Delta-T Flicker Noise Demonstrated with Molecular Junctions.

Electronic flicker noise is recognized as the most abundant noise in electronic conductors, either as an unwanted contribution or as a source of information on electron transport mechanisms and material properties. This noise is typically observed when a voltage difference is applied across a conductor or current is flowing through it. Here, we identify an unknown type of electronic flicker noise that is found when a temperature difference is applied across a nanoscale conductor in the absence of a net charge current or voltage bias.

Electrically Controlled Bimetallic Junctions for Atomic-Scale Electronics.

Forming atomic-scale contacts with attractive geometries and material compositions is a long-term goal of nanotechnology. Here, we show that a rich family of bimetallic atomic-contacts can be fabricated in break-junction setups. The structure and material composition of these contacts can be controlled by atomically precise electromigration, where the metal types of the electron-injecting and sink electrodes determine the type of atoms added to, or subtracted from, the contact structure.

Structural Regulation of Mechanical Gating in Molecular Junctions.

In contrast to silicon-based transistors, single-molecule junctions can be gated by simple mechanical means. Specifically, charge can be transferred between the junction's electrodes and its molecular bridge when the interelectrode distance is modified, leading to variations in the electronic transport properties of the junction. While this effect has been studied extensively, the influence of the molecular orientation on mechanical gating has not been addressed, despite its potential influence on the gating effectiveness.

Archaeometallurgical Analysis of the Provincial Silver Coinage of Judah: More on the Chaîne Opératoire of the Minting Process.

Silver coins were the first coins to be manufactured by mass production in the southern Levant. An assemblage of tiny provincial silver coins of the local (Judahite standard) and (Attic) -based denominations from the Persian and Hellenistic period Yehud and dated to the second half of the fourth century BCE were analyzed to determine their material composition. Of the 50 silver coins, 32 are defined as Type 5 (Athena/Owl) of the Persian period Yehud series (ca.

Magnetic control over the fundamental structure of atomic wires.

When reducing the size of materials towards the nanoscale, magnetic properties can emerge due to structural variations. Here, we show the reverse effect, where the structure of nanomaterials is controlled by magnetic manipulations. Using the break-junction technique, we find that the interatomic distance in platinum atomic wires is shorter or longer by up to ∼20%, when a magnetic field is applied parallel or perpendicular to the wires during their formation, respectively.

Quantum Flicker Noise in Atomic and Molecular Junctions.

We report on a quantum form of electronic flicker noise in nanoscale conductors that contains valuable information on quantum transport. This noise is experimentally identified in atomic and molecular junctions and theoretically analyzed by considering quantum interference due to fluctuating scatterers. Using conductance, shot-noise, and flicker-noise measurements, we show that the revealed quantum flicker noise uniquely depends on the distribution of transmission channels, a key characteristic of quantum conductors.

Theory of Chirality Induced Spin Selectivity: Progress and Challenges.

A critical overview of the theory of the chirality-induced spin selectivity (CISS) effect, that is, phenomena in which the chirality of molecular species imparts significant spin selectivity to various electron processes, is provided. Based on discussions in a recently held workshop, and further work published since, the status of CISS effects-in electron transmission, electron transport, and chemical reactions-is reviewed. For each, a detailed discussion of the state-of-the-art in theoretical understanding is provided and remaining challenges and research opportunities are identified.

Richness of molecular junction configurations revealed by tracking a full pull-push cycle.

In the field of molecular electronics, the interplay between molecular orientation and the resulting electronic transport is of central interest. At the single molecule level, this topic is extensively studied with the aid of break junction setups. In such experiments, two metal electrodes are brought into contact, and the conductance is typically measured when the electrodes are pulled apart in the presence of molecules, until a molecule bridges the two electrodes.

A giant right atrial myxoma-The growth rate and multi-modality imaging.

A young and healthy woman presented with progressive dyspnea on exertion. An echocardiogram showed a giant right atrial mass. Cardiac CT angiography provided the most accurate estimate for the tumor size, while 2-D echo, 2-D, and 3-D trans-esophageal echo underestimated the dimensions of the cardiac tumor when referenced by the surgical specimen.

Nonmagnetic single-molecule spin-filter based on quantum interference.

Key spin transport phenomena, including magnetoresistance and spin transfer torque, cannot be activated without spin-polarized currents, in which one electron spin is dominant. At the nanoscale, the relevant length-scale for modern spintronics, spin current generation is rather limited due to unwanted contributions from poorly spin-polarized frontier states in ferromagnetic electrodes, or too short length-scales for efficient spin splitting by spin-orbit interaction and magnetic fields. Here, we show that spin-polarized currents can be generated in silver-vanadocene-silver single molecule junctions without magnetic components or magnetic fields.

Electronic noise due to temperature differences in atomic-scale junctions.

Since the discovery a century ago of electronic thermal noise and shot noise, these forms of fundamental noise have had an enormous impact on science and technology research and applications. They can be used to probe quantum effects and thermodynamic quantities, but they are also regarded as undesirable in electronic devices because they obscure the target signal. Electronic thermal noise is generated at equilibrium at finite (non-zero) temperature, whereas electronic shot noise is a non-equilibrium current noise that is generated by partial transmission and reflection (partition) of the incoming electrons.

Electronic conduction during the formation stages of a single-molecule junction.

Single-molecule junctions are versatile test beds for electronic transport at the atomic scale. However, not much is known about the early formation steps of such junctions. Here, we study the electronic transport properties of premature junction configurations before the realization of a single-molecule bridge based on vanadocene molecules and silver electrodes.

Enhanced Magnetoresistance in Molecular Junctions by Geometrical Optimization of Spin-Selective Orbital Hybridization.

Molecular junctions based on ferromagnetic electrodes allow the study of electronic spin transport near the limit of spintronics miniaturization. However, these junctions reveal moderate magnetoresistance that is sensitive to the orbital structure at their ferromagnet-molecule interfaces. The key structural parameters that should be controlled in order to gain high magnetoresistance have not been established, despite their importance for efficient manipulation of spin transport at the nanoscale.

Vibration-mediated Kondo transport in molecular junctions: conductance evolution during mechanical stretching.

The vibration-mediated Kondo effect attracted considerable theoretical interest during the last decade. However, due to lack of extensive experimental demonstrations, the fine details of the phenomenon were not addressed. Here, we analyze the evolution of vibration-mediated Kondo effect in molecular junctions during mechanical stretching.

Indication of Complete Spin Filtering in Atomic-Scale Nickel Oxide.

Generating highly spin-polarized currents at the nanoscale is essential for spin current manipulations and spintronic applications. We find indications for up to 100% spin-polarized currents across nickel oxide atomic junctions formed between two nickel electrodes. The degree of spin polarization is probed by analyzing the shot noise resulting from the discrete statistics of spin-polarized electron transport.

Probing the orbital origin of conductance oscillations in atomic chains.

We investigate periodical oscillations in the conductance of suspended Au and Pt atomic chains during elongation under mechanical stress. Analysis of conductance and shot noise measurements reveals that the oscillations are mainly related to variations in a specific conduction channel as the chain undergoes transitions between zigzag and linear atomic configurations. The calculated local electronic structure shows that the oscillations originate from varying degrees of hybridization between the atomic orbitals along the chain as a function of the zigzag angle.

Electron-vibration interaction in multichannel single-molecule junctions.

The effect of electron-vibration interaction in atomic-scale junctions with a single conduction channel was widely investigated both theoretically and experimentally. However, the more general case of junctions with several conduction channels has received very little attention. Here we study electron-vibration interaction in multichannel molecular junctions, formed by introduction of either benzene or carbon dioxide between platinum electrodes.

Atomically wired molecular junctions: connecting a single organic molecule by chains of metal atoms.

Using a break junction technique, we find a clear signature for the formation of conducting hybrid junctions composed of a single organic molecule (benzene, naphthalene, or anthracene) connected to chains of platinum atoms. The hybrid junctions exhibit metallic-like conductance (~0.1-1G0), which is rather insensitive to further elongation by additional atoms.

Fluid structure interaction with contact surface methodology for evaluation of endovascular carotid implants for drug-resistant hypertension treatment.

Drug-resistant hypertensive patients may be treated by mechanical stimulation of stretch-sensitive baroreceptors located in the sinus of carotid arteries. To evaluate the efficacy of endovascular devices to stretch the carotid sinus such that the induced strain might trigger baroreceptors to increase action potential firing rate and thereby reduce systemic blood pressure, numerical simulations were conducted of devices deployed in subject-specific carotid models. Two models were chosen--a typical physiologic carotid and a diminutive atypical physiologic model representing a clinically worst case scenario--to evaluate the effects of device deployment in normal and extreme cases, respectively.

Analytical and numerical analyses of the micromechanics of soft fibrous connective tissues.

State of the art research and treatment of biological tissues require accurate and efficient methods for describing their mechanical properties. Indeed, micromechanics-motivated approaches provide a systematic method for elevating relevant data from the microscopic level to the macroscopic one. In this work, the mechanical responses of hyperelastic tissues with one and two families of collagen fibers are analyzed by application of a new variational estimate accounting for their histology and the behaviors of their constituents.

Narrow-band imaging without high magnification to differentiate polyps during real-time colonoscopy: improvement with experience.

Background: There is no widely adopted, easily applied method for distinguishing between adenomatous and nonadenomatous polyps during real-time colonoscopy.

Objective: To compare white light (WL) with narrow-band imaging (NBI) for the differentiation of colorectal polyps in vivo and to assess for a learning curve.

Design: A prospective polyp series.

An Oct-1 binding site mediates activation of the gata2 promoter by BMP signaling.

The gata2 gene encodes a transcription factor implicated in regulating early patterning of ectoderm and mesoderm, and later in numerous cell-specific gene expression programs. Activation of the gata2 gene during embryogenesis is dependent on the bone morphogenetic protein (BMP) signaling pathway, but the mechanism for how signaling controls gene activity has not been defined. We developed an assay in Xenopus embryos to analyze regulatory sequences of the zebrafish gata2 promoter that are necessary to mediate the response to BMP signaling during embryogenesis.

Hematopoiesis and retinoids: development and disease.

Retinoids function as activating ligands for a class of nuclear receptors that control gene expression programs for a wide range of tissues and organs during embryogenesis and throughout life. Over the years, three sets of observations have spurred interest in the function of retinoids with respect to development and disease of hematopoietic cells. Since the 1920s, epidemiological studies indicated altered hematopoiesis in vitamin A-deficient (VAD) human populations.