Performance evaluation of several well-known and new scintillators for MeV X-ray imaging

International audienceDigital X-ray imaging systems for MeV range photon beams are based on a combination of a scintillator screen and either a camera or an amorphous silicon array. To limit dose rate on electronics and enhance imaging device lifetime, the scintillator screen is mirror-coupled to the camera. Performances of such devices are a compromise between exposure time and spatial resolution. These technical characteristics are especially scintillator dependent. In this paper, we present a performance evaluation of six different scintillators with a 9 MeV Bremsstrahlung X-ray source. The tested scintillators are composed of one micro-structured CsI(Tl) scintillator, two phosphor (GOS) screens and three transparent scintillators. These scintillators present a wide range of density, thickness and conversion efficiency. Each scintillator's performance is assessed based on the combination of light output (ADU number) and modulation transfer function (spatial resolution) obtained. The results are helpful to guide design and engineering of high energy imaging devices adapted to specific requirements

Magnetically responsive tropoelastin hydrogel as a platform for soft tissue regeneration applications

Publicado em "European Cells and Materials. ISSN 1473-2262. Vol. 33, Suppl. 2, 2017 (0006)"The natural polymer tropoelastin is a structural protein of ECM of tissues requiring elasticity as part of their function, including ligaments and tendons. Tropoelastin has an innate capacity of self-assembly into high-order structures, and together with elastic resilience, structural stability and bioactivity bring forth pleasant singularities in adopting it as a building block to fabricate hydrogels. Moreover, easy tailoring of properties can be attained via incorporation of specific components into the polymeric network, including magnetic nanoparticles (MNPs), which are beneficial for on-demand therapies. Thus, the main goal of this work consisted in developing a magnetically responsive tropoelastin (MagTro) hydrogel as a platform to study the response of tendon cells to a mechanical stimulus induced by application of an external magnetic field (EMF). For this purpose, to first produce hydrogels, a solution of recombinant human tropoelastin was first freeze-dried overnight inside a mould and then chemically cross-linked inside an open desiccator via vapour glutaraldehyde. Thereafter, MagTro hydrogels were obtained through in situ precipitation of MNPs by immersing tropoelastin hydrogels in FeCl2 and FeCl3 solution overnight and secondly by soaking them in NaOH. Hydrogels were then analysed morphologically by Scanning Electron Microscopy (SEM and Cryo-SEM). Enzyme-triggered degradation was studied after 72h at 37oC in a human neutrophil elastase solution. Hydrogels exhibited a quick magnetic responsiveness to an EMF (Fig.1). Interestingly, MagTro hydrogels exhibited smaller pores as observed by Cryo-SEM. This feature can be tuned according to different soft tissue requirements by controlling different parameters of the fabrication process. Additionally, the release of tropoelastin into solution decreased, which suggests the formation of a surface coating of MNPs on tropoelastin network, protecting the hydrogel from a faster degradation. Preliminary results also indicate that cultured cells are viable and spread at the surface of the hydrogel. The application of an EMF to cell-laden MagTro hydrogels will be further investigated. Overall, the streamlined fabrication of MagTro hydrogels was successfully attained and the hydrogel formulation represents a promising potential platform for soft tissue regeneration.The authors acknowledge to BEAM-Master Joint Mobility Project an EU Australian cooperation in Biomedical Engineering Grant Agreement, 2014-1843/001 001-CPT EU-ICI-ECP and to FCT–Fundação para a Ciência e a Tecnologia in the framework of FCT-POPH-FSE, RC-A PhD grant SFRH/BD/96593/2013 and MEG grant IF/00685/2012.info:eu-repo/semantics/publishedVersio

Effects of Nitrogen in Soybean Seed Quality Definition During Seed-Filling Period

During the seed filling period (SFP), parallel to the seed changes, translocation of assimilates and nutrients takes place from different plant organs to the seed in order to provide sufficient supply for the seed storage components (i.e., starch, oil, and protein) that ultimately will determine the seed quality. There are two processes that define the final seed weight in any crop: 1) the amount of dry mass deposited per unit of time (rate) and 2) the duration of this process from beginning of seed formation to physiological maturity. As seed number is defined, any source limitation during the SFP can affect the final weight and quality of the seeds. This study aims to investigate if nitrogen (N) is limiting potential seed weight and, in consequence, final seed yield as well as the characterization of the deposition of seed components (i.e., oil and protein) that define soybean seed quality among different N conditions and genotypic background

Modelo agrícola e impacto socioambiental en la Argentina: monocultivo y agronegocios

Este trabajo está animado por el hecho de disentir con todas aquellas interpretaciones aferradas al paradigma epistemológico positivista, que niega el reconocimiento de la intencionalidad, la autoreflexividad, la creación y la pasión que acompañan a toda producción de conocimiento. En consonancia con ello, nos permitimos destacar la interdisciplinaridad de la propuesta, que conjuga nuestros avances en la investigación en el campo de las Ciencias Médicas, la Ecología y la Antropología Social, contemplando y fortaleciendo la necesidad de pensar en términos de la diversidad sociocultural que poseen las poblaciones afectadas por el modelo agrícola, en particular por la explotación sojera, así como la desigualdad estructural que las atraviesa y las condiciona. Las investigaciones se caracterizan por reconocer que lo que nos sucede y nos preocupa, respecto de nuestra sociedad y de la humanidad en su conjunto, puede y debe ser pensado superando la noción de un hombre estándar que no existe más que en la ficción (Foucault, 1966), la de un hombre en sentido genérico, superando al mismo tiempo la noción de pensamiento único.Asociación de Universidades Grupo Montevideo (AUGM

A platelet lysate antibacterial bioactive patch for tendon repair

Platelet lysate (PL) is a class of platelet-rich hemoderivatives produced by cryogenic disruption of platelet concentrates, originating a pool of supra-physiological concentrations of growth factors (GFs) that is being widely explored in the medical field, namely in sports medicine and orthopaedics. In this concern, patch augmentation strategies have been receiving increased attention as the basis for the development of novel biomaterials aiming at tendon regeneration. In the present work, we assessed PL- membranes as prospective bioinstructive patches under the hypothesis that tendon cells positively respond to PL-derived biochemical signals. For this purpose, PL membranes were fabricated as previously described by Babo et al1 and characterized in terms of degradation, PL-derived proteins and GF release profiles. Cell behaviour was studied in terms of metabolic activity and proliferation, as well as extracellular matrix (ECM) production by culturing human tendon-derived cells (hTDCs) up to 21 days. In addition, the potential of PL membranes as antibacterial surfaces for biomedical implants was evaluated against Staphylococcus aureus ATCC 29213 by determining the number of viable counts, as well as biofilm formation and distribution up to 72h, using PDMS films as controls. Overall, our results showed that PL membranes remained stable for up to 30 days in PBS. In addition, PL-derived proteins, as well as specific GFs like basic fibroblast growth factor (bFGF) and platelet derived growth factor (PDGF)-BB followed a typical controlled release profile, as described by Babo et al1. Regarding the biological performance, PL-membranes were able to control the proliferation of seeded hTDCs, as demonstrated by maintenance of DNA content over 21 days of culture, in comparison to the controls in standard culture plastic. This result strongly suggests that PL-membranes can avoid an extensive proliferative phase, which in vivo is responsible for the formation of scar tissue, a major concern during tendon healing. These cells were metabolically active over time in culture and deposited tendon-related ECM proteins, including collagen types 1 and 3 and tenascin-C. Additionally, PL- membranes exhibited a significantly reduced number of viable counts of S. aureus, together with diminished bacteria adherence after 24h of incubation. No biofilm formation was observed in comparison to PDMS controls. Altogether, our results demonstrate that these PL-membranes can modulate cellular activity in situ, acting as a reservoir of bioactive molecules derived from PL, which supports their application as bioinstructive and protective patches for tendon regeneration. Finally, exploring the multitude of features of crosslinked PL proteins can potentially uncover uncharted prospective applications in regenerative medicine. References: 1. Babo P. Inflamm Regen. 2014; 34:33-44. Acknowledgements: The authors thank FCTâ Fundação para a Ciência e a Tecnologia in the framework of FCT-POPH-FSE, RC-A PhD grant SFRH/BD/96593/2013, ARF Post-Doc grant SFRH/BPD/100760/2014, and MEG grant IF/00685/2012. FCT–Fundação para a Ciência e a Tecnologia in the framework of FCT-POPH-FSE, RC-A PhDgrant SFRH/BD/96593/2013, ARF Post-Doc grant SFRH/BPD/100760/2014, and MEG grant F/00685/2info:eu-repo/semantics/publishedVersio

The Decrease of Uch-L1 Activity Is a Common Mechanism Responsible for Aβ 42 Accumulation in Alzheimer's and Vascular Disease.

Alzheimer's disease (AD) is a multifactorial pathology causing common brain spectrum disorders in affected patients. These mixed neurological disorders not only include structural AD brain changes but also cerebrovascular lesions. The main aim of the present issue is to find the factors shared by the two pathologies. The decrease of ubiquitin C-terminal hydrolase L1 (Uch-L1), a major neuronal enzyme involved in the elimination of misfolded proteins, was observed in ischemic injury as well as in AD, but its role in the pathogenesis of AD is far to be clear. In this study we demonstrated that Uch-L1 inhibition induces BACE1 up-regulation and increases neuronal and apoptotic cell death in control as well as in transgenic AD mouse model subjected to Bengal Rose, a light-sensitive dye inducing that induces a cortical infarction through photo-activation. Under the same conditions we also found a significant activation of NF-κB. Thus, the restoration of Uch-L1 was able to completely prevent both the increase in BACE1 protein levels and the amount of cell death. Our data suggest that the Uch-L1-mediated BACE1 up-regulation could be an important mechanism responsible for Aβ peptides accumulation in vascular injury and indicate that the modulation of the activity of this enzyme could provide new therapeutic strategies in AD