Quantifying the level of eusociality

The evolution of animal societies in which some individuals forego direct reproduction to help others to reproduce poses an evolutionary paradox. Societies where all individuals reproduce equally and societies where a single individual completely monopolizes reproduction represent the end points of a continuum of variance in the reproductive output among group members. This led Sherman et al. (1995) to propose that cooperative breeding and eusociality (a term originally applied only to insects) are not discrete phenomena. Rather they form a continuum whose main difference is the extent to which individuals forego their own reproductive opportunity to help other members of the group. Here we present a new index: the eusociality index. It quantifies the decrease in direct reproduction of group members as a resut of altruistic acts directed to other members of the group (i.e. a measure of the level of eusociality). The rationale for this index lies in the fundamental duality of the reproductive process, in which organisms supply two distinct elements: (i) genetic material (genes); and (ii) power (energy). In non-eusocial animals, all individuals transmit genes and power in the same ratio (notwithstanding individual variance in offspring size and parental investment). By contrast, amongst eusocial animals some individuals contribute proportionally more to gene transfer, and others more to energy, resulting in high interindividual variation in the ratio of gene to power transfer.

Wireless GPS-based phase-locked synchronization system for outdoor environment.

Synchronization of data coming from different sources is of high importance in biomechanics to ensure reliable analyses. This synchronization can either be performed through hardware to obtain perfect matching of data, or post-processed digitally. Hardware synchronization can be achieved using trigger cables connecting different devices in many situations; however, this is often impractical, and sometimes impossible in outdoors situations. The aim of this paper is to describe a wireless system for outdoor use, allowing synchronization of different types of - potentially embedded and moving - devices. In this system, each synchronization device is composed of: (i) a GPS receiver (used as time reference), (ii) a radio transmitter, and (iii) a microcontroller. These components are used to provide synchronized trigger signals at the desired frequency to the measurement device connected. The synchronization devices communicate wirelessly, are very lightweight, battery-operated and thus very easy to set up. They are adaptable to every measurement device equipped with either trigger input or recording channel. The accuracy of the system was validated using an oscilloscope. The mean synchronization error was found to be 0.39 μs and pulses are generated with an accuracy of <2 μs. The system provides synchronization accuracy about two orders of magnitude better than commonly used post-processing methods, and does not suffer from any drift in trigger generation.

Plutonium from above-ground nuclear tests in milk teeth: investigation of placental transfer in children born between 1951 and 1995 in Switzerland.

BACKGROUND: Occupational risks, the present nuclear threat, and the potential danger associated with nuclear power have raised concerns regarding the metabolism of plutonium in pregnant women. OBJECTIVE: We measured plutonium levels in the milk teeth of children born between 1951 and 1995 to assess the potential risk that plutonium incorporated by pregnant women might pose to the radiosensitive tissues of the fetus through placenta transfer. METHODS: We used milk teeth, whose enamel is formed during pregnancy, to investigate the transfer of plutonium from the mother's blood plasma to the fetus. We measured plutonium using sensitive sector field inductively coupled plasma mass spectrometry techniques. We compared our results with those of a previous study on strontium-90 ((90)Sr) released into the atmosphere after nuclear bomb tests. RESULTS: Results show that plutonium activity peaks in the milk teeth of children born about 10 years before the highest recorded levels of plutonium fallout. By contrast, (90)Sr, which is known to cross the placenta barrier, manifests differently in milk teeth, in accordance with (90)Sr fallout deposition as a function of time. CONCLUSIONS: These findings demonstrate that plutonium found in milk teeth is caused by fallout that was inhaled around the time the milk teeth were shed and not from any accumulation during pregnancy through placenta transfer. Thus, plutonium may not represent a radiologic risk for the radiosensitive tissues of the fetus.