The closed-edge structure of graphite and the effect of electrostatic charging

The properties of graphite, and of few-layer graphene, can be strongly influenced by the edge structure of the graphene planes, but there is still much that we do not understand about the geometry and stability of these edges. We present an experimental and theoretical study of the closed edges of graphite crystals, and of the effect of an electric field on their structure. High-resolution transmission electron microscopy is used to image the edge structure of fresh graphite and of graphite that has been exposed to an electric field, which experiences a separation of the graphene layers. Computer simulations based on density functional theory are used to rationalise and quantify the preference for the formation of multiple concentric loops at the edges. A model is also presented to explain how the application of an electric field leads to the separation of the folded edges

Electronic structure of Pd multi-layers on Re(0001): the role of charge transfer

Understanding the origin of the properties of metal-supported metal thin films is important for the rational design of bimetallic catalysts and other applications, but it is generally difficult to separate effects related to strain from those arising from interface interactions. Here we use density functional (DFT) theory to examine the structure and electronic behavior of few-layer palladium films on the rhenium (0001) surface, where there is negligible interfacial strain and therefore other effects can be isolated. Our DFT calculations predict stacking sequences and interlayer separations in excellent agreement with quantitative low-energy electron diffraction experiments. By theoretically simulating the Pd core-level X-ray photoemission spectra (XPS) of the films, we are able to interpret and assign the basic features of both low-resolution and high-resolution XPS measurements. The core levels at the interface shift to more negative energies, rigidly following the shifts in the same direction of the valence d-band center. We demonstrate that the valence band shift at the interface is caused by charge transfer from Re to Pd, which occurs mainly to valence states of hybridized s-p character rather than to the Pd d-band. Since the d-band filling is roughly constant, there is a correlation between the d-band center shift and its bandwidth. The resulting effect of this charge transfer on the valence d-band is thus analogous to the application of a lateral compressive strain on the adlayers. Our analysis suggests that charge transfer should be considered when describing the origin of core and valence band shifts in other metal / metal adlayer systems

A Q-Ising model application for linear-time image segmentation

A computational method is presented which efficiently segments digital grayscale images by directly applying the Q-state Ising (or Potts) model. Since the Potts model was first proposed in 1952, physicists have studied lattice models to gain deep insights into magnetism and other disordered systems. For some time, researchers have realized that digital images may be modeled in much the same way as these physical systems (i.e., as a square lattice of numerical values). A major drawback in using Potts model methods for image segmentation is that, with conventional methods, it processes in exponential time. Advances have been made via certain approximations to reduce the segmentation process to power-law time. However, in many applications (such as for sonar imagery), real-time processing requires much greater efficiency. This article contains a description of an energy minimization technique that applies four Potts (Q-Ising) models directly to the image and processes in linear time. The result is analogous to partitioning the system into regions of four classes of magnetism. This direct Potts segmentation technique is demonstrated on photographic, medical, and acoustic images.Comment: 7 pages, 8 figures, revtex, uses subfigure.sty. Central European Journal of Physics, in press (2010

Bounding Anomalous Gauge-Boson Couplings

In this version we have corrected some minor errors in the tables, corrected typos, and added a reference. We have also updated our comparison with earlier workers. Figures are now included as uuencoded compressed tar files.Comment: 32 page

Cavitation of Electrons Bubbles in Liquid Helium Below saturation Pressure

We have used a Hartree-type electron-helium potential together with a density functional description of liquid $^4$He and $^3$He to study the explosion of electron bubbles submitted to a negative pressure. The critical pressure at which bubbles explode has been determined as a function of temperature. It has been found that this critical pressure is very close to the pressure at which liquid helium becomes globally unstable in the presence of electrons. It is shown that at high temperatures the capillary model overestimates the critical pressures. We have checked that a commonly used and rather simple electron-helium interaction yields results very similar to those obtained using the more accurate Hartree-type interaction. We have estimated that the crossover temperature for thermal to quantum nucleation of electron bubbles is very low, of the order of 6 mK for $^4$He.Comment: 22 pages, 9 figure

Patterns of Care Quality and Prognosis Among Hospitalized Ischemic Stroke Patients With Chronic Kidney Disease

Background: Relatively little is known about the quality of care and outcomes for hospitalized ischemic stroke patients with chronic kidney disease (CKD). We examined quality of care and in‐hospital prognoses among patients with CKD in the Get With The Guidelines–Stroke (GWTG‐Stroke) program Methods and Results: We analyzed 679 827 patients hospitalized with ischemic stroke from 1564 US centers participating in the GWTG‐Stroke program between January 2009 and December 2012. Use of 7 predefined ischemic stroke performance measures, composite “defect‐free” care compliance, and in‐hospital mortality were examined based on glomerular filtration rate (GFR) categorized as a dichotomous (+CKD as <60) or rank‐ordered variable: normal (≥90), mild (≥60 to <90), moderate (≥30 to <60), severe (≥15 to <30), and kidney failure (<15 or dialysis). There were 236 662 (35%) ischemic stroke patients with CKD. Patients with severe renal dysfunction or failure were significantly less likely to receive guideline‐based therapies. Compared with patients with normal kidney function (≥90), those with CKD (adjusted OR 0.91 [95% CI: 0.89 to 0.92]), moderate dysfunction (adjusted OR 0.94 [95% CI: 0.92 to 0.97]), severe dysfunction (adjusted OR 0.80 [95% CI: 0.77 to 0.84]), or failure (adjusted OR 0.72 [95% CI: 0.68 to 0.0.76]), were less likely to receive 100% defect‐free care measure compliance. Inpatient mortality was higher for patients with CKD (adjusted odds ratio 1.44 [95% CI: 1.40 to 1.47]), and progressively rose with more severe renal dysfunction. Conclusions: Despite higher in‐hospital mortality rates, ischemic stroke patients with CKD, especially those with greater severity of renal dysfunction, were less likely to receive important guideline‐recommended therapies

Uses and Abuses of Effective Lagrangians

Motivated by past and recent analyses we critically re-examine the use of effective lagrangians in the literature to constrain new physics and to determine the `physics reach' of future experiments. We demonstrate that many calculations, such as those involving anomalous trilinear gauge-boson couplings, either considerably overestimate loop-induced effects, or give ambiguous answers. The source of these problems is the use of cutoffs to evaluate the size of such operators in loop diagrams. In contrast to other critics of these loop estimates, we prove that the inclusion of nonlinearly-realized gauge invariance into the low-energy lagrangian is irrelevant to this conclusion. We use an explicit example using known multi-Higgs physics above the weak scale to underline these points. We show how to draw conclusions regarding the nature of the unknown high-energy physics without making reference to low-energy cutoffs.Comment: 36 page

How Can Reasoner Performance of ABox Intensive Ontologies Be Predicted?

Reasoner performance prediction of ontologies in OWL 2 language has been studied so far from different dimensions. One key aspect of these studies has been the prediction of how much time a particular task for a given ontology will consume. Several approaches have adopted different machine learning techniques to predict time consumption of ontologies already. However, these studies focused on capturing general aspects of the ontologies (i.e., mainly the complexity of their TBoxes), while paying little attention to ABox intensive ontologies. To address this issue, in this paper, we propose to improve the representativeness of ontology metrics by developing new metrics which focus on the ABox features of ontologies. Our experiments show that the proposed metrics contribute to overall prediction accuracy for all ontologies in general without causing side-effects

Filling a blank on the map: 60 years of fisheries in Equatorial Guinea

Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea

Improved catalytic activity of ruthenium–arene complexes in the reduction of NAD+

A series of neutral Ru-II half-sandwich complexes of the type [(eta(6)-arene)Ru(N,N')Cl] where the arene is para-cymene (p-cym), hexamethylbenzene (hmb), biphenyl (bip), or benzene (bn) and N,N' is N-(2-aminoethyl) -4-(trifluoromethyl)benzenesulfonamide (TfEn), N-(2-aminoethyl)-4-toluenesulfonamide (TsEn), or N-(2-aminoethyl)-methylenesulfonamide (MsEn) were synthesized and characterized. X-ray crystal structures of [(p-cym)Ru(MsEn)Cl] (1), [(hmb)Ru(TsEn)Cl] (5), [(hmb)Ru(TfEn)Cl] (6), [(bip)Ru(MsEn)Cl] (7), and [(bip)Ru(TsEn)Cl] (8) have been determined. The complexes can regioselectively catalyze the transfer hydrogenation of NAD(+) to give 1,4-NADH in the presence of formate. The turnover frequencies (TOF) when the arene is varied decrease in the order bn > bip > p-cym > hmb for complexes with the same N,N' chelating ligand. The TOF decreased with variation in the N,N' chelating ligand in the order TfEn > TsEn > MsEn for a given arene. [(bn)Ru(TfEn)Cl] (12) was the most active, with a TOP of 10.4 h(-1). The effects of NAD(+) and formate concentration on the reaction rates were determined for [(p-cym)Ru(TsEn)Cl] (2). Isotope studies implicated the formation of [(arene)Ru(N,N')(H)] as the rate-limiting step. The coordination of formate and subsequent CO2 elimination to generate the hydride were modeled computationally by density functional theory (DFT). CO2 elimination occurs via a two-step process with the coordinated formate first twisting to present its hydrogen toward the metal center. The computed barriers for CO2 release for arene = benzene follow the order MsEn > TsEn > TfEn, and for the Ms En system the barrier followed bn < hmb, both consistent with the observed rates. The effect of methanol on transfer hydrogenation rates in aqueous solution was investigated. A study of pH dependence of the reaction in D2O gave the optimum pH* as 7.2 with a TOF of 1.58 h(-1) for 2. The series of compounds reported here show an improvement in the catalytic activity by an order of magnitude compared to the ethylenediamine analogues