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Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range of morphologies, elemental compositions, and carbon functional chemistries consistent with those of carbonaceous chondrites that have experienced low‐temperature aqueous alteration. Both nanoglobules and diffuse organic matter are abundant. Non‐globular organic particles are also present, and including some that contain nanodiamond clusters. Diffuse organic matter is finely distributed in and around phyllosilicates, forms coatings on other minerals, and is also preserved in vesicles in secondary minerals such as carbonate and pyrrhotite. The average elemental compositions determined by energy‐dispersive spectroscopy of extracted, demineralized insoluble organic matter samples A0107 and C0106 are C100N3O9S1 and C100N3O7S1, respectively, with the difference in O/C slightly outside the difference in the standard error of the mean. The functional chemistry of the nanoglobules varies from mostly aromatic C=C to mixtures of aromatic C=C, ketone C=O, aliphatic (CHn), and carboxyl (COOH) groups. Diffuse organic matter associated with phyllosilicates has variable aromatic C, ketone and carboxyl groups, and some localized aliphatics, but is dominated by molecular carbonate (CO3) absorption, comparable to prior observations of clay‐bound organic matter in CI meteorites. [ABSTRACT FROM AUTHOR]

To shed light on the mechanism of formation of nanophase iron particles (npFe) in space‐weathered materials from airless bodies, we analyzed exsolved and unexsolved space‐weathered lunar pyroxenes from Apollo 17 sample 71501. The exsolved pyroxene allowed for the observation of the effects of space weathering on similar mineral phases with variable composition. Using coordinated scanning transmission electron microscopy with energy‐dispersive X‐ray spectroscopy and electron energy loss spectroscopy (EELS), we determined that two coexisting pyroxenes in the exsolved grain showed systematic variations in response to space weathering, despite equivalent exposure conditions. The npFe in the space‐weathered rim of augite lamellae were smaller and fewer than the npFe in the rim of pigeonite lamellae. EELS spectrum imaging revealed the presence and heterogeneous distribution of Fe0, Fe2+, and Fe3+ in the exsolved pyroxene. Metallic iron occurred in the npFe, a mixture of Fe2+ and Fe3+ occurred in the pigeonite lamellae, and the augite lamellae contained virtually all Fe3+. Approximately 50% of the total Fe measured in the exsolved pyroxene grain was ferric. Partitioning of Fe2+ and Fe3+ among the lamellae is invoked to explain the difference in npFe development in pigeonite and augite. The results of this study, the first to identify Fe3+ in a crystalline lunar ferromagnesian silicate, have implications for our understanding of how space weathering might proceed in oxidized phases. Furthermore, the discovery of an Fe3+‐rich pyroxene also supports attribution of the 0.7 μm absorption feature observed in Galileo Solid State Imager data to oxidized Fe in clinopyroxenes. [ABSTRACT FROM AUTHOR]

The formation of extended planar defects in minerals such as olivine is related to high point defect concentration and can be driven by large gradients in chemical potential, where the energy of the system is lowered by the ordering of defects along specific planes in the crystal. The presence of extended defects has the potential to create the (apparently) anomalous ionic diffusion in olivine as reported recently (Spandler and O'Neill in Contrib Mineral Petrol 159(6):791-818, 2010). High-resolution transmission electron microscopy and energyfiltered imaging were done using experimental samples designed to examine the impact of [a.sub.TiO2] and [f.sub.O2] on the potential to form such defects in ferromagnesian olivine. Doped basalt (5 wt% Ti[O.sub.2])-olivine reaction couple experiments were run at 1 atm and 1,310 and 1,410°C for 50 h at various [f.sub.O2], ranging from [10.sup.2] below to [10.sup.2] above the quartz-fayalite-magnetite buffer. Our results show that extended planar defects in olivine, parallel to [{101}.sub.ol] and occurring in ordered 'clusters' with a prolate spheroid geometry ~5-25 nm across and extending up to 150 nm into the olivine, are present near the olivine-glass interfaces in all of our experimental high-Ti[O.sub.2] basalt-olivine samples. Increased Ti content in the olivine is associated with the defects; ordering of [Ti.sup.4+] and octahedral site vacancies leads to a two- or three-layer superstructure in the olivine. Defect nucleation and growth is driven by the large Ti[O.sub.2] chemical potential gradient across the phase boundary at the start of the experiments, which provides access to microstructures not otherwise present. Keywords Extended defects * Olivine * Ti * Diffusion in olivine * TEM, Introduction In measurements and modeling of diffusion in solids in the presence of a chemical potential gradient, the physical mechanism is frequently assumed to be chemical diffusion on the crystalline [...]

Debate continues over whether skeletal muscle performance and injury risk vary over the course of the menstrual cycle. Alterations in tendon properties may play a role in the potential fluctuations of both of these variables. The aim of the current study was to determine any association between menstrual cycle phase and corresponding levels of female sex hormones and tendon properties. Fifteen normally menstruating (28-32-day cycles) healthy females (age 23 [+ or -] 1 years, mass 63.1 [+ or -] 2.6 kg, height 1.66 [+ or -] 0.02 m) not taking any form of hormonal contraceptive took part in this study. In vivo patellar tendon properties and associated circulating hormonal levels were assessed on 3 occasions including days 3 [+ or -] 0.4, 13 [+ or -] 0.2, and 21 [+ or -] 0.3. Dynamometry, ultrasonography, electromyography, and biochemical assessment of circulating levels of estradiol and progesterone were utilized. No significant differences were seen in tendon mechanical properties among the 3 phases of the menstrual cycle (p > 0.05). Regressions were carried out and revealed that estrogen and maximal voluntary tendon force explained 17.8% (p = 0.043) of the variance in young's modulus. Our findings link estrogen to a chronic, rather than an acute, impact on tendon behavior. These findings are relevant to clinical outcomes, exercise performance, and injury risk. In terms of tendon properties, menstrual cycle phase does not necessarily need to be considered when organizing training and competition schedules. KEY WORDS compliance, ELISA, in vivo test, soft tissue biomechanics, tendon

In 1999, the Southeast Advanced Technological Education Consortium (SEATEC) held two national forums on the campus of Vanderbilt University. The first forum addressed the design of case studies for technological education. The second focused on best practices in teaching technological content through case studies (TEFATE, 1999). The second event featured an address by an especially distinguished guest, Dr. Howard S. Barrows. Dr. Barrows, often referred to as "The Father of Problem-based Learning," forwarded both a presentation and a paper (Barrows, 1999a, 1999b). In his contribution to the forums, Dr. Barrows speaks specifically to faculty interested in teaching technical content through case studies. Based on his extensive experience in medical education as well as his work with teachers in secondary education, college, and other professional schools, Dr. Barrows concluded that problems, not case studies, produce the most powerful learning outcomes for students in technical fields (Barrows, 1999a, 1999b).