Multi-scale simulation of the nano-metric cutting process

Molecular dynamics (MD) simulation and the finite element (FE) method are two popular numerical techniques for the simulation of machining processes. The two methods have their own strengths and limitations. MD simulation can cover the phenomena occurring at nano-metric scale but is limited by the computational cost and capacity, whilst the FE method is suitable for modelling meso- to macro-scale machining and for simulating macro-parameters, such as the temperature in a cutting zone, the stress/strain distribution and cutting forces, etc. With the successful application of multi-scale simulations in many research fields, the application of simulation to the machining processes is emerging, particularly in relation to machined surface generation and integrity formation, i.e. the machined surface roughness, residual stress, micro-hardness, microstructure and fatigue. Based on the quasi-continuum (QC) method, the multi-scale simulation of nano-metric cutting has been proposed. Cutting simulations are performed on single-crystal aluminium to investigate the chip formation, generation and propagation of the material dislocation during the cutting process. In addition, the effect of the tool rake angle on the cutting force and internal stress under the workpiece surface is investigated: The cutting force and internal stress in the workpiece material decrease with the increase of the rake angle. Finally, to ease multi-scale modelling and its simulation steps and to increase their speed, a computationally efficient MATLAB-based programme has been developed, which facilitates the geometrical modelling of cutting, the simulation conditions, the implementation of simulation and the analysis of results within a unified integrated virtual-simulation environment

Deubiquitinase USP1 influences the dedifferentiation of mouse pancreatic β-cells

Loss of insulin-secreting β-cells in diabetes may be either due to apoptosis or dedifferentiation of β-cell mass. The ubiquitin-proteasome system comprising E3 ligase and deubiquitinases (DUBs) controls several aspects of β-cell functions. In this study, screening for key DUBs identified USP1 to be specifically involved in dedifferentiation process. Inhibition of USP1 either by genetic intervention or small-molecule inhibitor ML323 restored epithelial phenotype of β-cells, but not with inhibition of other DUBs. In absence of dedifferentiation cues, overexpression of USP1 was sufficient to induce dedifferentiation in β-cells; mechanistic insight showed USP1 to mediate its effect via modulating the expression of inhibitor of differentiation (ID) 2. In an in vivo streptozotocin (STZ)-induced dedifferentiation mouse model system, administering ML323 alleviated hyperglycemic state. Overall, this study identifies USP1 to be involved in dedifferentiation of β-cells and its inhibition may have a therapeutic application of reducing β-cell loss during diabetes

Quantification of Ultraprecision Surface Morphology using an Algebraic Graph Theoretic Approach

Assessment of progressive, nano-scale variation of surface morphology during ultraprecision manufacturing processes, such as fine-abrasive polishing of semiconductor wafers, is a challenging proposition owing to limitations with traditional surface quantifiers. We present an algebraic graph theoretic approach that uses graph topological invariants for quantification of ultraprecision surface morphology. The graph theoretic approach captures heterogeneous multi-scaled aspects of surface morphology from optical micrographs, and is therefore valuable for in situ real-time assessment of surface quality. Extensive experimental investigations with specular finished (Sa ~ 5 nm) blanket copper wafers from a chemical mechanical planarization (CMP) process suggest that the proposed method was able to quantify and track variations in surface morphology more effectively than statistical quantifiers reported in literature

Recurrence of intestinal metaplasia and early neoplasia after endoscopic eradication therapy for Barrett’s esophagus: A systematic review and meta-analysis

Abstract Background Conflicting data exist with regard to recurrence rates of intestinal metaplasia (IM) and dysplasia after achieving complete eradication of intestinal metaplasia (CE-IM) in Barrett’s esophagus (BE) patients. Aim (i) To determine the incidence of recurrent IM and dysplasia achieving CE-IM and (ii) to compare recurrence rates between treatment modalities [radiofrequency ablation (RFA) with or without endoscopic mucosal resection (EMR) vs stepwise complete EMR (SRER)]. Methods A systematic search was performed for studies reporting on outcomes and estimates of recurrence rates after achieving CE-IM. Pooled incidence [per 100-patient-years (PY)] and risk ratios with 95 %CI were obtained. Heterogeneity was measured using the I 2 statistic. Subgroup analyses, decided a priori, were performed to explore heterogeneity in results. Results A total of 39 studies were identified (25-RFA, 13-SRER, and 2 combined). The pooled incidence of any recurrence was 7.5 (95 %CI 6.1 – 9.0)/100 PY with a pooled incidence of IM recurrence rate of 4.8 (95 %CI 3.8 – 5.9)/100 PY, and dysplasia recurrence rate of 2.0 (95 %CI 1.5 – 2.5)/100 PY. Compared to the SRER group, the RFA group had significantly higher overall [8.6 (6.7 – 10.5)/100 PY vs. 5.1 (3.1 – 7)/100 PY, P = 0.01] and IM recurrence rates [5.8 (4.3 – 7.3)/100 PY vs. 3.1 (1.7 – 4)/100 PY, P &lt; 0.01] with no difference in recurrence rates of dysplasia. Significant heterogeneity between studies was identified. The majority of recurrences were amenable to repeat endoscopic eradication therapy (EET). Conclusion The results of this study demonstrate that the incidence rates of overall, IM, and dysplasia recurrence rates post-EET are not inconsiderable and reinforce the importance of close surveillance after achieving CE-IM.</jats:p

Spatiotemporal representation of cardiac vectorcardiogram (VCG) signals

Background: Vectorcardiogram (VCG) signals monitor both spatial and temporal cardiac electrical activities along three orthogonal planes of the body. However, the absence of spatiotemporal resolution in conventional VCG representations is a major impediment for medical interpretation and clinical usage of VCG. This is especially so because time-domain features of 12-lead ECG, instead of both spatial and temporal characteristics of VCG, are widely used for the automatic assessment of cardiac pathological patterns.Materials and methods: We present a novel representation approach that captures critical spatiotemporal heart dynamics by displaying the real time motion of VCG cardiac vectors in a 3D space. Such a dynamic display can also be realized with only one lead ECG signal (e.g., ambulatory ECG) through an alternative lag-reconstructed ECG representation from nonlinear dynamics principles. Furthermore, the trajectories are color coded with additional dynamical properties of space-time VCG signals, e.g., the curvature, speed, octant and phase angles to enhance the information visibility.Results: In this investigation, spatiotemporal VCG signal representation is used to characterize various spatiotemporal pathological patterns for healthy control (HC), myocardial infarction (MI), atrial fibrillation (AF) and bundle branch block (BBB). The proposed color coding scheme revealed that the spatial locations of the peak of T waves are in the Octant 6 for the majority (i.e., 74 out of 80) of healthy recordings in the PhysioNet PTB database. In contrast, the peak of T waves from 31.79% (117/368) of MI subjects are found to remain in Octant 6 and the rest (68.21%) spread over all other octants. The spatiotemporal VCG signal representation is shown to capture the same important heart characteristics as the 12-lead ECG plots and more.Conclusions: Spatiotemporal VCG signal representation is shown to facilitate the characterization of space-time cardiac pathological patterns and enhance the automatic assessment of cardiovascular diseases.Peer reviewedIndustrial Engineering and ManagementMechanical and Aerospace Engineerin

Voltage-programmable liquid optical interface

Recently, there has been intense interest in photonic devices based on microfluidics, including displays and refractive tunable microlenses and optical beamsteerers, that work using the principle of electrowetting. Here, we report a novel approach to optical devices in which static wrinkles are produced at the surface of a thin film of oil as a result of dielectrophoretic forces. We have demonstrated this voltage-programmable surface wrinkling effect in periodic devices with pitch lengths of between 20 and 240 µm and with response times of less than 40 µs. By a careful choice of oils, it is possible to optimize either for high-amplitude sinusoidal wrinkles at micrometre-scale pitches or more complex non-sinusoidal profiles with higher Fourier components at longer pitches. This opens up the possibility of developing rapidly responsive voltage-programmable, polarization-insensitive transmission and reflection diffraction devices and arbitrary surface profile optical devices

Ti alloy with enhanced machinability in UAT turning

Metastable β-titanium alloys such as Ti 15V 3Al 3Cr 3Sn are of great technological interest thanks to their high fatigue strength-to-density ratio. However, their high hardness and poor machinability increase machining costs. Additionally, formation of undesirable long chips increases the machining time. To address those issues, a metastable β-titanium alloy (Ti 15V 3Al 3Cr 2Zr 0.9La) with enhanced machinability was developed to produce short chips even at low cutting speeds. A hybrid ultrasonically assisted machining technique, known to reduce cutting forces, was employed in this study. Cutting force components and surface quality of the finished work-pieces were analyzed for a range of cutting speeds in comparison with those for more traditional Ti 15V 3Al 3Cr 3Sn. The novel alloy demonstrated slightly improved machining characteristics at higher cutting speeds and is now ready for industrial applications

Simple Nudges for Better Password Creation

Recent security breaches have highlighted the consequences of reusing passwords across online accounts. Recent guidance on password policies by the UK government recommend an emphasis on password length over an extended character set for generating secure but memorable passwords without cognitive overload. This paper explores the role of three nudges in creating website-specific passwords: financial incentive (present vs absent), length instruction (long password vs no instruction) and stimulus (picture present vs not present). Mechanical Turk workers were asked to create a password in one of these conditions and the resulting passwords were evaluated based on character length, resistance to automated guessing attacks, and time taken to create the password. We found that users created longer passwords when asked to do so or when given a financial incentive and these longer passwords were harder to guess than passwords created with no instruction. Using a picture nudge to support password creation did not lead to passwords that were either longer or more resistant to attacks but did lead to account-specific passwords

Performance measures for upper gastrointestinal endoscopy:A European Society of Gastrointestinal Endoscopy (ESGE) Quality Improvement Initiative

N/

Prognostic factors for outcomes of patients with refractory or relapsed acute myelogenous leukemia or myelodysplastic syndromes undergoing allogeneic progenitor cell transplantation

AbstractAllogeneic progenitor cell transplantation is the only curative therapy for patients with refractory acute myelogenous leukemia or myelodysplastic syndromes. To identify prognostic factors in these patients, we performed a retrospective analysis of transplantation outcomes. Patients were selected if they had undergone an allogeneic transplantation between January 1988 and January 2002 and were not in remission or first untreated relapse at the time of transplantation. A total of 135 patients were identified. The median age was 49.5 years (range, 19-75 years). At the time of transplantation, 39.3% of patients had not responded to induction therapy, 37% had not responded to first salvage therapy, and 23.7% were beyond first salvage. Forty-one patients (30%) received unrelated donor progenitor cells. Eighty patients (59%) received either a reduced-intensity or a nonmyeloablative regimen. A total of 104 (77%) of 135 patients died, with a median survival time of 4.9 months (95% confidence interval, 3.9-6.6 months). The median progression-free survival was 2.9 months (95% confidence interval, 2.5-4.2 months). A Cox regression analysis showed that Karnofsky performance status, peripheral blood blasts, and tacrolimus exposure during the first 11 days after transplantation were predictive of survival. These data support the use of allogeneic transplantation for patients with relapsed or refractory acute myelogenous leukemia/myelodysplastic syndromes and suggest that optimal immune suppression early after transplantation is essential for long-term survival even in patients with refractory myeloid leukemias