Single crystal field-effect transistors based on an organic selenium-containing semiconductor

We report on the fabrication and characterization of single crystal field-effect transistors (FETs) based on diphenylbenzo diselenophene (DPh-BDSe). These organic field-effect transistors (OFETs) function as p-channel accumulation-mode devices. At room temperature, for the best devices, the threshold voltage is less than -7V and charge carrier mobility is nearly gate bias independent, ranging from 1cm2/Vs to 1.5 cm2/Vs depending on the source-drain bias. Mobility is increased slightly by cooling below room temperature and decreases below 280 K

Competing Ground States of a Peierls-Hubbard Nanotube

Motivated by iodo platinum complexes assembled within a quadratic-prism lattice, [Pt(C$_2$H$_8$N$_2$)(C$_{10}$H$_8$N$_2$)I]$_4$(NO$_3$)$_8$, we investigate the ground-state properties of a Peierls-Hubbard four-legged tube. Making a group-theoretical analysis, we systematically reveal a variety of valence arrangements, including half-metallic charge-density-wave states. Quantum and thermal phase competition is numerically demonstrated with particular emphasis on doping-induced successive insulator-to-metal transitions with conductivity increasing stepwise.Comment: 6 pages, 4 figures. to be published in Europhys. Lett. 87 (2009) 1700

6,7,6′,7′-Tetra­phenyl-2,2′-bi[1,3-dithia-5,8-diaza­cyclo­penta­[b]naphthalenyl­idene] chloro­form disolvate

The title compound, C42H24N4S4·2CHCl3, a symmetrical tetra­thia­fulvalene (TTF) derivative, was prepared by a tri­ethyl­phos­phite-mediated self-coupling reaction of 6,7-diphenyl-1,3-dithia-5,8-diaza­cyclo­penta­[b]napthalen-2-one. The asymmetric unit contains two TTF mol­ecules and four chloro­form solvent mol­ecules. Cl⋯Cl inter­actions [contact distances = 3.263 (1)–3.395 (2) Å] are present between the solvent mol­ecules, resulting in a tape along the bc plane. The crystal packing features weak C—H⋯Cl and C—H⋯N hydrogen bonds, resulting in the formation of a two-dimensional supramolecular network

The influence of particle surface roughness on elastic stiffness and dynamic response

Discrete-element method (DEM) simulations of planar wave propagation are used to examine the effect of particle surface roughness on the stiffness and dynamic response of granular materials. A new contact model that considers particle surface roughness is implemented in the DEM simulations. Face-centred cubic lattice packings and random configurations are used; uniform spheres are considered in both cases to isolate fabric and contact model effects from inertia effects. For the range of values considered here surface roughness caused a significant reduction in stiffness, particularly at lower confining stresses. The simulations confirm that surface roughness effects can at least partially explain the value of the exponent in the relationship between stiffness and mean confining stress for an assembly of spherical particles. Frequency domain analyses showed that the maximum frequency transmitted through the sample is reduced when surface roughness is considered. The assumption of homogeneity of stress and contacts in analytical micromechanical models is shown to lead to an overestimation of stiffness

Computational modelling of meiotic entry and commitment

In response to developmental and environmental conditions, cells exit the mitotic cell cycle and enter the meiosis program to generate haploid gametes from diploid germ cells. Once cells decide to enter the meiosis program they become irreversibly committed to the completion of meiosis irrespective of the presence of cue signals. How meiotic entry and commitment occur due to the dynamics of the regulatory network is not well understood. Therefore, we constructed a mathematical model of the regulatory network that controls the transition from mitosis to meiosis in Schizosaccharomyces pombe. Upon nitrogen starvation, yeast cells exit mitosis and undergo conjugation and meiotic entry. The model includes the regulation of Mei2, an RNA binding protein required for conjugation and meiotic entry, by multiple feedback loops involving Pat1, a kinase that keeps cells in mitosis, and Ste11, a transcription activator required for the sexual differentiation. The model accounts for various experimental observations and demonstrates that the activation of Mei2 is bistable, which ensures the irreversible commitment to meiosis. Further, we show by integrating the meiosis-specific regulation with a cell cycle model, the dynamics of cell cycle exit, G1 arrest and entry into meiosis under nitrogen starvation. © 2017 The Author(s)

The globular cluster VVV CL002 falling down to the hazardous Galactic centre

© 2024 The Author(s). Published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Context. The Galactic centre is hazardous for stellar clusters because of the strong tidal force in action there. It is believed that many clusters were destroyed there and contributed stars to the crowded stellar field of the bulge and the nuclear stellar cluster. However, the development of a realistic model to predict the long-term evolution of the complex inner Galaxy has proven difficult, and observations of surviving clusters in the central region would provide crucial insights into destruction processes. Aims: Among the known Galactic globular clusters, VVV CL002 is the closest to the centre, at 0.4 kpc, but has a very high transverse velocity of 400 km s−1. The nature of this cluster and its impact on Galactic astronomy need to be addressed with spectroscopic follow up. Methods: Here we report the first measurements of its radial velocity and chemical abundance based on near-infrared high-resolution spectroscopy. Results: We find that this cluster has a counter-rotating orbit constrained within 1.0 kpc of the centre, and as close as 0.2 kpc at the perigalacticon, confirming that the cluster is not a passerby from the halo but a genuine survivor enduring the harsh conditions of the tidal forces of the Galactic mill. In addition, its metallicity and α abundance ([α/Fe] ≃ +0.4 and [Fe/H] = −0.54) are similar to those of some globular clusters in the bulge. Recent studies suggest that stars with such α-enhanced stars were more common at 3-6 kpc from the centre around 10 Gyr ago. Conclusions: We infer that VVV CL002 was formed outside but is currently falling down to the centre, showcasing a real-time event that must have occurred to many clusters a long time ago.Peer reviewe