The rheological parameters required to print viscoelastic nanoparticle suspensions toward tough elastomers via Digital Light Synthesis (DLS) (an inverted projection stereolithography system) are ...reported. With a model material of functionalized silica nanoparticles suspended in a poly(dimethylsiloxane) matrix, the rheological‐parameters‐guided DLS can print structures seven times tougher than those formed from the neat polymers. The large yield stress and high viscosity associated with these high concentration nanoparticle suspensions, however, may prevent pressure‐driven flow, a mechanism essential to stereolithography‐based printing. Thus, to better predict and evaluate the printability of high concentration nanoparticle suspensions, the boundary of rheological properties compatible with DLS is defined using a non‐dimensional Peclet number (Pe). Based on the proposed analysis of rheological parameters, the border of printability at standard temperature and pressure (STP) is established by resin with a silica nanoparticle mass fraction (ϕsilica) of 0.15. Above this concentration, nanoparticle suspensions have Pe > 1 and are not printable. Beyond STP, the printability can be further extended to ϕsilica = 0.20 via a heating module with lower shear rate to reduce the Pe < 1. The printed rubber possesses even higher toughness (Γ ≈ 155 kJ m−3), which is 40% higher over that of ϕsilica = 0.15.
The pressure‐driven flow in continuous Digital Light Synthesis is analyzed through the dimensionless Peclet number. This mechanism enables the 3D printing of resins with yield stress (≈10 Pa) and high viscosity (≈200 Pa s), which are the typical rheological features of suspensions with high nanoparticle content. This concept is applied to fabricate silicone–silica nanocomposites with enhanced toughness.
An acoustic liquefaction approach to enhance the flow of yield stress fluids during Digital Light Processing (DLP)‐based 3D printing is reported. This enhanced flow enables processing of ...ultrahigh‐viscosity resins (μapp > 3700 Pa s at shear rates γ˙ = 0.01 s–1) based on silica particles in a silicone photopolymer. Numerical simulations of the acousto–mechanical coupling in the DLP resin feed system at different agitation frequencies predict local resin flow velocities exceeding 100 mm s–1 at acoustic transduction frequencies of 110 s–1. Under these conditions, highly loaded particle suspensions (weight fractions, ϕ = 0.23) can be printed successfully in complex geometries. Such mechanically reinforced composites possess a tensile toughness 2000% greater than the neat photopolymer. Beyond an increase in processible viscosities, acoustophoretic liquefaction DLP (AL‐DLP) creates a transient reduction in apparent viscosity that promotes resin recirculation and decreases viscous adhesion. As a result, acoustophoretic liquefaction Digital Light Processing (AL‐DLP) improves the printed feature resolution by more than 25%, increases printable object sizes by over 50 times, and can build parts >3 × faster when compared to conventional methodologies.
Acoustophoretic‐liquefaction Digital Light Processing (AL‐DLP) permits manipulation of resin rheology during 3D printing. Acoustic transduction reduces the viscosity of nanopartice suspensions by up to three orders of magnitude to promote resin recirculation and reduce viscous adhesion. Consequently, AL‐DLP improves resolution (>25%), increases printable area (≈50 × ), and reduces build times (>3 × faster) when compared to conventional methods for printing composite.
Additive manufacture (AM) is receiving significant attention globally, reflected in the volume of research being carried out to support the commercialisation of the technology for industrial ...applications and the interest shown by government and policy makers in the technology. The lack of distinction between 3D printing and AM, as well as the portrayal of some highly publicised applications, may imply that the technology is now firmly established. However, this is not the case. The aim of this study is to identify the current barriers to the progression of AM for end-use products from an industrial perspective and to understand the nature of those barriers. Case study research has been conducted with organisations in the UK aerospace, automotive, defence, heavy machinery and medical device industries. Eighteen barriers are identified: education, cost, design, software, materials, traceability, machine constraints, in-process monitoring, mechanical properties, repeatability, scalability, validation, standards, quality, inspection, tolerances, finishing and sterilisation. Explanation building and logic models are used to generalise the findings. The results are discussed in the context of current academic research on AM. The outcomes of this study help to inform the frontiers of research in AM and how AM research agendas can be aligned with the requirements for industrial applications.
•A paradigm shift in education is required to increase graduates understanding of AM.•Design for AM requires increased creativity reinforced by knowledge and experience.•Software is severely fragmented, it requires streamlining and tailoring for AM.•Industry requires parameter dependent operational windows for materials.•Developing inspection and finishing methods are a focus in research and industry.
Abstract Objectives Four randomized phase II/III trials investigated the addition of cetuximab to platinum-based, first-line chemotherapy in patients with advanced non-small cell lung cancer (NSCLC). ...A meta-analysis was performed to examine the benefit/risk ratio for the addition of cetuximab to chemotherapy. Materials and methods The meta-analysis included individual patient efficacy data from 2018 patients and individual patient safety data from 1970 patients comprising respectively the combined intention-to-treat and safety populations of the four trials. The effect of adding cetuximab to chemotherapy was measured by hazard ratios (HRs) obtained using a Cox proportional hazards model and odds ratios calculated by logistic regression. Survival rates at 1 year were calculated. All applied models were stratified by trial. Tests on heterogeneity of treatment effects across the trials and sensitivity analyses were performed for all endpoints. Results The meta-analysis demonstrated that the addition of cetuximab to chemotherapy significantly improved overall survival (HR 0.88, p = 0.009, median 10.3 vs 9.4 months), progression-free survival (HR 0.90, p = 0.045, median 4.7 vs 4.5 months) and response (odds ratio 1.46, p < 0.001, overall response rate 32.2% vs 24.4%) compared with chemotherapy alone. The safety profile of chemotherapy plus cetuximab in the meta-analysis population was confirmed as manageable. Neither trials nor patient subgroups defined by key baseline characteristics showed significant heterogeneity for any endpoint. Conclusion The addition of cetuximab to platinum-based, first-line chemotherapy for advanced NSCLC significantly improved outcome for all efficacy endpoints with an acceptable safety profile, indicating a favorable benefit/risk ratio.
Although prognostic gene expression signatures for survival in early-stage lung cancer have been proposed, for clinical application, it is critical to establish their performance across different ...subject populations and in different laboratories. Here we report a large, training-testing, multi-site, blinded validation study to characterize the performance of several prognostic models based on gene expression for 442 lung adenocarcinomas. The hypotheses proposed examined whether microarray measurements of gene expression either alone or combined with basic clinical covariates (stage, age, sex) could be used to predict overall survival in lung cancer subjects. Several models examined produced risk scores that substantially correlated with actual subject outcome. Most methods performed better with clinical data, supporting the combined use of clinical and molecular information when building prognostic models for early-stage lung cancer. This study also provides the largest available set of microarray data with extensive pathological and clinical annotation for lung adenocarcinomas.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
BACKGROUND AND PURPOSEHigh-resolution T2-weighted sequences are frequently used in magnetic resonance imaging (MRI) studies to assess the cerebellopontine angle and internal auditory canal (IAC) in ...sensorineural hearing loss patients but have low yield and lengthened examinations. Because image content in the Wavelet domain is sparse, compressed sensing (CS) that uses incoherent undersampling of k-space and iterative reconstruction can accelerate MRI acquisitions. We hypothesized that an accelerated CS T2 Sampling Perfection with Application optimized Contrasts using different flip angle Evolution (SPACE) sequence would produce acceptable diagnostic quality for IAC screening protocols.
MATERIAL AND METHODSSeventy-six patients underwent 3 T MRI using conventional SPACE and a CS T2 SPACE prototype sequence for screening the IACs were identified retrospectively. Unilateral reconstructions for each sequence were separated, then placed into mixed folders for independent, blinded review by 3 neuroradiologists during 2 sessions 4 weeks apart. Radiologists reported if a lesion was present. Motion and visualization of specific structures were rated using ordinal scales. McNemar, Wilcoxon, Cohen κ, and Mann-Whitney U tests were performed for accuracy, equivalence, and interrater and intrarater reliability.
RESULTST2 SPACE using CS reconstruction reduced scan time by 80% to 50 seconds and provided 98.7% accuracy for IAC mass detection by 3 raters. Radiologists preferred conventional images (0.7–1.0 reduction on 5-point scale, P < 0.001), but rated CS SPACE acceptable. The 95% confidence for reduction in any cerebellopontine angle, IAC, or fluid-filled inner ear structure assessment with CS SPACE did not exceed 0.5.
CONCLUSIONSInternal auditory canal screening MRI protocols can be performed using a 5-fold accelerated T2 SPACE sequence with compressed sensing while preserving diagnostic image quality and acceptable lesion detection rate.
Since the mid 1970s, project management associations around the world have made serious attempts to conduct themselves as professional associations. Traditional professions distinguished themselves ...by emphasising standards such as service to the public and competence in their field, and by ensuring that their membership meets these standards. An important element of a profession is ownership of a body of knowledge that is distinctive to the professional group. Project management associations have spent considerable time and effort in developing Bodies of Knowledge (BOKs) and their associated certification programs, and indeed the popularity of these has been notable. Yet there are problems, some relating to the broader issue of whether the project management associations really are equipped to act as professional bodies, others related to the specific challenge of agreeing the ‘distinctive body of knowledge’ and to the value of certification.
This paper draws on insights from the
rethinking project management EPSRC project as well as several separate research programs to explore the development of project management as a profession and the role of the formal BOKs in this professionalization, and to suggest a research agenda for critiquing, contributing to, and maintaining both the formal BOKs and the more general body of knowledge relevant to the needs of the discipline.
Isogeometric analysis has received extensive attention in the last decade, but despite its merits, many isogeometric models are still produced manually or semi-manually. In this work, we introduce a ...new technique using Ricci flow and a carefully constrained minimization to convert trimmed and faceted open geometries into watertight spline models free of trim and suitable for isogeometric analysis with potential for automation. This technique is used to rebuild parts of the US Army’s DEVCOM Generic Hull vehicle and portions of a 1996 Dodge Neon finite element model into trim-free spline models. Isogeometric modal analysis is performed on each to show the viability of this reconstruction framework in generating IGA-suitable splines for shell analysis.
•Define criteria on a mesh that, if satisfied, yield a surface quadrilateral layout•Define PDEs that, with Ricci flow, yield a surface quadrilateral parameterization•Employ the technique to reconstruct trimmed and faceted shell geometries as splines•Demonstrate that the spline surfaces are suitable for isogeometric shell analysis
The boundary representation or B-rep is the prevalent geometry description in computer aided design (CAD). It combines aspects from explicit and implicit geometry and is incompatible with many ...downstream applications such as finite element analysis (FEA) and computer aided manufacturing (CAM). We develop a semi-automatic frame-field guided parameterization approach that converts trimmed B-rep geometry to conforming, watertight analysis-suitable NURBS. The resulting geometry description is simultaneously suitable for design as well as analysis and therefore avoids the need for further meshing and geometry-processing. While existing frame-field based global parameterization methods offer the high quality necessary in our application, they suffer from several robustness issues. Current challenges mainly stem from the lack of integrability of the frame-field which causes the computed parameterization to fold-over, particularly near parameterization singularities. We propose specialized constraints that incorporate properties of an analytical solution that resolve the poor behavior near singularities. Furthermore, we present a convenient and efficient solution framework that directly incorporates such constraints into a reduced basis. Improved behavior around parameterization singularities simplifies the extraction of a quadrilateral layout. This layout is subsequently fitted with C0 NURBS to yield a conforming watertight model that is analysis suitable. The latter is illustrated by performing isogeometric shell modal analysis on several geometric models.
•We develop a semi-automatic frame-field guided parameterization approach that converts trimmed Brep geometry to conforming, watertight analysis-suitable NURBS; thus avoiding the need for further meshing and geometry-processing.•We propose specialized constraints that incorporate properties of an analytical solution that completely resolve the poor behavior near parameterization singularities. This simplifies the extraction of a quadrilateral layout.•We present a convenient and efficient solution framework that directly incorporates linear constraints into a reduced basis.
Surgical resection is curative for some patients with early lung squamous cell carcinoma. Staging and clinical factors do not adequately predict recurrence risk. We sought to validate the ...discriminative performance of proposed prognostic gene expression signatures at a level of rigor sufficient to support clinical use.
The two-stage validation used independent core laboratories, objective quality control standards, locked test parameters, and large multi-institutional specimen and data sets. The first stage validation confirmed a signature’s ability to stratify patient survival. The second-stage validation determined which signature(s) optimally improved risk discrimination when added to baseline clinical predictors. Participants were prospectively enrolled in institutional (cohort I) or cooperative group (cohort II) biospecimen and data collection protocols. All cases underwent a central review of clinical, pathologic, and biospecimen parameters using objective criteria to determine final inclusion (cohort I: n = 249; cohort II: n = 234). Primary selection required that a signature significantly predict a 3-year survival after surgical resection in cohort I. Signatures meeting this criterion were further tested in cohort II, comparing risk prediction using baseline risk factors alone versus in combination with the signature.
Male sex, advanced age, and higher stage were associated with shorter survival in cohort I and established a baseline clinical model. Of the three signatures validated in cohort I, one signature was validated in cohort II and statistically significantly enhanced the prognosis relative to the baseline model (C-index difference 0.122; p < 0.05).
These results represent the first rigorous validation of a test appropriate to direct adjuvant treatment or clinical trials for patients with lung squamous cell carcinoma.
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