The phase retrieval problem, where one aims to recover a complex-valued image from far-field intensity measurements, is a classic problem encountered in a range of imaging applications. Modern phase ...retrieval approaches usually rely on gradient descent methods in a nonlinear minimization framework. Calculating closed-form gradients for use in these methods is tedious work, and formulating second order derivatives is even more laborious. Additionally, second order techniques often require the storage and inversion of large matrices of partial derivatives, with memory requirements that can be prohibitive for data-rich imaging modalities. We use a reverse-mode automatic differentiation (AD) framework to implement an efficient matrix-free version of the Levenberg-Marquardt (LM) algorithm, a longstanding method that finds popular use in nonlinear least-square minimization problems but which has seen little use in phase retrieval. Furthermore, we extend the basic LM algorithm so that it can be applied for more general constrained optimization problems (including phase retrieval problems) beyond just the least-square applications. Since we use AD, we only need to specify the physics-based forward model for a specific imaging application; the first and second-order derivative terms are calculated automatically through matrix-vector products, without explicitly forming the large Jacobian or Gauss-Newton matrices typically required for the LM method. We demonstrate that this algorithm can be used to solve both the unconstrained ptychographic object retrieval problem and the constrained "blind" ptychographic object and probe retrieval problems, under the popular Gaussian noise model as well as the Poisson noise model. We compare this algorithm to state-of-the-art first order ptychographic reconstruction methods to demonstrate empirically that this method outperforms best-in-class first-order methods: it provides excellent convergence guarantees with (in many cases) a superlinear rate of convergence, all with a computational cost comparable to, or lower than, the tested first-order algorithms.
To characterize the effect of elemental composition and manufacturing process on the electrochemical properties of Co-Cr-Mo, Co-Cr-W and Co-Cr-Mo-W alloys.
Six Co-Cr based alloys were included in ...this study. All alloys are Co-Cr based alloys, classified in three different types according to their elemental composition. The first group has Mo as the third alloying element while the second one has W instead of Mo. The third one has both alloying elements. The groups are further divided by the manufacturing process (casting or Selective Laser Melting(SLM)). All groups were subjected to static immersion, open circuit potential, anodic scan, SEM/EDX analysis, static and cyclic tarnish testing according to ISO 10271 requirements. The ionic release was evaluated by inductively coupled plasma mass spectrometry and the results were statistically analyzed by two way ANOVA and Tukey test (a=0.05).
No statistical differences were identified for Co-Cr-Mo alloy for all elements and their total ionic release between casting and SLM manufacturing processes, in contrast to significantly lower values for SLM groups for the other two groups. All groups tested demonstrated similar performance in OCP and AS testing while no gross elemental changes before and after AS were identified following EDX analysis. All alloys fulfilled the requirements of tarnish resistance
The ionic release is dependent on alloy type and manufacturing process while all groups were found to fulfill the requirements of international standards for ionic release, corrosion and tarnish resistance and thus an acceptable clinical performance is anticipated.
The rapid adoption of the smart grid’s nascent load-management capabilities, such as demand-side management and smart home systems, and the emergence of new classes of controllable high-wattage ...loads, such as energy storage systems and electric vehicles, magnify the smart grid’s exposure to load-altering cyberattacks. These attacks aim at disrupting power grid services by staging a synchronized activation/deactivation of numerous customers’ high-wattage appliances. A proper defense plan is needed to respond to such attacks and maintain the stability of the grid, and would include prevention, detection, mitigation, incident response, and/or recovery strategies. In this paper, we propose a solution to detect load-altering cyberattacks using a time-delay neural network that monitors the grid’s load profile. As a case study, we consider a cyberattack scenario against demand-side management programs that control the loads of residential electrical water heaters in order to perform peak shaving. The proposed solution can be adapted to other load-altering attacks involving different demand-side management programs or other classes of loads. Experiments verify the proposed solution’s efficacy in detecting load-altering attacks with high precision and low false alarm and latency.
The metabolic variation in the essential oil composition of
leaves obtained from different seasons was quantitatively and qualitatively determined employing GC/MS (Gas Chromatography coupled with ...Mass Spectrometry) and GC/FID (Gas chromatography equipped with flame ionization detector) techniques. It displayed the existence of 97 constituents accounting for 94.19%, 92.27%, 91.95% and 92.63% for POS (spring), POM (summer), POA (autumn) and POW (winter) whole essential oils.
-Caryophyllene constituting the main metabolite in the oil in the different seasons. To better visualize the differences between them, GC data were exposed to chemometric analysis. A PCA (principal component analysis) score plot revealed the closeness of POS and POW. Molecular modelling on collagenase, elastase and hyaluronidase enzymes active centres shows that different compounds existing in the essential oil of
leaves shows binding to the active sites with variable degrees that suggested its anti-ageing potential. Palmitic acid displayed the highest fitting for both the collagenase and elastase active centres in both pH-based and rule-based ionization methods with ∆G equals -78.27 and -44.77 kcal/mol, respectively; meanwhile, heptacosane showed the highest fitting score in the hyaluronidase centre with ∆G = -43.78 kcal/mol. In vitro assays consolidates the obtained modelling studies in which essential oil shows considerable anti-elastase and anti-hyaluronidase potential as evidenced by their IC
values being 49.3 and 37.7 μg/mL, respectively; meanwhile, the essential oil of
leaves displayed mild anti-collagenase potential. Thus, it can be concluded that
could serve as a promising anti-ageing naturally occurring drug that could be effectively incorporated by pharmaceutical industries in cosmetics combating ageing and skin wrinkling.
There is limited knowledge about morphological molecular-imaging-derived parameters to further characterize hemodynamically relevant coronary lesions.
The aim of this study was to describe and ...differentiate specific parameters between hemodynamically significant and non-significant coronary lesions using various invasive and non-invasive measures.
This clinical study analyzed patients with symptoms suggestive of coronary artery disease (CAD) who underwent native T1-weighted CMR and gadofosveset-enhanced CMR as well as invasive coronary angiography. OCT of the culprit vessel to determine the plaque type was performed in a subset of patients. Functional relevance of all lesions was examined using quantitative flow reserve (QFR-angiography). Hemodynamically significant lesions were defined as lesions with a QFR <0.8. Signal intensity (contrast-to-noise ratios; CNRs) on native T1-weighted CMR and gadofosveset-enhanced CMR was defined as a measure for intraplaque hemorrhage and endothelial permeability, respectively.
Overall 29 coronary segments from 14 patients were examined. Segments containing lesions with a QFR <0.8 (n = 9) were associated with significantly higher signal enhancement on Gadofosveset-enhanced CMR as compared to segments containing a lesions without significant stenosis (lesion-QFR>0.8; n = 19) (5.32 (4.47-7.02) vs. 2.42 (1.04-5.11); p = 0.042). No differences in signal enhancement were seen on native T1-weighted CMR (2.2 (0.68-6.75) vs. 2.09 (0.91-6.57), p = 0.412). 66.7% (4 out of 6) of all vulnerable plaque and 33.3% (2 out of 6) of all non-vulnerable plaque (fibroatheroma) as assessed by OCT were hemodynamically significant lesions.
The findings of this pilot study suggest that signal enhancement on albumin-binding probe-enhanced CMR but not on T1-weighted CMR is associated with hemodynamically relevant coronary lesions.
The influence of Al content and α2 precipitation on the fatigue crack growth (FCG) behaviors of binary Ti - xAl (x = 2, 4, 6, 8 wt %) alloys was investigated. Ti–Al binary alloys with different Al ...contents were solution-treated and followed by aging treatment to obtain Widmanstatten microstructure and promote α2 precipitation at higher Al content. Results show that the increase of Al content dramatically reduces the FCG rate. The enhanced resistance to FCG propagation is related to the increase of the critical resolved shear stress (CRSS) for dislocation slipping that acts as crack initiation sites, basing on solution strengthening with the addition of Al. Furthermore, roughness-induced crack closure with increasing the Al content also contributes to the decrease of FCG rate. With the increment of the Al content, the early fatigue crack propagation stage, in which the crack propagation significantly affected by microstructural factors, will be enlarged due to the decrease of crack tip plastic zone, leading to crack deflection and the reduction of FCG rate. In Ti–8Al alloy, the presence of α2 precipitates and the increment of its size and volume fraction after aging treatment will result in significant increase of FCG rate. Moreover, the activation of large-scale slipping in relatively larger colonies promotes the crack to propagate along the large-scale slipping that induces smoother crack path and higher FCG rate.
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•Increasing the Al content reduces the FCG rate due to increasing the CRSS for slipping and roughness-induced crack closure.•The early stage enlargement due to the decrease of MPZ size with the increase of Al content decreases the FCG rate.•The presence of α2 phase and increasing its size and volume fraction result in increasing the FCG rate of Ti-8Al alloy.
Purpose of review
The current systematic review aims to provide novel insights into the distinct pathological features of acute coronary syndrome (ACS) with intact fibrous cap, also known as ‘plaque ...erosion’. A more detailed understanding of its underlying pathomechanisms provides the basis for future personalized therapeutic approaches to ACS.
Recent findings
In the past years, a mounting proportion of evidence point towards the concept of plaque erosion being responsible for more than one-third of all cases of ACS and representing an autonomous ACS-causing entity driven by biomechanical forces, immunological alternations and systemic elevation of inflammatory mediators. First pilot studies proved a therapeutic paradigm shift from primary PCI at the ACS-causing culprit lesion to systemic therapies in patients with ACS caused by plaque erosion.
Summary
This review provides the current status of the broad basic and clinical studies focused to the topic of plaque erosion: a new ACS-causing pathophysiology with different pathological aspects providing appropriate implications for personalized therapies in ACS.
Abstract
Aims
Acute coronary syndromes with intact fibrous cap (IFC-ACS), i.e. caused by coronary plaque erosion, account for approximately one-third of ACS. However, the underlying ...pathophysiological mechanisms as compared with ACS caused by plaque rupture (RFC-ACS) remain largely undefined. The prospective translational OPTICO-ACS study programme investigates for the first time the microenvironment of ACS-causing culprit lesions (CL) with intact fibrous cap by molecular high-resolution intracoronary imaging and simultaneous local immunological phenotyping.
Methods and results
The CL of 170 consecutive ACS patients were investigated by optical coherence tomography (OCT) and simultaneous immunophenotyping by flow cytometric analysis as well as by effector molecule concentration measurements across the culprit lesion gradient (ratio local/systemic levels). Within the study cohort, IFC caused 24.6% of ACS while RFC-ACS caused 75.4% as determined and validated by two independent OCT core laboratories. The IFC-CL were characterized by lower lipid content, less calcification, a thicker overlying fibrous cap, and largely localized near a coronary bifurcation as compared with RFC-CL. The microenvironment of IFC-ACS lesions demonstrated selective enrichment in both CD4+ and CD8+ T-lymphocytes (+8.1% and +11.2%, respectively, both P < 0.05) as compared with RFC-ACS lesions. T-cell-associated extracellular circulating microvesicles (MV) were more pronounced in IFC-ACS lesions and a significantly higher amount of CD8+ T-lymphocytes was detectable in thrombi aspirated from IFC-culprit sites. Furthermore, IFC-ACS lesions showed increased levels of the T-cell effector molecules granzyme A (+22.4%), perforin (+58.8%), and granulysin (+75.4%) as compared with RFC plaques (P < 0.005). Endothelial cells subjected to culture in disturbed laminar flow conditions, i.e. to simulate coronary flow near a bifurcation, demonstrated an enhanced adhesion of CD8+T cells. Finally, both CD8+T cells and their cytotoxic effector molecules caused endothelial cell death, a key potential pathophysiological mechanism in IFC-ACS.
Conclusions
The OPTICO-ACS study emphasizes a novel mechanism in the pathogenesis of IFC-ACS, favouring participation of the adaptive immune system, particularly CD4+ and CD8+ T-cells and their effector molecules. The different immune signatures identified in this study advance the understanding of coronary plaque progression and may provide a basis for future development of personalized therapeutic approaches to ACS with IFC.
Trial registration
The study was registered at clinicalTrials.gov (NCT03129503).
Graphical Abstract
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