Moment transfer and influence of transverse beams in interior waffle flat plate-column connections under lateral loading

This paper addresses two aspects of the behavior of interior reinforced concrete waffle flat plate?column connections under lateral loads: the share of the unbalanced moment between flexure and excentric shear, and the effect of the transverse beams. A non-linear finite element model (benchmark model) was developed and calibrated with the results of quasi-static cyclic tests conducted on a 3/5 scale specimen. First, from this numerical model, the portion cv of the unbalanced moment transferred by the excentricity of shear about the centroid of the critical sections defined by Eurocode 2 (EC-2) and by ACI 318-11 was calculated and compared with the share-out prescribed by these codes. It is found that while the critical section of EC-2 is consistent with the cv provided by this code, in the case of ACI 318-11, the value assigned to cv is far below (about 50% smaller) the actual one obtained with the numerical simulations. Second, from the benchmark model, seven additional models were developed by varying the depth D of the transverse beam over the thickness h of the plate. It was found that the ductility of the connection and the effective width of the plate can respectively be increased up to 50% and 10% by raising D/h to 2 and 1.5.

Effect of strain and magnetic field on the critical current and electric resistance of the joints between HTS coated conductors

Engineering of devices and systems such as magnets, fault current limiters or cables, based on High Temperature Superconducting wires requires a deep characterization of the possible degradation of their properties by handling at room temperature as well as during the service life thus establishing the limits for building up functional devices and systems. In the present work we report our study regarding the mechanical behavior of spliced joints between commercial HTS coated conductors based on YBCO at room temperature and service temperature, 77 K. Tensile tests under axial stress and the evolution of the critical current and the electric resistance of the joints have been measured. The complete strain contour for the tape and the joints has been obtained by using Digital Image Correlation. Also, tensile tests under external magnetic field have been performed and the effect of the applied field on the critical current and the electric resistance of the joints has been studied. Additionally, fatigue tests under constant cyclic stress and loading-unloading ramps have been carried out in order to evaluate the electromechanical behavior of the joints and the effect of maximum applied stress on the critical current. Finally, a preliminary numerical study by means of the Finite Element Method (FEM) of the electromechanical behavior of the joints between commercial HTS is presented.

Strain rate effect on semi‐crystalline plla mechanical properties measured by instrumented indentation tests

Poly(L‐lactide) is a widely studied biomaterial, currently approved for use in a range of medical devices. Its mechanical properties can be tailored giving the material different crystallinity degrees. PLLA presents a complex non‐linear behaviour that depends not only on structural parameters such as crystallinity degree but also on external parameters such as strain rate and temperature. Failure of polymeric implants is attributed to their intrinsic time‐dependent performance under static loading conditions.

Microwave-assisted catalysis by iron oxide nanoparticles on MCM-41: Effect of the support morphology

Catalytically active heterogeneous catalysts have been prepared via microwave deposition of iron oxide nanoparticles (0.5–1.2 wt%) on MCM-41 type silica materials with different morphologies (particles, helical and spheres). This methodology leads to iron oxide nanoparticles composed by a mixture of FeO and Fe2O3 species, being the Fe(II)/Fe(III) peak ratio near to 1.11 by XPS. DRUV spectroscopy indicates the presence of tetrahedral coordinated Fe3+ in the silica framework of the three catalysts as well as some extraframework iron species in the catalysts with particle and sphere-like morphologies. The loading of the nanoparticles does neither affect the mesopore arrangement nor the textural properties of the silica supports, as indicated by SAXS and nitrogen adsorption/desorption isotherms. A detailed investigation of the morphology of the supports in various microwave-assisted catalyzed processes shows that helical mesostructures provide optimum catalytic activities and improved reusabilities in the microwave-assisted redox (selective oxidation of benzyl alcohol) catalyzed process probably due to a combination of lower particle size and higher acidity in comparison with the supports with particle and sphere morphology.

The influence of surfactant loading level in a montmorillonite on the thermal, mechanical and rheological properties of EVA nanocomposites

In this work, montmorillonite (Mt) has been organically modified with ethyl hexadecyl dimethyl ammonium (EHDDMA) in 20, 50, 80 and 100% of the nominal exchange capacity (CEC) of the Mt. A full characterization of the organo-montmorillonite (OMt) obtained has been made, including thermal analysis, X-Ray Diffraction, elemental analysis CHN and nitrogen adsorption. According to the results, 12% in mass of the surfactant added is strongly retained by the Mt. When the mass percentage of EHDDMA exchanged in the OMt is increased up to this level, the interactions OMt–EHDDMA are steeply reduced depending on the EHDDMA content. Clay polymer nanocomposites (CPN) were prepared by melt mixing of EVA and different loads of OMt. The CPN were compress molded to obtain 1 mm thick sheets, which have been characterized according to their mechanical, thermal and rheological behaviors. The major changes in the structure of the OMt are obtained for low contents of EHDDMA. Nevertheless, the CPN containing OMt exchanged at 20 and 50% of the CEC show relatively low effect of the EHDDMA while the mechanical response and rheological behavior of CPN with OMt modified at 80 and 100% of the CEC are much more pronounced.

Carbon nanotube-supported Ni–CeO2 catalysts. Effect of the support on the catalytic performance in the low-temperature WGS reaction

The low temperature water-gas shift (WGS) reaction has been studied over two commercial multiwall carbon nanotubes-supported nickel catalysts promoted by ceria. For comparison purposes, activated carbon-supported catalysts have also been studied. The catalytic performance and the characterization by N2 adsorption analysis, powder X-ray diffraction (XRD), temperature-programmed reduction with H2 (TPR-H2), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis showed that the surface chemistry has an important effect on the dispersion of ceria. As a result, ceria was successfully dispersed over the carbon nanotubes (CNTs) with less graphitic character, and the catalyst afforded better activity in WGS than the catalyst prepared over massive ceria. Moreover, a 20 wt.% CeO2 loading over this support was more active than the analogous catalyst with a 40 wt.% loading. The ceria nanoparticles were smaller when the support was previously oxidized, however this resulted in a decrease of the activity.

Numerical and experimental investigation of structural stiffness influence on ratcheting convection cell in granular soils under cyclic loading

Lateral cyclic loaded structures in granular soils can lead to an accumulation of irreversible strains by changing their mechanical response (densification) and forming a closed convective cell in the upper layer of the bedding. In the present thesis the convective cell dimension, formation and grain migration inside this closed volume have been studied and presented in relation to structural stiffness and different loads. This relation was experimentally investigated by applying a cyclic lateral force to a scaled flexible vertical element embedded in dry granular soil. The model was monitored with a camera in order to derive the displacement field by means of the PIV technique. Modelling large soil deformation turns out to be difficult, using mesh-based methods. Consequently, a mesh-free approach (DEM) was chosen in order to investigate the granular flow with the aim of extracting interesting micromechanical information. In both the numerical and experimental analyses the effect of different loading magnitudes and different dimensions of the vertical element were considered. The main results regarded the different development, shape and dimensions of the convection cell and the surface settlements. Moreover, the Discrete Element Method has proven to give satisfactory results in the modelling of large deformation phenomena such as the ratcheting convective cell.

Compression Loading Induced Cellular Stress Response of Intervertebral Disc Cells in Organ Culture

Introduction: Mechanical stress is often associated to interverterbal disc (IVD) degeneration and the effect of mechanical loading on IVD has been studied and reviewed.1,2 Previously, expression of heat shock proteins, HSP70 and HSP27 has been found in pathological discs.3 However, there is no direct evidence on whether IVD cells respond to the mechanical loading by expression of HSPs. The objective of this study is to investigate the stress response of IVD cells during compressive loading in an organ culture. Materials and Methods: Fresh adult bovine caudal discs were cultured with compressive loading applied at physiological range. Effect of loading type (static and dynamic) and repeated loading (2 hours per day for 2 days) were studied. Nucleus pulposus (NP) and annulus fibrosus (AF) of the IVD were retrieved at different time points: right after loading and right after resting. Positive control discs were heat shocked (43°C). Cell activity was assessed and expression of stress response genes (HSP70 and HSF1) and matrix remodeling genes (ACAN, COL2, COL1, ADAMTS4, MMP3 and MMP13) were studied. Results: Cell activity was maintained in all groups. Both NP and AF expressed high level of HSP70 in heat shock groups, confirming their expression in response to stress. In NP, expression of HSP70 was up-regulated after static loading and dynamic loading with higher fold change was observed after static loading. During repeated loading, HSP70 appeared to be upregulated right after loading and decreased after resting. Such trend was not observed in AF and HSF1 levels. Expressions of matrix remodeling genes did not change significantly with loading except ADAMTS4 decreased in AF during static loading. Conclusion: This study demonstrated that NP cells upregulate expression of HSP70 in response to loading induced stress without changing cell activity and matrix remodeling significantly. Acknowledgments: This project was funded by AO Spine (AOSPN) (grant number: SRN_2011_14) and a fellowship exchange award by AO Spine Scientific Research Network (SRN).

Effect of locally increased zinc contents on zinc transport from the flag leaf lamina to the maturing grains of wheat

From previous experiments, it was evident that the accumulation of zinc in maturing wheat grains is highly regulated, but the regulatory mechanisms involved are not yet identified. In this study, we determined the transfer of radiolabelled zinc (fed directly into a leaf flap) from the flag leaf lamina to the grains. We also determined how this zinc transfer was affected by feeding additional unlabeled zinc (1 μmol per plant) either into the flag leaf sheath or the peduncle. Most of the 65Zn was retained in the feeding flap. A high percentage of the zinc exported from the flap accumulated in the grains with little accumulation of radiolabel in the other parts of the shoot. Unlabeled zinc remained mainly in the feeding flap and in the parts reached by the transpiration stream from the feeding position. The transfer of radiolabelled zinc was essentially not influenced by unlabeled zinc fed into another plant part. Our results suggest that the loading of zinc into the phloem and the mass flow in the sieve tubes might regulate zinc redistribution within the wheat shoot.

Computation by the method of characteristics of disturbance in an elastic half-space caused by blast-like surface loading

Mode of access: Internet.

Encapsulation of lipopeptides within liposomes: Effect of number of lipid chains, chain length and method of liposome preparation

The purpose of this study was to systematically investigate the effect of lipid chain length and number of lipid chains present on lipopeptides on their ability to be incorporated within liposomes. The peptide KAVYNFATM was synthesized and conjugated to lipoamino acids having acyl chain lengths of C-8, C-12 and C-16. The C-12 construct was also prepared in the monomeric, dimeric and trimeric form. Liposomes were prepared by two techniques: hydration of dried lipid films (Bangham method) and hydration of freeze-dried monophase systems. Encapsulation of lipopeptide within liposomes prepared by hydration of dried lipid films was incomplete in all cases ranging from an entrapment efficiency of 70% for monomeric lipoamino acids at a 5% (w/w) loading to less than 20% for di- and trimeric forms at loadings of 20% (w/w). The incomplete entrapment of lipopeptides within liposomes appeared to be a result of the different solubilities of the lipopeptide and the phospholipids in the solvent used for the preparation of the lipid film. In contrast, encapsulation of lipopeptide within liposomes prepared by hydration of freeze-dried monophase systems was high, even up to a loading of 20% (w/w) and was much less affected by the acyl chain length and number than when liposomes were prepared by hydration of dried lipid films. Freeze drying of monophase systems is better at maintaining a molecular dispersion of the lipopeptide within the solid phospholipid matrix compared to preparation of lipid film by evaporation, particularly if the solubility of the lipopeptide in solvents is markedly different from that of the polar lipids used for liposome preparation. Consequently, upon hydration, the lipopeptide is more efficiently intercalated within the phospholipid bilayers. (C) 2005 Elsevier B.V. All rights reserved.

Effect of cyclic pneumatic soft tissue compression on simulated distal radius fractures

We investigated the effect of pneumatic pressure applied to the proximal musculature of the sheep foreleg on load at the site of a transverse osteotomy of the distal radius. The distal radii of 10 fresh sheep foreleg specimens were osteotomized and a pressure sensor was inserted between the two bone fragments. An inflatable cuff, connected to a second pressure sensor, was positioned around the proximal forelimb musculature and the leg then was immobilized in a plaster cast. The inflatable cuff was inflated and deflated repeatedly to various pressures. Measurements of the cuff pressure and corresponding change in pressure at the osteotomy site were recorded. The results indicated that application of pneumatic pressure to the proximal foreleg musculature produced a corresponding increase in load at the osteotomy site. For the cuff pressures tested (109.8-238.4 mm Hg), there was a linear correlation with the load at the osteotomy site with a gradient of 12 mm Hg/N. It is conceivable, based on the results of this study, that a technique could be developed to provide dynamic loading to accelerate fracture healing in the upper limb of humans.

How is leflunomide prescribed and used in Australia? analysis of prescribing and adverse effect reporting

Purpose To evaluate the use of leflunomide in the Australian community since introduction in 2000. Trends in adverse drug reaction (ADR) reporting were also studied. Methods Annual Australian prescription and dispensing statistics were analysed. Drug utilisation was estimated as defined daily doses (DDD)/1000 inhabitants/day. ADR data from the Therapeutic Goods Administration's Adverse Drug Reactions Advisory Committee (ADRAC) national monitoring system were compared with the World Health Organisation (WHO) Vigibase records. Results Leflunomide use in Australia (dispensing data) increased from 0.2 in 2000 to 0.4 DDD/1000 inhabitants/day in 2002. The same overall pattern was observed in the 'authority to prescribe' data. From 2000-2002, prescribing of the starter pack (3 x 100 mg loading dose plus 30 x 20 mg tablets) declined (down 74%); likewise for the 20mg (30 tablets) pack. Gradual increases were noted for the 10 mg (30 tablets) pack (up 40%). Approximately 135 reports, detailing about 370 individual ADR, were generated annually. Gastro-intestinal disorders predominated, accounting for 24% of reactions reported to ADRAC. Skin and appendages disorders constituted 14% of reported reactions. Deaths in leflunomide users were attributed to a combination of haematological and gastro-intestinal complications, but it was not possible to ascertain other medication usage or contributing factors. Trends observed with the ADRAC reports were consistent with the WHO database. Conclusions Leflunomide was the first registered DMARD in Australia in over a decade and its use has increased within the community. The ADR reports might have contributed to Australian rheumatologists gradually abandoning loading patients with high doses of leflunomide in favour of starting therapy at lower doses. Copyright (c) 2006 John Wiley & Sons, Ltd.

Uptake and transport of orally-deliverable drugs across caco-2 cell monolayers:the effect of lipid formulations

The aim of this thesis is to investigate the physicochemical parameters which can influence drug loading within liposomes and to characterise the effect such formulations have on drug uptake and transport across in vitro epithelial barrier models. Liposomes composed of phosphatidylcholine (PC) or distearoyl phosphatidylcholine (DSPC) and cholesterol (0, 4, 8, 16 µM) were prepared and optimised in terms of drug loading using the hand-shaking method (Bangham et al., 1965). Subsequently, liposomes composed of 16 µM PC or DSPC and cholesterol (4 µM) were used to monitor hydroxybenzoate release and transport from Iiposomes. The MIT (3[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) and crystal violet assays were employed to determine toxicity of the Iiposome. formulations towards the Caco-2 cell line, employed to model the epithelial barrier in vitro. Uptake and transport of mannitol, propranolol, glutamine and digoxin was measured in the presence and absence of Iiposome formulations to establish changes in absorption resulting from the presence of lipid formulations. Incorporation of the four hydroxybenzoates was shown to be influenced by a number of factors, including liposome composition and drug conformation. Methyl hydroxybenzo.ate (MP) was incorporated into the bilayer most effectively with percentage incorporation of 68% compared to 45% for butyl hydroxybenzoate (BP), despite its increased Iipophilicity. This was attributed to the decreased packing ability of BP within the hydrocarbon core of the lipid bilayer compared to MP. Release studies also suggested that the smaller MP was more strongly incorporated within the lipid bilayer with only 8% of the incorporated solute being released after 48-hours compared to 17% in the case of BP. Model transport studies were seen to reflect drug release profiles from the liposome bilayers with significantly (p < 0.01) higher amounts of BP partitioning from the liposome compared to MP, Caco-2 cell viability was maintained above 86% in the presence of all Iiposome formulations tested indicating the liposome formulations are non-toxic towards Caco-2 cells. Paracellular (apical-to-basolateral) transport of mannitol was significantly increased in the presence of DSPC, PC / DSPC:Cholesterol (16:4 µM; 1000 µg). Glutamine uptake and transport via the carrier-mediated route was Significantly (p < 0.01) increased in the presence of PC I DSPC:Cholesterol (16:0; 16:4 µM). Digoxin apical-to-basolateral transport was significantly increased (p < 0,01) in the presence of PC / DSPC:Cholesterol (16:0; 16:4 µM); thus reducing digoxin efflux via P-glycoprotein. In contrast, PC:ChoJesterol (16:0; 16:4 µM) significantly (p < 0.01) decreased propranolol uptake via the passive transcellular route. Bi-directional transport of propranolol was significantly (p < 0,01) decreased in the presence of PC/DSPC:Cholesterol (16:0; 16:4 µM). The structure of a solute is an important determinant for the incorporation and release of a solute from liposome formulations. PC, DSPC and cholesterol liposome formulations are nontoxic towards Caco-2 cell monolayers and improved uptake and transport of mannitol, glutamine. and digoxin across Caco-2 cell monolayers; thus providing a potential alternative delivery vehicle.

Using organoclay to promote morphology refinement and co-continuity in high-density polyethylene/polyamide 6 blends - Effect of filler content and polymer matrix composition

We investigate the gradual changes of the microstructure of two blends of high-density polyethylene (HDPE) and polyamide 6 (PA6) at opposite composition filled with increasing amounts of an organomodified clay. The filler locates preferentially inside the polyamide phase, bringing about radical alterations in the micron-scale arrangement of the polymer phases. When the host polyamide represents the major constituent, a sudden reduction of the average sizes of the polyethylene droplets was observed upon addition of even low amounts of organoclay. A morphology refinement was also noticed at low filler contents when the particles distributes inside the minor phase. In this case, however, keep increasing the organoclay content eventually results in a high degree of PA6 phase continuity. Rheological analyses reveal that the filler loading at which the polyamide assembles in a continuous network corresponds to the critical threshold for its rheological transition from a liquid- to a gel-like behaviour, which is indicative of the structuring of the filler inside the host PA6. On the basis of this finding, a schematic mechanism is proposed in which the role of the filler in driving the space arrangement of the polymer phases is discussed. Finally, we show that the synergism between the reinforcing action of the filler and its ability to affect the blend microstructure can be exploited in order to enhance relevant technological properties of the materials, such as their high temperature structural integrity.