לוח שנה משולב

Understanding human brain structure and function organization in health, disease and development is one of the great challenges for neuroscience. Magnetic resonance imaging (MRI) is the most valuable technique for noninvasive in vivo imaging of human brain. However, the use of MRI is currently limited, due to the lack of theory that links the specific biological structures to the measured signal. In my presentation I will describe a new quantitative MRI (qMRI) method that directly measures two biophysical properties of the human brain tissue: the macromolecular tissue volume and the macromolecular physico-chemical environment. I will discuss how such quantities can be used for 1) individualize diagnostic applications and 2) mapping structure-function relations in cognitive processes such as reading.

Quantum nonlinear optics refers to a new physical regime where the electromagnetic re-sponse is not linear already at the level of single photons. We will discuss recent devel-opments in this field, new analysis tools, and future applications to light manipulation and to the study of many-body physics. A focus will be given to a current promising technique, where strong interaction between propagating photons is obtained via their coherent coupling to the strong electric-dipole of Rydberg atoms. A variety of engineered Hamiltonian dynamics will be presented, as well as recent demonstrations of photon blockade
and two-photon phase shifts.

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.