6,518 research outputs found
Christianity and Religious Diversity: Clarifying Christian Commitments in a Globalizing Age
This is a sweeping treatment of navigating the difficulties of engaging a religiously pluralistic culture and offers sage and compassionate advice from one of the leading Christian thinkers today. His special treatment of Buddhism is engaging and should be carefully considered by all. Whether believer, nonbeliever, or none, this book engages all readership with careful research and deserves a wide audience
Evaluation of a stall-flutter spring-damper pushrod in the rotating control system of a CH-54B helicopter
Results of a design and flight test program conducted to define the effect of rotating pushrod damping on stall-flutter induced control loads are presented. The CH-54B helicopter was chosen as the test aircraft because it exhibited stall induced control loads. Damping was introduced into the CH-54B control system by replacing the standard pushrod with spring-damper assemblies. Design features of the spring-damper are described and the results of a dynamic analysis are shown which define the pushrod stiffness and damping requirements. Flight test measurements taken at 47,000 lb gross weight with and without the damper are presented. The results indicate that the spring-damper pushrods reduced high frequency, stall-induced rotating control loads by almost 50%. Fixed system control loads were reduced by 40%. Handling qualities in stall were unchanged, as expected
Generalized X-ray and neutron crystallographic analysis: more accurate and complete structures for biological macromolecules
X-ray and neutron crystallographic data have been combined in a joint structure-refinement procedure that has been developed using recent advances in modern computational methodologies, including cross-validated maximum-likelihood target functions with gradient-based optimization and simulated annealing
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Improved chemistry restraints for crystallographic refinement by integrating the Amber force field into Phenix.
The refinement of biomolecular crystallographic models relies on geometric restraints to help to address the paucity of experimental data typical in these experiments. Limitations in these restraints can degrade the quality of the resulting atomic models. Here, an integration of the full all-atom Amber molecular-dynamics force field into Phenix crystallographic refinement is presented, which enables more complete modeling of biomolecular chemistry. The advantages of the force field include a carefully derived set of torsion-angle potentials, an extensive and flexible set of atom types, Lennard-Jones treatment of nonbonded interactions and a full treatment of crystalline electrostatics. The new combined method was tested against conventional geometry restraints for over 22 000 protein structures. Structures refined with the new method show substantially improved model quality. On average, Ramachandran and rotamer scores are somewhat better, clashscores and MolProbity scores are significantly improved, and the modeling of electrostatics leads to structures that exhibit more, and more correct, hydrogen bonds than those refined using traditional geometry restraints. In general it is found that model improvements are greatest at lower resolutions, prompting plans to add the Amber target function to real-space refinement for use in electron cryo-microscopy. This work opens the door to the future development of more advanced applications such as Amber-based ensemble refinement, quantum-mechanical representation of active sites and improved geometric restraints for simulated annealing
Intensity statistics in the presence of translational noncrystallographic symmetry.
In the case of translational noncrystallographic symmetry (tNCS), two or more copies of a component in the asymmetric unit of the crystal are present in a similar orientation. This causes systematic modulations of the reflection intensities in the diffraction pattern, leading to problems with structure determination and refinement methods that assume, either implicitly or explicitly, that the distribution of intensities is a function only of resolution. To characterize the statistical effects of tNCS accurately, it is necessary to determine the translation relating the copies, any small rotational differences in their orientations, and the size of random coordinate differences caused by conformational differences. An algorithm to estimate these parameters and refine their values against a likelihood function is presented, and it is shown that by accounting for the statistical effects of tNCS it is possible to unmask the competing statistical effects of twinning and tNCS and to more robustly assess the crystal for the presence of twinning
First Science Results From SOFIA/FORCAST: Super-Resolution Imaging of the S140 Cluster at 37\micron
We present 37\micron\ imaging of the S140 complex of infrared sources
centered on IRS1 made with the FORCAST camera on SOFIA. These observations are
the longest wavelength imaging to resolve clearly the three main sources seen
at shorter wavelengths, IRS 1, 2 and 3, and are nearly at the diffraction limit
of the 2.5-m telescope. We also obtained a small number of images at 11 and
31\micron\ that are useful for flux measurement. Our images cover the area of
several strong sub-mm sources seen in the area -- SMM 1, 2, and 3 -- that are
not coincident with any mid-infrared sources and are not visible in our longer
wavelength imaging either. Our new observations confirm previous estimates of
the relative dust optical depth and source luminosity for the components in
this likely cluster of early B stars. We also investigate the use of
super-resolution to go beyond the basic diffraction limit in imaging on SOFIA
and find that the van Cittert algorithm, together with the "multi-resolution"
technique, provides excellent results
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