Photometry of the Didymos System across the DART Impact Apparition

On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite’s orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ∼1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG 1 G 2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact

Adolescents' Neural Processing of Risky Decisions: Effects of Sex and Behavioral Disinhibition

<div><p>Background</p><p>Accidental injury and homicide, relatively common among adolescents, often follow risky behaviors; those are done more by boys and by adolescents with greater behavioral disinhibition (BD).</p><p>Hypothesis</p><p>Neural processing during adolescents' risky decision-making will differ in youths with greater BD severity, and in males vs. females, both before cautious behaviors and before risky behaviors.</p><p>Methodology/Principal Findings</p><p>81 adolescents (Patients with substance and conduct problems, and comparison youths (Comparisons)), assessed in a 2 x 2 design (Patients:Comparisons x Male:Female) repeatedly decided between doing a cautious behavior that earned 1 cent, or a risky one that either won 5 or lost 10 cents. Odds of winning after risky responses gradually decreased. Functional magnetic resonance imaging captured brain activity during 4-sec deliberation periods preceding responses. Most neural activation appeared in known decision-making structures. Patients, who had more severe BD scores and clinical problems than Comparisons, also had extensive neural hypoactivity. Comparisons' greater activation before cautious responses included frontal pole, medial prefrontal cortex, striatum, and other regions; and before risky responses, insula, temporal, and parietal regions. Males made more risky and fewer cautious responses than females, but before cautious responses males activated numerous regions more than females. Before risky behaviors female-greater activation was more posterior, and male-greater more anterior.</p><p>Conclusions/Significance</p><p>Neural processing differences during risky-cautious decision-making may underlie group differences in adolescents' substance-related and antisocial risk-taking. Patients reported harmful real-life decisions and showed extensive neural hypoactivity during risky-or-cautious decision-making. Males made more risky responses than females; apparently biased toward risky decisions, males (compared with females) utilized many more neural resources to make and maintain cautious decisions, indicating an important risk-related brain sexual dimorphism. The results suggest new possibilities for prevention and management of excessive, dangerous adolescent risk-taking.</p></div

Individual Participants' Medications.

<p>Footnote:</p><p>⁺ indicates a combination medication</p><p>Individual Participants' Medications.</p

Assessing possible confounds by changing samples or procedures.

<p>Clusters activating significantly differently in groups appear as shadows on a 2-dimensional surface; activations preceding cautious or risky behaviors are shown separately. Abbreviations: <i>Cmp</i>, comparison participants. <i>F</i>, females. <i>M</i>, males. <i>Pt</i>, patients. Row A: entire sample, data analyzed as in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t004" target="_blank">4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t005" target="_blank">5</a>. Row B: same sample, additional adjustment for depression severity (Carroll Rating Scale). Rows C-E: analyses as in Row A, but excluding: left-handed participants (Row C: 2 patient males, 1 comparison male, 3 patient females, no comparison females); or participants receiving psychotropic medications (Row D: see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t001" target="_blank">Table 1</a>); or recent regular tobacco smokers (Row E: 6 patient males, 1 comparison male, 20 patient females, 1 comparison female). All images modified identically to increase contrast between the white brain figure and its gray background.</p

Game; Participants' Behavioral Disinhibition Scores.

<p><b>(a) Colorado Balloon Game</b>. <i>A</i>: Decision Trial begins, yellow illuminated 4 sec. <i>B</i>: Chosen press executed during 0.5-second green light. Next, red light signals outcome, 3.5 sec. If left press in <i>B</i>, then <i>C</i> (counter increases 1 cent, dull sound, no change in balloon). If right press in <i>B</i>, then either <i>D</i> (counter decreases 10 cents, frowney face, popping sound, balloon shrinks), or <i>E</i> (counter increases 5 cents, smiley face, coin-drop sound, balloon puffs up). <i>F</i>: Fixation screen 2–4 sec. <i>G</i>: Directed Trial begins with 4-sec yellow half-light. Illuminated side (left here) indicates side to press when light turns green. Counter: current earnings. Then, the B-F sequence from the paired Decision Trial follows exactly, but participant knows that "the computer is playing the game now", and that only the counter increase of 2 cents upon the directed press affects participant. <b>(b) 81 Participants’ BD Scores</b>. Crosses: means, standard deviations.</p

Demographic and Clinical Information.

<p>Abbreviations:</p><p>ANOVA, analysis of variance. CBCL, Child Behavior Checklist. Cmp, Comparison. Dep, dependence. FE, Fisher exact test. K-W <b>X</b> Sq, Kruskall-Wallis Chi-square. n, number. NA, not assessed. NS, not significant. Pt, patient. SD, standard deviation. SES, socioeconomic status. <b>X</b> Sq, Pearson Chi-square.</p><p>Footnotes:</p><p>¹Not provided if test is NS.</p><p>²If interactions/overall test was significant, 4 post-hoc comparisons, as shown by arrows: Cmp Male ←→ Pt Male Cmp Female ←→ Pt Female</p><p>³NS: p > 0.05, two-tailed. NA: Not assessed because of significant interaction.</p><p>⁴Highest class = V. Comparison mean score falls in Class IV, patient in Class III.</p><p>⁵n = 18.</p><p>⁶In one patient with no CBCL, YSR score was substituted for CBCL.</p><p>⁷Median (range) provided for very skewed values.</p><p>⁸"Regular" is at least monthly. All patient males had been regular smokers, but 14 were now in a smoke-free residential treatment facility.</p><p>⁹DSM-IV abuse or dependence on any drug not listed above.</p><p>^w-yWithin one row values sharing a superscript are significantly different.</p><p>Demographic and Clinical Information.</p

Decline in risky presses as probability of loss increased.

<p>Four groups: patient males, comparison males, patient females, comparison females. Raw (not fitted) data shown. Comparison males' error bars: red to reduce confusing overlaps. Trials required a choice: a cautious response earned 1 cent; a risky response either won 5 or lost 10 cents. Probability of winning after risky choices declined from 0.78 to 0.22 as game progressed.</p

The Groups' Activity Differences before Cautious Responses.

<p>Abbreviations (Tables 4 and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t005" target="_blank">5</a>):</p><p>Ant, anterior. Br, brain. Cerebell, cerebellum. Cing, cingulate. Cmp, comparison participants. dl, dorsolateral. Fr, frontal. Glob Pall, globus pallidus. Gy, gyrus. Hippoc, hippocampus. Hypothal, hypothalamus. Inf, inferior. L, left. Lob, lobule. m or Med, medial. Nucl, nucleus. Pt, patients. Occip, occipital. OFC, orbitofrontal cortex. Par, parietal. Paracent, paracentral. Parahip, parahippocampal. PFC, prefrontal cortex. Postcent, postcentral. Precent, precentral. R, right. Sens, sensory. Sens Integ, sensory integration. SMA, supplementary motor area. Subcall, subcallosal. Subthal, subthalamic. Sup, superior. Supramarg, supramarginal. Temp, temporal. Thal, thalamus. vl, ventrolateral.</p><p>Footnotes (Tables 4 and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t005" target="_blank">5</a>):</p><p>^aContrast: [(Decision Trial - Directed Trial)Group 1 - (Decision Trial - Directed Trial)Group 2]. Cluster-level family-wise error correction (pcorr < 0.05).</p><p>^bIf bilateral, the larger maximum is shown.</p><p>^cTotal voxels in each cluster. A structure with a number here, and the following structures without numbers, comprise one cluster.</p><p>^dMaximally activated voxel in region.</p><p>The Groups' Activity Differences before Cautious Responses.</p

Cortical regions near scalp where groups' activations differed significantly.

<p>These regions are potentially accessible to transcranial direct current stimulation. Row labels: <i>Cau</i>, before cautious responses. <i>Ris</i>, before risky responses. <i>Cmp</i>, comparison participants. <i>F</i>, females. <i>M</i>, males. <i>Pt</i>, patients. Three rows of possible activations not shown: (a) Cau: Pt>Cmp and (b) Ris: Pt>Cmp, were both devoid of activation; (c) Cau: F>M had activation only at site marked by <i>Green pointer tip</i> in Ris: M>F. Significant t-values range from 2.64 (dark red) to 7.76 (white); details in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t004" target="_blank">4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t005" target="_blank">5</a>.</p

Participants' Behavior in Task.

<p>Abbreviations: As in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132322#pone.0132322.t002" target="_blank">Table 2</a>.</p><p>Footnotes:</p><p>¹Mean (Standard Deviation).</p><p>²"Really, really happy" = 0 mm; "Really, really sad" = 100 mm.</p><p>³Based on completed responses.</p><p>⁴"I told myself" = 0 mm; "the computer told me" = 100 mm.</p><p>⁵Median (Range) provided for very skewed values.</p><p>⁶If interactions/overall test was significant, 4 post-hoc comparisons, as shown by arrows: Cmp Male ←→ Pt Male Cmp Female ←→ Pt Female</p><p>^w-zWithin one row values sharing a superscript are significantly different.</p><p>Participants' Behavior in Task.</p