A very long baseline interferometry sky survey

A systematic very long baseline interferometry (VLBI) sky survey, undertaken to find a suitable set of compact celestial radio sources from which a more complete VLBI reference frame can be constructed, discussed. The survey was conducted by searching known celestial radio sources for compact components by means of VLBI observations. Baseline lengths were about 7 x 10 to the 7th power RF wavelengths (lambda = 13.1 cm), so the spatial wavelengths being sampled by the interferometer were generally on the order of a few milliarcseconds. Hence, the radio sources detected have a measurable portion of their total flux density contained in components that are no more than a few milliarcseconds in angular extent. Existing information of radio sources were used as clues to source size

Improving our knowledge in PD-L1 testing in lung cancer: the archival sample is 'promoted'!

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Design and optimization of a laser-PIXE beamline for material science applications

Multi-MeV proton beams can be generated by irradiating thin solid foils with ultra-intense (>10^18 W/cm^2) short laser pulses. Several of their characteristics, such as high bunch charge and short pulse duration, make them a complementary alternative to conventional radio frequency-based accelerators. A potential material science application is the chemical analysis of cultural heritage (CH) artifacts. The complete chemistry of the bulk material (ceramics, metals) can be retrieved through sophisticated nuclear techniques such as particle-induced X-ray emission (PIXE). Recently, the use of laser-generated proton beams was introduced as diagnostics in material science (laser-PIXE or laser-driven PIXE): Coupling laser-generated proton sources to conventional beam steering devices successfully enhances the capture and transport of the laser-accelerated beam. This leads to a reduction of the high divergence and broad energy spread at the source. The design of our hybrid beamline is composed of an energy selector, followed by permanent quadrupole magnets aiming for better control and manipulation of the final proton beam parameters. This allows tailoring both, mean proton energy and spot sizes, yet keeping the system compact. We performed a theoretical study optimizing a beamline for laser-PIXE applications. Our design enables monochromatizing the beam and shaping its final spot size. We obtain spot sizes ranging between a fraction of mm up to cm scale at a fraction of nC proton charge per shot. These results pave the way for a versatile and tunable laserPIXE at a multi-Hz repetition rate using modern commercially available laser systems

Transient increases in intracellular calcium and reactive oxygen species levels in TCam-2 cells exposed to microgravity

The effects of microgravity on functions of the human body are well described, including alterations in the male and female reproductive systems. In the present study, TCam-2 cells, which are considered a good model of mitotically active male germ cells, were used to investigate intracellular signalling and cell metabolism during exposure to simulated microgravity, a condition that affects cell shape and cytoskeletal architecture. After a 24 hour exposure to simulated microgravity, TCam-2 cells showed 1) a decreased proliferation rate and a delay in cell cycle progression, 2) increased anaerobic metabolism accompanied by increased levels of intracellular Ca(2+), reactive oxygen species and superoxide anion and modifications in mitochondrial morphology. Interestingly, all these events were transient and were no longer evident after 48 hours of exposure. The presence of antioxidants prevented not only the effects described above but also the modifications in cytoskeletal architecture and the activation of the autophagy process induced by simulated microgravity. In conclusion, in the TCam-2 cell model, simulated microgravity activated the oxidative machinery, triggering transient macroscopic cell events, such as a reduction in the proliferation rate, changes in cytoskeleton-driven shape and autophagy activation

Laser-Generated Proton Beams for High-Precision Ultra-Fast Crystal Synthesis

We present a method for the synthesis of micro-crystals and micro-structured surfaces using laseraccelerated protons. In this method, a solid surface material having a low melting temperature is irradiated with very-short laser-generated protons, provoking in the ablation process thermodynamic conditions that are between the boiling and the critical point. The intense and very quick proton energy deposition (in the ns range) induces an explosive boiling and produces microcrystals that nucleate in a plasma plume composed by ions and atoms detached from the laser-irradiated surface. The synthesized particles in the plasma plume are then deposited onto a cold neighboring, non-irradiated, solid secondary surface. We experimentally verify the synthesizing methods by depositing low-meltingmaterial microcrystals - such as gold - onto nearby silver surfaces and modeling the proton/matter interaction via a Monte Carlo code, confrming that we are in the above described thermodynamic conditions. Morphological and crystallinity measurements indicate the formation of gold octahedral crystals with dimensions around 1.2 μm, uniformly distributed onto a silver surface with dimensions in the tens of mm2. This laser-accelerated particle based synthesis method paves the way for the development of new material synthesis using ultrashort laser-accelerated particle beams

Modeling, assessment, and design of porous cells based on schwartz primitive surface for bone scaffolds

The design of bone scafolds for tissue regeneration is a topic of great interest, which involves diferent issues related to geometry of architectures, mechanical behavior, and biological requirements, whose optimal combination determines the success of an implant. Additive manufacturing (AM) has widened the capability to produce structures with complex geometries, which should potentially satisfy the diferent requirements. These architectures can be obtained by means of refned methods and have to be assessed in terms of geometrical and mechanical properties. In this paper a triply periodic minimal surface (TPMS), the Schwarz's Primitive surface (P-surface), has been considered as scafold unit cell and conveniently parameterized in order to investigate the efect of modulation of analytical parameters on the P-cell geometry and on its properties. Several are the cell properties, which can afect the scafold performance. Due to the important biofunctional role that the surface curvature plays in mechanisms of cellular proliferation and diferentiation, in this paper, in addition to properties considering the cell geometry in its whole (such as volume fraction or pore size), new properties were proposed. Tese properties involve, particularly, the evaluation of local geometrical-diferential properties of the P-surface. Te results of this P-cell comprehensive characterization are very useful for the design of customized bone scafolds able to satisfy both biological and mechanical requirements. A numerical structural evaluation, by means of fnite element method (FEM), was performed in order to assess the stifness of solid P-cells as a function of the changes of the analytical parameters of outer surface and the thickness of cell. Finally, the relationship between stifness and porosity has been analyzed, given the relevance that this property has for bone scafolds design

Towards the automation of product geometric verification: An overview

The paper aims at providing an overview on the current automation level of geometric verification process with reference to some aspects that can be considered crucial to achieve a greater efficiency, accuracy and repeatability of the inspection process. Although we are still far from making this process completely automatic, several researches were made in recent years to support and speed up the geometric error evaluation and to make it less human-intensive. The paper, in particular, surveys: (1) models of specification developed for an integrated approach to tolerancing; (2) state of the art of Computer-Aided Inspection Planning (CAIP); (3) research efforts recently made for limiting or eliminating the human contribution during the data processing aimed at geometric error evaluation. Possible future perspectives of the research on the automation of geometric verification process are finally described

An investigation on skeleton-based top-down modelling approaches of complex industrial product

In industry, today's approach to assembly design is still largely based on a bottom-up approach which, in contrast with the most advanced top-down techniques, is unfit to deal with very large and complex products. The reason for this lies in the high number of relationships to be established between parts and in the lack of a high-level control of the assembly design. This makes the management of design changes a labor-intensive process and the capture of design intent difficult to achieve. The paper, referring to the most advanced research fields of Concurrent Engineering and Knowledge-Based Engineering, focuses on a top-down modelling approach based on skeleton, which constitutes the most natural but still scarcely exploited way to attain a high reactivity to design modifications. Through the application of suitable methodologies, such as that one for a SKeLeton geometry-based Assembly Context Definition (SKL-ACD), the skeleton is also able to capture and codify assembly process engineering information since the early phases of the product development process. With the purpose of promoting the knowledge of these skeleton-based modelling techniques, that have a great relevance for training professional, technical and mechanical engineers, this paper implements the SKL-ACD methodology to an industrial case study in order to identify, with a unique and repeatable workflow, the reference geometrical entities and the mutual relationships to embed into the product skeleton. The skeleton types and the related fields of use are also described, placing particular emphasis on problems or shortcomings still not resolved, especially in consideration of the need to assist the designer in defining the impact of a parameter on assembly modification and in avoiding loops while defining formulas. A new tool, in the form of a multilayer graph, is finally proposed that is able to display and differentiate clearly the formulas, the design parameters and the impact of their modification on skeleton entities and members of the assembly