Less than 50% sublattice polarization in an insulating S=3/2 kagome' antiferromagnet at low T

We have found weak long range antiferromagnetic order in the quasi-two-dimensional insulating oxide $KCr_3(OD)_6(SO_4)_2$ which contains Cr$^{3+}$ S=3/2 ions on a kagom\'{e} lattice. In a sample with $\approx$ 76% occupancy of the chromium sites the ordered moment is 1.1(3)$\mu_B$ per chromium ion which is only one third of the N\'{e}el value $g\mu_BS=3\mu_B$. The magnetic unit cell equals the chemical unit cell, a situation which is favored by inter-plane interactions. Gapless quantum spin-fluctuations ($\Delta/k_B >$T_N$= 1.6K are the dominant contribution to the spin correlation function,$S(Q,\omega)$ in the ordered phase.Comment: 18 pages, RevTex/Latex, with 6 figure

Corresponding States of Structural Glass Formers

The variation with respect to temperature T of transport properties of 58 fragile structural glass forming liquids (68 data sets in total) are analyzed and shown to exhibit a remarkable degree of universality. In particular, super-Arrhenius behaviors of all super-cooled liquids appear to collapse to one parabola for which there is no singular behavior at any finite temperature. This behavior is bounded by an onset temperature To above which liquid transport has a much weaker temperature dependence. A similar collapse is also demonstrated, over the smaller available range, for existing numerical simulation data.Comment: 6 pages, 2 figures. Updated References, Table Values, Submitted for Publicatio

A phase II study of the histone deacetylase inhibitor vorinostat combined with tamoxifen for the treatment of patients with hormone therapy-resistant breast cancer

BackgroundHistone deacetylases (HDACs) are crucial components of the oestrogen receptor (ER) transcriptional complex. Preclinically, HDAC inhibitors can reverse tamoxifen/aromatase inhibitor resistance in hormone receptor-positive breast cancer. This concept was examined in a phase II combination trial with correlative end points.MethodsPatients with ER-positive metastatic breast cancer progressing on endocrine therapy were treated with 400 mg of vorinostat daily for 3 of 4 weeks and 20 mg tamoxifen daily, continuously. Histone acetylation and HDAC2 expression in peripheral blood mononuclear cells were also evaluated.ResultsIn all, 43 patients (median age 56 years (31-71)) were treated, 25 (58%) received prior adjuvant tamoxifen, 29 (67%) failed one prior chemotherapy regimen, 42 (98%) progressed after one, and 23 (54%) after two aromatase inhibitors. The objective response rate by Response Evaluation Criteria in Solid Tumours criteria was 19% and the clinical benefit rate (response or stable disease >24 weeks) was 40%. The median response duration was 10.3 months (confidence interval: 8.1-12.4). Histone hyperacetylation and higher baseline HDAC2 levels correlated with response.ConclusionThe combination of vorinostat and tamoxifen is well tolerated and exhibits encouraging activity in reversing hormone resistance. Correlative studies suggest that HDAC2 expression is a predictive marker and histone hyperacetylation is a useful pharmacodynamic marker for the efficacy of this combination

Molecular Dynamics Simulations of Spinodal-Assisted Polymer Crystallization

Large scale molecular dynamics simulations of bulk melts of polar (poly(vinylidene fluoride) (pVDF)) polymers are utilized to study chain conformation and ordering prior to crystallization under cooling. While the late stages of polymer crystallization have been studied in great detail, recent theoretical and experimental evidence indicates that there are important phenomena occurring in the early stages of polymer crystallization that are not understood to the same degree. When the polymer melt is quenched from a temperature above the melting temperature to the crystallization temperature, crystallization does not occur instantaneously. This initial interval without crystalline order is characterized as an induction period. It has been thought of as a nucleation period in the classical theories of polymer crystallization, but recent experiments, computer simulations, and theoretical work suggest that the initial period in polymer crystallization is assisted by a spinodal decomposition type mechanism. In this study we have achieved physically realistic length scales to study early stages of polymer ordering, and show that spinodal-assisted ordering prior to crystallization is operative in polar polymers suggesting general applicability of this process

Combining speed and separation monitoring with power and force limiting for safe collaborative robotics applications

Enabling humans and robots to safely work close to each other deserves careful consideration. With the publication of ISO/TS 15066 directives on this matter, two different strategies, namely the Speed and Separation Monitoring and the Power and Force Limiting, have been proposed. This letter proposes a method to efficiently combine the two aforementioned safety strategies for collaborative robotics operations. By exploiting the combination of the two, it is then possible to achieve higher levels of productivity, while still preserving safety of the human operators. This is achieved by the optimal scaling of the initially prescribed velocity, while preserving the path consistency of the robot trajectory. In a nutshell, the state of motion of each point of the robot is monitored so that at every time instant the robot is able to modulate its speed to eventually come into contact with a body region of the human, consistently with the corresponding biomechanical limit. Validation experiments have been conducted to establish that the proposed method enables substantially less stringent limits on robot performance while still allowing for the safety limits prescribed by ISO directives

Chain Dynamics of Ring and Linear Polyethylene Melts from Molecular Dynamics Simulations

The dynamical characteristics of ring and linear polyethylene (PE) molecules in the melt have been studied by employing atomistic molecular dynamics simulations for linear PEs with carbon atom numbers N up to 500 and rings with N up to 1500. The single-chain dynamic structure factors S(q,t) from entangled linear PE melt chains, which show strong deviations from the Rouse predictions, exhibit quantitative agreement with experimental results. Ring PE melt chains also show a transition from the Rouse-type to entangled dynamics, as indicated by the characteristics of S(q,1) and mean-square monomer displacements g(1)(t). For entangled ring PE melts, we observe g(1)(t) similar to t(0.35) and the chain-length dependence of diffusion coefficients D-N proportional to N-1.9, very similar to entangled linear chains. Moreover, the diffusion coefficients D-N remain larger for the entangled rings than the corresponding entangled linear chains, due to about a 3-fold larger chain length for entanglement. Since rings reptate, our results point toward other important dynamical modes, based on mutual relaxations of neighboring chains, for entangled polymers in general. do no