Although water has been extensively studied, not all of its unique properties have been fully understood. There is still controversy about the temperature at which hydrogen bonds are broken or weakened, producing the anomalous temperature dependence of many water properties. Different temperatures between 23 and 48 °C have been reported, but no study has scrutinized the reasons for this discrepancy. We suggest the determining role of pH in the alteration of the water anomaly temperature. We employed a luminescent europium trisbipyridine cryptate, which is highly sensitive to changes in the arrangement of water molecules and whose luminescence intensity and lifetime are not significantly influenced by variations over a broad pH range. Our results revealed an increase of the crossover temperature from circa 35 °C at pH 3.5 to circa 45 °C at pH 7 to 9, which explains the discrepancies of previous studies. The pH dependence of water anomaly temperature is an important property for a better understanding of water and water-based systems and applications.

Skeletal muscle is made from multinuclear myofiber, where myonuclei are positioned at the periphery or clustered below neuromuscular junctions (NMJs). While mispositioned myonuclei are the hallmark of numerous muscular diseases, the molecular machinery maintaining myonuclei positioning in mature muscle is still unknown. Here, we identified microtubule-associated protein MACF1 as an evolutionary conserved regulator of myonuclei positioning, in vitro and in vivo, controlling the “microtubule code” and stabilizing the microtubule dynamics during myofibers maturation, preferentially at NMJs. Specifically, MACF1 governs myonuclei motion, mitochondria positioning and structure and acetylcholine receptors (AChRs) clustering. Macf1-KO in young and adult mice decreases muscle excitability and causes evolutionary myonuclei positioning alterations in adult mice, paralleled with high mitochondria content and improved resistance to fatigue. We present MACF1 as a primary actor of the maintenance of synaptic myonuclei and AChRs clustering, peripheral myonuclei positioning and mitochondria organization through the control of microtubule network dynamics in muscle fibers.

Aqueous solutions of luminescent metal–ion complexes, in particular, those of lanthanide ions, can play an essential role in biomedical applications. For all of these applications, the knowledge ab...

Curie-Weiss temperature dependence of the dielectric permittivity has been shown to take place in water. A bilinear change at has been reported recently. In this work an effective field statistical theory is developed for polar liquids such as water. A change of elementary dipole moment at describes well its behavior with temperature. It implies a change in dipole moment from a value close to that in ice to another close to that in water vapor. The Lindemann relationship is used to estimate the fractional oscillation of the water molecule from melting temperature T=0 degrees C to in terms of the water Debye temperature and basic geometrical parameters.

•Optical spectroscopic studies of nanoparticles CaF2 doped with Nd3+ ions clearly identified core and surface related luminescence defect centers.•The origin of the surface or near surface defect, A′, centre has been ascertained to be derived from a single-ion centre most probably charge compensated by a hydroxyl group.•It highlight the power and usefulness of the spectroscopic technique of zero-order excitation in the characterisation of the luminescence of sub-micron particles.

The tendency to the miniaturization of devices and the peculiar properties of the nanoparticles have raised the interest of the scientific community in nanoscience. In particular, those systems consisting of nanoparticles dispersed in fluids, known as nanofluids, have made it possible to overcome many technological and scientific challenges, as they show extraordinary properties. In this work, the loss of the spectral stability in heterogeneous luminescent nanofluids is studied revealing the critical role played by the exchange of ions between different nanoparticles. Such ion exchange is favored by changes in the molecular properties of the solvent, making heterogeneous luminescent nanofluids highly unstable against temperature changes. This work demonstrates how both temporal and thermal stabilities of heterogeneous luminescent nanofluids can be substantially improved by core–shell engineering. This simultaneously avoids the leakage of luminescent ions and the effects of the solvent molecular changes.

Luminescence of a single upconverting particle (NaYF4:Er3+,Yb3+) can be used to determine the optical trap temperature due to the partial absorption of the trapping beam either by the medium (water) or the optically trapped particle itself. This fact is an important drawback can be reduced by shifting the trapping wavelength out of the water absorption band, or by using time-modulated laser trapping beams. Both approaches have been studied and the results have shown that the thermal loading due to the trapping radiation can be minimized.

Nowadays a large variety of applications are based on solid nanoparticles dispersed in liquids—so called nanofluids. The interaction between the fluid and the nanoparticles plays a decisive role in the physical properties of the nanofluid. A novel approach based on the nonradiative energy transfer between two small luminescent nanocrystals (GdVO 4 :Nd 3+ and GdVO 4 :Yb 3+ ) dispersed in water is used in this work to investigate how temperature affects both the processes of interaction between nanoparticles and the effect of the fluid on the nanoparticles. From a systematic analysis of the effect of temperature on the GdVO 4 :Nd 3+ → GdVO 4 :Yb 3+ interparticle energy transfer, it can be concluded that a dramatic increase in the energy transfer efficiency occurs for temperatures above 45 °C. This change is properly explained by taking into account a crossover existing in diverse water properties that occurs at about this temperature. The obtained results allow elucidation on the molecular arrangement of water molecules below and above this crossover temperature. In addition, it is observed that an energy transfer process is produced as a result of interparticle collisions that induce irreversible ion exchange between the interacting nanoparticles.

3D optical manipulation of a thermal-sensing upconverting particle allows for the determination of the extension of the thermal gradient created in the surroundings of a plasmonic-mediated photo thermal-treated HeLa cancer cell.

This work reviews several properties of liquid water, including the dielectric constant and the proton-spin lattice relaxation, and draws attention to a bilinear behaviour defining a crossover in the temperature range 50 ± 10°C between two possible states in liquid water. The existence of these two states in liquid water plays an important role in nanometric and biological systems. For example, the optical properties of metallic (gold and silver) nanoparticles dispersed in water, used as nanoprobes, and the emission properties of CdTe quantum dots (QDs), used for fluorescence bioimaging and tumour targeting, show a singular behaviour in this temperature range. In addition, the structural changes in liquid water may be associated with the behaviour of biological macromolecules in aqueous solutions and in particular with protein denaturation.

In this study, the photoluminescence properties of congruent codoped LiNbO3:Cr3+; W4+' crystals have been syftematically investigated by performing photoluminescence studies at room temperature in the 0-280 kbar pressure range. In particular, we focus on the influence that hydrostatic pressure has on the E-2 -> (4)A(2) (R-lines) transitions of Cr3+. It has been observed that the pressure dependence of the spectral position of the R-lines associated with both Cr3+ centres beta and gamma shows a bilinear behaviour with an abrupt slope change near 210 kbar. This change is related to the existence of a pressure-induced structural phase transition in the LiNbO3 host. The analysis of experimental results provides the Racah parameters B and C and the crystal field parameter 10Dq and their pressure and volume, through the crystal field theory and equation of state, dependences. (C) 2016 Elsevier B.V. All rights reserved.

This work has been partially supported by Ministerio de Ciencia e Innovacion (project TEC2010-21574-C02-01) and Comunidad de Madrid (P2009/TIC-1476), Spain. E. Camarillo G. recognizes to DGAPA-UNAM support for a sabbatical year at UAM

Recently, the paraelectric response of water was investigated in the range 0-100 degrees C. It showed an almost perfect Curie-Weiss behaviour up to 60 degrees C, but a slight change in slope of 1/epsilon(d) versus T at 60 degrees C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 degrees C. An anomalous response at 60 degrees C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 degrees C. A reanalysis of 1/epsilon(d) (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0-60 degrees C) configuration with a dipole moment mu(1)=2.18 D (close to the molecular dipole moment of ice) to a high temperature (60-100 degrees C) configuration with mu(2)=1.87 D (identical to the molecular dipole moment in water vapour).

The absorption efficiencies of gold nanorods working in the first and second biological windows are investigated.

This paper presents a study of the behaviour as optical superlattices of periodically poled LiNbO3 and LiTaO3 crystals using the Scanning Near-field Optical Microscopy (SNOM) technique. The periodic ferroelectric domains were formed either by electric field poling technique or by the "off-centre Czochralski method" during crystal growth. SNOM patterns were recorded in both collective and reflective configuration, simultaneously with surface topography measurement by AFM (Atomic Force Microscopy). It has been found that regardless of the method used to create the domains, a modulation in the SNOM signal intensity is correlated with the ferroelectric domain structure. The maximum intensity of the collected or reflected SNOM light intensity is centred on the negative domains, whereas the minimum intensity is positioned on the positive domains. This result demonstrates that the modulation of the refractive index is related to the domains and not with the wall between them.

Se han instalado en el cono sur de nuestro continente 16 medidores simples de ozono construidos mediante una colaboración entre Argentina y España. Durante la primavera de 1993 se realizó una campaña de mediciones simultáneas con objeto de cuantificar la posible influencia del episodio anual antártico en terreno continental. En Argentina, los equipos fueron instalados en Río Grande, Bariloche, Carmen de Patagones, Mar del Plata, Tandil, Mercedes (Provincia de Buenos Aires), La Plata, San Luis, Rosario y Salta. Seis equipos similares fueron enviados a Chile para realizar medidas en distintos paralelos que cubrirán desde la Antártida hasta Arica. El funcionamiento de los sensores está basado en la dependencia de la distribución espectral de la radiación ultravioleta solar con el contenido de ozono atmosférico. Es sabido que, para longitudes de onda cercanas a 300 nm, esa distribución espectral está prácticamente gobernada por el ozono y que otros agentes que filtran la radiación sólo modifican levemente la distribución. Las mediciones realizadas en Río Grande, las únicas analizadas hasta el momento, muestran claramente la llegada del agujero de ozono a esa ciudad el 27 de setiembre de 1993.