Bismuth incorporation and the role of ordering in GaAsBi/GaAs structures

The structure and composition of single GaAsBi/GaAs epilayers grown by molecular beam epitaxy were investigated by optical and transmission electron microscopy techniques. Firstly, the GaAsBi layers exhibit two distinct regions and a varying Bi composition profile in the growth direction. In the lower (25 nm) region, the Bi content decays exponentially from an initial maximum value, while the upper region comprises an almost constant Bi content until the end of the layer. Secondly, despite the relatively low Bi content, CuPtB-type ordering was observed both in electron diffraction patterns and in fast Fourier transform reconstructions from high-resolution transmission electron microscopy images. The estimation of the long-range ordering parameter and the development of ordering maps by using geometrical phase algorithms indicate a direct connection between the solubility of Bi and the amount of ordering. The occurrence of both phase separation and atomic ordering has a significant effect on the optical properties of these layers

Orientation Dependence of the Anomalous Hall Resistivity in Single Crystals of Yb14MnSb11

The Hall resistivity, electrical resistivity and magnetization of single crystals of the tetragonal ferromagnet Yb14MnSb11 are reported as a function of the direction of the current, I, and magnetic field, H with respect to the principal crystallographic axes. With I along the unique c direction and H in the a-b plane, the anomalous Hall resistivity in the limit of zero applied field is negative for all temperatures T less than Tc= 53 K. In this direction, the anomalous Hall effect behaves in a manner similar to that observed in other ferromagnets such as Fe, Co, Mn5Ge3, and EuFe4Sb12. However, with I in the a-b plane and H along the c direction, the anomalous Hall behavior is completely different. The anomalous Hall resistivity data are positive for all T less than Tc and a similar analysis of these data fails. In this direction, the anomalous response is not a simple linear function of the magnetization order parameter, and for a fixed temperature (T less than Tc) does not depend on the magnitude of the magnetization perpendicular to the current in the a-b plane. That is, when the magnetization and applied field are rotated away from the c direction, the anomalous Hall resistivity does not change. In all other soft ferromagnets that we have examined (including La doped crystals of Yb14MnSb11, i.e. Yb13.3La0.7MnSb11) rotation of the magnetization and magnetic field by an angle theta away from a direction perpendicular to I results in a decrease in both the anomalous and normal portions of the Hall resistivity that approximately scales as cos(theta). We suggest that the unique response exhibited by Yb14MnSb11 is a direct reflection of the delicate balance between ferromagnetism and Kondo screening.Comment: 20 pages, 12 Figures, Submitted to Physical Review B, July 18, 200

Label-free quantum dot conjugates for human protein IL-2 based on molecularly imprinted polymer

The authors acknowledge the financial support from European Research Council though the Starting Grant, ERC-StG-3P´s/2012, GA 311086, (to MGF Sales) and from the CANCER project (NORTE-01-0145- FEDER-000029).info:eu-repo/semantics/publishedVersio

Electronic Structure and Thermoelectric Prospects of Phosphide Skutterudites

The prospects for high thermoelectric performance in phosphide skutterudites are investigated based on first principles calculations. We find that stoichiometric CoP_3 differs from the corresponding arsenide and antimonide in that it is metallic. As such the band structure must be modified if high thermopowers are to be achieved. In analogy to the antimonides it is expected that this may be done by filling with La. Calculations for LaFe_4P_12 show that a gap can in fact be opened by La filling, but that the valence band is too light to yield reasonable p-type thermopowers at appropriate carrier densities; n-type La filled material may be more favorable.Comment: 3 pages, 3 figures, 1 tabl

Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

3 páginas, 3 figuras.-- Progress in Applied Surface, Interface and Thin Film Science - SURFINT SREN II.-- PACS codes: 68.37.Lp; 81.05.Ea; 81.15.HiThe compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.This work was supported by the Spanish MCI (TEC2008-06756-C03-02/TEC), CONSOLIDER CSD2009-00013, and the Junta de Andalucia (PAI research groups TEP-120 and TIC-145, project P08-TEP-03516).Peer reviewe

Analytical methodologies based on LC–MS/MS for monitoring selected emerging compounds in liquid and solid phases of the sewage sludge

In this work, two analytical methodologies based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) were developed for quantification of emerging pollutants identified in sewage sludge after a previous wide-scope screening. The target list included 13 emerging contaminants (EC): thiabendazole, acesulfame, fenofibric acid, valsartan, irbesartan, salicylic acid, diclofenac, carbamazepine, 4-aminoantipyrine (4- AA), 4-acetyl aminoantipyrine (4-AAA), 4-formyl aminoantipyrine (4-FAA), venlafaxine and benzoylecgonine. The aqueous and solid phases of the sewage sludge were analyzed making use of Solid-Phase Extraction (SPE) and UltraSonic Extraction (USE) for sample treatment, respectively. The methods were validated at three concentration levels: 0.2, 2 and 20mg L 1 for the aqueous phase, and 50, 500 and 2000mg kg 1 for the solid phase of the sludge. In general, the method was satisfactorily validated, showing good recoveries (70–120%) and precision (RSD < 20%). Regarding the limit of quantification (LOQ), it was below 0.1mg L 1 in the aqueous phase and below 50mg kg 1 in the solid phase for the majority of the analytes. The method applicability was tested by analysis of samples from a wider study on degradation of emerging pollutants in sewage sludge under anaerobic digestion. The key benefits of these methodologies are: SPE and USE are appropriate sample procedures to extract selected emerging contaminants from the aqueous phase of the sewage sludge and the solid residue. LC–MS/MS is highly suitable for determining emerging contaminants in both sludge phases. Up to our knowledge, the main metabolites of dipyrone had not been studied before in sewage sludge. ãFinancial support of Generalitat Valenciana (Prometeo II/2014/023,ISIC/2014/016

Behaviour of emerging contaminants in sewage sludge after anaerobic digestion

Nowadays, there is an increasing concern over the presence of contaminants in the aquatic environment, where they can be introduced from wastewater after their incomplete removal in the treatment plants. In this work, degradation of selected emerging pollutants in the aqueous and solid phases of sewage sludge has been investigated after anaerobic digestion using two different digesters: mesophilic and thermophilic. Initially, sludge samples were screened by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS) for identification of emerging contaminants in the samples. In a second step, a target quantitative method based on LC coupled to tandem MS was applied for selected pollutants identified in the previous screening. The behaviour of the compounds under anaerobic conditions was studied estimating the degradation efficiency and distribution of compounds between both sludge phases. Irbesartan and benzoylecgonine seemed to be notably degraded in both phases of the sludge. Venlafaxine showed a significant concentration decrease in the aqueous phase in parallel to an increase in the solid phase. The majority of the compounds showed an increase of their concentrations in both phases after the digestion. Concentrations in the solid phase were commonly higher than in the aqueous for most contaminants, indicating that they were preferentially adsorbed onto the solid particles.The authors are very grateful to the Ecophysiology and Biotechnology group (University Jaume I) and to The Institute of Aquaculture “Torre de la Sal” (IATS) (Consejo Superior de Investigaciones Científicas, CSIC) for using their lyophilizer systems. The financial support of Generalitat Valenciana (Prometeo II/2014/023, ISIC/2014/016) is also acknowledged

Doenças primárias da pele e manifestações cutâneas de doenças sistêmicas em suínos

Skin diseases in pigs can negatively impact the production. They cause losses related to the death of the affected pigs, to the cost with the treatment, growth retardation and condemnations in the slaughterhouses. This study was developed to determine the frequency and describe the histopathological findings of skin diseases in pigs in different age groups through a retrospective study from 2006 to 2018. A total of 154 conclusive cases were analyzed, including skin restricted diseases (allergic dermatitis, exudative epidermitis, vesicular dermatitis, pityriasis rosea, swinepox, follicular cyst, papilloma and scrotal hemangioma) or skin lesions secondary to systemic diseases (erysipelas, porcine dermatitis and nephropathy syndrome [PDNS], bacterial septicemia and multiple hemorrhages without definite cause). The skin lesions were classified as bacterial (46.1%), viral (26.6%), allergic (12.3%), neoplastic (1.3%) and others (13.6%). Swine erysipelas was the most frequent diagnosis (47/154), followed by PDNS (23/154), allergic dermatitis (19/154) and exudative epidermitis (15/154). Vesicular dermatitis (9/154), pityriasis rosea (9/154), septicemia with cutaneous manifestations (9/154), swinepox (9/154) and multiple hemorrhages without definite cause (7/154) were also observed. Follicular cyst (3/154), hyperkeratosis without definite cause (2/154), papilloma (1/154), and scrotal hemangioma (1/154) were less frequently described. Of the conclusive diagnosis, age was reported in 138 cases, with the highest frequency of skin lesions observed at the inspection process during slaughter (56/138).As doenças de pele em suínos podem impactar negativamente a produção. Estas causam perdas relacionadas à morte dos acometidos, a custo com tratamentos, atraso no crescimento e condenações nos frigoríficos. Este trabalho foi desenvolvido para determinar a frequência e descrever os achados histopatológicos das doenças de pele em suínos nas diferentes faixas etárias, através de um estudo retrospectivo no período de 2006 a 2018. Foram analisados 154 casos conclusivos, incluindo as doenças restritas a pele (dermatites alérgicas, epidermite exsudativa, dermatite vesicular, pitiríase rósea, varíola suína, cisto folicular, papiloma e hemangioma escrotal) e as secundárias a doenças sistêmicas (erisipela, síndrome dermatite nefropatia suína [SDNS], septicemia bacteriana e hemorragias múltiplas de causa não determinada). Estas foram classificadas em bacterianas (46,1%), virais (26,6%), alérgicas (12,3%), neoplásicas (1,3%) e outras (13,6%). A erisipela suína foi a enfermidade mais diagnosticada (47/154), seguida por SDNS (23/154), dermatite alérgica (19/154) e epidermite exsudativa (15/154). Observamos ainda dermatite vesicular (9/154), pitiríase rósea (9/154), septicemia bacteriana com manifestações cutâneas (9/154), varíola suína (9/154) e hemorragias múltiplas de causa não determinada (7/154). Em menor número, cisto folicular (3/154), hiperqueratose sem causa definida (2/154), papiloma (1/154) e hemangioma escrotal (1/154). Dos casos conclusivos, a idade foi informada em 138 casos, sendo a maior frequência das lesões de pele observadas na linha de inspeção, durante o abate (56/138)

All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot

[EN] New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 mu eV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown & Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths.G Munoz-Matutano thanks the Spanish Juan de la Cierva program (JCI-2011-10686). We acknowledge the support of the Spanish MINECO through projects TEC2014-53727-C2-1-R & TEC2014-60378-C2-1-R, the Research Excellency Award Program GVA PROMETEO 2013/012 PROMETEOII/2014/059 and the Explora Ciencia Tecnologia TEC2013-50552-EXP MULTIFUN project, and the Nanoscale Quantum Optics MPNS COST Action MP1403.Muñoz Matutano, G.; Barrera Vilar, D.; Fernandez-Pousa, CR.; Chulia-Jordan, R.; Seravalli. L.; Trevisi, G.; Frigeri, P.... (2016). All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot. Scientific Reports. 6(2721):1-9. https://doi.org/10.1038/srep27214S1962721Walmsley, I. A. Quantum optics: Science and technology in a new light. Science 348, 525–530 (2015).Eisaman, M. D., Fan, J., Migdall, A. & Polyakov, S. Invited review article: single-photon sources and detectors. Rev. Sci. Instrum. 82, 071101 (2011).Lu, C.-L. & Pan, J.-W. Push-button photon entanglement. Nat. Photonics 8, 174–176 (2014).Benson, O., Santori, C., Pelton, M. & Yamamoto, Y. Regulated and entangled photons from a single quantum dot. Phys. Rev. Lett. 84, 2513–2516 (2000).Yuan, Z. et al. Electrically driven single-photon source. Science 295, 102–105 (2002).Salter, C. L. et al. An entangled-light-emitting diode. Nature 465, 594–597 (2010).Brunner, D. et al. A coherent single-hole spin in a semiconductor. Science 325, 70–72 (2009).Müller, M., Bounouar, S., Jöns, K. D., Glässl, M. & Michler, P. On-demand generation of indistinguishable polarization-entangled photon pairs. Nat. Photonics 8, 234–238 (2014).Seguin, R. et al. Size-dependent fine-structure splitting in self-organized InAs/GaAs quantum dots. Phys. Rev. Lett. 95, 257402 (2005).Hadfield, R. H. Single-photon detectors for optical quantum information applications. Nat. Photonics 3, 696–705 (2009).Zinoni, C. et al. Time-resolved and antibunching experiments on single quantum dots at 1300nm. Appl. Phys. Lett. 88, 131102 (2006).Liu, X. et al. Single-photon emission in telecommunication band from an InAs quantum dot grown on InP with molecular-beam epitaxy. Appl. Phys. Lett. 103, 061114 (2013).Benyoucef, M., Yacob, M., Reithmaier, J. P., Kettler, J. & Michler, P. Telecom-wavelength (1.5 μm) single-photon emission from InP-based quantum dots. Appl. Phys. Lett. 103, 162101 (2013).Ward, M. et al. Coherent dynamics of a telecom-wavelength entangled photon source. Nat. Commun. 5, 3316 (2014).Rakher, M. T. et al. Quantum transduction of telecommunications-band single photons from a quantum dot by frequency upconversion. Nat. Photonics 4, 786–791 (2010).Muñoz-Matutano, G. et al. Time resolved emission at 1.3 μm of a single InAs quantum dot by using a tunable fibre Bragg grating. Nanotechnology 25, 035204 (2014).Ediger, M. et al. Peculiar many-body effects revealed in the spectroscopy of highly charged quantum dots. Nature Phys. 3, 774–779 (2007).Gerardot, B. D. et al. Laser spectroscopy of individual quantum dots charged with a single hole. Appl. Phys. Lett. 99, 243112 (2011).Gomis-Bresco, J. et al. Random population model to explain the recombination dynamics in single InAs/GaAs quantum dots under selective optical pumping. New J. Phys. 13, 023022 (2011).Ediger, M. et al. Fine structure of negatively and positively charged excitons in semiconductor quantum dots: electron-hole asymmetry. Phys. Rev. Lett. 98, 036808 (2007).Warming, T. et al. Hole-hole and electron-hole exchange interactions in single InAs/GaAs quantum dots. Phys. Rev. B 79, 125316 (2009).Benny, Y. et al. Excitation spectroscopy of single quantum dots at tunable positive, neutral and negative charge states. Phys. Rev. B 86, 085306 (2012).Muñoz-Matutano, G. et al. Selective optical pumping of charged excitons in unintentionally doped InAs quantum dots. Nanotechnology 19, 145711 (2008).Ha, N. et al. Size-dependent line broadening in the emission spectra of single GaAs quantum dots: Impact of surface charge on spectral diffusion. Phys. Rev. B 92, 075306 (2015).Moskalenko, E. S. et al. Influence of excitation energy on charged exciton formation in self-assembled InAs single quantum dots. Phys. Rev. B 64, 085302 (2001).Rivas, D. et al. Two-color single-photon emission from InAs quantum dots: toward logic information management using quantum light. Nano Lett. 14, 456–463 (2014).Dekel, E. et al. Cascade evolution and radiative recombination of quantum dot multiexcitons studied by time-resolved spectroscopy. Phys. Rev. B 62, 11038 (2000).Wimmer, M., Nair, S. & Shumway, J. Biexciton recombination rates in self-assembled quantum dots. Phys. Rev. B 73, 165305 (2006).Dalgarno, P. A. et al. Coulomb interactions in single charged self-assembled quantum dots: Radiative lifetime and recombination energy. Phys. Rev. B 77, 245311 (2008).Muñoz-Matutano, G. et al. Exciton, biexciton and trion recombination dynamics in a single quantum dot under selective optical pumping. Physica E 40, 2100–2103 (2008).Birkedal, D., Leosson, K. & Hvam, J. M. Long lived coherence in self-assembled quantum dots. Phys. Rev. Lett. 87, 227401 (2001).Tartakovskii, A. et al. Effect of thermal annealing and strain engineering on the fine structure of quantum dot excitons. Phys. Rev. B 70, 193303 (2004).Goldmann, E., Barthel, S., Florian, M., Schuh, K. & Jahnke, F. Excitonic fine-structure splitting in telecom-wavelength InAs/GaAs quantum dots: statistical distribution and height-dependence. Appl. Phys. Lett. 103, 242102 (2004).Seravalli, L., Trevisi, G. & Frigeri, P. 2D–3D growth transition in metamorphic InAs/InGaAs quantum dots. Cryst. Eng. Comm. 14, 1155–1160 (2012).Akimov, I., Kavokin, K., Hundt, A. & Henneberger, F. Electron-hole exchange interaction in a negatively charged quantum dot. Phys. Rev. B 71, 075326 (2005).Brouri, R., Beveratos, A., Poizat, J. & Grangier, P. Photon antibunching in the fluorescence of individual color centers in diamond. Opt. Lett. 25, 1294–1296 (2000).Mandel, L. & Wolf, E. Optical Coherence and Quantum Optics. Cambridge University Press (1995).Seravalli, L., Frigeri, P., Trevisi, G. & Franchi, S. 1.59 μm room temperature emission from metamorphic InAs∕InGaAsInAs∕InGaAs quantum dots grown on GaAs substrates. Appl. Phys. Lett. 92, 213104 (2008).Gonzalez-Tudela, A., Laussy, F. P., Tejedor, C., Hartmann, M. J. & del Valle, E. Two-photon spectra of quantum emitters. New J. Phys. 15, 033036 (2013).Peiris, M. et al. Two-color photon correlations of the light scattered by a quantum dot. Phys. Rev. B 91, 195125 (2015).Venghaus, L. Wavelength Filters in Fibre Optics. Springer Series in Optical Sciences Vol 123 (2006).Seravalli, L. et al. Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates. Appl. Phys. Lett. 98, 173112 (2011).Seravalli, L. et al. Quantum dot strain engineering of InAs∕InGaAsInAs∕InGaAs nanostructures. J. Appl. Phys. 101, 024313 (2007).Seravalli, L., Trevisi, G. & Frigeri, P. Design and growth of metamorphic InAs/InGaAs quantum dots for single photon emission in the telecom window. Crys. Eng. Comm. 14, 6833–6838 (2012).Seravalli, L., Frigeri, P., Nasi, L., Trevisi, G. & Bocchi, C. Metamorphic quantum dots: quite different nanostructures. J. Appl. Phys. 108, 064324 (2010)

Aligned crystallite powder of NdFeAsO0.86_{0.86}F0.14_{0.14}: magnetic hysteresis and penetration depth

We report the basal-plane critical current and superfluid density of magnetically aligned NdFeAsO$_{0.86}$F$_{0.14}$ powder. This sample has individual crystallite grains permanently oriented with their c axis along the external field. Magnetic irreversibilities at high field suggest strong flux pinning of basal-plane critical currents, with monotonic field dependence and no evidence of the "fishtail" effect. The small particles provide a sensitive indicator of \textit{dc} flux penetration, and allow analysis of the temperature dependence of $ab-$plane London penetration depth $\lambda_{ab,\mathrm{L}}$, which is quadratic at low $T$. This feature may not necessarily be due to the nodes in the gap, but may be rather a sign of a strong pair-breaking. A quantitative determination of the absolute magnitude of $\lambda_{ab,\mathrm{L}}$ is hindered by the need for accurate knowledge of the particle size distribution.Comment: 6 pages, 6 figure