Doping Dependence of the Magnetic Resonance Peak in YBa_2 Cu_3 O_{6+x}

We report inelastic neutron scattering experiments on the doping dependence of the energy and spectral weight of the sharp magnetic resonance peak in YBa_2 Cu_3 O_{6+x}. These measurements also shed light on the relationship between the magnetic excitations in the normal and superconducting states.Comment: (mostly corrections to figures and minor change to caption in Fig.5) 5 figures. It will be published in the proceedings of M2S-HTSC-V. It needs the elsevier style file (not included) to convert to postscrip

Ground State and Spectral Properties of a Quantum Impurity in d-Wave Superconductors

The variational approach of Gunnarsson and Sch\"onhammer to the Anderson impurity model is generalized to study d-wave superconductors in the presence of dilute spin-1/2 impurities. We show that the local moment is screened when the hybridization exceeds a nonzero critical value at which the ground state changes from a spin doublet to a spin singlet. The electron spectral functions are calculated in both phases. We find that while a Kondo resonance develops above the Fermi level in the singlet phase, the spectral function exhibits a low-energy spectral peak below the Fermi level in the spin doublet phase. The origin of such a ``virtual Kondo resonance'' is the existence of low-lying collective excitations in the spin-singlet sector. We discuss our results in connection to recent spectroscopic experiments on Zn doped high-T$_c$ superconductors.Comment: 5 pages, 4figures, revised versio

Dynamical aspects of mean field plane rotators and the Kuramoto model

The Kuramoto model has been introduced in order to describe synchronization phenomena observed in groups of cells, individuals, circuits, etc... We look at the Kuramoto model with white noise forces: in mathematical terms it is a set of N oscillators, each driven by an independent Brownian motion with a constant drift, that is each oscillator has its own frequency, which, in general, changes from one oscillator to another (these frequencies are usually taken to be random and they may be viewed as a quenched disorder). The interactions between oscillators are of long range type (mean field). We review some results on the Kuramoto model from a statistical mechanics standpoint: we give in particular necessary and sufficient conditions for reversibility and we point out a formal analogy, in the N to infinity limit, with local mean field models with conservative dynamics (an analogy that is exploited to identify in particular a Lyapunov functional in the reversible set-up). We then focus on the reversible Kuramoto model with sinusoidal interactions in the N to infinity limit and analyze the stability of the non-trivial stationary profiles arising when the interaction parameter K is larger than its critical value K_c. We provide an analysis of the linear operator describing the time evolution in a neighborhood of the synchronized profile: we exhibit a Hilbert space in which this operator has a self-adjoint extension and we establish, as our main result, a spectral gap inequality for every K>K_c.Comment: 18 pages, 1 figur

Analisis Nilai-Nilai Pendidikan Karakter Dalam Buku Ilmu Pengetahuan Alam Kelas III Sekolah Dasar Terbitan Pusat Perbukuan Tahun 2008

This study aims to: 1) describe the values of character education in Natural Sciences Book Class III Primary School Published by Pusat Perbukuan of 2008 2) describe the advantages and disadvantages Natural Sciences Book Class III Primary School Published by Pusat Perbukuan of 2008. This type of research is descriptive qualitative research. The data in this study in the form sentences that show character values. Data collected by using read, see, and record. Data analysis technique used is content analysis. Found values of character education in Natural Sciences Book Class III Primary School Published by Pusat Perbukuan of 2008, among others: (1) Religious, (2) To be honest, (3) tolerance, (4) Discipline, (5) Hard work ( 6) Creative (7) Curiosity (8) Love the homeland (9) Appreciating the achievements (10) Friendly / communicative (11) Love peace (12) Joy of reading (13) Care for the environment (14) Caring social, and (15 ) Responsible. Meanwhile, Natural Sciences Book Class III Primary School Published by Pusat Perbukuan of 2008 values of character education that can not be found, among other things: (1) Independent, (2) democratic and (3) the National Spirit. In addition, the advantages and disadvantages of the four components of the book look at the preparation of the book, namely the feasibility of the content, language feasibility, feasibility presentation and feasibility graphic

Microwave conductivity of YBa2_2Cu3_3O6.99_{6.99} including inelastic scattering

The fluctuation spectrum responsible for the inelastic scattering in YBa$_2$Cu$_3$O$_{6.99}$ which was recently determined from consideration of the in-plane optical conductivity in the infrared, is used to calculate the temperature dependence of the microwave conductivity at several measured frequencies. Reasonable overall agreement can only be achieved if, in addition, some impurity scattering is included within a model potential intermediate between weak (Born) and strong (unitary) limit.Comment: 15 pages, 5 figures accepted for publication in Phys. Rev.

The CcmC-CcmE interaction during cytochrome c maturation by System I is driven by protein-protein and not protein-heme contacts.

Cytochromes c are ubiquitous proteins, essential for life in most organisms. Their distinctive characteristic is the covalent attachment of heme to their polypeptide chain. This post-translational modification is performed by a dedicated protein system, which in many Gram-negative bacteria and plant mitochondria is a nine-protein apparatus (CcmA-I) called System I. Despite decades of study, mechanistic understanding of the protein-protein interactions in this highly complex maturation machinery is still lacking. Here, we focused on the interaction of CcmC, the protein that sources the heme cofactor, with CcmE, the pivotal component of System I responsible for the transfer of the heme to the apocytochrome. Using in silico analyses, we identified a putative interaction site between these two proteins (residues Asp <sup>47</sup> , Gln <sup>50</sup> , and Arg <sup>55</sup> on CcmC; Arg <sup>73</sup> , Asp <sup>101</sup> , and Glu <sup>105</sup> on CcmE), and we validated our findings by in vivo experiments in Escherichia coli Moreover, employing NMR spectroscopy, we examined whether a heme-binding site on CcmE contributes to this interaction and found that CcmC and CcmE associate via protein-protein rather than protein-heme contacts. The combination of in vivo site-directed mutagenesis studies and high-resolution structural techniques enabled us to determine at the residue level the mechanism for the formation of one of the key protein complexes for cytochrome c maturation by System I

Hamiltonian Description of Composite Fermions: Magnetoexciton Dispersions

A microscopic Hamiltonian theory of the FQHE, developed by Shankar and myself based on the fermionic Chern-Simons approach, has recently been quite successful in calculating gaps in Fractional Quantum Hall states, and in predicting approximate scaling relations between the gaps of different fractions. I now apply this formalism towards computing magnetoexciton dispersions (including spin-flip dispersions) in the $\nu=1/3$, 2/5, and 3/7 gapped fractions, and find approximate agreement with numerical results. I also analyse the evolution of these dispersions with increasing sample thickness, modelled by a potential soft at high momenta. New results are obtained for instabilities as a function of thickness for 2/5 and 3/7, and it is shown that the spin-polarized 2/5 state, in contrast to the spin-polarized 1/3 state, cannot be described as a simple quantum ferromagnet.Comment: 18 pages, 18 encapsulated ps figure

The Cap in the Hat: Unoriented 2D Strings and Matrix(-Vector) Models

We classify the possible bosonic and Type 0 unoriented string theories in two dimensions, and find their dual matrix(-vector) models. There are no RP^2 R-R tadpoles in any of the models, but many of them possess a massless tachyon tadpole. Thus all the models we find are consistent two-dimensional string vacua, but some get quantum corrections to their classical tachyon background. Where possible, we solve the tadpole cancellation condition, and find all the tachyon tadpole-free theories.Comment: 34 pages, LaTeX; Errors corrected in some of the open string representations in tables 1, 2 and 3. References and acknowledgments adde

Higgs-Boson Production Induced by Bottom Quarks

Bottom quark-induced processes are responsible for a large fraction of the LHC discovery potential, in particular for supersymmetric Higgs bosons. Recently, the discrepancy between exclusive and inclusive Higgs boson production rates has been linked to the choice of an appropriate bottom factorization scale. We investigate the process kinematics at hadron colliders and show that it leads to a considerable decrease in the bottom factorization scale. This effect is the missing piece needed to understand the corresponding higher order results. Our results hold generally for charged and for neutral Higgs boson production at the LHC as well as at the Tevatron. The situation is different for single top quark production, where we find no sizeable suppression of the factorization scale. Turning the argument around, we can specify how large the collinear logarithms are, which can be resummed using the bottom parton picture.Comment: 18 page

Solidification of Al alloys under electromagnetic pulses and characterization of the 3D microstructures under synchrotron x-ray tomography

A novel programmable electromagnetic pulse device was developed and used to study the solidification of Al-15 pct Cu and Al-35 pct Cu alloys. The pulsed magnetic fluxes and Lorentz forces generated inside the solidifying melts were simulated using finite element methods, and their effects on the solidification microstructures were characterized using electron microscopy and synchrotron X-ray tomography. Using a discharging voltage of 120 V, a pulsed magnetic field with the peak Lorentz force of ~1.6 N was generated inside the solidifying Al-Cu melts which were showed sufficiently enough to disrupt the growth of the primary Al dendrites and the Al2Cu intermetallic phases. The microstructures exhibit a strong correlation to the characteristics of the applied pulse, forming a periodical pattern that resonates the frequency of the applied electromagnetic field