High-throughput determination of grain size distributions by EBSD with low-discrepancy sampling.

Because microstructure plays an important role in the mechanical properties of structural materials, developing the capability to quantify microstructures rapidly is important to enabling high-throughput screening of structural materials. Electron backscatter diffraction (EBSD) is a common method for studying microstructures and extracting information such as grain size distributions (GSDs), but is not particularly fast and thus could be a bottleneck in high-throughput systems. One approach to accelerating EBSD is to reduce the number of points that must be scanned. In this work, we describe an iterative method for reducing the number of scan points needed to measure GSDs using incremental low-discrepancy sampling, including on-the-fly grain size calculations and a convergence test for the resulting GSD based on the Kolmogorov-Smirnov test. We demonstrate this method on five real EBSD maps collected from magnesium AZ31B specimens and compare the effectiveness of sampling according to two different low discrepancy sequences, the Sobol and R2 sequences, and random sampling. We find that R2 sampling is able to produce GSDs that are statistically very similar to the GSDs of the full density grids using, on average, only 52% of the total scan points. For EBSD maps that contained monodisperse GSDs and over 1000 grains, R2 sampling only required an average of 39% of the total EBSD points.

Nonisocyanate Polyurethane Segmented Copolymers from Bis-Carbonylimidazolides.

Bis-carbonylimidazolide (BCI) functionalization enables an efficient synthetic strategy to generate high molecular weight segmented nonisocyanate polyurethanes (NIPUs). Melt phase polymerization of ED-2003 Jeffamine, 4,4'-methylenebis(cyclohexylamine), and a BCI monomer that mimics a 1,4-butanediol chain extender enables polyether NIPUs that contain varying concentrations of hard segments ranging from 40 to 80 wt. %. Dynamic mechanical analysis and differential scanning calorimetry reveal thermal transitions for soft, hard, and mixed phases. Hard segment incorporations between 40 and 60 wt. % display up to three distinct phases pertaining to the poly(ethylene glycol) (PEG) soft segment Tg, melting transition, and hard segment Tg, while higher hard segment concentrations prohibit soft segment crystallization, presumably due to restricted molecular mobility from the hard segment. Atomic force microscopy allows for visualization and size determination of nanophase-separated regimes, revealing a nanoscale rod-like assembly of HS. Small-angle X-ray scattering confirms nanophase separation within the NIPU, characterizing both nanoscale amorphous domains and varying degrees of crystallinity. These NIPUs, which are synthesized with BCI monomers, display expected phase separation that is comparable to isocyanate-derived analogues. This work demonstrates nanophase separation in BCI-derived NIPUs and the feasibility of this nonisocyanate synthetic pathway for the preparation of segmented PU copolymers.

Competency-Based Time-Variable Anesthesiology Residency Training: Identification of Problems and Solutions.

BACKGROUND: Global medical education is gradually moving toward more comprehensive implementations of a competency-based education (CBE) model. Elimination of standard time-based training and adoption of time-variable training (competency-based time-variable training [CB-TVT]) is one of the final stages of implementation of CBE. While CB-TVT has been implemented in some programs outside the United States, residency programs in the United States are still exploring this approach to training. The Accreditation Council for Graduate Medical Education (ACGME) and the American Board of Medical Specialties (ABMS) are encouraging member boards and residency review committees to consider innovative ways programs could implement CB-TVT. The goals of this study were to (1) identify potential problems with the implementation of CB-TVT in anesthesiology residency training, (2) rank the importance of the problems and the perceived difficulty of solving them, and (3) develop proposed solutions to the identified problems. METHODS: Study participants were recruited from key stakeholder groups in anesthesiology education, including current or former program directors, department chairs, residents, fellows, American Board of Anesthesiology (ABA) board members, ACGME residency review committee members or ACGME leaders, designated institutional officials, residency program coordinators, clinical operations directors, and leaders of large anesthesiology community practice groups. This study was conducted in 2 phases. In phase 1, survey questionnaires were iteratively distributed to participants to identify problems with the implementation of CB-TVT. Participants were also asked to rank the perceived importance and difficulty of each problem and to identify relevant stakeholder groups that would be responsible for solving each problem. In phase 2, surveys focused on identifying potential solutions for problems identified in phase 1. RESULTS: A total of 36 stakeholders identified 39 potential problems, grouped into 7 major categories, with the implementation of CB-TVT in anesthesiology residency training. Of the 39 problems, 19 (48.7%) were marked as important or very important on a 5-point scale and 12 of 19 (63.2%) of the important problems were marked as difficult or very difficult to solve on a 5-point scale. Stakeholders proposed 165 total solutions to the identified problems. CONCLUSIONS: CB-TVT is a promising educational model for anesthesiology residency, which potentially results in learner flexibility, individualization of curricula, and utilization of competencies to determine learner advancement. Because of the potential problems with the implementation of CB-TVT, it is important for future pilot implementations of CB-TVT to document realized problems, efficacy of solutions, and effects on educational outcomes to justify the burden of implementing CB-TVT.

Temporally Stable Supramolecular Polymeric Salts Enabling High-Performance 3D All-Aromatic Polyimide Lattices.

Vat photopolymerization (VP) Additive Manufacturing (AM), in which UV light is selectively applied to cure photo-active polymers into complex geometries with micron-scale resolution, has a limited selection of aliphatic thermoset materials that exhibit relatively poor thermal performance. Ring-opening dianhydrides with acrylate-containing nucleophiles yielded diacrylate ester-dicarboxylic acids that enabled photo-active polyimide (PI) precursors, termed polysalts, upon neutralization with an aromatic diamine in solution. In situ FTIR spectroscopy coupled with a solution and photo-rheological measurements revealed a previously unknown time-dependent instability of 4,4'-oxydianiline (ODA) polysalts due to an aza-Michael addition. Replacement of the electron-donating ether-containing diamine with an electron withdrawing sulfone-containing monomer, e.g., 4,4'-diaminodiphenyl sulfone (DDS), prohibited the aza-Michael addition of the aromatic amine to the activated acrylate double bond. Novel DDS polysalt photocurable solutions are similarly analyzed and validated long-term stability, which enabled reproducible printing of polyimide organogel intermediates. Subsequent VP AM afforded 3-dimensional (3D) structures of intricate complexity and excellent surface finish, as demonstrated with scanning electron microscopy. In addition, the novel PMDA-HEA/DDS solution enabled the production of the first beam latticed architecture comprised of all-aromatic polyimide. The versatility of a polysalt platform for multi-material printing is further demonstrated by printing parts with alternating polysalt compositions.

Development of a fluorescence screening assay for binding partners of the iron-sulfur mitochondrial protein mitoNEET.

MitoNEET belongs to the CDGSH Iron-Sulfur Domain (CISD)-gene family of proteins and is a [2Fe-2S] cluster-containing protein found on the outer membrane of mitochondria. The specific functions of mitoNEET/CISD1 remain to be fully elucidated, but the protein is involved in regulating mitochondrial bioenergetics in several metabolic diseases. Unfortunately, drug discovery efforts targeting mitoNEET to improve metabolic disorders are hampered by the lack of ligand-binding assays for this mitochondrial protein. We have developed a protocol amenable for high-throughput screening (HTS) assay, by modifying an ATP fluorescence polarization method to facilitate drug discovery targeting mitoNEET. Based on our observation that adenosine triphosphate (ATP) interacts with mitoNEET, ATP-fluorescein was used during assay development. We established a novel binding assay suitable for both 96- or 384-well plate formats with tolerance for the presence of 2% v/v dimethyl sulfoxide (DMSO). We determined the IC50-values for a set of benzesulfonamide derivatives and found the novel assay reliably ranked the binding-affinities of compounds compared to radioactive binding assay with human recombinant mitoNEET. The developed assay platform is crucial in identifying novel chemical probes for metabolic diseases. It will accelerate drug discovery targeting mitoNEET and potentially other members of the CISD gene family.

Applications and Opportunities in Using Disulfides, Thiosulfinates, and Thiosulfonates as Antibacterials.

Sulfur-containing molecules have a long history of bioactivity, especially as antibacterial agents in the fight against infectious pathogens. Organosulfur compounds from natural products have been used to treat infections throughout history. Many commercially available antibiotics also have sulfur-based moieties in their structural backbones. In the following review, we summarize sulfur-containing antibacterial compounds, focusing on disulfides, thiosulfinates, and thiosulfonates, and opportunities for future developments in the field.

Context-dependent activation of p53 target genes and induction of apoptosis by actinomycin D in aerodigestive tract cancers.

Actinomycin D (ActD) was the first anticancer antibiotic approved for the management of human cancers. However, the notorious toxicity profile limits its widespread application in cancers, including cancers of the aerodigestive tract. Recent studies show that combining low-dose ActD with existing chemotherapies could potentially protect normal cells from the toxicity of chemotherapy drugs through p53 activation (cyclotherapy). An understanding of ActD's effect on p53 signaling is critical for the meaningful application of ActD in cyclotherapy-based combinations. This study evaluated the anti-tumor efficacy and mechanism of action of ActD in aerodigestive tract cancers. We found that ActD strongly inhibited the growth of a panel of aerodigestive tract cancer cell lines and induced efficient apoptosis, although the sensitivity varies among cell lines. The IC50 values of ActD spanned between 0.021 and 2.96 nM. Mechanistic studies revealed that ActD increased the expression of total and phosphorylated p53 (ser15) in a time- and dose-dependent manner. Moreover, ActD-induced apoptosis is dependent on p53 in cells expressing wild-type p53 and that ActD induced context-dependent differential expression of downstream targets p21 and PUMA without significant effects on p27. In the final analysis, this study revealed that p53-p21 is the predominant pathway activated by low-dose ActD, supporting further development of ActD in cyclotherapy.

Effect of copper on the antifungal activity of disulfiram (Antabuse®) in fluconazole-resistant Candida strains.

Disulfiram (Antabuse®) is an alcohol use disorder medication that exhibits antifungal activity against Candida species. The purpose of this investigation was to determine if copper potentiates the antifungal effects of disulfiram based on prior observations that the combination demonstrates increased antitumor activity. Our findings revealed that copper addition conferred up to an eight-fold reduction in the minimum inhibitory concentrations (MICs) of disulfiram by broth microdilution assessment. Unexpectedly, copper was also found to nullify the fungicidal activity of disulfiram despite the significant reduction in MICs. It was therefore concluded that copper likely increased the antifungal potency of disulfiram through formation of a fungistatic chelation complex. LAY SUMMARY: The effect of copper on the antifungal activity of disulfiram was evaluated against fluconazole-resistant Candida species. The study establishes that copper addition confers greater inhibition of disulfiram-treated Candida cultures, but the combination antagonizes the killing effects of disulfiram.

Non-isocyanate Polyurethanes from 1,1'-Carbonyldiimidazole: A Polycondensation Approach.

1,1'-Carbonyldiimidazole (CDI) provides a platform to generate high molecular weight polyurethanes from industrially relevant diols and diamines. CDI, which is described in the literature for its use in amidation and functionalization reactions, enables the production of well-defined and stable polyurethane precursors, thus eliminating the need for isocyanates. Herein, the functionalization of 1,4-butanediol with CDI yields an electrophilic biscarbamate, bis-carbonylimidazolide (BCI), which is suitable for further step-growth polymerization in the presence of amines. Elevated reaction temperatures enable the solvent-, catalyst-, and isocyanate-free polycondensation reaction between the BCI monomer and various diamines. The thermoplastic polyurethanes produced from this reaction demonstrate high thermal stability, tunable glass transition temperatures based on incorporation of flexible polyether segments, and mechanically ductile thin films. CDI functionalized diols will allow the preparation of diverse polyurethanes without the use of isocyanate-containing monomers.

The Anesthesiology Milestones 2.0: An Improved Competency-Based Assessment for Residency Training.

The evolution of medical education, from a time-based to a competency-based platform, began nearly 30 years ago and continues to slowly take shape. The development of valid and reproducible assessment tools is the first step. Medical educators across specialties acknowledge the challenges and remain motivated to develop a relevant, generalizable, and measurable system. The Accreditation Council for Graduate Medical Education (ACGME) remains committed to its responsibility to the public by assuring that the process and outcome of graduate medical education in the nation's residency programs produce competent, safe, and compassionate doctors. The Milestones Project is the ACGME's current strategy in the evolution to a competency-based system, which allows each specialty to develop its own set of subcompetencies and 5-level progression, or milestones, along a continuum of novice to expert. The education community has now had nearly 5 years of experience with these rubrics. While not perfect, Milestones 1.0 provided important foundational information and insights. The first iteration of the Anesthesiology Milestones highlighted some mismatch between subcompetencies and current and future clinical practices. They have also highlighted challenges with assessment and evaluation of learners, and the need for faculty development tools. Committed to an iterative process, the ACGME assembled representatives from stakeholder groups within the Anesthesiology community to develop the second generation of Milestones. This special article describes the foundational data from Milestones 1.0 that was useful in the development process of Milestones 2.0, the rationale behind the important changes, and the additional tools made available with this iteration.

Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block.

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths.

Efficacy of Aerosolized Rifaximin versus Tobramycin for Treatment of Pseudomonas aeruginosa Pneumonia in Mice.

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that can cause chronic lung infections in patients with cystic fibrosis (CF). The current preferred treatment for CF lung infections includes inhaled tobramycin (TOB); however, studies suggest TOB cannot effectively inhibit biofilm formation. Using an NIH small compounds drug library approved for safe use in humans, we identified rifaximin (RFX), a semisynthetic, rifamycin family, nonsystemic antibiotic that inhibits alginate production and growth in P. aeruginosa Inhibition of alginate production was further analyzed using the uronic acid carbazole assay and a promoter reporter assay that measures the transcription of the alginate biosynthetic operon. Compared to TOB, RFX significantly reduced alginate production in laboratory and CF sputum isolates of P. aeruginosa In addition, RFX showed a narrow range of MICs when measured with multidrug-resistant bacterial species of clinical relevance, synergistic activities with TOB or amikacin against clinical isolates, as well as reduction toward in vitro preformed biofilms. In C57BL/6 mice, penetration of nebulized TOB into the lungs was shown at a higher level than that of RFX. Further, in vivo assessment using a DBA/2 mouse lung infection model found increased survival rates with a single-dose treatment of nebulized RFX and decreased P. aeruginosa PAO1 bioburden with a multiple-dose treatment of RFX plus TOB. In addition, mice treated with a single exposure to dimethyl sulfoxide (DMSO), a solvent that dissolves RFX, showed no apparent toxicity. In summary, RFX may be used to supplement TOB inhalation therapy to increase efficacy against P. aeruginosa biofilm infections.

Binding of thiazolidinediones to the endoplasmic reticulum protein nutrient-deprivation autophagy factor-1.

Nutrient-deprivation autophagy factor-1 (NAF-1, miner1; gene cisd2) is part of the [2Fe-2S]-containing protein family which includes mitoNEET (gene cisd1) and MiNT (miner2; gene cisd3). These proteins are redox active and are thought to play an important role in cellular energy homeostasis with NAF-1 playing a critical role in calcium regulation and aging. To date, no studies have investigated potential ligand interaction with NAF-1. Here we show that the thiazolidinediones pioglitazone and rosiglitazone along with the mitoNEET ligand, NL-1, bind to NAF-1 with low micromolar affinities. Further, we show that overexpression of NAF-1 in hepatocellular carcinoma (HepG2) cells reduces inhibition of mitochondrial respiration by pioglitazone. Our findings support the need for further efforts of the rational design of selective NAF-1 ligands.

Advances in Polymeric Materials for Electromechanical Devices.

Electroactive polymers (EAP) provide lightweight and cost-effective materials that enable the next generation of electromechanical devices. Commercial polymers have historically dominated research in EAP devices due to their availability. However, several drawbacks of these materials have limited their commercial applications, necessitating new materials for the commercial success of future EAP devices. This review highlights recent advances in novel EAPs for ionic polymer-metal composites (IPMC) and dielectric elastomer actuators (DEA). Ion-containing block copolymers and charged segmented condensation polymers demonstrate suitable electromechanical properties competitive with Nafion-based IPMCs. In addition, swelling ionic polymer membranes with free ionic liquid enhances ionic conductivity and promotes electromechanical actuation. Synthetic approaches to increasing permittivity in dielectric elastomers are also explored as a method of producing more efficient DEAs. Incorporating polar functional groups into siloxane and acrylic elastomers through grafting or blending provides high-dielectric elastomers for use in DEAs with low driving voltages.

Advanced Polymers for Reduced Energy Consumption in Architecture.

In an effort to slow the progress of climate change, the current scientific community has focused on the reduction of greenhouse gases in order to limit the global average temperature inflation to less than 2 °C. The improvement of thermally controlled construction materials can potentially result in lower energy homes/reduced emissions, and lowering the thermal conductivity of insulation materials improves home energy efficiency. Nanoporous insulation foams impart a drastic decrease in thermal conductivity but many polymer properties must be assessed to produce these materials. Passive phase-change materials also represent another key energy-saving device to control heat flux within a living space. Research into unique polymeric systems provides a novel means of encapsulation or creating polymeric cross-linked matrices to prevent leakage and improve mechanical robustness. These two areas of polymer research in architecture represent key advancements for construction materials aimed toward energy savings and energy-related emissions control.

Disulfiram-based disulfides as narrow-spectrum antibacterial agents.

Sixteen disulfides derived from disulfiram (Antabuse™) were evaluated as antibacterial agents. Derivatives with hydrocarbon chains of seven and eight carbons in length exhibited antibacterial activity against Gram-positive Staphylococcus, Streptococcus, Enterococcus, Bacillus, and Listeria spp. A comparison of the cytotoxicity and microsomal stability with disulfiram further revealed that the eight carbon chain analog was of lower toxicity to human hepatocytes and has a longer metabolic half-life. In the final analysis, this investigation concluded that the S-octylthio derivative is a more effective growth inhibitor of Gram-positive bacteria than disulfiram and exhibits more favorable cytotoxic and metabolic parameters over disulfiram.

Enhanced scattering induced by electrostatic correlations in concentrated solutions of salt-free dipolar and ionic polymers.

We present a generalized theory for studying the static monomer density-density correlation function (structure factor) in concentrated solutions and melts of dipolar as well as ionic polymers. The theory captures effects of electrostatic fluctuations on the structure factor and provides insights into the origin of experimentally observed enhanced scattering at ultralow wavevectors in salt-free ionic polymers. It is shown that the enhanced scattering can originate from a coupling between the fluctuations of electric polarization and monomer density. Local and non-local effects of the polarization resulting from finite sized permanent dipoles and ion-pairs in dipolar and charge regulating ionic polymers, respectively, are considered. Theoretical calculations reveal that, similar to the salt-free ionic polymers, the structure factor for dipolar polymers can also exhibit a peak at a finite wavevector and enhanced scattering at ultralow wavevectors. Although consideration of dipolar interactions leads to attractive interactions between monomers, the enhanced scattering at ultralow wavevectors is predicted solely on the basis of the electrostatics of weakly inhomogeneous dipolar and ionic polymers without considering the effects of any aggregates or phase separation. Thus, we conclude that neither aggregation nor phase separation is necessary for observing the enhanced scattering at ultralow wavevectors in salt-free dipolar and ionic polymers. For charge regulating ionic polymers, it is shown that electrostatic interactions between charged monomers get screened with a screening length, which depends not only on the concentration of "free" counterions and coions, but also on the concentration of "adsorbed" ions on the polymer chains. Qualitative comparisons with the experimental scattering curves for ionic and dipolar polymer melts are presented using the theory developed in this work.

Repurposing Thiram and Disulfiram as Antibacterial Agents for Multidrug-Resistant Staphylococcus aureus Infections.

Thiram and disulfiram were evaluated as antibacterial agents against multidrug-resistant Staphylococcus aureus Against a 30-member panel comprised of vancomycin-susceptible, vancomycin-intermediate, and vancomycin-resistant S. aureus strains, the MIC90 values of the respective test agents were 4 and 16 µg/ml. Additional analyses revealed that thiram and disulfiram are rapid-acting bacteriostatic agents with narrow, Gram-positive-bacterium spectrum activity. Synergy studies further determined that disulfiram increases the vancomycin susceptibility of three clinical vancomycin-resistant S. aureus strains in vitro, thus establishing a potential use in combination therapy.

3D Printing Polymers with Supramolecular Functionality for Biological Applications.

Supramolecular chemistry continues to experience widespread growth, as fine-tuned chemical structures lead to well-defined bulk materials. Previous literature described the roles of hydrogen bonding, ionic aggregation, guest/host interactions, and π-π stacking to tune mechanical, viscoelastic, and processing performance. The versatility of reversible interactions enables the more facile manufacturing of molded parts with tailored hierarchical structures such as tissue engineered scaffolds for biological applications. Recently, supramolecular polymers and additive manufacturing processes merged to provide parts with control of the molecular, macromolecular, and feature length scales. Additive manufacturing, or 3D printing, generates customizable constructs desirable for many applications, and the introduction of supramolecular interactions will potentially increase production speed, offer a tunable surface structure for controlling cell/scaffold interactions, and impart desired mechanical properties through reinforcing interlayer adhesion and introducing gradients or self-assembled structures. This review details the synthesis and characterization of supramolecular polymers suitable for additive manufacture and biomedical applications as well as the use of supramolecular polymers in additive manufacturing for drug delivery and complex tissue scaffold formation. The effect of supramolecular assembly and its dynamic behavior offers potential for controlling the anisotropy of the printed objects with exquisite geometrical control. The potential for supramolecular polymers to generate well-defined parts, hierarchical structures, and scaffolds with gradient properties/tuned surfaces provides an avenue for developing next-generation biomedical devices and tissue scaffolds.

Synthesis of Water-Soluble Imidazolium Polyesters as Potential Nonviral Gene Delivery Vehicles.

The inherent hydrolytic reactivity of polyesters renders them excellent candidates for a variety of biomedical applications. Incorporating ionic groups further expands their potential impact, encompassing charge-dependent function such as deoxyribonucleic acid (DNA) binding, antibacterial properties, and pH-responsiveness. Catalyst-free and solvent-free polycondensation of a bromomethyl imidazolium-containing (BrMeIm) diol with neopentylglycol (NPG) and adipic acid (AA) afforded novel charged copolyesters with pendant imidazolium sites. Varying ionic content influenced thermal properties and offered a wide-range, -41 to 40 °C, of composition-dependent glass transition temperatures (Tgs). In addition to desirable melt and thermal stability, polyesters with ionic concentrations ≥15 mol % readily dispersed in water, suggesting potential as nonviral gene delivery vectors. An electrophoretic gel shift assay confirmed the novel cationic copolyesters successfully bound DNA at an N/P ratio of 4 for 50 mol % and 75 mol % charged copolyesters (P(NA50-co-ImA50) and P(NA25-co-ImA75)), and an N/P ratio of 5 for 100 mol % Im (PImA). Polyplexes exhibited insignificant cytotoxicity even at high concentrations (200 µg/mL), and a Luciferase transfection assay revealed the ionic (co)polyesters transfected DNA significantly better than the untreated controls. The successful transfection of these novel (co)polyesters inspires future imidazolium-containing polyester design.