Ordered arrays of low-dimensional Au and Pd : synthesis and in situ observations

Electrodeposition of metals in templates of nano-porous anodic aluminum oxide (NP-AAO) is a versatile way of fabricating ordered arrays of metal nanowires. Thanks to the self-arranged long-range hexagonal order of the pores, electrodeposition in NP-AAO is an easily scalable bottom-up synthesis route and an attractive alternative to traditional top-down fabrication methods such as electron beam lithography.Since NP-AAO is a non-conductive medium and since it is potentially soluble in non-neutral pH solutions, the electrodeposition of metals in NP-AAO represents a challenge. These aspects are discussed in this thesis, aiming to establish a reproducible and reliable protocol for the electrodeposition of Au and Pd.By using ex situ x-ray diffraction, it has been found that the growth of Au and Pd in the confined environment of nano-pores leads (i) to a deformation of the crystalline structure, as the lattice constant is smaller along the nanowire radius and larger along the nanowire axis, compared to the bulk lattice constant, and (ii) to a crystallite size anisotropy: it is limited by the pore radius in the horizontal direction and it is larger in the direction of growth.The electrochemical growth of Au and Pd nanowires was followed in situ by x-ray scattering methods. In the case of Au nanowires, the time-resolved measurements revealed that the anisotropy of the lattice parameter progresses as a function of time, which suggests that the strain state of the nanomaterials can be artificially selected. This findings might be beneficial in the strain-engineering of Au nanoelectrode arrays for electrocatalysis. In the case of Pd nanowires, the measurements revealed strain variations, as well as phase transitions attributed to the existence of alpha- and beta-phase Pd hydride in the NP-AAO template, due to the exposure of Pd to hydrogen evolved at the working electrode. These findings suggest that Pd in NP-AAO has potential applications in the design of hydrogen storage devices

Modulated linear dynamics of nanobeams accounting for higher gradient effects

We present some numerical results for the linear dynamics of nanobeams modulated by an axial force, basing on a recent proposal of literature that encompasses both the standard nonlocal elasticity, according to Eringen, and second-order strain elasticity. Three different possibilities for the elastic potential energy provide different responses that highlight the contributions of nonlocality and strain gradient, plus their combination. An axial force affects the linear stationary dynamics of such nanobeams, inducing suitable variation of the natural angular frequencies for benchmark cases, until static buckling occurs when the natural angular frequency vanishes. Effects of the various elastic potentials on this modulation are investigated and thoroughly commented

Quantitative powder diffraction using a (2+3) surface diffractometer and an area detector

X-ray diffractometers primarily designed for surface x-ray diffraction are often used to measure the diffraction from powders, textured materials, and fiber-texture samples in so-called $2\theta$ scans. Unlike high-energy powder diffraction only a fraction of the powder rings is typically measured and the data consists of many detector images across the $2\theta$ range. Such diffractometers typically scan in directions not possible on a conventional lab-diffractometer, which gives enhanced control of the scattering vector relative to the sample orientation. There are, however, very few examples where the measured intensity is directly used, such as for profile/Rietveld refinement, as is common with other powder diffraction data. Although the underlying physics is known, converting the data is time-consuming and the appropriate corrections are dispersed across several publications, often not with powder diffraction in mind. In this paper we present the angle calculations and correction factors required to calculate meaningful intensities for $2\theta$ scans with a (2+3)-type diffractometer and an area detector. We also discuss some of the limitations with respect to texture, refraction, and instrumental resolution, and what kind of information one can hope to obtain.Comment: Research paper, 15 pages, 12 figures, 3 table

Anisotropic strain variations during the confined growth of Au nanowires

The electrochemical growth of Au nanowires in a template of nano-porous anodic aluminum oxide was investigated in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and 2-dimensional surface optical reflectance (2D-SOR). The XRF and the overall intensity of the GTWAXS patterns as a function of time were used to monitor the progress of the electrodeposition. Furthermore, we extracted powder diffraction patterns in the direction of growth and in the direction of confinement to follow the evolution of the direction-dependent strain. Quite rapidly after the beginning of the electrodeposition, the strain became tensile in the vertical direction and compressive in the horizontal direction, which showed that the lattice deformation of the nanostructures can be artificially varied by an appropriate choice of the deposition time. By alternating sequences of electrodeposition to sequences of rest, we observed fluctuations of the lattice parameter in the direction of growth, attributed to stress caused by electromigration.. Furthermore, the porous domain size calculated from the GTSAXS patterns was used to monitor how homogeneously the pores were filled.Comment: Short communication manuscript. Four figure

In situ\textit{In situ} hydride breathing during the template-assisted electrodeposition of Pd nanowires

We investigated the structural evolution of electrochemically fabricated Pd nanowires $\textit{in situ}$ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and 2-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that $\beta$-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from $\beta$- to $\alpha$-phase Pd hydride. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.Comment: 17 pages, 11 figures, 4 appendice

Neutralizing antibodies to Omicron after the fourth SARS-CoV-2 mRNA vaccine dose in immunocompromised patients highlight the need of additional boosters

IntroductionImmunocompromised patients have been shown to have an impaired immune response to COVID-19 vaccines.MethodsHere we compared the B-cell, T-cell and neutralizing antibody response to WT and Omicron BA.2 SARS-CoV-2 virus after the fourth dose of mRNA COVID-19 vaccines in patients with hematological malignancies (HM, n=71), solid tumors (ST, n=39) and immune-rheumatological (IR, n=25) diseases. The humoral and T-cell responses to SARS-CoV-2 vaccination were analyzed by quantifying the anti-RBD antibodies, their neutralization activity and the IFN-γ released after spike specific stimulation.ResultsWe show that the T-cell response is similarly boosted by the fourth dose across the different subgroups, while the antibody response is improved only in patients not receiving B-cell targeted therapies, independent on the pathology. However, 9% of patients with anti-RBD antibodies did not have neutralizing antibodies to either virus variants, while an additional 5.7% did not have neutralizing antibodies to Omicron BA.2, making these patients particularly vulnerable to SARS-CoV-2 infection. The increment of neutralizing antibodies was very similar towards Omicron BA.2 and WT virus after the third or fourth dose of vaccine, suggesting that there is no preferential skewing towards either virus variant with the booster dose. The only limited step is the amount of antibodies that are elicited after vaccination, thus increasing the probability of developing neutralizing antibodies to both variants of virus.DiscussionThese data support the recommendation of additional booster doses in frail patients to enhance the development of a B-cell response directed against Omicron and/or to enhance the T-cell response in patients treated with anti-CD20

17beta-estradiol inhibits apoptosis in MCF-7 cells, inducing bcl-2 expression via two estrogen-responsive elements present in the coding sequence.

IF = 8.8

IMPACT OF AN OPTIMIZED POWER TURBINE DISKS CAVITY ON GEARED OPEN ROTOR PERFORMANCE - A MULTIDISCIPLINARY APPROACH IN THE PRELIMINARY DESIGN

A constantly growing number of studies have been oriented to Green Aircraft and Green Engine concepts during last years in order to reduce pollutants and carbon-dioxide production by 2020. Ultra high by-pass engines are recently getting the highest interest by academia, research centers and industries. Among the most recent research activities, many studies are focused on geared architectures, the Geared Turbofan (GTF) and the Geared Open Rotor (GOR). The GOR architecture seems to be the most promising radical architecture for short-range aircraft as climbing and landing phases interest the major part of the whole mission. Our work takes place in the most recent research activities regarding a GOR-like engine, and can fit its preliminary design phase. A multidisciplinary modular simulation environment was developed to let researchers the chance to directly relate the considered disciplines. Introductory trade-off studies were carried on to effectively show GOR capabilities amongst the most innovative engines. A reference military core engine was used for the considered GOR engine, as previously done by General Electric for its original open rotor engine. GOR performance were predicted on-design and off-design, by relating to corporate inputs. Optimization studies of the GOR high-speed power turbine disks cavity were performed to reduce disks weight and cooling flows, complying with several engineering constraints provided by the industry. Finally the optimization outcomes were linked to the performance code to capture their impact on the overall engine efficiency and specific fuel consumption. Results show that it is possible to get an improvement in the specific fuel consumption by minimizing the required cooling flows of the GOR power turbine. Moreover, for a required thrust level, engine weight may be reduced