68 research outputs found
A Secular Trend toward Earlier Male Sexual Maturity: Evidence from Shifting Ages of Male Young Adult Mortality
This paper shows new evidence of a steady long-term decline in age of male sexual maturity since at least the mid-eighteenth century. A method for measuring the timing of male maturity is developed based on the age at which male young adult mortality accelerates. The method is applied to mortality data from Sweden, Denmark, Norway, the United Kingdom, and Italy. The secular trend toward earlier male sexual maturity parallels the trend toward earlier menarche for females, suggesting that common environmental cues influence the speed of both males' and females' sexual maturation
Regular and chaotic vibration in a piezoelectric energy harvester
We examine regular and chaotic responses of a vibrational energy harvester composed of a vertical beam and a tip mass. The beam is excited horizontally by a harmonic inertial force while mechanical vibrational energy is converted to electrical power through a piezoelectric patch. The mechanical resonator can be described by single or double well potentials depending on the gravity force from the tip mass. By changing the tip mass we examine bifurcations from single well oscillations, to regular and chaotic vibrations between the potential wells. The appearance of chaotic responses in the energy harvesting system is illustrated by the bifurcation diagram, the corresponding Fourier spectra, the phase portraits, and is confirmed by the 0β1 test. The appearance of chaotic vibrations reduces the level of harvested energy
ΠΠΎΡΡΠ΅ΠΊΡΠΈΡ Π΄Π²ΠΈΠ³Π°ΡΠ΅Π»ΡΠ½ΡΡ ΠΈ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΡΠ΅ΡΠΊΠΈΡ ΡΡΠ½ΠΊΡΠΈΠΉ Π² Π»Π΅ΡΠ΅Π½ΠΈΠΈ ΠΈ ΡΠ΅Π°Π±ΠΈΠ»ΠΈΡΠ°ΡΠΈΠΈ Π±ΠΎΠ»ΡΠ½ΡΡ ΡΠΈΠ·ΠΎΡΠΈΠΏΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠ°ΡΡΡΡΠΎΠΉΡΡΠ²ΠΎΠΌ
ΠΠ° ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠ΅ΠΉ Π½Π΅Π²Π΅ΡΠ±Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΠΈΡ Π±ΠΎΠ»ΡΠ½ΡΡ
ΡΠΈΠ·ΠΎΡΠΈΠΏΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠ°ΡΡΡΡΠΎΠΉΡΡΠ²ΠΎΠΌ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠ°Π½Ρ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΡΠ΅ΡΠΊΠΈΠ΅ ΠΌΠ΅ΡΠΎΠ΄Ρ, ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΊΠΎΡΠΎΡΡΡ
Π² ΠΈΡ
ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΠΎΠΉ ΡΠ΅ΡΠ°ΠΏΠΈΠΈ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ Π΄ΠΎΠ±ΠΈΡΡΡΡ Π±ΠΎΠ»Π΅Π΅ ΠΏΠΎΠ»Π½ΠΎΠΉ ΡΠ΅Π΄ΡΠΊΡΠΈΠΈ ΠΏΡΠΈΡ
ΠΎΠΏΠ°ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠΈΠΌΠΏΡΠΎΠΌΠ°ΡΠΈΠΊΠΈ.Behavioral methods were worked out basing of the peculiarities of nonβverbal behavior of the patients with schizotypical disorders. The use of the methods in complex therapy allows to achieve more complete reduction in psychopathological signs
Bonsai Trees in Your Head: How the Pavlovian System Sculpts Goal-Directed Choices by Pruning Decision Trees
When planning a series of actions, it is usually infeasible to consider all potential future sequences; instead, one must prune the decision tree. Provably optimal pruning is, however, still computationally ruinous and the specific approximations humans employ remain unknown. We designed a new sequential reinforcement-based task and showed that human subjects adopted a simple pruning strategy: during mental evaluation of a sequence of choices, they curtailed any further evaluation of a sequence as soon as they encountered a large loss. This pruning strategy was Pavlovian: it was reflexively evoked by large losses and persisted even when overwhelmingly counterproductive. It was also evident above and beyond loss aversion. We found that the tendency towards Pavlovian pruning was selectively predicted by the degree to which subjects exhibited sub-clinical mood disturbance, in accordance with theories that ascribe Pavlovian behavioural inhibition, via serotonin, a role in mood disorders. We conclude that Pavlovian behavioural inhibition shapes highly flexible, goal-directed choices in a manner that may be important for theories of decision-making in mood disorders
Anterior Medial Prefrontal Cortex Exhibits Activation during Task Preparation but Deactivation during Task Execution
BACKGROUND: The anterior prefrontal cortex (PFC) exhibits activation during some cognitive tasks, including episodic memory, reasoning, attention, multitasking, task sets, decision making, mentalizing, and processing of self-referenced information. However, the medial part of anterior PFC is part of the default mode network (DMN), which shows deactivation during various goal-directed cognitive tasks compared to a resting baseline. One possible factor for this pattern is that activity in the anterior medial PFC (MPFC) is affected by dynamic allocation of attentional resources depending on task demands. We investigated this possibility using an event related fMRI with a face working memory task. METHODOLOGY/PRINCIPAL FINDINGS: Sixteen students participated in a single fMRI session. They were asked to form a task set to remember the faces (Face memory condition) or to ignore them (No face memory condition), then they were given 6 seconds of preparation period before the onset of the face stimuli. During this 6-second period, four single digits were presented one at a time at the center of the display, and participants were asked to add them and to remember the final answer. When participants formed a task set to remember faces, the anterior MPFC exhibited activation during a task preparation period but deactivation during a task execution period within a single trial. CONCLUSIONS/SIGNIFICANCE: The results suggest that the anterior MPFC plays a role in task set formation but is not involved in execution of the face working memory task. Therefore, when attentional resources are allocated to other brain regions during task execution, the anterior MPFC shows deactivation. The results suggest that activation and deactivation in the anterior MPFC are affected by dynamic allocation of processing resources across different phases of processing
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