Rod MOFs are metal-organic frameworks in which the metal-containing secondary building units consist of infinite rods of linked metal-centered polyhedra. For such materials, we identify the points of extension, often atoms, which define the interface between the organic and inorganic components of the structure. The pattern of points of extension defines a shape such as a helix, ladder, helical ribbon, or cylinder tiling. The linkage of these shapes into a three-dimensional framework in turn defines a net characteristic of the original structure. Some scores of rod MOF structures are illustrated and deconstructed into their underlying nets in this way. Crystallographic data for all nets in their maximum symmetry embeddings are provided.
The Perspective “Structural nano-composites” (Y. Dzenis, 25 January, p. 419) describes a quest for improved structural materials and indicates that composites with nanoscale reinforcements would have “exceptional mechanical properties.” Is this true? Why would reinforcements that are small
We have previously presented a precursor-product stable isotopic technique for measuring in vivo the fraction of very low-density lipoprotein-fatty acids (VLDL-FA) derived from de novo lipogenesis (fractional DNL). Here, we propose a technique for converting fractional DNL into absolute rates of DNL and describe its explicit underlying assumptions. The technique combines the fractional DNL method with a modification of the method of S. Klein, V. R. Young, G. L. A. Blackburn, B. R. Bistrain, and R. R. Wolfe (J. Clin. Invest. 78: 928-933, 1986), for estimating hepatic reesterification of free fatty acids (FFA). Infusions of [1,2,3,4-13C]palmitate and [1-13C]acetate are performed concurrently with indirect calorimetry in human subjects. Fractional DNL (based on mass isotopomer distribution analysis of VLDL-FA), the rate of appearance of plasma FFA (Ra of FFA), and net fat oxidation in the whole body are measured. Equations from the hepatic reesterification model, modified to include the contribution from DNL, allow calculation of absolute DNL (= fractional DNL x [Ra of FFA - net whole body fat oxidation], when respiratory quotient < 1.0). Sample results from human subjects with different dietary energy intakes are presented, with calculations of absolute DNL, absolute reesterification, and absolute fat oxidation rates. The assumptions of this technique (in particular, that all fat oxidized is derived at steady state from circulating FFA and that DNL and reesterification of FFA both occur exclusively in liver) are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)
Background: Quality improvement collaboratives (QICs) have emerged as an important strategy to improve processes and outcomes of clinical care through interorganizational learning. Little is known about the organizational factors that support or deter physician practice participation in QICs. Purpose: The aim of this study was to examine organizational influences on physician practices' propensity to participate in QICs. We hypothesized that practice affiliation with an accountable care organization (ACO) and practice ownership by a system or community health center (CHC) would increase the propensity of physician practices to participate in a QIC. Methodology: Data from the third wave of the National Study of Physician Organizations, a nationally representative sample of medical practices ( n = 1,359), were analyzed. Weighted multivariate regression analyses were estimated to examine the association of ACO affiliation, ownership, and QIC participation, controlling for practice size, health information technology capacity, public reporting participation, and practice revenue from Medicaid and uninsured patients. The Sobel–Goodman Test was used to explore the extent to which practice use of quality improvement (QI) methods such as Lean, Six Sigma, and use of plan-do-study-act cycles mediates the relationship between ACO affiliation and QIC participation. Findings: Only 13.6% of practices surveyed in 2012–2013 participated in a QIC. In adjusted analyses, ACO affiliation (odds ratio [ OR ] = 1.51, p < .01), CHC ownership ( OR = 6.57, p < .001), larger practice size ( OR = 14.72, p < .001), and health information technology functionality ( OR = 1.15, p < .001) were positively associated with QIC participation. Practice use of QI methods partially mediated (13.1%–46.7%) the association of ACO affiliation with QIC participation. Practice Implications: ACO-affiliated practices are more likely than non-ACO practices to participate in QICs. Practice size rather than system ownership appears to influence QIC participation. QI methods often promoted and used by health care systems such as CHCs and ACOs may promote QIC participation.
A causal model of health services which includes patient and provider variables, perceived access to care, utilization of services, continuity of care, technical quality of the care process, technical quality of the care outcome, and patient satisfaction is applied to a group of diabetic patients enrolled in the Seattle Prepaid Health Care Project. The enrollees received comprehensive health services at zero out-of-pocket cost from either a prepaid group practice plan or an independent practice plan. Surveys were periodically conducted to determine health status, satisfaction, and demographic characteristics of the enrollees; utilization of services was monitored throughout the experiment. The causal model is operationalized through the use of path analysis. Significant relationships (p less than or equal to .10) were established between satisfaction and perceived access to care, family size, sex, and professional qualifications of the provider; between outcome of care and health status, female education, and physician performance; between physician performance and professional qualifications; between continuity of care and health status and female education; between utilization and perceived access, specialty of provider, and provider system; and between access to care and provider system. The policy implications of the results are discussed.
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A study on the iridium-catalyzed C-H borylation of heteroarenes is reported. Several heteroarenes containing multiple heteroatoms were found to be amenable to C-H borylation catalyzed by the combination of an iridium(I) precursor and tetramethylphenanthroline. The investigations of the scope of the reaction led to the development of powerful rules for predicting the regioselectivity of borylation, foremost of which is that borylation occurs distal to nitrogen atoms. One-pot functionalizations are reported of the heteroaryl boronate esters formed in situ, demonstrating the usefulness of the reported methodology for the synthesis of complex heteroaryl structures. Application of this methodology to the synthesis and late-stage functionalization of biologically active compounds is also demonstrated. Mechanistic studies show that basic heteroarenes can bind to the catalyst and alter the resting state from the olefin-bound complex observed during arene borylation to a species containing a bound heteroarene, leading to catalyst deactivation. Studies on the origins of the observed regioselectivity show that borylation occurs distal to N-H bonds due to rapid N-H borylation, creating an unfavorable steric environment for borylation adjacent to these bonds. Computational studies and mechanistic studies show that the lack of observable borylation of C-H bonds adjacent to basic nitrogen is not the result of coordination to a bulky Lewis acid prior to C-H activation, but the combination of a higher-energy pathway for the borylation of these bonds relative to other C-H bonds and the instability of the products formed from borylation adjacent to basic nitrogen.
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Intermolecular acceptorless dehydrogenative coupling of silanes with arene C−H bonds and intramolecular coupling of silanes with aryl and alkyl C−H bonds occur in good yield in the presence of 5 mol % of Tp<sup>Me</sup><sub><sup>2</sup></sub>PtMe<sub>2</sub>H (Tp<sup>Me</sup><sub><sup>2</sup></sub> = hydridotris(3,5-dimethylpyrazolyl)borate) and related platinum(IV) complexes. The intermolecular reactions of arenes occurred with both trialkyl and dialkylaryl silanes. Intramolecular reactions of dialkylsilylalkylarenes occurred at aryl C−H bonds, and reactions of tributylsilane or dibutylphenylsilane occurred intramolecularly at the aliphatic, primary C−H bond. The reactions of arenes occurred preferentially at the least sterically hindered C−H bonds and preferentially with more electron-poor arenes. Crossover experiments and the lack of reactivity of the arylsilanes with H<sub>2</sub> imply that the dehydrogenative silylation of arenes can be irreversible, even in a closed reaction vessel.
In this work, we propose a contour and region detector for video data that exploits motion cues and distinguishes occlusion boundaries from internal boundaries based on optical flow. This detector outperforms the state-of-the-art on the benchmark of Stein and Hebert, improving average precision from .58 to .72. Moreover, the optical flow on and near occlusion boundaries allows us to assign a depth ordering to the adjacent regions. To evaluate performance on this edge-based figure/ground labeling task, we introduce a new video dataset that we believe will support further research in the field by allowing quantitative comparison of computational models for occlusion boundary detection, depth ordering and segmentation in video sequences.
