Evaluating the stability and activity of dilute Cu-based alloys for electrochemical CO2 reduction.

Cu-based catalysts currently offer the most promising route to actively and selectively produce value-added chemicals via electrochemical reduction of CO2 (eCO2R); yet further improvements are required for their wide-scale deployment in carbon mitigation efforts. Here, we systematically investigate a family of dilute Cu-based alloys to explore their viability as active and selective catalysts for eCO2R through a combined theoretical-experimental approach. Using a quantum-classical modeling approach that accounts for dynamic solvation effects, we assess the stability and activity of model single-atom catalysts under eCO2R conditions. Our calculations identify that the presence of eCO2R intermediates, such as CO*, H*, and OH*, may dynamically influence the local catalyst surface composition. Additionally, we identify through binding energy descriptors of the CO*, CHO*, and OCCO* dimer intermediates that certain elements, such as group 13 elements (B, Al, and Ga), enhance the selectivity of C2+ species relative to pure Cu by facilitating CO dimerization. The theoretical work is corroborated by preliminary testing of eCO2R activity and selectivity of candidate dilute Cu-based alloy catalyst films prepared by electron beam evaporation in a zero-gap gas diffusion electrode-based reactor. Of all studied alloys, dilute CuAl was found to be the most active and selective toward C2+ products like ethylene, consistent with the theoretical predictions. We attribute the improved performance of dilute CuAl alloys to more favorable dimerization reaction energetics of bound CO species relative to that on pure Cu. In a broader context, the results presented here demonstrate the power of our simulation framework in terms of rational catalyst design.

Primary stability of implants placed at different angulations in artificial bone.

INTRODUCTION: The aim of this study was to evaluate the primary stability (PS) of titanium implants with a progressive thread design and more thread stability in the apical threads placed in artificial bone materials. MATERIALS AND METHODS: A total of 120 implants were placed in commercially available polyurethane composite bone blocks. The angulations that were chosen to place the implants in bone types II and IV were 0, 10, and 20 degrees, respectively. The implant dimensions were 11 mm in length and 3.5 mm in diameter. Two clinicians placed all implants, and an independent examiner evaluated the PS using the Osstell (ISQ) and Periotest devices. The χ test was used to evaluate the statistical differences between the PS at different angulations. RESULTS: This study showed that there was a statistically significant difference (P = 0.02) of the PS values, when measured using the Periotest values, among all 3 angulations in both bone qualities. Tilted implants with 10 degrees, angulation had a better stability than conventionally placed implants. CONCLUSIONS: The PS of dental implants is higher for implants placed in type II when compared with type IV artificial bone. A higher stability was found for implants placed with 10-degree angulations.

Dentin tubule occlusion and erosion protection effects of dentifrice containing bioadhesive PVM/MA copolymers.

OBJECTIVES: To study the effectiveness of a dentifrice containing polyvinylmethyl ether-maleic acid (PVM/MA) copolymer in occluding dentin tubules and investigate the interaction between PVM/MA and type I collagen using surface plasmon resonance (SPR). MATERIALS AND METHODS: Fifteen volunteers brushed dentin discs in situ using dentifrices with and without PVM/MA copolymer in a cross-over design. Dentin tubule occlusion was evaluated after brushing, after overnight saliva challenge in vivo for 12 h and after drinking 250 ml of orange juice. Dentin tubule occlusion and tubule size were compared between the two groups using repeated ANOVA and before and after erosive challenges using paired t tests. SPR using type I collagen as ligand and PVM/MA as analyte was performed to evaluate the binding of the two macromolecules. RESULTS: A median of 91% of dentin tubules were occluded after a single brushing in the PVM/MA group, as compared to 9% in the controls. After overnight saliva challenge and 10 min of erosion by orange juice, a median of 73% of the dentin tubules remained fully occluded in the PVM/MA group as compared to zero in the controls. Dentin tubule size increased after orange juice erosion in the controls but not in the PVM/MA group. SPR study showed that PVM/MA bound readily to collagen molecules in a 4 to 1 ratio. CONCLUSIONS: Dentifrice containing PVM/MA could effectively occlude dentin tubules and prevent dentin erosion. PVM/MA may improve adhesive retention of intra-tubular dentifrice plugs through binding to dentin surface collagen. CLINICAL RELEVANCE: Brushing with dentifrice containing adhesive polymers has preventive effect against dentin erosion and dentin sensitivity.

Evidence-based techniques to assess the performance of dental implants.

The clinical use of evidence-based medicine has been regarded as one of the most significant medical advancements of the last century. As the costs of medical care escalate, clinical decisions have to be made prudently and with a high degree of efficacy. One of the most expensive treatments in dentistry includes the use of dental implants to rehabilitate partial and fully edentulous patients. Due to the high costs of treatments and the ever increasing varieties of dental implants becoming available, the clinician is often faced with a challenging situation to decide the best prostheses for their patients. Furthermore, navigating through the vast database of literature pertaining to dental implants and their related research can be very time consuming and challenging to a dental surgeon before they can make appropriate clinical decisions. Similar to other orthopedic implants, dental implants need to be evaluated for their long-term efficacy in vivo before they are clinically acceptable. In order to help clinician(s) make patient oriented decisions, evidence-based techniques are becoming increasingly popular. This can be a very useful tool in translating research findings into clinical practice, thus narrowing the gap between research and clinical dentistry. This article discusses ways in which evidence-based techniques can help dental surgeons analyze and make informed clinical decisions about dental implant treatments.

Scalable Gas Diffusion Electrode Fabrication for Electrochemical CO2 Reduction Using Physical Vapor Deposition Methods.

Electrochemical CO2 reduction (ECR) promises the replacement of fossil fuels as the source of feedstock chemicals and seasonal storage of renewable energy. While much progress has been made in catalyst development and electrochemical reactor design, few studies have addressed the effect of catalyst integration on device performance. Using a microfluidic gas diffusion electrolyzer, we systematically studied the effect of thickness and the morphology of electron beam (EB) and magnetron-sputtered (MS) Cu catalyst coatings on ECR performance. We observed that EB-Cu outperforms MS-Cu in current density, selectivity, and energy efficiency, with 400 nm thick catalyst coatings performing the best. The superior performance of EB-Cu catalysts is assigned to their faceted surface morphology and sharper Cu/gas diffusion layer interface, which increases their hydrophobicity. Tests in a large-scale zero-gap electrolyzer yielded similar product selectivity distributions with an ethylene Faradaic efficiency of 39% at 200 mA/cm2, demonstrating the scalability for industrial ECR applications.

Ethics in biomaterials research.

There have been rapid advances in biomaterials research in the past few decades, which have influenced almost all areas of medicine and dentistry. Many ethical concerns related to the use of biomaterials fabricated from artificial substances including metals, polymers, and ceramics have been raised in the past. Most of these include safety and potential harmful effects on the human body. The development of biomaterials that incorporate biological materials such as cells with more traditional, non-biological materials will likely mean that new ethical questions will arise. With significant advances in molecular and cell biology and nanotechnology, the need for safe and effective therapies will also create unique ethical situations in the future. The use of animals in biomedical research has generated opposition from animal rights groups, which has created new challenges to scientists and researchers that warrant further actions. Responsible research by biomaterial scientists in the future will necessitate the incorporation of many new rules and regulations to the existing code of ethics. These will be necessary if new-age materials from emerging areas of science and technology are going to be morally and ethically acceptable to the scientific community and to society.

Fourth International Conference on Ethical Issues in Biomedical Engineering.

The Fourth International Conference on Ethical Issues in Biomedical Engineering was held at Polytechnic University in Brooklyn, New York, from April 20-22, 2007. The conference was attended by speakers from seven countries that included biomedical engineers, clinicians, philosophers, ethicists, lawyers, patient advocates, biomedical company representatives, and graduate and undergraduate students in biomedical engineering programs. The welcoming address was given by John R. Ryan, Vice Admiral, U.S. Navy (Ret) and the chancellor of the State University of New York, who was introduced by Dr. John C. LaRosa, president of SUNY Downstate Medical Center.

Temporomandibular joint disorders: artificial joint replacements and future research needs.

Temporomandibular disorders (TMD) affect a significant section of the American population. According to the National Institutes of Health (NIH), an estimated 3% to 5% of Americans suffer from temporomandibular disorders. Majority of TMDs can be treated by conservative methods, albeit surgical interventions are indicated for some pathological/clinical conditions (according to the American Association of Temporomandibular Joint Surgeons). A distinction can be made between the TMD and the TMJ disease/dysfunction. In the case of TMD, it most correctly relates to a neuromuscular type of problem in the general area of the Temporomandibular Joint (TMJ), but may not intrinsically be related to the TM joint itself. However, TMJ disease/dysfunction relates to a true joint type of pathology, which ultimately may lead to the use of either a partial or a total joint reconstruction. Degeneration of the meniscus and the actual bony portions of the joint is often seen in cases of true TMJ pathology. The use of custom made or predesigned partial and/or total artificial TMJ replacement remains one of the surgical alternatives for treating various TMJ diseases when other conservative treatments fail. The purpose of this article is to provide an overview of currently existing TMJ implants and to discuss relevant issues, including some of the challenges and current needs facing TMJ research. Additionally, this article describes some of the currently available TMJ surgical procedures, the use of autografts and alloplastic materials (with primary emphasis on TMJ implants) for TMJ reconstruction, and some suggestions for future research. Past incidents of clinical failures of TMJ implants have been attributed to several reasons. The important factors that are responsible for the past failures include lack of a sound scientific approach and inadequate basic research to study the underlying causes for pathologies and their remedies of the TMJ. All these previously mentioned concerns have prompted current biomedical researchers to address many overlooked issues in relation to studying temporomandibular disorders and TMJ implants. Future research should be aimed toward addressing TMJ problems with a multidisciplinary approach, emphasizing simultaneous involvement from clinical (i.e., dentists and physicians) and nonclinical personnel (i.e., oral biologists, bioengineers, biostatisticians, physiotherapists, and pain management specialists).

A comparison of stress distributions for different surgical procedures, screw dimensions and orientations for a Temporomandibular joint implant.

Finite element analysis is a useful analytical tool for the design of biomedical implants. The aim of this study was to investigate the behavior of temporomandibular joint implants with multiple design variables of the screws used for fixation of the implant. A commercially available implant with full mandible was analyzed using a finite element software package. The effects of different design variables such as orientation, diameter and stem length of the screws on the stress distribution in bone for two different surgical procedures were investigated. Considering the microstrain in bone as a principal factor, the acceptable ranges for screw diameter and length were determined. Parallel orientation of the screws performed better from a stress point of view when compared to the zig-zag orientation. Sufficient contact between the implant collar and mandibular condyle was shown to reduce the peak stresses which may lead to long term success. The distance between screw holes in the parallel orientation was much closer when compared to the zig-zag orientation. However, the stresses in bone near the screw hole area for the parallel orientation were within acceptable limits.