Removal of an obstruction from a tube by a collapsing bubble

The use of a collapsing bubble to clear an obstruction (in the form of a steel ball) near a tube, submerged in water, is studied with high speed photography. Tubes in horizontal and vertical configurations are studied. The bubble is generated via an electric spark discharge. The flow in the tubes resulting from the expansion of the bubble, or the high speed jet from the collapsing bubble pushes the ball away from the tubes and therefore clears the obstructions. In a case where airbacked tube is used, the bubble jets away from the tube. The resulting water plum at the hole (water-air interface) removes the blockage. The speed of the ball can be as high as 1 m/s shortly after the collapse of the bubble. Further studies are required to translate the phenomena observed to clinical applications such as the removal of blood clots in vessels or the clearing of blocked transplanted tubes..http://deepblue.lib.umich.edu/bitstream/2027.42/84282/1/CAV2009-final98.pd

Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns

Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition

Alternative splicing and nonsense-mediated decay regulate telomerase reverse transcriptase (TERT) expression during virus-induced lymphomagenesis in vivo

<p>Abstract</p> <p>Background</p> <p>Telomerase activation, a critical step in cell immortalization and oncogenesis, is partly regulated by alternative splicing. In this study, we aimed to use the Marek's disease virus (MDV) T-cell lymphoma model to evaluate TERT regulation by splicing during lymphomagenesis <it>in vivo</it>, from the start point to tumor establishment.</p> <p>Results</p> <p>We first screened cDNA libraries from the chicken MDV lymphoma-derived MSB-1 T- cell line, which we compared with B (DT40) and hepatocyte (LMH) cell lines. The chTERT splicing pattern was cell line-specific, despite similar high levels of telomerase activity. We identified 27 alternative transcripts of chicken TERT (chTERT). Five were in-frame alternative transcripts without <it>in vitro </it>telomerase activity in the presence of viral or chicken telomerase RNA (vTR or chTR), unlike the full-length transcript. Nineteen of the 22 transcripts with a premature termination codon (PTC) harbored a PTC more than 50 nucleotides upstream from the 3' splice junction, and were therefore predicted targets for nonsense-mediated decay (NMD). The major PTC-containing alternatively spliced form identified in MSB1 (ie10) was targeted to the NMD pathway, as demonstrated by UPF1 silencing. We then studied three splicing events separately, and the balance between in-frame alternative splice variants (d5f and d10f) plus the NMD target i10ec and constitutively spliced chTERT transcripts during lymphomagenesis induced by MDV indicated that basal telomerase activity in normal T cells was associated with a high proportion of in-frame non functional isoforms and a low proportion of constitutively spliced chTERT. Telomerase upregulation depended on an increase in active constitutively spliced chTERT levels and coincided with a switch in alternative splicing from an in-frame variant to NMD-targeted variants.</p> <p>Conclusions</p> <p>TERT regulation by splicing plays a key role in telomerase upregulation during lymphomagenesis, through the sophisticated control of constitutive and alternative splicing. Using the MDV T-cell lymphoma model, we identified a chTERT splice variant as a new NMD target.</p

Why evolutionary biologists should be demographers.

Evolution is driven by the propagation of genes, traits and individuals within and between populations. This propagation depends on the survival, fertility and dispersal of individuals at each age or stage during their life history, as well as on population growth and (st)age structure. Demography is therefore central to understanding evolution. Recent demographic research provides new perspectives on fitness, the spread of mutations within populations and the establishment of life histories in a phylogenetic context. New challenges resulting from individual heterogeneity, and instances where survival and reproduction are linked across generations are being recognized. Evolutionary demography is a field of exciting developments through both methodological and empirical advances. Here, we review these developments and outline two emergent research questions

All paths to fitness lead through demography

International audienc

Engineering effective cooperation and communication: a bottom-up approach

Abstract: Current research in crisis management research tends to overemphasise formal organisational modes and does not adequately support ground level teams. Following a case study, we identify five main problems experienced by rescuers at the start of an emergency intervention. The work shows a clear need to focus research on ground level communication and local coordination activities and to develop flexible communication tools and flexible coordination structures. We argue that robustness, flexibility and self-organisation are key issues in designing emergency communication systems. We give two simple examples of communication tools that can support flexible and robust communications. Engineering effective cooperation and communication 59 Bernard Pavard is CNRS Research Director of the Cognitive Engineering Research Group in Toulouse, France (GRIC-IRIT). Over the past 10 years, he has worked closely with the emergency services to develop technologies to support emergency management. His interests include modelling complexity in social sciences, virtual cooperative spaces and emergency management

The influence of maternal care in shaping human survival and fertility

International audienceThe influence of maternal care on child survival has evolved throughout human history due to variation in altriciality, allocare, and maternal behaviors. Here, we study the impact of these factors on the force of selection acting on age-specific survival and fertility (measured with elasticity analysis) in a model that incorporates the dependence of child survival on maternal survival. Results reveal life-history changes that cannot be elucidated when considering child's survival independent of maternal survival: decrease of late fertility and increase of late survival, and concomitant decrease of early and late fertility. We also show that an increase of child altriciality in early humans might explain the main human life-history traits: a high life expectancy and postreproductive life; a long juvenile period and a higher, and narrowed, fertility at the peak of the reproductive period