Long wavelength optical coherence tomography for painted objects

Optical Coherence Tomography has been successfully applied to the imaging of painted objects in recent years. However, a significant limitation is the low penetration depth of OCT in paint because of the high opacity of paint due to either scattering or absorption. It has been shown that the optimum spectral window for OCT imaging of paint layers is around 2.2μm in wavelength. In this paper, we demonstrate a 1950nm OCT for imaging painted objects using a superfluorescent fiber source at low power

High resolution fourier domain optical coherence tomography at 2 microns for painted objects

Optical Coherence Tomography has been successfully applied to the non-invasive imaging of subsurface microstructure of a variety of materials from biological tissues to painted objects of art. One of the limitations of the technique is the low depth of penetration due to the strong scattering and absorption in the material. Previous studies found that for paint materials, the optimum window for large depth of penetration is around 2.2 microns. This is also true for many other materials with low water content. We have previously demonstrated OCT systems in this wavelength regime for imaging with improved depth of penetration. In this paper, we present an improved 2 micron high resolution Fourier domain OCT system using a broadband supercontinuum source. The system achieved a depth resolution of 9 microns in air (or 6 microns in paint or any polymer)

High resolution Fourier domain optical coherence tomography in the 2 μm wavelength range using a broadband supercontinuum source

A 220 nm bandwidth supercontinuum source in the two-micron wavelength range has been developed for use in a Fourier domain optical coherence tomography (FDOCT) system. This long wavelength source serves to enhance probing depth in highly scattering material with low water content. We present results confirming improved penetration depth in high opacity paint samples while achieving the high axial resolution needed to resolve individual paint layers. This is the first FDOCT developed in the 2 μm wavelength regime that allows fast, efficient capturing of 3D image cubes at a high axial resolution of 13 μm in air (or 9 μm in paint)

Tumor volume in subcutaneous mouse xenografts measured by microCT is more accurate and reproducible than determined by 18F-FDG-microPET or external caliper

<p>Abstract</p> <p>Background</p> <p>In animal studies tumor size is used to assess responses to anticancer therapy. Current standard for volumetric measurement of xenografted tumors is by external caliper, a method often affected by error. The aim of the present study was to evaluate if microCT gives more accurate and reproducible measures of tumor size in mice compared with caliper measurements. Furthermore, we evaluated the accuracy of tumor volume determined from ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET.</p> <p>Methods</p> <p>Subcutaneously implanted human breast adenocarcinoma cells in NMRI nude mice served as tumor model. Tumor volume (n = 20) was determined <it>in vivo </it>by external caliper, microCT and ¹⁸F-FDG-PET and subsequently reference volume was determined <it>ex vivo</it>. Intra-observer reproducibility of the microCT and caliper methods were determined by acquiring 10 repeated volume measurements. Volumes of a group of tumors (n = 10) were determined independently by two observers to assess inter-observer variation.</p> <p>Results</p> <p>Tumor volume measured by microCT, PET and caliper all correlated with reference volume. No significant bias of microCT measurements compared with the reference was found, whereas both PET and caliper had systematic bias compared to reference volume. Coefficients of variation for intra-observer variation were 7% and 14% for microCT and caliper measurements, respectively. Regression coefficients between observers were 0.97 for microCT and 0.91 for caliper measurements.</p> <p>Conclusion</p> <p>MicroCT was more accurate than both caliper and ¹⁸F-FDG-PET for <it>in vivo </it>volumetric measurements of subcutaneous tumors in mice.¹⁸F-FDG-PET was considered unsuitable for determination of tumor size. External caliper were inaccurate and encumbered with a significant and size dependent bias. MicroCT was also the most reproducible of the methods.</p

Do people feel they belong? Socio‐political factors shaping the place attachment of Hong Kong citizens

Hong Kong citizens’ sense of belonging has gone through a period of fluctuation during the period of rapid socio‐political and legal change since the outbreak of the Anti‐Extradition Law Amendment Bill Movement in 2019. This study explored how multiple dimensions of the place attachment of Hong Kong citizens have been shaped by factors associated with these changes. Six socio‐political variables were incorporated into the three dimensions of the person–process–place (PPP) framework. Based on a representative survey of the local population (n = 768), we found that political inclination and identity were significantly associated with the sense of place, with citizens identifying as Chinese and aligning with the pro‐establishment camp showing higher levels of place attachment. Mobility was negatively associated with place attachment, whereas the correlation between attachment and perceptions of the law and legal system was positive. The study has implications for Hong Kong’s current socio‐political and institutional environment and for emigration. It also demonstrates the wider applicability of the PPP framework for identifying and clarifying the various predictors of different dimensions of place attachment

Goldstone Bosons in Effective Theories with Spontaneously Broken Flavour Symmetry

The Flavour Symmetry of the Standard Model (SM) gauge sector is broken by the fermion Yukawa couplings. Promoting the Yukawa matrices to scalar spurion fields, one can break the flavour symmetry spontaneously by giving appropriate vacuum expectation values (VEVs) to the spurion fields, and one encounters Goldstone modes for every broken flavour symmetry generator. In this paper, we point out various aspects related to the possible dynamical interpretation of the Goldstone bosons: (i) In an effective-theory framework with local flavour symmetry, the Goldstone fields represent the longitudinal modes for massive gauge bosons. The spectrum of the latter follows the sequence of flavour-symmetry breaking related to the hierarchies in Yukawa couplings and flavour mixing angles. (ii) Gauge anomalies can be consistently treated by adding higher-dimensional operators. (iii) Leaving the U(1) factors of the flavour symmetry group as global symmetries, the respective Goldstone modes behave as axions which can be used to resolve the strong CP problem by a modified Peccei-Quinn mechanism. (iv) The dynamical picture of flavour symmetry breaking implies new sources of flavour-changing neutral currents, which arise from integrating out heavy scalar spurion fields and heavy gauge bosons. The coefficients of the effective operators follow the minimal-flavour violation principle.Comment: 27 pages, abstract and introduction extended, more detailed discussion of heavy gauge boson spectrum and auxiliary heavy fermions, outline restructured. Matches version to be published in JHE

Cardiovascular outcomes and hospitalizations in Asian patients receiving immune checkpoint inhibitors: a population-based study.

Immune checkpoint inhibitors (ICI) have known associations with cardiotoxicity. However, a representative quantification of the adverse cardiovascular events and cardiovascular attendances amongst Asian users of ICI has been lacking. This retrospective cohort study identified all ICI users in Hong Kong, China, between 2013-2021. All patients were followed up until the end of 2021 for the primary outcome of major adverse cardiovascular event (MACE; a composite of cardiovascular mortality, myocardial infarction, heart failure, and stroke). Patients with prior diagnosis of any component of MACE were excluded from all MACE analyses. In total, 4324 patients were analysed (2905 (67.2%) males; median age 63.5 years old (interquartile range 55.4-70.7 years old); median follow-up 1.0 year (interquartile range 0.4-2.3 years)), of whom 153 were excluded from MACE analyses due to prior events. MACE occurred in 116 (2.8%) with an incidence rate (IR) of 1.7 [95% confidence interval: 1.4, 2.0] events per 100 patient-years; IR was higher within the first year of follow-up (2.9 [2.3, 3.5] events per 100 patient-years). Cardiovascular hospitalization(s) occurred in 188 (4.4%) with 254 episodes (0.5% of all episodes) and 1555 days of hospitalization (1.3% of all hospitalized days), for whom the IR of cardiovascular hospitalization was 5.6 [4.6, 6.9] episodes per 100 person-years with 52.9 [39.8, 70.3] days' stay per 100 person-years. Amongst Asian users of ICI, MACE was uncommon, and a small proportion of hospitalizations was cardiovascular in nature. Most MACE and cardiovascular hospitalizations occurred during the first year after initiating ICI. [Abstract copyright: Copyright © 2022. Published by Elsevier Inc.

Binaries and Globular Cluster Dynamics

We summarize the results of recent theoretical work on the dynamical evolution of globular clusters containing primordial binaries. Even a very small initial binary fraction (e.g., 10%) can play a key role in supporting a cluster against gravothermal collapse for many relaxation times. Inelastic encounters between binaries and single stars or other binaries provide a very significant energy source for the cluster. These dynamical interactions also lead to the production of large numbers of exotic systems such as ultracompact X-ray binaries, recycled radio pulsars, double degenerate systems, and blue stragglers. Our work is based on a new parallel supercomputer code implementing Henon's Monte Carlo method for simulating the dynamical evolution of dense stellar systems in the Fokker-Planck approximation. This new code allows us to calculate very accurately the evolution of a cluster containing a realistic number of stars (N ~ 10^5 - 10^6) in typically a few hours to a few days of computing time. The discrete, star-by-star representation of the cluster in the simulation makes it possible to treat naturally a number of important processes, including single and binary star evolution, all dynamical interactions of single stars and binaries, and tidal interactions with the Galaxy.Comment: 15 pages, to appear in `The Influence of Binaries on Stellar Population Studies', ed. D. Vanbeveren (Kluwer