Embryonic Diapause Is Conserved across Mammals

Embryonic diapause (ED) is a temporary arrest of embryo development and is characterized by delayed implantation in the uterus. ED occurs in blastocysts of less than 2% of mammalian species, including the mouse (Mus musculus). If ED were an evolutionarily conserved phenomenon, then it should be inducible in blastocysts of normally non-diapausing mammals, such as domestic species. To prove this hypothesis, we examined whether blastocysts from domestic sheep (Ovis aries) could enter into diapause following their transfer into mouse uteri in which diapause conditions were induced. Sheep blastocysts entered into diapause, as demonstrated by growth arrest, viability maintenance and their ED-specific pattern of gene expression. Seven days after transfer, diapausing ovine blastocysts were able to resume growth in vitro and, after transfer to surrogate ewe recipients, to develop into normal lambs. The finding that non-diapausing ovine embryos can enter into diapause implies that this phenomenon is phylogenetically conserved and not secondarily acquired by embryos of diapausing species. Our study questions the current model of independent evolution of ED in different mammalian orders

Creep characterization of Al alloy thin films for use in RF-MEMS switches

Creep is expected to be a major reliability problem in some MEMS, as for example RF-MEMS switches, especially at high RF powers. For this reason it should be avoided to use creep sensitive materials in these devices. In this paper we report on creep studies on Al-alloys, materials that are often used for the bridge in RF MEMS switches. Substrate curvature measurements were used to study Al98.3Cu1.7, Al99.7V0.2Pd0.1 and Al93.5Cu4.4Mg1.5Mn0.6 films during isothermal tensile stress relaxation. It is shown that to all studied aluminum compositions dislocation glide describes the relaxation data well for temperatures up to 110 °C. The paper discusses a very simple way of characterizing creep in thin Al-alloy films by the activation energy ¿F and the athermal flow stress t. A large difference in creep sensitivity of the studied alloys is measured: Al–Cu–Mg–Mn is found to be very creep resistant while Al–Cu is creep sensitive. It is shown that there is a direct relation between the measured creep parameters and the coherency, size and spacing of precipitates observed by TEM and SEM in the alloys. There is also a direct link between the creep-sensitivity and the obstacle strength of the precipitates

Creep as a reliability problem in MEMS

15th European Symposium on Reliability of Electron Devices, Failure Physics and Analysi

Grand-paternal age and the development of autism-like symptoms in mice progeny

Advanced paternal age (APA) contributes to the risk of autism spectrum disorders (ASDs) in children. In this study, we used a mouse model to investigate the effects of APA on behavioral features related to autistic syndromes (that is, social deficits, communication impairments and stereotypic/repetitive behaviors). We also examined whether such effects are transmitted across generations. To do this, males aged 15 months (APA) and 4 months (control) were bred with 4-month-old females, and the resulting offspring (F1) and their progeny (F2; conceived by 4-month-old parents) were tested for the presence and severity of ASD-like behaviors. Our results indicate that APA resulted in offspring that displayed distinctive symptoms of ASD. We found that both F1 conceived from old fathers and F2 derived from old grandfathers displayed increased ultrasound vocalization (USV) activity, decreased sociability, increased grooming activity and increased anxiety-like responses. Moreover, such abnormalities were partially transmitted to the second generation of mice, having APA grandfathers. In conclusion, our study suggests that the risk of ASD could develop over generations, consistent with heritable mutations and/or epigenetic alterations associated with APA

Mechanically probing time-dependent mechanics in metallic MEMS

The reliability of metallic micro-electromechanical systems (MEMS) depends on time-dependent deformation such as creep. To this end, a purely mechanical experimental methodology for studying the time-dependent deformation of free-standing microbeams has been developed. It is found most suitable for the investigation of creep due to the simplicity of sample handling and preparation and setup design, whilst maximizing long term stability and displacement resolution. The methodology entails the application of a constant deflection to a µm-sized free-standing aluminum cantilever beam for a prolonged period of time. After this load is removed, the deformation evolution is immediately recorded by acquiring surface height profiles through confocal optical profilometry. Image correlation and an algorithm based on elastic beam theory are applied to the full-field beam profiles to yield the tip deflection as a function of time. The methodology yields the tip deflection as function of time with ~3 nm precision