754 research outputs found

    Impact of polyphenol-rich sources on acute postprandial glycaemia: a systematic review

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    Increasingly, evidence suggests a role for polyphenols in blood glucose control. The objective of this systematic review was to evaluate the effect of polyphenol-rich sources in combination with carbohydrate sources on resulting postprandial glycaemic and insulin responses. A literature search was conducted using Medline, CINHAL and Web of Science databases. Selected studies included randomised controlled trials in which the association of polyphenol-containing food or beverage consumption with a carbohydrate source and effect on acute postprandial glycaemia and/or insulin was reported. A total of thirteen full articles were included in the review. Polyphenol sources included coffee, black tea, fruit juice, plant extracts, berries and different rye breads, and carbohydrate sources included bread, pancakes and simple sugars such as sucrose, glucose and fructose. Although glycaemic and insulin responses differed depending on the polyphenol-carbohydrate combination, overall, polyphenol sources were shown to reduce the peak and early-phase glycaemic response and maintain the glycaemic response in the later stages of digestion. To a lesser extent, polyphenol sources were also shown to reduce peak insulin response and sustain the insulin response, especially when consumed with bread. This review supports epidemiological data suggesting that polyphenols in foods and beverages may have a beneficial effect on reducing the risk of type 2 diabetes. However, the extent of this effect is variable depending on the polyphenol and carbohydrate source

    Extending complex conjugate control to nonlinear wave energy converters

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    This paper extends the concept of Complex Conjugate Control (CCC) of linear wave energy converters (WECs) to nonlinear WECs by designing optimal limit cycles with Hamiltonian Surface Shaping and Power Flow Control (HSSPFC). It will be shown that CCC for a regular wave is equivalent to a power factor of one in electrical power networks, equivalent to mechanical resonance in a mass-spring-damper (MSD) system, and equivalent to a linear limit cycle constrained to a Hamiltonian surface defined in HSSPFC. Specifically, the optimal linear limit cycle is defined as a second-order center in the phase plane projection of the constant energy orbit across the Hamiltonian surface. This concept of CCC described by a linear limit cycle constrained to a Hamiltonian surface will be extended to nonlinear limit cycles constrained to a Hamiltonian surface for maximum energy harvesting by the nonlinear WEC. The case studies presented confirm increased energy harvesting which utilizes nonlinear geometry realization for reactive power generation

    Nonlinear Hydrostatic Control Of A Wave Energy Converter

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    Increased energy harvesting is realized using a nonlinear buoy geometry for reactive power generation. By exploiting the nonlinear dynamic coupling between the buoy geometry and the potential wideband frequency spectrum of incoming waves in the controller/buoy design, increased power can be captured in comparison to conventional wave energy converter designs. In particular, the reactive power and energy storage system requirements are inherently embedded in the nonlinear buoy geometry, therefore requiring only simple rate-feedback control.https://digitalcommons.mtu.edu/patents/1159/thumbnail.jp

    Pseudo-spectral method to control three-degree-of-freedom wave energy converters

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    The invention provides optimal control of a three-degree-of-freedom wave energy converter using a pseudo-spectral control method. The three modes are the heave, pitch and surge. A dynamic model is characterized by a coupling between the pitch and surge modes, while the heave is decoupled. The heave, however, excites the pitch motion through nonlinear parametric excitation in the pitch mode. The invention can use a Fourier series as basis functions to approximate the states and the control. For the parametric excited case, a sequential quadratic programming approach can be implemented to numerically solve for the optimal control. The numerical results show that the harvested energy from three modes is greater than three times the harvested energy from the heave mode alone. Moreover, the harvested energy using a control that accounts for the parametric excitation is significantly higher than the energy harvested when neglecting this nonlinear parametric excitation term.https://digitalcommons.mtu.edu/patents/1143/thumbnail.jp

    Model predictive control of parametric excited pitch-surge modes in wave energy converters

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    A parametric excitation dynamic model is used for a three degrees-of-freedom (3-DOF) wave energy converter. Since the heave motion is uncoupled from the pitch and surge modes, the pitch-surge equations of motion can be treated as a linear time varying system, or a linear system with parametric excitation. In such case the parametric exciting frequency can be tuned to twice the natural frequency of the system for higher energy harvesting. A parametric excited 3-DOF wave energy converter can harvest more power, for both regular and irregular waves, compared to the linear 3-DOF. For example, in a Bretschneider wave, the harvested energy in the three modes is about 3.8 times the energy harvested in the heave mode alone; while the same device produces about 3.1 times the heave mode energy when using a linear 3-DOF model.https://digitalcommons.mtu.edu/patents/1147/thumbnail.jp

    Multi-resonant feedback control of multiple degree-of-freedom wave energy converters

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    Multi-resonant control of a 3 degree-of-freedom (heave-pitch-surge) wave energy converter enables energy capture that can be in the order of three times the energy capture of a heave-only wave energy converter. The invention uses a time domain feedback control strategy that is optimal based on the criteria of complex conjugate control. The multi-resonant control can also be used to shift the harvested energy from one of the coupled modes to another, enabling the elimination of one of the actuators otherwise required in a 3 degree-of-freedom wave energy converter. This feedback control strategy does not require wave prediction; it only requires the measurement of the buoy position and velocity.https://digitalcommons.mtu.edu/patents/1149/thumbnail.jp

    Nationwide Acute Care Physical Therapist Practice Analysis Identifies Knowledge, Skills, and Behaviors That Reflect Acute Care Practice

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    Background and Purpose. Acute care physical therapists have experienced the effects of dramatic changes in health care reimbursement systems and population demographics. Acute care hospitals now serve a patient population of much older, chronically ill patients who are hospitalized for shorter periods of time in a practice environment in which physical therapy staffing resources are often inadequate. The purposes of this study were to document common experiences in the practice of acute care physical therapy and to identify differences in the perceptions of physical therapists with varying levels of experience and in various sizes of acute care facilities. Subjects and Methods. A survey questionnaire was mailed to 500 randomly selected physical therapists employed in acute care facilities. The therapists answered questions regarding the frequency of various physical therapy evaluation and treatment practices, problems encountered in delivering physical therapy services, coordination of the discharge planning process, and perceptions of staffing trends in the acute care setting. The responses of 188 physical therapists who completed the survey were compared by their experience levels and the size of the institutions in which they practiced. Results. Subjects reported that patient factors, such as medical complications and cooperation; organizational factors, such as staffing shortages and large caseloads; and health care system constraints, such as difficulty changing orders and limited time in which to work with the patient interfered with patients reaching physical therapy goals. Conclusion and Discussion. Inadequate skills for successful acute care practice and maladaptive therapist beliefs about acute care career possibilities may adversely affect physical therapist career longevity in the acute care setting

    Nationwide Acute Care Physical Therapist Practice Analysis Identifies Knowledge, Skills, and Behaviors That Reflect Acute Care Practice

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    Background and Purpose. Acute care physical therapists have experienced the effects of dramatic changes in health care reimbursement systems and population demographics. Acute care hospitals now serve a patient population of much older, chronically ill patients who are hospitalized for shorter periods of time in a practice environment in which physical therapy staffing resources are often inadequate. The purposes of this study were to document common experiences in the practice of acute care physical therapy and to identify differences in the perceptions of physical therapists with varying levels of experience and in various sizes of acute care facilities. Subjects and Methods. A survey questionnaire was mailed to 500 randomly selected physical therapists employed in acute care facilities. The therapists answered questions regarding the frequency of various physical therapy evaluation and treatment practices, problems encountered in delivering physical therapy services, coordination of the discharge planning process, and perceptions of staffing trends in the acute care setting. The responses of 188 physical therapists who completed the survey were compared by their experience levels and the size of the institutions in which they practiced. Results. Subjects reported that patient factors, such as medical complications and cooperation; organizational factors, such as staffing shortages and large caseloads; and health care system constraints, such as difficulty changing orders and limited time in which to work with the patient interfered with patients reaching physical therapy goals. Conclusion and Discussion. Inadequate skills for successful acute care practice and maladaptive therapist beliefs about acute care career possibilities may adversely affect physical therapist career longevity in the acute care setting

    UVUDF: Ultraviolet Imaging of the Hubble Ultradeep Field with Wide-field Camera 3

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    We present an overview of a 90-orbit Hubble Space Telescope treasury program to obtain near ultraviolet imaging of the Hubble Ultra Deep Field using the Wide Field Camera 3 UVIS detector with the F225W, F275W, and F336W filters. This survey is designed to: (i) Investigate the episode of peak star formation activity in galaxies at 1<z<2.5; (ii) Probe the evolution of massive galaxies by resolving sub-galactic units (clumps); (iii) Examine the escape fraction of ionizing radiation from galaxies at z~2-3; (iv) Greatly improve the reliability of photometric redshift estimates; and (v) Measure the star formation rate efficiency of neutral atomic-dominated hydrogen gas at z~1-3. In this overview paper, we describe the survey details and data reduction challenges, including both the necessity of specialized calibrations and the effects of charge transfer inefficiency. We provide a stark demonstration of the effects of charge transfer inefficiency on resultant data products, which when uncorrected, result in uncertain photometry, elongation of morphology in the readout direction, and loss of faint sources far from the readout. We agree with the STScI recommendation that future UVIS observations that require very sensitive measurements use the instrument's capability to add background light through a "post-flash". Preliminary results on number counts of UV-selected galaxies and morphology of galaxies at z~1 are presented. We find that the number density of UV dropouts at redshifts 1.7, 2.1, and 2.7 is largely consistent with the number predicted by published luminosity functions. We also confirm that the image mosaics have sufficient sensitivity and resolution to support the analysis of the evolution of star-forming clumps, reaching 28-29th magnitude depth at 5 sigma in a 0.2 arcsecond radius aperture depending on filter and observing epoch.Comment: Accepted A
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