Cardiovagal Baroreflex Hysteresis Using Ellipses in Response to Postural Changes

The cardiovagal branch of the baroreflex is of high clinical relevance when detecting disturbances of the autonomic nervous system. The hysteresis of the baroreflex is assessed using provoked and spontaneous changes in blood pressure. We propose a novel ellipse analysis to characterize hysteresis of the spontaneous respiration-related cardiovagal baroreflex for orthostatic test. Up and down sequences of pressure changes as well as the working point of baroreflex are considered. The EuroBaVar data set for supine and standing was employed to extract heartbeat intervals and blood pressure values. The latter values formed polygons into which a bivariate normal distribution was fitted with its properties determining proposed ellipses of baroreflex. More than 80% of ellipses are formed out of nonoverlapping and delayed up and down sequences highlighting baroreflex hysteresis. In the supine position, the ellipses are more elongated (by about 46%) and steeper (by about 4.3° as median) than standing, indicating larger heart interval variability (70.7 versus 47.9 ms) and smaller blood pressure variability (5.8 versus 8.9 mmHg) in supine. The ellipses show a higher baroreflex sensitivity for supine (15.7 ms/mmHg as median) than standing (7 ms/mmHg). The center of the ellipse moves from supine to standing, which describes the overall sigmoid shape of the baroreflex with the moving working point. In contrast to regression analysis, the proposed method considers gain and set-point changes during respiration, offers instructive insights into the resulting hysteresis of the spontaneous cardiovagal baroreflex with respiration as stimuli, and provides a new tool for its future analysis.

Mechanical Properties of Tensile Strength of ITB Graft, a Promising Graft for Labral Reconstruction of the Hip

Introduction: Labral repair gives good results on damage in the labral area of the hip, but in cases with extensive labral damage, labral repair is less effective, reconstruction of labral is needed, recently labral reconstruction has been done using the Iliotibial band (ITB), but no one has measured the tensile strength of the ITB. this study intends to measure the ITB tensile strength based on diameter. Methode: This is an experimental research, the sample was taken from 8 cadaveric, consisted of 6 cadavercic male sex and 2 cadaveric female sex, the youngest cadaveric age was 25 years and the oldest 63 years with an average age of 47 years. Each cadaver was treated by taking ITB, The ITB were then measured by applying the Hydraulic Servo Pulser tensile test apparatus. ITB was rolled oval and tied with an unabsorbed polyster suture, the ITB which was oval shaped and had been tied with an unabsorbed polyster suture then measured its diameter from 4mm, 5mm, 6mm, 7mm, to 8mm. Samples that have been prepared are measured using a tensile strength gauge to assess ITB tensile strength ranging from 4mm, 5mm, 6mm, 7mm, to 8mm. Results: ITB’s tensile strength curve is sigmoid shape , the average tensile strength for all samples is 647 Psi. The larger the sample diameter, the greater the tensile strength it has. The largest tensile strength is obtained in 8 mm diameter, and the smallest tensile strength is obtained in 4 mm diameter. Conclusion: ITB is a promising autograft and can be used as an ingredient for the reconstruction of labral.

Stochastic model for the CheY-P molarity in the neighbourhood of E. coli flagella motors

Escherichia coli serves as prototype for the study of peritrichous enteric bacteria that perform runs and tumbles alternately. Bacteria run forward as a result of the counterclockwise (CCW) rotation of their flagella bundle, which is located rearward, and perform tumbles when at least one of their flagella rotates clockwise (CW), moving away from the bundle. The flagella are hooked to molecular rotary motors of nanometric diameter able to make transitions between CCW and CW rotations that last up to one hundredth of a second. At the same time, flagella move or rotate the bacteria’s body microscopically during lapses that range between a tenth and ten seconds. We assume that the transitions between CCW and CW rotations occur solely by fluctuations of CheY-P molarity in the presence of two threshold values, and that a veto rule selects the run or tumble motions. We present Langevin equations for the CheY-P molarity in the vicinity of each molecular motor. This model allows to obtain the run- or tumble-time distribution as a linear combination of decreasing exponentials that is a function of the steady molarity of CheY-P in the neighbourhood of the molecular motor, which fits experimental data. In turn, if the internal signaling system is unstimulated, we show that the runtime distributions reach power-law behaviour, a characteristic of self-organized systems, in some time range and, afterwards, exponential cutoff. In addition, our model explains without any fitting parameters the ultrasensitivity of the flagella motors as a function of the steady state of CheY-P molarity. In addition, we show that the tumble bias for peritrichous bacterium has a similar sigmoid-shape to the CW bias, although shifted to lower concentrations when the flagella number increases. Thus, the increment in the flagella number allows lower operational values for each motor increasing amplification and robustness of the chemotatic signaling pathway.

Individual growth of white shrimp Litopenaeus vannamei (Boone, 1931) and blue shrimp L. stylirostris (Stimpson, 1874) (Crustacea: Penaeidae) by multi-model approach

Individual growth of two shrimp species of the family Penaeidae, the white shrimp Litopenaeus vannamei and blue shrimp L. stylirostris were analyzed. The hypothesis was that both species would have an asymptotic growth type with sigmoid shape. The data comes from shrimp farming in earthen ponds of an aquaculture farm located in the Gulf of California, density was 25 post-larvae m-2 in ponds of 1.8 ha. Three asymptotic models were applied to averaged length at age data: von Bertalanffy, Gompertz, and logistic. The model’s parameters were computed by maximum likelihood criterion. Best model was selected according to the Akaike information criterion. The final total length of white shrimp was 128.8 mm and the estimated asymptotic length was 130 mm, after 140 rearing days. The blue shrimp final size was 142.2 mm, and the asymptotic length was 174 mm, after 158 rearing days. For both species, the model which better described the growth was the Gompertz model; consequently the conclusion was that the growth of both species must be sigmoid shape.

Piecewise function parameters as responses of the design of experiment in the development of a pulsatile release chronopharmaceutical system

The aim of this work was to develop a pulsatile release system with metoprolol for chronotherapeutical use by coating swellable mini-tablets with Eudragit RS. To study the influence of the formulation factors (amount of coating polymer, plasticizer percentage in film coating and swelling agent percentage in mini-tablets), a Box-Behnken design of experiment (DoE) was used. To evaluate the influence of the studied factors on the sigmoid shape of the dissolution profile, piecewise function parameters were used as the responses of DoE. The results show that higher concentrations of coating polymer and higher concentrations of plasticizer polymer led to a thicker and more elastic polymeric film, which led to a delay in drug release. Using the parameters of the piecewise function as DoE responses, an optimum formulation with a sigmoid shape dissolution profile and a 2.5-h lag time followed by rapid drug release were obtained.

The bivariate power-normal distribution and the bivariate Johnson system bounded distribution in forestry, including height curves

A bivariate diameter and height distribution yields a unified model of a forest stand. The bivariate Johnson system bounded distribution and the bivariate power-normal distribution are explored. The power-normal distribution originates from the well-known Box–Cox transformation. As evaluated by the bivariate Kolmogorov–Smirnov distance, the bivariate power-normal distribution seems to be superior to the bivariate Johnson system bounded distribution. The conditional median height given the diameter is a possible height curve and is compared with a simple hyperbolic height curve. Evaluated by the height deviance, the hyperbolic function yields the best height prediction. A close second is the curve generated by a bivariate power-normal distribution. Johnson system bounded distributions suffer from the sigmoid shape of the association between height and diameter. The bivariate power-normal distribution is easy to estimate and has good numerical properties; therefore, it is a good candidate model for use in forest stands.

An attempt at describing the growth of live organisms by means of a difference-differential equation

An attempt is made to create a formal growth model based on a difference-differential equation. The solution of this type of equation is a function of a continuous variable and of a variable assuming natural values. By using the Laplace transformation in respect to time and then solving a specific linear difference equation, a final relation showing the dependence of the amount of dry matter on a natural number and time -- w_n(t), was obtained. This function can be, in a certain sense, a generalization of the known Gregory-Naidenov monomolecular function. For n=1 the function w_n(t) transforms into a relation similar to the Mitscherlich equation, for n>1, its graphs have a characteristic sigmoid shape. Numerical methods are necessary to work out specific forms of the function w_n(t).

Hemispheric Patterns in Filament Chirality and Sigmoid Shape over the Solar Cycle

The motivation for our research was to study the correlation between the chirality of filaments and the handedness (S- or Z-shape) of sigmoids. It was assumed that sigmoids would mostly coincide with filaments and that the S-shaped sigmoids would correlate well with filaments of sinistral chirality, which we found that to be at best a very weak relation. Since we had a full solar cycle of filament metadata at hand it was easy to verify the supposedly known hemispheric preference of filament chirality. We discovered that the hemispheric chirality rule was confirmed for the epoch where a thorough manual study had been performed, but that at other phases of the solar cycle the rule seems to disappear and sometimes even reverse.