Sheared Ising models in three dimensions

The nonequilibrium phase transition in sheared three-dimensional Ising models is investigated using Monte Carlo simulations in two different geometries corresponding to different shear normals. We demonstrate that in the high shear limit both systems undergo a strongly anisotropic phase transition at exactly known critical temperatures T_c which depend on the direction of the shear normal. Using dimensional analysis, we determine the anisotropy exponent theta=2 as well as the correlation length exponents nu_parallel=1 and nu_perp=1/2. These results are verified by simulations, though considerable corrections to scaling are found. The correlation functions perpendicular to the shear direction can be calculated exactly and show Ornstein-Zernike behavior.Comment: 6 pages, 3 figure

New algorithm for the computation of the partition function for the Ising model on a square lattice

A new and efficient algorithm is presented for the calculation of the partition function in the $S=\pm 1$ Ising model. As an example, we use the algorithm to obtain the thermal dependence of the magnetic spin susceptibility of an Ising antiferromagnet for a $8\times 8$ square lattice with open boundary conditions. The results agree qualitatively with the prediction of the Monte Carlo simulations and with experimental data and they are better than the mean field approach results. For the $8\times 8$ lattice, the algorithm reduces the computation time by nine orders of magnitude.Comment: 7 pages, 3 figures, to appear in Int. J. Mod. Phys.

Embryonic and adult isoforms of XLAP2 form microdomains associated with chromatin and the nuclear envelope

Laminin-associated polypeptide 2 (LAP2) proteins are alternatively spliced products of a single gene; they belong to the LEM domain family and, in mammals, locate to the nuclear envelope (NE) and nuclear lamina. Isoforms lacking the transmembrane domain also locate to the nucleoplasm. We used new specific antibodies against the N-terminal domain of Xenopus LAP2 to perform immunoprecipitation, identification and localization studies during Xenopus development. By immunoprecipitation and mass spectrometry (LC/MS/MS), we identified the embryonic isoform XLAP2γ, which was downregulated during development similarly to XLAP2ω. Embryonic isoforms XLAP2ω and XLAP2γ were located in close association with chromatin up to the blastula stage. Later in development, both embryonic isoforms and the adult isoform XLAP2β were localized in a similar way at the NE. All isoforms colocalized with lamin B2/B3 during development, whereas XLAP2β was colocalized with lamin B2 and apparently with the F/G repeat nucleoporins throughout the cell cycle in adult tissues and culture cells. XLAP2β was localized in clusters on chromatin, both at the NE and inside the nucleus. Embryonic isoforms were also localized in clusters at the NE of oocytes. Our results suggest that XLAP2 isoforms participate in the maintenance and anchoring of chromatin domains to the NE and in the formation of lamin B microdomains

Bringing Agriculture into the GATT: Assessing the Benefits of Trade Liberalization

International Relations/Trade,

Non-equilibrium emission of complex fragments from p+Au collisions at 2.5 GeV proton beam energy

Energy and angular dependence of double differential cross sections d$^2\sigma$/d$\Omega$dE was measured for reactions induced by 2.5 GeV protons on Au target with isotopic identification of light products (H, He, Li, Be, and B) and with elemental identification of heavier intermediate mass fragments (C, N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction mechanisms give comparable contributions to the cross sections. The intranuclear cascade of nucleon-nucleon collisions followed by evaporation from an equilibrated residuum describes low energy part of the energy distributions whereas another reaction mechanism is responsible for high energy part of the spectra of composite particles. Phenomenological model description of the differential cross sections by isotropic emission from two moving sources led to a very good description of all measured data. Values of the extracted parameters of the emitting sources are compatible with the hypothesis claiming that the high energy particles emerge from pre-equilibrium processes consisting in a breakup of the target into three groups of nucleons; small, fast and hot fireball of $\sim$ 8 nucleons, and two larger, excited prefragments, which emits the light charged particles and intermediate mass fragments. The smaller of them contains $\sim$ 20 nucleons and moves with velocity larger than the CM velocity of the proton projectile and the target. The heavier prefragment behaves similarly as the heavy residuum of the intranuclear cascade of nucleon-nucleon collisions. %The mass and charge dependence of the total production cross %sections was extracted from the above analysis for all observed %reaction products. This dependence follows the power low behavior %(A$^{-\tau}$ or Z$^{-\tau}$)

Microtubule detyrosination guides chromosomes during mitosis

Before chromosomes segregate into daughter cells, they align at the mitotic spindle equator, a process known as chromosome congression. Centromere-associated protein E (CENP-E)/Kinesin-7 is a microtubule plus-end-directed kinetochore motor required for congression of pole-proximal chromosomes. Because the plus-ends of many astral microtubules in the spindle point to the cell cortex, it remains unknown how CENP-E guides pole-proximal chromosomes specifically toward the equator. We found that congression of pole-proximal chromosomes depended on specific posttranslational detyrosination of spindle microtubules that point to the equator. In vitro reconstitution experiments demonstrated that CENP-E-dependent transport was strongly enhanced on detyrosinated microtubules. Blocking tubulin tyrosination in cells caused ubiquitous detyrosination of spindle microtubules, and CENP-E transported chromosomes away from spindle poles in random directions. Thus, CENP-E-driven chromosome congression is guided by microtubule detyrosination.We thank F. I. Ataullakhanov for help with the laser trap and data analysis; A. Kiyatkin, V. Mustyatsa, M. Molodtsov, A. Gautreau, G. Lakisic, and M. Barisic for technical assistance; and members of our laboratories for stimulating discussions. This work was supported by National Institutes of Health grant R01-GM098389 and RSG-14-018-01-CCG from the American Cancer Society to E.L.G.; by the Institut Curie, the Centre National de la Recherche Scientifique, the Institut National de la Sante et de la Recherche Medicale, the L'Agence Nationale de la Recherche (ANR) award ANR-12-BSV2-0007, INCA_6517, ANR-10-LBX-0038, part of the IDEX Idex PSL, ANR-10-IDEX-0001-02 PSL to C.J.; and Fundacao Luso-Americana para o Desenvolvimento (FLAD) Life Science 2020 and PRECISE grant from the European Research Council to H.M. A.V.Z. is supported by the RAS Presidium Grants "Mechanisms of the Molecular Systems Integration," " Molecular and Cell Biology programs," and Russian Fund for Basic Research Grant 12-04-00111-a and 13-00-40188. R.S.S. is supported by a fellowship from the Programa Graduado em Areas da Biologia Basica e Aplicada (GABBA) PhD program from the University of Porto. A.L.P. is supported by fellowship SFRH/BPD/66707/2009 from Fundacao para a Ciencia e a Tecnologia of Portugal. M.B., R.S.S., S.K.T., M.M.M., C.J., E.L.G., and H.M. designed the experiments; M.B. performed all experiments in cells; M. M. M. established and performed the tubulin purification protocol from HeLa cells; R.S.S. performed single-molecule experiments; S.K.T. performed force measurements; A.L.P. provided reagents; all authors analyzed data; H.M., E.L.G., and M.B. wrote the paper, with contributions from all authors; H.M. conceived and coordinated the project. Data described can be found in the main figures and supplementary materials. The authors declare no conflict of interests

Upper limits for a narrow resonance in the reaction p + p -> K^+ + (Lambda p)

The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and \Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. Narrow S = -1 resonances predicted by bag model calculations are not visible in the missing mass spectrum. Small structures observed in a previous experiment are not confirmed. Upper limits for the production cross section of a narrow resonance are deduced for missing masses between 2058 and 2105 MeV/c^2.Comment: 8 pages, 5 figure