Multi-FPGA communication interface for electric circuit co-simulation

Real-time simulation of electric circuit is most often used to test real components connected to a real-time simulator. The increasing size and complexity of the simulation as well as the demand for better accuracy, lower time step, have pushed these simulations onto new hardware. For already more than a decade FPGA simulation is used by real-time simulation companies around the world to effectively simulate circuits under the μs. With the computation requirement growth, multi-FPGA simulation needs to be considered as a valuable asset but attention must be given to the latency between the simulations for accuracy and stability. In order to minimize the communication latency, a custom interface and communication architecture for co-FPGA simulation is proposed. This paper presents detailed work on this architecture and shows promising results

Can altered production of interleukin-1β, interleukin-6, transforming growth factor-β and prostaglandin E2 by isolated human subchondral osteoblasts identify two subgroups of osteoarthritic patients

AbstractObjective To determine the capacity of human subchondral osteoarthritic osteoblasts (Ob) to produce interleukin (IL)-1β, IL-6, transforming growth factor-β (TGF-β) and prostaglandin E2 (PGE2), and determine if a relationship exists between IL-1β, TGF-β, PGE2 and IL-6 production.Methods We measured the abundance of IL-1β, IL-6, TGF-β and PGE2 using very sensitive ELISA in conditioned-media of human primary subchondral Ob from normal individuals and osteoarthritic patients. Selective inhibition of IL-6 or IL-6 receptor signaling was performed to determine its effect on PGE2 production whereas the inhibiton of PGE2 production was performed to determine its effect on IL-6 production. The expression of bone cell markers and urokinase plasminogen activator (uPA) activity was also determined.Results Osteoarthritic Ob produced all these factors with greater variability than normal cells. Interestingly, the production of IL-6 and PGE2 by osteoarthritic Ob separated patients into two subgroups, those whose Ob produced levels comparable to normal (low producers) and those whose Ob produced higher levels (high producers). In those cells classified as high osteoarthritic Ob, PGE2 and IL-6 levels were increased two- to three-fold and five- to six-fold, respectively, compared with normal. In contrast, while using their IL-6 and PGE2 production to separate osteoarthritic Ob into low and high producers, we found that IL-1β levels were similar in normal and all osteoarthritic Ob. Using the same criteria, TGF-β levels were increased in all osteoarthritic Ob compared with normal. Reducing PGE2 synthesis by Indomethacin [a cyclo-oxygenase (COX) -1 and -2 inhibitor] reduced IL-6 levels in all osteoarthritic Ob, whereas Naproxen (a more selective COX-2 inhbitor) reduced PGE2 and IL-6 levels only in the high osteoarthritic group. Conversely, PGE2 addition to osteoarthritic Ob enhanced IL-6 production in both groups. Moreover, the addition of parathyroid hormone also stimulated IL-6 production to similar normal levels in both osteoarthritic groups. In contrast, using an antibody against IL-6 or IL-6 receptors did not reduce PGE2 levels in either group. The evaluation of alkaline phosphatase activity, osteocalcin release, collagen type I and uPA activity in osteoarthritic Ob failed to show any differences between these cells regardless to which subgroup they were assigned.Conclusions These results indicate that IL-6 and PGE2 production by subchondral Ob can discriminate two subgroups of osteoarthritic patients that cannot otherwise be separated by their expression of cell markers, and that endogenous PGE2 levels influence IL-6 synthesis in osteoarthritic Ob. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved

Arctic seabirds and shrinking sea ice: egg analyses reveal the importance of ice-derived resources

In the Arctic, sea-ice plays a central role in the functioning of marine food webs and its rapid shrinking has large effects on the biota. It is thus crucial to assess the importance of sea-ice and ice-derived resources to Arctic marine species. Here, we used a multi-biomarker approach combining Highly Branched Isoprenoids (HBIs) with δ13C and δ15N to evaluate how much Arctic seabirds rely on sea-ice derived resources during the pre-laying period, and if changes in sea-ice extent and duration affect their investment in reproduction. Eg

Secrecy energy efficiency maximization in cognitive radio networks

In this paper, we investigate a tradeoff between the secrecy rate (SR) and energy efficiency (EE) in an underlay cognitive radio network that consists of a cognitive base station (CBS), a cognitive user (CU), a primary user (PU), and multiple eavesdroppers (EDs). By using a so-called secrecy EE (SEE), which is defined as the ratio of SR to the total power consumption of CBS, as the design criterion, we formulate an SEE maximization (SEEM) problem for the CBS-CU transmission under the constraints of the transmit power of CBS, the SR of CU, and the quality-of-service (QoS) requirement of PU. Since the formulated optimization problem with a fractional objective function is non-convex and mathematically intractable, we first convert the original fractional objective function into an equivalent subtractive form, and then develop a method of combining the penalty function and the difference of two-convex functions (D.C.) approach to obtain an approximate convex problem. Based on this, an optimal beamforming (OBF) scheme is finally proposed to obtain the optimal solution. Furthermore, to reduce the computational complexity, we design a zero-forcing-based beamforming (ZFBF) scheme to achieve a sub-optimal solution to the SEEM problem. Simulation results are given to illustrate the effectiveness and advantage of the proposed SEE oriented OBF and ZFBF schemes over conventional SR maximization and EE maximization schemes

Hot-carrier photocurrent effects at graphene-metal interfaces

Photoexcitation of graphene leads to an interesting sequence of phenomena, some of which can be exploited in optoelectronic devices based on graphene. In particular, the efficient and ultrafast generation of an electron distribution with an elevated electron temperature and the concomitant generation of a photo-thermoelectric voltage at symmetry-breaking interfaces is of interest for photosensing and light harvesting. Here, we experimentally study the generated photocurrent at the graphene-metal interface, focusing on the time-resolved photocurrent, the effects of photon energy, Fermi energy and light polarization. We show that a single framework based on photo-thermoelectric photocurrent generation explains all experimental results

Distinctive effects of allochthonous and autochthonous organic matter on CDOM spectra in a tropical lake

Despite the increasing understanding about differences in carbon cycling between temperate and tropical freshwater systems, our knowledge on the importance of organic matter (OM) pools on light absorption properties in tropical lakes is very scarce. We performed a factorial mesocosm experiment in a tropical lake (Minas Gerais, Brazil) to evaluate the effects of increased concentrations of al-lochthonous and autochthonous OM, and differences in light availability on the light absorption characteristics of chromophoric dissolved organic matter (CDOM). Autochthonous OM deriving from phytoplankton (similar to Chl a) was stimulated by addition of nutrients, while OM from degradation of terrestrial leaves increased allochthonous OM, and neutral shading was used to manipulate light availability. Effects of the additions and shading on DOC, Chl a, nutrients, total suspended solid concentrations (TSM) and spectral CDOM absorption were monitored every 3 days. CDOM quality was characterized by spectral indices (S250-450, S275-295, S350-450, S-R and SUVA(254)). Effects of carbon sources and shading on the spectral CDOM absorption was investigated through principal component (PCA) and redundancy (RDA) analyses. The two different OM sources affected CDOM quality very differently and shading had minor effects on OM levels, but significant effects on OM quality, especially in combination with nutrient additions. Spectral indices (S250-450 and S-R) were mostly affected by allochthonous OM addition. The PCA showed that enrichment by allochthonous carbon had a strong effect on the CDOM spectra in the range between 300 and 400 nm, while the increase in autochthonous carbon increased absorption at wavelengths below 350 nm. Our study shows that small inputs of allochthonous OM can have large effects on the spectral light absorption compared to large production of autochthonous OM, with important implications for carbon cycling in tropical lakes.Peer reviewe

Generation of photovoltage in graphene on a femtosecond time scale through efficient carrier heating

Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies addressed the general operation of graphene-based photo-thermoelectric devices, and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster time scale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 femtoseconds. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 femtosecond laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity between 500 and 1500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.Comment: 6 pages, 4 figure

C5 Palsy After Cervical Spine Surgery: A Multicenter Retrospective Review of 59 Cases.

STUDY DESIGN: A multicenter, retrospective review of C5 palsy after cervical spine surgery. OBJECTIVE: Postoperative C5 palsy is a known complication of cervical decompressive spinal surgery. The goal of this study was to review the incidence, patient characteristics, and outcome of C5 palsy in patients undergoing cervical spine surgery. METHODS: We conducted a multicenter, retrospective review of 13 946 patients across 21 centers who received cervical spine surgery (levels C2 to C7) between January 1, 2005, and December 31, 2011, inclusive. P values were calculated using 2-sample t test for continuous variables and χ(2) tests or Fisher exact tests for categorical variables. RESULTS: Of the 13 946 cases reviewed, 59 patients experienced a postoperative C5 palsy. The incidence rate across the 21 sites ranged from 0% to 2.5%. At most recent follow-up, 32 patients reported complete resolution of symptoms (54.2%), 15 had symptoms resolve with residual effects (25.4%), 10 patients did not recover (17.0%), and 2 were lost to follow-up (3.4%). CONCLUSION: C5 palsy occurred in all surgical approaches and across a variety of diagnoses. The majority of patients had full recovery or recovery with residual effects. This study represents the largest series of North American patients reviewed to date

Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure

Ultrafast electron thermalization - the process leading to Auger recombination, carrier multiplication via impact ionization and hot carrier luminescence - occurs when optically excited electrons in a material undergo rapid electron-electron scattering to redistribute excess energy and reach electronic thermal equilibrium. Due to extremely short time and length scales, the measurement and manipulation of electron thermalization in nanoscale devices remains challenging even with the most advanced ultrafast laser techniques. Here, we overcome this challenge by leveraging the atomic thinness of two-dimensional van der Waals (vdW) materials in order to introduce a highly tunable electron transfer pathway that directly competes with electron thermalization. We realize this scheme in a graphene-boron nitride-graphene (G-BN-G) vdW heterostructure, through which optically excited carriers are transported from one graphene layer to the other. By applying an interlayer bias voltage or varying the excitation photon energy, interlayer carrier transport can be controlled to occur faster or slower than the intralayer scattering events, thus effectively tuning the electron thermalization pathways in graphene. Our findings, which demonstrate a novel means to probe and directly modulate electron energy transport in nanoscale materials, represent an important step toward designing and implementing novel optoelectronic and energy-harvesting devices with tailored microscopic properties.Comment: Accepted to Nature Physic