Showing papers by "University of Akron published in 2020"

RESTORE-IMI 1: A Multicenter, Randomized, Double-blind Trial Comparing Efficacy and Safety of Imipenem/Relebactam vs Colistin Plus Imipenem in Patients With Imipenem-nonsusceptible Bacterial Infections.

Abstract: BACKGROUND The β-lactamase inhibitor relebactam can restore imipenem activity against imipenem-nonsusceptible gram-negative pathogens. We evaluated imipenem/relebactam for treating imipenem-nonsusceptible infections. METHODS Randomized, controlled, double-blind, phase 3 trial. Hospitalized patients with hospital-acquired/ventilator-associated pneumonia, complicated intraabdominal infection, or complicated urinary tract infection caused by imipenem-nonsusceptible (but colistin- and imipenem/relebactam-susceptible) pathogens were randomized 2:1 to 5-21 days imipenem/relebactam or colistin+imipenem. Primary endpoint: favorable overall response (defined by relevant endpoints for each infection type) in the modified microbiologic intent-to-treat (mMITT) population (qualifying baseline pathogen and ≥1 dose study treatment). Secondary endpoints: clinical response, all-cause mortality, and treatment-emergent nephrotoxicity. Safety analyses included patients with ≥1 dose study treatment. RESULTS Thirty-one patients received imipenem/relebactam and 16 colistin+imipenem. Among mITT patients (n = 21 imipenem/relebactam, n = 10 colistin+imipenem), 29% had Acute Physiology and Chronic Health Evaluation II scores >15, 23% had creatinine clearance <60 mL/min, and 35% were aged ≥65 years. Qualifying baseline pathogens: Pseudomonas aeruginosa (77%), Klebsiella spp. (16%), other Enterobacteriaceae (6%). Favorable overall response was observed in 71% imipenem/relebactam and 70% colistin+imipenem patients (90% confidence interval [CI] for difference, -27.5, 21.4), day 28 favorable clinical response in 71% and 40% (90% CI, 1.3, 51.5), and 28-day mortality in 10% and 30% (90% CI, -46.4, 6.7), respectively. Serious adverse events (AEs) occurred in 10% of imipenem/relebactam and 31% of colistin+imipenem patients, drug-related AEs in 16% and 31% (no drug-related deaths), and treatment-emergent nephrotoxicity in 10% and 56% (P = .002), respectively. CONCLUSIONS Imipenem/relebactam is an efficacious and well-tolerated treatment option for carbapenem-nonsusceptible infections. CLINICAL TRIALS REGISTRATION NCT02452047.

High-efficiency improvement of thermal conductivities for epoxy composites from synthesized liquid crystal epoxy followed by doping BN fillers

Abstract: Liquid crystal epoxy resin presents high intrinsic thermal conductivity coefficient (λ). However, the complex molecular structure design and tedious synthesis process severely limit its rapid development and further industrial application. In this work, a kind of liquid crystal epoxy (LCE) based on biphenyl mesomorphic unit is synthesized from 4,4′-biphenol, triethylene glycol, and epichlorohydrin. Curing agent of 4,4′-diaminodiphenyl methane (DDM) and boron nitride (BN) fillers are both performed to prepare the intrinsic highly thermally conductive liquid crystal epoxy resin (LCER) and BN/LCER thermally conductive composites via casting method. LCE has been successfully synthesized with expected structure, presenting nematic liquid crystal with range of 135–165 °C. LCER shows liquid crystal property with intrinsic λ up to 0.51 W/mK, about 3 times higher than that of general bisphenol A epoxy resin (E−51, 0.19 W/mK). Simultaneously, LCER has good thermal stability with heat resistance index (THRI) being 183.9 °C. In addition, the λ values of the BN/LCER thermally conductive composites increase with the increasing loading of BN fillers. When the content of BN fillers is 30 wt%, the λ value of BN/LCER thermally conductive composites is 1.02 W/mK, twice as much as that of pure LCER, also much higher than that of 30 wt% BN/E−51 composites (0.52 W/mK).

Effect of energy density and scanning strategy on densification, microstructure and mechanical properties of 316L stainless steel processed via selective laser melting

Abstract: Laser-based additive manufacturing opens up a new horizon in terms of processing novel alloys that are difficult to process using conventional techniques. Selective laser melting (SLM) is a powder bed fusion type additive manufacturing (AM) process, for fabricating metallic parts where powder particles are fused using a high energy laser beam as a thermal source. Although SLM is widely used for manufacturing end-use metal tools and components, it requires careful tailoring of a range of parameters (e.g. layer thickness, laser spot size, laser power, hatch spacing, scanning strategy, etc.) to achieve the required densification, microstructures, and mechanical properties. Therefore, there is a critical need to systematically investigate the effect of these processing parameters on densification, microstructures and mechanical properties of materials. In this research work, 16 samples fabricated by SLM process with varying processing parameters have been investigated. We have studied the effect of scanning speed, scanning strategy, and energy density on microstructure and mechanical properties of these samples by performing microhardness tests, tensile tests, and a scanning electron microscopy (SEM) analysis. We have concluded that samples fabricated with alternate hatches and single pass of a laser beam exhibited highest densification and most refined microstructure. Furthermore, samples processed at higher scanning speeds had better densification, as well as excellent mechanical properties. We have also observed an increase in the width of dendrites as a result of decreasing the scanning speed primarily due to decrease in cooling rate.

Highly stretchable, self-adhesive, biocompatible, conductive hydrogels as fully polymeric strain sensors

Abstract: Development of highly stretchable and sensitive soft strain sensors is of great importance for broad applications in artificial intelligence, wearable devices, and soft robotics, but it proved to be a profound challenge to integrate the two seemingly opposite properties of high stretchability and sensitivity into a single material. Herein, we designed and synthesized a new fully polymeric conductive hydrogel with an interpenetrating polymer network (IPN) structure made of conductive PEDOT:PSS polymers and zwitterionic poly(HEAA-co-SBAA) polymers to achieve a combination of high mechanical, biocompatible, and sensing properties. The presence of hydrogen bonding, electrostatic interactions, and IPN structures enabled poly(HEAA-co-SBAA)/PEDOT:PSS hydrogels to achieve an ultra-high stretchability of 4000–5000%, a tensile strength of ∼0.5 MPa, a rapid mechanical recovery of 70–80% within 5 min, fast self-healing in 3 min, and a strong surface adhesion of ∼1700 J m−2 on different hard and soft substrates. Moreover, the integration of zwitterionic polySBAA and conductive PEDOT:PSS facilitated charge transfer via optimal conductive pathways. Due to the unique combination of superior stretchable, self-adhesive, and conductive properties, the hydrogels were further designed into strain sensors with high sensing stability and robustness for rapidly and accurately detecting subtle strain- and pressure-induced deformation and human motions. Moreover, an in-house mechanosensing platform provides a new tool to real-time explore the changes and relationship between network structures, tensile stress, and electronic resistance. This new fully polymeric hydrogel strain sensor, without any conductive fillers, holds great promise for broad human-machine interface applications.

From design to applications of stimuli-responsive hydrogel strain sensors

Abstract: Stimuli-responsive hydrogel strain sensors that synergize the advantages of both soft-wet hydrogels and smart functional materials have attracted rapidly increasing interest for exploring the opportunities from material design principles to emerging applications in electronic skins, health monitors, and human–machine interfaces. Stimuli-responsive hydrogel strain sensors possess smart and on-demand ability to specifically recognize various external stimuli and convert them into strain-induced mechanical, thermal, optical, and electrical signals. This review presents an up-to-date summary over the past five years on hydrogel strain sensors from different aspects, including material designs, gelation/fabrication methods, stimuli-responsive principles, and sensing performance. Hydrogel strain sensors are classified into five major categories based on the nature of the stimuli, and representative examples from each category are carefully selected and discussed in terms of structures, response mechanisms, and potential medical applications. Finally, current challenges and future perspectives of hydrogel strain sensors are tentatively proposed to stimulate more and better research in this emerging field.

Two forms of Opa1 cooperate to complete fusion of the mitochondrial inner-membrane.

Abstract: Mitochondrial membrane dynamics is a cellular rheostat that relates metabolic function and organelle morphology. Using an in vitro reconstitution system, we describe a mechanism for how mitochondrial inner-membrane fusion is regulated by the ratio of two forms of Opa1. We found that the long-form of Opa1 (l-Opa1) is sufficient for membrane docking, hemifusion and low levels of content release. However, stoichiometric levels of the processed, short form of Opa1 (s-Opa1) work together with l-Opa1 to mediate efficient and fast membrane pore opening. Additionally, we found that excess levels of s-Opa1 inhibit fusion activity, as seen under conditions of altered proteostasis. These observations describe a mechanism for gating membrane fusion.

Converting Pomelo Peel into Eco-friendly and Low-Consumption Photothermic Biomass Sponge toward Multifunctioal Solar-to-Heat Conversion

Abstract: Converting waste into versatile materials has been considered as an effective strategy to tackle environmental issues such as shortages in food, clean water, and energy. Conventional carbonization ...

Recent Advancements and Challenges for Low-Toxicity Perovskite Materials

Abstract: Lead-based organic-inorganic hybrid perovskite materials have been developed for advanced optoelectronic applications. However, the toxicity of lead and the chemical instability of lead-based perovskite materials have so far been demonstrated to be an overwhelming challenge. The discovery of perovskite materials based on low-toxicity elements, such as Sn, Bi, Sb, Ge, and Cu, with superior optoelectronic properties provides alternative approaches to realize high-performance perovskite optoelectronics. In this review, recent advances in the aspects of low-toxicity perovskite solar cells, photodetectors, light-emitting diodes, and thermoelectric devices are highlighted. The antioxidation stability of metal cation and the crystallization process of the low-toxicity perovskite materials are discussed. In the last part, the outlook toward addressing various issues requiring further attention in the development of low-toxicity perovskite materials is outlined.

Ownership strategies in knowledge-intensive cross-border acquisitions: Comparing Chinese and Indian MNEs

Abstract: Drawing on the comparative ownership framework, we perform a comparative analysis of Chinese and Indian multinational enterprises (MNEs)’ ownership strategies in knowledge-intensive cross-border acquisitions (CBAs). Specifically, we claim that due to their lower comparative ownership advantage, and the consequent higher information asymmetry, Chinese MNEs are more cautious (than Indian MNEs) in their ownership strategy. We rely on a dataset of acquisitions undertaken by high and medium-high tech Chinese and Indian MNEs worldwide during the period 2000–2014. Results confirm that Chinese MNEs prefer lower equity control than their Indian counterparts. However, such a preference for lower equity decreases with higher home-host institutional distance and host country-specific previous experience. These factors do not seem to modify the ownership preference of Indian MNEs in the same way.

Designing Champion Nanostructures of Tungsten Dichalcogenides for Electrocatalytic Hydrogen Evolution.

Abstract: Fine-tuning strain and vacancies in 2H-phase transition-metal dichalcogenides, although extremely challenging, is crucial for activating the inert basal plane for boosting the hydrogen evolution reaction (HER). Here, atomically curved 2H-WS2 nanosheets with precisely tunable strain and sulfur vacancies (S-vacancies) along with rich edge sites are synthesized via a one-step approach by harnessing geometric constraints. The approach is based on the confined epitaxy growth of WS2 in ordered mesoporous graphene derived from nanocrystal superlattices. The spherical curvature imposed by the graphitic mesopores enables the generation of uniform strain and S-vacancies in the as-grown WS2 nanosheets, and simultaneous manipulation of these two key parameters can be realized by simply adjusting the pore size. In addition, the formation of unique mesoporous WS2 @graphene van der Waals heterostructures ensures the ready access of active sites. Fine-tuning the WS2 layer number, strain, and S-vacancies enables arguably the best-performing HER 2H-WS2 electrocatalysts ever reported. Density functional theory calculations indicate that compared with strain, S-vacancies play a more critical role in enhancing the HER activity.

A Polymer with “Locked” Degradability: Superior Backbone Stability and Accessible Degradability Enabled by Mechanophore Installation

Abstract: Though numerous applications require degradable polymers, there are surprisingly few polymer systems that combine superior stability and controllable degradability. Particularly, the degradability ...

Bioinspired Melanin-Based Optically Active Materials

Abstract: Melanin is a widespread multifunctional biological pigment that has emerged as a promising platform for applications in coating, catalysis, energy, drug delivery, and medical therapy. Melanin is also a compelling material for photonic applications because of its favorable material characteristics, including broadband absorption, high refractive index, tunable fluorescence, and UV blocking capabilities. However, there is not yet a critical review focusing on optical functions of melanin. This review summarizes current advances in bioinspired melanin-based optically active materials, covering melanin's inherent optical properties and functions both in nature and in optics-related applications. It is envisioned that this work will provide a better understanding of melanin's photonic functions and insights into the future development of melanin-based or melanin-inspired optically active materials for wide applications.

Polymeric Active Materials for Redox Flow Battery Application

Abstract: The redox flow battery (RFB) is one of the most promising systems for large scale electrochemical energy storage applications. The development of redox-active materials is an essential part of RFB ...

Holistically Engineered Polymer-Polymer and Polymer-Ion Interactions in Biocompatible Polyvinyl Alcohol Blends for High-Performance Triboelectric Devices in Self-Powered Wearable Cardiovascular Monitorings.

Abstract: The capability of sensor systems to efficiently scavenge their operational power from stray, weak environmental energies through sustainable pathways could enable viable schemes for self-powered health diagnostics and therapeutics Triboelectric nanogenerators (TENG) can effectively transform the otherwise wasted environmental, mechanical energy into electrical power Recent advances in TENGs have resulted in a significant boost in output performance However, obstacles hindering the development of efficient triboelectric devices based on biocompatible materials continue to prevail Being one of the most widely used polymers for biomedical applications, polyvinyl alcohol (PVA) presents exciting opportunities for biocompatible, wearable TENGs Here, the holistic engineering and systematic characterization of the impact of molecular and ionic fillers on PVA blends' triboelectric performance is presented for the first time Triboelectric devices built with optimized PVA-gelatin composite films exhibit stable and robust triboelectricity outputs Such wearable devices can detect the imperceptible skin deformation induced by the human pulse and capture the cardiovascular information encoded in the pulse signals with high fidelity The gained fundamental understanding and demonstrated capabilities enable the rational design and holistic engineering of novel materials for more capable biocompatible triboelectric devices that can continuously monitor vital physiological signals for self-powered health diagnostics and therapeutics

Metapopulation Network Models for Understanding, Predicting, and Managing the Coronavirus Disease COVID-19

Abstract: Mathematical models of SARS-CoV-2 (the virus which causes COVID-19) spread are used for guiding the design of mitigation steps and helping identify impending breaches of health care system surge capacity The challenges of having only lacunary information about daily new infections and mortality counts are compounded by geographic heterogeneity of the population This complicates prediction, particularly when homogenized population models assume well mixed To address this problem, we account for the differences between rural and urban settings using network-based, distributed models where the spread of the pandemic is described in distinct local cohorts with nested SE(A)IR models, ie, modified SEIR models that include infectious asymptomatic individuals The model parameters account for the SARS-CoV-2 transmission mostly via human-to-human contact, and the fact that contact frequency among individuals differs between urban and rural areas, and may change over time The probability that the virus spreads into an uninfected community is associated with influx of individuals from communities where the infection is already present, thus each node is characterized by its internal contact and by its connectivity with other nodes Census and cell phone data used to set up the adjacency matrix of the network, which can be modified to simulate changes in mitigation measures Our network SE(A)IR model depends on easily interpretable parameters estimated from available community level data The parameters estimated with Bayesian techniques include transmission rate and the ratio asymptomatic to symptomatic infectious individuals The methodology predicts that the latter quantity approaches 05 as the epidemic reaches an equilibrium, in full agreement with the May 22, 2020 CDC modeling The network model gives rise to a spatially distributed computational model that explains the geographic dynamics of the contagion, eg, in larger cities surrounded by suburban and rural areas The time courses of the infected cohorts in the different counties predicted by the network model are remarkably similar to the reported observations Moreover, the model shows that monitoring the infection prevalence in each county, and adopting local mitigation measures as infections climb beyond a certain threshold, is almost as effective as blanket measures, and more effective than reducing inter-county mobility

4D Printing of Resorbable Complex Shape-Memory Poly(propylene fumarate) Star Scaffolds.

Abstract: 3D/4D printing is enabling transformative advances in device manufacturing and medicine but remains limited by the lack of printable resorbable materials with advanced properties and functions. Herein, we report the rapid and precise 4D printing of shape-memory scaffolds based on poly(propylene fumarate) (PPF) star polymers. Scaffolds with tunable and distinguishable properties can be produced with identical polymer formulation and stoichiometry. The resulting scaffold glass transition temperatures and Young's moduli increase with the postcuring time. Significantly, both the extent and rate of shape recovery following compression can be tuned by varying the strut design, the postcuring step duration, and/or the temperature applied for the recovery step. Finally, accelerated degradation studies confirmed the resorbability of the PPF star polymer gyroid scaffolds.

Molecular simulations and understanding of antifouling zwitterionic polymer brushes.

Abstract: Zwitterionic materials are an important class of antifouling biomaterials for various applications. Despite such desirable antifouling properties, molecular-level understanding of the structure–property relationship associated with surface chemistry/topology/hydration and antifouling performance still remains to be elucidated. In this work, we computationally studied the packing structure, surface hydration, and antifouling property of three zwitterionic polymer brushes of poly(carboxybetaine methacrylate) (pCBMA), poly(sulfobetaine methacrylate) (pSBMA), and poly((2-(methacryloyloxy)ethyl)phosporylcoline) (pMPC) brushes and a hydrophilic PEG brush using a combination of molecular mechanics (MM), Monte Carlo (MC), molecular dynamics (MD), and steered MD (SMD) simulations. We for the first time determined the optimal packing structures of all polymer brushes from a wide variety of unit cells and chain orientations in a complex energy landscape. Under the optimal packing structures, MD simulations were further conducted to study the structure, dynamics, and orientation of water molecules and protein adsorption on the four polymer brushes, while SMD simulations to study the surface resistance of the polymer brushes to a protein. The collective results consistently revealed that the three zwitterionic brushes exhibited stronger interactions with water molecules and higher surface resistance to a protein than the PEG brush. It was concluded that both the carbon space length between zwitterionic groups and the nature of the anionic groups have a distinct effect on the antifouling performance, leading to the following antifouling ranking of pCBMA > pMPC > pSBMA. This work hopefully provides some structural insights into the design of new antifouling materials beyond traditional PEG-based antifouling materials.

Lower Critical Solution Temperature-Driven Self-Coacervation of Nonionic Polyester Underwater Adhesives.

Abstract: To enable attachment to underwater surfaces, aquatic fauna such as mussels and sandcastle worms utilize the advantages of coacervation to deliver concentrated protein-rich adhesive cocktails in an aqueous environment onto underwater surfaces. Recently, a mussel adhesive protein Mfp-3s, was shown to exhibit a coacervation-based adhesion mechanism. Current synthetic strategies to mimic Mfp-3s often involve complexation of oppositely charged polymers. Such complex coacervates are more sensitive to changes in pH and salt, thereby limiting their utility to narrow ranges of pH and ionic strength. In this study, by taking advantage of the lower critical solution temperature-driven coacervation, we have created mussel foot protein-inspired, tropoelastin-like, bioabsorbable, nonionic, self-coacervating polyesters for the delivery of photo-cross-linkable adhesives underwater and to overcome the challenges of adhesion in wet or underwater environments. We describe the rationale for their design and the underwater adhesive properties of these nonionic adhesives. Compared to previously reported coacervate adhesives, these "charge-free" polyesters coacervate in wide ranges of pH (3-12) and ionic strength (0-1 M NaCl) and rapidly (<300 s) adhere to substrates submerged underwater. The study introduces smart materials that mimic the self-coacervation and environmental stability of Mfp-3s and demonstrate the potential for biological adhesive applications where high water content, salts, and pH changes can be expected.

Ancestral Absence of Electron Transport Chains in Patescibacteria and DPANN.

Abstract: Recent discoveries suggest that the candidate superphyla Patescibacteria and DPANN constitute a large fraction of the phylogenetic diversity of Bacteria and Archaea Their small genomes and limited coding potential have been hypothesized to be ancestral adaptations to obligate symbiotic lifestyles To test this hypothesis, we performed cell-cell association, genomic, and phylogenetic analyses on 4,829 individual cells of Bacteria and Archaea from 46 globally distributed surface and subsurface field samples This confirmed the ubiquity and abundance of Patescibacteria and DPANN in subsurface environments, the small size of their genomes and cells, and the divergence of their gene content from other Bacteria and Archaea Our analyses suggest that most Patescibacteria and DPANN in the studied subsurface environments do not form specific physical associations with other microorganisms These data also suggest that their unusual genomic features and prevalent auxotrophies may be a result of ancestral, minimal cellular energy transduction mechanisms that lack respiration, thus relying solely on fermentation for energy conservation

Mesoatom alloys via self-sorting approach of giant molecules blends

Abstract: The bottom-up construction of Frank–Kasper (FK) phases in soft matter requires intricating tuning to balance entropic and enthalpic interactions. In contrast, sophisticated rules have been established in Metallurgy to dictate the packing structures of metal alloys. Inspired by alloy metallurgy, we develop a new self-sorting approach to construct nanostructures in condensed soft matters. This approach utilizes blends of nano-sized giant molecules to construct supramolecular motifs (“mesoatoms”) with controlled size heterogeneity, which is the key in rational design of diverse FK nanostructures. Especially, the scarcely observed thermodynamically stable Laves C14 and C15 phases are widely found. This approach sheds light on next-generation material engineering which allows nanostructure construction in a more predictable and straightforward way

The Next 100 years of polymer science

Abstract: The year 2020 marks the 100th anniversary of the first article on polymerization, published by Hermann Staudinger. It is Staudinger who realized that polymers consist of long chains of covalently linked building blocks. Polymers have had a tremendous impact on the society ever since this initial publication. People live in a world that is almost impossible to imagine without synthetic polymers. But what does the future hold for polymer science? In this article, the editors and advisory board of Macromolecular Chemistry and Physics reflect on this question.

A Review of Damping Models for Structures With Mechanical Joints1

Abstract: In standard design practice, it is often necessary to assemble engineered structures from individually manufactured parts. Ideally, the assembled system should perform as if the connections between the components were perfect, that is, as if the system were a single monolithic piece. However, the fasteners used in those connections, such as mechanical lap joints, are imperfect and highly nonlinear. In particular, these jointed connections dissipate energy, often through friction over highly localized microscale regions near connection points, and are known to exhibit history dependent, or hysteretic behavior. As a result, while mechanical joints are one of the most common elements in structural dynamics problems, their presence implies that assembled structural systems are difficult to model and analyze. Through rigorous experimental, analytical, and numerical work over the past century, researchers from several different disciplines have developed numerous damping models that give rise to the dynamical behavior attributed to joints. The present work seeks to review, compare, and contrast several linear and nonlinear damping models that are known to be relevant to modeling assembled structural systems. These models are presented and categorized to place them in the proper historical and mathematical context as well as presenting numerous examples of their applications. General properties of hysteretic friction damping models are also studied and compared analytically. Connections are drawn between the different models so as to not only identify differences between models, but also highlight commonalities not normally seen to be in association.