Disc measurement and nucleus calibration in a smoothened lumbar model increases the accuracy and efficiency of in-silico study

Backgrounds Finite element analysis (FEA) is an important tool during the spinal biomechanical study. Irregular surfaces in FEA models directly reconstructed based on imaging data may increase the computational burden and decrease the computational credibility. Definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard in FEA. Methods To increase the accuracy and efficiency of FEA, nucleus position and cross-sectional area ratio were measured from imaging data. A FEA model with smoothened surfaces was constructed using measured values. Nucleus position was calibrated by estimating the differences in the range of motion (RoM) between the FEA model and that of an in-vitro study. Then, the differences were re-estimated by comparing the RoM, the intradiscal pressure, the facet contact force, and the disc compression to validate the measured and calibrated indicators. The computational time in different models was also recorded to evaluate the efficiency. Results Computational results indicated that 99% of accuracy was attained when measured and calibrated indicators were set in the FEA model, with a model validation of greater than 90% attained under almost all of the loading conditions. Computational time decreased by around 70% in the fitted model with smoothened surfaces compared with that of the reconstructed model. Conclusions The computational accuracy and efficiency of in-silico study can be improved in the lumbar FEA model constructed using smoothened surfaces with measured and calibrated relative nucleus position and its cross-sectional area ratio.

Disc Measurement and Nucleus Calibration in a Smoothened Lumbar Model Increases the Accuracy and Efficiency of in-silico Study

Backgrounds: Finite element analysis (FEA) is an important tool during the spinal biomechanical study. Irregular surfaces in FEA models directly reconstructed based on imaging data may increase the computational burden and decrease the computational credibility. Definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard in FEA. Methods: To increase the accuracy and efficiency of FEA, nucleus position and cross-sectional area ratio were measured from imaging data. A FEA model with smoothened surfaces was constructed using measured values, nucleus position was calibrated by estimating the differences in the range of motion (RoM) between the FEA model and that of an in-vitro study. Then, the differences was re-estimated by comparing the RoM, the intradiscal pressure, the facet contact force and the disc compression to validate the measured and calibrated indicators. The computational time in different models was also recorded to evaluate the efficiency. Results: Computational results indicated that 99% of accuracy was attained when measured and calibrated indicators were set in the FEA model, with a model validation of greater than 90% attained under almost all of the loading conditions. Computational time decreased by around 70% in the fitted model with smoothened surfaces compared with that of the reconstructed model. Conclusions: The computational accuracy and efficiency of in-silico study can be guaranteed in the lumbar FEA model constructed using smoothened surfaces with measured and calibrated relative nucleus position and its cross-sectional area ratio.

A stochastic model of homeostasis: the roles of noise and nuclear positioning in deciding cell fate

We study a population based cellular model starting from a single stem cell which stochastically divides to give rise to either daughter stem cells or differentiated daughter cells. There are three main components in the model: nucleus position, gene-regulatory network, and stochastic segregation of transcription factors in daughter cells. We study the proportion of self-renewal and differentiated cell lines as a function of the nucleus position, which in turn decides the plane of cleavage. Both nuclear position and noise play an important role in determining the stem cell genealogies and these results can be compared with a Markov model that ignores nucleus position. We have observed long and short genealogies from model simulation which compares well with experimental results from neuroblast and B-cell division. Symmetric cellular divisions were observed when the nucleus is apical, while asymmetric division occurs when the nucleus is towards the base. The number of clones decreases as a function of time in this model, although the average clone size increases.

Haploid Embryogenesis in Isolated Microspore Culture of Carrots (Daucus carota L.)

The process of embryogenesis in isolated microspore culture was studied in eight carrot accessions of different origin. The ½NLN-13 medium supplemented with 0.2 mg/L 2,4D and 0.2mg/L kinetin was used to induce embryogenesis. The temperature treatment was performed at 5–6 °C for three days, followed by cultivation at 25 °C in darkness. As was shown, the first embryogenesis was only observed in microspores at the late vacuolated stage when the nucleus moved from the center to one pole following the long cell axis. Depending on the nucleus position, the microspore can divide into two equal or two different sized cells. Following divisions occurred either in one of these cells or in two. However, microspores that divided into two unequal cells were morphologically different form bi-cellular pollen grain. Embryogenic divisions in bi-cellular pollen grains were not observed. First divisions began by the third day of cultivation, and continued until the globular embryoid stage that was well-seen after the fourth week of cultivation. The already-formed embryoids can develop the secondary embryoids on their surface. Depending on the genotype, up to 1000 secondary embryoids can be produced from one embryoid in the liquid MSm medium supplemented with 0.1 mg/L of kinetin for regeneration. All carrot accessions studied were split into three groups: responsive genotypes, weakly responsive genotypes, and reluctant genotypes. The highest yield was 53 initial embryoids per a 6 cm diameter petri dish. Thus, the Nantskaya 4 cultivar totally produced 256 initial embryoids, out of which 94 developed into green plantlets and 162 into albino plantlets, whereas 97 initial embryoids with 45 albino plantlets formed from them were obtained from Chantenay cultivar.

Exploring Spelling Errors with Relation to the Phonological Syllable Structure in the Writings of Saudi ESL Learners

Making spelling errors is one of the common issues faced by learners in any language as Second Language (SL) at the early stage of learning. This study investigated the spelling errors in the writings of undergraduate B.A. English students, University of Bisha, Al-Namas, Saudi Arabia. The study explored the spelling errors’ phenomenon with relation to the phonological syllable structure of words where the spelling errors were classified into three categories of words, (1) mono-syllabic, (2) di-syllabic, and (3) tri-syllabic and complex syllabic words. The researcher analyzed the spelling errors with relation to the sounds/phonemes positions in each syllable, (a) onset position, (b) nucleus position, and (c) coda position spelling errors. The results showed that Arabic-speaking learners made more spelling errors in tri-syllabic and complex syllabic words compared to the spelling errors in mono-syllabic words. The results explored that learners made more spelling errors in the nucleus position with 54.85% and fewer errors in the coda position 36.40%. Interestingly learners made a small number of errors than the other groups with 8.75% in the onset position. This suggested that English vowels, being in the nucleus position, are a more problematic position for Arab learners than consonants. The omission and the substitution spelling errors were more frequent and high compared to other categories. The study explored that the spelling errors are attributed to the different orthographical and morpho-phonological systems of L1 and L2 including the letter-to-sound correspondence and sound-to-letter correspondence, homophones, silent letters. The study concluded with some solutions to help learners avoid the spelling errors such as the importance of the phonological awareness of ESL.

Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

Backgrounds: As a widely used biomechanical research method, finite element analysis (FEA) is an important tool for investigating the pathogenesis of disc degenerative diseases and optimizing spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA.Objectives: This study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase the ACC of the following FEA studies.Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were used. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motion (ROM) between the model, wherein the ligaments, facet joints and nucleus were suppressed, and that of an in vitro study. Then, the ACC was re-estimated in the model with all non-bony structures by comparing the ROM, the intradiscal pressure (IDP), the facet contact force (FCF) and the disc compression (DC) under different sizes and directions of moments magnitudes to validate the measured and calibrated indicators.Results: The interobserver homogeneity was acceptable, and the measured P1 and P2 values were 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under almost all of the loading conditions considering the different indicators and moment magnitudes.Conclusions: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model and can therefore be used in subsequent studies.

Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

Background: As a widely used biomechanical research method, finite element analysis (FEA) is an important tool for investigating the pathogenesis of disc degenerative diseases and optimizing spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA. Hence, this study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase the ACC of the following FEA studies. Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were used. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motion (ROM) between the model, wherein the ligaments, facet joints and nucleus were suppressed, and that of an in vitro study. Then, the ACC was re-estimated in the model with all non-bony structures by comparing the ROM, the intradiscal pressure (IDP), the facet contact force (FCF) and the disc compression (DC) under different sizes and directions of moments magnitudes to validate the measured and calibrated indicators. Results: The interobserver homogeneity was acceptable, and the measured P1 and P2 values were 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under al most all of the loading conditions considering the different indicators and moment magnitude s. Conclusion: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model and can therefore be used in subsequent studies.

Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

Background: As a widely used biomechanical research method, finite element analysis (FEA) is a significant tool for investigating the pathogenesis of disc degenerative diseases and optimizing of spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA. Hence, this study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase ACC of following FEA studies. Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data, and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were recruited. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motions (ROMs) between the model, wherein the ligaments, facet joints and nucleus were supressed, and an in vitro study. Then, ACC were re-estimated in the model with all non-bony structures to validate the measured and calibrated indicators. Results: The interobserver homogeneity is acceptable, and the measured P1 and P2 values are 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under all loading conditions. Conclusion: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model, and can therefore be used in subsequent studies.

Live cell imaging of meiosis in Arabidopsis thaliana

To follow the dynamics of meiosis in the model plant Arabidopsis, we have established a live cell imaging setup to observe male meiocytes. Our method is based on the concomitant visualization of microtubules (MTs) and a meiotic cohesin subunit that allows following five cellular parameters: cell shape, MT array, nucleus position, nucleolus position, and chromatin condensation. We find that the states of these parameters are not randomly associated and identify 11 cellular states, referred to as landmarks, which occur much more frequently than closely related ones, indicating that they are convergence points during meiotic progression. As a first application of our system, we revisited a previously identified mutant in the meiotic A-type cyclin TARDY ASYNCHRONOUS MEIOSIS (TAM). Our imaging system enabled us to reveal both qualitatively and quantitatively altered landmarks in tam, foremost the formation of previously not recognized ectopic spindle- or phragmoplast-like structures that arise without attachment to chromosomes.