Multi-step nucleation pathway of C-S-H during cement hydration from atomistic simulations.

The Calcium Silicate Hydrate (C-S-H) nucleation is a crucial step during cement hydration and determines to a great extent the rheology, microstructure, and properties of the cement paste. Recent evidence indicates that the C-S-H nucleation involves at least two steps, yet the underlying atomic scale mechanism, the nature of the primary particles and their stability, or how they merge/aggregate to form larger structures is unknown. In this work, we use atomistic simulation methods, specifically DFT, evolutionary algorithms (EA), and Molecular Dynamics (MD), to investigate the structure and formation of C-S-H primary particles (PPs) from the ions in solution, and then discuss a possible formation pathway for the C-S-H nucleation. Our simulations indicate that even for small sizes the most stable clusters encode C-S-H structural motifs, and we identified a C4S4H2 cluster candidate to be the C-S-H basic building block. We suggest a formation path in which small clusters formed by silicate dimers merge into large elongated aggregates. Upon dehydration, the C-S-H basic building blocks can be formed within the aggregates, and eventually crystallize.

Impacto de las fracturas por fragilidad en mujeres españolas con osteoporosis posmenopáusica / Impact of fragility fractures in postmenopausal Spanish women with osteoporosis

Objetivo: dada la repercusión que tienen las fracturas por fragilidad y sus secuelas en la vida de las mujeres con osteoporosis posmenopáusica (OPM), el objetivo de este estudio es describir y analizar su impacto en esta población. Material y métodos: se realizó una encuesta a mujeres posmenopáusicas con fractura por fragilidad en un diseño observacional transversal. Se recogieron variables sociodemográficas, impacto de la fractura (necesidad de cuidados, productividad laboral), calidad de vida relacionada con la salud (CVRS, mediante cuestionario QUALEFFO-31) y disposición a pagar (DAP) por recuperarla. Resultados: participaron 120 mujeres, promedio de edad 62 ± 7 años. Las fracturas más frecuentes fueron las de radio distal (29,9 %) y las vertebrales (21,3 %). Un 53,3 % necesitó cuidados durante su recuperación (76,5 % informales; 24,9 % formales) y un 4,2 % tuvo que ingresar en un centro/residencia sociosanitaria. De aquellas que trabajaban cuando se produjo la fractura (62,5 %), el 56 % vio su vida laboral afectada (69,3 % incapacidad temporal; 17,3 % incapacidad permanente; 10,7 % reducción de jornada; 10,7 % abandono laboral; 5,3 % permiso/excedencia; 3,6 % prejubilación). El impacto de la fractura se debió principalmente al dolor (71,7 %), dificultad para realizar actividades cotidianas (48,3 %), problemas de movilidad (46,7 %) y estado emocional (41,7 %). La mayor DAP se ofreció por recuperar la capacidad para realizar actividades cotidianas y el estado emocional. La puntuación total QUALEFFO-31 (0-100) fue 49,9 ± 10,8 (función mental: 68,3 ± 7,3; dolor: 56 ± 22,6; función física: 39,3 ± 15,5). Conclusiones: las fracturas por fragilidad tienen un alto impacto en la calidad de vida de las mujeres con OPM. Resulta fundamental poner en valor aquellos aspectos que más les preocupan para optimizar su abordaje. (AU)

Objective: Given the impact of fragility fractures and their consequences on the lives of women with postmenopausal osteoporosis (PMO), the objective of this study is to describe and analyze the impact of this kind of fractures on this population. Materials and methods: A survey was conducted among postmenopausal women with fragility fractures in a cross-sectional observational design. Sociodemographic variables, fracture impact (need for care, work productivity), and data on health-related quality of life (HRQoL, assessed using the QUALEFFO-31 questionnaire), and willingness to pay (WTP) to regain HRQoL were collected. Results: A total of 120 women participated, with a mean age of 62 ± 7 years. The most frequent fractures described were distal radius fractures (29.9 %), followed by vertebral fractures (21.3 %). A total of 53.3 % required care during their recovery (76.5 %, informal; 24.9 %, formal), and 4.2 % had to be admitted to a health care or nursing home. Among those who were working when the fracture occurred (62.5 %), 56 % had their working life affected (69.3 %, temporary disability; 17.3 %, permanent disability; 10.7 %, reduced working hours; 10.7 %, quit their jobs; 5.3 %, leave of absence; and 3.6 %, early retirement). The impact of the fracture was primarily due to pain (71.7 %), difficulty performing activities of daily living (48.3 %), mobility problems (46.7 %), and emotional state (41.7 %). The highest WTP was offered to regain the ability to perform activities of daily living and improve the emotional state. The overall QUALEFFO-31 score (0-100) was 49.9 ± 10.8 (mental function, 68.3 ± 7.3; pain, 56 ± 22.6; physical function, 39.3 ± 15.5). Conclusions: Fragility fractures play a significant role on the quality of life of women with PMO. It is of paramount importance to value the aspects that concern them the most to optimize their management. (AU)

ænet-PyTorch: A GPU-supported implementation for machine learning atomic potentials training.

In this work, we present ænet-PyTorch, a PyTorch-based implementation for training artificial neural network-based machine learning interatomic potentials. Developed as an extension of the atomic energy network (ænet), ænet-PyTorch provides access to all the tools included in ænet for the application and usage of the potentials. The package has been designed as an alternative to the internal training capabilities of ænet, leveraging the power of graphic processing units to facilitate direct training on forces in addition to energies. This leads to a substantial reduction of the training time by one to two orders of magnitude compared to the central processing unit implementation, enabling direct training on forces for systems beyond small molecules. Here, we demonstrate the main features of ænet-PyTorch and show its performance on open databases. Our results show that training on all the force information within a dataset is not necessary, and including between 10% and 20% of the force information is sufficient to achieve optimally accurate interatomic potentials with the least computational resources.

Multiple vertebral fractures after suspension of denosumab. A series of 56 cases.

BACKGROUND: Denosumab is a monoclonal antibody approved for the treatment of postmenopausal osteoporosis. The withdrawal of denosumab produces an abrupt loss of bone mineral density and may cause multiple vertebral fractures (MVF). OBJECTIVE: The objective of this study is to study the clinical, biochemical, and densitometric characteristics in a large series of postmenopausal women who suffered MVF after denosumab withdrawal. Likewise, we try to identify those factors related to the presence of a greater number of vertebral fractures (VF). PATIENTS AND METHODS: Fifty-six patients (54 women) who suffered MVF after receiving denosumab at least for three consecutive years and abruptly suspended it. A clinical examination was carried out. Biochemical bone remodelling markers (BBRM) and bone densitometry at the lumbar spine and proximal femur were measured. VF were diagnosed by magnetic resonance imaging MRI, X-ray, or both at dorsal and lumbar spine. RESULTS: Fifty-six patients presented a total of 192 VF. 41 patients (73.2%) had not previously suffered VF. After discontinuation of the drug, a statistically significant increase in the BBRM was observed. In the multivariate analysis, only the time that denosumab was previously received was associated with the presence of a greater number of VF (P = .04). CONCLUSIONS: We present the series with the largest number of patients collected to date. 56 patients accumulated 192 new VF. After the suspension of denosumab and the production of MVF, there was an increase in the serum values of the BBRM. The time of denosumab use was the only parameter associated with a greater number of fractures.

Characterizing modulated structures with first-principles calculations: a unified superspace scheme of ordering in mullite.

The benefit of computational methods applying density functional theory for the description and understanding of modulated crystal structures is investigated. A method is presented which allows one to establish, improve and test superspace models including displacive and occupational modulation functions from first-principles calculations on commensurate structures. The total energies of different configurations allow one to distinguish stable and less stable structure models. The study is based on a series of geometrically optimized superstructures of mullite (Al4+2xSi2-2xO10-x) derived from the superspace group Pbam(α0½)0ss. Despite the disordered and structurally complex nature of mullite, the calculations on ordered superstructures are very useful for determining the ideal Al/Si ordering in mullite, extracting atomic modulation functions as well as understanding the SiO2-Al2O3 phase diagram. The results are compared with experimentally established models which confirm the validity and utility of the presented method.

Exploiting superspace to clarify vacancy and Al/Si ordering in mullite.

Synchrotron single-crystal X-ray diffraction has revealed diffuse scattering alongside sharp satellite reflections for different samples of mullite (Al4+2x Si2-2x O10-x ). Structural models have been developed in (3+1)-dimensional superspace that account for vacancy ordering and Al/Si ordering based on harmonic modulation functions. A constraint scheme is presented which explains the crystal-chemical relationships between the split sites of the average structure. The modulation amplitudes of the refinements differ significantly by a factor of ∼3, which is explained in terms of different degrees of ordering, i.e. vacancies follow the same ordering principle in all samples but to different extents. A new approach is applied for the first time to determine Al/Si ordering by combining density functional theory with the modulated volumes of the tetrahedra. The presence of Si-Si diclusters indicates that the mineral classification of mullite needs to be reviewed. A description of the crystal structure of mullite must consider both the chemical composition and the degree of ordering. This is of particular importance for applications such as advanced ceramics, because the physical properties depend on the intrinsic structure of mullite.

Ordered vacancy distribution in 2/1 mullite: a superspace model.

A mullite single crystal with composition Al4.84Si1.16O9.58 (2) exhibiting sharp satellite reflections was investigated by means of X-ray diffraction. For the refinement of a superspace model in the superspace group Pbam(α0½)0ss different scale factors for main and satellite reflections were used in order to describe an ordered mullite structure embedded in a disordered polymorph. The ordered fraction of the mullite sample exhibits a completely ordered vacancy distribution and can be described as a block structure of vacancy blocks (VBs) that alternate with vacancy-free blocks (VFBs) along a and c. The incommensurate nature of mullite originates from a modulation of the block size, which depends on the composition. The displacive modulation is analyzed with respect to the vacancy distribution and a possible Al/Si ordering scheme is derived, although the measurement itself is not sensitive to the Al/Si distribution. An idealized, commensurate approximation for 2/1 mullite is also presented. Comparison of the ordered superspace model with different preceding models reconciles many key investigations of the last decades with partly contradicting conclusions, where mullite was usually treated as either ordered or disordered instead of considering simultaneously different states of order.

Burden of First Osteoporotic Hip Fracture in Spain: A Prospective, 12-Month, Observational Study.

The purpose of this study was to estimate the burden of osteoporotic fractures beyond the hospitalization period covering up to the first year after the fracture. This was a prospective, 12-month, observational study including patients aged ≥65 years hospitalized due to a first low-trauma hip fracture, in six Spanish regions. Health resource utilization (HRU), quality of life (QoL) and autonomy were collected and total costs calculated. Four hundred and eighty seven patients (mean ± SD age 83 ± 7 years, 77 % women) were included. Twenty-two percent of patients reported a prior non-hip low-trauma fracture, 16 % were receiving osteoporotic treatment at baseline, and 3 % had densitometry performed (1.8 % T-score ≤-2.5). Sixteen percent of patients died (women 14 %; men 25 %; p = 0.0011) during the first year. Mean hospital stay was 11.8 ± 7.9 days and 95.1 % of patients underwent surgery. Other relevant HRUs were: outpatient visits in 78 % of patients (mean 9.2 ± 9.7); walking aids, 58.7 %; rehabilitation facilities, 35.5 % (28.7 ± 41.2 sessions); and formal and informal home care, 22.2 % (49.6 ± 72.2 days) and 53.4 % (77.1 ± 101.0 h), respectively. Mean direct cost was €9690 (95 % confidence interval: 9184-10,197) in women and €9019 (8079-9958) in men. Main cost drivers were: first hospitalization episode (women €7067 [73 %]; men €7196 [80 %]); outpatient visits (€1323 [14 %]; €997 [11 %]); and home care (€905 [9 %]; €767 [9 %]). QoL and autonomy showed a marked decrease during hospitalization, not entirely recovered at 12 months (p < 0.05 vs. baseline for EQ-5D, Harris hip score and modified Barthel index). In a Spanish setting, osteoporotic hip fractures incur a high societal and economic cost, mainly due to the first hospitalization HRU, but also due to subsequent outpatient visits and home care.

Isolated intra-articular fracture of the distal ulna: a rare injury related to airbag deployment.

An isolated intra-articular and adjacent shaft fracture of the distal ulna is described. A 38-old-year woman driver sustained an automobile accident with subsequent airbag deployment injuring her left wrist. Imaging studies showed displacement of a radiovolar fragment and deformity of the ulnar articular surface. The fracture was reduced and internally fixed with 3, 3.5-mm, cannulated screws to avoid future difficulties in forearm rotation, ulnocarpal impaction, and late posttraumatic arthritis. The final outcome was excellent. Careful clinical and radiologic examination is strongly recommended for this type of fracture, which seems to be a part of the spectrum of upper limb injuries associated with airbag deployment. Such injuries can be expected to occur more frequently with the increasing use of airbags.

Posttraumatic ectopic nail: case report.

Ectopic nail, also known as onychoheterotopia or onychoheterotropia, is an extremely rare disorder. It is characterized by the growth of nail-like tissue in a different location other than the nail bed. Congenital and acquired deformities have been reported. We describe a case of posttraumatic ectopic nail and review the literature on this unusual condition.