MECHANICAL PROPERTIES OF 3D PRINTED FACIAL PROSTHESES COMPARED TO HANDMADE SILICONE POLYMER PROSTHESES

Purpose: To evaluate the mechanical properties of the 3D printed starch models infiltrated with maxillofacial silicone polymers used for fabrication of maxillofacial prostheses compared to the mechanical properties of pure silicone polymer models. Materials and methods: The test and control specimens were designed according to industry standards ASTM specifications using SolidWorks 2008 software for testing tensile strength tear strength, percentage elongation and hardness properties of starch infiltrated silicone polymer. Ten Dumbbell-shaped specimens and ten Trousershaped specimens with four hardness test specimens were printed by Zcorp 510 3D printer and infiltrated with Sil-25 maxillofacial silicone polymer. Whereas, control samples made from pure Sil-25 silicone polymers using a stainless steel mould and following a similar specification of test specimens. Lloyd LRX tensile instrument; load rating 100 N at a constant crosshead speed of 25 mm/min for testing tensile, tear strength and percentage elongation and Hardness Tester (England) was used to measure shore A durometer hardness. Results: Silicone polymer infiltrated starch (test) specimens demonstrated significantly lower tensile strength, tear strength and percentage elongation than the pure silicone polymer (control) samples (p<0.05). However, a significant increase (p<0.05) in the hardness of the printed specimens was recorded against the pure silicone samples. Conclusion: The 3D printed soft tissue prostheses – the final product showed significantly different mechanical properties compared to the handmade prostheses; they were significantly harder and reported lower mechanical properties

MECHANICAL PROPERTIES OF 3D PRINTED FACIAL PROSTHESES COMPARED TO HANDMADE SILICONE POLYMER PROSTHESES

Purpose: To evaluate the mechanical properties of the 3D printed starch models infiltrated with maxillofacial silicone polymers used for fabrication of maxillofacial prostheses compared to the mechanical properties of pure silicone polymer models. Materials and methods: The test and control specimens were designed according to industry standards ASTM specifications using SolidWorks 2008 software for testing tensile strength tear strength, percentage elongation and hardness properties of starch infiltrated silicone polymer. Ten Dumbbell-shaped specimens and ten Trousershaped specimens with four hardness test specimens were printed by Zcorp 510 3D printer and infiltrated with Sil-25 maxillofacial silicone polymer. Whereas, control samples made from pure Sil-25 silicone polymers using a stainless steel mould and following a similar specification of test specimens. Lloyd LRX tensile instrument; load rating 100 N at a constant crosshead speed of 25 mm/min for testing tensile, tear strength and percentage elongation and Hardness Tester (England) was used to measure shore A durometer hardness. Results: Silicone polymer infiltrated starch (test) specimens demonstrated significantly lower tensile strength, tear strength and percentage elongation than the pure silicone polymer (control) samples (p<0.05). However, a significant increase (p<0.05) in the hardness of the printed specimens was recorded against the pure silicone samples. Conclusion: The 3D printed soft tissue prostheses – the final product showed significantly different mechanical properties compared to the handmade prostheses; they were significantly harder and reported lower mechanical properties

MECHANICAL PROPERTIES OF 3D PRINTED FACIAL PROSTHESES COMPARED TO HANDMADE SILICONE POLYMER PROSTHESES

Purpose: To evaluate the mechanical properties of the 3D printed starch models infiltrated with maxillofacial silicone polymers used for fabrication of maxillofacial prostheses compared to the mechanical properties of pure silicone polymer models. Materials and methods: The test and control specimens were designed according to industry standards ASTM specifications using SolidWorks 2008 software for testing tensile strength tear strength, percentage elongation and hardness properties of starch infiltrated silicone polymer. Ten Dumbbell-shaped specimens and ten Trousershaped specimens with four hardness test specimens were printed by Zcorp 510 3D printer and infiltrated with Sil-25 maxillofacial silicone polymer. Whereas, control samples made from pure Sil-25 silicone polymers using a stainless steel mould and following a similar specification of test specimens. Lloyd LRX tensile instrument; load rating 100 N at a constant crosshead speed of 25 mm/min for testing tensile, tear strength and percentage elongation and Hardness Tester (England) was used to measure shore A durometer hardness. Results: Silicone polymer infiltrated starch (test) specimens demonstrated significantly lower tensile strength, tear strength and percentage elongation than the pure silicone polymer (control) samples (p<0.05). However, a significant increase (p<0.05) in the hardness of the printed specimens was recorded against the pure silicone samples. Conclusion: The 3D printed soft tissue prostheses – the final product showed significantly different mechanical properties compared to the handmade prostheses; they were significantly harder and reported lower mechanical properties

MECHANICAL DURABILITY OF 3D PRINTED FACIAL PROSTHESES COMPARED TO TRADITIONAL SILICONE POLYMER PROSTHESES

Purpose: To test the effect of natural and accelerated weathering conditions on the mechanical properties of 3D printed starch samples infiltrated with a maxillofacial silicone polymer. Materials and Methods: A total of 72 samples (dumbbell-shaped, trouserlegs samples, and hardness blocks) were manufactured from silicone polymer (SP) and starch printed and infiltrated silicone polymer (SPIS) according to industry standards (ASTM). Thus, they were set out to evaluate the key mechanical properties of the SPIS (tensile strength, tear strength, percentage elongation, and hardness test). Specimens were exposed to different natural weathering (outdoor, ambient, and dark environment for 4 months) and artificial weathering conditions (2 weeks exposure and 6 weeks exposure) were compared to those of pure silicone polymer (SP). One way analysis of variance ANOVA was used to test the results statistically. Results: Exposure to 4 month natural weathering conditions recorded a significant difference in tensile strength between the control group and the three test groups for SP samples (p<0.05). However, there was no significant differences between the three test groups (p>0.05).Tear strength statistical analysis showed a significant differences between the control group for the SP samples and the other three test samples (p<0.05). Furthermore, SPIS samples demonstrated a significant increase in tear strength of the indoor samples compared to the control samples and the outdoor samples (p<0.05). However, there was no significant difference (p>0.05) observed between the control values and the two other test groups. However, percentage elongation recorded no significant differences between the control group and the test groups for SP samples, or between the test samples in the same group (p>0.05). Percentage elongation for SPIS recorded non-significant differences (p>0.05) between the control values and the dark samples. However, when compared to the outdoor samples, there was a significant difference (p<0.05) between the control and the indoor samples. Hardness test also recorded significant differences (p<0.05) statistically between the control data and the test data for both SP and SPIS samples. Furthermore, artificial weathering condition was more detrimental and showed significant deterioration of some of the mechanical properties of both SP and SPIS specimens when they were exposed for 2 weeks and 6 weeks. Deterioration was more significant at six weeks exposure than 2 weeks when compared to non weathered control group. Conclusions The general properties of facial prostheses were affected non-significantly by exposure to four months natural weathering for both pure silicone polymer SP and starch printed infiltrated polymers SPIS. However, accelerated weathering conditions were significantly deteriorated for the silicone polymer infiltrated starch models SPIS

Making Science Relevant: a Faculty-wide Initiative Towards Enhancing the Student Experience Through Authentic Learning Activities

Authentic learning describes an educational approach in which students are presented with problems of real-world relevance within an environment that mirrors professional practice. (Herrington and Herrington 2006). There is substantial evidence that authentic learning is a powerful tool with which to encourage deeper learning and improve learning outcomes (Newmann et al. 1995). Our project aims to improve student learning outcomes and engagement by embedding authentic learning practice into the curriculum across our large and diverse faculty. We are employing a hub and spoke model of project management: the project team forms the hub, with discipline participants as the spokes, firmly connected to the rim of school-based colleagues. We have devised checklists that allow evaluation of units or learning activities against the principles of authentic learning articulated by Herrington and Herrington (2006). To date, we have run two workshops with discipline participants, who have received peer feedback on teaching initiatives they will trial in semester 2, 2010. In addition, we have initiated a faculty-wide scan for examples of good practice in authentic learning. Outcomes of this project include: broad dissemination of the concept of authentic learning; a web-based resource of exemplars of authentic learning activities; and increased engagement of our students

Designing and mapping a generic attributes curriculum for science undergraduate students: a faculty-wide collaborative project

Our project took a faculty-wide approach to mapping the teaching of GAs across the Schools contributing to the BSc. An initiative at the School of Music at the University of Queensland demonstrates the power of such an approach for improving students’ learning outcomes (Bath, Smith, Stein and Swann 2004). That School went beyond the required mapping and embedding of their university’s graduate attributes to an on-going cycle of review, reflection and renewal of their graduate attributes curriculum based on evidence from student and staff surveys. However, many of the perceived barriers to implementation of a generic attributes curriculum, such as questions of duplication of teaching, need to be addressed across programs rather than within disciplines. Our project aims were: • to develop Faculty-specific exemplars for the University’s GAs; • to facilitate School-level reflection on how the University’s GAs could be interpreted in a discipline-specific context, and thus, • to develop discipline-specific exemplars of the generic GAs; • to develop a GA curriculum for each discipline/major; and • to map current teaching against that curriculum as a basis for curriculum review

Distributed Stochastic Power Control in Ad-hoc Networks: A Nonconvex Case

Utility-based power allocation in wireless ad-hoc networks is inherently nonconvex because of the global coupling induced by the co-channel interference. To tackle this challenge, we first show that the globally optimal point lies on the boundary of the feasible region, which is utilized as a basis to transform the utility maximization problem into an equivalent max-min problem with more structure. By using extended duality theory, penalty multipliers are introduced for penalizing the constraint violations, and the minimum weighted utility maximization problem is then decomposed into subproblems for individual users to devise a distributed stochastic power control algorithm, where each user stochastically adjusts its target utility to improve the total utility by simulated annealing. The proposed distributed power control algorithm can guarantee global optimality at the cost of slow convergence due to simulated annealing involved in the global optimization. The geometric cooling scheme and suitable penalty parameters are used to improve the convergence rate. Next, by integrating the stochastic power control approach with the back-pressure algorithm, we develop a joint scheduling and power allocation policy to stabilize the queueing systems. Finally, we generalize the above distributed power control algorithms to multicast communications, and show their global optimality for multicast traffic.Comment: Contains 12 pages, 10 figures, and 2 tables; work submitted to IEEE Transactions on Mobile Computin

Biomarker-guided antibiotic stewardship in suspected ventilator-associated pneumonia (VAPrapid2) : a randomised controlled trial and process evaluation

Background Ventilator-associated pneumonia is the most common intensive care unit (ICU)-acquired infection, yet accurate diagnosis remains difficult, leading to overuse of antibiotics. Low concentrations of IL-1β and IL-8 in bronchoalveolar lavage fluid have been validated as effective markers for exclusion of ventilator-associated pneumonia. The VAPrapid2 trial aimed to determine whether measurement of bronchoalveolar lavage fluid IL-1β and IL-8 could effectively and safely improve antibiotic stewardship in patients with clinically suspected ventilator-associated pneumonia. Methods VAPrapid2 was a multicentre, randomised controlled trial in patients admitted to 24 ICUs from 17 National Health Service hospital trusts across England, Scotland, and Northern Ireland. Patients were screened for eligibility and included if they were 18 years or older, intubated and mechanically ventilated for at least 48 h, and had suspected ventilator-associated pneumonia. Patients were randomly assigned (1:1) to biomarker-guided recommendation on antibiotics (intervention group) or routine use of antibiotics (control group) using a web-based randomisation service hosted by Newcastle Clinical Trials Unit. Patients were randomised using randomly permuted blocks of size four and six and stratified by site, with allocation concealment. Clinicians were masked to patient assignment for an initial period until biomarker results were reported. Bronchoalveolar lavage was done in all patients, with concentrations of IL-1β and IL-8 rapidly determined in bronchoalveolar lavage fluid from patients randomised to the biomarker-based antibiotic recommendation group. If concentrations were below a previously validated cutoff, clinicians were advised that ventilator-associated pneumonia was unlikely and to consider discontinuing antibiotics. Patients in the routine use of antibiotics group received antibiotics according to usual practice at sites. Microbiology was done on bronchoalveolar lavage fluid from all patients and ventilator-associated pneumonia was confirmed by at least 104 colony forming units per mL of bronchoalveolar lavage fluid. The primary outcome was the distribution of antibiotic-free days in the 7 days following bronchoalveolar lavage. Data were analysed on an intention-to-treat basis, with an additional per-protocol analysis that excluded patients randomly assigned to the intervention group who defaulted to routine use of antibiotics because of failure to return an adequate biomarker result. An embedded process evaluation assessed factors influencing trial adoption, recruitment, and decision making. This study is registered with ISRCTN, ISRCTN65937227, and ClinicalTrials.gov, NCT01972425. Findings Between Nov 6, 2013, and Sept 13, 2016, 360 patients were screened for inclusion in the study. 146 patients were ineligible, leaving 214 who were recruited to the study. Four patients were excluded before randomisation, meaning that 210 patients were randomly assigned to biomarker-guided recommendation on antibiotics (n=104) or routine use of antibiotics (n=106). One patient in the biomarker-guided recommendation group was withdrawn by the clinical team before bronchoscopy and so was excluded from the intention-to-treat analysis. We found no significant difference in the primary outcome of the distribution of antibiotic-free days in the 7 days following bronchoalveolar lavage in the intention-to-treat analysis (p=0·58). Bronchoalveolar lavage was associated with a small and transient increase in oxygen requirements. Established prescribing practices, reluctance for bronchoalveolar lavage, and dependence on a chain of trial-related procedures emerged as factors that impaired trial processes