לוח שנה משולב

Neuronal networks have many tunable parameters such as synaptic strengths that are shaped during learning of a task. The number of degrees of freedom for representing a task can vastly exceed the minimum required for good performance. I will describe recent work that explores the consequences of such additional ‘redundant’ degrees of freedom for learning and for task representation. We find that additional redundancy in network parameters can make a fixed task easier to learn and compensate for deficiencies in learning rules. However, we also find that in a biologically relevant setting where synapses are subject to unavoidable noise there is an upper limit to the level of useful redundancy in a network, suggesting an optimal network size for a given task.

Transition-metal mediated bond cleavage and formation has made a great contribution in synthetic organic chemistry. A metal-ligand cooperativity often plays essential roles in the bond cleavage and formation reactions. Shvo and Casey studied the heterolytic cleavage/formation of H–H bond mediated by cyclopentadienone metal complexes with simultaneous oxidation/reduction of the central metal.
Here in this presentation, this cooperativity is applied to the new type of bond cleavage/formation reactions such as C–O, C–H, and B–H Bonds.

More than one-third of the 4000+ planet candidates found by NASA’s Kepler spacecraft are associated with target stars that have more than one planet candidate, and such “multis” account for the vast majority of candidates that have been verified as true planets. The large number of multis tells us that flat multiplanet systems like our Solar System are common. Virtually all of the candidate planetary systems are stable, as tested by numerical integrations that assume a physically motivated mass-radius relationship. Statistical studies performed on these candidate systems reveal a great deal about the architecture of planetary systems, including the typical spacing of orbits and flatness.
The characteristics of several of the most interesting confirmed Kepler & TESS multi-planet systems will also be discussed.

The brain is no longer considered a completely autonomous tissue with respect to its immune activity. Rather, immune surveillance is required for supporting brain functional plasticity and repair. Essential immune cells include the microglia, the resident immune cells of the brain, and circulating immune cells. Both the resident microglia and the circulating immune cells are under tight regulatory control to allow risk-free benefit from immunological interventions. We found that access of circulating immune cells to the brain is controlled by the brain’s epithelial barrier, the blood cerebrospinal barrier. Using immunological and immunogenomic tools, we discovered that in brain aging and under neurodegenerative conditions, this barrier does not optimally function to enable brain repair. We further showed in mouse models of Alzheimer’s disease (AD), that activating the immune system by immunotherapy directed against the inhibitory PD-1/PD-L1 immune checkpoint pathway drives an immune-dependent cascade of processes that start in the periphery and culminate with recruitment of monocyte-derived macrophages to the brain, which contribute to disease modification, reversing and slowing-down cognitive loss, reducing brain inflammation, and mitigating disease pathology in a mouse models of AD and Dementia (tauopathy). Overall, our results indicate that targeting the immune system outside the brain, rather than brain-specific disease-escalating factors within the central nervous system, can potentially provide a multi-dimensional disease-modifying therapy for AD and dementia.

Due to the direct correlation among the physical properties and crystal structure of materials, study of the latter is crucial for fundamental understanding of the properties. In the era of nano-science, objects of interest are getting smaller and traditional single-crystal and powder X-ray diffraction methods cannot be applied for characterization of their atomic structures due to the unavailability of single crystals and/or small quantity and size of these crystals in the multiphase specimens. Thus, electron crystallography (EC) (which is defined as a combination of electron diffraction and imaging methods) is sometimes the only viable tool for the analysis of their structure.
In the previous century, electron diffraction (ED) was considered to be unsuitable for structure determination due to the problems of data quality arising from dynamical effects. At the last decades, researchers have shown that influence of dynamical effects can be substantially reduced if beam precession (PED) is used and/or data collection is performed in the off-axis conditions - enabling solution of atomic structures with various complexity (from inorganics to proteins).
Our group focuses on development and application of EC methods for structure solution of nano-sized precipitates and characterization of structural defects in steels and light alloys. This study is technologically essential since precipitates and defects dictate physical properties of these structural materials. It must be noted that, atomic structures of intermetallics were not solved previously using solely ED methods. Reason for that is in the nature of intermetallic compound's structures. Contrarily to other complex materials, the atomic distances and angles of intermetallics are not fixed and coordination polyhedra are usually unknown. Thus, structure solution of these compounds is harder to validate.
In the present seminar, contribution of our group in the development of routine structure solution path for aluminides (as an example of intermetallics) will be presented. In addition, characterization of structural defects, influencing the performance of the studied materials, will be shown.

The 39-m ELT is under construction by the European Southern Observatory. When completed
it will be the largest optical/NIR telescope in the world at one of the best sites. The talk shall
focus on the challenges associated with building this telescope and will describe the first generation
instrumentation complement and science drivers.