170,227 research outputs found
Investigation and characterization of an Al-Mg-Zr-Sc alloy with reduced Sc content for laser powder bed fusion
No full textOnly few high strength Al alloys are processable by Laser Powder Bed Fusion due to the occurrence of hot cracks during solidification. In recent years, the addition of Zr and Sc in Al-Mg alloys revealed an effective solutions to suppress solidification cracking and improve strength. Nevertheless, since Sc is classified as a critical raw material by European Commission due to its high cost and supply risk, its content should be desiderably reduced. It is therefore necessary to focus on novel Al alloys featuring both enhanced processability and low amount of Sc. In this study, we investigated the microstructure and mechanical behavior of an Al-5.2Mg-0.8Zr-0.3Sc alloy, commercially available as m4pTM StrengthAl, produced by Laser Powder Bed Fusion. Simulations of equilibrium phase diagrams and Scheil solidification curves showed the precipitation of primary Al3Zr and Al3(Sc,Zr) in the liquid phase on cooling. These particles revealed able to act as nuclei for heterogeneous nucleation of grains, giving rise to a fine equiaxed structure which is able to suppress hot cracking and increase the processability of the Al-Mg-Zr-Sc alloy. Despite the reduced Sc content, the formation of secondary Al3(Sc,Zr) nano-phases during the annealing treatment led to a sharp increase of micro-hardness values, whereas a stress relief effect was monitored by residual stress measurements during aging. Both as-built and aged alloys show a bimodal grain size distribution and a similar crystallographic texture. Yield strength and ultimate tensile strength of 460 MPa and 485 MPa, respectively, were recorded in samples aged at 350 °C for 24 h and at 375 °C for 8 h
Preliminare analisi strutturale ai loci ACACA e FASN nella bufala Mediterranea italiana.
No full textImportanti funzioni nella biosintesi degli acidi grassi a catena lunga nei mammiferi sono svolte dagli enzimi ACACA e FASN. Il gene ACACA codifica per l’enzima citosolico Acetil-Coenzima-A Carbossilasi che catalizza la carbossilazione ATP-dipendente dell'acetil-CoA in malonil-CoA. Il gene FASN codifica per l’enzima multifunzionale acido grasso sintasi che catalizza la reazione di sintesi NADPH-dipendente di acido palmitico da acetil-CoA e malonil-CoA. Tali geni sono stati già investigati in altre specie di interesse zootecnico, ma nessuna informazione è attualmente disponibile per la specie bufalina. Pertanto obiettivo del lavoro è stato una preliminare analisi strutturale dei geni ACACA e FASN ed una caratterizzazione della naturale variabilità genetica a tali loci.
Il DNA genomico è stato estratto da 17 campioni individuali di sangue di bufale proveniente da diversi allevamenti campani. Mediante PCR sono state amplificate e sequenziate l’esone 1, 7 e 8 per il gene ACACA e le regioni esone 6-esone 9 del gene FASN, usando primers disegnati sull’omologa sequenze bovina. Metodiche PCR-RFLP sono state sviluppate per gli SNP g.34T>C (esone 1) e g.557T>G (introne 8) rispettivamente per i geni ACACA e FASN.
Per il gene ACACA è stato sequenziato un frammento di 257bp del 1°esone e 923bp appartenenti alla regione esonica 7-8. L’analisi delle sequenze di 7 individui ha messo in evidenza 1 SNP al 34°nt del 1°esone. Si tratta di una transversione T>C, che non è responsabile di alcun cambiamento aminoacidico. Per il gene FASN è stato sequenziato un frammento di ~1400bp, includente gli esoni 6-9. Dal confronto delle sequenze sono emersi 7 SNP (5 intronici e 2 esonici). Entrambe le mutazioni esoniche sono responsabili di cambiamento aminoacidico. In particolare lo SNP al 14nt dell’esone 6 (AAC>CAC) cambia Asn>His, mentre lo SNP al 16nt nell’esone 7 ACT>TCT è responsabile del cambio Thr>Ser.
Sia per lo SNP trovato sul gene ACACA che per uno degli SNP messi in evidenza al locus FASN è stato possibile sviluppare un protocollo PCR-RFLP per una rapida ed economica genotipizzazione degli animali. In particolare per g.34T>C la digestione con MnlI (CCTCNNNNNNN!) ha prodotto nei campioni analizzati il seguente pattern elettroforetico: 106, 67, 43 e 41bp (omozigote T/T), il secondo contraddistinto da tre frammenti di restrizione di 147, 67 e 43bp (omozigote C/C) ed il terzo rappresentato da cinque bande: 147, 106, 67, 43 e 41bp (eterozigote T/C); mentre per lo SNP g.557T>G, il pattern di restrizione generato dall’endonucleasi TspEI (!AATT) è 1246bp (omozigote G/G), 1014 e 232bp (omozigote T/T); e 1246,1014 e 232bp (eterozigote T/G). Una genotipizzione condotta su un elevato numero di individui sottoposti a controlli funzionali sarebbe auspicabile al fine di poter utilizzare tali SNP in studi di associazione per il miglioramento delle caratteristiche quali-quantitative del grasso nel latte di bufala
Dural MALT Lymphoma Detected by 11C-Methionine PET/CT
No full textA 53-year-old man had a diagnosis of mucosa-associated lymphoid tissue lymphomas of the dura in the left tentorium. The patient underwent whole-body F-FDG PET/CT and C-methionine PET/CT in order to complete the staging of dural mucosa-associated lymphoid tissue lymphoma. C-methionine uptake was detected in multiple meningeal sites, including left tentorium, with no significant FDG uptake in the same regions
The expression of p27BBP/eIF6 is highly modulated during Xenopus laevis embryogenesis.
No full textProtein p27BBP/eIF6 is necessary for ribosomal function of all cells. Previous data showed that from mammals to yeast p27BBP/eIF6 is involved in the biogenesis of ribosomal subunit 60S and its association with the 60S prevents premature 80S formation regulated by PKC signaling, indicating that phosphorylation of p27BBP/eIF6 is needed for translation to occur. While in vitro p27BBP/eIF6 is constitutively expressed, and it has a high level of expression in cycling cells, in vivo its expression varies according to tissues and appears regulated by factors up to now unknown. p27BBP/eIF6 has never been investigated in developing organisms where its upregulation can be correlated with tissue growth and differentiation. In this study we have sequenced p27BBP/eIF6 cDNA and studied its expression during development of Xenopus laevis, as the first step for studying its regulation. The amino acid sequence is highly conserved with two putative PKC phosphorylation sites in serine, one site being typical of Xenopus. At the end of gastrulation, the p27BBP/eIF6 riboprobe localizes in the neural plate and in the paraxial mesoderm. In particular, from stage 24, a clear-cut localization occurs in the perspective head. In embryos exposed to teratogens, the localization of p27BBP/eIF6 riboprobe varies according to the change of head size caused by the treatment. p27BBP/eIF6 expression is particularly evident in differentiating olfactory pits, the lens, otic vesicles, and in branchial arches. Features of particular interest are p27BBP/eIF6 high level of expression in the eye field, and in the mid-hindbrain-boundary, two regions with high proliferative activity. Altogether, data indicate that a modulated expression of p27BBP/eIF6 occurs in developing anlagens in addition to a basal level of expression, and may suggest a correlation between p27BBP/eIF6 and proliferative activity. Moreover, the X. laevis cDNA isolation and characterization offer new hints for further studies in relation to potential p27BBP/eIF6 phosphorylation
Bioassay-based ecotoxicological investigation on marine and freshwater impact of cigarette butt littering
No full textDespite representing an extremely relevant portion (20–40%) of worldwide coastal litter, cigarette butts are still an underestimate environmental issue of limited scientific interest. Public authorities of different countries promote active removal of cigarette butts, but the issue remains problematic in terms of aesthetic, environmental and health-related impacts. There are few studies on the environmental side-effects of smoked cigarette butt litter despite being a worldwide issue. In this work, two ecotoxicological bioassay batteries were adopted to evaluate the environmental consequences of cigarette butt water-soluble ingredient release in both marine water and freshwater. Marine assays were generally more affected compared to freshwater. Interesting outcomes were observed with crustacean tests, showing a lower effect of smoked cigarette butt leachate when tested at maximum concentration. This finding were supported by heartbeat measures of Daphnia magna, which were accelerated at 100% of smoked cigarette butt leachate
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Strain-rate and temperature dependent material properties of Agar and Gellan Gum used in biomedical applications
No full textAgar and Gellan Gum are biocompatible polymers extensively used in several fields of tissue engineering research (e.g. tissue replacement, tissue support, tissue mimicking), due to their mechanical behaviour effectively representative of actual biological tissues. Since mechanical properties of artificial tissues are related to biocompatibility and functionality of medical implants and significantly influence adhesion, growth and differentiation of cells in tissue-engineering scaffolds, an accurate characterization of Young׳s modulus and relaxation time processes is needed. In this study, the strain-rate and temperature dependent material properties of Agarose and one among the numerous kind of Gellan Gum commercially available, known as Phytagel®, have been investigated. Nine hydrogel samples have been realized with different mechanical properties: the first one Agar-based as a reference material, the further eight samples Gellan Gum based in which the effect of dispersed solid particles like kieselguhr and SiC, as enhancing mechanical properties factors, have been investigated as a function of concentration. Stress-strain has been investigated in compression and relaxation time has been evaluated by means of the Kohlrausch-Williams-Watts time decay function. Mechanical properties have been measured as a function of temperature between 20°C and 35°C and at different strain rates, from ~10-3s-1 and ~10-2s-1 (or deformation rate from ~0.01mms-1 to ~0.1mms-1). From experimental data, the combined temperature and strain-rate dependence of hydrogels Young׳s modulus is determined on the basis of a constitutive model. In addition to a dependence of Young׳s modulus on temperature, a remarkable influence of strain-rate has been observed, especially in the sample containing solid particles; in same ranges of temperature and strain-rate, also relaxation time variations have been monitored in order to identify a possible dependence of damping properties on temperature and strain-rate. The result is the impossibility to determine univocally mechanical properties of studied biomaterials without a proper definition of boundary conditions at which they have been obtained
UV-filters in marine environments: a review of research trends, meta-analysis, and ecotoxicological impacts of 4-methylbenzylidene-camphor and benzophenone-3 on marine invertebrate communities
No full textThe potential adverse effects of UV-filter pollution in marine environments have been the focus of research in recent years. This systematic review aims to determine the extent of this emerging problem, both quantitatively and qualitatively, combining temporal and science mapping analyses to explore the development of the field of UV-filters in the marine environment (from 1990 to 2021), and to outline new research frontiers. The temporal trend analysis revealed an exponential growth of published studies over the last decade (70% since 2016), confirming the emerging role of this topic in environmental science. The meta-analysis determined that 4-methylbenzylidene-camphor (4-MBC) and benzophenone-3 (BP-3) are top-priority environmental pollutants due to their increasing usage and, in turn, a frequent occurrence in marine ecosystems. This meta-analysis determined the focus on these two contaminants for this review. A critical discussion of the applications, regulatory aspects, and environmental occurrences of these selected compounds was provided. The present study also focused on the most recent (2015–2021) field and laboratory studies investigating the ecotoxicological impacts of 4-MBC and BP-3 on marine invertebrates. This review highlights the need for more research efforts to fill the knowledge gaps on the realistic effects these compounds may have when considered individually, in combination, or as subsequent exposures. Overall, this review aims to establish guidelines for further studies to understand the effect of UV-filters on marine ecosystems and marine invertebrate communities
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