Adjusting the melting point of a model system via Gibbs-Duhem integration: application to a model of Aluminum

Model interaction potentials for real materials are generally optimized with respect to only those experimental properties that are easily evaluated as mechanical averages (e.g., elastic constants (at T=0 K), static lattice energies and liquid structure). For such potentials, agreement with experiment for the non-mechanical properties, such as the melting point, is not guaranteed and such values can deviate significantly from experiment. We present a method for re-parameterizing any model interaction potential of a real material to adjust its melting temperature to a value that is closer to its experimental melting temperature. This is done without significantly affecting the mechanical properties for which the potential was modeled. This method is an application of Gibbs-Duhem integration [D. Kofke, Mol. Phys.78, 1331 (1993)]. As a test we apply the method to an embedded atom model of aluminum [J. Mei and J.W. Davenport, Phys. Rev. B 46, 21 (1992)] for which the melting temperature for the thermodynamic limit is 826.4 +/- 1.3K - somewhat below the experimental value of 933K. After re-parameterization, the melting temperature of the modified potential is found to be 931.5K +/- 1.5K.Comment: 9 pages, 5 figures, 4 table

Improved lattice QCD with quarks: the 2 dimensional case

QCD in two dimensions is investigated using the improved fermionic lattice Hamiltonian proposed by Luo, Chen, Xu, and Jiang. We show that the improved theory leads to a significant reduction of the finite lattice spacing errors. The quark condensate and the mass of lightest quark and anti-quark bound state in the strong coupling phase (different from t'Hooft phase) are computed. We find agreement between our results and the analytical ones in the continuum.Comment: LaTeX file (including text + 10 figures

Antiferromagnetism in metals: from the cuprate superconductors to the heavy fermion materials

The critical theory of the onset of antiferromagnetism in metals, with concomitant Fermi surface reconstruction, has recently been shown to be strongly coupled in two spatial dimensions. The onset of unconventional superconductivity near this critical point is reviewed: it involves a subtle interplay between the breakdown of fermionic quasiparticle excitations on the Fermi surface, and the strong pairing glue provided by the antiferromagnetic fluctuations. The net result is a logarithm-squared enhancement of the pairing vertex for generic Fermi surfaces, with a universal dimensionless co-efficient independent of the strength of interactions, which is expected to lead to superconductivity at the scale of the Fermi energy. We also discuss the possibility that the antiferromagnetic critical point can be replaced by an intermediate `fractionalized Fermi liquid' phase, in which there is Fermi surface reconstruction but no long-range antiferromagnetic order. We discuss the relevance of this phase to the underdoped cuprates and the heavy-fermion materials.Comment: Talk at SCES 2011; 19 pages, 12 figures; (v2) corrected typo

Experimental realization of a 218-ion multi-qubit quantum memory

Storage lifetime and capacity are two important factors to characterize the performance of a quantum memory. Here we report the stable trapping of above 200 ions in a cryogenic setup, and demonstrate the combination of the multi-qubit capacity and long storage lifetime by measuring the coherence time of randomly chosen ions to be on the order of hundreds of milliseconds. We apply composite microwave pulses to manipulate qubit states globally for efficient characterization of different storage units simultaneously, and we compare the performance of the quantum memory with and without the sympathetic cooling laser, thus unambiguously show the necessity of sympathetic cooling for the long-time storage of multiple ionic qubits

Effect of cryogenic and heat treatment on microstructure and mechanical properties of Al-7Si-1,5Cu-Mg

An Al-7Si-1.5Cu-Mg alloy was synthesized through the modification of a commercial A356 alloy with the inclusion of alloying elements. This alloy underwent a treatment regime comprising solid solution, cryogenic treatment, and ageing. The results indicate that cryogenic treatment increased nucleation rate of precipitates, which increases the number of precipitates and reduces their sizes, ultimately improving the mechanical properties and reduce secondary dendrite arm spacing of the alloy. Under the optimal treatment conditions (solid solution at 520 °C for 10 hours, followed by deep cooling for 48 hours, and ageing at 160 °C for 10 hours), the secondary dendrite arm spacing of the alloy was reduced by approximately 37,5 %, exhibiting hardness of 102,8 HV and plasticity of 4,2 %

Effect of cryogenic and heat treatment on microstructure and mechanical properties of Al-7Si-1,5Cu-Mg

An Al-7Si-1.5Cu-Mg alloy was synthesized through the modification of a commercial A356 alloy with the inclusion of alloying elements. This alloy underwent a treatment regime comprising solid solution, cryogenic treatment, and ageing. The results indicate that cryogenic treatment increased nucleation rate of precipitates, which increases the number of precipitates and reduces their sizes, ultimately improving the mechanical properties and reduce secondary dendrite arm spacing of the alloy. Under the optimal treatment conditions (solid solution at 520 °C for 10 hours, followed by deep cooling for 48 hours, and ageing at 160 °C for 10 hours), the secondary dendrite arm spacing of the alloy was reduced by approximately 37,5 %, exhibiting hardness of 102,8 HV and plasticity of 4,2 %

Equivalence of conservation laws and equivalence of potential systems

We study conservation laws and potential symmetries of (systems of) differential equations applying equivalence relations generated by point transformations between the equations. A Fokker-Planck equation and the Burgers equation are considered as examples. Using reducibility of them to the one-dimensional linear heat equation, we construct complete hierarchies of local and potential conservation laws for them and describe, in some sense, all their potential symmetries. Known results on the subject are interpreted in the proposed framework. This paper is an extended comment on the paper of J.-q. Mei and H.-q. Zhang [Internat. J. Theoret. Phys., 2006, in press].Comment: 10 page

ACBD3 functions as a scaffold to organize the Golgi stacking proteins and a Rab33b-GAP

Golgin45 plays important roles in Golgi stack assembly and is known to bind both the Golgi stacking protein GRASP55 and Rab2 in the medial‐Golgi cisternae. In this study, we sought to further characterize the cisternal adhesion complex using a proteomics approach. We report here that Acyl‐CoA binding domain containing 3 (ACBD3) is likely to be a novel binding partner of Golgin45. ACBD3 interacts with Golgin45 via its GOLD domain, while its co‐expression significantly increases Golgin45 targeting to the Golgi. Furthermore, ACBD3 recruits TBC1D22, a Rab33b GTPase activating protein (GAP), to a large multi‐protein complex containing Golgin45 and GRASP55. These results suggest that ACBD3 may provide a scaffolding to organize the Golgi stacking proteins and a Rab33b‐GAP at the medial‐Golgi