Detection and Characterization of Defects by the Electric Current Perturbation Method

The electric current perturbation (ECPl method of nondestructive evaluation is a powerful technique for detection and characterization of very small defects in nonferromagnetic material. It consists of establishing a current flow in the material to be inspected and then measuring current perturbations caused by nonconducting defects such as fatigue cracks. The current perturbation is sensed by a non-contacting magnetometer probe which detects the associated magnetic field perturbation. Recent findings from ECP investigations are reviewed in this paper. First, analytical modeling and experimental results show that single and multiple, closely spaced slots can be characterized from their unique ECP signatures; second, ECP inspection results from tiebolt holes in TF-33 gas turbine ·engine disks demonstrate the capability to characterize very small (0.305 mm long by 0.137 mm deep), tightly-closed, service-induced fatigue cracks; and third, preliminary results of an ECP experiment on a two layer fastener configuration show that radial slots in fastener holes can be detected in the second layer with the fastener installed

Flaw Detection in Aluminum Welds by the Electric Current Perturbation Method

The integrity of the Space Shuttle external fuel tank is vital to the success of each shuttle mission. These giant tanks (154 ft long and 28 ft diameter) are manufactured for NASA by Martin Marietta Aerospace, New Orleans, LA. An important part of the quality assurance for each tank is detection of defects in the welds using nondestructive evaluation (NDE) methods. The tank is manufactured from aluminum panels which are welded together, and due to the large physical size of the tank, several thousand feet of weld must be inspected for each tank. Therefore, to be cost effective, the NDE methods used must not only be reliable but also must be rapid

Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes

Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at √s = 13 TeV

The central exclusive production of charged-hadron pairs in ⁢ collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high-* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, +⁢−1.8  GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and +⁢− are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities ||<2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton

A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer

A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp → pp + Z/γ + X, in proton-tagged events from proton–proton collisions at √s = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. odelindependent upper limits on the visible production cross section of pp → pp + Z/γ + X are set

Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer

The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb-1 in proton-proton (pp) collisions at the LHC at 13 TeV (Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider

Measurement of single-diffractive dijet production in proton-proton collisions at root s=8 TeV with the CMS and TOTEM experiments

A Publisher's Erratum to this article was published on 03 May 2021. https://doi.org/10.1140/epjc/s10052-021-08863-wPeer reviewe