48 research outputs found
Bond characterization of monolithic and layered glass panels and ultrasonic tests to control glued surfaces
No full textAn experimental investigation is presented regarding the compressive and shear strength of monolithic and PVB laminated glass elements connected by acrylic glue. Ultrasonic tests were also used to control the efficiency of glued surfaces of glass panels.
Twenty-four triplets composed of three float glass elements glued with acrylic adhesive were prepared to perform bond tests. Of these twelve triplets were made with monolithic glass elements with a nominal thickness of 20 mm, while twelve were made with layered glass elements 20 mm thick. Three single elements of monolithic glass and three of layered glass were tested for compressive strength. Ultrasonic tests were performed on a sample made by gluing two layered glass panels 200 × 300 × 20 mm in thickness in which defects in glued surfaces were generated artificially. Experimental stress-strain curves in compression for glass elements and shear stress-slippage curves from bond tests were also derived with crack patterns at rupture
Finite element method on fractional visco-elastic frames
No full textIn this study the Finite Element Method (FEM) on viscoelastic frames is presented. It is assumed that the Creep function of the constituent material is of power law type, as a consequence the local constitutive law is ruled by fractional operators. The Euler Bernoulli beam and the FEM for the frames are introduced. It is shown that the whole system is ruled by a set of coupled fractional differential equations. In quasi static setting the coupled fractional differential equations may be decomposed into a set of fractional viscoelastic Kelvin-Voigt units whose solution may be obtained in a very easy way
Sorgenti carsiche ed erosione chimica nelle Prealpi Venete
No full textLa ricerca esamina il chimismo di 19 sorgenti carsiche delle Prealpi Venete, al fine di valutare l'entità dell'erosione carsica di tipo "chimico", cioé il processo morfodinamico di asportazione delle rocce in soluzione chimica. L'erosione è risultata correlata con la mediana della quota dei bacini idrogeologici e varia da 25 a 70 m3/km2/anno
FRP-Substrate bonding quality investigation making use of ultrasonic waves
No full textFiber reinforced polymer (FRP) composite systems are widely used to repair structurally deficient constructions thanks to their good immunity to corrosion, low weight and excellent mechanical properties. The quality of the FRP-substrate interface bond is a crucial parameter affecting the performance of retrofitted structures. In this framework, ultrasonic testing could be used to assess the quality of the bonding [1-2]. In the case of FRP laminates adhesively bonded to roughly inhomogeneous materials, such as concrete, high scattering attenuation occurs due to the presence of heterogeneities. The concrete behaves almost like a perfect absorber generating a considerable number of short-spaced echo peaks that make the defect echo not distinguishable. In order to avoid scattering, waves longer than the discontinuity have to be used, but this expedient makes bonding defects undetectable. The most common practices involve the use of the first echo amplitude, the peak-to-peak or the average amplitude of the signal in a given time window. It is however well known that, when a direct-contact technique is applied, the ultrasonic response in terms of pulses amplitude is affected by two main factors, i.e. the thin film of couplant between the probe and the medium and the pressure of the transducers on the sample. Furthermore the presence of fibers strongly affects the ultrasonic response.
The technique developed in this study is based on the energy distribution measurement of ultrasonic signals by means of a statistical parameter, named Equivalent Time Length (ETL), whose expression is the following:
∑N A(tk)2(tk −tAIC)2
ETL= k=AIC+1 , k=[1,2,...,N] (1)
Where N is the number of point samples k, A(tk) is the amplitude of the signal at the time tk, tAIC is the onset time of the signal that was selected by using the Akaike Information Criterion (AIC) function [3]. The ETL is sensitive to the presence of bonding defects in the sense that lower values mean higher reflection of wave energy and higher values mean lower reflection and higher penetration through the concrete bonding. In addition to that, it has the advantage not to be affected by the reflected echoes amplitude variations, which often make the amplitude not a reasonable parameter for bonding quality investigation.
In order to apply the ETL to the detection of bonding defect, a preliminary numerical study involving a 1-D system with a material discontinuity was performed. A simple situation of reflection and transmission of longitudinal waves incident on the interfaces between three different media was simulated. 2D finite element (FE) analyses were also performed using the commercial software COMSOL Multiphysics 5.0.
∑N A(tk )2 k=AIC+1
The study was conducted experimentally both in vitro, on FRP reinforcements bonded to concrete substrates with imposed well-known defects, and in situ, on reinforced concrete beams in a floor slab and on Seismic retrofitted concrete walls.
Laboratory tests were conducted on four concrete specimens with outer dimensions of 180x250x150 mm3, reinforced by carbon fiber reinforced polymer plates set in accordance with the manufacturer's application guideline, using commercial epoxy resin. In order to simulate the lack of bonding of the FRP, three types of defects of well-known dimensions were located on three of the samples by means of the interposition of foils of Teflon between the concrete surface and the adhesive layer (Fig. 1). The samples were named from D0 (absence of defect, i.e. pristine state) to D3 (large defect), according to the size of the employed Teflon foil(s). The setups involved the use of an excitation signal equal to five cycles of sine function generated by a house-built ultrasonic pulser-receiver, two ultrasonic transducers arranged in a pitch-catch mode, and an ultrasonic preamplifier. The experimental study confirmed the numerical findings and may pave the road towards an effective ultrasonic non-destructive approach
A microarray analysis highlights the role of tetrapyrrole pathways in grapevine responses to "stolbur" phytoplasma, phloem virus infections and recovered status.
No full textAfter providing a picture of the global transcriptomic changes of grapevine responses to “stolbur” phytoplasma, the recovery status and molecular responses to the phytoplasma and virus co-presence were analyzed. NimbleGen® Vitis vinifera genome arrays were used. Lower transcript abundance of the genes involved in photosynthesis, trehalose, phospholipids was observed in response to the presence of “stolbur” phytoplasma. The expression of the genes involved in tetrapyrrole increased. The recovered plants showed that the transcripts involved in ATP synthesis and amino acid metabolism, secondary metabolism and biotic stress-related pathways increased. Recovery was associated with tetrapyrrole pathway repression. Co-infection with viruses induced the genes involved in the hormone categories (cytokinin, gibberellin, salicylic acid and jasmonates)
Composite laminates buckling optimization through Levy based Ant Colony Optimization
No full textIn this paper, the authors propose the use of the Lévy probability distribution as leading mechanism for solutions differentiation in an efficient and bio-inspired optimization algorithm, ant colony optimization in continuous domains, ACOR. In the classical ACOR, new solutions are constructed starting from one solution, selected from an archive, where Gaussian distribution is used for parameter diversification. In the proposed approach, the Lévy probability distributions are properly introduced in the solution construction step, in order to couple the ACOR algorithm with the exploration properties of the Lévy distribution. The proposed approach has been tested on mathematical test functions and on a real world problem of structural engineering, the composite laminates buckling load maximization. In the latter case, as in many other cases in real world problems, the function to be optimized is multi-modal, and thus the exploration ability of the Levy perturbation operator allow the attainment of better results
Transcriptome Analysis of Phoenix canariensis Chabaud in Response to Rhynchophorus ferrugineus Olivier Attacks
No full textRed Palm Weevil (RPW, Rhynchophorusferrugineus Olivier) threatens most palm species worldwide. Until now, no studies have analyzed the gene regulatory networks of Phoenix canariensis (Chabaud) in response to RPW attacks. The aim of this study was to fill this knowledge gap. Providing this basic knowledge is very important to improve its management. RESULTS: A deep transcriptome analysis was performed on fully expanded leaves of healthy non-infested trees and attacked trees at two symptom stages (middle and late infestation). A total of 54 genes were significantly regulated during middle stage. Pathway enrichment analysis showed that phenylpropanoid-related pathways were induced at this stage. More than 3300 genes were affected during late stage of attacks. Higher transcript abundances were observed for lipid fatty acid metabolism (fatty acid and glycerolipids), tryptophan metabolism, phenylpropanoid metabolism. Key RPW-modulated genes involved in innate response mediated by hormone crosstalk were observed belonging to auxin, jasmonate and salicylic acid pathways. Among transcription factors, some WRKYs were clearly induced. qRT-PCR validation confirmed the upregulation of key genes chosen as validation of transcriptomic analysis. CONCLUSION: A subset of these genes may be further analyzed in future studies to confirm their specificity to be induced by RPW infestations
Molecular responses to small regulating molecules against Huanglongbing disease
No full textHuanglongbing (HLB; citrus greening) is the most devastating disease of citrus worldwide. No cure is yet available for this disease and infected trees generally decline after several months. Disease management depends on early detection of symptoms and chemical control of insect vectors. In this work, different combinations of organic compounds were tested for the ability to modulate citrus molecular responses to HLB disease beneficially. Three small-molecule regulating compounds were tested: 1) L-arginine, 2) 6-benzyl-adenine combined with gibberellins, and 3) sucrose combined with atrazine. Each treatment contained K-phite mineral solution and was tested at two different concentrations. Two trials were conducted: one in the greenhouse and the other in the orchard. In the greenhouse study, responses of 42 key genes involved in sugar and starch metabolism, hormone-related pathways, biotic stress responses, and secondary metabolism in treated and untreated mature leaves were analyzed. TGA5 was significantly induced by arginine. Benzyladenine and gibberellins enhanced two important genes involved in biotic stress responses: WRKY54 and WRKY59. Sucrose combined with atrazine mainly upregulated key genes involved in carbohydrate metabolism such as sucrose-phosphate synthase, sucrose synthase, starch synthase, and α-amylase. Atrazine also affected expression of some key genes involved in systemic acquired resistance such as EDS1, TGA6, WRKY33, and MYC2. Several treatments upregulated HSP82, which might help protect protein folding and integrity. A subset of key genes was chosen as biomarkers for molecular responses to treatments under field conditions. GPT2 was downregulated by all small-molecule treatments. Arginine-induced genes involved in systemic acquired resistance included PR1, WRKY70, and EDS1. These molecular data encourage long-term application of treatments that combine these regulating molecules in field trials
Subcutaneous immunoglobulin for maintenance therapy in stiff-person syndrome: One-year follow-up in two patients
No full textStiff person syndrome is a rare condition characterised by prolonged stiffness with superimposed muscle spasms. Immunotherapy relies mainly on intravenous immunoglobulin, steroids and plasma exchange. Azathioprine or rituximab are other possible options. We describe two patients who showed a good clinical response with intravenous immunoglobulin and persistence of the clinical improvement after shifting to equivalent dosage of subcutaneous immunoglobulin. Both patients received a diagnosis of stiff person syndrome based on their clinical symptoms (episodes of stiffness and spasms) and presence of antiglutamic acid decarboxylase. Treatment with intravenous immunoglobulin was started with improvement of symptoms as reported by patients and confirmed also by the spasm frequency scale and modified Ashworth scale. After clinical stabilisation in order to avoid the hospitalisation required for intravenous immunoglobulin treatment a switch to subcutaneous immunoglobulins was made. After one year of follow-up from the switch, the patients show clinical stability. Their scores on the modified Ashworth scale, spasm frequency scale and on the 10 Meter Walking Test were also stable. Subcutaneous formulation of immunoglobulin could be as effective as intravenous immunoglobulin in the maintenance treatment of Stiff person syndrome, although studies involving a larger cohort of patients are needed in order to confirm our anecdotal experience
Proteomic analysis highlights the role of detoxification pathways in increased tolerance to Huanglongbing disease
No full textBackground
Huanglongbing (HLB) disease is still the greatest threat to citriculture worldwide. Although there is not any resistance source in the Citrus germplasm, a certain level of moderated tolerance is present. A large-scale analysis of proteomic responses of Citrus may help: 1) clarifying physiological and molecular effects of disease progression, 2) validating previous data at transcriptomic level, and 3) identifying biomarkers for development of early diagnostics, short-term therapeutics and long-term genetic resistance.
Results
In this work we have conducted a proteomic analysis of mature leaves of two Citrus genotypes with well-known differing tolerances to HLB: Navel orange (highly susceptible) and Volkameriana (moderately tolerant). Pathway enrichment analysis showed that amino acid degradation processes occurred to a larger degree in the Navel orange. No clear differences between the two genotypes were observed for primary metabolic pathways. The most important finding was that four glutathione-S-transferases were upregulated in Volkameriana and not in Navel orange. These proteins are involved in radical ion detoxification.
Conclusions
Upregulation of proteins involved in radical ion detoxification should be considered as an important mechanism of increased tolerance to HLB
