Substantia nigra hyperechogenicity in Polish patients with Parkinson’s disease

Background: Hyperechogenicity of the substantia nigra (SN) measured by transcranial sonography (TCS) is a characteristic feature observed in patients with Parkinson’s disease (PD). To our knowledge, no SN hyperechogenicity data are available for Polish population. Moreover most of studies come from few centres, which used the one type of ultrasound device. The main aim of the study was to investigate the association between PD and SN hyperechogenicity measured by sonographic machine, not assessed so far.Materials and methods: In this study cross-sectional study SN hyperechogenicity was evaluated in 102 PD patients and 95 control subjects. Midbrain was visualised by Aloka Prosound 7 ultrasound device. SN area measurement, the relation to the clinical features of PD, inter- and intra-observer reliability were evaluated.Results: We confirmed that SN echogenicity is significantly increased in PD patients compared to control subjects (p < 0.001). The area under curve for PD patients vs. controls was 0.93. Receiver operating characteristic analysis indicated a cut-offs for SN echogenicity at 0.19 cm2 with accuracy equal to 90%, specificity — 86% and sensitivity — 93.7%. The SN hyperechogenicity was not related to PD clinical findings. Reliability was good if an experienced sonographer performed the SN measurements.Conclusions: This study shows that the SN abnormality observed by TCS isa specific feature, which can be helpful in the process of PD diagnosing

Magnetization reversal processes in epitaxial Fe/GaAs(001) films

Copyright © 1994 American Institute of PhysicsIn this article we present the results of a detailed study of the switching behavior observed in epitaxial single Fe films of thickness between 30 and 450 Å, and a wedge shaped Fe film with a thickness range of 10–60 Å grown on GaAs (001). These films have cubic and uniaxial anisotropies which change with film thickness. For the fixed thickness films the values of the anisotropy constants were accurately determined by Brillouin light scattering (BLS) measurements together with polar magneto‐optic Kerr effect (MOKE) measurements that gave the value of the magnetization. The switching behavior of these samples was observed with in‐plane MOKE magnetometry as a function of the angle between the applied field and the in‐plane crystallographic axes. Measurements of the component of magnetization perpendicular to the applied field allow a precise determination of the relative orientation of the hard and easy in‐plane anisotropy axes. This can be used to accurately determine the ratio of uniaxial to cubic anisotropy constants, when this ratio is less than one. The ratios obtained from MOKE agree well with those obtained from BLS. Minimum energy calculations predict that the reversal process should proceed by a continuous rotation of the magnetization vector with either one or two irreversible jumps, depending on the applied field orientation and the nature of the anisotropy of the film. The calculations provide a good qualitative description of the observed reversal process, although the magnetic microstructure influences the exact values of the switching fields

Exchange Anisotropy in Epitaxial and Polycrystalline NiO/NiFe Bilayers

(001) oriented NiO/NiFe bilayers were grown on single crystal MgO (001) substrates by ion beam sputtering in order to determine the effect that the crystalline orientation of the NiO antiferromagnetic layer has on the magnetization curve of the NiFe ferromagnetic layer. Simple models predict no exchange anisotropy for the (001)-oriented surface, which in its bulk termination is magnetically compensated. Nonetheless exchange anisotropy is present in the epitaxial films, although it is approximately half as large as in polycrystalline films that were grown simultaneously. Experiments show that differences in exchange field and coercivity between polycrystalline and epitaxial NiFe/NiO bilayers couples arise due to variations in induced surface anisotropy and not from differences in the degree of compensation of the terminating NiO plane. Implications of these observations for models of induced exchange anisotropy in NiO/NiFe bilayer couples will be discussed.Comment: 23 pages in RevTex format, submitted to Phys Rev B

The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies

Dynamic-mechanical-thermal investigations of homogeneous, solid, double-base rocket propellants

W artykule przedstawiono badania stałych, homogenicznych paliw rakietowychdwubazowych, których podstawowymi składnikami są nitroceluloza i nitrogliceryna. Badania dynamiczno-mechaniczno-termiczne (określane skrótem DMA albo DMTA) paliw rakietowych realizowano za pomocą analizatora DMA Q800 brytyjskiej firmy „TA Instruments”. Próbka materiałowa zamocowana była na jednym końcu do nieruchomego, zaś na drugim - do ruchomego uchwytu, poprzez który poddawana była dynamicznemu obciążeniu okresowemu o częstotliwości 1 Hz, przy kontrolowanej deformacji wynoszącej 0,2 mm. Jednocześnie próbka znajdowała się w komorze termostatującej, ogrzewanej z szybkością 2°C/min. Analizę DMA prowadzono w zakresie temperatur od 30°C do 100°C, określając dynamiczny moduł sprężystości paliwa rakietowego, jego dynamiczny moduł stratności, tangens kąta przesunięcia fazowego między obu modułami oraz względne odkształcenie dynamiczne. Znajomość ww. parametrów umożliwia min. ocenę wytrzymałości paliwa na mechaniczne obciążenia dynamiczne w badanym zakresie temperaturowym oraz temperaturę mięknienia paliwa.Investigations of solid, homogeneous, double-base, rocket propellants composed of two main ingredients i.e. – nitrocellulose and nitroglycerine, by means of Dynamic-Mechanical-Thermal Analysis (detrmined by abbreviation DMA or DMTA) were presented in this paper. The tests of solid rocket propellant samples were conducted with usage of DMA Q800 Analyser of british “TA Instruments” Company. The tested sample was mounted in single cantilever clamp system i.e. the sample was fixed at one end, and through the second end the sample was subjected to mechanical dynamic cyclic loads of frequency 1 Hz , at controlled sample deformation of 0.2 mm. Simultaneously the sample was heated in the apparatus conditioning chamber with the rate of temperature rise of 2°C /min. DMA analyses for tested samples were realised in the range of temperature from 30°C to 100°C. By means of DMA analysis dynamic loss modulus, dynamic storage modulus, tangent of angle of phase shift between these moduli and relative dynamic strain of tested samples were determined. Knowledge about above mentioned parameters makes possible int. al. assessment of solid rocket propellant specimens strength towards dynamic loads subjected to them in the given temperature region and also allows to determine the solid rocket propellant specimens softening point

An application of standardization Agreement 4540 in solid rocket propellant testing

W artykule przedstawiono sposób badania stałych paliw rakietowych metodą dynamicznej analizy mechanicznej (DMA) w oparciu o porozumienie STANAG 4540. Scharakteryzowano metodę DMA oraz opisano prawidłowe warunki eksperymentu zalecane przez STANAG oraz instrukcje obsługi urządzenia. Próbka stałego dwubazowego paliwa rakietowego została zbadana za pomocą urządzenia Netzsch DMA 242C. Dynamiczne właściwości mechaniczne takie jak moduł zachowaw-czy (E’), moduł stratności (E”) oraz tgδ zostały zmierzone w zakresie temperatury od -120° C do +110° C, przy prędkości ogrzewania wynoszącej 1K/min. Zastosowano trzy częstotliwości uginania próbki wynoszące 0,1 Hz, 1 Hz oraz 10 Hz. Szczególną uwagę poświęcono określeniu temperatury zeszklenia badanego paliwa.The article describes dynamic mechanical analysis (DMA) test procedure of solid rocket propellants on the basis of STANAG Agreement 4540. DMA principle of operation and proper experimental conditions recommended by the STANAG and DMA manual are described. A sample of solid rocket propellant was tested by using Netzsch DMA 242C analyzer. Dynamic mechanical properties such as the storage modulus (E’), loss modulus (E”) and tanδ were measured within temperature range from -120° C to +110° C at heating rate of 1K/min. The sample was tested at three bending frequencies of 0.1, 1.0 and 10.0 Hz. Special attention was paid to the determination of tested propellant glass transition temperature

Determination of Glass Transition Temperature of Double-Base Rocket Propellants with the Use of Dynamic Mechanical Analysis

The paper presents results of Dynamic Mechanical Analysis (DMA) of double-base (DB) solid rocket propellant with special attention paid to determining the glass transition temperature. The presented experiments were carried out with the use of Netzsch DMA 242C analyzer with the dual cantilever operation mode. Advantages and drawbacks of the DMA method, measured values, as well as important characteristics of solid double-base rocket propellants were briefly described. Obtained values of the storage modulus E', the loss modulus E", and tand were represented in dependence on temperature. The glass transition temperature of the tested propellant was determined according to NATO standard 4540 [7] at the peak of the loss modulus curve