Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We ...found that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes allow unimpeded permeation of water (H₂0 permeates through the membranes at least 10¹⁰ times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two-dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water.
In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We ...report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies.
Introduction Increased physical activity and functional ability are the goals of total knee replacement surgery. Therefore, adequate rehabilitation is required for the recovery of patients after ...discharge from hospital following total knee arthroplasty (TKA). This systematic literature review aimed to evaluate the effectiveness of home telerehabilitation in patients who underwent TKA. Methods Studies published in the English language between 2000 and 2014 were retrieved from Embase, PubMed, and Cochrane databases using relevant search strategies. Two researchers independently reviewed the studies as per the Cochrane methodology for systematic literature review. We considered telerehabilitation sessions as those that were conducted by experienced physiotherapists, using videoconferencing to patients' homes via an internet connection. The outcomes assessed included: knee movement (knee extension and flexion); quadriceps muscle strength; functional assessment (the timed up-and-go test); and assessment of pain, stiffness, and functional capacity using the Western Ontario and McMaster Universities Osteoarthritis Index and visual analogue scale for pain. Results In total, 160 potentially relevant studies were screened. Following the screening of studies as abstracts and full-text publications, six primary publications (four randomized controlled trials, one non-randomized controlled trial, and one single-arm trial) were included in the review. Patients experienced high levels of satisfaction with the use of telerehabilitation alone. There was no significant difference in change in active knee extension and flexion in the home telerehabilitation group as compared to the control group (mean difference (MD) -0.52, 95% CI -1.39 to 0.35, p = 0.24 and MD 1.14, 95% CI -0.61 to 2.89, p = 0.20, respectively). The patients in the home telerehabilitation group showed improvement in physical activity and functional status similar to patients in the conventional therapy group. Discussion The evidence from this systematic literature review demonstrated that telerehabilitation is a practical alternative to conventional face-to-face rehabilitation therapy in patients who underwent TKA.
Graphene-based materials can have well-defined nanometer pores and can exhibit low frictional water flow inside them, making their properties of interest for filtration and separation. We investigate ...permeation through micrometer-thick laminates prepared by means of vacuum filtration of graphene oxide suspensions. The laminates are vacuum-tight in the dry state but, if immersed in water, act as molecular sieves, blocking all solutes with hydrated radii larger than 4.5 angstroms. Smaller ions permeate through the membranes at rates thousands of times faster than what is expected for simple diffusion. We believe that this behavior is caused by a network of nanocapillaries that open up in the hydrated state and accept only species that fit in. The anomalously fast permeation is attributed to a capillary-like high pressure acting on ions inside graphene capillaries.
There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is ...Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc feminine 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.
Although graphite is known as one of the most chemically inert materials, we have found that graphene, a single atomic plane of graphite, can react with atomic hydrogen, which transforms this highly ...conductive zero-overlap semimetal into an insulator. Transmission electron microscopy reveals that the obtained graphene derivative (graphane) is crystalline and retains the hexagonal lattice, but its period becomes markedly shorter than that of graphene. The reaction with hydrogen is reversible, so that the original metallic state, the lattice spacing, and even the quantum Hall effect can be restored by annealing. Our work illustrates the concept of graphene as a robust atomic-scale scaffold on the basis of which new two-dimensional crystals with designed electronic and other properties can be created by attaching other atoms and molecules.
Graphene is increasingly explored as a possible platform for developing novel separation technologies. This interest has arisen because it is a maximally thin membrane that, once perforated with ...atomic accuracy, may allow ultrafast and highly selective sieving of gases, liquids, dissolved ions and other species of interest. However, a perfect graphene monolayer is impermeable to all atoms and molecules under ambient conditions: even hydrogen, the smallest of atoms, is expected to take billions of years to penetrate graphene's dense electronic cloud. Only accelerated atoms possess the kinetic energy required to do this. The same behaviour might reasonably be expected in the case of other atomically thin crystals. Here we report transport and mass spectroscopy measurements which establish that monolayers of graphene and hexagonal boron nitride (hBN) are highly permeable to thermal protons under ambient conditions, whereas no proton transport is detected for thicker crystals such as monolayer molybdenum disulphide, bilayer graphene or multilayer hBN. Protons present an intermediate case between electrons (which can tunnel easily through atomically thin barriers) and atoms, yet our measured transport rates are unexpectedly high and raise fundamental questions about the details of the transport process. We see the highest room-temperature proton conductivity with monolayer hBN, for which we measure a resistivity to proton flow of about 10 Ω cm(2) and a low activation energy of about 0.3 electronvolts. At higher temperatures, hBN is outperformed by graphene, the resistivity of which is estimated to fall below 10(-3) Ω cm(2) above 250 degrees Celsius. Proton transport can be further enhanced by decorating the graphene and hBN membranes with catalytic metal nanoparticles. The high, selective proton conductivity and stability make one-atom-thick crystals promising candidates for use in many hydrogen-based technologies.
The worldwide incidence trends of the lip, oral cavity, and pharyngeal cancers (LOCPs) need to be updated. This study aims to examine the temporal incidence trends of LOCPs from 1990 to 2017, using ...the latest Global Burden of Disease (GBD) study data to explore sex, age, and regional differences. GBD incidence data for LOCPs were driven by population cancer registries and were estimated from mortality data. Age-standardized incidence rates (ASIRs) were directly extracted from the 2017 GBD database to calculate the estimated annual percentage change (EAPC) over the study period. Incidence trends are mapped and compared separately by sex (females vs. males), age groups (15–49, 50–69, and 70+ y), regions (21 geographical and 5 sociodemographic regions), and countries. Among 678,900 incident cases of LOCPs notified in 2017, more than half were lip and oral cavity cancers. From 1990 to 2017, the estimated global incidence for nasopharyngeal cancers decreased dramatically (EAPC = −1.52; 95% confidence interval CI, –1.70 to −1.34), while the incidence for lip and oral cavity cancers (EAPC = 0.26; 95% CI, 0.16–0.37) and other pharyngeal cancers (EAPC = 0.62; 95% CI, 0.54–0.71) increased. Higher ASIRs were observed among males than females across all age groups. However, females had larger EAPC variation when compared to males. Population groups aged 15 to 49 y presented the lowest ASIRs, with larger values of EAPC than those aged 50 to 69 and 70+ y. While high-income countries had higher ASIRs with little EAPC variation, ASIRs varied across low/middle-income regions with larger EAPC variations. South Asia and East Asia had the highest ASIRs and EAPC for lip and oral cavity cancers, respectively. In conclusion, the global incidence of LOCPs has increased among females, those aged 15 to 49 y, and people from low/middle-income countries over the study period, excepting nasopharyngeal cancers, which had a decreasing worldwide trend.
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