Terminal attack trajectories of peregrine falcons are described by the proportional navigation guidance law of missiles
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 1 year ago
The ability to intercept uncooperative targets is key to many diverse flight behaviors, from courtship to predation. Previous research has looked for simple geometric rules describing the attack trajectories of animals, but the underlying feedback laws have remained obscure. Here, we use GPS loggers and onboard video cameras to study peregrine falcons, Falco peregrinus, attacking stationary targets, maneuvering targets, and live prey. We show that the terminal attack trajectories of peregrines are not described by any simple geometric rule as previously claimed, and instead use system identification techniques to fit a phenomenological model of the dynamical system generating the observed trajectories. We find that these trajectories are best-and exceedingly well-modeled by the proportional navigation (PN) guidance law used by most guided missiles. Under this guidance law, turning is commanded at a rate proportional to the angular rate of the line-of-sight between the attacker and its target, with a constant of proportionality (i.e., feedback gain) called the navigation constant (N). Whereas most guided missiles use navigation constants falling on the interval 3 ≤ N ≤ 5, peregrine attack trajectories are best fitted by lower navigation constants (median N < 3). This lower feedback gain is appropriate at the lower flight speed of a biological system, given its presumably higher error and longer delay. This same guidance law could find use in small visually guided drones designed to remove other drones from protected airspace.
Functional imaging using positron emission tomography and later functional magnetic resonance imaging revealed a particular brainstem area that is believed to be specifically activated in migraine during, but not outside of the attack, and consequently has been coined the ‘migraine generator’. However, the pathophysiological concept behind this term is not undisputed and typical migraine premonitory symptoms such as fatigue and yawning, but also a typical association of attacks to circadian and menstrual cycles, all make the hypothalamus a possible regulating region of migraine attacks. Neuroimaging studies investigating native human migraine attacks however are scarce and for methodological but also clinical reasons there are currently no studies investigating the last 24 h before headache onset. Here we report a migraine patient who had magnetic resonance imaging every day for 30 days, always in the morning, to cover, using functional imaging, a whole month and three complete, untreated migraine attacks. We found that hypothalamic activity as a response to trigeminal nociceptive stimulation is altered during the 24 h prior to pain onset, i.e. increases towards the next migraine attack. More importantly, the hypothalamus shows altered functional coupling with the spinal trigeminal nuclei and the region of the migraine generator, i.e. the dorsal rostral pons during the preictal day and the pain phase of native human migraine attacks. These data suggest that although the brainstem is highly linked to the migraine biology, the real driver of attacks might be the functional changes in hypothalamo-brainstem connectivity.
Conflicts between humans and crocodilians are a widespread conservation challenge and the number of crocodile attacks is increasing worldwide. We identified the factors that most effectively decide whether a victim is injured or killed in a crocodile attack by fitting generalized linear models to a 42-year dataset of 87 attacks (27 fatal and 60 non-fatal) by saltwater crocodiles (Crocodylus porosus) in Australia. The models showed that the most influential factors were the difference in body mass between crocodile and victim, and the position of victim in relation to the water at the time of an attack. In-water position (for diving, swimming, and wading) had a higher risk than on-water (boating) or on-land (fishing, and hunting near the water’s edge) positions. In the in-water position a 75 kg person would have a relatively high probability of survival (0.81) if attacked by a 300 cm crocodile, but the probability becomes much lower (0.17) with a 400 cm crocodile. If attacked by a crocodile larger than 450 cm, the survival probability would be extremely low (<0.05) regardless of the victim's size. These results indicate that the main cause of death during a crocodile attack is drowning and larger crocodiles can drag a victim more easily into deeper water. A higher risk associated with a larger crocodile in relation to victim's size is highlighted by children's vulnerability to fatal attacks. Since the first recently recorded fatal attack involving a child in 2006, six out of nine fatal attacks (66.7%) involved children, and the average body size of crocodiles responsible for these fatal attacks was considerably smaller (384 cm, 223 kg) than that of crocodiles that killed adults (450 cm, 324 kg) during the same period (2006-2014). These results suggest that culling programs targeting larger crocodiles may not be an effective management option to improve safety for children.
- Cephalalgia : an international journal of headache
- Published almost 6 years ago
BackgroundHeadache associated with sexual activity is a well-known primary headache disorder. In contrast, some case reports in the literature suggest that sexual activity during a migraine or cluster headache attack might relieve the pain in at least some patients. We performed an observational study among patients of a tertiary headache clinic.MethodsA questionnaire was sent to 800 unselected migraine patients and 200 unselected cluster headache patients. We asked for experience with sexual activity during a headache attack and its impact on headache intensity. The survey was strictly and completely anonymous.ResultsIn total, 38% of the migraine patients and 48% of the patients with cluster headache responded. In migraine, 34% of the patients had experience with sexual activity during an attack; out of these patients, 60% reported an improvement of their migraine attack (70% of them reported moderate to complete relief) and 33% reported worsening. In cluster headache, 31% of the patients had experience with sexual activity during an attack; out of these patients, 37% reported an improvement of their cluster headache attack (91% of them reported moderate to complete relief) and 50% reported worsening. Some patients, in particular male migraine patients, even used sexual activity as a therapeutic tool.ConclusionsThe majority of patients with migraine or cluster headache do not have sexual activity during headache attacks. Our data suggest, however, that sexual activity can lead to partial or complete relief of headache in some migraine and a few cluster headache patients.
Temperature-driven range expansion of an irruptive insect heightened by weakly coevolved plant defenses
- Proceedings of the National Academy of Sciences of the United States of America
- Published almost 6 years ago
Warming climate has increased access of native bark beetles to high-elevation pines that historically received only intermittent exposure to these tree-killing herbivores. Here we show that a dominant, relatively naïve, high-elevation species, whitebark pine, has inferior defenses against mountain pine beetle compared with its historical lower-elevation host, lodgepole pine. Lodgepole pines respond by exuding more resin and accumulating higher concentrations of toxic monoterpenes than whitebark pine, where they co-occur. Furthermore, the chemical composition of whitebark pine appears less able to inhibit the pheromonal communication beetles use to jointly overcome tree defenses. Despite whitebark pine’s inferior defenses, beetles were more likely to attack their historical host in mixed stands. This finding suggests there has been insufficient sustained contact for beetles to alter their complex behavioral mechanisms driving host preference. In no-choice assays, however, beetles readily entered and tunneled in both hosts equally, and in stands containing less lodgepole pine, attacks on whitebark pines increased. High-elevation trees in pure stands may thus be particularly vulnerable to temperature-driven range expansions. Predators and competitors were more attracted to volatiles from herbivores attacking their historical host, further increasing risk in less coevolved systems. Our results suggest cold temperatures provided a sufficient barrier against herbivores for high-elevation trees to allocate resources to other physiological processes besides defense. Changing climate may reduce the viability of that evolutionary strategy, and the life histories of high-elevation trees seem unlikely to foster rapid counter adaptation. Consequences extend from reduced food supplies for endangered grizzly bears to altered landscape and hydrological processes.
Herbivores employ a variety of chemical, behavioural and morphological defences to reduce mortality from natural enemies. In some caterpillars the head capsules of successive instars are retained and stacked on top of each other and it has been suggested that this could serve as a defence against natural enemies. We tested this hypothesis by comparing the survival of groups of the gumleaf skeletoniser Uraba lugens Walker caterpillars, allocated to one of three treatments: “-HC,” where stacked head capsules were removed from all individuals, “+HC,” where the caterpillars retained their stacked head capsules, and “mixed,” where only half of the caterpillars in a group had their stacked head capsules removed. We found no difference in predation rate between the three treatments, but within the mixed treatment, caterpillars with head capsules were more than twice as likely to survive. During predator choice trials, conducted to observe how head capsule stacking acts as a defence, the predatory pentatomid bug attacked the -HC caterpillar in four out of six trials. The two attacks on +HC caterpillars took over 10 times longer because the bug would poke its rostrum through the head capsule stack, while the caterpillar used its head capsule stack to deflect the bug’s rostrum. Our results support the hypothesis that the retention of moulted head capsules by U. lugens provides some protection against their natural enemies and suggest that this is because stacked head capsules can function as a false target for natural enemies as well as a weapon to fend off attackers. This represents the first demonstration of a defensive function.
Paroxysmal nonkinesigenic dyskinesia (PNKD) is a rare disorder in autosomal dominant inheritance. The clinical features and genetic findings of PNKD, rarely described in the Asians, were mostly delineated from European families. The present study characterized the clinical and genetic findings of a Taiwanese PNKD family. The clinical features of our five patients in successive three generations included onset age less than 10years, attack duration between 3min and 4h, and a variety of aura symptoms. The attacks were provoked not by sudden action but by emotional stress, caffeine, fatigue, heavy exercise and sleep deprivation. Sleep could abolish or diminish the attack and the attacks responded well to clonazepam. Sequencing the whole coding region of PNKD/MR-1 gene identified a heterozygous c.20C>T (p.Ala7Val) mutation which was clearly segregated in the five affected patients. Comparing our patients with previously reported 18 families with PNKD/MR-1 mutations, the majority of the patients exhibited quite similar manifestations in attack patterns and precipitating factors. The recurrent conservative mutations in different ethnicities indicate importance in the pathogenesis of PNKD.
O-Picolinyl and O-picoloyl groups at remote positions (C-3, C-4, and C-6) can mediate glycosylation reactions by providing high or even complete facial selectivity for the attack of the glycosyl acceptor. The set of data presented herein offers a strong evidence of the inter-molecular H-bond tethering between the glycosyl donor and glycosyl acceptor counterparts while providing a practical new methodology for the synthesis of either 1,2-cis or 1,2-trans linkages. Challenging glycosidic linkages including α-gluco, β-manno, and β-rhamno have seen obtained with high or complete stereocontrol.
Eighteen male cluster headache (CH) inpatients within a CH series participated in this research. Blood samples were drawn from patients at least 6-hour pain-free after the last acute CH episode and then shortly prior (SP), during, and soon after (SA) a new acute CH attack. Three healthy male, age-comparable drug-free volunteers served as controls; 5 samples were obtained from each of these individual over a 24-hour period. Individual patient’s methionine-enkephalin (MET) plasma concentration showed significant changes, and in some subjects, dramatic changes, during the different phases of a single CH episode. Peptide levels followed a general pattern of higher plasma concentration SP to an acute CH attack, followed by decreased levels during the attack itself, and falling even further SA the acute episode. Consistently, 16 of the 18 patients tested showed pre-CH peptide levels significantly higher (arbitrarily the authors considered values 20% or more as “significant”) than their own values obtained during the acute CH pain phase, with observed differences reaching 80% or more in 7 of these individuals. For about half of these patients, peptide concentration during the acute CH episode was significantly above the control’s range (68.2-87.6 pg MET/mL; control’s circulating MET concentration remaining essentially unchanged during a 24-hour period). MET levels were further decreased in essentially all of the post-CH samples, with values falling within (n = 6) or even further below than those in the control’s range (n = 11). Neither age, time of CH occurrence, nor patient’s use of a number of medications known for failing to influence plasma MET degradation kinetics seemed to significantly influence MET levels. These results might help in the biochemical characterization of the actual phases of a CH episode. Developing drugs modulating MET bioavailability could lead to novel antinociceptive agents useful for the treatment of CH’s associated pain.
Grape berries attacked by Lobesia botrana larvae are more easily infected by Aspergillus section Nigri (black aspergilli) ochratoxigenic species. Two-year field trials were carried out in Apulia (Italy) to evaluate a bioinsecticide control strategy against L. botrana and the indirect effect on reducing ochratoxin A (OTA) contamination in vineyards. A commercial Bacillus thuringiensis formulate and an experimental Beauveria bassiana (ITEM-1559) formulate were tested in two vineyards cultivated with the same grape variety, Negroamaro, but with two different training systems (espalier and little-arbor techniques). In both years and training systems the treatments by B. bassiana ITEM-1559 significantly controlled L. botrana larvae attacks with effectiveness similar to B. thuringensis (more than 20%). A significant reduction of OTA concentrations (up to 80% compared to untreated controls) was observed only in the first year in both training systems, when the metereological parameters prior to harvest were more favorable to the insect attack. Results of field trials showed that B. bassiana ITEM-1559 is a valid bioinsecticide against L. botrana and that grape moth biocontrol is a strategy to reduce OTA contamination in vineyard in seasons with heavy natural infestation.