21 research outputs found
Retinitis pigmentosa (RP): the role of oxidative stress in the degenerative process progression
No full textPurpose: Retinitis Pigmentosa is a term that includes a group of inherited bilateral and progressive retinal degenerations, with the involvement of rod photoreceptors, which frequently leads to blindness; oxidative stress may be involved in the degeneration progression as proposed by several recent studies. The goal of this study is to evaluate whether circulating free radicals taken from capillary blood are related to one of the most important features of Retinitis pigmentosa that can affect frequently patients: cystoid macular oedema (CME). Materials: A total of 186 patients with Retinitis Pigmentosa (range: 25–69 years) were enrolled; all patients completed an ophthalmologic examination and SD-OCT at baseline and were divided into three subgroups according to the SD-OCT features. ROS blood levels were determined using FORT with monitoring of free oxygen radicals. Results: Test levels of free oxygen radicals were significantly increased, almost twice, in RP patients showing cystoid macular oedema and significantly increased compared to the control group. (p < 0.001). Discussion: Our findings suggest that oxidative stress may speed cone photoreceptors’ morphological damage (CMT); because long lasting oxidative stress in the RP may cause oxidative damage, with animal models of RP suggesting this is a micromolecular mechanism of photoreceptors’ (cone) death, it can be similar to cone damage in human RP eyes. The limitations of this paper are the relatively small sample, the horizontal design of the study, and the lack of data about the levels of ROS in the vitreous body. View Full-Tex
Materiali per il design: caratterizzazione di blend polimerici e studio di fenomeni dei degrado
No full textThe degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the effect of dibutyl phthalate plasticizer. Part 1
No full textThe influence of dibutyl phthalate (DBP) plasticizer on poly(vinyl acetate) (PVAc) degradation was investigated. A multi-analytical approach (combining FTIR and Fluorescence spectroscopy, NMR and DSC analyses) was used to study how thermal- and photo-oxidative ageing treatments act on the polymer and assess the role of the additive in the degradation pattern. Standard and plasticized PVAc films were artificially aged at 60 °C in a thermal regime and irradiated at wavelengths above 290 nm in a photo-oxidative ageing regime, with exposure between 100 and 2000 h. The two types of ageing differ mainly in the formation of C{double bond, long}C double bonds along the polymer backbone, enhanced by thermal ageing, and the formation of aldehydic structures, following photo-oxidative treatment and in the degree to which plasticizer is lost. The integration of results from different analytical methods highlights the utility in combining complementary analyses for the study of PVAc degradation
The degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the Cocoon lamps. Part 2
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Fluorescence and Fourier-transform infrared spectroscopyfor the analysis of iconic Italian design lamps madeof polymeric materials
No full textPolymeric materials used for industrial design during XX century. Degradation study, structure/properties relations and conservations strategies
No full textPolymeric materials have been extensively used in works of art and in design objects since last century. A large number of handmade and industrial objects, made of polymeric materials, represent today the development of 20th century society, and are conserved in museums and private collections. The polymeric material, if not suitably protected, may rapidly deteriorate: the knowledge about the stability and condition (state of conservation, restoration and treatment) of such objects is still limited and only few examples of protocols for the investigation and management of these items are available.
In the work carried out during this thesis, the conservation issues of the Triennale Design Museum of Milano have been thoroughly investigated. A selection of very famous objects has been chosen for the scientific examination on the basis of the most urgent conservation needs. The items of the museum have been studied and compared to other items coming from a private collection.
Starting from selected case-studies, three different polymeric materials have been analysed -poly(vinylacetate), ABS and cellulose acetate - with the aim of achieving enhanced competences in the field of polymer degradation in museum environment.
The goal of this thesis is to define and test a micro- and non-invasive protocol for polymer characterization and degradation assessment: vibrational spectroscopic techniques have proved to be suitable for the analysis of micro-samples of few mg and combination with innovative imaging techniques (Fluorescence Multispectral imaging, Fluorescence Life Time Imaging) has been used extensively to assess the degradation of polymers under mild artificial and natural aging conditions.
The degradation of PVAc in natural ageing condition proved to lead to the deacetilation of the polymer and to its localised deep oxidation. The degradation patterns under photo and thermal-oxidative aging have been studied since the initial degradation steps, revealing differences in the degradation behaviour: the phenomenon is mainly a temperature driven process, which leads to increasing unsaturation content. The presence of the plasticiser (DBP) enhances the deacetilation of the polymer and modifies the degradation patter of the polymer.
Design objects made of ABS present diffuse phenomena of degradation of the rubber constituent and mechanical failure is a diffuse conservation problem. The assessment of the molecular modification have been implemented by the systematic analysis of specimens under mild and controlled aging treatment: ABS resin have been proved to be stable in thermal-oxidative conditions, while the photo-oxidative treatment leads to rapid degradation of the rubber phase, with formation of increasing content of oxidised groups.
The analysis of cellulose acetate case-study revealed slight degradation phenomena affecting the internal side of the lamp. The analysis of the aged specimens revealed that cellulose acetate is stable under thermal-oxidative aging and only a partial degradation have been evidenced by spectroscopic data; on the other hand the photo-oxidative treatment leads to a greater modification of the polymer.
The correlation between FTIR, NMR and fluorescence data permits the comprehension of the degradation phenomena of the studied polymers. Fluorescence multispectral imaging has proved to be a reliable method for the monitoring activity on site for polymeric works of art, granted that the degradation pathway of the polymeric material had been thoroughly elucidated.Polymeric materials have been extensively used in works of art and in design objects since last century. A large number of handmade and industrial objects, made of polymeric materials, represent today the development of 20th century society, and are conserved in museums and private collections. The polymeric material, if not suitably protected, may rapidly deteriorate: the knowledge about the stability and condition (state of conservation, restoration and treatment) of such objects is still limited and only few examples of protocols for the investigation and management of these items are available.
In the work carried out during this thesis, the conservation issues of the Triennale Design Museum of Milano have been thoroughly investigated. A selection of very famous objects has been chosen for the scientific examination on the basis of the most urgent conservation needs. The items of the museum have been studied and compared to other items coming from a private collection.
Starting from selected case-studies, three different polymeric materials have been analysed -poly(vinylacetate), ABS and cellulose acetate - with the aim of achieving enhanced competences in the field of polymer degradation in museum environment.
The goal of this thesis is to define and test a micro- and non-invasive protocol for polymer characterization and degradation assessment: vibrational spectroscopic techniques have proved to be suitable for the analysis of micro-samples of few mg and combination with innovative imaging techniques (Fluorescence Multispectral imaging, Fluorescence Life Time Imaging) has been used extensively to assess the degradation of polymers under mild artificial and natural aging conditions.
The degradation of PVAc in natural ageing condition proved to lead to the deacetilation of the polymer and to its localised deep oxidation. The degradation patterns under photo and thermal-oxidative aging have been studied since the initial degradation steps, revealing differences in the degradation behaviour: the phenomenon is mainly a temperature driven process, which leads to increasing unsaturation content. The presence of the plasticiser (DBP) enhances the deacetilation of the polymer and modifies the degradation patter of the polymer.
Design objects made of ABS present diffuse phenomena of degradation of the rubber constituent and mechanical failure is a diffuse conservation problem. The assessment of the molecular modification have been implemented by the systematic analysis of specimens under mild and controlled aging treatment: ABS resin have been proved to be stable in thermal-oxidative conditions, while the photo-oxidative treatment leads to rapid degradation of the rubber phase, with formation of increasing content of oxidised groups.
The analysis of cellulose acetate case-study revealed slight degradation phenomena affecting the internal side of the lamp. The analysis of the aged specimens revealed that cellulose acetate is stable under thermal-oxidative aging and only a partial degradation have been evidenced by spectroscopic data; on the other hand the photo-oxidative treatment leads to a greater modification of the polymer.
The correlation between FTIR, NMR and fluorescence data permits the comprehension of the degradation phenomena of the studied polymers. Fluorescence multispectral imaging has proved to be a reliable method for the monitoring activity on site for polymeric works of art, granted that the degradation pathway of the polymeric material had been thoroughly elucidated.DIPARTIMENTO DI CHIMICA, MATERIALI E INGEGNERIA CHIMICA GIULIO NATTA24LEVI, MARINELLACASTIGLIONI, CHIAR
Conversion of Polymeric Substrates by Aerobic Granular Sludge
No full textDomestic wastewater is treated prior to its return to natural water bodies, to minimize its polluting effect. Biological wastewater treatment removes organic matter and nutrients from the wastewater, by employing the activity of microorganisms, which consume polluting compounds present in wastewater to grow. One of such technologies is aerobic granular sludge (AGS), which consists of self-immobilized microorganisms growing in spherical biofilms. The granular structure facilitates the separation between treated water and the biomass due to its excellent settling properties. This way, energy and space are saved in comparison to flocculent sludge-based treatment. Despite its many advantages, the granular structure can pose some challenges too, particularly regarding the degradation of polymeric substrates. The higher mass-transfer resistance in granules compared to flocs challenges the degradation of these substrates, which have a size spanning from a few kDa to several micrometres. Polymeric substrates, furthermore, need to undergo hydrolysis before microorganisms can take them up, which is generally a slow process. Most AGS applications rely on microbial selection driven by the application of a sequencing batch reactor (SBR) cycle. The cycle consists of an anaerobic substrate feeding and a subsequent aerobic starvation period, which selects for intracellular polymer-storing organisms, such as polyphosphate accumulating organisms (PAO) and glycogen accumulating organisms (GAO). Substrates that experience high mass-transfer limitation and low degradation rates may interfere with the microbial selection strategy applied to AGS, especially when they are not (fully) taken up in the anaerobic feeding period and continue degrading aerobically in the next cycle phase. Some lab-scale studies have reported detrimental effects of polymeric substrates in AGS structure and activity, while others have managed to maintain a stable granule bed and suggest that the microbial utilization of polymeric substrates can contribute to good nutrient removal. The degradation of polymeric substrates by full-scale aerobic granules is still poorly understood. Sanitary Engineerin
Anaerobic hydrolysis of complex substrates in full-scale aerobic granular sludge: enzymatic activity determined in different sludge fractions
No full textComplex substrates, like proteins, carbohydrates, and lipids, are major components of domestic wastewater, and yet their degradation in biofilm-based wastewater treatment technologies, such as aerobic granular sludge (AGS), is not well understood. Hydrolysis is considered the rate-limiting step in the bioconversion of complex substrates, and as such, it will impact the utilization of a large wastewater COD (chemical oxygen demand) fraction by the biofilms or granules. To study the hydrolysis of complex substrates within these types of biomass, this paper investigates the anaerobic activity of major hydrolytic enzymes in the different sludge fractions of a full-scale AGS reactor. Chromogenic substrates were used under fully mixed anaerobic conditions to determine lipase, protease, α-glucosidase, and β-glucosidase activities in large granules (>1 mm in diameter), small granules (0.2–1 mm), flocculent sludge (0.045–0.2 mm), and bulk liquid. Furthermore, composition and hydrolytic activity of influent wastewater samples were determined. Our results showed an overcapacity of the sludge to hydrolyze wastewater soluble and colloidal polymeric substrates. The highest specific hydrolytic activity was associated with the flocculent sludge fraction (1.5–7.5 times that of large and smaller granules), in agreement with its large available surface area. However, the biomass in the full-scale reactor consisted of 84% large granules, making the large granules account for 55–68% of the total hydrolytic activity potential in the reactor. These observations shine a new light on the contribution of large granules to the conversion of polymeric COD and suggest that large granules can hydrolyze a significant amount of this influent fraction. The anaerobic removal of polymeric soluble and colloidal substrates could clarify the stable granule formation that is observed in full-scale installations, even when those are fed with complex wastewaters. Key points: • Large and small granules contain >70% of the hydrolysis potential in an AGS reactor. • Flocculent sludge has high hydrolytic activity but constitutes <10% VS in AGS. • AGS has an overcapacity to hydrolyze complex substrates in domestic wastewater. <!-- Query ID="Q2" Text=" Graphical abstract contains text below the minimum required font size of 6pts inside the artwork, and there is no sufficient space available for the text to be enlarged. Please provide replacement figure file." -->Graphical abstract: [Figure not available: see fulltext.
Effect of an increased particulate cod load on the aerobic granular sludge process: A full scale study
No full textHigh concentrations of particulate COD (pCOD) in the influent of aerobic granular sludge (AGS) systems are often associated to small granule diameter and a large fraction of flocculent sludge. At high particulate concentrations even granule stability and process performance might be compromised. However, pilot-or full-scale studies focusing on the effect of real wastewater partic-ulates on AGS are scarce. This study describes a 3-month period of increased particulate loading at a municipal AGS wastewater treatment plant. The pCOD concentration of the influent increased from 0.5 g COD/L to 1.3 g COD/L, by adding an untreated slaughterhouse wastewater source to the influent. Sludge concentration, waste sludge production and COD and nutrient removal performance were monitored. Furthermore, to investigate how the sludge acclimatises to a higher influent particulate content, lipase and protease hydrolytic activities were studied, as well as the microbial community composition of the sludge. The composition of the granule bed and nutrient removal efficiency did not change considerably by the increased pCOD. Interestingly, the biomass-specific hydrolytic activities of the sludge did not increase during the test period either. However, already during normal operation the aerobic granules and flocs exhibited a hydrolytic potential that ex-ceeded the influent concentrations of proteins and lipids. Microbial community analysis also revealed a high proportion of putative hydrolysing and fermenting organisms in the sludge, both during normal operation and during the test period. The results of this study highlight the robust-ness of the full-scale AGS process, which can bear a substantial increase in the influent pCOD concentration during an extended period.Sanitary EngineeringWater ManagementBT/Environmental Biotechnolog
