175 research outputs found
BIAXIAL CURVATURE AND DUCTILITY CAPACITY OF RC COLUMN BASE CROSS SECTIONS
The deformation performance of the base cross sections of reinforced concrete buildings is
fundamental when large seismic events occur allowing the structure to have large excursions in
nonlinear field and guaranteeing an overall ductile behaviour.
It is well known that the axial force acting on columns significantly reduces the curvature capacity of
the sections and for this reason the technical codes give design criteria stating a limitation in order to
preserve the displacement capacity. It is also recognized that when biaxial bending occur the cross
section undergo a loss in strength capacity. Starting the study of from Bresler (1960), which provided
suitable expression to predict 3D limit interaction surfaces, several numerical and analytical models
were developed to take into account the biaxial interaction in strength.
Simultaneously it is noteworthy to point out that the presence of biaxial bending also influences the
deformation capacity of sections causing in most of the cases a relevant loss of the curvature and
ductility available with respect to the one owned along the principal axes. This important issue is not
faced by technical codes and not exhaustively treated in scientific literature as it was done for strength.
Moreover nonlinear structural models based on lumped plasticity do not take into account these
interaction aspects when defining plastic hinge properties in terms of curvature capacity.
The paper presents a numerical study in which the deformation capacity of RC cross sections
subjected to axial load and biaxial bending is investigated by means of a fiber discretization.
A procedure for the numerical definition of biaxial domains of ultimate curvature, yielding curvature
and curvature ductility is provided and the sensitivity of the biaxial deformation performance to some
geometrical and mechanical parameters (aspect ratio, concrete strength and confinement efficacy) is
discussed.The deformation performance of the base cross sections of reinforced concrete buildings is
fundamental when large seismic events occur allowing the structure to have large excursions in
nonlinear field and guaranteeing an overall ductile behaviour.
It is well known that the axial force acting on columns significantly reduces the curvature capacity of
the sections and for this reason the technical codes give design criteria stating a limitation in order to
preserve the displacement capacity. It is also recognized that when biaxial bending occur the cross
section undergo a loss in strength capacity. Starting the study of from Bresler (1960), which provided
suitable expression to predict 3D limit interaction surfaces, several numerical and analytical models
were developed to take into account the biaxial interaction in strength.
Simultaneously it is noteworthy to point out that the presence of biaxial bending also influences the
deformation capacity of sections causing in most of the cases a relevant loss of the curvature and
ductility available with respect to the one owned along the principal axes. This important issue is not
faced by technical codes and not exhaustively treated in scientific literature as it was done for strength.
Moreover nonlinear structural models based on lumped plasticity do not take into account these
interaction aspects when defining plastic hinge properties in terms of curvature capacity.
The paper presents a numerical study in which the deformation capacity of RC cross sections
subjected to axial load and biaxial bending is investigated by means of a fiber discretization.
A procedure for the numerical definition of biaxial domains of ultimate curvature, yielding curvature
and curvature ductility is provided and the sensitivity of the biaxial deformation performance to some
geometrical and mechanical parameters (aspect ratio, concrete strength and confinement efficacy) is
discussed
Definition of seismic vulnerability maps for civil protection systems: The case of lampedusa Island
The opportunity to locate and quantify the major criticalities associated to natural catastrophic events on a territory allows to plan adequate strategies and interventions by civil protection bodies involved in local and international emergencies. Seismic risk depends, most of all, on the vulnerability of buildings belonging to the urban areas. For this reason, the definition, by a deep analysis of the territory, of instruments identifying and locating vulnerability, largely favours the activities of institutions appointed to safeguard the safety of citizens. This paper proposes a procedure for the definition of vulnerability maps in terms of vulnerability indexes and critical peak ground accelerations for mid-small urban centres belonging to Mediterranean areas. The procedure, tested on the city centre of the Island of Lampedusa, is based on a preliminary historical investigation of the urban area and of the main formal and technological features of buildings involved. Moreover, the vulnerability of the constructions is evaluated by fast assessment methods (filling of evaluation forms). The vulnerability model, allowing the definition of the fragility curves, is calibrated on the basis of the results of an identification process of prototype buildings, selected to be adequately representative. Their characterizations have been provided using the results of an experimental dynamic investigation to develop high representative numerical model. Critical PGA values have been determined by pushover analyses. The results presented provided an unambiguous representation of the major criticalities with respect to seismic vulnerability and risk, of the city centre of the island, being a suitable tool for planning and handling of emergencies
Anti-inflammatory and antioxidant effects of muscarinic acetylcholine receptor (mAChR) activation in the rat hippocampus
Recently we found that acute treatment with Oxotremorine (Oxo), a non-selective mAChRs agonist, up-regulates heat shock proteins and activates their transcription factor heat shock factor 1 in the rat hippocampus. Here we aimed to investigate: a) if acute treatment with Oxo may regulate pro-inflammatory or anti-inflammatory cytokines and oxidative stress in the rat hippocampus; b) if chronic restraint stress (CRS) induces inflammatory or oxidative alterations in the hippocampus and whether such alterations may be affected by chronic treatment with Oxo. In the acute experiment, rats were injected with single dose of Oxo (0.4 mg/kg) and sacrificed at 24 h, 48 h and 72 h. In the CRS experiment, the rats were exposed for 21 days to the CRS and then were treated with Oxo (0.2 mg/kg) for further 10 days. The acute Oxo treatment showed an ability to significantly reduce reactive oxygen species (ROS), singlet oxygen (1O2), pro-inflammatory cytokines levels (IL-1β and IL-6) and phosphorylated NF-κB-p65. Acute Oxo treatment also increased superoxide dismutase (SOD)-2 protein levels and stimulated SOD activity. No differences were detected in the anti-inflammatory cytokine levels, including IL-10 and TGF-β1. In the group of rats exposed to the CRS were found increased hippocampal IL-1β and IL-6 levels, together with a reduction of SOD activity level. These changes produced by CRS were counteracted by chronic Oxo treatment. In contrast, the upregulation of ROS and 1O2 levels in the CRS group was not counteracted by chronic Oxo treatment. The results revealed a hippocampal anti-inflammatory and antioxidant effect of Oxo treatment in both basal conditions and anti-inflammatory in the CRS rat model
Potential impact of a nonavalent HPV vaccine on HPV related low-and high-grade cervical intraepithelial lesions: A referral hospital-based study in Sicily
While bivalent and quadrivalent HPV vaccines have been used for about 10 years, a nonavalent vaccine against HPV types 6/11/16/18/31/33/45/52 and 58 has been recently approved by FDA and EMA and is now commercially available. The objective of our study was to evaluate the potential impact of the nonavalent vaccine on HPV infection and related low- and high-grade squamous intraepithelial lesions (LSIL, HSIL), compared to the impact of the quadrivalent vaccine, in a female population living in Sicily (Italy). Low estimates of HPV vaccine impact were calculated as prevalence of HPV 6/11/16/18/31/33/45/52 and 58 genotypes, alone or in association, but excluding presence of other HPV types; high estimates were calculated as prevalence of HPV 6/11/16/18/31/33/45/52 and 58 genotypes alone or in association, in the presence of other HPV types. The nonavalent HPV vaccine showed increased impact, compared to the quadrivalent vaccine. Estimates of potential impact varied from 30.9% (low estimate) to 53.3% (high estimate) for LSIL, and from 56.9% to 81,0% for HSIL. The proportion of additional cases potentially prevented by the nonavalent vaccine was 14.4%\u201323.8% for LSIL, and 19.0%\u201332.8% for HSIL. The benefit of the nonavalent vaccine compared to the quadrivalent vaccine was more than 80% for both low and high impact estimates for LSIL and more than 50% for both low and high impact estimates for HSIL. The present study confirms that the switch from a first generation HPV vaccines to a nonavalent vaccine would increase the prevention of cervical HSIL in up to 90% of cases
Epigenetic control of pheromone MAPK signaling determines sexual fecundity in Candida albicans
Several pathogenic Candida species are capable of heritable and reversible switching between two epigenetic states, "white" and "opaque." In Candida albicans, white cells are essentially sterile, whereas opaque cells are mating-proficient. Here, we interrogate the mechanism by which the white-opaque switch regulates sexual fecundity and identify four genes in the pheromone MAPK pathway that are expressed at significantly higher levels in opaque cells than in white cells. These genes encode the beta subunit of the G-protein complex (STE4), the pheromone MAPK scaffold (CST5), and the two terminal MAP kinases (CEK1/CEK2). To define the contribution of each factor to mating, C. albicans white cells were reverse-engineered to express elevated, opaque-like levels of these factors, either singly or in combination. We show that white cells co-overexpressing STE4, CST5, and CEK2 undergo mating four orders of magnitude more efficiently than control white cells and at a frequency approaching that of opaque cells. Moreover, engineered white cells recapitulate the transcriptional and morphological responses of opaque cells to pheromone. These results therefore reveal multiple bottlenecks in pheromone MAPK signaling in white cells and that alleviation of these bottlenecks enables efficient mating by these "sterile" cell types. Taken together, our findings establish that differential expression of several MAPK factors underlies the epigenetic control of mating in C. albicans We also discuss how fitness advantages could have driven the evolution of a toggle switch to regulate sexual reproduction in pathogenic Candida species
Reversible Keap1 inhibitors are preferential pharmacological tools to modulate cellular mitophagy
Mitophagy orchestrates the autophagic degradation of dysfunctional mitochondria preventing their pathological accumulation and contributing to cellular homeostasis. We previously identified a novel chemical tool (hereafter referred to as PMI), which drives mitochondria into autophagy without collapsing their membrane potential (ΔΨm). PMI is an inhibitor of the protein-protein interaction (PPI) between the transcription factor Nrf2 and its negative regulator, Keap1 and is able to up-regulate the expression of autophagy-associated proteins, including p62/SQSTM1. Here we show that PMI promotes mitochondrial respiration, leading to a superoxide-dependent activation of mitophagy. Structurally distinct Keap1-Nrf2 PPI inhibitors promote mitochondrial turnover, while covalent Keap1 modifiers, including sulforaphane (SFN) and dimethyl fumarate (DMF), are unable to induce a similar response. Additionally, we demonstrate that SFN reverses the effects of PMI in co-treated cells by reducing the accumulation of p62 in mitochondria and subsequently limiting their autophagic degradation. This study highlights the unique features of Keap1-Nrf2 PPI inhibitors as inducers of mitophagy and their potential as pharmacological agents for the treatment of pathological conditions characterized by impaired mitochondrial quality control
Molecular imaging of cell death in vivo by a novel small molecule probe
Apoptosis has a role in many medical disorders, therefore assessment of apoptosis in vivo can be highly useful for diagnosis, follow-up and evaluation of treatment efficacy. ApoSense is a novel technology, comprising low molecular-weight probes, specifically designed for imaging of cell death in vivo. In the current study we present targeting and imaging of cell death both in vitro and in vivo, utilizing NST-732, a member of the ApoSense family, comprising a fluorophore and a fluorine atom, for both fluorescent and future positron emission tomography (PET) studies using an 18F label, respectively. In vitro, NST-732 manifested selective and rapid accumulation within various cell types undergoing apoptosis. Its uptake was blocked by caspase inhibition, and occurred from the early stages of the apoptotic process, in parallel to binding of Annexin-V, caspase activation and alterations in mitochondrial membrane potential. In vivo, NST-732 manifested selective uptake into cells undergoing cell-death in several clinically-relevant models in rodents: (i) Cell-death induced in lymphoma by irradiation; (ii) Renal ischemia/reperfusion; (iii) Cerebral stroke. Uptake of NST-732 was well-correlated with histopathological assessment of cell-death. NST-732 therefore represents a novel class of small-molecule detectors of apoptosis, with potential useful applications in imaging of the cell death process both in vitro and in vivo
Giorgio Vasari a Palazzo Abatellis. Percorsi del Rinascimento in Sicilia
La mostra si inserisce nell'ambito delle celebrazioni per i 500 anni della nascita di Giorgio Vasari (1511-2011), ricorrenza che, nel corso dell'anno, \ue8 stata oggetto di numerosi eventi culturali italiani e internazionali. L'iniziativa nasce dalla collaborazione tra la Biblioteca Centrale della Regione siciliana "A. Bombace", la sezione "Sfera" del Dipartimento di Architettura dell'Universit\ue0 degli Studi di Palermo, e la Galleria Interdisciplinare Regionale della Sicilia, istituzione che custodisce, nella prestigiosa sede di Palazzo Abatellis, due grandi dipinti su tavola di Vasari, costituenti le ricurve parti laterali del trittico della "Caduta della manna" realizzato nel 1545 per il refettorio di Santa Maria di Monteoliveto a Napoli. Le lunette vasariane, esposte in modo permanente dal 2009 ma ancora quasi del tutto sconosciute a studiosi e pubblico, per l'occasione sono state ricollocate secondo gli originali rapporti dimensionali con il perduto quadro centrale e poste in relazione con il disegno preparatorio dello stesso Vasari, oggi custodito presso l'Ecole nationale superieure des beaux-arts di Parigi. Il percorso analitico, che si \ue8 avvalso anche del prezioso contributo di Claudia Conforti, tra le pi\uf9 autorevoli studiose dell'artista aretino, e delle competenze tecniche dell'Associazione culturale LapiS, \ue8 stato svolto secondo tre tematiche connesse alla poliedrica attivit\ue0 vasariana e al suo contesto culturale: la pittura e l'arte del disegno, la produzione letteraria, l'architettura. Al patrimonio pittorico e grafico della Galleria, riconducibile a quella che lo stesso Vasari definisce \uabmaniera moderna\ubb, sono stati quindi associati preziosi volumi a stampa, a partire dalla rara edizione del 1568 delle "Vite de' pi\uf9 eccellenti architetti, pittori e scultori italiani", e pannelli illustrativi riferiti a opere siciliane di architetti e scultori citati nelle "Vite" vasariane, costituenti alcune pregnanti testimonianze del Rinascimento in Sicili
Chick Embryo Partial Ischemia Model: A New Approach to Study Ischemia Ex Vivo
Background: Ischemia is a pathophysiological condition due to blockade in blood supply to a specific tissue thus damaging the physiological activity of the tissue. Different in vivo models are presently available to study ischemia in heart and other tissues. However, no ex vivo ischemia model has been available to date for routine ischemia research and for faster screening of anti-ischemia drugs. In the present study, we took the opportunity to develop an ex vivo model of partial ischemia using the vascular bed of 4th day incubated chick embryo.
Methodology/Principal Findings: Ischemia was created in chick embryo by ligating the right vitelline artery using sterile surgical suture. Hypoxia inducible factor- 1 alpha (HIF-1a), creatine phospho kinase-MB and reactive oxygen species in animal tissues and cells were measured to confirm ischemia in chick embryo. Additionally, ranolazine, N-acetyl cysteine and trimetazidine were administered as an anti-ischemic drug to validate the present model. Results from the present study depicted that blocking blood flow elevates HIF-1a, lipid peroxidation, peroxynitrite level in ischemic vessels while ranolazine administration partially attenuates ischemia driven HIF-1a expression. Endothelial cell incubated on ischemic blood vessels elucidated a higher level of HIF-1a expression with time while ranolazine treatment reduced HIF-1a in ischemic cells. Incubation of caprine heart strip on chick embryo ischemia model depicted an elevated creatine phospho kinase-MB activity under ischemic condition while histology of the treated heart sections evoked edema and disruption of myofibril structures.
Conclusions/Significance: The present study concluded that chick embryo partial ischemia model can be used as a novel ex vivo model of ischemia. Therefore, the present model can be used parallel with the known in vivo ischemia models in understanding the mechanistic insight of ischemia development and in evaluating the activity of anti-ischemic drug.status: publishe
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