1,721,113 research outputs found
A novel X-ray diffraction approach to assess the crystallinity of regenerated cellulose fibers
No full textPublisher Copyright: © 2022 International Union of Crystallography. All rights reserved.Here, a new accurate approach is presented to quantify the degree of crystallinity of regenerated cellulose textile fibers using wide-angle X-ray scattering. The approach is based on the observation that the contributions to the scattering from crystalline and amorphous domains of the fibers can be separated due to their different degree of orientation with respect to the fiber direction. The method is tested on Ioncell-F fibers, dry jet wet spun with different draw ratios from an ionic liquid solution. The analysis output includes, apart from an accurate estimate of the fiber crystallinity, the degrees of orientation of the cellulose nanocrystals and the cellulose chains in the amorphous domains.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Atomic resolution studies detect new biologic evidences on the Turin Shroud
No full textWe performed reproducible atomic resolution Transmission Electron Microscopy and Wide Angle X-ray Scanning Microscopy experiments studying for the first time the nanoscale properties of a pristine fiber taken from the Turin Shroud. We found evidence of biologic nanoparticles of creatinine bounded with small nanoparticles of iron oxide. The kind, size and distribution of the iron oxide nanoparticles cannot be dye for painting but are ferrihydrate cores of ferritin. The consistent bound of ferritin iron to creatinine occurs in human organism in case of a severe polytrauma. Our results point out that at the nanoscale a scenario of violence is recorded in the funeral fabric and suggest an explanation for some contradictory results so far published
Multifunctional TiO2/FexOy/Ag based nanocrystalline heterostructures for photocatalytic degradation of a recalcitrant pollutant
No full textThe photocatalytic degradation of pollutants is a key technological application for nanomaterials. Our work aims at developing a multifunctional nanocrystalline heterostructure based on TiO2nanorods, FexOyand Ag nanoparticles (NPs), TiO2NRs/FexOy/Ag, integrating in one nanostructure a visible light photoactive moiety (TiO2NRs/Ag) and a magnetic domain (FexOy), in order to address the photoactivity under visible light and the possibility of recovery and reuse the photocatalyst. The synthesis was carried by preparing first the TiO2NRs/FexOybased heterostructure and then growing Ag NPs with control on size. The resulting multidomain structures were characterized by FTIR and absorption spectroscopy, TEM and SEM microscopy, EDS and XRD analysis. The influence of the Ag NP domain and of its size on the photoactivity of the TiO2NRs/FexOy/Ag nanostructures under visible light were investigated in the photocatalytic degradation of the Nalidixic Acid, an antibiotic used as a model compound representative of recalcitrant pollutants. In the presence of the Ag domain a significant increase of the photoactivity with respect to TiO2NRs/FexOyheterostructures and to the commercially available TiO2P25 was observed. Such an enhanced photocatalytic efficiency was found dependent on the size of the Ag domain and explained taking into account the plasmonic properties and the different possible photoactivation mechanisms
Colloidal PbTe-Au nanocrystal heterostructures
No full textColloidal PbTe nanocrystals are reacted with AuCl(3) in the presence of dodecylamine and tetraoctylammonium bromide in a toluene solution. At room temperature, only homogenous nucleation of isolated Au nanocrystals in solution is observed. At higher temperatures (i.e. 60 degrees C or higher) the gold ions/atoms are able to diffuse through the PbTe nanocrystals and to form one or more metallic gold regions inside them, while most of the remaining volume of each nanocrystal becomes amorphous. Longer reaction times lead to the growth of a single balloon-shaped Au domain attached via its apex to the surface of each nanocrystal. The structural and compositional quantification of the starting PbTe nanocrystals and of the various reaction products is often complicated by several reactive processes occurring during in situ analysis by electron microscopy. Evidences of the formation of a metastable Au(3)Te compound are presented
Table-top combined scanning X-ray small angle scattering and transmission microscopies of lipid vesicles dispersed in free-standing gel
No full textA mm thick free-standing gel containing lipid vesicles made of 2-oleoyl-1-palmitoyl-sn-glycero-3-
phosphocholine (POPC) was studied by scanning Small Angle X-ray Scattering (SAXS) and X-ray
Transmission (XT) microscopies. Raster scanning relatively large volumes, besides reducing the risk of
radiation damage, allows signal integration, improving the signal-to-noise ratio (SNR), as well as high
statistical significance of the dataset. The persistence of lipid vesicles in gel was demonstrated, while
mapping their spatial distribution and concentration gradients. Information about lipid aggregation and
packing, as well as about gel density gradients, was obtained. A posteriori confirmation of lipid presence
in well-defined sample areas was obtained by studying the dried sample, featuring clear Bragg peaks
from stacked bilayers. The comparison between wet and dry samples allowed it to be proved that lipids
do not significantly migrate within the gel even upon drying, whereas bilayer curvature is lost by
removing water, resulting in lipids packed in ordered lamellae. Suitable algorithms were successfully
employed for enhancing transmission microscopy sensitivity to low absorbing objects, and allowing full
SAXS intensity normalization as a general approach. In particular, data reduction includes normalization
of the SAXS intensity against the local sample thickness derived from absorption contrast maps. The
proposed study was demonstrated by a room-sized instrumentation, although equipped with a high
brilliance X-ray micro-source, and is expected to be applicable to a wide variety of organic, inorganic,
and multicomponent systems, including biomaterials. The employed routines for data reduction and
microscopy, including Gaussian filter for contrast enhancement of low absorbing objects and a region
growing segmentation algorithm to exclude no-sample regions, have been implemented and made
freely available through the updated in-house developed software SUNBIM
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Hierarchical Analysis of Self-Assembled PEGylated Hexaphenylalanine Photoluminescent Nanostructures
No full textDespite the growing literature about diphenylalanine-
based peptide materials, it still remains a challenge to
delineate the theoretical insight into peptide nanostructure
formation and the structural features that could permit materials
with enhanced properties to be engineered. Herein,
we report the synthesis of a novel peptide building block
composed of six phenylalanine residues and eight PEG units,
PEG8-F6. This aromatic peptide self-assembles in water in
stable and well-ordered nanostructures with optoelectronic
properties. A variety of techniques, such as fluorescence,
FTIR, CD, DLS, SEM, SAXS, and WAXS allowed us to correlate
the photoluminescence properties of the self-assembled
nanostructures with the structural organization of the peptide
building block at the micro- and nanoscale. Finally,
a model of hexaphenylalanine in aqueous solution by molecular
dynamics simulations is presented to suggest structural
and energetic factors controlling the formation of nanostructures
Synthesis of semicrystalline nanocapsular structures obtained by Thermally Induced Phase Separation in nanoconfinement
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