Gravitational waves from single neutron stars: an advanced detector era survey

With the doors beginning to swing open on the new gravitational wave astronomy, this review provides an up-to-date survey of the most important physical mechanisms that could lead to emission of potentially detectable gravitational radiation from isolated and accreting neutron stars. In particular we discuss the gravitational wave-driven instability and asteroseismology formalism of the f- and r-modes, the different ways that a neutron star could form and sustain a non-axisymmetric quadrupolar "mountain" deformation, the excitation of oscillations during magnetar flares and the possible gravitational wave signature of pulsar glitches. We focus on progress made in the recent years in each topic, make a fresh assessment of the gravitational wave detectability of each mechanism and, finally, highlight key problems and desiderata for future work.Comment: 39 pages, 12 figures, 2 tables. Chapter of the book "Physics and Astrophysics of Neutron Stars", NewCompStar COST Action 1304. Minor corrections to match published versio

The essential mycobacterial genes, fabG1 and fabG4, encode 3-oxoacyl-thioester reductases that are functional in yeast mitochondrial fatty acid synthase type 2

Mycobacterium tuberculosis represents a severe threat to human health worldwide. Therefore, it is important to expand our knowledge of vital mycobacterial processes, such as that effected by fatty acid synthase type 2 (FASII), as well as to uncover novel ones. Mycobacterial FASII undertakes mycolic acid biosynthesis, which relies on a set of essential enzymes, including 3-oxoacyl-AcpM reductase FabG1/Rv1483. However, the M. tuberculosis genome encodes four additional FabG homologs, designated FabG2–FabG5, whose functions have hitherto not been characterized in detail. Of the four candidates, FabG4/Rv0242c was recently shown to be essential for the survival of M. bovis BCG. The present work was initiated by assessing the suitability of yeast oar1Δ mutant cells lacking mitochondrial 3-oxoacyl-ACP reductase activity to act as a surrogate system for expressing FabG1/MabA directed to the mitochondria. Mutant yeast cells producing this targeted FabG1 variant were essentially wild type for all of the chronicled phenotype characteristics, including respiratory growth on glycerol medium, cytochrome assembly and lipoid acid production. This indicated that within the framework of de novo fatty acid biosynthesis in yeast mitochondria, FabG1 was able to act on shorter (C4) acyl substrates than was previously proposed (C8–20) during mycolic acid biosynthesis in M. tuberculosis. Thereafter, FabG2–FabG5 were expressed as mitochondrial proteins in the oar1Δ strain, and FabG4 was found to complement the mutant phenotype and contain high levels of 3-oxoacyl-thioester reductase activity. Hence, like FabG1, FabG4 is also an essential, physiologically functional 3-oxoacyl-thioester reductase, albeit the latter’s involvement in mycobacterial FASII remains to be explored

A C. elegans Model for Mitochondrial Fatty Acid Synthase II: The Longevity-Associated Gene W09H1.5/mecr-1 Encodes a 2-trans-Enoyl-Thioester Reductase

Our recognition of the mitochondria as being important sites of fatty acid biosynthesis is continuously unfolding, especially in light of new data becoming available on compromised fatty acid synthase type 2 (FASII) in mammals. For example, perturbed regulation of murine 17β-HSD8 encoding a component of the mitochondrial FASII enzyme 3-oxoacyl-thioester reductase is implicated in polycystic kidney disease. In addition, over-expression in mice of the Mecr gene coding for 2-trans-enoyl-thioester reductase, also of mitochondrial FASII, leads to impaired heart function. However, mouse knockouts for mitochondrial FASII have hitherto not been reported and, hence, there is a need to develop alternate metazoan models such as nematodes or fruit flies. Here, the identification of Caenorhabditis elegans W09H1.5/MECR-1 as a 2-trans-enoyl-thioester reductase of mitochondrial FASII is reported. To identify MECR-1, Saccharomyces cerevisiae etr1Δ mutant cells were employed that are devoid of mitochondrial 2-trans-enoyl-thioester reductase Etr1p. These yeast mutants fail to synthesize sufficient levels of lipoic acid or form cytochrome complexes, and cannot respire or grow on non-fermentable carbon sources. A mutant yeast strain ectopically expressing nematode mecr-1 was shown to contain reductase activity and resemble the self-complemented mutant strain for these phenotype characteristics. Since MECR-1 was not intentionally targeted for compartmentalization using a yeast mitochondrial leader sequence, this inferred that the protein represented a physiologically functional mitochondrial 2-trans-enoyl-thioester reductase. In accordance with published findings, RNAi-mediated knockdown of mecr-1 in C. elegans resulted in life span extension, presumably due to mitochondrial dysfunction. Moreover, old mecr-1(RNAi) worms had better internal organ appearance and were more mobile than control worms, indicating a reduced physiological age. This is the first report on RNAi work dedicated specifically to curtailing mitochondrial FASII in metazoans. The availability of affected survivors will help to position C. elegans as an excellent model for future pursuits in the emerging field of mitochondrial FASII research

Age-related differences in street-crossing safety before and after training of older pedestrians

International accident statistics indicate that elderly pedestrians make up an extremely vulnerable road-user group. Past research has shown that older adults make many unsafe street-crossing decisions and adopt insufficient safety margins, especially when vehicles are approaching at high speed. A part from studies on road design and speed limit countermeasures, there is surprisingly no road-safety research on behavior- based measures to improve older pedestrians' safety. In this line,the present study was aimed at (i) assessing the effectiveness of at raining program for older pedestrians that combined behavioral and educational interventions, and (ii) examining whether and to what extent age-related differences in street-crossing safety could be reduced after training older adults. Twenty seniors were enrolled in a training program. Before, immediately after, and six months after training, street-crossing behavior was assessed using a simulated street-crossing task.Twenty younger participants performed the same simulated task to obtain a baseline measure. The results showed that the training produced significant short- and long-term benefits, due to a shifting of the decision criteria among the older participants towards more conservative judgments. When compared with the younger group, the older participants improved their behavior considerably so that significant differences in the mean safety-related indicators were no longer observed. However, the older participants' ability to take the oncoming car's speed into account did not improve. Even after training, and contrary to younger adults, older participants were found to make more and more unsafe decisions as the car's speed increased, putting them at a higher risk at high speeds. This finding may reflect age-related perceptual and cognitive difficulties that cannot be remedied by a behavioral or educational training method. The present findings underline that high speed is an important risk factor for elderly pedestrians that should be handled by effective speed reduction measures

The effect of traffic complexity and speed on young and elderly pedestrians' street-crossing decisions

This experiment aimed at studying the effects of age, traffic complexity and speed of the approaching cars on the probability of a pedestrian to be involved in a crash. Fifty nine participants aged between 20-84 years took part in a street-crossing estimation task in a simulated road environment. The results showed an overall higher number of 'collisions' with increasing age. While the number of collisions did not vary according to traffic complexity and speed of the approaching cars in the young group, the older participants were more likely to make decisions that led to collisions when the traffic was approaching from two rather than one direction, and at a high speed. The findings were discussed in relation to the effects of age-related cognitive and perceptual limitation on difficulties in selecting safe gaps. The present results have implications for improving older pedestrians' safety in terms of road design, speed reduction measures, and training opportunities

Cognitive, perceptual and motor decline as predictors of risky street-crossing decisions in older pedestrians

DA 2011 - 6th International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design, TAHOE, ETATS-UNIS, 27-/06/2012 - 30/06/2012Older pedestrians are well known to be over-involved in road crashes compared to younger pedestrians. This study investigates the extent to which risky street-crossing decisions in older pedestrians can be explained by agerelated declines of cognitive, perceptual and physical abilities. Three age groups of participants (young, young-old, old-old) were evaluated in a street-crossing task and performed a series of functional tests. The results showed that agerelated slowing in walking speed as well as a decline in cognitive flexibility and in visual acuity play a substantial role in risky decisions by the elderly. The implications of these findings, particularly in the development of a mixed physical-cognitive training to enhance the older pedestrians' road crossing decisions in complex environments, are discussed