The role of the coherence in the cross-correlation analysis of diffraction patterns from two-dimensional dense mono-disperse systems

The investigation of the static and dynamic structural properties of colloidal systems relies on techniques capable of atomic resolution in real space and femtosecond resolution in time. Recently, the cross-correlation function (CCF) analysis of both X-rays and electron diffraction patterns from dilute and dense aggregates has demonstrated the ability to retrieve information on the sample's local order and symmetry. Open questions remain regarding the role of the beam coherence in the formation of the diffraction pattern and the properties of the CCF, especially in dense systems. Here, we simulate the diffraction patterns of dense two-dimensional monodisperse systems of different symmetries, varying the transverse coherence of the probing wave, and analyze their CCF. We study samples with different symmetries at different size scale, as for example, pentamers arranged into a four-fold lattice where each pentamer is surrounded by triangular lattices, both ordered and disordered. In such systems, different symmetry modulations are arising in the CCF at specific scattering vectors. We demonstrate that the amplitude of the CCF is a fingerprint of the degree of the ordering in the sample and that at partial transverse coherence, the CCF of a dense sample corresponds to that of an individual scattering object.Comment: 22 pages, 7 figure

Local photo-mechanical stiffness revealed in gold nanoparticles supracrystals by ultrafast small-angle electron diffraction

We demonstrate that highly-ordered two-dimensional crystals of ligand-capped gold nanoparticles display a local photo-mechanical stiffness as high as that of solids such as graphite. In out-of equilibrium electron diffraction experiments, a strong temperature jump is induced in a thin film with a femtosecond laser pulse. The initial electronic excitation transfers energy to the underlying structural degrees of freedom, with a rate generally proportional to the stiffness of the material. With femtosecond small-angle electron diffraction, we observe the temporal evolution of the diffraction feature associated to the nearest-neighbor nanoparticle distance. The Debye-Waller decay for the octanethiol-capped nanoparticles supracrystal, in particular, is found to be unexpectedly fast, almost as fast as the stiffest solid known and observed by the same technique, i.e. graphite. Our observations unravel that local stiffness in a dense supramolecular assembly can be created by Van der Waals interactions up to a level comparable to crystalline systems characterized by covalent bonding

Order/Disorder Dynamics in a Dodecanethiol-Capped Gold Nanoparticles Supracrystal by Small-Angle Ultrafast Electron Diffraction

The design and the characterization of functionalized gold nanoparticles supracrystals require atomically resolved information on both the metallic core and the external organic ligand shell. At present, there is no known approach to characterize simultaneously the static local order of the ligands and of the nanoparticles, nor their dynamical evolution. In this work, we apply femtosecond small-angle electron diffraction combined with angular cross-correlation analysis, to retrieve the local arrangement from nanometer to interatomic scales in glassy aggregates. With this technique we study a two-dimensional distribution of functionalized gold nanoparticles deposited on amorphous carbon. We show that the dodecanethiol ligand chains, coating the gold cores, order in a preferential orientation on the nanoparticle surface and throughout the supracrystal. Furthermore, we retrieve the dynamics of the supracrystal upon excitation with light and show that the positional disorder is induced by light pulses, while its overall homogeneity is surprisingly found to transiently increase. This new technique will enable the systematic investigation of the static and dynamical structural properties of nanoassembled materials containing light elements, relevant for several applications including signal processing and biology

Effects of Dietary Supplementation with Honeybee Pollen and Its Supercritical Fluid Extract on Immune Response and Fillet’s Quality of Farmed Gilthead Seabream (Sparus aurata)

The awareness of the correlation between administered diet, fish health and products’ quality has led to the increase in the research for innovative and functional feed ingredients. Herein, a plant-derived product rich in bioactive compounds, such as honeybee pollen (HBP), was includ-ed as raw (HBP) and as Supercritical Fluid Extracted (SFE) pollen (HBP_SFE) in the diet for gilt-head seabream (Sparus aurata). The experiment was carried out on 90 fish with an average body weight of 294.7 ± 12.8 g, divided into five groups, according to the administration of five diets for 30 days: control diet (CTR); two diets containing HBP at 5% (P5) and at 10% (P10) level of in-clusion; two diets containing HBP_SFE, at 0.5% (E0.5) and at 1% (E1) level of inclusion. Their ef-fects were evaluated on 60 specimens (336.2 ± 11.4 g average final body weight) considering the fish growth, the expression of some hepatic genes involved in the inflammatory response (il-1β, il-6 and il-8) through quantitative real-time PCR, and physico-chemical characterization (namely color, texture, water holding capacity, fatty acid profile and lipid peroxidation) of the fish fillets monitored at the beginning (day 0) and after 110 days of storage at −20 °C. The results obtained showed that the treatment with diet E1 determined the up-regulation of il-1β, il-6, and il-8 (p < 0.05); however, this supplementation did not significantly contribute to limiting the oxidative stress. Nevertheless, no detrimental effect on color and the other physical characteristics was observed. These results suggest that a low level of HBP_SFE could be potentially utilized in aq-uaculture as an immunostimulant more than an antioxidant, but further investigation is neces-sary

Femtosecond diffractive imaging of structures, charge and spin textures

The study of the dynamical evolution of a system, e.g. a chemical reaction or a phase transition, has become nowadays a subject of growing scientific interest. The direct observation of the steps and the structural changes through which chemical reactions and phase transitions occur requires the study of out-of-equilibrium intermediate states, with a typical time scale of femtoseconds (10─15s) and with high spatial resolution (10─10m), for molecules as well as for complex biological samples and for condensed matter systems. In this frame, Ultrafast Electron Diffraction (UED) allows for the observation of changes in the response function of different systems through phase transitions and chemical reactions, with atomic resolution, at the femtosecond (fs) time scale. In this thesis the implementation of a flexible UED set-up capable of working in both transmission and RHEED geometries with 30 keV electrons is described; the experiment is characterized by 300 fs time-resolution for bunches containing up to 105 electrons at 20 kHz, and constitutes the first demonstration of far-field and small-angle diffraction (from few Å to a few tens of nm spatial resolution) with electrons in a single diffractometer. The transverse coherence of the probing electrons can be tuned at the cost of brightness, enabling the observation of the speckle pattern originating from the constructive and destructive interference of the scattered waves from a sample. Diffractive Imaging is carried out to study complex ordering/disordering phenomena in structure, charge and spin textures, with time resolution. The investigation of the dynamics of a supracrystal of alkanethiol-coated gold nanoparticles is reported, and its photo-induced thermal disorder is reconstructed in a real-space movie alongside with an ordering transition of the organic ligands in the picosecond (ps) time scale, by means of UED. The same principles developed for the analysis of the gold nanoparticles diffraction patterns, based on Angular Cross-Correlation and Angular Normalized Intensity Analysis, are applied to the speckle pattern from spin textures detected in Lorentz microscopy. With this aim, magnetic field-dependent diffractive imaging of spin textures in the Dzyaloshinkii-Moriya chiral insulator Cu2OSeO3 is carried out with cryo- Lorentz TEM. Following a similar approach, ultrafast diffractive imaging on the charge density modulation in the Charge Density Waves system 1T-TaS2 is demonstrated. Finally, the main conclusions are summarized and the potential for extending the applicability of the UED system to the regime of ultrafast coherent diffractive imaging and inline holography using 30 keV electrons on a table-top is described

Design and implementation of a flexible beamline for fs electron diffraction experiments

Ultrafast Electron Diffraction (UED) has been widely used to investigate the structural dynamics of molecules and materials. Femtosecond (fs) electron bunches are used to obtain diffraction images of a specimen upon photo-excitation by a temporally delayed light pulse. The high cross-section of electrons makes it a very flexible tool for the study of light elements, monolayers and surfaces; at the same time, electrons can travel down to few nanometers (nm) and structural information from the bulk can also be retrieved. In this article, we discuss the design and implementation of a flexible beamline for fs electron diffraction experiments in transmission or reflection geometry. By the use of a radiofrequency (RF) compression cavity synchronized to our laser system, in combination with a set of electron optics, we demonstrate that we can control the beam properties in terms of charge per pulse, transverse spot-size on the sample and temporal duration of the bunches. The characterization of the beam is performed via a light-electrons cross-correlation experiment and we demonstrate an overall temporal resolution around 300 fs for bunches containing up to 10(5) electrons at a repetition rate of 20 kHz. (c) 2012 Elsevier B.V. All rights reserved

Effect of the housing system (free-range vs. open air cages) on growth performance, carcass and meat quality and antioxidant capacity of rabbits

Growth performances and meat quality of free-range or cage raised rabbits were compared in 36 male animals. Rabbits were raised in free-range areas (2000 cm2/head) or in open-air cages (800 cm2/head) from weaning to 99 days old. Daily weight gain and final live weight were higher (P < 0.05) for the rabbits raised in cages which presented a more favourable feed conversion ratio (P < 0.05) than in the free-range group. The average feed intake, liver and empty gastro-intestinal tract weights were higher (P < 0.05) in the free-range group, while the interscapular fat percentage was higher (P < 0.05) in the caged rabbits. Loins of free-range rabbits had higher amount of PUFA n-6 in neutral lipids (P < 0.05) whereas their polar lipids were richer in PUFA n-6 and n-3 than in those of the cage group. Muscular fat of free-raised rabbits was found to be less susceptible to be oxidized, having a higher antioxidant capacity than the caged group

Development of Approaches and Metrics to Measure the Impact and Improve the Clinical Outcomes of Patients With Frailty in the Era of COVID-19. The COMETA Italian Protocol

The outbreak of the coronavirus 2 disease 2019 (COVID-19) puts an enormous burden on healthcare systems worldwide. This may worsen outcomes in patients with severe chronic diseases such as cancer, autoimmune diseases, and immune deficiencies. In this critical situation, only a few available data exist, which do not allow us to provide practical guides for the treatment of oncological or immunocompromised patients. Therefore, a further step forward is needed, addressing the specific needs and demands of frail patients in the pandemic era. Here we aim to present a protocol of a study approved by an ethical committee named "CO.M.E.TA". CO.M.E.TA protocol is a network project involving six Italian institutions and its goals are: i) to measure and compare the impact of the pandemic on the access of cancer and immunocompromised patients to therapies in three Italian regions; ii) to assess how reorganizational measures put in place in these different institutions have impacted specific metrics of performance; iii) to establish a COVID-19 Biobank of biological samples from SARS-CoV-2 infected patients to be used to study immunological alterations in patients with immune frailty