Although the main Raman features of semiconducting transition metal dichalcogenides are well known for the monolayer and bulk, there are important differences exhibited by few layered systems which ...have not been fully addressed. WSe2 samples were synthesized and ab-initio calculations carried out. We calculated phonon dispersions and Raman-active modes in layered systems: WSe2, MoSe2, WS2 and MoS2 ranging from monolayers to five-layers and the bulk. First, we confirmed that as the number of layers increase, the E', E″ and E2g modes shift to lower frequencies, and the A'1 and A1g modes shift to higher frequencies. Second, new high frequency first order A'1 and A1g modes appear, explaining recently reported experimental data for WSe2, MoSe2 and MoS2. Third, splitting of modes around A'1 and A1g is found which explains those observed in MoSe2. Finally, exterior and interior layers possess different vibrational frequencies. Therefore, it is now possible to precisely identify few-layered STMD.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Flexible electronics incorporate all the functional attributes of conventional rigid electronics in formats that have been altered to survive mechanical deformations. Understanding the evolution of ...device performance during bending, stretching, or other mechanical cycling is, therefore, fundamental to research efforts in this area. Here, we review the various classes of flexible electronic devices (including power sources, sensors, circuits and individual components) and describe the basic principles of device mechanics. We then review techniques to characterize the deformation tolerance and durability of these flexible devices, and we catalogue and geometric designs that are intended to optimize electronic systems for maximum flexibility.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In vivo and in vitro studies demonstrate that mitochondria in the oocyte, are susceptible to damage by suboptimal pre/pregnancy conditions, such as obesity. These suboptimal conditions have been ...shown to induce mitochondrial dysfunction (MD) in multiple tissues of the offspring, suggesting that mitochondria of oocytes that pass from mother to offspring, can carry information that can programme mitochondrial and metabolic dysfunction of the next generation. They also suggest that transmission of MD could increase the risk of obesity and other metabolic diseases in the population inter- and trans-generationally. In this review, we examined whether MD observed in offspring tissues of high energetic demand, is the result of the transmission of damaged mitochondria from the oocytes of obese mothers to the offspring. The contribution of genome-independent mechanisms (namely mitophagy) in this transmission were also explored. Finally, potential interventions aimed at improving oocyte/embryo health were investigated, to see if they may provide an opportunity to halter the generational effects of MD.
•Damaged oocyte-mitochondria can be transmitted from obese mother to the offspring.•Maternal obesity damages oocyte-mitochondrial metabolism and embryonic development.•Maternal obesity induces mitophagy-defective oocytes with reduced functionality.•Genome-independent mechanism could explain metabolic syndromes in next generations.•Combined pre-conceptional interventions could improve the health of oocytes/embryos.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this report, we compare the toxicological effects between pure carbon multiwalled nanotubes (MWNTs) and N-doped multiwalled carbon (CN x ) nanotubes. Different doses of tubes were administered in ...various ways to mice: nasal, oral, intratracheal, and intraperitoneal. We have found that when MWNTs were injected into the mice's trachea, the mice could die by dyspnea depending on the MWNTs doses. However, CN x nanotubes never caused the death of any mouse. We always found that CN x nanotubes were far more tolerated by the mice when compared to MWNTs. Extremely high concentrations of CN x nanotubes administrated directly into the mice's trachea only induced granulomatous inflammatory responses. Importantly, all other routes of administration did not induce signs of distress or tissue changes on any treated mouse. We therefore believe that CN x nanotubes are less harmful than MWNTs or SWNTs and might be more advantageous for bioapplications.
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IJS, KILJ, NUK, PNG, UL, UM
The development of glutamatergic synapses involves changes in the number and type of receptors present at the postsynaptic density. To elucidate molecular mechanisms underlying these changes, we ...combine in utero electroporation of constructs that alter the molecular composition of developing synapses with dual whole-cell electrophysiology to examine synaptic transmission during two distinct developmental stages. We find that SAP102 mediates synaptic trafficking of AMPA and NMDA receptors during synaptogenesis. Surprisingly, after synaptogenesis, PSD-95 assumes the functions of SAP102 and is necessary for two aspects of synapse maturation: the developmental increase in AMPA receptor transmission and replacement of NR2B-NMDARs with NR2A-NMDARs. In PSD-95/PSD-93 double-KO mice, the maturational replacement of NR2B- with NR2A-NMDARs fails to occur, and PSD-95 expression fully rescues this deficit. This study demonstrates that SAP102 and PSD-95 regulate the synaptic trafficking of distinct glutamate receptor subtypes at different developmental stages, thereby playing necessary roles in excitatory synapse development.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Abstract Humans and mice with loss-of-function mutations of the genes encoding kisspeptins ( Kiss1 ) or kisspeptin receptor ( Kiss1r ) are infertile due to hypogonadotropic hypogonadism. Within the ...hypothalamus, Kiss1 mRNA is expressed in the anteroventral periventricular nucleus (AVPV) and the arcuate nucleus (Arc). In order to better study the different populations of kisspeptin cells we generated Kiss1 -Cre transgenic mice. We obtained one line with Cre activity specifically within Kiss1 neurons (line J2–4), as assessed by generating mice with Cre-dependent expression of green fluorescent protein or β-galactosidase. Also, we demonstrated Kiss1 expression in the cerebral cortex and confirmed previous data showing Kiss1 mRNA in the medial nucleus of amygdala and anterodorsal preoptic nucleus. Kiss1 neurons were more concentrated towards the caudal levels of the Arc and higher leptin-responsivity was observed in the most caudal population of Arc Kiss1 neurons. No evidence for direct action of leptin in AVPV Kiss1 neurons was observed. Melanocortin fibers innervated subsets of Kiss1 neurons of the preoptic area and Arc, and both populations expressed melanocortin receptors type 4 (MC4R). Specifically in the preoptic area, 18–28% of Kiss1 neurons expressed MC4R. In the Arc, 90% of Kiss1 neurons were glutamatergic, 50% of which also were GABAergic. In the AVPV, 20% of Kiss1 neurons were glutamatergic whereas 75% were GABAergic. The differences observed between the Kiss1 neurons in the preoptic area and the Arc likely represent neuronal evidence for their differential roles in metabolism and reproduction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The performance of time-independent, orbital-optimized calculations of excited states is assessed with respect to charge transfer excitations in organic molecules in comparison to the linear-response ...time-dependent density functional theory (TD-DFT) approach. A direct optimization method to converge on saddle points of the electronic energy surface is used to carry out calculations with the local density approximation (LDA) and the generalized gradient approximation (GGA) functionals PBE and BLYP for a set of 27 excitations in 15 molecules. The time-independent approach is fully variational and provides a relaxed excited state electron density from which the extent of charge transfer is quantified. The TD-DFT calculations are generally found to provide larger charge transfer distances compared to the orbital-optimized calculations, even when including orbital relaxation effects with the Z-vector method. While the error on the excitation energy relative to theoretical best estimates is found to increase with the extent of charge transfer up to ca. −2 eV for TD-DFT, no correlation is observed for the orbital-optimized approach. The orbital-optimized calculations with the LDA and the GGA functionals provide a mean absolute error of ∼0.7 eV, outperforming TD-DFT with both local and global hybrid functionals for excitations with a long-range charge transfer character. Orbital-optimized calculations with the global hybrid functional B3LYP and the range-separated hybrid functional CAM-B3LYP on a selection of states with short- and long-range charge transfer indicate that inclusion of exact exchange has a small effect on the charge transfer distance, while it significantly improves the excitation energy, with the best-performing functional CAM-B3LYP providing an absolute error typically around 0.15 eV.
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IJS, KILJ, NUK, PNG, UL, UM
8.
Luminescence Concentration Quenching Mechanism in Gd2O3:Eu3 Meza, Octavio; Villabona-Leal, E. G; Diaz-Torres, L. A ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
02/2014, Volume:
118, Issue:
8
Journal Article
Peer reviewed
Luminescence concentration quenching in Gd2O3:Eu3+ nanocrystals results from strong interactions among O2– ions and Eu3+ ions. Because all synthesized Gd2O3:Eu3+ nanocrystals present the same cubic ...crystalline phase regardless of Eu3+ concentration, it is possible to study the optical properties as a function of the dopant concentration. The emission intensities and lifetime curves for Gd2O3:Eu3+ were analyzed by a simple rate equation model to study the interaction between the O2– ions and Eu3+ ions. The rate equation model considers that such interaction is driven by the following energy transfer processes: the direct energy transfer (O2– → Eu3+), back-transfer (Eu3+ → O2–), and direct energy migration (Eu3+ → Eu3+). The exact solution of this model agrees with the experimental results, luminescence concentration quenching is reproduced and the corresponding energy transfer rates are reported. Quantitative results suggest that the direct energy transfer and direct energy migration processes are the main responsible for the luminescence concentration quenching, whereas the back-transfer process promotes the Eu3+ emission.
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IJS, KILJ, NUK, PNG, UL, UM
Superlattices have attracted great interest because their use may make it possible to modify the spectra of two-dimensional electron systems and, ultimately, create materials with tailored electronic ...properties. In previous studies (see, for example, refs 1-8), it proved difficult to realize superlattices with short periodicities and weak disorder, and most of their observed features could be explained in terms of cyclotron orbits commensurate with the superlattice. Evidence for the formation of superlattice minibands (forming a fractal spectrum known as Hofstadter's butterfly) has been limited to the observation of new low-field oscillations and an internal structure within Landau levels. Here we report transport properties of graphene placed on a boron nitride substrate and accurately aligned along its crystallographic directions. The substrate's moiré potential acts as a superlattice and leads to profound changes in the graphene's electronic spectrum. Second-generation Dirac points appear as pronounced peaks in resistivity, accompanied by reversal of the Hall effect. The latter indicates that the effective sign of the charge carriers changes within graphene's conduction and valence bands. Strong magnetic fields lead to Zak-type cloning of the third generation of Dirac points, which are observed as numerous neutrality points in fields where a unit fraction of the flux quantum pierces the superlattice unit cell. Graphene superlattices such as this one provide a way of studying the rich physics expected in incommensurable quantum systems and illustrate the possibility of controllably modifying the electronic spectra of two-dimensional atomic crystals by varying their crystallographic alignment within van der Waals heterostuctures.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
We present a detailed analysis of XMM-Newton X-ray spectra of the Narrow-Line Seyfert 1 galaxy Mrk 1044. We find robust evidence for a multiphase, ultrafast outflow, traced by four separate ...components in the grating spectrum. One component has high column density and ionization state, and is outflowing at ∼0.15
c
. The other three wind components have lower temperature, lower column density, and have outflow velocities ∼0.08
c
. This wind structure is strikingly similar to that found in IRAS 17020+4544, suggesting that stratified winds may be a common feature of ultrafast outflows. Such structure is likely produced by fluid instabilities that form when the nuclear wind shocks the ambient medium. We show that, in an energy-driven wind scenario, the wind in Mrk 1044 might carry enough energy to produce significant feedback on its host galaxy. We further discuss the implications of the presence of a fast wind in yet another NLS1 galaxy with high Eddington ratio.
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