לוח שנה משולב

Almost all energy (and hence most fuels and organic chemicals) derive from fossil fuels (natural gas, oil or coal) that in turn derive from solar energy. However the fuels must first be converted and refined (purified) into easily usable forms. For transportation (ca. 27% of global energy use) the fuel should be in a convenient liquid form. The Second Law of Thermodynamics .indicates that conversion can involve large losses which should be minimised The most usual technology involves reforming the fossil fuel into syngas, CO + H2. The syngas is then converted into largely n-alkanes and n-1-alkenes over heterogeneous catalysts (metallic Fe or Co, 250-350oC) in the very exothermic Fischer-Tropsch (FT) reaction. The precise processes that occur on the FT catalyst are still not completely clear, but the Dual Path mechanism seems to answer most questions. Here the reaction paths are determined by the interplay of the metal and support surfaces and the surface organics. In the (classical) Dissociative Mechanism the surface is regarded as neutral and only neutral organic / species, eg., {C}, {CH}, {CHn}, etc are involved. In the Associative Mechanism, more polar steps involving electrophiles and nucleophiles, eg., {CHOH}; {CHδ+} occur,
The key building block in the normal FT process is CO, but “climate change” considerations indicate that CO2 would be a very useful raw material. Can this work?

We are interested in understanding how memories are encoded and retained in the brain and use different methods to uncover the basic molecular and cellular mechanisms underlying learning. Following accumulation of basic science research and data, we recently try to find new ways to enhance memory. Very little is known about drugs which can enhance the consolidation phase of memories in the cortex, the brain structure considered to store at least partially, long term memories. We tested the hypothesis that pharmacological and genetic manipulation of translation machinery, known to be involved in the molecular consolidation phase, enhances positive or negative forms of cortical dependent memories. We found that dephosphorylation (Ser51) of eIF2α specifically in the cortex is both correlated and necessary for normal memory consolidation. In order to reduce eIF2α phosphorylation and improve memory consolidation, we pharmacologically or genetically inhibited the different eIF2α kinases expressed in the brain. In addition, we tested the involvement of eIF2α pathway in mice models of aging and sporadic Alzheimer disease and found strong link between the two.
Relevant recent publications:
1. Costa-Mattioli M, Gobert D, Stern E, Gamache K, Colina R, Cuello C, Sossin W, Kaufman R, Pelletier J, Rosenblum K, Krnjević K, Lacaille JC, Nader K, Sonenberg N (2007). eIF2 phosphorylation regulates the switch from short to long-term synaptic plasticity and memory. Cell 6;129(1):195-206. http://www.ncbi.nlm.nih.gov/pubmed/17418795
2. ApoE ε4 is associated with eIF2α phosphorylation and impaired learning in young mice (2013). Yifat Segev, Daniel M. Michaelson, Kobi Rosenblum Neurobiology of Aging.
http://www.ncbi.nlm.nih.gov/pubmed/22883908
3. Blocking eIF2a kinase – PKR – Enhances Positive and Negative Forms of Cortex-Dependent Taste Memory (2013). Stern Elad, Chinnakkaruppan Adaikkan, David Orit ,Sonenberg Nahum and Rosenblum Kobi. Journal of Neuroscience (in press).

We argue that type Ia supernovae (SNe Ia) are the result of head-on collisions of White Dwarfs (WDs) in
triple systems. The thermonuclear explosions resulting from the zero-impact-parameter collisions of WDs
are calculated from first principles by using 2D hydrodynamical simulations. Collisions of typical WDs with
masses 0.5-0.9 Msun result in explosions that synthesize 56Ni masses in the range of 0.15-0.8M Msun, spanning the wide distribution of yields observed for the majority of SNe Ia. The robustness of the shock ignition process is verified with a detailed study using a one-dimensional toy model and analytic tools. The late-time (& 50 days after peak) bolometric light curve is equal to the instantaneous energy deposition and is calculated exactly, by solving the transport of gmma-rays emitted by the decay of 56Ni using a Monte-Carlo code. All collisions are found to have the same late-time light curves, when normalized to the amount of synthesized 56Ni. This universal light curve is shown to agree with the majority of the supernovae in the compilation made by M. Stritzinger to an accuracy of better than 30% in the range 40 < t < 80 days after bolometric peak. The widths of the 56Ni mass- weighted-line-of-sight velocity distributions are correlated with the 56Ni yield and in agreement with the observed Mazzali relation. The continuous distribution of observed SN Ia features, is naturally reproduced with the distribution of WD masses involved in the collisions.