5,053 research outputs found

    Generalized Newton-Raphson trajectory optimization-generator 1

    Get PDF
    Computer program constructs a sequence of optimal solutions to dynamically-approximate linear equations. Specification of the number and type of subarcs in the optimal solution allows simultaneous satisfaction of all switching criteria

    The Role of the Leaving Group in the Photo-Favorskii Rearrangement of p-Hydroxyphenacyl

    Get PDF
    The p-hydroxyphenacyl group has several features that make it an attractive photoremovable protecting group. Literature examples support this statement and the benzoate, formate, and sulfonate derivatives are not exceptions. The synthesis of these targets is straight forward involving few synthetic steps that produce the desired product in good to excellent yield. The purification of these targets is simplified by the fact that these derivatives are all solids. Their solubility and stability in polar organic solvents and in water at low concentrations, the formate solubility in water is the exception, make them ideal for use in organic synthesis and in biological applications. The bulk of the photochemical reactions on these derivatives were performed using a low intensity commercially available Southern New England Photoreactor fitted with RPR 3000 Å lamps in order to excite the chromophore in the region where reasonable absorptivity is displayed, at or above 300 nm. Departure of the substrate or leaving group from the p-hydroxyphenacyl chromophore occurs by the heterolytic rupture of the covalent bond connecting the two and is a primary photochemical process. The reaction results in the formation of two major photoproducts, the released substrate and a product resulting from the rearrangement of chromophore. Their lack of photochemical or chemical reactivity with other reagents, solvent, or other products established the stability of these two products. Finally, the photochemical release is fast (108 s-1) and efficient (Φdis = 0.20 - 1.00). p-Hydroxyphenacyl (pHP) caged compounds release substrates through a novel photo-Favorskii rearrangement. In an effort to systematically explore the effects of the leaving group on the efficacy of photorelease, a series of pHP substituted phenol, benzoate, formate, phosphate, and sulfonate esters have been examined. The quantum yields (Φ), Stern-Volmer quenching rates (kq), and release rates (kr) were determined. When this data was combined with the data from laser flash photolysis data, a correlation between the release rate and the pKa of the leaving group was observed. The βLG for this correlation was calculated to be roughly -0.24 showing that photorelease of the substrate is less sensitive to the structure and pKa of the leaving group than is the reference deprotonation reaction of water. The modest value of βLG suggests a small amount of bond cleavage to leaving group in the transition state. The mechanism of photorelease in aqueous or mixed aqueous solvents follows an ionic pathway with the substrate and a proton release occurring from the triplet ester forming a triplet biradical. This biradical then decays forming a spirodienedione intermediate which can either react with water as part of a Favorskii-like rearrangement yielding p-hydroxyphenylacetic acid, or it can undergo decarbonylation to form p-quinone methide. Subsequent reaction of p-quinone methide with water results in the formation of p-hydroxybenzyl alcohol. This mechanism is supported by the results of the quenching of the reaction of the benzoates by a triplet quencher (piperylene), the formation of only photoproducts when pHP formate, mesylate, and tosylate were photolyzed in the presence of a triplet sensitizer (acetone), the absorption bands for the triplet biradical and p-quinone methide that were observed using laser flash photolysis, and the appearance and decay of singlet and triplet species in the time resolved spectra of pHP benzoate and tosylate. A Brønsted correlation relating the rate constant for photorelease to the pKa of the substrate leaving group for several pHP derivatives, including the benzoate, formate, and sulfonate esters, which indicated there is a moderate degree of bond cleavage in the transition state for the adiabatic triplet fragmentation step. These results have added further insight into the mechanism for the photo-Favorskii rearrangements of p-hydroxyphenacyl derivatives

    The Tertiary Formations of the Central Region of the United States

    Get PDF
    n/

    Effects of radiation on charge-coupled devices

    Get PDF
    The effects of 1 MeV electron irradiation upon the performance of two phase, polysilicon aluminum gate CCDs are reported. Both n- and p-surface channel and n-buried channel devices are investigated using 64- and 128-stage line arrays. Characteristics measured as a function of radiation dose include: Transfer inefficiency, threshold voltage, field effect mobility, interface state density, full well signal level and dark current. Surface channel devices are found to degrade considerably at less than 10 to the 5th power rads (Si) due to the large increase in fast interface state density caused by radiation. Buried channel devices maintain efficient operation to the highest dose levels used

    Realising the Benefits of Sports and Physical Activity : The Human Capital Model

    Get PDF
    Despite the fact that physical activity is universally acknowledged to be an important part of healthy functioning and well being, the full scope of its value is rarely appreciated. This paper introduces a novel framework for understanding the relationships between physical activity (and specific forms of activity like sports) and different aspects of human development. It proposes that the outcomes of physical activity can be framed as differential �capitals� that represent investments in domain-specific assets � Emotional, Financial, Individual, Intellectual, Physical, and Social. These investments, especially when made early in the life course, can yield significant rewards, both at that time and for years to come. The paper also outlines some of the conditions necessary for the realization of Human Capital growth through sports and physical activity, focusing on the social factors that influence participation for children and young people.A pesar de que la actividad física es reconocida universalmente como una parte importante del funcionamiento saludable y el bienestar, el alcance total de su valor es raramente apreciado. Este artículo presenta un novedoso marco para la comprensión de las relaciones entre la actividad física (y formas específicas de actividad como los deportes) y diferentes aspectos del desarrollo humano. Propone que los resultados de la actividad física pueden enmarcarse como �capitales� diferenciales que representan inversiones en activos relacionados con ámbitos específicos - emocional, financiero, individual, intelectual, físico y social. Estas inversiones, especialmente cuando se realizan pronto en el curso de la vida, pueden dar ventajas significativas, tanto en ese momento como en los años venideros. En el documento también se describen algunas de las condiciones necesarias para la realización de un crecimiento del capital humano a través del deporte y la actividad física, centrándose en los factores sociales que influyen en la participación de los niños y los jóvene

    Factors influencing medical decision- Making for seriously ill patients in the Acute Care Hospital

    Get PDF
    Aim: To acquire a fuller understanding of the influences on decision-making in an acute care hospital for seriously ill patients. Background: Fromthe moment of a diagnosis of serious, potentially life-limiting illness, patients and their families are faced withmultiple, complex and significant decisions that will influence the entire illness trajectory, including their end-of-life care (EOLC). Compounding personal factors is the complexity of dying today with acute ward areas in tertiary hospitals use of technological interventions to prolong life, at all costs being the norm. If hospice care is initiated, in these areas, it is often at too late a stage to relieve distressing symptoms and to offer the person the best possible path of care for a dignified death. Design and methods: A retrospective cohort research design was used for this study. Results: Thirty nine (39) medical records that met the inclusion criteria were audited. While medical records are limited in terms of the quality of the information contained in them in terms of social, behavioural and other qualitative information, the audit obtained detailed clinical information on patient characteristics, clinical care, and family and clinician involvement in the care of these patients. Communication between health professionals and patient and or family were limited. Poor documentation in the medical record did not support shared decision-making with decisions to amend the care pathway to palliative not undertaken in most instances despite no improvement in response to care or deterioration in the patient’s condition. Conclusion: Communication between health care professions, patients and their family’s needs to be addressed. The management of patients who are seriously ill in acute ward areas should be altered to reflect the patient’s condition. Nurses, using a person-centred approach, have a role in advocating for the patient and the family in times of stress. Discussions concerning end-oflife of seriously ill patients need to be open, transparent and communicated as these discussions are critical to ensuring the patient’s wishes are realised

    A new model for the segmentation, propagation and linkage of the Tan-Lu fault zone, East Asia

    Get PDF
    The Tan-Lu fault zone (TLF) is a major strike-slip fault with a long and complex history in East Asia, whose evolution provides a new perspective on the formation of large-scale faults (\u3e1000 km long). Fault displacement analysis, geological mapping and U-Pb LA-ICP-MS dating have been performed to understand the evolution of the TLF. Along-strike displacement variation reveals that the TLF consists of two kinematically independent segments, the northern and southern TLF, with opposite long-term propagation directions. Structural and geochronological studies in the eastern Yanshan belt, located around the linkage area of the southern and northern TLF, indicate that NNE-trending sinistral strike-slip faults initiated at 167–164 Ma and were reactivated at 124–121 Ma. Structural analysis suggests that these early NNE-trending strike-slip faults transferred sinistral motion along the northern TLF into southward thrusting along the Yanshan belt, representing the Middle Jurassic southern termination of the northern TLF. Our studies suggest that the through-going TLF formed when the younger southward-propagating northern TLF merged with the older northward-propagating southern TLF in the Late Jurassic. A new model is thus proposed for the Mesozoic evolution of the TLF. The initiation and southward propagation of the northern TLF is interpreted to have resulted from the southward indentation of the Siberian craton into the amalgamated Central Asian Orogenic Belt and North China block. The divergent mega-splays of the northern TLF likely resulted from westward-younging formation during the clockwise rotation of northeast Asia. Coalescence of two genetically unrelated faults could be an alternative mode for large-scale fault formation
    • …
    corecore