Lateral Gene Transfer Drives Metabolic Flexibility in the Anaerobic Methane-Oxidizing Archaeal Family Methanoperedenaceae

Anaerobic oxidation of methane (AOM) is an important biological process responsible for controlling the flux of methane into the atmosphere. Members of the archaeal family Methanoperedenaceae (formerly ANME-2d) have been demonstrated to couple AOM to the reduction of nitrate, iron, and manganese. Here, comparative genomic analysis of 16 Methanoperedenaceace metagenome-assembled genomes (MAGs), recovered from diverse environments, revealed novel respiratory strategies acquired through lateral gene transfer (LGT) events from diverse archaea and bacteria. Comprehensive phylogenetic analyses suggests that LGT has allowed members of the Methanoperedenaceae to acquire genes for the oxidation of hydrogen and formate, and the reduction of arsenate, selenate and elemental sulfur. Numerous membrane-bound multi-heme c type cytochrome complexes also appear to have been laterally acquired, which may be involved in the direct transfer of electrons to metal oxides, humics and syntrophic partners

Web user interface design strategy: Designing for device independence

Until recently, Web services were available only through a desktop web browser. Nowadays, methods of access move beyond the desktop computer towards ubiquitous access through portable devices. As a consequence, users have the chance to interact with a growing diversity of computing devices such as PDAs, smart phones, etc., with diverse characteristics that tend to replace conventional laptop and desktop computers. User interface designers, on the other hand, strive to design usable interfaces to cater for the diverse requirements of these devices. The design strategy proposed in this paper aims at assisting user interface designers in designing for diverse devices recommending a specific line of activities in the process of design. A case study of application of the proposed design strategy is presented, outlining its advantages

The effects of combined micron-/submicron-scale surface roughness and nanoscale features on cell proliferation and differentiation

Titanium (Ti) osseointegration is critical for the success of dental and orthopedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in vivoTitanium (Ti) osseointegration is critical for the success of dental and orthopedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in viv

Reversible, Opto-Mechanically Induced Spin-Switching in a Nanoribbon-Spiropyran Hybrid Material

It has recently been shown that electronic transport in zigzag graphene nanoribbons becomes spin-polarized upon application of an electric field across the nanoribbon width. However, the electric fields required to experimentally induce this magnetic state are typically large and difficult to apply in practice. Here, using both first-principles density functional theory (DFT) and time-dependent DFT, we show that a new spiropyran-based, mechanochromic polymer noncovalently deposited on a nanoribbon can collectively function as a dual opto-mechanical switch for modulating its own spin-polarization. These calculations demonstrate that upon mechanical stress or photoabsorption, the spiropyran chromophore isomerizes from a closed-configuration ground-state to a zwitterionic excited-state, resulting in a large change in dipole moment that alters the electrostatic environment of the nanoribbon. We show that the electronic spin-distribution in the nanoribbon-spiropyran hybrid material can be reversibly modulated via noninvasive optical and mechanical stimuli without the need for large external electric fields. Our results suggest that the reversible spintronic properties inherent to the nanoribbon-spiropyran material allow the possibility of using this hybrid structure as a resettable, molecular-logic quantum sensor where opto-mechanical stimuli are used as inputs and the spin-polarized current induced in the nanoribbon substrate is the measured output.Comment: Accepted by Nanoscal

Topological Nature of Anomalous Hall Effect in Ferromagnet

The anomalous Hall effect in two-dimensional ferromagnets is discussed to be the physical realization of the parity anomaly in (2+1)D, and the band crossing points behave as the topological singularity in the Brillouin zone. This appears as the sharp peaks and the sign changes of the transverse conductance $\sigma_{xy}$ as a function of the Fermi energy and/or the magnetization. The relevance to the experiments including the three dimensional systems is also discussed.Comment: LaTeX 13 pages, 3 figure

Discriminant Analysis and Secondary-Beam Charge Recognition

The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around 124La and 107Sn were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable 124Sn projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods.Comment: 6 pages, 7 eps figures, elsart, submitted to Nucl. Instr. and Meth.

Dirac Nodes and Quantized Thermal Hall Effect in the Mixed State of d-wave Superconductors

We consider the vortex state of d-wave superconductors in the clean limit. Within the linearized approximation the quasiparticle bands obtained are found to posess Dirac cone dispersion (band touchings) at special points in the Brillouin zone. They are protected by a symmetry of the linearized Hamiltonian that we call T_Dirac. Moreover, for vortex lattices that posess inversion symmetry, it is shown that there is always a Dirac cone centered at zero energy within the linearized theory. On going beyond the linearized approximation and including the effect of the smaller curvature terms (that break T_Dirac), the Dirac cone dispersions are found to acquire small gaps (0.5 K/Tesla in YBCO) that scale linearly with the applied magnetic field. When the chemical potential for quasiparticles lies within the gap, quantization of the thermal-Hall conductivity is expected at low temperatures i.e. kappa_{xy}/T = n[(pi k_B)^2/(3h)] with the integer `n' taking on values n=+2, -2, 0. This quantization could be seen in low temperature thermal transport measurements of clean d-wave superconductors with good vortex lattices.Comment: (23 pages in all [7 pages in appendices], 9 figures

The Stellar Mass Distribution in the Giant Star Forming Region NGC 346

Deep F555W and F814W Hubble Space Telescope ACS images are the basis for a study of the present day mass function (PDMF) of NGC346, the largest active star forming region in the Small Magellanic Cloud (SMC). We find a PDMF slope of Gamma=-1.43+/-0.18 in the mass range 0.8-60 Mo, in excellent agreement with the Salpeter Initial Mass Function (IMF) in the solar neighborhood. Caveats on the conversion of the PDMF to the IMF are discussed. The PDMF slope changes, as a function of the radial distance from the center of the NGC 346 star cluster, indicating a segregation of the most massive stars. This segregation is likely primordial considering the young age (~3 Myr) of NGC346, and its clumpy structure which suggests that the cluster has likely not had sufficient time to relax. Comparing our results for NGC346 with those derived for other star clusters in the SMC and the Milky Way (MW), we conclude that, while the star formation process might depend on the local cloud conditions, the IMF does not seem to be affected by general environmental effects such as galaxy type, metallicity, and dust content.Comment: 26 pages, 7 figures, 1 table, accepted for publication in A

Sub‐nanometer thick gold nanosheets as highly efficient catalysts

2D metal nanomaterials offer exciting prospects in terms of their properties and functions. However, the ambient aqueous synthesis of atomically‐thin, 2D metallic nanomaterials represents a significant challenge. Herein, freestanding and atomically‐thin gold nanosheets with a thickness of only 0.47 nm (two atomic layers thick) are synthesized via a one‐step aqueous approach at 20 °C, using methyl orange as a confining agent. Owing to the high surface‐area‐to‐volume ratio, abundance of unsaturated atoms exposed on the surface and large interfacial areas arising from their ultrathin 2D nature, the as‐prepared Au nanosheets demonstrate excellent catalysis performance in the model reaction of 4‐nitrophenol reduction, and remarkable peroxidase‐mimicking activity, which enables a highly sensitive colorimetric sensing of H2O2 with a detection limit of 0.11 × 10−6 m. This work represents the first fabrication of freestanding 2D gold with a sub‐nanometer thickness, opens up an innovative pathway toward atomically‐thin metal nanomaterials that can serve as model systems for inspiring fundamental advances in materials science, and holds potential across a wide region of applications