לוח שנה משולב

The BCC phase of solid helium-4 has a gapped excitation mode, as revealed by inelastic neutron scattering experiments. This mode is unexpected, since BCC is a Bravais lattice and therefore acoustic modes are the only low-lying excitations expected in the harmonic solid. I will give a simple model for this new collective excitation based on the amplitude fluctuations of a quantum solid

Membrane proteins are an exciting class of biomacromolecules and play important roles in a variety of biological processes that are directly linked to major diseases including cancer, aging-related diseases, and infectious diseases. A complete understanding of their function can only be accomplished using high-resolution structures. In spite of recent developments in structural biology, membrane proteins continue to pose tremendous challenges to most biophysical techniques. A major area of research in my group is focused on the development of NMR techniques to study the dynamic structures of membrane bound proteins such as cytochrome b5, cytochrome P450 and cytochrome P450-reductase. In the first-half of my talk, I will present strategies to study the structure and dynamics of these challenging systems and also on the electron transfer mechanism that enables the enzymatic
function of P450. The accumulation of misfolded proteins is a hallmark feature in numerous human disorders such as blood diseases like sickle cell anemia, neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease, and metabolic diseases such as type II diabetes. Misfolded protein aggregates may deposit in tissues, can be intracellular, extracellular, or both. The conformational changes accompanying misfolding can result in disruption of the regular function of the protein or may result in a gain of function that is often associated with toxicity. Amyloid peptides represent a subset of misfolded proteins whose misfolded state shares unique characteristics. Our research group has been investigating the high-resolution structures of early amyloid intermediates, amyloid-membrane interaction and membrane disruption, and the interaction of polyphenols with amyloid proteins. In the second-half of my presentation, NMR structures of early intermediates of amyloid peptides, mechanisms of amyloid-induced membrane disruption, and amyloid inhibition by polyphenolic compounds will be discussed. Solid-state NMR results on the interaction of amyloid fibers with lipid bilayers, and novel NMR approaches to investigate amyloid formation will also be presented.
1. BBA Biomembranes 1768 (2007) 3235.
2. Acc. Chem. Res. 116 (2012) 3650.
3. Chem. Soc. Rev. 41 (2012) 608.

The procedure for diagnostics of laser induced plasma (LIP) by optical emission spectroscopy technique is described. LIP was generated by focusing Nd:YAG laser radiation (1.064 nm, 50 mJ, 15 ns pulse duration) on the surface of pellet containing among other elements lithium. Details of the experimental setup and experimental data processing are presented.
High speed plasma photography was used to study plasma evolution and decay. From those images optimum time for plasma diagnostics is located.
The electron number density, Ne, is determined by fitting profiles of Li I lines while electron temperature, Te, was determined from relative intensities of Li I lines using Boltzmann plot (BP) technique. All spectral line recordings were tested for the presence of self-absorption and then if optically thin, Abel inverted and used for plasma diagnostic purposes.

Examine random walk in a stationary, ergodic, random environment which is bistochastic i.e. the sum of probabilities to enter any fixed vertex is 1. Consider the drift as a function on the probability space on the environments, and assume it belongs to domain of definition of where D is the symmetrized generator of the walk (this is the famous H_{-1} condition). We show that under these conditions the walk satisfies a central limit theorem. The proof uses the "relaxed sector condition" which shows an unexpected connection to the spectral theory of unbounded operators.

All terms will be explained in the talk. This is joint work with B??lint T?³th.