Rack-and-pinion effects in molecular rolling friction

Rolling lubrication with spherical molecules working as 'nanobearings' has failed experimentally so far, without a full understanding of the physics involved and of the reasons why. Past model simulations and common sense have shown that molecules can only roll when they are not too closely packed to jam. The same type of model simulations now shows in addition that molecular rolling friction can develop deep minima once the molecule's peripheral 'pitch' can match the substrate periodicity, much as ordinary cogwheels do in a rack-and-pinion system. When the pinion-rack matching is bad, the driven molecular rolling becomes discontinuous and noisy, whence energy is dissipated and friction is large. This suggests experiments to be conducted by varying the rack-and-pinion matching. That could be pursued not only by changing molecules and substrates, but also by applying different sliding directions within the same system, or by applying pressure, to change the effective matching.Comment: 5 figure

Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes

Nanolaminated materials are important because of their exceptional properties and wide range of applications. Here, we demonstrate a general approach to synthesize a series of Zn-based MAX phases and Cl-terminated MXenes originating from the replacement reaction between the MAX phase and the late transition metal halides. The approach is a top-down route that enables the late transitional element atom (Zn in the present case) to occupy the A site in the pre-existing MAX phase structure. Using this replacement reaction between Zn element from molten ZnCl2 and Al element in MAX phase precursors (Ti3AlC2, Ti2AlC, Ti2AlN, and V2AlC), novel MAX phases Ti3ZnC2, Ti2ZnC, Ti2ZnN, and V2ZnC were synthesized. When employing excess ZnCl2, Cl terminated MXenes (such as Ti3C2Cl2 and Ti2CCl2) were derived by a subsequent exfoliation of Ti3ZnC2 and Ti2ZnC due to the strong Lewis acidity of molten ZnCl2. These results indicate that A-site element replacement in traditional MAX phases by late transition metal halides opens the door to explore MAX phases that are not thermodynamically stable at high temperature and would be difficult to synthesize through the commonly employed powder metallurgy approach. In addition, this is the first time that exclusively Cl-terminated MXenes were obtained, and the etching effect of Lewis acid in molten salts provides a green and viable route to prepare MXenes through an HF-free chemical approach.Comment: Title changed; experimental section and discussion revise

Incidence, prevalence and mortality of bullous pemphigoid in England 1998-2017: a population-based cohort study

BACKGROUND: A rising incidence and high mortality were found for bullous pemphigoid (BP) over a decade ago in the UK. Updated estimates of its epidemiology are required to understand the healthcare needs of an ageing population. OBJECTIVES: To determine the incidence, prevalence and mortality rates of BP in England from 1998 to 2017. METHODS: We conducted a cohort study of longitudinal electronic health records using the Clinical Practice Research Datalink and linked Hospital Episode Statistics. Incidence was calculated per 100 000 person-years and annual point prevalence per 100 000 people. Multivariate analysis was used to determine incidence rate ratios by sociodemographic factors. Mortality was examined in an age-, sex- and practice-matched cohort, using linked Office of National Statistics death records. Hazard ratios (HRs) were stratified by matched set. RESULTS: The incidence was 7·63 [95% confidence interval (CI) 7·35-7·93] per 100 000 person-years and rose with increasing age, particularly for elderly men. The annual increase in incidence was 0·9% (95% CI 0·2-1·7). The prevalence almost doubled over the observation period, reaching 47·99 (95% CI 43·09-53·46) per 100 000 people and 141·24 (95% CI 125·55-158·87) per 100 000 people over the age of 60 years. The risk of all-cause mortality was highest in the 2 years after diagnosis (HR 2·96; 95% CI 2·68-3·26) and remained raised thereafter (HR 1·54; 95% CI 1·36-1·74). CONCLUSIONS: We report a modest increase in the incidence rate of BP, but show that the burden of disease in the elderly population is considerable. Mortality is high, particularly in the first 2 years after diagnosis

Chemical-scissor-mediated structural editing of layered transition metal carbides

Intercalation of non-van der Waals (vdW) layered materials can produce new 2D and 3D materials with unique properties, but it is difficult to achieve. Here, we describe a structural editing protocol for 3D non-vdW layered ternary carbides and nitrides (MAX phases) and their 2D vdW derivatives (MXenes). Gap-opening and species-intercalating stages were mediated by chemical scissors and guest intercalants, creating a large family of layered materials with unconventional elements and structures in MAX phases, as well as MXenes with versatile termination species. Removal of surface terminations by metal scissors and stitching of carbide layers by metal atoms leads to a reverse transformation from MXenes to MAX phases, and metal-intercalated 2D carbides. This scissor-mediated structural editing may enable structural and chemical tailoring of other layered ceramics

Using electronic health records to inform trial feasibility in a rare autoimmune blistering skin disease in England.

BACKGROUND: Trials of novel agents are required to improve the care of patients with rare diseases, but trial feasibility may be uncertain due to concerns over insufficient patient numbers. We aimed to determine the size of the pool of potential participants in England 2015-2017 for trials in the autoimmune blistering skin disease bullous pemphigoid. METHODS: The size of the pool of potential participants was estimated using routinely collected healthcare data from linked primary care (Clinical Practice Research Datalink; CPRD) and secondary care (Hospital Episode Statistics; HES) databases. Thirteen consultant dermatologists were surveyed to determine the likelihood that a patient would be eligible for a trial based on the presence of cautions or contra-indications to prednisolone use. These criteria were applied to determine how they influenced the potential pool of participants. RESULTS: Extrapolated to the population of England, we would expect approximately 10,800 (point estimate 10,747; 95% CI 7191 to 17,239) new cases of bullous pemphigoid to be identified in a three-year period. For a future trial involving oral prednisolone (standard care), the application of cautions to its use as exclusion criteria would result in approximately 365 potential participants unlikely to be recruited, a further 5332 could be recruited with caution, and 5104 in whom recruitment is still possible. 11-17% of potential participants may have pre-existing dementia and require an alternative consent process. CONCLUSIONS: Routinely collected electronic health records can be used to inform the feasibility of clinical trials in rare diseases, such as whether recruitment is feasible nationally and how long recruitment might take to meet recruitment targets. Future trials of bullous pemphigoid in England may use the data presented to inform trial design, including eligibility criteria and consent processes for enrolling people with dementia

Green function techniques in the treatment of quantum transport at the molecular scale

The theoretical investigation of charge (and spin) transport at nanometer length scales requires the use of advanced and powerful techniques able to deal with the dynamical properties of the relevant physical systems, to explicitly include out-of-equilibrium situations typical for electrical/heat transport as well as to take into account interaction effects in a systematic way. Equilibrium Green function techniques and their extension to non-equilibrium situations via the Keldysh formalism build one of the pillars of current state-of-the-art approaches to quantum transport which have been implemented in both model Hamiltonian formulations and first-principle methodologies. We offer a tutorial overview of the applications of Green functions to deal with some fundamental aspects of charge transport at the nanoscale, mainly focusing on applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references, submitted to Springer series "Lecture Notes in Physics

Acquisition of Growth-Inhibitory Antibodies against Blood-Stage Plasmodium falciparum

Background: Antibodies that inhibit the growth of blood-stage Plasmodium falciparum may play an important role in acquired and vaccine-induced immunity in humans. However, the acquisition and activity of these antibodies is not well understood. Methods: We tested dialysed serum and purified immunoglobulins from Kenyan children and adults for inhibition of P. falciparum blood-stage growth in vitro using different parasite lines. Serum antibodies were measured by ELISA to bloodstage parasite antigens, extracted from P. falciparum schizonts, and to recombinant merozoite surface protein 1 (42 kDa Cterminal fragment, MSP1-42). Results: Antibodies to blood-stage antigens present in schizont protein extract and to recombinant MSP1-42 significantly increased with age and were highly correlated. In contrast, growth-inhibitory activity was not strongly associated with age and tended to decline marginally with increasing age and exposure, with young children demonstrating the highest inhibitory activity. Comparison of growth-inhibitory activity among samples collected from the same population at different time points suggested that malaria transmission intensity influenced the level of growth-inhibitory antibodies. Antibodies to recombinant MSP1-42 were not associated with growth inhibition and high immunoglobulin G levels were poorly predictive of inhibitory activity. The level of inhibitory activity against different isolates varied. Conclusions: Children can acquire growth-inhibitory antibodies at a young age, but once they are acquired they do not appear to be boosted by on-going exposure. Inhibitory antibodies may play a role in protection from early childhood malaria

Activity and Enantioselectivity of the Hydroxynitrile Lyase MeHNL in Dry Organic Solvents

Water concentration affects both the enantioselectivity and activity of enzymes in dry organic media. Its influence has been investigated using the hydrocyanation of benzaldehyde catalyzed by hydroxynitrile lyase cross-linked enzyme aggregate (MeHNL-CLEA) as a model reaction. The enzyme displayed higher enantioselectivity at higher water concentration, thus suggesting a positive effect of enzyme flexibility on selectivity. The activity increased on reducing the solvent water content, but drastic dehydration of the enzyme resulted in a reversible loss of activity