Diffusion-controlled phase growth on dislocations

We treat the problem of diffusion of solute atoms around screw dislocations. In particular, we express and solve the diffusion equation, in radial symmetry, in an elastic field of a screw dislocation subject to the flux conservation boundary condition at the interface of a new phase. We consider an incoherent second-phase precipitate growing under the action of the stress field of a screw dislocation. The second-phase growth rate as a function of the supersaturation and a strain energy parameter is evaluated in spatial dimensions d=2 and d=3. Our calculations show that an increase in the amplitude of dislocation force, e.g. the magnitude of the Burgers vector, enhances the second-phase growth in an alloy. Moreover, a relationship linking the supersaturation to the precipitate size in the presence of the elastic field of dislocation is calculated.Comment: 10 pages, 4 figures, a revised version of the paper presented in MS&T'08, October 5-9, 2008, Pittsburg

Size-dependent spinodal and miscibility gaps for intercalation in nano-particles

Using a recently-proposed mathematical model for intercalation dynamics in phase-separating materials [Singh, Ceder, Bazant, Electrochimica Acta 53, 7599 (2008)], we show that the spinodal and miscibility gaps generally shrink as the host particle size decreases to the nano-scale. Our work is motivated by recent experiments on the high-rate Li-ion battery material LiFePO4; this serves as the basis for our examples, but our analysis and conclusions apply to any intercalation material. We describe two general mechanisms for the suppression of phase separation in nano-particles: (i) a classical bulk effect, predicted by the Cahn-Hilliard equation, in which the diffuse phase boundary becomes confined by the particle geometry; and (ii) a novel surface effect, predicted by chemical-potential-dependent reaction kinetics, in which insertion/extraction reactions stabilize composition gradients near surfaces in equilibrium with the local environment. Composition-dependent surface energy and (especially) elastic strain can contribute to these effects but are not required to predict decreased spinodal and miscibility gaps at the nano-scale

Epitaxial growth in dislocation-free strained alloy films: Morphological and compositional instabilities

The mechanisms of stability or instability in the strained alloy film growth are of intense current interest to both theorists and experimentalists. We consider dislocation-free, coherent, growing alloy films which could exhibit a morphological instability without nucleation. We investigate such strained films by developing a nonequilibrium, continuum model and by performing a linear stability analysis. The couplings of film-substrate misfit strain, compositional stress, deposition rate, and growth temperature determine the stability of film morphology as well as the surface spinodal decomposition. We consider some realistic factors of epitaxial growth, in particular the composition dependence of elastic moduli and the coupling between top surface and underlying bulk of the film. The interplay of these factors leads to new stability results. In addition to the stability diagrams both above and below the coherent spinodal temperature, we also calculate the kinetic critical thickness for the onset of instability as well as its scaling behavior with respect to misfit strain and deposition rate. We apply our results to some real growth systems and discuss the implications related to some recent experimental observations.Comment: 26 pages, 13 eps figure

Effects of anharmonic strain on phase stability of epitaxial films and superlattices: applications to noble metals

Epitaxial strain energies of epitaxial films and bulk superlattices are studied via first-principles total energy calculations using the local-density approximation. Anharmonic effects due to large lattice mismatch, beyond the reach of the harmonic elasticity theory, are found to be very important in Cu/Au (lattice mismatch 12%), Cu/Ag (12%) and Ni/Au (15%). We find that is the elastically soft direction for biaxial expansion of Cu and Ni, but it is for large biaxial compression of Cu, Ag, and Au. The stability of superlattices is discussed in terms of the coherency strain and interfacial energies. We find that in phase-separating systems such as Cu-Ag the superlattice formation energies decrease with superlattice period, and the interfacial energy is positive. Superlattices are formed easiest on (001) and hardest on (111) substrates. For ordering systems, such as Cu-Au and Ag-Au, the formation energy of superlattices increases with period, and interfacial energies are negative. These superlattices are formed easiest on (001) or (110) and hardest on (111) substrates. For Ni-Au we find a hybrid behavior: superlattices along and like in phase-separating systems, while for they behave like in ordering systems. Finally, recent experimental results on epitaxial stabilization of disordered Ni-Au and Cu-Ag alloys, immiscible in the bulk form, are explained in terms of destabilization of the phase separated state due to lattice mismatch between the substrate and constituents.Comment: RevTeX galley format, 16 pages, includes 9 EPS figures, to appear in Physical Review

Immediate effect of the COVID-19 pandemic on patient health, health-care use, and behaviours : results from an international survey of people with rheumatic diseases

Funding Information: We would like to thank all the clinicians, health-care providers, and patient organisations who helped to develop and disseminate this survey. A full list of all the contributors can be found in the appendix (pp 44?45). Preliminary results were presented at the American College of Rheumatology 2020 conference. The views expressed here are those of the authors and participating members of the COVID-19 Global Rheumatology Alliance and do not necessarily represent the views of the American College of Rheumatology, the European League Against Rheumatism, the UK National Health Service, the National Institute for Health Research, the UK Department of Health, or any other organisation. Funding Information: JSH reports grants from Childhood Arthritis and Rheumatology Research Alliance and Rheumatology Research Alliance; and personal fees from Novartis, Pfizer, and Biogen, outside of the submitted work. JWL reports grants from Pfizer, outside of the submitted work. JAS reports grants and personal fees from Bristol-Myers Squibb; and personal fees from Gilead, Inova Diagnostics, Optum, and Pfizer, outside of the submitted work. CH reports personal fees from AstraZeneca and Aurinia Pharmaceuticals, outside of the submitted work. MJL reports grants from American College of Rheumatology during the conduct of the study and consulting fees from AbbVie, Amgen, Actelion, Boehringer Ingelheim, BMS, Celgene, Gilead, Johnson & Johnson, Mallinckrodt, Novartis, Pfizer, Roche, Sandoz, Sanofi, Sobi, and UCB, outside of the submitted work. SES is supported by the Vasculitis Clinical Research Consortium and Vasculitis Foundation outside of the submitted work. KLD reports grants from Novartis, Sobi, National Institutes of Health, and Horizon Bio, outside of the submitted work. EFM reports that the Liga Portuguesa Contra as Doenças Reumaticas received support for specific activities: grants from Abbvie, Novartis, Janssen-Cilag, Lilly Portugal, Sanofi, Grünenthal SA, MSD, Celgene, Medac, Pharmakern, GAfPA, AMGEN, A Menarini Portugal; grants and non-financial support from Pfizer; and non-financial support from Grünenthal GmbH and Tilray, outside of the submitted work. DPR is the volunteer Vice President of the Canadian Arthritis Patient Alliance, which is primarily supported by independent grants from pharmaceutical companies. DPR reports consulting fees from NovoNordisk Canada and speaking fees and an honoraria from Eli Lilly Canada, outside of the submitted work. DPR also lives with rheumatoid arthritis. SB reports personal fees from Novartis, AbbVie, Pfizer, and Horizon Pharma, outside of the submitted work. RG reports personal fees from AbbVie New Zealand, Cornerstones, Janssen New Zealand; and personal fees and non-financial support from Pfizer New Zealand, (all <$10 000) outside of the submitted work. PMM reports personal fees from Abbvie, Eli Lilly, Janssen, Novartis, Pfizer, and UCB; and grants and personal fees from Orphazyme, outside of the submitted work. PCR reports personal fees from Abbvie, Gilead, Lilly, and Roche; grants and personal fees from Novartis, UCB Pharma, Janssen, and Pfizer; and non-financial support from BMS, outside of the submitted work. PS reports honoraria from being a social media editor for @ACR_Journals, outside of the submitted work. ZSW reports grants from National Institutes of Health, BMS, and Sanofi; and personal fees from Viela Bio and MedPace, outside of the submitted work. JY reports personal fees from Pfizer and Eli Lilly, and grants and personal fees from Astra Zeneca, outside of the submitted work. ES is a Board Member of the Canadian Arthritis Patient Alliance, which is a patient-run, volunteer-based organisation whose activities are primarily supported by independent grants from pharmaceutical companies. All other authors declare no competing interests. Publisher Copyright: © 2021 Elsevier LtdBackground: The impact and consequences of the COVID-19 pandemic on people with rheumatic disease are unclear. We developed the COVID-19 Global Rheumatology Alliance Patient Experience Survey to assess the effects of the COVID-19 pandemic on people with rheumatic disease worldwide. Methods: Survey questions were developed by key stakeholder groups and disseminated worldwide through social media, websites, and patient support organisations. Questions included demographics, rheumatic disease diagnosis, COVID-19 diagnosis, adoption of protective behaviours to mitigate COVID-19 exposure, medication access and changes, health-care access and communication with rheumatologists, and changes in employment or schooling. Adults age 18 years and older with inflammatory or autoimmune rheumatic diseases were eligible for inclusion. We included participants with and without a COVID-19 diagnosis. We excluded participants reporting only non-inflammatory rheumatic diseases such as fibromyalgia or osteoarthritis. Findings: 12 117 responses to the survey were received between April 3 and May 8, 2020, and of these, 10 407 respondents had included appropriate age data. We included complete responses from 9300 adults with rheumatic disease (mean age 46·1 years; 8375 [90·1%] women, 893 [9·6%] men, and 32 [0·3%] participants who identified as non-binary). 6273 (67·5%) of respondents identified as White, 1565 (16·8%) as Latin American, 198 (2·1%) as Black, 190 (2·0%) as Asian, and 42 (0·5%) as Native American or Aboriginal or First Nation. The most common rheumatic disease diagnoses included rheumatoid arthritis (3636 [39·1%] of 9300), systemic lupus erythematosus (2882 [31·0%]), and Sjögren's syndrome (1290 [13·9%]). Most respondents (6921 [82·0%] of 8441) continued their antirheumatic medications as prescribed. Almost all (9266 [99·7%] of 9297) respondents adopted protective behaviours to limit SARS-CoV-2 exposure. A change in employment status occurred in 2524 (27·1%) of 9300) of respondents, with a 13·6% decrease in the number in full-time employment (from 4066 to 3514). Interpretation: People with rheumatic disease maintained therapy and followed public health advice to mitigate the risks of COVID-19. Substantial employment status changes occurred, with potential implications for health-care access, medication affordability, mental health, and rheumatic disease activity. Funding: American College of Rheumatology.publishersversionPeer reviewe

TNF Drives Monocyte Dysfunction with Age and Results in Impaired Anti-pneumococcal Immunity

Monocyte phenotype and output changes with age, but why this occurs and how it impacts anti-bacterial immunity are not clear. We found that, in both humans and mice, circulating monocyte phenotype and function was altered with age due to increasing levels of TNF in the circulation that occur as part of the aging process. Ly6C+ monocytes from old (18–22 mo) mice and CD14+CD16+ intermediate/inflammatory monocytes from older adults also contributed to this “age-associated inflammation” as they produced more of the inflammatory cytokines IL6 and TNF in the steady state and when stimulated with bacterial products. Using an aged mouse model of pneumococcal colonization we found that chronic exposure to TNF with age altered the maturity of circulating monocytes, as measured by F4/80 expression, and this decrease in monocyte maturation was directly linked to susceptibility to infection. Ly6C+ monocytes from old mice had higher levels of CCR2 expression, which promoted premature egress from the bone marrow when challenged with Streptococcus pneumoniae. Although Ly6C+ monocyte recruitment and TNF levels in the blood and nasopharnyx were higher in old mice during S. pneumoniae colonization, bacterial clearance was impaired. Counterintuitively, elevated TNF and excessive monocyte recruitment in old mice contributed to impaired anti-pneumococcal immunity since bacterial clearance was improved upon pharmacological reduction of TNF or Ly6C+ monocytes, which were the major producers of TNF. Thus, with age TNF impairs inflammatory monocyte development, function and promotes premature egress, which contribute to systemic inflammation and is ultimately detrimental to anti-pneumococcal immunity