505 research outputs found
Conductance of graphene nanoribbon junctions and the tight binding model
Planar carbon-based electronic devices, including metal/semiconductor junctions, transistors and interconnects, can now be formed from patterned sheets of graphene. Most simulations of charge transport within graphene-based electronic devices assume an energy band structure based on a nearest-neighbour tight binding analysis. In this paper, the energy band structure and conductance of graphene nanoribbons and metal/semiconductor junctions are obtained using a third nearest-neighbour tight binding analysis in conjunction with an efficient nonequilibrium Green’s function formalism. We find significant differences in both the energy band structure and conductance obtained with the two approximations
An extracellular transglutaminase is required for apple pollen tube growth
An extracellular form of the calcium-dependent protein-crosslinking enzyme TGase (transglutaminase) was demonstrated to be involved in the apical growth of Malus domestica pollen tube. Apple pollen TGase and its substrates were co-localized within aggregates on the pollen tube surface, as determined by indirect immunofluorescence staining and the in situ cross-linking of fluorescently labelled substrates. TGase-specific inhibitors and an anti-TGase monoclonal antibody blocked pollen tube growth, whereas incorporation of a recombinant fluorescent mammalian TGase substrate (histidine-tagged green fluorescent protein:His6– Xpr–GFP) into the growing tube wall enhanced tube length and germination, consistent with a role of TGase as a modulator of cell wall building and strengthening. The secreted pollen TGase catalysed the cross-linking of both PAs (polyamines) into proteins (released by the pollen tube) and His6-Xpr-GFP into endogenous or exogenously added substrates. A similar distribution of TGase activitywas observed in planta on pollen tubes germinating inside the style, consistent with a possible additional role for TGase in the interaction between the pollen tube and the style during fertilization
Chromosome numbers for the Italian flora: 6
In this contribution, new chromosome data obtained on material collected in Italy are presented. It includes
three chromosome counts for Bupleurum baldense Turra, Colchicum lusitanum Brot., and Euphorbia
gasparrinii Boiss. subsp. gasparrinii
Many-body current formula and current conservation for non-equilibrium fully interacting nanojunctions
We consider the electron transport properties through fully interacting
nanoscale junctions beyond the linear-response regime. We calculate the current
flowing through an interacting region connected to two interacting leads, with
interaction crossing at the left and right contacts, by using a non-equilibrium
Green's functions (NEGF) technique. The total current at one interface (the
left one for example) is made of several terms which can be regrouped into two
sets. The first set corresponds to a very generalised Landauer-like current
formula with physical quantities defined only in the interacting central region
and with renormalised lead self-energies. The second set characterises
inelastic scattering events occurring in the left lead. We show how this term
can be negligible or even vanish due to the pseudo-equilibrium statistical
properties of the lead in the thermodynamic limit. The expressions for the
different Green's functions needed for practical calculations of the current
are also provided. We determine the constraints imposed by the physical
condition of current conservation. The corresponding equation imposed on the
different self-energy quantities arising from the current conservation is
derived. We discuss in detail its physical interpretation and its relation with
previously derived expressions. Finally several important key features are
discussed in relation to the implementation of our formalism for calculations
of quantum transport in realistic systems
Ultrastructural features of Mimulus aurantiacus (Scrophulariaceae) pollen tubes in vivo
Phase 1 dose-escalation study of S-222611, an oral reversible dual tyrosine kinase inhibitor of EGFR and HER2, in patients with solid tumours.
BACKGROUND: S-222611 is a reversible inhibitor of EGFR, HER2 and HER4 with preclinical activity in models expressing these proteins. We have performed a Phase 1 study to determine safety, maximum tolerated dose (MTD), pharmacokinetic profile (PK) and efficacy in patients with solid tumours expressing EGFR or HER2. PATIENTS AND METHODS: Subjects had advanced tumours not suitable for standard treatment, expressing EGFR or HER2, and/or with amplified HER2. Daily oral doses of S-222611 were escalated from 100mg to 1600 mg. Full plasma concentration profiles for drug and metabolites were obtained. RESULTS: 33 patients received S-222611. It was well tolerated, and the most common toxicities, almost all mild (grade 1 or 2), were diarrhoea, fatigue, rash and nausea. Only two dose-limiting toxicities occurred (diarrhoea and rash), which resolved on interruption. MTD was not reached. Plasma exposure increased with dose up to 800 mg, exceeding levels eliciting pre-clinical responses. The plasma terminal half-life was more than 24h, supporting once daily dosing. Responses were seen over a wide range of doses in oesophageal, breast and renal tumours, including a complete clinical response in a patient with HER2-positive breast carcinoma previously treated with lapatinib and trastuzumab. Four patients have remained on treatment for more than 12 months. Downregulation of pHER3 was seen in paired tumour biopsies from a responding patient. CONCLUSIONS: Continuous daily oral S-222611 is well tolerated, modulates oncogenic signalling, and has significant antitumour activity. The recommended Phase 2 dose, based on PK and efficacy, is 800 mg/day.The authors acknowledge financial support from the UK Department of Health via the National Institute for Health Research (NIHR) Biomedical Research Centre (BRC) award to Guy’s & St Thomas’ NHS Foundation Trust in partnership with King’s College London and King’s College Hospital NHS Foundation Trust (and NIHR Clinical Research Facility), and to The University of Cambridge and Cambridge University Hospital NHS Foundation Trust. Cambridge, King’s College London, and Newcastle are Experimental Cancer Medicine Centres.This is the accepted manuscript. The final version is available from http://www.sciencedirect.com/science/article/pii/S0959804914010922
Distinct endocytic pathways identified in tobacco pollen tubes using charged nanogold
In an attempt to dissect endocytosis in Nicotiana tabacum L. pollen tubes, two different probes \u2013 positively or
negatively charged nanogold \u2013 were employed. The destiny of internalized plasma membrane domains, carrying
negatively or positively charged residues, was followed at the ultrastructural level and revealed distinct endocytic
pathways. Time-course experiments and electron microscopy showed internalization of subapical plasmamembrane domains that were mainly recycled to the secretory pathway through the Golgi apparatus and a
second mainly degradative pathway involving plasma membrane retrieval at the tip. In vivo time-lapse experiments using FM4-64 combined with quantitative analysis confirmed the existence of distinct internalization regions. Ikarugamycin, an inhibitor of clathrin-dependent endocytosis, allowed us to further dissect the endocytic process: electron microscopy and time-lapse studies suggested that clathrin-dependent endocytosis occurs in the
tip and subapical regions, because recycling of positively charged nanogold to the Golgi bodies and the consignment
of negatively charged nanogold to vacuoles were affected.
However, intact positively charged-nanogold transport to vacuoles supports the idea that an endocytic pathway that does not require clathrin is also present in pollen tubes
Towards Graphene Nanoribbon-based Electronics
The successful fabrication of single layer graphene has greatly stimulated
the progress of the research on graphene. In this article, focusing on the
basic electronic and transport properties of graphene nanoribbons (GNRs), we
review the recent progress of experimental fabrication of GNRs, and the
theoretical and experimental investigations of physical properties and device
applications of GNRs. We also briefly discuss the research efforts on the spin
polarization of GNRs in relation to the edge states.Comment: 9pages,10figure
Interplay between edge states and simple bulk defects in graphene nanoribbons
We study the interplay between the edge states and a single impurity in a
zigzag graphene nanoribbon. We use tight-binding exact diagonalization
techniques, as well as density functional theory calculations to obtain the
eigenvalue spectrum, the eigenfunctions, as well the dependence of the local
density of states (LDOS) on energy and position. We note that roughly half of
the unperturbed eigenstates in the spectrum of the finite-size ribbon hybridize
with the impurity state, and the corresponding eigenvalues are shifted with
respect to their unperturbed values. The maximum shift and hybridization occur
for a state whose energy is inverse proportional to the impurity potential;
this energy is that of the impurity peak in the DOS spectrum. We find that the
interference between the impurity and the edge gives rise to peculiar
modifications of the LDOS of the nanoribbon, in particular to oscillations of
the edge LDOS. These effects depend on the size of the system, and decay with
the distance between the edge and the impurity.Comment: 10 pages, 15 figures, revtex
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