A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting

Observations on Fisheries Activities at Navassa Island

Unmanaged and unquantified artisanal fishing is ongoing at Navassa Island, a small oceanic island about 70 km west of Haiti that is part of the U.S. Caribbean Islands National Wildlife Refuge. Concern has been expressed regarding the possible impact of these fishing activities on reef resources, and no quantitative catch or effort data are available. However, informal qualitative observations made during a cruise in November 2002 suggest that escalation in fishing activity (and impact) has occurred since previous observations made in April 2000. Namely, size structure of fish was markedly reduced and the adoption of net fishing has allowed the exploitation of queen conch, Strombas gigas, and hawksbill turtles, Eretmochelys imbricata

Leptin-induced lipolysis opposes the tonic inhibition of endogenous adenosine in white adipocytes

The aim of the present study was to gain insight into the signaling pathway used by leptin to stimulate lipolysis. The lipolytic rate of white adipocytes from sex- and age-matched lean (+/+) and fa/fa rats was determined in the absence or presence of leptin together with a number of agents acting at different levels of the signaling cascade. Leptin did not modify FSK-, dbcAMP-, and IBMX-stimulated lipolysis. Lipolysis can also be maximally stimulated by lowering media adenosine levels with adenosine deaminase (ADA), i.e., in the ligand-free state. Although ADA produced near maximal lipolysis in adipocytes of lean animals, only half of the maximal lipolytic rate (50.9+/-3.2%) was achieved in fat cells from fa/fa rats (P=0.0034). In adipocytes from lean animals preincubated with ADA, leptin caused a concentration-related stimulation of lipolysis (P=0.0001). However, leptin had no effect on the lipolytic activity of adipocytes in the ligand-free state from fa/fa rats. The adenosine A1 receptor agonist CPA effectively inhibited basal lipolysis in both lean and obese adipocytes (P=0.0001 and P=0.0090, respectively). Leptin had no effect on the lipolytic rate of adipocytes isolated from fa/fa rats and preincubated with CPA. When adipocytes were incubated with the A1 receptor antagonist DPCPX, a significant increase in glycerol release was observed in fa/fa fat cells (P=0.009), whereas cells isolated from lean rats showed no differences to ADA-stimulated lipolysis. After pretreatment with PTX, which inactivates receptor-mediated Gi function, adipocytes of obese rats became as responsive to the stimulatory actions of ISO as cells from lean rats (P=0.0090 vs. ISO in fa/fa rats; P=0.2416 vs. lean rats, respectively). PTX treatment of lean cells, however, did not alter their response to this lipolytic agent. It can be concluded that the lipolytic effect of leptin is located at the adenylate cyclase/Gi proteins level and that leptin-induced lipolysis opposes the tonic inhibition of endogenous adenosine in white adipocytes

Berenstein-Zelevinsky triangles, elementary couplings and fusion rules

We present a general scheme for describing su(N)_k fusion rules in terms of elementary couplings, using Berenstein-Zelevinsky triangles. A fusion coupling is characterized by its corresponding tensor product coupling (i.e. its Berenstein-Zelevinsky triangle) and the threshold level at which it first appears. We show that a closed expression for this threshold level is encoded in the Berenstein-Zelevinsky triangle and an explicit method to calculate it is presented. In this way a complete solution of su(4)_k fusion rules is obtained.Comment: 14 page

Small iron oxide nanoparticles as MRI T1 contrast agent: scalable inexpensive water-based synthesis using a flow reactor

Small iron oxide nanoparticles (IONPs) were synthesised in water via co-precipitation by quenching particle growth after the desired magnetic iron oxide phase formed. This was achieved in a millifluidic multistage flow reactor by precisely timed addition of an acidic solution. IONPs (≤5 nm), a suitable size for positive T1 magnetic resonance imaging (MRI) contrast agents, were obtained and stabilised continuously. This novel flow chemistry approach facilitates a reproducible and scalable production, which is a crucial paradigm shift to utilise IONPs as contrast agents and replace currently used Gd complexes. Acid addition had to be timed carefully, as the inverse spinel structure formed within seconds after initiating the co-precipitation. Late quenching allowed IONPs to grow larger than 5 nm, whereas premature acid addition yielded undesired oxide phases. Use of a flow reactor was not only essential for scalability, but also to synthesise monodisperse and non-agglomerated small IONPs as (i) co-precipitation and acid addition occurred at homogenous environment due to accurate temperature control and rapid mixing and (ii) quenching of particle growth was possible at the optimum time, i.e., a few seconds after initiating co-precipitation. In addition to the timing of growth quenching, the effect of temperature and dextran present during co-precipitation on the final particle size was investigated. This approach differs from small IONP syntheses in batch utilising either growth inhibitors (which likely leads to impurities) or high temperature methods in organic solvents. Furthermore, this continuous synthesis enables the low-cost (<£10 per g) and large-scale production of highly stable small IONPs without the use of toxic reagents. The flow-synthesised small IONPs showed high T1 contrast enhancement, with transversal relaxivity (r2) reduced to 20.5 mM−1 s−1 and longitudinal relaxivity (r1) higher than 10 mM−1 s−1, which is among the highest values reported for water-based IONP synthesis

Towards nanoprinting with metals on graphene

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a `pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections

A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting

Prospective Study of Zinc Intake and Risk of Type 2 Diabetes in Women

OBJECTIVE: The aim of this study is to investigate the intake of zinc in relation to risk of type 2 diabetes in U.S. women. RESEARCH DESIGN AND METHODS: Dietary intakes of zinc and other nutrients were assessed and updated using a validated food frequency questionnaire from 1980 to 2002 among 82,297 women who were aged 33–60 years at baseline in 1980 and followed up to 2004 in the Nurses' Health Study. RESULTS: During the 24 years of follow-up, 6,030 incident cases of type 2 diabetes were ascertained. After adjustment of lifestyle and dietary risk factors, the relative risks (RRs) (95% CI) of type 2 diabetes comparing the highest with the lowest quintiles were 0.90 (0.82–0.99) (Ptrend = 0.04) for total zinc intake and 0.92 (0.84–1.00) (Ptrend = 0.009) for dietary zinc intake from food sources, respectively. We further found an inverse association for dietary zinc to heme iron ratio. After multivariate adjustment of covariates, the RRs (95% CI) across quintiles of this ratio were 1.0 (reference), 0.93 (0.86–1.01), 0.86 (0.79–0.94), 0.82 (0.75–0.90), and 0.72 (0.66–0.80), respectively (Ptrend < 0.0001). CONCLUSIONS: Higher zinc intake may be associated with a slightly lower risk of type 2 diabetes in women. More studies are warranted to confirm this association and to explore potential mechanisms