Dissipative and nonaxisymmetric standard-MRI in Kepler disks

Deviations from axial symmetry are necessary to maintain self-sustained MRI-turbulence. We define the parameters region where nonaxisymmetric MRI is excited and study dependence of the unstable modes structure and growth rates on the relevant parameters. We solve numerically the linear eigenvalue problem for global axisymmetric and nonaxisymmetric modes of standard-MRI in Keplerian disks with finite diffusion. For small magnetic Prandtl number the microscopic viscosity completely drops out from the analysis so that the stability maps and the growth rates expressed in terms of the magnetic Reynolds number Rm and the Lundquist number S do not depend on the magnetic Prandtl number Pm. The minimum magnetic field for onset of nonaxisymmetric MRI grows with Rm. For given S all nonaxisymmetric modes disappear for sufficiently high Rm. This behavior is a consequence of the radial fine-structure of the nonaxisymmetric modes resulting from the winding effect of differential rotation. It is this fine-structure which presents severe resolution problems for the numerical simulation of MRI at large Rm. For weak supercritical magnetic fields only axisymmetric modes are unstable. Nonaxisymmetric modes need stronger fields and not too fast rotation. If Pm is small its real value does not play any role in MRI.Comment: 4 pages, 6 figures, A&A Lette

Detecting Differential Rotation and Starspot Evolution on the M dwarf GJ 1243 with Kepler

We present an analysis of the starspots on the active M4 dwarf GJ 1243, using four years of time series photometry from Kepler. A rapid $P = 0.592596\pm0.00021$ day rotation period is measured due to the $\sim$2.2\% starspot-induced flux modulations in the light curve. We first use a light curve modeling approach, using a Monte Carlo Markov Chain sampler to solve for the longitudes and radii of the two spots within 5-day windows of data. Within each window of time the starspots are assumed to be unchanging. Only a weak constraint on the starspot latitudes can be implied from our modeling. The primary spot is found to be very stable over many years. A secondary spot feature is present in three portions of the light curve, decays on 100-500 day timescales, and moves in longitude over time. We interpret this longitude shearing as the signature of differential rotation. Using our models we measure an average shear between the starspots of 0.0047 rad day$^{-1}$, which corresponds to a differential rotation rate of $\Delta\Omega = 0.012 \pm 0.002$ rad day$^{-1}$. We also fit this starspot phase evolution using a series of bivariate Gaussian functions, which provides a consistent shear measurement. This is among the slowest differential rotation shear measurements yet measured for a star in this temperature regime, and provides an important constraint for dynamo models of low mass stars.Comment: 13 pages, 7 figures, ApJ Accepte

The Role of Utah Farmers in Farm to School Programming

Many studies have observed the involvement of stakeholders in farm to school (FTS) programming to further understand their role, yet no study had previously assessed the role of Utah farmers in FTS programming. As a result, the purpose of this research was to describe Utah farmers\u27 role in FTS programming and their interest in institutional marketing of local foods. The researcher sent an online descriptive survey to 5,470 farmers belonging to the Utah Farm Bureau. The survey used Dillman\u27s Tailored Design Method. Of the 184 survey responses received, 143 surveys were usable. The theory of planned behavior was the theoretical framework for the study. Respondents reported a positive attitude toward FTS programming, although a majority (83.6%) had not participated. They indicated that building relationships with community members and increasing awareness of local food were top benefits associated with FTS programming. Top barriers to participating in FTS programming included a lack of information about schools seeking to purchase local products and restriction of growing seasons. Respondents indicated that they intended to host farm tours for students and food service personnel. Their training and resource needs related to FTS programming included small business assistance. Demographics characteristics revealed a majority of respondents were male and had more than 22 years of farming experience. The subjective norm and perceived behavioral control components of the theory of planned behavior statistically predicted the intention of respondents to participate in farm to school programming. Theory components, including attitude, accounted for 67.2% of the variance in intention to participate in FTS programming. These findings suggest other influences contributed to the intention of respondents to participate in FTS programming. One future research recommendation for FTS programming includes conducting similar studies with different groups of farmers. The researcher recommends continued use of the theory of planned behavior as a theoretical framework for studies assessing involvement in FTS programming. Variables not included in this study may discover further influences on farmers\u27 intention to participate in FTS programming. One recommendation is to increase outreach and marketing to farmers who may be interested in FTS programming

Dietary Regulation of Successful Aging

The current growth of the older population is unprecedented in U.S. history. Chronic disease and functional limitation commonly develop prior to old age, leading to prolonged physical disability and decreased well-being. The development of chronic disease and loss of independence is associated with lean body mass (LBM) loss and fat mass gain beginning in middle age. Therefore, it is important to identify modifiable factors to mitigate deleterious shifts in body composition to promote successful aging (SA). The concept of SA is associated with longevity, the absence of disease and disability, and subjective components of well-being, however, an operational definition has yet to be established. For this thesis, we defined SA as low cardiometabolic risk, preservation of physical function, and a positive state of well-being. Nutrition is a key driver of SA and is a proposed modulator of cardiometabolic risk, physical function, and well-being in adults. Among nutrients, several studies have identified dietary protein and the omega-3 polyunsaturated fatty acids (n-3 PUFAs), eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (DHA; 22:6 n-3), as key supportive nutrients for SA in older adults. Therefore, the overall objective of this dissertation was to determine the effect of nutrition, specifically dietary protein and n-3 PUFAs on SA outcomes of cardiometabolic risk, physical function, and well-being. The central hypothesis of this dissertation was that increased intake of high-quality dietary protein or n-3 PUFAs would improve SA outcomes of cardiometabolic risk, physical function, and well-being in adults. Therefore, one meta-analysis (study 1) and two clinical trials (studies 2 and 3) were designed to test our hypothesis. The objective of the first study was to systematically evaluate the available evidence of randomized control trials assessing the effect of beef and beef’s nutrients on well-being in healthy, adults ≥ 50 years of age to increase physical function and well-being to promote SA. The objective of the second study was to determine and compare the acute effects of a high-protein breakfast containing either animal protein or plant protein on appetite, food intake, energy expenditure, and substrate oxidation in young versus older men to decrease cardiometabolic risk and promote SA. The objective of the third study was to determine the individual and combined effect of protein and n-3 PUFAs on body composition, cardiometabolic risk, indexes of sleep, and mood states in postmenopausal women to decrease cardiometabolic risk and increase physical function, and well-being to promote SA. Collectively, the results suggest high-quality protein and n-3 PUFAs act as potential regulators of SA outcomes. However, additional research is necessary to determine the effectiveness of protein and n-3 PUFA-based nutrition strategies to promote SA