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We report a morbidly obese 72-year-old man admitted with acute right-sided chest pain and hypoxemia following bouts of vigorous coughing. This case illustrates the need to consider unusual etiologies of a common clinical presentation.

Single-layer h-BN is known to have edges with unique magnetism; however, in the commonly fabricated multilayer AA′-h-BN, edge relaxations occur that create interlayer bonds and eliminate the unpaired electrons at the edge. Recently, a robust method of growing the unconventional Bernal-stacked h-BN (AB-h-BN) has been reported. Here, we use theoretical approaches to investigate the nitrogen-terminated zigzag edges in AB-h-BN that can be formed in a controlled fashion using a high-energy electron beam. We find that these "open"edges remain intact in bilayer and multilayer AB-h-BN, enabling researchers potentially to investigate these edge states experimentally. We also investigate the thermodynamics of the spin configurations at the edge by constructing a lattice model that is based on parameters extracted from a set of first-principles calculations. We find that the edge spins in neighboring layers interact very weakly, resulting in a sequence of independent spin chains in multilayer samples. By solving this model using Monte Carlo simulations, we can determine nm-scale correlation lengths at liquid-N2 temperatures and lower. At low temperatures, these edges may be utilized in magnetoresistance and spintronics applications.

Controlling the size and shape of nanopores in two-dimensional materials is a key challenge in applications such as DNA sequencing, sieving, and quantum emission in artificial atoms. We here experimentally and theoretically investigate triangular vacancies in (unconventional) Bernal-stacked AB-h-BN formed using a high-energy electron beam. Due to the geometric configuration of AB-h-BN, triangular pores in different layers are aligned, and their sizes are controlled by the duration of the electron irradiation. Interlayer covalent bonding at the vacancy edge is not favored, as opposed to what occurs in the more common AA′-stacked BN. A variety of monolayer, concentric, and bilayer pores in the bilayer AB-h-BN are observed in high-resolution transmission electron microscopy and characterized using ab initio simulations. Bilayer pores in AB-h-BN are commonly formed and grow without breaking the bilayer character. Nanopores in AB-h-BN exhibit a wide range of electronic properties, ranging from half-metallic to non-magnetic and magnetic semiconductors. Therefore, because of the controllability of the pore size, the electronic structure is also highly controllable in these systems and can potentially be tuned for particular applications.

Carbon has numerous one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) allotropic structures. The study of carbon materials has long been a major focus of material sciences and condensed matter physics. Recently, a number of topological semi-metallic carbon allotropes with vastly different topological phases have been predicted from first-principles, showing exceptionally clean and robust topological properties near the Fermi surfaces. In this review, we provide a brief summary of the development of carbon allotropes from 1D to 3D. Then, we discuss topological properties of pure carbon materials, despite their exceedingly small spin–orbit coupling. Instead, the nearest-neighbor p z orbit interaction has been identified as the origin for the non-trivial topological properties, which vary due to different p z connectivity:​ zigzag, armchair, or pentagonal, as well as the interactions among further neighboring atoms. Next, we consider possible expansions of the topological properties of carbon materials to other light-element materials such as boron. Finally, we discuss future prospects in light of experimental feasibility and the recent surge in pursue of exotic carbon physics due to twisted graphene, which may also be viewed as a subset of the topological physics involving sp 2 /p z carbon.

We present the G0W0 band structure, core levels, and deformation potential of monolayer FeSe in the paramagnetic phase based on a starting mean field of the Kohn-Sham density functional theory (DFT) with the Perdew, Burke, and Ernzerhof functional. We find the GW correction increases the bandwidth of the states forming the M pocket near the Fermi energy, while leaving the Γ pocket roughly unchanged. We then compare the G0W0 quasiparticle band energies with the band structure from a simple empirical +A approach, which was recently proposed to capture the renormalization of the electron-phonon interaction going beyond DFT in FeSe, when used as a starting point in density functional perturbation theory. We show that this empirical correction succeeds in approximating the GW nonlocal and dynamical self-energy in monolayer FeSe and reproduces the GW band structure near the Fermi surface, the core energy levels, and the deformation potential (electron-phonon coupling).

We examine physical properties of heavily boron-doped sp3-hybridized carbon allotropes: cubic diamond, hexagonal diamond, and body centered tetragonal C4. The structural similarity between cubic diamond and hexagonal diamond leads to similar responses to substitutional boron doping. On the other hand, body centered tetragonal C4 exhibits distinct structural and electronic properties because of its characteristic structure. Our study also shows that the superconducting transition temperatures up to 60 K are possible in heavily doped carbon materials despite their various atomistic structures.

We study strong electron-phonon interacting systems where the geometry of the crystalline lattice frustrates the formation of charge order. Our results show that under such condition, high-Tc superconductivity can occur in a wide range of electron-phonon coupling strengths. This result is obtained by studying the Holstein model on triangular lattice using sign-problem-free quantum Monte Carlo method.

We study the effect of atomic coordination (orbital hybridization) on superconducting properties of boron-doped amorphous carbon. The ratio of threefold coordinated (sp2-hybridized) and fourfold coordinated (sp3-hybridized) atoms in the system is found to have an impact on their electronic, vibrational, and superconducting properties. Our findings show that a high proportion of fourfold coordination in both carbon and boron atoms is important for realizing a high superconducting transition temperature.

The quasi-one-dimensional linear chain compound HfTe3 is experimentally and theoretically explored in the few- to single-chain limit. Confining the material within the hollow core of carbon nanotubes allows isolation of the chains and prevents the rapid oxidation which plagues even bulk HfTe3. High-resolution transmission electron microscopy combined with density functional theory calculations reveals that, once the triple-chain limit is reached, the normally parallel chains spiral about each other, and simultaneously a short-wavelength trigonal antiprismatic rocking distortion occurs that opens a significant energy gap. This results in a size-driven metal-insulator transition.

The relative orientation of successive sheets, i.e. the stacking sequence, in layered 2D materials is central to the electronic, thermal, and mechanical properties of the material. Often different stacking sequences have comparable cohesive energy, leading to alternative stable crystal structures. Here we theoretically and experimentally explore different stacking sequences in the van der Waals bonded material hexagonal boron nitride (h-BN). We examine the total energy, electronic bandgap, and dielectric response tensor for five distinct high symmetry stacking sequences for both bulk and bilayer forms of h-BN. Two sequences, the generally assumed AA′ sequence and the relatively unknown (for h-BN) AB (Bernal) sequence, are predicted to have comparably low energy. We present a scalable modified chemical vapor deposition method that produces large flakes of virtually pure AB stacked h-BN; this new material complements the generally available AA′ stacked h-BN.

We propose insulating titanium oxynitrides TinN2O2n-3 as promising water-splitting photocatalytic materials in the visible light range. Using first-principles many-body perturbation theory based on the GW approximation, we show that corundum-type Ti2N2O (an example TinN2O2n-3 compound with n=2) has a smaller band gap of about 2.5 eV, which is more suitable to absorb visible light, compared to other Ti-based oxides such as TiO2 and SrTiO3 with a band gap of more than 3 eV. Band-gap reduction in Ti2N2O is caused by an upward shift of the valence band (negative shift to the oxidation potential of H2O to O2) due to the presence of nitrogen 2p states. The conduction band is dominated by Ti 3d states and the conduction-band minimum is nearly unchanged. As a result, the band-edge potentials of Ti2N2O are better aligned to the water reduction and oxidation levels. Our theoretical predictions provide useful insights for the discovery of efficient visible-light-driven photocatalysts for water splitting.

We report investigation of the geometry and electronic structure of iridium atoms adsorbed onto graphene through a combined experimental and theoretical study. Ir atoms were deposited onto a flake of graphene on a Pt(111) surface and found to form clusters even at low temperatures. The areal density of the observed clusters on the graphene flake suggests the clusters are most likely pairs of Ir atoms. Theoretical ab initio density functional (DFT) calculations indicate that these Ir dimers are oriented horizontally, near neighboring "bridge" sites of the graphene lattice, as this configuration has the strongest adsorption energy of all high-symmetry configurations for the Ir dimer. A large peak in the local density of states (LDOS) at the Dirac point energy was measured via scanning tunneling spectroscopy, and this result is reproduced by a DFT calculation of the LDOS. The peak at the Dirac point energy is found to be from the Ir s and p states. The LDOS in the monomer case was also calculated, and is found to significantly differ from the experimentally determined data, further supporting the hypothesis of low-temperature clustering.

Repeated impact of foreign bodies on laminated composites may give rise to delamination damage. In this paper, experimental information is employed to formulate a growth law for delamination damage in terms of the impact energy per impact and number of impacts. The growth of regions of delamination is considered a stochastic problem, and hence the growth law is placed in a probabilistic setting by considering the evolution of a probability density function of delamination damage as the number of impacts increases. For a specific number of impacts, this formulation is used to determine the probability of a delamination in a selected range of delamination sizes. The formulation has been extended to include the effect of probability of detection as well as the effect of variable impact energy according to a probability density function. Finally, random variation of impact location is taken into account by the equivalent effect of a discrete probability function for the number of impacts at a fixed location. [ABSTRACT FROM PUBLISHER]

Take control of your samples before they take control of you. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To compare the effectiveness of exercise therapy aimed at restoring neuromuscular control mechanisms at the shoulder with other conservative interventions for the treatment of chronic shoulder pain with and without accompanying stiffness. DESIGN: Randomized control trial. Patients: A total of 138 volunteers with unilateral shoulder pain of local mechanical origin. METHODS: Subjects were randomly allocated to receive exercise therapy aimed at restoring dynamic stabilizing mechanisms and muscle co-ordination at the shoulder; or subacromial corticosteroid injection; or a combination of physical modalities and range of motion exercises. Outcome measurements of pain intensity, functional impairment, active range of motion, isometric muscle force and self-assessed improvement were taken at baseline and after 5 weeks of treatment. RESULTS: The mean/median changes in all outcome measurements at 5 weeks indicated that subjects in each treatment group, improved significantly with no difference between the treatment groups. Comparison with an earlier no-treatment trial would suggest that this improvement is greater than that which could be expected by natural recovery. CONCLUSION: Exercise therapy aimed at restoring neuromuscular control, corticosteroid injection and multiple physical modalities and range of motion exercises are equally effective in the short-term treatment of shoulder pain, with exercise therapy and corticosteroid injection being less costly to administer. [ABSTRACT FROM AUTHOR]

Canine and rabbit vascular contractile responses to serotonergic agonists have been used to predict antimigraine efficacy for several antimigraine agents, including sumatriptan. The purpose of the present study was to establish the assumed predictive value of contractile responses in canine and rabbit saphenous veins to contractile efficacy for a series of agonists in human cerebral and coronary arteries and to understand better the receptors mediating such responses. The canine and rabbit saphenous veins contracted similarly (both qualitatively and quantitatively) to series of structurally diverse serotonergic agonists, suggesting that the receptors mediating serotonin-induced contractility in these tissues were similar. In addition, the contractile potency (estimated as EC50 values) for these structurally diverse serotonergic agonists in either the rabbit or canine saphenous vein significantly correlated with contractile potency for these agonists in human cerebral arteries. Thus, to the extent that contractile responsiveness of human cerebral arteries may predict antimigraine agents, contractile responses of the rabbit and/or canine saphenous vein may be useful surrogates for antimigraine efficacy. In addition, the contractile potency for this series of serotonergic agonists in the rabbit and/or canine saphenous vein significantly correlated with contractile potency of these agonists in human coronary arteries. These data suggest that the use of the saphenous vein to identify potent vasoconstrictors will also reveal agents capable of contracting human coronary arteries, a liability for using this approach to evaluate promising antimigraine therapies. [ABSTRACT FROM AUTHOR]

The emergence of newly identified fungal pathogens and the reemergence of previously uncommon fungal diseases is primarily related to increases in the numbers of susceptible persons: people with HIV infection, bone marrow and organ transplant recipients, cancer patients being treated with chemotherapy, critically ill persons, and very low birth weight ( < or = 1500 g) infants. These immunocompromised populations are at risk for infection not only with opportunistic pathogens (for example, Pneumocystis, Candida, Cryptococcus, Trichosporon, Malassezia, Aspergillus, Penicillium marneffei, and numerous other moulds or yeasts) but also with fungal pathogens that usually infect otherwise healthy persons not previously exposed to endemic fungi (for example, Coccidioides immitis, Histoplasma capsulatum, and Blastomyces dermatitidis) and Sporothrix schenckii. Morbidity, mortality, and health care costs associated with fungal infections are high. Addressing the emergence of fungal diseases will require increased surveillance coupled with the availability of rapid, noninvasive diagnostic tests; monitoring the development of resistance to antifungal agents; and research focused on the understanding, prevention, and control of fungal infections. [ABSTRACT FROM AUTHOR]

It's a clinical Catch-22: More and more powerful agents are needed for treatment -- yet such treatment itself selects out more and more resistant strains of pathogens. Can this dangerous cycle be stopped? [ABSTRACT FROM AUTHOR]

An introduction to blogs may help take the fear out of the blogosphere. [ABSTRACT FROM AUTHOR]

New guidelines and a multidisciplinary approach have the potential to help patients in need while minimising inappropriate use of opioids. [ABSTRACT FROM AUTHOR]

When facing the pain of a malpractice lawsuit, physicians need the compassion and support of their colleagues. [ABSTRACT FROM AUTHOR]