Enhancing the detection capabilities of nano-avalanches via data-driven classification of acoustic emission signals.

Acoustic emission (AE) is a powerful experimental method for studying discrete and impulsive events termed avalanches that occur in a wide variety of materials and physical phenomena. A particular challenge is the detection of small-scale avalanches, whose associated acoustic signals are at the noise level of the experimental setup. The conventional detection approach is based on setting a threshold significantly larger than this level, ignoring "false" events with low AE amplitudes that originate from noise. At the same time, this approach overlooks small-scale events that might be true and impedes the investigation of avalanches occurring at the nanoscale, constituting the natural response of many nanoparticles and nanostructured materials. In this work, we develop a data-driven method that allows the detection of small-scale AE events, which is based on two propositions. The first includes a modification of the experimental conditions by setting a lower threshold compared to the conventional threshold, such that an abundance of small-scale events with low amplitudes are considered. Second, instead of analyzing several conventional scalar features (e.g., amplitude, duration, energy), we consider the entire waveform of each AE event and obtain an informative representation using dynamic mode decomposition. We apply the developed method to AE signals measured during the compression of platinum nanoparticles and demonstrate a significant enhancement of the detection range toward small-scale events that are below the conventional threshold.

Keys to Driving Implementation of the New Kidney Care Models.

Contemporary nephrology practice is heavily weighted toward in-center hemodialysis, reflective of decisions on infrastructure and personnel in response to decades of policy. The Advancing American Kidney Health initiative seeks to transform care for patients and providers. Under the initiative's framework, the Center for Medicare and Medicaid Innovation has launched two new care models that align patient choice with provider incentives. The mandatory ESRD Treatment Choices model requires participation by all nephrology practices in designated Hospital Referral Regions, randomly selecting 30% of all Hospital Referral Regions across the United States for participation, with the remaining Hospital Referral Regions serving as controls. The voluntary Kidney Care Choices model offers alternative payment programs open to nephrology practices throughout the country. To help organize implementation of the models, we developed Driver Diagrams that serve as blueprints to identify structures, processes, and norms and generate intervention concepts. We focused on two goals that are directly applicable to nephrology practices and central to the incentive structure of the ESRD Treatment Choices and Kidney Care Choices: (1) increasing utilization of home dialysis, and (2) increasing the number of kidney transplants. Several recurring themes became apparent with implementation. Multiple stakeholders from assorted backgrounds are needed. Communication with primary care providers will facilitate timely referrals, education, and comanagement. Nephrology providers (nephrologists, nursing, dialysis organizations, others) must lead implementation. Patient engagement at nearly every step will help achieve the aims of the models. Advocacy with federal and state regulatory agencies will be crucial to expanding home dialysis and transplantation access. Although the models hold promise to improve choices and outcomes for many patients, we must be vigilant that they not do reinforce existing disparities in health care or widen known racial, socioeconomic, or geographic gaps. The Advancing American Kidney Health initiative has the potential to usher in a new era of value-based care for nephrology.

Impact of Ambulatory Care Pharmacist-Led Diabetes Mellitus Management on Hemoglobin A1c Values Among Patients With Diabetes in a Primary Care Clinic Over Two Years.

Background: Previous evaluation in the literature of ambulatory care pharmacist management on glycosylated hemoglobin (HgbA1c) has been positive, but often limited to 6 to 12 months of follow up. Objective: The objective of this study is to evaluate the impact of an ambulatory care pharmacist on HgbA1c among patients with diabetes in a primary care clinic over two years. Methods: Retrospective chart review was conducted on patients with type 2 diabetes managed by the ambulatory care pharmacist. Patients with at least one HgbA1c value ≥7% in the two-year pre-intervention period were included. The primary outcome was the change in mean HgbA1c from baseline to two years post-intervention. The secondary outcome was the change in mean of all HgbA1c values over two years pre-intervention compared to two years post-intervention. Results: Data for 116 patients was analyzed two years prior to and two years after ambulatory care pharmacist service initiation. The mean HgbA1c at baseline pre-intervention was 8.8% compared to a mean HgbA1c of 7.8% two years post-intervention. A total of 12.9% of patients (n=15) had a baseline HgbA1c of less than 7% pre-intervention, compared to 42.2% of patients (n=49) two years post-intervention (p<0.001). The overall mean HgbA1c was 8.8% in the two-year pre-intervention period and 8.2% in the two-year post-intervention period (p<0.001). Among patients with an overall mean HgbA1c ≥8% in the pre-intervention period, the mean HgbA1c was 9.8% pre-intervention and 8.7% post-intervention. Conclusion: Ambulatory care pharmacist interventions demonstrated a significant impact on HgbA1c reduction over two years of follow up.

Emicizumab Use in Treatment of Acquired Hemophilia A: A Case Report.

BACKGROUND Acquired hemophilia A (AHA) is a rare hemorrhagic disorder that is caused by producing autoantibodies against factor VIII. It is usually characterized by severe, spontaneous bleeding, which can be life-threatening. The current standard treatments for bleeding prophylaxis are highly effective but accompanied with some disadvantages such as frequent intravenous infusions, high cost, and risk of thromboembolic complications. Emicizumab is a bispecific antibody with a therapeutic FVIII-mimetic nature. Emicizumab has shown a reduction in annualized bleeding rate in congenital hemophilia patients with and without inhibitors. The pathophysiological concepts and preclinical data suggest that Emicizumab can be effectively used for treating AHA. CASE REPORT We present the case of an 87-year-old woman admitted for symptomatic anemia and large chest wall and pelvic hematomas confirmed by imaging, without history of trauma. Her coagulation studies showed isolated prolonged activated partial thromboplastin time (aPTT), low factor VIII activity level, and high levels of factor VIII inhibitor. She was successfully treated with activated prothrombin complex concentrate (aPCC), which was transitioned to Emicizumab on discharge. No recurrent bleeding episodes or adverse events related to Emicizumab were reported during the 2-month follow-up period. CONCLUSIONS A subcutaneous weekly or biweekly injection of Emicizumab, a recombinant monoclonal antibody, offers several advantages: less frequent infusions, good hemostatic efficacy, possible outpatient therapy, and even more cost-effective than bypassing agents. More clinical studies should be conducted to compare Emicizumab with the current standards of care.

Large-scale atomistic simulations of helium-3 bubble growth in complex palladium alloys.

Palladium is an attractive material for hydrogen and hydrogen-isotope storage applications due to its properties of large storage density and high diffusion of lattice hydrogen. When considering tritium storage, the material's structural and mechanical integrity is threatened by both the embrittlement effect of hydrogen and the creation and evolution of additional crystal defects (e.g., dislocations, stacking faults) caused by the formation and growth of helium-3 bubbles. Using recently developed inter-atomic potentials for the palladium-silver-hydrogen system, we perform large-scale atomistic simulations to examine the defect-mediated mechanisms that govern helium bubble growth. Our simulations show the evolution of a distribution of material defects, and we compare the material behavior displayed with expectations from experiment and theory. We also present density functional theory calculations to characterize ideal tensile and shear strengths for these materials, which enable the understanding of how and why our developed potentials either meet or confound these expectations.

Breaking Badly: DFT-D2 Gives Sizeable Errors for Tensile Strengths in Palladium-Hydride Solids.

Dispersion interactions play a crucial role in noncovalently bound molecular systems, and recent studies have shown that dispersion effects are also critical for accurately describing covalently bound solids. While most studies on bulk solids have solely focused on equilibrium properties (lattice constants, bulk moduli, and cohesive energies), there has been little work on assessing the importance of dispersion effects for solid-state properties far from equilibrium. In this work, we present a detailed analysis of both equilibrium and highly nonequilibrium properties (tensile strengths leading to fracture) of various palladium-hydride systems using representative DFT methods within the LDA, GGA, DFT-D2, DFT-D3, and nonlocal vdw-DFT families. Among the various DFT methods, we surprisingly find that the empirically constructed DFT-D2 functional gives extremely anomalous and qualitatively incorrect results for tensile strengths in palladium-hydride bulk solids. We present a detailed analysis of these effects and discuss the ramifications of using these methods for predicting solid-state properties far from equilibrium. Most importantly, we suggest caution in using DFT-D2 (or other coarse-grained parametrizations obtained from DFT-D2) for computing material properties under large stress/strain loads or for evaluating solid-state properties under extreme structural conditions.

The application of an atomistic J-integral to a ductile crack.

In this work we apply a Lagrangian kernel-based estimator of continuum fields to atomic data to estimate the J-integral for the emission dislocations from a crack tip. Face-centered cubic (fcc) gold and body-centered cubic (bcc) iron modeled with embedded atom method (EAM) potentials are used as example systems. The results of a single crack with a K-loading compare well to an analytical solution from anisotropic linear elastic fracture mechanics. We also discovered that in the post-emission of dislocations from the crack tip there is a loop size-dependent contribution to the J-integral. For a system with a finite width crack loaded in simple tension, the finite size effects for the systems that were feasible to compute prevented precise agreement with theory. However, our results indicate that there is a trend towards convergence.

Comparison of Molecular and Primitive Solvent Models for Electrical Double Layers in Nanochannels.

In a recent article (Lee et al. J. Comput. Theor. Chem., 2012, 8, 2012-2022.), it was shown that an electrolyte solution can be modeled in molecular dynamics (MD) simulations using a uniform dielectric constant in place of a polar solvent to validate Fluid Density Functional Theory (f-DFT) simulations. This technique can be viewed as a coarse-grained approximation of the polar solvent and reduces computational cost by an order of magnitude. However, the consequences of replacing the polar solvent with an effective permittivity are not well characterized, despite its common usage in f-DFT, Monte Carlo simulation, and Poisson-Boltzmann theory. In this paper, we have examined two solvent models of different fidelities with MD simulation of nanochannels. We find that the models produce qualitatively similar ion density profiles, but physical quantities such as electric field, electric potential, and capacitance differ by over an order of magnitude. In all cases, the bulk is explicitly modeled so that surface properties can be evaluated relative to a reference state. Moreover, quantities that define the reference state, such as bulk ion density, bulk solvent density, applied electric field, and temperature, are measurable, so cases with the same thermodynamic state can be compared. Insights into the solvent arrangement, most of which can not be determined from the coarse-grained model, are drawn from the model with an explicitly described polar solvent.

Molecular Dynamics Studies of Dislocations in CdTe Crystals from a New Bond Order Potential.

Cd(1-x)Zn(x)Te (CZT) crystals are the leading semiconductors for radiation detection, but their application is limited by the high cost of detector-grade materials. High crystal costs primarily result from property nonuniformity that causes low manufacturing yield. Although tremendous efforts have been made in the past to reduce Te inclusions/precipitates in CZT, this has not resulted in an anticipated improvement in material property uniformity. Moreover, it is recognized that in addition to Te particles, dislocation cells can also cause electric field perturbations and the associated property nonuniformities. Further improvement of the material, therefore, requires that dislocations in CZT crystals be understood and controlled. Here, we use a recently developed CZT bond order potential to perform representative molecular dynamics simulations to study configurations, energies, and mobilities of 29 different types of possible dislocations in CdTe (i.e., x = 1) crystals. An efficient method to derive activation free energies and activation volumes of thermally activated dislocation motion will be explored. Our focus gives insight into understanding important dislocations in the material and gives guidance toward experimental efforts for improving dislocation network structures in CZT crystals.

A Long-Range Electric Field Solver for Molecular Dynamics Based on Atomistic-to-Continuum Modeling.

Understanding charge transport processes at a molecular level is currently hindered by a lack of appropriate models for incorporating nonperiodic, anisotropic electric fields in molecular dynamics (MD) simulations. In this work, we develop a model for including electric fields in MD using an atomistic-to-continuum framework. This framework provides the mathematical and the algorithmic infrastructure to couple finite element (FE) representations of continuous data with atomic data. Our model represents the electric potential on a FE mesh satisfying a Poisson equation with source terms determined by the distribution of the atomic charges. Boundary conditions can be imposed naturally using the FE description of the potential, which then propagate to each atom through modified forces. The method is verified using simulations where analytical solutions are known or comparisons can be made to existing techniques. In addition, a calculation of a salt water solution in a silicon nanochannel is performed to demonstrate the method in a target scientific application in which ions are attracted to charged surfaces in the presence of electric fields and interfering media.

Shape memory and pseudoelasticity in metal nanowires.

Structural reorientations in metallic fcc nanowires are controlled by a combination of size, thermal energy, and the type of defects formed during inelastic deformation. By utilizing atomistic simulations, we show that certain fcc nanowires can exhibit both shape memory and pseudoelastic behavior. We also show that the formation of defect-free twins, a process related to the material stacking fault energy, nanometer size scale, and surface stresses is the mechanism that controls the ability of fcc nanowires of different materials to show a reversible transition between two crystal orientations during loading and thus shape memory and pseudoelasticity.