Vascular endothelial growth factor in eye disease

Collectively, angiogenic ocular conditions represent the leading cause of irreversible vision loss in developed countries. In the U.S., for example, retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration are the principal causes of blindness in the infant, working age and elderly populations, respectively. Evidence suggests that vascular endothelial growth factor (VEGF), a 40 kDa dimeric glycoprotein, promotes angiogenesis in each of these conditions, making it a highly significant therapeutic target. However, VEGF is pleiotropic, affecting a broad spectrum of endothelial, neuronal and glial behaviors, and confounding the validity of anti-VEGF strategies, particularly under chronic disease conditions. In fact, among other functions VEGF can influence cell proliferation, cell migration, proteolysis, cell survival and vessel permeability in a wide variety of biological contexts. This article will describe the roles played by VEGF in the pathogenesis of retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration. The potential disadvantages of inhibiting VEGF will be discussed, as will the rationales for targeting other VEGF-related modulators of angiogenesis

Rotating Resonator-Oscillator Experiments to Test Lorentz Invariance in Electrodynamics

In this work we outline the two most commonly used test theories (RMS and SME) for testing Local Lorentz Invariance (LLI) of the photon. Then we develop the general framework of applying these test theories to resonator experiments with an emphasis on rotating experiments in the laboratory. We compare the inherent sensitivity factors of common experiments and propose some new configurations. Finally we apply the test theories to the rotating cryogenic experiment at the University of Western Australia, which recently set new limits in both the RMS and SME frameworks [hep-ph/0506074].Comment: Submitted to Lecture Notes in Physics, 36 pages, minor modifications, updated list of reference

Global Retinoblastoma Presentation and Analysis by National Income Level

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4) were female. Most patients (n = 3685 84.7%) were from low-and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 62.8%), followed by strabismus (n = 429 10.2%) and proptosis (n = 309 7.4%). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 95% CI, 12.94-24.80, and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 95% CI, 4.30-7.68). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs. © 2020 American Medical Association. All rights reserved

Temperature fluctuations in a solid-nitrogen cooled secondary frequency standard

Abstract not availableJ.G Hartnett, M.E Tobar, E.N Ivanov, P Bilsk

High-Q frequency stable dual-mode whispering gallery sapphire resonator

The design and experimental test of a dual mode high-Q Whispering Gallery (WG) sapphire resonator is presented. Dual mode operation is realized by designing the WGE/sub 7,0,0/ and the WGH/sub 9,0,0/ mode near 9 GHz and separated in frequency by approximately 80 MHz. Design was achieved by implementing finite element software, which is shown to agree very well with measurement, Due to the anisotropy of sapphire, WGH and WGE modes have different temperature coefficient of frequency (TCF). We show that the difference frequency can be used to stabilize the temperature, resulting in a temperature limited frequency stability of better than one part in 10/sup 13/. This type of resonator has the potential to improve substantially the close to the carrier phase noise in current state-of-the-art low noise oscillators.Michael E. Tobar, Eugene N. Ivano, John G. Hartnett and Dominique Cro

Dielectric characterisation of barium fluoride at cryogenic temperatures using TE011 and quasi TE0mn mode dielectric resonators

Barium Fluoride (BaF2), mainly used in optical applications, has similar properties to those of CaF2 but better stability under environmental conditions. In this paper, we report measurements of loss tangent and the real part of the relative permittivity εr of single crystal BaF2 in the temperature range from 14 to 290 K at frequencies of 8, 10.4, 12.1, 17.6, 21.1 and 24.4 GHz. Microwave properties of BaF2 were determined by measurements of the resonance frequency and the unloaded Q-factor of TE011 and quasi TE0mn modes cylindrical cavities containing the sample under test. Two techniques namely Hakki–Coleman Dielectric Resonator and dielectric post resonators have been used for characterizing the dielectric material. Losses due to the uncalibrated cables and adaptors inside the cryocooler are accounted in the calculation of unloaded Q-factor using the Transmission Mode Q-Factor data processing technique. The permittivity of BaF2 exhibited a 5% increase from 6.9 (14 K) to 7.35 (290 K). The loss tangent increased from 1 × 10−5 to 1.1 × 10−4 over the measured temperature range, 14–290 K at a frequency of 10.4 GHz. The measured microwave properties show that BaF2 can be used in many microwave devices

Lithium tantalate - a high permittivity dielectric material for microwave communication systems

Lithium tantalate single crystal is characterized by very low thermal expansion and exhibits excellent electro-optical, piezoelectric and pyroelectric properties. We have studied the real part of relative permittivity (εr) perpendicular to the crystal axis and the loss tangent of LiTaO3 over the temperature range from 15 K to room temperature at a frequency of 11.4 GHz. The εr and tanδ were determined by measurements of the resonance frequency and the unloaded Q-factor of a TE011 mode cylindrical cavity containing the sample under test. The permittivity of LiTaO3 was found to change from 38.9 to 41.1 and the loss tangent increased from 1.1 × 10-4 to 6.5 × 10-4 over the temperature range from 15 K to 295 K. Due to the low losses and high permittivity this material can be used in many microwave applications