לוח שנה משולב

Organic material accounts for a large fraction of atmospheric aerosol, with the majority being secondary organic aerosol (SOA) formed through oxidation processes. Primary emissions leading to SOA include thousands of chemicals from a variety of natural and anthropogenic sources ranging over approximately 15 orders of magnitude of volatility. As organics are oxidized they fragment to form smaller volatiles or add functionality leading to SOA formation, dramatically increasing the complexity of compounds present. A continuing challenge in aerosol research is to elucidate the sources, structure, chemistry, fate, climate and health impacts of these organic atmospheric constituents.

The complex chemical composition of organic aerosols presents unique measurement challenges. My group and close collaborators have developed the Thermal Desorption Aerosol Gas chromatograph (TAG) system for hourly in-situ speciation of a wide range of primary and secondary organic compounds in aerosols. This instrument combines a particle collector with thermal desorption followed by GCMS detection to provide hourly separation, identification, and quantification of organic constituents at the molecular level. We incorporated two-dimensional chromatography (GCxGC), providing dramatically enhanced speciation. We developed a semivolatile collection and analysis system that allows simultaneous measurement of specific organics in the gas and particle phases, enabling analysis of their partitioning. We also developed a combined TAG-AMS (Aerosol Mass Spectrometer) instrument for simultaneous measurements of the total and speciated aerosol composition. We are currently exploring soft ionization with vacuum ultraviolet radiation using a high resolution time of flight mass spectrometer (GCxGC/VUV-HRTOFMS) to more fully separate and identify compounds in complex mixtures such as diesel fuel, motor oil, fire emissions, in controlled oxidation studies, and in ambient samples. This talk will review recent developments (TAG, 2DTAG, SVTAG, TAG-AMS, GCxGC/VUV-HRTOFMS), and present new atmospheric observations, source characterizations, and controlled oxidation studies to more fully characterize atmospheric organic sources and transformation processes.

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).