908 research outputs found
Point defects on graphene on metals
Understanding the coupling of graphene with its local environment is critical
to be able to integrate it in tomorrow's electronic devices. Here we show how
the presence of a metallic substrate affects the properties of an atomically
tailored graphene layer. We have deliberately introduced single carbon
vacancies on a graphene monolayer grown on a Pt(111) surface and investigated
its impact in the electronic, structural and magnetic properties of the
graphene layer. Our low temperature scanning tunneling microscopy studies,
complemented by density functional theory, show the existence of a broad
electronic resonance above the Fermi energy associated with the vacancies.
Vacancy sites become reactive leading to an increase of the coupling between
the graphene layer and the metal substrate at these points; this gives rise to
a rapid decay of the localized state and the quenching of the magnetic moment
associated with carbon vacancies in free-standing graphene layers
Determining the physical conditions of extremely young Class 0 circumbinary disk around VLA1623A
We present detailed analysis of high-resolution C18O (2-1), SO (88-77), CO
(3-2) and DCO+ (3-2) data obtained by the Atacama Large
Millimeter/sub-millimeter Array (ALMA) towards a Class 0 Keplerian circumbinary
disk around VLA1623A, which represents one of the most complete analysis
towards a Class 0 source. From the dendrogram analysis, we identified several
accretion flows feeding the circumbinary disk in a highly anisotropic manner.
Stream-like SO emission around the circumbinary disk reveals the complicated
shocks caused by the interactions between the disk, accretion flows and
outflows. A wall-like structure is discovered south of VLA1623B. The discovery
of two outflow cavity walls at the same position traveling at different
velocities suggests the two outflows from both VLA1623A and VLA1623B overlays
on top of each other in the plane of sky. Our detailed flat and flared disk
modeling shows that Cycle 2 C18O J = 2-1 data is inconsistent with the combined
binary mass of 0.2 Msun as suggested by early Cycle 0 studies. The combined
binary mass for VLA1623A should be modified to 0.3 ~ 0.5 Msun.Comment: 26 pages, 20 figures, accepted by ApJ 2020.2.2
Painful adult scoliosis with kyphosant evolution and sagittal anterior trunk imbalance treated with physical therapy techniques: three case reports
Metallic properties of magnesium point contacts
We present an experimental and theoretical study of the conductance and
stability of Mg atomic-sized contacts. Using Mechanically Controllable Break
Junctions (MCBJ), we have observed that the room temperature conductance
histograms exhibit a series of peaks, which suggests the existence of a shell
effect. Its periodicity, however, cannot be simply explained in terms of either
an atomic or electronic shell effect. We have also found that at room
temperature, contacts of the diameter of a single atom are absent. A possible
interpretation could be the occurrence of a metal-to-insulator transition as
the contact radius is reduced, in analogy with what it is known in the context
of Mg clusters. However, our first principle calculations show that while an
infinite linear chain can be insulating, Mg wires with larger atomic
coordinations, as in realistic atomic contacts, are alwaysmetallic. Finally, at
liquid helium temperature our measurements show that the conductance histogram
is dominated by a pronounced peak at the quantum of conductance. This is in
good agreement with our calculations based on a tight-binding model that
indicate that the conductance of a Mg one-atom contact is dominated by a single
fully open conduction channel.Comment: 14 pages, 5 figure
La ictiofauna
La composiciĂł especĂfica de la fauna ictiològica de l'Arxipèlag de Cabrera no presenta diferències significatives respecte a la de la resta de les Balears. Aquest treball es composa d'una llista exhaustiva dels peixos coneguts fins al moment a Cabrera, amb 218 espècies litorals o de plataforma, i d'un capĂtol de comentaris a les espècies mĂ©s interessants, destacant la confirmaciĂł de la presència de Serranus atricauda a Balears i primera referencia a Mallorca, la primera cita de Gobius vittatus a aigĂĽes ibèriques, la primera cita a Balears de Pomadasys incisus i la primera referència a Mallorca de Diplodus cervinus. A l'annex s'inclou una llista dels peixos ordenats pel tipus d'hĂ bitat.The specific composition of the icthyologic fauna of Cabrera Archipelago does not appear to be significantly different from that of the rest of the Balearic Islands. The present study gives an exhaustive list of the fishes know to live in Cabrera, with 128 coastal or platform species and includes a section commenting on the most interesting ones. The presence of Serranus atricauda in the Balearic Islands and its first citation in Mallorca is confirmed. Gobius vittatus is first cited for Iberian waters. Pomadasys incisus is first cited for Mallorca. A list of fishes ranked by that type is also given
Barcelona Scoliosis Physical Therapy School – BSPTS – based on classical Schroth principles: short term effects on back asymmetry in idiopathic scoliosis
Voltage balancing scheme for the multilevel flying capacitor converter using phase-shifted PWM
In flying capacitor (FC) converters, phase-shifted pulse-width modulation (PS-PWM) provides natural voltage balancing. However, for a practical application, a more robust balancing mechanism of maintaining the FC voltages at the desired values is required. This paper proposes a new closed-loop voltage balancing method for multilevel FC converters using PS-PWM. The proposed method balances the voltages of the FCs by modifying the duty cycle of each switch of the FC converter using a proportional (P) controller. The crossed effect between FC currents and duty cycles is considered and is used for FC voltage balancing. The Simulation results verify that the proposed voltage balancing method is very robust to different operating conditions, such as load transients and non-linear loads.Postprint (author’s final draft
Voltage balancing strategy for a five-level flying capacitor converter using phase disposition PWM with sawtooth-shaped arriers
The flying capacitor (FC) multilevel converter has attracted a great deal of interest in the recent years because of its easier extension to a higher number of levels (n>;3), as compared to its counterpart, the diode-clamped converter (DCC). The main focus of this paper is to develop a voltage balancing scheme of FCs for a five-level FC converter based on phase disposition pulse-width modulation (PD-PWM). Since there are multiple states that produce the same output voltage at the leg of the converter, such a redundancy is used to regulate the FC voltages at their desired levels. The selection of the optimal states is performed by minimizing a cost function. A drawback observed when using standard symmetrical triangular carriers for the PD-PWM, is the additional switching events that are produced due to transitions within the same voltage level. Nevertheless, this fact can be avoided by using sawtooth carrier waveforms instead. Simulation results verify the robustness of the proposed voltage balancing scheme against static and dynamic load conditions. Moreover, using sawtooth carriers a significant reduction of the switching frequency is achieved as compared to the use of standard triangle carriers while maintaining the FC voltage balanced.Peer ReviewedPostprint (author’s final draft
Fabrication and deposition of copper and copper oxide nanoparticles by laser ablation in open air
The proximity of the “post-antibiotic era”, where infections and minor injuries could be a cause of death, there are urges to seek an alternative for the cure of infectious diseases. Copper nanoparticles and their huge potential as a bactericidal agent could be a solution. In this work, Cu and Cu oxide nanoparticles were synthesized by laser ablation in open air and in argon atmosphere using 532 and 1064 nm radiation generated by nanosecond and picosecond Nd:YVO4 lasers, respectively, to be directly deposited onto Ti substrates. Size, morphology, composition and the crystalline structure of the produced nanoparticles have been studied by the means of field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), the energy dispersive spectroscopy of X-rays (EDS), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The UV-VIS absorbance of the thin layer of nanoparticles was also measured, and the antibacterial capacity of the obtained deposits tested against Staphylococcus aureus. The obtained deposits consisted of porous coatings composed of copper and copper oxide nanoparticles interconnected to form chain-like aggregates. The use of the argon atmosphere contributed to reduce significantly the formation of Cu oxide species. The synthesized and deposited nanoparticles exhibited an inhibitory effect upon S. aureus.Peer ReviewedPostprint (published version
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