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The set of all adjacency-preserving automorphisms of the vertex set of a graph form a group which is called the (automorphism) group of the graph. In 1938 Frucht (2) showed that every finite group is isomorphic to the group of some graph. Since then Frucht, Izbicki, and Sabidussi have considered various other properties that a graph having a given group may possess. (For pertinent references and definitions not given here see Ore (4).) The object in this paper is to treat by similar methods a corresponding problem for a class of oriented graphs. It will be shown that a finite group is isomorphic to the group of some complete oriented graph if and only if it has an odd number of elements.
A graph G = G(n, e) consists of a set of n nodes e pairs of which are joined by a single edge; we assume that no edge joins a node to itself. A graph with modes is called a complete -graph if each pair of its nodes is joined by an edge. The graphs belonging to some collection of graphs are independent if no two of them have a node in common. The maximum number of independent complete -graphs contained in a given graph G will be denoted by Ik(G).
f(n, k) sera l'entier maximum t tel qu'il existe un graphe G ayant les propriétés suivantes:
(a) G possède n sommets;
(b) le nombre chromatique de G est égal à k;
(c) Gest minimal par rapport à la propriété (b); c'est-à-dire, la suppression ede n'importe quelle arête rend G(k – 1)-colorable;
(d) il existe t sommets indépendants de G, c'est-à-dire dont nulle paire ne se joigne par une arête.
Un graphe sera k-minimal s'il possède les propriétés (b) et (c). Puisque les graphes 3-minimaux sont tous des polygones impairs, il s'ensuit que f(n, 3) = [n/2] (n = 3, 5, 7, …), Il y a quelque temps T. Gallai a posé la conjecture:
M. Simonovits a réfuté l'inégalité stricte dans (1.1) en prouvant que
An attempt has been made to examine the nature of 3-minute umbral oscillations in order to identify their origin. For this purpose we have calculated, on the basis of Musielak and Rosner (1987), the fast-mode energy spectra generated in a typical sunspot convection zone (Yun 1968). The computed energy spectrum is fed into the lower boundary of the sub-photospheric resonant cavity to examine the characteristics of the wave propagation through the SS umbral atmosphere (Avrett 1981). The upward velocity spectra computed at various heights are presented and their behaviour compared with observations.
Manual surveillance of healthcare-associated infections is cumbersome and vulnerable to subjective interpretation. Automated systems are under development to improve efficiency and reliability of surveillance, for example by selecting high-risk patients requiring manual chart review. In this study, we aimed to validate a previously developed multivariable prediction modeling approach for detecting drain-related meningitis (DRM) in neurosurgical patients and to assess its merits compared to conventional methods of automated surveillance.
Prospective cohort study in 3 hospitals assessing the accuracy and efficiency of 2 automated surveillance methods for detecting DRM, the multivariable prediction model and a classification algorithm, using manual chart review as the reference standard. All 3 methods of surveillance were performed independently. Patients receiving cerebrospinal fluid drains were included (2012–2013), except children, and patients deceased within 24 hours or with pre-existing meningitis. Data required by automated surveillance methods were extracted from routine care clinical data warehouses.
In total, DRM occurred in 37 of 366 external cerebrospinal fluid drainage episodes (12.3/1000 drain days at risk). The multivariable prediction model had good discriminatory power (area under the ROC curve 0.91–1.00 by hospital), had adequate overall calibration, and could identify high-risk patients requiring manual confirmation with 97.3% sensitivity and 52.2% positive predictive value, decreasing the workload for manual surveillance by 81%. The multivariable approach was more efficient than classification algorithms in 2 of 3 hospitals.
Automated surveillance of DRM using a multivariable prediction model in multiple hospitals considerably reduced the burden for manual chart review at near-perfect sensitivity.
After an outbreak of pandemic influenza A/H1N1 (pH1N1) virus, we had previously reported the emergence of a recombinant canine influenza virus (CIV) between the pH1N1 virus and the classic H3N2 CIV. Our ongoing routine surveillance isolated another reassortant H3N2 CIV carrying the matrix gene of the pH1N1 virus from 2012. The infection dynamics of this H3N2 CIV variant (CIV/H3N2mv) were investigated in dogs and ferrets via experimental infection and transmission. The CIV/H3N2mv-infected dogs and ferrets produced typical symptoms of respiratory disease, virus shedding, seroconversion, and direct-contact transmissions. Although indirect exposure was not presented for ferrets, CIV/H3N2mv presented higher viral replication in MDCK cells and more efficient transmission was observed in ferrets compared to classic CIV H3N2. This study demonstrates the effect of reassortment of the M gene of pH1N1 in CIV H3N2.
We consider the dynamics of actively entraining turbulent density currents on a conical sloping surface in a rotating fluid. A theoretical plume model is developed to describe both axisymmetric flow and single-stream currents of finite angular extent. An analytical solution is derived for flow dominated by the initial buoyancy flux and with a constant entrainment ratio, which serves as an attractor for solutions with alternative initial conditions where the initial fluxes of mass and momentum are non-negligible. The solutions indicate that the downslope propagation of the current halts at a critical level where there is purely azimuthal flow, and the boundary layer approximation breaks down. Observations from a set of laboratory experiments are consistent with the dynamics predicted by the model, with the flow approaching a critical level. Interpretation in terms of the theory yields an entrainment coefficient
$E\propto 1/\Omega $
where the rotation rate is
. We also derive a corresponding theory for density currents from a line source of buoyancy on a planar slope. Our theoretical models provide a framework for designing and interpreting laboratory studies of turbulent entrainment in rotating dense flows on slopes and understanding their implications in geophysical flows.
Equine influenza virus (EIV) causes a highly contagious respiratory disease in equids, with confirmed outbreaks in Europe, America, North Africa, and Asia. Although China, Mongolia, and Japan have reported equine influenza outbreaks, Korea has not. Since 2011, we have conducted a routine surveillance programme to detect EIV at domestic stud farms, and isolated H3N8 EIV from horses showing respiratory disease symptoms. Here, we characterized the genetic and biological properties of this novel Korean H3N8 EIV isolate. This H3N8 EIV isolate belongs to the Florida sublineage clade 1 of the American H3N8 EIV lineage, and surprisingly, possessed a non-structural protein (NS) gene segment, where 23 bases of the NS1-encoding region were naturally truncated. Our preliminary biological data indicated that this truncation did not affect virus replication; its effect on biological and immunological properties of the virus will require further study.
In order to clarify the relationship between excimer laser fluence gradient and the length of lateral grain growth, the laser fluence is modulated by a beam mask. The fluence distribution is measured by using a negative UV photoresist. The lateral growth length and the grain directionality are improved with increasing fluence gradient. Lateral growth length of about 1.5 [.proportional]m is achieved by using a single laser pulse without substrate heating on a 50 nm-thick a-Si film by enforcing high fluence gradient. Electrical conductance measurement is used to probe the solidification dynamics. The lateral solidification velocity is found to be about 7 m/s.
The effect of magnetic fields to 15T on the electrical resistance (R) of Bi-Sr-Ca-Cu-O superconductors has been measured at precise temperatures during the transition to the superconducting state. The results show that the temperature at which the externally-applied magnetic field causes a divergence of resistance (R) as a function of inverse temperature is approximately at the same temperature where the positive Hall coefficient begins its steep descent to zero. At slightly higher temperature the Hall coefficient shows a singularity peak akin to a delta function. Internal electric field calculations show that the structure of the superconducting oxides, having more than a single building block polyhedron, gives rise to strong electrostatic fields in the unit cell which in turn causes charge separation or polarization. The charge separation is in accord with the importance of high oxidation states of the multivalence cations and suggests the use of high oxygen overpressure during processing. The magnitude of Tc scales closely with the number of bound holes (associated with the charge transfer excitations) per unit cell. Extensive computer calculations using this model indicate attractive pairing of electrons at inter-electron separations of about 10–15A.
Y-Ba-Cu-o fine powders were prepared by coprecipitating in the oxalate form from metal nitrates solution. The stoichiometry of metals in the precipitate was adjusted by systematic change of copper nitrate (or yttrium nitrate) concentration for a fixed concentration of barium nitrate in the ruactant. Approximately one micron size powders, with a uniform size distribution, were obtained by this new approach. The optimum condition for calcination and sintering was studied by thermal gravimetric analysis(TGA), X-ray powder diffraction(XRD) and scanning electron microscopy(SEM).
A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapour deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of ∼2 μm thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilised to amorphise the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In0.53Ga0.47As and SixGe1-x samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphised GaAs, are shown.
To lower the temperature of oxide-passivation processing the high- purity ozone (more than 98 mole %) was used instead of usual thermal oxidation. Initial oxide formation on a Si(111) surface with high-purity ozone is investigated by X-ray photoelectron spectroscopy (XPS). From the comparison of the suboxides formed with ozone and oxygen exposures, it is clear that ozone forms less suboxide than oxygen. The oxidation with ozone also proceeds on the hydrogen passivated surface which oxygen molecules do not oxidize.
The fabrication and characterization of polyaniline (PANI) derivatives deposited on ITO coated glass is investigated as possible hole injection layers for MEH-PPV based polymer light emitting diode (PLED) devices. This involved multilayer ordering by the alternate polyelectrolyte adsorption of polyaniline and sulfonated poyaniline with an oppositely charged polyelectrolyte from solution. A combination of spectroscopic and microscopic techniques was utilized to determine the layer ordering, film structure, morphology, and homogeneity. The deposition process generally showed a linear behavior for all pairs as shown by ellipsometry and UV-vis spectroscopy. However, surface plasmon spectroscopy (SPS) and AFM revealed that thicker films are accompanied by increased surface roughness regardless of concentration. Comparison in performance was made between bare ITO and PANI or SPANI coated devices. Initial investigations of PLED performance showed significant improvements in lifetime and efficiency compared to bare ITO.
High quality ZnS epilayers were grown on GaAs and GaP substrates by hot wall epitaxy. The optimum temperature conditions for high quality ZnS epilayer were found. The photoluminescence(PL) spectrum of high quality ZnS epilayers showed sharp and narrow exciton peaks and no self-activated peaks. The room temperature energy gap of ZnS/GaAs was found to be 3.729 eV from the experimentally observed free exciton PL peaks. The temperature dependence of the PL intensity showed a two step quenching process and the temperature dependence of the PL linewidth broadening was tried to analyze in terms of exciton scattering process. From the splitting of the heavy hole and the light hole exciton peaks, the strain was identified.
Au nanorod arrays were grown by electrodeposition in Au-backed nanoporous alumina templates modified with polyethylenimine (PEI) as an adhesion layer. By varying the concentration and molecular weight of PEI, the length of nanorod arrays could be finely controlled. The local length distribution was extremely narrow with relative standard deviations on the order of 2% for rod lengths from 700 nm to 17 microns. The uniform growth rate appears to be determined by the adsorbed PEI matrix, which controls the growth kinetics of the grains comprising the nanorods. Templates coated with poly(acrylic acid) did not impart fine control in nanorod growth. The nanorods could also be thermally annealed within the template and released as monodisperse particles of uniform size.
Cryptosporidium parvum is an intracellular protozoan parasite that causes cryptosporidiosis in mammals including humans. In the current study, the gene encoding the cysteine protease of C. parvum (cryptopain-1) was identified and the biochemical properties of the recombinant enzyme were characterized. Cryptopain-1 shared common structural properties with cathepsin L-like papain family enzymes, but lacked a typical signal peptide sequence and contained a possible transmembrane domain near the amino terminus and a unique insert in the front of the mature domain. The recombinant cryptopain-1 expressed in Escherichia coli and refolded to the active form showed typical biochemical properties of cathepsin L-like enzymes. The folding determinant of cryptopain-1 was characterized through multiple constructs with or without different lengths of the pro-domain of the enzyme expressed in E. coli and assessment of their refolding abilities. All constructs, except one that did not contain the full-length mature domain, successfully refolded into the active enzymes, suggesting that cryptopain-1 did not require the pro-domain for folding. Western blot analysis showed that cryptopain-1 was expressed in the sporozoites and the enzyme preferentially degraded proteins, including collagen and fibronectin, but not globular proteins. This suggested a probable role for cryptopain-1 in host cell invasion and/or egression by the parasite.