For more than fifty years, observations of the cosmic microwave background (CMB) have provided fundamental insights into the universe we inhabit. Through a combination of ground-based and balloon- ...and satellite-borne experiments, we have measured the CMB's temperature anisotropy and power spectrum to high precision (Barrow and Coles, 1991; de Bernardis et al., 2000; Planck Collaboration, 2016a). Most recently, experiments are attempting to measure the CMB's polarization anisotropy. Measurements of polarization anisotropy will provide insight into the epoch of reoinization, information about the energy scale of inflation, and characterization of galactic dust, for instance (Barkana and Loeb, 2001; Hu, 2003; Planck Collaboration, 2016b). These are difficult measurements to make, however. They require observations at both large and small angular scales, and sensitive instruments capable of observing at multiple wavelengths in order to constrain foreground contamination. One of the experiments contributing to this effort is the third generation survey camera on board the South Pole Telescope (SPT-3G; Benson et al., 2014}). SPT is located at the geographic South Pole (elevation ~2800 m), which is an exceptionally arid environment (Radford and Holdaway, 1998; Radford, 2011). A fifty year study of precipitable water vapor (PWV) at the South Pole found the average PWV is far less than 1 mm, making the South Pole one of the driest regions on Earth (Chamberlin and Grossman, 2012). This is important for telescopes observing at mm wavelengths, where atmospheric water vapor can severely attenuate the interesting radiation. Other perks of observing from the Pole are that the SPT can easily avoid the galactic plane and its dust-contaminated signal, enabling it to integrate on a patch of extragalactic sky for long periods. In addition, the low temperature variability of the six-month long polar night keeps the atmosphere stable for long stretches. The SPT optics and structure benefit from the low temperature variability as well, since thermal gradients across the SPT are small. SPT's 10 m primary aperture and diffraction-limited optics uniquely position it to map the CMB at arcminute-scale angular resolution. SPT-3G---the new survey camera installed during the 2016/2017 austral summer---is polarization sensitive, and observes in three band passes that correspond to atmospheric transmission windows. Although there are other polarization-sensitive experiments that observe at multiple wavelengths, there are relatively few that do so with multichroic, polarization-sensitive pixels. SPT-3G fits all three colors (hence multichroic) and both polarizations within a single ~5 mm diameter pixel footprint---that's six detectors per pixel footprint. To top it off, the camera contains more than 2700 of these pixels. As it happens, building a multichroic, polarization-sensitive mm wave camera with exceptionally high detector density is an engineering challenge---or, seemingly, a countably infinite set of challenges. This dissertation attempts to address one of them: antireflection (AR) coatings for high-refractive index optics. I say "attempts to address" because the problem is far from solved. Rather, what follows is the first iteration of a process that can complement the growing need for high detector density CMB experiments. With the upcoming CMB-S4 project intending to field hundreds of thousands of detectors, the days of bespoke quasi-optical coupling elements are drawing to a close. What we will need going forward is a scalable, high-throughput manufacturing process for quasi-optical coatings. That is to say, something like the process detailed in this work. I also address the similar challenge that is AR coating large-scale reimaging optics. Again, this isn't a solved problem, but we've developed a method that works well enough. The materials needed to manufacture both the small-scale (i.e., quasi-optical) and large-scale AR coatings are inexpensive: about $1 per pixel for the quasi-optical coating; about $1500 per SPT-3G-sized lens. Both coatings increase the amount of radiation transmitted through the optics by >25% across all three observing bands. In addition to the manufacturing methods described above, this work introduces an open-source Python package that will be beneficial to those who design and model mm wave AR coatings, as well as laboratory measurements of SPT-3G AR coatings and their constituent materials. These measurements include optical measurements (in the form of Fourier-transform spectroscopy, vector network analysis, and reflectometry), x-ray spectroscopy, and scanning electron microscopy. There is also a discussion of the end-to-end optical efficiency of the SPT-3G survey camera and some of the factors that impact it.
The third-generation South Pole Telescope camera is designed to measure the cosmic microwave background across three frequency bands (95, 150 and 220 GHz) with ~16,000 transition-edge sensor (TES) ...bolometers. Each multichroic pixel on a detector wafer has a broadband sinuous antenna that couples power to six TESs, one for each of the three observing bands and both polarization directions, via lumped element filters. Ten detector wafers populate the focal plane, which is coupled to the sky via a large-aperture optical system. Here we present the frequency band characterization with Fourier transform spectroscopy, measurements of optical time constants, beam properties, and optical and polarization efficiencies of the focal plane. The detectors have frequency bands consistent with our simulations, and have high average optical efficiency which is 86%, 77% and 66% for the 95, 150 and 220 GHz detectors. The time constants of the detectors are mostly between 0.5 ms and 5 ms. The beam is round with the correct size, and the polarization efficiency is more than 90% for most of the bolometers
CMB-S4 Technology Book, First Edition Abitbol, Maximilian H; Ahmed, Zeeshan; Barron, Darcy ...
arXiv (Cornell University),
07/2017
Paper, Journal Article
Odprti dostop
CMB-S4 is a proposed experiment to map the polarization of the Cosmic Microwave Background (CMB) to nearly the cosmic variance limit for angular scales that are accessible from the ground. The ...science goals and capabilities of CMB-S4 in illuminating cosmic inflation, measuring the sum of neutrino masses, searching for relativistic relics in the early universe, characterizing dark energy and dark matter, and mapping the matter distribution in the universe have been described in the CMB-S4 Science Book. This Technology Book is a companion volume to the Science Book. The ambitious science goals of CMB-S4, a "Stage-4" experiment, require a step forward in experimental capability from the current Stage=II experiments. To guide this process, we summarize the current state of CMB instrumentation technology, and identify R&D efforts necessary to advance it for use in CMB-S4. The book focuses on technical challenges in four broad areas: Telescope Design; Receiver Optics; Focal-Plane Optical Coupling; and Focal-Plane Sensor and Readout.
Chyloptysis, or the expectoration of triglyceride-rich sputum, is rare and typically treated with diet modification and thoracic duct ligation. This article describes 2 patients with prolonged ...histories of chyloptysis who failed conservative treatment and thoracic duct ligation. Dynamic contrast-enhanced magnetic resonance imaging delineated the lymphatic anatomy and identified the abnormal pulmonary lymphatic perfusion pathways in both patients. This imaging provided guidance for successful percutaneous lymphatic embolization which resulted in resolution of symptoms in both patients.
Analysis of photoreceptor morphology and gene expression in mispatterned eyes of zebrafish growth differentiation factor 6a (gdf6a) mutants.
Rod and cone photoreceptors were compared between gdf6a ...mutant and control zebrafish from larval to late adult stages using transgenic labels, immunofluorescence, and confocal microscopy, as well as by transmission electron microscopy. To compare transcriptomes between larval gdf6a mutant and control zebrafish, RNA-Seq was performed on isolated eyes.
Although rod and cone photoreceptors differentiate in gdf6a mutant zebrafish, the cells display aberrant growth and morphology. The cone outer segments, the light-detecting sensory endings, are reduced in size in the mutant larvae and fail to recover to control size at subsequent stages. In contrast, rods form temporarily expanded outer segments. The inner segments, which generate the required energy and proteins for the outer segments, are shortened in both rods and cones at all stages. RNA-Seq analysis provides a set of misregulated genes associated with the observed abnormal photoreceptor morphogenesis.
GDF6 mutations were previously identified in patients with Leber congenital amaurosis. Here, we reveal a unique photoreceptor phenotype in the gdf6a mutant zebrafish whereby rods and cones undergo abnormal maturation distinct for each cell type. Further, subsequent development shows partial recovery of cell morphology and maintenance of the photoreceptor layer. By conducting a transcriptomic analysis of the gdf6a larval eyes, we identified a collection of genes that are candidate regulators of photoreceptor size and morphology.
Background: Studies have estimated that a large backlog of procedures was generated by emergency measures implemented in Ontario, Canada, at the onset of the COVID-19 pandemic, when nonessential and ...scheduled procedures were postponed. Understanding the impact of the COVID-19 pandemic on the time needed to perform a procedure may help to determine the resources needed to tackle the substantial backlog caused by the deferral of cases. The purpose of this study was to examine the duration of operating room (OR) procedures before and after the onset of the COVID-19 pandemic to inform planning around changes in required resources. Methods: A population-based, retrospective cohort study was conducted using Ontario Health Insurance Plan claims data and other administrative health care data from Apr. 1, 2019, to Sept. 30, 2020. Statistical analysis was conducted using multivariate regression, with procedure duration as the outcome variable. Results: Results showed that the average duration of nonelective procedures increased by 34 minutes during the COVID-19 period and by 19 minutes after the resumption of scheduled procedures. Controlling for physician, patient and hospital characteristics, and the procedure code submitted, procedure duration increased by 12 minutes in the nonelective COVID-19 period and by 5 minutes when scheduled procedures resumed, compared with the pre-COVID-19 period. Conclusion: Procedures may take longer in the COVID-19 period. This will affect wait times, which had already increased because of the deferral of procedures at the beginning of the pandemic, and will have an impact on Ontario's ability to provide patients with timely care. Contexte : Selon des etudes, on estime que la mise en place des mesures d'urgence en Ontario (Canada) au debut de la pandemie de COVID-19, qui ont entraine le report de toutes les interventions planifiees et non essentielles, a mene a l'accumulation d'un retard important des interventions chirurgicales. Comprendre l'incidence de la pandemie de COVID-19 sur le temps necessaire pour realiser une intervention pourrait aider a determiner les ressources requises pour s'attaquer a cet arriere considerable. Le but de cette etude etait d'observer la duree des interventions en salle d'operation avant et apres le debut de la pandemie de COVID-19 pour mieux planifer les changements aux ressources necessaires. Methodes : Une etude de cohorte retrospective populationnelle a ete menee a l'aide des donnees sur les reclamations medicales soumises au Regime d'assurance-sante de l'Ontario et d'autres donnees administratives sur les soins de sante du 1 (er) avril 2019 au 30 septembre 2020. L'analyse statistique a ete realisee au moyen d'une regression multivariable, ou la duree de l'intervention constituait la variable dependante. Resultats : Les resultats ont montre que la duree moyenne des interventions non urgentes a augmente de 34 minutes durant la periode de restrictions associees a la COVID-19, et de 19 minutes apres la reprise des interventions planifees. En tenant compte de variables comme les caracteristiques du medecin, du patient et de l'hopital ainsi que des codes d'acte soumis, le temps moyen des interventions a augmente de 12 minutes pendant la periode de restrictions associees a la COVID-19 pour les interventions non urgentes et de 5 minutes apres la reprise des interventions planifees comparativement a la periode precedant la COVID-19. Conclusion : Les interventions peuvent prendre plus de temps en contexte de COVID-19. Cela influencera les temps d'attente, qui ont deja augmente en raison du report des interventions au debut de la pandemie, et aura des repercussions sur la capacite de l'Ontario a fournir aux patients des soins dans des delais raisonnables.
Limited information exists about the epidemiology and outcome of surgical patients at increased risk of postoperative pulmonary complications (PPCs), and how intraoperative ventilation was managed in ...these patients.
To determine the incidence of surgical patients at increased risk of PPCs, and to compare the intraoperative ventilation management and postoperative outcomes with patients at low risk of PPCs.
This was a prospective international 1-week observational study using the 'Assess Respiratory Risk in Surgical Patients in Catalonia risk score' (ARISCAT score) for PPC for risk stratification.
Adult patients requiring intraoperative ventilation during general anaesthesia for surgery in 146 hospitals across 29 countries.
The primary outcome was the incidence of patients at increased risk of PPCs based on the ARISCAT score. Secondary outcomes included intraoperative ventilatory management and clinical outcomes.
A total of 9864 patients fulfilled the inclusion criteria. The incidence of patients at increased risk was 28.4%. The most frequently chosen tidal volume (VT) size was 500 ml, or 7 to 9 ml kg predicted body weight, slightly lower in patients at increased risk of PPCs. Levels of positive end-expiratory pressure (PEEP) were slightly higher in patients at increased risk of PPCs, with 14.3% receiving more than 5 cmH2O PEEP compared with 7.6% in patients at low risk of PPCs (P < 0.001). Patients with a predicted preoperative increased risk of PPCs developed PPCs more frequently: 19 versus 7%, relative risk (RR) 3.16 (95% confidence interval 2.76 to 3.61), P < 0.001) and had longer hospital stays. The only ventilatory factor associated with the occurrence of PPCs was the peak pressure.
The incidence of patients with a predicted increased risk of PPCs is high. A large proportion of patients receive high VT and low PEEP levels. PPCs occur frequently in patients at increased risk, with worse clinical outcome.
The study was registered at Clinicaltrials.gov, number NCT01601223.
The aim of this post hoc analysis of a large cohort study was to evaluate the association between night-time surgery and the occurrence of intraoperative adverse events (AEs) and postoperative ...pulmonary complications (PPCs).
LAS VEGAS (Local Assessment of Ventilatory Management During General Anesthesia for Surgery) was a prospective international 1-week study that enrolled adult patients undergoing surgical procedures with general anaesthesia and mechanical ventilation in 146 hospitals across 29 countries. Surgeries were defined as occurring during ‘daytime’ when induction of anaesthesia was between 8:00 AM and 7:59 PM, and as ‘night-time’ when induction was between 8:00 PM and 7:59 AM.
Of 9861 included patients, 555 (5.6%) underwent surgery during night-time. The proportion of patients who developed intraoperative AEs was higher during night-time surgery in unmatched (43.6% vs 34.1%; P<0.001) and propensity-matched analyses (43.7% vs 36.8%; P=0.029). PPCs also occurred more often in patients who underwent night-time surgery (14% vs 10%; P=0.004) in an unmatched cohort analysis, although not in a propensity-matched analysis (13.8% vs 11.8%; P=0.39). In a multivariable regression model, including patient characteristics and types of surgery and anaesthesia, night-time surgery was independently associated with a higher incidence of intraoperative AEs (odds ratio: 1.44; 95% confidence interval: 1.09–1.90; P=0.01), but not with a higher incidence of PPCs (odds ratio: 1.32; 95% confidence interval: 0.89–1.90; P=0.15).
Intraoperative adverse events and postoperative pulmonary complications occurred more often in patients undergoing night-time surgery. Imbalances in patients' clinical characteristics, types of surgery, and intraoperative management at night-time partially explained the higher incidence of postoperative pulmonary complications, but not the higher incidence of adverse events.
NCT01601223.
Outcomes of interventional lymphangiographic treatment of nontraumatic chylous pleural effusions using traditional approaches have been highly variable. Recent advances in lymphatic imaging have ...revealed variations in underlying pathophysiology, enabling improved targeting of therapeutic interventions.
To assess outcomes of an algorithm for management of nontraumatic chylous pleural effusions based on advanced magnetic resonance (MR) identification of various abnormalities in the thoracoabdominal lymphatic network that give rise to chylothorax.
Novel lymphatic MR imaging was performed in 52 patients aged 11-89 years. Three distinct pathophysiological patterns were found:
) abnormal pulmonary lymphatic flow from the thoracic duct only;
) abnormal pulmonary lymphatic flow from retroperitoneal lymphatic networks with or without involvement of the thoracic duct; and
) chylous ascites presenting as chylous pleural effusion. Lymphatic interventions were individualized to the underlying pathophysiological patterns.
In 41/52 (79%) patients, imaging revealed abnormal pulmonary lymphatic flow from the thoracic duct and/or retroperitoneal lymphatic networks. Thoracic duct embolization and/or interstitial embolization of retroperitoneal lymphatic resulted in resolution of chylothorax in this group in 38/41 (93%) of those patients. Five patients experienced grade 1 or 2 complications. One patient succumbed to postoperative stress-induced cardiomyopathy and pulmonary embolism. Chylous ascites was the cause of chylothorax in 11/52 (21%) patients. Eight chose to undergo interventions for chylous ascites with clinical success in 6/8 (75%).
Application of magnetic resonance imaging-guided intervention algorithm resulted in successful control of nontraumatic chylothorax in 93% patients with abnormal pulmonary lymphatic flow. Appropriate treatment of chylous ascites presenting as a pleural effusion requires systematic evaluation and diagnosis prior to potential treatments.
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