Adatoms in graphene as a source of current polarization: Role of the local magnetic moment

We theoretically investigate spin-resolved currents flowing in large-area graphene, with and without defects, doped with single atoms of noble metals (Cu, Ag and Au) and 3d-transition metals (Mn,Fe,Co and Ni). We show that the presence of a local magnetic moment is a necessary but not sufficient condition to have a non zero current polarization. An essential requirement is the presence of spin-split localized levels near the Fermi energy that strongly hybridize with the graphene pi-bands. We also show that a gate potential can be used to tune the energy of these localized levels, leading to an external way to control the degree of spin-polarized current without the application of a magnetic field.Comment: 7 pages, 6 figure

Can the X(3872) be a 1^{++} four-quark state?

We use QCD spectral sum rules to test the nature of the meson X(3872), assumed to be an exotic four-quark (c\bar{c}q\bar{q}) state with J^{PC}=1^{++}. For definiteness, we work with the current proposed recently by Maiani et al [1], at leading order in \alpha_s, consider the contributions of higher dimension condensates and keep terms which are linear in the light quark mass m_q. We find M_X=(3925+- 127) MeV which is compatible, within the errors, with he experimental candidate X(3872), while the SU(3) breaking-terms lead to an unusual mass-splitting M_{X^{s}}-M_X=- (61+-30) MeV. The mass-difference between the neutral states due to isospin violation of about (2.6-3.9) MeV is much smaller than the value (8+-3) MeV proposed in [1]. For the b-quark, we predict M_{X_b}= (10144+-106) MeV for the X_b(b\bar{b}q \bar{q}), which is much below the {\bar B}B* threshold in contrast to the {\bar B}B* molecule prediction [2], and for the X_b^s(b\bar{b}s \bar{s}), a mass-splitting M_{X^s_{b}}-M_{X_b}=-(121+-182) MeV. Our analysis also indicates that the mass-splitting between the ground state and the radial excitation of about (225~250) MeV is much smaller than in the case of ordinary mesons and is (within the errors) flavour-independent. We also extract the decay constants, analogous to f_\pi, of such mesons, which are useful for further studies of their leptonic and hadronic decay widths. The uncertainties of our estimates are mainly due to the ones from the c and b quark masses.Comment: 16 pages, 10 figures. Version to appear in Phys. Rev.

On time-varying collaboration networks

The patterns of scientific collaboration have been frequently investigated in terms of complex networks without reference to time evolution. In the present work, we derive collaborative networks (from the arXiv repository) parameterized along time. By defining the concept of affine group, we identify several interesting trends in scientific collaboration, including the fact that the average size of the affine groups grows exponentially, while the number of authors increases as a power law. We were therefore able to identify, through extrapolation, the possible date when a single affine group is expected to emerge. Characteristic collaboration patterns were identified for each researcher, and their analysis revealed that larger affine groups tend to be less stable

Kajian Cekaman Kekeringan Dan Dosis Pupuk Nitrogen Terhadap Hasil Padi Gogo (Oryza Sativa L)

The Study of the Droght Stress and The Nitrogen Fertilizer Doses For the Plant Gogo Produce. The research had taken place in glasses house BPTP Naibonat Kupang from Junni to October 2008. The aims of the research is to know the influences of the value of the drought sress and the nitrogen of Fertilizer doses for the product of Rice plant Gogo. The research was done by using Randomized Complete Design factorial research which consist of two factors which is used without barren, the droght stess 21 -25 HST, 76 -80 HST and 111 – 115 HST. The secont factor is Nitrogen fertilizer doses which used and without nitrogen fertilizer, 45 kg N/ha, 90 kg N/ha and 135 kg N/ha, with 3 replication. The variabel which observed is the number of plant seed, the panicle number the qualiy of one thousand seeds, the qualiity of the seeds, and harvest index per plantation. The result of the research souws that the effect of drounght and doses nitrogen fertilazer of Riceland field for the fariabel which observed is seed number, the seed quality and the quality of the seed per plantation. The treatmen of the second droht stress (C2) with nitrogen fertilizer doses 90 kg/ha (N2) gives the average seed quality per plantation, whichis higher than the onther tretment

Rancang Bangun Model USAhatani Konservasi Sebagai Upaya Peningkatan Produktivitas Lahan Kering

Model Plan Usahatani Conservation As Dry Farming ProductivityEnhanced Efforts. In the effort erosion trouble-shooting and the low of dry farming productivity, has been executed serangkian research which in focussed in area of Praktek Politani Kupang having location in Oesao Kabupaten Kupang. Research aim to study specific USAhatani model of dry farming. Three kinds of model USAhatani conservation has been checked, yakti bench terrace, terrace;core gulud and without terrace;core. Measurement of level of erosion is done in emperis with method USLE. To evaluate farm productivity also is done cultivation of green peanut crop Result of research indicates that technically, model USAhatani conservation of bench terrace and terrace;core gulud gives repair impact to degradation of erosion speed and improvement of farm productivity. Bench terrace earns effectively lessens erosion until under admissible erosion boundary, however memerlukn technical clauses in its(the making in order not to harm plant growth. Terrace;core gulud is one of alternative of conservation that need to be considered, especially at soil;land;grounds having [shallow/ superficial] solum, because cost in its(the making is cheap and doesn\u27t require many labours, and top layer soil is not annoyed