Synthesis of Silver nanoparticles (AgNPs) with Antibacterial Activity

The synthesis of nanomaterials is currently one of the most active in nanoscience branches; especially those help improve the human quality life. Silver nanoparticles (AgNPs) are an example of this as it is known to have inhibitory and bactericidal effects. In this work, we report the synthesis of silver nanoparticles by chemical reduction method of silver nitrate (AgNO3) from aqueous solution, using a mix of polivinyl pyrrolidone (PVP) - Aloe Vera as reducing agent and for stabilization and control of particle size. Silver nanoparticles obtained were characterized by Scanning Electron Microscopy (SEM), UV-visible spectroscopy and measurements using Zetasizer Nano ZS were applied to size estimation. The existence of surface plasmon resonance peak at λmax ∼ 420 nm is evidence of silver nanoparticles formation. It was possible to standardize an appropriate protocol for the evaluation of bactericidal activity of the nanoparticles, for mesophilic microorganisms. Bactericidal activity above 90% against these kinds of bacteria was demonstrated. © Published under licence by IOP Publishing Ltd

Interaction of Hydrogen with Graphitic Surfaces, Clean and Doped with Metal Clusters

Producción CientíficaHydrogen is viewed as a possible alternative to the fossil fuels in transportation. The technology of fuel-cell engines is fully developed, and the outstanding remaining problem is the storage of hydrogen in the vehicle. Porous materials, in which hydrogen is adsorbed on the pore walls, and in particular nanoporous carbons, have been investigated as potential onboard containers. Furthermore, metallic nanoparticles embedded in porous carbons catalyze the dissociation of hydrogen in the anode of the fuel cells. For these reasons the interaction of hydrogen with the surfaces of carbon materials is a topic of high technological interest. Computational modeling and the density functional formalism (DFT) are helping in the task of discovering the basic mechanisms of the interaction of hydrogen with clean and doped carbon surfaces. Planar and curved graphene provide good models for the walls of porous carbons. We first review work on the interaction of molecular and atomic hydrogen with graphene and graphene nanoribbons, and next we address the effects due to the presence of metal clusters on the surface because of the evidence of their role in enhancing hydrogen storage.Ministerio de Economía, Industria y Competitividad (Grant MAT2014-54378-R

Structural and optical anisotropy of nanoporous anodic aluminum oxide

Porous aluminum oxide has stimulated considerable interest as a nanostructural template, primarily because of the self-organized formation of extremely well-aligned cylindrical pores. One of the fascinating aspects is the tunability of the interpore distance and pore diameter by simple variation of the anodization parameters such as voltage and electrolyte solution composition. Apart from the application of aluminum oxide films as filtration membranes, they are frequently used to fabricate nanowires with large aspect ratios. Many different materials, such as metals, both magnetic and nonmagnetic, semiconductors, nanotubes, and even heterostructures, have been grown in the porous membranes using primarily electrodeposition. Furthermore, porous aluminum oxide membranes have also been used as humidity sensors, or as cathodes for organic light-emitting diodes

ATLAS TDAQ System Administration: an overview and evolution

The ATLAS Trigger and Data Acquisition (TDAQ) system is responsible for the online processing of live data streaming from the ATLAS experiment at the Large Hadron Collider (LHC) at CERN. The system processes the direct data readout from ~100 million channels on the detector through multiple trigger levels, selecting interesting events for analysis with a factor of $10^{7}$ reduction on the data rate with a latency of less than a few seconds. Most of the functionality is implemented on ~3000 servers composing the online farm. Due to the critical functionality of the system a sophisticated computing environment is maintained, covering the online farm and ATLAS control rooms, as well as a number of development and testing labs. The specificity of the system required the development of dedicated applications (e.g. ConfDB, BWM) for system configuration and maintenance; in parallel other Open Source tools (Puppet and Quattor) are used to centrally configure the operating systems. The health monitoring of the TDAQ system hardware and OS performs ~60 thousand checks every 5 minutes; it is currently implemented over Nagios, and it is being complemented and replaced by Ganglia and Icinga. The online system adopted a sophisticated user management, based on the Active Directory infrastructure and integrated with Access Manager, a dedicated Role Based Access Control (RBAC) tool. The RBAC and its underlying LDAP database control user rights from the external access to the farm down to specific user actions. A web-based user interface allows delegated administrators to manage specific role assignments. The current activities of the SysAdmin group include the daily monitoring, troubleshooting and maintenance of the online system, storage and farm upgrades, and readying systems for an upgrade to Scientific Linux 6 with the related global integration, configuration, optimisation and hardware updates necessary. In addition, during the 2013 shutdown the team will provide support for the usage of a large fraction of the online farm for GEANT4 simulations of ATLAS

ATLAS TDAQ application gateway upgrade during LS1

The ATLAS Gateway service is implemented with a set of dedicated computer nodes to provide a fine-grained access control between CERN General Public Network (GPN) and ATLAS Technical Control Network (ATCN). ATCN connects the ATLAS online farm used for ATLAS Operations and data taking, including the ATLAS TDAQ (Trigger and Data Aquisition) and DCS (Detector Control System) nodes. In particular, it provides restricted access to the web services (proxy), general login sessions (via SSH and RDP protocols), NAT and mail relay from ATCN. At the Operating System level the implementation is based on virtualization technologies. Here we report on the Gateway upgrade during Long Shutdown 1 (LS1) period: it includes the transition to the last production release of the CERN Linux distribution (SLC6), the migration to the centralized configuration management system (based on Puppet) and the redesign of the internal system architecture