Room-temperature spin-oriented photocurrent under near-infrared irradiation and comparison of optical means with Shubnikov de-Haas measurements in AlXGa1-XN/GaN heterostructures

The admixture of linear and circular photogalvanic effects and (CPGEs) in AlxGa1-xN/GaN heterostructures has been investigated quantitatively by near-infrared irradiation at room temperature. The spin-based photocurrent that the authors have observed solidly indicates the sizable spin-orbital interaction of the two-dimensional electron gas in the heterostructures. Further analysis shows consistency between studies by optical and magnetic (Shubnikov de-Haas) measurements on the spin-orbital coupling effects among different AlxGa1-xN/GaN heterostructures, indicating that the CPGE measurement is a good way to investigate the spin splitting and the spin polarization in semiconductors. (C) 2007 American Institute of Physics.

ELECTRONIC-STRUCTURES OF THE ALKALI-CONTAINING BUCKMINSTERFULLERENES (A-DELTA-C60) (A=LI,NA,K,RB,CS) AND THE HALOGEN-CONTAINING BUCKMINSTERFULLERENES (H-DELTA-C60) (H=F,CL,BR,I)

The geometrical parameters and electronic structures of C60, (A partial derivative C60) (A = Li, Na, K, Rb, Cs) and (H partial derivative C60) (H = F, Cl, Br, I) have been calculated by the EHMO/ASED (atom superposition and electron delocalization) method. When putting a central atom into the C60 cage, the frontier and subfrontier orbitals of (A partial derivative C60) (A = Li, Na, K, Rb, Cs) and (H partial derivative C60) (H = F, Cl) relative to those of C60 undergo little change and thus, from the viewpoint of charge transfer, A (A = Li, Na, K, Rb, Cs) and H (H = F, Cl) are simply electron donors and acceptors for the C60 cage resPeCtively. Br is an electron acceptor but it does influence the frontier and subfrontier MOs for the C60 cage, and although there is no charge transfer between I and the C60 cage, the frontier and subfrontier MOs for the C60 cage are obviously influenced by I. The stabilities DELTAE(X) (DELTAE(X) = (E(X) + E(C60)) - E(x partial derivative C60)) follow the sequence I < Br < None < Cl < F < Li < Na < K < Rb < Cs while the cage radii r follow the inverse sequence. The stability order and the cage radii order have been explained by means of the (exp-6-1) potential.

Measurement of the isospin-filtering dd → 4He K+K- reaction at Q = 39 MeV

The total cross-section for the dd → 4HeK+K− reaction has been measured at a beam momentum of 3.7GeV/c, corresponding to an excess energy of 39MeV, which is the maximum possible atthe Cooler Synchrotron COSY-Jülich. A deuterium cluster-jet target and the ANKE forward magnetic spectrometer, placed inside the storage ring, have been employed in this investigation. We find a total cross-section of σtot < 14 pb, which brings into question the viability of investigating the dd → 4He a0(980)reaction as a means of studying isospin violation.

New typical ionic cluster K+(KNO3)(n) and NO3-(KNO3)(m)

New typical ionic clusters with complex anions could be formed directly from the KNO3 aqueous solution by means of the electrospray ionization mass spectrometry(ESIMS). The difference between the neighboring peaks(m/z), which corresponded to the molecule weight of KNO3 being 101 in the full mass spectrometry of the positive-ion and the negative-ion. The general formula of the ionic clusters belonged to K+(KNO3)(n) and NO3- (KNO3)(m).

STUDY ON THE ACTIVE-CENTERS OF METHANE COUPLING CATALYSTS BY MEANS OF FLUORESCENCE EMISSION OF EU3+

Eu3+ ion was adopted as a probe to detect the probability of entrance of alkali elements into the crystal lattice of MgO, CaO and La2O3 by means of its characteristic emission. Based on the experimental data it is concluded that Li+ and Na+ ions can substitute Mg2+ and Ca2+ ions and only a small amount of K+ ion can enter into the lattice of CaO. Whilst Li+ ion can not enter into the lattice of lanthana. The conclusion of this investigation is in good agreement with that obtained by Lunsford by ESR studies.

One-step synthesis of 2-pentanone from ethanol over K-Pd/MnOx-ZrO2-ZnO catalyst

A highly active and selective K-Pd/MnOx-ZrO2-ZnO catalyst for the one-step synthesis of 2-pentanone from ethanol is described. The possible reaction pathways for ethanol reaction over K-Pd/MnOx-ZrO2-ZnO catalyst were investigated by means of TPSR, CO2- and NH3-TPD techniques. The reactions were performed in a fixed bed continuous flow reactor. Complete conversion with high selectivity for 2-pentanone, was observed under 370 similar to 390degreesC, 2 similar to 4 MPa, GHSV = 8000 similar to 10,000 h(-1) and LHSV < 1.25 h(-1) conditions. Ethanol reactions over K-Pd/MnOx-ZrO2-ZnO catalyst showed that the catalyst could catalyze dehydrogenation. aldol. dehydration and hydrogenation reactions. Both acidic and basic properties are found on the surface of K-Pd/MnOx-ZrO2-ZnO catalyst, whose multifunctionality with the combination of basic, acid and metal sites may be responsible for the efficiency of the K-PdMnOx-ZrO2-ZnO catalyst. (C) 2004 Elsevier B.V. All rights reserved.

Probabilistic Fréchet means for time varying persistence diagrams

© 2015, Institute of Mathematical Statistics. All rights reserved.In order to use persistence diagrams as a true statistical tool, it would be very useful to have a good notion of mean and variance for a set of diagrams. In [23], Mileyko and his collaborators made the first study of the properties of the Fréchet mean in (Dp, Wp), the space of persistence diagrams equipped with the p-th Wasserstein metric. In particular, they showed that the Fréchet mean of a finite set of diagrams always exists, but is not necessarily unique. The means of a continuously-varying set of diagrams do not themselves (necessarily) vary continuously, which presents obvious problems when trying to extend the Fréchet mean definition to the realm of time-varying persistence diagrams, better known as vineyards. We fix this problem by altering the original definition of Fréchet mean so that it now becomes a probability measure on the set of persistence diagrams; in a nutshell, the mean of a set of diagrams will be a weighted sum of atomic measures, where each atom is itself a persistence diagram determined using a perturbation of the input diagrams. This definition gives for each N a map (Dp)^N→ℙ(Dp). We show that this map is Hölder continuous on finite diagrams and thus can be used to build a useful statistic on vineyards.

Simulation of 2-D metal cutting by means of a distributed algorithm

Temperature distributions involved in some metal-cutting or surface-milling processes may be obtained by solving a non-linear inverse problem. A two-level concept on parallelism is introduced to compute such temperature distribution. The primary level is based on a problem-partitioning concept driven by the nature and properties of the non-linear inverse problem. Such partitioning results to a coarse-grained parallel algorithm. A simplified 2-D metal-cutting process is used as an example to illustrate the concept. A secondary level exploitation of further parallel properties based on the concept of domain-data parallelism is explained and implemented using MPI. Some experiments were performed on a network of loosely coupled machines consist of SUN Sparc Classic workstations and a network of tightly coupled processors, namely the Origin 2000.

PVT Property Measurements for Some Aliphatic Esters from (298 to 393) K and up to 35 MPa

The results of PVT measurements of the liquid phase within the temperature range of (298 to 393) K and up to 35 MPa are presented for some aliphatic esters. Measurements were made by means of a vibrating-tube densimeter, model DMA 512P from Anton Parr. The calibration of the densimeter was performed with water and n-heptane as reference fluids. The experimental PVT data have been correlated by a Tait equation. This equation gives excellent results when used to predict the density of the esters using the method proposed by Thomson et al. (AIChE J. 1982, 28, 671-676). Isothermal compressibilities, isobaric expansivities, thermal pressure coefficients, and changes in the isobaric heat capacity have been calculated from the volumetric data.

Beta2 integrins target Rap GTPases to the plasma membrane by means of degranulation.

We report the novel observation that engagement of ß2 integrins on human neutrophils is accompanied by increased levels of the small GTPases Rap1 and Rap2 in a membrane-enriched fraction and a concomitant decrease of these proteins in a granule-enriched fraction. In parallel, we observed a similar time-dependent decrease of gelatinase B (a marker of specific and gelatinase B-containing granules) but not myeloperoxidase (a marker of azurophil granules) in the granule fraction, and release of lactoferrin (a marker of specific granules) in the extracellular medium. Furthermore, inhibition of Src tyrosine kinases, or phosphoinositide 3-kinase with PP1 or LY294002, respectively, blocked ß2 integrin-induced degranulation and the redistribution of Rap1 and Rap2 to a membrane-enriched fraction. Consequently, the ß2 integrin-dependent exocytosis of specific and gelatinase B-containing granules occurs via a Src tyrosine kinase/phosphoinositide 3-kinase signaling pathway and is responsible for the translocation of Rap1 and Rap2 to the plasma membrane in human neutrophils.

TlCu1.73Fe0.27Se2 studied by means of Mössbauer spectroscopy and SQUID magnetometry

TlCu2-xFexSe2 is a p-type metal for x < 0.5 which crystallizes in a body-centred tetragonal structure. The metal atoms are situated in ab-planes, similar to 7 angstrom apart, while the metal - metal distance within the plane is similar to 2.75 angstrom. Due to the large difference in cation distances, the solid solutions show magnetic properties of mainly two-dimensional character. The SQUID measurements performed for x = 0.27 give the c-axis as the easy axis of magnetization, but also show clear hysteresis effects at 10 K, indicating a partly ferromagnetic coupling. The magnetic ordering temperature T-c is 55( 5) K as found from both SQUID and Mossbauer spectra. At T << Tc the magnetic hyperfine fields are distributed with a maximum at about 30 T, which are compared to the measured magnetic moment per iron atom, which is 0.97 mu(B)/Fe as found from SQUID measurements. The experimental results are compared to results using other methods on isostructural Tl selenides.

Power Scaling of Uplink Massive MIMO Systems with Arbitrary-Rank Channel Means

This paper investigates the uplink achievable rates of massive multiple-input multiple-output (MIMO) antenna systems in Ricean fading channels, using maximal-ratio combining (MRC) and zero-forcing (ZF) receivers, assuming perfect and imperfect channel state information (CSI). In contrast to previous relevant works, the fast fading MIMO channel matrix is assumed to have an arbitrary-rank deterministic component as well as a Rayleigh-distributed random component. We derive tractable expressions for the achievable uplink rate in the large-antenna limit, along with approximating results that hold for any finite number of antennas. Based on these analytical results, we obtain the scaling law that the users' transmit power should satisfy, while maintaining a desirable quality of service. In particular, it is found that regardless of the Ricean K-factor, in the case of perfect CSI, the approximations converge to the same constant value as the exact results, as the number of base station antennas, M, grows large, while the transmit power of each user can be scaled down proportionally to 1/M. If CSI is estimated with uncertainty, the same result holds true but only when the Ricean K-factor is non-zero. Otherwise, if the channel experiences Rayleigh fading, we can only cut the transmit power of each user proportionally to 1/√M. In addition, we show that with an increasing Ricean K-factor, the uplink rates will converge to fixed values for both MRC and ZF receivers.