Pulse-Height and 2-D Charge-Spread Single-Pixels Studies on a LuYAP:Ce Scintillation Array

The present work deals with a 10 × 10 array of (Lu0.7Y0.3)AP:Ce 2 × 2 × 10 mm3 pixels, manufactured by Crytur (Cz), that has been utilized in a previous paper. The crystal-array has been coupled to an 8 × 8 anodes H10966 model Hamamatsu (Jp) Position-Sensitive Photo Multiplier Tube (PSPMT) connected to electronics for single events scintillation read-out. The response of such a detector has been studied under Co-57, or Ba-133, or Cs-137 gamma-ray emissions, as well as with Lu-176 self-activity only. The present work is aimed at characterizing the individual crystal-pixels’ single-event responses in terms of pulse-height and of spreads of the 2-D charge-distributions. In particular, the charge-spread characterization pointed out several defects in the crystal-array assembly, not detected by usual pulse-height studies. The diagnostic method based on charge-spread analysis seems also well suited for scintillation array characterizations for gamma-ray detectors studies, as well as for quality controls of such pixelated devices during the lifetime of systems in the field of radionuclide medical imaging (SPECT and PET). The method is also appropriate for other applications where gamma-ray spectroscopy is required, like nuclear physics, astrophysics, astroparticle physics, homeland security, and non-proliferation.

Out-of-sequence skeletal growth causing oscillatory zoning in arc olivines

Primitive olivines from the monogenetic cones Los Hornitos, Central-South Andes, preserve dendritic, skeletal, and polyhedral growth textures. Consecutive stages of textural maturation occur along compositional gradients where high Fo–Ni cores of polyhedral olivines (Fo92.5, Ni ~3500 ppm) contrast with the composition of dendritic olivines (Fo < 91.5, Ni < 3000 ppm), indicating sequential nucleation. Here we present a new growth model for oscillatory Fo–Ni olivine zoning that contrasts with the standard interpretation of continuous, sequential core-to-rim growth. Olivine grows rapidly via concentric addition of open-structured crystal frames, leaving behind compositional boundary layers that subsequently fill-in with Fo–Ni-depleted olivine, causing reversals. Elemental diffusion modeling reveals growth of individual crystal frames and eruption at the surface occurred over 3.5–40 days. Those timescales constrain magma ascent rates of 40–500 m/h (0.011 to 0.14 m/s) from the deep crust. Compared to ocean island basalts, where dendritic and skeletal olivines have been often described, magmas erupted at arc settings, experiencing storage and degassing, may lack such textures due to fundamentally different ascent histories.

Exploring microstructures in lower mantle mineral assemblages with synchrotron x-rays

Understanding dynamics across phase transformations and the spatial distribution of minerals in the lower mantle is crucial for a comprehensive model of the evolution of the Earth’s interior. Using the multigrain crystallography technique (MGC) with synchrotron x-rays at pressures of 30 GPa in a laser-heated diamond anvil cell to study the formation of bridgmanite [(Mg,Fe)SiO3] and ferropericlase [(Mg,Fe)O], we report an interconnected network of a smaller grained ferropericlase, a configuration that has been implicated in slab stagnation and plume deflection in the upper part of the lower mantle. Furthermore, we isolated individual crystal orientations with grain-scale resolution, provide estimates on stress evolutions on the grain scale, and report {110} twinning in an iron-depleted bridgmanite, a mechanism that appears to aid stress relaxation during grain growth and likely contributes to the lack of any appreciable seismic anisotropy in the upper portion of the lower mantle.

Investigation of the Light Yield Distribution in LYSO Crystals by the Optical Spectroscopy Method for the Electromagnetic Calorimeters of the COMET Experiment

The distribution of the light yield and luminescence intensity along LYSO:Ce crystal length is investigated. These distributions, determined by different defects and emission centers of the dopant in the crystalline structure and its distribution along the length, is measured by two methods: the gamma spectroscopy using radiation sources and the optical spectroscopy using ultraviolet sources. It is shown that crystals have considerable variation of the light yield and luminescence intensity both over the length of an individual crystal (in the growing direction) and for different crystals. It is established that the correction factors for the segmented calorimeter of the COMET experiment can be obtained using optical spectroscopy methods. Consideration of the correction factors will significantly reduce an error of energy measurement in a segmented calorimeter during data handling.

MIXED COMPLEX COMPOUNDS OF PALMITATE, OLEATE CALCIUM WITH ACETAMIDE, NICOTINAMIDE AND THIOCARBAMIDE

The purpose of the study was the synthesis and study of the structure of mixed complexes of palmitate, calcium oleate with acetamide, nicotinamide and thiocarbamide. The mixed coordination compounds of palmitate and calcium oleate were synthesized. The composition, individuality, thermal behavior, methods of coordinating the palmitate and oleate fragments, acetamide, nicotinamide and thiocarbamide molecules have been established. Comparison of the diffraction patterns of calcium palmitate and oleate, free ligand molecules and synthesized compounds showed the mismatch of the diffractograms, conseqently that the synthesized complexes have an individual crystal lattice different from the starting materials. The method of coordination of amide molecules, the environment of the central ion, are proved by IR spectroscopy. Acetamide molecules are coordinated with the central atom through an oxygen atom, thiocarbamide and nicotinamide

DUROPHAGOUS FISH PREDATION TRACES VERSUS TUMBLING-INDUCED SHELL DAMAGE—A PALEOBIOLOGICAL PERSPECTIVE

ABSTRACT Durophagous (shell-crushing) fish predation is considered to have been a major force of evolutionary change in the history of marine communities. However, because fish predators are very rarely preserved in the act of predation, fossil evidence of such interactions is commonly indirect. For instance, it has been argued that shell fragments with sharp margins constitute a good proxy for durophagy. However, drawing a distinction between predation- and abiotic-induced shell damage can be challenging. Notably, experimental data on shell fragmentation by marine durophagous fishes are almost lacking. In this study, we explore whether shell breakage caused by durophagous marine fishes versus physical factors can be distinguished. Aquarium experiments involving commercially available predatory fishes (Diodon) and thin-shelled invertebrate preys (gastropods Nassarius and brachiopods Frenulina) show that the predation by some fish produces shell fragments displaying extremely low roundness and varying degree of sphericity. Importantly, these fragments typically display sharp and jagged margins, and reveal distortion of individual crystal fibers. Tumbling experiments showed that the disintegration of brachiopod shells proceeds much more rapidly than that of gastropods, which may suggest that abiotic-induced fragmentation of brachiopods may be eventually confused with predation. However, the tumbling-induced fragmentation and damage in both groups are typically characterized by the presence of spherical or discoidal and rounded shell fragments displaying smooth edges (without any microstructural distortion), and numerous abrasive scratches and wear scars on the surface. These data underscore that the shell fragments produced by a durophagous fish, if not subsequently abraded by physical factors, can be recognized in the fossil record.

Measuring energy-dependent photoelectron escape in microcrystals

With the increasing trend of using microcrystals and intense microbeams at synchrotron X-ray beamlines, radiation damage becomes a more pressing problem. Theoretical calculations show that the photoelectrons that primarily cause damage can escape microcrystals. This effect would become more pronounced with decreasing crystal size as well as at higher energies. To prove this effect, data from cryocooled lysozyme crystals of dimensions 5 × 3 × 3 and 20 × 8 × 8 µm mounted on cryo-transmission electron microscopy (cryo-TEM) grids were collected at 13.5 and 20.1 keV using a PILATUS CdTe 2M detector, which has a similar quantum efficiency at both energies. Accurate absorbed doses were calculated through the direct measurement of individual crystal sizes using scanning electron microscopy after the experiment and characterization of the X-ray microbeam. The crystal lifetime was then quantified based on the D 1/2 metric. In this first systematic study, a longer crystal lifetime for smaller crystals was observed and crystal lifetime increased at higher X-ray energies, supporting the theoretical predictions of photoelectron escape. The use of detector technologies specifically optimized for data collection at energies above 20 keV allows the theoretically predicted photoelectron escape to be quantified and exploited, guiding future beamline-design choices.

Characterization of Texture Evolution during Recrystallization by Laser-Induced Transient Thermal Grating Method

The analyses of texture evolution of cold rolled interstitial free (IF) steel sheets during annealing and recrystallization are presented, in which the dispersion curves of surface acoustic waves (SAW) excited by laser-induced transient thermal grating method are measured. The results show that the angular anisotropy of the SAW velocity changes due to the texture changes at different stages of recrystallization. The theoretically simulated angular dispersion of SAW velocity within individual crystal revealed that the change of SAW velocity is closely related to recrystallization texture evolution. A model for the angular dependence of the SAW velocity in textured polycrystalline IF steel with different oriented crystals is presented and the simulations are yielded, which show that the results agree with those of experiments.

New type of evidence for secondary ice formation at around −15 °C in mixed-phase clouds

Ice crystal numbers can exceed the numbers of ice-nucleating particles (INPs) observed in mixed-phase clouds (MPCs) by several orders of magnitude, also at temperatures that are colder than −8 ∘C. This disparity provides circumstantial evidence of secondary ice formation, also other than via the Hallett–Mossop process. In a new approach, we made use of the fact that planar, branched ice crystals (e.g. dendrites) grow within a relatively narrow temperature range (i.e. −12 to −17 ∘C) and can be analysed individually for INPs using a field-deployable drop-freezing assay. The novelty of our approach lies in comparing the growth temperature encoded in the habit of an individual crystal with the activation temperature of the most efficient INP contained within the same crystal to tell whether it may be the result of primary ice formation. In February and March 2018, we analysed a total of 190 dendritic crystals (∼3 mm median size) deposited within MPCs at the high-altitude research station Jungfraujoch (3580 m a.s.l.). Overall, one in eight of the analysed crystals contained an INP active at −17 ∘C or warmer, while the remaining seven most likely resulted from secondary ice formation within the clouds. The ice multiplication factor we observed was small (8), but relatively stable throughout the course of documentation. These measurements show that secondary ice can be observed at temperatures around −15 ∘C and thus advance our understanding of the extent of secondary ice formation in MPCs, even where the multiplication factor is smaller than 10.

Crystallization kinetics of amorphous calcium carbonate in confinement

In situ observation of amorphous calcium carbonate (ACC) confined in ∼500 pL emulsion droplets allows determination of the timing of individual crystal nucleation events. Statistical analysis of events in hundreds of droplets establishes an upper limit for the steady-state nucleation rate of 1.2 cm−3 s−1 for the crystallization from ACC.