Electron transport through a metal-molecule-metal junction

Molecules of bisthiolterthiophene have been adsorbed on the two facing gold electrodes of a mechanically controllable break junction in order to form metal-molecule(s)-metal junctions. Current-voltage (I-V) characteristics have been recorded at room temperature. Zero bias conductances were measured in the 10-100 nS range and different kinds of non-linear I-V curves with step-like features were reproducibly obtained. Switching between different kinds of I-V curves could be induced by varying the distance between the two metallic electrodes. The experimental results are discussed within the framework of tunneling transport models explicitly taking into account the discrete nature of the electronic spectrum of the molecule.Comment: 12 pages, 12 figures to appear in Phys. Rev. B 59(19) 199

Comparative Study of Vibration Response in Steel and Braided-Carbon-Fiber Bicycle Handlebars: A Numerical-Experimental Approach with Various Sensors

\ua9 2024 by the authors. The comfort and safety of a cyclist are directly influenced by the vibrational behavior of the handlebar. Hence, the objective of this article is to comparatively assess the vibrational characteristics of two bicycle handlebars: one made of steel and the other made of braided composite material. The transmissibility function represents the relationship between the excitation applied to both handlebars through their stems and the corresponding response in the handle area, which was experimentally obtained by applying a random vibrating signal (constant amplitude of 0.01 g2/Hz) using a shaker. This signal was applied in a frequency range between 100 Hz and 1200 Hz, and the response was measured at one of the two cantilevered ends of the handlebar. Different sensors, including a laser vibrometer and a control accelerometer in the shaker, were utilized. The transmissibility, natural frequencies and damping functions were obtained. Subsequently, another experimental analysis was carried out with the instrumented handlebars mounted on a bicycle, placing three accelerometers and a GPS meter and traveling through a real test circuit, with a rough surface, speed bumps and areas with shaped warning bands. Power Spectral Density (PSD) curves were obtained for the steel and carbon-fiber-composite handlebars in order to quantify the signal intensity. Finally, a fatigue analysis was carried out in order to evaluate the expected life of both handlebars under the experimentally applied load, which is considered the reference cycle. This study offers a comparative analysis of the vibration behavior exhibited by steel and carbon-fiber-composite bicycle handlebars under experimentally applied load. In conclusion, data on natural frequencies, damping functions and fatigue life expectancy for both handlebar materials were obtained. Our study provides valuable insights into the vibrational behavior and performance characteristics of steel and carbon-fiber-composite bicycle handlebars, contributing to the understanding of their comfort and safety implications for cyclists

Electron transport through rectifying self-assembled monolayer diodes on silicon: Fermi level pinning at the molecule-metal interface

We report the synthesis and characterization of molecular rectifying diodes on silicon using sequential grafting of self-assembled monolayers of alkyl chains bearing a pi group at their outer end (Si/sigma-pi/metal junctions). We investigate the structure-performance relationships of these molecular devices and we examine to what extent the nature of the pi end-group (change in the energy position of their molecular orbitals) drives the properties of these molecular diodes. For all the pi-groups investigated here, we observe rectification behavior. These results extend our preliminary work using phenyl and thiophene groups (S. Lenfant et al., Nano Letters 3, 741 (2003)).The experimental current-voltage curves are analyzed with a simple analytical model, from which we extract the energy position of the molecular orbital of the pi-group in resonance with the Fermi energy of the electrodes. We report the experimental studies of the band lineup in these silicon/alkyl-pi conjugated molecule/metal junctions. We conclude that Fermi level pinning at the pi-group/metal interface is mainly responsible for the observed absence of dependence of the rectification effect on the nature of the pi-groups, even though they were chosen to have significant variations in their electronic molecular orbitalsComment: To be published in J. Phys. Chem.

Quantitative Analysis of Apache Storm Applications: The NewsAsset Case Study

The development of Information Systems today faces the era of Big Data. Large volumes of information need to be processed in real-time, for example, for Facebook or Twitter analysis. This paper addresses the redesign of NewsAsset, a commercial product that helps journalists by providing services, which analyzes millions of media items from the social network in real-time. Technologies like Apache Storm can help enormously in this context. We have quantitatively analyzed the new design of NewsAsset to assess whether the introduction of Apache Storm can meet the demanding performance requirements of this media product. Our assessment approach, guided by the Unified Modeling Language (UML), takes advantage, for performance analysis, of the software designs already used for development. In addition, we converted UML into a domain-specific modeling language (DSML) for Apache Storm, thus creating a profile for Storm. Later, we transformed said DSML into an appropriate language for performance evaluation, specifically, stochastic Petri nets. The assessment ended with a successful software design that certainly met the scalability requirements of NewsAsset

A UML Profile for the Design, Quality Assessment and Deployment of Data-intensive Applications

Big Data or Data-Intensive applications (DIAs) seek to mine, manipulate, extract or otherwise exploit the potential intelligence hidden behind Big Data. However, several practitioner surveys remark that DIAs potential is still untapped because of very difficult and costly design, quality assessment and continuous refinement. To address the above shortcoming, we propose the use of a UML domain-specific modeling language or profile specifically tailored to support the design, assessment and continuous deployment of DIAs. This article illustrates our DIA-specific profile and outlines its usage in the context of DIA performance engineering and deployment. For DIA performance engineering, we rely on the Apache Hadoop technology, while for DIA deployment, we leverage the TOSCA language. We conclude that the proposed profile offers a powerful language for data-intensive software and systems modeling, quality evaluation and automated deployment of DIAs on private or public clouds

Control theory applied to the design of AGC circuits

Applications of control theory in the design of automatic gain control (AGC) circuits are presented. A general model for AGC circuits is presented, and an equivalent linear system is proposed. Its behavior is compared with the dynamical response of two implemented AGC circuits. The results of classic and state variable correctors based on the model are presented. These results show the usefulness of this linear model in the design of the AGC dynamic response. By using a linear and t-variant system the dynamical behavior is improved. This approach is used to design hyperstability and Lyapunov-based correctorsPeer ReviewedPostprint (published version

Anomaly Detection for Diagnosing Failures in a Centrifugal Compressor Train

Predicting machine failures is of the utmost importance in industrial systems as it can turn expensive crashes and repair costs into affordable maintenance costs. To this end, this paper presents preliminary work for detecting failures in a centrifugal compressor train based on sensorial data. We show the detection capabilities of a two-step process consisting of: (1) a preprocessing step to reduce the dimensionality of the input data using Principal Component Analysis, and (2) an anomaly detection step using the Mahalanobis distance to detect anomalous observations on the sensors' data. The experiments using real-world data demonstrate the feasibility of our approach and the ability of the method to detect the failures eight days in advance

Exploring reported genes of microglia RNA-sequencing data:Uses and considerations

The advent of RNA-sequencing techniques has made it possible to generate large, unbiased gene expression datasets of tissues and cell types. Several studies describing gene expression data of microglia from Alzheimer's disease or multiple sclerosis have been published, aiming to generate more insight into the role of microglia in these neurological diseases. Though the raw sequencing data are often deposited in open access databases, the most accessible source of data for scientists is what is reported in published manuscripts. We observed a relatively limited overlap in reported differentially expressed genes between various microglia RNA-sequencing studies from multiple sclerosis or Alzheimer's diseases. It was clear that differences in experimental set up influenced the number of overlapping reported genes. However, even when the experimental set up was very similar, we observed that overlap in reported genes could be low. We identified that papers reporting large numbers of differentially expressed microglial genes generally showed higher overlap with other papers. In addition, though the pathology present within the tissue used for sequencing can greatly influence microglia gene expression, often the pathology present in samples used for sequencing was underreported, leaving it difficult to assess the data. Whereas reanalyzing every raw dataset could reduce the variation that contributes to the observed limited overlap in reported genes, this is not feasible for labs without (access to) bioinformatic expertise. In this study, we thus provide an overview of data present in manuscripts and their supplementary files and how these data can be interpreted