Applying robust control theory to solve problems in bio-medical sciences: study of an apoptotic model

Biological models of an apoptotic process are studied using models describing a system of differential equations derived from reaction kinetics information. The mathematical model is re-formulated in a state-space robust control theory framework where parametric and dynamic uncertainty can be modelled to account for variations naturally occurring in biological processes. We propose to handle the nonlinearities using neural networks

Determination of the Age and Optimal Cutting Time Based on the Concentration of Soluble Carbohydrates in a Rye grass Tetraploide

This study was conducted in Toacaso Town in the northwest of Latacunga City, Cotopaxi Province, Ecuador. The researchers aimed to establish in situ the optimal age and cutting time of REMINGTON Ryegrass (Lolium perenne) based on the concentration of soluble carbohydrates using a digital refractometer. The research used 48 experimental units, each with an area of 16 m2 (4×4 m) and a total area of 768 m2. The experiment was carried out for 60 days in which the highest concentration of carbohydrates was evaluated taking into account (i) the age of the pasture – 45 and 60 days (factor A) and (ii) the cutting time – 08H00, 10H00, 12H00, 14H00, 16H00, and 18H00 hours (factor B0) for which a randomized complete block design (RCBD) was used under a bifactorial arrangement with four repetitions per treatment. The results reported that the highest concentration of soluble carbohydrates was obtained at 60 days of age with 13.15º Brix (ºBx), while the optimal cut-off time was 2:00 p.m. with a concentration of 16.33 ºBx. The authors conclude that the older the pasture, and considering the time of the day, the higher the concentration of soluble carbohydrates will be. The highest cost-benefit was obtained at 4:00 p.m. presenting a cost-benefit of $1.44 which means that for every dollar invested a profit of 44 cents was obtained. Therefore, it is recommended to harvest the REMINGTON Ryegrass at 60 days of age at 2:00 p.m. Keywords: soluble carbohydrates, Ryegrass (Lolium perenne), remintong, digital refractometer, Brix degrees. RESUMEN Se estableció in situ la edad y hora de corte óptima sobre la concentración de carbohidratos solubles en un Rye grass tetraploide (Lolium perenne) variedad REMINTONG, mediante la utilización de un refractómetro digital en la parroquia Toacaso ubicada al noroccidente del cantón Latacunga, provincia de Cotopaxi. En la investigación se utilizó 48 unidades experimentales con un área de 16 m2 (4 m x 4 m), en una superficie total de 768 m2. El trabajo experimental tuvo una duración de 60 días en los cuales se e valuó la mayor concentración de carbohidratos con relación a la edad del pasto 45 y 60 días (factor A), y la hora de corte 08H00, 10H0 0, 12H00, 14H00, 16H00 y 18H00 horas (factor B), para lo cual se aplicó un Diseño de Bloques Completamente al Azar (DBCA) bajo arreglo bifactorial con cuatro repeticiones por tratamiento. Los resultados reportaron que la mayor concentración de carbohidratos solubles se obtuvo a los 60 días de edad con 13,15 grados Brix (∘Bx), relacionados con la hora de corte optima que fue a las 14h00 con una concentración de 16,33 ∘Bx, concluyendo que a mayor edad y conforme la hora del día, mayor será la concentración de carbohidr atos solubles. El mayor beneficio costo se obtuvo a las 16h00 presentando un beneficio/costo de$ 1,44 USD, lo que quiere decir que por cada dólar invertido se obtuvo una ganancia de 44 centavos, por lo tanto, se recomienda cosechar el pasto Rye grass variedad REMINGTON a los 60 días de edad a las 14h00. Palabras Clave: Carbohidratos Solubles, Rye grass (Lolium perenne), Remintong, Refractómetro digital, grados brix

Origin of spatial variations of scattering polarization in the wings of the Ca {\sc i} 4227 \AA line

Polarization that is produced by coherent scattering can be modified by magnetic fields via the Hanle effect. According to standard theory the Hanle effect should only be operating in the Doppler core of spectral lines but not in the wings. In contrast, our observations of the scattering polarization in the Ca {\sc i} 4227 \AA line reveals the existence of spatial variations of the scattering polarization throughout the far line wings. This raises the question whether the observed spatial variations in wing polarization have a magnetic or non-magnetic origin. A magnetic origin may be possible if elastic collisions are able to cause sufficient frequency redistribution to make the Hanle effect effective in the wings without causing excessive collisional depolarization, as suggested by recent theories for partial frequency redistribution with coherent scattering in magnetic fields. To model the wing polarization we apply an extended version of the technique based on the "last scattering approximation". This model is highly successful in reproducing the observed Stokes $Q/I$ polarization (linear polarization parallel to the nearest solar limb), including the location of the wing polarization maxima and the minima around the Doppler core, but it fails to reproduce the observed spatial variations of the wing polarization in terms of magnetic field effects with frequency redistribution. This null result points in the direction of a non-magnetic origin in terms of local inhomogeneities (varying collisional depolarization, radiation-field anisotropies, and deviations from a plane-parallel atmospheric stratification).Comment: Accepted in May 2009 for publication in The Astrophysical Journa

Dysfunctional telomeres in primary cells from Fanconi anemia FANCD2 patients

© 2012 Joksic et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been made available through the Brunel Open Access Publishing Fund.Background: Fanconi anemia (FA) is characterized by sensitivity to DNA cross-linking agents, mild cellular, and marked clinical radio sensitivity. In this study we investigated telomeric abnormalities of non-immortalized primary cells (lymphocytes and fibroblasts) derived from FA patients of the FA-D2 complementation group, which provides a more accurate physiological assessment than is possible with transformed cells or animal models. Results: We analyzed telomere length, telomere dysfunction-induced foci (TIFs), sister chromatid exchanges (SCE), telomere sister chromatid exchanges (T-SCE), apoptosis and expression of shelterin components TRF1 and TRF2. FANCD2 lymphocytes exhibited multiple types of telomeric abnormalities, including premature telomere shortening, increase in telomeric recombination and aberrant telomeric structures ranging from fragile to long-string extended telomeres. The baseline incidence of SCE in FANCD2 lymphocytes was reduced when compared to control, but in response to diepoxybutane (DEB) the 2-fold higher rate of SCE was observed. In contrast, control lymphocytes showed decreased SCE incidence in response to DEB treatment. FANCD2 fibroblasts revealed a high percentage of TIFs, decreased expression of TRF1 and invariable expression of TRF2. The percentage of TIFs inversely correlated with telomere length, emphasizing that telomere shortening is the major reason for the loss of telomere capping function. Upon irradiation, a significant decrease of TIFs was observed at all recovery times. Surprisingly, a considerable percentage of TIF positive cells disappeared at the same time when incidence of γ-H2AX foci was maximal. Both FANCD2 leucocytes and fibroblasts appeared to die spontaneously at higher rate than control. This trend was more evident upon irradiation; the percentage of leucocytes underwent apoptosis was 2.59- fold higher than that in control, while fibroblasts exhibited a 2- h delay before entering apoptosis. Conclusion: The results of our study showed that primary cells originating from FA-D2 patients display shorten telomeres, elevated incidence of T-SCEs and high frequency of TIFs. Disappearance of TIFs in early response to irradiation represent distinctive feature of FANCD2 cells that should be examined further.This article is made available through the Brunel Open Access Publishing Fund. This work was supported by the Ministry of Education and Science of the Republic of Serbia (Project No.173046)

Recent Advances in Chromospheric and Coronal Polarization Diagnostics

I review some recent advances in methods to diagnose polarized radiation with which we may hope to explore the magnetism of the solar chromosphere and corona. These methods are based on the remarkable signatures that the radiatively induced quantum coherences produce in the emergent spectral line polarization and on the joint action of the Hanle and Zeeman effects. Some applications to spicules, prominences, active region filaments, emerging flux regions and the quiet chromosphere are discussed.Comment: Review paper to appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S. S. Hasan and R. J. Rutten, Astrophysics and Space Science Proceedings, Springer-Verlag, 200

Grip Force Control Using Prosthetic and Anatomical Limbs

Introduction Skillful object manipulation in various activities of daily living requires accurate and economical modulation of grip force, yet experimental studies investigating grip force using a prosthesis are lacking. The purpose of this study was to compare grip force output between two types of upper-limb prosthetic prehensors. We hypothesized a relationship between grip force output and the muscular tension needed to control the prehensor. Materials and Methods Ten able-bodied participants attempted to produce a static target grip force using a voluntary opening and voluntary closing prosthetic simulator and their anatomical hand. The target forces were 0.49 N, 4 N, and 10.5 N. Each target force was produced three times, with and without augmented visual feedback. Performance was evaluated for error and variability. Results Using the voluntary closing device resulted in more accuracy and less variability for two of the three grip forces and followed the same trends as the anatomical hand, both of which performed inversely to the voluntary opening device. Conclusions Compared with the voluntary opening prosthesis, there may exist a more intuitive compatibility between the muscle tension used to control cable tension of a voluntary closing prosthesis and the resulting grip force of the prehensor that may benefit performance on some tasks

The 2016 Reactivations of Main-Belt Comets 238P/Read and 288P/(300163) 2006 VW139

We report observations of the reactivations of main-belt comets 238P/Read and 288P/(300163) 2006 VW139, that also track the evolution of each object's activity over several months in 2016 and 2017. We additionally identify and analyze archival SDSS data showing 288P to be active in 2000, meaning that both 238P and 288P have now each been confirmed to be active near perihelion on three separate occasions. From data obtained of 288P from 2012-2015 when it appeared inactive, we find best-fit R-band H,G phase function parameters of H_R=16.80+/-0.12 mag and G_R=0.18+/-0.11, corresponding to effective component radii of r_c=0.80+/-0.04 km, assuming a binary system with equally-sized components. Fitting linear functions to ejected dust masses inferred for 238P and 288P soon after their observed reactivations in 2016, we find an initial average net dust production rate of 0.7+/-0.3 kg/s and a best-fit start date of 2016 March 11 (when the object was at a true anomaly of -63 deg) for 238P, and an initial average net dust production rate of 5.6+/-0.7 kg/s and a best-fit start date of 2016 August 5 (when the object was at a true anomaly of -27 deg) for 288P. Applying similar analyses to archival data, we find similar start points for previous active episodes for both objects, suggesting that minimal mantle growth or ice recession occurred between the active episodes in question. Some changes in dust production rates between active episodes are detected, however. More detailed dust modeling is suggested to further clarify the process of activity evolution in main-belt comets.Comment: 21 pages, 9 figures, accepted by A