3He-rich SEP Events Observed by STEREO-A

Using the SIT (Suprathermal Ion Telescope) instrument on STEREO-A we have examined the abundance of the rare isotope 3He during the rising activity phase of solar cycle 24 between January 2010 and December 2011. We have identified six solar energetic particle (SEP) events with enormous abundance enhancements of 3He (3He/4He >1). The events were short lasting, typically ~0.5-1 day and most of them occurred in association with high-speed solar wind streams and corotating interaction regions. With one exception the events were not associated with ~100 keV solar electron intensity increases. The events showed also enhanced NeS/O and Fe/O ratios. The solar images indicate that the events were generally associated with the active regions located near a coronal hole.Comment: accepted for publication in AIP Conference Proceedings for 'Thirteenth International Solar Wind Conference

The effect of rippling on the mechanical properties of graphene

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very bendable. Consequently, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient of free-standing graphene. We also observed an increase of the Young's modulus with global applied strain and with the introduction of small density defects that we attributed to the decrease of rippling. Here, we will focus on a surprising feature observed in the data: the experiments consistently indicate that only the rippling with wavelengths between 5-10nm influences the mechanics of graphene. The rippling responsible of the negative TEC and anomalous elasticity is thought to be dynamic, i.e. flexural phonons. However, flexural phonons with these wavelengths should have minor effects on the mechanics of graphene, therefore other mechanisms must be considered to address our observations. We propose static ripples as one of the key elements to correctly understand the thermomechanics of graphene and suggest that rippling arises naturally due to a competition of symmetry breaking and anharmonic fluctuations

Design of an Efficient Interconnection Network of Temperature Sensors

Temperature has become a first class design constraint because high temperatures adversely affect circuit reliability, static power and degrade the performance. In this scenario, thermal characterization of ICs and on-chip temperature monitoring represent fundamental tasks in electronic design. In this work, we analyze the features that an interconnection network of temperature sensors must fulfill. Departing from the network topology, we continue with the proposal of a very light-weight network architecture based on digitalization resource sharing. Our proposal supposes a 16% improvement in area and power consumption compared to traditional approache

Multi-Spacecraft Observations of Recurrent 3He-Rich Solar Energetic Particles

We study the origin of 3He-rich solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) solar regions with long-lasting conditions for 3He acceleration and 2) solar energetic 3He that is temporary confined/re-accelerated in interplanetary space.Comment: accepted for publication in The Astrophysical Journa

3He-Rich Solar Energetic Particles in Helical Jets on the Sun

Particle acceleration in stellar flares is ubiquitous in the Universe, however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of ten thousand) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by non-relativistic electron events and type III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories STEREO on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3He and Fe enrichments.Comment: accepted for publication in The Astrophysical Journa

A cryopreservation method for bioengineered 3D cell culture models

Technologies to cryogenically preserve (a.k.a. cryopreserve) living tissue, cell lines and primary cells have matured greatly for both clinicians and researchers since their first demonstration in the 1950s and are widely used in storage and transport applications. Currently, however, there remains an absence of viable cryopreservation and thawing methods for bioengineered, three-dimensional (3D) cell models, including patients' samples. As a first step towards addressing this gap, we demonstrate a viable protocol for spheroid cryopreservation and survival based on a 3D carboxymethyl cellulose scaffold and precise conditions for freezing and thawing. The protocol is tested using hepatocytes, for which the scaffold provides both the 3D structure for cells to self-arrange into spheroids and to support cells during freezing for optimal post-thaw viability. Cell viability after thawing is improved compared to conventional pellet models where cells settle under gravity to form a pseudo-tissue before freezing. The technique may advance cryobiology and other applications that demand high-integrity transport of pre-assembled 3D models (from cell lines and in future cells from patients) between facilities, for example between medical practice, research and testing facilities

A self-timed multipurpose delay sensor for field programmable gate arrays (FPGAs)

This paper presents a novel self-timed multi-purpose sensor especially conceived for Field Programmable Gate Arrays (FPGAs). The aim of the sensor is to measure performance variations during the life-cycle of the device, such as process variability, critical path timing and temperature variations. The proposed topology, through the use of both combinational and sequential FPGA elements, amplifies the time of a signal traversing a delay chain to produce a pulse whose width is the sensor’s measurement. The sensor is fully self-timed, avoiding the need for clock distribution networks and eliminating the limitations imposed by the system clock. One single off- or on-chip time-to-digital converter is able to perform digitization of several sensors in a single operation. These features allow for a simplified approach for designers wanting to intertwine a multi-purpose sensor network with their application logic. Employed as a temperature sensor, it has been measured to have an error of ±0.67 °C, over the range of 20–100 °C, employing 20 logic elements with a 2-point calibration

Formation of conductive DNA-based nanowires via conjugation of dsDNA with cationic peptide

A novel conductive DNA-based nanomaterial, DNA-peptide wire, composed of a DNA core and a peripheral peptide layer, is presented. The electrical conductivity of the wire is found to be at least three orders in magnitude higher than that of native double-stranded DNA (dsDNA). High conductivity of the wires along with a better resistance to mechanical deformations caused by interactions between the substrate and electrode surface make them appealing for a wide variety of nanoelectronic and biosensor applications

Privacy-preserving comparison of variable-length data with application to biometric template protection

The establishment of cloud computing and big data in a wide variety of daily applications has raised some privacy concerns due to the sensitive nature of some of the processed data. This has promoted the need to develop data protection techniques, where the storage and all operations are carried out without disclosing any information. Following this trend, this paper presents a new approach to efficiently compare variable-length data in the encrypted domain using homomorphic encryption where only encrypted data is stored or exchanged. The new variable-length-based algorithm is fused with existing fixed-length techniques in order to obtain increased comparison accuracy. To assess the soundness of the proposed approach, we evaluate its performance on a particular application: a multi-algorithm biometric template protection system based on dynamic signatures that complies with the requirements described in the ISO/IEC 24745 standard on biometric information protection. Experiments have been carried out on a publicly available database and a free implementation of the Paillier cryptosystem to ensure reproducibility and comparability to other schemes.This work was supported in part by the German Federal Ministry of Education and Research (BMBF); in part by the Hessen State Ministry for Higher Education, Research, and the Arts (HMWK) within the Center for Research in Security and Privacy (CRISP); in part by the Spanish Ministerio de Economia y Competitividad / Fondo Europeo de Desarrollo Regional through the CogniMetrics Project under Grant TEC2015-70627-R; and in part by Cecaban