System Of Loops Research Articles

Detection of parallel executable steps for programs with arrays

The detection of informational and logical program step dependencies is a key problem when performing equivalent transformations. In this article we consider this problem for systems of loops which represent concentration of mass computations and are the biggest challenge in parallel execution. The prototype of program formalization is C language just because of it's popularity and it being an intermediate language for compilation of most programming languages including object-oriented ones. We present a shorter version of proof of existence of an algorithm for transforming any system of loops to separated form where data selection for processing is represented as a chain of procedures that select data at least for the immediately following procedures. Last procedure is called a loop kernel; other procedures are referred to as loop controllers. For such programs informational dependencies of loop iterations are determined by a system of natural number equations that connect loop controller functions and index expressions of array variables or array pointers. For the programs where these functions are linear, the solution of such systems is an algorithmically solvable problem. For more complex cases, for example when the functions are arbitrary polynomials, the problem is algorithmically unsolvable. This result points a way to construct programming languages with algorithmically detectable parallelism in the loop kernels. We introduce a notion of data fullness for program classes as ability to select array data elements with any algorithmic function. This characteristic is different from an algorithmic fullness for the classes-class may be full in one sense but not in another.

Statistical mechanics and thermodynamics of turbulent quantum vortex tangles

In this paper we present some phenomenological ideas about the thermodynamics of quantized vortex loops arising in superfluid turbulence. The system of vortex loops may be seen as a dissipative structure, not existing on its own but only under the influence of an external heat flux. Starting from a simple definition of the temperature of the vortex tangle and from the relation between energy and vortex length, we obtain the entropy of the system, as well as the caloric and thermal equations of state, relating internal energy and pressure to temperature and volume. We discuss the connection between our macroscopic results and microscopic results on vortex length distribution function having a potential form.

EXPERIMENTAL ANALYSIS OF SOIL HEAT EXTRACTION SYSTEMS

A 5 kW heat pump water-water function on R22 was built in the Renewable Energy Source Laboratory within the Petroleum Gas University of Ploiesti. The pump was equipped with 4 types of heat extraction systems from the soil: a groundwater well, a 40 m vertical well with a recirculation loop, a system of spiral loops buried at 2 m depth and a 60 m simple loop. This paper deals with the description of the performance obtained with the heat pump operating on a simple polyethylene loop. The experiment confirms that for this type of exchanger there occurs a decline of the thermal power extracted from soil and that the best mathematical description of this phenomenon is obtained with the function generated by the hyperbolic decline.

MAGNETIC RECONNECTION DURING THE TWO-PHASE EVOLUTION OF A SOLAR ERUPTIVE FLARE

We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 A show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for ~11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (~15 km s–1) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Hα flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra during the first phase are soft and indicative of hot thermal emission from flaring loops with temperatures T > 25 MK at the early stage. On the other hand, the spectra at high energies (e 25 keV) follow hard power laws during the second phase (γ = 2.6-2.8). We show that the observed motion of the LT and FP sources can be understood as a consequence of three-dimensional magnetic reconnection at a separator in the corona. During the first phase of the flare, the reconnection releases an excess of magnetic energy related to the magnetic tensions generated before a flare by the shear flows in the photosphere. The relaxation of the associated magnetic shear in the corona by the reconnection process explains the descending motion of the LT source. During the second phase, the ordinary reconnection process dominates describing the energy release in terms of the standard model of large eruptive flares with increasing FP separation and upward motion of the LT source.

New insights into the organization of the basal ganglia

Understanding the functional organization of the basal ganglia requires a broad array of complementary theoretical models. Although the basal ganglia operate as part of a system of parallel cortico-basal ganglia-thalamocortical loops, there is clearly integration between the loops and there are probably more of these loops than previously conceived. Moreover, modulation by external inputs, particularly from the brainstem (eg, pedunculopontine nucleus, raphe nucleus, and locus coeruleus) adds to the complexity of the system. We now appreciate that the organization of the basal ganglia is not static and shows significant plasticity that allows the ganglia to function in learning processes and in response to age or disease, either as components of the pathophysiology or as compensatory mechanisms to reduce the functional impact of disease.

TRANSVERSE OSCILLATIONS OF SYSTEMS OF CORONAL LOOPS

We study the collective kinklike normal modes of a system of several cylindrical loops using the T-matrix theory. Loops that have similar kink frequencies oscillate collectively with a frequency which is slightly different from that of the individual kink mode. On the other hand, if the kink frequency of a loop is different from that of the others, it oscillates individually with its own frequency. Since the individual kink frequency depends on the loop density but not on its radius for typical 1 MK coronal loops, a coupling between kink oscillations of neighboring loops takes place when they have similar densities. The relevance of these results in the interpretation of the oscillations studied by Schrijver & Brown in 2000 and Verwichte et al. in 2004, in which transverse collective loop oscillations seem to be detected, is discussed. In the first case, two loops oscillating in antiphase are observed; interpreting this motion as a collective kink mode suggests that their densities are roughly equal. In the second case, there are almost three groups of tubes that oscillate with similar periods, and therefore their dynamics can be collective, which again seems to indicate that the loops of each group share a similar density. All the other loops seem to oscillate individually and their densities can be different from the rest.

An external body in protected area

In practice, often there is a need for modeling systems for canceling the Earth electrostatic field. For this purpose, a linear circular loop can be used. The realized protection is as better as the used ring is thicker. In practical applications, a system of coaxial linear loops is used instead of one thick ring. In order to find the influence of protected object shape and volume to the electrostatic protection efficiency, a protected object is modeled as a half spherical electrode, placed with its flat side on the ground. According to the theoretical analysis, a general numerical program has been developed and numerical results are shown graphically. .

Asylum seekers' expectations of and trust in general practice: a qualitative study

The UK has substantial minority populations of short-term and long-term migrants from countries with various types of healthcare systems. This study explored how migrants' previous knowledge and experience of health care influences their current expectations of health care in a system relying on clinical generalists performing a gatekeeping role. Two qualitative methods. Glasgow, UK. Focus groups or semi-structured interviews were conducted with 52 asylum seekers. Analyses identified several areas where previous experience affected current expectations. An overview of health systems in each country of origin was established by combining responders' accounts with World Health Organization statistics. Asylum seekers had previous experience of a diverse range of healthcare systems, most of which were characterised by a lack of GPs and direct access to hospital-based specialists. For some responders, war or internal conflict resulted in a complete breakdown of healthcare systems. Responders' accounts also highlighted the difficulties that marginalised groups had in accessing health care. Although asylum seekers were generally pleased with the care they received from the NHS, there were areas where they experienced difficulties: confidence in their GP and access to hospital-based specialists and medication. These difficulties encountered might be explained by previous experience. GPs and other healthcare professionals need to be aware that experience of different systems of care can have an impact on individuals' expectations in a GP-led system. If these are not acknowledged and addressed, a lack of confidence and trust in the GP may undermine the effectiveness of the clinical consultation.

CME liftoff with high-frequency fragmented type II burst emission

Aims. Solar radio type II bursts are rarely seen at frequencies hig her than a few hundred MHz. Since metric type II bursts are thought to be signatures of propagating shock waves, it is of interes t to know how these shocks, and the type II bursts, are formed. In particular, how are high-frequency, fragmented type II bursts created? Are there differences in shock acceleration or in the surrounding medium that could explain the differences to the “typical” metric type IIs? Methods. We analyse one unusual metric type II event in detail, with comparison to white-light, EUV, and X-ray observations. As the radio event was associated with a flare and a coronal mass ejec tion (CME), we investigate their connection. We then utilize numerical MHD simulations to study the shock structure induced by an erupting CME in a model corona including dense loops. Results. Our simulations show that the fragmented part of the type II burst can be formed when a coronal shock driven by a mass ejection passes through a system of dense loops overlying the active region. To produce fragmented emission, the conditions for plasma emission have to be more favourable inside the loop than in the interloop area. The obvious hypothesis, consistent with our simulation model, is that the shock strength decreases significantly in the space between the denser loops. The later, mo re typical type II burst appears when the shock exits the dense loop system and finally, outside the active region, the type II burst dies ou t when the changing geometry no longer favours the electron shock-acceleration.

Fragmented type II burst emission during CME liftoff

AbstractWe have performed multiwavelength analysis on an event with a metric type II burst, which appeared first as fragmented emission lanes in the radio dynamic spectrum. The start frequency was unusually high. Since type II bursts are thought to be signatures of propagating shock waves, it is of interest to know how the shocks, and the type II bursts, are formed. This radio event was associated with a flare and a coronal mass ejection (CME), and we investigate their connection. Observations suggested that a propagating shock was formed due to the erupting structures, and the observed radio emission reflects the high densities in active region loops. We then utilised numerical MHD simulations, to study the shock structure induced by an erupting CME, in a model corona including dense loops. Our simulations show that the fragmented part of the type II burst can be formed when a coronal shock driven by a CME passes through a system of dense loops overlying an active region. To produce fragmented emission, the conditions for plasma emission have to be more favourable inside the loop than in the inter-loop area. The obvious hypothesis, consistent with our simulation model, is that the shock strength decreases significantly in the space between the denser loops. Outside the active region, the type II burst dies out when the changing geometry no longer favours the electron shock-acceleration.

Observation of a System of Linear Loops Formed by Re‐Growing Hairs on Rat Skin

This paper details linear hair re-growth patterns observed in rats. Adult rats were shaved and observed. The first wave of hair re-growth did not distribute everywhere, but along specific craniocaudally-oriented lines. The hair-lines were 2-15 mm wide and ran from the head, through the torso to the limbs, and were symmetrical along the left and right sides of the body. The symmetric hair-lines from both sides of the body converged around the mouth, nose, and at the pubic region or ventral midline to form a system of hair-loop-lines (HLLs). The loops can be differentiated into four main patterns. The Dorsal Loop and the Lateral Dorsal Loop run along the dorsum and hindlimb. The Ventral Loop and Lateral Ventral Loop travel along the thorax, abdomen, and forelimb. These hair-lines coincide with our previously observed sympathetic-substance lines (SSLs) in the rat's skin. Histological observation indicates that rat hair follicles along the hair-lines were at anagen phase. The catecholamine histofluorescent check showed abundant sympathetic nerve fibers beneath the hair-lines. After the rats' hairs were dyed, and selected portions shaved, re-growth was only observed on the shaved portions, indicating that the linear hair growth closely correlated with the shaving. Lastly we examine the cause of the preferential re-growth and briefly discuss the purpose and physiological role of the HLL.

On Solar Intermediate Drift Radio Bursts at Decimeter and Meter Wavelength

Fiber – or intermediate drift – bursts are a continuum fine structure in some complex solar radio events. We present the analysis of such bursts in the X17 flare on 28 Oct. 2003. Based on the whistler wave model of fiber bursts we derive the 3D magnetic field structures that carry the radio sources in different stages of the event and obtain insight into the energy release evolution in the main flare phase, the related paths of nonthermal particle propagation in the corona, and the involved magnetic field structures. Additionally, we test the whistler wave model of fiber bursts for the meter and the decimeter wave range. Radio spectral data (Astrophysikalisches Institut Potsdam, Astronomical Observatory Ondřejov) show a continuum with fibers for ≈ 6 min during the main flare phase. Radio imaging data (Nancay Radio Heliograph) yield source centroid positions of the fibers at three frequencies in the spectrometer band. We compare the radio positions with the potential coronal magnetic field extrapolated from SOHO/MDI data. Given the detected source site configuration and evolution, and the change of the fiber burst frequency range with time, we can also extract those coronal flux tubes where the high-frequency fiber bursts are situated even without decimeter imaging data. To this aim we use a kinetic simulation of whistler wave growth in sample flux tubes modeled by selected potential field lines and a barometric density model. The whistler wave model of fiber bursts accurately explains the observations on 28 Oct. 2003. A laterally extended system of low coronal loops is found to guide the whistler waves. It connects several neighboring active regions including the flaring AR 10486. For varying source sites the fiber bursts are emitted at the fundamental mode of the plasma frequency over the whole range (1200 – 300 MHz). The present event can be understood without assuming two different generation mechanisms for meter and decimeter wave fiber bursts. It gives new insight into particle acceleration and propagation in the low flare and post-CME corona.

Cytokines.

During physiological and pathological skeletal remodelling, immune cells and stromal fibroblasts near active bone-forming and bone-resorbing surfaces might modulate the functions of skeletal tissue cells. Osteoblasts, osteoclasts and their progenitor cells are the probable direct targets of these effector cells (e.g. lymphocytes and monocytes) which act through direct contact or the release of soluble ligands (e.g. interleukin 1 or tumour necrosis factor, lymphotoxins, transforming growth factors). These cytokines bind to specific cellular receptors, resulting in changes in the form and function of the target bone cells and variable activation of genes coding for extracellular matrix proteins and proteinases which are responsible for remodelling the matrix. The synthesis and release of eicosanoids such as prostaglandins (e.g. PGE2) are frequent associated events. PGE2, in turn, affects several functions of the skeletal tissue cells as well as the lymphocytes and monocytes in their environment. The mesenchymal cells may also be induced to release ligands such as colony-stimulating factors, other cellular products or hormones resulting in a system of feedback and amplification loops. The cellular responses are thus subject to multiple controls not only determined by these ligands acting on their respective receptors but also by the pathways of signal transduction and how they, in turn, are influenced by interactions with molecules within the cells.

Solar proton flare 4B/X17.2 on October 28, 2003. Photometric results

The powerful flare 4B/X17.2 of October 28, 2003 in the NOAA 10486 active region is studied by using Hα filtergrams. This active region had a complicated βγδ magnetic configuration and a sigmoidal pattern of the polarity inversion line, it had the largest AR area in the cycle 23. Local filaments, loops, and systems of loops were also observed in the AR. The light curves obtained for all flare knots clearly reveal two stages in their evolution. The first stage is the pre-flare one, when the accumulation of the nonpotential magnetic energy (the energy of electric currents) comes to an end and the situation becomes favorable for the realization of the second period. The intensity of flare knots (except one knot) changed slightly and slowly, and some structure features (twists and connections) became more active. By the end of the first stage a new magnetic flux emerged and a system of interrelated filaments and loops (IFL) was formed at the center of the AR as well as at its periphery. New flare knots appeared about the main S-like filament. The second flare stage began at about 11:02 UT with a dramatic increase of the intensity and area of all flare knots and the formation of new knots. In a space of 8 min the major part of the AR around the main filament was covered with flare emission which fluctuated at its maximum period. The intensity of all knots was observed to drop slowly after the maximum, at the decay phase. As the IFL system extended over the entire AR, the magnetic field energy accumulated in it was released in the form of powerful electromagnetic and corpuscular emission by way of magnetic reconnection.

Wingless Directly Represses DPP Morphogen Expression via an Armadillo/TCF/Brinker Complex

BackgroundSpatially restricted morphogen expression drives many patterning and regeneration processes, but how is the pattern of morphogen expression established and maintained? Patterning of Drosophila leg imaginal discs requires expression of the DPP morphogen dorsally and the wingless (WG) morphogen ventrally. We have shown that these mutually exclusive patterns of expression are controlled by a self-organizing system of feedback loops that involve WG and DPP, but whether the feedback is direct or indirect is not known.Methods/FindingsBy analyzing expression patterns of regulatory DNA driving reporter genes in different genetic backgrounds, we identify a key component of this system by showing that WG directly represses transcription of the dpp gene in the ventral leg disc. Repression of dpp requires a tri-partite complex of the WG mediators armadillo (ARM) and dTCF, and the co-repressor Brinker, (BRK), wherein ARM•dTCF and BRK bind to independent sites within the dpp locus.Conclusions/SignificanceMany examples of dTCF repression in the absence of WNT signaling have been described, but few examples of signal-driven repression requiring both ARM and dTCF binding have been reported. Thus, our findings represent a new mode of WG mediated repression and demonstrate that direct regulation between morphogen signaling pathways can contribute to a robust self-organizing system capable of dynamically maintaining territories of morphogen expression.

Dickens on "Lost": Text, Paratext, Fan-based Media

Dickens on "Lost": Text, Paratext, Fan-based Media

The role of plasma ejections in the development of large solar flares of various durations

Recent observations indicate that relatively strong plasma ejections are accompanied by the formation of systems of coronal loops with two glowing ribbons near their footpoints. However, while two-ribbon flares can sometimes last for many hours, for example, soft X rays, they sometimes decay within tens of minutes. We study here factors affecting the durations of flares using four major flares occurring in July 15–18, 2002, as examples. Various ground-based and satellite observations are used to show that short-duration events involved collimated (narrow) plasma ejections directed to the north and the subsequent formation of compact loops in the leading part of the active region. During one event, a powerful eastward ejection in a wide solid angle was followed by the formation of an extended arch system in the trailing part, which determined the long duration of the flare. It is proposed that in events involving collimated jets and corresponding narrow features in coronal mass ejections (CMEs), systems of coronal loops do form, but post-eruptive energy release either does not occur or is expressed very faintly. So the energy does not go downward from this region, and the plasma is emitted free in the coronal loops. In contrast to such rapid flares, wide ejections and bright, large-scale CMEs are accompanied by the formation and prolonged existence of an extended arch system. Thus, powerful nonstationary solar processes involve a large-scale CME and the flare itself, with the pattern of a particular event determined by the reconnection scenario and the evolution of the ejected plasma.

Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

RHESSI and TRACE observations of an M 2.5 flare: a direct application of the Kopp and Pneuman model

Context. The processes of current sheet formation and magnetic reconnection are nowadays believed to be at the basis of several solar phenomena, including erupting prominences, flares, and CMEs. However, the possibility of determining clear signatures of the occurrence of these processes in erupting active regions is still lacking in several aspects. Aims. In this paper we analyze coronal images relevant to a system of loops involved in a very energetic flare, to search for observational signatures of current sheet formation and magnetic reconnection and compare them with what is expected from theory. Methods. X-ray and EUV data acquired by the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Transition Region and Coronal Explorer (TRACE) satellites have been used to analyze an M2.5 flare that occurred in NOAA 9901 on 16 April 2002. The evolution of the flare loops, the EUV footpoints, and the X-ray loop tops have been studied. Results. The event shows a simple morphology in which the EUV and X-ray sources change from an X to a Y configuration; the formation of a thin, filamentary structure, compatible with what is expected from the collapse of an X -point in a current sheet, is observed; the height of the top of the observed EUV loops and the separation between the footpoints show an increase with time. Conclusions. The study of this event provides several observational signatures, expected from theory during the formation of a current sheet and consequent reconnection, which allowed us to interpret it in the framework of the Kopp and Pneuman model.

Uncertainty about nest position influences systematic search strategies in desert ants

Foraging desert ants return to their starting point, the nest, by means of path integration. If the path-integration vector has been run off but the nest has not yet been reached, the ants engage in systematic search behavior. This behavior results in a system of search loops of ever increasing size and finally leads to a search density profile peaking at the location where the path integration system has been reset to zero. In this study we investigate whether this systematic search behavior is adapted to the uncertainty resulting from the preceding foraging run. We show first that the longer the distances of the foraging excursions, the larger the errors occurring during path integration, and second that the ants adapt their systematic search strategy to their increasing uncertainty by extending their search pattern. Hence, the density of the systematic search pattern is correlated with the ants' confidence in their path integrator. This confidence decreases with increasing foraging distances.