Leslieadams4158

The urgent need to address the high-cost issue of proton-exchange membrane fuel cell (PEMFC) technologies, particularly for transportation applications, drives the development of simultaneously highly active and durable platinum group metal-free (PGM-free) catalysts and electrodes. The past decade has witnessed remarkable progress in exploring PGM-free cathode catalysts for the oxygen reduction reaction (ORR) to overcome sluggish kinetics and catalyst instability in acids. Among others, scientists have identified the newly emerging atomically dispersed transition metal (M Fe, Co, or/and Mn) and nitrogen co-doped carbon (M-N-C) catalysts as the most promising alternative to PGM catalysts. Here, we provide a comprehensive review of significant breakthroughs, remaining challenges, and perspectives regarding the M-N-C catalysts in terms of catalyst activity, stability, and membrane electrode assembly (MEA) performance. A variety of novel synthetic strategies demonstrated effectiveness in improving intrinsic activg the comprehensive evaluation of M-N-C catalysts in MEAs. The most considerable challenge of current M-N-C catalysts is the unsatisfied stability and rapid performance degradation in MEAs. Therefore, we further discuss practical methods and strategies to mitigate catalyst and electrode degradation, which is fundamentally essential to make M-N-C catalysts viable in PEMFC technologies.Retinopathy of prematurity (ROP) is a blinding morbidity of preterm infants, which represents a significant clinical problem, accounting for up to 40% of all childhood blindness. ROP displays a range of severity, though even mild disease may result in life-long visual impairment. This is complicated by the fact that our current treatments have significant ocular and potentially systemic effects. Therefore, disease prevention is desperately needed to mitigate the life-long deleterious effects of ROP for preterm infants. Although ROP demonstrates a delayed onset of retinal disease following preterm birth, representing a potential window for prevention, we have been unable to sufficiently alter the natural disease course and meaningfully prevent ROP. Prevention therapeutics requires knowledge of early ROP molecular changes and risk, occurring prior to clinical retinal disease. While we still have an incomplete understanding of these disease mechanisms, emerging data integrating contributions of maternal/placental pathobiology with ROP are poised to inform novel approaches to prevention. Herein, we review the molecular basis for current prevention strategies and the clinical outcomes of these interventions. We also discuss how insights into early ROP pathophysiology may be gained by a better understanding of maternal and placental factors playing a role in preterm birth.Cranial radiotherapy has several side effects. One of the most important complications is radiation caries that endangers the treatment prognosis. In the literature, the use of crowns and bridges for irradiated patients has been suggested as a contraindication. In addition, due to the risk of osteoradionecrosis (ORN), there are doubts about tooth extraction and implant placement. Here, we present a treatment sequence and recalls for an irradiated young patient. For irradiated patients, it is recommended to replace teeth with implants when there is no possibility for supragingival prosthetic margin. Copyright© Dental Research Center, Tehran University of Medical Sciences.Objectives The dental profession has a special place of trust in the society, and dental clinicians must adhere to ethical standards in all dental procedures. Ethical conduct is one of the main expectations of individuals from this profession. The aim of this study was to design and develop dental ethical codes for national implementation in Iran. Materials and Methods This qualitative study was performed using directed content analysis method and purposive sampling. Data were collected until saturation through 15 semi-structured face-to-face individual interviews and two expert panels with academic staffs from dental faculties in Tehran, Iran. Results Data were classified into five principles and 90 codes. The principles included consideration of patients' interest as a priority, respect for human dignity and patient autonomy, confidentiality of patient information, the excellence of knowledge and skills, and building trust. Conclusion The ethical codes for Iranian dentists were drafted considering Islamic teachings and the prevailing culture. Some codes were exclusively developed for the cultural atmosphere of Iran especially on topics such as interaction with patients previously treated by other dentists. Some codes addressed the principles of consultation and continuing the therapeutic communication with such patients. Some items have not been considered in codes released by other associations, such as religious considerations in Islamic cover and alcohol consumption that were taken into consideration in this draft. These codes can serve as a guide for professional practice of dentists. It seems that these sets can help us reach the standardized code. Copyright© Dental Research Center, Tehran University of Medical Sciences.Objectives This study aimed to assess the effect of three commonly consumed beverages on surface roughness of polished and glazed zirconia-reinforced lithium silicate (ZLS) glass ceramics. Materials and Methods In this experimental study, 104 rectangular specimens were cut from Vita Suprinity blocks with 2 mm thickness. After ultrasonic cleaning and firing of the specimens, they were finished and polished in two groups. Specimens in the first group were polished using a 2-step polishing kit while the second group specimens were glazed and heated in a porcelain firing oven according to the manufacturer's instructions. Baseline surface roughness was measured using a profilometer. Specimens in each group were then randomly divided into 4 subgroups (n=13) for immersion in artificial saliva (control group), cola, orange juice and black tea. selleck chemical Surface roughness was measured again and data were analyzed using two-way ANOVA. Results The highest and the lowest mean Ra were found in orange juice and saliva subgroups, respectively in both glazed and polished groups.