Approximate Threshold Research Articles

Skeletal muscle magnetic resonance biomarkers correlate with function and sentinel events in Duchenne muscular dystrophy.

ObjectiveTo provide evidence for quantitative magnetic resonance (qMR) biomarkers in Duchenne muscular dystrophy by investigating the relationship between qMR measures of lower extremity muscle pathology and functional endpoints in a large ambulatory cohort using a multicenter study design.MethodsMR spectroscopy and quantitative imaging were implemented to measure intramuscular fat fraction and the transverse magnetization relaxation time constant (T2) in lower extremity muscles of 136 participants with Duchenne muscular dystrophy. Measures were collected at 554 visits over 48 months at one of three imaging sites. Fat fraction was measured in the soleus and vastus lateralis using MR spectroscopy, while T2 was assessed using MRI in eight lower extremity muscles. Ambulatory function was measured using the 10m walk/run, climb four stairs, supine to stand, and six minute walk tests.ResultsSignificant correlations were found between all qMR and functional measures. Vastus lateralis qMR measures correlated most strongly to functional endpoints (|ρ| = 0.68–0.78), although measures in other rapidly progressing muscles including the biceps femoris (|ρ| = 0.63–0.73) and peroneals (|ρ| = 0.59–0.72) also showed strong correlations. Quantitative MR biomarkers were excellent indicators of loss of functional ability and correlated with qualitative measures of function. A VL FF of 0.40 was an approximate lower threshold of muscle pathology associated with loss of ambulation.DiscussionLower extremity qMR biomarkers have a robust relationship to clinically meaningful measures of ambulatory function in Duchenne muscular dystrophy. These results provide strong supporting evidence for qMR biomarkers and set the stage for their potential use as surrogate outcomes in clinical trials.

Numerical assessment of tsunami attack on a rubble mound breakwater using OpenFOAM®

A numerical assessment study of tsunami attack on the rubble mound breakwater of Haydarpasa Port, located at the southern entrance of the Istanbul Bosphorus Strait in the Sea of Marmara, Turkey, is carried out in this study using a Volume-Averaged Reynolds-Averaged Navier-Stokes solver, IHFOAM, developed in OpenFOAM® environment. The numerical model is calibrated with and validated against the data from solitary wave and tsunami overflow experiments representing tsunami attack. Furthermore, attack of a potential tsunami near Haydarpasa Port is simulated to investigate effects of a more realistic tsunami that cannot be generated in a wave flume with the present state of the art technology. Discussions on practical engineering applications of this type of numerical modeling studies are given focusing on pressure distributions around the crown-wall of the rubble mound breakwater, and the forces acting on the single stone located behind the crown-wall at the rear side of the breakwater. Numerical modeling of stability/failure mechanism of the overall cross-section is studied throughout the paper.The present study shows that hydrodynamics along the wave flume and over the breakwater can be simulated properly for both solitary wave and tsunami overflow experiments. Stability of the overall cross-section can only be simulated qualitatively for solitary wave cases; on the other hand, the effect of the time elapsed during tsunami overflow cannot be reflected in the simulations using the present numerical tool. However, the stability of the overall cross-section under tsunami overflow is assessed by evaluating forces acting on the rear side armor unit supporting the crown-wall of the rubble mound breakwater as a practical engineering application in the present paper. Furthermore, two non-dimensional parameters are derived to discuss the stability of this armor unit; and thus, the stability condition of the overall cross-section. Approximate threshold values for these non-dimensional parameters are presented comparing experimental and numerical results as a starting point for engineers in practice. Finally, investigations on the solitary wave and tsunami overflow experiments/simulations are extended to the potential tsunami simulation in the scope of both representation of a realistic tsunami in a wave flume and stability of the rubble mound breakwater.

Experimental and theoretical analysis of solid particle erosion of a steel compressor blade based on incubation time concept

Abstract This paper considers experimental and theoretical study of a compressor blade steel (EI-961 grade), subjected to solid particle erosion. Material samples were cut from the first stage compressor blades and then tested in a modified wind tunnel, capable of mixing abrasive media into an accelerated airflow. Velocity of the abrasive stream vas varied and additionally abrasive powders with different average particle sizes were used. Erosion resistance was assessed in two ways: measurements of the sample mass degradation and investigation of the surface roughness change due to erosion. Moreover, data fitting was used to calculate approximate threshold velocities for the abrasive powders used in the tests. Incubation time concept was applied in order to obtain dependence of the threshold particle velocity on the particle radius and to perform theoretical analysis of the material's resistance to the solid particle erosion.

Approximate thresholds for Salo-Hamalainen index

This paper deals with the consistency of judgments expressed by pairwise comparisons. A consistency check is performed to ensure that judgments are neither random nor illogical. Several measures have been proposed in the literature to verify the rationality of decision makers. Here, we propose approximate thresholds for the Salo-Hamalainen index: we derive an inconsistency tolerance level analogous to that proposed for the Consistency Ratio by Saaty, and for the Geometric Consistency Index by Aguaron-Moreno Jimenez. Furthermore, via a simulation, we propose a threshold for ordinal consistency ensuring the reliability of preferences.

Morphometry of terrestrial shield volcanoes

Shield volcanoes are described as low-angle edifices built primarily by the accumulation of successive lava flows. This generic view of shield volcano morphology is based on a limited number of monogenetic shields from Iceland and Mexico, and a small set of large oceanic islands (Hawaii, Galápagos). Here, the morphometry of 158 monogenetic and polygenetic shield volcanoes is analyzed quantitatively from 90-meter resolution SRTM DEMs using the MORVOLC algorithm. An additional set of 24 lava-dominated ‘shield-like’ volcanoes, considered so far as stratovolcanoes, are documented for comparison. Results show that there is a large variation in shield size (volumes from 0.1 to >1000km3), profile shape (height/basal width (H/WB) ratios mostly from 0.01 to 0.1), flank slope gradients (average slopes mostly from 1° to 15°), elongation and summit truncation. Although there is no clear-cut morphometric difference between shield volcanoes and stratovolcanoes, an approximate threshold can be drawn at 12° average slope and 0.10 H/WB ratio. Principal component analysis of the obtained database enables to identify four key morphometric descriptors: size, steepness, plan shape and truncation. Hierarchical cluster analysis of these descriptors results in 12 end-member shield types, with intermediate cases defining a continuum of morphologies. The shield types can be linked in terms of growth stages and shape evolution, related to (1) magma composition and rheology, effusion rate and lava/pyroclast ratio, which will condition edifice steepness; (2) spatial distribution of vents, in turn related to the magmatic feeding system and the tectonic framework, which will control edifice plan shape; and (3) caldera formation, which will condition edifice truncation.

Estimation of catch losses resulting from overexploitation in the global marine fisheries

Many fish stocks in the world are depleted as a result of overexploitation, which reduces stock productivity and results in loss of potential yields. In this study we analyzed the catch trends and approximate thresholds of sustainable fishing for fished stocks to estimate the potential loss of catch and revenue of global fisheries as a result of overexploitation during the period of 1950–2010 in 14 FAO fishing areas. About 35% of stocks in the global marine ocean have or had suffered from overexploitation at present. The global catch losses amounted to 332.8 million tonnes over 1950–2010, resulting in a direct economic loss of US$298.9 billion (constant 2005 US$). Unsustainable fishing caused substantial potential losses worldwide, especially in the northern hemisphere. Estimated potential losses due to overfishing for different groups of resources showed that the low-value but abundant small-medium pelagics made the largest contribution to the global catch loss, with a weight of 265.0 million tonnes. The geographic expansion of overfishing not only showed serial depletion of world’s fishery resources, but also reflected how recent trends towards sustainability can stabilize or reverse catch losses. Reduction of global fishing capacity and changes in fishery management systems are necessary if the long-term sustainability of marine fisheries in the world is to be achieved.

Cooperation and distributed optimization for the unreliable wireless game with indirect reciprocity

Cooperation in packet forwarding among users and operators of a distributed wireless network has been widely studied.However, because of the limited computational resources, users in wireless communication do not prefer to cooperate with others unless cooperation may improve their own performance.Therefore, the key problem in cooperation enforcement must be solved first to enable a wireless network to be efficient.Yet, most of the existing game-theoretic cooperation stimulation approaches assume that the interactions between any pair of players (users) are long-lasting.In this paper, we apply game theory to optimize the communication efficiency of a distributed wireless network with finite number of interactions between any pair of players.Based on the mechanism of indirect reciprocity, we theoretically analyze the optimal action rule with the method of dynamic programming,and derive the approximate threshold of benefit-to-cost ratio to achieve the optimal action rule.Furthermore, we adopt the replicator dynamics to assess the evolutionary stability of the optimal action rule against the perturbation effect.Numerical illustrations verify the performance of the proposed method on wireless cooperation.

Tissue-type plasminogen activator regulates macrophage activation and innate immunity

AbstractTissue-type plasminogen activator (tPA) is the major intravascular activator of fibrinolysis and a ligand for receptors involved in cell signaling. In cultured macrophages, tPA inhibits the response to lipopolysaccharide (LPS) by a pathway that apparently requires low-density lipoprotein receptor-related protein-1 (LRP1). Herein, we show that the mechanism by which tPA neutralizes LPS involves rapid reversal of IκBα phosphorylation. tPA independently induced transient IκBα phosphorylation and extracellular signal-regulated kinase 1/2 (ERK1/2) activation in macrophages; however, these events did not trigger inflammatory mediator expression. The tPA signaling response was distinguished from the signature of signaling events elicited by proinflammatory LRP1 ligands, such as receptor-associated protein (RAP), which included sustained IκBα phosphorylation and activation of all 3 MAP kinases (ERK1/2, c-Jun kinase, and p38 MAP kinase). Enzymatically active and inactive tPA demonstrated similar immune modulatory activity. Intravascular administration of enzymatically inactive tPA in mice blocked the toxicity of LPS. In mice not treated with exogenous tPA, the plasma concentration of endogenous tPA increased 3-fold in response to LPS, to 116 ± 15 pM, but remained below the approximate threshold for eliciting anti-inflammatory cell signaling in macrophages (∼2.0 nM). This threshold is readily achieved in patients when tPA is administered therapeutically for stroke. In addition to LRP1, we demonstrate that the N-methyl-D-aspartic acid receptor (NMDA-R) is expressed by macrophages and essential for anti-inflammatory cell signaling and regulation of cytokine expression by tPA. The NMDA-R and Toll-like receptor-4 were not required for proinflammatory RAP signaling. By mediating the tPA response in macrophages, the NMDA-R provides a pathway by which the fibrinolysis system may regulate innate immunity.

Estimation of bubble-mediated air–sea gas exchange from concurrent DMS and CO<sub>2</sub> transfer velocities at intermediate–high wind speeds

Abstract. Simultaneous air–sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2) were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (Δkw) over a range of wind speeds up to 21 m s−1. These differences occur at and above the approximate wind speed threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with Δkw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of Δkw with whitecap fraction is no stronger than with wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange.

Rapid Nanogram Scale Screening Method of Microarrays to Evaluate Drug-Polymer Blends Using High-Throughput Printing Technology.

A miniaturized, high-throughput assay was optimized to screen polymer-drug solid dispersions using a 2-D Inkjet printer. By simply printing nanoliter amounts of polymer and drug solutions onto an inert surface, drug/polymer microdots of tunable composition were produced in an easily addressable microarray format. The amount of material printed for each dried spot ranged from 25 ng to 650 ng. These arrays were used to assess the stability of drug/polymer dispersions with respect to recrystallization, using polarized light microscopy. One array with a panel of 6 drugs formulated at different ratios with a poly(vinylpyrrolidone-vinyl acetate) (PVPVA) copolymer was developed to estimate a possible bulk (gram-scale) approximation threshold from the final printed nanoamount of formulation. Another array was printed at a fixed final amount of material to establish a literature comparison of one drug formulated with different commercial polymers for validation. This new approach may offer significant efficiency in pharmaceutical formulation screening, with each experiment in the nanomicro-array format requiring from 3 up to 6 orders of magnitude lower amounts of sample than conventional screening methods.

Minimum error rate detection: An adaptive bayesian approach

This paper addresses the thresholding problem which is an important issue in detection theory. A new thresholding methodology is proposed, namely the Minimum Error Rate (MER), related to the minimization of the error probability instead of minimizing only the miss probability for a Constant False Alarm Rate (CFAR). In an adaptive detection scheme, the proposed thresholding technique is combined with Cell Averaging (CA) and Order-Statistics OS estimation methods giving birth to the (CA-MER) and (OS-MER) detectors. Their performance statistics are analyzed for both homogeneous and heterogeneous environments. Moreover, a simplified approximate threshold expression is proposed and its effect on the whole detection process is studied. Theoretical and numerical results show that the MER-based detectors operate better than the classical CFAR-based ones. In particular, the proposed method is shown to be robust w.r.t. estimation errors on the different parameters (priors). Comparative study of MER versus CFAR-based detectors used for the delay detection in multipath context show that OS-MER detector outperforms the OS-CFAR which induces more accurate mobile positioning.

Enantioselective synthesis and sensory properties of 3‐methylthiodecanal

AbstractThe enantioselective synthesis of two enantiomers of 3‐methylthiodecanal was described, in which the optically active 1‐undecen‐4‐ols prepared by asymmetric catalytic addition of n‐octanal with allyltributylstannane went through oxidation of double bond and nucleophilic substitution of hydroxy group via mesylate to afford the target molecules with about 90% ee values. Odour properties and approximate thresholds were determined by means of GC/Olfactory. The data indicated that two enantiomers of 3‐methylthiodecanal presented distinctive odour feature from each other and also a slight difference in odour intensity.

Toward a generalized theory of epidemic awareness in social networks

We discuss the dynamics of a susceptible-infected-susceptible (SIS) model with local awareness in networks. Individual awareness to the infectious disease is characterized by a general function of epidemic information in its neighborhood. We build a high-accuracy approximate equation governing the spreading dynamics and derive an approximate epidemic threshold above which the epidemic spreads over the whole network. Our results extend the previous work and show that the epidemic threshold is dependent on the awareness function in terms of one infectious neighbor. Interestingly, when a pow-law awareness function is chosen, the epidemic threshold can emerge in infinite networks.

Dislocation dynamics in polycrystals with atomistic-informed mechanisms of dislocation - grain boundary interactions

In polycrystalline materials, dislocations can interact with grain boundaries (GBS) through a number of mechanisms including dislocation absorption, pile-up formation, dissociation reactions within the GB plane and (possibly) dislocation nucleation from the interface itself. The effects of dislocation pile-ups contribute significantly to the mechanical behavior of polycrystalline materials by creating back-stresses that inactivate the primary slip systems in the vicinity of the interface, corresponding with the celebrated Hall–Petch relationship between size and strength. However, dislocation pile-ups cannot be contained within the small grain sizes that can be accommodated by molecular dynamics simulations, which to-date remain the primary computational method used to study the discrete structure of GBs. Dislocation dynamics (DD) simulations are a promising framework for computational modeling that are used to provide insights about phenomena that can only be explained from the intermediate scale between atomistic and macro scales. However, a robust framework for modeling dislocation interactions with internal microstructure such as grain boundaries (GBs) has yet to be achieved for 3D models of DD. Furthermore, this is the first implementation which explicitly includes the dislocation content of the interface. The framework described in this paper is effective for studying GB-dislocation interactions (including inter-granular effects) and the approach for partitioning the DD simulation domain. To achieve a robust method to differentiate between crystal regions, the present framework utilizes a mesh-based partitioning system. Within each grain, slip systems are determined by the grain orientation. The versatile construction described, allows modeling of an arbitrary crystallography, size and grain geometry. Extrinsic dislocations that intersect the interface are constrained to glide on the line of intersection between the glide plane and GB plane. Atomistically informed criteria for slip transmission are implemented, based on the geometrically optimal outgoing glide plane which shares a common line of intersection on the GB plane. Slip transmission is only initiated when the resolved shear stress in one of the compatible outgoing slip directions exceeds an approximate threshold resolved shear stress, which is based on observations made with molecular dynamics studies. The primary aim of the present study was to establish a sufficiently ‘generic’ framework to enable the modelling of various GB structures, polycrystal geometries and crystallographic orientations. The framework described in the present work provides a means to study multi-grain deformation processes governed by dislocations pile-ups at GBs, in detail beyond feasible limits of experiments or atomistic simulation approaches.

근사 임계값 추정을 통한 Otsu 알고리즘의 연산량 개선

근사 임계값 추정을 통한 Otsu 알고리즘의 연산량 개선

BEAT CLASSIFICATION USING HYBRID WAVELET TRANSFORM BASED FEATURES AND SUPERVISED LEARNING APPROACH

This paper describes an automatic heartbeat recognition based on QRS detection, feature extraction and classification. In this paper five different type of ECG beats of MIT BIH arrhythmia database are automatically classified. The proposed method involves QRS complex detection based on the differences and approximation derivation, inversion and threshold method. The computation of combined Discrete Wavelet Transform (DWT) and Dual Tree Complex Wavelet Transform (DTCWT) of hybrid features coefficients are obtained from the QRS segmented beat from ECG signal which are then used as a feature vector. Then the feature vectors are given to Extreme Learning Machine (ELM) and k- Nearest Neighbor (kNN) classifier for automatic classification of heartbeat. The performance of the proposed system is measured by sensitivity, specificity and accuracy measures.

ϕϕ and J/ψϕ mass spectra in decay Bs0→J/ψϕϕ

The mass spectra of the $\phi\phi$ and $J/\psi\phi$ states in the decay $B^0_s\to J/\psi\phi\phi$ recently observed by LHCb are calculated in the model which takes into account the $J^P=0^+,0^-,2^+$ intermediate resonances $R_1$, $R_2$ in the $\phi\phi$ channel and the $J^P=1^+$ ones, $X_1$, $X_2$, in the $J/\psi\phi$ channel. When obtaining the expressions for the effective amplitudes and mass spectra, the approximate threshold kinematics of the decay is used essentially. The $R_1-R_2$ and $X_1-X_2$ mixings arising due to the common decay modes $\phi\phi$ and $J/\psi\phi$, respectively, are also taken into account. The obtained expressions for the mass spectra are applied for extracting the information about masses and coupling constants of the resonances in the $\phi\phi$ and $J/\psi\phi$ final states.

Experimental experience of cold starting a spark ignition UAV engine using low volatility fuel

PurposeThe purpose of this paper is to present results of practical experience of cold starting a gasoline engine on low volatility fuel suitable for unmanned aerial vehicle (UAV) deployment.Design/methodology/approachExperimental research and development is carried out via dynamometer testing of systems capable of achieving cold start of a spark ignition UAV engine on kerosene JET A-1 fuel.FindingsRepeatable cold starts have been satisfactorily achieved at ambient temperatures of 5°C. The approximate threshold for warm engine restart has also been established.Practical implicationsFor safety and supply logistical reasons, the elimination of the use of gasoline fuel offers major advantages not only for UAVs but also for other internal combustion engine-powered equipment to be operated in military theatres of operation. For gasoline crankcase-scavenged two-stroke cycle engines, this presents development challenges in terms of modification of the lubrication strategy, achieving acceptable performance characteristics and the ability to successfully secure repeatable engine cold start.Originality/valueThe majority of UAVs still operate on gasoline-based fuels. Successful modification to allow low volatility fuel operation would address single fuel policy objectives.

Mathematical Model for Cyber Attack in Computer Network

This investigation focuses to develop an e-SEIRS (susceptible, exposed, infectious, recovered) epidemic computer network model to study the transmission of malicious code in a computer network and derive the approximate threshold condition (basic reproduction number) to examine the equilibrium and stability of the model. The authors have simulated the results for various parameters used in the model and Runge-Kutta Fehlberg fourth-fifth order method is employed to solve system of equations developed. They have studied the stability of crime level to equilibrium and found the critical value of threshold value determining whether or not the infectious free equilibrium is globally asymptotically stable and endemic equilibrium is locally asymptotically stable. The simulation results using MATLAB agree with the real life situations.

Percolation in finite matching lattices

We derive an exact, simple relation between the average number of clusters and the wrapping probabilities for two-dimensional percolation. The relation holds for periodic lattices of any size. It generalizes a classical result of Sykes and Essam, and it can be used to find exact or very accurate approximations of the critical density. The criterion that follows is related to the criterion used by Scullard and Jacobsen to find precise approximate thresholds, and our work provides a different perspective on their approach.