Synthesis of extended uridine phosphonates derived from an allosteric P2Y2 receptor ligand

In this study we report the synthesis of C5/C6-fused uridine phosphonates that are structurally related to earlier reported allosteric P2Y2 receptor ligands. A silyl-Hilbert-Johnson reaction of six quinazoline-2,4-(1H,3H)-dione-like base moieties with a suitable ribofuranosephosphonate afforded the desired analogues after full deprotection. In contrast to the parent 5-(4-fluoropheny)uridine phosphonate, the present extended-base uridine phosphonates essentially failed to modulate the P2Y2 receptor

Electronic g-factor and Magneto-transport in InSb Quantum Wells

High mobility InSb quantum wells with tunable carrier densities are investigated by transport experiments in magnetic fields tilted with respect to the sample normal. We employ the coincidence method and the temperature dependence of the Shubnikov-de Haas oscillations and find a value for the effective g-factor of $\mid g^{\ast}\mid$ =35$\pm$4 and a value for the effective mass of $m^*\approx0.017 m_0$, where $m_0$ is the electron mass in vacuum. Our measurements are performed in a magnetic field and a density range where the enhancement mechanism of the effective g-factor can be neglected. Accordingly, the obtained effective g-factor and the effective mass can be quantitatively explained in a single particle picture. Additionally, we explore the magneto-transport up to magnetic fields of 35 T and do not find features related to the fractional quantum Hall effect.Comment: 18 Pages, 5 Figure

Improving numerical reasoning capabilities of inductive logic programming systems

Inductive Logic Programming (ILP) systems have been largely applied to classification problems with a considerable success. The use of ILP systems in problems requiring numerical reasoning capabilities has been far less successful. Current systems have very limited numerical reasoning capabilities, which limits the range of domains where the ILP paradigm may be applied. This paper proposes improvements in numerical reasoning capabilities of ILP systems. It proposes the use of statistical-based techniques like Model Validation and Model Selection to improve noise handling and it introduces a new search stopping criterium based on the PAG method to evaluate learning performance. We have found these extensions essential to improve on results mer statistical-based algorithms for time series forecasting used in the empirical evaluation study

Scaling Boosting by Margin-based Inclusion of Features and Relations

Boosting is well known to increase the accuracy of propositional and multi-relational classification learners. However, the base learner’s efficiency vitally determines boosting’s efficiency since the complexity of the underlying learner is amplified by iterated calls of the learner in the boosting framework. The idea of restricting the learner to smaller feature subsets in order to increase efficiency is widely used. Surprisingly, little attention has been paid so far to exploiting characteristics of boosting itself to include features based on the current learning progress. In this paper, we show that the dynamics inherent to boosting offer ideal means to maximize the efficiency of the learning process. We describe how to utilize the training examples’ margins—which are known to be maximized by boosting—to reduce learning times without a deterioration of the learning quality. We suggest to stepwise include features in the learning process in response to a slowdown in the improvement of the margins. Experimental results show that this approach significantly reduces the learning time while maintaining or even improving the predictive accuracy of the underlying fully equipped learner

Gate-defined quantum point contact in an InSb two-dimensional electron gas

We investigate an electrostatically defined quantum point contact in a high-mobility InSb two-dimensional electron gas. Well-defined conductance plateaus are observed, and the subband structure of the quantum point contact is extracted from finite-bias measurements. The Zeeman splitting is measured in both in-plane and out-of-plane magnetic fields. We find an in-plane g factor |g^∗_∥|≈ 40. The out-of-plane g factor is measured to be |g^∗_⊥|≈ 50, which is close to the g factor in the bulk.ISSN:2643-156