CHANGES IN VISITORS\u27 ENVIRONMENTAL FOCUS DURING AN APPRECIATIVE RECREATION EXPERIENCE

Recreation that involves learning, viewing, observing, studying, identifying, or photographing nature (e.g., birds, plants, or wildlife) may be termed appreciative recreation. As appreciative wildland recreation participation continues to increase, an understanding of the development of on-site experiences for recreationists will be important for helping managers meet visitor needs, meet objectives for education during experiences, and managing social and ecological impacts related to the activity. The purpose of this study is to investigate the developmental nature of appreciative recreation experiences. Clawson and Knetsch (1966) are typically cited as the first researchers to identify that an outdoor recreation experience has multiple phases and changes over the course of an experience. Specifically, this study investigates the on-site phase of an appreciative recreation experience and seeks to determine the effects of time spent in the natural environment. The intent is to measure how time influences the appreciative qualities (environmental focus) of those who are participating in this form of recreation. Data were collected at Congaree National Park, where appreciative recreation opportunities are abundant. A version of the experiential sampling method (ESM) was used to measure dependent variables a number of times during a recreationist\u27s experience. A sample of 158 visitors each completed 4 experience sampling forms. Data were then subjected to confirmatory factor analysis and multi-level modeling analysis. It was found that time does have a significant influence on the development of an appreciative recreation experience. Finally, it was found that there are three phases of an on-site, appreciative recreation experience (preparation, immersion, and separation)

Inferring the CO2 Abundance in Comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a from [O I] Observations: Implications for the Source of Icy Grains in Cometary Comae

The study of cometary composition is important for understanding our solar system's early evolutionary processes. Carbon dioxide (CO2) is a common hypervolatile in comets that can drive activity but is more difficult to study than other hypervolatiles due to severe telluric absorption. CO2 can only be directly observed from space-borne assets. Therefore, a proxy is needed to measure CO2 abundances in comets using ground-based observations. The flux ratio of the [O I] 5577 A line to the sum of the [O I] 6300 A and [O I] 6364 A lines (hereafter referred to as the [O I] line ratio) has, with some success, been used in the past as such a proxy. We present an [O I] line ratio analysis of comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a (HMP), using data obtained with the Tull Coud\'e Spectrograph on the 2.7-meter Harlan J. Smith telescope at McDonald Observatory, taken from UT February 21-23, 2017 when the comet was at heliocentric distances of 1.12-1.15 AU. HMP is a hyperactive Jupiter family comet (JFC). Icy grains driven out by CO2 sublimation have been proposed as a driver of hyperactivity, but the CO2 abundance of HMP has not been measured. From our [O I] line ratio measurements, we find a CO2/H2O ratio for HMP of 22.9 +/- 1.4%. We compare the CO2/H2O ratios to the active fractions of the nine comets (including HMP) in the literature that have data for both values. We find no correlation. These findings imply that CO2 sublimation driving out icy grains is not the only factor influencing active fractions for cometary nuclei.Comment: 17 pages, 8 figures. To be published in The Planetary Science Journa

Housing wealth effects: the long view

We provide new time-varying estimates of the housing wealth effect back to the 1980s. We use three identification strategies: OLS with a rich set of controls, the Saiz housing supply elasticity instrument, and a new instrument that exploits systematic differences in city-level exposure to regional house price cycles. All three identification strategies indicate that housing wealth elasticities were if anything slightly smaller in the 2000s than in earlier time periods. This implies that the important role housing played in the boom and bust of the 2000s was due to larger price movements rather than an increase in the sensitivity of consumption to house prices. Full-sample estimates based on our new instrument are smaller than recent estimates, though they remain economically important. We find no significant evidence of a boom-bust asymmetry in the housing wealth elasticity. We show that these empirical results are consistent with the behavior of the housing wealth elasticity in a standard life-cycle model with borrowing constraints, uninsurable income risk, illiquid housing, and long-term mortgages. In our model, the housing wealth elasticity is relatively insensitive to changes in the distribution of LTV for two reasons: First, low-leverage homeowners account for a substantial and stable part of the aggregate housing wealth elasticity; Second, a rightward shift in the LTV distribution increases not only the number of highly sensitive constrained agents but also the number of underwater agents whose consumption is insensitive to house prices.1623801, - National Science FoundationAccepted manuscrip

Regulation of Muscle Satellite Cell Activation and Chemotaxis by Angiotensin II

The role of angiotensin II (Ang II) in skeletal muscle is poorly understood. We report that pharmacological inhibition of Ang II signaling or ablation of the AT1a receptor significantly impaired skeletal muscle growth following myotrauma, in vivo, likely due to impaired satellite cell activation and chemotaxis. In vitro experiments demonstrated that Ang II treatment activated quiescent myoblasts as evidenced by the upregulation of myogenic regulatory factors, increased number of β-gal+, Myf5-LacZ myoblasts and the acquisition of cellular motility. Furthermore, exogenous treatment with Ang II significantly increased the chemotactic capacity of C2C12 and primary cells while AT1a−/− myoblasts demonstrated a severe impairment in basal migration and were not responsive to Ang II treatment. Additionally, Ang II interacted with myoblasts in a paracrine-mediated fashion as 4 h of cyclic mechanical stimulation resulted in Ang II-induced migration of cocultured myoblasts. Ang II-induced chemotaxis appeared to be regulated by multiple mechanisms including reorganization of the actin cytoskeleton and augmentation of MMP2 activity. Collectively, these results highlight a novel role for Ang II and ACE inhibitors in the regulation of skeletal muscle growth and satellite cell function

Association of Interleukin-6 Signalling with the Muscle Stem Cell Response Following Muscle-Lengthening Contractions in Humans

BACKGROUND: The regulation of muscle stem cells in humans in response to muscle injury remains largely undefined. Recently, interleukin-6 (IL-6) has been implicated in muscle stem cell (satellite cell)-mediated muscle hypertrophy in animals; however, the role of IL-6 in the satellite cell (SC) response following muscle-lengthening contractions in humans has not been studied. METHODOLOGY/PRINCIPAL FINDINGS: Eight subjects (age 22+/-1 y; 79+/-8 kg) performed 300 maximal unilateral lengthening contractions (3.14 rad.s(-1)) of the knee extensors. Blood and muscle samples were collected before and at 4, 24, 72, and 120 hours post intervention. IL-6, IL-6 receptor, IL-6R(alpha), cyclin D1, suppressor of cytokine signling-3 (SOCS3) mRNA were measured using quantitative RT-PCR and serum IL-6 protein was measured using an ELISA kit. JAK2 and STAT3 phosphorylated and total protein was measured using western blotting techniques. Immunohistochemical analysis of muscle cross-sections was performed for the quantification of SCs (Pax7(+) cells) as well as the expression of phosphorylated STAT3, IL-6, IL-6R(alpha), and PCNA across all time-points. The SC response, as defined by an amplification of Pax7(+) cells, was rapid, increasing by 24 h and peaking 72 h following the intervention. Muscle IL-6 mRNA increased following the intervention, which correlated strongly (R(2) = 0.89, p<0.002) with an increase in serum IL-6 concentration. SC IL-6R(alpha) protein was expressed on the fiber, but was also localized to the SC, and IL-6(+) SC increased rapidly following muscle-lengthening contractions and returned to basal levels by 72 h post-intervention, demonstrating an acute temporal expression of IL-6 with SC. Phosphorylated STAT3 was evident in SCs 4 h after lengthening contraction, and the downstream genes, cyclin D1 and SOCS3 were significantly elevated 24 hours after the intervention. CONCLUSIONS/SIGNIFICANCE: The increased expression of STAT3 responsive genes and expression of IL-6 within SCs demonstrate that IL-6/STAT3 signaling occurred in SCs, correlating with an increase in SC proliferation, evidenced by increased Pax7(+)/PCNA(+) cell number in the early stages of the time-course. Collectively, these data illustrate that IL-6 is an important signaling molecule associated with the SC response to acute muscle-lengthening contractions in humans

Lytic Water Dynamics Reveal Evolutionarily Conserved Mechanisms of ATP Hydrolysis by TIP49 AAA+ ATPases

SummaryEukaryotic TIP49a (Pontin) and TIP49b (Reptin) AAA+ ATPases play essential roles in key cellular processes. How their weak ATPase activity contributes to their important functions remains largely unknown and difficult to analyze because of the divergent properties of TIP49a and TIP49b proteins and of their homo- and hetero-oligomeric assemblies. To circumvent these complexities, we have analyzed the single ancient TIP49 ortholog found in the archaeon Methanopyrus kandleri (mkTIP49). All-atom homology modeling and molecular dynamics simulations validated by biochemical assays reveal highly conserved organizational principles and identify key residues for ATP hydrolysis. An unanticipated crosstalk between Walker B and Sensor I motifs impacts the dynamics of water molecules and highlights a critical role of trans-acting aspartates in the lytic water activation step that is essential for the associative mechanism of ATP hydrolysis