Ferromagnetism in bulk Co-Zn-O

The origin of ferromagnetism in diluted magnetic semiconductors is still an open question, yielding a great deal of research across the world. This work focuses on the Co-Zn-O system. Room-temperature ferromagnetism is observed after a partial reaction of Co_3O_4 and ZnO, which can be ascribed neither to carrier mediation nor segregated cobalt metallic clusters. Another mechanism is yielding room-temperature ferromagnetism. This mechanism is associated with a partial reaction of ZnO and Co_3O_4 grains, and always appears when the starting phases (Co_3O_4 and ZnO) are present in the sample, suggesting that interfaces are involved in the origin of the observed ferromagnetism

Decay of solutions to the Maxwell equation on the Schwarzschild background

A new Morawetz or integrated local energy decay estimate for Maxwell test fields on the exterior of a Schwarzschild black hole spacetime is proved. The proof makes use of a new superenergy tensor $H_{ab}$ defined in terms of the Maxwell field and its first derivatives. The superenergy tensor, although not conserved, yields a conserved higher order energy current $H_{ab} (\partial_t)^b$. The tensor $H_{ab}$ vanishes for the static Coulomb field, and the Morawetz estimate proved here therefore yields integrated decay for the Maxwell field to the Coulomb solution on the Schwarzschild exterior.Comment: 15 pages, updated reference

Interferometric inverse synthetic aperture radar experiment using an interferometric linear frequency modulated continuous wave millimetre-wave radar

D. Felguera-Martín,1 J.-T. González-Partida,1 P. Almorox-González,1 M. Burgos-García,1 and B.-P. Dorta-Naranjo2 1Universidad Politécnica de Madrid, Ciudad Universitaria s/n, Grupo de Microondas y Radar. Departamento de Señales, Sistemas y Radiocomunicaciones, Madrid, Spain 2Universidad de Las Palmas de Gran Canaria, Departamento de Señales y Comunicaciones, Las Palmas de Gran Canaria, Spain An interferometric linear frequency modulated continuous wave (LFMCW) millimetre-wave radar is presented, along with the results of an experiment conducted to study the feasibility of using it in a future millimetre-wave interferometric inverse synthetic aperture radar (InISAR) system. First, a description of the radar is given. Then, the signal processing chain is described, with special attention to the phase unwrapping technique. The interferometric phase is obtained by unwrapping the prominent target's phase in each antenna using a sliding frame processing technique. Cell migration issues in this method are also addressed. Simulations were carried out to illustrate and assess the processing chain and to show the effects of multipath echoes on the height measurement. In the real experiment, the range, speed and height of a moving target were tracked over consecutive inverse synthetic aperture radar (ISAR) image frames, verifying the performance of the whole system

Regional hazard assessment of earthquake-triggered slope instabilities considering site effects and seismic scenarios in Lorca basin (Spain)

We present a regional hazard assessment of earthquake- triggered slope instabilities based on specific seismic scenarios and taking into account soil and topographic amplification effects. We followed Newmark's sliding rigid-block methodology implemented in a geographic information system (GIS) with the aim of producing regional maps in terms of critical acceleration and Newmark displacements for selected seismic scenarios. Strong ground-motion amplification site effects have been considered, particularly the topographic factor, by means of designing a GIS tool based on terrain geometry features and Eurocode-8 provisions. Three different concepts of seismic scenarios are considered in this work: probabilistic, pseudo-probabilistic, and deterministic. The study area is the Lorca Basin, located in the Eastern Betic Cordillera, one of the most seismically active regions of southeast Spain. The obtained Newmark displacement maps are compared to the distribution of known slope instabilities in the area. Future seismically induced slope instabilities in the Lorca Basin appear to be limited to isolated rock slides and rockfalls. Only the deterministic scenario (M w >6.7) seems capable of producing widespread slope instabilities, mainly rock slides, rockfalls, and landslides

Bio-Based Aromatic Polyesters from a Novel Bicyclic Diol Derived from d‑Mannitol

2,4:3,5-Di-<i>O</i>-methylene-d-mannitol, abbreviated as Manx, is a d-mannitol-derived compound with the secondary hydroxyl groups acetalized with formaldehyde. The bicyclic structure of Manx consists of two fused 1,3-dioxane rings, with two primary hydroxyl groups standing free for reaction. A homopolyester made of Manx and dimethyl terephthalate as well as a set of copolyesters of poly­(butylene terephthalate) (PBT) in which 1,4-butanediol was replaced by Manx up to 50% were synthesized and characterized. The polyesters had <i>M</i>_w in the 30 000–52 000 g mol^–1 range and a random microstructure and were thermally stable up to nearly 370 °C. They displayed outstanding high <i>T</i>_g with values from 55 to 137 °C which steadily increased with the content in Manx. Copolyesters containing up to 40% of Manx were semicrystalline and adopted the crystal structure of PBT. Their stress–strain parameters were sensitively affected by the presence of carbohydrate-based units with elongation at break decreasing but tensile strength and elastic moduli steadily increasing with the degree of replacement

Substituent and Solvent Effects on the UV–vis Absorption Spectrum of the Photoactive Yellow Protein Chromophore

Solvent effects on the UV–vis absorption spectra and molecular properties of four models of the photoactive yellow protein (PYP) chromophore have been studied with ASEP/MD, a sequential quantum mechanics/molecular mechanics method. The anionic <i>trans</i>-<i>p</i>-coumaric acid (pCA^–), thioacid (pCTA^–), methyl ester (pCMe^–), and methyl thioester (pCTMe^–) derivatives have been studied in gas phase and in water solution. We analyze the modifications introduced by the substitution of sulfur by oxygen atoms and hydrogen by methyl in the coumaryl tail. We have found some differences in the absorption spectra of oxy and thio derivatives that could shed light on the different photoisomerization paths followed by these compounds. In solution, the spectrum substantially changes with respect to that obtained in the gas phase. The n → π₁* state is destabilized by a polar solvent like water, and it becomes the third excited state in solution displaying an important blue shift. Now, the π → π₁* and π → π₂* states mix, and we find contributions from both transitions in S1 and S2. The presence of the sulfur atom modulates the solvent effect and the first two excited states become practically degenerate for pCA^– and pCMe^– but moderately well-separated for pCTA^– and pCTMe^–

A “Nanopore Lithography” Strategy for Synthesizing Hierarchically Micro/Mesoporous Carbons from ZIF-8/Graphene Oxide Hybrids for Electrochemical Energy Storage

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications, but their almost exclusively microporous texture can be an obstacle to their performance in practical uses. Here, we introduce a novel strategy for the generation of very uniform mesoporosity in a prototypical MOF, namely, zeolitic imidazolate framework-8 (ZIF-8). The process, referred to as “nanopore lithography”, makes use of graphene oxide (GO) nanosheets enclosing ZIF-8 particles as masks or templates for the transfer of mesoporous texture to the latter. Upon controlled carbonization and activation, nanopores created in the GO envelope serve as selective entry points for localized etching of carbonized ZIF-8, so that such nanopores are replicated in the MOF-derived carbonaceous structure. The resulting porous carbons are dominated by uniform mesopores ∼3–4 nm in width and possess specific surface areas of ∼1300–1400 m² g^–1. Furthermore, we investigate and discuss the specific experimental conditions that afford the mesopore-templating action of the GO nanosheets. Electrochemical characterization revealed an improved capacitance as well as a faster, more reversible charge/discharge kinetics for the ZIF-8-derived porous carbons obtained through nanopore lithography, relative to those for their counterparts with standard activation (no GO templating), thus indicating the potential practical advantage of the present approach in capacitive energy storage applications

Methodology for the Absolute Configuration Determination of Epoxythymols Using the Constituents of <i>Ageratina glabrata</i>

A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of <i>Ageratina glabrata</i>. The methodology is based on enantiomeric purity determination employing 1,1′-bi-2-naphthol (BINOL) as a chiral solvating agent combined with vibrational circular dichroism (VCD) measurements and calculations. The conformational searching included an extensive Monte Carlo protocol that considered the rotational barriers to cover the whole conformational spaces. (+)-(8<i>S</i>)-10-Benzoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (<b>1</b>), (+)-(8<i>S</i>)-10-acetoxy-6-methoxy-8,9-epoxythymol isobutyrate (<b>4</b>), and (+)-(8<i>S</i>)-10-benzoyloxy-6-methoxy-8,9-epoxythymol isobutyrate (<b>5</b>) were isolated as enantiomerically pure constituents, while 10-isobutyryloxy-8,9-epoxythymol isobutyrate (<b>2</b>) was obtained as a 75:25 (8<i>S</i>)/(8<i>R</i>) scalemic mixture. In the case of 10-benzoyloxy-8,9-epoxythymol isobutyrate (<b>3</b>), the BINOL methodology revealed a 56:44 scalemic mixture and the VCD measurement was beyond the limit of sensitivity since the enantiomeric excess is only 12%. The racemization process of epoxythymol derivatives was studied using compound <b>1</b> and allowed the clarification of some stereochemical aspects of epoxythymol derivatives since their ACs have been scarcely analyzed and a particular behavior in their specific rotations was detected. In more than 30 oxygenated thymol derivatives, including some epoxythymols, the reported specific rotation values fluctuate from −1.6 to +1.4 passing through zero, suggesting the presence of scalemic and close to racemic mixtures, since enantiomerically pure natural constituents showed positive or negative specific rotations greater than 10 units