Negative Staircase Effect Precedes Twitch Potentiation in Human Dorsiflexor Muscles

Coordinated contraction of thoracic and pharyngeal upper airway respiratory muscles optimizes ventilation, whereas pharyngeal muscle dysfunction may lead to obstructive apneas during sleep. We hypothesized that the force potentiation exhibited by the pharyngeal respiratory muscle, the sternohyoid, in keeping with its faster contractile kinetics, would be greater than that of the thoracic respiratory muscle, the diaphragm. Rat muscles were studied in vitro at 37 degrees C with three force-potentiating protocols: posttetanic twitch potentiation, staircase phenomenon (twitch potentiation), and a classic fatigue paradigm. The sternohyoid had a faster isometric contraction time, a more rightward located force-frequency relationship, and both a more rapid onset and a greater degree of fatigue than the diaphragm. During the early portion of the fatigue protocols, the increase in force was significantly greater for the sternohyoid muscle than the diaphragm (e.g., 33 vs. 3% increase at 20 Hz, P < 0.005). During repetitive twitches at 2, 3, and 5 Hz (staircase test), sternohyoid muscle force increased more than diaphragm force at the higher stimulus frequencies (e.g., by 38 vs. 23% at 5 Hz, P < 0.01). After brief tetanic stimuli, sternohyoid twitch force increased more than diaphragm twitch force (e.g., 73 vs. 14% increase after 125 Hz tetanus, P < 0.005). These data indicate that force potentiation is exhibited by both diaphragm and sternohyoid respiratory muscles, but to different extents, when activated repetitively.(ABSTRACT TRUNCATED AT 250 WORDS)

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The relationship between stimulus-induced antidromic firing and twitch potentiation produced by paraoxon in rat phrenic nerve-diaphragm preparations

British Journal of Pharmacology ◽

10.1111/j.1476-5381.1983.tb11044.x ◽

1983 ◽

Vol 80 (1) ◽

pp. 17-25 ◽

Cited By ~ 10

Author(s):

A.L. Clark ◽

F. Hobbiger ◽

D.A. Terrar

Keyword(s):

Phrenic Nerve ◽

Twitch Potentiation ◽

The Relationship

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Improving Staircase Effect in the Process of Ceramic Laser Gelling

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.284-286.43 ◽

2011 ◽

Vol 284-286 ◽

pp. 43-47

Author(s):

Hsiao Chuan Yen ◽

Hwa Hsing Tang ◽

Chun Hung Wu

Keyword(s):

Water Content ◽

Casting Process ◽

High Water ◽

Thin Layers ◽

High Water Content ◽

Layer Manufacturing ◽

Staircase Effect ◽

Alumina Particles ◽

Ceramic Laser ◽

Average Size

Based on ceramic laser gelling process, the purpose of this research is to obtain a proper slurry, which can be employed to cast layer with a thickness smaller than 100 μm to improve the staircase effect occurred in layer manufacturing, by optimization of the water content to fabricate ceramic part with better surface. The slurry was composed of alumina particles with average size of 0.5 μm as the structure element, silica sol as an inorganic binder and ammonium polymethacrylate as a dispersant. The slurry was dispersed uniformly by a ball mill. The results revealed the variation of water content will significantly influence the viscosity of the slurry and the formability of the ceramic green part. High water content led to poor binding of the particles and induced the delamination of the consolidated layers. On the contrary, low water content led to high shear force between scraper and slurry surface; such force damaged the previous layer during the casting process. As a result, the water content of 34 wt% was the most favorable to casting thin layers. The capability of casting 40 μm layer, which is smaller than that obtained by previous studies, was achieved. Because of the thinner layer, the staircase effect was improved.

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A compensating total variation image denoising model combining L1 and L2 norm

International Journal of Electrical Engineering Education ◽

10.1177/0020720920923305 ◽

2020 ◽

pp. 002072092092330

Author(s):

Liqiong Zhang ◽

Min Li ◽

Xiaohua Qiu

Keyword(s):

Image Denoising ◽

Total Variation ◽

Structural Information ◽

Signal To Noise Ratio ◽

Similarity Index ◽

Structural Similarity ◽

Isotropic Diffusion ◽

Model Combining ◽

L2 Norm ◽

Staircase Effect

To overcome the “staircase effect” while preserving the structural information such as image edges and textures quickly and effectively, we propose a compensating total variation image denoising model combining L1 and L2 norm. A new compensating regular term is designed, which can perform anisotropic and isotropic diffusion in image denoising, thus making up for insufficient diffusion in the total variation model. The algorithm first uses local standard deviation to distinguish neighborhood types. Then, the anisotropic diffusion based on L1 norm plays the role of edge protection in the strong edge region. The anisotropic and the isotropic diffusion simultaneously exist in the smooth region, so that the weak textures can be protected while overcoming the “staircase effect” effectively. The simulation experiments show that this method can effectively improve the peak signal-to-noise ratio and obtain the higher structural similarity index and the shorter running time.

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