The Dimorphos ejecta plume properties revealed by LICIACube

The Double Asteroid Redirection Test (DART) had an impact with Dimorphos (a satellite of the asteroid Didymos) on 26 September 20221. Ground-based observations showed that the Didymos system brightened by a factor of 8.3 after the impact because of ejecta, returning to the pre-impact brightness 23.7 days afterwards2. Hubble Space Telescope observations made from 15 minutes after impact to 18.5 days after, with a spatial resolution of 2.1 kilometres per pixel, showed a complex evolution of the ejecta3, consistent with other asteroid impact events. The momentum enhancement factor, determined using the measured binary period change4, ranges between 2.2 and 4.9, depending on the assumptions about the mass and density of Dimorphos5. Here we report observations from the LUKE and LEIA instruments on the LICIACube cube satellite, which was deployed 15 days in advance of the impact of DART. Data were taken from 71 seconds before the impact until 320 seconds afterwards. The ejecta plume was a cone with an aperture angle of 140 ± 4 degrees. The inner region of the plume was blue, becoming redder with increasing distance from Dimorphos. The ejecta plume exhibited a complex and inhomogeneous structure, characterized by filaments, dust grains and single or clustered boulders. The ejecta velocities ranged from a few tens of metres per second to about 500 metres per second.

Can extreme experiences enhance creativity? The case of the underwater nightclub

Creativity is a valuable commodity. Research has revealed some identifying characteristics of creative people and some of the emotional states that can bring out the most creativity in all of us. It has also been shown that the long-term experience of different cultures and lifestyles that is the result of travel and immigration can also enhance creativity. However, the role of one-off, extreme, or unusual experiences on creativity has not been directly observed before. In part, that may be because, by their very nature, such experiences are very difficult to bring into the laboratory. Here, we brought the tools and empirical methods of the laboratory into the wild, measuring the psychological effects of a unique multisensory experience: an underwater nightclub. We showed – with fully randomized and experimentally controlled conditions – that such an experience boosted measures of divergent thinking in participants. This demonstrates that one element of creativity can be directly enhanced by unusual situations, and that experimental tools of psychology can be used to investigate a range of consumer experiences.

Video meeting signals: Experimental evidence for a technique to improve the experience of video conferencing

We found evidence from two experiments that a simple set of gestural techniques can improve the experience of online meetings. Video conferencing technology has practical benefits, but psychological costs. It has allowed industry, education and social interactions to continue in some form during the covid-19 lockdowns. But it has left many users feeling fatigued and socially isolated, perhaps because the limitations of video conferencing disrupt users’ ability to coordinate interactions and foster social affiliation. Video Meeting Signals (VMS™) is a simple technique that uses gestures to overcome some of these limitations. First, we carried out a randomised controlled trial with over 100 students, in which half underwent a short training session in VMS. All participants rated their subjective experience of two weekly seminars, and transcripts were objectively coded for the valence of language used. Compared to controls, students with VMS training rated their personal experience, their feelings toward their seminar group, and their perceived learning outcomes as significantly higher. Also, they were more likely to use positive language and less likely to use negative language. A second, larger experiment replicated the first, and added a condition where groups were given a version of the VMS training but taught to use emoji response buttons rather than gestures to signal the same information. The emoji-trained groups did not experience the same improvement as the VMS groups. By exploiting the specific benefits of gestural communication, VMS has great potential to overcome the psychological problems of group video meetings.

We predict a riot: inequity, relative deprivation and collective destruction in the laboratory

Riots are unpredictable and dangerous. Our understanding of the factors that cause riots is based on correlational observations of population data, or post hoc introspection of individuals. To complement these accounts, we developed innovative experimental techniques, investigated the psychological factors of rioting and explored their consequences with agent-based simulations. We created a game, 'Parklife', that physically co-present participants played using smartphones. In two teams, participants tapped on their screen to grow trees and flowerbeds on separate but adjacent virtual parks. Participants could also tap to vandalize the other team's park. In some conditions, we surreptitiously introduced inequity between the teams so that one (the disadvantaged team) had to tap more for each reward. The experience of inequity caused the disadvantaged team to engage in more destruction, and to report higher relative deprivation and frustration. Agent-based models suggested that acts of destruction were driven by the interaction between individual level of frustration and the team's behaviour. Our results provide insights into the psychological mechanisms underlying collective action.

Acting Surprised: Comparing Perceptions of Different Dynamic Deliberate Expressions

People are accurate at classifying emotions from facial expressions but much poorer at determining if such expressions are spontaneously felt or deliberately posed. We explored if the method used by senders to produce an expression influences the decoder’s ability to discriminate authenticity, drawing inspiration from two well-known acting techniques: the Stanislavski (internal) and Mimic method (external). We compared spontaneous surprise expressions in response to a jack-in-the-box (genuine condition), to posed displays of senders who either focused on their past affective state (internal condition) or the outward expression (external condition). Although decoders performed better than chance at discriminating the authenticity of all expressions, their accuracy was lower in classifying external surprise compared to internal surprise. Decoders also found it harder to discriminate external surprise from spontaneous surprise and were less confident in their decisions, perceiving these to be similarly intense but less genuine-looking. The findings suggest that senders are capable of voluntarily producing genuine-looking expressions of emotions with minimal effort, especially by mimicking a genuine expression. Implications for research on emotion recognition are discussed.

Veracity judgement, not accuracy: Reconsidering the role of facial expressions, empathy, and emotion recognition training on deception detection

People hold strong beliefs about the role of emotional cues in detecting deception. While research on the diagnostic value of such cues has been mixed, their influence on human veracity judgements is yet to be fully explored. Here, we address the relationship between emotional information and veracity judgements. In Study 1, the role of emotion recognition in the process of detecting naturalistic lies was investigated. Decoders’ veracity judgements were compared based on differences in trait empathy and their ability to recognise microexpressions and subtle expressions. Accuracy was found to be unrelated to facial cue recognition and negatively related to empathy. In Study 2, we manipulated decoders’ emotion recognition ability and the type of lies they saw: experiential or affective (emotional and unemotional). Decoders received either emotion recognition training, bogus training, or no training. In all scenarios, training did not affect veracity judgements. Experiential lies were easier to detect than affective lies; however, affective unemotional lies were overall the hardest to judge. The findings illustrate the complex relationship between emotion recognition and veracity judgements, with abilities for facial cue detection being high yet unrelated to deception accuracy.

Self-categorization as a basis of behavioural mimicry: Experiments in The Hive

INTRODUCTION

Do we always do what others do, and, if not, when and under what conditions do we do so? In this paper we test the hypothesis that mimicry is moderated by the mere knowledge of whether the source is a member of the same social category as ourselves.

METHODS

We investigated group influence on mimicry using three tasks on a software platform which interfaces with mobile computing devices to allow the controlled study of collective behaviour in an everyday environment.

RESULTS

Overall, participants (N = 965) were influenced by the movements of confederates (represented as dots on a screen) who belonged to their own category in both purposive and incidental tasks.

CONCLUSION

Our results are compatible with collective level explanations of social influence premised on shared social identification. This includes both a heuristic of unintended mimicry (the acts of group members are diagnostic of how one should act), and communication of affiliation (based on a desire to make one's group cohesive). The results are incompatible with traditional 'contagion' accounts which suggest mimicry is automatic and inevitable. The results have practical implications for designing behavioural interventions which can harness the power of copying behaviour, for example in emergency evacuations.

Engagement in video and audio narratives: contrasting self-report and physiological measures

Stories play a fundamental role in human culture. They provide a mechanism for sharing cultural identity, imparting knowledge, revealing beliefs, reinforcing social bonds and providing entertainment that is central to all human societies. Here we investigated the extent to which the delivery medium of a story (audio or visual) affected self-reported and physiologically measured engagement with the narrative. Although participants self-reported greater involvement for watching video relative to listening to auditory scenes, stronger physiological responses were recorded for auditory stories. Sensors placed at their wrists showed higher and more variable heart rates, greater electrodermal activity, and even higher body temperatures. We interpret these findings as evidence that the stories were more cognitively and emotionally engaging at a physiological level when presented in an auditory format. This may be because listening to a story, rather than watching a video, is a more active process of co-creation, and that this imaginative process in the listener's mind is detectable on the skin at their wrist.

Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu

Asteroid shapes and hydration levels can serve as tracers of their history and origin. For instance, the asteroids (162173) Ryugu and (101955) Bennu have an oblate spheroidal shape with a pronounced equator, but contain different surface hydration levels. Here we show, through numerical simulations of large asteroid disruptions, that oblate spheroids, some of which have a pronounced equator defining a spinning top shape, can form directly through gravitational reaccumulation. We further show that rubble piles formed in a single disruption can have similar porosities but variable degrees of hydration. The direct formation of top shapes from single disruption alone can explain the relatively old crater-retention ages of the equatorial features of Ryugu and Bennu. Two separate parent-body disruptions are not necessarily required to explain their different hydration levels.

The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt

The New Horizons spacecraft's encounter with the cold classical Kuiper Belt object (486958) Arrokoth (provisional designation 2014 MU₆₉) revealed a contact-binary planetesimal. We investigated how Arrokoth formed and found that it is the product of a gentle, low-speed merger in the early Solar System. Its two lenticular lobes suggest low-velocity accumulation of numerous smaller planetesimals within a gravitationally collapsing cloud of solid particles. The geometric alignment of the lobes indicates that they were a co-orbiting binary that experienced angular momentum loss and subsequent merger, possibly because of dynamical friction and collisions within the cloud or later gas drag. Arrokoth's contact-binary shape was preserved by the benign dynamical and collisional environment of the cold classical Kuiper Belt and therefore informs the accretion processes that operated in the early Solar System.

Association of Periodontal Disease and Histologic Lesions in Multiple Organs from 45 Dogs

Forty-five mixed breed dogs were evaluated for the presence and extent of periodontal disease. Histopathology was performed on samples of lung, myocardium, liver, kidney, tonsil, spleen, submandibular lymph node and tracheobronchial lymph node. Mitral valves were evaluated grossly. Statistical analysis was used to determine if there was a relationship between the extent of periodontal disease and histopathologic changes in the tissues examined. In the forty-five dogs studied, an association was found between periodontal disease and histopathologic changes in kidney, myocardium (papillary muscle), and liver.

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU₆₉, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU₆₉ is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU₆₉'s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

Detecting Genuine and Deliberate Displays of Surprise in Static and Dynamic Faces

People are good at recognizing emotions from facial expressions, but less accurate at determining the authenticity of such expressions. We investigated whether this depends upon the technique that senders use to produce deliberate expressions, and on decoders seeing these in a dynamic or static format. Senders were filmed as they experienced genuine surprise in response to a jack-in-the-box (Genuine). Other senders faked surprise with no preparation (Improvised) or after having first experienced genuine surprise themselves (Rehearsed). Decoders rated the genuineness and intensity of these expressions, and the confidence of their judgment. It was found that both expression type and presentation format impacted decoder perception and accurate discrimination. Genuine surprise achieved the highest ratings of genuineness, intensity, and judgmental confidence (dynamic only), and was fairly accurately discriminated from deliberate surprise expressions. In line with our predictions, Rehearsed expressions were perceived as more genuine (in dynamic presentation), whereas Improvised were seen as more intense (in static presentation). However, both were poorly discriminated as not being genuine. In general, dynamic stimuli improved authenticity discrimination accuracy and perceptual differences between expressions. While decoders could perceive subtle differences between different expressions (especially from dynamic displays), they were not adept at detecting if these were genuine or deliberate. We argue that senders are capable of producing genuine-looking expressions of surprise, enough to fool others as to their veracity.

The Choreography of Group Affiliation

When two people move in synchrony, they become more social. Yet it is not clear how this effect scales up to larger numbers of people. Does a group need to move in unison to affiliate, in what we term unitary synchrony; or does affiliation arise from distributed coordination, patterns of coupled movements between individual members of a group? We developed choreographic tasks that manipulated movement synchrony without explicitly instructing groups to move in unison. Wrist accelerometers measured group movement dynamics and we applied cross-recurrence analysis to distinguish the temporal features of emergent unitary synchrony (simultaneous movement) and distributed coordination (coupled movement). Participants' unitary synchrony did not predict pro-social behavior, but their distributed coordination predicted how much they liked each other, how they felt toward their group, and how much they conformed to each other's opinions. The choreography of affiliation arises from distributed coordination of group movement dynamics.

Social Beliefs and Visual Attention: How the Social Relevance of a Cue Influences Spatial Orienting

We are highly tuned to each other's visual attention. Perceiving the eye or hand movements of another person can influence the timing of a saccade or the reach of our own. However, the explanation for such spatial orienting in interpersonal contexts remains disputed. Is it due to the social appearance of the cue—a hand or an eye—or due to its social relevance—a cue that is connected to another person with attentional and intentional states? We developed an interpersonal version of the Posner spatial cueing paradigm. Participants saw a cue and detected a target at the same or a different location, while interacting with an unseen partner. Participants were led to believe that the cue was either connected to the gaze location of their partner or was generated randomly by a computer (Experiment 1), and that their partner had higher or lower social rank while engaged in the same or a different task (Experiment 2). We found that spatial cue‐target compatibility effects were greater when the cue related to a partner's gaze. This effect was amplified by the partner's social rank, but only when participants believed their partner was engaged in the same task. Taken together, this is strong evidence in support of the idea that spatial orienting is interpersonally attuned to the social relevance of the cue—whether the cue is connected to another person, who this person is, and what this person is doing—and does not exclusively rely on the social appearance of the cue. Visual attention is not only guided by the physical salience of one's environment but also by the mental representation of its social relevance.

Joint action aesthetics

Synchronized movement is a ubiquitous feature of dance and music performance. Much research into the evolutionary origins of these cultural practices has focused on why humans perform rather than watch or listen to dance and music. In this study, we show that movement synchrony among a group of performers predicts the aesthetic appreciation of live dance performances. We developed a choreography that continuously manipulated group synchronization using a defined movement vocabulary based on arm swinging, walking and running. The choreography was performed live to four audiences, as we continuously tracked the performers' movements, and the spectators' affective responses. We computed dynamic synchrony among performers using cross recurrence analysis of data from wrist accelerometers, and implicit measures of arousal from spectators' heart rates. Additionally, a subset of spectators provided continuous ratings of enjoyment and perceived synchrony using tablet computers. Granger causality analyses demonstrate predictive relationships between synchrony, enjoyment ratings and spectator arousal, if audiences form a collectively consistent positive or negative aesthetic evaluation. Controlling for the influence of overall movement acceleration and visual change, we show that dance communicates group coordination via coupled movement dynamics among a group of performers. Our findings are in line with an evolutionary function of dance-and perhaps all performing arts-in transmitting social signals between groups of people. Human movement is the common denominator of dance, music and theatre. Acknowledging the time-sensitive and immediate nature of the performer-spectator relationship, our study makes a significant step towards an aesthetics of joint actions in the performing arts.

Verbal Synchrony and Action Dynamics in Large Groups

While synchronized movement has been shown to increase liking and feelings of togetherness between people, we investigated whether collective speaking in time would change the way that larger groups played a video game together. Anthropologists have speculated that the function of interpersonal coordination in dance, chants, and singing is not just to produce warm, affiliative feelings, but also to improve group action. The group that chants and dances together hunts well together. Direct evidence for this is sparse, as research so far has mainly studied pairs, the effects of coordinated physical movement, and measured cooperation and affiliative decisions. In our experiment, large groups of people were given response handsets to play a computer game together, in which only joint coordinative efforts lead to success. Before playing, the synchrony of their verbal behavior was manipulated. After the game, we measured group members’ affiliation toward their group, their performance on a memory task, and the way in which they played the group action task. We found that verbal synchrony in large groups produced affiliation, enhanced memory performance, and increased group members’ coordinative efforts. Our evidence suggests that the effects of synchrony are stable across modalities, can be generalized to larger groups and have consequences for action coordination.

The Art of Conversation Is Coordination

When two people discuss something they can see in front of them, what is the relationship between their eye movements? We recorded the gaze of pairs of subjects engaged in live, spontaneous dialogue. Cross-recurrence analysis revealed a coupling between the eye movements of the two conversants. In the first study, we found their eye movements were coupled across several seconds. In the second, we found that this coupling increased if they both heard the same background information prior to their conversation. These results provide a direct quantification of joint attention during unscripted conversation and show that it is influenced by knowledge in the common ground.

Breaking the Fourth Wall of Cognitive Science

Research in cognitive science typically places a boundary between participants and the stimuli they are asked to process. While this separation affords experimental control, it can also severely limit the generalizability of the conclusions that are drawn. Here, we review new evidence that some conclusions that have been drawn about social attention do not extend beyond the laboratory. They fundamentally misrepresent how social attention operates in natural social contexts. Critically, these difficulties have led to renewed interest in the dual function of gaze—when in authentic social situations, the eyes both collect information from the environment (an encoding function) and communicate one’s mental states to others (a signaling function)—which traditional social-attention paradigms arguably have failed to capture. We review this recent work and discuss the utility of adopting more naturalistic methods in cognitive science.

Conversation and coordinative structures

People coordinate body postures and gaze patterns during conversation. We review literature showing that (1) action embodies cognition, (2) postural coordination emerges spontaneously when two people converse, (3) gaze patterns influence postural coordination, (4) gaze coordination is a function of common ground knowledge and visual information that conversants believe they share, and (5) gaze coordination is causally related to mutual understanding. We then consider how coordination, generally, can be understood as temporarily coupled neuromuscular components that function as a collective unit known as a coordinative structure in the motor control literature. We speculate that the coordination of gaze and body sway found in conversation may be understood as a cross-person coordinative structure that embodies the goals of the joint action system.

Exploring the movement dynamics of deception

Both the science and the everyday practice of detecting a lie rest on the same assumption: hidden cognitive states that the liar would like to remain hidden nevertheless influence observable behavior. This assumption has good evidence. The insights of professional interrogators, anecdotal evidence, and body language textbooks have all built up a sizeable catalog of non-verbal cues that have been claimed to distinguish deceptive and truthful behavior. Typically, these cues are discrete, individual behaviors—a hand touching a mouth, the rise of a brow—that distinguish lies from truths solely in terms of their frequency or duration. Research to date has failed to establish any of these non-verbal cues as a reliable marker of deception. Here we argue that perhaps this is because simple tallies of behavior can miss out on the rich but subtle organization of behavior as it unfolds over time. Research in cognitive science from a dynamical systems perspective has shown that behavior is structured across multiple timescales, with more or less regularity and structure. Using tools that are sensitive to these dynamics, we analyzed body motion data from an experiment that put participants in a realistic situation of choosing, or not, to lie to an experimenter. Our analyses indicate that when being deceptive, continuous fluctuations of movement in the upper face, and somewhat in the arms, are characterized by dynamical properties of less stability, but greater complexity. For the upper face, these distinctions are present despite no apparent differences in the overall amount of movement between deception and truth. We suggest that these unique dynamical signatures of motion are indicative of both the cognitive demands inherent to deception and the need to respond adaptively in a social context.

Joint perception: gaze and social context

We found that the way people looked at images was influenced by their belief that others were looking too. If participants believed that an unseen other person was also looking at what they could see, it shifted the balance of their gaze between negative and positive images. The direction of this shift depended upon whether participants thought that later they would be compared against the other person or would be collaborating with them. Changes in the social context influenced both gaze and memory processes, and were not due just to participants' belief that they are looking at the same images, but also to the belief that they are doing the same task. We believe that the phenomenon of joint perception reveals the pervasive and subtle effect of social context upon cognitive and perceptual processes.

Infants learn about objects from statistics and people

In laboratory experiments, infants are sensitive to patterns of visual features that co-occur (e.g., Fiser & Aslin, 2002). Once infants learn the statistical regularities, however, what do they do with that knowledge? Moreover, which patterns do infants learn in the cluttered world outside of the laboratory? Across 4 experiments, we show that 9-month-olds use this sensitivity to make inferences about object properties. In Experiment 1, 9-month-old infants expected co-occurring visual features to remain fused (i.e., infants looked longer when co-occurring features split apart than when they stayed together). Forming such expectations can help identify integral object parts for object individuation, recognition, and categorization. In Experiment 2, we increased the task difficulty by presenting the test stimuli simultaneously with a different spatial layout from the familiarization trials to provide a more ecologically valid condition. Infants did not make similar inferences in this more distracting test condition. However, Experiment 3 showed that a social cue did allow inferences in this more difficult test condition, and Experiment 4 showed that social cues helped infants choose patterns among distractor patterns during learning as well as during test. These findings suggest that infants can use feature co-occurrence to learn about objects and that social cues shape such foundational learning in distraction-filled environments.

The dynamics of reference and shared visual attention

In the tangram task, two participants are presented with the same set of abstract shapes portrayed in different orders. One participant must instruct the other to arrange their shapes so that the orders match. To do this, they must find a way to refer to the abstract shapes. In the current experiment, the eye movements of pairs of participants were tracked while they were engaged in a computerized version of the task. Results revealed the canonical tangram effect: participants became faster at completing the task from round 1 to round 3. Also, their eye-movements synchronized over time. Cross-recurrence analysis was used to quantify this coordination, and showed that as participants' words coalesced, their actions approximated a single coordinated system.

Spatial language, visual attention, and perceptual simulation

Spatial language descriptions, such as The bottle is over the glass, direct the attention of the hearer to particular aspects of the visual world. This paper asks how they do so, and what brain mechanisms underlie this process. In two experiments employing behavioural and eye tracking methodologies we examined the effects of spatial language on people's judgements and parsing of a visual scene. The results underscore previous claims regarding the importance of object function in spatial language, but also show how spatial language differentially directs attention during examination of a visual scene. We discuss implications for existing models of spatial language, with associated brain mechanisms.

When facts go down the rabbit hole: contrasting features and objecthood as indexes to memory

People will often look to empty, uninformative locations in the world when trying to recall spoken information. This spatial indexing behaviour occurs when the information had previously been associated with those locations. It remains unclear, however, whether this behaviour is an example of a simple association across perceptual and cognitive systems, or whether location information plays a role in memory retrieval. In the current study, we investigate whether higher-level cognitive processes, such as object-based attention, are involved in spatial indexing. Participants saw creatures burrowing around the screen, appearing from underground to tell them facts. They saw the same creature in two locations, or two identical creatures in two locations, depending on spatiotemporal cues conveyed by a burrowing animation. While answering questions, we found that participants relied on these spatiotemporal cues, fixating the previous locations of the creature associated with the relevant fact, rather than the location of an identical creature. We interpret these findings in terms of an object-based attentional mechanism that is common to semantic memory and scene perception, and allows 'external memory' to be exploited in a dynamic environment.

Location, location, location: development of spatiotemporal sequence learning in infancy

We investigated infants' sensitivity to spatiotemporal structure. In Experiment 1, circles appeared in a statistically defined spatial pattern. At test 11-month-olds, but not 8-month-olds, looked longer at a novel spatial sequence. Experiment 2 presented different color/shape stimuli, but only the location sequence was violated during test; 8-month-olds preferred the novel spatial structure, but 5-month-olds did not. In Experiment 3, the locations but not color/shape pairings were constant at test; 5-month-olds showed a novelty preference. Experiment 4 examined "online learning": We recorded eye movements of 8-month-olds watching a spatiotemporal sequence. Saccade latencies to predictable locations decreased. We argue that temporal order statistics involving informative spatial relations become available to infants during the first year after birth, assisted by multiple cues.

RNA backbone rotamers – finding your way in seven dimensions

Despite the importance of local structural detail for a mechanistic understanding of RNA catalysis and binding functions, RNA backbone conformation has been recalcitrant to analysis. There are too many variable dihedral angles per residue, and their raw empirical distributions are poorly clustered. This study applies quality-filtering techniques (using resolution, crystallographic B factor and all-atom-steric clashes) to the backbone dihedral angle distributions from a selected 8636 residue RNA database. With noise levels significantly decreased, clear signal appears for the underlying angle preferences. We analyse the multidimensional backbone dihedral distributions within sugar-to-sugar ‘suites’ rather than chemical residues due to the greater base interaction and steric interdependence within the suite. The final result is a small library of RNA backbone rotamers, each represented by a data cluster in seven-dimensional dihedral space, which should provide valid conformations for nearly all RNA backbones encountered in experimental structures. We are in the process of improving that library, and developing tools and applications for it in structure determination and analysis.

Markers of bone metabolism in dog breeds of different size

Serum and urinary markers of bone turnover may be of value in animals as noninvasive tools for determining the response of the skeleton to disease and injury. Although normal values for bone markers have been reported for the Beagle, concerns remain that breed to breed differences will complicate the interpretation of bone marker data in dogs. To explore this, we examined serum bone markers in two breeds of vastly different size, Pomeranians and Irish Wolfhounds. Our hypothesis was that serum concentrations of bone markers are similar in toy and giant dog breeds and fall within the same range as those reported for Beagles. Bone alkaline phosphatase (BALP) and carboxy-terminal telopeptide of type I collagen (ICTP), respectively markers of bone formation and bone resorption, were measured in age matched Pomeranians (n=14) and Irish Wolfhounds (n=14). No statistically significant differences between the mean BALP and mean ICTP serum concentrations from Pomeranians and Irish Wolfhounds were found. All BALP and ICTP concentrations were within the reference range reported for Beagles. The results of this study suggest that serum BALP and ICTP concentrations in giant and toy breeds are the same as in Beagles and that these assays may be used for dogs of all sizes.

Multimodal Events and Moving Locations: Eye Movements of Adults and 6-Month-Olds Reveal Dynamic Spatial Indexing

The ability to keep track of locations in a dynamic, multimodal environment is crucial for successful interactions with other people and objects. The authors investigated the existence and flexibility of spatial indexing in adults and 6-month-old infants by adapting an eye-tracking paradigm from D. C. Richardson and M. J. Spivey (2000). Multimodal events were presented in specific locations, and eye movements were measured when the auditory portion of the stimulus was presented without its visual counterpart. Experiment 1 showed that adults spatially index auditory information even when the original associated locations move. Experiments 2 and 3 showed that infants are capable of both binding multimodal events to locations and tracking those locations when they move.

Biological variability in serum and urinary indices of bone formation and resorption in dogs

Serum and urinary assays of bone markers provide a noninvasive alternative to bone biopsy in the study of bone metabolism in humans. Many of the commercial assays that were originally developed for use in humans have been shown to cross-react in dogs, and it should therefore be possible to use these assays to study bone remodeling in dogs. The interpretation of bone marker data in humans is hampered by extensive inter- and intra-subject variability. The specific aim of this study was therefore to determine the extent of biological variability in bone markers in dogs. Serum and urine samples were collected every 4 hours over a 24-hour period (short-term study), and every week over a 12-week period (long-term study). Serum bone-specific alkaline phosphatase (BALP) and urinary deoxypyridinoline (Dpd) and N-terminal telopeptide of collagen (NTx) were measured with commercial enzyme immunoassays. Serum osteocalcin (OC) and carboxyterminal crosslinked telopeptide of type I collagen (ICTP) were measured with commercial radioimmunoassays. In the short-term study, statistically significant diurnal rhythms were identified for OC, BALP, ICTP, and Dpd. No clear rhythm was evident for NTx. There was no evidence of statistically significant long-term variability in marker excretion over the 12 weeks. Our findings confirm the utility of these assays in dogs. However, as in humans, care must be taken to ensure that specimens are collected at a consistent time of day. Moreover, given the inherent variability in marker excretion in individual animals, the most appropriate use for these assays is as a screening tool for cohort studies, rather than as a diagnostic or prognostic tool in the individual animal.

Collisions and gravitational reaccumulation: forming asteroid families and satellites

Numerical simulations of the collisional disruption of large asteroids show that although the parent body is totally shattered, subsequent gravitational reaccumulation leads to the formation of an entire family of large and small objects with dynamical properties similar to those of the parent body. Simulations were performed in two different collisional regimes representative of asteroid families such as Eunomia and Koronis. Our results indicate that all large family members must be made of gravitationally reaccumulated fragments; that the post-collision member size distribution and the orbital dispersion are steeper and smaller, respectively, than for the evolved families observed today; and that satellites form frequently around family members.

Evaluation of susceptibility testing to detect fluoroquinolone resistance mechanisms in Streptococcus pneumoniae

To determine if susceptibility testing of Streptococcus pneumoniae could detect those isolates that had one of the recognized mechanisms of fluoroquinolone resistance, 101 isolates were selected; the levofloxacin MIC for 28 of these isolates was > or =4 microg/ml. Only isolates with both parC and gyrA mutations or with no recognized resistance mechanisms were reliably identified by using these results. Isolates with only a parC mutation could not be detected reliably using any susceptibility testing method.

Trimethoprim-sulfamethoxazole induced aseptic meningitis in a renal transplant patient

A 45-year-old man underwent renal transplant for end-stage renal disease complicating systemic lupus erythematosis. Within 24 hours of initiating Pneumocystis carinii pneumonia (PCP) prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) he developed fever and confusion. Cerebrospinal fluid examination revealed a pleocytosis but cultures were negative. The patient improved within three days after cessation of the TMP-SMX but symptoms recurred rapidly upon drug rechallenge. Drug-induced aseptic meningitis is an uncommon but well described clinical entity. This is the first case described in a patient following renal transplantation. The literature is reviewed and the clinical features, diagnostic challenges and possible mechanisms of TMP-SMX-induced aseptic meningitis are discussed. This problem may be more common in the transplant population than is recognized given the difficulty of diagnosis combined with the widespread use of TMP-SMX as PCP prophylaxis.

Exploring steric constraints on protein mutations using MAGE/PROBE

When planning a mutation to test some hypothesis, one crucial question is whether the new side chain is compatible with the existing structure; only if it is compatible can the interpretation of mutational results be straightforward. This paper presents a simple way of using the sensitive geometry of all-atom contacts (including hydrogens) to answer that question. The interactive MAGE/PROBE system lets the biologist explore conformational space for the mutant side chain, with an interactively updated kinemage display of its all-atom contacts to the original structure. The Autobondrot function in PROBE systematically explores that same conformational space, outputting contact scores at each point, which are then contoured and displayed. These procedures are applied here in two types of test cases, with known mutant structures. In ricin A chain, the ability of a neighboring glutamate to rescue activity of an active-site mutant is modeled successfully. In T4 lysozyme, six mutations to Leu are analyzed within the wild-type background structure, and their Autobondrot score maps correctly predict whether or not their surroundings must shift significantly in the actual mutant structures; interactive examination of contacts for the conformations involved explains which clashes are relieved by the motions. These programs are easy to use, are available free for UNIX or Microsoft Windows operating systems, and should be of significant help in choosing good mutation experiments or in understanding puzzling results.