7,229 research outputs found
Phylogenetic relationships of the newly discovered sexual state of Talaromyces flavovirens, comb. nov.
Typical Talaromyces ascomata were observed on dry Quercus suber leaf litter amongst the characteristic synnemata of Penicillium aureocephalum, and they appear to represent the sexual state of the latter species. The species is a synonym of the older Lasioderma flavovirens, and we propose the new combination Talaromyces flavovirens. Lectotype and epitype specimens are designated for this name. The defining characters of the asexual state include yellow, short-stalked, mycetozoan-like synnemata with an unusual, almost closed terminal head of penicillate conidiophores intermixed with sinuous hyphae, and dark green conidia. Ascomata could not be induced in culture, but PCR amplifications of mating-type genes indicate the species is heterothallic. In nature, ascocarp initials appear to be antheridia coiled around clavate ascogonia, similar to those of T. flavus, and the thick-walled, spiny ascospores are also similar to those of T. flavus. ITS barcodes and β-tubulin sequences place T. flavovirens in a clade with T. apiculatus, T. flavus, T. funiculosus, T. galapagensis, T. pinophilus, T. macrosporus, and seven other species
Penicillium aureocephalum Munt.-Cvetk., Hoyo et Gómez-Bolea, un interessant ascomicet anamòrfic amb aspecte de mixomicet : distribució, ecologia i fenologia
Cinc anys
després de la descripció de Penicillium aureocephalum per Muntañola-Cvetkovic, Hoyo i GórnezBolea,
els autors del present treball han anat afegint Inés dades de camp a les ja existents, que
comencen a subministrar una imatge més viva d'aquest curiós anamorf saprotrófic dins de les
comunitats naturals on esporula. El present treball és un resum d'aquestes dades corológiques,
ecológiques i fenológiques, acompanyat de comentaris. La principal conclu sió és que I'espécie se' ns
presenta com un fong termófil que colonit za preferentm ent fulles caigudes de surera (Quercus suber),
que han mort a l' arbre per la calor produída per incendis, pero que també pot créixer, menys sovint,
sobre altres substrats, com ara fulles o fruits de Cistus salviifolius, C. ladanifer, Quercus coccifera, etc.
que han estat descarre gats per les plantes com a resposta a un fort estrés hídric. El treball inclou un
mapa de la distribuci ó de I'espécie en el Pare Natural del Cap de Creus, fins ara I' área óptima de
creixement, i un altre mapa amb la distribució coneguda actualment en els Paisos Catalans, on apareix
provisionahnent endémica. S'ofereix un estudi macrofotográfic de l'especie, útil per ajudar els
mic ólegs a trobar noves localitat s d'aquest curiosa especie d'anamorf, tan diferent de les més
conegudes de Penicillium , ja que té aspect e de mixomic et, que es comporta COIll a term ófila i
saprotrófica sobre fulles riques en nutrients.Five years after
the description of Penicillium aureocephalum by Muntañola-C vetkovic, Hoyo and G ómez-Bolea, an
increasing wealth of field data has been gathered by the authors, which provide a vivid image of the
anamorph of this curious saprotrophic species. Chorological, ecological and phenological data are here
summarized and discussed. The species appears to be thermophilou s, preferentially colonizing fallen
leaves of cork trees (Quercus suber) killed by wildfires, but also growing sometimes on other substrata,
such as dead leaves of Cistus salviifolius,C. ladanifer, Quercus coccifera, etc. which may have dropped as
a response to severe water stress. A distribution map of the species in the Natural Park of Cap de Creus,
which apparently is its natural habitat and another nowith showing the currently known distribution in the
Catalan Countries, are given. A macrophotographic survey ofthe species is also included in order to aid in
the recognition of this curious myxomycete-looking thermophilou s, anamorphic species, saprotrophic on
nutrient-rich substrata, and so different from the usual Penicillium taxa
Local soil classification and crop suitability: Implications for the historical land use and soil management in Monti di Trapani (Sicily)
In the past, the lack of technologies (e.g. synthetic fertilizers) to overcome biophysical limitations has played a
central role in land use planning. Thus, landscape management and agronomic practices are reactions to local
knowledge and perceptions on natural resources, particularly soil. In the framework of the European research
project MEMOLA (FP7), the role of local farmers knowledge and perceptions on soil for the historical land
use through the spatial distribution of crops and the various management practices have been assessed in three
different areas of Monti di Trapani region (Sicily). The identification of the soil classification systems of farmers
and the criteria on which it is based, linked to the evaluation of the farmers\u2019 ability to identify and map the
different soil types, was a key step. Nevertheless, beyond the comparison of the ethnopedological classification
approach versus standard soil classification systems, the study also aims at understanding local soil management
and land use decisions. The applied methodology was based on an interdisciplinary approach, combining soil
science methods and participatory appraisal tools, particularly: i) semi-structured interviews; ii) soil sampling
and analysis; iii) discussion groups; and iv) a workshop with local edafologists and agronomists. A rich local
glossary of terms associated with the soil conditions and an own soil classification system have been identified in
the region. Also, a detailed soil map, including process of soil degradation and soil capability, has been generated.
This traditional soil knowledge has conditioned the management and the spatial distribution of the crops, and
therefore the configuration of the landscape, until the 1990s
Recent Technological Developments on LGAD and iLGAD Detectors for Tracking and Timing Applications
This paper reports the last technological development on the Low Gain
Avalanche Detector (LGAD) and introduces a new architecture of these detectors
called inverse-LGAD (iLGAD). Both approaches are based on the standard
Avalanche Photo Diodes (APD) concept, commonly used in optical and X-ray
detection applications, including an internal multiplication of the charge
generated by radiation. The multiplication is inherent to the basic n++-p+-p
structure, where the doping profile of the p+ layer is optimized to achieve
high field and high impact ionization at the junction. The LGAD structures are
optimized for applications such as tracking or timing detectors for high energy
physics experiments or medical applications where time resolution lower than 30
ps is required. Detailed TCAD device simulations together with the electrical
and charge collection measurements are presented through this work.Comment: Keywords: silicon detectors, avalanche multiplication, timing
detectors, tracking detectors. 8 pages. 8 Figure
Canted Spin Texture and Quantum Spin Hall Effect in WTe2
We report an unconventional quantum spin Hall phase in the monolayer
T-WTe, which exhibits hitherto unknown features in other
topological materials. The low-symmetry of the structure induces a canted spin
texture in the plane, which dictates the spin polarization of
topologically protected boundary states. Additionally, the spin Hall
conductivity gets quantized () with a spin quantization axis parallel
to the canting direction.
These findings are based on large-scale quantum simulations of the spin Hall
conductivity tensor and nonlocal resistances in multi-probe geometries using a
realistic tight-binding model elaborated from first-principle methods.
The observation of this canted quantum spin Hall effect, related to the
formation of topological edge states with nontrivial spin polarization, demands
for specific experimental design and suggests interesting alternatives for
manipulating spin information in topological materials.Comment: For comments please contact [email protected]
Spin-orbit torques for current parallel and perpendicular to a domain wall
We report field- and current-induced domain wall (DW) depinning experiments
in Ta/Co20Fe60B20/MgO nanowires through a Hall cross geometry. While purely
field-induced depinning shows no angular dependence on in-plane fields, the
effect of the current depends crucially on the internal DW structure, which we
manipulate by an external magnetic in-plane field. We show for the first time
depinning measurements for a current sent parallel to the DW and compare its
depinning efficiency with the conventional case of current flowing
perpendicularly to the DW. We find that the maximum efficiency is similar for
both current directions within the error bars, which is in line with a
dominating damping-like spin-orbit torque (SOT) and indicates that no large
additional torques arise for currents parallel to the DW. Finally, we find a
varying dependence of the maximum depinning efficiency angle for different DWs
and pinning levels. This emphasizes the importance of our full angular scans
compared to previously used measurements for just two field directions
(parallel and perpendicular to the DW) and shows the sensitivity of the
spin-orbit torque to the precise DW structure and pinning sites.Comment: 11 pages, 3 figure
Gas Dynamics in the LINER Galaxy NGC 5005: Episodic Fueling of a Nuclear Disk
We report high-resolution CO(1-0) observations in the central 6 kpc of the
LINER galaxy NGC 5005 with the Owens Valley Radio Observatory millimeter array.
Molecular gas is distributed in three components - a ring at a radius of about
3 kpc, a strong central condensation, and a stream to the northwest of the
nucleus but inside the 3 kpc ring. The central condensation is a disk of about
1 kpc radius with a molecular gas mass of 2 x 10^9 M_sun. The stream between
the 3 kpc ring and the nuclear disk lies on a straight dust lane seen in the
optical. If this material moves in the plane of the galaxy, it has a velocity
offset by up to ~ 150 km/s from galactic rotation. We suggest that an optically
inconspicuous stellar bar lying within the 3 kpc ring can explain the observed
gas dynamics. This bar is expected to connect the nuclear disk and the ring
along the position angle of the northwest stream. A position-velocity cut in
this direction reveals features which match the characteristic motions of gas
in a barred potential. Our model indicates that gas in the northwest stream is
on an x_1 orbit at the bar's leading edge; it is falling into the nucleus with
a large noncircular velocity, and will eventually contribute about 2 x 10^8
M_sun to the nuclear disk. If most of this material merges with the disk on its
first passage of pericenter, the gas accretion rate during the collision will
be 50 M_sun/yr. We associate the nuclear disk with an inner 2:1 Lindblad
resonance, and the 3 kpc ring with an inner 4:1 Lindblad resonance. The high
rate of bar-driven inflow and the irregular appearance of the northwest stream
suggest that a major fueling event is in progress in NGC 5005. Such episodic
(rather than continuous) gas supply can regulate the triggering of starburst
and accretion activity in galactic nuclei. (abridged)Comment: 26 pages, 12 figures, AASTeX, ApJ in press (Feb. 10, 2000). For
full-resolution figures, see
http://www.ovro.caltech.edu/mm/science/science.htm
The nature of domain walls in ultrathin ferromagnets revealed by scanning nanomagnetometry
The recent observation of current-induced domain wall (DW) motion with large
velocity in ultrathin magnetic wires has opened new opportunities for
spintronic devices. However, there is still no consensus on the underlying
mechanisms of DW motion. Key to this debate is the DW structure, which can be
of Bloch or N\'eel type, and dramatically affects the efficiency of the
different proposed mechanisms. To date, most experiments aiming to address this
question have relied on deducing the DW structure and chirality from its motion
under additional in-plane applied fields, which is indirect and involves strong
assumptions on its dynamics. Here we introduce a general method enabling
direct, in situ, determination of the DW structure in ultrathin ferromagnets.
It relies on local measurements of the stray field distribution above the DW
using a scanning nanomagnetometer based on the Nitrogen-Vacancy defect in
diamond. We first apply the method to a Ta/Co40Fe40B20(1 nm)/MgO magnetic wire
and find clear signature of pure Bloch DWs. In contrast, we observe left-handed
N\'eel DWs in a Pt/Co(0.6 nm)/AlOx wire, providing direct evidence for the
presence of a sizable Dzyaloshinskii-Moriya interaction (DMI) at the Pt/Co
interface. This method offers a new path for exploring interfacial DMI in
ultrathin ferromagnets and elucidating the physics of DW motion under current.Comment: Main text and Supplementary Information, 33 pages and 12 figure
Charge-to-Spin Interconversion in Low-Symmetry Topological Materials
The spin polarization induced by the spin Hall effect (SHE) in thin films
typically points out of the plane. This is rooted not in a fundamental
constraint but on the specific symmetries of traditionally studied systems. We
theoretically show that the reduced symmetry of strong spin-orbit coupling
materials such as or enables new forms of
intrinsic SHE that produce large and robust in-plane spin polarizations.
Through quantum transport calculations on realistic device geometries with
disorder, we show that the charge-to-spin interconversion efficiency can reach
\% and is gate tunable. The numerically extracted spin
diffusion lengths () are long and yield large values of the figure
of merit nm, largely superior to
conventional SHE materials. These findings vividly emphasize how crystal
symmetry governs the intrinsic SHE, and how it can be exploited to broaden the
range and efficiency of spintronic functionalities.Comment: Any comments are appreciated. 6 pages + 4 figures. Supplemental
material available upon reques
The Pattern Speeds of M51, M83 and NGC 6946 Using CO and the Tremaine-Weinberg Method
In spiral galaxies where the molecular phase dominates the ISM, the molecular
gas as traced by CO emission will approximately obey the continuity equation on
orbital timescales. The Tremaine-Weinberg method can then be used to determine
the pattern speed of such galaxies. We have applied the method to single-dish
CO maps of three nearby spirals, M51, M83 and NGC 6946 to obtain estimates of
their pattern speeds: 38 +/- 7 km/s/kpc, 45 +/- 8 km/s/kpc and 39 +/- 8
km/s/kpc, respectively, and we compare these results to previous measurements.
We also analyze the major sources of systematic errors in applying the
Tremaine-Weinberg method to maps of CO emission.Comment: 33 pages, figures already in pdf. To appear in 2004 ApJ 607 28
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