Athena MIMOS II Mossbauer spectrometer investigation

Mössbauer spectroscopy is a powerful tool for quantitative mineralogical analysis of Fe-bearing materials. The miniature Mössbauer spectrometer MIMOS II is a component of the Athena science payload launched to Mars in 2003 on both Mars Exploration Rover missions. The instrument has two major components: (1) a rover-based electronics board that contains power supplies, a dedicated central processing unit, memory, and associated support electronics and (2) a sensor head that is mounted at the end of the instrument deployment device (IDD) for placement of the instrument in physical contact with soil and rock. The velocity transducer operates at a nominal frequency of 25 Hz and is equipped with two 57Co/Rh Mössbauer sources. The reference source (5 mCi landed intensity), reference target (alpha-Fe2O3 plus alpha-Fe0), and PIN-diode detector are configured in transmission geometry and are internal to the instrument and used for its calibration. The analysis Mössbauer source (150 mCi landed intensity) irradiates Martian surface materials with a beam diameter of 1.4 cm. The backscatter radiation is measured by four PIN-diode detectors. Physical contact with surface materials is sensed with a switch-activated contact plate. The contact plate and reference target are instrumented with temperature sensors. Assuming 18% Fe for Martian surface materials, experiment time is 6–12 hours during the night for quality spectra (i.e., good counting statistics); 1–2 hours is sufficient to identify and quantify the most abundant Fe-bearing phases. Data stored internal to the instrument for selectable return to Earth include Mössbauer and pulse-height analysis spectra (512 and 256 channels, respectively) for each of the five detectors in up to 13 temperature intervals (65 Mössbauer spectra), engineering data for the velocity transducer, and temperature measurements. The total data volume is 150 kB. The mass and power consumption are 500 g (400 g for the sensor head) and 2 W, respectively. The scientific measurement objectives of the Mössbauer investigation are to obtain for rock, soil, and dust (1) the mineralogical identification of iron-bearing phases (e.g., oxides, silicates, sulfides, sulfates, and carbonates), (2) the quantitative measurement of the distribution of iron among these iron-bearing phases (e.g., the relative proportions of iron in olivine, pyroxenes, ilmenite, and magnetite in a basalt), (3) the quantitative measurement of the distribution of iron among its oxidation states (e.g., Fe2+, Fe3+, and Fe6+), and (4) the characterization of the size distribution of magnetic particles. Special geologic targets of the Mössbauer investigation are dust collected by the Athena magnets and interior rock and soil surfaces exposed by the Athena Rock Abrasion Tool and by trenching with rover wheels

Decommissioning normal: COVID‐19 as a disruptor of school norms for young people with learning disabilities

To slow the spread of COVID-19, on 20 March 2020, nurseries, schools and colleges across England were closed to all learners, apart from those who were children of key workers or were considered “vulnerable.” As young people with learning disabilities, families, professionals and schools become acquainted with the Erfahrung of the new horizon brought about by COVID-19, the negativity of altered social inclusion is becoming the “new normal.” Capturing this transitory moment in time, this paper reflexively analyses the curiously productive variables of altered ecological pathways to social inclusion for people with learning disabilities. Taking a hermeneutic stance, this paper draws on Gadamer's construction of the nature of new experiences. Focussed on the experience of social inclusion during the COVID-19 pandemic, semi-structured interviews were conducted with six key stakeholders. As the phenomenon in question was new, an inductive approach to thematic analysis was applied. The critical tenet of this paper is that the Erfahrung of COVID-19 has created the conditions for a “new normal” which have afforded children with learning disabilities altered opportunities for social inclusion, whether that be through increased power/agency for them and their families and/or new modes of connectedness leading to enhanced relationships. Whilst the impact of COVID-19 has been a negative one for many aspects of society, application of Simplican and Gadamer's theories on social inclusion and the nature of new experiences has permitted the surfacing of new possibilities for the social inclusion of children with learning disabilities.N/

CONCLUDING REMARKS

With this conference we are celebrating the twentieth anniversary of the Mössbauer effect. With twenty years one reaches the age of maturity and it then seems appropriate to remember and recount some of the events of childhood. As you all know, the first paper was published in 1958, but there is still some darkness (and room for further research) concerning the creative early moments - in other words, how Mössbauer "fathered" his effect. Unfortunately, Rudolf Mössbauer could not come to this celebration and give us further details on this point

AMORPHOUS METALS AND γ-FE

In recent years two aspects of physical metallurgy have attracted considerable interest from a scientific as well as from a technological point of view : amorphous metals of the T80M20 type (T→ metal, M → metalloid) and the magnetic structure of γ-Fe

PRECISION PHASE ANALYSIS

La haute précision dans la détermination des limites dans des diagrammes de phase obtenus à l'aide de l'effet Mössbauer sera démontrée dans le cas de la solubilité du Fe dans le Ti à une température se situant entre 585 °C et 810 °C.The high precision in the determination of boundaries in phase diagrams obtainable by Mössbauer spectroscopy will be demonstrated for the case of the solubility of Fe in Ti in the temperature range of 585-810 °C

SIMULTANEOUS TRANSMISSION AND SCATTERING MÖSSBAUER STUDY ON AMORPHOUS Fe40Ni40P14B6

57Fe Mössbauer spectra of Metglas 2826 (Fe40Ni40P14B6) were obtained simultaneously in transmission geometry by measuring γ-rays and in scattering geometry by measuring conversion electrons. From simultaneous measurements differences in bulk and surface states were clearly observed and summarized as follows : 1) Surfaces exhibit larger mean magnetic fields than the bulk. 2) Magnetic moments in surfaces are more aligned in the plane of the ribbon than the magnetic moments of the bulk. 3) After annealing at 545 K surfaces exhibit larger magnetic fields than the bulk but the degree of alignment of the magnetic moments in the plane of the ribbon is reduced

A NEW ATTEMPT TO OBSERVE THE RESONANCE IN Ag109

Le rayonnement gamma de 88 keV d'Ag109m émis par un monocristal d'argent dopé par du Cd109 a été mesuré en fonction de la température. La diminution de l'intensité d'émission entre 78 K et 4.2 K était plus grande qu'entre la température ambiante et 78 K. Ce comportement s'explique par la variation de l'auto-absorption résonante (effet Mössbauer) avec la température.The counting rate of the 88 keV Ag109m γ-rays emitted from a cd109-doped silver single crystal was measured as a function of temperature. The decrease in emission intensity between 78 K and 4.2 K was greater than the decrease between room temperature and 78 K. This behaviour is explained in terms of the temperature dependence of the resonant self absorption (Mössbauer effect)

Mössbauer Effect in Hemoglobin and Some Iron-Containing Biological Compounds

The Mössbauer effect in Fe(57) has been used to study the molecules, hemoglobin, O(2)-hemoglobin, CO(2)-hemoglobin, and CO-hemoglobin (within red cells) and the molecules, hemin and hematin (in the crystalline state). Quadrupole splittings and isomeric shifts observed in the Mössbauer spectra of these molecules are tabulated. The temperature dependence of the quadrupole splitting and relative recoil-free fraction for hemoglobin with different ligands has been investigated. An estimate of the Debye-Waller factor in O(2)-hemoglobin at 5°K is 0.83. An asymmetry in the quadrupole splitting observed in hemoglobin is attributed to a directional dependence of the recoil-free fraction which establishes the sign of the electric field gradient in the molecule and indicates that the lowest lying d orbital of the Fe atoms is |xy>. This asymmetry indicates that the iron atoms in hemoglobin are vibrating farther perpendicular to the heme planes than parallel to them, and, in fact, the ratio of the mean square displacements perpendicular and parallel to the heme planes in hemoglobin is ≈5.5 at 5°K. The temperature dependence of the quadrupole splitting in hemoglobin has been used to estimate a splitting between the lowest lying iron atom d orbitals of ≈420 cm(-1)