Study of CYTOP and deuterated polyethylene coatings for ultracold neutron storage

In his 1920 Bakerian Lecture on the Nuclear Constitution of Atoms, Ernest Rutherford speculated on the properties of the then undiscovered neutron, remarking that "it may be impossible to contain it in a sealed vessel". Nevertheless, trapping of very low energy---or "ultracold"---neutrons (UCN) is possible due to an effective "optical potential" experienced by neutrons in matter. At present, storage times in the best material traps are essentially limited only by the free neutron lifetime, approximately 880 seconds, offering a precise method of measuring this quantity, whose value has important consequences in theoretical physics. Another important use of stored UCN is in experimental efforts to measure a nonzero neutron electric dipole moment (EDM). In contrast to neutron lifetime measurements, EDM experiments require storage materials that are capable of supporting large electric fields. In many cases, continued progress in these experiments will also be driven by the increased outputs expected from new UCN sources that will use novel storage materials suitable to cryogenic environments. In this work, we report on UCN storage in vessels coated with the fluoropolymer CYTOP and with deuterated polyethylene (dPE), carried out at the SUN-2 prototype UCN source at the Institute Laue-Langevin (ILL) in Grenoble, France. The two materials were investigated for their potential use as coatings for the UCN production volume of the SuperSUN source, and for part of the storage cells of the PanEDM neutron EDM experiment, respectively, both of which are currently under construction at the ILL. In Chapter 1, we motivate the development of improved coatings for UCN storage by discussing the use of neutron EDM measurements as probes of physics beyond the Standard Model. This is followed in Chapter 2 by a brief review of UCN physics, and a discussion in some detail of several models for nonideal UCN storage. The CYTOP and dPE storage results are then presented in Chapter 3, in addition to a measurement of the optical potential of CYTOP, which is found to be 115.2(2) neV. In Chapter 4, we present the results of simulations that can be used to extract an intrinsic storage property of the CYTOP and dPE coatings, the loss factor, $\eta$, from the experimental storage data. This analysis is discussed in Chapter 5, in which conservative estimates of $\eta$ are made: the loss factor of CYTOP is found to be $\eta=2.7(2) \times 10^{-5}$ at 11.7 K and $\eta = 1.1(1) \times 10^{-4}$ at 295.8 K, and the loss factor of dPE is found to be $\eta = 3.1(1) \times 10^{-5}$ at 11.9 K and $\eta = 2.6(1) \times 10^{-4}$ at 295.1 K

Keeping it in the family: coevolution of latrunculid sponges and their dominant bacterial symbionts

publisher versionThe Latrunculiidae are a family of cold water sponges known for their production of bioactive pyrroloiminoquinone alkaloids. Previously it was shown that the bacterial community associated with a Tsitsikamma sponge species comprises unusual bacterial taxa and is dominated by a novel Betaproteobacterium. Here, we have characterized the bacterial communities associated with six latrunculid species representing three genera (Tsitsikamma, Cyclacanthia, and Latrunculia) as well as a Mycale species, collected from Algoa Bay on the South African southeast coast. The bacterial communities of all seven sponge species were dominated by a single Betaproteobacterium operational taxonomic unit (OTU0.03), while a second OTU0.03 was dominant in the Mycale sp. The Betaproteobacteria OTUs from the different latrunculid sponges are closely related and their phylogenetic relationship follows that of their hosts. We propose that the latrunculid Betaproteobacteria OTUs are members of a specialized group of sponge symbionts that may have coevolved with their hosts. A single dominant Spirochaetae OTU0.03 was present in the Tsitsikamma and Cyclacanthia sponge species, but absent from the Latrunculia and Mycale sponges. This study sheds new light on the interactions between latrunculid sponges and their bacterial communities and may point to the potential involvement of dominant symbionts in the biosynthesis of the bioactive secondary metabolites.This research was supported by a SARChI grant from the South African National Research Foundation (NRF, GUN: 87583) and the Rhodes University Sandisa Imbewu Programme. S. C. W. was supported by an NRF Innovation PhD Scholarship and a Rhodes University Henderson PhD Scholarship. T. A. W. was supported by PhD Fellowships from the NRF and the German Academic Exchange Service (DAAD

Ultracold neutron storage in a bottle coated with the fluoropolymer CYTOP

The fluoropolymer CYTOP was investigated in order to evaluate its suitability as a coating material for ultracold neutron (UCN) storage vessels. Using neutron reflectometry on CYTOP-coated silicon wafers, its neutron optical potential was measured to be 115.2(2) neV. UCN storage measurements were carried out in a 3.8 l CYTOP-coated aluminum bottle, in which the storage time constant was found to increase from 311(9) s at room temperature to 564(7) s slightly above 10 K. By combining experimental storage data with simulations of the UCN source, the neutron loss factor of CYTOP is estimated to decrease from 1.1(1)$$\times 10^{-4}$$ to 2.7(2)$$\times 10^{-5}$$ at these temperatures, respectively. These results are of particular importance to the next-generation superthermal UCN source SuperSUN, currently under construction at the Institut Laue-Langevin, for which CYTOP is a possible top-surface coating in the UCN production volume

Epitaxial growth and surface studies of the Half Heusler compound NiTiSn (001)

The Half Heuslers are currently an attractive family of compounds for high temperature thermoelectrics research, and recently, there has been renewed interest since some of these compounds are proposed to be topological insulators. NiTiSn belongs to the family of 18 valence electron Half Heuslers that are predicted to be semiconducting, despite being composed entirely of metallic elements. The growth of the Half Heusler compound NiTiSn by molecular beam epitaxy is demonstrated. The NiTiSn films are epitaxial and single crystalline as observed by reflection high-energy electron diffraction and x-ray diffraction. Temperature dependent transport measurements suggest the films may be semiconducting, but with a high background carrier density indicative of a high density of electrically active defect states. Methods of protecting the sample surface for synchrotron-based photoemission measurements are explored. These methods may be applied to the study of surface electronic structure in unconventional materials. (C) 2013 American Vacuum Society

Concurrent validity and reliability of measuring range of motion during the cervical flexion rotation test with a novel digital goniometer

Background!#!Headache is a common and costly health problem. Although the pathogenesis of headache is heterogeneous, reported contributing factors are dysfunctions of the upper cervical spine. The flexion rotation test (FRT) is a commonly used diagnostic test to detect upper cervical movement impairment. A digital goniometer may support precise measurement of movement impairment in the upper cervical spine. However, its reliability and validity is not assessed, yet. The aim of this study was to investigate the reliability and validity of the digital goniometer compared to an ultrasound-based movement analysis system.!##!Methods!#!Two separate cross-sectional studies were conducted using the digital goniometer EasyAngle (Meloq AB, Stockholm, Sweden) for a) investigating the concurrent validity of upper cervical range of motion (ROM) during the FRT and b) determining the inter- and intra-rater reliability in the target population of patients with head and neck pain. Sixty-two participants, 39 with and 23 without head and neck pain, were recruited for the concurrent validity study. For the reliability study, a total of 50 participants were recruited. Intraclass correlation coefficients (ICC) and Bland Altmann plots were used to assess validity and ICC values, Bland Altmann plots as well as Kappa coefficients were used for estimating intra-rater and inter-rater reliability.!##!Results!#!Concurrent validity was strong with an ICC (2,1) of 0.97 for ROM to either side (95%CI = 0.95-0.98). Bland Altman Plots revealed a mean difference between measurement systems of 0.5° for the left and 0.11° for the right side. The inter-rater ICC (2,1) was 0.66 (95%CI 0.47-0.79, p <  0.001, SEM 6.6°), indicating good reliability. The limits of agreement were between 10.25° and - 11.89°, the mean difference between both raters was - 0.82°. Intra-rater reliability for the measurement of ROM during the FRT was between 0.96 (ICC 3,1) for rater 1 and 0.94 (ICC 3,1) for rater 2.!##!Conclusions!#!The digital goniometer demonstrated strong concurrent validity and good to strong reliability and can be used in clinical practice to accurately determine movement impairment in the upper cervical spine.!##!Trial registration!#!German Registry of Clinical Trials DRKS00013051

Human Retrotransposons and the Global Shutdown of Homeostatic Innate Immunity by Oncolytic Parvovirus H-1PV in Pancreatic Cancer

Although the oncolytic parvovirus H-1PV has entered clinical trials, predicting therapeutic success remains challenging. We investigated whether the antiviral state in tumor cells determines the parvoviral oncolytic efficacy. The interferon/interferon-stimulated genes (IFN/ISG)-circuit and its major configurator, human endogenous retroviruses (HERVs), were evaluated using qRT-PCR, ELISA, Western blot, and RNA-Seq techniques. In pancreatic cancer cell lines, H-1PV caused a late global shutdown of innate immunity, whereby the concomitant inhibition of HERVs and IFN/ISGs was co-regulatory rather than causative. The growth-inhibitory IC50 doses correlated with the power of suppression but not with absolute ISG levels. Moreover, H-1PV was not sensitive to exogenous IFN despite upregulated antiviral ISGs. Such resistance questioned the biological necessity of the oncotropic ISG-shutdown, which instead might represent a surrogate marker for personalized oncolytic efficacy. The disabled antiviral homeostasis may modify the activity of other viruses, as demonstrated by the reemergence of endogenous AluY-retrotransposons. This way of suppression may compromise the interferogenicity of drugs having gemcitabine-like mechanisms of action. This shortcoming in immunogenic cell death induction is however amendable by immune cells which release IFN in response to H-1PV