1,728 research outputs found
Vicia incisa (Fabaceae). Taxonomical and chorological notes
The classification of the Vicia sativa aggregate is unsatisfactory. Concerning the taxonomic value and choice of rank of some of these
taxa, there are disagreements among botanists. Vicia incisa, which was originally described at species level, was mostly treated at subspecies rank
of V. sativa. However, chemical and molecular data pointed out that this taxon, not only should be treated at species rank, but it should be removed
from the group of V. sativa, being more related to V. barbazitae, V. grandiflora, and V. sepium. Based on morphometric measurements and cultivation
tests, as well as nomenclatural investigations, the present research was carried out with the main aim to define the better taxonomic rank for the
studied taxon. The results obtained support the published molecular data concerning both the recognition of the studied taxon at species level and the
morphological similarity among V. incisa, V. barbazitae, V. grandiflora and V. sepium
Rediscovering the scientific and didactic value of minor herbarium collections: the seeds and fruits collection by Gustavo Bonaventura
Seeds and fruits collections are very important from a systematic point of view and represent useful references in several disciplines and research fields. The Herbarium of Sapienza University of Rome (RO) hosts a Spermoteque/Carpoteque, which was organized by Gustavo Bonaventura (1902-1976). The purpose of this paper is to describe the heritage of Bonaventura's collection. It consists of 42 wooden boxes, globally hosting 3411 glass tubes containing seeds, fruits, and other materials. The collection was first of all catalogued; then, analysis were conducted regarding taxonomic composition, temporal and geographic coverage, institutions of provenience, collectors, content, and preservation status. The specimens refer to 2740 taxa, belonging to 890 genera and 135 families. Many genera of agricultural interest are present, each one with different cultivars. The collection spans across 130 years (1843-1975) and hosts specimens coming from all over the world. Materials were provided by several herbaria, botanical gardens and agrarian institutes, and by 50 collectors. The Bonaventura's collection is still a useful reference collection, testifying biodiversity over times and thus being useful for diachronic studies; moreover, it documents the interests of collectors and the past network activity between institutions
Radiation and magnetic field effects on new semiconductor power devices for HL-LHC experiments
The radiation hardness of commercial Silicon Carbide and Gallium Nitride
power MOSFETs is presented in this paper, for Total Ionizing Dose effects and
Single Event Effects, under gamma, neutrons, protons and heavy ions. Similar
tests are discussed for commercial DC-DC converters, also tested in operation
under magnetic field
Relations between morphological settings and vegetation covers in a medium relief landscape of Central Italy
Mount area, a medium relief structure within the Italian Latium region. The study aims at defining the relationships
between vegetation and landform types and highlighting the main morphological characteristics within examined
land cover classes. These were the result of the application of a supervised classification method to the first 28 (VISNIR)
bands of the airborne MIVIS data collected within an extensive survey campaign over Rome Province. The
analysis was supported by photo-interpretation of peculiar MIVIS band combinations and by data acquired during
field surveys and from a pre-existing vegetation map. The morphometric data were obtained by processing a raster
DEM created from topographic maps. These data were processed by means of a new morphometric classification
method based on the statistical multivariate investigation of local topographic gradients, calculated along the 8 azimuth
directions of each pixel neighbourhood. Such approach quickly estimates the spatial distribution of different
types of homogeneous terrain units, emphasizing the impact of erosional and tectonic processes on the overall relief.
Mutual relations between morphometric units and vegetation types were assessed by performing a correspondence
analysis between the results of the two classifications
Chiral Polyalkylthiophenes for Organic Light Emitting Diodes
Chiral polyalkylthiophenes are noncentrosymmetric organic materials which can be used
both in second harmonic-generation devices and in polarized light emitting diodes. In this work
we present the synthesis and the characterization of a polyalkylthiophene with a chiral center
very close to the conjugated backbone: poly(3-[(S)-2-methylbutyl]thiophene) (PMBT). Circular
dichroism (CD) measurements have been carried out to ascertain the chirality of these materials.
The CD spectra show intense signals both in mixed solvents and in the solid state. The strong
Cotton effect can be associated to a highly ordered aggregated phase whose nature is still under
investigation. We also present the photo and electroluminescence characterization of single layer
light emitting diode (LED) with the following configuration: ITO (Tin Indium Oxide)/PMBT/Al
Current driven rotating kink mode in a plasma column with a non-line-tied free end
First experimental measurements are presented for the kink instability in a
linear plasma column which is insulated from an axial boundary by finite sheath
resistivity. Instability threshold below the classical Kruskal-Shafranov
threshold, axially asymmetric mode structure and rotation are observed. These
are accurately reproduced by a recent kink theory, which includes axial plasma
flow and one end of the plasma column that is free to move due to a
non-line-tied boundary condition.Comment: 4 pages, 6 figure
Compensation temperatures and exchange bias in La1.5Ca0.5CoIrO6
We report on the study of magnetic properties of the La1.5Ca0.5CoIrO6 double
perovskite. Via ac magnetic susceptibility we have observed evidence of weak
ferromagnetism and reentrant spin glass behavior on an antiferromagnetic
matrix. Regarding the magnetic behavior as a function of temperature, we have
found that the material displays up to three inversions of its magnetization,
depending on the appropriate choice of the applied magnetic field. At low
temperature the material exhibit exchange bias effect when it is cooled in the
presence of a magnetic field. Also, our results indicate that this effect may
be observed even when the system is cooled at zero field. Supported by other
measurements and also by electronic structure calculations, we discuss the
magnetic reversals and spontaneous exchange bias effect in terms of magnetic
phase separation and magnetic frustration of Ir4+ ions located between the
antiferromagnetically coupled Co ions.Comment: 10 pages, 8 figures and supplemental materia
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