137 research outputs found
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Six-fold Coordinated Carbon Dioxide VI
Under standard conditions, carbon dioxide (CO{sub 2}) is a simple molecular gas and an important atmospheric constituent while silicon dioxide (SiO{sub 2}) is a covalent solid, and represents one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO{sub 2} transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO{sub 2} tridymite. Here, we present the discovery of a new extended-solid phase of carbon dioxide (CO{sub 2}): a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO{sub 2}-II above 50GPa at 530-650K. Together with the previously reported CO{sub 2}-V and a-carbonia, this new extended phase indicates a fundamental similarity between CO{sub 2}--a prototypical molecular solid, and SiO{sub 2}--one of Earth's fundamental building blocks. The phase diagram suggests a limited stability domain for molecular CO{sub 2}-I, and proposes that the conversion to extended-network solids above 40-50 GPa occurs via intermediate phases II, III, and IV. The crystal structure of phase VI suggests strong disorder along the caxis in stishovite-like P4{sub 2}/mnm, with carbon atoms manifesting an average six-fold coordination within the framework of sp{sup 3} hybridization
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Pressure Induced Bonding Changes in Carbon Dioxide: Six Fold Coordinated CO2
In this LDRD, we examined in detail the pressure-induced bonding and local coordination changes leading to the molecular {yields} associated {yields} extended-solid transitions in carbon dioxide (CO{sub 2}). We studied the progressive delocalization of electrons from the C=O molecular double bond at high pressures and temperatures, and determined the phase stability and physical properties of a new extended-solid CO{sub 2} phase (VI). We find that the new CO{sub 2} phase VI is based on a network of six-fold coordinated (octahedral) CO{sub 6} structures similar to the ultra-hard SiO{sub 2} phase stishovite
Extracellular Vesicles in Musculoskeletal Pathologies and Regeneration
The incidence of musculoskeletal diseases is steadily increasing with aging of the population. In the past years, extracellular vesicles (EVs) have gained attention in musculoskeletal research. EVs have been associated with various musculoskeletal pathologies as well as suggested as treatment option. EVs play a pivotal role in communication between cells and their environment. Thereby, the EV cargo is highly dependent on their cellular origin. In this review, we summarize putative mechanisms by which EVs can contribute to musculoskeletal tissue homeostasis, regeneration and disease, in particular matrix remodeling and mineralization, pro-angiogenic effects and immunomodulatory activities. Mesenchymal stromal cells (MSCs) present the most frequently used cell source for EV generation for musculoskeletal applications, and herein we discuss how the MSC phenotype can influence the cargo and thus the regenerative potential of EVs. Induced pluripotent stem cell-derived mesenchymal progenitor cells (iMPs) may overcome current limitations of MSCs, and iMP-derived EVs are discussed as an alternative strategy. In the last part of the article, we focus on therapeutic applications of EVs and discuss both practical considerations for EV production and the current state of EV-based therapies
Robust ferromagnetism in the compressed permanent magnet Sm2Co17
FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESPThe compound Sm2CO17 displays magnetic properties amenable to permanent magnet applications owing to both the 3d electrons of Co and the 4f electrons of Sm. The long-standing description of the magnetic interactions between the Sm and Co ions implies a truly ferromagnetic configuration, but some recent calculations challenge this axiom, suggesting at least a propensity for ferrimagnetic behavior. We have used high-pressure synchrotron x-ray techniques to characterize the magnetic and structural properties of Sm2Co17 to reveal a robust ferromagnetic state. The local Sm moment is at most weakly affected by compression, and the ordered moments show a surprising resilience to volumetric compressions of nearly 20%. Density functional theory calculations echo the magnetic robustness of Sm2Co17.9010112FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESPFUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESP2013/14338-3We graciously thank K. Visbeck for assistance with DAC preparation and C. Kenney-Benson for assistance with setup at the Advanced Photon Source. This work was performed under LDRD (Tracking Code 12-ERD-013) and under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract No. DE-AC52-07NA27344. L. S. I. Veiga is supported by FAPESP (SP-Brazil) under Contract No. 2013/14338-3. Portions of this work were performed at Sector 4 and at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. Beamtime was provided by the General User Proposal system and the Carnegie DOE-Alliance Center (CDAC). Identification of commercial materials or equipment does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose
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High Pressure Materials Research using Advanced Third-Generation Synchrotron X-ray
The recent discoveries of nonmolecular phases of simple molecular solids [1,2] demonstrate the proof-of-the-principles for producing exotic phases by application of high pressure. Modern advances in theoretical and computational methodologies now make possible to explain or even predict novel structures and properties in a relatively wide range of length scales on the basis of thermodynamic stability [3]. Equally important in materials research is the recent developments in advanced x-ray and laser diagnostics that enable in-situ observations at the formidable pressure-temperature conditions [4]. Having benefited by all these developments, we discuss the first principle of the pressure-induced chemistry, 'Mbar Chemistry', with a few examples that may have important implications in materials research
Primary alterations during the development of hidradenitis suppurativa
BACKGROUND: Hidradenitis suppurativa (HS) is a chronic, inflammatory disease of the apocrine glandârich (AGR) skin region. The initial steps of disease development are not fully understood, despite intense investigations into immune alterations in lesional HS skin. OBJECTIVES: We aimed to systematically investigate the inflammatory molecules involved in three stages of HS pathogenesis, including healthy AGR, nonâlesional HS and lesional HS skin, with the parallel application of multiple mRNA and proteinâbased methods. METHODS: Immune cell counts (T cells, dendritic cells, macrophages), Th1/Th17ârelated molecules (ILâ12B, TBX21, IFNG, TNFA, ILâ17, IL10, ILâ23A, TGFB1, RORC, CCL20), keratinocyteârelated sensors (TLR2,4), mediators (S100A7, S100A8, S100A9, DEFB4B, LCN2, CAMP, CCL2) and proâinflammatory molecules (IL1B, IL6, TNFA, ILâ23A) were investigated in the three groups by RNASeq, RTâqPCR, immunohistochemistry and immunofluorescence. RESULTS: Epidermal changes were already detectable in nonâlesional HS skin; the epidermal occurrence of antimicrobial peptides (AMPs), ILâ1ÎČ, TNFâα and ILâ23 was highly upregulated compared with healthy AGR skin. In lesional HS epidermis, TNFâα and ILâ1ÎČ expression remained at high levels while AMPs and ILâ23 increased even more compared with nonâlesional skin. In the dermis of nonâlesional HS skin, signs of inflammation were barely detectable (vs. AGR), while in the lesional dermis, the number of inflammatory cells and Th1/Th17ârelated mediators were significantly elevated. CONCLUSIONS: Our findings that nonâlesional HS epidermal keratinocytes produce not only AMPs and ILâ1ÎČ but also high levels of TNFâα and ILâ23 confirm the driver role of keratinocytes in HS pathogenesis and highlight the possible role of keratinocytes in the transformation of nonâinflammatory Th17 cells (of healthy AGR skin) into inflammatory cells (of HS) via the production of these mediators. The fact that epidermal TNFâα and ILâ23 appear also in nonâlesional HS seems to prove these cytokines as excellent therapeutic targets
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