A repeating fast radio burst source in a globular cluster.

Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.

A repeating fast radio burst source localized to a nearby spiral galaxy.

Fast radio bursts (FRBs) are brief, bright, extragalactic radio flashes1,2. Their physical origin remains unknown, but dozens of possible models have been postulated3. Some FRB sources exhibit repeat bursts4-7. Although over a hundred FRB sources have been discovered8, only four have been localized and associated with a host galaxy9-12, and just one of these four is known to emit repeating FRBs9. The properties of the host galaxies, and the local environments of FRBs, could provide important clues about their physical origins. The first known repeating FRB, however, was localized to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources were localized to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. Here we report the precise localization of a second repeating FRB source6, FRB 180916.J0158+65, to a star-forming region in a nearby (redshift 0.0337 ± 0.0002) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. The lack of both a comparably luminous persistent radio counterpart and a high Faraday rotation measure6 further distinguish the local environment of FRB 180916.J0158+65 from that of the single previously localized repeating FRB source, FRB 121102. This suggests that repeating FRBs may have a wide range of luminosities, and originate from diverse host galaxies and local environments.

An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102.

Fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. The only known repeating fast radio burst source-FRB 121102-has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46 × 105 radians per square metre to +1.33 × 105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.

A direct localization of a fast radio burst and its host.

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

A strong magnetic field around the supermassive black hole at the centre of the Galaxy.

Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way. Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei. X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed. The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed. Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission--from radio to X-ray wavelengths--from the black hole.

Mental models in narrative comprehension.

Readers of stories construct mental models of the situation and characters described. They infer causal connections relating characters' actions to their goals. They also focus attention on characters' movements, thereby activating nearby parts of the mental model. This activation is revealed in readers' faster answering of questions about such parts, with less facilitation the greater their distance from the focus. Recently visited as well as imagined locations are also activated for several seconds. These patterns of temporary activation facilitate comprehension.

A turning point in mathematical learning theory.

This target article by Estes (1950) sparked the mathematical learning theory movement, which took seriously the goal of predicting quantitative details of behavioral data from standard learning experiments. The central constructs of Estes's theory were stimulus variability, stimulus sampling, and stimulus-response association by contiguity, all cast within a framework enabling predictions of response probabilities and latencies. The math models enterprise flourished during the period 1950-1975 and provided successful quantitative accounts of data from Pavlovian and instrumental conditioning, probability learning, verbal learning, concept identification, and other standard learning paradigms. The techniques have been assimilated into the armamentarium of theoretical psychology. Stimulus sampling theory has faded away as it has been transformed into modern descendants such as connectionism and information-processing models of cognition.

Radionuclide arthrography and transmission imaging for assessment of painful hip prostheses.

UNLABELLED: Interpretation of the radionuclide hip arthrogram may present difficulty because of a lack of anatomical reference information. Additional transmission images to determine tracer localization may facilitate scan interpretation. METHODS: Isotope arthrography (20 MBq 99mTc-tin colloid and 57Co transmission imaging) was prospectively performed on 21 patients with painful hip prostheses and suspected stem loosening. RESULTS: The radionuclide arthrogram was positive in 10 patients and negative in 9 patients. Extravasation of tracer, confirmed by transmission images, resulted in two nondiagnostic studies. Surgery was undertaken in 10 patients and loosening was confirmed in 6 patients. In this surgical subgroup, the scan was true-positive in six patients, true-negative in two patients, false-positive in one patient and nondiagnostic in one patient. CONCLUSIONS: The combination of radionuclide arthrography and transmission imaging facilitates scan interpretation and is a recommended method for investigating suspected loosening of the femoral stem.

Chronic (exertional) compartment syndrome of the legs diagnosed with thallous chloride scintigraphy.

Over the past 4 yr, we obtained 201Tl lower leg scans on 14 patients with suspected chronic exertional compartment syndrome. Qualitative assessment of the images revealed that 12 scans showed reversible compartment ischemia. Retrospective quantitation confirmed redistribution in seven of nine patients. Seven patients had surgery with partial or complete resolution of their symptoms.

Comparison of "direct" and "indirect" radionuclide cystography.

Thirty children were studied using both direct (catheter) and indirect techniques of radionuclide cystography. Of 54 ureters able to be compared, six showed vesico-ureteric reflux (VUR) on the direct study but were read as negative on the indirect cystogram, and five showed no reflux on the direct cystogram but were read as positive for VUR on the indirect study. (Sensitivity of 68% and specificity of 86%). Regarding ureters read as true positives on indirect study, if that ureter has ever shown reflux at any time, or if it drained a scarred kidney specificity was improved to 97% without changing the sensitivity. Concerns about the validity of indirect cystogram results and the ease of assessment and low radiation dose from the direct cystogram has made direct cystography our preferred technique.

Acute pulmonary hypersensitivity to carbamazepine.

Acute pulmonary hypersensitivity to carbamazepine (Tegretol) is reported, manifested by diffuse pulmonary infiltrates, skin rash, and eosinophilia. The reaction cleared on cessation of the drug. A lymphocyte transformation test was reactive to carbamazepine.

From conditioning to category learning: an adaptive network model.

We used adaptive network theory to extend the Rescorla-Wagner (1972) least mean squares (LMS) model of associative learning to phenomena of human learning and judgment. In three experiments subjects learned to categorize hypothetical patients with particular symptom patterns as having certain diseases. When one disease is far more likely than another, the model predicts that subjects will substantially overestimate the diagnosticity of the more valid symptom for the rare disease. The results of Experiments 1 and 2 provide clear support for this prediction in contradistinction to predictions from probability matching, exemplar retrieval, or simple prototype learning models. Experiment 3 contrasted the adaptive network model with one predicting pattern-probability matching when patients always had four symptoms (chosen from four opponent pairs) rather than the presence or absence of each of four symptoms, as in Experiment 1. The results again support the Rescorla-Wagner LMS learning rule as embedded within an adaptive network model.

Naturally occurring mood and learning: comment on Hasher, Rose, Zacks, Sanft, and Doren.

We comment on the article by Hasher, Rose, Zacks, Sanft, & Doren (1985) in which they failed to find mood-congruent learning (MCL). MCL occurs whenever subjects learn more about materials that are congruent with their moods (e.g., depressed subjects learn more sad material). Hasher et al. failed to observe MCL with normal college students who scored high versus low on the Beck Depression Inventory and an affect checklist; in contrast, positive MCL has been observed with clinically depressed patients and with normals given laboratory mood inductions. Hasher et al. argue that moderately depressed normal students may be qualitatively different from clinically depressed patients and mood-induced subjects. Although we accept the findings of Hasher et al., we think it is also plausible that MCL may be a general though small effect which is present among normal college students as well.

Massive hemoptysis: control by transcatheter bronchial artery embolization.

Massive hemoptysis (600 ml in 48 hours) has an ominous prognosis with a mortality of 50 to 100% in medically treated patients and up to 35% in patients undergoing operation. Surgical resection has been the procedure of choice in patients with massive hemoptysis. Those with a contraindication to operation present a particularly frustrating problem. We have treated 7 such patients with massive hemoptysis by transcatheter bronchial artery embolization. In all 7, the bleeding was arrested. Two patients died of recurrent hemoptysis, 1 ten days and the other 2 months following embolization, and 5 are well 1 month to one year later. Transcatheter bronchial artery embolization is a valuable therapeutic modality in patients with massive hemoptysis. However, the procedure is palliative, and, therefore, elective resection must be considered as definitive treatment in those patients who have no contraindication to operation.

Mood effects on person-perception judgments.

How does mood affect the way we learn about, judge, and remember characteristics of other people? This study looked at the effects of mood on impression formation and person memory. Realistic person descriptions containing positive and negative details were presented to subjects experiencing a manipulated happy or sad mood. Next, impression-formation judgments were obtained, and subjects' recall and recognition of details of the characters were assessed. Results showed that subjects spent longer learning about mood-consistent details but were faster in making mood-consistent judgments. Overall, happy subjects formed more favorable impressions and made more positive judgments than did sad subjects. Both cued recall and recognition memory were superior for mood-consistent characteristics. Positive mood had a more pronounced effect on judgments and memory than did negative mood. These findings are discussed in terms of recent theories of mood effects on cognition, and the likely implications of the results for everyday person-perception judgments are considered.

Learning and memory for personality prototypes.

Although personality traits are commonly assumed to be represented in memory as schemata, little research has addressed whether such schemata can be learned from observation. Subjects in three studies classified 60 person instances into group members and nonmembers as defined by the instances' match to a complex personality prototype. To simulate learning of fuzzy categories, each person instance provided conflicting cues to group membership. Learning for instances' group membership was excellent across studies. In Study 1, frequency of cues indicating group membership was greatly overestimated among nongroup instances. In Study 2, schema-consistent memory bias was revealed for person instances. In Study 3, schemata of consistently positive (or negative) traits were learned faster than arbitrary schemata. The findings implicated frequency sensitivity of memory (Estes, 1986), and a model of probabilistic cued-memory retrieval was developed to account for the effects. The findings were then discussed in relation to everyday cognitive performance.

Praise or blame? Affective influences on attributions for achievement.

Three experiments showed that mood influences achievement attributions and that cognitive processes underlie these effects. In Experiment 1, happy Ss made more internal and stable attributions for success than failure in typical 'life dilemmas'. In Experiment 2, attributions for real-life exam performance were more internal and stable in a happy than in a sad mood. Dysphoric moods resulted in self-critical rather than self-enhancing attributions, contrary to motivational theories, but consistent with cognitive models and the clinical literature on depression. In Experiment 3 this pattern was repeated with direct self vs. other comparisons, and for self-efficacy judgements. The results are interpreted as supporting cognitive rather than motivational theories of attribution biases. The implications of the results for clinical research, and contemporary affect-cognition theories are considered.

Eliciting cryptomnesia: unconscious plagiarism in a puzzle task.

In three experiments we investigated cryptomnesia (unconscious plagiarism) and source memory using a word-search puzzle task. Subjects first alternated with a "computer partner" in locating words from 4 puzzles. They then attempted to recall their previously generated items as well as to locate additional new words. Substantially more plagiarism was committed in these tasks than was observed in a study by A. S. Brown and D. R. Murphy (1989), in which Ss generated category exemplars. Manipulations of retention interval (Experiment 1) and degree of encoding (Experiments 2a and 2b) reliably influenced plagiarism rates. Source confusions from a modified recognition memory task (Experiment 3) were used as the basis for a unitary relative strength model to explain both source and occurrence (item) forgetting.

Improving recall by recoding interfering material at the time of retrieval.

Our experiments demonstrate that interference of an interpolated list of items with recall of an original list can be substantially reduced by forming Ss just before testing how to reorganize and simplify the interpolated material. In Experiments 1 and 2, Ss better recalled an initial serial list of letters when informed at testing that an interpolated list spelled a certain phrase backward. Similarly, in Experiments 3 and 4, Ss better recalled an initial list of cities when told that the interpolated cities were also names of former U.S. presidents. Control experiments rule out several simple explanations. In contrast to an editing hypothesis, the postorganizing clue helped recall even when problems of list differentiation were minimized. Current memory models appear unable to explain this benefit of a postlearning clue that enables Ss to segregate the interpolated material from the to-be-remembered material.

Selecting one among many referents in spatial situation models.

Five experiments related anaphor resolution to a classic memory variable, namely, interference created by multiple uses of a given object-concept, and by spatial distance of the referent from the reader's focus of attention. Participants memorized a diagram of a building with rooms containing objects, and then read narratives describing characters' activities there. Reading was self-paced word by word. Accessibility was measured by readers' time to understand anaphoric sentences containing a definite noun phrase referring to an object in its room. Spatial distance between the object and the current focus of attention increased reading times for names of the object, the room, and sentence wrap-up. Multiple examples of a target-object increased its reading time only if they were scattered across different rooms. An associative model of memory retrieval during text comprehension was used to interpret the complex pattern of results.