586 research outputs found
Double polarization hysteresis loop induced by the domain pinning by defect dipoles in HoMnO3 epitaxial thin films
We report on antiferroelectriclike double polarization hysteresis loops in
multiferroic HoMnO3 thin films below the ferroelectric Curie temperature. This
intriguing phenomenon is attributed to the domain pinning by defect dipoles
which were introduced unintentionally during film growth process. Electron
paramagnetic resonance suggests the existence of Fe1+ defects in thin films and
first principles calculations reveal that the defect dipoles would be composed
of oxygen vacancy and Fe1+ defect. We discuss migration of charged point
defects during film growth process and formation of defect dipoles along
ferroelectric polarization direction, based on the site preference of point
defects. Due to a high-temperature low-symmetry structure of HoMnO3, aging is
not required to form the defect dipoles in contrast to other ferroelectrics
(e.g., BaTiO3).Comment: 4 figure
Field-Shift Aging Protocol on the 3D Ising Spin-Glass Model: Dynamical Crossover between the Spin-Glass and Paramagnetic States
Spin-glass (SG) states of the 3-dimensional Ising Edwards-Anderson model
under a static magnetic field are examined by means of the standard Monte
Carlo simulation on the field-shift aging protocol at temperature . For each
process with (T; \tw, h), \tw being the waiting time before the field is
switched on, we extract the dynamical crossover time, \tcr(T; \tw, h). We
have found a nice scaling relation between the two characteristic length scales
which are properly determined from \tcr and \tw and then are normalized by
the static field crossover length introduced in the SG droplet theory. This
scaling behavior implies the instability of the SG phase in the equilibrium
limit even under an infinitesimal . In comparison with this numerical result
the field effect on real spin glasses is also discussed.Comment: 4 pages, 5 figures, jpsj2, Changed conten
Aging and memory effects in beta-hydrochinone-clathrate
The out-of-equilibrium low-frequency complex susceptibility of the
orientational glass methanol(73%)-beta-hydrochinone-clathrate is studied using
temperature-stop protocols in aging experiments . Although the material does
not have a sharp glass transition aging effects including rejuvenation and
memory are found at low temperatures. However, they turn out to be much weaker,
however, than in conventional magnetic spin glasses.Comment: 5 pages RevTeX, 6 eps-figures include
Magnetic oxide semiconductors
Magnetic oxide semiconductors, oxide semiconductors doped with transition
metal elements, are one of the candidates for a high Curie temperature
ferromagnetic semiconductor that is important to realize semiconductor
spintronics at room temperature. We review in this paper recent progress of
researches on various magnetic oxide semiconductors. The magnetization,
magneto-optical effect, and magneto-transport such as anomalous Hall effect are
examined from viewpoint of feasibility to evaluate the ferromagnetism. The
ferromagnetism of Co-doped TiO2 and transition metal-doped ZnO is discussed.Comment: 26 pages, 5 tables, 6 figure
A model for integrating home-work tour scheduling with time-varying network congestion and marginal utility profiles for home and work activities.
The existing literature on activity-based modeling emphasizes that individuals schedule their activities by keeping the whole-day activity pattern in mind. Several attempts have been made to integrate this with network congestion; however, for explicit explanation of travel behavior of individuals, further improvements are required. The proposed model is a combined model that addresses the scheduling of the home-work tour with time-varied network congestion in a fixed-point problem frame-work. Marginal utility profiles that represent individual time-of-day preferences and satiation effect of the activities are incorporated for the measurement of the utility of activity engagement along with the disutility of travel. Consideration of only time-of-day dependent marginal utility profiles of activities in the utility function does not appropriately integrate activities and travel within the tour. The proof is shown analytically and numerically. This finding contradicts earlier research into integration of morning and evening commutes with network congestion. Additionally, the results of two numerical experiments are presented. In the first experiment, an arbitrary dynamic tolling strategy is assumed, and then a detailed analysis is performed to show variation in the balance of trade-offs involved in the process. The second experiment assesses the sensitivity of the combined model through incorporation of different dynamic traffic loading models. Some meaningful observations are drawn from these experiments and are discussed with the identification of avenues for future research
Simplicity of State and Overlap Structure in Finite-Volume Realistic Spin Glasses
We present a combination of heuristic and rigorous arguments indicating that
both the pure state structure and the overlap structure of realistic spin
glasses should be relatively simple: in a large finite volume with
coupling-independent boundary conditions, such as periodic, at most a pair of
flip-related (or the appropriate number of symmetry-related in the non-Ising
case) states appear, and the Parisi overlap distribution correspondingly
exhibits at most a pair of delta-functions at plus/minus the self-overlap. This
rules out the nonstandard SK picture introduced by us earlier, and when
combined with our previous elimination of more standard versions of the mean
field picture, argues against the possibility of even limited versions of mean
field ordering in realistic spin glasses. If broken spin flip symmetry should
occur, this leaves open two main possibilities for ordering in the spin glass
phase: the droplet/scaling two-state picture, and the chaotic pairs many-state
picture introduced by us earlier. We present scaling arguments which provide a
possible physical basis for the latter picture, and discuss possible reasons
behind numerical observations of more complicated overlap structures in finite
volumes.Comment: 22 pages (LaTeX; needs revtex), 1 figure (PostScript); to appear in
Physical Review
Critical Behavior of the Three-Dimensional Ising Spin Glass
We have simulated, using parallel tempering, the three dimensional Ising spin
glass model with binary couplings in a helicoidal geometry. The largest lattice
(L=20) has been studied using a dedicated computer (the SUE machine). We have
obtained, measuring the correlation length in the critical region, a strong
evidence for a second-order finite temperature phase transition ruling out
other possible scenarios like a Kosterlitz-Thouless phase transition. Precise
values for the and critical exponents are also presented.Comment: RevTex; 12 pages plus 5 ps figures. Final version to be published in
PR
Mean-field theory of temperature cycling experiments in spin-glasses
We study analytically the effect of temperature cyclings in mean-field
spin-glasses. In accordance with real experiments, we obtain a strong
reinitialization of the dynamics on decreasing the temperature combined with
memory effects when the original high temperature is restored. The same
calculation applied to mean-field models of structural glasses shows no such
reinitialization, again in accordance with experiments. In this context, we
derive some relations between experimentally accessible quantities and propose
new experimental protocols. Finally, we briefly discuss the effect of field
cyclings during isothermal aging.Comment: Some misprints corrected, references updated, final version to apper
in PR
Selection of Conditions for Cellulase and Xylanase Extraction from Switchgrass Colonized by Acidothermus cellulolyticus
Solid-state fermentation has been widely used for enzyme production. However, secreted enzymes often bind to the solid substrate preventing their detection and recovery. A series of screening studies was performed to examine the role of extraction buffer composition including NaCl, ethylene glycol, sodium acetate buffer, and Tween 80, on xylanase and cellulase recovery from switchgrass. Our results indicated that the selection of an extraction buffer is highly dependent on the nature and source of the enzyme being extracted. While a buffer containing 50Â mM sodium acetate at pHÂ 5 was found to have a positive effect on the recovery of commercial fungal-derived cellulase and xylanase amended to switchgrass, the same buffer had a significant negative effect on enzyme extraction from solid fermentation samples colonized by the bacterium Acidothermus cellulolyticus. Xylanase activity was more affected by components in the extraction buffers compared to cellulase. This study demonstrated that extraction followed by diafiltration is important for assessing enzyme recovery from solid fermentation samples. Reduction in activity due to compounds present in the switchgrass extracts is reversible when the compounds are removed via diafiltration
The Terminal Immunoglobulin-Like Repeats of LigA and LigB of Leptospira Enhance Their Binding to Gelatin Binding Domain of Fibronectin and Host Cells
Leptospira spp. are pathogenic spirochetes that cause the zoonotic disease leptospirosis. Leptospiral immunoglobulin (Ig)-like protein B (LigB) contributes to the binding of Leptospira to extracellular matrix proteins such as fibronectin, fibrinogen, laminin, elastin, tropoelastin and collagen. A high-affinity Fn-binding region of LigB has been localized to LigBCen2, which contains the partial 11th and full 12th Ig-like repeats (LigBCen2R) and 47 amino acids of the non-repeat region (LigBCen2NR) of LigB. In this study, the gelatin binding domain of fibronectin was shown to interact with LigBCen2R (KD = 1.91±0.40 µM). Not only LigBCen2R but also other Ig-like domains of Lig proteins including LigAVar7'-8, LigAVar10, LigAVar11, LigAVar12, LigAVar13, LigBCen7'-8, and LigBCen9 bind to GBD. Interestingly, a large gain in affinity was achieved through an avidity effect, with the terminal domains, 13th (LigA) or 12th (LigB) Ig-like repeat of Lig protein (LigAVar7'-13 and LigBCen7'-12) enhancing binding affinity approximately 51 and 28 fold, respectively, compared to recombinant proteins without this terminal repeat. In addition, the inhibited effect on MDCKs cells can also be promoted by Lig proteins with terminal domains, but these two domains are not required for gelatin binding domain binding and cell adhesion. Interestingly, Lig proteins with the terminal domains could form compact structures with a round shape mediated by multidomain interaction. This is the first report about the interaction of gelatin binding domain of Fn and Lig proteins and provides an example of Lig-gelatin binding domain binding mediating bacterial-host interaction
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