לוח שנה משולב

Confining hydrogen molecules in nanoscale cavities leads to the quantization of their translational degrees of freedom, in addition to the quantized rotational states. This opens the door for the investigations of the quantum dynamics of coupled translational and rotational motions of the guest molecules, and how it is affected by the size, shape, symmetry, and chemical composition of the host cavity. We will review our rigorous treatment in the past couple of years of the quantum translation-rotation (T-R) dynamics of hydrogen molecules trapped in the small and large cages of the structure II clathrate hydrate and inside the fullerenes C60 and C70, and also in their open-cage derivatives. These studies have determined the maximum H2 occupancy of the host cavities, and demonstrated the key role that the T-R zero-point energy plays in it. They have also have quantified the temperature dependence of the spatial distributions of the guest molecules, as well as their intricate T-R energy level structure exhibiting conspicuous patterns of degeneracies and level splittings. Quantum methodology for rigorous calculations of the inelastic neutron scattering (INS) spectra of nanoconfined molecules has been developed and implemented. Our findings are in excellent agreement with the recent spectroscopic measurements of these systems.

Magnetic resonance imaging (MRI) is a powerful and widely used medical imaging modality in clinical practice. When MRI is used to study mice, the roles of individual genes involved in human diseases, ranging from cancers to diabetes and heart disease, can be elucidated. Typically, when studying the heart with MRI, cardiac MRI (CMR) is used to phenotype genetically altered mice in terms of left ventricular (LV) structure and global function, contractile function, and infarct size and LV remodeling after myocardial infarction (MI). In addition, MRI has been used to assess cardiac structural and functional changes after MI in mice, but changes in myocardial perfusion after acute MI have not previously been examined. Development of novel CMR methods can enable more comprehensive measurements in the healthy and diseased mouse heart as part of preclinical cardiac research.
In this presentation, I will first discuss the development and applications of a dynamic manganeses (Mn)-enhanced CMR method for assessing an index of LTCC function (LTCCI). The roles of nitric oxide synthase (NOS) isoforms in modulating calcium cycling in the mouse heart have been examined primarily using in vitro or invasive in vivo techniques in genetically altered mice. However, the roles of neuronal NOS (nNOS) and endothelial NOS (eNOS) in regulating LTCC and contractile functions remain controversial. Using cine-DENSE MRI to study contractile function, and dynamic Mn-enhanced CMR to study LTCC function, we comprehensively examined the roles of nNOS and eNOS in modulating in vivo calcium cycling and contractile function in the heart. In contrast to the prevailing model of NO signaling, our novel in vivo study demonstrated that nNOS, and not eNOS, plays a dominant role in modulating calcium cycling in the mammalian heart.
Experimental myocardial infarction (MI) in mice is an important disease model in part due to the ability to study genetic manipulations. MRI has been used to assess cardiac structural and functional changes after MI in mice, but changes in myocardial perfusion after acute MI have not previously been examined. I will discuss the development of an improved arterial spin labeling (ASL) method for measurement of myocardial perfusion in the mouse heart. ASL non-invasively measures perfusion, but is sensitive to respiratory motion and heart rate variability, and is difficult to apply after acute MI in mice. To account for these factors, a cardio-respiratory gated (CRG) ASL sequence using a fuzzy C-means algorithm to retrospectively reconstruct images was developed. Using this method, myocardial perfusion was measured in remote and infarcted regions at 1, 7, 14, and 28 days post-MI. Baseline perfusion was 4.9 ± 0.5 (ml/g•min) and one day post-MI decreased to 0.9 ± 0.8 (ml/g•min) in infarcted myocardium (P

The standard cosmological model in which structure formation is driven by the gravitational pull of the dark matter, has passed stringent observational constraints. The success of this model
will be reviewed with special emphasis on a recent analysis of the large scale motions of galaxies.
Despite its success, new challenges to this model keep surfacing as high quality observational data continue to
accumulate. Challenges in explaining observations of the nearby by Universe may be resolved by
minor modifications of the physics of the dark sector.