57Fe Mössbauer Study of One-Hour Annealing in Argon of Radiation Damage in Metamict Gadolinite from Ytterby

Hyperfine Interactions - Gadolinite, REE2FeBe2Si2O10, belongs to the group of metamict minerals. Metamict minerals incorporate uranium and thorium in their structures. Alpha-decays of uranium and...     

57Fe Mössbauer spectroscopy and X-ray diffraction study of complex metamict minerals. Part II

The magnetic behaviour of the nanocrystalline Ni_0.5Cu_0.5Fe₂O₄, synthesized by the co-precipitation method has been studied. The X-ray diffraction patterns confirm the formation of cubic spinel structure. The dc magnetization measurements show that the samples are superparamagnetic above the blocking temperatures and the blocking temperature increases with particle size. The reduction in saturation magnetization in the case of nanoparticles as compared to their bulk counterpart has been explained on the basis that the magnetic moments in the surface layers of a nanoparticle are in a state of frozen disorder. The hump in ZFC curve progressively shift to a lower temperature with increasing field and broader curves at higher field, suggests the spin-glass nature of the system.     

Gamma background measurements in the Laboratoire Souterrain de Modane

In situ gamma-ray measurements were taken at six locations in the Modane Underground Laboratory. Count rates for gamma radiation within the energy range of 7–2734 keV varied from 15 to 108 γs⁻¹. The arithmetic mean was 79 γs⁻¹ for measurements taken without a collimator. The metamorphic rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium equal to 12 and 10 Bq kg⁻¹, respectively.     

Gamma background measurements in the Boulby Underground Laboratory

To determine background radiation levels that might influence experiments, we measured in situ gamma-ray emissions at ten locations in the Boulby Underground Laboratory. For gamma radiation in the energy range of 7–2,734 keV, the counts varied from 6.5 to 28 γ s^?1. For measurements inside the Lab, the arithmetic mean was 24 γ s^?1. The sedimentary rocks that surrounded the Lab, halite and mudstone, were characterized by very low activity concentrations of uranium (0.8–7.1 Bq kg^?1) and thorium (0.6–3.9 Bq kg^?1).     

Rapid Diffusion Weighted Imaging with Enhanced Resolution

In this paper, a new, fast compressively sensed diffusion magnetic resonance image enhancement technique is presented. This algorithm aims to overcome two major obstacles—image resolution limitation and algorithm reconstruction time efficiency-by combining a highly sparse k–q-space sampling pattern with super-resolution (SR) image enhancement. Similar to the RoSA (rotating single-shot acquisition) acceleration scheme, the presented algorithm takes advantage of simultaneous k–q-space sampling procedures being able to implement directly with no hardware modifications. The method sequentially processes compressively sensed k-space’s semi-PROPELLER blades with respect to appropriately synchronized diffusion directions. The dMR image structure is expressed as a kind of minimum-spanning tree. It fades out distortions of the image’s features. Moreover, as contrasted with numerous other super-resolution algorithms, the presented method overcomes the simplifying motion model as well as blur kernel and noise estimation issues. The simulation and experimental studies have been conducted using a dMRI scanner as well as a phantom input. Combining super-resolution with time-efficient data sets resulted in a reduction of motion artifacts, improving edge delineation as well as spatial resolution.     

Gamma background measurements in the Gran Sasso National Laboratory

In situ gamma-ray measurements were taken at eight locations in the Gran Sasso National Laboratory (Italy). Count rates for gamma radiation within the energy range of 7–2,734 keV varied from 8 to 60 γ s^?1. The arithmetic mean was 49 γ s^?1 for measurements taken without a collimator. The average gamma flux inside the Lab was 0.25 γ cm^?2 s^?1. The sedimentary rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium, equal to 1.7 and 1.4 Bq kg^?1, respectively.     

57Fe Mössbauer spectroscopy and x-ray diffraction study of some complex metamict minerals

Metamict minerals are a class of natural amorphous materials which were initially crystalline but self-radiation damage mainly from alpha decays of ²³⁸U and ²³²Th series inside the structure can produce partially or fully amorphization (metamictization) of these minerals. This paper reports the results of ⁵⁷Fe Mössbauer spectroscopy, gamma-ray spectrometry and X-ray diffraction (XRD) study of some complex metamict minerals like: davidite-(La), gadolinite, steenstrupine-(Ce), vesuvianite and comparatively epidote. The absorbed α-dose for these minerals varies in wide range from 1.9 × 10¹⁴ α-decay/mg (epidote) to as high as 2.7 × 10¹⁶ α-decay/mg (steenstrupine). The Mössbauer spectra show decreasing IS values (except steenstrupine) for Fe²⁺ components with absorbed α-dose. Rather unexpected feature of these spectra is a noticeable decrease of the spectral line widths with increasing absorbed α-dose both Fe²⁺ and Fe³⁺ components in gadolinite, davidite and steenstrupine.     

Natural radioactivity in rocks of the Modane–Aussois region (SE France)

The activity concentrations of ⁴⁰K, ²³²Th, and ²³⁸U in the characteristic rocks of the Modane-Aussois region (Western Alps, France) were determined using an HPGe gamma-ray spectrometry system. The activity concentrations of ⁴⁰K varied from 18 Bqkg⁻¹ (limestone dolomite) to 392 Bqkg⁻¹ (calcschist), while those of ²³²Th varied from 0.7 Bqkg⁻¹ (limestone dolomite) to 18 Bqkg⁻¹ (calcschist). The activities associated with ²³⁸U ranged from 9 (quartzite) to 29 Bqkg⁻¹ (dolomite). In the investigated rock samples, concentrations of ²³⁸U (ppm) and ⁴⁰K (%) had a strong negative correlation.     

The microstructure development in arc-melt and melt-spun Fe50Ni10Cu20P10Si5B5 immiscible alloy

A six-component Fe₅₀Ni₁₀Cu₂₀P₁₀Si₅B₅ immiscible alloy was arc-melt in argon and it was melt-spun from various temperatures. The morphology and chemical composition of the cross-section of the ingot and melt-spun ribbons were analysed with a scanning electron microscope SEM/EDS. The melt-spun ribbon was investigated by a transmission electron microscope (TEM). The melting range of the alloy was investigated by means of differential thermal analysis (DTA) and for reference, the temperature change during free cooling of the alloy was controlled by pyrometer in the melt spinning device. The slow cooling rate resulted in the fractal surface structures formed by the Fe-rich regions and Cu-rich regions typical for the alloying system with a miscibility gap. The structures of the melt-spun ribbons were dependent on ejection temperatures before the melt spinning. The lower ejection temperatures resulted in the formation of the structures separated into Fe-rich and Cu-rich regions. This was due to rapid cooling within the miscibility gap. Ejection at higher temperatures led to the formation of a uniform amorphous/crystalline composite.     

Natural radioactivity in granites and gneisses of the Opava Mountains (Poland): a comparison between laboratory and in situ measurements

The natural radioactivities of five characteristic igneous rocks of the eastern foreland of the Opava Mountains (Eastern Sudetes, Poland), obtained in the laboratory and under in situ conditions, are presented. The activity concentrations of ²³²Th, ²³⁸U, and ⁴⁰K were measured using an HPGe gamma-ray spectrometry system. The ranges of the activity concentrations of ²³²Th were 7–71 Bq kg^?1 in the laboratory and 6–68 Bq kg^?1 for the in situ measurements. For ²³⁸U, the ranges of the activity concentrations were 5–52 Bq kg^?1 in the laboratory and 9–48 Bq kg^?1 for the in situ measurements, and for ⁴⁰K, the ranges were 520–1560 Bq kg^?1 in the laboratory and 537–1700 Bq kg^?1 for the in situ measurements. These determined activity concentrations were compared with the average activity concentrations of the radionuclides in similar types of rocks and with data from the Sudetes available in the literature. No significant differences were found between the in situ and laboratory measurements.