1,199 research outputs found

    Interpretive Habit Is Strengthened by Cognitive Bias Modification

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    We investigated the nature of the memory mechanisms underlying cognitive bias modification by applying Jacoby’s (1991) process-dissociation procedure to responses during the transfer task. In the two training conditions (negative and benign), students imagined themselves in 100 ambiguous scenarios, most with potentially negative resolutions; the ambiguity was resolved in a consistently negative or benign direction by completing the fragment of a final word. Control participants completed nonambiguous, nonemotional scenarios. Next, all participants responded on a final training block, where half of the scenarios were completed negatively and half benignly. Transfer was assessed by examining choices in the completion of test scenarios when participants were instructed to respond in the same way as they had to a final-block training scenario that was situationally similar. Benign training facilitated correct responding to benign analogs and impaired correct responding to negative analogs. Performance in the negative-training and control conditions was similar. Process-dissociation procedures revealed that this newly established habit and not controlled recollection provided the basis for transfer

    Brooding Deficits in Memory: Focusing Attention Improves Subsequent Recall

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    Ruminative habits of thought about one’s problems and the resulting consequences are correlated with symptoms of depression and cognitive biases (Nolen-Hoeksema, Wisco, & Lyubomirsky, 2008). In our orienting task, brooders and nonbrooders concentrated on self-focusing phrases while they were also exposed to neutral target words. On each trial in the unfocused condition, participants saw and then reported the target before concentrating on the phrase; in the focused condition, the target was reported after phrase concentration. A brooding-related deficit on a subsequent unexpected test of free and forced recall was obtained in the unfocused condition only. Brooders recalled more successfully in the focused than in the unfocused condition. Thus, impaired recall of material unrelated to self-concerns may be corrected in situations that constrain attention

    Recollection Is Impaired by the Modification of Interpretation Bias

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    The interpretation paradigm of cognitive-bias modification (CBM-I) was modified with instructions used in process-dissociation procedures for the purpose of investigating processes contributing to performance on the transfer task. In Experiment 1 nonanxious students were trained to interpret ambiguous situations in either a negative or benign way (or they read nonambiguous scenarios). They were then asked to respond to new ambiguous situations in the same way as contextually similar analogues during training, or to respond differently. Benign training proactively impaired memory for negative outcomes. This effect was replicated by anxious students in Experiment 2 and discussed with respect to the assumptions underlying process-dissociation procedures and directions for future research

    Itinerant-Electron Magnet of the Pyrochlore Lattice: Indium-Doped YMn2Zn20

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    We report on a ternary intermetallic compound, "YMn2Zn20", comprising a pyrochlore lattice made of Mn atoms. A series of In-doped single crystals undergo no magnetic long-range order down to 0.4 K, in spite of the fact that the Mn atom carries a local magnetic moment at high temperatures, showing Curie-Weiss magnetism. However, In-rich crystals exhibit spin-glass transitions at approximately 10 K due to a disorder arising from the substitution, while, with decreasing In content, the spin-glass transition temperature is reduced to 1 K. Then, heat capacity divided by temperature approaches a large value of 280 mJ K-2 mol-1, suggesting a significantly large mass enhancement for conduction electrons. This heavy-fermion-like behavior is not induced by the Kondo effect as in ordinary f-electron compounds, but by an alternative mechanism related to the geometrical frustration on the pyrochlore lattice, as in (Y,Sc)Mn2 and LiV2O4, which may allow spin entropy to survive down to low temperatures and to couple with conduction electrons.Comment: 5 pages, 4 figures, J. Phys. Soc. Jpn., in pres

    Search for a Correlation Between Very-High-Energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

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    We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E γ \u3e 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On ~8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits

    Active Galactic Nuclei under the scrutiny of CTA

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    Active Galactic Nuclei (hereafter AGN) produce powerful outflows which offer excellent conditions for efficient particle acceleration in internal and external shocks, turbulence, and magnetic reconnection events. The jets as well as particle accelerating regions close to the supermassive black holes (hereafter SMBH) at the intersection of plasma inflows and outflows, can produce readily detectable very high energy gamma-ray emission. As of now, more than 45 AGN including 41 blazars and 4 radiogalaxies have been detected by the present ground-based gamma-ray telescopes, which represents more than one third of the cosmic sources detected so far in the VHE gamma-ray regime. The future Cherenkov Telescope Array (CTA) should boost the sample of AGN detected in the VHE range by about one order of magnitude, shedding new light on AGN population studies, and AGN classification and unification schemes. CTA will be a unique tool to scrutinize the extreme high-energy tail of accelerated particles in SMBH environments, to revisit the central engines and their associated relativistic jets, and to study the particle acceleration and emission mechanisms, particularly exploring the missing link between accretion physics, SMBH magnetospheres and jet formation. Monitoring of distant AGN will be an extremely rewarding observing program which will inform us about the inner workings and evolution of AGN. Furthermore these AGN are bright beacons of gamma-rays which will allow us to constrain the extragalactic infrared and optical backgrounds as well as the intergalactic magnetic field, and will enable tests of quantum gravity and other "exotic" phenomena.Comment: 28 pages, 23 figure

    Observation of Markarian 421 in TeV Gamma Rays Over a 14-Year Time Span

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    The variability of the blazar Markarian 421 in TeV gamma rays over a 14-year time period has been explored with theWhipple 10 m telescope. It is shown that the dynamic range of its flux variations is large and similar to that in X-rays. A correlation between the X-ray and TeV energy bands is observed during some bright flares and when the complete data sets are binned on long timescales. The main database consists of 878.4 hours of observation with theWhipple telescope, spread over 783 nights. The peak energy response of the telescope was 400 GeV with 20% uncertainty. This is the largest database of any TeV-emitting active galactic nucleus (AGN) and hence was used to explore the variability profile of Markarian 421. The time-averaged flux from Markarian 421 over this period was 0.446+/-0.008 Crab flux units. The flux exceeded 10 Crab flux units on three separate occasions. For the 2000-2001 season the average flux reached 1.86 Crab units, while in the 1996-1997 season the average flux was only 0.23 Crab units

    A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30

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    B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2 1215+30 during routine monitoring observations of the blazar 1ES 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of . Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a one-zone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor , and an electron population with spectral index
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