Emotion dysregulation is cross-diagnostic and impairing. Most research has focused on dysregulated expressions of negative affect, often measured as irritability, which is associated with multiple forms of psychopathology and predicts negative outcomes. However, the Research Domain Criteria (RDoC) include both negative and positive valence systems. Emerging evidence suggests that dysregulated expressions of positive affect, or excitability, in early childhood predict later psychopathology and impairment above and beyond irritability. Typically, irritability declines from early through middle childhood; however, the developmental trajectory of excitability is unknown. The impact of excitability across childhood on later emotion dysregulation is also yet unknown. In a well-characterized, longitudinal sample of 129 children studied from ages 3 to 5.11 years through 14 to 19 years, enriched for early depression and disruptive symptoms, we assessed the trajectory of irritability and excitability using multilevel modeling and how components of these trajectories impact later emotion dysregulation. While irritability declines across childhood, excitability remains remarkably stable both within and across the group. Overall levels of excitability (excitability intercept) predict later emotion dysregulation as measured by parent and self-report and predict decreased functional magnetic resonance imaging activity in cognitive emotion regulation regions during an emotion regulation task. Irritability was not related to any dysregulation outcome above and beyond excitability.

To evaluate the aptness of a navigation system in a particular application, the designer needs to assess its performance over typical trajectories travelled by the vehicle itself. Moreover, he or she may be required to judge which components of the kinematics state may be better estimated (and which will not). The main contributions of this work are two novel and complementary performance measures that, in concert, allow for the assessment of a navigation system within the actual context of its application over specific trajectories. For a given on board instrumental configuration, the “excitability metric” permits the isolation of the contribution of the information conveyed by the vehicle's motion itself, while, the “sensability metric” measures the resultant overall quality of the kinematics state estimation. The same tools could help the designer planning appropriate vehicles manoeuvres in order to obtain a required precision for each estimated component. While emphasis is given on the mathematical justification of those metrics, their use is also illustrated with real flight data recorded from a sounding rocket.

Relaxation oscillations are limit cycles with two clearly differenttime scales. In this article the spatio-temporal dynamics of astandard prey-predator system in the parameter region of relaxationoscillation is investigated. Both prey and predator population aredistributed irregularly at a relatively high average level between amaximal and a minimal value. However, the slowly developing complexpattern exhibits a feature of “inverse excitability”: Bothpopulations show collapses which occur erratically both in space andin time. The nature of these collapses is analysed statistically andit is shown that the model behaviour can be interpreted as aresolution of the paradox of enrichment.

The exposure of freshly spawned, immotile carp sperm to hypoosmotic media triggers the initiation of calcium-dependent flagellar motility. Intracellular calcium concentration has been thought to be the critical component in motility initiation, possibly acting through a novel signalling pathway. The sensitivity of sperm cells to changes of osmolality of the environment raises the question whether a mechanoregulated osmosensitive calcium pathway is involved in the activation mechanism of carp sperm motility. The sperm cells are in a depolarized state in the seminal plasma (Ψ = –2.6 ± 3 mV) and they hyperpolarize upon hypoosmosis-induced activation of motility (Ψ = –29 ± 4 mV). The intracellular sodium [Na+]i, potassium [K+]i and calcium [Ca2+]i ion concentrations were determined in quiescent cells, and at 20, 60 and 300 s after activation. The [Na+]i and [K+]i of the quiescent cells were similar to the [Na+]e and [K+]e of the seminal plasma. Following hypoosmotic shock-induced motility, both [Na+]i and [K+]i decreased to one-fourth of the initial concentration. The [Ca2+]i doubled at initiation of the motility of the sperm cells and remained unchanged for 5 min. Bepridil (50–250 μM), a blocker of the Na+/Ca2+ exchanger, blocked carp sperm motility reversibly. Gadolinium, a blocker of stretch-activated channels (10–20 μM), inhibited sperm motility in a dose-dependent manner and its effect was reversible. Hypoosmotic shock fluidized the membrane and gadolinium treatment made it more rigid in both quiescent cells and hypotonic shock treated but immotile sperm cells. Based on these observations, it is suggested that, besides the well-known function of potassium and calcium channels, stretch-induced conformational changes of membrane proteins are also involved in the sperm activation mechanism of common carp.

Patch-clamp and calcium-indicator measurements were used to examine the electrical excitability of large-terminal bipolar neurons from goldfish retina. Large, transient increases in intracellular calcium occurred spontaneously in the synaptic terminal but not in the soma of bipolar neurons. Calcium transients were blocked by hyperpolarization, by external application of calcium-channel blockers, and by the neurotransmitters GABA and glutamate. These observations suggest that calcium action potentials are responsible for the spontaneous increases in intraterminal calcium, which was directly confirmed by electrical recordings of calcium-dependent action potentials in both whole-cell and perforated-patch recordings. We suggest that regenerative depolarization produced by the opening of calcium channels in the synaptic terminal of on-type bipolar neurons represents an amplification mechanism in the high-sensitivity ON pathway in the dark-adapted fish retina.