474 research outputs found
Finding instabilities in the community structure of complex networks
The problem of finding clusters in complex networks has been extensively
studied by mathematicians, computer scientists and, more recently, by
physicists. Many of the existing algorithms partition a network into clear
clusters, without overlap. We here introduce a method to identify the nodes
lying ``between clusters'' and that allows for a general measure of the
stability of the clusters. This is done by adding noise over the weights of the
edges of the network. Our method can in principle be applied with any
clustering algorithm, provided that it works on weighted networks. We present
several applications on real-world networks using the Markov Clustering
Algorithm (MCL).Comment: 4 pages, 5 figure
Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment
We present the investigation on the modifications of structural and magnetic
properties of MnAs thin film epitaxially grown on GaAs induced by slow highly
charged ions bombardment under well-controlled conditions. The ion-induced
defects facilitate the nucleation of one phase with respect to the other in the
first-order magneto-structural MnAs transition with a consequent suppression of
thermal hysteresis without any significant perturbation on the other structural
and magnetic properties. In particular, the irradiated film keeps the giant
magnetocaloric effect at room temperature opening new perspective on magnetic
refrigeration technology for everyday use
Characterization and Modeling of DHBT in InP/GaAsSb Technology for the Design and Fabrication of a Ka Band MMIC Oscillator
This paper presents the design of an MMIC oscillator operating at a 38âGHz frequency. This circuit was fabricated by the IIIâV Lab with the new InP/GaAsSb Double Heterojunction Bipolar Transistor (DHBT) submicronic technology (We=700ânm). The transistor used in the circuit has a 15 ÎŒm long two-finger emitter. This paper describes the complete nonlinear modeling of this DHBT, including the cyclostationary modeling of its low frequency (LF) noise sources. The specific interest of the methodology used to design this oscillator resides in being able to choose a nonlinear operating condition of the transistor from an analysis in amplifier mode. The oscillator simulation and measurement results are compared. A 38âGHz oscillation frequency with 8.6âdBm output power and a phase noise of â80âdBc/Hz at 100âKHz offset from carrier have been measured
Modulating the phase transition temperature of giant magnetocaloric thin films by ion irradiation
Magnetic refrigeration based on the magnetocaloric effect at room temperature
is one of the most attractive alternative to the current gas
compression/expansion method routinely employed. Nevertheless, in giant
magnetocaloric materials, optimal refrigeration is restricted to the narrow
temperature window of the phase transition (Tc). In this work, we present the
possibility of varying this transition temperature into a same giant
magnetocaloric material by ion irradiation. We demonstrate that the transition
temperature of iron rhodium thin films can be tuned by the bombardment of ions
of Ne 5+ with varying fluences up to 10 14 ions cm --2 , leading to optimal
refrigeration over a large 270--380 K temperature window. The Tc modification
is found to be due to the ion-induced disorder and to the density of new
point-like defects. The variation of the phase transition temperature with the
number of incident ions opens new perspectives in the conception of devices
using giant magnetocaloric materials
Magnetic properties changes of MnAs thin films irradiated with highly charged ions
We present the first investigation on the effect of highly charged ion
bombardment on a manganese arsenide thin film. The MnAs films, 150 nm thick,
are irradiated with 90 keV Ne ions with a dose varying from
to ions/cm. The structural and
magnetic properties of the film after irradiation are investigated using
different techniques, namely, X-ray diffraction, magneto-optic Kerr effect and
magnetic force microscope. Preliminary results are presented. From the study of
the lattice spacing, we measure a change on the film structure that depends on
the received dose, similarly to previous studies with other materials.
Investigations on the surface show a strong modification of its magnetic
properties
Mastering disorder in a first-order transition by ion irradiation
The effect of ion bombardment on MnAs single crystalline thin films is
studied. The role of elastic collisions between ions and atoms of the material
is singled-out as the main process responsible for modifying the properties of
the material. Thermal hysteresis suppression, and the loss of sharpness of the
magneto-structural phase transition are studied as a function of different
irradiation conditions. While the latter is shown to be associated with the ion
induced disorder at the scale of the transition correlation length, the former
is related to the coupling between disorder and the large-scale elastic field
associated with the phase coexistence pattern
Comparative genomics study reveals Red Sea Bacillus with characteristics associated with potential microbial cell factories (MCFs)
© 2019, The Author(s). Recent advancements in the use of microbial cells for scalable production of industrial enzymes encourage exploring new environments for efficient microbial cell factories (MCFs). Here, through a comparison study, ten newly sequenced Bacillus species, isolated from the Rabigh Harbor Lagoon on the Red Sea shoreline, were evaluated for their potential use as MCFs. Phylogenetic analysis of 40 representative genomes with phylogenetic relevance, including the ten Red Sea species, showed that the Red Sea species come from several colonization events and are not the result of a single colonization followed by speciation. Moreover, clustering reactions in reconstruct metabolic networks of these Bacillus species revealed that three metabolic clades do not fit the phylogenetic tree, a sign of convergent evolution of the metabolism of these species in response to special environmental adaptation. We further showed Red Sea strains Bacillus paralicheniformis (Bac48) and B. halosaccharovorans (Bac94) had twice as much secreted proteins than the model strain B. subtilis 168. Also, Bac94 was enriched with genes associated with the Tat and Sec protein secretion system and Bac48 has a hybrid PKS/NRPS cluster that is part of a horizontally transferred genomic region. These properties collectively hint towards the potential use of Red Sea Bacillus as efficient protein secreting microbial hosts, and that this characteristic of these strains may be a consequence of the unique ecological features of the isolation environment
Atmospheric gas absorption knowledge in the submillimeter: Modeling, field measurements, and uncertainty quantification
Members of the atmospheric and astronomical science communities met to review the current state of the art of the submillimeter spectral region. Knowledge of gas spectroscopy is still questionable at these frequencies but is important to fully exploit upcoming
meteorological satellite measurements
Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)
The Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH4) emissions. A multi-model comparison is essential to evaluate the key uncertainties in the mechanisms and parameters leading to methane emissions. Ten modelling groups joined WETCHIMP to run eight global and two regional models with a common experimental protocol using the same climate and atmospheric carbon dioxide (CO2) forcing datasets. We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2013). Here we provide technical details for the six experiments, which included an equilibrium, a transient, and an optimized run plus three sensitivity experiments (temperature, precipitation, and atmospheric CO2 concentration). The diversity of approaches used by the models is summarized through a series of conceptual figures, and is used to evaluate the wide range of wetland extent and CH4 fluxes predicted by the models in the equilibrium run. We discuss relationships among the various approaches and patterns in consistencies of these model predictions. Within this group of models, there are three broad classes of methods used to estimate wetland extent: prescribed based on wetland distribution maps, prognostic relationships between hydrological states based on satellite observations, and explicit hydrological mass balances. A larger variety of approaches was used to estimate the net CH4 fluxes from wetland systems. Even though modelling of wetland extent and CH4 emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH4 emissions: there is little consensus on model structure or complexity due to knowledge gaps, different aims of the models, and the range of temporal and spatial resolutions of the models
Generation of recombinant single-chain antibodies neutralizing the cytolytic activity of vaginolysin, the main virulence factor of Gardnerella vaginalis
Generated scFvs is the first example of recombinant single-chain antibodies with VLY-neutralizing activity produced in prokaryote expression system. G. vaginalis caused infections continue to be a world-wide problem, therefore neutralizing recombinant antibodies may provide novel therapeutic agents useful in the treatment of bacterial vaginosis and other diseases caused by G. vaginalis
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