Search

We prove the harmonicity of totally geodesic maps from a Riemannian manifold to a nonpositively curved metric space in the sense of Alexandrov for both Korevaar-Schoen-type and Cheeger-type energies. This enables us to make many examples of harmonic maps of an unknown type. We also construct an example of totally geodesic map between CAT(0)-spaces which is not harmonic.

In this paper, we consider the natural generalization of Cheeger type Sobolev spaces to maps into a metric space. We solve Dirichlet problem for CAT(0)-space targets, and obtain some results about the relation between Cheeger type Sobolev spaces for maps into a Banach space and those for maps into a subset of that Banach space. We also prove the minimality of upper pointwise Lipschitz constant functions for locally Lipschitz maps into an Alexandrov space of curvature bounded above.

Organic light-emitting diodes (OLEDs) with a nanostructured fullerene (C60) layer at and near the interface between the electron- and hole-transport layers were fabricated using a vacuum evaporation method. The OLEDs had a fundamental structure of indium-tin-oxide (ITO) anode/copper phtalocyanine (CuPc)/N,N'-dephenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD)/8-hydroxyquinoline aluminum (Alq3)/LiF/Al cathode. The electroluminescent (EL) properties have been investigated for the OLEDs with a nanostructured C60 layer at the TPD/Alq3 interface and at the different positions in the Alq3 layer near the TPD/Alq3 interface. The dependences of the EL properties on the thickness of the inserted C60 layer and on the position from the interface were examined. The OLEDs with a C60 monolayer inserted at the TPD/Alq3 interface showed the highest efficiency.

We generalize the theory of gradient flows of semi-convex functions on CAT(0)-spaces, developed by Mayer and Ambrosio--Gigli--Savar\'e, to CAT(1)-spaces. The key tool is the so-called "commutativity" representing a Riemannian nature of the space, and all results hold true also for metric spaces satisfying the commutativity with semi-convex squared distance functions. Our approach combining the semi-convexity of the squared distance function with a Riemannian property of the space seems to be of independent interest, and can be compared with Savar\'e's work on the local angle condition under lower curvature bounds. Applications include the convergence of the discrete variational scheme to a unique gradient curve, the contraction property and the evolution variational inequality of the gradient flow, and a Trotter--Kato product formula for pairs of semi-convex functions., Comment: 27 pages; minor revisions; to appear in Amer. J. Math

This is the lecture notes on the interplay between optimal transport and Riemannian geometry. On a Riemannian manifold, the convexity of entropy along optimal transport in the space of probability measures characterizes lower bounds of the Ricci curvature. We then discuss geometric properties of general metric measure spaces satisfying this convexity condition.

We develop the theory of discrete-time gradient flows for convex functions on Alexandrov spaces with arbitrary upper or lower curvature bounds. We employ different resolvent maps in the upper and lower curvature bound cases to construct such a flow, and show its convergence to a minimizer of the potential function. We also prove a stochastic version, a generalized law of large numbers for convex function valued random variables, which not only extends Sturm's law of large numbers on nonpositively curved spaces to arbitrary lower or upper curvature bounds, but this version seems new even in the Euclidean setting. These results generalize those in nonpositively curved spaces (partly for squared distance functions) due to Ba\v{c}\'ak, Jost, Sturm and others, and the lower curvature bound case seems entirely new., Comment: 28 pages; minor corrections; to appear in Calc. Var. PDE

CuGaS 2 films have been grown on (1 0 0) GaAs and GaP wafers by the vacuum evaporation technique using constituent elementary substances as sources. RHEED patterns of the films that use 〈0 1 1〉 azimuths in a substrate show two different patterns in mutually orthogonal directions. In one direction, the observed pattern is a single pattern which illustrates that CuGaS 2 grows in the [0 0 1] orientation direction (the c -axis growth). In another direction, however, additional patterns appeared. This phenomenon indicates that one pair of the 180 rotated {1 1 2} twins exists in addition to c -axis growth in a film, and it also indicates that additional orientations except for c -axis growth are reduced in films grown on compound substrates as compared with ones on (1 0 0) Si.

We extend the range of $N$ to negative values in the $(K,N)$-convexity (in the sense of Erbar--Kuwada--Sturm), the weighted Ricci curvature $Ric_N$ and the curvature-dimension condition $CD(K,N)$. We generalize a number of results in the case of $N>0$ to this setting, including Bochner's inequality, the Brunn--Minkowski inequality and the equivalence between $Ric_N \ge K$ and $CD(K,N)$. We also show an expansion bound for gradient flows of Lipschitz $(K,N)$-convex functions., 29 pages; Minor corrections, to appear in J. Geom. Anal

The spatial distributions of the cathodoluminescence (CL) emissions from thin ZnS films on GaAs(100) have been examined by the low‐temperature CL measurement system combined with a transmission electron microscope (TEM). The correlation between these CL emissions and structural defects were studied by comparing the monochromatic CL images with the TEM images for both plan‐view and cross‐sectional observations. It is found that the neutral acceptor–bound exciton associated emission (A0,X) and the free‐electron‐to‐ionized acceptor transition emission (e,A) are affected by the stacking fault distribution. The localization of the emission due to the deep‐level emission transition near the interface suggest the diffusion of Ga atoms from the GaAs substrate. The characteristic distributions of the CL emission regions can be explained by considering the competitions among the recombination channels of those radiative processes for each type of an excess carrier, an electron, or a hole.

AgGaS 2 thin films have been prepared by the vacuum evaporation method on GaAs(100). Elemental silver, gallium and sulfur have been used as the source materials. The X-ray diffraction and the RHEED analysis show that the good epitaxial films with the c -axis normal to the GaAs(100) substrate are grown for the stoichiometric composition. The non-stoichiometric films show that the two different orientational types coexist in a film. One type is that the c -axis is normal to the substrate. The other type is that the c -axis is parallel to the two a -axes of GaAs.

The spatial distributions of the cathodoluminescence (CL) emissions from thin ZnS and ZnSe films on GaAs(100) have been examined by the low-temperature CL imaging system combined with a transmission electron microscope (TEM). The correlation between these CL emissions and structural defects were studied by comparing the monochromatic CL images with TEM images for both plan-view and cross-sectional observations. It is found that the bound exciton associated emission (A0, X) and the (e, A) emission are affected by the stacking fault distribution. The localization of the emission due to the DLE transition near the interface suggest the diffusion of Ga or As atoms from the GaAs substrate.

We develop the differential geometric and geometric analytic studies of Hamiltonian systems. Key ingredients are the curvature operator, the weighted Laplacian, and the associated Riccati equation. We prove the appropriate generalizations of Bochner--Weitzenb\"ock formula and Laplacian comparison theorem, and study the heat flow., Comment: 45 pages; Minor modifications everywhere, added Example 7.4, expanded Example 8.8; To appear in Anal. Geom. Metr. Spaces

We prove that on compact Alexandrov spaces with curvature bounded below the gradient flow of the Dirichlet energy in the $L^2$-space produces the same evolution as the gradient flow of the relative entropy in the $L^2$-Wasserstein space. This means that the heat flow is well defined by either one of the two gradient flows. Combining properties of these flows, we are able to deduce the Lipschitz continuity of the heat kernel as well as Bakry-\'Emery gradient estimates and the $\Gamma_2$-condition. Our identification is established by purely metric means, unlike preceding results relying on PDE techniques. Our approach generalizes to the case of heat flow with drift., Comment: 27 pages; minor modifications, to appear in Comm. Pure Appl. Math

The atomic layer epitaxy (ALE) growth of monocrystalline ZnS is successfully carried out onto (100)GaAs substrates at 185–;200°C by the use of a molecular beam epitaxy system, and the growth mechanism is considered with the results of reflection high energy electron diffraction (RHEED). The ALE growth is performed with alternative irradiations of Zn and S molecular beams. The orientation of the epilayer is 〈100〉 and the epilayer is free from twins. The RHEED patterns suggest that the progress of the growth of ALE-ZnS is based on the alternative change of the surface structures of c(2 × 2)-Zn and (2 × 1)-S. The growth rate per cycle is remarkably dependent on the substrate temperature and the origins of the growth rate variation are presumably due to the temperature dependences of the dissociations of cluster molecules or polyatomic molecules and of sticking coefficients for Zn and S.

We investigate barycenters of probability measures on proper Alexandrov spaces of curvature bounded below, and show that they enjoy several properties relevant to or different from those in metric spaces of curvature bounded above. We prove the reverse variance inequality, and show that the push forward of a measure to the tangent cone at its barycenter has the flat support.

We extend results proved by the second author (Amer. J. Math., 2009) for nonnegatively curved Alexandrov spaces to general compact Alexandrov spaces X with curvature bounded below. The gradient flow of a geodesically convex functional on the quadratic Wasserstein space ((X),W2) satisfies the evolution variational inequality. Moreover, the gradient flow enjoys uniqueness and contractivity. These results are obtained by proving a first variation formula for the Wasserstein distance.

We introduce a class of generalized relative entropies (inspired by the Bregman divergence in information theory) on the Wasserstein space over a weighted Riemannian or Finsler manifold. We prove that the convexity of all the entropies in this class is equivalent to the combination of the nonnegative weighted Ricci curvature and the convexity of another weight function used in the definition of the generalized relative entropies. This convexity condition corresponds to Lott and Villani's version of the curvature-dimension condition. As applications, we obtain appropriate variants of the Talagrand, HWI and logarithmic Sobolev inequalities, as well as the concentration of measures. We also investigate the gradient flow of our generalized relative entropy., 76 pages, to appear in Communications in Analysis and Geometry

Monocrystalline CdS films are successfully grown on (100)GaAs at the low temperature of 340°C by atomic layer epitaxy (ALE) using a molecular beam epitaxy (MBE) system. The growth orientation of the epilayer is 〈100〉 of a zincblende structure with no twinning. The film thickness is in good agreement with the predesigned atomic layer numbers. The variation of the film thickness is uniform in the whole area of the epilayer and the surface morphology is flat and smooth. The photoluminescence spectra show dominant near-band-edge emission, suggesting a high crystallographic quality. It is indicated that the ALECdS epilayer is advantageous, especially for the ultrathin multilayer structure preparation.

CdS ZnS superlattices (SLs), which contain 4 molecular layers of CdS and 16 molecular layers of ZnS, were successfully obtained on (100)GaAs substrates by means of atomic layer epitaxy (ALE) using a molecular beam epitaxy (MBE) system. It is suggested that each constituent layer has compressive and tensile strain. The layer configuration of the SL is in good agreement with the predesigned scheme, as shown by the results of X-ray diffraction analysis and transmission electron microscope pictures. This emphasizes that the ALE growth is effective in forming fine multilayer structures. The photoluminescence spectrum shows a dominant sharp peak at around 450 nm. The cathodoluminescence spectrum measured at room temperature also indicates a sharp peak at 453 nm. These emissions have originated from quantum levels formed in CdS well layers in the SL.

Chemical modifications of the carboxyl group in the alanine moiety of pradimicin A were performed and in vitro and in vivo antifungal activities of the derivatives were examined in comparison with those of pradimicin A. The amide derivatives showed activities comparable to pradimicin A, indicating that the free carboxyl group can be modified without impairing the antifungal activity.

We study contractivity properties of gradient flows for functions on normed spaces or, more generally, on Finsler manifolds. Contractivity of the flows turns out to be equivalent to a new notion of convexity for the functions. This is different from the usual convexity along geodesics in non-Riemannian Finsler manifolds. As an application, we show that the heat flow on Minkowski normed spaces other than inner product spaces is not contractive with respect to the quadratic Wasserstein distance., 26 pages; minor revisions, to appear in Arch. Ration. Mech. Anal

The surface of a glucose sensor is covered with a poly(2-methacryloyloxyethyl phosphorylcholine-co-butylmethacrylate) membrane and the effects of the membrane on the sensitivity and respons of the sensor are investigated in the presence of plasma proteins. The membrane was found to be effective for improving the sensitivity and response of the sensor.

We present two approaches to the heat flow on a Finsler manifold $(M,F)$: either as gradient flow on $L^2(M,m)$ for the energy; or as gradient flow on the reverse $L^2$-Wasserstein space $\mathcal{P}_2(M)$ of probability measures on $M$ for the relative entropy. Both approaches depend on the choice of a measure $m$ on $M$ and then lead to the same nonlinear evolution semigroup. We prove $\mathcal{C}^{1,\alpha}$-regularity for solutions to the (nonlinear) heat equation on the Finsler space $(M,F,m)$. Typically, solutions to the heat equation will not be $\mathcal{C}^2$. Moreover, we derive pointwise comparison results a la Cheeger-Yau and integrated upper Gaussian estimates a la Davies., Comment: 36 pages, v4: minor corrections in Lemma 3.8, Theorem 3.9 (figures are not included from technical reasons, see the published one or the authors' websites for them)

The (2×1) and (5×1) surface reconstructions accompanied with the surface smoothing have been observed at ZnS:Ga layers grown on (100) GaAs by molecular‐beam epitaxy (MBE) and followed by postannealing at 600 °C for 20 min. The origin of these reconstructions are discussed and it is suggested that the reconstruction of (5×1) is due to the misfit strain relaxation in the ZnS:Ga epilayer or at the ZnS:Ga/GaAs interface. The simple lattice model of (2×1) and (5×1) surfaces are proposed on the basis of a dimer model. It is confirmed that the surface lattice models proposed give the diffraction patterns of (2×1) and (5×1) by a laser simulation.

The (CdS)n/(ZnS)m superlattices (SLs) have been prepared on (100)GaAs at low growth temperature of 185 or 190°C by atomic layer epitaxy using a molecular beam epitaxy system. The SL growth progresses with the surface reconstruction change from c(2 × 2)-Zn to (2 × 1)-S for ZnS and from (1 × 1)-Cd or c(2 × 2)-Cd to (2 × 1)-S for CdS. The SL structures are confirmed by the satellite peaks observed in X-ray diffraction spectra. The SLs exhibit flat and smooth surfaces. The photoluminescence spectrum of the ((CdS)8/(ZnS)20)55 SL shows a sharp peak at 440 nm and suggests that the light emission originated from the quantum level in the SL.

The AC thin-film electroluminescent (ACTFEL) devices were prepared by using 1 μm-thick ZnS:Mn luminescent layers formed by molecular beam deposition (MBD). The devices had a structure of glass/In2O3/barium-titanate/ZnS:Mn/Al. The EL properties of the device are remarkably dependent on the temperature of a Mn effusion cell (TMn) during the ZnS:Mn deposition. Although the crystalline quality of the layers was poor and the surface morphology was rough, a low threshold field (Eth) of 0.82×106 V/cm, and a high maximum luminance (Lmax) of 4200 cd/m2 were obtained at 5 kHz sinusoidal operation. The ACEL properties were dependent not only on the crystallographic quality but also on the Mn concentration in the luminescent layer.

We introduce a measure contraction property of metric measure spaces which can be regarded as a generalized notion of the lower Ricci curvature bound on Riemannian manifolds. It is actually equivalent to the lower bound of the Ricci curvature in the Riemannian case. We will generalize the Bonnet?Myers theorem, and prove that this property is preserved under the measured Gromov?Hausdorff convergence.

Organic light emitting diodes (OLEDs) containing cathode buffer layers of nanometer thickness were fabricated and their electrical and emitting properties were investigated. The OLEDs have an indium tin oxide (ITO) anode/ copper phthalocyanine (CuPc) / N, N'-dephenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) / 8- hydroxyquinoline aluminum (Alq3) / buffer layer / Al cathode structure with the buffer layers made from alternating thin films of Alq3 and Al with nanometer thickness. Improvement of driving voltage and the efficiency for the devices were observed by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode. A model of the band structure at the buffer layer was proposed.

The cathodoluminescence (CL) spectra of (CdS)4/(ZnS)16 superlattices are studied at room temperature. There are three peaks in the CL spectra. These emissions are the CL from GaAs at 850 nm and from the CdS quantum wells at 385 nm and at 453 nm. It is found that the CL measurement is one of the effective techniques to obtain the depth profile informations by varying the acceleration voltage of the probing electron beam. From the results of CL measurements at different acceleration voltage, the peak at 453 nm is ascribed to be the emission from the quantum level in four molecular layer CdS well. However, the 385 nm emission is speculated that the emission is due two molecular layer CdS well at the bottom side of the superlattice.

The steady shear viscosity η(k) and the stress decay function (the shear stress divided by the rate of shear k after cessation of steady shear flow) were measured for concentrated solutions of polystyrene in diethyl phthalate. Ranges of molecular weight M and concentration c were 7.10 × 105 to 7.62 × 106 and 0.112–0.329 g/cm3, respectively. Measurements were performed with a rheometer of the cone-and-plate type in the range 10−4 τ2 > …, and the values of τ1, τ2 η1 and η2 were determined for some solutions. The relaxation times τ1 and τ2 were found to be independent of k and equal to the relaxation times of linear viscoelasticity. At the limit of k → 0, η1 and η2 were approximately 60 and 20–30%, respectively, of η and the non-Newtonian behavior was due to large decreases of η1 and η2 with increasing k. It was shown that η1(k) may be evaluated from the relaxation strength G1(s) for the longest relaxation time of the strain-dependent relaxation modulus with a constitutive model for relatively high c–M systems as well as for low c–M systems.

The crystallographic quality and the surface morphology of ZnS films on (100) Si substrates by molecular‐beam epitaxy are profoundly dependent on the substrate temperature Ts. When the Ts was below 300 °C, single crystalline films with twins grew along 〈100〉 directions in the initial stage of growth. However, when the film thickness was increased, the growth orientation changed from 〈100〉 to two 〈511〉 directions of the Si substrate. Namely, the relation of growth orientations between overgrowth and substrate is ZnS(111)∥Si(511). When the Ts was set between 340 and 370 °C, the grown films were single crystal with twins appearing initially and grew with a 〈100〉 orientation, but decreased with increasing film thickness. Especially in the case of Ts=340 °C, the ZnS film became best crystallized and exhibited the twin‐free streaky pattern in the reflection high‐energy electron diffraction pattern with a smooth surface morphology.

New antitumor antibiotic glidobactins A, B and C were isolated from the cultured broth of a gliding bacterium, Polyangium brachysporum sp. nov. No. K481-B101. They are novel molecules carrying the common cyclic tripeptide nucleus substituted with different alpha, beta, gamma, delta-unsaturated fatty acids. Glidobactins exhibit broad inhibitory activity against fungi and yeasts, and prolong the life span of mice inoculated with P388 leukemia cells.

Undoped ZnS epilayers were grown on (100)GaAs by molecular beam epitaxy (MBE). The epilayers had a granulated surface and their photoluminescence (PL) showed three peaks. The peaks could be recognized to be a near-band-edge emission, a defect-related emission and an As-related red luminiscence. Furthermore, the post-annealing at 500°C for 30 min made the shape of the granules unclear and reduced the intensity of the defect-related emission in PL.

The glass/In2O3:Sn/BaTiO3/ZnS:Mn/HfO2/SiO2/HfO2/Al a.c. thin film electroluminescent (EL) device was fabricated. The ZnS:Mn luminescent film of 4000 A thickness was deposited by molecular beam epitaxy (MBE). The crystalline quality of the film was worse than that of the ZnS:Mn prepared by vacuum deposition (VD) because the deposition conditions were unoptimized. Even though the MBE ZnS:Mn film had a poor crystalline quality, the EL properties were superior to those of a VD film. The threshold voltage and the maximum brightness of an MBE EL cell were 56.5 V (r.m.s.) and 2500 cd m-2 respectively, at 5 kHz sinusoidal operation. It was suggested that these improved EL properties are due to more effective incorporation of mangenese light-emitting centres into ZnS.

The stress development at the start of steady shear flow was calculated from experimental data for the strain-dependent relaxation modulus of a concentrated polymer solution with the use of a constitutive equation based on the strain-dependent relaxation spectrum. Calculated results were in close agreement with those observed in the range of relatively low rate of shear, where no stress overshoot at the start of steady shear flow was observed. When stress overshoot was present, the calculated result was in close agreement with the observed up to the time at which the stress reached its maximum value. This time corresponded to a certain value sB of the shear strain, irrespective of the rate of shear, and was accurately predicted from the relaxation modulus using the strain-dependent constitutive model. At longer times the calculated result for the rate of decrease of the stress was too small, compared with the observed, so that the predicted peak of the stress overshoot was too broad. It was concluded that the strain-dependent constitutive model may be applied to polymer solutions when the shear strain is smaller than sB or when the rate of shear is smaller than sB/τm, where τm is the maximum relaxation time of the polymer solution.

ZnS films grown on (100) Si substrates were successfully obtained by molecular beam epitaxy. The dependence of the crystal quality on growth conditions was studied. The substrate temperature ( T s ) and the molecular beam flux ration of Zn to S ( J Zn / J S affect the crystal quality and the growth rate of the ZnS films profoundly. Crystallographic quality and surface morphology were significantly improved by growing at temperatures higher than 300°C. Below 300°C, growth orientation and growing planes of ZnS are different from others, namely ZnS(111) ‖ Si(511). The films grown at higher T s ( > 300°C) have the relation of ZnS(100) ‖ Si(100). By increasing J Zn / J S , the surface morphology became worse. It is found that the optimum growth conditions are T s = 340° C and J Zn / J S =1 or 2. The growth rate of ZnS decreases with incresing T s , and increases with increasing J Zn / J S and t hen saturates above J Zn / J S = 3. From these results, it is presumable that ZnS growth is controlled by the sticking coefficient of the minority molecular species.

Croissance epitaxique de ZnS dope par Ga sur un support (100) GaAs par microscopie electronique a balayage. Les couches epitaxiques sont de grande qualite cristallographique avec l'orientation et montrent une morphologie de surface lisse. Le spectre de photoluminescence montre une emission bleue a 425 nm, due au gallium et une emission plus large a 640 nm, due a des defauts

The molecular‐beam epitaxial growth of undoped ZnS layers on Si (111) is reported. Reflection high energy electron diffraction observations of grown films indicated that the optimum growth conditions necessary to obtain good crystallographic quality ZnS films exhibiting surface reconstruction are a substrate temperature of 300 °C and a molecular‐beam flux ratio of 1. The layer growth rate depends on both substrate temperature and the molecular‐beam flux ratio of Zn to S, JZn/JS. It was found that the growth rate became constant for JZn/JS ratios larger than 1. For the substrate temperatures larger than 400 °C the growth rate was found to decrease to nearly zero, abruptly.

Phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis caused the release of alkaline phosphatase from KB III cells and plasma membrane preparations prepared from the cells. Phosphatidylinositol-specific phospholipase C added to the culture of KB III cells inhibited cell growth by 30%. The release of alkaline phosphatase induced by phospholipase C was dependent on, or proportional to, the reaction time and the concentrations of the phospholipase C, KB III cells and plasma membrane preparation. The Arrhenius plot for phosphatase-release reaction showed a single break at 18.1 degrees C for KB III cells or at 27.3 degrees C for the plasma membrane preparation. The activation energies of the phosphatase-release reaction were 3.2 and 29.2 kcal/mol for KB III cells, and 4.3 and 26.5 kcal/mol for the plasma membrane preparation. The released alkaline phosphatase had a mol. wt of 105,000 and isoelectric points of 4.05 (major) and 4.4 (minor).

ZnS films were successfully grown by molecular beam epitaxy on (100) Si substrates. These high quality films, grown at a substrate temperature of 340 °C with a molecular beam flux ratio of Zn to S of unity, exhibited high crystallographic quality and revealed a flat surface. Secondary ion mass spectroscopic analysis showed that the film contained little impurity. In photoluminescence, a broad peak was observed at 2.6 eV at room temperature while an additional sharp peak at 3.6 eV appeared at 77 K. The latter is considered to be band‐to‐band emission and the former may be due to the Cu‐blue emission.