The Mating-Type Chromosome in the Filamentous Ascomycete Neurospora tetrasperma Represents a Model for Early Evolution of Sex Chromosomes

We combined gene divergence data, classical genetics, and phylogenetics to study the evolution of the mating-type chromosome in the filamentous ascomycete Neurospora tetrasperma. In this species, a large non-recombining region of the mating-type chromosome is associated with a unique fungal life cycle where self-fertility is enforced by maintenance of a constant state of heterokaryosis. Sequence divergence between alleles of 35 genes from the two single mating-type component strains (i.e. the homokaryotic mat A or mat a-strains), derived from one N. tetrasperma heterokaryon (mat A+mat a), was analyzed. By this approach we were able to identify the boundaries and size of the non-recombining region, and reveal insight into the history of recombination cessation. The non-recombining region covers almost 7 Mbp, over 75% of the chromosome, and we hypothesize that the evolution of the mating-type chromosome in this lineage involved two successive events. The first event was contemporaneous with the split of N. tetrasperma from a common ancestor with its outcrossing relative N. crassa and suppressed recombination over at least 6.6 Mbp, and the second was confined to a smaller region in which recombination ceased more recently. In spite of the early origin of the first “evolutionary stratum”, genealogies of five genes from strains belonging to an additional N. tetrasperma lineage indicate independent initiations of suppressed recombination in different phylogenetic lineages. This study highlights the shared features between the sex chromosomes found in the animal and plant kingdoms and the fungal mating-type chromosome, despite fungi having no separate sexes. As is often found in sex chromosomes of plants and animals, recombination suppression of the mating-type chromosome of N. tetrasperma involved more than one evolutionary event, covers the majority of the mating-type chromosome and is flanked by distal regions with obligate crossovers

Posttraumatic stress among not-exposed traumatically bereaved relatives after the MS Estonia disaster

Background: Little is known about posttraumatic stress (PTS) reactions in bereaved individuals following loss in disaster who were not directly exposed to disaster. The aim of the present study was to examine the course of PTS up to three years after losing relatives in the MS Estonia ferry disaster, one of the worst maritime disasters in modern times. Methods: Seven postal surveys were sent out over three years post-disaster. The respondents were invited and added consecutively during the three years and 938 relatives participated in one or more of the surveys, representing 89% of the MS Estonia's Swedish victims. The survey included the Impact of Event Scale (IES) to measure PTS. Latent growth curve modeling was used to analyze PTS over time. Results: The majority of bereaved individuals had high levels of PTS. At three years post-loss, 62% of the respondents scored above the recommended cut-off value on the IES. Over time, PTS symptoms declined, but initially high symptoms of PTS were associated with a slower recovery rate. Conclusion: The present finding suggests that being an indirectly-exposed disaster-bereaved close-relative can lead to very high levels of PTS which are sustained for several years

Fracture morphology of carbon fiber reinforced plastic composite laminates

Carbon fiber reinforced plastic (CFRP) composites have been extensively used in fabrication of primary structures for aerospace, automobile and other engineering applications. With continuous and widespread use of these composites in several advanced technology, the frequency of failures is likely to increase. Therefore, to establish the reasons for failures, the fracture modes should be understood thoroughly and unambiguously. In this paper, CFRP composite have been tested in tension, compression and flexural loadings; and microscopic study with the aid of Scanning Electron Microscope (SEM) has been performed on failed (fractured) composite surfaces to identify the principle features of failure. Efforts have been made in correlating the fracture surface characteristics to the failure mode. The micro-mechanics analysis of failure serves as a useful guide in selecting constituent materials and designing composites from the failure behavior point of view. Also, the local failure initiation results obtained here has been reliably extended to global failure prediction

Posttraumatic stress in survivors 1 month to 19 years after an airliner emergency landing

Posttraumatic stress (PTS) is common in survivors from life-threatening events. Little is known, however, about the course of PTS after life threat in the absence of collateral stressors (e.g., bereavement, social stigma, property loss) and there is a scarcity of studies about PTS in the long term. This study assessed the short- and long-term course of PTS, and the influence of gender, education and age on the level and course of PTS, in survivors from a non-fatal airliner emergency landing caused by engine failure at an altitude of 1 km. There were 129 persons on board. A survey including the Impact of Event Scale was distributed to 106 subjects after 1 month, 4 months, 14 months, and 25 months, and to 95 subjects after 19 years (response rates 64–83%). There were initially high levels of PTS. The majority of changes in PTS occurred from 1 to 4 months after the event. There were small changes from 4 to 25 months but further decrease in PTS thereafter. Female gender was associated with higher levels of PTS whereas gender was unrelated to the slope of the short- and long-term trajectories. Higher education was related to a quicker recovery although not to initial or long-term PTS. Age was not associated with PTS. The present findings suggest that a life-threatening experience without collateral stressors may produce high levels of acute posttraumatic stress, yet with a benign prognosis. The findings further implicate that gender is unrelated to trajectories of recovery in the context of highly similar exposure and few collateral stressors.Long-term posttraumatic stress in survivors from disasters and major accident