2,042 research outputs found

    Two-electron atoms, ions and molecules

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    The quantum mechanics of two-electron systems is reviewed, starting with the ground state of the helium atom and helium-like ions, with central charge Z2Z\ge 2. For Z=1, demonstrating the stability of the negative hydrogen ion, H^-, cannot be achieved using a mere product of individual electron wave functions, and requires instead an explicit account for the anticorrelation among the two electrons. The wave function proposed by Chandrasekhar is revisited, where the permutation symmetry is first broken and then restored by a counter-term. More delicate problems can be studied using the same strategy: the stability of hydrogen-like ions (M+,m,m)(M^+,m^-,m^-) for any value of the proton-to-electron mass ratio M/mM/m; the energy of the lowest spin-triplet state of helium and helium-like ions; the stability of the doubly-excited hydrogen ion with unnatural parity. The positronium molecule (e+,e+,e,e)(e^+,e^+,e^-,e^-), which has been predicted years ago and discovered recently, can also be shown to be stable against spontaneous dissociation, though the calculation is a little more involved. Emphasis is put on symmetry breaking which can either spoil or improve the stability of systems.Comment: 16 pages, 2 figure

    Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments

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    We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The NanoImprint lithography is used to align perpendicularly lamellar phases, over distances much larger than the natural lamellar periodicity. The modeling relies on self-consistent field calculations done in two- and three-dimensions. We get a good agreement with the NanoImprint lithography setups. We find that, at thermodynamical equilibrium, the ordered BCP lamellae are much better aligned than when the films are deposited on uniform planar surfaces

    An Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System

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    We present an improved measurement of the standard model CP violation parameter sin2phi_1 (also known as sin2beta) based on a sample of 85 times 10^6 B Bbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed in a J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K^{*0}, or J/psi K_L CP-eigenstate decay channel and the flavor of accompanying B meson is identified from itsdecay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain sin2phi_1 = 0.719 +/- 0.074(stat) +/- 0.035(syst). We also report measurements of CP violation parameters for the related B^0 -> J/psi pi^0 decay mode and the penguin-dominated processes B^0 -> eta' K_S, phi K_S and K^+K^- K_S.Comment: 11 pages, 4 figures, 4 tables, contributed to ICHEP200

    Objective response by mRECIST as a predictor and potential surrogate end point of overall survival in advanced HCC

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    Background & Aims: The Modified Response Evaluation Criteria in Solid Tumors (mRECIST) was developed to overcome the limitations of standard RECIST criteria in response assessment of hepatocellular carcinoma (HCC). We aimed to investigate whether objective response by mRECIST accurately predicted overall survival (OS) in patients with advanced HCC treated with systemic targeted therapies and also to preliminarily assess this endpoint as a potential surrogate of OS.Methods: Individual patient data from the BRISK-PS randomized phase III trial comparing brivanib vs. placebo (the first to prospectively incorporate mRECIST) were used to analyze objective response as a predictor of OS in a time-dependent covariate analysis. Patients with available imaging scans during follow-up were included (n = 334; 85% of those randomized). Moreover, a correlation of the survival probability in deciles vs. the observed objective response was performed to evaluate its suitability as a surrogate end-point.Results: Objective response was observed in 11.5% and 1.9% of patients treated with brivanib and placebo respectively, and was associated with a better survival (median OS 15.0 vs. 9.4 months, p < 0.001). In addition, objective response had an independent prognostic value (HR = 0.48; 95% confidence interval [CI], 0.26-0.91, p = 0.025) along with known prognostic factors. Finally, objective response showed promising results as a surrogate of OS in this trial (R = -0.92; 95% CI, -1 to -0.73, p < 0.001). It was an early indicator of the treatment effect (median time to objective response was 1.4 months).Conclusions: Objective response by mRECIST in advanced HCC predicts OS and thus can be considered as a candidate surrogate end-point. Further studies are needed to support this finding.Lay summary: There is a need to identify surrogate end-points for overall survival in advanced hepatocellular carcinoma. We studied patients from the phase III BRISK trial, comparing brivanib treatment with placebo after sorafenib progression. We demonstrate that objective response is an independent predictor of survival and qualifies as a potential surrogate end-point for overall survival in this patient population.Clinical trial number: NCT00825955

    Emerging New Approaches in Desensitization: Targeted Therapies for HLA Sensitization

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    There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or de novo donor-specific HLA antibodies (DSA). The risk of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively, de novo DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response

    Azimuthal Angle Correlations for Rapidity Separated Hadron Pairs in d+Au Collisions at sqrt(s_NN) = 200 GeV

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    We report on two-particle azimuthal angle correlations between charged hadrons at forward/backward (deuteron/gold going direction) rapidity and charged hadrons at mid-rapidity in deuteron-gold (d+Au) and proton-proton (p+p) collisions at sqrt(s_NN) = 200 GeV. Jet structures are observed in the correlations which we quantify in terms of the conditional yield and angular width of away side partners. The kinematic region studied here samples partons in the gold nucleus carrying nucleon momentum fraction x~0.1 to x~0.01. Within this range, we find no x dependence of the jet structure in d+Au collisions.Comment: 330 authors, 6 pages text, 4 figures, no tables. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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