Blue luminescence at room temperature in defective MgO films

Luminescence spectroscopy has been used to characterize MgO films prepared by rf-sputtering. A clear correlation is found between the appearance of an emission peak centered at approximately 460 nm and the detection of ferromagnetic ordering in the samples. We suggest that cationic vacancies are responsible for the blue-light emission by introducing p states into the electronic band-gap. In accordance with this, our results strongly indicate that cationic vacancies are at the heart of the appearance of long-range magnetic ordering in MgO films.

Comment on: Deuterium nuclear fusion at room temperature: A pertinent inequality on barrier penetration

In a recent letter, Rosen claims to justify ...

Atomic structure of the nanocrystalline Si particles appearing in nanostructured Si thin films produced in low-temperature radiofrequency plasmas

Nanostructured Si thin films, also referred as polymorphous, were grown by plasma-enhanced chemical vapor deposition. The term "polymorphous" is used to define silicon material that consists of a two-phase mixture of amorphous and ordered Si. The plasma conditions were set to obtain Si thin films from the simultaneous deposition of radical and ordered nanoparticles. Here, a careful analysis by electron transmission microscopy and electron diffraction is reported with the aim to clarify the specific atomic structure of the nanocrystalline particles embedded in the films. Whatever the plasma conditions, the electron diffraction images always revealed the existence of a well-defined crystalline structure different from the diamondlike structure of Si. The formation of nanocrystallinelike films at low temperature is discussed. A Si face-cubic-centered structure is demonstrated here in nanocrystalline particles produced in low-pressure silane plasma at room temperature.

1.48 and 1.84 µm thulium emissions in monoclinic KGd(WO4)2 single crystals

By exciting at 788 nm, we have characterized the near infrared emissions of trivalent thulium ions in monoclinic KGd(WO4)2 single crystals at 1.48 and 1.84 mm as a function of dopant concentration from 0.1% to 10% and temperature from 10 K to room temperature. We used the reciprocity method to calculate the maximum emission cross-section of 3.0310220 cm2 at 1.838 mm for the polarization parallel to the Nm principal optical direction. These results agrees well with the experimental data. Experimental decay times of the 3H4!3F4 and 3F4!3H6 transitions have been measured as a function of thulium concentration.

Estimulació beta-adrenèrgica en la síndrome del destret respiratori agut (SDRA)

Estudi elaborat a partir d’una estada al Royal Brompton Hospital, Londres, Regne Unit, durant octubre i novembre del 2006.Els beneficis de la estimulació beta-adrenèrgica en pacients amb lesió pulmonar aguda (LPA) són coneguts, però no es disposa de dades sobre el possible efecte antiinflamatori. El condensat d'aire exhalat (CAE) és una tècnica no-invasiva de recollida de mostres del tracte respiratori inferior, podent ser útil en la monitorització de patologies respiratòries. S’ha usat marcadors biològics en el CAE de pacients ventilats mecànicament amb LPA per estudiar el possible efecte antiinflamatori que el salbutamol hi podria exercir. El CAE va ser recollit abans i després de l'administració de salbutamol inahalat. Inmediatament després es va mesurar la conductivitat i el pH abans i després de la desgasificació amb heli. Es va mesurar la concentració de nitrits i nitrats. Les mostres varen ser liofilitzades i guardades a -80ºC. La concentració de leucotriè B4 es va mesurar després de la reconstitució de la mostra. Els resultats s'expressen com a mitjana (error estàndard de la mostra). No s'han detectat diferències entre els valors de CAE basals dels pacients amb LPA i els de referència de la població sana de Barcelona. Es conclou doncs que el CAE és una tècnica no invasiva que pot ser usada en la monitorització de paceints ventilats mecànicament. El salbutamol inhalat incrementa de manera significativa el pH del CAE dels paceints amb LPA, tot i que un efecte directe de la inhalació de slabutamol no pot ser desestimat.

Materials nanocomposits a partir de whiskers de cel•lulosa i matriu polimèrica de cautxú

De acuerdo con los objetivos generales del proyecto y plan de trabajo previsto, para esta anualidad, se obtuvieron fibras y microfibras de celulosa a partir de dos fuentes: celulosa vegetal de pino y eucalipto y celulosa bacterial. Las microfibrillas han sido utilizadas como material de refuerzo para la fabricación de materiales compuestos a partir de caucho natural, policaprolactona y polivinil alcohol. Las muestras se fabricaron mediante la técnica de "casting" en medio acuoso y temperatura ambiente. Las muestras fueron caracterizados en sus propiedades mecánicas, físicas y térmicas. Se observó que, en general, la adición de las microfibrillas de celulosa en las matrices poliméricas provoca una mejora sustancial en las propiedades mecánicas del material en comparación con el polímero sin reforzar. Los resultados pueden resumirse de la siguiente manera: 1.Fabricación de materiales compuestos a base de caucho natural y fibras de celulosa. Se obtuvieron fibras y nanofibras de celulosa que fueron modificadas químicamente y usadas como refuerzo en matriz de caucho. Los resultados mostraron mejora de propiedades mecánicas del material, principalmente en los materiales compuestos reforzados con nanofibras. 2. Obtención de whiskers de celulosa y su utilización como material de refuerzo en una matriz de policaprolactona. Se obtuvieron whiskers de celulosa a partir de pasta blanqueada. La adición en una matriz de policaprolactona produjo materiales compuestos con propiedades mecánicas superiores a la matriz, con buena dispersión de los whiskers. 3. Obtención de fibras de celulosa bacterial y nanofibras de celulosa, aislamiento y utilización sobre una matriz de polivinil alcohol. Se obtuvo celulosa bacterial a partir de la bacteria Gluconacetobacter xylinum. Además se fabricaron nanofibras de celulosa a partir eucalipto blanqueado. La celulosa bacterial como material de refuerzo no produjo importantes mejoras en las propiedades mecánicas de la matriz; en cambio se observaron mejoras destacables con la nanofibra como refuerzo.

New Radicals and new applications of Dynamic Nuclear Polarization of biological systems

Dynamic Nuclear Polarization (DNP) is an emerging technique that could revolutionize the NMR study of small molecules at very low concentrations by the increase in sensitivity that results from transfer of polarization between electronic and nuclear spins. Although the underlying physics has been known for a long time, in the last few years there has been a lot of excitement on the chemistry and biology NMR community caused by the demonstration that the highly polarized nuclei that are prepared in solid state at very low temperatures (1-2 K) could be rapidly transferred to liquid samples at room temperature and studied in solution by conventional NMR techniques. In favorable cases several order of magnitude increases in sensitivity have been achieved. The technique is now mature enough that a commercial instrument is available. The efficiency of DNP depends on two crucial aspects: i) the efficiency of the nuclear polarization process and ii) the efficiency of the transfer from the initial solid state to the fluid state in which NMR is measured. The preferred areas of application (iii) will be dictated by situations in which the low concentration of the sample or its intrinsic low receptivity are the limiting factors .

THC prevents MDMA neurotoxicity in mice

The majority of MDMA (ecstasy) recreational users also consume cannabis. Despite the rewarding effects that both drugs have, they induce several opposite pharmacological responses. MDMA causes hyperthermia, oxidative stress and neuronal damage, especially at warm ambient temperature. However, THC, the main psychoactive compound of cannabis, produces hypothermic, anti-inflammatory and antioxidant effects. Therefore, THC may have a neuroprotective effect against MDMA-induced neurotoxicity. Mice receiving a neurotoxic regimen of MDMA (20 mg/kg ×4) were pretreated with THC (3 mg/kg ×4) at room (21°C) and at warm (26°C) temperature, and body temperature, striatal glial activation and DA terminal loss were assessed. To find out the mechanisms by which THC may prevent MDMA hyperthermia and neurotoxicity, the same procedure was carried out in animals pretreated with the CB1 receptor antagonist AM251 and the CB2 receptor antagonist AM630, as well as in CB1, CB2 and CB1/CB2 deficient mice. THC prevented MDMA-induced-hyperthermia and glial activation in animals housed at both room and warm temperature. Surprisingly, MDMA-induced DA terminal loss was only observed in animals housed at warm but not at room temperature, and this neurotoxic effect was reversed by THC administration. However, THC did not prevent MDMA-induced hyperthermia, glial activation, and DA terminal loss in animals treated with the CB1 receptor antagonist AM251, neither in CB1 and CB1/CB2 knockout mice. On the other hand, THC prevented MDMA-induced hyperthermia and DA terminal loss, but only partially suppressed glial activation in animals treated with the CB2 cannabinoid antagonist and in CB2 knockout animals. Our results indicate that THC protects against MDMA neurotoxicity, and suggest that these neuroprotective actions are primarily mediated by the reduction of hyperthermia through the activation of CB1 receptor, although CB2 receptors may also contribute to attenuate neuroinflammation in this process.

Estudio sobre la resistencia quimica de baldosas ceramicas no-esmaltadas para pavimentos industriales

The chemical resistance of ceramic tiles is the subject of the European Standard UNE-EN ISO 10545-13. In order to evaluate the effect of aqueous solutions of several chemicals agents on the aspect of the tile surface, this standard establishes a series of tests at room temperature followed by visual inspection. According to this standard the tiles of this study are classified as being of maximum resistance (UHA). However operating conditions can be more aggressive than those detailed in the standard. So, a systematic study has been undertaken. In the present work, the effect of aqueous solutions of several organic and inorganic acids on the tile surface is evaluated. Samples immersed in different solutions are subjected to the following conditions: T= 60º C; pH=2 and to agitation processes. Visual analysis, as well as optical microscopy and scanning electron microscopy (SEM) were performed in order to determine the possible variation of the superficial aspect of tiles. Moreover, atomic absorption spectrophotometry has been used in order to obtain quantitative information concerning the solubility of system M (III)-L (M= Fe; L= H2O or L= ligand). The results obtained show, in all cases, a progressive dissolution of iron oxide precipitates presents in the ceramic body

Thermal activation and ATP dependence of the cytoskeleton remodeling dynamics

The cytoskeleton (CSK) is a nonequilibrium polymer network that uses hydrolyzable sources of free energy such as adenosine triphosphate (ATP) to remodel its internal structure. As in inert nonequilibrium soft materials, CSK remodeling has been associated with structural rearrangements driven by energy-activated processes. We carry out particle tracking and traction microscopy measurements of alveolar epithelial cells at various temperatures and ATP concentrations. We provide the first experimental evidence that the remodeling dynamics of the CSK is driven by structural rearrangements over free-energy barriers induced by thermally activated forces mediated by ATP. The measured activation energy of these forces is ~40kBTr (kB being the Boltzmann constant and Tr being the room temperature). Our experiments provide clues to understand the analogy between the dynamics of the living CSK and that of inert nonequilibrium soft materials.

Nanocrystalline M-type hexaferrite powders: preparation, geometric and magnetic propertiess

Co-Ti-Sn-Ge substituted M-type bariumhexaferrite powders with mean grain sizes between about 10 nm and about 1 ¿m and a narrow size distribution were prepared reproducibly by means of a modified glass crystallization method. At annealing temperatures between 560 and 580°C of the amorphous flakes nanocrystalline particles grow. They behave superparamagnetically at room temperature and change into stable magnetic single domains at lower temperatures. The magnetic volume of the powders is considerably less than the geometric one. However, the effective anisotropy fields are larger by a Factor of two to three.

Optical response of Cu3Ge thin films

We report an investigation on the optical properties of Cu3Ge thin films displaying very high conductivity, with thickness ranging from 200 to 2000 Å, deposited on Ge substrates. Reflectance, transmittance, and ellipsometric spectroscopy measurements were performed at room temperature in the 0.01-6.0, 0.01-0.6, and 1.4-5.0 eV energy range, respectively. The complex dielectric function, the optical conductivity, the energy-loss function, and the effective charge density were obtained over the whole spectral range. The low-energy free-carrier response was well fitted by using the classical Drude-Lorentz dielectric function. A simple two-band model allowed the resulting optical parameters to be interpreted coherently with those previously obtained from transport measurements, hence yielding the densities and the effective masses of electrons and holes.

Vacancy and interstitial depth profiles in ion-implanted silicon

An experimental method of studying shifts between concentration-versus-depth profiles of vacancy- and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy measurements utilizing the filling pulse variation technique. The vacancy profile, represented by the vacancy¿oxygen center, and the interstitial profile, represented by the interstitial carbon¿substitutional carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse. The effect of the capture in the Debye tail has been extensively studied and taken into account. Thus, the two profiles can be recorded with a high relative depth resolution. Using low doses, point defects have been introduced in lightly doped float zone n-type silicon by implantation with 6.8 MeV boron ions and 680 keV and 1.3 MeV protons at room temperature. The effect of the angle of ion incidence has also been investigated. For all implantation conditions the peak of the interstitial profile is displaced towards larger depths compared to that of the vacancy profile. The amplitude of this displacement increases as the width of the initial point defect distribution increases. This behavior is explained by a simple model where the preferential forward momentum of recoiling silicon atoms and the highly efficient direct recombination of primary point defects are taken into account.