-12-01

    Full Text Available This article shows the most usual fire detection and forest extinction application technologies at present. We will see all different methods used by these applications that can be found in the Market and some examples. Also, some basic questions about the most influent parameters when a fire must be extinct are shown. Finally, after having shown all the technologies, we will build a model about an intelligent system which not only detects, but also extinguish wildfires.

  1. Extinction rates of established spatial populations

    Science.gov (United States)

    Meerson, Baruch; Sasorov, Pavel V.

    2011-01-01

    This paper deals with extinction of an isolated population caused by intrinsic noise. We model the population dynamics in a “refuge” as a Markov process which involves births and deaths on discrete lattice sites and random migrations between neighboring sites. In extinction scenario I, the zero population size is a repelling fixed point of the on-site deterministic dynamics. In extinction scenario II, the zero population size is an attracting fixed point, corresponding to what is known in ecology as the Allee effect. Assuming a large population size, we develop a WKB (Wentzel-Kramers-Brillouin) approximation to the master equation. The resulting Hamilton’s equations encode the most probable path of the population toward extinction and the mean time to extinction. In the fast-migration limit these equations coincide, up to a canonical transformation, with those obtained, in a different way, by Elgart and Kamenev [Phys. Rev. EPHYADX1539-375510.1103/PhysRevE.70.041106 70, 041106 (2004)]. We classify possible regimes of population extinction with and without an Allee effect and for different types of refuge, and solve several examples analytically and numerically. For a very strong Allee effect, the extinction problem can be mapped into the overdamped limit of the theory of homogeneous nucleation due to Langer [Ann. Phys. (NY)APNYA60003-491610.1016/0003-4916(69)90153-5 54, 258 (1969)]. In this regime, and for very long systems, we predict an optimal refuge size that maximizes the mean time to extinction.

  2. Extinction as the loss of evolutionary history

    OpenAIRE

    Erwin, Douglas H.

    2008-01-01

    Current plant and animal diversity preserves at most 1–2% of the species that have existed over the past 600 million years. But understanding the evolutionary impact of these extinctions requires a variety of metrics. The traditional measurement is loss of taxa (species or a higher category) but in the absence of phylogenetic information it is difficult to distinguish the evolutionary depth of different patterns of extinction: the same species loss can encompass very different losses of evolu...

  3. Demography and the extinction of European Neanderthals

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2011-01-01

    Causes previously suggested for the sudden extinction of Neanderthals (Homo neanderthalensis) in Europe, starting around 35,000 years ago, comprise food shortage, climatic effects and violence from Modern Humans. The aim here is to formulate a demographic model with reconstructed fertility and de...... Human newcomers during the last part of the period. The conclusion is that other reasons for extinction than climate or starvation must be sought....

  4. A depth refugium from catastrophic coral bleaching prevents regional extinction.

    Science.gov (United States)

    Smith, Tyler B; Glynn, Peter W; Maté, Juan L; Toth, Lauren T; Gyory, Joanna

    2014-06-01

    Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Niño events on record (1982-1983 and 1997 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (> 11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other hydrocorals without deep-water populations were driven to regional extinction. Evidence from the subfossil record in the same area showed shallow-water persistence of abundant M. intricata populations from 5000 years ago, through severe El Niño-Southern Oscillation cycles, suggesting a potential depth refugium on a millennial timescale. Our data confirm the deep refuge hypothesis for corals under thermal stress.

  5. How does climate change cause extinction?

    Science.gov (United States)

    Cahill, Abigail E; Aiello-Lammens, Matthew E; Fisher-Reid, M Caitlin; Hua, Xia; Karanewsky, Caitlin J; Ryu, Hae Yeong; Sbeglia, Gena C; Spagnolo, Fabrizio; Waldron, John B; Warsi, Omar; Wiens, John J

    2013-01-07

    Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.

  6. Spontaneous Thigh Compartment Syndrome

    Directory of Open Access Journals (Sweden)

    Khan, Sameer K

    2011-02-01

    Full Text Available A young man presented with a painful and swollen thigh, without any history of trauma, illness, coagulopathic medication or recent exertional exercise. Preliminary imaging delineated a haematoma in the anterior thigh, without any fractures or muscle trauma. Emergent fasciotomies were performed. No pathology could be identified intra-operatively, or on follow-up imaging. A review of thigh compartment syndromes described in literature is presented in a table. Emergency physicians and traumatologists should be cognisant of spontaneous atraumatic presentations of thigh compartment syndrome, to ensure prompt referral and definitive management of this limb-threatening condition. [West J Emerg Med. 2011;12(1:134-138].

  7. Spontaneous bacterial peritonitis

    Directory of Open Access Journals (Sweden)

    Al Amri Saleh

    1995-01-01

    Full Text Available Spontaneous bacterial peritonitis (SBP is an infection of the ascitic fluid without obvious intra-abdominal source of sepsis; usually complicates advanced liver disease. The pathogenesis of the disease is multifactorial: low ascitic protein-content, which reflects defi-cient ascitic fluid complement and hence, reduced opsonic activity is thought to be the most important pathogenic factor. Frequent and prolonged bacteremia has been considered as another pertinent cause of SBP. This disease is associated with high mortality and recurrence. Therefore, orompt recognition and institution of therapy and plan of prophylaxis is vital.

  8. Spontaneously broken mass

    CERN Document Server

    Endlich, Solomon; Penco, Riccardo

    2013-01-01

    The Galilei group involves mass as a central charge. We show that the associated superselection rule is incompatible with the observed phenomenology of superfluid helium 4: this is recovered only under the assumption that mass is spontaneously broken. This remark is somewhat immaterial for the real world, where the correct space-time symmetries are encoded by the Poincar\\'e group, which has no central charge. Yet it provides an explicit example of how superselection rules can be experimentally tested. We elaborate on what conditions must be met for our ideas to be generalizable to the relativistic case of the integer/half-integer angular momentum superselection rule.

  9. Spontaneous Intracranial Hypotension: An Etiology for Consciousness Disorder and Coma.

    Science.gov (United States)

    Collange, Olivier; Wolff, Valérie; Cebula, Hélène; Pradignac, Alain; Meyer, Alain; Kindo, Michel; Diemunsch, Pierre; Proust, François; Mertes, Paul-Michel; Kremer, Stéphane

    2016-11-15

    We report 3 cases of spontaneous intracranial hypotension (SIH) associated with consciousness disorder and coma. In patients, SIH was suspected on a computed tomography scan and diagnosed by cerebral magnetic resonance imaging (MRI). Spinal MRI confirmed cerebrospinal fluid leakage. SIH should be seen as an underestimated cause of consciousness disorder and coma, especially in patients with a history of orthostatic headache, spinal injury, or oculomotor signs. Computed tomography scans should be examined for signs of SIH before operating on patients with a spontaneous subdural hematoma. Brain and spine MRI should be performed when SIH is suspected. Our 3 patients have shown good recovery without any neurological sequelae.

  10. An Unusual Etiology of Spontaneous Pyometra Perforation; A Case Report

    Science.gov (United States)

    Agarwal, Rachna; Suneja, Amita; Sharma, Abha; Vaid, Neelam Bala

    2011-01-01

    Introduction By presenting this case we aimed to describe an uncommon complication of generalized peritonitis following spontaneous pyometra perforation in untreated cervical carcinoma. Case Presentation This report describes a 60-year-old postmenopausal woman presenting with clinical features mimicking intestinal perforation who was later diagnosed as cervical carcinoma with pyometra perforation at exploratory laparotomy. The patient had good post-operative recovery following drainage and peritoneal lavage. Conclusion Spontaneous pyometra perforation in a case of untreated carcinoma of cervix is a rare condition, yet it should be suspected and kept in the differential diagnosis of acute abdomen in elderly women. PMID:23926508

  11. Disaster Debris Recovery Database - Recovery

    Data.gov (United States)

    U.S. Environmental Protection Agency — The US EPA Region 5 Disaster Debris Recovery Database includes public datasets of over 6,000 composting facilities, demolition contractors, transfer stations,...

  12. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    Nollkaemper, A.

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  13. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    A. Nollkaemper

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  14. Extinction rates in North American freshwater fishes, 1900-2010

    Science.gov (United States)

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  15. Quantum Spontaneous Stochasticity

    CERN Document Server

    Eyink, Gregory L

    2015-01-01

    The quantum wave-function of a massive particle with small initial uncertainties (consistent with the uncertainty relation) is believed to spread very slowly, so that the dynamics is deterministic. This assumes that the classical motions for given initial data are unique. In fluid turbulence non-uniqueness due to "roughness" of the advecting velocity field is known to lead to stochastic motion of classical particles. Vanishingly small random perturbations are magnified by Richardson diffusion in a "nearly rough" velocity field so that motion remains stochastic as the noise disappears, or classical spontaneous stochasticity, . Analogies between stochastic particle motion in turbulence and quantum evolution suggest that there should be quantum spontaneous stochasticity (QSS). We show this for 1D models of a particle in a repulsive potential that is "nearly rough" with $V(x) \\sim C|x|^{1+\\alpha}$ at distances $|x|\\gg \\ell$ , for some UV cut-off $\\ell$, and for initial Gaussian wave-packet centered at 0. We consi...

  16. Immediate Extinction Causes a Less Durable Loss of Performance than Delayed Extinction following Either Fear or Appetitive Conditioning

    Science.gov (United States)

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In…

  17. Trophically Unique Species Are Vulnerable to Cascading Extinction

    OpenAIRE

    Petchey, Owen L.; Eklöf, Anna; Borrvall, Charlotte; Ebenman, Bo

    2008-01-01

    Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a communi...

  18. Recovery Spirituality

    Directory of Open Access Journals (Sweden)

    Ernest Kurtz

    2015-01-01

    Full Text Available There is growing interest in Alcoholics Anonymous (A.A. and other secular, spiritual, and religious frameworks of long-term addiction recovery. The present paper explores the varieties of spiritual experience within A.A., with particular reference to the growth of a wing of recovery spirituality promoted within A.A. It is suggested that the essence of secular spirituality is reflected in the experience of beyond (horizontal and vertical transcendence and between (connection and mutuality and in six facets of spirituality (Release, Gratitude, Humility, Tolerance, Forgiveness, and a Sense of Being-at-home shared across religious, spiritual, and secular pathways of addiction recovery. The growing varieties of A.A. spirituality (spanning the “Christianizers” and “Seculizers” reflect A.A.’s adaptation to the larger diversification of religious experience and the growing secularization of spirituality across the cultural contexts within which A.A. is nested.

  19. 76 FR 31973 - Endangered and Threatened Wildlife and Plants; Notice of Availability of Draft Recovery Plan for...

    Science.gov (United States)

    2011-06-02

    ... address. SUPPLEMENTARY INFORMATION: Background Recovery of endangered or threatened animals and plants to..., as well as the consequent vulnerability to extinction through deterministic or stochastic (chance... populations that may exist but are currently unknown. In order to reduce the potential for extinction due...

  20. Conservation Risks: When Will Rhinos be Extinct?

    Science.gov (United States)

    Haas, Timothy C; Ferreira, Sam M

    2016-08-01

    We develop a risk intelligence system for biodiversity enterprises. Such enterprises depend on a supply of endangered species for their revenue. Many of these enterprises, however, cannot purchase a supply of this resource and are largely unable to secure the resource against theft in the form of poaching. Because replacements are not available once a species becomes extinct, insurance products are not available to reduce the risk exposure of these enterprises to an extinction event. For many species, the dynamics of anthropogenic impacts driven by economic as well as noneconomic values of associated wildlife products along with their ecological stressors can help meaningfully predict extinction risks. We develop an agent/individual-based economic-ecological model that captures these effects and apply it to the case of South African rhinos. Our model uses observed rhino dynamics and poaching statistics. It seeks to predict rhino extinction under the present scenario. This scenario has no legal horn trade, but allows live African rhino trade and legal hunting. Present rhino populations are small and threatened by a rising onslaught of poaching. This present scenario and associated dynamics predicts continued decline in rhino population size with accelerated extinction risks of rhinos by 2036. Our model supports the computation of extinction risks at any future time point. This capability can be used to evaluate the effectiveness of proposed conservation strategies at reducing a species' extinction risk. Models used to compute risk predictions, however, need to be statistically estimated. We point out that statistically fitting such models to observations will involve massive numbers of observations on consumer behavior and time-stamped location observations on thousands of animals. Finally, we propose Big Data algorithms to perform such estimates and to interpret the fitted model's output.

  1. Elevational distribution and extinction risk in birds.

    Directory of Open Access Journals (Sweden)

    Rachel L White

    Full Text Available Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures - notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species' current elevational ranges and increased efforts to digitise and centralise such data.

  2. An abrupt extinction in the Middle Permian (Capitanian) of the Boreal Realm with a causal link to anoxia, acidification and mercury poisoning

    Science.gov (United States)

    Bond, David; Wignall, Paul; Joachimski, Michael; Sun, Yadong; Savov, Ivan; Grasby, Stephen; Beauchamp, Benoit; Blomeier, Dierk

    2016-04-01

    The controversial Capitanian (Middle Permian, 262 Ma) extinction event is mostly known from equatorial latitudes and consequently its global extent is poorly resolved. We demonstrate that there were two, severe extinctions amongst brachiopods in northern Boreal latitudes (Spitsbergen), in the Middle to Late Permian, separated by a recovery phase. New age dating of the Kapp Starostin Formation of Spitsbergen using strontium and carbon isotopic trends suggests that the first crisis occurred in the Capitanian. This age assignment indicates that this Middle Permian extinction is manifest at higher latitudes. Redox proxies (pyrite framboids and trace metals) show that the Boreal crisis coincided with an intensification of oxygen depletion, implicating anoxia in the extinction scenario. The highly toxic metal mercury becomes enriched in strata at the Middle Permian extinction level implicating death-by-toxicity (and a possible link to volcanism). Finally, the near-total loss of carbonates across the Boreal Realm in the Middle to Late Permian also suggests a role for acidification. New in prep. data from Ellesmere Island, Arctic Canada (samples collected July 2015) tentatively suggests that this potent "three strikes and you're out" extinction mechanism was a Boreal-wide phenomenon. The Late Permian recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors, and an increased mollusk dominance, resulting in an assemblage reminiscent of younger Mesozoic assemblages. The subsequent end-Permian mass extinction terminated this Late Permian radiation.

  3. Spontaneous Coronary Artery Dissection.

    Science.gov (United States)

    Tweet, Marysia S; Gulati, Rajiv; Hayes, Sharonne N

    2016-07-01

    Spontaneous coronary artery dissection is an important etiology of nonatherosclerotic acute coronary syndrome, myocardial infarction, and sudden death. Innovations in the catheterization laboratory including optical coherence tomography and intravascular ultrasound have enhanced the ability to visualize intimal disruption and intramural hematoma associated with SCAD. Formerly considered "rare," these technological advances and heightened awareness suggest that SCAD is more prevalent than prior estimates. SCAD is associated with female sex, young age, extreme emotional stress, or extreme exertion, pregnancy, and fibromuscular dysplasia. The clinical characteristics and management strategies of SCAD patients are different than for atherosclerotic heart disease and deserve specific consideration. This review will highlight recent discoveries about SCAD as well as describe current efforts to elucidate remaining gaps in knowledge.

  4. Spontaneous aortocaval fistula.

    Directory of Open Access Journals (Sweden)

    Rajmohan B

    2002-07-01

    Full Text Available Spontaneous aortocaval fistula is rare, occurring only in 4% of all ruptured abdominal aortic aneurysms. The physical signs can be missed but the presence of low back pain, palpable abdominal aortic aneurysm, machinery abdominal murmur and high-output cardiac failure unresponsive to medical treatment should raise the suspicion. Pre-operative diagnosis is crucial, as adequate preparation has to be made for the massive bleeding expected at operation. Successful treatment depends on management of perioperative haemodynamics, control of bleeding from the fistula and prevention of deep vein thrombosis and pulmonary embolism. Surgical repair of an aortocaval fistula is now standardised--repair of the fistula from within the aneurysm (endoaneurysmorraphy followed by prosthetic graft replacement of the aneurysm. A case report of a 77-year-old woman, initially suspected to have unstable angina but subsequently diagnosed to have an aortocaval fistula and surgically treated successfully, is presented along with a review of literature.

  5. Molecular hydrogen reduces LPS-induced neuroinflammation and promotes recovery from sickness behaviour in mice.

    Directory of Open Access Journals (Sweden)

    Stefan Spulber

    Full Text Available Molecular hydrogen has been shown to have neuroprotective effects in mouse models of acute neurodegeneration. The effect was suggested to be mediated by its free-radical scavenger properties. However, it has been shown recently that molecular hydrogen alters gene expression and protein phosphorylation. The aim of this study was to test whether chronic ad libitum consumption of molecular hydrogen-enriched electrochemically reduced water (H-ERW improves the outcome of lipopolysaccharide (LPS-induced neuroinflammation. Seven days after the initiation of H-ERW treatment, C57Bl/6 mice received a single injection of LPS (0.33 mg/kg i.p. or an equivalent volume of vehicle. The LPS-induced sickness behaviour was assessed 2 h after the injection, and recovery was assessed by monitoring the spontaneous locomotor activity in the homecage for 72 h after the administration of LPS. The mice were killed in the acute or recovery phase, and the expression of pro- and antiinflammatory cytokines in the hippocampus was assessed by real-time PCR. We found that molecular hydrogen reduces the LPS-induced sickness behaviour and promotes recovery. These effects are associated with a shift towards anti-inflammatory gene expression profile at baseline (downregulation of TNF- α and upregulation of IL-10. In addition, molecular hydrogen increases the amplitude, but shortens the duration and promotes the extinction of neuroinflammation. Consistently, molecular hydrogen modulates the activation and gene expression in a similar fashion in immortalized murine microglia (BV-2 cell line, suggesting that the effects observed in vivo may involve the modulation of microglial activation. Taken together, our data point to the regulation of cytokine expression being an additional critical mechanism underlying the beneficial effects of molecular hydrogen.

  6. Facilitation of extinction and re-extinction of operant behavior in mice by chlordiazepoxide and D-cycloserine.

    Science.gov (United States)

    Leslie, Julian C; Norwood, Kelly

    2013-05-01

    The aim was to compare operant extinction with re-extinction following re-acquisition and to investigate neuropharmacological mechanisms through administration of drugs potentiating GABAergic or glutamatergic systems. Groups of C57Bl/6 mice were trained to lever press for food on a fixed ratio schedule, then extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine administration (15mg/kg in each case), then retrained to lever press for food, then re-extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine. Under vehicle injections, extinction and re-extinction curves were indistinguishable, but drug treatments showed that there was less resistance to extinction in the re-extinction phase. Chlordiazepoxide facilitated extinction and re-extinction, with an earlier effect during re-extinction. d-Cycloserine also facilitated extinction and re-extinction, with some evidence of an earlier effect during re-extinction. These results replicate and extend earlier findings with operant extinction, but differ from some previous reports of d-cycloserine on re-extinction of Pavlovian conditioned fear. Implications for accounts of the similarities and differences between neural mechanisms of extinction following either Pavlovian or operant conditioning, and applications of these findings, are discussed.

  7. Quantitative analysis of forest fire extinction efficiency

    Directory of Open Access Journals (Sweden)

    Miguel E. Castillo-Soto

    2015-08-01

    Full Text Available Aim of study: Evaluate the economic extinction efficiency of forest fires, based on the study of fire combat undertaken by aerial and terrestrial means. Area of study, materials and methods: Approximately 112,000 hectares in Chile. Records of 5,876 forest fires that occurred between 1998 and 2009 were analyzed. The area further provides a validation sector for results, by incorporating databases for the years 2010 and 2012. The criteria used for measuring extinction efficiency were economic value of forestry resources, Contraction Factor analysis and definition of the extinction costs function. Main results: It is possible to establish a relationship between burnt area, extinction costs and economic losses. The method proposed may be used and adapted to other fire situations, requiring unit costs for aerial and terrestrial operations, economic value of the property to be protected and speed attributes of fire spread in free advance. Research highlights: The determination of extinction efficiency in containment works of forest fires and potential projection of losses, different types of plant fuel and local conditions favoring the spread of fire broaden the admissible ranges of a, φ and Ce considerably.

  8. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids.

    Science.gov (United States)

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-05-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders.

  9. Determining the extragalactic extinction law with SALT

    CERN Document Server

    Finkelman, Ido; Kniazev, Alexei Y; Buckley, David; O'Donoghue, Darragh; Hashimoto, Yas; Loaring, Nicola; Romero, Encarni; Still, Martin; Vaisanen, Petri

    2008-01-01

    We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11mu m^{-1} < lambda^{-1} < 2.94 mu m^{-1} by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic enviroment are similar to those of the Milky Way. The ratio of the total V band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82+-0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust.

  10. Disease and the dynamics of extinction.

    Science.gov (United States)

    McCallum, Hamish

    2012-10-19

    Invading infectious diseases can, in theory, lead to the extinction of host populations, particularly if reservoir species are present or if disease transmission is frequency-dependent. The number of historic or prehistoric extinctions that can unequivocally be attributed to infectious disease is relatively small, but gathering firm evidence in retrospect is extremely difficult. Amphibian chytridiomycosis and Tasmanian devil facial tumour disease (DFTD) are two very different infectious diseases that are currently threatening to cause extinctions in Australia. These provide an unusual opportunity to investigate the processes of disease-induced extinction and possible management strategies. Both diseases are apparently recent in origin. Tasmanian DFTD is entirely host-specific but potentially able to cause extinction because transmission depends weakly, if at all, on host density. Amphibian chytridiomycosis has a broad host range but is highly pathogenic only to some populations of some species. At present, both diseases can only be managed by attempting to isolate individuals or populations from disease. Management options to accelerate the process of evolution of host resistance or tolerance are being investigated in both cases. Anthropogenic changes including movement of diseases and hosts, habitat destruction and fragmentation and climate change are likely to increase emerging disease threats to biodiversity and it is critical to further develop strategies to manage these threats.

  11. Mass Extinctions and Biosphere-Geosphere Stability

    Science.gov (United States)

    Rothman, Daniel; Bowring, Samuel

    2015-04-01

    Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with significant environmental change recorded in the carbon-isotopic composition of sedimentary rocks. There are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? Two factors appear important: the size of the environmental perturbation, and the time scale over which it occurs. We show that the natural perturbations of Earth's carbon cycle during the past 500 million years exhibit a characteristic rate of change over two orders of magnitude in time scale. This characteristic rate is consistent with the maximum rate that limits quasistatic (i.e., near steady-state) evolution of the carbon cycle. We identify this rate with marginal stability, and show that mass extinctions occur on the fast, unstable side of the stability boundary. These results suggest that the great extinction events of the geologic past, and potentially a "sixth extinction" associated with modern environmental change, are characterized by common mechanisms of instability.

  12. The transition from memory retrieval to extinction

    Directory of Open Access Journals (Sweden)

    Cammarota Martín

    2004-01-01

    Full Text Available Memory is measured by measuring retrieval. Retrieval is often triggered by the conditioned stimulus (CS; however, as known since Pavlov, presentation of the CS alone generates extinction. One-trial avoidance (IA is a much used conditioned fear paradigm in which the CS is the safe part of a training apparatus, the unconditioned stimulus (US is a footshock and the conditioned response is to stay in the safe area. In IA, retrieval is measured without the US, as latency to step-down from the safe area (i.e., a platform. Extinction is installed at the moment of the first unreinforced test session, as clearly shown by the fact that many drugs, including PKA, ERK and protein synthesis inhibitors as well as NMDA receptor antagonists, hinder extinction when infused into the hippocampus or the basolateral amygdala at the moment of the first test session but not later. Some, but not all the molecular systems required for extinction are also activated by retrieval, further endorsing the hypothesis that although retrieval is behaviorally and biochemically necessary for the generation of extinction, this last process constitutes a new learning secondary to the unreinforced expression of the original trace.

  13. Spontaneous fracture of the mandibular genial tubercles. A case report.

    Science.gov (United States)

    Gallego, Lorena; Junquera, Luis; Villarreal, Pedro; de Vicente, Juan Carlos

    2007-12-01

    Fracture of the mandibular genial tubercles is an uncommon pathology affecting edentulous patients with severe maxillary atrophy. Usually occurs spontaneously which complicates the diagnosis. Their importance lies in the functional alterations, which occur as a consequence of the disinsertion of the genihyoid and genioglossus muscles. The treatment of fracture of the genial tubercles is controversial, including no surgical intervention, excision of the avulsed bone fragments, and muscular repositioning. There have been only 11 cases reported in the literature of this fracture, most of them spontaneous. We present a difficult diagnosis situation of spontaneous fracture of the genial tubercles in an 86-year-old edentulous female with a painful sublingual and submental hematoma and anterior cervical echimosis. Computerized Tomography should be made to confirm the diagnosis. Surgical treatment was not necessary, and follow-up at 6 months revealed complete symptomatic recovery, and full return of function.

  14. Body size reductions in nonmammalian eutheriodont therapsids (Synapsida during the end-Permian mass extinction.

    Directory of Open Access Journals (Sweden)

    Adam K Huttenlocker

    Full Text Available The extent to which mass extinctions influence body size evolution in major tetrapod clades is inadequately understood. For example, the 'Lilliput effect,' a common feature of mass extinctions, describes a temporary decrease in body sizes of survivor taxa in post-extinction faunas. However, its signature on existing patterns of body size evolution in tetrapods and the persistence of its impacts during post-extinction recoveries are virtually unknown, and rarely compared in both geologic and phylogenetic contexts. Here, I evaluate temporal and phylogenetic distributions of body size in Permo-Triassic therocephalian and cynodont therapsids (eutheriodonts using a museum collections-based approach and time series model fitting on a regional stratigraphic sequence from the Karoo Basin, South Africa. I further employed rank order correlation tests on global age and clade rank data from an expanded phylogenetic dataset, and performed evolutionary model testing using Brownian (passive diffusion models. Results support significant size reductions in the immediate aftermath of the end-Permian mass extinction (ca. 252.3 Ma consistent with some definitions of Lilliput effects. However, this temporal succession reflects a pattern that was underscored largely by Brownian processes and constructive selectivity. Results also support two recent contentions about body size evolution and mass extinctions: 1 active, directional evolution in size traits is rare over macroevolutionary time scales and 2 geologically brief size reductions may be accomplished by the ecological removal of large-bodied species without rapid originations of new small-bodied clades or shifts from long-term evolutionary patterns.

  15. Species recovery in the United States: Increasing the effectiveness of the Endangered Species Act

    Science.gov (United States)

    Daniel M. Evans; Judy P. Che-Castaldo; Deborah Crouse; Frank W. Davis; Rebecca Epanchin-Niell; Curtis H. Flather; R. Kipp Frohlich; Dale D. Goble; Ya-Wei Li; Timothy D. Male; Lawrence L. Master; Matthew P. Moskwik; Maile C. Neel; Barry R. Noon; Camille Parmesan; Mark W. Schwartz; J. Michael Scott; Byron K. Williams

    2016-01-01

    The Endangered Species Act (ESA) has succeeded in shielding hundreds of species from extinction and improving species recovery over time. However, recovery for most species officially protected by the ESA - i.e., listed species - has been harder to achieve than initially envisioned. Threats to species are persistent and pervasive, funding has been insufficient...

  16. Screening for spontaneous preterm birth

    NARCIS (Netherlands)

    van Os, M.A.; van Dam, A.J.E.M.

    2015-01-01

    Preterm birth is the most important cause of perinatal morbidity and mortality worldwide. In this thesis studies on spontaneous preterm birth are presented. The main objective was to investigate the predictive capacity of mid-trimester cervical length measurement for spontaneous preterm birth in a l

  17. Pregnancy outcome following spontaneous abortions

    Directory of Open Access Journals (Sweden)

    Swati Agrawal

    2015-12-01

    Conclusions: Previous history of spontaneous abortion is associated with adverse pregnancy outcome. There is increased risk of abortion, preterm delivery, need for caesarean sections and fetal loss in cases of previous spontaneous abortions. These complications and fetal loss can be reduced by booking the patients and giving due antenatal care. [Int J Reprod Contracept Obstet Gynecol 2015; 4(6.000: 1891-1893

  18. Screening for spontaneous preterm birth

    NARCIS (Netherlands)

    van Os, M.A.; van Dam, A.J.E.M.

    2015-01-01

    Preterm birth is the most important cause of perinatal morbidity and mortality worldwide. In this thesis studies on spontaneous preterm birth are presented. The main objective was to investigate the predictive capacity of mid-trimester cervical length measurement for spontaneous preterm birth in a

  19. Spontaneous pneumomediastinum and Ecstasy abuse.

    OpenAIRE

    Pittman, J A; Pounsford, J C

    1997-01-01

    Ecstasy is an illegal recreationally used drug. A case of a young woman who had taken this drug and was found to have a spontaneous pneumomediastinum is reported. The association of spontaneous pneumomediastinum with drug abuse is discussed. The possible mechanism for this complication of Ecstasy, which has not been previously reported, is discussed.

  20. Astrophysical life extinctions what killed the dinosaurs?

    CERN Document Server

    Dar, Arnon

    1999-01-01

    Geological records indicate that the exponential diversification of marine and continental life on Earth in the past 500 My was interrupted by many life extinctions. They also indicate that the major mass extinctions were correlated in time with large meteoritic impacts, gigantic volcanic eruptions, sea regressions and drastic changes in global climate. Some of these catastrophes coincided in time. The astrophysical life extinction mechanisms which were proposed so far, in particular, meteoritic impacts, nearby supernova explosions, passage through molecular or dark matter clouds, and Galactic gamma/cosmic ray bursts cannot explain the time coincidences between these catastrophes. However, recent observations suggest that many planetary-mass objects may be present in the outer solar system between the Kuiper belt and the Oort cloud. Gravitational perturbations may occasionally bring them into the inner solar system. Their passage near Earth could have generated gigantic tidal waves, large volcanic eruptions, ...

  1. Life extinctions by neutron star mergers

    CERN Document Server

    Dar, Arnon; Shaviv, N J; Dar, Arnon; Laor, Ari; Shaviv, Nir J.

    1997-01-01

    High energy cosmic ray jets from nearby mergers or accretion induced collapse (AIC) of neutron stars (NS) that hit the atmosphere can produce lethal fluxes of atmospheric muons at ground level, underground and underwater, destroy the ozone layer and radioactivate the environment. They could have caused most of the massive life extinctions on planet Earth in the past 600 My. Biological mutations due to ionizing radiations could have caused the fast appearance of new species after the massive extinctions. An early warning of future extinctions due to NS mergers may be obtained by identifying, mapping and timing all the nearby binary neutron stars systems. A warning of an approaching cosmic ray burst from a nearby NS merger/AIC may be provided by a very intense gamma ray burst which preceeds it.

  2. Mammal extinctions, body size, and paleotemperature

    Science.gov (United States)

    Bown, T.M.; Holroyd, P.A.; Rose, K.D.

    1994-01-01

    There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

  3. Does supplementary reinforcement of stereotypy facilitate extinction?

    Science.gov (United States)

    Dozier, Claudia L; Iwata, Brian A; Wilson, David M; Thomason-Sassi, Jessica L; Roscoe, Eileen M

    2013-01-01

    Results of several studies suggest that delivery of supplemental (social) reinforcement for stereotypy might facilitate its subsequent extinction. We examined this possibility with 9 subjects who engaged in stereotypy by including methodological refinements to ensure that (a) subjects' stereotypy was maintained in the absence of social consequences, (b) supplementary reinforcers were highly preferred and were shown to be reinforcers for some behavior, and (c) subjects were exposed to lengthy reinforcement and extinction conditions. In spite of these modifications, only 4 subjects' stereotypy increased when supplementary reinforcement was delivered contingent on stereotypy, and no subject's stereotypy decreased below initial baseline levels when social reinforcement was subsequently withheld. Decreases in stereotypy occurred with the implementation of noncontingent reinforcement. Thus, delivery of supplementary reinforcers either did not increase stereotypy or did not facilitate extinction of stereotypy maintained by automatic reinforcement. We discuss the practical and conceptual bases of these results with respect to our current understanding of function-based interventions.

  4. Opportunities and costs for preventing vertebrate extinctions

    DEFF Research Database (Denmark)

    Conde, Dalia Amor; Colchero, Fernando; Güneralp, Burak

    2015-01-01

    -oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 ‘trigger’ sites [3] . These are arguably the most irreplaceable category of important...... causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2] , a consortium of conservation...... biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1] . Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species...

  5. Extinction in four species cyclic competition

    Science.gov (United States)

    Intoy, Ben; Pleimling, Michel

    2013-08-01

    When four species compete stochastically in a cyclic way, the formation of two teams of mutually neutral partners is observed. In this paper we study through numerical simulations the extinction processes that can take place in this system both in the well mixed case as well as on different types of lattices. The different routes to extinction are revealed by the probability distribution of the domination time, i.e. the time needed for one team to fully occupy the system. If swapping is allowed between neutral partners, then the probability distribution is dominated by very long-lived states where a few very large domains persist, each domain being occupied by a mix of individuals from species that form one of the teams. Many aspects of the possible extinction scenarios are lost when only considering averaged quantities, such as for example the mean domination time.

  6. Opportunities and costs for preventing vertebrate extinctions

    DEFF Research Database (Denmark)

    Conde, Dalia Amor; Colchero, Fernando; Güneralp, Burak

    2015-01-01

    -oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 ‘trigger’ sites [3] . These are arguably the most irreplaceable category of important...... causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2] , a consortium of conservation...... biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1] . Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species...

  7. The Dynamic Response of Marine Life to Extreme Temperature and Low Oxygen Events Following the End-Permian Mass Extinction.

    Science.gov (United States)

    Pietsch, C.; Bottjer, D. J.

    2014-12-01

    The end-Permian mass extinction was the most devastating taxonomic and ecological crisis in the history of life on Earth. The recovery lasted 5 My making it the longest in geologic history, although the cause of the delay is still heavily debated. We find that additional environmental changes during the recovery interval reset the attempts that marine communities made toward ecological complexity, resulting in the overall appearance of a stagnant recovery. The extinction mechanisms during the end-Permian include extreme temperature change and low oxygen environments resulting from the volcanic emission of carbon dioxide and other toxic gasses to the atmosphere. The biotic response to ancient environmental change is a direct analog for the ecological impacts of modern anthropogenic climate change. We applied an ecological recovery rubric to benthic, sea floor dwelling, communities throughout the Early Triassic recovery in two major ocean basins. Newly collected bulk fossil data from the Moenkopi and Thaynes Formations from the Southwest US and the Werfen Formation in Italy were analyzed along with literature data. In Italy, directly following the extinction, low oxygen environments prevented an ecological rebound. Once low oxygen conditions receded, 600 kyr after the extinction, taxonomic diversity, fossil body size, and trace fossil complexity rebounded. A little more than 1 My into the Early Triassic, an extreme temperature event resulted in a reset of community complexity in both Italy and the Southwest US. The body size of gastropods and the repopulation of echinoderms were significantly inhibited as was trace fossil complexity. Low oxygen conditions that developed in the last ~2My of the Early Triassic limited diversity and body size in the Southwest United States. The stagnant recovery is re-interpreted as dynamic resets and rapid rebounds driven by environmental perturbations throughout the Early Triassic.

  8. Abrupt climate change and extinction events

    Science.gov (United States)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  9. Extinction Mapping of Nearby Galaxies Using LEGUS

    Science.gov (United States)

    Kahre, Lauren; Walterbos, Rene A. M.; Calzetti, Daniela; Sabbi, Elena; Ubeda, Leonardo; LEGUS Collaboration

    2017-01-01

    Extinction by dust affects studies of star formation and stellar evolution in galaxies. There are different ways to measure the distribution of dust column densities across galaxies. Here we present work based on extinctions measured towards individual massive stars.Isochrones of massive stars lie in the same location on a color-color diagram with little dependence on metallicity and luminosity class, so the extinction can be directly derived from the observed photometry. We develop a method for generating extinction maps using photometry of massive stars from the Hubble Space Telescope for the nearly 50 galaxies observed by the Legacy Extragalactic Ultraviolet Survey (LEGUS). The derived extinction maps will allow us to correct ground-based and HST Halpha maps for extinction, and will be used to constrain changes in the dust-to-gas ratio across the galaxy sample and in different star formation, metallicity and morphological environments. Previous studies have found links between galaxy metallicity and the dust-to-gas mass ratio. Dust abundance and gas metallicity are critical constraints for chemical and galaxy evolution models. We present a study of LEGUS galaxies spanning a range of distances, metallicities, and galaxy morphologies, including metal-poor dwarfs Holmberg I and II and giant spirals NGC 6503 and NGC 628. We see clear evidence for changes in the dust-to-gas mass ratio with changing metallicity. We also examine changes in the dust-to-gas mass ratio with galactocentric radius. Ultimately, we will provide constraints on the dust-to-gas mass ratio across a wide range of galaxy environments.

  10. Extinction rate fragility in population dynamics.

    Science.gov (United States)

    Khasin, M; Dykman, M I

    2009-08-01

    Population extinction is of central interest for population dynamics. It may occur from a large rare fluctuation. We find that, in contrast to related large-fluctuation effects like noise-induced interstate switching, quite generally extinction rates in multipopulation systems display fragility, where the height of the effective barrier to be overcome in the fluctuation depends on the system parameters nonanalytically. We show that one of the best-known models of epidemiology, the susceptible-infectious-susceptible model, is fragile to total population fluctuations.

  11. Collapse and recovery of marine fishes.

    Science.gov (United States)

    Hutchings, J A

    2000-08-24

    Overexploitation and subsequent collapse of marine fishes has focused attention on the ability of affected populations to recover to former abundance levels and on the degree to which their persistence is threatened by extinction. Although potential for recovery has been assessed indirectly, actual changes in population size following long-term declines have not been examined empirically. Here I show that there is very little evidence for rapid recovery from prolonged declines, in contrast to the perception that marine fishes are highly resilient to large population reductions. With the possible exception of herring and related species that mature early in life and are fished with highly selective equipment, my analysis of 90 stocks reveals that many gadids (for example, cod, haddock) and other non-clupeids (for example, flatfishes) have experienced little, if any, recovery as much as 15 years after 45-99% reductions in reproductive biomass. Although the effects of overfishing on single species may generally be reversible, the actual time required for recovery appears to be considerable. To exempt marine fishes from existing criteria used to assign extinction risk would be inconsistent with precautionary approaches to fisheries management and the conservation of marine biodiversity.

  12. Extinction space--a method for the quantification and classification of changes in morphospace across extinction boundaries.

    Science.gov (United States)

    Korn, Dieter; Hopkins, Melanie J; Walton, Sonny A

    2013-10-01

    Three main modes of extinction are responsible for reductions in morphological disparity: (1) random (caused by a nonselective extinction event); (2) marginal (a symmetric, selective extinction event trimming the margin of morphospace); and (3) lateral (an asymmetric, selective extinction event eliminating one side of the morphospace). These three types of extinction event can be distinguished from one another by comparing changes in three measures of morphospace occupation: (1) the sum of range along the main axes; (2) the sum of variance; and (3) the position of the centroid. Computer simulations of various extinction events demonstrate that the pre-extinction distribution of taxa (random or normal) in the morphospace has little influence on the quantification of disparity changes, whereas the modes of the extinction events play the major role. Together, the three disparity metrics define an "extinction-space" in which different extinction events can be directly compared with one another. Application of this method to selected extinction events (Frasnian-Famennian, Devonian-Carboniferous, and Permian-Triassic) of the Ammonoidea demonstrate the similarity of the Devonian events (selective extinctions) but the striking difference from the end-Permian event (nonselective extinction). These events differ in their mode of extinction despite decreases in taxonomic diversity of similar magnitude.

  13. Periaqueductal gray c-Fos expression varies relative to the method of conditioned taste aversion extinction employed.

    Science.gov (United States)

    Mickley, G Andrew; Wilson, Gina N; Remus, Jennifer L; Ramos, Linnet; Ketchesin, Kyle D; Biesan, Orion R; Luchsinger, Joseph R; Prodan, Suzanna

    2011-11-14

    A conditioned taste aversion (CTA) is acquired when an animal consumes a novel taste (CS) and then experiences the symptoms of poisoning (US). Following CTA training, animals will avoid the taste that was previously associated with malaise. This defensive reaction to a learned fear can be extinguished by repeated exposure to the CS alone (CS-only; CSO-EXT). However, following a latency period in which the CS is not presented, the CTA will spontaneously recover (SR). Through the use of an explicitly unpaired extinction procedure (EU-EXT) we have shown that we can speed up extinction and attenuate SR of the CTA. Here we compared and contrasted the ability of CSO and EU extinction procedures to affect c-Fos expression in the periaqueductal gray (PAG). Fluid-deprived Sprague-Dawley rats acquired a strong CTA [via 3 pairings of 0.3% oral saccharin (SAC; the CS) and 81mg/kg i.p. lithium chloride (LiCl; the US)] followed by extinction trials consisting of multiple exposures to either, (a) the CS every-other day (CSO-EXT), or (b) CS and US on alternate days (EU-EXT). A different group of rats did not receive multiple CS exposures and served as a "no extinction" (NE) control. Both extinction procedures resulted in ≥90% reacceptance of SAC (achieving asymptotic extinction). Some of the animals were sacrificed for c-Fos immunohistochemical analysis following asymptotic extinction. Other rats entered a 30-day latency period where they drank water only. These remaining animals were then tested for SR with a final exposure to SAC before being sacrificed for c-Fos immunohistochemistry. As reported previously, rats in the CS-only group exhibited a significant SR of the CTA. However, animals in the EU extinction group reached asymptotic extinction more rapidly than did CSO rats and they did not show SR of the CTA. As compared to rats that retained their CTA, both groups of extinguished rats showed suppression in the number of c-Fos-labeled neurons in all 4 longitudinal columns of

  14. D-cycloserine effects on extinction of conditioned responses to drug-related cues.

    Science.gov (United States)

    Myers, Karyn M; Carlezon, William A

    2012-06-01

    D-cycloserine (DCS) is an N-methyl-D-aspartate (NMDA) receptor partial agonist that facilitates extinction of conditioned fear in animals and cue exposure therapy (CET) for fear and anxiety disorders in people. Recent preclinical and clinical studies have examined the effect of DCS on extinction of conditioned responses elicited by cues paired with administration of or withdrawal from drugs of abuse, including physiological responses, craving, withdrawal, and drug-seeking behavior. DCS facilitates extinction and blunts postextinction recovery of these responses in animal models, including place conditioning and drug self-administration, but DCS effects on CET in substance users/abusers are less robust. Some of the null effects in the clinical literature might be attributable to issues related to sample size, data characteristics, DCS administration, and participant characteristics, among others. In this review we describe the preclinical and clinical literatures on DCS modulation of extinction of addiction-related conditioned responses, consider possible limitations of the clinical studies that have been published to date, and propose ways of designing future clinical studies so as to maximize the probability of detecting a DCS effect. We also discuss concerns with regard to potential harmful effects of DCS-coupled CET in addicts and describe how these concerns might be mitigated. We conclude that it is as yet unclear whether DCS-coupled CET might be a useful approach in the treatment of addiction.

  15. Spontaneous subgaleal aerocele.

    Science.gov (United States)

    Ibe, M O N; Onu, D O; Igwe, N N

    2014-01-01

    Apart from reporting about a case of spontaneous subgaleal aerocele this paper looks at the possible causes and management also. A 35-year-old Igbo-Nigerian female, about 4 weeks post-natal, with a 10-month old steadily and gradually enlarging mass around the back of her head, including both temporal regions was referred to us. Plain skull radiographs showed air in this mass. Needle puncture produced air leading to immediate and complete flattening of the lesion. A few hours after this procedure while still in the hospital premises, she had generalized convulsions, for which she was hospitalized and treated. With no further attacks, her request for discharge the following day was granted. At the next visit, 7 days later, there was a re-accumulation, which was treated the same way as previously and with the same result. She has not reported back since then, though she was advised to visit us again in 7 day-time. This lesion should be considered when masses on the head are presented. Our health institutions should have adequate investigative facilities.

  16. Spontaneous bacterial peritonitis

    Institute of Scientific and Technical Information of China (English)

    Anastasios Koulaouzidis; Shivaram Bhat; Athar A Saeed

    2009-01-01

    Since its initial description in 1964, research has transformed spontaneous bacterial peritonitis (SBP) from a feared disease (with reported mortality of 90%) to a treatable complication of decompensated cirrhosis,albeit with steady prevalence and a high recurrence rate. Bacterial translocation, the key mechanism in the pathogenesis of SBP, is only possible because of the concurrent failure of defensive mechanisms in cirrhosis.Variants of SBP should be treated. Leucocyte esterase reagent strips have managed to shorten the 'tap-toshot' time, while future studies should look into their combined use with ascitic fluid pH. Third generation cephalosporins are the antibiotic of choice because they have a number of advantages. Renal dysfunction has been shown to be an independent predictor of mortality in patients with SBP. Albumin is felt to reduce the risk of renal impairment by improving effective intravascular volume, and by helping to bind proinflammatory molecules. Following a single episode of SBP, patients should have long-term antibiotic prophylaxis and be considered for liver transplantation.

  17. Severest crisis overlooked-Worst disruption of terrestrial environments postdates the Permian-Triassic mass extinction.

    Science.gov (United States)

    Hochuli, Peter A; Sanson-Barrera, Anna; Schneebeli-Hermann, Elke; Bucher, Hugo

    2016-06-24

    Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian-Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian-Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ(13)Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian-Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.

  18. Severest crisis overlooked—Worst disruption of terrestrial environments postdates the Permian–Triassic mass extinction

    Science.gov (United States)

    Hochuli, Peter A.; Sanson-Barrera, Anna; Schneebeli-Hermann, Elke; Bucher, Hugo

    2016-06-01

    Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian–Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian–Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ13Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian–Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.

  19. Temporal dynamics of relief in avoidance conditioning and fear extinction: Experimental validation and clinical relevance.

    Science.gov (United States)

    Vervliet, Bram; Lange, Iris; Milad, Mohammed R

    2017-09-01

    The learning principles that guide the acquisition and extinction of avoidance are not fully understood. We developed a novel paradigm to study the temporal dynamics of relief, a putative reinforcer of avoidance, and the recovery of fear and avoidance following extinction. During conditioning, the avoidance action canceled the aversive unconditional stimulus (US), without terminating the predictive conditional stimulus (CS). Relief pleasantness was rated after fixed CS offsets, when US omission occured. Avoidance was effective to one CS, but not to another, to track stimulus-specific avoidance learning. Fear was extinguished under response prevention in a separate context. Recovery tests took place 24 h later, in both contexts and with a monetary cost added to the avoidance action. We found that avoidance gradually became stimulus-specific during conditioning, but hardly recovered during delayed testing. Across all phases, initial omissions of the aversive US triggered relief that gradually declined over consecutive omissions, in line with a theoretical prediction error signal. Participants that scored low on distress tolerance, however, displayed sustained levels of relief over continuous omissions. We propose that such forms of sustained relief may produce over-reinforcement of foregoing avoidance actions and promote the development of pathological avoidance. The current paradigm represents an efficacious tool to study the temporal dynamics of relief across avoidance learning and fear extinction and to characterize relief dysregulations in relation to psychopathology. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Optical atmospheric extinction over Cerro Paranal

    NARCIS (Netherlands)

    Patat, F.; Moehler, S.; O'Brien, K.; Pompei, E.; Bensby, T.; Carraro, G.; de Ugarte Postigo, A.; Fox, A.; Gavignaud, I.; James, G.; Korhonen, H.; Ledoux, C.; Randall, S.; Sana, H.A.A.; Smoker, J.; Stefl, S.; Szeifert, T.

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass-1.

  1. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the ex

  2. Molar extinction coefficients of some fatty acids

    DEFF Research Database (Denmark)

    Sandhu, G.K.; Singh, K.; Lark, B.S.;

    2002-01-01

    ) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement...

  3. Methylphenidate Enhances Extinction of Contextual Fear

    Science.gov (United States)

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show…

  4. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the

  5. Mass extinctions caused by large bolide impacts

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, L.W.

    1987-07-01

    Evidence indicates that the collision of Earth and a large piece of Solar System derbris such as a meteoroid, asteroid or comet caused the great extinctions of 65 million years ago, leading to the transition from the age of the dinosaurs to the age of the mammals.

  6. Self-extinction through optimizing selection

    Science.gov (United States)

    Parvinen, Kalle; Dieckmann, Ulf

    2013-01-01

    Evolutionary suicide is a process in which selection drives a viable population to extinction. So far, such selection-driven self-extinction has been demonstrated in models with frequency-dependent selection. This is not surprising, since frequency-dependent selection can disconnect individual-level and population-level interests through environmental feedback. Hence it can lead to situations akin to the tragedy of the commons, with adaptations that serve the selfish interests of individuals ultimately ruining a population. For frequency-dependent selection to play such a role, it must not be optimizing. Together, all published studies of evolutionary suicide have created the impression that evolutionary suicide is not possible with optimizing selection. Here we disprove this misconception by presenting and analyzing an example in which optimizing selection causes self-extinction. We then take this line of argument one step further by showing, in a further example, that selection-driven self-extinction can occur even under frequency-independent selection. PMID:23583808

  7. Subwoofer and nanotube butterfly acoustic flame extinction

    Science.gov (United States)

    Aliev, Ali E.; Mayo, Nathanael K.; Baughman, Ray H.; Mills, Brent T.; Habtour, Ed

    2017-07-01

    Nonchemical flame control using acoustic waves from a subwoofer and a lightweight carbon nanotube thermoacoustic projector was demonstrated. The intent was to manipulate flame intensity, direction and propagation. The mechanisms of flame suppression using low frequency acoustic waves were discussed. Laminar flame control and extinction were achieved using a thermoacoustic ‘butterfly’ projector based on freestanding carbon nanotube sheets.

  8. Acupuncture Treatment for Spontaneous Polyhidrosis

    Institute of Scientific and Technical Information of China (English)

    WANG wei-zhi; ZHAO Liang

    2008-01-01

    objective;To compare the therapeutic effects of acupuncture and western medicine on spontaneous polyhidrosis.Methods;Acupuncture at Huatuojiaji points was used to treat 30 cases of spontaneous polyhidrosis and the western medicine was used treat 26 cases for comparison.Results;The total effective rate of the fomler was 96.7%and that of the latter 57.7%.The difference in therapeutic effect between the two groups was significant(P<0.01).Conclusion;The thempeutic effect of acupuncture at Huatuojiaji points on spontaneous polyhidrosis was better than that of western medicine.

  9. Spontaneous Baryogenesis without Baryon Isocurvature

    CERN Document Server

    De Simone, Andrea

    2016-01-01

    We propose a new class of spontaneous baryogenesis models that does not produce baryon isocurvature perturbations. The baryon chemical potential in these models is independent of the field value of the baryon-generating scalar, hence the scalar field fluctuations are blocked from propagating into the baryon isocurvature. We demonstrate this mechanism in simple examples where spontaneous baryogenesis is driven by a non-canonical scalar field. The suppression of the baryon isocurvature allows spontaneous baryogenesis to be compatible even with high-scale inflation.

  10. Modeling the Infrared Extinction toward the Galactic Center

    CERN Document Server

    Gao, Jian; Jiang, B W

    2013-01-01

    We model the ~1--19$\\mum$ infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be Av~38--42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep ~1--3$\\mum$ near-IR extinction and the flat ~3--8$\\mum$ mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small Rv and steep near-IR extinction), and dust in dense regions (characterized by large Rv and flat UV extinction).

  11. Preservation of Natural Diversity: The Problem of Extinction Prone Species

    Science.gov (United States)

    Terborgh, John

    1974-01-01

    Examines threatened extinction of birds and recommends agencies adopt policies which minimize the pace of extinctions through the setting aside of large preserves which protect natural vegetation formation and the animal life. (BR)

  12. A REMARK ON EXTINCTION OF A CLASS OF SUPERPROCESSES

    Institute of Scientific and Technical Information of China (English)

    ZHAOXUELEI

    1996-01-01

    The extinction of a class of superprocesses associated with general branching characteristics and underlying Markov processes is investigted, The extinction is closely associated with the branching characteristics and the recurrence and transience of underlying processes.

  13. Inferring modern extinction risk from fossil occupancy trajectories

    Science.gov (United States)

    Kiessling, Wolfgang; Kocsis, Adam

    2016-04-01

    Besides providing information on ancient mass extinctions and intrinsic extinction risk, the fossil record may also provide useful data for assessing the extinction risk of extant species. Here we analyse the palaeontological trajectories of geographical occupancy in extant marine species to identify species that have been declining over geological time scales and may thus be more prone to extinction than expanding species. The slopes of these occupancy trajectories are used to categorize evolutionary extinction risk. Mapping the risk at global scale we find that low to mid latitude regions are at significantly higher risk than high latitude regions. We also find a moderate correspondence between high extinction risk on geological time scales and modern extinction risk for reef corals and propose to add fossil data to the assessment of current extinction risk, especially for the notoriously data deficient marine taxa.

  14. Trends in extinction risk for imperiled species in Canada.

    Directory of Open Access Journals (Sweden)

    Brett Favaro

    Full Text Available Protecting and promoting recovery of species at risk of extinction is a critical component of biodiversity conservation. In Canada, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC determines whether species are at risk of extinction or extirpation, and has conducted these assessments since 1977. We examined trends in COSEWIC assessments to identify whether at-risk species that have been assessed more than once tended to improve, remain constant, or deteriorate in status, as a way of assessing the effectiveness of biodiversity conservation in Canada. Of 369 species that met our criteria for examination, 115 deteriorated, 202 remained unchanged, and 52 improved in status. Only 20 species (5.4% improved to the point where they were 'not at risk', and five of those were due to increased sampling efforts rather than an increase in population size. Species outcomes were also dependent on the severity of their initial assessment; for example, 47% of species that were initially listed as special concern deteriorated between assessments. After receiving an at-risk assessment by COSEWIC, a species is considered for listing under the federal Species at Risk Act (SARA, which is the primary national tool that mandates protection for at-risk species. We examined whether SARA-listing was associated with improved COSEWIC assessment outcomes relative to unlisted species. Of 305 species that had multiple assessments and were SARA-listed, 221 were listed at a level that required identification and protection of critical habitat; however, critical habitat was fully identified for only 56 of these species. We suggest that the Canadian government should formally identify and protect critical habitat, as is required by existing legislation. In addition, our finding that at-risk species in Canada rarely recover leads us to recommend that every effort be made to actively prevent species from becoming at-risk in the first place.

  15. Endangered Species and Natural Resource Exploitation: Extinction vs. Coexistence

    OpenAIRE

    Tsur, Yacov; Zemel, Amos

    1994-01-01

    The threat on the survival of animal species due to intensive use of natural resources is incorporated within resource management models, paying special attention to uncertainty regarding the conditions that lead to extinction. The manner in which the potential benefits forgone due to the species extinction (denoted extinction penalty) induce more conservative exploitation policies is studied in detail. When the extinction penalty is ignored, the optimal policy is to drive the resource stock ...

  16. Grey Milky Way Extinction from SDSS Stellar Photometry

    OpenAIRE

    Gorbikov, Evgeny; Brosch, Noah

    2009-01-01

    We report results concerning the distribution and properties of galactic extinction at high galactic latitudes derived from stellar statistics using the Sloan Digital Sky Survey (SDSS). We use the classical Wolf diagram method to identify regions with extinction, and derive the extinction and the extinction law of the dust using all five SDSS spectral bands. We estimate the distance to the extinguishing medium using simple assumptions about the stellar populations in the line of sight. We rep...

  17. Spontaneous intraorbital hematoma: case report

    Directory of Open Access Journals (Sweden)

    Vinodan Paramanathan

    2010-12-01

    Full Text Available Vinodan Paramanathan, Ardalan ZolnourianQueen's Hospital NHS Foundation Trust, Burton on Trent, Staffordshire DE13 0RB, UKAbstract: Spontaneous intraorbital hematoma is an uncommon clinical entity seen in ophthalmology practice. It is poorly represented in the literature. Current evidence attributes it to orbital trauma, neoplasm, vascular malformations, acute sinusitis, and systemic abnormalities. A 65-year-old female presented with spontaneous intraorbital hematoma manifesting as severe ocular pains, eyelid edema, proptosis, and diplopia, without a history of trauma. Computer tomography demonstrated a fairly well defined extraconal lesion with opacification of the paranasal sinuses. The principal differential based on all findings was that of a spreading sinus infection and an extraconal tumor. An unprecedented finding of a spontaneous orbital hematoma was discovered when the patient was taken to theater. We discuss the rarity of this condition and its management.Keywords: hemorrhage, ophthalmology, spontaneous, intra-orbital, hematoma

  18. Spontaneous emphysema of the neck.

    Science.gov (United States)

    El-Ghazali, A M

    1983-04-01

    A case of spontaneous emphysema in the neck in a 17-year-old male was reported. Pathogenesis and management are discussed. Although it is a benign and self-limiting condition, it may carry a potential for serious complications.

  19. Extinction of chained instrumental behaviors: Effects of consumption extinction on procurement responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2016-03-01

    Operant behavior is typically organized into sequences of responses that eventually lead to a reinforcer. Response elements can be categorized as those that directly lead to reward consumption (i.e., a consumption response) and those that lead to the opportunity to make the consumption response (i.e., a procurement response). These responses often differ topographically and in terms of the discriminative stimuli that set the occasion for them. We have recently shown that extinction of the procurement response acts to weaken the specific associated consumption response, and that active inhibition of the procurement response is required for this effect. To expand the analysis of the associative structure of chains, in the present experiments we asked the reverse question: whether extinction of consumption behavior results in a decrease in the associated procurement response in a discriminated heterogeneous chain. In Experiment 1, extinction of consumption alone led to an attenuation of the associated procurement response only when rats were allowed to make the consumption response in extinction. Exposure to the consumption stimulus alone was not sufficient to produce weakened procurement responding. In Experiment 2, rats learned two distinct heterogeneous chains, and extinction of one consumption response specifically weakened the procurement response associated with it. The results add to the evidence suggesting that rats learn a highly specific associative structure in behavior chains, emphasizing the role of learning response inhibition in extinction.

  20. Inhibition of Estradiol Synthesis Impairs Fear Extinction in Male Rats

    Science.gov (United States)

    Graham, Bronwyn M.; Milad, Mohammed R.

    2014-01-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole,…

  1. Slower Reacquisition after Partial Extinction in Human Contingency Learning

    Science.gov (United States)

    Morís, Joaquín; Barberia, Itxaso; Vadillo, Miguel A.; Andrades, Ainhoa; López, Francisco J.

    2017-01-01

    Extinction is a very relevant learning phenomenon from a theoretical and applied point of view. One of its most relevant features is that relapse phenomena often take place once the extinction training has been completed. Accordingly, as extinction-based therapies constitute the most widespread empirically validated treatment of anxiety disorders,…

  2. Fibroblast Growth Factor-2 Alters the Nature of Extinction

    Science.gov (United States)

    Graham, Bronwyn M.; Richardson, Rick

    2011-01-01

    These experiments examined the effects of the NMDA-receptor (NMDAr) antagonist MK801 on reacquisition and re-extinction of a conditioned fear that had been previously extinguished before injection of fibroblast growth factor-2 (FGF2) or vehicle. Recent findings have shown that relearning and re-extinction, unlike initial learning and extinction,…

  3. Global distribution and drivers of language extinction risk

    DEFF Research Database (Denmark)

    Amano, Tatsuya; Sandel, Brody; Eager, Heidi;

    2014-01-01

    Many of the world's languages face serious risk of extinction. Efforts to prevent this cultural loss are severely constrained by a poor understanding of the geographical patterns and drivers of extinction risk. We quantify the global distribution of language extinction risk-represented by small...

  4. Estimating how many undescribed species have gone extinct.

    Science.gov (United States)

    Tedesco, P A; Bigorne, R; Bogan, A E; Giam, X; Jézéquel, C; Hugueny, B

    2014-10-01

    Because both descriptions of species and modern human-driven extinctions started around the same time (i.e., eighteenth century), a logical expectation is that a large proportion of species may have gone extinct without ever having been recorded. Despite this evident and widely recognized assumption, the loss of undescribed species has never been estimated. We quantified this loss for several taxonomic groups and regions for which undescribed species extinctions are likely to have occurred. Across a wide range of taxonomic groups, we applied known extinction rates computed from recorded species losses to assumed exponential decay in the proportion of species remaining undiscovered. Because all previous modeling attempts to project total species richness implicitly assumed that undescribed species extinctions could be neglected, we also evaluated the effect of neglecting them. Finally, because we assumed constant description and extinction probabilities, we applied our model to simulated data that did not conform to this assumption. Actual species losses were severely underestimated by considering only known species extinctions. According to our estimates, the proportion of undiscovered extinct species over all extinctions ranged from 0.15 to 0.59, depending on the taxonomic group and the region considered. This means that recent extinctions may be up to twice as large as the number recorded. When species differed in their extinction or description probabilities, our model underestimated extinctions of undescribed species by up to 20%. © 2014 Society for Conservation Biology.

  5. Spontaneous ischaemic stroke in dogs

    DEFF Research Database (Denmark)

    Gredal, Hanne Birgit; Skerritt, G. C.; Gideon, P.

    2013-01-01

    Translation of experimental stroke research into the clinical setting is often unsuccessful. Novel approaches are therefore desirable. As humans, pet dogs suffer from spontaneous ischaemic stroke and may hence offer new ways of studying genuine stroke injury mechanisms.......Translation of experimental stroke research into the clinical setting is often unsuccessful. Novel approaches are therefore desirable. As humans, pet dogs suffer from spontaneous ischaemic stroke and may hence offer new ways of studying genuine stroke injury mechanisms....

  6. Evaluating the temporal link between Siberian Traps magmatism and the end-Permian mass extinction (Invited)

    Science.gov (United States)

    Burgess, S. D.; Bowring, S. A.

    2013-12-01

    Interest in Large Igneous Provinces as agents for massive climatic and biological change is steadily increasing, though the temporal constraints on both are seldom precise enough to allow detailed testing of a causal relationship. The end-Permian mass extinction is one of the most biologically important and intensely studied events in Earth history and has been linked to many possible trigger mechanisms, from voluminous volcanism to bolide impact. Proposed kill mechanisms range from acidic and/or anoxic oceans to a cocktail of toxic gases, although the link between trigger and kill mechanisms is unconstrained due to the lack of a high-precision timeline. Critical to assessing the plausibility of different trigger and kill mechanisms is an accurate age model for the biotic crisis and the perturbations to the global carbon cycle and ocean chemistry. Recent work using the EARTHTIME U/Pb tracer solution has refined the timing of the onset and duration of the marine mass extinction event and the earliest Triassic recovery at the GSSP for the Permian-Triassic boundary in Meishan, China. This work constrains the mass extinction duration to less than 100 kyr and provides an accurate and precise time point for the onset of extinction, against which the timing of potential trigger mechanisms may be compared. For more than two decades, eruption and emplacement of the Siberian traps has been implicated as a potential trigger of the end-Permian extinction. In this scenario, magmatism drives the biotic crisis through mobilization of volatiles from the sedimentary rock with which intruding and erupting magmas interact. Massive volatile release is believed to trigger major changes in atmospheric chemistry and temperature, both of which have been proposed as kill mechanisms. Current temporal constrains on the timing and duration of the Siberian magmatism are an order of magnitude less precise than those for the mass extinction event and associated environmental perturbations

  7. Spontaneous contractions in elasmobranch vessels in vitro.

    Science.gov (United States)

    Olson, K R; Forster, M E; Bushnell, P G; Duff, D W

    2000-05-01

    Isolated vessels from four elasmobranchs, yellow stingray (Urolophus jamaicensis), clearnose skate (Raja eglanteria), ghost shark (Hydrolagus novaezelandiae), and spiny dogfish (Squalus acanthias), were examined for the presence of spontaneous contractions (SC). SC were observed in otherwise unstimulated dorsal aortas (DA) from stingray and ghost shark, but not in skate DA. Unstimulated ventral aortas (VA) did not exhibit SC. After treatment of VA with a contractile agonist, SC appeared in stingray and skate but not ghost shark or dogfish. SC in stingray VA were subsequently inhibited by either epinephrine (10(-5) M) or indomethacin (10(-4) M). Agonist contraction also elicited strong SC in ductus Cuvier from stingray, but not from ghost shark or dogfish. SC in dogfish hepatic portal veins (HPV) produced a rhythmical oscillation in tension. The frequency of HPV SC was highest (approximately 1 min(-1)) in intact veins and lower (approximately 3 min(-1)) in vein segments, indicative of a dominant pacemaker in the intact vessel. SC in HPV were depressed during the first 30 min of hypoxia, but there was substantial recovery over an additional 30 min of hypoxia and complete recovery upon return to normoxia. Addition of 80 mM KCl completely inhibited HPV SC and lowered resting tone. These results show that SC are a common feature of elasmobranch vessels and there appears to be a correlation between swimming behavior and the propensity for SC. KCl inhibition of SC and tonus in HPV is highly unusual for vascular smooth muscle.

  8. Mass Extinction in a Simple Mathematical Biological Model

    CERN Document Server

    Tokita, K; Tokita, Kei; Yasutomi, Ayumu

    1997-01-01

    Introducing the effect of extinction into the so-called replicator equations in mathematical biology, we construct a general model of ecosystems. The present model shows mass extinction by its own extinction dynamics when the system initially has a large number of species ( diversity). The extinction dynamics shows several significant features such as a power law in basin size distribution, induction time, etc. The present theory can be a mathematical foundation of the species-area effect in the paleontologic theory for mass extinction.

  9. Single-ended measurement of infrared extinction using lidar.

    Science.gov (United States)

    Murray, E R; Williams, M F; van der Laan, J E

    1978-01-15

    The goal of this study was to investigate the feasibility of single-ended measurement of the total extinction coefficient using an ir lidar system. Extinction was measured using a CO(2) laser radar system at four wavelengths near 10.3 microm. The measured results agree with theoretical estimates of extinction over a wide range. Single-ended measurements of extinction appear feasible to a horizontal range of 10 km using commercially available components. The system could potentially generate extinction data in a 3-D grid, enabling one to determine ir transmission between any two points in the field.

  10. The Relationship among Spontaneity, Impulsivity, and Creativity

    Science.gov (United States)

    Kipper, David A.; Green, Doreen J.; Prorak, Amanda

    2010-01-01

    The present study was designed to investigate two characteristics of spontaneity, its relationship to creativity and to impulsivity. We hypothesized a positive relationship between spontaneity and creativity, consistent with Moreno, 1953 "canon of spontaneity-creativity." We also predicted a negative relationship between spontaneity and…

  11. Taste-immunosuppression engram: reinforcement and extinction.

    Science.gov (United States)

    Niemi, Maj-Britt; Härting, Margarete; Kou, Wei; Del Rey, Adriana; Besedovsky, Hugo O; Schedlowski, Manfred; Pacheco-López, Gustavo

    2007-08-01

    Several Pavlovian conditioning paradigms have documented the brain's abilities to sense immune-derived signals or immune status, associate them with concurrently relevant extereoceptive stimuli, and reinstate such immune responses on demand. Specifically, the naturalistic relation of food ingestion with its possible immune consequences facilitates taste-immune associations. Here we demonstrate that the saccharin taste can be associated with the immunosuppressive agent cyclosporine A, and that such taste-immune associative learning is subject to reinforcement. Furthermore, once consolidated, this saccharin-immunosuppression engram is resistant to extinction when avoidance behavior is assessed. More importantly, the more this engram is activated, either at association or extinction phases, the more pronounced is the conditioned immunosuppression.

  12. The role of extraterrestrial phenomena in extinction.

    Science.gov (United States)

    Raup, D M

    1988-01-01

    In the several years since the Alvarez report of anomalously high iridium concentrations at the Cretaceous-Tertiary boundary, evidence for the involvement of meteorite impacts in biological extinction has increased dramatically. Much more research will be needed, however, before meteorite impact is established as a general causal factor in extinction. Of ever greater long-term interest is the possibility that other extraterrestrial forces have had important influences on the evolution of life. To recognize the effects of such forces, it will be necessary to coordinate the research of astronomy and paleontology so that testable predictions can be formulated. It is possible that known, systematic changes in the Solar System or Galaxy have had effects on global biology and that these effects have been preserved in the paleontological record.

  13. Visuomotor links in awareness: evidence from extinction.

    Science.gov (United States)

    Ricci, Raffaella; Genero, Rosanna; Colombatti, Simona; Zampieri, Daniela; Chatterjee, Anjan

    2005-05-31

    In patients with extinction, ipsilesional stimuli may abolish awareness of contralesional stimuli. Explanations of extinction often assume a serial model of processing in which sensory competition and identification precedes the selection of responses. We tested the adequacy of this assumption by examining the effects of response variables on visual awareness in six patients using signal detection analysis. Ipsilesional stimuli modulated patients' response criteria in deciding whether a contralesional stimulus was a target, and response modality (verbal or motor) modulated patients' abilities to discriminate between contralesional targets and distractors. This pattern of input variables modulating response criteria and output variables modulating discriminability indicates the extent to which attentional and intentional systems are tightly intertwined, with bi-directional effects in producing visual awareness.

  14. Predicting extinction risk of Brazilian Atlantic forest angiosperms.

    Science.gov (United States)

    Leão, Tarciso C C; Fonseca, Carlos R; Peres, Carlos A; Tabarelli, Marcelo

    2014-10-01

    Understanding how plant life history affects species vulnerability to anthropogenic disturbances and environmental change is a major ecological challenge. We examined how vegetation type, growth form, and geographic range size relate to extinction risk throughout the Brazilian Atlantic Forest domain. We used a database containing species-level information of 6,929 angiosperms within 112 families and a molecular-based working phylogeny. We used decision trees, standard regression, and phylogenetic regression to explore the relationships between species attributes and extinction risk. We found a significant phylogenetic signal in extinction risk. Vegetation type, growth form, and geographic range size were related to species extinction risk, but the effect of growth form was not evident after phylogeny was controlled for. Species restricted to either rocky outcrops or scrub vegetation on sandy coastal plains exhibited the highest extinction risk among vegetation types, a finding that supports the hypothesis that species adapted to resource-limited environments are more vulnerable to extinction. Among growth forms, epiphytes were associated with the highest extinction risk in non-phylogenetic regression models, followed by trees, whereas shrubs and climbers were associated with lower extinction risk. However, the higher extinction risk of epiphytes was not significant after correcting for phylogenetic relatedness. Our findings provide new indicators of extinction risk and insights into the mechanisms governing plant vulnerability to extinction in a highly diverse flora where human disturbances are both frequent and widespread. © 2014 Society for Conservation Biology.

  15. Extracellular citrulline levels in the nucleus accumbens during the acquisition and extinction of a classical conditioned reflex with pain reinforcement.

    Science.gov (United States)

    Savel'ev, S A; Saul'skaya, N B

    2007-03-01

    Studies on Sprague-Dawley rats using in vivo microdialysis and HPLC showed that the acquisition and performance of a classical conditioned reflex with pain reinforcement was accompanied by increases in the concentrations of citrulline (a side product of nitric oxide formation) and arginine (the substrate of NO synthase) in the intercellular space of the nucleus accumbens. During extinction of the reflex, there was a decrease in the elevation of extracellular citrulline in this brain structure, which correlated with the extent of extinction of the reflex. Recovery of the reflex led to increases in arginine and citrulline levels in the nucleus accumbens. These data suggest that there is an increase in nitric oxide production in the nucleus accumbens during the acquisition and performance of a classical conditioned reflex with pain reinforcement, which decreases as the reflex is extinguished and recovers with recovery of the reflex.

  16. Simple models of evolution and extinction

    CERN Document Server

    Newman, M E J

    1999-01-01

    This article gives a brief introduction to the mathematical modeling of large-scale biological evolution and extinction. We give three examples of simple models in this field: the coevolutionary avalanche model of Bak and Sneppen, the environmental stress model of Newman, and the increasing fitness model of Sibani, Schmidt, and Alstrom. We describe the features of real evolution which these models are intended to explain and compare the results of simulations against data drawn from the fossil record.

  17. Clumpy cold dark matter and biological extinctions

    CERN Document Server

    Collar, J I

    1995-01-01

    Cosmological models with cosmic string and texture seeded universes predict a present abundance of very dense clumps of Cold Dark Matter particles. Their crossing through the solar system would induce a non-negligible amount of radiation damage to all living tissue; the severity of such an episode is assessed. The estimated frequency of these crossings agrees with the apparent periodicity of the paleontological record of biological extinctions. (Phys. Lett. B, in press)

  18. Opportunities and costs for preventing vertebrate extinctions.

    Science.gov (United States)

    Conde, Dalia A; Colchero, Fernando; Güneralp, Burak; Gusset, Markus; Skolnik, Ben; Parr, Michael; Byers, Onnie; Johnson, Kevin; Young, Glyn; Flesness, Nate; Possingham, Hugh; Fa, John E

    2015-03-16

    Despite an increase in policy and management responses to the global biodiversity crisis, implementation of the 20 Aichi Biodiversity Targets still shows insufficient progress [1]. These targets, strategic goals defined by the United Nations Convention on Biological Diversity (CBD), address major causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2], a consortium of conservation-oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 'trigger' sites [3]. These are arguably the most irreplaceable category of important biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1]. Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species [2]. However, averting human-induced species extinctions within AZE sites requires enhanced planning tools to increase the chances of success [3]. Here, we assess the potential for ensuring the long-term conservation of AZE vertebrate species (157 mammals, 165 birds, 17 reptiles and 502 amphibians) by calculating a conservation opportunity index (COI) for each species. The COI encompasses a set of measurable indicators that quantify the possibility of achieving successful conservation of a species in its natural habitat (COIh) and by establishing insurance populations in zoos (COIc).

  19. Rewinding the process of mammalian extinction

    OpenAIRE

    Saragusty, J.; Diecke, S.; Drukker, M.; Durrant, B.; Friedrich Ben-Nun, I.; Galli, C; Goeritz, F.; Hayashi, K; Hermes, R.; Holtze, S.; Johnson, S.; Lazzari, G.; Loi, P; Loring, J. F.; Okita, K

    2016-01-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road m...

  20. Dynamics of extinction debt across five taxonomic groups.

    Science.gov (United States)

    Halley, John M; Monokrousos, Nikolaos; Mazaris, Antonios D; Newmark, William D; Vokou, Despoina

    2016-07-25

    Species extinction following habitat loss is well documented. However, these extinctions do not happen immediately. The biodiversity surplus (extinction debt) declines with some delay through the process of relaxation. Estimating the time constants of relaxation, mainly the expected time to first extinction and the commonly used time for half the extinction debt to be paid off (half-life), is crucial for conservation purposes. Currently, there is no agreement on the rate of relaxation and the factors that it depends on. Here we find that half-life increases with area for all groups examined in a large meta-analysis of extinction data. A common pattern emerges if we use average number of individuals per species before habitat loss as an area index: for mammals, birds, reptiles and plants, the relationship has an exponent close to a half. We also find that the time to first determined extinction is short and increases slowly with area.

  1. Role of the hippocampus in contextual modulation of fear extinction

    Institute of Scientific and Technical Information of China (English)

    Lingzhi Kong; Xihong Wu; Liang Li

    2008-01-01

    Fear extinction is an important form of emotional learning, and affects neural plasticity. Cue fear extinction is a classical form of inhibitory learning that can be used as an exposure-based treatment for phobia, because the long-term extinction memory produced during cue fear extinction can limit the over-expression of fear. The expression of this inhibitory memory partly depends on the context in which the extinction learning occurs. Studies such as transient inhibition, electrophysiology and brain imaging have proved that the hippocampus - an important structure in the limbic system - facilitates memory retrieval by contextual cues.Mediation of the hippocampus-medial prefrontal lobe circuit may be the neurobiological basis of this process.This article has reviewed the role of the hippocampus in the learning and retrieval of fear extinction.Contextual modulation of fear extinction may rely on a neural network consisting of the hippocampus, the medial prefrontal cortex and the amygdala.

  2. Extinction and dust properties in a clumpy medium

    CERN Document Server

    Scicluna, P

    2015-01-01

    (abridged) The dust content of the universe is primarily explored via its interaction with stellar photons, producing interstellar extinction. However, owing to the physical extension of the observing beam, observations may detect scattered photons, resulting in a change in the observed (or effective) extinction, depending on the spatial distribution of the dust and the resolution of the instrument. We investigate the influence of clumpy dust distributions on effective extinction toward embedded sources and those in the diffuse ISM. We use Monte Carlo radiative transfer to examine effective extinction for various geometries. By varying the number, optical depth and volume-filling factor of clumps in models of spherical shells and the diffuse ISM, we explore the evolution of extinction. Depending on the number of scattering events in the beam, the extinction curve steepens in homogeneous media and flattens in clumpy media. As a result, clumpy dust distributions can to reproduce extinction curves with arbitrary...

  3. Spontaneous evaluative inferences and their relationship to spontaneous trait inferences.

    Science.gov (United States)

    Schneid, Erica D; Carlston, Donal E; Skowronski, John J

    2015-05-01

    Three experiments are reported that explore affectively based spontaneous evaluative impressions (SEIs) of stimulus persons. Experiments 1 and 2 used modified versions of the savings in relearning paradigm (Carlston & Skowronski, 1994) to confirm the occurrence of SEIs, indicating that they are equivalent whether participants are instructed to form trait impressions, evaluative impressions, or neither. These experiments also show that SEIs occur independently of explicit recall for the trait implications of the stimuli. Experiment 3 provides a single dissociation test to distinguish SEIs from spontaneous trait inferences (STIs), showing that disrupting cognitive processing interferes with a trait-based prediction task that presumably reflects STIs, but not with an affectively based social approach task that presumably reflects SEIs. Implications of these findings for the potential independence of spontaneous trait and evaluative inferences, as well as limitations and important steps for future study are discussed. (c) 2015 APA, all rights reserved).

  4. Minimizing extinction risk through genetic rescue

    Directory of Open Access Journals (Sweden)

    Waite, T. A.

    2005-12-01

    Full Text Available According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus. We ask how many migrants per generation (MPG are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations. During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10. Compared with the 0-MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi-extinction suggests that replicate populations in the 1-MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue.

  5. Glucocorticoids enhance extinction-based psychotherapy.

    Science.gov (United States)

    de Quervain, Dominique J-F; Bentz, Dorothée; Michael, Tanja; Bolt, Olivia C; Wiederhold, Brenda K; Margraf, Jürgen; Wilhelm, Frank H

    2011-04-19

    Behavioral exposure therapy of anxiety disorders is believed to rely on fear extinction. Because preclinical studies have shown that glucocorticoids can promote extinction processes, we aimed at investigating whether the administration of these hormones might be useful in enhancing exposure therapy. In a randomized, double-blind, placebo-controlled study, 40 patients with specific phobia for heights were treated with three sessions of exposure therapy using virtual reality exposure to heights. Cortisol (20 mg) or placebo was administered orally 1 h before each of the treatment sessions. Subjects returned for a posttreatment assessment 3-5 d after the last treatment session and for a follow-up assessment after 1 mo. Adding cortisol to exposure therapy resulted in a significantly greater reduction in fear of heights as measured with the acrophobia questionnaire (AQ) both at posttreatment and at follow-up, compared with placebo. Furthermore, subjects receiving cortisol showed a significantly greater reduction in acute anxiety during virtual exposure to a phobic situation at posttreatment and a significantly smaller exposure-induced increase in skin conductance level at follow-up. The present findings indicate that the administration of cortisol can enhance extinction-based psychotherapy.

  6. Rewinding the process of mammalian extinction.

    Science.gov (United States)

    Saragusty, Joseph; Diecke, Sebastian; Drukker, Micha; Durrant, Barbara; Friedrich Ben-Nun, Inbar; Galli, Cesare; Göritz, Frank; Hayashi, Katsuhiko; Hermes, Robert; Holtze, Susanne; Johnson, Stacey; Lazzari, Giovanna; Loi, Pasqualino; Loring, Jeanne F; Okita, Keisuke; Renfree, Marilyn B; Seet, Steven; Voracek, Thomas; Stejskal, Jan; Ryder, Oliver A; Hildebrandt, Thomas B

    2016-07-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280-292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

  7. Modelling dust extinction in the Magellanic Clouds

    CERN Document Server

    Zonca, Alberto; Mulas, Giacomo; Aresu, Giambattista; Cecchi-Pestellini, Cesare

    2015-01-01

    We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting by core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons. All different flavors of the extinction curves observed in the Magellanic Clouds can be described by the present model, that has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the Magellanic Clouds the extinction produced by classic grains is generally larger than absorption by polycyclic aromatic hydrocarbons. Within this model, the non-linear far-UV rise is accounted for by polycyclic aromatic hydrocarbons, whose presence in turn is always associated to a gap in the size distribution of classical particles. This hints either a physical connection between (e.g., a common cause for) polycyclic aromatic hydrocarbons and the absence of middle-sized dust particles, or the need for an additional component...

  8. Permo-Triassic vertebrate extinctions: A program

    Science.gov (United States)

    Olson, E. C.

    1988-01-01

    Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

  9. Optical antenna enhanced spontaneous emission.

    Science.gov (United States)

    Eggleston, Michael S; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C

    2015-02-10

    Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼ 200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ∼ 115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼ 2,500 × spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d(2). Unfortunately, at d antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.

  10. Extinction of chained instrumental behaviors: Effects of procurement extinction on consumption responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2015-07-01

    Instrumental behavior often consists of sequences or chains of responses that minimally include procurement behaviors that enable subsequent consumption behaviors. In such chains, behavioral units are linked by access to one another and eventually to a primary reinforcer, such as food or a drug. The present experiments examined the effects of extinguishing procurement responding on consumption responding after training of a discriminated heterogeneous instrumental chain. Rats learned to make a procurement response (e.g., pressing a lever) in the presence of a distinctive discriminative stimulus; making that response led to the presentation of a second discriminative stimulus that set the occasion for a consumption response (e.g., pulling a chain), which then produced a food-pellet reinforcer. Experiment 1 showed that extinction of either the full procurement-consumption chain or procurement alone weakened the consumption response tested in isolation. Experiment 2 replicated the procurement extinction effect and further demonstrated that the opportunity to make the procurement response, as opposed to simple exposure to the procurement stimulus alone, was required. In Experiment 3, rats learned 2 distinct discriminated heterogeneous chains; extinction of 1 procurement response specifically weakened the consumption response that had been associated with it. The results suggest that learning to inhibit the procurement response may produce extinction of consumption responding through mediated extinction. The experiments suggest the importance of an associative analysis of instrumental behavior chains. (PsycINFO Database Record

  11. Dust properties along anomalous extinction sightlines. II. Studying extinction curves with dust models

    CERN Document Server

    Mazzei, Paola

    2010-01-01

    The large majority of extinction sight lines in our Galaxy obey a simple relation depending on one parameter, the total-to-selective extinction coefficient, Rv. Different values of Rv are able to match the whole extinction curve through different environments so characterizing normal extinction curves. In this paper more than sixty curves with large ultraviolet deviations from their best-fit one parameter curve are analyzed. These curves are fitted with dust models to shed light into the properties of the grains, the processes affecting them, and their relations with the environmental characteristics. The extinction curve models are reckoned by following recent prescriptions on grain size distributions able to describe one parameter curves for Rv values from 3.1 to 5.5. Such models, here extended down to Rv=2.0, allow us to compare the resulting properties of our deviating curves with the same as normal curves in a self-consistent framework, and thus to recover the relative trends overcoming the modeling unce...

  12. Spontaneous emission and absorber theory

    Science.gov (United States)

    Pegg, David T.

    1997-01-01

    One of the long term interests of George Series was the construction of a theory of spontaneous emission which does not involve field quantisation. His approach was written in terms of atomic operators only and he drew a parallel with the Wheeler-Feynman absorber theory of radiation. By making a particular extra postulate, he was able to obtain the correct spontaneous emission rate and the Lamb shift reasonably simply and directly. An examination of his approach indicates that this postulate is physically reasonable and the need for it arises because quantisation in his theory occurs after the response of the absorber has been accounted for by means of the radiative reaction field. We review briefly an alternative absorber theory approach to spontaneous emission based on the direct action between the emitting atom and a quantised absorber, and outline some applications to more recent effects of interest in quantum optics.

  13. Relationships between ocean anoxia, the biological pump, and marine animal life during the Permian-Triassic mass extinction (Invited)

    Science.gov (United States)

    Meyer, K. M.; Schaal, E. K.; Payne, J.

    2013-12-01

    Ocean anoxia/euxinia and carbon cycle instability have long been linked to the end-Permian mass extinction and the Early Triassic interval of delayed or interrupted biotic recovery. Many hypotheses to explain this extinction event invoke the release of greenhouse gases during the emplacement of the Siberian Traps, which likely triggered abrupt changes in marine biogeochemical cycling, atmospheric chemistry, and biodiversity. However, the precise ways in which volcanism and these perturbations are linked and how they governed the tempo and mode of biotic recovery remain poorly understood. Here we highlight new C, Ca, and Sr isotopic data that serve to link volcanic CO2 inputs to changes in marine biogeochemistry and environmental change. We then examine the relationship between ocean biogeochemistry, the biological pump, and marine animal ecosystems during the end-Permian mass extinction and Early Triassic recovery. Finally, we use numerical simulations to probe whether these relationships also explain broad Phanerozoic trends in ocean nutrient status, anoxia, and productivity of marine ecosystems.

  14. Conservation triage or injurious neglect in endangered species recovery.

    Science.gov (United States)

    Gerber, Leah R

    2016-03-29

    Listing endangered and threatened species under the US Endangered Species Act is presumed to offer a defense against extinction and a solution to achieve recovery of imperiled populations, but only if effective conservation action ensues after listing occurs. The amount of government funding available for species protection and recovery is one of the best predictors of successful recovery; however, government spending is both insufficient and highly disproportionate among groups of species, and there is significant discrepancy between proposed and actualized budgets across species. In light of an increasing list of imperiled species requiring evaluation and protection, an explicit approach to allocating recovery funds is urgently needed. Here I provide a formal decision-theoretic approach focusing on return on investment as an objective and a transparent mechanism to achieve the desired recovery goals. I found that less than 25% of the $1.21 billion/year needed for implementing recovery plans for 1,125 species is actually allocated to recovery. Spending in excess of the recommended recovery budget does not necessarily translate into better conservation outcomes. Rather, elimination of only the budget surplus for "costly yet futile" recovery plans can provide sufficient funding to erase funding deficits for more than 180 species. Triage by budget compression provides better funding for a larger sample of species, and a larger sample of adequately funded recovery plans should produce better outcomes even if by chance. Sharpening our focus on deliberate decision making offers the potential to achieve desired outcomes in avoiding extinction for Endangered Species Act-listed species.

  15. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  16. Spontaneous isolated celiac artery dissection

    Directory of Open Access Journals (Sweden)

    Tuba Cimilli Ozturk

    2011-01-01

    Full Text Available Dyspepsia with mild, stabbing epigastric discomfort without history of trauma is a very common symptom that emergency physicians see in their daily practice. Vascular emergencies, mostly the aortic dissection and aneurysm, are always described in the differential diagnosis with persistent symptoms. Isolated celiac artery dissection occurring spontaneously is a very rare diagnosis. The involvement of branch vessels is generally observed and patients show various clinical signs and symptoms according to the involved branch vessel. Here we are presenting a case with spontaneous isolated celiac artery dissection, without any branch vessel involvement or visceral damage, detected by computed tomography scans taken on admission.

  17. Spontaneous rupture of vaginal enterocele

    DEFF Research Database (Denmark)

    Svendsen, Jesper Hastrup; Galatius, H; Hansen, P K

    1985-01-01

    Spontaneous rupture of an enterocele is a rare complication. Only 24 cases including the present case have been reported in the literature. The patients were elderly and had had at least one vaginal operation. The patients were remarkably unaffected symptomatically on admission.......Spontaneous rupture of an enterocele is a rare complication. Only 24 cases including the present case have been reported in the literature. The patients were elderly and had had at least one vaginal operation. The patients were remarkably unaffected symptomatically on admission....

  18. Spontaneous rupture of vaginal enterocele

    DEFF Research Database (Denmark)

    Svendsen, Jesper Hastrup; Galatius, H; Hansen, P K

    1985-01-01

    Spontaneous rupture of an enterocele is a rare complication. Only 24 cases including the present case have been reported in the literature. The patients were elderly and had had at least one vaginal operation. The patients were remarkably unaffected symptomatically on admission.......Spontaneous rupture of an enterocele is a rare complication. Only 24 cases including the present case have been reported in the literature. The patients were elderly and had had at least one vaginal operation. The patients were remarkably unaffected symptomatically on admission....

  19. Spontaneous waves in muscle fibres

    Science.gov (United States)

    Günther, Stefan; Kruse, Karsten

    2007-11-01

    Mechanical oscillations are important for many cellular processes, e.g. the beating of cilia and flagella or the sensation of sound by hair cells. These dynamic states originate from spontaneous oscillations of molecular motors. A particularly clear example of such oscillations has been observed in muscle fibers under non-physiological conditions. In that case, motor oscillations lead to contraction waves along the fiber. By a macroscopic analysis of muscle fiber dynamics we find that the spontaneous waves involve non-hydrodynamic modes. A simple microscopic model of sarcomere dynamics highlights mechanical aspects of the motor dynamics and fits with the experimental observations.

  20. Cortisol modifies extinction learning of recently acquired fear in men.

    Science.gov (United States)

    Merz, Christian Josef; Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-09-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS-) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS- than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS- differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear.

  1. A window of vulnerability: impaired fear extinction in adolescence.

    Science.gov (United States)

    Baker, Kathryn D; Den, Miriam L; Graham, Bronwyn M; Richardson, Rick

    2014-09-01

    There have been significant advances made towards understanding the processes mediating extinction of learned fear. However, despite being of clear theoretical and clinical significance, very few studies have examined fear extinction in adolescence, which is often described as a developmental window of vulnerability to psychological disorders. This paper reviews the relatively small body of research examining fear extinction in adolescence. A prominent finding of this work is that adolescents, both humans and rodents, exhibit a marked impairment in extinction relative to both younger (e.g., juvenile) and older (e.g., adult) groups. We then review some potential mechanisms that could produce the striking extinction deficit observed in adolescence. For example, one neurobiological candidate mechanism for impaired extinction in adolescence involves changes in the functional connectivity within the fear extinction circuit, particularly between prefrontal cortical regions and the amygdala. In addition, we review research on emotion regulation and attention processes that suggests that developmental changes in attention bias to threatening cues may be a cognitive mechanism that mediates age-related differences in extinction learning. We also examine how a differential reaction to chronic stress in adolescence impacts upon extinction retention during adolescence as well as in later life. Finally, we consider the findings of several studies illustrating promising approaches that overcome the typically-observed extinction impairments in adolescent rodents and that could be translated to human adolescents. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Cortisol modifies extinction learning of recently acquired fear in men

    Science.gov (United States)

    Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-01-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS−) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS− than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS− differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear. PMID:23945999

  3. Community stability and selective extinction during the Permian-Triassic mass extinction

    Science.gov (United States)

    Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2015-10-01

    The fossil record contains exemplars of extreme biodiversity crises. Here, we examined the stability of terrestrial paleocommunities from South Africa during Earth's most severe mass extinction, the Permian-Triassic. We show that stability depended critically on functional diversity and patterns of guild interaction, regardless of species richness. Paleocommunities exhibited less transient instability—relative to model communities with alternative community organization—and significantly greater probabilities of being locally stable during the mass extinction. Functional patterns that have evolved during an ecosystem's history support significantly more stable communities than hypothetical alternatives.

  4. Mass extinction efficiency and extinction hygroscopicity of ambient PM2.5 in urban China.

    Science.gov (United States)

    Cheng, Zhen; Ma, Xin; He, Yujie; Jiang, Jingkun; Wang, Xiaoliang; Wang, Yungang; Sheng, Li; Hu, Jiangkai; Yan, Naiqiang

    2017-07-01

    The ambient PM2.5 pollution problem in China has drawn substantial international attentions. The mass extinction efficiency (MEE) and hygroscopicity factor (f(RH)) of PM2.5 can be readily applied to study the impacts on atmospheric visibility and climate. The few previous investigations in China only reported results from pilot studies and are lack of spatial representativeness. In this study, hourly average ambient PM2.5 mass concentration, relative humidity, and atmospheric visibility data from China national air quality and meteorological monitoring networks were retrieved and analyzed. It includes 24 major Chinese cities from nine city-clusters with the period of October 2013 to September 2014. Annual average extinction coefficient in urban China was 759.3±258.3Mm(-1), mainly caused by dry PM2.5 (305.8.2±131.0Mm(-1)) and its hygroscopicity (414.6±188.1Mm(-1)). High extinction coefficient values were resulted from both high ambient PM2.5 concentration (68.5±21.7µg/m(3)) and high relative humidity (69.7±8.6%). The PM2.5 mass extinction efficiency varied from 2.87 to 6.64m(2)/g with an average of 4.40±0.84m(2)/g. The average extinction hygroscopic factor f(RH=80%) was 2.63±0.45. The levels of PM2.5 mass extinction efficiency and hygroscopic factor in China were in comparable range with those found in developed countries in spite of the significant diversities among all 24 cities. Our findings help to establish quantitative relationship between ambient extinction coefficient (visual range) and PM2.5 & relative humidity. It will reduce the uncertainty of extinction coefficient estimation of ambient PM2.5 in urban China which is essential for the research of haze pollution and climate radiative forcing. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Spontaneous resolution of macrocytic anemia: old disease revisited

    Directory of Open Access Journals (Sweden)

    Imashuku S

    2012-08-01

    Full Text Available Shinsaku Imashuku, Naoko Kudo, Shigehiro KanedaDivision of Hematology, Takasago-seibu Hospital, Takasago, JapanAbstract: We report here on a 60-year-old male with alcohol-related macrocytic anemia. He was hospitalized on three occasions with hemoglobin < 9.0 g/dL and mean corpuscular volume > 130 fL. Careful history taking and observation of his blood status led us to make a correct diagnosis. At the time of each of his admissions, only with bed rest and abstinence from alcohol did our patient dramatically show spontaneous recovery of anemia in association with a rapid decline of serum γ-glutamyl transpeptidase values. It is well recognized that marrow abnormalities in alcoholic patients are reversible. Physicians should be aware that there is a subset of patients with macrocytic anemia that could be improved without medication.Keywords: macrocytic anemia, alcohol, spontaneous resolution, γ-glutamyl transpeptidase

  6. Extinction debt as a driver of amphibian declines: An example with imperiled flatwoods salamanders

    Science.gov (United States)

    Semiltsch, Raymond D; Walls, Susan; Barichivich, William J.; O'Donnell, Katherine

    2017-01-01

    A comprehensive view of population declines and their underlying causes is necessary to reverse species loss. Historically, in many cases, a narrow view may have allowed species declines to continue, virtually undetected, for long periods of time (perhaps even decades). We suggest that extinction debt is likely responsible for numerous (perhaps most) amphibian declines and that this perspective should be incorporated into the structure of amphibian research and management. Extinction debt, originally proposed to explain changes in species richness following environmental disturbance, also may refer to the proportion of populations of an individual species that is expected to eventually be lost because of habitat change. A conservation framework to address extinction debt focuses research on threats at the individual, population, and metapopulation levels. This approach will help enhance, restore, and protect specific processes and habitats at the proper scale by directing management to the most vulnerable level and stage of a species. We illustrate this approach using Flatwoods Salamanders, Ambystoma cingulatumand Ambystoma bishopi, which occurred historically throughout the Coastal Plain of the southeastern United States but have experienced a greater than 85% loss of populations in recent years. Reversal of these losses is possible only if conservation and recovery efforts encompass individual, population, and metapopulation levels. We illustrate our framework by outlining actions that could be taken at each of these levels to help guide conservation and management of amphibians with complex life cycles and provide options for how to prioritize conservation actions in the face of logistical and budgetary shortfalls.

  7. Gradual extinction prevents the return of fear: Implications for the discovery of state

    Directory of Open Access Journals (Sweden)

    Samuel Joseph Gershman

    2013-11-01

    Full Text Available Fear memories are notoriously difficult to erase, often recovering over time. The longstanding explanation for this finding is that, in extinction training, a new memory is formed that competes with the old one for expression but does not otherwise modify it. This explanation is at odds with traditional models of learning such as Rescorla-Wagner and reinforcement learning. A possible reconciliation that was recently suggested is that extinction training leads to the inference of a new state that is different from the state that was in effect in the original training. This solution, however, raises a new question: under what conditions are new states, or new memories formed? Theoretical accounts implicate persistent large prediction errors in this process. As a test of this idea, we reasoned that careful design of the reinforcement schedule during extinction training could reduce these prediction errors enough to prevent the formation of a new memory, while still decreasing reinforcement sufficiently to drive modification of the old fear memory. In two Pavlovian fear-conditioning experiments, we show that gradually reducing the frequency of aversive stimuli, rather than eliminating them abruptly, prevents the recovery of fear. This finding has important implications for theories of state discovery in reinforcement learning.

  8. Remifentanil used to supplement propofol does not improve quality of sedation during spontaneous respiration

    NARCIS (Netherlands)

    Moerman, AT; Struys, MMRF; Vereecke, HE; Herregods, LL; De Vos, Martine M.; Mortier, EP

    Study Objective: To evaluate whether the use of remifentanil to supplement propofol during spontaneous respiration confers any benefits in terms of quality of sedation and recovery, or in terms of reduction in Propofol requirements. Design: Prospective, randomized, double-blind study. Setting:

  9. Modeling of wettability alteration during spontaneous imbibition of mutually soluble solvents in mixed wet fractured reservoirs

    NARCIS (Netherlands)

    Chahardowli, M.; Bruining, J.

    2014-01-01

    Mutually-soluble solvents can enhance oil recovery both in mixed-wet fractured reservoirs. When a partially waterwet matrix is surrounded by an immiscible wetting phase in the fracture, spontaneous imbibition is the most important production mechanism. Initially, the solvent moves with the imbibing

  10. Chemical pleurodesis for spontaneous pneumothorax.

    Science.gov (United States)

    How, Cheng-Hung; Hsu, Hsao-Hsun; Chen, Jin-Shing

    2013-12-01

    Pneumothorax is defined as the presence of air in the pleural cavity. Spontaneous pneumothorax, occurring without antecedent traumatic or iatrogenic cause, is sub-divided into primary and secondary. The severity of pneumothorax could be varied from asymptomatic to hemodynamically compromised. Optimal management of this benign disease has been a matter of debate. In addition to evacuating air from the pleural space by simple aspiration or chest tube drainage, the management of spontaneous pneumothorax also focused on ceasing air leakage and preventing recurrences by surgical intervention or chemical pleurodesis. Chemical pleurodesis is a procedure to achieve symphysis between the two layers of pleura by sclerosing agents. In the current practice guidelines, chemical pleurodesis is reserved for patients unable or unwilling to receive surgery. Recent researches have found that chemical pleurodesis is also safe and effective in preventing pneumothorax recurrence in patients with the first episode of spontaneous pneumothorax or after thoracoscopic surgery and treating persistent air leakage after thoracoscopic surgery. In this article we aimed at exploring the role of chemical pleurodesis for spontaneous pneumothorax, including ceasing air leakage and preventing recurrence. The indications, choice of sclerosants, safety, effects, and possible side effects or complications of chemical pleurodesis are also reviewed here.

  11. Silicosis with bilateral spontaneous pneumothorax

    Directory of Open Access Journals (Sweden)

    Fotedar Sanjay

    2010-01-01

    Full Text Available Presentation with simultaneous bilateral pneumothorax is uncommon and usually in the context of secondary spontaneous pneumothorax.The association of pneumothorax and silicosis is infrequent and most cases are unilateral. Bilateral pneumothorax in silicosis is very rare with just a few reports in medical literature.

  12. Shell theorem for spontaneous emission

    DEFF Research Database (Denmark)

    Kristensen, Philip Trøst; Mortensen, Jakob Egeberg; Lodahl, Peter;

    2013-01-01

    and therefore is given exactly by the dipole approximation theory. This surprising result is a spontaneous emission counterpart to the shell theorems of classical mechanics and electrostatics and provides insights into the physics of mesoscopic emitters as well as great simplifications in practical calculations....

  13. Spontaneous resolution of subfoveal perfluorocarbon

    Directory of Open Access Journals (Sweden)

    Oellers P

    2015-03-01

    Full Text Available Patrick Oellers,1 Leon D Charkoudian,2 Paul Hahn11Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA; 2Cape Fear Retinal Associates, Wilmington, NC, USA Abstract: Perfluorocarbon liquids (PFCL have transformed the surgical approach to complex retinal detachments, but their use can be complicated by subretinal retention. Migration of peripherally located subretinal PFCL towards the fovea is well established, but spontaneous resolution of subfoveal PFCL without surgical evacuation or displacement has rarely been described. We present a case of a large single retained subfoveal PFCL droplet following vitrectomy with membrane peeling, inferior relaxing retinectomy, and silicone oil tamponade that demonstrated spontaneous resolution 3 weeks postoperatively, with subsequent anatomic and visual improvement. No residual subretinal PFCL was noted, and we hypothesize that the PFCL droplet spontaneously extruded through a transient hole created in the thinned retina overlying the droplet, which subsequently closed spontaneously. Further understanding of the mechanisms of PFCL migration and resolution may facilitate improved treatments for this complication.Keywords: perfluorocarbon, subretinal, retained, resolution

  14. Spontaneous bilateral quadriceps tendon rupture.

    Science.gov (United States)

    Vigneswaran, N; Lee, K; Yegappan, M

    2007-11-01

    Spontaneous bilateral quadriceps tendon ruptures are uncommon. We present a 30-year-old man with end-stage renal failure, who sustained this injury, and subsequently had surgical repair of both tendons on separate occasions. He has since regained full range of movement of both knees.

  15. Biomarkers of spontaneous preterm birth

    DEFF Research Database (Denmark)

    Polettini, Jossimara; Cobo, Teresa; Kacerovsky, Marian

    2017-01-01

    Despite decades of research on risk indicators of spontaneous preterm birth (PTB), reliable biomarkers are still not available to screen or diagnose high-risk pregnancies. Several biomarkers in maternal and fetal compartments have been mechanistically linked to PTB, but none of them are reliable...

  16. Student Experiments in Spontaneous Fission.

    Science.gov (United States)

    Becchetti, F. D.; Ying, J. S.

    1981-01-01

    Advanced undergraduate experiments utilizing a commercially available, thin spontaneous fission source are described, including studies of the energy and mass distribution of the fission fragments and their energy and angular correlation. The experiments provide a useful introduction to fission, nuclear mass equations, heavy-ion physics, and…

  17. Prediction of Spontaneous Preterm Birth

    NARCIS (Netherlands)

    Dijkstra, Karolien

    2002-01-01

    Preterm birth is a leading cause of neonatal morbidity and mortality. It is a major goal in obstetrics to lower the incidence of spontaneous preterm birth (SPB) and related neonatal morbidity and mortality. One of the principal objectives is to discover early markers that would allow us to identify

  18. Prediction of Spontaneous Preterm Birth

    NARCIS (Netherlands)

    Dijkstra, Karolien

    2002-01-01

    Preterm birth is a leading cause of neonatal morbidity and mortality. It is a major goal in obstetrics to lower the incidence of spontaneous preterm birth (SPB) and related neonatal morbidity and mortality. One of the principal objectives is to discover early markers that would allow us to identify

  19. Late Pennsylvanian climate changes and palynomorph extinctions

    Energy Technology Data Exchange (ETDEWEB)

    Kosanke, R.M.; Cecil, C.B. [US Geological Survey, Denver, CO (United States)

    1996-01-01

    A major floral change occurs in the Upper Pennsylvanian strata in the Midcontinent, Illinois basin, and in the northern Appalachian basin of eastern United States. Lycospora spp. (derived from arborescent lycopsids) became extinct along with some other palynomorph taxa. This investigation is concerned with the importance of this major floral change. Samples were studied from western Pennsylvania, eastern Ohio, and West Virgina (from a previous study) cover the stratigraphic interval from the Upper Freeport coal bed, uppermost part of the Allegheny Formation, to the Mahoning, Mason, Brush Creek, Wilgus, and Anderson coal beds in the lower part of the Conemaugh Formation. The floral change occurs either at or below the accepted Desmoinesian-Missourian boundary in the Midcontinent and Illinois basin, whereas in the northern Appalachians this change occurs in the lower part of the Conemaugh Formation, between the Mahoning and Brush Creek coal beds, or when the Mason is present, between the Mahoning and Mason coal beds. The first coal bed above the extinction of Lycospora spp. is dominated by the palynomorph taxon Endosporites globiformis which is derived from a heterosporous, herbaceous lycopsid. However, Sigillaria, another arborescent lycopsid, did not become extinct at this time as evidenced by the presence of the palynomorph genus Crassispora which is derived from Sigillaria. The reason for the survival of Sigillaria is now known, but it may have been able to adapt, in a limited fashion, to some sort of specialized microenvironment. The ferns, based on palynomorph occurrence, become numerically more important throughout the balance of the Conemaugh Formation, and dominate the Pittsburgh No. 8 and Pomeroy coal beds in the overlying Monogahela Formation.

  20. Self-Organized Criticality and Mass Extinction in Evolutionary Algorithms

    DEFF Research Database (Denmark)

    Krink, Thiemo; Thomsen, Rene

    2001-01-01

    niches after mass extinction events. Furthermore, paleontological studies have shown that there is a power law relationship between the frequency of species extinction events and the sue of the extinction impact. Power law relationships of this kind are typical for complex systems, which operate...... at a critical state between chaos and order, known as self-organized criticality (SOC). Based on this background, we used SOC to control the size of spatial extinction zones in a diffusion model. The SOC selection process was easy to implement and implied only negligible computational costs. Our results show...... that the SOC spatial extinction model clearly outperforms simple evolutionary algorithms (EAs) and the difffision model (CGA). Further, our results support the biological hypothesis that mass extinctions might play an important role in evolution. However, the success of simple EAs indicates that evolution...

  1. [GABA-Receptors in Modulation of Fear Memory Extinction].

    Science.gov (United States)

    Dubrovina, N I

    2016-01-01

    GABA is the major inhibitory neurotransmitter in the central nervous system determining the efficacy of neuronal interaction. GABA-receptors play a key role in different aspects of fear memory--acquisition and consolidation, retention, reconsolidation and extinction. Extinction is an important behavioural phenomenon which allows organism to adapt its behavior to a changing environment. Extinction of fear memory is a form of new inhibitory learning which interferes with expression of the initial acquired fear conditioning. Resistance to extinction is symptom of depression and posttraumatic stress disorder. The aim of the present review was to summarize own and literary data about GABAergic modulation of fear extinction and pharmacological correction of extinction impairment at influences on GABA(A)- and GABA(B)- receptors.

  2. Chemical antipredator defence is linked to higher extinction risk

    Science.gov (United States)

    2016-01-01

    Many attributes of species may be linked to contemporary extinction risk, though some such traits remain untested despite suggestions that they may be important. Here, I test whether a trait associated with higher background extinction rates, chemical antipredator defence, is also associated with current extinction risk, using amphibians as a model system—a group facing global population declines. I find that chemically defended species are approximately 60% more likely to be threatened than species without chemical defence, although the severity of the contemporary extinction risk may not relate to chemical defence. The results confirm that background and contemporary extinction rates can be predicted from the same traits, at least in certain cases. This suggests that associations between extinction risk and phenotypic traits can be temporally stable over long periods. The results also provide novel insights into the relevance of antipredator defences for species subject to conservation concerns. PMID:28018657

  3. Modeling Extinction Risk of Endemic Birds of Mainland China

    Directory of Open Access Journals (Sweden)

    Youhua Chen

    2013-01-01

    Full Text Available The extinction risk of endemic birds of mainland China was modeled over evolutionary time. Results showed that extinction risk of endemic birds in mainland China always tended to be similar within subclades over the evolutionary time of species divergence, and the overall evolution of extinction risk of species presented a conservatism pattern, as evidenced by the disparity-through-time plot. A constant-rate evolutionary model was the best one to quantify the evolution of extinction risk of endemic birds of mainland China. Thus, there was no rate shifting pattern for the evolution of extinction risk of Chinese endemic birds over time. In a summary, extinction risk of endemic birds of mainland China is systematically quantified under the evolutionary framework in the present work.

  4. Late Devonian red tide and mass extinction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Molecular stratigraphical, carbonate carbon isotopic, stratigraphical and paleontological data show that algal booming, eutrophication, anoxia, hypersalinity, positive ( 13C excursion and biomass decreasing occurred in the offshore carbonate environments of the Frasnian-Famennian (F-F) transition, which hints that red tide might frequently take place in the F-F transition of Guangxi, South China. We suggest that the mass extinction of the reef ecosystems and the shallow-water marine organisms in the F-F transition of the lower-middle latitudes may be related to the frequent occurrence of red tide in that time.

  5. Mass Extinctions and a Dark Disk

    CERN Document Server

    Kramer, Eric David

    2016-01-01

    We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constaints on the Galaxy's gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.

  6. Extinct 244Pu in Ancient Zircons

    Science.gov (United States)

    Turner, Grenville; Harrison, T. Mark; Holland, Greg; Mojzsis, Stephen J.; Gilmour, Jamie

    2004-10-01

    We have found evidence, in the form of fissiogenic xenon isotopes, for in situ decay of 244Pu in individual 4.1- to 4.2-billion-year-old zircons from the Jack Hills region of Western Australia. Because of its short half-life, 82 million years, 244Pu was extinct within 600 million years of Earth's formation. Detrital zircons are the only known relics to have survived from this period, and a study of their Pu geochemistry will allow us to date ancient metamorphic events and determine the terrestrial Pu/U ratio for comparison with the solar ratio.

  7. Gray Extinction in the Orion Trapezium

    Science.gov (United States)

    Krełowski, J.; Galazutdinov, G. A.; Strobel, A.; Mulas, G.

    2016-12-01

    We estimated distances to several Orion Trapezium stars using our CaII-method and confirm the distance recommended by Menten et al. However, we found that in the case of HD 37020 both individual distances (based on the trigonometric VLBI parallax and/or CaII-method) differ from the spectrophotometric distance by a factor of 2.5. We interpret this fact as a result of presence of gray (neutral) extinction of about 1.8 mag in front of this star. The correctness of the applied spectral type/ luminosity class, Sp/L, (based on new original spectra from HARPS-N) and measurements of color indices is discussed.

  8. The risk of extinction - the mutational meltdown or the overpopulation

    OpenAIRE

    Malarz, K.

    2006-01-01

    The phase diagrams survival-extinction for the Penna model with parameters: (mutations rate)-(birth rate), (mutation rate)-(harmful mutations threshold), (harmful mutation threshold)-(minimal reproduction age) are presented. The extinction phase may be caused by either mutational meltdown or overpopulation. When the Verhulst factor is responsible for removing only newly born babies and does not act on adults the overpopulation is avoided and only genetic factors may lead to species extinction.

  9. Extinction and dust properties in a clumpy medium

    OpenAIRE

    Scicluna, P.; Siebenmorgen, R.

    2015-01-01

    (abridged) The dust content of the universe is primarily explored via its interaction with stellar photons, producing interstellar extinction. However, owing to the physical extension of the observing beam, observations may detect scattered photons, resulting in a change in the observed (or effective) extinction, depending on the spatial distribution of the dust and the resolution of the instrument. We investigate the influence of clumpy dust distributions on effective extinction toward embed...

  10. A Comprehensive Quantitative Assessment of Bird Extinction Risk in Brazil

    OpenAIRE

    Nathália Machado; Rafael Dias Loyola

    2013-01-01

    In an effort to avoid species loss, scientists have focused their efforts on the mechanisms making some species more prone to extinction than others. However, species show different responses to threats given their evolutionary history, behavior, and intrinsic biological features. We used bird biological features and external threats to (1) understand the multiple pathways driving Brazilian bird species to extinction, (2) to investigate if and how extinction risk is geographically structured,...

  11. Experience with Dynamic Reinforcement Rates Decreases Resistance to Extinction

    OpenAIRE

    Craig, Andrew R.; Shahan, Timothy A

    2016-01-01

    The ability of organisms to detect reinforcer-rate changes in choice preparations is positively related to two factors: the magnitude of the change in rate and the frequency with which rates change. Gallistel (2012) suggested similar rate-detection processes are responsible for decreases in responding during operant extinction. Although effects of magnitude of change in reinforcer rate on resistance to extinction are well known (e.g., the partial-reinforcement-extinction effect), effects of f...

  12. The Effect of Size and Ecology on Extinction Susceptibility

    Science.gov (United States)

    Huynh, C.; Yuan, A.; Heim, N.; Payne, J.

    2015-12-01

    Although life on Earth first emerged as prokaryotic organisms, it eventually evolved into billions of different species. However, extinctions on Earth, especially the five mass extinctions, have decimated species. So what leads to a species survival or demise during a mass extinction? Are certain species more susceptible to extinctions based on their size and ecology? For this project, we focused on the data of marine animals. To examine the impact of size and ecology on a species's likelihood of survival, we compared the sizes and ecologies of the survivors and victims of the five mass extinctions. The ecology, or life mode, of a genus consists of the combination of tiering, motility, and feeding mechanism. Tiering refers to the animal's typical location in the water column and sediments, motility refers to its ability to move, and feeding mechanism describes the way the organism eats; together, they describe the animal's behavior. We analyzed the effect of ecology on survival using logistic regression, which compares life mode to the success or failure of a genus during each mass extinction interval. For organism size, we found the extinct organisms' mean size (both volume and length) and compared it with the average size of survivors on a graph. Our results show that while surviving genera of mass extinctions tended to be slightly larger than those that went extinct, there was no significant difference. Even though the Permian (Changhsingian) and Triassic (Rhaetian) extinctions had larger surviving species, likewise the difference was small. Ecology had a more obvious impact on the likelihood of survival; fast-moving, predatory pelagic organisms were the most likely to go extinct, while sedentary, infaunal suspension feeders had the greatest chances of survival. Overall, ecology played a greater role than size in determining the survival of a species. With this information, we can use ecology to predict which species would survive future extinctions.

  13. Evaluating the presence versus absence of the reinforcer during extinction.

    Science.gov (United States)

    Castillo, Mariana I; Borrero, John C; Mendres-Smith, Amber E

    2014-01-01

    The purpose of this study was to assess the effects of extinction when the reinforcer was present versus absent. These effects were examined with 2 human operant procedures (i.e., a computer program and a mechanical apparatus) with college students as participants. Discriminable properties of the apparatus appeared to influence responding during extinction. In general, responding during extinction was less likely with the mechanical apparatus when the reinforcer was absent and more likely with the computer program.

  14. How humans drive speciation as well as extinction

    DEFF Research Database (Denmark)

    Bull, Joseph William; Maron, M.

    2016-01-01

    A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinct...... and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity....

  15. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies : Testing "standard" extinction maps

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    2003-01-01

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  16. Primate extinction risk and historical patterns of speciation and extinction in relation to body mass.

    Science.gov (United States)

    Matthews, Luke J; Arnold, Christian; Machanda, Zarin; Nunn, Charles L

    2011-04-22

    Body mass is thought to influence diversification rates, but previous studies have produced ambiguous results. We investigated patterns of diversification across 100 trees obtained from a new Bayesian inference of primate phylogeny that sampled trees in proportion to their posterior probabilities. First, we used simulations to assess the validity of previous studies that used linear models to investigate the links between IUCN Red List status and body mass. These analyses support the use of linear models for ordinal ranked data on threat status, and phylogenetic generalized linear models revealed a significant positive correlation between current extinction risk and body mass across our tree block. We then investigated historical patterns of speciation and extinction rates using a recently developed maximum-likelihood method. Specifically, we predicted that body mass correlates positively with extinction rate because larger bodied organisms reproduce more slowly, and body mass correlates negatively with speciation rate because smaller bodied organisms are better able to partition niche space. We failed to find evidence that extinction rates covary with body mass across primate phylogeny. Similarly, the speciation rate was generally unrelated to body mass, except in some tests that indicated an increase in the speciation rate with increasing body mass. Importantly, we discovered that our data violated a key assumption of sample randomness with respect to body mass. After correcting for this bias, we found no association between diversification rates and mass.

  17. Spontaneous rupture of intrahepatic biliary ducts with biliary peritonitis.

    Science.gov (United States)

    Aydin, Unal; Yazici, Pinar; Coker, Ahmet

    2007-01-01

    Spontaneous rupture of intrahepatic biliary ducts is a rare cause of acute abdomen due to biliary peritonitis. We report a 92-year-old woman with 48-h history of upper abdominal pain, nausea and vomiting and peritoneal signs. CT scan showed free fluid in the abdomen and mild dilatation of the common bile duct. Exploratory laparotomy showed bile in the abdominal cavity with leak-age from a ruptured bile duct radicle in segment 3, as confirmed on intraoperative cholangiography. She underwent cholecystectomy, choledochotomy with removal of gallstones, repair of the perforation with primary suture and placement of a T-tube. She had an uneventful recovery.

  18. Extinction of Learned Fear Induces Hippocampal Place Cell Remapping.

    Science.gov (United States)

    Wang, Melissa E; Yuan, Robin K; Keinath, Alexander T; Ramos Álvarez, Manuel M; Muzzio, Isabel A

    2015-06-17

    The extinction of learned fear is a hippocampus-dependent process thought to embody new learning rather than erasure of the original fear memory, although it is unknown how these competing contextual memories are represented in the hippocampus. We previously demonstrated that contextual fear conditioning results in hippocampal place cell remapping and long-term stabilization of novel representations. Here we report that extinction learning also induces place cell remapping in C57BL/6 mice. Specifically, we observed cells that preferentially remapped during different stages of learning. While some cells remapped in both fear conditioning and extinction, others responded predominantly during extinction, which may serve to modify previous representations as well as encode new safe associations. Additionally, we found cells that remapped primarily during fear conditioning, which could facilitate reacquisition of the original fear association. Moreover, we also observed cells that were stable throughout learning, which may serve to encode the static aspects of the environment. The short-term remapping observed during extinction was not found in animals that did not undergo fear conditioning, or when extinction was conducted outside of the conditioning context. Finally, conditioning and extinction produced an increase in spike phase locking to the theta and gamma frequencies. However, the degree of remapping seen during conditioning and extinction only correlated with gamma synchronization. Our results suggest that the extinction learning is a complex process that involves both modification of pre-existing memories and formation of new ones, and these traces coexist within the same hippocampal representation.

  19. Experience with dynamic reinforcement rates decreases resistance to extinction.

    Science.gov (United States)

    Craig, Andrew R; Shahan, Timothy A

    2016-03-01

    The ability of organisms to detect reinforcer-rate changes in choice preparations is positively related to two factors: the magnitude of the change in rate and the frequency with which rates change. Gallistel (2012) suggested similar rate-detection processes are responsible for decreases in responding during operant extinction. Although effects of magnitude of change in reinforcer rate on resistance to extinction are well known (e.g., the partial-reinforcement-extinction effect), effects of frequency of changes in rate prior to extinction are unknown. Thus, the present experiments examined whether frequency of changes in baseline reinforcer rates impacts resistance to extinction. Pigeons pecked keys for variable-interval food under conditions where reinforcer rates were stable and where they changed within and between sessions. Overall reinforcer rates between conditions were controlled. In Experiment 1, resistance to extinction was lower following exposure to dynamic reinforcement schedules than to static schedules. Experiment 2 showed that resistance to presession feeding, a disruptor that should not involve change-detection processes, was unaffected by baseline-schedule dynamics. These findings are consistent with the suggestion that change detection contributes to extinction. We discuss implications of change-detection processes for extinction of simple and discriminated operant behavior and relate these processes to the behavioral-momentum based approach to understanding extinction.

  20. Has the Earth's sixth mass extinction already arrived?

    Science.gov (United States)

    Barnosky, Anthony D; Matzke, Nicholas; Tomiya, Susumu; Wogan, Guinevere O U; Swartz, Brian; Quental, Tiago B; Marshall, Charles; McGuire, Jenny L; Lindsey, Emily L; Maguire, Kaitlin C; Mersey, Ben; Ferrer, Elizabeth A

    2011-03-03

    Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.

  1. Extinction and ecosystem function in the marine benthos.

    Science.gov (United States)

    Solan, Martin; Cardinale, Bradley J; Downing, Amy L; Engelhardt, Katharina A M; Ruesink, Jennifer L; Srivastava, Diane S

    2004-11-12

    Rapid changes in biodiversity are occurring globally, yet the ecological impacts of diversity loss are poorly understood. Here we use data from marine invertebrate communities to parameterize models that predict how extinctions will affect sediment bioturbation, a process vital to the persistence of aquatic communities. We show that species extinction is generally expected to reduce bioturbation, but the magnitude of reduction depends on how the functional traits of individual species covary with their risk of extinction. As a result, the particular cause of extinction and the order in which species are lost ultimately govern the ecosystem-level consequences of biodiversity loss.

  2. Matrine ameliorates spontaneously developed colitis in interleukin-10-deficient mice.

    Science.gov (United States)

    Wu, Cong; Xu, Zheng; Gai, Renhua; Huang, Kehe

    2016-07-01

    Interleukin-10 (IL-10)-deficient mice spontaneously develop T cell-mediated colitis. Previous reports have shown that Matrine may reduce the symptoms of acute colitis induced by trinitrobenzene sulfonic acid (TNBS). However, whether Matrine impacts chronic colitis remains unknown. In this study, we investigated whether Matrine could limit the symptoms of spontaneously developed colitis and its potential molecular mechanisms. IL-10 deficient mice were given Matrine or a PBS control by oral gavage daily for 4weeks and were euthanized at week 2 or week 4. We measured body weight, colon length and weight, and histological scores. We also evaluated the spontaneous secretion of IL-12/23p40, IFN-γ and IL-17 in colon explant cultures as well as IFN-γ and IL-17 secretion in unseparated mesenteric lymph node (MLN) cells, and assessed IFN-γ, IL-17, IL-1β and IL-6 mRNA expression in colon tissue. In addition, we analyzed the proportions of CD4-positive and CD8-positive cells in unseparated MLN cells. Our results show that Matrine-treated mice exhibited better body weight recovery than controls and that histological scores and spontaneously secreted IL-12/23p40, IFN-γ and IL-17 in colon tissue were significantly decreased in treated mice compared with controls. The proportion of CD4-positive cells of MLNs in treated mice was significantly smaller than that in controls at week 4. Both cytokine production and mRNA expression of IFN-γ and IL-17 were significantly reduced in treated mice compared with controls. Taken together, our results indicate that Matrine may ameliorate spontaneously developed chronic colitis and could be considered as a therapeutic alternative for chronic colitis.

  3. Science observed: The mass-extinction debates

    Science.gov (United States)

    Glen, W.

    1994-01-01

    The upheaval triggered in 1980 by the Alvarez-Berkeley group impact hypothesis transformed the literature of mass extinctions from an unfocused, sporadic collection of papers that virtually ignored extraterrestrial causes and treated endogenous ones only sparingly better to an integrated, diverse body of literature. Research programs organized seemingly overnight spawned collaborative teams whose members, often from distant, isolated disciplines, redirected their careers in order to address the captivating, high-stakes issues. The initial, generally skeptical, cool reception of the impact hypothesis might have been predicted for any of a number of reasons: such an instantaneous catastrophe contravened earth science's reigning philosophy of uniformitarianism; it was formulated from a form of evidence - siderophile element anomalies - alien to the community charged with its appraisal; it advanced a causal mechanism that was improbable in terms of canonical knowledge; and it was proffered mainly by specialists alien to earth and biological science, especially paleobiology. Early on it became clear that irrespective of which causal hypothesis was chosen, the chosen one would be the strongest predictor of how the chooser would select and apply standards in assessing evidence bearing on all such hypothesis. Less strong correlation also appeared between disciplinary speciality and the assessment of evidence. Such correlations varied with the level of specialization; the most robust correlations appeared in the broadest areas of science practice. The gestalt (mindset) seemingly engendered by the embrace of an extinction hypothesis overrode, or was stronger than, the intellectual predispositions attributable to disciplinary specialty.

  4. Critical Multitype Branching Systems: Extinction Results

    CERN Document Server

    Kevei, Peter

    2011-01-01

    We consider a critical branching particle system in $\\R^d$, composed of individuals of a finite number of types $i\\in\\{1,...,K\\}$. Each individual of type $i$ moves independently according to a symmetric $\\alpha_i$-stable motion. We assume that the particle lifetimes and offspring distributions are type-dependent. Under the usual independence assumptions in branching systems, we prove extinction theorems in the following cases: (1) all the particle lifetimes have finite mean, or (2) there is a type whose lifetime distribution has heavy tail, and the other lifetimes have finite mean. We get a more complex dynamics by assuming in case (2) that the most mobile particle type corresponds to a finite-mean lifetime: in this case, local extinction of the population is determined by an interaction of the parameters (offspring variability, mobility, longevity) of the long-living type and those of the most mobile type. The proofs are based on a precise analysis of the occupation times of a related Markov renewal process...

  5. Patterns of species ranges, speciation, and extinction.

    Science.gov (United States)

    Birand, Aysegul; Vose, Aaron; Gavrilets, Sergey

    2012-01-01

    The exact nature of the relationship among species range sizes, speciation, and extinction events is not well understood. The factors that promote larger ranges, such as broad niche widths and high dispersal abilities, could increase the likelihood of encountering new habitats but also prevent local adaptation due to high gene flow. Similarly, low dispersal abilities or narrower niche widths could cause populations to be isolated, but such populations may lack advantageous mutations due to low population sizes. Here we present a large-scale, spatially explicit, individual-based model addressing the relationships between species ranges, speciation, and extinction. We followed the evolutionary dynamics of hundreds of thousands of diploid individuals for 200,000 generations. Individuals adapted to multiple resources and formed ecological species in a multidimensional trait space. These species varied in niche widths, and we observed the coexistence of generalists and specialists on a few resources. Our model shows that species ranges correlate with dispersal abilities but do not change with the strength of fitness trade-offs; however, high dispersal abilities and low resource utilization costs, which favored broad niche widths, have a strong negative effect on speciation rates. An unexpected result of our model is the strong effect of underlying resource distributions on speciation: in highly fragmented landscapes, speciation rates are reduced.

  6. Evolutionary Catastrophes: The Science of Mass Extinction

    Science.gov (United States)

    Hames, Willis

    The stories behind the greatest scientific controversies are more than entertaining. They provide windows into the evolution of scientific thought, scientific method, technological achievements and their research applications, and the influence of individuals and personalities on a community's acceptance of a theory Epic controversies surround the theories for Earth's mass extinction events, and none is more spectacular than the continuing polemic over the Cretaceous-Tertiary (K/T) mass extinctions and ultimate demise of the dinosaurs.In contrast to other great scientific debates, we tend to view the K/T event in the context of a crime scene, where the spectacularly diverse flora and fauna of a primordial Eden were unwittingly slain by one or more ruthless and efficient killers. A “foreign” suspect has been fingered; an intruder that killed suddenly and randomly has become the principal suspect. The main clues uncovered in the case include a global K/T iridium anomaly; shock-deformed minerals in K/T boundary sediments; the ˜6 5 m.y-old Deccan flood-basalt province, which covered an area roughly the size of France; and the ˜6 5 m.y-old Chicxulub impact crater in the Yucatan peninsula, which seems to be among the largest to have formed in the inner solar system over the past billion years.

  7. A robust nonparametric method for quantifying undetected extinctions.

    Science.gov (United States)

    Chisholm, Ryan A; Giam, Xingli; Sadanandan, Keren R; Fung, Tak; Rheindt, Frank E

    2016-06-01

    How many species have gone extinct in modern times before being described by science? To answer this question, and thereby get a full assessment of humanity's impact on biodiversity, statistical methods that quantify undetected extinctions are required. Such methods have been developed recently, but they are limited by their reliance on parametric assumptions; specifically, they assume the pools of extant and undetected species decay exponentially, whereas real detection rates vary temporally with survey effort and real extinction rates vary with the waxing and waning of threatening processes. We devised a new, nonparametric method for estimating undetected extinctions. As inputs, the method requires only the first and last date at which each species in an ensemble was recorded. As outputs, the method provides estimates of the proportion of species that have gone extinct, detected, or undetected and, in the special case where the number of undetected extant species in the present day is assumed close to zero, of the absolute number of undetected extinct species. The main assumption of the method is that the per-species extinction rate is independent of whether a species has been detected or not. We applied the method to the resident native bird fauna of Singapore. Of 195 recorded species, 58 (29.7%) have gone extinct in the last 200 years. Our method projected that an additional 9.6 species (95% CI 3.4, 19.8) have gone extinct without first being recorded, implying a true extinction rate of 33.0% (95% CI 31.0%, 36.2%). We provide R code for implementing our method. Because our method does not depend on strong assumptions, we expect it to be broadly useful for quantifying undetected extinctions. © 2016 Society for Conservation Biology.

  8. Atmospheric extinction in simulation tools for solar tower plants

    Science.gov (United States)

    Hanrieder, Natalie; Wilbert, Stefan; Schroedter-Homscheidt, Marion; Schnell, Franziska; Guevara, Diana Mancera; Buck, Reiner; Giuliano, Stefano; Pitz-Paal, Robert

    2017-06-01

    Atmospheric extinction causes significant radiation losses between the heliostat field and the receiver in a solar tower plants. These losses vary with site and time. State of the art is that in ray-tracing and plant optimization tools, atmospheric extinction is included by choosing between few constant standard atmospheric conditions. Even though some tools allow the consideration of site and time dependent extinction data, such data sets are nearly never available. This paper summarizes and compares the most common model equations implemented in several ray-tracing tools. There are already several methods developed and published to measure extinction on-site. An overview of the existing methods is also given here. Ray-tracing simulations of one exemplary tower plant at the Plataforma Solar de Almería (PSA) are presented to estimate the plant yield deviations between simulations using standard model equations instead of extinction time series. For PSA, the effect of atmospheric extinction accounts for losses between 1.6 and 7 %. This range is caused by considering overload dumping or not. Applying standard clear or hazy model equations instead of extinction time series lead to an underestimation of the annual plant yield at PSA. The discussion of the effect of extinction in tower plants has to include overload dumping. Situations in which overload dumping occurs are mostly connected to high radiation levels and low atmospheric extinction. Therefore it can be recommended that project developers should consider site and time dependent extinction data especially on hazy sites. A reduced uncertainty of the plant yield prediction can significantly reduce costs due to smaller risk margins for financing and EPCs. The generation of extinction data for several locations in form of representative yearly time series or geographical maps should be further elaborated.

  9. 3,4-Methylenedioxymethamphetamine facilitates fear extinction learning.

    Science.gov (United States)

    Young, M B; Andero, R; Ressler, K J; Howell, L L

    2015-09-15

    Acutely administered 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') has been proposed to have long-term positive effects on post-traumatic stress disorder (PTSD) symptoms when combined with psychotherapy. No preclinical data support a mechanistic basis for these claims. Given the persistent nature of psychotherapeutic gains facilitated by MDMA, we hypothesized that MDMA improves fear extinction learning, a key process in exposure-based therapies for PTSD. In these experiments, mice were first exposed to cued fear conditioning and treated with drug vehicle or MDMA before extinction training 2 days later. MDMA was administered systemically and also directly targeted to brain structures known to contribute to extinction. In addition to behavioral measures of extinction, changes in mRNA levels of brain-derived neurotrophic factor (Bdnf) and Fos were measured after MDMA treatment and extinction. MDMA (7.8 mg kg(-1)) persistently and robustly enhanced long-term extinction when administered before extinction training. MDMA increased the expression of Fos in the amygdala and medial prefrontal cortex (mPFC), whereas increases in Bdnf expression were observed only in the amygdala after extinction training. Extinction enhancements were recapitulated when MDMA (1 μg) was infused directly into the basolateral complex of the amygdala (BLA), and enhancement was abolished when BDNF signaling was inhibited before extinction. These findings suggest that MDMA enhances fear memory extinction through a BDNF-dependent mechanism, and that MDMA may be a useful adjunct to exposure-based therapies for PTSD and other anxiety disorders characterized by altered fear learning.

  10. Spontaneous internal carotid artery dissection.

    Science.gov (United States)

    Khimenko, L P; Esham, H R; Ahmed, W

    2000-10-01

    Once considered uncommon, spontaneous dissection of the carotid artery is an increasingly recognized cause of stroke, headache, cranial nerve palsy, or ophthalmologic events, especially in young adults. Even in the presence of existing signs and symptoms, the diagnosis can be missed by experienced physicians of all specialties. We report a case of spontaneous internal carotid artery dissection in a 38-year-old woman with a cortical stroke and visual disturbances as initial symptoms. The diagnosis was confirmed by magnetic resonance imaging/angiography and by angiography. Prompt anticoagulation was instituted, and the patient had complete resolution of symptoms. Cervicocephalic arterial dissection should be included in the differential diagnosis of the causes of cerebrovascular events.

  11. Spontaneous Photon Emission in Cavities

    Directory of Open Access Journals (Sweden)

    Alber G.

    2014-01-01

    Full Text Available We investigate spontaneous photon emission processes of two-level atoms in parabolic and ellipsoidal cavities thereby taking into account the full multimode scenario. In particular, we calculate the excitation probabilities of the atoms and the energy density of the resulting few-photon electromagnetic radiation field by using semiclassical methods for the description of the multimode scenario. Based on this approach photon path representations are developed for relevant transition probability amplitudes which are valid in the optical frequency regime where the dipole and the rotating-wave approximations apply. Comparisons with numerical results demonstrate the quality of these semiclassical results even in cases in which the wave length of a spontaneously emitted photon becomes comparable or even larger than characteristic length scales of the cavity. This is the dynamical regime in which diffraction effects become important so that geometric optical considerations are typically not applicable.

  12. Spontaneous Rotational Inversion in Phycomyces

    KAUST Repository

    Goriely, Alain

    2011-03-01

    The filamentary fungus Phycomyces blakesleeanus undergoes a series of remarkable transitions during aerial growth. During what is known as the stagea IV growth phase, the fungus extends while rotating in a counterclockwise manner when viewed from above (stagea IVa) and then, while continuing to grow, spontaneously reverses to a clockwise rotation (stagea IVb). This phase lasts for 24-48Ah and is sometimes followed by yet another reversal (stageAIVc) before the overall growth ends. Here, we propose a continuum mechanical model of this entire process using nonlinear, anisotropic, elasticity and show how helical anisotropy associated with the cell wall structure can induce spontaneous rotation and, under appropriate circumstances, the observed reversal of rotational handedness. © 2011 American Physical Society.

  13. Spontaneous resolution of subfoveal perfluorocarbon

    OpenAIRE

    Oellers P; Charkoudian LD; Hahn P

    2015-01-01

    Patrick Oellers,1 Leon D Charkoudian,2 Paul Hahn11Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA; 2Cape Fear Retinal Associates, Wilmington, NC, USA Abstract: Perfluorocarbon liquids (PFCL) have transformed the surgical approach to complex retinal detachments, but their use can be complicated by subretinal retention. Migration of peripherally located subretinal PFCL towards the fovea is well established, but spontaneous resolution of subfoveal PFCL witho...

  14. CSIR helps prevent spontaneous combustion

    Energy Technology Data Exchange (ETDEWEB)

    Vuuren, M. van (CSIR Energy Technology (South Africa))

    1992-03-01

    Heaps of stockpiled coal could present a fire hazard due to the risk of spontaneous combustion. Regular monitoring of stockpiles and bunker testing of coals help to prevent stockpile fires. This brief article describes the recent upgrading of the CSIR's bunker test facility that enables coal producers, users and exporters to test their products under simulated conditions that duplicate the actual conditions under which coal is stored. 2 photos.

  15. Spontaneous Perforation of Rectosigmoid Colon

    Directory of Open Access Journals (Sweden)

    Farhad Haj Sheikholeslami

    2010-12-01

    Full Text Available Spontaneous perforation of the sigmoid colon or rectom is definedas a sudden perforation of the colon in the absence of diseasessuch as tumors, diverticulosis or external injury. It is avery rare finding, and if neglected, results in severe peritonitisand high mortality. The causes of this rare condition are numerous,and in this case it might be due to the chronic constipationinduced by an anticholinergic antipsychotic.Iran J Med Sci 2010; 35(4: 339-341.

  16. Spontaneous Splenic Rupture in Melanoma

    Directory of Open Access Journals (Sweden)

    Hadi Mirfazaelian

    2014-01-01

    Full Text Available Spontaneous rupture of spleen due to malignant melanoma is a rare situation, with only a few case reports in the literature. This study reports a previously healthy, 30-year-old man who came with chief complaint of acute abdominal pain to emergency room. On physical examination, abdominal tenderness and guarding were detected to be coincident with hypotension. Ultrasonography revealed mild splenomegaly with moderate free fluid in abdominopelvic cavity. Considering acute abdominal pain and hemodynamic instability, he underwent splenectomy with splenic rupture as the source of bleeding. Histologic examination showed diffuse infiltration by tumor. Immunohistochemical study (positive for S100, HMB45, and vimentin and negative for CK, CD10, CK20, CK7, CD30, LCA, EMA, and chromogranin confirmed metastatic malignant melanoma. On further questioning, there was a past history of a nasal dark skin lesion which was removed two years ago with no pathologic examination. Spontaneous (nontraumatic rupture of spleen is an uncommon situation and it happens very rarely due to neoplastic metastasis. Metastasis of malignant melanoma is one of the rare causes of the spontaneous rupture of spleen.

  17. Late Pennsylvanian climate changes and palynomorph extinctions

    Science.gov (United States)

    Kosanke, R.M.; Cecil, C.B.

    1996-01-01

    A major floral change occurs in the Upper Pennsylvanian strata in the Midcontinent, Illinois basin, and in the northern Appalachian basin of eastern United States. Lycospora spp. (derived from arborescent lycopsids) became extinct along with some other palynomorph taxa. This investigation is concerned with the importance of this major floral change. Samples were studied from western Pennsylvania, eastern Ohio, and West Virginia (from a previous study) cover the stratigraphic interval from the Upper Freeport coal bed, uppermost part of the Allegheny Formation, to the Mahoning, Mason, Brush Creek, Wilgus, and Anderson coal beds in the lower part of the Conemaugh Formation. The floral change occurs either at or below the accepted Desmoinesian-Missourian boundary in the Midcontinent and Illinois basin, whereas in the northern Appalachians this change occurs in the lower part of the Conemaugh Formation, between the Mahoning and Brush Creek coal beds, or when the Mason is present, between the Mahoning and Mason coal beds. With the advent of late Middle Pennsylvanian time, the climate began to change from wet tropical to seasonal tropical. The Middle-Upper Pennsylvanian boundary is the culmination of this drying trend, which was marked by reduction of available water. The peat swamps are interpreted as having changed from the domed type of bog to the planar type under these circumstances. Thus, in general, the coals of the Conemaugh Formation are characteristically much thinner than those of the Allegheny Formation. This was caused by a number of factors including reduced or more seasonal rainfall, decline of arborescent lycopsids, and the increased dominance of herbaceous and fern plants. As a result, there are fewer minable coal beds in the Conemaugh Formation. The first coal bed above the extinction of Lycospora spp. is dominated by the palynomorph taxon Endosporites globiformis which is derived from a heterosporous, herbaceous lycopsid. However, Sigillaria, another

  18. Brachiopod faunas after the end Ordovician mass extinction from South China: Testing ecological change through a major taxonomic crisis

    Science.gov (United States)

    Huang, Bing; Harper, David A. T.; Rong, Jiayu; Zhan, Renbin

    2017-05-01

    Classification of extinction events and their severity is generally based on taxonomic counts. The ecological impacts of such events have been categorized and prioritized but rarely tested with empirical data. The ecology of the end Ordovician extinction and subsequent biotic recovery is tracked through abundant and diverse brachiopod faunas in South China. The spatial and temporal ranges of some 6500 identified specimens, from 10 collections derived from six localities were investigated by network and cluster analyses, nonmetric multidimensional scaling and a species abundance model. Depth zonations and structure of brachiopod assemblages along an onshore-offshore gradient in the late Katian were similar to those in the latest Ordovician-earliest Silurian (post-extinction fauna). Within this ecological framework, deeper-water faunas are partly replaced by new taxa; siliciclastic substrates continued to be dominated by the more 'Ordovician' orthides and strophomenides, shallow-water carbonate environments hosted atrypides, athyridides and pentamerides, with the more typical Ordovician brachiopod fauna continuing to dominate until the late Rhuddanian. The end Ordovician extinctions tested the resilience of the brachiopod fauna without damage to its overall ecological structure; that commenced later at the end of the Rhuddanian.

  19. Endangered Species. Management Improvements Could Enhance Recovery Program. Report to the Chairman, Subcommittee on Fisheries and Wildlife Conservation and the Environment, Committee on Merchant Marine and Fisheries, House of Representatives.

    Science.gov (United States)

    General Accounting Office, Washington, DC. Resources, Community, and Economic Development Div.

    Extinction of animal and plant species has become a serious problem that threatens to become more acute in coming years. The endangered species program was established to prevent further extinctions and ultimately recover species designated as threatened or endangered through the development and implementation of species recovery plans. Concerned…

  20. A comprehensive quantitative assessment of bird extinction risk in Brazil.

    Directory of Open Access Journals (Sweden)

    Nathália Machado

    Full Text Available In an effort to avoid species loss, scientists have focused their efforts on the mechanisms making some species more prone to extinction than others. However, species show different responses to threats given their evolutionary history, behavior, and intrinsic biological features. We used bird biological features and external threats to (1 understand the multiple pathways driving Brazilian bird species to extinction, (2 to investigate if and how extinction risk is geographically structured, and (3 to quantify how much diversity is currently represented inside protected areas. We modeled the extinction risk of 1557 birds using classification trees and evaluated the relative contribution of each biological feature and external threat in predicting extinction risk. We also quantified the proportion of species and their geographic range currently protected by the network of Brazilian protected areas. The optimal classification tree showed different pathways to bird extinction. Habitat conversion was the most important predictor driving extinction risk though other variables, such as geographic range size, type of habitat, hunting or trapping and trophic guild, were also relevant in our models. Species under higher extinction risk were concentrated mainly in the Cerrado Biodiversity Hotspot and were not quite represented inside protected areas, neither in richness nor range. Predictive models could assist conservation actions, and this study could contribute by highlighting the importance of natural history and ecology in these actions.