Revisiting borehole stresses in anisotropic elastic media : comparison of analytical versus numerical solutions

We present a rigorous validation of the analyticalAmadei solution for the stress concentration around arbitrarily orientated borehole in general anisotropic elastic media. First, we revisit the theoretical framework of the Amadei solution and present analytical insights that show that the solution does indeed contain all special cases of symmetry, contrary to previous understanding, provided that the reduced strain coefficients β11 and β55 are not equal. It is shown from theoretical considerations and published experimental data that the β11 and β55 are not equal for realistic rocks. Second, we develop a 3D finite-element elastic model within a hybrid analyticalnumerical workflow that circumvents the need to rebuild and remesh the model for every borehole and material orientation. Third, we show that the borehole stresses computed from the numerical model and the analytical solution match almost perfectly for different borehole orientations (vertical, deviated and horizontal) and for several cases involving isotropic and transverse isotropic symmetries. It is concluded that the analytical Amadei solution is valid with no restrictions on the borehole orientation or elastic anisotropy symmetry.

Synthesis of biodegradable polymer-mesoporous silica composite microspheres for DNA prime-protein boost vaccination

DNA vaccines or proteins are capable of inducing specific immunity; however, the translation to the clinic has generally been problematic, primarily due to the reduced magnitude of immune response and poor pharmacokinetics. Herein we demonstrate a composite microsphere formulation, composed of mesoporous silica spheres (MPS) and poly(d,l-lactide-co-glycolide) (PLGA), enables the controlled delivery of a prime-boost vaccine via the encapsulation of plasmid DNA (pDNA) and protein in different compartments. Method with modified dual-concentric-feeding needles attached to a 40 kHz ultrasonic atomizer was studied. These needles focus the flow of two different solutions, which passed through the ultrasonic atomizer. The process synthesis parameters, which are important to the scale-up of composite microspheres, were also studied. These parameters include polymer concentration, feed flowrate, and volumetric ratio of polymer and pDNA-PEI/MPS-BSA. This fabrication technique produced composite microspheres with mean D[4,3] ranging from 6 to 34 μm, depending upon the microsphere preparation. The resultant physical morphology of composite microspheres was largely influenced by the volumetric ratio of pDNA-PEI/MPS-BSA to polymer, and this was due to the precipitation of MPS at the surface of the microspheres. The encapsulation efficiencies were predominantly in the range of 93-98% for pDNA and 46-68% for MPS. In the in vitro studies, the pDNA and protein showed different release kinetics in a 40 day time frame. The dual-concentric-feeding in ultrasonic atomization was shown to have excellent reproducibility. It was concluded that this fabrication technique is an effective method to prepare formulations containing a heterologous prime-boost vaccine in a single delivery system.

Transmittance properties of contact lens multipurpose solutions and their effects on a hydrogel lens

Purpose The aim was to assess the compatibility of different multipurpose solutions (MPSs) with one type of silicone hydrogel (SiH) contact lens by, assessing the changes in both ultraviolet (UV) and visible light transmissibility of the hydrogel lens caused by the MPSs. Methods The light transmittance from 200-700 nm were measured for the lotrafilcon B blister pack solution (BPS), six MPSs namely, ReNuMultiPlus Multi-Purpose Solution (Bausch and Lomb Inc., Rochester NY, USA.); Complete RevitaLens Multi-Purpose (Abbott Medical Optics Inc., Quarryvale Co. Dublin, Ireland); All In One Light (Sauflon Pharmaceuticals Ltd., Twickenham, England); SOLO-care AQUA™ (Ciba Vision Corporation Duluth, Georgia, USA.); Biomedics All-in-one solution (CooperVision, Hamble, UK); and HippiaMultiPlus All-in-one solution (Interojo Inc., Kyeonggi-do, Korea), and a lotrafilcon B SiH lens (before and after storage), using a spectrophotometer. Results The UV transmitted through the BPS and the MPS were similar (p >.05, for all), except for the HippiaMultiPlus which was lower (p < 0.001) by 19.8%. Mean transparency values were statistically (p<.001) significantly different between the BPS and the MPSs. All MP solution/SiH lens combinations resulted in relatively high UV transmittance values especially in the UVC spectrum, and significantly increased (p <.001) the visible light transmittance values of the SiH lens. Greater changes in transparency were observed in the ReNu/SiH lens (28.5%) and the Complete RevitaLens/SiH lens (24.9%) combinations. Conclusion The six MPSs showed significant variations in the transmitted UV and visible light. Similar to the BPS, all MPSs were equally transparent, but showed very poor UVA & UVB attenuation, except for the Hippia MultiPlus. The MPS/SiH lens combinations did not significantly affect the lens transparency but it significant increased the lens transmittance of UV radiation, after storage. Further in-vivo studies are needed to validate if this effect is constant.

Equilibrium and column studies of iron exchange with strong acid cation resin

The exchange of iron species from iron (III) chloride solutions with a strong acid cation resin has been investigated in relation to a variety of water and wastewater applications. A detailed equilibrium isotherm analysis was conducted wherein models such as Langmuir Vageler, Competitive Langmuir, Freundlich, Temkin, Dubinin Astakhov, Sips and Brouers-Sotolongo were applied to the experimental data. An important conclusion was that both the bottle-point method and solution normality used to generate the ion exchange equilibrium information influenced which sorption model fitted the isotherm profiles optimally. Invariably, the calculated value for the maximum loading of iron on strong acid cation resin was substantially higher than the value of 47.1 g/kg of resin which would occur if one Fe3+ ion exchanged for three “H+” sites on the resin surface. Consequently, it was suggested that above pH 1, various iron complexes sorbed to the resin in a manner which required less than 3 sites per iron moiety. Column trials suggested that the iron loading was 86.6 g/kg of resin when 1342 mg/L Fe (III) ions in water were flowed at 31.7 bed volumes per hour. Regeneration with 5 to 10 % HCl solutions reclaimed approximately 90 % of exchange sites.

The mechanical and inflammatory low back pain (MIL) index: development and validation

Abstract Background The purpose of this study was the development of a valid and reliable “Mechanical and Inflammatory Low Back Pain Index” (MIL) for assessment of non-specific low back pain (NSLBP). This 7-item tool assists practitioners in determining whether symptoms are predominantly mechanical or inflammatory. Methods Participants (n = 170, 96 females, age = 38 ± 14 years-old) with NSLP were referred to two Spanish physiotherapy clinics and completed the MIL and the following measures: the Roland Morris Questionnaire (RMQ), SF-12 and “Backache Index” (BAI) physical assessment test. For test-retest reliability, 37 consecutive patients were assessed at baseline and three days later during a non-treatment period. Face and content validity, practical characteristics, factor analysis, internal consistency, discriminant validity and convergent validity were assessed from the full sample. Results A total of 27 potential items that had been identified for inclusion were subsequently reduced to 11 by an expert panel. Four items were then removed due to cross-loading under confirmatory factor analysis where a two-factor model yielded a good fit to the data (χ2 = 14.80, df = 13, p = 0.37, CFI = 0.98, and RMSEA = 0.029). The internal consistency was moderate (α = 0.68 for MLBP; 0.72 for ILBP), test-retest reliability high (ICC = 0.91; 95%CI = 0.88-0.93) and discriminant validity good for either MLBP (AUC = 0.74) and ILBP (AUC = 0.92). Convergent validity was demonstrated through similar but weak correlations between the ILBP and both the RMQ and BAI (r = 0.34, p < 0.001) and the MLBP and BAI (r = 0.38, p < 0.001). Conclusions The MIL is a valid and reliable clinical tool for patients with NSLBP that discriminates between mechanical and inflammatory LBP. Keywords: Low back pain; Psychometrics properties; Pain measurement; Screening tool; Inflammatory; Mechanical

Tracking control of a class of Hamiltonian mechanical systems with disturbances

This paper presents a trajectory-tracking control strategy for a class of mechanical systems in Hamiltonian form. The class is characterised by a simplectic interconnection arising from the use of generalised coordinates and full actuation. The tracking error dynamic is modelled as a port-Hamiltonian Systems (PHS). The control action is designed to take the error dynamics into a desired closed-loop PHS characterised by a constant mass matrix and a potential energy with a minimum at the origin. A transformation of the momentum and a feedback control is exploited to obtain a constant generalised mass matrix in closed loop. The stability of the close-loop system is shown using the close-loop Hamiltonian as a Lyapunov function. The paper also considers the addition of integral action to design a robust controller that ensures tracking in spite of disturbances. As a case study, the proposed control design methodology is applied to a fully actuated robotic manipulator.

Effect of nano-silica on the mechanical and transport properties of lightweight concrete

This paper investigated the influence of nano-silica (NS) on the mechanical and transport properties of lightweight concrete (LWC). The resistance of LWC to water and chloride ions penetration was enhanced despite strength marginally increased. Water penetration depth, moisture sorptivity, chloride migration and diffusion coefficient was reduced by 23% and 49%, 23% and 10%, 5% and 0%, 22% and 12% compared to the two reference LWC mixes (pure cement and 60% slag blended cement), respectively with 1% NS. Such improvements were attributed to more compact microstructures because the micropore system was refined and the interface between aggregates and paste was enhanced.

Experimental and numerical investigation of strain-rate dependent mechanical properties of single living cells

The objective of this project is to investigate the strain-rate dependent mechanical behaviour of single living cells using both experimental and numerical techniques. The results revealed that living cells behave as porohyperlastic materials and that both solid and fluid phases within the cells play important roles in their mechanical responses. The research reported in this thesis provides a better understanding of the mechanisms underlying the cellular responses to external mechanical loadings and of the process of mechanical signal transduction in living cells. It would help us to enhance knowledge of and insight into the role of mechanical forces in supporting tissue regeneration or degeneration.

Generalized element load method for first- and second-order element solutions with element load effect

The finite element method in principle adaptively divides the continuous domain with complex geometry into discrete simple subdomain by using an approximate element function, and the continuous element loads are also converted into the nodal load by means of the traditional lumping and consistent load methods, which can standardise a plethora of element loads into a typical numerical procedure, but element load effect is restricted to the nodal solution. It in turn means the accurate continuous element solutions with the element load effects are merely restricted to element nodes discretely, and further limited to either displacement or force field depending on which type of approximate function is derived. On the other hand, the analytical stability functions can give the accurate continuous element solutions due to element loads. Unfortunately, the expressions of stability functions are very diverse and distinct when subjected to different element loads that deter the numerical routine for practical applications. To this end, this paper presents a displacement-based finite element function (generalised element load method) with a plethora of element load effects in the similar fashion that never be achieved by the stability function, as well as it can generate the continuous first- and second-order elastic displacement and force solutions along an element without loss of accuracy considerably as the analytical approach that never be achieved by neither the lumping nor consistent load methods. Hence, the salient and unique features of this paper (generalised element load method) embody its robustness, versatility and accuracy in continuous element solutions when subjected to the great diversity of transverse element loads.

A framework for understanding and generating integrated solutions for residential peak energy demand

Supplying peak energy demand in a cost effective, reliable manner is a critical focus for utilities internationally. Successfully addressing peak energy concerns requires understanding of all the factors that affect electricity demand especially at peak times. This paper is based on past attempts of proposing models designed to aid our understanding of the influences on residential peak energy demand in a systematic and comprehensive way. Our model has been developed through a group model building process as a systems framework of the problem situation to model the complexity within and between systems and indicate how changes in one element might flow on to others. It is comprised of themes (social, technical and change management options) networked together in a way that captures their influence and association with each other and also their influence, association and impact on appliance usage and residential peak energy demand. The real value of the model is in creating awareness, understanding and insight into the complexity of residential peak energy demand and in working with this complexity to identify and integrate the social, technical and change management option themes and their impact on appliance usage and residential energy demand at peak times.

Bisphenol A sorption by organo-montmorillonite: Implications for the removal of organic contaminants from water

Remediation of bisphenol A (BPA) from aqueous solutions by adsorption using organoclays synthesized from montmorillonite (MMT) with different types of organic surfactant molecules was demonstrated. High adsorption capacities of the organoclays for the uptake of BPA were observed and these demonstrated their potential application as strong adsorbents for noxious organic water contaminants. The adsorption of BPA was significantly influenced by pH, with increased adsorption of BPA in acidic pH range. However, the organoclays intercalated with highly loaded surfactants and/or large surfactant molecules were less influenced by the pH of the environment and this was thought to be due to the shielding the negative charge from surfactant molecules and the development of more positive charge on the clay surface, which leads to the attraction of anionic BPA even at alkaline pH. The hydrophobic phase created by loaded surfactant molecules contributed to a partitioning phase, interacting with BPA molecules strongly through hydrophobic interaction. Pseudo-second order kinetic model and Langmuir isotherm provided the best fit for the adsorption of BPA onto the organoclays. In addition, the adsorption process was spontaneous and exothermic with lower temperature facilitating the adsorption of BPA onto the organoclays. The described process provides a potential pathway for the removal of BPA from contaminated waters.

Environmental contamination and hospital-acquired infection: factors that are easily overlooked

There is an ongoing debate about the reasons for and factors contributing to healthcare-associated infection (HAI). Different solutions have been proposed over time to control the spread of HAI, with more focus on hand hygiene than on other aspects such as preventing the aerial dissemination of bacteria. Yet, it emerges that there is a need for a more pluralistic approach to infection control; one that reflects the complexity of the systems associated with HAI and involves multidisciplinary teams including hospital doctors, infection control nurses, microbiologists, architects, and engineers with expertise in building design and facilities management. This study reviews the knowledge base on the role that environmental contamination plays in the transmission of HAI, with the aim of raising awareness regarding infection control issues that are frequently overlooked. From the discussion presented in the study, it is clear that many unknowns persist regarding aerial dissemination of bacteria, and its control via cleaning and disinfection of the clinical environment. There is a paucity of good-quality epidemiological data, making it difficult for healthcare authorities to develop evidence-based policies. Consequently, there is a strong need for carefully designed studies to determine the impact of environmental contamination on the spread of HAI.

Impact of agricultural chemicals on the environment and human health in Asia: Are there solutions?

Modern commercial agricultural practices in Asia during the last three to four decades involving chemicals (fertilisers and pesticides) have been associated with large increases in food production never witnessed before, especially under the Green Revolution technology in South Asia. This also involves large-scale increases in commercial vegetable crops. However, the high reliance on chemical inputs to bring about these increases in food production is not without problems. A visible, parallel correlation between higher productivity, high artificial input use and environmental degradation and human ill-health is evident in many countries where commercial agriculture is widespread. In this chapter, we focus on the impact of chemical inputs, in particular the impact of pesticides on the environment and on human health in South Asia with special reference to Sri Lanka...

Mechanical Behavior of Nanostructured Materials

This Special Issue presents recent research advances in various aspects of advanced nanomaterials including synthesis, micro- and nanostructures, mechanical properties, modeling, and applications for material nanotechnology community. In particular, it aims to reflect recent advances in mechanical behaviors, for example, stiffness, strength, ductility, fatigue, and wear resistance, of various nanomaterials including nanocrystalline, inorganic, nonmetallic nanomaterials, composites with nanosized fillers, and biomaterials with nanosized structures. The role of this Special Issue is to bridge the gaps among fabrication techniques, experimental techniques, numerical modeling, and applications for some new nanomaterials and to investigate some key issues related to the mechanical properties of the nanomaterials. It brings together researchers working at the frontier of the mechanical behavior of nanomaterials...

Psychological services for asylum seekers in the community: Challenges and solutions

Objective: Given the Australian government’s current policy of placing asylum seekers into the community while their applications for asylum are being considered, it is important that mental health practitioners are able to offer culturally safe, sensitive, and competent services in this context. Method: A qualitative approach was used to interview seven practitioners, who provided services to asylum seekers at a specialist health clinic in the community. These professionals used their experience to identify the psychosocial issues faced by these asylum seekers, the challenges of providing culturally effective services to this group, and how these services can be improved. Result: Data were thematically analysed using NVivo. The findings indicated that participants perceived that clients experienced psychological, health, and cultural difficulties. The stress and uncertainty around visa applications emerged as the most severe factor impacting asylum seekers’ mental health. Working effectively with interpreters and culturally adapting assessment and treatment for these clients emerged as effective strategies. Gathering information in a conversational way and using clients’ different cultural explanatory models were methods used to identify and address mental health issues, rather than using formal measures. Interventions were eclectic and holistic, and reflected treatments that were appropriate for the clients’ cultural backgrounds. Conclusion: The study has implications for how psychological services are offered to asylum seekers in the community. Further, it identifies areas that can be incorporated in the future training of practitioners.