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Well-formed crystals are polyhedral with flat facets and sharp edges. Nevertheless, a remarkable number of molecular crystals can bend and twist during growth. Many others can be distorted by applying external forces or creating heterogeneities by temperature gradient or photochemical reaction. As part of an effort to identify the forces that so commonly deform molecular crystals and to characterize their consequences, a force field is evaluated for its ability to predict mechanical distortions in nanocrystals. Macroscopic materials provide estimates of the expected responses that were tested here in silico for "molecular bimetallic strips" created from rods of iodoform and bromoform in smooth contact and nanocrystalline rods of iodoform with left and right screw dislocations. It was demonstrated that an optimized force field based largely on AMBER parameters matches expectations for elastic and plastic distortions, despite the fact that these mechanical responses are far removed from the force field parametrization set.

Spiral hillocks on n-alkane crystal surfaces were observed immediately after Frank recognized the importance of screw dislocations for crystal growth, yet their structures and energies in molecular crystals remain ill-defined. To illustrate the structural chemistry of screw dislocations that are responsible for plasticity in organic crystals and upon which the organic electronics and pharmaceutical industries depend, molecular dynamics was used to examine heterochiral dislocation pairs with Burgers vectors along [001] in n-hexane, n-octane, and n-decane crystals. The cores were anisotropic and elongated in the (110) slip plane, with significant local changes in molecular position, orientation, conformation, and energy. This detailed atomic level picture produced a distribution of strain consistent with linear elastic theory, giving confidence in the simulations. Dislocations with doubled Burgers vectors split into pairs with elementary displacements. These results suggest a pathway to understanding the mechanical properties and failure associated with elastic and plastic deformation in soft crystals.

Maximal oxygen consumption (VO2) is the "gold standard" by which to assess functional capacity; however, it is effort dependent. VO2@RER1.0 is defined when VO2 = VCO2. Between December 22, 1997 and November 9, 2004, 305 pediatric subjects underwent cycle ergometer cardiopulmonary exercise testing, exercised to exhaustion, and reached a peak respiratory exchange ratio >=1.10. Group 1 subjects achieved a peak VO2>=80% of predicted VO 2max; group 2 subjects achieved a peak VO2/<=60% of predicted VO2max; and group 3 subjects achieved a peak VO 2 between 61 and 79% of predicted VO2max. Linear regression analysis was performed for VO2@RER1.0 as a function of predicted VO2max for group 1 subjects. A -2 SD regression line and equation was created. VO2@RER1.0 data from groups 2 and 3 were plotted onto the normative graph. Contingency table and relative-risk analysis showed that an abnormal VO2@RER1.0 predicted an abnormal peak VO2 (positive-predictive value 83%, negative-predictive value 85%, sensitivity 84%, and specificity 84%). VO 2@RER1.0 is a highly sensitive, specific, and predictive submaximal index of functional capacity. This submaximal index is easy to identify without subjectivity. This index may aid in the evaluation of subjects who cannot exercise to maximal parameters. © 2009 Springer Science+Business Media, LLC.

The PHM is a high-speed patrol craft under development for possible NATO use. Small size, along with extensive weapon and communications requirements, complicates the problems of antenna selection and location. This document presents the results of an NELC study to provide two hf antennas (1) with maximum possible isolation between them, (2) with reasonable antenna system efficiency, and (3) so arranged that they meet the HERO requirement for the PHM weapons. NELC recommends that a fan antenna be installed for one hf transceive circuit and a 5.33-meter whip for the other. A second whip is recommended for backup. Impedance, pattern, and isolation data are presented. (Author), See also AD-900 485L.

This is a report of a study of operational requirements for the AN/VCC-2 rf distribution system, a multichannel, FM duplex system (manufactured by Radio Engineering Products) operating in the vhf band. Information was obtained by surveys of VCC-2 installations on 22 ships representing four major amphibious classes, and one heavy cruiser; and by consultation with commands having knowledge of the system. Antenna arrangements and rf distribution systems on the ships are described. Seven possible antenna and rf distribution system approaches are discussed and illustrated. These approaches are theoretically evaluated for comparison, in terms of range and performance.