On Modulus and Fracture Toughness of Rigid Particulate Filled High Density Polyethylene

A Kaolin-filled, high-density polyethylene (HDPE) system was used to illustrate the influence of particulates on modulus and toughness of the bulk material. A variation of filler content, particulate size and coupling quality for two HDPE-matrix systems with different viscosity led to a strong dependency of elastic modulus and fracture toughness under various testing conditions, e.g. static loading, fatigue and impact.

A stiffness improvement with increasing filler content was achieved by all coupling qualities. The developed Kaolin reinforcement of HDPE with optimised coupling offers an improvement of the stiffness and toughness under all investigated loading conditions. The degree of improvement depends on the particulate size and matrix viscosity. The energy dissipation mechanisms were investigated by fractographic analysis.     

Evaluation of Reliability Indicators for WDNs with Demand-Driven and Pressure-Driven Models

Reliability of water distribution networks (WDNs) has received much attention in recent years due to progressive aging of infrastructures and climate change. Several reliability indicators, focusing on hydraulic aspects rather than water quality, have been proposed in literature. Reliability is generally assessed resorting to well established methods coupling hydraulic simulations and stochastic techniques that describe the WDNs hydraulic performance and component availability respectively. Two main algorithms are employed to simulate WDNs: the demand driven approach (DDA) that disregards the physical relationship between actual water demand and nodal pressure, and the pressure driven approach (PDA) that explicitly incorporates it. In this paper, we show how the choice of hydraulic solver may affect reliability indicators. We modify existing quantitative indicators at nodal and network level, and define novel indicators to consider water quality aspects. These indicators are evaluated for three example WDNs; discrepancies between results obtained with the two approaches depend on network size, feeding scheme and skeletonization. Results suggest to use with caution the DDA for reliability assessment at both local and global level.     

Absolute emission quantum yield determination of self-assembled mesoporous titania films grafted with a luminescent zinc complex

A luminescent zinc complex was successfully incorporated to mesostructured porous titania films through a grafting process. The resulting films show an intense blue-emission increasing with functionalization time. The emission quantum yield of these newly synthesized films was quantitatively and accurately determined by measurements carried by an integrating sphere.     

Electrochemically Induced Addition Reactions in the Absence of Solvent and Supporting Electrolyte

Solvent‐ and supporting electrolyte‐free electrolysis in a two‐compartment cell proved to be effective for the direct electroactivation of C H acid‐containing compounds vs. catalytic addition processes. Michael adducts (including quaternary carbon centres) and 2‐nitroalkanols were obtained in very good yields and selectivity on application of a catalytic amount of electricity under galvanostatic conditions.     

Size effects and ductile-brittle transition of polypropylene

The influence of specimen width on fracture parameters has been investigated. The range examined was sufficiently large to obtain ductile and brittle fractures. With reference to previously published work, the phenomenology has been analysed by combining BCS model and Carpinteri's brittleness number approach.Nomenclature a crack length - f(a/W) shape function according to ASTM specification [16] - F(a/W) shape function according to Tada Paris notation [21] - E elastic modulus - K _IC plane strain fracture toughness - K _IC ^f fictitious plane strain fracture toughness - K _IC2 plane stress fracture toughness - J _IC ^f J-integral at maximum load - L span - weight average molecular weight - number average molecular weight - polydispersity - P _M maximum load - P _F load of brittle fracture - p _P load of plastic collapse - s brittleness number - V machine cross speed - W specimen width - _y yield stress - strain rate     

Stereochemical composition-properties relationships in isotactic polypropylenes obtained with different catalyst systems

The influence of stereochemical composition of the radial growth rate of spherulites, the nucleation density, the overall rate of crystallization and the thermal behaviour of fractions of iPP samples synthesized with different catalyst systems (low, high and very high yield) was investigated. The study used ¹³C n.m.r., differential scanning calorimetry (d.s.c.) and optical microscopy. The ¹³C n.m.r. analysis showed that due to the presence of catalytic sites with different stereoregulating capability the catalyst system produces polypropylene with different stereoregularity. It was found that the growth rate of spherulites and the overall rate of crystallization are strictly related to the stereochemical structure of the polypropylene. Moreover, for the low yield iPP, phenomena of secondary crystallization were observed by Avrami analysis of the overall kinetics. Values of the equilibrium melting temperature (T_m), energy of nucleation (Δø1) and surface free energy of folding (σe) of iPP lamellar crystals have been determined according to the kinetic theory of polymer crystallization. The values of such thermodynamic quantities as well as the thermal behaviour of various iPP are strongly dependent upon the amount and distribution of configurational irregularities existing along the chains and upon the molecular mass distribution.     

Crosstalk between β2- and α2-Adrenergic Receptors in the Regulation of B16F10 Melanoma Cell Proliferation

Adrenergic receptors (AR) belong to the G protein-coupled receptor superfamily and regulate migration and proliferation in various cell types. The objective of this study was to evaluate whether β-AR stimulation affects the antiproliferative action of α2-AR agonists on B16F10 cells and, if so, to determine the relative contribution of β-AR subtypes. Using pharmacological approaches, evaluation of Ki-67 expression by flow cytometry and luciferase-based cAMP assay, we found that treatment with isoproterenol, a β-AR agonist, increased cAMP levels in B16F10 melanoma cells without affecting cell proliferation. Propranolol inhibited the cAMP response to isoproterenol. In addition, stimulation of α2-ARs with agonists such as clonidine, a well-known antihypertensive drug, decreased cancer cell proliferation. This effect on cell proliferation was suppressed by treatment with isoproterenol. In turn, the suppressive effects of isoproterenol were abolished by the treatment with either ICI 118,551, a β2-AR antagonist, or propranolol, suggesting that isoproterenol effects are mainly mediated by the β2-AR stimulation. We conclude that the crosstalk between the β2-AR and α2-AR signaling pathways regulates the proliferative activity of B16F10 cells and may therefore represent a therapeutic target for melanoma therapy.     

Removal of MuRF1 Increases Muscle Mass in Nemaline Myopathy Models,but Does Not Provide Functional Benefits

Nemaline myopathy (NM) is characterized by skeletal muscle weakness and atrophy. No curative treatments exist for this debilitating disease. NM is caused by mutations in proteins involved in thin-filament function, turnover, and maintenance. Mutations in nebulin, encoded by NEB, are the most common cause. Skeletal muscle atrophy is tightly linked to upregulation of MuRF1, an E3 ligase, that targets proteins for proteasome degradation. Here, we report a large increase in MuRF1 protein levels in both patients with nebulin-based NM, also named NEM2, and in mouse models of the disease. We hypothesized that knocking out MuRF1 in animal models of NM with muscle atrophy would ameliorate the muscle deficits. To test this, we crossed MuRF1 KO mice with two NEM2 mouse models, one with the typical form and the other with the severe form. The crosses were viable, and muscles were studied in mice at 3 months of life. Ultrastructural examination of gastrocnemius muscle lacking MuRF1 and with severe NM revealed a small increase in vacuoles, but no significant change in the myofibrillar fractional area. MuRF1 deficiency led to increased weights of various muscle types in the NM models. However, this increase in muscle size was not associated with increased in vivo or in vitro force production. We conclude that knocking out MuRF1 in NEM2 mice increases muscle size, but does not improve muscle function.     

Dissociation of changes in metabolic rate and blood pressure with erythrocyte Na-K pump activity in older men after endurance training

We examined whether changes in resting metabolic rate (RMR) and blood pressure in older normotensive men in response to endurance training were associated with alterations in the Na-K pump activity of plasma-bathed erythrocytes. Eleven men performed cycling exercise three times a week for 8 weeks, and six other men served as controls. Measurements included: RMR by indirect calorimetry, supine blood pressure, body composition by underwater weighing, plasma and erythrocyte Na and K parameters using flame photometry and ouabain. Peak VO2 increased 12% (p < .001), RMR increased 10% (p < .01), mean blood pressure decreased 5% (p < .05), erythrocyte K increased 5% (p < .01), plasma K decreased 7% (p < .001), and plasma Na decreased by 4% (p < .001) in response to training. Erythrocyte Na and Na-K pump rate did not change, nor did the individual changes correlate with changes in RMR or mean blood pressure. Exercise training increases RMR and reduces blood pressure in older men, but these changes are dissociated with erythrocyte Na-K pump activity.     

Rheumatoid arthritis and hydroxyapatite-coated hip prostheses: five-year results. International ABG Study Group

Medium- and long-term results from cemented total hip arthroplasty (THA) in patients with rheumatoid arthritis (RA) show a higher incidence of infection and aseptic loosening when compared to other diagnoses. Early results using uncemented prostheses are variable. Hydroxyapatite (HA) coatings are thought to improve early osseointegration in uncemented THA. In a prospective, international, multicenter clinical study, 32 RA patients who received 33 uncemented HA-coated prostheses were followed up for a minimum of 5 years. Medium-term clinical results are excellent. No infection or aseptic loosening has been recorded. Excellent osseointegration was observed radiographically. Bone remodeling was consistent with mainly proximal to midstem stress transfer. We conclude that uncemented, proximally HA-coated prostheses are a promising alternative to cemented prostheses for RA patients.