Thermodynamic quantum critical behavior of the Kondo necklace model

We obtain the phase diagram and thermodynamic behavior of the Kondo necklace model for arbitrary dimensions $d$ using a representation for the localized and conduction electrons in terms of local Kondo singlet and triplet operators. A decoupling scheme on the double time Green's functions yields the dispersion relation for the excitations of the system. We show that in $d\geq 3$ there is an antiferromagnetically ordered state at finite temperatures terminating at a quantum critical point (QCP). In 2-d, long range magnetic order occurs only at T=0. The line of Neel transitions for $d>2$ varies with the distance to the quantum critical point QCP $|g|$ as, $T_N \propto |g|^{\psi}$ where the shift exponent $\psi=1/(d-1)$. In the paramagnetic side of the phase diagram, the spin gap behaves as $\Delta\approx \sqrt{|g|}$ for $d \ge 3$ consistent with the value $z=1$ found for the dynamical critical exponent. We also find in this region a power law temperature dependence in the specific heat for $k_BT\gg\Delta$ and along the non-Fermi liquid trajectory. For $k_BT \ll\Delta$, in the so-called Kondo spin liquid phase, the thermodynamic behavior is dominated by an exponential temperature dependence.Comment: Submitted to PR

Superparamagnetic particles in ZSM-5-type ferrisilicates

As-synthesized, low iron content, ferrisilicates of ZSM-5-type contain well-separated Fe(III) ions in a tetrahedral environment and display paramagnetic behavior. After hydrothermal treatment, the iron ions are partially extracted from the framework, generating nanosize iron oxide or oxyhydroxide ferrimagnetic particles. This process has been studied by transmission electron microscopy (TEM), Mossbauer spectroscopy, magnetic ac susceptibility (chi(ac)), and field dependent magnetization, on samples containing up to 6.7 wt. % Fe. The experiments evidence the growth of nonaggregated particles, with a typical size around 3 nm, presumably located at the surface of the ferrisilicate crystallites, From a thorough granulometric analysis involving TEM and chi(ac) data, it is concluded that, in the range from 1.5 to 4.6 wt. % Fe, the particle size distributions are significantly independent of the iron content

Electron backscattering diffraction as a complementary analytical approach to the microstructural characterization of ancient materials by electron microscopy

Since the development of electron backscattering diffraction (EBSD), scanning electron microscopy (SEM) has become a powerful tool for characterizing the local crystallography of bulk materials at the nanoscale. Although EBSD is now a well-established characterization method in materials science, it has rarely been used in art and archaeology, and nearly exclusively in metallic materials. However, EBSD could also be exploited to characterize ancient materials and to highlight their local crystallography (e.g., in the study of natural or artificial pigments). We discuss the potential of EBSD, as outlined in studies and from its application with an ancient material - Egyptian blue - in identification of crystalline phases, drawing phase maps, and the extraction of several microstructural parameters (e.g., the grain size and the aspect-ratio distribution of phases).The authors acknowledge funding by CTQ2011-24882 (Ministerio de Ciencia e Innovación) and MAT2012-30763 (Ministerio de Economía y Competitividad) projects, which are financed by the Spanish Government and the Federal program of the European Union.Peer Reviewe

Calculation of the orientation relationships of directionally solidified eutectic ceramics by a modified Coincidence of Reciprocal Lattice Points model (CRLP)

The Coincidence of Reciprocal Lattice Points (CRLP) method was used to predict, according to geometric considerations, the most favorable orientation relationships (ORs) between the component phases in a family of directionally solidified eutectic ceramics (DSEC) (NiO-YSZ, CoO-YSZ, NiO-CeO2, NiO-GDC, CoO-CeO2, and CoO-GDC) grown by the laser floating zone method. The ORs predicted by the CRLP model are consistent with those experimentally found in a previous work by means of Electron Backscatter Diffraction (EBSD). In this article, we also present a modification to the model with the aim of taking into account that the most stable ceramic-ceramic interfaces are usually formed between atomic planes with low Miller indices, due to their higher atomic density and bigger interplanar spacing. Thus, we introduce in the calculation of the overall coincidence volume a weighting factor which is a function of the interplanar spacing. This modified CRLP method has been applied to the aforementioned eutectic ceramics, and the results are presented and discussed in comparison with the traditional CRLP results and the experimental findings.This study was funded by the MAT2012-30763 project, which is financed by the Spanish Government (Ministerio de Economía y Competitividad) and the Feder program of the European Union.Peer Reviewe

Measurements of three-dimensional glenoid erosion when planning the prosthetic replacement of osteoarthritic shoulders.

The three-dimensional (3D) correction of glenoid erosion is critical to the long-term success of total shoulder replacement (TSR). In order to characterise the 3D morphology of eroded glenoid surfaces, we looked for a set of morphological parameters useful for TSR planning. We defined a scapular coordinates system based on non-eroded bony landmarks. The maximum glenoid version was measured and specified in 3D by its orientation angle. Medialisation was considered relative to the spino-glenoid notch. We analysed regular CT scans of 19 normal (N) and 86 osteoarthritic (OA) scapulae. When the maximum version of OA shoulders was higher than 10°, the orientation was not only posterior, but extended in postero-superior (35%), postero-inferior (6%) and anterior sectors (4%). The medialisation of the glenoid was higher in OA than normal shoulders. The orientation angle of maximum version appeared as a critical parameter to specify the glenoid shape in 3D. It will be very useful in planning the best position for the glenoid in TSR

Algorithms For Extracting Timeliness Graphs

We consider asynchronous message-passing systems in which some links are timely and processes may crash. Each run defines a timeliness graph among correct processes: (p; q) is an edge of the timeliness graph if the link from p to q is timely (that is, there is bound on communication delays from p to q). The main goal of this paper is to approximate this timeliness graph by graphs having some properties (such as being trees, rings, ...). Given a family S of graphs, for runs such that the timeliness graph contains at least one graph in S then using an extraction algorithm, each correct process has to converge to the same graph in S that is, in a precise sense, an approximation of the timeliness graph of the run. For example, if the timeliness graph contains a ring, then using an extraction algorithm, all correct processes eventually converge to the same ring and in this ring all nodes will be correct processes and all links will be timely. We first present a general extraction algorithm and then a more specific extraction algorithm that is communication efficient (i.e., eventually all the messages of the extraction algorithm use only links of the extracted graph)

Efficient production of hybrid bio-nanomaterials by continuous microchannel emulsification: Dye-doped SiO2 and Au-PLGA nanoparticles

A novel microfluidic system was designed to produce in a continuous manner hybrid nanomaterials using the microchannel double w/o/w emulsification technique. Double w/o/w nanoemulsions were produced combining two inter-digital micromixers that afford working in continuous flow and with a high reproducibility and control on the reaction conditions. High throughput production of two hybrid nanomaterials, dye-doped SiO2 (4 mg/min) and Au-loaded poly(lactic-co-glycolic) acid (PLGA) (168 mg/min) nanoparticles, were achieved, showing the resulting nanomaterials excellent and reproducible optical properties and tunable loading. These hybrid nanomaterials could be potentially used in different biomedical applications. In addition, the microfluidic system designed for carrying out double emulsification enabled to decrease the particle size distribution of dye-doped SiO2 nanoparticles (NPs) up to 20 nm and to improve the Au NPs loading efficiency in Au-loaded PLGA hybrid nanoparticles. The excellent control achieved in the Au NPs loading allowed tuning the payload on demand. Finally, the microfluidic system designed in this work overpasses the productivity described in previously published batch-type reactors, while assuring the same properties of the resulting hybrid nanomaterials

Lanthanide nickelates for their application on Solid Oxide Cells

High-temperature technologies like solid oxide cells (SOC) have been employed to provide power-to-fuel and vice versa for energy conversion and storage. These technologies are a work in progress due to durability and compatibility issues between components at high temperatures. For this reason, the pursuit of optimal physical, mechanical, and chemical properties of SOC materials at lower temperatures has become more diligent. Finding suitable air electrodes has become one of the more notable obstacles to complete implementation in the industry. One of the most recent alternatives is the use of lanthanide nickelates with the Ruddlesden-Popper (RP), Lnn+1NinO3n±1 (Ln = La, Nd or Pr), and perovskite, LnNiO3-δ, structures. These materials present fast ionic and electronic transport, as well as flexible oxygen stoichiometry that makes them compelling for this purpose. As part of an ongoing study on alternative air electrode advanced materials, this review is focused on documenting the relevant findings of RP nickelates over the years, especially focusing on the current status in research and development while comparing the electrochemical performance of nickelate air electrodes

Microfluidic Continuous Approaches to Produce Magnetic Nanoparticles with Homogeneous Size Distribution

We present a gas-liquid microfluidic system as a reactor to obtain magnetite nanoparticles with an excellent degree of control regarding their crystalline phase, shape and size. Several types of microflow approaches were selected to prevent nanomaterial aggregation and to promote homogenous size distribution. The selected reactor consists of a mixer stage aided by ultrasound waves and a reaction stage using a N2-liquid segmented flow to prevent magnetite oxidation to non-magnetic phases. A milli-fluidic reactor was developed to increase the production rate where a magnetite throughput close to 450 mg/h in a continuous fashion was obtained