TY  - JOUR
A1  - Pena-Angulo, D.
A1  - Nadal-Romero, E.
A1  - Gonzalez-Hidalgo, J. C.
A1  - Albaladejo, J.
A1  - Andreu, V
A1  - Bagarello, V
A1  - Barhi, H.
A1  - Batalla, R. J.
A1  - Bernal, S.
A1  - Bienes, R.
A1  - Campo, J.
A1  - Campo-Bescos, M. A.
A1  - Canatario-Duarte, A.
A1  - Canton, Y.
A1  - Casali, J.
A1  - Castillo, V
A1  - Cerda, Artemi
A1  - Cheggour, A.
A1  - Cid, Patricio
A1  - Cortesi, N.
A1  - Desir, G.
A1  - Diaz-Pereira, E.
A1  - Espigares, T.
A1  - Estrany, Joan
A1  - Fernandez-Raga, M.
A1  - Ferreira, Carla S. S.
A1  - Ferro, Vito
A1  - Gallart, Francesc
A1  - Gimenez, R.
A1  - Gimeno, E.
A1  - Gomez, J. A.
A1  - Gomez-Gutierrez, A.
A1  - Gomez-Macpherson, H.
A1  - Gonzalez-Pelayo, O.
A1  - Hueso-Gonzalez, P.
A1  - Kairis, O.
A1  - Karatzas, G. P.
A1  - Klotz, S.
A1  - Kosmas, C.
A1  - Lana-Renault, Noemi
A1  - Lasanta, T.
A1  - Latron, J.
A1  - Lazaro, R.
A1  - Le Bissonnais, Y.
A1  - Le Bouteiller, C.
A1  - Licciardello, F.
A1  - Lopez-Tarazon, José Andrés
A1  - Lucia, A.
A1  - Marin, C.
A1  - Marques, M. J.
A1  - Martinez-Fernandez, J.
A1  - Martinez-Mena, M.
A1  - Martinez-Murillo, J. F.
A1  - Mateos, L.
A1  - Mathys, N.
A1  - Merino-Martin, L.
A1  - Moreno-de las Heras, M.
A1  - Moustakas, N.
A1  - Nicolau, J. M.
A1  - Novara, A.
A1  - Pampalone, V
A1  - Raclot, D.
A1  - Rodriguez-Blanco, M. L.
A1  - Rodrigo-Comino, Jesús
A1  - Romero-Diaz, A.
A1  - Roose, E.
A1  - Rubio, J. L.
A1  - Ruiz-Sinoga, J. D.
A1  - Schnabel, S.
A1  - Senciales-Gonzalez, J. M.
A1  - Simonneaux, V
A1  - Sole-Benet, A.
A1  - Taguas, E.
A1  - Taboada-Castro, M. M.
A1  - Taboada-Castro, M. T.
A1  - Todisco, Francesca
A1  - Ubeda, X.
A1  - Varouchakis, E. A.
A1  - Vericat, Damia
A1  - Wittenberg, L.
A1  - Zabaleta, A.
A1  - Zorn, M.
T1  - Spatial variability of the relationships of runoff and sediment yield with weather types throughout the Mediterranean basin
JF  - Journal of hydrology
N2  - Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) W and SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures.
KW  - Synoptic weather types
KW  - Erosion
KW  - Sediment yield
KW  - Runoff
KW  - Mediterranean basin
Y1  - 2019
U6  - https://doi.org/10.1016/j.jhydrol.2019.01.059
SN  - 0022-1694
SN  - 1879-2707
VL  - 571
SP  - 390
EP  - 405
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Pena, M
A1  - Peimbert, A.
A1  - Hamann, Wolf-Rainer
A1  - Ruiz, M. T.
A1  - Peimbert, M.
T1  - The extraordinary planetary nebula N66 in the LMC
N2  - Morphology of the planetary nebula LMC-N66 (ionized by a [WN] star) indicates that the nebula is a multipolar object with a very narrow waist. It shows several jets, knots and filaments in opposite directions from the central star. A couple of twisted long filaments could be interpreted as due to point-symmetric type ejection. If such is the case, the progenitor would be a binary precessing system. High resolution spectroscopy shows that most of the material is approaching or receding from the star. However the line profiles are very complex, showing several components at different velocities. Our high resolution spectroscopic data show that the different structures (knots, filaments, ...) present different radial velocities spreading from 240 to more than 400 km/s. The system velocity is 300 km/s. There are high velocity knots located to the north of the central star, moving at more than 100 km/s relative to the system velocity.
Y1  - 2004
SN  - 3-12-283174-0
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
A1  - Ruiz, M. T.
A1  - Peimbert, A.
A1  - Peimbert, M.
T1  - A high resolution spectroscopic study of the extraordinary planetary nebula LMC-N66
N2  - The planetary nebula N66 in the Large Magellanic Cloud is an extraordinary object, as it is the only confirmed PN where the central star is a Wolf-Rayet star of the nitrogen sequence, i.e. of type [WN]. Moreover, the star showed a dramatic brightness outburst in 1993-1994. In a previous paper (Hamann et al. 2003) we analyzed the changing stellar spectra and found evidence that the central star is most likely a binary system where a white dwarf presently accretes matter from a non-degenerate companion at a high rate. Thus the object is a candidate for a future type Ia supernova in our cosmic neighborhood. In the present paper we analyze the morphology and kinematics of the nebula, using images and high-resolution spectra obtained with the Hubble Space Telescope (HST) and the Very Large Telescope (ESO-VLT). The object presents a complex multipolar structure, dominated by very bright lobes located at both sides of the central star and separated by a narrow waist. In addition there is a pair of very extended and twisted loops, also pointing in opposite directions; their symmetry axis and collimation angle differs from those of the bright lobes. High resolution spectroscopy reveals two main velocity components, "approaching" material at an average heliocentric radial velocity Of V-rad = 248 30 km s(-1) and similarly bright "receding" material at V-rad = 331 +/- 25 km s(-1). A systemic velocity of about 300 km s(-1) is derived. Opposite lobes and loops possess opposite velocities. Furthermore there are knots and filaments of complex structure and kinematics. Close to the central star, nebular gas is found, receding at very high velocity (125 km s(-1) relative to the system). The morphology and kinematics of LMC-N66 can be explained as the result of episodic bipolar ejections with changing axis. The bipolar structures could have been produced by collimated streams ejected from a precessing central source. We suggest that the precession could have been produced by an external torque, possibly due to a binary companion. Young, fast-moving nebular knots close to the star appear slightly He- and N-richer than the main body of the nebula, but are still hydrogen-rich in contrast to the helium-dominated atmosphere of the [WN]- type central star. In the binary scenario, this nebular matter must have been accreted from the non-degenerate companion and re-ejected before it was fully burnt
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
A1  - Maza, J.
A1  - Mendez, R. H.
A1  - Peimbert, M.
A1  - Ruiz, M. T.
A1  - Torres-Peimbert, S.
T1  - HST spectrophotometric data of the central star of the planetary nebula LMC-N66
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
A1  - Maza, J.
A1  - Mendez, R. H.
A1  - Peimbert, M.
A1  - Ruiz, M. T.
A1  - Torres-Peimbert, S.
T1  - Spectrophotometric data of the central star of the large magellanic cloud planetary nebula N66. Quantitative analysis of its WN type spectrum
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
A1  - Ruiz, M. T.
T1  - The LMC planetary nebula N66 revisited. Nebular kinematics and stellar models
Y1  - 2003
SN  - 1-583-81148-6
ER  - 
TY  - THES
A1  - Hamann, Wolf-Rainer
A1  - Pena, M.
A1  - Gräfener, Götz
A1  - Ruiz, M. T.
T1  - The central star of the planetary nebula N66 in the Large Magellanic Cloud : a detailed analysis of its dramatic evolution 1983 - 2000
Y1  - 2003
SN  - 0004-6361
ER  - 
TY  - JOUR
A1  - Heringer-Walther, Silvia
A1  - Moreira, M. C. V.
A1  - Wessel, Niels
A1  - Saliba, J. L.
A1  - Silvia-Barra, J.
A1  - Pena, J. L. B.
A1  - Becker, S.
A1  - Siems, W. E.
A1  - Schultheiss, H. P.
A1  - Walther, T.
T1  - Brain natriuretic peptide predicts survival in Chagas' disease more effectively than atrial natriuretic peptide
Y1  - 2005
SN  - 1355-6037
ER  - 
TY  - JOUR
A1  - Stastinska, G.
A1  - Gräfener, Götz
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
A1  - Szczerba, Ryszard
T1  - Comprehensive modelling of the planetary nebula LMC-SMP 61 and its [WC]-type central star
N2  - We present a comprehensive study of the Magellanic Cloud planetary nebula SMP 61 and of its nucleus, a Wolf- Rayet type star classified [WC 5-6]. The observational material consists of HST STIS spectroscopy and imaging, together with optical and UV spectroscopic data collected from the literature and infrared fluxes measured by IRAS. We have performed a detailed spectral analysis of the central star, using the Potsdam code for expanding atmospheres in non-LTE. For the central star we determine the following parameters: L-star = 10(3.96) L-., R-star = 0.42 R-., T-star = 87.5 kK, (M) over dot = 10(-6.12) M-. yr(-1), v(infinity) = 1400 km s(-1), and a clumping factor of D = 4. The elemental abundances by mass are X-He = 0.45, X-C = 0.52, X-N < 5 x 10(-5), X-O = 0.03, and X-Fe < 1 x 10(-4). The fluxes from the model stellar atmosphere were used to compute photoionization models of the nebula. All the available observations, within their error bars, were used to constrain these models. We find that the ionizing fluxes predicted by the stellar model are consistent with the fluxes needed by the photoionization model to reproduce the nebular emission, within the error margins. However, there are indications that the stellar model overestimates the number and hardness of Lyman continuum photons. The photoionization models imply a clumped density structure of the nebular material. The observed C III] lambda1909/C II lambda4267 line ratio implies the existence of carbon-rich clumps in the nebula. Such clumps are likely produced by stellar wind ejecta, possibly mixed with the nebular material. We discuss our results with regard to the stellar and nebular post-AGB evolution. The observed Fe-deficiency for the central star indicates that the material which is now visible on the stellar surface has been exposed to s-process nucleosynthesis during previous thermal pulses. The absence of nitrogen allows us to set an upper limit to the remaining H-envelope mass after a possible AGB final thermal pulse. Finally, we infer from the total amount of carbon detected in the nebula that the strong [WC] mass- loss may have been active only for a limited period during the post-AGB evolution
Y1  - 2004
SN  - 0004-6361
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Hamann, Wolf-Rainer
T1  - The central star of the planetary nebula LMC-N66 : a massive accreting white dwarf?
N2  - The central star of the PN LMC-N66 showed an impressive outburst in 1993 - 1994, returning to its initial conditions about 8 years later. Its spectrum resembles that of a WN4.5 star, being the only confirmed central star of planetary nebulae showing such a spectral type. Recent analysis for the central star parameters, performed by Hamann et al. (2003) is presented. They have found that the bolometric luminosity increased by a factor larger than 6, during the outburst. We discuss the possible scenarios which have been proposed to explain the exceptional stellar parameters and the outburst mechanism. The stellar characteristics and the morphology and kinematics of the planetary nebula suggest the presence of binary system (massive star with a less massive companion or, a white dwarf accreting matter in a close- binary system). These cases pose the least severe contradictions with observational constraints.
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Penone, Caterina
A1  - Allan, Eric
A1  - Soliveres, Santiago
A1  - Felipe-Lucia, Maria R.
A1  - Gossner, Martin M.
A1  - Seibold, Sebastian
A1  - Simons, Nadja K.
A1  - Schall, Peter
A1  - van der Plas, Fons
A1  - Manning, Peter
A1  - Manzanedo, Ruben D.
A1  - Boch, Steffen
A1  - Prati, Daniel
A1  - Ammer, Christian
A1  - Bauhus, Juergen
A1  - Buscot, Francois
A1  - Ehbrecht, Martin
A1  - Goldmann, Kezia
A1  - Jung, Kirsten
A1  - Mueller, Joerg
A1  - Mueller, Joerg C.
A1  - Pena, Rodica
A1  - Polle, Andrea
A1  - Renner, Swen C.
A1  - Ruess, Liliane
A1  - Schoenig, Ingo
A1  - Schrumpf, Marion
A1  - Solly, Emily F.
A1  - Tschapka, Marco
A1  - Weisser, Wolfgang W.
A1  - Wubet, Tesfaye
A1  - Fischer, Markus
T1  - Specialisation and diversity of multiple trophic groups are promoted by different forest features
JF  - Ecology letters
N2  - While forest management strongly influences biodiversity, it remains unclear how the structural and compositional changes caused by management affect different community dimensions (e.g. richness, specialisation, abundance or completeness) and how this differs between taxa. We assessed the effects of nine forest features (representing stand structure, heterogeneity and tree composition) on thirteen above- and belowground trophic groups of plants, animals, fungi and bacteria in 150 temperate forest plots differing in their management type. Canopy cover decreased light resources, which increased community specialisation but reduced overall diversity and abundance. Features increasing resource types and diversifying microhabitats (admixing of oaks and conifers) were important and mostly affected richness. Belowground groups responded differently to those aboveground and had weaker responses to most forest features. Our results show that we need to consider forest features rather than broad management types and highlight the importance of considering several groups and community dimensions to better inform conservation.
KW  - biodiversity exploratories
KW  - dark diversity
KW  - forest management
KW  - global change
KW  - land-use
KW  - multidiversity
KW  - specialisation
KW  - temperate forests
Y1  - 2018
U6  - https://doi.org/10.1111/ele.13182
SN  - 1461-023X
SN  - 1461-0248
VL  - 22
IS  - 1
SP  - 170
EP  - 180
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Stastinska, G.
A1  - Esteban, C.
A1  - Koesterke, Lars
A1  - Medina, S.
A1  - Kingsburgh, R.
T1  - Galactic planetary nebulae with Wolf-Rayet nuclei : I. Objects with [WC]-early type stars
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Reyes-Pérez, J.
A1  - Morisset, C.
A1  - Pena, M.
A1  - Mesa-Delgado, A.
T1  - A consistent spectral model of WR 136 and its associated bubble NGC 6888
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - We analyse whether a stellar atmosphere model computed with the code CMFGEN provides an optimal description of the stellar observations of WR 136 and simultaneously reproduces the nebular observations of NGC 6888, such as the ionization degree, which is modelled with the pyCloudy code. All the observational material available (far and near UV and optical spectra) were used to constrain such models. We found that the stellar temperature T∗, at τ = 20, can be in a range between 70 000 and 110 000 K, but when using the nebula as an additional restriction, we found that the stellar models with T∗ ∼ 70 000 K represent the best solution for both, the star and the nebula.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88274
SP  - 321
EP  - 324
ER  - 
TY  - JOUR
A1  - Pena, M.
A1  - Stastinska, G.
A1  - Esteban, C.
A1  - Koesterke, Lars
A1  - Medina, S.
A1  - Kingsburgh, R.
T1  - Spectroscopy of planetary nebulae with [WR] nuclei
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Pena-Camargo, Francisco
A1  - Thiesbrummel, Jarla
A1  - Hempel, Hannes
A1  - Musiienko, Artem
A1  - Le Corre, Vincent M.
A1  - Diekmann, Jonas
A1  - Warby, Jonathan
A1  - Unold, Thomas
A1  - Lang, Felix
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - Revealing the doping density in perovskite solar cells and its impact on device performance
JF  - Applied physics reviews
N2  - Traditional inorganic semiconductors can be electronically doped with high precision. Conversely, there is still conjecture regarding the assessment of the electronic doping density in metal-halide perovskites, not to mention of a control thereof. This paper presents a multifaceted approach to determine the electronic doping density for a range of different lead-halide perovskite systems. Optical and electrical characterization techniques, comprising intensity-dependent and transient photoluminescence, AC Hall effect, transfer-length-methods, and charge extraction measurements were instrumental in quantifying an upper limit for the doping density. The obtained values are subsequently compared to the electrode charge per cell volume under short-circuit conditions ( CUbi/eV), which amounts to roughly 10(16) cm(-3). This figure of merit represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results consistently demonstrate that the doping density is below this critical threshold 10(12) cm(-3), which means << CUbi / e V) for all common lead-based metal-halide perovskites. Nevertheless, although the density of doping-induced charges is too low to redistribute the built-in voltage in the perovskite active layer, mobile ions are present in sufficient quantities to create space-charge-regions in the active layer, reminiscent of doped pn-junctions. These results are well supported by drift-diffusion simulations, which confirm that the device performance is not affected by such low doping densities.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0085286
SN  - 1931-9401
VL  - 9
IS  - 2
PB  - AIP Publishing
CY  - Melville
ER  - 
TY  - JOUR
A1  - Brinkmann, Kai Oliver
A1  - Becker, Tim
A1  - Zimmermann, Florian
A1  - Kreusel, Cedric
A1  - Gahlmann, Tobias
A1  - Theisen, Manuel
A1  - Haeger, Tobias
A1  - Olthof, Selina
A1  - Tückmantel, Christian
A1  - Günster, M.
A1  - Maschwitz, Timo
A1  - Göbelsmann, Fabian
A1  - Koch, Christine
A1  - Hertel, Dirk
A1  - Caprioglio, Pietro
A1  - Peña-Camargo, Francisco
A1  - Perdigón-Toro, Lorena
A1  - Al-Ashouri, Amran
A1  - Merten, Lena
A1  - Hinderhofer, Alexander
A1  - Gomell, Leonie
A1  - Zhang, Siyuan
A1  - Schreiber, Frank
A1  - Albrecht, Steve
A1  - Meerholz, Klaus
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
A1  - Riedl, Thomas
T1  - Perovskite-organic tandem solar cells with indium oxide interconnect
JF  - Nature
N2  - Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. The bandgap tunability of metal halide perovskite solar cells renders them attractive for multijunction architectures(1). Combinations with silicon and copper indium gallium selenide (CIGS), as well as all-perovskite tandem cells, have been reported(2-5). Meanwhile, narrow-gap non-fullerene acceptors have unlocked skyrocketing efficiencies for organic solar cells(6,7). Organic and perovskite semiconductors are an attractive combination, sharing similar processing technologies. Currently, perovskite-organic tandems show subpar efficiencies and are limited by the low open-circuit voltage (V-oc) of wide-gap perovskite cells(8) and losses introduced by the interconnect between the subcells(9,10). Here we demonstrate perovskite-organic tandem cells with an efficiency of 24.0 per cent (certified 23.1 per cent) and a high V-oc of 2.15 volts. Optimized charge extraction layers afford perovskite subcells with an outstanding combination of high V-oc and fill factor. The organic subcells provide a high external quantum efficiency in the near-infrared and, in contrast to paradigmatic concerns about limited photostability of non-fullerene cells(11), show an outstanding operational stability if excitons are predominantly generated on the non-fullerene acceptor, which is the case in our tandems. The subcells are connected by an ultrathin (approximately 1.5 nanometres) metal-like indium oxide layer with unprecedented low optical/electrical losses. This work sets a milestone for perovskite-organic tandems, which outperform the best p-i-n perovskite single junctions(12) and are on a par with perovskite-CIGS and all-perovskite multijunctions(13).
Y1  - 2022
U6  - https://doi.org/10.1038/s41586-022-04455-0
SN  - 0028-0836
SN  - 1476-4687
VL  - 604
IS  - 7905
SP  - 280
EP  - 286
PB  - Nature Research
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Le Corre, Vincent M.
A1  - Diekmann, Jonas
A1  - Peña-Camargo, Francisco
A1  - Thiesbrummel, Jarla
A1  - Tokmoldin, Nurlan
A1  - Gutierrez-Partida, Emilio
A1  - Peters, Karol Pawel
A1  - Perdigón-Toro, Lorena
A1  - Futscher, Moritz H.
A1  - Lang, Felix
A1  - Warby, Jonathan
A1  - Snaith, Henry J.
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - Quantification of efficiency losses due to mobile ions in Perovskite solar cells via fast hysteresis measurements
JF  - Solar RRL
N2  - Perovskite semiconductors differ from most inorganic and organic semiconductors due to the presence of mobile ions in the material. Although the phenomenon is intensively investigated, important questions such as the exact impact of the mobile ions on the steady-state power conversion efficiency (PCE) and stability remain. Herein, a simple method is proposed to estimate the efficiency loss due to mobile ions via "fast-hysteresis" measurements by preventing the perturbation of mobile ions out of their equilibrium position at fast scan speeds (approximate to 1000 V s(-1)). The "ion-free" PCE is between 1% and 3% higher than the steady-state PCE, demonstrating the importance of ion-induced losses, even in cells with low levels of hysteresis at typical scan speeds (approximate to 100mv s(-1)). The hysteresis over many orders of magnitude in scan speed provides important information on the effective ion diffusion constant from the peak hysteresis position. The fast-hysteresis measurements are corroborated by transient charge extraction and capacitance measurements and numerical simulations, which confirm the experimental findings and provide important insights into the charge carrier dynamics. The proposed method to quantify PCE losses due to field screening induced by mobile ions clarifies several important experimental observations and opens up a large range of future experiments.
KW  - hysteresis
KW  - mobile ions
KW  - perovskite solar cells
Y1  - 2021
U6  - https://doi.org/10.1002/solr.202100772
SN  - 2367-198X
VL  - 6
IS  - 4
PB  - Wiley-VCH
CY  - Weinheim
ER  -