לוח שנה משולב

Cerebral Blood Flow (CBF) and Blood-oxygen-level dependent (BOLD) are contrasts enabling investigation of cerebral haemodynamics. Multi-echo EPI-based techniques have been used to measure CBF and BOLD simultaneously at 3T. At 7T, however, the shorter T2* times call for the use of the more efficient k-space coverage of spiral trajectories: undersampled spiral-out spiral-in trajectory enables sufficient coverage with central k-space echo times fit for both contrasts, with reduced crosstalk. The difficulty of the ill-conditioned inverse problem is enhanced by the stronger field inhomogeneities at 7T, causing significant artifacts when using standard methods for image reconstruction. We introduce Minimal Linear Network (MLN), a learning-based technique with restricted, interpretable model closely following the MR signal model. MLN shows the ability to produce clear reconstructed images under these conditions, while preserving sensitivity to the minute signal changes of ASL. Using the suggested technique, perfusion maps and functional CBF- and BOLD- based activation maps are obtained, showing low BOLD contamination in the CBF measurement, and indicating the variable contribution of flow to the BOLD contrast in the motor and visual cortex.

Over the past decade, the field of topological states has boosted frontline research in condensed matter physics. It is witnessed that the prediction and discovery of topological materials have stimulated the rapid development of this field. In this talk, I will overview the general concepts of topological states. In combination with computational methods, chemistry insights are found to be rather helpful to discover topological materials, to realize the beautiful concepts and phenomena in physics. For example, the topological Weyl fermions were recently discovered in realistic materials with topological Fermi arcs on the surface and exotic transport phenomena in the bulk.

The heart is a fascinatingly efficient pump with intricate design criteria. While many aspects of heart function remain a mystery, investigations through the prism of mechanics, physics, and mathematics can provide invaluable insights – presented as three examples in this talk. First, we consider the problem of automatically characterizing cardiac tissue architecture over multiple length-scales. Through, the use of existing and creation of new order parameters, multiple discoveries were made such as the existence of consistently sized spontaneous patches of organization in isotropic cardiac tissues. Second, we explore the relationship between cell organization and tissue force generation. Through a tissue engineering trick, the global (~1mm) and local (~100 microns) architecture effects were separated, and it was discovered that the reduction in developed force due purely to changes in global tissue architecture can be predicted by an astonishingly simple physical model, while local changes trigger complex biological responses. Third, we investigate the relationship among genetic mutations to the nuclear lamina protein, Lamin A/C (LMNA), detrimental consequences to cellular architecture, and cardiac function. LMNA mutations can lead to a devastating early aging disease (progeria) or have a subtler effect with patients presenting only with heart disease symptoms. However, the mechanisms by which the LMNA mutation emerges in the heart muscle are unknown. Thus far we have uncovered a relationship between nuclear defects in patient-specific cells and the age at which these patients present with heart disease symptoms. Additionally, we have found that the pathology that takes decades to develop in patients can be recapitulated in a dish within a few weeks. Through all three of these examples, we will also explore newly generated mysteries that can again be elucidated in the future through the application of physical principles.

Cells both actively generate and sensitively react to forces, typically behaving as elastic solids on short
time-scales and resembling a viscous liquid on long time-scales. The long-term behavior is the most
relevant to shaping of tissues. However, measurement of long-term multicellular properties is difficult
because cells are adaptive entities that actively respond to external ques by changing their properties.
Accumulating experimental evidences show that active nematic hydrodynamic theory provides an excellent
framework to help to dissect and understand the complex dynamics across different cell types. In our
recent papers (Nature Physics 2018, Physical Review Letters 2018) [1, 2] we have shown existence of
different nemato-dynamic modes and estimated multicellular physical properties (e.g. activity, viscosity,
friction, Frank elastic constant) using high-throughput screening of in vitro cell cultures. I will present
spontaneous emergence of collective shear flows and activity driven turbulence in cultured tissues. I will
discuss the mechanism behind these phenomena and their effect on cell organization and function

Processes at the interface of inorganic solids and polymers mimic a large variety of natural processes such as stimuli responsive behavior, self-healing, actuation, transport and delivery, pH-buffering, but they are not well understood. Polyelectrolyte multilayers are suitable for studying this, as they can be manipulated at will between glassy, rubbery, hydrogel or organogel. We suggest to investigate photocatalytically triggered local pH changes in titania / polyelectrolyte Layer-by-Layer (LbL) / lipid bilayer assembled interfaces, mimicking natural processes in a novel design strategy for inorganic / polymer interfaces as well as to further brain-inspired computing.
We have shown recently that under irradiation of TiO2 a series of photocatalytic reactions leads to a local change in pH, which modulates the pH sensitive LbL assembly. Prime questions are: (i) how many photons are needed to locally change the pH on titania? (ii) what is the optimum LbL architecture to understand the basis of proton trapping and storage, the pH gradient under local irradiation? And (iii) how to achieve reversible actuation of different assemblies for advanced applications?
We focus for the first time on the possibility of efficient transformation of energy of electromagnetic irradiation into local pH shift to actuate soft matter. This is used to demonstrate the application on cell surface interactions, self-repairing strategies, use of a chemical systems to communicate with bacteria, in general control on non-linear chemical processes at interfaces.