University of Bordeaux

About: University of Bordeaux is a education organization based out in Bordeaux, France. It is known for research contribution in the topics: Population & Laser. The organization has 28811 authors who have published 55536 publications receiving 1619635 citations. The organization is also known as: UB.

Long‐term effects of prenatal stress and postnatal handling on age‐related glucocorticoid secretion and cognitive performance: a longitudinal study in the rat

Abstract: There is growing evidence that stress during prenatal and postnatal periods of life can modify adaptive capacities in adulthood. The hypothalamo-pituitary-adrenal axis may mediate an animal's responses to perinatal stressful events and thus serve as a neurobiological substrate of the behavioural consequences of these early events. However, little is known about the long-term effects of prenatal stressors throughout the entire life of the animals. The focus of the present study was to examine the long-term influences of a prenatal and postnatal stress on glucocorticoid secretion and cognitive performance. Prenatal stress of rat dams during the last week of pregnancy and postnatal daily handling of rat pups during the first 3 weeks of life were used as stressors. The long-term effects of these manipulations were analysed using a longitudinal approach throughout the entire life of the animals, and were repeatedly tested in adulthood (4-7 months), middle age (13-16 months) and in later life (20-24 months). The study demonstrated that prenatal stress and postnatal handling induced opposite effects on both glucocorticoid secretion and cognitive performance. Prenatal stress accelerated the age-related hypothalamo-pituitary-adrenal axis dysfunctions; indeed, circulating glucocorticoids levels of prenatally stressed middle-aged animals are similar to old control ones, and also induced cognitive impairments. In contrast, postnatal handling protected from the age-related neuroendocrine and behavioural alterations. These results show that the altered glucocorticoid secretion induced by early environmental manipulations is primary to the cognitive alterations observed only later in life and could be one cause of age-related memory deficits.

Boltzmann Samplers for the Random Generation of Combinatorial Structures

Abstract: This article proposes a surprisingly simple framework for the random generation of combinatorial configurations based on what we call Boltzmann models. The idea is to perform random generation of possibly complex structured objects by placing an appropriate measure spread over the whole of a combinatorial class – an object receives a probability essentially proportional to an exponential of its size. As demonstrated here, the resulting algorithms based on real-arithmetic operations often operate in linear time. They can be implemented easily, be analysed mathematically with great precision, and, when suitably tuned, tend to be very efficient in practice.

A clock network for geodesy and fundamental science.

Abstract: Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10−17 via a newly established phase-coherent frequency link connecting Paris and Braunschweig using 1,415 km of telecom fibre. The remote comparison is limited only by the instability and uncertainty of the strontium lattice clocks themselves, with negligible contributions from the optical frequency transfer. A fractional precision of 3 × 10−17 is reached after only 1,000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than any previous long-distance clock comparison. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second. Comparing the frequency of two distant optical clocks will enable sensitive tests of fundamental physics. Here, the authors compare two strontium optical-lattice clocks 690 kilometres apart to a degree of accuracy that is limited only by the uncertainty of the individual clocks themselves.