299 research outputs found
Content adaptive sparse illumination for Fourier ptychography
Fourier Ptychography (FP) is a recently proposed technique for large field of
view and high resolution imaging. Specifically, FP captures a set of low
resolution images under angularly varying illuminations and stitches them
together in Fourier domain. One of FP's main disadvantages is its long
capturing process due to the requisite large number of incident illumination
angles. In this letter, utilizing the sparsity of natural images in Fourier
domain, we propose a highly efficient method termed as AFP, which applies
content adaptive sparse illumination for Fourier ptychography by capturing the
most informative parts of the scene's spatial spectrum. We validate the
effectiveness and efficiency of the reported framework with both simulations
and real experiments. Results show that the proposed AFP could shorten the
acquisition time of conventional FP by around 30%-60%
Motion-corrected Fourier ptychography
Fourier ptychography (FP) is a recently proposed computational imaging
technique for high space-bandwidth product imaging. In real setups such as
endoscope and transmission electron microscope, the common sample motion
largely degrades the FP reconstruction and limits its practicability. In this
paper, we propose a novel FP reconstruction method to efficiently correct for
unknown sample motion. Specifically, we adaptively update the sample's Fourier
spectrum from low spatial-frequency regions towards high spatial-frequency
ones, with an additional motion recovery and phase-offset compensation
procedure for each sub-spectrum. Benefiting from the phase retrieval redundancy
theory, the required large overlap between adjacent sub-spectra offers an
accurate guide for successful motion recovery. Experimental results on both
simulated data and real captured data show that the proposed method can correct
for unknown sample motion with its standard deviation being up to 10% of the
field-of-view scale. We have released our source code for non-commercial use,
and it may find wide applications in related FP platforms such as endoscopy and
transmission electron microscopy
Fourier ptychographic reconstruction using Poisson maximum likelihood and truncated Wirtinger gradient
Fourier ptychographic microscopy (FPM) is a novel computational coherent
imaging technique for high space-bandwidth product imaging. Mathematically,
Fourier ptychographic (FP) reconstruction can be implemented as a phase
retrieval optimization process, in which we only obtain low resolution
intensity images corresponding to the sub-bands of the sample's high resolution
(HR) spatial spectrum, and aim to retrieve the complex HR spectrum. In real
setups, the measurements always suffer from various degenerations such as
Gaussian noise, Poisson noise, speckle noise and pupil location error, which
would largely degrade the reconstruction. To efficiently address these
degenerations, we propose a novel FP reconstruction method under a gradient
descent optimization framework in this paper. The technique utilizes Poisson
maximum likelihood for better signal modeling, and truncated Wirtinger gradient
for error removal. Results on both simulated data and real data captured using
our laser FPM setup show that the proposed method outperforms other
state-of-the-art algorithms. Also, we have released our source code for
non-commercial use
Validated model of thermochemical energy storage based on cobalt oxides
Thermal Energy Storage (TES) can play a critical role through provision of reliable energy supply and increase the market penetration of renewable energy sources. Thermochemical Energy Storage (TCES) based on reversible reactions offers distinguished advantages in comparison with sensible and latent heat storage: higher energy density, higher temperature range and possibility of seasonal storage. TCES systems based on the redox cycle of metallic oxides shows significant potential for integration with Concentrated Solar Power (CSP) plants using air as the heat transfer fluid, which also acts as a reactant for the redox reaction. A pilot scale thermochemical storage reactor designed for a CSP plant has been developed and tested in the framework of a collaborative European funded project \u201cRESTRUCTURE\u201d at the Solar Tower Julich (STJ). TCES system is proposed with the aim of achieving higher energy storage capacity and higher storage temperature. Numerical modeling of a TCES prototype presented in this study is a contribution towards this effort. The present work is focused on the innovative one-dimensional modeling of a TCES system based on the redox cycle of cobalt oxides (Co3O4/CoO), coated on the ceramics honeycomb structures. The numerical model for TCES involved the energy balance and reaction kinetics describing the redox reaction of cobalt oxides, to simulate the phenomena of thermochemical storage. The simulation results were presented as the temperature profiles at different positions inside the storage vessel and they were validated against experimental data published in literature by other groups. This validation proved that this model can simulate the overall thermochemical storage process with reasonable accuracy. The simulation tool was also used to perform the parametric analysis of the storage module, which provides guidance to optimize the performance of the storage system. Moreover, due to its good compromise between reliability and computational time, the established 1-D thermochemical storage model can be integrated with the CSP plant model for dynamic analysis of the whole system, which is the aim of this study
The role of the neutrophil Fcγ receptor I (CD64) index in diagnosing spontaneous bacterial peritonitis in cirrhotic patients
SummaryObjectiveTo investigate the role of the neutrophil Fcγ receptor I (CD64) index in the diagnosis of spontaneous bacterial peritonitis (SBP) in cirrhotic patients.MethodsA total of 123 cirrhotic patients with ascites who fulfilled the inclusion criteria were enrolled in this study. Ascites and blood samples were collected; the polymorphonuclear neutrophil (PMN) count, bacterial culture, and related laboratory tests were performed. The CD64 index was determined for each sample using flow cytometry.ResultsThe neutrophil CD64 index results were significantly higher in cirrhotic patients with SBP than in those without SBP (p<0.001). There was a positive correlation between the neutrophil CD64 index and the PMN count in ascites. In the receiver operating characteristic curve (ROC) analysis, the area under the curve (AUC) was 0.894 (95% confidence interval 0.823–0.964, p<0.001). The optimal cut-off value for the neutrophil CD64 index was 2.02. The sensitivity and specificity of the neutrophil CD64 index for cirrhotic patients with SBP were 80.49% and 93.90%, respectively. The elevated neutrophil CD64 index was down-regulated by antibiotic therapy (p=0.002).ConclusionsThe neutrophil CD64 index could be used as a sensitive and specific indicator for the diagnosis of SBP in cirrhotic patients with ascites and is also modulated by antibiotic therapy
M2-like macrophages in the fibrotic liver protect mice against lethal insults through conferring apoptosis resistance to hepatocytes.
Acute injury in the setting of liver fibrosis is an interesting and still unsettled issue. Most recently, several prominent studies have indicated the favourable effects of liver fibrosis against acute insults. Nevertheless, the underlying mechanisms governing this hepatoprotection remain obscure. In the present study, we hypothesized that macrophages and their M1/M2 activation critically involve in the hepatoprotection conferred by liver fibrosis. Our findings demonstrated that liver fibrosis manifested a beneficial role for host survival and apoptosis resistance. Hepatoprotection in the fibrotic liver was tightly related to innate immune tolerance. Macrophages undertook crucial but divergent roles in homeostasis and fibrosis: depleting macrophages in control mice protected from acute insult; conversely, depleting macrophages in fibrotic liver weakened the hepatoprotection and gave rise to exacerbated liver injury upon insult. The contradictory effects of macrophages can be ascribed, to a great extent, to the heterogeneity in macrophage activation. Macrophages in fibrotic mice exhibited M2-preponderant activation, which was not the case in acutely injured liver. Adoptive transfer of M2-like macrophages conferred control mice conspicuous protection against insult. In vitro, M2-polarized macrophages protected hepatocytes against apoptosis. Together, M2-like macrophages in fibrotic liver exert the protective effects against lethal insults through conferring apoptosis resistance to hepatocytes
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