The influence of barefoot and shod running on Triceps-surae muscle strain characteristics

The aim of the current investigation was to determine the effects of barefoot and shod running on the kinematics of the Triceps-Surae muscle group. Twelve male participants ran at 4.0 m.s-1 (± 5%) in both barefoot and shod conditions. Kinematics were measured using an eight-camera motion analysis system. Muscle kinematics from the lateral Gastrocnemius, medial Gastrocnemius and Soleus were obtained using musculoskeletal modelling software (Opensim v3.2). The results showed that muscle strain for the lateral Gastrocnemius (barefoot = 1.10 & shod = 0.33 %), medial Gastrocnemius (barefoot = 1.07 & shod = 0.32 %) and Soleus (barefoot = 3.43 & shod = 2.18 %) were significantly larger for the barefoot condition. Given the proposed association between the extent of muscle strain and the etiology of chronic muscle strain pathologies, the current investigation shows that running barefoot may place runners at greater risk from Triceps-Surae strain injuries

Moment tensors for the mainshock and aftershocks of the 2018-11-30 Mw 7.1 Anchorage earthquake

We determine moment tensor solutions for 18 aftershocks of the 2018-11-30 Mw 7.1 Anchorage earthquake, as well as for the mainshock

Anisotropy in the Alaska subduction zone: shear-wave splitting observations from local and teleseismic earthquakes

Thesis (M.S.) University of Alaska Fairbanks, 2020Shear-wave splitting observations can provide insight to mantle flow due to the link between the deformation of mantle rocks and their direction dependent seismic wave velocities. We identify shear-wave anisotropy in the Cook Inlet segment of the Alaska subduction zone by analyzing splitting parameters of S phases from local intraslab earthquakes between 50 and 200 km depths and SKS waves from teleseismic events. These earthquakes were recorded from 2015-2017 (local S) and 2007-2017 (SKS) by stations from SALMON (Southern Alaska Lithosphere and Mantle Observation Network), TA (EarthScope Transportable Array), MOOS (Multidisciplinary Observations Of Subduction), AVO (Alaska Volcano Observatory), and the permanent network. Automatic phase picking (dbshear) of 12095 local earthquakes (Ml ≥ 1.5) recorded at 84 stations yielded 678 high-quality splitting measurements (filtered 0.2-1 Hz). Teleseismic SKS phases recorded at 112 stations with 26,143 event-station pairs resulted in 360 high-quality SKS splitting measurements (filtered 0.02-1 Hz and 0.01-1 Hz). Measurements for both datasets were made using the SC91 minimum eigenvalue method with software package MFAST. We compare local S and SKS splitting patterns both from previous studies and our own analysis and find that they are most similar in the far forearc, at the Kenai Peninsula, below which there is no mantle wedge. Anisotropy in the subducting Pacific lithosphere and subslab asthenosphere is likely here as both S and SKS display plate convergence fast directions and SKS measurements exhibit delay times too long (∼2 s) to be explained solely by lithospheric anisotropy. Large splitting delay times (∼0.5 s) for local measurements that mainly sample slab further indicate that the Pacific slab lithosphere contains significant anisotropy. We also observe anisotropy in the mantle wedge indicated by an increase in delay time as focal depth increases for stations with ray paths dominantly sampling wedge. These measurements display trench-perpendicular and plate convergence fast directions consistent with 2D corner flow in the mantle wedge. Both datasets show trench-parallel splitting directions in select areas of the arc/forearc that overlie parts of the mantle wedge and nose. B-type olivine in the mantle nose, subslab asthenospheric flow, flow around the slab edge, and anisotropy in the Pacific lithosphere all could be invoked to explain this pattern. While we are unable to distill the anisotropy to a single responsible structure, the sharp transition in the local S data splitting pattern from trench-perpendicular in the backarc to trench-parallel across the arc suggests B-type olivine in the mantle nose. For an overall model, we favor 2D corner flow of A-type olivine in the mantle wedge induced by downdip motion of the slab, B-type olivine in the nose, and plate convergence parallel anisotropy in the subslab asthenosphere and subducting Pacific lithosphere to explain the observed splitting patterns. It is clear that the subducting slab's structure and motion are the dominant influence on anisotropy and mantle flow regimes here. The differences in local S and SKS splitting results motivate further study on frequency dependence of splitting measurements and emphasize the need for a better understanding of which earth structures are responsible for the observed splitting patterns globally. This study constitutes the first comprehensive local splitting study in Alaska and refutes the common interpretation of along arc flow in the mantle wedge proposed by many previous splitting studies in Alaska

Using nodal seismic sensors to estimate seismic moment tensors

This report has two documents pertaining to seismic data recorded by a 400-sensor array in central Alaska between February and March, 2019. The first part examines the influence of removing the instrument response on the amplitude of filtered waveforms. The second part shows how the array of sensors can be used to estimate source mechanisms for local earthquakes.The seismic deployment was support by National Science Foundation awards EAR 1736223 and EAR 1917482. Seismic instruments and database preparations were provided by NSF PASSCAL. The seismic waveforms are archived at the IRIS Data Management Center

Hadronic Resonances from Lattice QCD

The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.Comment: 8 pages, VII Latin American Symposium on Nuclear Physics and Application

Results and Frontiers in Lattice Baryon Spectroscopy

The Lattice Hadron Physics Collaboration (LHPC) baryon spectroscopy effort is reviewed. To date the LHPC has performed exploratory Lattice QCD calculations of the low-lying spectrum of Nucleon and Delta baryons. These calculations demonstrate the effectiveness of our method by obtaining the masses of an unprecedented number of excited states with definite quantum numbers. Future work of the project is outlined.Comment: To appear in the proceedings for the VII Latin American Symposium of Nuclear Physics and Application

Importance of chirality and reduced flexibility of protein side chains: A study with square and tetrahedral lattice models

In simple models side chains are often represented implicitly (e.g., by spin-states) or simplified as one atom. We study side chain effects using square lattice and tetrahedral lattice models, with explicitly side chains of two atoms. We distinguish effects due to chirality and effects due to side chain flexibilities, since residues in proteins are L-residues, and their side chains adopt different rotameric states. Short chains are enumerated exhaustively. For long chains, we sample effectively rare events (eg, compact conformations) and obtain complete pictures of ensemble properties of these models at all compactness region. We find that both chirality and reduced side chain flexibility lower the folding entropy significantly for globally compact conformations, suggesting that they are important properties of residues to ensure fast folding and stable native structure. This corresponds well with our finding that natural amino acid residues have reduced effective flexibility, as evidenced by analysis of rotamer libraries and side chain rotatable bonds. We further develop a method calculating the exact side-chain entropy for a given back bone structure. We show that simple rotamer counting often underestimates side chain entropy significantly, and side chain entropy does not always correlate well with main chain packing. Among compact backbones with maximum side chain entropy, helical structures emerges as the dominating configurations. Our results suggest that side chain entropy may be an important factor contributing to the formation of alpha helices for compact conformations.Comment: 16 pages, 15 figures, 2 tables. Accepted by J. Chem. Phy

Binary Quasars at High Redshift I: 24 New Quasar Pairs at z ~ 3-4

The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142 deg^2 of SDSS imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high redshift binaries (24 of them new discoveries) at redshifts 2.9 < z < 4.3 with proper transverse separations 10 kpc < R_{\perp} < 650 kpc increases the number of such objects known by an order of magnitude. Eight members of this sample are very close pairs with R_{\perp} 3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is ~ 50% complete. Our companion paper uses this knowledge to make the first measurement of the small scale clustering (R < 1 Mpc/h comoving) of high-redshift quasars. High redshift binaries constitute exponentially rare coincidences of two extreme (M >~ 10^9 Msun) supermassive black holes. At z ~ 4 there is about one close binary per 10 Gpc^3, thus these could be the highest sigma peaks, the analogs of superclusters, in the early Universe.Comment: Submitted to Ap

Variability selected high-redshift quasars on SDSS Stripe 82

The SDSS-III BOSS Quasar survey will attempt to observe z>2.15 quasars at a density of at least 15 per square degree to yield the first measurement of the Baryon Acoustic Oscillations in the Ly-alpha forest. To help reaching this goal, we have developed a method to identify quasars based on their variability in the u g r i z optical bands. The method has been applied to the selection of quasar targets in the SDSS region known as Stripe 82 (the Southern equatorial stripe), where numerous photometric observations are available over a 10-year baseline. This area was observed by BOSS during September and October 2010. Only 8% of the objects selected via variability are not quasars, while 90% of the previously identified high-redshift quasar population is recovered. The method allows for a significant increase in the z>2.15 quasar density over previous strategies based on optical (ugriz) colors, achieving a density of 24.0 deg^{-2} on average down to g~22 over the 220 deg^2 area of Stripe 82. We applied this method to simulated data from the Palomar Transient Factory and from Pan-STARRS, and showed that even with data that have sparser time sampling than what is available in Stripe 82, including variability in future quasar selection strategies would lead to increased target selection efficiency in the z>2.15 redshift range. We also found that Broad Absorption Line quasars are preferentially present in a variability than in a color selection.Comment: 14 pages, 21 figures, accepted for publication in A&

Analytical strategies in human growth research

Human growth research requires knowledge of longitudinal statistical methods that can be analytically challenging. Even the assessment of growth between two ages is not as simple as subtracting the first measurement from the second, for example. This article provides an overview of the key analytical strategies available to human biologists in increasing order of complexity, starting with a review on how to express cross-sectional measurements of size, before covering growth (conditional regression models, regression with conditional growth measures), growth curves (individual growth curves, mixed effects growth curves, latent growth curves), and patterns of growth (growth mixture modeling). The article is not a statistical treatise and has been written by a human biologist for human biologists; as such, it should be accessible to anyone with training in at least basic statistics. A summary table linking each analytical strategy to its applications is provided to help investigators match their hypotheses and measurement schedules to an analysis plan. In addition, worked examples using data on non-Hispanic white participants in the Fels Longitudinal Study are used to illustrate how the analytical strategies might be applied to gain novel insight into human growth and its determinants and consequences. All too often, serial measurements are treated as cross-sectional in analyses that do not harness the power of longitudinal data. The broad goal of this article is to encourage the rigorous application of longitudinal statistical methods to human growth research