Theory of the Eigler-swith

We suggest a simple model to describe the reversible field-induced transfer of a single Xe-atom in a scanning tunneling microscope, --- the Eigler-switch. The inelasticly tunneling electrons give rise to fluctuating forces on and damping of the Xe-atom resulting in an effective current dependent temperature. The rate of transfer is controlled by the well-known Arrhenius law with this effective temperature. The directionality of atom transfer is discussed, and the importance of use of non-equlibrium-formalism for the electronic environment is emphasized. The theory constitutes a formal derivation and generalization of the so-called Desorption Induced by Multiple Electron Transitions (DIMET) point of view.Comment: 13 pages (including 2 figures in separate LaTeX-files with ps-\specials), REVTEX 3.

EffectiveSan: Type and Memory Error Detection using Dynamically Typed C/C++

Low-level programming languages with weak/static type systems, such as C and C++, are vulnerable to errors relating to the misuse of memory at runtime, such as (sub-)object bounds overflows, (re)use-after-free, and type confusion. Such errors account for many security and other undefined behavior bugs for programs written in these languages. In this paper, we introduce the notion of dynamically typed C/C++, which aims to detect such errors by dynamically checking the "effective type" of each object before use at runtime. We also present an implementation of dynamically typed C/C++ in the form of the Effective Type Sanitizer (EffectiveSan). EffectiveSan enforces type and memory safety using a combination of low-fat pointers, type meta data and type/bounds check instrumentation. We evaluate EffectiveSan against the SPEC2006 benchmark suite and the Firefox web browser, and detect several new type and memory errors. We also show that EffectiveSan achieves high compatibility and reasonable overheads for the given error coverage. Finally, we highlight that EffectiveSan is one of only a few tools that can detect sub-object bounds errors, and uses a novel approach (dynamic type checking) to do so.Comment: To appear in the Proceedings of 39th ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI2018

Graphene Oxide: Fundamentals and Applications

© 2017 John Wiley & Sons, Ltd. All rights reserved.Due to its unique properties, graphene oxide has become one of the most studied materials of the last decade and a great variety of applications have been reported in areas such as sensors, catalysis and biomedical applications. This comprehensive volume systematically describes the fundamental aspects and applications of graphene oxide. The book is designed as an introduction to the topic, so each chapter begins with a discussion on fundamental concepts, then proceeds to review and summarize recent advances in the field. Divided into two parts, the first part covers fundamental aspects of graphene oxide and includes chapters on formation and chemical structure, characterization methods, reduction methods, rheology and optical properties of graphene oxide solutions. Part Two covers numerous graphene oxide applications including field effect transistors, transparent conductive films, sensors, energy harvesting and storage, membranes, composite materials, catalysis and biomedical applications. In each case the differences and advantages of graphene oxide over its non-oxidised counterpart are discussed. The book concludes with a chapter on the challenges of industrial-scale graphene oxide production. Graphene Oxide: Fundamentals and Applications is a valuable reference for academic researchers, and industry scientists interested in graphene oxide, graphene and other carbon materials

Site determination and thermally assisted tunneling in homogenous nucleation

A combined low-temperature scanning tunneling microscopy and density functional theory study on the binding and diffusion of copper monomers, dimers, and trimers adsorbed on Cu(111) is presented. Whereas atoms in trimers are found in fcc sites only, monomers as well as atoms in dimers can occupy the stable fcc as well as the metastable hcp site. In fact the dimer fcc-hcp configuration was found to be only 1.3 meV less favorable with respect to the fcc-fcc configuration. This enables a confined intra-cell dimer motion, which at temperatures below 5 K is dominated by thermally assisted tunneling.Comment: 4 pages, 4 figure

Functionalization and Reduction of Graphene Oxide

© 2017 John Wiley & Sons, Ltd.The chemistry of graphene oxide (GO) is a growing field of research. The modification of the surface properties of GO is the main goal in application-driven research. Successful functionalization protocols must be interpreted in accordance with the chemical structure of the original GO, and therefore, in this chapter, crucial aspects of the chemical structure of GO are introduced first. Next, the thermal and chemical stability of GO is reviewed, followed by introducing wet-chemical non-covalent and covalent reaction principles. The covalent functionalization of GO requires special attention. When chemical reaction principles, well known from organic chemistry, are applied to GO, it remains challenging to prove the successful accomplishment of reactions by analyzing the as-modified GO product. We pay special attention to the reactivity of the edges of defects and provide alternative explanations for interpreting experimental results, where necessary. Next, chemical reduction methods are summarized; special accent is placed on differentiating true chemical reduction from so-called "thermal reduction". Several examples for the functionalization of reduced graphene oxide (RGO) are considered next. While discussing GO chemical properties, in parallel with typical GO, we discuss these properties for the oxo-functionalized graphene (oxo-G1), a type of GO with very low density of structural defects. This sheds additional light on the role of defects in GO chemistry. Finally, additional properties of oxo-G1 are introduced. Oxo-G1 can act as a compound that enables the controlled chemistry for the design and synthesis of functional materials and devices

Theoretical aspects of vertical and lateral manipulation of atoms

Using total energy calculations, based on interaction potentials from the embedded atom method, we show that the presence of the tip not only lowers the barrier for lateral diffusion of the adatom towards it, but also shifts the corresponding saddle point. For a Cu adatom at a (100) microfacetted step on Cu(111) this shift is 0.6 A. The effect of the tip geometry and shape on the energetics of lateral manipulation was found to be subtle. In the case of vertical manipulation of a Cu adatom on flat, stepped, and kinked Cu surfaces we find an unusual but interesting result. It is found that as the tip approaches the surface, it becomes easier to extract the adatom from the stepped and kinked surfaces, as compared to the flat surface. This counter intuitive result can be explained in terms of tip induced changes in the bonding of the adatom to its low coordinated surroundings.Comment: 8figures, to appear in Surf. Sci., VAS10 proceeding

Surface Screening Charge and Effective Charge

The charge on an atom at a metallic surface in an electric field is defined as the field-derivative of the force on the atom, and this is consistent with definitions of effective charge and screening charge. This charge can be found from the shift in the potential outside the surface when the atoms are moved. This is used to study forces and screening on surface atoms of Ag(001) c$(2\times 2)$ -- Xe as a function of external field. It is found that at low positive (outward) fields, the Xe with a negative effective charge of -0.093 $|{e}|$ is pushed into the surface. At a field of 2.3 V \AA$^{-1}$ the charge changes sign, and for fields greater than 4.1 V \AA$^{-1}$ the Xe experiences an outward force. Field desorption and the Eigler switch are discussed in terms of these results.Comment: 4 pages, 1 figure, RevTex (accepted by PRL

Polymerization in carbone : a novel method for the synthesis of more sustainable electrodes and their application as cathodes for lithium–organic energy storage materials based on vanillin

Sustainable energy storage materials are needed to implement necessary transitions to a more sustainable society. Therefore, we present novel vanillin (and thus ultimately possibly lignin)-derived electrode materials for lithium-ion-based energy storage systems. In the present approach, vanillin is first modified in two sustainable steps to afford bisvanillonitrile (BVN). The precursor materials for the electrodes are made from BVN and carbon black and are subsequently treated in the atmosphere of triflic acid in order to polymerize BVN. Used as a cathode material in a lithium-ion-based energy storage device, the resulting material shows capacities up to 90 mAh g–1 (respective to the whole electrode mass). This extraordinary performance can be attributed to a combination of non-Faradaic and Faradaic charge storage involving quinone units, which are abundantly found in the polymer backbone. In contrast to conventional organic electrode materials, excellent contact to carbon as a conductive additive is established by performing the polymerization in a mixture with carbon (in carbone), allowing the omission of additional unsustainable binder materials. Due to the sustainable synthesis and good performance, such sustainable electrodes may be applied in future energy storage devices

967-21 Long Term Results of Balloon Expandable Slotted-Tube Nitinol Stents in Canine Coronary Arteries

This study evaluated delivery performance, quantitative angiographic parameters, intravascular ultrasound appearance. long term patency and vascular histology of radio-opaque, slotted-tube nickel titanium (nitinoll stents permanently implanted in canine coronary arteries. Dogs were treated with aspirin for 1 month. Follow-up angiography and histology were performed at 0.5, 1, 3, and 6 months (number of vessels = 2, 4, 6, and 26, respectively).ResultsThirty-eight of 39 (97%) stents were successfully implanted in the mid LAD and LCX of 20 dogs. One stent, which was undersized, was successfully removed by thermal recovery. Tandem stents were placed in 2 dogs without difficulty. Intravascular ultrasound of 6 stents showed symmetrical expansion with good wall contact. Acute angiographic parameters:nominal stent size (mm)ANOVA p3.03.54.0number42212–inflation pressure (atm)5.5±056.1±1.45.9±1.60.47minimal diameter (mm)2.93±0.073.24±0.143.48±0.160.0003balloon to artery ratio1.23±0.031.25±0.101.25±0.080.65stent to artery ratio1.09±0.031.14±0.091.13±0.070.30percent recoil11.0±1.88.4±1.89.9±1.80.05At follow-up, all vessels and 9 of 9 stented sidebranches were patent. The mean percent stenosis at 3 to 6 months was –1.6±5.2 and the late loss was 0.2±0.3 mm. All struts were covered with neointima at 2 weeks. At 6 months the maximal neointimal thickness was 260±50 μm and was located adjacent to the struts. No thrombi and only occasional areas of granulation tissue with rare inflammatory cells were seen.ConclusionsA slotted tube nitinol stent has delivery performance characteristics and recoil similar to stainless steel slotted-tube stents. Nitinol stents endothelialize rapidly and intimal proliferation is insufficient to create a stenosis in this animal model. These data suggest that a slotted-tube, balloon expandable nitinol stent is sufficiently reliable and biocompatible to warrant clinical trials