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71.
72.
Goennenwein ST Wassner TA Huebl H Brandt MS Philipp JB Opel M Gross R Koeder A Schoch W Waag A 《Physical review letters》2004,92(22):227202
We show that upon exposure to a remote dc hydrogen plasma, the magnetic and electronic properties of the dilute magnetic semiconductor Ga1-xMnxAs change qualitatively. While the as-grown Ga1-xMnxAs thin films are ferromagnetic at temperatures T less, similar 70 K, the samples are found to be paramagnetic after the hydrogenation, with a Brillouin-type magnetization curve even at T=2 K. Comparing magnetization and electronic transport measurements, we conclude that the density of free holes p is significantly reduced by the plasma process, while the density of Mn magnetic moments does not change. 相似文献
73.
Abazov VM Abbott B Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Aoki M Askew A Åsman B Atkins S Atramentov O Augsten K Avila C BackusMayes J Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bazterra V Bean A Begalli M Belanger-Champagne C Bellantoni L Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatia S Bhatnagar V Blazey G Blessing S Bloom K Boehnlein A Boline D Boos EE 《Physical review letters》2012,108(13):131802
We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a pp center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R(-1)>260 GeV in a minimal UED model. 相似文献
74.
Abazov VM Abbott B Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Alves GA Aoki M Askew A Åsman B Atkins S Atramentov O Augsten K Avila C BackusMayes J Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bazterra V Bean A Begalli M Belanger-Champagne C Bellantoni L Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatnagar V Blazey G Blessing S Bloom K Boehnlein A Boline D Boos EE 《Physical review letters》2012,108(18):181803
We study WW and WZ production with ?νqq (?=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from pp collisions at sqrt[s]=1.96 TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9(-3.2)(+3.7) pb and σ(WZ)=3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions. 相似文献
75.
Bernd Schmidt 《Journal of statistical physics》2013,153(4):727-738
We investigate ground state configurations for a general finite number N of particles of the Heitmann-Radin sticky disc pair potential model in two dimensions. Exact energy minimizers are shown to exhibit large microscopic fluctuations about the asymptotic Wulff shape which is a regular hexagon: There are arbitrarily large N with ground state configurations deviating from the nearest regular hexagon by a number of ~N 3/4 particles. We also prove that for any N and any ground state configuration this deviation is bounded above by ~N 3/4. As a consequence we obtain an exact scaling law for the fluctuations about the asymptotic Wulff shape. In particular, our results give a sharp rate of convergence to the limiting Wulff shape. 相似文献
76.
Stange CF Spott O Apelt B Russow RW 《Isotopes in environmental and health studies》2007,43(3):227-236
On the basis of the principle of reaction continuous-flow quadrupole mass spectrometry, an automated sample preparation unit for inorganic nitrogen (SPIN) species was developed and coupled to a quadrupole Mass Spectrometer (MAS). The SPINMAS technique was designed for an automated, sensitive, and rapid determination of 15N abundance and concentration of a wide variety of N-species involved in nitrogen cycling (e.g. NH4+, NO3-, NH2OH etc.). In this paper, the SPINMAS technique is evaluated with regard to the determination of 15N abundance and concentration of the most fundamental inorganic nitrogen compounds in ecosystems such as NH4+, NO2-, and NO3-. The presented paper describes the newly developed system in detail and demonstrates the general applicability of the system. For a precise determination of 15N abundance and concentration, a minimum total N-amount of 10 microg NH4+ - N, 0.03 microg NO2- - N, or 0.3 microg NO3- - N has to be supplied. Currently, the SPINMAS technique represents the most rapid and only fully automated all-round method for a simultaneous determination of 15N abundance and total N-amount of NH4+, NO2-, or NO3- in aqueous samples. 相似文献
77.
G. Dersch R. Beckmann G. Feige T. Lund P. Vater R. Brandt 《Isotopes in environmental and health studies》2013,49(6):303-304
A recent article interpreted the experiment by Dersch et al. on the formation of 24Na in 40Ar + Cu interactions in a very simple manner. The results from emulsion experiments performed with 3.6 AGeV 22Ne were adapted for the interpretation of the experiments with 1.8 AGeV 40Ar. The model used the same mean value for the energy of minimum ionizing protons and pions at all angles. It is argued that a more complex approach is needed for a satisfactory interpretation. 相似文献
78.
Abdul Aleem Jamali Bernd Witzigmann Rodica Morarescu Thomas Baumert Frank Träger Frank Hubenthal 《Applied Physics A: Materials Science & Processing》2013,110(4):743-749
In this contribution we present recent experimental and theoretical results on local near-field assisted laser ablation. Along these lines, we have generated sub-diffraction sized nanostructures on fused silica substrates, exploiting the local near fields of highly ordered triangular gold nanoparticle arrays generated by nanosphere lithography. After preparation, the nanoparticle arrays were irradiated with a single 35 fs long laser pulse with a central wavelength of λ=790 nm. The pulse energy was set to E=3.9 μJ, resulting in a fluence well below the ablation threshold of the fused silica substrates. In addition, 3D electromagnetic simulations using a finite integration technique in time domain have been performed. The simulations demonstrate that indeed the local field in the vicinity of the tips of the triangular nanoparticles overcome the ablation threshold and easily explain the generated nanostructures. Most importantly, the simulations show, that higher order modes contribute to the ablation process. These modes cause ablation along the side edges of the nanoparticles. Finally, we demonstrate, that the optical properties of the triangular nanoparticles, which can be tuned by their morphology, are crucial parameters for the generation of the ablation structures. 相似文献
79.
Signatures of the non-Abelian statistics of quasiparticles in the ν=5/2 quantum Hall state are predicted to be present in the current-voltage characteristics of tunneling through one or two quantum Hall puddles of Landau filling ν(a) embedded in a bulk of filling ν(b) with (ν(a),ν(b))=(2,5/2) and (ν(a),ν(b))=(5/2,2). 相似文献
80.
The decomposition of chloroform by the combination of hydrodynamic and acoustic cavitation (Hydrodynamic-Acoustic-Cavitation/HAC) has been investigated. The flow rate and the hole diameter of the orifice plate remarkably affect the conversion of chloroform in the combined system. The conversion increases with increasing fluid velocity without any restriction. With a 2.8mm orifice plate the conversion reaches an optimal value. A synergistic effect has been obtained by the hybrid method of acoustic and hydrodynamic cavitation. The total synergistic effect achieves 17% and 73% per pass, respectively. The analysis of the energy efficiencies shows different results. Due to high optimization potential, this hybrid method can be visualized as a new step for wastewater treatment. 相似文献