Interactions between 2D materials and living matter: a review on graphene and hexagonal boron nitride coatings

Two-dimensional material (2DM) coatings exhibit complex and controversial interactions with biological matter, having shown in different contexts to induce bacterial cell death and contribute to mammalian cell growth and proliferation in vitro and tissue differentiation in vivo. Although several reports indicate that the morphologic and electronic properties of the coating, as well as its surface features (e.g., crystallinity, wettability, and chemistry), play a key role in the biological interaction, these kinds of interactions have not been fully understood yet. In this review, we report and classify the cellular interaction mechanisms observed in graphene and hexagonal boron nitride (hBN) coatings. Graphene and hBN were chosen as study materials to gauge the effect of two atomic-thick coatings with analogous lattice structure yet dissimilar electrical properties upon contact with living matter, allowing to discern among the observed effects and link them to specific material properties. In our analysis, we also considered the influence of crystallinity and surface roughness, detailing the mechanisms of interaction that make specific coatings of these 2DMs either hostile toward bacterial cells or innocuous for mammalian cells. In doing this, we discriminate among the material and surface properties, which are often strictly connected to the 2DM production technique, coating deposition and post-processing method. Building on this knowledge, the selection of 2DM coatings based on their specific characteristics will allow to engineer desired functionalities and devices. Antibacterial coatings to prevent biofouling, biocompatible platforms suitable for biomedical applications (e.g., wound healing, tissue repairing and regeneration, and novel biosensing devices) could be realized in the next future. Overall, a clear understanding on how the 2DM coating's properties may modulate a specific bacterial or cellular response is crucial for any future innovation in the field.AC acknowledges the support of the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement no. 71364

Strain-modulated optical response in 2D MoSe2 made by Na-assisted CVD on glass

Extended investigations on 2D transition metal dichalcogenides (TMDCs) have opened sound possibilities to apply these materials in several technological fields such as sensing. To this end, fully reproducible methods for the wafer-scale production of crystalline and uniform 2D TMDCs are in demand. In this work, atomically thin MoSe2 was grown by atmospheric-pressure chemical vapor deposition using the Na-assisted process with Se powder and Mo foil precursors on a glass substrate. The samples were extensively characterized via Raman and photoluminescence spectroscopy, atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy. The MoSe2 samples consist of submillimeter, monolayer single-crystals with 2H phase configuration. Being monolayer and crystalline, the samples exhibit well-defined and intense photoluminescence. CVD-grown 2D MoSe2 was integrated into a device with strain-tunable optical properties and tested. Under tensile strain (in the range of 0.2%–0.4%), the spectral emission responded to an in-plane strain with marked peak shifts toward lower energies for increasing levels of strain (∼3 and ∼2 nm shift for the main PL component at 0.2% and 0.4%, respectively), indicating a reduction of the bandgap.We acknowledge the financial support of the project “GEMIS—Graphene-enhanced Electro Magnetic Interference Shielding” with Reference No. POCI-01-0247-FEDER-045939, co-funded by COMPETE 2020—Operational Programme for Competitiveness and Internationalization and FCT—Science and Technology Foundation, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund. This work was supported by FCT, through IDMEC-Mechanical Engineering Institute, under LAETA-Associate Laboratory of Energy, Transports and Aeronautics, Project No. UIDB/50022/2020 and via the Strategic Funding UIDB/04650/2020. We thank Dr. S. Sadewasser and Mr. B. Baumgartner for their assistance in preliminary experiments

Surrogacy Among Filipinos Who Have Struggled With Infertility: A Discourse Analysis

Surrogacy continues to be practiced to address infertility in the Philippines; however, discussions on the method are sparse, given its limited accessibility and morally questionable procedures that may concern potential parents in a developing country. Using discourse analysis, the researchers interviewed ten (10) Filipino Roman Catholics who were struggling with infertility, to uncover how they construct the idea of surrogacy. The study shows the discourses on surrogacy are often approached in a detached manner, where potential parents describe the method as a last choice or one that is never considered. They articulate this position by highlighting the emotional factors surrogacy would entail; the women, in particular, described the involvement of another individual as “taking over” the role of the mother. Participants placed themselves in positions of both power and vulnerability, reconciling the split between surrogacy as a compassionate act or a transactional business. The ambiguous role of faith was also negotiated by the participants, where they argued for surrogacy using alternative teachings or through God-given “free will”. The discourses present considerations for the continued practice of surrogacy among key players in reproductive health in developing countries, recognizing the concerns of infertile couples to enable informed decision-making and policy creation

Unsupervised machine learning approaches to the qq-state Potts model

In this paper with study phase transitions of the $q$-state Potts model, through a number of unsupervised machine learning techniques, namely Principal Component Analysis (PCA), $k$-means clustering, Uniform Manifold Approximation and Projection (UMAP), and Topological Data Analysis (TDA). Even though in all cases we are able to retrieve the correct critical temperatures $T_c(q)$, for $q = 3, 4$ and $5$, results show that non-linear methods as UMAP and TDA are less dependent on finite size effects, while still being able to distinguish between first and second order phase transitions. This study may be considered as a benchmark for the use of different unsupervised machine learning algorithms in the investigation of phase transitions.Comment: Added computation of critical exponents; exposition improve

Renewal processes and fluctuation analysis of molecular motor stepping

We model the dynamics of a processive or rotary molecular motor using a renewal processes, in line with the work initiated by Svoboda, Mitra and Block. We apply a functional technique to compute different types of multiple-time correlation functions of the renewal process, which have applications to bead-assay experiments performed both with processive molecular motors, such as myosin V and kinesin, and rotary motors, such as F1-ATPase

Self-organized network evolution coupled to extremal dynamics

The interplay between topology and dynamics in complex networks is a fundamental but widely unexplored problem. Here, we study this phenomenon on a prototype model in which the network is shaped by a dynamical variable. We couple the dynamics of the Bak-Sneppen evolution model with the rules of the so-called fitness network model for establishing the topology of a network; each vertex is assigned a fitness, and the vertex with minimum fitness and its neighbours are updated in each iteration. At the same time, the links between the updated vertices and all other vertices are drawn anew with a fitness-dependent connection probability. We show analytically and numerically that the system self-organizes to a non-trivial state that differs from what is obtained when the two processes are decoupled. A power-law decay of dynamical and topological quantities above a threshold emerges spontaneously, as well as a feedback between different dynamical regimes and the underlying correlation and percolation properties of the network.Comment: Accepted version. Supplementary information at http://www.nature.com/nphys/journal/v3/n11/suppinfo/nphys729_S1.htm

Genome of Mycoplasma haemofelis, unraveling its strategies for survival and persistence

Mycoplasma haemofelis is a mycoplasmal pathogen (hemoplasma) that attaches to the host's erythrocytes. Distributed worldwide, it has a significant impact on the health of cats causing acute disease and, despite treatment, establishing chronic infection. It might also have a role as a zoonotic agent, especially in immunocompromised patients. Whole genome sequencing and analyses of M. haemofelis strain Ohio2 was undertaken as a step toward understanding its survival and persistence. Metabolic pathways are reduced, relying on the host to supply many of the nutrients and metabolites needed for survival. M. haemofelis must import glucose for ATP generation and ribose derivates for RNA/DNA synthesis. Hypoxanthine, adenine, guanine, uracil and CMP are scavenged from the environment to support purine and pyrimidine synthesis. In addition, nicotinamide, amino acids and any vitamins needed for growth, must be acquired from its environment. The core proteome of M. haemofelis contains an abundance of paralogous gene families, corresponding to 70.6% of all the CDSs. This "paralog pool" is a rich source of different antigenic epitopes that can be varied to elude the host's immune system and establish chronic infection. M. haemofelis also appears to be capable of phase variation, which is particularly relevant to the cyclic bacteremia and persistence, characteristics of the infection in the cat. The data generated herein should be of great use for understanding the mechanisms of M. haemofelis infection. Further, it will provide new insights into its pathogenicity and clues needed to formulate media to support the in vitro cultivation of M. haemofelis

New applanation tonometer for myopic patients after laser refractive surgery

Ajuts: MI received a personal research grant from the Catalonian Ophthalmology Society 2016-2018 Barcelona, Spain. This society played no role in the design or conduct of this research.This study assesses the agreement between intraocular pressure (IOP) measurements taken with the Goldmann applanation tonometer (GAT) and a new experimental applanation tonometer with a convexly shaped apex (CT) after laser myopic refractive surgery. Two different CT radii (CT1 and CT2) were designed with a finite element analyser, and a prospective double masked study on 102 eyes from 102 patients was carried out. A Bland-Altman plot and intra-class correlation coefficient (ICC) were calculated to assess the agreement between GAT measurements and the measurements of both CT1 and CT2 before and after myopic laser assisted in situ keratomileusis (LASIK; n = 73) and photorefractive keratectomy (PRK; n = 29). We evaluated a subset of two subgroups (n = 36 each) for intra and inter-observer (IA/IE) error. From the whole cohort, the best IOP agreement was observed between GATpre and CT1post surgery: 16.09 ± 2.92 vs 16.42 ± 2.87 (p 0.8 (95% CI) in all cases. CT1 proved more accurate in the LASIK subgroup. In conclusion, our new version of GAT could be used with post-surgery LASIK patients as a more accurate measurement device compared to the current reference tonometer

Folksonomies and clustering in the collaborative system CiteULike

We analyze CiteULike, an online collaborative tagging system where users bookmark and annotate scientific papers. Such a system can be naturally represented as a tripartite graph whose nodes represent papers, users and tags connected by individual tag assignments. The semantics of tags is studied here, in order to uncover the hidden relationships between tags. We find that the clustering coefficient reflects the semantical patterns among tags, providing useful ideas for the designing of more efficient methods of data classification and spam detection.Comment: 9 pages, 5 figures, iop style; corrected typo

On the definition of a unique effective temperature for non-equilibrium critical systems

We consider the problem of the definition of an effective temperature via the long-time limit of the fluctuation-dissipation ratio (FDR) after a quench from the disordered state to the critical point of an O(N) model with dissipative dynamics. The scaling forms of the response and correlation functions of a generic observable are derived from the solutions of the corresponding Renormalization Group equations. We show that within the Gaussian approximation all the local observables have the same FDR, allowing for a definition of a unique effective temperature. This is no longer the case when fluctuations are taken into account beyond that approximation, as shown by a computation up to the first order in the epsilon-expansion for two quadratic observables. This implies that, contrarily to what often conjectured, a unique effective temperature can not be defined for this class of models.Comment: 32 pages, 5 figures. Minor changes, published versio