It takes a village to raise a tide: nonlinear multiple-mode coupling and mode identification in KOI-54

We explore the tidal excitation of stellar modes in binary systems using Kepler observations of the remarkable eccentric binary KOI-54 (HD 187091; KIC 8112039), which displays strong ellipsoidal variation as well as a variety of linear and nonlinear pulsations. We report the amplitude and phase of over 120 harmonic and anharmonic pulsations in the system. We use pulsation phases to determine that the two largest-amplitude pulsations, the 90th and 91st harmonics, most likely correspond to axisymmetric m=0 modes in both stars, and thus cannot be responsible for resonance locks as had been recently proposed. We find evidence that the amplitude of at least one of these two pulsations is decreasing with a characteristic timescale of ~100 yr. We also use the pulsations' phases to confirm the onset of the traveling wave regime for harmonic pulsations with frequencies <~50 Omega_orbit, in agreement with theoretical expectations. We present evidence that many pulsations that are not harmonics of the orbital frequency correspond to modes undergoing simultaneous nonlinear coupling to multiple linearly driven parent modes. Since coupling among multiple modes can lower the threshold for nonlinear interactions, nonlinear phenomena may be easier to observe in highly eccentric systems, where broader arrays of driving frequencies are available. This may help to explain why the observed amplitudes of the linear pulsations are much smaller than the theoretical threshold for decay via three-mode coupling.Comment: Accepted for publication in MNRAS. Only minor corrections. 16 Pages; 8 Figures; 3 Table

Does opportunistic testing bias cognitive performance in primates? Learning from drop-outs

Dropouts are a common issue in cognitive tests with non-human primates. One main reason for dropouts is that researchers often face a trade-off between obtaining a sufficiently large sample size and logistic restrictions, such as limited access to testing facilities. The commonly-used opportunistic testing approach deals with this trade-off by only testing those individuals who readily participate and complete the cognitive tasks within a given time frame. All other individuals are excluded from further testing and data analysis. However, it is unknown if this approach merely excludes subjects who are not consistently motivated to participate, or if these dropouts systematically differ in cognitive ability. If the latter holds, the selection bias resulting from opportunistic testing would systematically affect performance scores and thus comparisons between individuals and species. We assessed the potential effects of opportunistic testing on cognitive performance in common marmosets (Callithrix jacchus) and squirrel monkeys (Saimiri sciureus) with a test battery consisting of six cognitive tests: two inhibition tasks (Detour Reaching and A-not-B), one cognitive flexibility task (Reversal Learning), one quantity discrimination task, and two memory tasks. Importantly, we used a full testing approach in which subjects were given as much time as they required to complete each task. For each task, we then compared the performance of subjects who completed the task within the expected number of testing days with those subjects who needed more testing time. We found that the two groups did not differ in task performance, and therefore opportunistic testing would have been justified without risking biased results. If our findings generalise to other species, maximising sample sizes by only testing consistently motivated subjects will be a valid alternative whenever full testing is not feasible.</p

How task format affects cognitive performance:a memory test with two species of New World monkeys

In cognitive tests, animals are often given a choice between two options and obtain a reward if they choose correctly. We investigated whether task format affects subjects' performance in a physical cognition test. In experiment 1, a two-choice memory test, 15 marmosets, Callithrix jacchus, had to remember the location of a food reward over time delays of increasing duration. We predicted that their performance would decline with increasing delay, but this was not found. One possible explanation was that the subjects were not sufficiently motivated to choose correctly when presented with only two options because in each trial they had a 50% chance of being rewarded. In experiment 2, we explored this possibility by testing eight naïve marmosets and seven squirrel monkeys, Saimiri sciureus, with both the traditional two-choice and a new nine-choice version of the memory test that increased the cost of a wrong choice. We found that task format affected the monkeys' performance. When choosing between nine options, both species performed better and their performance declined as delays became longer. Our results suggest that the two-choice format compromises the assessment of physical cognition, at least in memory tests with these New World monkeys, whereas providing more options, which decreases the probability of obtaining a reward when making a random guess, improves both performance and measurement validity of memory. Our findings suggest that two-choice tasks should be used with caution in comparisons within and across species because they are prone to motivational biases

Energy Metabolism and the Induction of the Unfolded Protein Response: A Dissertation

White adipose plays a major role in the regulation of whole body metabolism through the storage and hydrolysis of triglycerides and by secretion of adipokines. The function of endocrine cells is highly dependent on the unfolded protein response (UPR), a homeostatic signaling mechanism that balances the protein folding capacity of the endoplasmic reticulum (ER) with the cell\u27s secretory protein load. Here we demonstrate that the adipocyte UPR pathway is necessary for its secretory functions, and can thus play a crucial role in the control of whole body energy homeostasis. ER protein folding capacity is dependent both on the number of available chaperones as well as on their activity, which requires a sufficient ATP supply. In 3T3-L1 adipocytes, mitochondrial biogenesis occurred in parallel with induction of the UPR; therefore, we tested whether it was necessary for efficient ER function. Inhibition of mitochondrial ATP synthesis through depletion of Tfam, a mitochondrial transcription factor, or treatment with inhibitors of oxidative phosphorylation, demonstrate that ER function is sensitive to acute changes in adenine nucleotide levels. In addition, adenylate kinase 2 (AK2), which regulates mitochondrial adenine nucleotide interconversion, is markedly induced during adipocyte and B cell differentiation. AK2 depletion impairs induction of the UPR and secretion in both cell types. Interestingly, cytosolic adenylate kinase 1 (AK1) does not have the same effect upon UPR induction. We show that adenine nucleotides promote proper ER function and alterations in specific aspects of ATP synthesis can impair UPR signaling. Understanding the complex energetic regulation of the UPR may provide insight into the relationship between UPR and disease

The Roles of Myosin XI and ROP in Moss Tip Growth

Because of the large number of myosin XI and ROP genes found in many angiosperms, it has been difficult to determine their precise role with respect to tip growth. In contrast, there are only two myosin XI genes in four ROP genes in the moss Physcomitrella patens. To determine their role in tip growth using a loss-of-function approach, I used RNA interference (RNAi) and found that both of these proteins are essential for tip growth. Consistent with a role in tip growth, I show that a functional, full-length fusion of mEGFP to myosin XI accumulates at a subcortical, apical region of actively growing protonemal cells. Myosin XI RNAi plants also appear to have decreased cellulose in the cell wall, suggesting a role in secretion of cellulose synthases. I found that silencing ROP increases cortical actin dynamics but does not appear to have a specific affect on the microtubule cytoskeleton. Further investigation found that ROP recruits class II formins to the cell cortex where they actively nucleate and elongate actin filaments. Loss of ROP also causes a decrease in intracellular adhesion. Unlike myosin XI RNAi plants, examination of the crystalline cellulose content of the cell wall shows that the deposition of the cell wall is not inhibited in the absence of ROP. Taken together my findings suggest that ROP defines a membrane region where myosin XI delivers secretory vesicles containing cellulose synthase and other materials needed to build new cell wall during tip growth

Prolonged myocardial stunning after thrombolysis: can left ventricular function be assessed definitely at hospital discharge?

To assess whether myocardial dysfunction after acute reperfusion (‘stunning') may show delayed recovery, 33 patients of the European Cooperative Study (rtPA vs placebo) had radionuclide angiocardiography on day 9 and after 3-6 months. Sixteen patients (13 inferior, three anterior infarcts) had a normal left ventricular ejection fraction (LVEF) which remained unchanged (55.4 vs 53.9%). In contrast, LVEF of 17 patients (10 inferior, seven anterior infarcts) with depressed values on day 9 improved during follow-up from 38.8 to 45.2% (P<0.01). Improvement was only observed in patients with early reperfusion defined a priori as peak creatine kinase valuè ≤ 15 h of pain onset (from 40.9 to 49.3%; P<0.05) in contrast to patients without reperfusion (from 34.0 to 35.2%; ns). Accordingly, LVEF increased in patients with open infarct-related arteries at hospital discharge (n = 8; P = 0.053) but not with persistent occlusion (n = 7; P = 0.11). Thus, a depressed LVEF observed 9 days after reperfusion may show delayed recovery due to prolonged stunning. Therefore, after thrombolysis, left ventricular function may not be evaluated definitively at hospital discharge; results of such studies should be interpreted with cautio

Prognostic significance of right ventricular ejection fraction for persistent complex ventricular arrhythmias and/or sudden cardiac death after first myocardial infarction: Relation to infarct location, size and left ventricular function

To assess the prognostic significance of right ventricular dysfunction after a first myocardial infarction for complex ventricular arrhythmias and or sudden cardiac death in relation to infarct location, size and left ventricular function, a series of 127 consecutive patients was prospectively studied and followed up for one year. Prior to hospital discharge, a 24-hour electrocardiographic recording and radionuclide angiocardiography were performed. Right ventricular ejection fraction was related to inferior infarct location and size (r = 0.45, P 0.40 vs. ≤ 0.40 showed that presence of complex ventricular ectopic activity and/or sudden cardiac death after myocardial infarction was related not only to left, but also independently to right ventricular dysfunction. These results imply a significant prognostic contribution of right ventricular dysfunction to the occurrence of severe ventricular arrhythmias and/or sudden cardiac death after myocardial infarction independent of and additive to left ventricular dysfunctio

No evidence for general intelligence in a fish

The average mammal or bird has a roughly ten times larger brain relative to body size than the average ectotherm vertebrate. It has been surprisingly challenging to determine how this translates into increased cognitive performance. In particular, it is unclear whether the brain size differences translate into qualitative differences in specific cognitive abilities. Here, we provide a first exploratory study to examine the possibility that the larger brains of endotherms support a different organisation of information processing, rather than specific differences in cognitive processes. In mammals, individual performance across domain-general cognitive tasks is positively correlated, resulting in the psychometric factor g. The value of g is positively correlated with brain size. We tested wild-caught female cleaner fish Labroides dimidiatus, known for its highly sophisticated social behaviour, in four ecologically nonrelevant cognitive tasks that have been used to varying degrees to assess g in mammals. Cleaner fish solved three of these four tasks, flexibility (reversal learning), self-control (detour around an obstacle) and numerical competence (simultaneous two-choice task), while also providing enough interindividual variation to test for g. They did not perform above chance levels in the fourth task, which tested for object permanence. For the three retained tasks, individual performance did not load positively on one principal component. Furthermore, all pairwise correlation coefficients were close to zero. These negative results contradict a frequent criticism of g studies, which proposes that g is a default result of how brains are designed. Rather, the results provide a first indication that endotherm and ectotherm vertebrates may process cognitive tasks in fundamentally different ways due to differences in brain organisation. Our relatively low number of experiments compared to mammalian studies enhances this hypothesis, as the probability of finding a g factor by chance would have been higher