Linear displacement and force characterisation of a 3D-printed flexure-based delta actuator

Piezoelectric beams provide a fast, high-force and scalable actuation mechanism that could offer precise motion control to medical microdevices including invasive micromanipulators, catheters and diagnosis tools. Their small displacement range can be addressed by motion amplification mechanisms. In this paper, a piezoelectric-actuated delta-robot actuator is proposed for probe-based confocal laser endomicroscopy (pCLE) microsystems. A prototype is designed and fabricated using three-dimensional (3D) polymer compound printing for a multi-flexure compliant motion amplifier and commercial piezoelectric beams. The flexure material is optimised for maximum linear output motion. The overall robot length is 76 mm and its maximum lateral dimension is 32 mm, with 10 g overall mass, including three piezoelectric beams. An axial motion control range of 0.70 mm and a maximum axial force of 20 mN are demonstrated, at 140 V actuation voltage. The proposed actuator architecture is promising for controlling lens, fibre and micromanipulator components for medical microrobotic applications

Influence of Post-Welding Heat Treatment on the Corrosion Behavior of a 2050-T3 Aluminum-Copper-Lithium Alloy Friction Stir Welding Joint

The corrosion behavior of a Friction Stir Welding joint in 2050-T3 Al-Cu-Li alloy was studied in 1 M NaCl solution and the influence of T8 post-welding heat treatment on its corrosion susceptibility was analyzed. After exposure to 1 M NaCl solution, the heat affected zone (HAZ) of the weld without post-welding heat treatment was found to be the most extensively corroded zone with extended intergranular corrosion damage while, following T8 post-welding heat treatment, no intergranular corrosion was observed in the HAZ and the global corrosion behavior of the weld was significantly improved. The corrosion damage observed on the welded joints after immersion in 1 M NaCl solution was compared to that obtained after 750 h Mastmaasis Wet Bottom tests. The same corrosion damage was observed. Various stationary electrochemical tests were carried out on the global welded joint and/or each of the metallurgical zones of the welded joint to understand the corrosion damage observed. TEM observations helped in bringing meaningful elements to analyze the intrinsic electrochemical behavior of the different zones of the weld related to their microstructure. However, galvanic coupling tests showed that galvanic coupling effects between the different zones of the weld were at least partially responsible for its corrosion behavior

Itinerant ferromagnetism and intrinsic anomalous Hall effect in amorphous iron-germanium

The amorphous iron-germanium system (a-FexGe1-x) lacks long-range structural order and hence lacks a meaningful Brillouin zone. The magnetization of a-FexGe1-x is well explained by the Stoner model for Fe concentrations x above the onset of magnetic order around x=0.4, indicating that the local order of the amorphous structure preserves the spin-split density of states of the Fe-3d states sufficiently to polarize the electronic structure despite k being a bad quantum number. Measurements reveal an enhanced anomalous Hall resistivity ρxyAH relative to crystalline FeGe; this ρxyAH is compared to density-functional theory calculations of the anomalous Hall conductivity to resolve its underlying mechanisms. The intrinsic mechanism, typically understood as the Berry curvature integrated over occupied k states but shown here to be equivalent to the density of curvature integrated over occupied energies in aperiodic materials, dominates the anomalous Hall conductivity of a-FexGe1-x (0.38≤x≤0.61). The density of curvature is the sum of spin-orbit correlations of local orbital states and can hence be calculated with no reference to k space. This result and the accompanying Stoner-like model for the intrinsic anomalous Hall conductivity establish a unified understanding of the underlying physics of the anomalous Hall effect in both crystalline and disordered systems

The role of hydrophobic amino acid grafts in the enhancement of membrane-disruptive activity of pH-responsive pseudo-peptides

pH-responsive polymers have been synthesised by grafting l-valine (PV-75), l-leucine (PL-75) and l-phenylalanine (PP-75) onto the pendant carboxylic acid moieties of a pseudo-peptide, poly(l-lysine iso-phthalamide), at a stoichiometric degree of substitution of 75 mol%. The effect of such modification on the pH-, concentration- and time-dependent cell membrane-disruptive activity of the grafted polymers has been investigated using a haemolysis model. At 0.025 mg mL(−1), the grafted polymers were almost non-haemolytic at pH 7.4, but mediated considerable membrane lysis after 60 min in the pH range characteristic of early endosomes, which ranked in the order: PP-75 > PL-75 > PV-75 > poly(l-lysine iso-phthalamide). PP-75 was 35-fold more lytic on a molar basis than the membrane-lytic peptide melittin. With increasing concentration, the grafted polymers showed an increased ability to lyse cell membranes and caused noticeable membrane disruption at physiological pH. The mechanism of the polymer-mediated membrane destabilisation has been investigated. The in-vitro cytotoxicity of the grafted polymers has been assessed using a propidium iodide fluorescence assay. It has been demonstrated by confocal microscopy that the grafted polymers can induce a significant release of endocytosed materials into the cytoplasm of HeLa cells, which is a feature critical for drug delivery applications

Presentation of glaucoma in the greater Accra Metropolitan Area of Ghana

Background: This study addresses the prevalence and clinical presentation of patients with primary open angle glaucoma (POAG) in the greater Accra metropolitan area.Methods: This is a retrospective case series of 455 patients (813 eyes) at the Emmanuel Eye Clinic. Patients were diagnosed from May 2008 to Nov 2011. The definition of POAG conformed to the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria. Information collected included basic demographic data, distribution of glaucoma subtypes, measured intraocular pressure (IOP), best corrected visual acuity (BCVA) and optic disc measurements.Results: Nearly 24% presented blind in at least one eye. The average age was 56.7 +/-16.7 years and the average IOP was 33.9 mmHg +/- 12.7 mmHg for right eyes and 33.5 mmHg +/-12.0 mmHg for left eyes. Themean vertical cup to disc ratio (vCDR) was 0.83 for right eyes versus 0.82 for left eyes. A total of 32 patients (53 eyes) were diagnosed with normal tension glaucoma (NTG). Statistically significant differences between the NTG and high tension groups included age (45.3 +/- 16.7 vs. 56.7 +/-16.7, p<0.001), mean IOP (19.1 mmHg +/- 4.5 mmHg vs. 33.7 +/- 12.4 mmHg,p<0.001) and mean vCDR (0.76 +/- 0.17 vs. 0.83 +/- 0.10, p<0.01). Comparing age-matched NTG patients with high tension glaucoma patients showed no significant difference in vCDR.Conclusions: The clinical presentation of POAG at the Emmanuel Eye Center is characterized by elevated IOP and grossly advanced optic neuropathy. Significant differences between high tension glaucoma and NTG were identified.Keywords: Primary Open Angle Glaucoma, Normal Tension Glaucoma, Ghana, Accra, Afric

Compliance error compensation in robotic-based milling

The paper deals with the problem of compliance errors compensation in robotic-based milling. Contrary to previous works that assume that the forces/torques generated by the manufacturing process are constant, the interaction between the milling tool and the workpiece is modeled in details. It takes into account the tool geometry, the number of teeth, the feed rate, the spindle rotation speed and the properties of the material to be processed. Due to high level of the disturbing forces/torques, the developed compensation technique is based on the non-linear stiffness model that allows us to modify the target trajectory taking into account nonlinearities and to avoid the chattering effect. Illustrative example is presented that deals with robotic-based milling of aluminum alloy

Human capability evaluation approach for cybersecurity in critical industrial infrastructure

Every organization is as frail as its frailest human link in the cyber security of Industry Control System (ICS), which is without predisposition to conceivable technological solutions for enforcing security. Noticeably, human-involved systems are becoming more chaotic, and gravely under attacks due to irregular actions or inactions of human entities in the constituent chain. Many industrial cyber-attacks have successfully defeated technological security solutions through preying on human weaknesses in knowledge and skills, and manipulating insiders within organizations into unsuspectingly delivering entry and access to sensitive industrial assets. In order to help enterprises assess the level of employees’ cyber security awareness and responsiveness, and enhance ICS Cyber security knowledge and skills for ICS protection, a Workforce Cyber Security Capability evaluation model is presented, and theoretically validated. A capability evaluation will allow industries to have a better understanding of the potential state of consciousness, readiness and diagnostic abilities of the industries; thus improve the prevention, detection, and response to any cyber-specific incidents

Speciation and fate of copper in sewage treatment works with and without tertiary treatment: The effect of return flows

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 Taylor & Francis.The removal of metals from wastewaters is becoming an important issue, with new environmental quality standards putting increased regulatory pressure on operators of sewage treatment works. The use of additional processes (tertiary treatment) following two-stage biological treatment is frequently seen as a way of improving effluent quality for nutrients and suspended solids, and this study investigates the impact of how back washes from these tertiary processes may impact the removal of copper during primary sedimentation. Seven sites were studied, three conventional two-stage biological treatment, and four with tertiary processes. It was apparent that fluxes of copper in traditional return flows made a significant contribution to the load to the primary treatment tanks, and that<1% of this was in the dissolved phase. Where tertiary processes were used, back wash liquors were also returned to the primary tanks. These return flows had an impact on copper removal in the primary tanks, probably due to their aerobic nature. Returning such aerobic back wash flows to the main process stream after primary treatment may therefore be worth consideration. The opportunity to treat consolidated liquor and sludge flows in side-stream processes to remove toxic elements, as they are relatively concentrated, low volume flow streams, should also be evaluated