2,470 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
Study on determining stability domains for nonlinear dynamical systems Final report 1 May 1966 - 1 Feb. 1967
Numerical procedure for determining stability domains in nonlinear dynamical system
Isotropic properties of the photonic band gap in quasicrystals with low-index contrast
We report on the formation and development of the photonic band gap in
two-dimensional 8-, 10- and 12-fold symmetry quasicrystalline lattices of low
index contrast. Finite size structures made of dielectric cylindrical rods were
studied and measured in the microwave region, and their properties compared
with a conventional hexagonal crystal. Band gap characteristics were
investigated by changing the direction of propagation of the incident beam
inside the crystal. Various angles of incidence from 0 \degree to 30\degree
were used in order to investigate the isotropic nature of the band gap. The
arbitrarily high rotational symmetry of aperiodically ordered structures could
be practically exploited to manufacture isotropic band gap materials, which are
perfectly suitable for hosting waveguides or cavities.Comment: 16 pages, 7 figures, submitted to PR
Study on determining stability domains for nonlinear dynamical systems, II Quarterly progress report, 1 Aug. - 31 Oct. 1966
Stability domain determination for nonlinear dynamical syste
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
Experimental Methods for Measuring Optical Rotatory Dispersion:Survey and Outlook
The measurement of optical rotation (OR) and optical rotatory dispersion has been finding renewed interest for some years, because of advancement in computational methods and in the performance of new experiments. Here, we shortly review the traditional and most-used experimental methods. We define and discuss the two main types of approaches in measuring OR: the intensity method and the optical null method. We report on some new results obtained by redesigning experiments based on the first approach, by adapting nonsophisticated hardware to current circular dichroism instrumentation
Dipole and rotational strengths for overtone transitions of a C2-symmetry HCCH molecular fragment using Van Vleck perturbation theory
Contact transformation theory up to second order is employed to treat CH-stretching overtone
transitions and to calculate dipole and rotational strengths. A general Hamiltonian describing two
interacting CH-stretching oscillators is considered, and the Darling–Dennison resonance is
appropriately taken into account. The two CH bonds are supposed to be dissymmetrically disposed,
so as to represent a chiral HCCH fragment, endowed with C2 symmetry. Analytical expressions of
transition moments and dipole and rotational strengths are given in the hypothesis of general electric
and magnetic dipole moments with quadratic dependence on coordinates and momenta. Dipole and
rotational strengths are then calculated together with frequencies for the fundamental and first three
overtone regions in the simplifying hypothesis of the valence optical approach on the
coupled-oscillator framework. Simplified analytical expressions thereof in the relevant parameters
are presented
PROSPECTIVE UPON MULTI-SOURCE URBAN SCALE DATA FOR 3D DOCUMENTATION AND MONITORING OF URBAN LEGACIES
Abstract. The investigation on the built urban heritage and its current transformations can progressively benefit from the use of geospatial data related to urban environment. This is even more interesting when urban design studies of historical and stratified cities meet the contribution of 4D geospatial data within the urban morphology researches, aiming at quickly and accurately identifying and then measuring with a spatial relationship, both localized transformation (volumes demolitions, addition, etc…) and wide-scale substantial modification resulting from urban zones of diversification spaces that incorporates urban legacies. In this domain, the comparison and analysis of multi-source and multi-scale information belonging to Spatial Data Infrastructures (SDI) organized by Municipality and Region Administration (mainly, orthoimages and DSM and digital mapping) are a crucial support for multi-temporal spatial analysis, especially if compared with new DSMs related to past urban situations. The latter can be generated by new solution of digital image-matching techniques applicable to the available historical aerial images. The goal is to investigate the amount of available data and their effectiveness, to later test different experimental tools and methods for quick detection, localization and quantification of morphological macro-transformation at urban scale. At the same time, it has been examined the opportunity to made available, with up-and-coming Mobile Mapping Systems (MMS) based on image- and range-based techniques, a rapid and effective approach of data gathering, updating and sharing at validated urban scales. The presented research, carried out in the framework of the FULL@Polito research lab, applies to urban legacies and their regeneration, and is conducted on a key redevelopment area in northern Torino, the Parco Dora, that was occupied by steel industries actively working up to 1992. The long-standing steel structures of the Ferriere FIAT lot have been refurbished and incorporated in the new urban park, generating a contemporary space with a new evolving urban fabric, and being integrated in the new updated geo-spatial databases as well.</p
A Vibrational Circular Dichroism Approach To The Determination Of The Absolute Configuration Of Flexible And Transparent Molecules: Fluorenone Ketals Of 1,N-Diols
The infrared absorption (IR) and vibrational circular dichroism (VCD) spectra for five ketal
molecules, three of which obtained from 1,2-diols and two from 1,3-diols, were recorded in the
mid-IR region. The spectra have been satisfactorily reproduced by DFT calculations, even with
not too large wavefunction basis sets, especially due to the low number of conformers to be
considered. The mobility of some moieties provides a recognizable signature. A characteristic
couplet of VCD bands attributed to normal modes involving the methine and a phenyl ring
bonded to the stereogenic carbon atom is evidenced for two ketals of the series as a signature
of the absolute configuration; due comparison with existing literature is made. A relation is
discussed of the present VCD data with the literature VCD data of simple alcohols and diols
Experimental and ab-initio calculated vcd spectra of the first OH-stretching overtone of (1R)-(-) and (1S)-(+)-endo-borneol
The near infrared (NIR) absorption and NIR-vibrational circular dichroism (NIR-VCD) spectra
of dilute solutions of the two enantiomers of endo-borneol have been measured in the first
OH-stretching overtone region (1600–1300 nm). By density functional theory (DFT) we calculate
mechanical parameters, i.e. the harmonic mechanical frequency and the anharmonicity constant
for the OH stretching, and anharmonic electrical parameters; i.e. the dependence on OH-bond
length of atomic polar tensors and atomic axial tensors. We evaluate transition integrals for the
calculations of rotational and dipole strengths by Morse anharmonic wavefunctions depending on
mechanical harmonic frequencies and mechanical anharmonicity parameters that are calculated
ab initio. Experimental and calculated spectra compare quite well and this fact allows us to
associate differently signed NIR-VCD features with different conformational states of the
OH-bond. Absorption features for the fundamental and for the second overtone of the OH
stretching are also compared with experiment
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