Exchange-dependent relaxation in the rotating frame for slow and intermediate exchange - modeling off-resonant spin-lock and chemical exchange saturation transfer

Chemical exchange observed by NMR saturation transfer (CEST) and spin-lock (SL) experiments provide an MRI contrast by indirect detection of exchanging protons. The determination of the relative concentrations and exchange rates is commonly achieved by numerical integration of the Bloch-McConnell equations. We derive an analytical solution of the Bloch-McConnell equations that describes the magnetization of coupled spin populations under radiofrequency irradiation.As CEST and off-resonant SL are equivalent, their steady-state magnetization and dynamics can be predicted by the same single eigenvalue: the longitudinal relaxation rate in the rotating frame R1rho. For the case of slowly exchanging systems, e.g. amide protons, the saturation of the small proton pool is affected by transverse relaxation (R2b). It turns out, that R2b is also significant for intermediate exchange, such as amine- or hydroxyl-exchange or paramagnetic CEST agents, if pools are only partially saturated. We propose a solution for R1rho that includes R2 of the exchanging pool by extending existing approaches, and verify it by numerical simulations. With the appropriate projection factors, we obtain an analytical solution for CEST and SL for nonzero R2 of the exchanging pool, whilst considering the dilution by direct water saturation across the entire Z-spectra. This allows the optimization of irradiation parameters and the quantification of pH-dependent exchange rates and metabolite concentrations. In addition, we propose evaluation methods that correct for concomitant direct saturation effects. It is shown that existing theoretical treatments for CEST are special cases of this approach

International reserves, growth and effective demand

During the last decade, developing (and some developed) economies have accumulated large amounts of international reserves, mainly for precautionary reasons. This phenomenon has been coupled with moderate economic growth. The resources being amassed largely overwhelm protective needs, there is an excess of resources that is being wasted, and which could be utilised for alternative productive projects, namely to promote growth. If insufficient aggregate demand can largely explain low growth, it is clear that this excess of international reserves can be used to stimulate aggregate demand. This paper argues that the excess of international reserves represents a potential source to boost growth.international reserves; aggregate demand; economic growth

Fernsehen als Ideologie (Teil II). Zur Inszenierung eines Erziehungskonflikts in der "Lindenstrasse"

Die TV-Serie „Lindenstraße“, von der die ARD seit 1985 mehr als 450 Folgen ausstrahlte, gilt als avanciertes Beispiel moderner Fernsehunterhaltung, da sie nicht nur von der Eigenstruktur her „flexibel“ ist, mithin unter Bedingungen und Vorgaben produziert wird, die unmittelbar die Wirkung auf Zuschauer im Blick haben, sondern auch, weil sie als populäre Familienserie einen aufklärenden Anspruch verteidigt und kontinuierlich ein Millionenpublikum bindet. Diese Eigenschaften prädestinieren die „Lindenstraße“ als Untersuchungsobjekt. Mit Hilfe einer qualitativen Inhaltsanalyse werden einige Dialog-Szenen auf Struktur, Geschehen sowie Art der Präsentation hin untersucht. Dadurch lassen sich die feinen Methoden, mit denen die „Lindenstraße“-Macher den Stoff im Dialog, in der Kameraführung, in der Schnitttechnik, in der Regieanweisung sowie in der Auswahl der Themen darbieten, leichter entschlüsseln und erhellen. (DIPF/Orig.

Towards magnetic resonance in scanning tunneling microscopy using heterodyne detection

The present work introduces a new concept for magnetic resonance measurements in the GHz regime inside a scanning tunneling microscope. It is based on heterodyne detection in a spin-polarized tunneling barrier. The experimental requirements, including a new method to suppress transmission effects, are explained. Measurements on three model systems which were studied to validate the new technique are presented and compared to simulations

Towards magnetic resonance in scanning tunneling microscopy using heterodyne detection

The present work introduces a new concept for magnetic resonance measurements in the GHz regime inside a scanning tunneling microscope. It is based on heterodyne detection in a spin-polarized tunneling barrier. The experimental requirements, including a new method to suppress transmission effects, are explained. Measurements on three model systems which were studied to validate the new technique are presented and compared to simulations

Fast and scalable non-parametric Bayesian inference for Poisson point processes

We study the problem of non-parametric Bayesian estimation of the intensity function of a Poisson point process. The observations are $n$ independent realisations of a Poisson point process on the interval $[0,T]$. We propose two related approaches. In both approaches we model the intensity function as piecewise constant on $N$ bins forming a partition of the interval $[0,T]$. In the first approach the coefficients of the intensity function are assigned independent gamma priors, leading to a closed form posterior distribution. On the theoretical side, we prove that as $n\rightarrow\infty,$ the posterior asymptotically concentrates around the "true", data-generating intensity function at an optimal rate for $h$-H\"older regular intensity functions ($0 < h\leq 1$). In the second approach we employ a gamma Markov chain prior on the coefficients of the intensity function. The posterior distribution is no longer available in closed form, but inference can be performed using a straightforward version of the Gibbs sampler. Both approaches scale well with sample size, but the second is much less sensitive to the choice of $N$. Practical performance of our methods is first demonstrated via synthetic data examples. We compare our second method with other existing approaches on the UK coal mining disasters data. Furthermore, we apply it to the US mass shootings data and Donald Trump's Twitter data.Comment: 45 pages, 22 figure