The process of data formation for the Spectrometer/Telescope for Imaging X-rays (STIX) in Solar Orbiter

The Spectrometer/Telescope for Imaging X-rays (STIX) is a hard X-ray imaging spectroscopy device to be mounted in the Solar Orbiter cluster with the aim of providing images and spectra of solar flaring regions at different photon energies in the range from a few keV to around 150 keV. The imaging modality of this telescope is based on the Moire pattern concept and utilizes 30 sub-collimators, each one containing a pair of co-axial grids. This paper applies Fourier analysis to provide the first rigorous description of the data formation process in STIX. Specifically, we show that, under first harmonic approximation, the integrated counts measured by STIX sub-collimators can be interpreted as specific spatial Fourier components of the incoming photon flux, named visibilities. Fourier analysis also allows the quantitative assessment of the reliability of such interpretation. The description of STIX data in terms of visibilities has a notable impact on the image reconstruction process, since it fosters the application of Fourier-based imaging algorithms.Comment: submitted to SIAM Journal on Imaging Science

Rolly Protein (ROLP)-Epb4.1/3: A Potential Protein-Protein Interaction Relevant for the Maintenance of Cell Adhesion

We recently described Rolly Protein (ROLP), a small protein synthesized by substrate-adherent cells in a broad range of tissues. In a first set of experiments performed taking advantage of bone forming tibial cartilage as an experimental model we showed that ROLP transcription is associated to cells in an active proliferation state, whereas its downregulation is observed when cell proliferation decreases. Taking advantage of siRNA technology we also documented the expression modulation of some apoptosis-related genes in ROLP-silenced cells. In this work we search for the possible molecular interactors of ROLP by using both the antibody array approach as well as the co-immunoprecipitation approach. Results suggest the occurrence of an interaction of ROLP with Erythrocyte membrane Protein Band 4.1/3 (Epb4.1/3), an oncosuppressor downregulated in tumor development and in metastatic tissues; in addition we report experimental results that keep in line also with a potential interaction of ROLP with other PDZ-containing proteins. We also present experimental evidences supporting a role played by ROLP in cell adhesion thus supporting the existence of a biologically relevant link between ROLP and Epb4.1/3. We here suggest that ROLP might exert its biological role cooperating with Epb4.1/3, a protein that is involved in biological pathways that are often inhibited in tumor metastasis. Given the role of Epb4.1/3 in contrasting cancerogenesis we think that its cooperation with ROLP might be relevant in cancer studies and deserves further investigation

RNA polymerase III drives alternative splicing of the potassium channel–interacting protein contributing to brain complexity and neurodegeneration

An RNA polymerase III–transcribed noncoding RNA promotes alternative splicing of KCNIP4, altering amyloid precursor protein processing and contributing to neurodegeneration

NDM29, a RNA polymerase III-dependent non coding RNA, promotes amyloidogenic processing of APP and amyloid β secretion

open8noNeuroblastoma Differentiation Marker 29 (NDM29) is a RNA polymerase (pol) III-transcribed non-coding (nc) RNA whose synthesis drives neuroblastoma (NB) cell differentiation to a nonmalignant neuron-like phenotype. Since in this process a complex pattern of molecular changes is associated to plasma membrane protein repertoire we hypothesized that the expression of NDM29 might influence also key players of neurodegenerative pathways. In this work we show that the NDM29-dependent cell maturation induces amyloid precursor protein (APP) synthesis, leading to the increase of amyloid β peptide (Aβ) secretion and the concomitant increment of Aβ x-42/Aβ x-40 ratio. We also demonstrate that the expression of NDM29 RNA, and the consequent increase of Aβ formation, can be promoted by inflammatory stimuli (and repressed by anti-inflammatory drugs). Moreover, NDM29 expression was detected in normal human brains although an abnormal increased synthesis of this ncRNA is induced in patients affected by neurodegenerative diseases. Therefore, the complex of events triggered by NDM29 expression induces a condition that favors the formation of Aβ peptides in the extracellular space, as it may occur in Alzheimer's Disease (AD). In addition, these data unexpectedly show that a pol III-dependent small RNA can act as key regulator of brain physiology and/or pathology suggesting that a better knowledge of this portion of the human transcriptome might provide hints for neurodegeneration studies.openMassone S; Ciarlo E; Vella S; Nizzari M; Florio T; Russo C; Cancedda R; Pagano A.Massone, Sara; Ciarlo, E; Vella, SERENA LUISA; Nizzari, Mario; Florio, Tullio; Russo, C; Cancedda, Ranieri; Pagano, Ald

In ritonavir-treated monocytes normalization of proteasome activity by vitamin E is independent of free radical scavenging

The treatment of THP‐1 monocytes by ritonavir inhibits proteasome activity and increases CD36 scavenger receptor expression, events that are normalized by α‐tocopherol co‐treatment. Since α‐tocopherol can reduce oxidative stress it appeared possible that normalization occurred by scavenging free radicals produced by proteasome inhibition. Alternatively, α‐tocopherol may interfere with the ability of ritonavir to inhibit the proteasome. Indeed, in THP‐1 monocytes, cellular proteasome inhibition by ritonavir or ALLN is associated with the production of oxidative stress. Both, ritonavir and ALLN produced similar amounts of oxidative stress; however, normalization of oxidative stress by α‐tocopherol occurred only after inhibition by ritonavir and not by ALLN. Similar to that, α‐tocopherol could normalize the reduced formation of 3‐nitrotyrosine‐modified proteins only after ritonavir treatment. In the absence of any proteasome inhibitor, intrinsic cellular proteasome activity was not modulated by α‐, β‐, and γ‐tocopherols; however, δ‐tocopherol, α‐tocotrienol, and α‐tocopheryl phosphate could significantly inhibit cellular proteasome activity and increased the level of p27Kip1 and p53. Since oxidative stress was only reduced by α‐tocopherol after proteasome inhibition by ritonavir and not by ALLN, it is concluded that in this experimental system, α‐tocopherol acts not as an antioxidant but interferes with proteasome inhibition by ritonavir

Imparare dall'arte: \ue8 possibile un incontro tra i bambini e gli artisti?

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Attraverso l\u2019arte. Percorsi filosofici ed esperienze educative

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Forward fitting STIX visibilities

Aims. We seek to determine to what extent the problem of forward fitting visibilities measured by the Spectrometer/Telescope Imaging X-rays (STIX) on board Solar Orbiter becomes more challenging with respect to the same problem in the case of previous hard X-ray solar imaging missions. In addition, we aim to identify an effective optimization scheme for parametric imaging for STIX. Methods. This paper introduces a global search optimization for forward-fitting STIX visibilities and compares its effectiveness with respect to the standard simplex-based optimization used so far for the analysis of visibilities measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We made this comparison by considering experimental visibilities measured by both RHESSI and STIX, as weel as synthetic visibilities generated by accounting for the STIX signal formation model. Results. We found that among the three global search algorithms for parametric imaging, particle swarm optimization (PSO) exhibits the best performances in terms of both stability and computational effectiveness. This method is as reliable as the simplex method in the case of RHESSI visibilities. However, PSO is significantly more robust when applied to STIX simulated and experimental visibilities. Conclusions. A standard optimization based on local search of minima is not effective enough for forward-fitting the few visibilities sampled by STIX in the spatial frequency plane. Therefore, more sophisticated optimization schemes based on global search must be introduced for parametric imaging in the case of the Solar Orbiter X-ray telescope. The forward-fitting routine based on PSO proved to be significantly robust and reliable, and it could be considered as an effective candidate tool for parametric imaging in the STIX context