Vulnerability of CMOS image sensors in megajoule class laser harsh environment

CMOS image sensors (CIS) are promising candidates as part of optical imagers for the plasma diagnostics devoted to the study of fusion by inertial confinement. However, the harsh radiative environment of Megajoule Class Lasers threatens the performances of these optical sensors. In this paper, the vulnerability of CIS to the transient and mixed pulsed radiation environment associated with such facilities is investigated during an experiment at the OMEGA facility at the Laboratory for Laser Energetics (LLE), Rochester, NY, USA. The transient and permanent effects of the 14 MeV neutron pulse on CIS are presented. The behavior of the tested CIS shows that active pixel sensors (APS) exhibit a better hardness to this harsh environment than a CCD. A first order extrapolation of the reported results to the higher level of radiation expected for Megajoule Class Laser facilities (Laser Megajoule in France or National Ignition Facility in the USA) shows that temporarily saturated pixels due to transient neutron-induced single event effects will be the major issue for the development of radiation-tolerant plasma diagnostic instruments whereas the permanent degradation of the CIS related to displacement damage or total ionizing dose effects could be reduced by applying well known mitigation techniques

Hardening approach to use CMOS image sensors for fusion by inertial confinement diagnostics

A hardening method is proposed to enable the use of CMOS image sensors for Fusion by Inertial Confinement Diagnostics. The mitigation technique improves their radiation tolerance using a reset mode implemented in the device. The results obtained evidence a reduction of more than 70% in the number of transient white pixels induced in the pixel array by the mixed neutron and γ-ray pulsed radiation environment

Chromatin Immunoprecipitation Protocol for Histone Modifications and Protein-DNA binding analyses in arabidopsis

Epigenetic control of plant development via histone modifications is involved in different processes ranging from embryonic development, vegetative development, flowering time control, floral organ development, to pollen tube growth. The identification of an increasing number of epigenetically regulated processes was greatly advanced by methods allowing the survey of genome-wide histone modifications and chromatin-protein interactions. However, genome-wide approaches are too broad to access in detail a large number of histone modifications taking place at a single locus. Here, we provide a robust chromatin immunoprecipitation (ChIP) protocol, allowing in vivo analyses of multiple chromatin modifications and binding of histone modifiers in different plant organs and tissues. This method is quantitative and provides a way to study the dynamic state of chromatin during plant development and also in response to different environmental stimuli

Induction of Differentiation in the Shoot Apical Meristem by Transient Overexpression of a Retinoblastoma-Related Protein

The shoot apical meristem contains cells that undergo continual growth and division to generate the building blocks for the aerial portion of the plant. As cells leave the meristem, they undergo differentiation to form specific cell types. Most notably, heterotrophic cells of the meristem rapidly gain autotrophic capability by synthesis and assembly of components of the chloroplast. At the same time, cells undergo enlargement via vacuolation. Despite significant advances in the characterization of transcriptional networks involved in meristem maintenance and leaf determination, our understanding of the actual mechanism of meristem cell differentiation remains very limited. Using a microinduction technique, we show that local, transient overexpression of a retinoblastoma-related (RBR) protein in the shoot apical meristem is sufficient to trigger cells in the meristem to undergo the initial stages of differentiation. Taken together with recent data showing that RBR protein plays a key role in restricting stem cell differentiation in the root apical meristem, our data contribute to an emerging picture of RBR proteins as a central part of the mechanism controlling meristem cell differentiation

ARABIDOPSIS TRITHORAX1 Dynamically Regulates FLOWERING LOCUS C Activation via Histone 3 Lysine 4 Trimethylation[W]

Trithorax function is essential for epigenetic maintenance of gene expression in animals, but little is known about trithorax homologs in plants. ARABIDOPSIS TRITHORAX1 (ATX1) was shown to be required for the expression of homeotic genes involved in flower organogenesis. Here, we report a novel function of ATX1, namely, the epigenetic regulation of the floral repressor FLOWERING LOCUS C (FLC). Downregulation of FLC accelerates the transition from vegetative to reproductive development in Arabidopsis thaliana. In the atx1 mutant, FLC levels are reduced and the FLC chromatin is depleted of trimethylated, but not dimethylated, histone 3 lysine 4, suggesting a specific trimethylation function of ATX1. In addition, we found that ATX1 directly binds the active FLC locus before flowering and that this interaction is released upon the transition to flowering. This dynamic process stands in contrast with the stable maintenance of homeotic gene expression mediated by trithorax group proteins in animals but resembles the dynamics of plant Polycomb group function

Short Integuments1/suspensor1/carpel Factory, a Dicer Homolog, Is a Maternal Effect Gene Required for Embryo Development in Arabidopsis

The importance of maternal cells in controlling early embryogenesis is well understood in animal development, yet in plants the precise role of maternal cells in embryogenesis is unclear. We demonstrated previously that maternal activity of the SIN1 (SHORT INTEGUMENTS1) gene of Arabidopsis is essential for embryo pattern formation and viability, and that its postembryonic activity is required for several processes in reproductive development, including flowering time control and ovule morphogenesis. Here, we report the cloning of SIN1, and demonstrate its identity to the CAF (CARPEL FACTORY) gene important for normal flower morphogenesis and to the SUS1 (SUSPENSOR1) gene essential for embryogenesis. SIN1/SUS1/CAF has sequence similarity to the Drosophila melanogaster gene Dicer, which encodes a multidomain ribonuclease specific for double-stranded RNA, first identified by its role in RNA silencing. The Dicer protein is essential for temporal control of development in animals, through the processing of small RNA hairpins that in turn inhibit the translation of target mRNAs. Structural modeling of the wild-type and sin1 mutant proteins indicates that the RNA helicase domain of SIN1/SUS1/CAF is important for function. The mRNA was detected in floral meristems, ovules, and early embryos, consistent with the mutant phenotypes. A 3.3-kb region 5′ of the SIN1/SUS1/CAF gene shows asymmetric parent-of-origin activity in the embryo: It confers transcriptional activation of a reporter gene in early embryos only when transmitted through the maternal gamete. These results suggest that maternal SIN1/SUS1/CAF functions early in Arabidopsis development, presumably through posttranscriptional regulation of specific mRNA molecules