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

Considerazioni etiche sulla procreazione medicalmente assistita

Desde que las técnicas de reproducción asistida (TRA) han sido introducidas en la práctica clínica, sus aplicaciones se han ampliado mucho, abriendo una caja de Pandora a los dilemas éticos y promoviendo el debate. Lo que en principio era únicamente una solución médica a pacientes con las trompas de Falopio no permeables, actualmente se presenta como una opción terapéutica para una amplia variedad de situaciones que en algunos casos, han perdido su indicación médica (como en la elección de sexo por razones sociales), o se han transformado en una medida preventiva (como en el diagnóstico genético preimplantacional para enfermedades de aparición tardía). A pesar de que son muchos los aspectos controvertidos de las TRA que se pueden tratar, desde la subrogación uterina hasta la edad materna avanzada, en este artículo nos centraremos sobretodo en el debate ético provocado de la aplicación del diagnostico genético preimplantacional para la determinación de los antígenos del HLA para el transplante de células hematopoyéticas a terceros y en las enfermedades de aparición tardía

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

Anti-carbamylated protein antibodies as a new biomarker of erosive joint damage in systemic lupus erythematosus

Background: The application of more sensitive imaging techniques, such as ultrasonography (US), changed the concept of non-erosive arthritis in systemic lupus erythematosus (SLE), underlining the need for biomarkers to identify patients developing the erosive phenotype. Anti-citrullinated peptide antibodies (ACPA), associated with erosions in inflammatory arthritis, have been identified in about 50% of patients with SLE with erosive arthritis. More recently, anti-carbamylated proteins antibodies (anti-CarP) have been associated with erosive damage in rheumatoid arthritis. We aimed to assess the association between anti-CarP and erosive damage in a large SLE cohort with joint involvement. Methods: We evaluated 152 patients (male/female patients 11/141; median age 46years, IQR 16; median disease duration 108months, IQR 168). All patients underwent blood draw to detect rheumatoid factor (RF) and ACPA (commercial enzyme-linked immunosorbent assay (ELISA) kit), and anti-CarP ("home-made" ELISA, cutoff 340aU/mL). The bone surfaces of the metacarpophalangeal and proximal interphalangeal joints were assessed by US: the presence of erosions was registered as a dichotomous value (0/1), obtaining a total score (0-20). Results: The prevalence of anti-CarP was 28.3%, similar to RF (27.6%) and significantly higher than ACPA (11.2%, p=0.003). Erosive arthritis was identified in 25.6% of patients: this phenotype was significantly associated with anti-CarP (p=0.004). Significant correlation between anti-CarP titer and US erosive score was observed (r=0.2, p=0.01). Conclusions: Significant association was identified between anti-CarP and erosive damage in SLE-related arthritis, in terms of frequency and severity, suggesting that these antibodies can represent a biomarker of severity in patients with SLE with joint involvement

Prevalence, sensitivity and specificity of antibodies against carbamylated proteins in a monocentric cohort of patients with rheumatoid arthritis and other autoimmune rheumatic diseases

Antibodies against carbamylated proteins (anti-CarP) have been recently identified in the sera of patients with rheumatoid arthritis (RA). The objective of the study was to evaluate the prevalence, sensitivity and specificity of anti-CarP compared to anti-citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF), replicating the existing data in a large cohort of Italian patients with RA and extending the evaluation to other autoimmune rheumatic diseases (AIRDs)

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

A pilot study on brain plasticity of functional connectivity modulated by cognitive training in mild Alzheimer's disease and mild cognitive impairment

Alzheimer's disease (AD) alters the functional connectivity of the default mode network (DMN) but also the topological properties of the functional connectome. Cognitive training (CT) is a tool to slow down AD progression and is likely to impact on functional connectivity. In this pilot study, we aimed at investigating brain functional changes after a period of CT and active control (AC) in a group of 26 subjects with mild AD (mAD), 26 with amnestic mild cognitive impairment (aMCI), and a control group of 29 healthy elderly (HE) people. They all underwent a CT and AC in a counterbalanced order following a crossover design. Resting-state functional MRI and neuropsychological testing were acquired before and after each period. We tested post-CT and post-AC changes of cognitive abilities, of the functional connectivity of the DMN, and of topological network properties derived from graph theory and network-based statistics. Only CT produced functional changes, increasing the functional connectivity of the posterior DMN in all three groups. mAD also showed functional changes in the medial temporal lobe and topological changes in the anterior cingulum, whereas aMCI showed more widespread topological changes involving the frontal lobes, the cerebellum and the thalamus. Our results suggest specific functional connectivity changes after CT for aMCI and mAD

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