N-Heterocyclic Carbene Iron Silyl Hydride Complexes

Reaction of N-heterocyclic carbene iron(0) tetracarbonyl complexes with hydrosilanes (triphenylsilane, methyldiphenylsilane and diphenylsilane) under UV irradiation (350 nm) afforded the octahedral N-heterocyclic carbene iron(II) silyl hydride complexes in yields up to 95 %, resulting from the oxidative addition of the hydrosilane. Eight iron silyl hydrides were obtained and characterized by NMR and X-ray diffraction analysis. Noticeably, the geometry of the iron-hydride complexes and the bent structures of the carbonyl ligands were rationalized by DFT calculations.     

An investigation of the object relations theory of depression.

The current study investigated a particular aspect shared by a number of theories of depression under the common heading of object relations theory (ORT), namely that depression is associated with a continuing pattern of poor attachment that is laid out in childhood and continues into adulthood. The study examined the relationship between attachment (both parental and peer) and depressive symptoms in young adults (N = 85) of Northern Ireland. Results provided support for the continuity of perceptions of attachment styles across the life span and revealed that perceptions of early attachment experiences, as well as continuing peer attachment styles, appeared to be predictive of current depressive symptoms. More specifically, the analyses revealed a statistically significant positive correlation between perceived quality of current peer attachment and symptoms of depression, as well as a statistically significant negative correlation between self-reported childhood maternal care and symptoms of depression. However, other self-reported measures of childhood attachment were not found to be significant predictors of depressive symptoms (i.e., paternal care, maternal overprotection, paternal overprotection). Taken together, the findings lend some support for this important element of a number of object relations theories, as they pertain to depression. Further empirical research is indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Real time TEM observation of alumina ceramic nano-particles during compression

The behavior of alumina nano-particles taken from a commercial powder is investigated during in situ compression experiments in a transmission electron microscope (TEM). Small particles of 40 nm in diameter can undergo severe plastic deformation without failure, whereas brittle fracture is observed for 120 nm sized nano-particles. This is evidence of a critical size under which alumina, at least in the form of nano-particles, cannot be considered as brittle materials even at room temperature and a direct observation of the grinding limit generally observed during ball milling.     

Optimization of the synthesis of polyhydroxyurethanes using dynamic rheometry

Polyhydroxyurethanes (PHUs) produced by the reaction between dicyclocarbonate and diamine groups are often presented as possible candidates to substitute for classical polyurethanes based on isocyanate precursors. In the literature, the synthesis of this class of polymers is often performed according to arbitrary conditions of time and temperature without any scientific justification. As such, the real potential of PHUs is probably not fully known. Numerous contradictions in previously published results seem to support this hypothesis. Our paper proposes two methodologies based on dynamic rheometry to determine optimized conditions for the synthesis of PHUs. The case of a PHU formed by the reaction between 1,10‐diaminodecane and a dicyclocarbonate bearing a central aromatic group is described more precisely. The first approach consists of conducting various rheological experiments (kinetics, thermomechanical analyses) in situ on the reaction mixture. The second one retains the same technique to qualify the viscoelastic properties of PHUs synthesized according to various conditions. In this latter case, all samples show thermomechanical behaviour of amorphous thermoplastic polymers. But discrepancies are observed with regard to the value of the glass transition temperature and the existence or not of a rubbery zone. Comparison of these data with size exclusion chromatography results shows that these differences are direct consequences of the polymer molecular weight that can be predicted using macromolecular theory. The properties of the PHUs obtained after optimization of the polymerization reaction were compared with literature data in order to complete the evaluation of the efficiency of the rheological methodology. Copyright © 2012 Society of Chemical Industry     

数字交互式电视网络架构

导言 数字电视基础设施日新月异,正迅速地从模拟电视过渡到数字电视。虽然数字传输仅在10年前才得以实现,但全球的数字接收机已超过5,000万台。卫星电视的数字化改造速度最快,有线电视也正在进行数字化改造。一些国     

Study of the tribologically transformed structure created during fretting tests

In fretting, without a lubricant, structures fail through wear involving debris. Various metallographic assessments show that this debris creation derives from a special structure, hereafter called the “tribologically transformed structure” (TTS). The latter is nucleated at the very beginning of a contact's life, and eventually masks the initial material's tribological behaviour. This TTS is very hard and brittle, and is quickly destroyed, which explains why TTS is rather difficult to observe. This study focuses on initiation mechanisms which, up to now, are still highly controversial. Large amounts of TTS are observed after fretting tests, which is the reason why they were chosen as the means of investigation. In this paper, the various possible creation mechanisms for TTS will be analysed. From this overview, two nucleation models are chosen: one is based on “mechanical alloying” considerations, and the other is linked to high-strain-recrystallisation phenomena. Transmission electron microscopy (TEM) investigations are used to check these assumptions.     

Pyruvate-Kinase-Coupled Glycosyltransferase Assays: Limitations,Struggles and Problem Resolution

Enzyme assays involving coupled pyruvate kinase (PK) have been used for many years to monitor the activity of major classes of enzymes including glycosyltransferases. Numerous potent inhibitors have been discovered and kinetically characterized thanks to this technology. However, when inhibitors of these important enzymes are screened, PK inhibitors or activators are very often observed. In this study we report solutions to resolve the problems encountered either during the screening or during the kinetic characterization of glycosyltransferase inhibitors by means of PK-coupled assays. The enzyme under study—WaaC—is an important glycosyltransferase involved in the bacterial lipopolysaccharide (LPS) biosynthesis pathway. Firstly we showed that alternative kinases such as nucleoside 5-diphosphate kinase (NDPK), myokinase (MK), and ADPdependent hexokinase that catalyze similar reactions to PK are prone to the same troubles. Moreover, an ADP chemosensor was used as an alternative but the sensitivity was not sufficient to allow a proper screening. Finally, we found that a stepwise PK/luciferase assay resolved the problems encountered with PK inhibitors and that a WaaC HPLC assay allowed the identification of WaaC inhibitors acting as PK activators, thus allowing false positive and false negative results linked to the coupling to PK to be eliminated.