Wavefront errors in a two-beam interferometer

This paper deals with the impact of wavefront errors, due to the optical aberrations of a two-beam interferometer, on the period of the travelling fringe observed by integrating the interference pattern. A Monte Carlo simulation of the interferometer operation showed that the fringe-period estimate is unbiased if evaluated on the basis of the angular spectrum of the beam entering the interferometer, but the wavefront errors increase the uncertainty

Forward scattering in two-beam laser interferometry

A fractional error as large as 25 pm mm(-1) at the zero optical-path difference has been observed in an optical interferometer measuring the displacement of an x-ray interferometer used to determine the lattice parameter of silicon. Detailed investigations have brought to light that the error was caused by light forward-scattered from the beam feeding the interferometer. This paper reports on the impact of forward-scattered light on the accuracy of two-beam optical interferometry applied to length metrology, and supplies a model capable of explaining the observed error

Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition

We report on the magnetic field induced isothermal entropy change, \Delta s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are performed by direct calorimetry. Single crystals of the composition BaCo$_0.62$Zn$_1.38$Fe$_16$O$_27$, prepared by the flux method, are measured at different fixed temperatures under an applied field perpendicular and parallel to the c axis. At 296 K one deduces a value of K$_1$ = 8.7 \times 10^{4} J m$^-3$ for the first anisotropy constant, which is in good agreement with the literature. The spin reorientation transition temperature is estimated to take place between 200 and 220 K

A Three-Dimensional Code for Muon Propagation through the Rock: MUSIC

We present a new three-dimensional Monte-Carlo code MUSIC (MUon SImulation Code) for muon propagation through the rock. All processes of muon interaction with matter with high energy loss (including the knock-on electron production) are treated as stochastic processes. The angular deviation and lateral displacement of muons due to multiple scattering, as well as bremsstrahlung, pair production and inelastic scattering are taken into account. The code has been applied to obtain the energy distribution and angular and lateral deviations of single muons at different depths underground. The muon multiplicity distributions obtained with MUSIC and CORSIKA (Extensive Air Shower simulation code) are also presented. We discuss the systematic uncertainties of the results due to different muon bremsstrahlung cross-sections.Comment: 24 pages, 11 Postscript figures, LaTeX, to be published in Astroparticle Physic

A comparison of the shock-absorbing properties of cervical disc prosthesis bearing materials

BACKGROUND DATA: Cervical arthroplasty offers theoretical advantages over traditional spinal fusion, including elimination of adjacent segment disease and elimination of the risk of pseudoarthrosis formation. Initial studies of cervical arthroplasty have shown promising results, however, the ideal design characteristics for disc replacement constructs have not been determined. The current study seeks to quantify the differences in the shock absorption characteristics of three commonly used materials in cervical disc arthroplasty. METHODS: Three different nucleus materials, polyurethane (PU), polyethylene (PE) and a titanium-alloy (Ti) were tested in a humidity- and temperature-controlled chamber. Ten of each nucleus type underwent three separate mechanical testing protocols to measure 1) dynamic stiffness, 2) quasi-static stiffness, 3) energy absorption, and 4) energy dissipation. The results were compared using analysis of variance. RESULTS: PU had the lowest mean dynamic stiffness (435 ± 13 N/mm, P < .0001) and highest energy absorption (19.4 ± 0.1 N/mm, P < .0001) of all three nucleus materials tested. PU was found to have significantly higher energy dissipation (viscous damping ratio 0.017 ± 0,001, P < .0001) than the PE or TI nuclei. PU had the lowest quasi-static stiffness (598 ± 23 N/mm, P < .0001) of the nucleus materials tested. A biphasic response curve was observed for all of the PU nuclei tests. CONCLUSIONS: Polyurethane absorbs and dissipates more energy and is less stiff than either polyethylene or titanium. LEVEL OF EVIDENCE: Basic Science/Biomechanical Study. CLINICAL RELEVANCE: This study characterizes important differences in biomechanical properties of materials that are currently being used for different cervical disc prostheses

AB0844 HAND GRIP STRENGTH EVALUATION IN RHEUMATOLOGIC DISEASES

Background:Handgrip muscle strength test describes the strength of the hand muscles used to grasp or grip. Currently, hand grip evaluation is often used in clinical practice, as a marker of function and disability. In fact, it has already been applied as an outcome measure in arthritis rheumatoid clinical trials, to demonstrate the benefits of several treatments [1]. However, hand disability should also be considered in all other rheumatological diseases.Objectives:The main aim of this study is to assess the handgrip muscle strength test in a rheumatological cohort of patients as compared to a control group.Methods:This is a cross-sectional pilot study. We considered eligible 35 rheumatological consecutive female patients followed at our outpatients' clinic of Internal Medicine (I Policlinico of Naples) and 35 healthy control females (HC). Both groups included only right-handed individuals. Rheumatological patients were distributed as follows: 5 rheumatoid arthritis (14,3%), 9 psoriatic arthritis (25,7%), 4 systemic lupus erythematosus (11,4%), 10 systemic sclerosis (28,6%), 4 fibromyalgia (11,4%), 3 juvenile idiopathic arthritis (8,6%). The course of disease was under optimal treatment in all patients.The type of hand grip used is the power grip, in which an object is held firmly by wrapping the fingers around it, pressing the object against the palm, and using the thumb to apply counter-pressure. We considered as either right or left hand valid measure the mean of three consecutive tests per arm. Between-groups differences were tested both by a uni- and multivariable analysis.Results:The two subgroups were homogeneously distributed for age (median age 42 yrs. [IQR 33-48] vs. 36 yrs. [IQR 30-52] in HC; p=0.902). At univariate analysis, hand grip strength was significantly lower in the rheumatological patients, both at right hand (right 19.5 kg [IQR 13.6-24.8] vs. 24.5 kg [IQR 20.8-29] in HC; p=0.004) and left hand (18.5 kg [IQR 13.9-22.5] vs. 23.7 kg [IQR 19-27.3] in HC; p=0.002), as compared to HC. This finding was further confirmed at multivariable analysis only as for the left hand (OR 0.919, 95%CI: 0.858-0.984; p=0.016).Conclusion:Rheumatological diseases are burdened by hand disability, mostly affecting daily activities performance [2,3]. Beyond an optimal disease control, our pilot study shows a decrease in left hand strength as compared to healthy controls. This might be due to a reduced use of the non-dominant hand, which may lead over time to a higher deficit of strength. As such, these patients should be prescribed to a left hand exercise to improve both mobility and strength and, consequently, hand function.References:[1]Eberhardt K, Sandqvist G, Geborek P (2008) Hand function tests are important and sensitive tools for assessment of treatment response in patients with rheumatoid arthritis. Scand J Rheumatol 37(2):109–112.[2]Feced Olmos CM, Alvarez-Calderon O, Hervás Marín D, et al. Relationship between structural damage with loss of strength and functional disability in psoriatic arthritis patients. Clin Biomech (Bristol, Avon). 2019 Aug;68:169-174. doi: 10.1016/j.clinbiomech.2019.06.009.[3]Maddali-Bongi S, Del Rosso A, Mikhaylova S, et al. Impact of hand and face disabilities on global disability and quality of life in systemic sclerosis patients. Clin Exp Rheumatol. 2014 Nov-Dec;32(6 Suppl 86):S-15-20.Disclosure of Interests:None declare