Graphene, a single layer of graphite, has recently attracted considerable attention owing to its remarkable electronic and structural properties and its possible applications in many emerging areas such as graphene-based electronic devices. The charge carriers in graphene behave like massless Dirac fermions, and graphene shows ballistic charge transport, turning it into an ideal material for circuit fabrication. However, graphene lacks a bandgap around the Fermi level, which is the defining concept for semiconductor materials and essential for controlling the conductivity by electronic means. Theory predicts that a tunable bandgap may be engineered by periodic modulations of the graphene lattice, but experimental evidence for this is so far lacking. Here, we demonstrate the existence of a bandgap opening in graphene, induced by the patterned adsorption of atomic hydrogen onto the Moiré superlattice positions of graphene grown on an Ir(111) substrate.

Following emergence of the SARS-CoV-2 variant Omicron in November 2021, the dominant BA.1 sub-lineage was replaced by the BA.2 sub-lineage in Denmark. We analysed the first 2,623 BA.2 cases from 29 November 2021 to 2 January 2022. No epidemiological or clinical differences were found between individuals infected with BA.1 versus BA.2. Phylogenetic analyses showed a geographic east-to-west transmission of BA.2 from the Capital Region with clusters expanding after the Christmas holidays. Mutational analysis shows distinct differences between BA.1 and BA.2.

The electron dynamics of the topological surface state on Bi2Se3(111) is investigated by temperature-dependent angle-resolved photoemission. The electron-phonon coupling strength is determined in a spectral region for which only intraband scattering involving the topological surface band is possible. The electron-phonon coupling constant is found to be λ = 0.25(5), more than an order of magnitude higher than the corresponding value for intraband scattering in the noble metal surface states. The stability of the topological state with respect to surface irregularities was also tested by introducing a small concentration of surface defects via ion bombardment. It is found that, in contrast to the bulk states, the topological state can no longer be observed in the photoemission spectra and this cannot merely be attributed to surface defect-induced momentum broadening. PACS numbers: 73.20.At,71.70.Ej, Topological insulators are one of of the most intriguing subjects of current condensed matter physics [1-3]. Despite of their insulating bulk, these materials support metallic edge and surface states with an unconventional spin texture [4,5], electron dynamics [6, 7] and stability. Exploiting these properties is the key to several applications, e. g. in spintronics and quantum computing. Moreover, several novel physical phenomena are predicted in connection with the topological states [8-10].The stable existence of a gap-closing surface state [11][12][13] is a property derived from the bulk band structure of a topological insulator, rather than a mere coincidence. The topological state is also stable in a dynamical sense. A hallmark is the absence of back-scattering near nonmagnetic defects. Edge states in the quantum spin Hall effect, a two-dimensional topological insulator, are completely protected from (elastic) scattering [11] whereas the scattering phase space is strongly reduced for surface states on a three dimensional topological insulator [7,14], preventing localization by weak disorder.The stability of the topological state is essential for many phenomena and applications, however, only a few experimental studies have addressed this issue. Experimental measurements using angle resolved photoemission spectroscopy (ARPES) and scanning tunnelling microscopy (STM) have shown that the topological surface states are robust against a small number of adsorbates [15,16] and detectable at room temperature [15], but other results question their stability with respect to surface scattering processes [17]. Here we determine the electron-phonon (el − ph) coupling strength on the topological insulator Bi 2 Se 3 (111) [18,19]. In the absence of defects, el−ph scattering can be expected to be the dominant scattering mechanism at finite temperature and it is therefore of exceptional importance for any application.We concentrate on the spectral region in which only the topological state exists and thus only intraband scattering is possible and we show that while the el − ph coupling constant λ is of moderate size, it is surprisi...

The field of drug discovery and development has seen tremendous activity over the past decade to better tackle the increasing occurrence of drugresistant bacterial infections and to alleviate some of the pressure we put on the last-resort drugs on the market. One of the new and promising drug candidates is derived from naturally occurring antimicrobial peptides. However, despite promising results in early-stage clinical trials, these molecules have faced some difficulties securing FDA approval, which can be linked to their poor metabolic stability. Hence, mimetics of these antimicrobial peptides have been suggested as new templates for antibacterial compound design, because these mimetics are resistant against degradation by proteases. This review will discuss the structural features of two different types of mimetics, b-peptides and a-peptoids, in relation to their antibacterial activity and conclude on their potential as new candidates for bacterial intervention.

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The limitations of graphene as an effective corrosion-inhibiting coating on metal surfaces, here exemplified by the hex-reconstructed Pt(100) surface, are probed by scanning tunneling microscopy measurements and density functional theory calculations. While exposure of small molecules directly onto the Pt(100) surface will lift the reconstruction, a single graphene layer is observed to act as an effective coating, protecting the reactive surface from O(2) exposure and thus preserving the reconstruction underneath the graphene layer in O(2) pressures as high as 10(-4) mbar. A similar protective effect against CO is observed at CO pressures below 10(-6) mbar. However, at higher pressures CO is observed to intercalate under the graphene coating layer, thus lifting the reconstruction. The limitations of the coating effect are further tested by exposure to hot atomic hydrogen. While the coating can withstand these extreme conditions for a limited amount of time, after substantial exposure, the Pt(100) reconstruction is lifted. Annealing experiments and density functional theory calculations demonstrate that the basal plane of the graphene stays intact and point to a graphene-mediated mechanism for the H-induced lifting of the reconstruction.

In several years after its discovery in the placenta, the human leukocyte antigen (HLA) class Ib protein, HLA-G, was not given much attention, nor was it assigned great importance. As time has unraveled, HLA-G has proven to have distinctive functions and an unforeseen and possibly important role in reproduction. HLA-G is characterized mainly by its low polymorphism and restricted tissue distribution in non-pathological conditions. In fact, its expression pattern is primarily limited to extravillous cytotrophoblast cells at the maternal-fetal interface during pregnancy. Due to low polymorphism, almost the same protein is expressed by virtually all individuals. It is these unique features that make HLA-G differ from its highly polymorphic HLA class Ia counterparts, the HLA-A, -B, and -C molecules. Its function, seemingly diverse, is typically receptor-mediated, and involves interactions with a wide range of immune cells. As the expression of HLA-G primarily is limited to gestation, this has given rise to the hypothesis that HLA-G plays an important role in the immunological tolerance of the fetus by the mother. In keeping with this, it might not be surprising that polymorphisms in the HLA-G gene, and levels of HLA-G expression, have been linked to reproductive failure and pre-eclampsia. Based on recent studies, we speculate that HLA-G might be involved in mechanisms in reproductive immunology even before conception because HLA-G can be detected in the genital tract and in the blood of non-pregnant women, and is present in seminal fluid from men. In addition, HLA-G expression has been found in the pre-implanted embryo. Therefore, we propose that a combined contribution from the mother, the father, and the embryo/fetus is likely to be important. Furthermore, this review presents important aspects of HLA-G in relation to reproduction: from genetics to physiological effects, from pregnancy and pregnancy complications to a short discussion on future possible means of preventative measures and therapy.

The adsorption of polycyclic aromatic hydrocarbon (PAH) molecules on graphitic surfaces provides a model system with which to investigate weak van der Waals (vdW) interactions. There are few experimental investigations of either the interaction between large PAH molecules and graphite or the binding between graphite layers. Determining the adsorption energy in these molecular systems provides a valuable benchmark for validating theoretical methods for implementing van der Waals interactions and, hence, also a means to investigate the interlayer binding in graphite. Here, we investigate the interaction between the coronene molecule and highly oriented pyrolytic graphite by using temperatureprogrammed desorption. We show how entropic effects play an important role in governing the desorption kinetics for large molecules such as coronene and must be taken into account in order to derive a realistic binding energy. DFT calculations demonstrate that the optB88-vdW functional is able to reproduce the experimentally derived binding energy. We use our experimental value to estimate the interlayer binding energy in graphite, considering the effect of intermolecular interactions found in the molecular system. The resulting value is again well reproduced by the optB88-vdW functional, indicating that the optB88-vdW functional is well-suited to describe the interaction between systems dominated by graphitic vdW interactions.