Biophysical compartment models for single-shell diffusion MRI in the human brain: a model fitting comparison

Clinically oriented studies commonly acquire diffusion MRI (dMRI) data with a single non-zero b-value (i.e. single-shell) and diffusion weighting of b=1000 s/mm2. To produce microstructural parameter maps, the tensor model is usually used, despite known limitations. Although compartment models have demonstrated improved fits in multi-shell dMRI data, they are rarely used for single-shell parameter maps, where their effectiveness is unclear from the literature. Here, various compartment models combining isotropic balls and symmetric tensors were fitted to single-shell dMRI data to investigate model fitting optimization and extract the most information possible. Full testing was performed in 5 subjects, and 3 subjects with multi-shell data were included for comparison. The results were tested and confirmed in a further 50 subjects. The Markov chain Monte Carlo (MCMC) model fitting technique outperformed non-linear least squares. Using MCMC, the 2-fibre-orientation mono-exponential ball & stick model (BSME 2) provided artifact-free, stable results, in little processing time. The analogous ball & zeppelin model (BZ2) also produced stable, low-noise parameter maps, though it required much greater computing resources (50 000 burn-in steps). In single-shell data, the gamma-distributed diffusivity ball & stick model (BSGD 2) underperformed relative to other models, despite being an often-used software default. It produced artifacts in the diffusivity maps even with extremely long processing times. Neither increased diffusion weighting nor a greater number of gradient orientations improved BSGD 2 fits. In white matter (WM), the tensor produced the best fit as measured by Bayesian information criterion. This result contrasts with studies using multi-shell data. However, in crossing fibre regions the tensor confounded geometric effects with fractional anisotropy (FA): the planar/linear WM FA ratio was 49%, while BZ2 and BSME 2 retained 76% and 83% of restricted fraction, respectively. As a result, the BZ2 and BSME 2 models are strong candidates to optimize information extraction from single-shell dMRI studies.

Enabling complex fibre geometries using 3D printed axon-mimetic phantoms

PurposeTo introduce a method to create 3D-printed axon-mimetic phantoms with complex fibre orientations to characterize the performance of diffusion MRI models and representations in the presence of orientation dispersion.MethodsAn extension to an open source 3D printing package was created to 3D print a set of five 3D-printed axon-mimetic (3AM) phantoms with various combinations of bending and crossing fibre orientations. A two-shell diffusion MRI scan of the five phantoms in water was performed at 9.4T. Diffusion tensor imaging (DTI), diffusion kurtosis imaging (DKI), the ball and stick model, neurite orientation density and dispersion imaging (NODDI), and Bingham-NODDI were all fit to the resulting diffusion MRI data. A fiducial in each phantom was used to register a ground truth map of that phantom’s crossing angles and/or arc radius to the diffusion-weighted images. Metrics from each model and representation were compared to the ground-truth maps, and a quadratic regression model was fit to each combination of output metric and ground-truth metric.ResultsThe mean diffusivity (MD) metric defined by DTI was insensitive to crossing angle, but increased with fibre curvature. Axial diffusivity (AD) decreased sharply with increasing crossing angle. DKI’s diffusivity metrics replicated the trends seen in DTI, and its mean kurtosis (MK) metric, decreased with fibre curvature, except in regions with high crossing angles. The estimated stick volume fraction in the ball and stick model decreased with increasing fibre curvature and crossing angle. NODDI’s intra-neurite volume fraction was insensitive to crossing angle, and its orientation dispersion index (ODI) was strongly correlated to crossing angle. Bingham-NODDI’s intra-neurite volume fraction was also insensitive to crossing angle, while its primary ODI (ODIP) was also strongly correlated to crossing angle and its secondary ODI (ODIS) was insensitive to crossing angle. For both NODDI models, the volume fractions of the extra-neurite and CSF compartments had low reliability with no clear relationship to crossing angle.ConclusionsThis study demonstrates that inexpensive 3D-printed axon-mimetic phantoms can be used to investigate the effect of fibre curvature and crossings on diffusion MRI representations and models of diffusion signal. As a proof of concept, the dependence of several representations and models on fibre dispersion/crossing were investigated. As expected, Bingham-NODDI was best able to characterize planar fibre dispersion in the phantoms.

Penerapan Model Talking Stick untuk Meningkatkan Hasil Belajar Materi Pola Irama

Penelitian ini bertujuan untuk mengetahui penerapan model Talking Stick dan peningkatan hasil belajar pada materi pola irama kelas III SDN I Baledono. Jenis penelitian ini adalah Penelitian Tindakan Kelas yang dilaksanakan pada semester I tahun ajaran 2020/ 2021 dengan menggunakan dua siklus dan setiap siklus terdiri dari dua pertemuan. Subjek penelitian ini adalah siswa kelas III yang berjumlah 15 siswa. Teknik pengumpulan data diperoleh melalui wawancara, observasi, tes dan dokumentasi. Hasil penelitian ini menunjukkan bahwa penerapan model Talking Stick dapat meingkatkan hasil belajar pada materi pola irama. Hal tersebut dibuktikan dengan data yang diperoleh melalui tes. Perolehan nilai pada tahap pra siklus yaitu 73 naik menjadi 83,33 pada siklus I meningkat menjadi 86,67 pada siklus II. Persentase Ketuntasan pada pra siklus yaitu 40% menjadi 73,33% pada siklus I meningkat menjadi 86,67% pada siklus II. Berdasarkan data tersebut bahwa ketercapaian hasil belajar yang diperoleh dengan persentase 86,67% melebihi indikator keberhasilan yang telah ditentukan peneliti yaitu 80%. This study aims to determine the application of the Talking Stick model and the improvement of learning outcomes in the material of the rhythm pattern of class III Elementary School I Baledono. This type of research is a classroom action research conducted in the first semester of the 2020/ 2021 academic year using two cycles and each cycle consisting of two meetings. The subjects of this study were 15 grade students. Data collection techniques obtained through interviews, observation, tests and documentation. The results this study indicate that the application of the Talking Stick model can improve learning outcomes on rhythm pattern material. This is evidenced by the data obtained through tests. The acquisition value in the pre-cycle stage, as 73, increased to 83,33 in the first cycle and increased to 86,67 in the second cycle. The percentage completeness in the pre-cycle, as 40% to 73,33% in the first cycle, increased to 86,67% in the second cycle. Based on these data, the achievement of learning outcomes obtained with a percentage of 86,67% exceeds the indicator of success that has been determined by the researcher, as 80%.

COMPARISON OF GIVING MIND MAP AS A RECITATION AND GIVING QUESTION THAT START TALKING STICK LEARNING COOPERATIVE MODEL TO BIOLOGY COMPETENCIES

The problem at SMPN 3 Padang Panjang is the low level of student learning competencies including knowledge, attitudes, and skills. Efforts that can be done are applying giving recitation in the form of mind mapping with giving questions that start cooperative learning model talking stick to student biology learning competencies. This type of research is a experimental research design, namely the The Statis Group Comparison Design. The population in the study of all students of class VII SMPN 3 Padang Panjang who were enrolled in the 2018/2019 Academic Year grouped in 7 classes. Sampling used purposive sampling technique. Based on the results of the study using the t-test on the competency of students' knowledge the value of tcount was 1,69>1.67 ttable, and the competency skill of the experimental class 1 is 80% with very good categories while the experimental class II are 76 % with good categories. In the attitude competence of the experimental class 1 is 85% are good categories while the experimental class II are 81% with sufficient categories. This shows that the hypothesis is accepted in the competence of knowledge, attitudes and skills. The conclusion of the study ,there is a difference in giving recitation in the form of mind mapping with the provision of questions that initiate cooperative learning the talking stick model to biology learning competencies in the realm of knowledge, attitudes and skills in class VII of SMPN 3 Padang Panjang.

A Discrete Element Methods-Based Model for Particulate Deposition and Rebound in Gas Turbines

The secondary air system and cooling passages of gas turbine components are prone to blockage from sand and dust. Prediction of deposition requires accurate models of particle transport and thermo-mechanical interaction with walls. Bounce stick models predict whether a particle will bounce, stick, or shatter upon impact and calculate rebound trajectories if applicable. This paper proposes an explicit bounce stick model that uses analytical solutions of adhesion, plastic deformation and viscoelasticity to time-resolve collision physics. The Discrete-Element Methods (DEM) model shows good agreement when compared to experimental studies of micron and millimetre-scale particle collisions, requiring minimal parametric fitting. Non-physical values mechanical properties, artifices of previous models, are thus eliminated. Further comparison is made to the best resolved and industry standard semi-empirical models available in literature. In addition to coefficients of restitution, other variables crucial to accurately model rebound, for example angular velocity, are predicted. The time-stepping explicit approach allows full coupling between internal processes during contact, and shows that particle deformation and hence viscoelasticity play a significant role in adhesion. Modelling time-dependent internal variables such as wall-normal force create functionality for future modelling of arbitrarily shaped particles, the physics of which has been shown by previous work to differ significantly from that of spheres. To date these effects have not been captured well using by higher-level energy-based models.

MENINGKATKAN PERKEMBANGAN BAHASA ANAK MELALUI METODE STORY TELLING, MODEL TALKING STICK DAN MODEL PICTURE AND PICTURE

Ketertarikan anak TK pada cerita yang ditampilkan akan dapat memunculkan ide-ide baru atau gagasan yang dapat meningkatkan bahasa anak. Dalam hal tersebut anak dilatih untuk berpikir logis,anak dapat berbicara dalam menjawab beberapa pertanyaan, mengungkapkan alasan-alasan dari pertanyaan-pertanyaan yang menjadi acuan pada gambar-gambar yang telah mereka lihat tersebut. Tujuan penelitian ini untuk mendeskripsikan kegiatan guru, anak serta meneliti aktivitas belajar anak dalam kemampuan menjawab pertanyaan yang lebih komplek. Penelitian ini menggunakan jenis PTK yang dilaksanakan dalam 4 kali pertemuan. Hasil penelitian ini berkaitan dengan aktivitas guru terlaksana dengan langkah-langkah yang ditetapkan dalam kategori sangat baik, aktivitas anak secara klasikal sebesar 100% dalam kategori sangat aktif. Disarankan bagi guru, diharapkan hasil dari penelitian tersebut bisa menjadi sebagai pedoman upayanya dengan meningkatkan pembelajaran yang bermutu dalam pembelajaran bahasa dan hasil perkembangan anak.Kata kunci: Perkembangan Bahasa, Metode story telling, Model talking stick, model picture and picture

Price Stickiness in US-Corn Market: Evidence from Dsge-Var Simulation

This study examines price stickiness in the United States (US) corn market using annual series data, on the dollar price of corn per bushel, obtained from the United States Department of Agriculture (USDA) and Federal Reserve Bank of Saint Louis (FRED), between 1930 and 2017. The study implemented the Calvo price stick model based on an agent in a general equilibrium and New Keynesian type, simulated using DSGE-VAR. The approach permits the indexing formula to include expected corn inflation rather than lagged inflation. The results show that corn price inflation only persists by 2% every trading year, resulting from changes in the immediate future corn-price inflation and output-gap, respectively. The shock to stochastic term only causes a partial decline in the corn price, converging at a future date with its long-run equilibrium. The experiment confirmed that corn price fluctuations are beyond the purview of the domestic economy, and any attempt to impose price policies will offset the price setting, creating further distortions and a wider gap in the corn yield. The study provides fresh insight into the Calvo price stick model of the New Keynesian type and its use to forecast agricultural outcomes.

A New, Ecologically Self-Significant Metric of Species-Abundance Unevenness, Reliably Highlighting the Intensity of Interspecific Competition

A wide series of commonly used metrics of abundance-evenness (or -unevenness) have been proposed to characterize synthetically the distributions of species-abundances, accounting for the hierarchic-like organization of species within natural communities. Among them, most – if not all–have been relevantly criticized on their serious limitations regarding both their “descriptive” and their “interpretative” capacities. From the descriptive point of view, many authors have already repeatedly emphasized the formal non-independenceof conventional (un-)evenness metrics with respect to species-richness, leading, in particular, to unacceptable bias when comparing communities differing by their species-richness, thus making these metrics unreliable descriptors in this respect. Now, as regards the capacity to provide relevant ecological interpretations, especially in terms of the intensity of competition among co-occurring species, the weakness of conventional (un-)evenness metrics is readily highlighted by the usual absence of any associated interpretation of this kind in the literature: the conventional (un-)evenness metrics beingrestricted to purely descriptive purpose only. Accordingly, a newly designed abundance-unevenness metric – the “standardized abundance-unevenness” index is proposed, positively addressing both kinds of limitations evoked above. By standardizing a conventional measure,U,of abundance-unevenness to the corresponding measure, U’, of the abundance-unevenness in the well-known “broken-stick” model, the resulting “standardized unevenness” index (Istr = U/U’) proves to be efficient against both themajor limitations pointed-out above:indeed,the new index does benefit by being both (i) formally independent from species-richness, thereby allowing reliable,unbiased comparisons of abundance unevenness between species-communities, whatever their difference in species-richness; (ii) able to relevantly quantify the mean intensity of interspecific-competition within community, in term of its direct outcomeuponthe degree of species-abundance unevenness. This double success being, of course, the direct consequences of the properties of the “broken-stick” distribution model, originally putforth in a well-known, yet insufficiently thoroughly exploited paper by the regretted Robert MacArthur.

UPAYA MENINGKATKAN HASIL BELAJAR MENGGUNAKAN MODEL TALKING STICK PADA MATA PELAJARAN PAI DI SMP

This study aims to improve the learning value of class VII A students of SMP Negeri 4 Pontianak. This research was conducted in two cycles, each of which had planning, implementation, observation and reflection. Data anatysis techniques that guide data management use a percentage (%) with a constant size of 100. Learning values are obtained from students test score of formative tests in the evaluation activities of each cycle. The result of study in cycle I showed that the average of learning value of students was 76.8 dan in cycle II showed that the average of learneng value of students increased to 80.9. Keywords : Enhancement, Learning Value, PAI, Talking Stick Model,

Pore Structure Characterization of Undisturbed Weathered Crust Elution-Deposited Rare Earth Ore Based on X-ray Micro-CT Scanning

As an environmentally compliant hydrometallurgical process, in situ leaching is extensively used by the mining industry to recover rare earth from weathered crust elution-deposited rare earth ore. In the in situ leaching system, the pore structure plays a dominant role in the permeability of the rare earth orebody and is one of the most important factors that influence the leaching performance. To study the pore structure characteristics of the rare earth ore, an undisturbed ore sample was scanned using X-ray micro-computed tomography. Based on the image processing techniques, visualization of the pore structure was realized and several parameters of 2D and 3D pore structures, such as porosity, pore volume, length, width, aspect ratio, and orientation, were obtained and statistically analyzed. The ball-and-stick model of large pore clusters was built by the maximal ball algorithm, and some of their detailed characteristics were obtained. The results indicate that the pore structure of weathered crust elution-deposited rare earth ore exhibits a multi-scale and strong heterogeneity characteristic. The distribution characteristics of pores between the vertical direction and the horizontal direction are obviously different. The small pores are more prevalent in number, but they make only a small contribution to the total pore volume. In addition, the orientation of the pores is anisotropic in both vertical and horizontal directions. Furthermore, the ball-and-stick model reveals that large pore clusters are composed of several interconnected void spaces, and most of them are small and irregular.