1,153 research outputs found
Information Content in Data Sets for a Nucleated-Polymerization Model
We illustrate the use of tools (asymptotic theories of standard error
quantification using appropriate statistical models, bootstrapping, model
comparison techniques) in addition to sensitivity that may be employed to
determine the information content in data sets. We do this in the context of
recent models [23] for nucleated polymerization in proteins, about which very
little is known regarding the underlying mechanisms; thus the methodology we
develop here may be of great help to experimentalists
Extension of charge-state-distribution calculations for ion-solid collisions towards low velocities and many-electron ions
Knowledge of the detailed evolution of the whole charge-state distribution of projectile ions colliding with targets is required in several fields of research such as material science and atomic and nuclear physics but also in accelerator physics, and in particular in regard to the several foreseen large-scale facilities. However, there is a lack of data for collisions in the nonperturbative energy domain and that involve many-electron projectiles. Starting from the etacha model we developed [Rozet, Nucl. Instrum. Methods Phys. Res., Sect. B 107, 67 (1996)10.1016/0168-583X(95)00800-4], we present an extension of its validity domain towards lower velocities and larger distortions. Moreover, the system of rate equations is able to take into account ions with up to 60 orbital states of electrons. The computed data from the different new versions of the etacha code are compared to some test collision systems. The improvements made are clearly illustrated by 28.9MeVu-1Pb56+ ions, and laser-generated carbon ion beams of 0.045 to 0.5MeVu-1, passing through carbon or aluminum targets, respectively. Hence, those new developments can efficiently sustain the experimental programs that are currently in progress on the "next-generation" accelerators or laser facilities.Fil: Lamour, E.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Fainstein, Pablo Daniel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. ComisiĂłn Nacional de EnergĂa AtĂłmica. Centro AtĂłmico Bariloche; ArgentinaFil: Galassi, Mariel Elisa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de FĂsica de Rosario. Universidad Nacional de Rosario. Instituto de FĂsica de Rosario; ArgentinaFil: Prigent, C.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Ramirez, C. A.. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de FĂsica de Rosario. Universidad Nacional de Rosario. Instituto de FĂsica de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de FĂsica de Rosario. Universidad Nacional de Rosario. Instituto de FĂsica de Rosario; ArgentinaFil: Rozet, J. P.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Trassinelli, M.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; FranciaFil: Vernhet, D.. Centre National de la Recherche Scientifique; Francia. Universite de Paris; Franci
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
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
Low Energy Electron Point Projection Microscopy of Suspended Graphene, the Ultimate "Microscope Slide"
Point Projection Microscopy (PPM) is used to image suspended graphene using
low-energy electrons (100-200eV). Because of the low energies used, the
graphene is neither damaged or contaminated by the electron beam. The
transparency of graphene is measured to be 74%, equivalent to electron
transmission through a sheet as thick as twice the covalent radius of
sp^2-bonded carbon. Also observed is rippling in the structure of the suspended
graphene, with a wavelength of approximately 26 nm. The interference of the
electron beam due to the diffraction off the edge of a graphene knife edge is
observed and used to calculate a virtual source size of 4.7 +/- 0.6 Angstroms
for the electron emitter. It is demonstrated that graphene can be used as both
anode and substrate in PPM in order to avoid distortions due to strong field
gradients around nano-scale objects. Graphene can be used to image objects
suspended on the sheet using PPM, and in the future, electron holography
Ground subsidence effects on simulating dynamic high-latitude surface inundation under permafrost thaw using CLM5
Simulating surface inundation is particularly challenging for the high-latitude permafrost regions. Ice-rich permafrost thaw can create expanding thermokarst lakes as well as shrinking large wetlands. Such processes can have major biogeochemical implications and feedbacks to the climate system by altering the pathways and rates of permafrost carbon release. However, the processes associated with it havenot yet been properly represented in Earth system models. We show a new model parameterization that allows direct representation of surface water dynamics in CLM (Community Land Model), the land surface model of several Earth System Models. Specifically, we coupled permafrost-thaw-induced ground subsidence and surface microtopography distribution to represent surface water dynamics in the high latitudes. Our results show increased surface water fractions around western Siberian plains and northeastern territories of Canada. Additionally, localized drainage events correspond well to severe ground subsidence events. Our parameterization is one of the first steps towards a process-oriented repre-sentation of surface hydrology, which is crucial to assess the biogeochemical feedbacks between land and the atmosphere under changing climat
Changes in Land Surface Water Dynamics since the 1990s and Relation to Population Pressure
We developed a remote sensing approach based on multi-satellite observations, which provides an unprecedented estimate of monthly distribution and area of land-surface open water over the whole globe. Results for 1993 to 2007 exhibit a large seasonal and inter-annual variability of the inundation extent with an overall decline in global average maximum inundated area of 6% during the fifteen-year period, primarily in tropical and subtropical South America and South Asia. The largest declines of open water are found where large increases in population have occurred over the last two decades, suggesting a global scale effect of human activities on continental surface freshwater: denser population can impact local hydrology by reducing freshwater extent, by draining marshes and wetlands, and by increasing water withdrawals. Citation: Prigent, C., F. Papa, F. Aires, C. Jimenez, W. B. Rossow, and E. Matthews (2012), Changes in land surface water dynamics since the 1990s and relation to population pressure, in section 4, insisting on the potential applications of the wetland dataset
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