A general strategy to stabilize 1T-MoS2 using MXene heterostructures and unlock its hydrogen evolution reaction capabilities.

The two-dimensional (2D) metallic phase of MoS2, 1T-MoS2, has extraordinary electrical conductivity in contrast to the common 2D semiconducting phase, 2H-MoS2. However, the thermodynamic instabilities of 1T-MoS2 hinder its application. In this work, we investigate the possibilities of stabilizing 1T-MoS2 through heterostructure design using first-principles calculations. We found that MXene-based heterostructures could hamper phase transitions from 1T-MoS2 to 2H-MoS2 enabled by a larger phase transition kinetic energy barrier. Based on this finding, we propose a general and effective strategy for stabilizing 1T-MoS2, that is, building heterostructures using 1T-MoS2 and oxygen-functionalized MXenes. Besides, we have also observed that due to the occurrence of electron transfer in the heterostructure, 1T-MoS2 in the heterostructure exhibits improved hydrogen adsorption free energy and more active sites compared to the monolayer 1T-MoS2. These findings provide guidance for promoting and developing 1T-MoS2 for practical applications. In addition, the proposed heterostructure design strategy could inspire the study of phase transition behaviors and electrochemical properties of materials using interfaces.

Unraveling the Oxidation Behaviors of MXenes in Aqueous Systems by Active-Learning-Potential Molecular-Dynamics Simulation.

MXenes are 2D materials with great potential in various applications. However, the degradation of MXenes in humid environments has become a main obstacle in their practical use. Here we combine deep neural networks and an active learning scheme to develop a neural network potential (NNP) for aqueous MXene systems with ab initio precision but low cost. The oxidation behaviors of super large aqueous MXene systems are investigated systematically at nanosecond timescales for the first time. The oxidation process of MXenes is clearly displayed at the atomic level. Free protons and oxides greatly inhibit subsequent oxidation reactions, leading to the degree of oxidation of MXenes to exponentially decay with time, which is consistent with the oxidation rate of MXenes measured experimentally. Importantly, this computational study represents the first exploration of the kinetic process of oxidation of super-sized aqueous MXene systems. It opens a promising avenue for the future development of effective protection strategies aimed at controlling the stability of MXenes.

Surface Rearrangement and Sublimation Kinetics of Supported Gold Nanoparticle Catalysts.

Heterogeneous catalysts consisting of supported metallic nanoparticles typically derive exceptional catalytic activity from their large proportion of undercoordinated surface sites which promote adsorption of reactant molecules. Simultaneously, these high energy surface configurations are unstable, leading to nanoparticle growth or degradation and eventually a loss of catalytic activity. Surface morphology of catalytic nanoparticles is paramount to catalytic activity, selectivity, and degradation rates, however it is well-known that harsh reaction conditions can cause the surface structure to change. Still, limited research has focused on understanding the link between nanoparticle surface facets and degradation rates or mechanisms. Here, we study a model Au supported catalyst system over a range of temperatures using a combination of in situ transmission electron microscopy, kinetic Monte Carlo simulations, and density functional theory calculations to establish an atomistic picture of how variations in surface structures and atomic coordination environments lead to shifting evolution mechanisms as a function of temperature. By combining experimental results, which yield direct observation of dynamic shape changes and particle sublimation rates, with computational techniques, which enable understanding the fundamental thermodynamics and kinetics of nanoparticle evolution, we illustrate a two-step evolution mechanism in which mobile adatoms form through desorption from low-coordination facets and subsequently sublimate off the particle surface. By understanding the role of temperature in the competition between surface diffusion and sublimation, we are able to show how individual atomic movements lead to particle scale morphological changes and rationalize why sublimation rates vary between particles in a system of nearly identical nanoparticles.

Anatomic and MRI bases for medullary infarctions with patients' presentation.

OBJECTIVE: There is a low incidence of the medullary infarctions and sparse data about the vascular territories, as well as a correlation among the anatomic, magnetic resonance imaging (MRI) and neurologic signs. MATERIALS AND METHODS: Arteries of the 10 right and left sides of the brain stem were injected with India ink, fixed in formalin and microdissected. The enrolled 34 patients with medullary infarctions underwent a neurologic, MRI and Doppler examination. RESULTS: Four types of the infarctions were distinguished according to the involved vascular territories. The isolated medial medullary infarctions (MMIs) were present in 14.7%. The complete MMIs comprised one bilateral infarction (2.9%), whilst the incomplete and partial MMIs were observed in 5.9% and 8.9%, respectively. The anterolateral infarctions (ALMIs) were very rare (2.9%). The complete and incomplete lateral infarctions (LMIs), noted in 35.3%, comprised 11.8% and 23.6%, respectively, that is, the anterior (5.9%), posterior (8.9%), deep (2.9%), and peripheral (5.9%). Dorsal ischemic lesions (DMIs) occurred in 11.8%, either as a complete (2.9%), or isolated lateral (5.9%) or medial infarctions (2.9%). The remaining ischemic regions belonged to various combined infarctions of the MMI, ALMI, LMI and DMI (35.3%). The infarctions most often affected the upper medulla (47.1%), middle (11.8%), or both (29.5%). Several motor and sensory signs were manifested following infarctions, including vestibular, cerebellar, ocular, sympathetic, respiratory and auditory symptoms. CONCLUSIONS: There was a good correlation among the vascular territories, MRI ischemia features, and neurologic findings regarding the medullary infarctions.

The Effect of Fe Dopant Location in Co(Fe)OOHx Nanoparticles for the Oxygen Evolution Reaction.

The addition of iron (Fe) can in certain cases have a strong positive effect on the activity of cobalt and nickel oxide nanoparticles in the electrocatalytic oxygen evolution reaction (OER). The reported optimal Fe dopant concentrations are, however, inconsistent, and the origin of the increased activity due to Fe dopants in mixed oxides has not been identified so far. Here, we combine density functional theory calculations, scanning tunneling microscopy, and OER activity measurements on atomically defined Fe-doped Co oxyhydroxide nanoparticles supported on a gold surface to establish the link between the activity and the Fe distribution and concentration within the oxyhydroxide phase. We find that addition of Fe results in distinct effects depending on its location on edge or basal plane sites of the oxyhydroxide nanoparticles, resulting in a nonlinear OER activity as a function of Fe content. Fe atom substitution itself does not lead to intrinsically more active OER sites than the best Co sites. Instead, the sensitivity to Fe promoter content is explained by the strong preference for Fe to locate on the most active edge sites of oxyhydroxide nanoparticles, which for low Fe concentrations stabilizes the particles but in higher concentrations leads to a shell structure with less active Fe on all edge positions. The optimal Fe content thereby becomes dependent on nanoparticle size. Our findings demonstrate that synthesis strategies that adjust not only the Fe concentration in mixed oxides but also its distribution within a catalyst nanoparticle can lead to enhanced OER performance.

Surface stability of perovskite oxides under OER operating conditions: a first principles approach.

The activity-stability conundrum has long been the Achilles' heel in the design of catalysts, in particular, for electrochemical reactions such as water splitting. Here, we use ab initio thermodynamics to delineate the surface stoichiometry of a group of perovskite oxides with different activities towards the oxygen evolution reaction (OER), in order to get a measure of their stability under OER operating conditions. In particular, we compare the surface stability of SrIrO3, SrRuO3 and SrTiO3, establishing atomistic insights into the stability and dissolution of these oxide surfaces.

2H-MoS2 on Mo2CTx MXene Nanohybrid for Efficient and Durable Electrocatalytic Hydrogen Evolution.

The development of highly efficient and durable earth-abundant hydrogen evolution reaction (HER) catalysts is crucial for the extensive implementation of the hydrogen economy. Members of the 2D MXenes family, particularly Mo2CTx, have recently been identified as promising HER catalysts. However, their inherent oxidative instability in air and aqueous electrolyte solutions is hindering their widespread use. Herein, we present a simple and scalable method to circumvent adventitious oxidation in Mo2CTx MXenes via in situ sulfidation to form a Mo2CTx/2H-MoS2 nanohybrid. The intimate epitaxial coupling at the Mo2CTx/2H-MoS2 nanohybrid interface afforded superior HER activities, requiring only 119 or 182 mV overpotential to yield -10 or -100 mA cm-2geom current densities, respectively. Density functional theory calculations reveal strongest interfacial adhesion was found within the nanohybrid structure as compared to the physisorbed nanohybrid, and the possibility to tune the HER overpotential through manipulating the extent of MXene sulfidation. Critically, the presence of 2H-MoS2 suppresses further oxidation of the MXene layer, enabling the nanohybrid to sustain industrially relevant current densities of over -450 mA cm-2geom with exceptional durability. Less than 30 mV overpotential degradation was observed after 10 continuous days of electrolysis at a fixed -10 mA cm-2geom current density or 100,000 successive cyclic voltammetry cycles. The exceptional HER durability of the Mo2CTx/2H-MoS2 nanohybrid presents a major step forward to realize practical implementation of MXenes as noble metal free catalysts for broad-based applications in water splitting and energy conversion.

Role of Undercoordinated Sites for the Catalysis in Confined Spaces Formed by Two-Dimensional Material Overlayers.

Adding a two-dimensional (2D) overlayer on a metal surface is a promising route for activating reactants confined in the interfacial space. However, an atomistic understanding of the role played by undercoordinated sites of the 2D overlayer in the activation of molecules in this nanoscaled confined space is yet to be developed. In this paper, we study CO dissociation as a prototypical reaction to investigate CO activation in the confined space enclosed by Rh(111) and a monolayer of hexagonal boron nitride (h-BN). The effect of the space size (i.e., the distance between h-BN and the metal surface), the type of undercoordinated sites, and the size of the defect are explicitly studied by density functional theory with dispersion correction. The following temperature-programmed X-ray photoelectron spectroscopy measurement suggests that a small portion of the CO dissociated during the desorption, leaving the residual atomic oxygen incorporated into the h-BN lattice, which validates the theoretical prediction. The combination of theory and experiment calls for further attention to be paid to the role of undercoordinated sites in the 2D overlayers in confined systems forming potential new catalytic environments.

Using nature's blueprint to expand catalysis with Earth-abundant metals.

Numerous redox transformations that are essential to life are catalyzed by metalloenzymes that feature Earth-abundant metals. In contrast, platinum-group metals have been the cornerstone of many industrial catalytic reactions for decades, providing high activity, thermal stability, and tolerance to chemical poisons. We assert that nature's blueprint provides the fundamental principles for vastly expanding the use of abundant metals in catalysis. We highlight the key physical properties of abundant metals that distinguish them from precious metals, and we look to nature to understand how the inherent attributes of abundant metals can be embraced to produce highly efficient catalysts for reactions crucial to the sustainable production and transformation of fuels and chemicals.

Yeast extract demonstrates rapid itch relief in chronic pruritus.

BACKGROUND: Pruritus is the most common complaint encountered in dermatological practice. It is estimated that up to 4% of the world population suffers from chronic itch. Chronic pruritus can be associated with both cutaneous or systemic conditions. While a plethora of treatments attempt to address itch, most carry risk of significant adverse events with chronic use; thus, there exists an unmet need to develop safe treatments for chronic pruritus. A recent study demonstrated that a novel extract from Saccharomyces cerevisiae, that is, Baker's yeast, blocks various histamine receptors as well as inhibits numerous inflammatory cytokines. METHODS: Given the long-term safety profile of Baker's yeast, we set to investigate the efficacy of the novel extract in the treatment of chronic pruritus. KEY RESULTS: In our study, we demonstrated that within 30 minutes, the novel extract significantly reduced itch when compared to a placebo lotion (P = .0020). CONCLUSIONS: To our knowledge, this is the first study demonstrating that a novel extract from Saccharomyces cerevisiae can provide rapid and sustained itch relief to chronic pruritus patients.

Complications of botulinum toxin and fillers: A narrative review.

BACKGROUND: Cosmetic surgery and esthetic procedures have become a billion dollar industry owing to the ever-growing demand of the population to stay young. The injectable treatments including fillers and botulinum toxin have become highly popular because of their quick, predictable and lasting results in the management of facial wrinkles and rejuvenation. Although these treatment modalities are relatively safe, they are associated with certain side effects. AIMS: In this review, we will focus on the complications of fillers and botulinum toxin. PATIENTS/METHODS: The literature research considered published journal articles (clinical trials or scientific reviews). Studies were identified by searching electronic databases (MEDLINE and PubMed) and reference lists of respective articles. Only articles available in English were considered for this review. RESULTS: Brow ptosis and asymmetry are common adverse effects of botulinum toxin while the most common adverse effects associated with fillers are the local injection related effects manifesting as erythema, edema, pain, and ecchymosis. CONCLUSION: It is important that the treating physician is well verse with the various fillers and botulinum toxin complications and their management as some of the complications can be severely debilitating.

Therapeutic options in vitiligo with special emphasis on immunomodulators: A comprehensive update with review of literature.

Vitiligo is a relatively common disorder characterized by areas of depigmented skin. It may be associated with social stigma and adversely affects the quality of life. Although many treatment options are available, none is curable. The search continues for an effective therapeutic option. New targeted options include biologics and other immunomodulatory agents, with varying degrees of evidence. We have discussed briefly the therapeutic options with special emphasis on the newer immunomodulatory agents. We undertook a comprehensive English literature search across multiple databases such as PubMed, SCOPUS, EMBASE, MEDLINE, and Cochrane using keywords (alone and in combination) and MeSH items such as "vitiligo," "treatment," "recent," and "immunomodulators" to obtain several relevant articles, priority being given to prospective randomized controlled trials. We scanned all the relevant articles and summarized them to obtain the latest information about the treatment of this condition to prepare the current article.

Efficacy of topical latanoprost in the treatment of eyelid vitiligo: A randomized, double-blind clinical trial study.

Numerous studies have demonstrated that the pigmentation of iris and around the eyelid is a common side effect of latanoprost, a prostaglandin F2alpha analogue used in the treatment of glaucoma. Hence, the authors decided to study the effectiveness of topical latanoprost on vitiligo patches around the eyelid. In this randomized, double-blind, clinical trial study, 31 patients with vitiligo vulgaris and focal vitiligo involving the eyelids were evaluated. Patients were randomly divided into two groups. First group received topical latanoprost gel twice daily for 12 weeks, whereas the second group received placebo with the same protocol. To evaluate severity of the disease the VIDA rating system was used. Serial photos of the patches were taken to compare and evaluate the repigmentation percentage of the patches. The patients in both groups had almost similar VIDA score (p > .05). First group showed improved pigmentation, whereas participants in the second group did not show any improvement in the pigmentation. The group treated with latanoprost showed significant reduction in the symptoms of the disease, whereas those treated with placebo did not show any alteration (p > .05). No significant complications were observed in either groups. Latanoprost proved effective in treating vitiligo disease involving eyelids.

Clinical updating study at 3 years on 278 patients treated by modern artificial hair implant technique (automatic biofibre®).

In this study, we report our multicentric experience of synthetic medical certified polyamide hair implants in male androgenetic, female menopausal, and chronic alopecia. Biofibre hair implantation was performed by means of a standardized, mini-invasive technique followed by regular postoperative care along 3 years. From May 2015, 278 patients were enrolled and 253 completed the trial; 202 men (79.9%) versus 51 women (20,1%). The average age was 43(± 4.29); 179 patients (70.1%) had taken previous treatments for alopecia. We evaluated efficacy (as judged by Hamilton scale grading, covered area percent, surgeon, and patient's subjective evaluation) and safety (as judged by adverse events). The overall scalp surface restored with artificial hair (mm2 spaced) and pre-postoperative general customers' satisfaction (by Hamilton scale grading) are reported, showing a significant (98,14%) subjective and objective improvement of the self-image. Twenty-two cases (8.75%) declared minor side effects generally counteracted by topical or short course systemic antibiotic and anti-inflammatory treatment. The average number of implanted fibers was 2,295 (SD 2.805; SE 200.9) ranging from 300 to 16,000. The average duration of pain and tenderness at the implant area was 2.2 days (SD 4.096; SE 0.2933) ranging from 1 to 20 days. A diagrammatic comparison of the Hamilton scale grading before and after the trial showed a dramatic improvement with the majority of the patients being in Hamilton grade II after implantation.

Autologous Fat Graft: Not Only an Aesthetic Solution.

Subcutaneous adipose tissue was defined as the "perfect filler" as is soft and malleable and is usually enough present in the body for correcting volume defects and small remodelling purposes. The first attempts to implant autologous adipose tissue dates back to the end of the twentieth century, and with the refinement of harvesting, processing and replanting techniques today a uniform and predictable amount of survival rate were achieved. Those improvements have led to wider use of autologous fat grafts in many medical specialities not only in aesthetic or reconstructive treatments.

Immunocompromised Districts of Skin: A Case Series and a Literature Review.

BACKGROUND: The concept of immunocompromised districts of skin has been developed by Ruocco and helps to explain certain aspects of the macromorphology of skin diseases. This concept unites the isomorphic response of Koebner and the isotopic response of Wolf. CASE REPORTS: We present different cutaneous conditions which can lead to immunocompromised districts of skin such as scars, radiodermatitis, lymphedema, disturbed innervation or mechanical friction etc. Typical and rarer skin disorders associated with them are discussed and illustrated by their observations. CONCLUSION: At this moment, we wish to inform dermatologists and non-dermatologists about Ruocco's concept and its implications.

Botulin Toxin Use in Scars/Keloids Treatment.

Botulinum toxin (BTX) is a neurotoxin protein derived from the Clostridium botulinum bacterium that inhibits the release of acetylcholine at the neuromuscular junction level whose effects has been used for many years to treat a variety of muscular/neuromuscular conditions and more recently also for cosmetic use. BTX has experimented in some dermatological conditions which include scar prevention and treatment with good results The complex mechanism underlying those results is not completely understood but several mechanisms were proposed release inhibition of different substances like (TGF)-ß, substance P, calcitonin gene-related peptide (CGRP) and glutamate thus modulating cutaneous inflammation and wound healing. We analysed the published data on BTX off label applications on scars and keloids retrieved from PubMed.

Cutaneous Angiosarcoma of Head and Neck - A Single-Centre Analysis.

BACKGROUND: Cutaneous angiosarcoma of the head and neck region is a subtype of cutaneous angiosarcoma with an unfavourable prognosis. Diagnosis is often delayed. PATENTS AND METHODS: The setting is an Academic Teaching Hospital Skin Cancer Center. Eight Caucasian patients could be identified, 5 men and 3 women. Delay to diagnosis was between 12 to 4 months (mean 7.8 ± 2.9 months). The diagnosis was confirmed in all cases by histopathology and immunohistochemistry. Hematoxylin-eosin, Giemsa, PAS, iron and reticulin stains were performed. Endothelial markers such as CD31, CD34, and Ki67 for proliferation assessment were used in all tumours. Other markers used included pan-cytokeratin (CK), CK7, CK20, ERG, CD 40 and c-MYC. Tumours were classified as localised versus multifocal or diffuse form. Tumour staging was performed according to the 8th edition of the AJCC. The mean age of patients was 79 years ± 26.4 years. The male to female ratio was 1.7. Tumour classification was diffuse in 2 patients, multilocular in one and localised in 5 patients. In 5 of 8 patients, a multimodal treatment was performed, one had radiotherapy alone, in another patient surgery was performed, and radiotherapy is planned. The mean OS was 26.4 months ± 24.5 months. CONCLUSION: Cutaneous angiosarcoma of the head and neck is an aggressive tumour with a poor prognosis. Although surgery remains a cornerstone of treatment, the tumour size at first presentation may be too large, and the elderly patients maybe not suitable for extensive surgery. Therefore, multimodal treatment with adjuvant radiotherapy and/ or chemotherapy is necessary. Multimodal treatment offers a better outcome than radiotherapy or chemotherapy alone. Stealth liposomal encapsulated doxorubicin is a therapeutic option for elderly patients with improved safety compared to conventional doxorubicin.