26 research outputs found

    When Plans Change: Examining How People Evaluate Timing Changes in Work Organizations

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    Thrombotic Thrombocytopenic Purpura Associated with Pneumococcal Sepsis

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    The first documented case of thrombotic thrombocytopenic purpura (TTP) associated with pneumococcal septicemia is reported. This association has been previously demonstrated with hemolytic uremic syndrome. The patient presented with recurrent seizures, oliguric renal failure, fever, thrombocytopenia and microangiopathic hemolytic anemia; coagulation studies were normal. Blood and sputum cultures were positive for Streptococcus pneumoniae. The patient responded to therapy with plasmapheresis and antiplatelet agents as well as antibiotics. Coincident infection should be searched for in all cases of TTP.Peer Reviewe

    Thrombotic thrombocytopenic purpura associated with pneumococcal sepsis

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    The first documented case of thrombotic thrombocytopenic purpura (TTP) associated with pneumococcal septicemia is reported. This association has been previously demonstrated with hemolytic uremic syndrome. The patient presented with recurrent seizures, oliguric renal failure, fever, thrombocytopenia and microangiopathic hemolytic anemia; coagulation studies were normal. Blood and sputum cultures were positive for Streptococcus pneumoniae. The patient responded to therapy with plasmapheresis and antiplatelet agents as well as antibiotics. Coincident infection should be searched for in all cases of TTP

    CLIFF: A component-based, machine-learned, intermolecular force field

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    Computation of intermolecular interactions is a challenge in drug discovery because accurate ab initio techniques are too computationally expensive to be routinely applied to drug-protein models. Classical force fields are more computationally feasible, and force fields designed to match symmetry adapted perturbation theory (SAPT) interaction energies can remain accurate in this context. Unfortunately, the application of such force fields is complicated by the laborious parameterization required for computations on new molecules. Here, we introduce the component-based machine-learned intermolecular force field (CLIFF), which combines accurate, physics-based equations for intermolecular interaction energies with machine-learning models to enable automatic parameterization. The CLIFF uses functional forms corresponding to electrostatic, exchange-repulsion, induction/polarization, and London dispersion components in SAPT. Molecule-independent parameters are fit with respect to SAPT2+(3)ήMP2/aug-cc-pVTZ, and molecule-dependent atomic parameters (atomic widths, atomic multipoles, and Hirshfeld ratios) are obtained from machine learning models developed for C, N, O, H, S, F, Cl, and Br. The CLIFF achieves mean absolute errors (MAEs) no worse than 0.70 kcal mol−1 in both total and component energies across a diverse dimer test set. For the side chain-side chain interaction database derived from protein fragments, the CLIFF produces total interaction energies with an MAE of 0.27 kcal mol−1 with respect to reference data, outperforming similar and even more expensive methods. In applications to a set of model drug-protein interactions, the CLIFF is able to accurately rank-order ligand binding strengths and achieves less than 10% error with respect to SAPT reference values for most complexes

    P si 4N um P y: An Interactive Quantum Chemistry Programming Environment for Reference Implementations and Rapid Development

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    Psi4NumPy demonstrates the use of efficient computational kernels from the open-source Psi4 program through the popular NumPy library for linear algebra in Python to facilitate the rapid development of clear, understandable Python computer code for new quantum chemical methods, while maintaining a relatively low execution time. Using these tools, reference implementations have been created for a number of methods, including self-consistent field (SCF), SCF response, many-body perturbation theory, coupled-cluster theory, configuration interaction, and symmetry-adapted perturbation theory. Furthermore, several reference codes have been integrated into Jupyter notebooks, allowing background, underlying theory, and formula information to be associated with the implementation. Psi4NumPy tools and associated reference implementations can lower the barrier for future development of quantum chemistry methods. These implementations also demonstrate the power of the hybrid C++/Python programming approach employed by the Psi4 program

    PSI4 1.4 : Open-source software for high-throughput quantum chemistry

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    PSI4 is a free and open-source ab initio electronic structure program providing implementations of Hartree-Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient, thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows; method developers also have access to most of PSI4's core functionalities via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSCHEMA data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCARCHIVE INFRASTRUCTURE project, makes the latest version of PSI4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs.Peer reviewe
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