Ruolo della composizione e metodo di preparazione nelle proprietà di catalizzatori contenenti cerio per l'ossidazione parziale catalitica del metano

Questo a lavoro di tesi si è incentrato sullo sviluppo di catalizzatori attivi nella reazione di ossidazione parziale catalitica (CPO) del metano per la produzione di idrogeno o/e syngas, con un rapporto ottimale di H2/CO, utile per la produzione idrocarburi attraverso la reazione di Fischer-Tropsch o per l’alimentazione delle fuels cells. La scarsa diffusione di questo processo è da attribuirsi alla mancanza di catalizzatori adatti a resistere agli elevati flussi e alle elevate temperature raggiunte nel letto senza subire processi di disattivazione; pertanto, è necessario lo sviluppo di nuovi catalizzatori non soltanto attivi, ma anche stabili nelle condizioni di reazione. In questa tesi si sono studiati catalizzatori con differenti fasi attive Rh e Ru supportati su CeO2-Al2O3, utilizzati in pellets. L'attenzione di questo lavoro di tesi si è focalizzata sullo studio delle proprietà e del ruolo della fase attiva e del promotore ceria nei catalizzatori. Per questo studio sono stati sintetizzati per coprecipitazione due catalizzatori con ugual concentrazione di cerio ma diversa fase attiva, Rodio e Rutenio e se ne sono studiate le proprietà. Della fase attiva con migliori prestazioni, il Rh, se ne è approfondito lo studio, indagando sulla migliore metodologia di attivazione e sul miglior metodo di sintesi del catalizzatore. Infine, per lo studio dell’effetto del cerio sia nelle proprietà chimico-fisiche che nella attività catalitica, sono stati preparati per coprecipitazione diversi catalizzatori di tipo Rh-CeO2-Al2O3, con un contenuto di cerio variabile ma con ugual concentrazione di fase attiva, cosi come dei campioni di riferimento contenti soltanto ceria o allumina. Questi catalizzatori sono stati testati in severe condizioni e per lunghi tempi di reazione per simulare l’utilizzo industriale ed evidenziarne le caratteristiche.

Population doublings and percentage of S100-positive cells as predictors of in vitro chondrogenicity of expanded human articular chondrocytes

The aim of this study was to investigate the interconnection between the processes of proliferation, dedifferentiation, and intrinsic redifferentiation (chondrogenic) capacities of human articular chondrocyte (HAC), and to identify markers linking HAC dedifferentiation status with their chondrogenic potential. Cumulative population doublings (PD) of HAC expanded in monolayer culture were determined, and a threshold range of 3.57-4.19 PD was identified as indicative of HAC loss of intrinsic chondrogenic capacity in pellets incubated without added chondrogenic factors. While several specific gene and surface markers defined early HAC dedifferentiation process, no clear correlation with the loss of intrinsic chondrogenic potential could be established. CD90 expression during HAC monolayer culture revealed two subpopulations, with sorted CD90-negative cells showing lower proliferative capacity and higher chondrogenic potential compared to CD90-positive cells. Although these data further validated PD as critical for in vitro chondrogenesis, due to the early shift in expression, CD90 could not be considered for predicting chondrogenic potential of HAC expanded for several weeks. In contrast, an excellent mathematically modeled correlation was established between PD and the decline of HAC expressing the intracellular marker S100, providing a direct link between the number of cell divisions and dedifferentiation/loss of intrinsic chondrogenic capacity. Based on the dynamics of S100-positive HAC during expansion, we propose asymmetric cell division as a potential mechanism of HAC dedifferentiation, and S100 as a marker to assess chondrogenicity of HAC during expansion, of potential value for cell-based cartilage repair treatments.

Micromass co-culture of human articular chondrocytes and human bone marrow mesenchymal stem cells to investigate stable neocartilage tissue formation in vitro

Cell therapies for articular cartilage defects rely on expanded chondrocytes. Mesenchymal stem cells (MSC) represent an alternative cell source should their hypertrophic differentiation pathway be prevented. Possible cellular instruction between human articular chondrocytes (HAC) and human bone marrow MSC was investigated in micromass pellets. HAC and MSC were mixed in different percentages or incubated individually in pellets for 3 or 6 weeks with and without TGF-beta1 and dexamethasone (±T±D) as chondrogenic factors. Collagen II, collagen X and S100 protein expression were assessed using immunohistochemistry. Proteoglycan synthesis was evaluated applying the Bern score and quantified using dimethylmethylene blue dye binding assay. Alkaline phosphatase activity (ALP) was detected on cryosections and soluble ALP measured in pellet supernatants. HAC alone generated hyaline-like discs, while MSC formed spheroid pellets in ±T±D. Co-cultured pellets changed from disc to spheroid shape with decreasing number of HAC, and displayed random cell distribution. In -T-D, HAC expressed S100, produced GAG and collagen II, and formed lacunae, while MSC did not produce any cartilage-specific proteins. Based on GAG, collagen type II and S100 expression chondrogenic differentiation occurred in -T-D MSC co-cultures. However, quantitative experimental GAG and DNA values did not differ from predicted values, suggesting only HAC contribution to GAG production. MSC produced cartilage-specific matrix only in +T+D but underwent hypertrophy in all pellet cultures. In summary, influence of HAC on MSC was restricted to early signs of neochondrogenesis. However, MSC did not contribute to the proteoglycan deposition, and HAC could not prevent hypertrophy of MSC induced by chondrogenic stimuli.

The Crystallization Kinetics of Polylactic Acid (Pla) Processed Through Solid-State/Melt Extrusion

Polylactic acid (PLA) is a bio-derived, biodegradable polymer with a number of similar mechanical properties to commodity plastics like polyethylene (PE) and polyethylene terephthalate (PETE). There has recently been a great interest in using PLA to replace these typical petroleum-derived polymers because of the developing trend to use more sustainable materials and technologies. However, PLA¿s inherent slow crystallization behavior is not compatible with prototypical polymer processing techniques such as molding and extrusion, and in turn inhibits its widespread use in industrial applications. In order to make PLA into a commercially-viable material, there is a need to process the material in such a way that its tendency to form crystals is enhanced. The industry standard for producing PLA products is via twin screw extrusion (TSE), where polymer pellets are fed into a heated extruder, mixed at a temperature above its melting temperature, and molded into a desired shape. A relatively novel processing technique called solid-state shear pulverization (SSSP) processes the polymer in the solid state so that nucleation sites can develop and fast crystallization can occur. SSSP has also been found to enhance the mechanical properties of a material, but its powder output form is undesirable in industry. A new process called solid-state/melt extrusion (SSME), developed at Bucknell University, combines the TSE and SSSP processes in one instrument. This technique has proven to produce moldable polymer products with increased mechanical strength. This thesis first investigated the effects of the TSE, SSSP, and SSME polymer processing techniques on PLA. The study seeks to determine the process that yields products with the most enhanced thermal and mechanical properties. For characterization, percent crystallinity, crystallization half time, storage modulus, softening temperature, degradation temperature and molecular weight were analyzed for all samples. Through these characterization techniques, it was observed that SSME-processed PLA had enhanced properties relative to TSE- and SSSP-processed PLA. Because of the previous findings, an optimization study for SSME-processed PLA was conducted where throughput and screw design were varied. The optimization study determined PLA processed with a low flow rate and a moderate screw design in an SSME process produced a polymer product with the largest increase in thermal properties and a high retention of polymer structure relative to TSE-, SSSP-, and all other SSME-processed PLA. It was concluded that the SSSP part of processing scissions polymer chains, creating defects within the material, while the TSE part of processing allows these defects to be mixed thoroughly throughout the sample. The study showed that a proper SSME setup allows for both the increase in nucleation sites within the polymer and sufficient mixing, which in turn leads to the development of a large amount of crystals in a short period of time.

Endothelin antagonism prevents diabetic retinopathy in NOD mice: a potential role of the angiogenic factor adrenomedullin

Altered activity of retinal endothelin-1 (ET-1) and nitric oxide may play a causal role in the hemodynamic and histopathological changes of diabetic retinopathy. This study evaluated the therapeutic potential of long-term selective blockade of the ET-1(A) receptor (ETRA) to prevent the development of retinopathy in a genetic mouse model of nonobese type 1 diabetes (NOD). Mice with NOD that received subcutaneous implantation of insulin pellets and wild-type control mice were treated for 4 months with the selective ETRA antagonist LU208075 (30 mg/kg/day) via drinking water. At the end of the study, blood glucose levels were evaluated, and animals were anesthetized and perfused intracardially with FITC-labeled dextran. Retinas were removed and either fixed in formalin for confocal microscope evaluation of retinal vascular filling or transferred to RNALater for quantitative reverse transcriptase-polymerase chain reaction to evaluate expression of NOS-3, NOS-1, ET-1, ETRA, ETRB, and the angiogenic factor adrenomedullin. Compared with wild-type controls, expression of ET-1, ETRA, ETRB, and adrenomedullin in mice with NOD were markedly upregulated in the retinas of nontreated mice (cycle time values relative to GAPDH [deltaCt], 14.8 vs. 13.7, 18.57 vs. 17.5, 10.76 vs. 9.9, and 11.7 vs. 9.1, respectively). Mean integral fluorescence intensity (MIFI) of retinal vascular filling was reduced from normal values of 24 to 12.5 in nontreated animals. LU208075 treatment normalized the upregulated expression of ET-1 and adrenomedullin, as well as the deficit in MIFI, but did not affect the increased ETRA and ETRB expression or the elevated plasma glucose levels found in nontreated animals. NOS isoform expression was essentially unchanged. ETRA antagonists may provide a novel therapeutic strategy to slow or prevent progression of retinal microvascular damage and proliferation in patients for whom there is clear evidence of activation of the ET-1 system.

Visual histological grading system for the evaluation of in vitro-generated neocartilage

Here we present the development of a visual evaluation system for routine assessment of in vitro-engineered cartilaginous tissue. Neocartilage was produced by culturing human articular chondrocytes in pellet culture systems or in a scaffold-free bioreactor system. All engineered tissues were embedded in paraffin and were sectioned and stained with Safranin O-fast green. The evaluation of each sample was broken into 3 categories (uniformity and intensity of Safranin O stain, distance between cells/amount of matrix produced, and cell morphology), and each category had 4 components with a score ranging from 0 to 3. Three observers evaluated each sample, and the new system was independently tested against an objective computer-based histomorphometry system. Pellets were also assessed biochemically for glycosaminoglycan (GAG) content. Pellet histology scores correlated significantly with GAG contents and were in agreement with the computer-based histomorphometry system. This system allows a valid and rapid assessment of in vitro-generated cartilaginous tissue that has a relevant association with objective parameters indicative of cartilage quality.

Expansion on specific substrates regulates the phenotype and differentiation capacity of human articular chondrocytes

In this study, we investigated if monolayer expansion of adult human articular chondrocytes (AHAC) on specific substrates regulates cell phenotype and post-expansion multilineage differentiation ability. AHAC isolated from cartilage biopsies of five donors were expanded on plastic dishes (PL), on dishes coated with collagen type II (COL), or on slides coated with a ceramic material (Osteologic, OS). The phenotype of expanded chondrocytes was assessed by flow cytometry and real-time RT-PCR. Cells were then cultured in previously established conditions promoting differentiation toward the chondrogenic or osteogenic lineage. AHAC differentiation was assessed histologically, biochemically, and by real-time RT-PCR. As compared to PL-expanded AHAC, those expanded on COL did not exhibit major phenotypic changes, whereas OS-expanded cells expressed (i) higher bone sialoprotein (BSP) (22.6-fold) and lower collagen type II (9.3-fold) mRNA levels, and (ii) lower CD26, CD90 and CD140 surface protein levels (1.4-11.1-fold). Following chondrogenic differentiation, COL-expanded AHAC expressed higher mRNA levels of collagen type II (2.3-fold) and formed tissues with higher glycosaminoglycan (GAG) contents (1.7-fold), whereas OS-expanded cells expressed 16.5-fold lower collagen type II and generated pellets with 2.0-fold lower GAG contents. Following osteogenic differentiation, OS-expanded cells expressed higher levels of BSP (3.9-fold) and collagen type I (2.8-fold) mRNA. In summary, AHAC expansion on COL or OS modulated the de-differentiated cell phenotype and improved the cell differentiation capacity respectively toward the chondrogenic or osteogenic lineage. Phenotypic changes induced by AHAC expansion on specific substrates may mimic pathophysiological events occurring at different stages of osteoarthritis and may be relevant for the engineering of osteochondral tissues.

PERFORMANCE EVALUATION OF LLDPE/CaCO3 MODIFIERS WITH AND WITHOUT TITANATE COUPLING AGENT ON ASPHALT BINDER AND MIXTURE

The complexity and challenge created by asphalt material motivates researchers and engineers to investigate the behavior of this material to develop a better understanding, and improve the performance of asphalt pavement. Over decades, a wide range of modification at macro, meso, micro and nano scales have been conducted to improve the performance of asphalt pavement. This study was initiated to utilize the newly developed asphalt modifier pellets. These pellets consisted of different combinations of calcium carbonate (CaCO3), linear low-density polyethylene (LLDPE) and titanate coupling agent (CA) to improve the asphalt binder as well as pavement performance across a wide range of temperature and loading pace. These materials were used due to their unique characteristics and promising findings from various industries, especially as modifiers in pavement material. The challenge is to make sure the CaCO3 disperses very well in the mixture. The rheological properties of neat asphalt binder PG58-28 and modified asphalt binder (PG58-28/LLDPE, PG58-28/CaCO3, PG58-28/CaCO3/LLDPE, and PG58-28/CaCO3/LLDPE/CA), were determined using rotational viscometer (RV) test, dynamic shear rheometer (DSR) test and bending beam rheometer test. In the DSR test, the specimens were evaluated using frequency sweep and multiple shear creep recovery (MSCR). The asphalt mixtures (aggregate/PG58-28, aggregate/ PG58-28/LLDPE, aggregate/PG58-28/CaCO3, aggregate/PG58-28/LLDPE/CaCO3 and aggregate/PG58-28/LLDPE/CaCO3/CA) were evaluated using the four point beam fatigue test, the dynamic modulus (E*) test, and tensile strength test (to determines tensile strength ratio, TSR). The RV test results show that all modified asphalt binders have a higher viscosity compared to the neat asphalt binder (PG58-28). Based on the Jnr results (using MSCR test), all the modified asphalt binders have a better resistance to rutting compared to the neat asphalt binder. A higher modifier contents have resulted in a better recovery percentage of asphalt binder (higher resistance to rutting), except the specimens prepared using PECC’s modified asphalt binder (PG58-28/CaCO3/LLDPE). The BBR test results show that all the modified asphalt binders have shown comparable performance in term of resistance to low temperature cracking, except the specimen prepared using the LLDPE modifier. Overall, 5 wt% LLDPE modified asphalt binder was found to be the best asphalt binder in terms of resistance to rutting. Meanwhile, 3 wt% PECC-1CA’s modified asphalt binder can be considered as the best (in terms of resistance to thermal cracking) with the lowest mean critical cracking temperature. The appearance of CaCO3 was found useful merely in improving the resistance to fatigue cracking of asphalt mixture. However, application of LLDPE has undermined the fatigue life of asphalt mixtures. Adding LLDPE and coupling agent throughout this study does not sufficiently help in terms of elastic behavior which essential to enhance the resistance to fatigue cracking. In contrast, application of LLDPE has increased the indirect tensile strength values and TSR of asphalt mixtures, indicates a better resistance to moisture damage. The usage of the coupling agent does not change the behavior of the asphalt mixture, which could be due to imbalance effects resulted by combination of LLDPE and CaCO3 in asphalt binder. Further investigations without incorporating CaCO3 should be conducted further. To investigate the feasibility of using LLDPE and coupling agent as modifiers in asphalt pavements, more research should be conducted on different percentages of LLDPE (less than 3 wt%), and at the higher and w wider range of coupling agent content, from 3 wt% to 7 wt% based on the polymer mass.

THE INFLUENCE OF DIET COMPOSITION, PLANT DEFENSIVE CHEMICALS, AND WINTER SEVERITY ON THE NUTRITIONAL CONDITION OF A FREERANGING, GENERALIST HERBIVORE

Herbivory requires animals to manage intake of toxic phytochemicals. Detoxification and excretion of these chemicals prevents toxicity, but is energetically expensive. I investigated the relationship between investment in detoxification and nutritional condition for moose on Isle Royale National Park (Alces alces) during winter, using urinary indices from urine samples collected in snow. The ratio of urinary urea nitrogen:creatinine is an indicator of nutritional condition, and the ratio of glucuronic acid:creatinine is an indicator of investment in detoxification. Nutritional condition declined with greater investment in detoxification. An alternative means of managing defensive chemical intake is to diversify the diet. Microhistological analysis of fecal pellets determined diet composition. Diet diversity was weakly associated with improved nutritional condition. However, the strongest predictors of nutritional condition were winter severity and proportion of balsam fir in the diet (a dominant food for moose in this ecosystem).

Production of Iron-Tin Compacts by Powder Metallurgy and a Synopsis of their Principle Properties

This thesis is concerned primarily with the production of metal powder compacts of iron and tin. In producing these compacts, the effects of process­ing variables on some of the essential properties of the pellets made were investigated.

Tissue neogenesis and STRO-1 expression in immature and mature articular cartilage

This study determined the potential for neotissue formation and the role of STRO-1+ cells in immature versus mature articular cartilage. Cartilage explants from immature and mature bovine knee joints were cultured for up to 12 weeks and stained with safranin-O, for type II collagen and STRO-1. Bovine chondrocyte pellet cultures and murine knee joints at the age of 2 weeks and 3 months, and surgically injured cartilage, were analyzed for changes in STRO-1 expression patterns. Results show that immature explants contained more STRO-1+ cells than mature explants. After 8 weeks in culture, immature explants showed STRO-1+ cell proliferation and newly formed tissue, which contained glycosaminoglycan and type II collagen. Mature cartilage explants showed only minimal cell expansion and neotissue formation. Pellet cultures with chondrocytes from immature cartilage showed increased glycosaminoglycan synthesis and STRO-1+ staining, as compared to pellets with mature chondrocytes. The frequency of STRO-1+ cells in murine knee joints significantly declined with joint maturation. Following surgical injury, immature explants had higher potential for tissue repair than mature explants. In conclusion, these findings suggest that the high percentage of STRO-1+ cells in immature cartilage changes with joint maturation. STRO-1+ cells have the potential to form new cartilage spontaneously and after tissue injury. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Apoptotic cell death in the lactating mammary gland is enhanced by a folding variant of alpha-lactalbumin

Apoptosis is essential to eliminate secretory epithelial cells during the involution of the mammary gland. The environmental regulation of this process is however, poorly understood. This study tested the effect of HAMLET (human alpha-lactalbumin made lethal to tumor cells) on mammary cells. Plastic pellets containing HAMLET were implanted into the fourth inguinal mammary gland of lactating mice for 3 days. Exposure of mammary tissue to HAMLET resulted in morphological changes typical for apoptosis and in a stimulation of caspase-3 activity in alveolar epithelial cells near the HAMLET pellets but not more distant to the pellet or in contralateral glands. The effect was specific for HAMLET and no effects were observed when mammary glands were exposed to native a-lactalbumin or fatty acid alone. HAMLET also induced cell death in vitro in a mouse mammary epithelial cell line. The results suggest that HAMLET can mediate apoptotic cell death in mammary gland tissue.

Beef Cow Feeding Demonstration

Pregnant mature beef cows were fed one of five rations: tub ground hay, low corn supplementation plus hay, high corn plus hay, low corn gluten feed (CGF) pellets plus hay, and high CGF plus hay. All treatments resulted in weight gains and limited body condition score changes. The hay and high CGF pellet diet resulted in statistically different weight gains compared with the other supplementation programs.

Effects of different types of solid feeds on health status and performance of Swiss veal calves. II. Basic feeding with whole milk

The objective of this study was to identify a suitable alternative to the current practice of complementing the feeding of whole milk with straw. The influence of 3 different solid supplements on the health and performance of Swiss veal calves was investigated during 3 production cycles of 90 veal calves each with a mean initial age of 42 days and a mean initial weight of 68.7 kg. The calves were housed in groups of 30 in stalls strewn with wheat straw without outside pen. Liquid feeding consisted of whole milk combined with an additional skim milk powder ad libitum. Groups were assigned to one of the three following experimental solid feeds provided ad libitum: Pellet mix (composition: oat hulls, corn [whole plant], barley, sunflower seeds, squeezed grains of corn, molasses and a pellet binder), whole plant corn pellets, and wheat straw as control. Calves of the straw group showed significantly more abomasal lesions in the fundic part as compared to the pellet mix and corn pellets groups (P < 0.001), the prevalence of insufficient papillae was highest (P < 0.05), and ruminating behavior was unsatisfactory. In contrast to the pellet mix and straw groups, performance of calves in the corn pellets group was good. Additionally, prevalence of abomasal fundic lesions was lowest (P < 0.001), and rumen development was best in calves of the corn pellets group (P < 0.01). As in part I, the results reveal that whole-plant corn pellets are most consistent with an optimal result combining the calves' health and fattening performance. Therefore, it can be recommended as a solid supplement for veal calves basically fed whole milk under Swiss conditions.

Effects of different types of solid feeds on health status and performance of Swiss veal calves. I. Basic feeding with milk by-products

The objective of this study was to identify a suitable alternative to the current practice of complementing the feeding of milk by-products with straw. The influence of 5 different types of solid feeds on health and performance of Swiss veal calves was investigated in 2 production cycles of 200 veal calves each with a mean initial age of 40 days (d). The calves were housed in groups of 40 in stalls with outside pen. Liquid feeding consisted of a milk by-product combined with an additional skim milk powder ad libitum. Groups were assigned to 1 of the 5 following experimental solid feeds provided ad libitum: mix (composition: soy flakes, corn, barley, wheat, oat, barley middling, plant oil, molasses), whole plant corn pellets, corn silage, hay, and wheat straw as control. Daily dry matter intake per calf averaged 2.25 kg of the liquid food, 0.16 kg of straw, 0.33 kg of mix, 0.47 kg of corn silage, 0.38 kg of corn pellets, and 0.39 kg of hay. No significant differences (P > 0.05) among groups were found in calf losses that amounted to 4.8 % (68 % because of gastrointestinal disorders). Four percent of the calves were slaughtered prematurely. Daily doses of antibiotics were higher in the mix (36.9 d, P < 0.01) and in the corn silage groups (35 d, P < 0.01) compared to control. Compared to the 4 other groups, calves of the straw group showed the highest prevalence of abnormal ruminal content (73 %, P < 0.05), of abnormal ruminal papillae (42 %, P < 0.05), of abomasal fundic lesions (13.5 %, P < 0.1), and the lowest number of chewing movements per bolus (45, P < 0.05). The hemoglobin concentration averaged 85 g/l at the beginning and 99 g/l at the end of the fattening period with no significant differences among groups (P > 0.1). The duration of the fattening period averaged 114 d, slaughter age 157 d, and carcass weight 122 kg. The average daily weight gain (ADG) was highest in the control group straw (1.35 kg), and lowest in the hay group (1.22 kg, P < 0.01). The number of carcasses classified as C, H, and T (very high to medium quality) was lower in the hay group compared to straw (P < 0.01). No significant differences between groups were found in meat color (P > 0.1): 73 % of the carcasses were assessed as pale (267/364), 18 % as pink (66/364), and 9 % (31/364) as red. The results reveal that whole-plant corn pellets are most consistent with an optimal result combining the calves' health and fattening performance. Therefore, it can be recommended as an additional solid feed for veal calves under Swiss conditions.