On the nonlinear stability of mKdV breathers

A mathematical proof for the stability of mKdV breathers is announced. This proof involves the existence of a nonlinear equation satisfied by all breather profiles, and a new Lyapunov functional which controls the dynamics of small perturbations and instability modes. In order to construct such a functional, we work in a subspace of the energy one. However, our proof introduces new ideas in order to attack the corresponding stability problem in the energy space. Some remarks about the sine-Gordon case are also considered.Comment: 7 p

REQUERIMIENTOS NUTRIMENTALES DE LA FLOR AVE DE PARAÍSO (Strelitzia reginae Aiton)

With the aim of understanding the nutritional balance and requirement of the bird of paradise flower (Strelitzia reginae Aiton), the need for nutrients under a commercial production system was quantified, in a plot established 10 years ago, with use of fertilization, pruning, irrigation, pest and disease control, with a population density of 1,250 plants ha-1, through the chemical analysis of nutritional concentration in the biomass produced in a year. It was concluded that the annual nutrient requirement in the crop was the following: macronutrients (Kg ha-1) N (68.22), P2O5 (23.23), K2O (145.73), CaO (134.66), MgO (10.38) and micronutrients (g ha-1), Cu (174.7), Fe (282.4), Mn (288.2) and Zn (390.6).Con la finalidad de conocer el balance y requerimiento nutrimental de la flor Ave del pparaíso (Strelitzia reginae Aiton), se cuantificó la necesidad de nutrimentos bajo sistema comercial de producción, en una parcela de 10 años de establecida, con manejo de fertilización, poda, riego, control de plagas y enfermedades, con una densidad de población de 1,250 matas ha-1, mediante el análisis químico de concentración nutrimental en la biomasa producida en un año. Se concluyó que el requerimiento nutrimental anual en el cultivo fue el siguiente: Macronutrimentos (Kg ha-1) N (68.22), P2O5 (23.23), K2O (145.73), CaO (134.66), MgO (10.38) y micronutrimentos (g ha-1), Cu (174.7), Fe (282.4), Mn (288.2) y Zn (390.6)

Evidence for a large fraction of Compton-thick quasars at high redshift

Using mid-infrared and radio selection criteria, we pre-select a sample of candidate high-redshift type-2 quasars in the Subaru XMM-Newton Deep Field (SXDF). To filter out starburst contaminants, we use a bayesian method to fit the spectral energy distributions (SEDs) between 24-microns and B-band, obtain photometric redshifts, and identify the best candidates for high-z type-2 quasars. This leaves us with 12 z_phot >= 1.7 type-2 quasar candidates in an area ~0.8 deg^2, of which only two have secure X-ray detections. The two detected sources have estimated column densities N_H~2 & 3x10^27 m^-2, i.e. heavily obscured but Compton-thin quasars. Given the large bolometric luminosities and redshifts of the undetected objects, the lack of X-ray detections suggests extreme absorbing columns N_H >= 10^28 m^-2 are typical. We have found evidence for a population of ``Compton-thick'' high-redshift type-2 quasars, at least comparable to, and probably larger than the type-1 quasar population, although spectroscopic confirmation of their AGN nature is important.Comment: 6 pages, 2 colour figures. Accepted by MNRAS. Full resolution version and supplementary figures can be found at: http://www.mpia.de/homes/martinez/publications.htm

Controlled release of bupivacaine using hybrid thermoresponsive nanoparticles activated via photothermal heating

Near-infrared (NIR) responsive nanoparticles are of great interest in the biomedical field as antennas for photothermal therapy and also as triggers for on-demand drug delivery. The present work reports the preparation of hollow gold nanoparticles (HGNPs) with plasmonic absorption in the NIR region covalently bound to a thermoresponsive polymeric shell that can be used as an on-demand drug delivery system for the release of analgesic drugs. The photothermal heating induced by the nanoparticles is able to produce the collapse of the polymeric shell thus generating the release of the local anesthetic bupivacaine in a spatiotemporally controlled way. Those HGNPs contain a 10 wt.% of polymer and present excellent reversible heating under NIR light excitation. Bupivacaine released at physiological temperature (37 °C) showed a pseudo-zero order release that could be spatiotemporally modified on-demand after applying several pulses of light/temperature above and below the lower critical solution temperature (LCST) of the polymeric shell. Furthermore, the nanomaterials obtained did not displayed detrimental effects on four mammalian cell lines at doses up to 0.2 mg/mL. From the results obtained it can be concluded than this type of hybrid thermoresponsive nanoparticle can be used as an externally activated on-demand drug delivery system

One-dimensional thermal pressure-driven expansion of a pair cloud into an electron-proton plasma

Recently a filamentation instability was observed when a laser-generated pair cloud interacted with an ambient plasma. The magnetic field it drove was strong enough to magnetize and accelerate the ambient electrons. It is of interest to determine if and how pair cloud-driven instabilities can accelerate ions in the laboratory or in astrophysical plasma. For this purpose, the expansion of a localized pair cloud with the temperature 400 keV into a cooler ambient electron-proton plasma is studied by means of one-dimensional particle-in-cell (PIC) simulations. The cloud's expansion triggers the formation of electron phase space holes that accelerate some protons to MeV energies. Forthcoming lasers might provide the energy needed to create a cloud that can accelerate protons.Comment: 5 pages 4 figures, accepted for publication in Physics of Plasma

Climate fluctuations during the Holocene in NW Iberia: high and low latitude linkages

International audienceHigh resolution benthic foraminiferal oxygen and carbon stable isotopes (?18O, ?13C) from core EUGC-3B are used here to infer rapid climatic changes for the last 8500 yr in the Ría de Muros (NW Iberian Margin). Benthic foraminiferal ?18O and ?13C potentially register migrations in the position of the hydrographic front formed between two different intermediate water masses: Eastern North Atlantic Central Water of subpolar origin (ENACWsp), and subtropical origin (ENACWsp). The isotopic records have been compared with two well established North Atlantic marine Holocene paleoceanographic records from low (Sea Surface Temperatures anomalies off Cape Blanc, NW Africa) and high latitudes (Hematite Stained Grains percentage, subpolar North Atlantic). This comparison clearly demonstrates that there is a strong link between high- and low-latitude climatic perturbations at centennial-millennial time scales during the Holocene. Spectral analyses also points at a pole-to-equator propagation of the so-called 1500 yr cycles. Our results demonstrate that during the Holocene, the NW Iberian Margin has undergone a series of cold episodes which are likely triggered at high latitudes in the North Atlantic and are rapidly propagated towards lower latitudes. Conceivably, the propagation of these rapid climatic changes involves a shift of atmospheric and oceanic circulatory systems and so a migration of the hydrographical fronts and water masses all along the North Atlantic area

Stellar populations in the Carina region : The Galactic plane at l = 291°

Context. Previous studies of the Carina region have revealed its complexity and richness as well as a significant number of early-type stars. However, in many cases, these studies only concentrated on the central region (Trumpler 14/16) or were not homogeneous. This latter aspect, in particular, is crucial because very di erent ages and distances for key clusters have been claimed in recent years. Aims. The aim of this work is to study in detail an area of the Galactic plane in Carina, eastward η Carina.We analyze the properties of di erent stellar populations and focus on a sample of open clusters and their population of young stellar objects and highly reddened early stars. We also studied the stellar mass distribution in these clusters and the possible scenario of their formation. Finally, we outline the Galactic spiral structure in this direction. Methods. We obtained deep and homogeneous photometric data (UBVIKC) for six young open clusters: NGC 3752, Trumpler 18, NGC 3590, Hogg 10, 11, and 12, located in Carina at l ~ 291°, and their adjacent stellar fields, which we complemented with spectroscopic observations of a few selected targets. We also culled additional information from the literature, which includes stellar spectral classifications and near-infrared photometry from 2MASS.We finally developed a numerical code that allowed us to perform a homogeneous and systematic analysis of the data. Our results provide more reliable estimates of distances, color excesses, masses, and ages of the stellar populations in this direction. Results. We estimate the basic parameters of the studied clusters and find that they identify two overdensities of young stellar populations located at about 1.8 kpc and 2.8 kpc, with EB-V ~ 0.1-0.6. We find evidence of pre-main-sequence populations inside them, with an apparent coeval stellar formation in the most conspicuous clusters. We also discuss apparent age and distance gradients in the direction NW-SE. We study the mass distributions of the covered clusters and several others in the region (which we took form the literature). They consistently show a canonical IMF slope (the Salpeter one). We discover and characterise an abnormally reddened massive stellar population, scattered between 6.6 and 11 kpc. Spectroscopic observations of ten stars of this latter population show that all selected targets were massive OB stars. Their location is consistent with the position of the Carina-Sagittarius spiral arm.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Photo-detection using Bose-condensed atoms in a micro trap

A model of photo-detection using a Bose--Einstein condensate in an atom-chip based micro trap is analyzed. Atoms absorb photons from the incident light field, receive part of the photon momentum and leave the trap potential. Upon counting of escaped atoms within predetermined time intervals, the photon statistics of the incident light is mapped onto the atom-count statistics. Whereas traditional photo-detection theory treats the emission centers of photo electrons as distinguishable, here the centers of escaping atoms are condensed and thus indistinguishable atoms. From this an enhancement of the photon-number resolution as compared to the commonly known counting formula is derived.Comment: 11 pages, 5 figures; revised versio

El efecto de exposición en el patrón sedimen- tario del sector submareal de tres playas en la Ría de Muros y Noia (NO de España)

En este trabajo se presenta la comparación de los sedimentos superficiales de la plataforma proximal de tres complejos playeros situados en las inmediaciones de la embocadura de la Ría de Muros y Noia. En cada uno de ellos, se han identificado las distintas poblaciones sedimentarias en función de los análisis granulométricos realizados. La aplicación de un análisis estadístico de componentes principales a las fracciones granulométricas, contenido en carbonatos y materia orgánica, ha permitido diferenciar poblaciones de muestras y la interpretación sedimentaria de las mismas. Las diferencias observadas en la distribución de las poblaciones sedimentarias de los tres complejos estudiados son una consecuencia del grado de exposición de cada complejo al oleaje dominante y de la presencia de afloramientos rocosos sumergidos que ejercen un efecto barrera.The subaquatic sediments from the inner continental shelf of three beach systems located in the surrondings of Ría de Muros y Noia mouth are compared. Different sedimentary populations have been stablished according to the granulometric distribution from each system. The grain-size distribution, carbonate and organic matter content have been compared by means of a principal component analysis. The results allow the identification of different populations as well as their sedimentary significance. The observed differences between the sedimentary populations from each system are explained as a consequence of their grade of exposure towards the dominant waves and the presence of subaquatic rocks, which introduce a barrier effect

Peptide Mass Spectra from Micrometer-Thick Ice Films Produced with Femtosecond Pulses

We present a cryogenic mass spectrometry protocol with the capability to detect peptides in the attomole dilution range from ice films. Our approach employs femtosecond laser pulses and implements neither substrate modification nor proton donor agents in the aqueous solution, known to facilitate analyte detection in mass spectrometry. In a systematic study, we investigated the impact of temperature, substrate composition, and irradiation wavelength (513 and 1026 nm) on the bradykinin signal onset. Our findings show that substrate choice and irradiation wavelength have a minor impact on signal intensity once the preparation protocol is optimized. However, if the temperature is increased from −140 to 0 °C, which is accompanied by ice film thinning, a somehow complex picture of analyte desorption and ionization is recognizable, which has not been described in the literature yet. Under cryogenic conditions (−140 °C), obtaining a signal is only possible from isolated sweet spots across the film. If the thin ice film is between −100 and −70 °C of temperature, these sweet spots appear more frequently. Ice sublimation triggered by temperatures above −70 °C leads to an intense and robust signal onset that could be maintained for several hours. In addition to the above findings, we notice that a vibrant fragmentation pattern produced is strikingly similar with both wavelengths. Our findings suggest that while following an optimized protocol, femtosecond mass spectrometry has excellent potential to analyze small organic molecules and peptides with a mass range of up to 2.5 kDa in aqueous solution without any matrix, as employed in matrix-assisted laser desorption/ionization (MALDI) or any substrate surface modification, found in surface-assisted laser desorption/ionization (SALDI)