A Platinum molecular complex immobilised on the surface of graphene as active catalyst in alkyne hydrosilylation

Abstract A platinum complex bearing a N‐heterocyclic carbene (NHC) ligand functionalised with a pyrene‐tag is immobilised onto the surface of reduced graphene oxide (rGO). The hybrid material composed of an organometallic complex and a graphene derivative is ready available in a single‐step process under mild reaction conditions. This methodology preserves the inherent properties of the active catalytic centre and the support. The platinum hybrid material is an efficient catalyst in hydrosilylation of alkynes and can be recycled and reused for ten runs without significant loss of activity due to its high stability. Interestingly, the catalytic properties of the platinum complex are enhanced after immobilisation onto graphene. The influence of graphene in hydrosilylation of alkynes is discussed

Minimax Forward and Backward Learning of Evolving Tasks with Performance Guarantees

For a sequence of classification tasks that arrive over time, it is common that tasks are evolving in the sense that consecutive tasks often have a higher similarity. The incremental learning of a growing sequence of tasks holds promise to enable accurate classification even with few samples per task by leveraging information from all the tasks in the sequence (forward and backward learning). However, existing techniques developed for continual learning and concept drift adaptation are either designed for tasks with time-independent similarities or only aim to learn the last task in the sequence. This paper presents incremental minimax risk classifiers (IMRCs) that effectively exploit forward and backward learning and account for evolving tasks. In addition, we analytically characterize the performance improvement provided by forward and backward learning in terms of the tasks' expected quadratic change and the number of tasks. The experimental evaluation shows that IMRCs can result in a significant performance improvement, especially for reduced sample sizes

Network Analysis Identifies SOD2 mRNA as a Potential Biomarker for Parkinson's Disease

Increasing evidence indicates that Parkinson's disease (PD) and type 2 diabetes (T2DM) share dysregulated molecular networks. We identified 84 genes shared between PD and T2DM from curated disease-gene databases. Nitric oxide biosynthesis, lipid and carbohydrate metabolism, insulin secretion and inflammation were identified as common dysregulated pathways. A network prioritization approach was implemented to rank genes according to their distance to seed genes and their involvement in common biological pathways. Quantitative polymerase chain reaction assays revealed that a highly ranked gene, superoxide dismutase 2 (SOD2), is upregulated in PD patients compared to healthy controls in 192 whole blood samples from two independent clinical trials, the Harvard Biomarker Study (HBS) and the Diagnostic and Prognostic Biomarkers in Parkinson's disease (PROBE). The results from this study reinforce the idea that shared molecular networks between PD and T2DM provides an additional source of biologically meaningful biomarkers. Evaluation of this biomarker in de novo PD patients and in a larger prospective longitudinal study is warranted

Gating Charge Immobilization in Kv4.2 Channels: The Basis of Closed-State Inactivation

Kv4 channels mediate the somatodendritic A-type K+ current (ISA) in neurons. The availability of functional Kv4 channels is dynamically regulated by the membrane potential such that subthreshold depolarizations render Kv4 channels unavailable. The underlying process involves inactivation from closed states along the main activation pathway. Although classical inactivation mechanisms such as N- and P/C-type inactivation have been excluded, a clear understanding of closed-state inactivation in Kv4 channels has remained elusive. This is in part due to the lack of crucial information about the interactions between gating charge (Q) movement, activation, and inactivation. To overcome this limitation, we engineered a charybdotoxin (CTX)-sensitive Kv4.2 channel, which enabled us to obtain the first measurements of Kv4.2 gating currents after blocking K+ conduction with CTX (Dougherty and Covarrubias. 2006J. Gen. Physiol. 128:745–753). Here, we exploited this approach further to investigate the mechanism that links closed-state inactivation to slow Q-immobilization in Kv4 channels. The main observations revealed profound Q-immobilization at steady-state over a range of hyperpolarized voltages (−110 to −75 mV). Depolarization in this range moves <5% of the observable Q associated with activation and is insufficient to open the channels significantly. The kinetics and voltage dependence of Q-immobilization and ionic current inactivation between −153 and −47 mV are similar and independent of the channel's proximal N-terminal region (residues 2–40). A coupled state diagram of closed-state inactivation with a quasi-absorbing inactivated state explained the results from ionic and gating current experiments globally. We conclude that Q-immobilization and closed-state inactivation at hyperpolarized voltages are two manifestations of the same process in Kv4.2 channels, and propose that inactivation in the absence of N- and P/C-type mechanisms involves desensitization to voltage resulting from a slow conformational change of the voltage sensors, which renders the channel's main activation gate reluctant to open

Cartilage Appearance Using an Environmental Scanning Electron Microscope.

Because of technical principles, samples to be observed with electron microscopy need to be fixed in a chemical process and exposed to vacuum conditions that can produce some changes in the morphology of the specimen. The aim of this work was to obtain high-resolution images of the fresh articular cartilage surface with an environmental scanning electron microscope (ESEM), which is an instrument that permits examination of biological specimens without fixation methods in a 10 Torr chamber pressure, thus minimizing the risk of creating artifacts in the structure. Samples from weight-bearing areas of femoral condyles of New Zealand white rabbits were collected and photographed using an ESEM. Images were analyzed using a categorization based in the Jurvelin classification system modified by Hong and Henderson. Appearance of the observed elevations and depressions as described in the classification were observed, but no fractures or splits of cartilage surface, thought to be artifacts, were detected. The ESEM is a useful tool to obtain images of fresh articular cartilage surface appearance without either employing fixation methods or exposing the specimen to extreme vacuum conditions, reducing the risk of introducing artifacts within the specimen. For all these reasons it could become a useful tool for quality control of the preservation process of osteochondral allografting in a bank of musculoskeletal tissues

Dual role of graphene as support of ligand-stabilized palladium nanoparticles and carbocatalyst for (de)hydrogenation of N-heterocycles

The hybrid material composed of palladium nanoparticles (PdNPs) functionalized with N-heterocyclic carbene ligands (NHCs) immobilized onto the surface of reduced graphene oxide (rGO) results in an efficient catalytic material towards hydrogenation and dehydrogenation of N-heterocycles. The rGO plays a dual role by acting as a carbocatalyst in acceptorless dehydrogenation of N-heterocycles and as a support for the palladium nanoparticles facilitating its interaction with molecular hydrogen turning this hybrid material into an effective hydrogenation catalyst. Hot filtration experiments support the heterogeneous nature of the process underlining the strong interaction of palladium nanoparticles with the graphene enabled by π-interactions of the ligand with the support. The mild conditions used in both transformations of this system without requiring any additives facilitates its potential application in hydrogen storage technologies in the form of liquid organic hydrogen carriers (LOHCs). At the same time, the hybrid material is a robust and efficient catalytic platform that can be recovered and reused up to eight runs in both transformations without significant deactivation. The use of a single solid catalysts that is recyclable in hydrogen conversion and reconversion through (de)hydrogenation of N-heterocycles paves the way for the development of efficient hydrogen storage materials