124,655 research outputs found
Nonlinear dynamics induced in liquid crystals in the presence of the orbital and spin angular momentum of light
No full textWe studied the dynamical effects induced in a homeotropic nematic film when a normally incident circularly polarized light beam with an elliptical intensity profile is used. A three dimensional dynamical model shows that, besides the spin, the orbital angular momentum of photons also plays a role in the reorientation process. Our measurements fairly reproduce the main dynamical features predicted by the model in the near threshold region. The model, however, does not work, as it is, at higher incident laser power where chaotic director rotation was reported [A. Vella, A. Setaro, B. Piccirillo, E. Santamato, Phys. Rev. E 67, 051704 (2003)]
L'archivio di Agostino Pirella. Inventario
No full textIl libro raccoglie l’inventario dell’archivio personale dello psichiatra “basagliano”, oggi conservato presso la Biblioteca Umanistica sede di Arezzo dell’Università di Siena. Donato nel 2017 dal figlio Martino, l’archivio è stato oggetto di riordino, inventariazione e studio. Insieme alle carte, il fondo Pirella è composto anche dai libri della sua biblioteca. Qui viene anche pubblicata la bibliografia completa dei suoi scritti. Lo scavo dentro queste carte disegna la sagoma di uno “psichiatra umanista”. Pirella, nella pratica e nel pensiero, ha costantemente ripensato e agito “il problema psichiatrico”: non più l’annullamento dei malati nell’internamento manicomiale, ma l’esercizio di cura e di autodeterminazione delle persone. Un cammino ancora tutto da percorrere, anche con l’ausilio delle sue memori
Effect of hybrid isolation on the luminescence enhancement of carbon nanotube-gold nanorod composites
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Identification of black sturgeon caviar pigment as eumelanin
No full textReported herein is the purification of the pigment of black sturgeon caviar and its unambiguous identification as a typical eumelanin by means of chemical degradation coupled with electron paramagnetic resonance (EPR) evidence. HPLC and LC-MS analysis of oxidative degradation mixtures revealed the formation of pyrrole-2,3,5-tricarboxylic acid (PTCA), a specific marker of eumelanin pigments, in yields compatible with a 6.5% w/w pigment content. EPR spectral features and parameters were in close agreement with those reported for a typical natural eumelanin such as Sepia melanin from squid ink. The identification for the first time of eumelanin in a fish roe is expected to provide a novel molecular basis for the valorization of black caviar and production wastes thereof in food chemistry and diet
Dispersion of carbon nanotubes using an azobenzene derivative
No full textAqueous dispersions of carbon nanotubes (CNTs) were
obtained by noncovalent adsorption of an azobenzene derivative
carrying polyglycerol dendric structures. UV/Vis absorption
spectra and photoluminescence maps were recorded to
confirm successful nanotube debundling and suspension.
Comparison to dispersion of nanotubes using sodium dodecyl
sulfate (SDS) revealed shifts of the nanotube E22 excitation
peaks from 28 to 67 meV as well as shifts from 21 to 37 meV of
the E11 emission peaks
Chirally enhanced solubilization through perylene-based surfactant
No full textRecently we introduced a rationally designed surfactant which forms energy transfer complexes with carbon nanotubes. We investigate the chiral selectivity of this compound, a perylene derived surfactant, through photoluminescence (PL) measurements, and find a strong enhancement of the luminescence intensity for one particular group of chiralities. The effect is striking, with luminescence increases of several hundred percent.
Chiral selectivity of the investigated surfactant compound as compared to solubilization through sodium cholate (SC). Small numbers indicate chirality, large numbers laola family
Interaction between single-walled carbon nanotubes and alkyl-polyglycerol derivatives
No full textWe use three alkyl-polyglycerol derivatives to suspend singlewalled
carbon nanotubes. The molecules differ by the aromatic
moieties between the alkyl tail and the polyglycerol head. The
suspended nanotubes are analysed by photoluminescence
spectroscopy. We observe a dependence of the luminescence
intensity and hence nanotube abundance on the aromatic
moieties. Interestingly, the strength of interaction depends on
the nanotube families
Amphiphile replacement on carbon nanotube surfaces: Effect of aromatic groups on the interaction strength
No full textCarbon nanotubes (CNTs) were solubilized using akyl/polyglycerol amphiphiles. Similar cosurfactants, bearing different aromatic moieties between head and tail, were added to these samples. The interaction strength between these amphiphiles and CNTs changes depending on the inserted aromatic moieties. The insertion of a phenyl ring allows the amphiphile to replace the starting one indicating a higher interaction strength, while the insertion of a triazol pentagon does not, suggesting that the interaction strength is lower. The replacement was monitored via PLE mapping
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