A new view of quiet-Sun topology from Hinode/SOT

Context. With the recent launch of the Hinode satellite our view of the nature and evolution of quiet-Sun regions has been improved. In light of the new high resolution observations, we revisit the study of the quiet Sun's topological nature. Aims. Topology is a tool to explain the complexity of the magnetic field, the occurrence of reconnection processes, and the heating of the corona. This Letter aims to give new insights to these different topics. Methods. Using a high-resolution Hinode/SOT observation of the line-of-sight magnetic field on the photosphere, we calculate the three dimensional magnetic field in the region above assuming a potential field. From the 3D field, we determine the existence of null points in the magnetic configuration. Results. From this model of a continuous field, we find that the distribution of null points with height is significantly different from that reported in previous studies. In particular, the null points are mainly located above the bottom boundary layer in the photosphere (54%) and in the chromosphere (44%) with only a few null points in the corona (2%). The density of null points (expressed as the ratio of the number of null points to the number of photospheric magnetic fragments) in the solar atmosphere is estimated to be between 3% and 8% depending on the method used to identify the number of magnetic fragments in the observed photosphere. Conclusions. This study reveals that the heating of the corona by magnetic reconnection at coronal null points is unlikely. Our findings do not rule out the heating of the corona at other topological features. We also report the topological complexity of the chromosphere as strongly suggested by recent observations from Hinode/SOT

The McDonald Site: An Analysis of WPA Excavations at a Caddo Site in the Glover River Drainage, McCurtain County, Oklahoma

Between December 1941 and March 1942, the final federally-sponsored WPA excavations in Oklahoma were conducted at the McDonald site, located along the Glover River. Because federal funds for analysis dried up as the country entered into World War II, the recovered artifacts were never fully analyzed. Between 2008-2009, I analyzed the non-mortuary artifacts, which are curated at the Sam Noble Oklahoma Museum of Natural History (SNOMNH) in Norman, and conducted an analysis of recovered stone and ceramic artifacts. Using previously unknown information from a recently unearthed final WPA Quarterly report, in this article I describe excavations and present the results of my analysis. I also incorporate Elsbeth Dowd’s previous analysis of the whole vessels recovered from burials into my study and compare the McDonald site material to the assemblages from two downstream mound sites, Clement and A.W. Davis

Passive propellant system

The system utilizes a spherical tank structure A separated into two equal volume compartments by a flat bulkhead B. Each compartment has four similar gallery channel legs located in the principal vehicle axes, ensuring that bulk propellant will contact at least one gallery leg during vehicle maneuvers. The forward compartment gallery channel legs collect propellant and feed it into the aft compartment through communication screens which protrude into the aft compartment. The propellant is then collected by the screened gallery channels in the aft compartment and supplied to the propellant outlet. The invention resides in the independent gallery assembly and screen structure by means of which propellant flow from forward to aft compartments is maintained. Liquid surface tension of the liquid on the screens is used to control liquid flow. The system provides gas-free propellants in low or zero-g environments regardless of axial accelerations and propellant orientation in bulk regions of the vessel

Differential interaction nets

AbstractWe introduce interaction nets for a fragment of the differential lambda-calculus and exhibit in this framework a new symmetry between the of course and the why not modalities of linear logic, which is completely similar to the symmetry between the tensor and par connectives of linear logic. We use algebraic intuitions for introducing these nets and their reduction rules, and then we develop two correctness criteria (weak typability and acyclicity) and show that they guarantee strong normalization. Finally, we outline the correspondence between this interaction nets formalism and the resource lambda-calculus

Report: Abstracts from the 2018 Caddo Conference in Idabel, Oklahoma

The 2018 Caddo Conference was held March 8-10, 2018 at the Museum of the Red River in Idabel, Oklahoma. Fifty attendees registered for the conference. The conference began with a reception at the museum on Thursday evening. On Friday, the program included eight papers and presentations covering archaeological work in Texas and Oklahoma and a longer presentation on the rebuilding of the Caddo house at Caddo Mounds State Park in Texas. A poster session was also held on Friday afternoon. Conference attendees were given a tour of the collections housed at the museum, which include a large collection of Caddo vessels and objects from all over the world. Friday ended with dances by the Metro Oklahoma City (OKC) Caddo Culture Club, beginning with the Turkey Dance and a delicious barbecue dinner held at the museum. On Saturday, the eight presentations covered sites in Arkansas and Oklahoma, Spiro iconography, and included a presentation on the Spiro exhibit forthcoming at the Cowboy and Western Heritage Museum in Oklahoma City. Just before breaking for lunch on Saturday, Caddo Culture Club and Metro OKC Caddo Culture Club members led a song using the large drum on exhibit in the museum

Filament Compliance Influences Cooperative Activation of Thin Filaments and the Dynamics of Force Production in Skeletal Muscle

Striated muscle contraction is a highly cooperative process initiated by Ca2+ binding to the troponin complex, which leads to tropomyosin movement and myosin cross-bridge (XB) formation along thin filaments. Experimental and computational studies suggest skeletal muscle fiber activation is greatly augmented by cooperative interactions between neighboring thin filament regulatory units (RU-RU cooperativity; 1 RU = 7 actin monomers+1 troponin complex+1 tropomyosin molecule). XB binding can also amplify thin filament activation through interactions with RUs (XB-RU cooperativity). Because these interactions occur with a temporal order, they can be considered kinetic forms of cooperativity. Our previous spatially-explicit models illustrated that mechanical forms of cooperativity also exist, arising from XB-induced XB binding (XB-XB cooperativity). These mechanical and kinetic forms of cooperativity are likely coordinated during muscle contraction, but the relative contribution from each of these mechanisms is difficult to separate experimentally. To investigate these contributions we built a multi-filament model of the half sarcomere, allowing RU activation kinetics to vary with the state of neighboring RUs or XBs. Simulations suggest Ca2+ binding to troponin activates a thin filament distance spanning 9 to 11 actins and coupled RU-RU interactions dominate the cooperative force response in skeletal muscle, consistent with measurements from rabbit psoas fibers. XB binding was critical for stabilizing thin filament activation, particularly at submaximal Ca2+ levels, even though XB-RU cooperativity amplified force less than RU-RU cooperativity. Similar to previous studies, XB-XB cooperativity scaled inversely with lattice stiffness, leading to slower rates of force development as stiffness decreased. Including RU-RU and XB-RU cooperativity in this model resulted in the novel prediction that the force-[Ca2+] relationship can vary due to filament and XB compliance. Simulations also suggest kinetic forms of cooperativity occur rapidly and dominate early to get activation, while mechanical forms of cooperativity act more slowly, augmenting XB binding as force continues to develop

Sarcomere Lattice Geometry Influences Cooperative Myosin Binding in Muscle

In muscle, force emerges from myosin binding with actin (forming a cross-bridge). This actomyosin binding depends upon myofilament geometry, kinetics of thin-filament Ca2+ activation, and kinetics of cross-bridge cycling. Binding occurs within a compliant network of protein filaments where there is mechanical coupling between myosins along the thick-filament backbone and between actin monomers along the thin filament. Such mechanical coupling precludes using ordinary differential equation models when examining the effects of lattice geometry, kinetics, or compliance on force production. This study uses two stochastically driven, spatially explicit models to predict levels of cross-bridge binding, force, thin-filament Ca2+ activation, and ATP utilization. One model incorporates the 2-to-1 ratio of thin to thick filaments of vertebrate striated muscle (multi-filament model), while the other comprises only one thick and one thin filament (two-filament model). Simulations comparing these models show that the multi-filament predictions of force, fractional cross-bridge binding, and cross-bridge turnover are more consistent with published experimental values. Furthermore, the values predicted by the multi-filament model are greater than those values predicted by the two-filament model. These increases are larger than the relative increase of potential inter-filament interactions in the multi-filament model versus the two-filament model. This amplification of coordinated cross-bridge binding and cycling indicates a mechanism of cooperativity that depends on sarcomere lattice geometry, specifically the ratio and arrangement of myofilaments

Influence of dietary constituents on intestinal absorption of aluminum

Orally-ingested aluminum compounds have been implicated in the development of dialysis encephalopathy, osteomalacic dialysis osteodystrophy and other disorders in both hemodialyzed and nonhemodialyzed patients suffering from chronic renal failure [1–10]. Both dialysate aluminum content [7, 11, 12] and aluminum-containing phosphate binding agents [12–15] have been identified as contributing to hyperaluminemia in uremic patients. The health threat from dialysate fluids has been reduced by the recommendation that the dialysate contains less than 10 µg/liter of aluminum [16]. Alternative phosphate-binding agents which do not contain aluminum are available but these agents are not free of problems [17], and uremic patients continue to ingest significant doses of aluminum-containing phosphate binding agents.Aluminum is the most common metal in the biosphere of humans but, aside from uremic patients, causes no widespread toxicity. This may be as a result of the extremely limited solubility of aluminum at the pH range of the small intestine and blood [18]. Advances in analytical chemistry have made it possible to measure picogram quantities of aluminum in body fluids, thus enabling accurate determination of plasma aluminum levels in the part per billion (µg/liter) range. These analytical techniques have shown that orally ingested aluminum-containing antacids elevate plasma aluminum levels in man [13]. Balance studies monitoring aluminum absorption and elimination revealed an average positive balance from 23 to 313mg of aluminum per day when diets were supplemented with 1 to 3g of aluminum per day [15]. These studies show that a small fraction of the ingested aluminum is absorbed. This absorption presents potential toxic effects to uremic patients whose ability to eliminate aluminum is impaired.In addition, Slanina et al [19] have shown that addition of citric acid to aluminum-supplemented dietary regimens results in blood aluminum levels that are significantly higher than those found in subjects treated with aluminum-supplemented dietary regimens alone. This result suggests that dietary factors may contribute to aluminum absorption.This study was undertaken to determine if the form of aluminum present in the intestinal lumen significantly affects the absorption of aluminum following oral ingestion

A Unifying look at d-dimensional periodicities ans space covering

We propose a formal characterization of d-dimensional periodicities. We show first that any periodic pattern has a canonical decomposition and a minimal generator, generalizing the 1D property. This allows to classify the d-dimensional patterns in d+1 classes, according to their periodicities, each class having subclasses. A full classification of the coverings of a 2-dimensional space by a pattern follows. These results have important algorithmic issues in pattern matching. First, the covering classification allows an efficient use of the now classical duel paradigm. Second, d-dimensional pattern matching complexity is intrinsically different for each class

Effect of Troponin Ca2+ Binding Properties on the Kinetics of Myofibril Force Initiation and Relaxation

Digitalitzat per Artypla