Consistent Estimation of Mixed Memberships with Successive Projections

This paper considers the parameter estimation problem in Mixed Membership Stochastic Block Model (MMSB), which is a quite general instance of random graph model allowing for overlapping community structure. We present the new algorithm successive projection overlapping clustering (SPOC) which combines the ideas of spectral clustering and geometric approach for separable non-negative matrix factorization. The proposed algorithm is provably consistent under MMSB with general conditions on the parameters of the model. SPOC is also shown to perform well experimentally in comparison to other algorithms

Urban Diabetic Women\u27s Perception of Healthy Eating Lifestyles From West Java

This study aimed to explore perceptions about a healthy-eating lifestyle and reasons to practice a healthy-eating lifestyle of women with type 2 diabetes in a city of West Java by using a case study design. Six female patients, with type 2 diabetes, ages 47–63 from a hospital were interviewed guided by the health promotion model. Their healthy-eating lifestyle included currently practicing or not practicing a healthy-eating lifestyle. Reasons to practice were: beliefs for health and for physical energy to work for family, definition of multidimensional health and self-efficacy increased by: support from God, support from family, support from health professionals and improved or deteriorated health status by prior experience. Reasons not to practice were: difficulty in arranging diet, rejecting eating, controlling appetite, and accessing health care services. Related difficulties were interpersonal relations with family and social situation such as social events, expensive medical fee, and distance to the hospital. These findings suggest that women with type 2 diabetes in Indonesia need to be supported with the reasons to practice a healthy-eating lifestyle

Growth-related profiles of remanent flux in bulk melt-textured YBaCuO crystal magnetized by pulsed fields

We have studied the remanent magnetic flux distribution in bulk melt-textured YBa2Cu3O7 (YBCO) crystals after their magnetization in quasi-static and pulsed magnetic fields up to 6T. It has been shown that, provided that the magnetic pulse is sharp enough and its amplitude much exceeds the twice penetration magnetic field, the pulse magnetization technique becomes extremely sensitive to the sample inhomogeneities. Using this method with appropriate parameters of the magnetic pulse, we have particularly demonstrated that the growth of YBCO crystals in the growth sectors (GSs) responds for a macroscopic arrangement of weaks links -- they mostly appear inside of GSs, but not along the GS boundaries.Comment: 8 pages in LaTeX2e, 5 figures. Revised version, submitted to Supercond. Sci. Techno

Coherent quasi-particles-to-incoherent hole-carriers crossover in underdoped cuprates

In underdoped cuprates, only a portion of the Fermi surface survives as Fermi arcs due to pseudogap opening. In hole-doped La$_{2}$CuO$_4$, we have deduced the "coherence temperature" $T_{coh}$ of quasi-particles on the Fermi arc above which the broadened leading edge position in angle-integrated photoemission spectra is shifted away from the Fermi level and the quasi-particle concept starts to lose its meaning. $T_{coh}$ is found to rapidly increase with hole doping, an opposite behavior to the pseudogap temperature $T^*$. The superconducting dome is thus located below both $T^*$ and $T_{coh}$, indicating that the superconductivity emerges out of the coherent Fermionic quasi-particles on the Fermi arc. $T_{coh}$ remains small in the underdoped region, indicating that incoherent charge carriers originating from the Fermi arc are responsible for the apparently metallic transport at high temperatures

Two dimensionality in quasi one-dimensional cobalt oxides

By means of muon spin rotation and relaxation ($\mu^+$SR) techniques, we have investigated the magnetism of quasi one-dimensional (1D) cobalt oxides $AE_{n+2}$Co$_{n+1}$O$_{3n+3}$ ($AE$=Ca, Sr and Ba, $n$=1, 2, 3, 5 and $\infty$), in which the 1D CoO$_3$ chain is surrounded by six equally spaced chains forming a triangular lattice in the $ab$-plane, using polycrystalline samples, from room temperature down to 1.8 K. For the compounds with $n$=1 - 5, transverse field $\mu^+$SR experiments showed the existence of a magnetic transition below $\sim$100 K. The onset temperature of the transition ($T_{\rm c}^{\rm on}$) was found to decrease with $n$; from 100 K for $n$=1 to 60 K for $n$=5. A damped muon spin oscillation was observed only in the sample with $n$=1 (Ca$_3$Co$_2$O$_6$), whereas only a fast relaxation obtained even at 1.8 K in the other three samples. In combination with the results of susceptibility measurements, this indicates that a two-dimensional short-range antiferromagnetic (AF) order appears below $T_{\rm c}^{\rm on}$ for all compounds with $n$=1 - 5; but quasi-static long-range AF order formed only in Ca$_3$Co$_2$O$_6$, below 25 K. For BaCoO$_3$ ($n$=$\infty$), as $T$ decreased from 300 K, 1D ferromagnetic (F) order appeared below 53 K, and a sharp 2D AF transition occurred at 15 K.Comment: 12 pages, 14 figures, and 2 table

Fermi Surface-Brillouin Zone Interactions in 2/1-2/1-2/1 Bergman-Type Approximant Na27Au27Ga31

The X-ray diffraction studies on a newly synthesized Na26Au25Ga29 single crystal revealed the formation of a single phase 2/1-2/1-2/1 Bergman-type approximant and the presence of Au/Ga mixed occupancies in its unit cell containing 680 atoms. The structure model of the 2/1-2/1-2/1 approximant with composition Na27Au27Ga31 was constructed by eliminating the chemical disorder with a minimum sacrifice of composition displacement. The full potential linearized augmented plane wave electronic structure calculations with subsequent full potential linearized augmented plane wave-Fourier analysis were performed for the 2/1-2/1-2/1 approximant Na27Au27Ga31 with space group P a¯3. The square of the Fermi diameter (2kF)2, electrons per atom ratio e/a and the critical reciprocal lattice vector |G|2 are determined. A shallow pseudogap at the Fermi level was interpreted as originating from interference of electrons having (2kF)2 = 109.2 ± 1.0 with sets of lattice planes with |G|2\u27s centered at 108. The effective e/a value for the compound is found to be 1.76 in good agreement with 1.73 derived from a composition average of (e/a)Na = 1.0, (e/a)Au = 1.0 and (e/a)Ga = 3.0

The pion-nucleon scattering lengths from pionic deuterium

We use the framework of effective field theories to discuss the determination of the S-wave \pi N scattering lengths from the recent high-precision measurements of pionic deuterium observables. The theoretical analysis proceeds in several steps. Initially, the precise value of the pion-deuteron scattering length a_{\pi d} is extracted from the data. Next, a_{\pi d} is related to the S-wave \pi N scattering lengths a_+ and a_-. We discuss the use of this information for constraining the values of these scattering lengths in the full analysis, which also includes the input from the pionic hydrogen energy shift and width measurements, and throughly investigate the accuracy limits for this procedure. In this paper, we also give a detailed comparison to other effective field theory approaches, as well as with the earlier work on the subject, carried out within the potential model and multiple scattering framework.Comment: The replacement includes an erratum, which is published in Eur. Phys. J.

Band-Gap Nonlinearity in Lead Chalcogenide (PbQ, Q = Te, Se, S) Alloys

Narrow band-gap lead chalcogenides have been developed for several optical and electronic applications. However, band-gap energies of the ternary and quaternary alloys have received little attention compared with the parent binary phases. Here, we have fabricated single-phase ternary (PbTe)1−x(PbSe)x and quaternary (PbTe)0.9−y(PbSe)0.1(PbS)y and (PbTe)0.65−z(PbSe)0.35(PbS)z alloys and shown that although lattice parameters follow Vegard’s law as a function of composition, the bandgap energies exhibit a substantial bowing effect. The ternary (PbTe)1−x(PbSe)x system features a smaller bowing parameter predominantly due to the difference in electronegativity between Se and Te, whereas the larger bowing parameters in quaternary alloys are generated from a larger crystal lattice mismatch and larger miscibility gap. These findings can lead to further advances in tuning the band-gap and lattice parameters for optical and electronic applications of lead chalcogenides

Magnetostrictive behaviour of thin superconducting disks

Flux-pinning-induced stress and strain distributions in a thin disk superconductor in a perpendicular magnetic field is analyzed. We calculate the body forces, solve the magneto-elastic problem and derive formulas for all stress and strain components, including the magnetostriction $\Delta R/R$. The flux and current density profiles in the disk are assumed to follow the Bean model. During a cycle of the applied field the maximum tensile stress is found to occur approximately midway between the maximum field and the remanent state. An effective relationship between this overall maximum stress and the peak field is found.Comment: 8 pages, 6 figures, submitted to Supercond. Sci. Technol., Proceed. of MEM03 in Kyot