20 resultados para ACTIVATION NEUTRON ANALYSIS
em Consorci de Serveis Universitaris de Catalunya (CSUC), Spain
Resumo:
Majolica pottery was the most characteristic tableware produced in Spain during the Medieval and Renaissance periods. A study of the three main production centers in the historical region of Aragon during Middle Ages and Renaissance was conducted on a set of 71 samples. The samples were analyzed by instrumental neutron activation analysis (INAA), and the resulting data were interpreted using an array of multivariate statistical procedures. Our results show a clear discrimination among different production centers allowing a reliable provenance attribution of ceramic sherds from the Aragonese workshops.
Resumo:
Majolica pottery is one of the most characteristic tableware produced during the Medieval and Renaissance periods. Majolica technology was introduced to the Iberian Peninsula by Islamic artisans during Medieval times, and its production and popularity rapidly spread throughout Spain and eventually to other locations in Europe and the Americas. The prestige and importance of Spanish majolica was very high. Consequently, this ware was imported profusely to the Americas during the Spanish Colonial period. Nowadays, Majolica pottery serves as an important horizon marker at Spanish colonial sites. A preliminary study of Spanish-produced majolica was conducted on a set of 246 samples from the 12 primary majolica production centers on the Iberian Peninsula. The samples were analyzed by neutron activation analysis (NAA), and the resulting data were interpreted using an array of multivariate statistical procedures. Our results show a clear discrimination between different production centers. In some cases, our data allow one to distinguish amongst shards coming from the same production location suggesting different workshops or group of workshops were responsible for production of this pre-industrial pottery.
Resumo:
We shall call an n × p data matrix fully-compositional if the rows sum to a constant, and sub-compositional if the variables are a subset of a fully-compositional data set1. Such data occur widely in archaeometry, where it is common to determine the chemical composition of ceramic, glass, metal or other artefacts using techniques such as neutron activation analysis (NAA), inductively coupled plasma spectroscopy (ICPS), X-ray fluorescence analysis (XRF) etc. Interest often centres on whether there are distinct chemical groups within the data and whether, for example, these can be associated with different origins or manufacturing technologies
Resumo:
Neutron diffraction has been used to study in situ the nanocrystallization process of Fe73.5Cu1Nb3Si22.5-xBx (x = 5, 9, and 12) amorphous alloys. Nanocrystallization results in a decrease of both the silicon content and the grain size of the Fe(Si) phase with increasing value of x. By comparing the radial distribution function peak areas with those predicted for ideal bcc and DO3 structure, it can be concluded that the ordering in DO3 Fe(Si) crystals increases with the silicon content.
Resumo:
In this study, 13 ceramic samples were subjected to dissolution using three different procedures: (a) acid attack in open PTFE vessels with a mixture of HF-HClO4, (b) fusion of the sample with lithium metaborate and (c) microwave digestion in PTFE bombs. The samples used in the study had been previously analyzed by neutron activation analysis (NAA), X-ray fluorescence (XRF) and X-ray diffraction (XRD) and they cover a wide range of ceramics fired in different atmospheres and temperatures as well as different mineralogical and chemical compositions. The effectiveness of each procedure is evaluated in terms of its ability to dissolve the various mineralogical phases of the samples, of the number of elements that can be determined and of the time needed for the whole scheme of analysis to be completed.
Resumo:
The neutron skin thickness of nuclei is a sensitive probe of the nuclear symmetry energy and has multiple implications for nuclear and astrophysical studies. However, precision measurements of this observable are difficult to obtain. The analysis of the experimental data may imply some assumptions about the bulk or surface nature of the formation of the neutron skin. Here we study the bulk or surface character of neutron skins of nuclei following from calculations with Gogny, Skyrme, and covariant nuclear mean-field interactions. These interactions are successful in describing nuclear charge radii and binding energies but predict different values for neutron skins. We perform the study by fitting two-parameter Fermi distributions to the calculated self-consistent neutron and proton densities. We note that the equivalent sharp radius is a more suitable reference quantity than the half-density radius parameter of the Fermi distributions to discern between the bulk and surface contributions in neutron skins. We present calculations for nuclei in the stability valley and for the isotopic chains of Sn and Pb.
Resumo:
Background: We use an approach based on Factor Analysis to analyze datasets generated for transcriptional profiling. The method groups samples into biologically relevant categories, and enables the identification of genes and pathways most significantly associated to each phenotypic group, while allowing for the participation of a given gene in more than one cluster. Genes assigned to each cluster are used for the detection of pathways predominantly activated in that cluster by finding statistically significant associated GO terms. We tested the approach with a published dataset of microarray experiments in yeast. Upon validation with the yeast dataset, we applied the technique to a prostate cancer dataset. Results: Two major pathways are shown to be activated in organ-confined, non-metastatic prostate cancer: those regulated by the androgen receptor and by receptor tyrosine kinases. A number of gene markers (HER3, IQGAP2 and POR1) highlighted by the software and related to the later pathway have been validated experimentally a posteriori on independent samples. Conclusion: Using a new microarray analysis tool followed by a posteriori experimental validation of the results, we have confirmed several putative markers of malignancy associated with peptide growth factor signalling in prostate cancer and revealed others, most notably ERRB3 (HER3). Our study suggest that, in primary prostate cancer, HER3, together or not with HER4, rather than in receptor complexes involving HER2, could play an important role in the biology of these tumors. These results provide new evidence for the role of receptor tyrosine kinases in the establishment and progression of prostate cancer.
Resumo:
Background: Cells have the ability to respond and adapt to environmental changes through activation of stress-activated protein kinases (SAPKs). Although p38 SAPK signalling is known to participate in the regulation of gene expression little is known on the molecular mechanisms used by this SAPK to regulate stress-responsive genes and the overall set of genes regulated by p38 in response to different stimuli.Results: Here, we report a whole genome expression analyses on mouse embryonic fibroblasts (MEFs) treated with three different p38 SAPK activating-stimuli, namely osmostress, the cytokine TNFα and the protein synthesis inhibitor anisomycin. We have found that the activation kinetics of p38α SAPK in response to these insults is different and also leads to a complex gene pattern response specific for a given stress with a restricted set of overlapping genes. In addition, we have analysed the contribution of p38α the major p38 family member present in MEFs, to the overall stress-induced transcriptional response by using both a chemical inhibitor (SB203580) and p38α deficient (p38α-/-) MEFs. We show here that p38 SAPK dependency ranged between 60% and 88% depending on the treatments and that there is a very good overlap between the inhibitor treatment and the ko cells. Furthermore, we have found that the dependency of SAPK varies depending on the time the cells are subjected to osmostress. Conclusions: Our genome-wide transcriptional analyses shows a selective response to specific stimuli and a restricted common response of up to 20% of the stress up-regulated early genes that involves an important set of transcription factors, which might be critical for either cell adaptation or preparation for continuous extra-cellular changes. Interestingly, up to 85% of the up-regulated genes are under the transcriptional control of p38 SAPK. Thus, activation of p38 SAPK is critical to elicit the early gene expression program required for cell adaptation to stress.
Resumo:
Background: The transcription factor NFAT5/TonEBP regulates the response of mammalian cells to hypertonicity. However, little is known about the physiopathologic tonicity thresholds that trigger its transcriptional activity in primary cells. Wilkins et al. recently developed a transgenic mouse carrying a luciferase reporter (9xNFAT-Luc) driven by a cluster of NFAT sites, that was activated by calcineurin-dependent NFATc proteins. Since the NFAT site of this reporter was very similar to an optimal NFAT5 site, we tested whether this reporter could detect the activation of NFAT5 in transgenic cells.Results: The 9xNFAT-Luc reporter was activated by hypertonicity in an NFAT5-dependent manner in different types of non-transformed transgenic cells: lymphocytes, macrophages and fibroblasts. Activation of this reporter by the phorbol ester PMA plus ionomycin was independent of NFAT5 and mediated by NFATc proteins. Transcriptional activation of NFAT5 in T lymphocytes was detected at hypertonic conditions of 360–380 mOsm/kg (isotonic conditions being 300 mOsm/kg) and strongly induced at 400 mOsm/kg. Such levels have been recorded in plasma in patients with osmoregulatory disorders and in mice deficient in aquaporins and vasopressin receptor. The hypertonicity threshold required to activate NFAT5 was higher in bone marrow-derived macrophages (430 mOsm/kg) and embryonic fibroblasts (480 mOsm/kg). Activation of the 9xNFAT-Luc reporter by hypertonicity in lymphocytes was insensitive to the ERK inhibitor PD98059, partially inhibited by the PI3-kinase inhibitor wortmannin (0.5 μM) and the PKA inhibitor H89, and substantially downregulated by p38 inhibitors (SB203580 and SB202190) and by inhibition of PI3-kinase-related kinases with 25 μM LY294002. Sensitivity of the reporter to FK506 varied among cell types and was greater in primary T cells than in fibroblasts and macrophages.Conclusion: Our results indicate that NFAT5 is a sensitive responder to pathologic increases in extracellular tonicity in T lymphocytes. Activation of NFAT5 by hypertonicity in lymphocytes was mediated by a combination of signaling pathways that differed from those required in other cell types. We propose that the 9xNFAT-Luc transgenic mouse model might be useful to study the physiopathological regulation of both NFAT5 and NFATc factors in primary cells.
Resumo:
We analyze the influence of the density dependence of the symmetry energy on the average excitation energy of the isoscalar giant monopole resonance (GMR) in stable and exotic neutron-rich nuclei by applying the relativistic extended Thomas-Fermi method in scaling and constrained calculations. For the effective nuclear interaction, we employ the relativistic mean field model supplemented by an isoscalar-isovector meson coupling that allows one to modify the density dependence of the symmetry energy without compromising the success of the model for binding energies and charge radii. The semiclassical estimates of the average energy of the GMR are known to be in good agreement with the results obtained in full RPA calculations. The present analysis is performed along the Pb and Zr isotopic chains. In the scaling calculations, the excitation energy is larger when the symmetry energy is softer. The same happens in the constrained calculations for nuclei with small and moderate neutron excess. However, for nuclei of large isospin the constrained excitation energy becomes smaller in models having a soft symmetry energy. This effect is mainly due to the presence of loosely-bound outer neutrons in these isotopes. A sharp increase of the estimated width of the resonance is found in largely neutron-rich isotopes, even for heavy nuclei, which is enhanced when the symmetry energy of the model is soft. The results indicate that at large neutron numbers the structure of the low-energy region of the GMR strength distribution changes considerably with the density dependence of the nuclear symmetry energy, which may be worthy of further characterization in RPA calculations of the response function.
Resumo:
The approaches of comparative studies and profile measurements, often used in order to detect post-depositional alterations of ceramics, have been applied simultaneously to two sets of Roman pottery, both of which include altered individuals. As analytical techniques, Neutron Activation Analysis and X-Ray Diffraction have been used. Both approaches lead to substantially different results. This shows that they detect different levels of alteration and should complement each other rather than being used exclusively. For the special process of a glassy phase decomposition followed by a crystallization of the Na-zeolite analcime, the results suggest that it changes high-fired calcareous pottery rapidly, and so fundamentally that the results of various archaeometric techniques can be severely disturbed.
Resumo:
This article studies alterations in the values, attitudes, and behaviors that emerged among U.S. citizens as a consequence of, and as a response to, the attacks of September 11, 2001. The study briefly examines the immediate reaction to the attack, before focusing on the collective reactions that characterized the behavior of the majority of the population between the events of 9/11 and the response to it in the form of intervention in Afghanistan. In studying this period an eight-phase sequential model (Botcharova, 2001) is used, where the initial phases center on the nation as the ingroup and the latter focus on the enemy who carried out the attack as the outgroup. The study is conducted from a psychosocial perspective and uses "social identity theory" (Tajfel & Turner, 1979, 1986) as the basic framework for interpreting and accounting for the collective reactions recorded. The main purpose of this paper is to show that the interpretation of these collective reactions is consistent with the postulates of social identity theory. The application of this theory provides a different and specific analysis of events. The study is based on data obtained from a variety of rigorous academic studies and opinion polls conducted in relation to the events of 9/11. In line with social identity theory, 9/11 had a marked impact on the importance attached by the majority of U.S. citizens to their identity as members of a nation. This in turn accentuated group differentiation and activated ingroup favoritism and outgroup discrimination (Tajfel & Turner, 1979, 1986). Ingroup favoritism strengthened group cohesion, feelings of solidarity, and identification with the most emblematic values of the U.S. nation, while outgroup discrimination induced U.S. citizens to conceive the enemy (al-Qaeda and its protectors) as the incarnation of evil, depersonalizing the group and venting their anger on it, and to give their backing to a military response, the eventual intervention in Afghanistan. Finally, and also in line with the postulates of social identity theory, as an alternative to the virtual bipolarization of the conflict (U.S. vs al-Qaeda), the activation of a higher level of identity in the ingroup is proposed, a group that includes the United States and the largest possible number of countries¿ including Islamic states¿in the search for a common, more legitimate and effective solution.
Resumo:
This article studies alterations in the values, attitudes, and behaviors that emerged among U.S. citizens as a consequence of, and as a response to, the attacks of September 11, 2001. The study briefly examines the immediate reaction to the attack, before focusing on the collective reactions that characterized the behavior of the majority of the population between the events of 9/11 and the response to it in the form of intervention in Afghanistan. In studying this period an eight-phase sequential model (Botcharova, 2001) is used, where the initial phases center on the nation as the ingroup and the latter focus on the enemy who carried out the attack as the outgroup. The study is conducted from a psychosocial perspective and uses "social identity theory" (Tajfel & Turner, 1979, 1986) as the basic framework for interpreting and accounting for the collective reactions recorded. The main purpose of this paper is to show that the interpretation of these collective reactions is consistent with the postulates of social identity theory. The application of this theory provides a different and specific analysis of events. The study is based on data obtained from a variety of rigorous academic studies and opinion polls conducted in relation to the events of 9/11. In line with social identity theory, 9/11 had a marked impact on the importance attached by the majority of U.S. citizens to their identity as members of a nation. This in turn accentuated group differentiation and activated ingroup favoritism and outgroup discrimination (Tajfel & Turner, 1979, 1986). Ingroup favoritism strengthened group cohesion, feelings of solidarity, and identification with the most emblematic values of the U.S. nation, while outgroup discrimination induced U.S. citizens to conceive the enemy (al-Qaeda and its protectors) as the incarnation of evil, depersonalizing the group and venting their anger on it, and to give their backing to a military response, the eventual intervention in Afghanistan. Finally, and also in line with the postulates of social identity theory, as an alternative to the virtual bipolarization of the conflict (U.S. vs al-Qaeda), the activation of a higher level of identity in the ingroup is proposed, a group that includes the United States and the largest possible number of countries¿ including Islamic states¿in the search for a common, more legitimate and effective solution.
Resumo:
Muscle-type carnitine palmitoyltransferase 1 (CPT1β) is considered to be the gene that controls fatty acid mitochondrial β-oxidation. A functional peroxisome proliferator-activated receptor (PPAR) responsive element (PPRE) and a myocite-specific (MEF2) site that binds MEF2A and MEF2C in the promoter of this gene had been previously identified. We investigated the roles of the PPRE and the MEF2 binding sites and the potential interaction between PPARα and MEF2C regulating the CPT1β gene promoter. Mutation analysis indicated that the MEF2 site contributed to the activation of the CPT1β promoter by PPAR in C2C12 cells. The reporter construct containing the PPRE and the MEF2C site was synergistically activated by co-expression of PPAR, retinoid X receptor (RXR) and MEF2C in non-muscle cells. Moreover, protein-binding assays demonstrated that MEF2C and PPAR specifically bound to one another in vitro. Also for the synergistic activation of the CPT1β gene promoter by MEF2C and PPARα-RXRα, a precise arrangement of its binding sites was essential.
Resumo:
Visual perception is initiated in the photoreceptor cells of the retina via the phototransduction system.This system has shown marked evolution during mammalian divergence in such complex attributes as activation time and recovery time. We have performed a molecular evolutionary analysis of proteins involved in mammalianphototransduction in order to unravel how the action of natural selection has been distributed throughout thesystem to evolve such traits. We found selective pressures to be non-randomly distributed according to both a simple protein classification scheme and a protein-interaction network representation of the signaling pathway. Proteins which are topologically central in the signaling pathway, such as the G proteins, as well as retinoid cycle chaperones and proteins involved in photoreceptor cell-type determination, were found to be more constrained in their evolution. Proteins peripheral to the pathway, such as ion channels and exchangers, as well as the retinoid cycle enzymes, have experienced a relaxation of selective pressures. Furthermore, signals of positive selection were detected in two genes: the short-wave (blue) opsin (OPN1SW) in hominids and the rod-specific Na+/Ca2+,K+ ion exchanger (SLC24A1) in rodents. The functions of the proteins involved in phototransduction and the topology of the interactions between them have imposed non-random constraints on their evolution. Thus, in shaping or conserving system-level phototransduction traits, natural selection has targeted the underlying proteins in a concerted manner.