Multistep self-assembly of heteroleptic magnesium and sodium-magnesium benzamidinate complexes

Reaction of the magnesium bis-alkyl Mg(CH2SiMe3)(2) and the sodium amide NaHMDS (where HMDS = N(SiMe3)(2)) with benzonitrile yields the homometallic heteroleptic complex [PhC(NSiMe3)(2)Mg{mu-NC(CH2SiMe3)Ph}](2) (1). It appears that at least six independent reactions must have occurred in this one-pot reaction to arrive at this mixed benzamidinate ketimido product. Two benzonitrile solvated derivatives of Mg(CH2SiMe3)(2) (5a and 5b) have been synthesized, with 5a crystallographically characterized as a centrosymmetric (MgC)(2) cyclodimer. When, the components of 5a are allowed to react for longer, partial addition of the Mg-alkyl unit across the C N triple bond occurs to yield the trimeric species (Me3SiCH2)(2)Mg-3[mu-N=C(CH2SiMe3)Ph](4)center dot 2N CPh (6), with bridging ketimido groups and terminal alkyl groups. Finally, using the same starting materials as that which produced 1, but altering their order of addition, a magnesium bis-alkyl unit is inserted into the Na-N bonds of a benzamidinate species to yield a new sodium magnesiate complex, PhC(NSiMe3)(2)Mg(mu-CH2SiMe3)(2)Na center dot 2TMEDA (7). The formation of 7 represents a novel (insertion) route to mixed-metal species of this kind and is the first Such example to contain a bidentate terminal anion attached to the divalent metal center. All new species are characterized by H-1 and C-13 NMR spectroscopy and where appropriate by IR spectroscopy. The solid-state structures of complexes 1, 5a, and 7 have also been determined and are disclosed within

Acute Resveratrol Administration Increases Neural Effort but Not Whole Body Metabolism or Cognitive Performance in Healthy, Young Participants

Research into the cognitive enhancing effects of polyphenols is small but growing. Single doses of the stilbene polyphenol resveratrol can increase cerebral blood flow (CBF) but have failed to improve cognitive performance in young, healthy cohorts. As both CBF and overall energy expenditure are closely related to neural activity, this randomised, double-blind, placebo-controlled, crossover investigation, assessed the metabolic consequences of resveratrol during high cognitive demand via indirect calorimetry (ICa). Twenty-seven, self-reported healthy participants (15 male, 12 female; mean age = 22) who reported themselves free of any food intolerances and any herbal supplementation or prescription medications were recruited for the current study. Participants arrived at the testing facility at 8 a.m. on three separate occasions to complete a serial subtraction demand battery 45 min and 2 and 3 h following administration with 500 mg, 250 mg trans-resveratrol or inert placebo, while connected to an online gas analysis system. A series of within-subjects ANOVAs (with planned comparisons) revealed a significant shift towards higher carbohydrate oxidisation during cognitive demand, as indexed by a significant increase in respiratory exchange ratio (RER) at 45-min and 3-h time points, following administration of 500 mg resveratrol. Despite this, no subsequent resveratrol-related benefits to cognitive performance were observed. These results show that acute supplementation with resveratrol in young, healthy adults can modulate fuel utilization during cognitive demand, yet this does not translate into clear improvements in cognitive performance. This study adds further understanding behind the lack of cognitive effects of resveratrol in young and or healthy individuals. Future research should direct efforts towards assessing the cognitive impact of resveratrol, and other vasoactive polyphenols, in populations with age-related or dietary-induced metabolic deficits

Communication Networks

Contains report on one research project.M.I. T. Vinton Hayes Fun

Resource exploitation at late neolithic domuztepe: Faunal and botanical evidence

Domuztepe, in southeastern Turkey, is one of the largest known Late Neolithic sites in the Near East. Ecofactual remains recovered at Domuztepe indicate that the site’s inhabitants relied on a well‐established mixed economy of domestic plants and animals to sustain the settlement’s large population, which may have peaked at more than 1,500 people. Evidence of a long and continuous occupation of this site attests to a successful agropastoral economy, even though Domuztepe was situated at the intersection of uplands, an alluvial plain, and marshy zones, an environment not traditionally considered ideal for agriculture. Integrated faunal and botanical analyses explore the diversity of domestic and wild resources used by the site’s inhabitants. The typical suite of Near Eastern domesticates dominates the excavated assemblage, with sheep, goats, cattle, pigs, and cereals prominent. In addition to a nutritional role, these food products were used for clothing, storage, and construction and had symbolic importance in ritual and prestige. Combined archaeobiological data point to a seasonal cycle of activities

The behaviour of ions in the presence of the liquid vapour interface in helium

The thesis is concerned with some of the properties of positive and negative ions in liquid Helium, and in particular with the passage of ions, which are generated inside the liquid, through the free liquid surface into vapour. It was found, for negative ions, that this process was inhibited by an energy barrier, in agreement with other workers who have examined this problem, although there is considerable disagreement as to the magnitude of the barrier. It has been observed in the present work that the energy barrier depends upon the field, the position of the liquid surface in an ion cell, and the nature of the ion cell itself. The dependence of the barrier on these three parameters probably explains why diverse values for it have been reported. It was originally intended to use the ions as probes to examine dissipation mechanisms in the mobile superfluid Helium film. It had been reliably reported that ions preferentially travelled in the film. This was observed not to be the case however. The negative ion currents sin the film were found to be extremely small, when they existed at all, and no real positive ion currents in the film could be detected. This has been interpreted as being due to the combination of the large image potential binding the ion to the substrate, and the intrinsic roughness of the substrate. The present work has revealed that what appears at first sight to be a current of positive ions crossing the liquid surface can be attributed to a current of photoelectrons due to photoelectric emission from the surface of the collector. Such photoemission can arise from the uv radiation produced largely by ionic recombination in the region close to the a-emitting source. Screening the collector from the direct view of the a-source greatly reduced the photoelectron current. In order to extend the temperature range available, for the study of ion currents, a vortex refrigerator was designed and constructed. This enabled measurements to be extended down to 0.8K. Since there has been only one publication on the vortex refrigerator, which appeared during the building of the present one, its properties and operation with various design parameters were studied in detail

Investigation of Oleic Acid As A Dispersant For Hydroxyapatite Powders For Use In Ceramic Filled Photo-Curable Resins For Stereolithography

Stereolithography allows production of porous hydroxyapatite scaffolds for bone regeneration but is limited by the challenging rheology of ceramic filled resins. Oleic acid, a natural fatty acid, was applied in concentrations of 0.0–0.3 wt% to improve the rheological properties of HAp resins for the fabrication of solid cylinders and scaffolds by digital light processing (DLP) printing in a wiperless system. Bonding by chemisorption was confirmed by FTIR analysis. The powders were then incorporated into a photo-curable resin of 1–6 hexanediol diacrylate at 18–30 vol%. The shear viscosity and sedimentation rates of photocurable resins containing HAp powder decreased with increasing concentration of oleic acid. The curing depth and width of resins containing the HAp were unchanged as a result of the presence of oleic acid. Oleic acid improved the printing behaviour of the resins allowing the fabrication of scaffolds with continuous macro-porosity on a wiperless DLP system

One-dimensional modelling of a trilateral flash cycle system with two-phase twin-screw expanders for industrial low-grade heat to power conversion

This paper provides an overview of a one-dimensional modelling methodology for equipment and systems for heat to power conversion based on a staggered grid space discretization and implemented in the commercial software GT-SUITE®. Particular attention is given to a newly developed modelling procedure for twin-screw machines that is based on a chamber modelling approach and considers leakage paths between cells and with the casing. This methodology is then applied to a low-grade heat to power conversion system based on a Trilateral Flash Cycle (TFC) equipped with two parallel two-phase twin-screw expanders and a control valve upstream of the machines to adapt the fluid quality for an optimal expander operation. The standalone expander model is used to generate performance maps of the machine, which serve as inputs for the TFC system model. Parametric analyses are eventually carried out to assess the impact of several operating parameters of the TFC unit on the recovered power and cycle thermal efficiency. The study shows that the most influencing factors on the TFC system’s performance are the inlet temperature of the heat source and the expander speed. While the first depends on the topping industrial process, the expander speed can be used to optimize and control the TFC system operation also in transient or off-design operating conditions

Disodium (2RS,3SR)-tartrate

The asymmetric unit of the anhydrous title compound, 2Na+·C4H4O6 2−, contains two sodium cations and one tartrate anion. Each sodium ion is six coordinate, with bonding to six O atoms from both the carboxyl­ate and hydroxyl groups of the anion. A three-dimensional coordination network is formed with sodium ions stacking in layers along the c-axis direction. This network is supported by additional O—H⋯O hydrogen bonds