Bidentate ligation of magnesium by 1,2-dimethoxyethane in the gas phase

International audienceThe 1:1 Mg[centered ellipsis]1,2-dimethoxyethane (Mg-DXE) complexes are studied experimentally and theoretically. They are generated by a laser ablation source in a supersonic expansion. They are studied spectroscopically by resonance two-photon ionization. Density functional theory/Becke three-dimensional Lee, Yang, and Parr and ab initio calculations using the MOLPRO quantum chemistry package are performed to document their ground and excited states in a series of geometry ranging from monodentate to bidentate ligation of Mg by the O atoms of DXE. An absorption band is observed in the 27 800–30 500 cm−1 range, which, thanks to the calculations, is attributed to the bidentate complex. The structure of the band is discussed in terms of the excitation of electronic states of the complex correlating adiabatically to the 3s3p 1P and 3s4s 1S states of Mg at large separation between Mg and DXE

Dynamics of excited tetrakis(dimethyl amino)ethylene solvated by argon atoms

The supersonic expansion of a mixture of the title molecule (TDMAE) with argon generates a beam carrying a log-normal distribution of TDAME(Ar)n clusters, broadly centered at . The femtosecond pump–probe technique is used to investigate the excited state dynamics of these clusters up to a 220 ps delay between the pump and the probe. This documents the effect of the argon environment on the TDMAE dynamics. The TDMAE molecule is excited in the valence state V within the cluster by the pump laser at 266 nm. It undergoes deformation in the excited potential energy surface that brings the initial wavepacket to a conical intersection (CI), where the electronic configuration of the molecule switches to a zwitterionic configuration Z. Compared to the behaviour of free TDMAE, the effect of the argon environment is a slow down of the wavepacket movement and an increase of the time scale of the V–Z energy transfer from 300 to 400±50 fs. This slow down effect, that we call a chistera effect, differs from a standard cage effect. Here, the deforming molecule does not experience a hard sphere collision with the argon cage, rather it pushes it away. Furthermore, umbrella oscillations of the dimethylamino groups are excited when the initial wavepacket passes the CI region. Because of the argon environment, the sharp 250 fs oscillation period of the free molecules is transformed into a broad structure of 40 fs width (FWHM) centred at about 240 fs. In addition, breathing oscillations of the argon environment with respect to the TDMAE molecule are observed with a period of 410±40 fs. Finally, long delays between the pump and the probe lasers allow us to investigate the nonradiative energy transfer from the Z electronic configuration of TDMAE(Ar)n to a charge transfer state. The effect of the evaporation of argon atoms in the neutral and the ionised clusters has been taken into account, as its time scale accompanies that of the observed phenomena

Femtosecond Photodissociation Dynamics of van der Waals Cationic Clusters: a tool for detecting metastable isomers of organic cations

A femtosecond pump (266 nm)–probe (800 nm) experiment as been performed on small clusters of tetrakis(dimethylamino)ethylene (TDMAE) with argon (TDMAE(Ar

Comparison of potato varieties between seasons and their potential for acrylamide formation

BACKGROUND: Acrylamide is a probable human carcinogen produced during food preparation, including frying of potato products. The aim of this study was to investigate the impact of seasonal variation on tuber composition and its acrylamide generation potential. RESULTS: The chemical composition of potato varieties used respectively for French fry (Bintje and Ramos) and crisp (Lady Rosetta and Saturna) production was studied throughout a storage period of 9 months during two growing seasons (2003 and 2004), in addition to their acrylamide generation potential during preparation of French fries. A significant impact of variable climatological conditions on the reducing sugar, dry matter, total free amino acid and free asparagine contents of tubers was observed. Exceptionally warm summers gave rise to a lower reducing sugar content (expressed on a dry matter basis) and thus a lower susceptibility to acrylamide generation during frying. CONCLUSION: It cannot be excluded that potato growers and the potato-processing industry are confronted with some harvests that are more prone to acrylamide generation than others owing to climatological variability, thus confirming the importance of a multifactorial approach to mitigate acrylamide generation in potato products.</p

m-Path:An easy-to-use and highly tailorable platform for ecological momentary assessment and intervention in behavioral research and clinical practice

In this paper, we present m-Path (www.m-Path.io), an online platform that provides an easy-to-use and highly tailorable framework for implementing smartphone-based ecological momentary assessment (EMA) and intervention (EMI) in both research and clinical practice in the context of blended care. Because real-time monitoring and intervention in people's everyday lives have unparalleled benefits compared to traditional data collection techniques (e.g., retrospective surveys or lab-based experiments), EMA and EMI have become popular in recent years. Although a surge in the use of these methods has led to a myriad of EMA and EMI applications, many existing platforms only focus on a single aspect of daily life data collection (e.g., assessment vs. intervention, active self-report vs. passive mobile sensing, research-dedicated vs. clinically-oriented tools). With m-Path, we aim to integrate all of these facets into a single platform, as it is exactly this all-in-one approach that fosters the clinical utility of accumulated scientific knowledge. To this end, we offer a comprehensive platform to set up complex and highly adjustable EMA and EMI designs with advanced functionalities, using an intuitive point-and click web interface that is accessible for researchers and clinicians with limited programming skills. We discuss the strengths of daily life data collection and intervention in general and m-Path in particular. We describe the regular workflow to set up an EMA or EMI design within the m-Path framework, and summarize both the basic functionalities and more advanced features of our software

Widespread dysregulation of MiRNAs by MYCN amplification and chromosomal imbalances in neuroblastoma: association of miRNA expression with survival

MiRNAs regulate gene expression at a post-transcriptional level and their dysregulation can play major roles in the pathogenesis of many different forms of cancer, including neuroblastoma, an often fatal paediatric cancer originating from precursor cells of the sympathetic nervous system. We have analyzed a set of neuroblastoma (n = 145) that is broadly representative of the genetic subtypes of this disease for miRNA expression (430 loci by stem-loop RT qPCR) and for DNA copy number alterations (array CGH) to assess miRNA involvement in disease pathogenesis. The tumors were stratified and then randomly split into a training set (n = 96) and a validation set (n = 49) for data analysis. Thirty-seven miRNAs were significantly over-or under-expressed in MYCN amplified tumors relative to MYCN single copy tumors, indicating a potential role for the MYCN transcription factor in either the direct or indirect dysregulation of these loci. In addition, we also determined that there was a highly significant correlation between miRNA expression levels and DNA copy number, indicating a role for large-scale genomic imbalances in the dysregulation of miRNA expression. In order to directly assess whether miRNA expression was predictive of clinical outcome, we used the Random Forest classifier to identify miRNAs that were most significantly associated with poor overall patient survival and developed a 15 miRNA signature that was predictive of overall survival with 72.7% sensitivity and 86.5% specificity in the validation set of tumors. We conclude that there is widespread dysregulation of miRNA expression in neuroblastoma tumors caused by both over-expression of the MYCN transcription factor and by large-scale chromosomal imbalances. MiRNA expression patterns are also predicative of clinical outcome, highlighting the potential for miRNA mediated diagnostics and therapeutics

Fingerprint resampling: A generic method for efficient resampling

Analysis and Stochastic

San Francisco Bay Area corporate history : a selected annotated bibliography

Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the structure of macrobenthic communities could affect the functioning of an entire ecosystem. We assessed the impact of sediment deposition on intertidal macrobenthic communities and on rates of an important ecosystem function, i.e. sediment community oxygen consumption (SCOC). An experiment was performed with undisturbed sediment samples from the Scheldt river estuary (SW Netherlands). The samples were subjected to four sedimentation regimes: one control and three with a deposited sediment layer of 1, 2 or 5 cm. Oxygen consumption was measured during incubation at ambient temperature. Luminophores applied at the surface, and a seawater–bromide mixture, served as tracers for bioturbation and bio-irrigation, respectively. After incubation, the macrofauna was extracted, identified, and counted and then classified into functional groups based on motility and sediment reworking capacity. Total macrofaunal densities dropped already under the thinnest deposits. The most affected fauna were surficial and low-motility animals, occurring at high densities in the control. Their mortality resulted in a drop in SCOC, which decreased steadily with increasing deposit thickness, while bio-irrigation and bioturbation activity showed increases in the lower sediment deposition regimes but decreases in the more extreme treatments. The initial increased activity likely counteracted the effects of the drop in low-motility, surficial fauna densities, resulting in a steady rather than sudden fall in oxygen consumption. We conclude that the functional identity in terms of motility and sediment reworking can be crucial in our understanding of the regulation of ecosystem functioning and the impact of habitat alterations such as sediment deposition