55 research outputs found
Gating a single-molecule transistor with individual atoms
Transistors, regardless of their size, rely on electrical gates to control the
conductance between source and drain contacts. In atomic-scale transistors,
this conductance is sensitive to single electrons hopping via individual
orbitals1, 2. Single-electron transport in molecular transistors has been
previously studied using top-down approaches to gating, such as lithography
and break junctions1, 3, 4, 5, 6, 7, 8, 9, 10, 11. But atomically precise
control of the gateâwhich is crucial to transistor action at the smallest size
scalesâis not possible with these approaches. Here, we used individual charged
atoms, manipulated by a scanning tunnelling microscope12, to create the
electrical gates for a single-molecule transistor. This degree of control
allowed us to tune the molecule into the regime of sequential single-electron
tunnelling, albeit with a conductance gap more than one order of magnitude
larger than observed previously8, 11, 13, 14. This unexpected behaviour arises
from the existence of two different orientational conformations of the
molecule, depending on its charge state. Our results show that strong coupling
between these charge and conformational degrees of freedom leads to new
behaviour beyond the established picture of single-electron transport in
atomic-scale transistors
Diseased muscles that lack dystrophin or laminin-α2 have altered compositions and proliferation of mononuclear cell populations
BACKGROUND: Multiple types of mononucleate cells reside among the multinucleate myofibers in skeletal muscles and these mononucleate cells function in muscle maintenance and repair. How neuromuscular disease might affect different types of muscle mononucleate cells had not been determined. In this study, therefore, we examined how two neuromuscular diseases, dystrophin-deficiency and laminin-α2-deficiency, altered the proliferation and composition of different subsets of muscle-derived mononucleate cells. METHODS: We used fluorescence-activated cell sorting combined with bromodeoxyuridine labeling to examine proliferation rates and compositions of mononuclear cells in diseased and healthy mouse skeletal muscle. We prepared mononucleate cells from muscles of mdx (dystrophin-deficient) or Lama2(-/- )(laminin-α2-deficient) mice and compared them to cells from healthy control muscles. We enumerated subsets of resident muscle cells based on Sca-1 and CD45 expression patterns and determined the proliferation of each cell subset in vivo by BrdU incorporation. RESULTS: We found that the proliferation and composition of the mononucleate cells in dystrophin-deficient and laminin-α2-deficient diseased muscles are different than in healthy muscle. The mdx and Lama2(-/- )muscles showed similar significant increases in CD45(+ )cells compared to healthy muscle. Changes in proliferation, however, differed between the two diseases with proliferation increased in mdx and decreased in Lama2(-/- )muscles compared to healthy muscles. In particular, the most abundant Sca-1(-)/CD45(- )subset, which contains muscle precursor cells, had increased proliferation in mdx muscle but decreased proliferation in Lama2(-/- )muscles. CONCLUSION: The similar increases in CD45(+ )cells, but opposite changes in proliferation of muscle precursor cells, may underlie aspects of the distinct pathologies in the two diseases
An Euclidean norm based criterion to assess robots' 2D path-following performance
A current need in the robotics field is the definition of methodologies for quantitatively evaluating the results of experiments. This paper contributes to this by defining a new criterion for assessing path-following tasks in the planar case, that is, evaluating the performance of robots that are required to follow a desired reference path. Such criterion comes from the study of the local differential geometry of the problem. New conditions for deciding whether or not the zero locus of a given polynomial intersects the neighbourhood of a point are defined. Based on this, new algorithms are presented and tested on both simulated data and experiments conducted at sea employing an Unmanned Surface Vehicle
CocoaLib
CocoaLib is a C++ library for computations in commutative algebra; it consists of more than 4MB of code. All the basic ideal/module theoretic operations are provided
CoCoA 4
Cocoa4 is a C software for computations in commutative algebra; it consists of more than 1MB of code. All the basic ideal/module theoretic operations are provided, together with a programming language and a basic environment
CoCoa 5
Cocoa 5 is a C++ frontend for the CocoaLib, and it consists of more than 2MB of code. It provides the libary with a programming language and an advanced environment
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